Oligoribonucleotides with enzymatic activity

Synthesis of Purine Nucleotide Triphosphates: 2′-O-methyl-guanosine-5′-Triphosphate

2′-O-methyl guanosine nucleoside (0.25 grams, 0.84 mmol) was dissolved in triethyl phosphate (5.0) ml by heating to 100° C. for 5 minutes. The resulting clear, colorless solution was cooled to 0° C. using an ice bath under an argon atmosphere. Phosphorous oxychloride (1.8 eq., 0.141 ml) was then added to the reaction mixture with vigorous stirring. The reaction was monitored by HPLC, using a sodium perchlorate gradient. After 5 hours at 0° C., tributylamine (0.65 ml) was added followed by the addition of anhydrous acetonitrile (10.0 ml), and after 5 minutes (reequilibration to 0° C.) tributylammonium pyrophosphate (4.0 eq., 1.53 g) was added. The reaction mixture was quenched with 20 ml of 2M TEAB after 15 minutes at 0° C. (HPLC analysis with above conditions showed consumption of monophosphate at 10 minutes) then stirred overnight at room temperature, the mixture was evaporated in vacuo with methanol co-evaporation (4×) then diluted in 50 ml 0.05M TEAB. DEAE sephadex purification was used with a gradient of 0.05 to 0.6 M TEAB to obtain pure triphosphate (0.52 g, 66.0% yield) (elutes around 0.3M TEAB); the purity was confirmed by HPLC and NMR analysis.

Synthesis of Pyrimdine Nucleotide Triphosphates: 2′-O-methylthiomethyl-uridine-5 ′-triphosphate

2′-O-methylthiomethyl uridine nucleoside (0.27 grams, 1.0 mmol) was dissolved in triethyl phosphate (5.0 ml). The resulting clear, colorless solution was cooled to 0° C. with an ice bath under an argon atmosphere. Phosphorus oxychloride (2.0 eq., 0.190 ml) was then added to the reaction mixture with vigorous stirring. Dimethylaminopyridine (DMAP, 0.2eq., 25 mg) was added, the solution warmed to room temperature and the reaction was monitored by HPLC, using a sodium perchlorate gradient. After 5 hours at 20° C., tributylamine (1.0 ml) was added followed by anhydrous acetonitrile (10.0 ml), and after 5 minutes tributylammonium pyrophosphate (4.0 eq., 1.8 g) was added. The reaction mixture was quenched with 20 ml of 2M TEAB after 15 minutes at 20° C. (HPLC analysis with above conditions showed consumption of monophosphate at 10 minutes) then stirred overnight at room temperature. The mixture was evaporated in vacuo with methanol co-evaporation (4×) then diluted in 50 ml 0.05M TEAB. DEAE fast flow Sepharose purification with a gradient of 0.05 to 1.0 M TEAB was used to obtain pure triphosphate (0.40 g, 44% yield) (elutes around 0.3M TEAB) as determined by HPLC and NMR analysis.

Utilization of DMAP in Uridine 5′-Triphosphate Synthesis

The reactions were performed on 20 mg aliquots of nucleoside dissolved in 1 ml of triethyl phosphate and 19 ul of phosphorus oxychloride. The reactions were monitored at 40 minute intervals automatically by HPLC to generate yield-of-product curves at times up to 18 hours. A reverse phase column and ammonium acetate/sodium acetate buffer system (50 mM & 100 mM respectively at pH 4.2) was used to separate the 5′, 3′, 2′ monophosphates (the monophosphates elute in that order) from the 5′-triphosphate and the starting nucleoside. The data is shown in Table III. These conditions doubled the product yield and resulted in a 10-fold improvement in the reaction time to maximum yield (1200 minutes down to 120 minutes for a 90% yield). Selectivity for 5′-monophosphorylation was observed for all reactions. Subsequent triphosphorylation occurred in nearly quantitative yield.

Materials Used in Bacteriophage T7 RNA Polymerase Reactions

Buffer 1: Reagents are mixed together to form a 10×stock solution of buffer 1 (400 mM Tris-Cl [pH 8.1], 200 mM MgCl 2 , 100 mM DTT, 50 mM spermidine, and 0.1% triton® X-100). Prior to initiation of the polymerase reaction methanol, LiCl is added and the buffer is diluted such that the final reaction conditions for condition 1 consisted of: 40 mM tris (pH 8.1), 20 mM MgCl 2 , 10 mM DTT, 5 mM spermidine, 0.01% triton® X-100, 10% methanol, and 1 mM LiCl.

BUFFER 2: Reagents are mixed together to form a 10×stock solution of buffer 2 (400 mM Tris-Cl [pH 8.1], 200 mM MgCl 2 , 100 mM DTT, 50 mM spernidine, and 0.1% triton® X-100). Prior to initiation of the polymerase reaction PEG, LiCl is added and the buffer is diluted such that the final reaction conditions for buffer 2 consisted of: 40 mM tris (pH 8.1), 20 mM MgCl 2 , 10 mM DTT, 5 mM spermidine, 0.01% triton® X-100, 4% PEG, and 1 mM LiCl.

BUFFER 3: Reagents are mixed together to form a 10×stock solution of buffer 3 (400 mM Tris-Ci [pH 8.0], 120 mM MgCl 2 , 50 mM DTT, 10 mM spermidine and 0.02% triton® X-100). Prior to initiation of the polymerase reaction PEG is added and the buffer is diluted such that the final reaction conditions for buffer 3 consisted of: 40 mM tris (pH 8.0), 12 mM MgCl 2 , 5 mM DTT, 1 mM spermidine, 0.002% triton® X-100, and 4% PEG.

BUFFER 4: Reagents are mixed together to form a 10×stock solution of buffer 4 (400 mM Tris-Cl [pH 8.0], 120 mM MgCl 2 , 50 mM DTT, 10 mM spermidine and 0.02% triton® X-100). Prior to initiation of the polymerase reaction PEG, methanol is added and the buffer is diluted such that the final reaction conditions for buffer 4 consisted of: 40 mM tris (pH 8.0), 12 mM MgCl 2 , 5 mM DTT, 1 mM spermidine, 0.002% triton® X-100, 10% methanol, and 4% PEG.

BUFFER 5: Reagents are mixed together to form a lOX stock solution of buffer 5 (400 mM Tris-Cl [pH 8.0], 120 mM MgCl 2 , 50 mM DTT, 10 mM spermidine and 0.02% triton® X-100). Prior to initiation of the polymerase reaction PEG, LiCl is added and the buffer is diluted such that the final reaction conditions for buffer S consisted of: 40 mM tris (pH 8.0), 12 mM MgCl 2 , 5 mM DTT, 1 mM spermidine, 0.002% triton® X-100, 1 mM LiCl and 4% PEG.

BUFFER 6: Reagents are mixed together to form a 10×stock solution of buffer 6 (400 mM Tris-Cl [pH 8.0], 120 mM MgCl 2 , 50 mM DTT, 10 mM spermidine and 0.02% triton® X-100). Prior to initiation of the polymerase reaction PEG, methanol is added and the buffer is diluted such that the final reaction conditions for buffer 6 consisted of: 40 mM tris (pH 8.0), 12 mM MgCl 2 , 5 mM DTT, 1 mM spermidine, 0.002% triton® X-100, 10% methanol, and 4% PEG.

BUFFER 7: Reagents are mixed together to form a 10×stock solution of buffer 6 (400 mM Tris-Cl [pH 8.0], 120 mM MgCl 2 , 50 mM DTT, 10 mM spermidine and 0.02% triton® X-100). Prior to initiation of the polymerase reaction PEG, methanol and LiCl is added and the buffer is diluted such that the final reaction conditions for buffer 6 consisted of: 40 mM tris (pH 8.0), 12 mM MgCl 2 , 5 mM DTT, 1 mM spermidine, 0.002% triton® X-100, 10% methanol, 4% PEG, and 1 mM LiCl.

Screening of Modified Nucleotide Triphosphates with Mutant T7 RNA

Polymerase

Modified nucleotide triphosphates were tested in buffers 1 through 6 at two different temperatures (25 and 37° C.). Buffers 1-6 tested at 25° C. were designated conditions 1-6 and buffers 1-6 tested at 37° C. were designated conditions 7-12 (Table IV). In each condition, Y639F mutant T7 polymerase (Sousa and Padilla, supra) (0.3-2 mg/20 ml reaction), NTP's (2 mM each), DNA template (10 pmol), inorganic pyrophosphatase (5 U/ml) and α- 32 P NTP (0.8 mCi/pmol template) were combined and heated at the designated temperatures for 1-2 hours. The radiolabeled NTP used was different from the modified triphosphate being testing. The samples were resolved by polyacrylamide gel electrophoresis. Using a phosphorimager (Molecular Dynamics, Sunnyvale, Calif.), the amount of full-length transcript was quantified and compared with an all-RNA control reaction. The data is presented in Table V; results in each reaction are expressed as a percent compared to the all-ribonucleotide triphosphate (rNTP) control. The control was run with the mutant T7 polymerase using commercially available polymerase buffer (Boehringer Mannheim, Indianapolis, Ind.).

Incorporation of Modified NTP's Using Wild-type T7 RNA Polymerase

Bacteriophage T7 RNA polymerase was purchased from Boehringer Mannheim at 0.4 U/μL concentration. Applicant used the commercial buffer supplied with the enzyme and 0.2 μCi alpha- 32 P NTP in a 50 μL reaction with nucleotides triphosphates at 2 mM each. The template was a double-stranded PCR fragment, which was used in previous screens. Reactions were carried out at 37° C. for 1 hour. Ten μL of the sample was run on a 7.5% analytical PAGE and bands were quantitated using a Phosphorlmager. Results are calculated as a comparison to an “all ribo” control (non-modified nucleotide triphosphates) and the results are in Table VI.

Incorporation of Multiple Modified Nucleotide Triphosphates Into Oligonucleotides

Combinations of modified nucleotide triphosphates were tested with the transcription protocol described in example 4, to determine the rates of incorporation of two or more of these triphosphates. Incorporation of 2′-Deoxy-2′-(L-histidine) amino uridine (2′-his-NH 2 -UTP) was tested with unmodified cytidine nucleotide triphosphates, rATP and rGTP in reaction condition number 9. The data is presented as a percentage of incorporation of modified NTP's compared to the all rNTP control and is shown in Table VII a.

Two modified cytidines (2′-NH 2 -CTP or 2′dCTP) were incorporated along with 2′-his-NH 2 -UTP with identical efficiencies. 2′-his-NH 2 -UTP and 2′-NH 2 -CTP were then tested with various unmodified and modified adenosine triphosphates in the same buffer (Table VII b). The best modified adenosine triphosphate for incorporation with both 2′-his-NH 2 -UTP and 2′-NH 2 -CTP was 2′-NH 2 -DAPTP.

Optimization of Reaction Conditions for Incorporation of Modified Nucleotide Triphosphate

The combination of 2′-his-NH 2 -UTP, 2′-NH 2 -CTP, 2′-NH 2 -DAP, and rGTP was tested in several reaction conditions (Table VIII) using the incorporation protocol described in example 9. The results demonstrate that of the buffer conditions tested, incorporation of these modified nucleotide triphosphates occur in the presence of both methanol and LiCl.

Selection of Novel Enzymatic Nucleic Acid Molecule Motifs Using 2′-deoxy-2′amino Modified GTP and CTP

For selection of new enzymatic nucleic acid molecule motifs, pools of enzymatic nucleic acid molecules were designed to have two substrate binding arms (5 and 16 nucleotides long) and a random region in the middle. The substrate has a biotin on the 5′ end, 5 nucleotides complementary to the short binding arm of the pool, an unpaired G (the desired cleavage site), and 16 nucleotides complementary to the long binding arm of the pool. The substrate was bound to column resin through an avidin-biotin complex. The general process for selection is shown in FIG. 2 . The protocols described below represent one possible method that may be utilized for selection of enzymatic nucleic acid molecules and are given as a non-limiting example of enzymatic nucleic acid molecule selection with combinatorial libraries.

Construction of Libraries: The oligonucleotides listed below were synthesized by Operon Technologies (Alameda, Calif.). Templates were gel purified and then run through a Sep-Pak™ cartridge (Waters, Millford, Mass.) using the manufacturers protocol. Primers (MST3, MST7c, MST3del) were used without purification.

N60 library was constructed using MSN60c as a template and MST3/MST7c as primers. N40 and N20 libraries were constructed using MSN40c (or MSN20c) as template and MST3deV/MST7c as primers.

Single-stranded templates were converted into double-stranded DNA by the following protocol: 5 nmol template, 10 nmol each primer, in 10 ml reaction volume using standard PCR buffer, dNTP's, and taq DNA polymerase (all reagents from Boerhinger Mannheim). Synthesis cycle conditions were 94° C., 4 minutes; (94° C., 1 minute; 42° C., 1 minute; 72° C., 2 minutes) x 4; 72° C., 10 minutes. Products were checked on agarose gel to confirm the length of each fragment (N60=123 bp, N40=91 bp, N20=71 bp) and then were phenouchloroform extracted and ethanol precipitated. The concentration of the double-stranded product was 25 μM.

Transcription of the initial pools was performed in a 1 ml volume comprising: 500 pmol double-stranded template (3×10 14 molecules), 40 mM tris-HCl (pH 8.0), 12 mM MgCl 2 , 1 mM spermidine, 5 mM DTT, 0.002% triton X-100, 1 mM LiCl, 4% PEG 8000, 10% methanol, 2 mM ATP (Pharmacia), 2 mM GTP (Pharmacia), 2 mM 2′-deoxy-2′-amino-CTP (USB), 2 mM 2′-deoxy-2′-amino-UTP (USB), 5 U/ml inorganic pyrophosphatase (Sigma), 5 U/μl T7 RNA polymerase (USB; Y639F mutant was used in some cases at 0.1 mg/ml (Sousa and Padilla, supra)), 37° C., 2 hours. Transcribed libraries were purified by denaturing PAGE (N60=106 ntds, N40=74, N20=54) and the resulting product was desalted using Sep-Pak™ columns and then ethanol precipitated.

Initial column-Selection: The following biotinylated substrate was synthesized using standard protocols (Usman el al., 1987 J. Am. Chem. Soc ., 109, 7845; Scaringe et al., 1990 Nucleic Acids Res ., 18, 5433; and Wincott et al., 1995 Nucleic Acids Res ., 23, 2677-2684):

5′-biotin-C18 spacer-GCC GUG GGU UGC ACA CCU UUC C-C18 spacer-thiol-modifier C6 S-S-inverted abasic-3′ (SEQ ID NO. 1521).

Substrate was purified by denaturing PAGE and ethanol precipitated. 10 nmol of substrate was linked to a NeutrAvidin™ column using the following protocol: 400 μl UltraLink Immobilized NeutrAvidin™ slurry (200 μl beads, Pierce, Rockford, Ill.) were loaded into a polystyrene column (Pierce). The column was washed twice with 1 ml of binding buffer (20 mM NaPO 4 (pH 7.5), 150 mM NaCl) and then capped off (i.e., a cap was put on the bottom of the column to stop the flow). 200 μl of the substrate suspended in binding buffer was applied and allowed to incubate at room temperature for 30 minutes with occasional vortexing to ensure even linking and distribution of the solution to the resin. After the incubation, the cap was removed and the column was washed with 1 ml binding buffer followed by 1 ml column buffer (50 mM tris-HCL (pH 8.5), 100 mM NaCl, 50 mM KCl). The column was then ready for use and capped off. 1 nmol of the initial pool RNA was loaded on the column in a volume of 200 μl column buffer. It was allowed to bind the substrate by incubating for 30 minutes at room temperature with occasional vortexing. After the incubation, the cap was removed and the column was washed twice with 1 ml column buffer and capped off. 200 μl of elution buffer (50 mM tris-HCl (pH 8.5), 100 mM NaCl, 50 mM KCl, 25 mM MgCl 2 ) was applied to the column followed by 30 minute incubation at room temperature with occasional vortexing. The cap was removed and four 200 μl fractions were collected using elution buffer.

Second-column-(counter-selection): A diagram for events in the second column is generally shown in FIG. 3 and substrate oligonucleotide used is shown below:

5′-GGU UGC ACA CCU UUC C-C18 spacer-biotin-inverted abasic-3′ (SEQ ID NO. ,1522).

This column substrate was linked to UltraLink NeutrAvidin™ resin as previously described (40 pmol) which was washed twice with elution buffer. The eluent from the first column purification was then run On the second column. The use of this column allowed for binding of RNA that non-specifically diluted from the first column, while RNA that performed a catalytic event and had product bound to it, flowed through the second column. The fractions were ethanol precipitated using glycogen as carrier and rehydrated in sterile water for amplification.

Amplification: RNA and primer MST3 (10-100 pmol) were denatured at 90° C. for 3 minutes in water and then snap-cooled on ice for one minute. The following reagents were added to the tube (final concentrations given): 1×PCR buffer (Boerhinger Mannheim), 1 mM dNTP's (for PCR, Boerhinger Mannheim), 2 U/μl RNase-Inhibitor (Boerhinger Mannheim), 10 U/μl Superscript™ II Reverse Transcriptase (BRL). The reaction was incubated for 1 hour at 42° C., then at 95° C. for 5 minutes in order to destroy the Superscript™. The following reagents were then added to the tube to increase the volume five-fold for the PCR step (final concentrations/amounts given): MST7c primer (10-100 pmol, same amount as in RT step), 1×PCR buffer, taq DNA polymerase (0.025-0.05 U/μl, Boerhinger Mannheim). The reaction was cycled as follows: 94° C., 4 minutes; (94° C., 30 s; 42-54° C., 30 s; 72° C., 1 minute)×4-30 cycles; 72° C., 5 minutes; 30° C., 30 minutes. Cycle number and annealing temperature were decided on a round by round basis. In cases where heteroduplex was observed, the reaction was diluted five-fold with fresh reagents and allowed to progress through 2 more amplification cycles. Resulting products were analyzed for size on an agarose gel (N60=123 bp, N40=103 bp, N20=83 bp) and then ethanol precipitated.

Transcriptions: Transcription of amplified products was done using the conditions described above with the following modifications: 10-20% of the amplification reaction was used as template, reaction volume was 100-500 μl, and the products sizes varied slightly (N60=106 ntds, N40=86, N20=66). A small amount of 32 P-GTP was added to the reactions for quantitation purposes.

Subsequent rounds: Subsequent rounds of selection used 20 pmols of input RNA and 40 pmol of the 22 nucleotide substrate on the column.

Activity of pools: Pools were assayed for activity under single turnover conditions every three to four rounds. Activity assay conditions were as follows: 50 mM tris-HCl (pH 8.5), 25 mM MgCl 2 , 100 mM NaCl, 50 mM KCl, trace 32 P-labeled substrate, 10 nM RNA pool. 2×pool in buffer and, separately, 2×substrate in buffer were incubated at 90° C. for 3 minutes, then at 37° C. for 3 minutes. Equal volume 2×substrate was then added the 2×pool tube (t=0). Initial assay time points were taken at 4 and 24 hours: 5 μl was removed and quenched in 8 μl cold Stop buffer (96% formamide, 20 mM EDTA, 0.05% bromphenyl blue/xylene cyanol). Samples were heated 90° C., 3 minutes, and loaded on a 20% sequencing gel. Quantitation was performed using a Molecular Dynamics Phosphorimager and ImageQuaNT™ software. The data is shown in Table IX.

Samples from the pools of oligonucleotide were cloned into vectors and sequenced using standard protocols (Sambrook et al., Molecular Cloning: A Laboratory Manual , Cold Spring Harbor Laboratory Press). The enzymatic nucleic acid molecules were transcribed from a representative number of these clones using methods described in this application. Individuals from each pool were tested for RNA cleavage from N60 and N40 by incubating the enzymatic nucleic acid molecules from the clones with 5/16 substrate in 2mM MgCl2, pH 7.5, 10 mM KCl at 37° C. The data in Table XI shows that the enzymatic nucleic acid molecules isolated from the pool are individually active.

Kinetic Activity: Kinetic activity of the enzymatic nucleic acid molecule shown in Table XI, was determined by incubating enzymatic nucleic acid molecule (10 nM) with substrate in a cleavage buffer (pH 8.5, 25 mM MgCl 2 , 100 mM NaCl, 50 mM KCl) at 37° C.

Magnesium Dependence: Magnesium dependence of round 15 of N20 was tested by varying MgCl 2 while other conditions were held constant (50 mM tris [pH 8.0], 100 mM NaCl, 50 mM KCl, single turnover, 10 nM pool). The data is shown in Table XII, which demonstrates increased activity with increased magnesium concentrations.

Selection of Novel Enzymatic Nucleic Acid Molecule Motifs Using 2′-Deoxy-2′-(N-histidyl) Amino UTP, 2′-Fluoro-ATP, and 2′-deoxy-2′-amino CTP and GTP

The method described in example 8 was repeated using 2′-Deoxy-2′-(N-histidyl) amino UTP, 2′-Fluoro-ATP, and 2′-deoxy-2′-amino CTP and GTP. However, rather than causing cleavage on the initial column with MgCl 2 , the initial random modified-RNA pool was loaded onto substrate-resin in the following buffer; 5 mM NaOAc pH 5.2, 1 M NaCl at 4° C. After ample washing, the resin was moved to 22° C. and the buffer switch 20 mM HEPES pH 7.4, 140 mM KCl, 10 mM NaCl, 1 mM CaCl 2 , 1 mM MgCl 2 . In one selection of N60 oligonucleotides, no divalent cations (MgCl 2 , CaCl 2 ) was used. The resin was incubated for 10 minutes to allow reaction and the eluant collected.

The enzymatic nucleic acid molecule pools were capable of cleaving 1-3% of the present substrate even in the absense of divalent cations, the background (in the absence of modified pools) was 0.2-0.4%.

Synthesis of 5-substituted 2′-modified Nucleosides

When designing monomeric nucleoside triphosphates for selection of therapeutic catalytic RNAs, one has to take into account nuclease stability of such molecules in biological sera. A common approach to increase RNA stability is to replace the sugar 2′-OH group with other groups like 2′-fluoro, 2′-O-methyl or 2′-amino. Fortunately such 2′-modified pyrimidine 5′triphosphates are shown to be substrates for RNA polymerases. 5,7 On the other hand it was shown that variety of substituents at pyrimidine 5-position is well tolerated by T7 RNA polymerase, 1 most likely because the natural hydrogen-bonding pattern of these nucleotides is preserved. We have chosen 2′-fluoro and 2′-O-methyl pyrimidine nucleosides as starting materials for attachment of different functionalities to the 5-position of the base. Both rigid (alkynyl) and flexible (alkyl) spacers are used. The choice of imidazole, amino and carboxylate pendant groups is based on their ability to act as general acids, general bases, nucleophiles and metal ligands, all of which can improve the catalytic effectiveness of selected nucleic acids. FIGS. 12-15 relate to the synthesis of these compounds.

2′-O-methyluridine was 3′,5′-bis-acetylated using acetic anhydride in pyridine and then converted to its 5-iodo derivative la using I 2 /ceric ammonium nitrate reagent 8 (Scheme 1). Both reactions proceeded in a quantitative yield and no chromatographic purifications were needed. Coupling between 1 and N-trifluoroacetyl propargylamine using copper(I) iodide and tetrakis(triphenylphosphine)palladium(0) catalyst as described by Hobbs 9 yielded 2a in 89% yield. Selective O-deacylation with aqueous NaOH afforded 3a which was phosphorylated with POCl 3 /triethylphosphate (TEP) in the presence of 1,8-bis(dimethylamino)naphthalene (Proton-Sponge) (Method A). 10 The intermediate nucleoside phosphorodichloridate was condensed in situ with tri-n-butylammonium pyrophosphate. At the end, the N-TFA group was removed with concentrated ammonia. 5′-Triphosphate was purified on Sephadex® DEAE A-25 ion exchange column using a linear gradient of 0.1-0.8M triethylammonium bicarbonate (TEAB) for elution. Traces of contaminating inorganic pyrophosphate are removed using C-18 RP HPLC to afford analytically pure material. Conversion into Na-salt was achieved by passing the aqueous solution of triphosphate through Dowex 50WX8 ion exchange resin in Na + form to afford 4a in 45% yield. When Proton-Sponge was omitted in the first phosphorylation step, yields were reduced to 10-20%. Catalytic hydrogenation of 3a yielded 5-aminopropyl derivative 5a which was phosphorylated under conditions identical to those described for propynyl derivative 3a to afford triphosphate 6a in 50% yield.

For the preparation of imidazole derivatized triphosphates 9a and 11a, we developed an efficient synthesis of N-diphenylcarbamoyl 4-imidazoleacetic acid (ImAA DPC ): Transient protection of carboxyl group as TMS-ester using TMS-Cl/pyridine followed by DPC-Cl allowed for a clean and quantitative conversion of 4-imidazoleacetic acid (ImAA) to its N-DPC protected derivative.

Complete deacylation of 2a afforded 5-(3-aminopropynyl) derivative 8a which was condensed with 4-imidazoleacetic acid in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) to afford 9a in 68% yield. Catalytic hydrogenation of 8a yielded 5-(3-aminopropyl) derivative 10a which was condensed with ImAA DPC to yield conjugate 11a in 32% yield. Yields in these couplings were greatly improved when 5′-OH was protected with DMT group (not shown) thus efficiently preventing undesired 5′-O-esterification. Both 9a and 11a failed to yield triphosphate products in reaction with POCl 3 /TEP/Proton-Sponge.

On the contrary, phosphorylation of 3′-O-acetylated derivatives 12a and 13a using 2-chloro-4H-1,3,2-benzodioxaphosphorin-4-one followed by pyrophosphate addition and oxidation (Method B, 11 Scheme 2) afforded the desired triphosphates 14a and 15a in 57% yield, respectively.

2′-Deoxy-2′-fluoro nucleoside 5′-triphosphates containing amino-(4b, 6b) and imidazole-(14b,15b) linked groups were synthesized in a manner analogous to that described for the preparation of 2′-O-methyl nucleoside 5′-triphosphates (Schemes 1 and 2). Again, only Ludwig-Eckstein's phosphorylation worked for the preparation of 4-imidazoleacetyl derivatized triphosphates.

It is worth noting that when “one-pot-two-steps” phosphorylation reaction 10 of 5b was quenched with 40% aqueous methylamine instead of TEAB or H 2 O, the—amidate 7b was generated as the only detectable product. Similar reaction was reported recently for the preparation of the γ-amidate of pppA2′p5′A2′p5′A. 12

Carboxylate group was introduced into 5-position of uridine both on the nucleoside level and post-synthetically (Method C) (Scheme 3). 5-Iodo-2′-deoxy-2′-fluorouridine (16) was coupled with methyl acrylate using modified Heck reaction, 3 to yield 17 in 85% yield. 5′-O-Dimethoxytritylation, followed by in situ 3′-O-acetylation and subsequent detritylation afforded 3′-protected derivative 18. Phosphorylation using 2-chloro-4H-1,3,2-benzodioxa-phosphorin-4-one followed by pyrophosphate addition and oxidation 1 afforded the desired triphosphate in 54% yield. On the other hand, 5-(3-aminopropyl)uridine 5′-triphosphate 6b was coupled with N-hydroxysuccinimide ester of Fmoc-Asp-OFm to afford, after removal of Fmoc and Fm groups with diethylamine, the desired aminoacyl conjugate 20 in 50% yield.

Cytidine derivatives comprising 3-aminopropyl and 3(N-succinyl)aminopropyl groups were synthesized according to Scheme 4. Peracylated 5-(3-aminopropynyl)uracil derivative 2b is reduced using catalytic hydrogenation and then converted in seven steps and 5% overall yield into 3′-acetylated cytidine derivative 25. This synthesis was plagued by poor solubility of intermediates and formation of the N 4 -cyclized byproduct during ammonia treatment of the 4-triazolyl intermediate. Phosphorylation of 25 as described in reference 11 yielded triphosphate 26 and N 4 -cyclized product 27 in 1:1 ratio. They were easily separated on Sephadex DEAE A-25 ion exchange column using 0.1-0.8M TEAB gradient. It appears that under basic conditions the free primary amine can displace any remaining intact 4-NHBz group leading to the cyclized product. This is similar to displacement of 4-triazolyl group by primary amine as mentioned above.

We reasoned that utilization of N 4 -unprotected cytidine will solve this problem. This lead to an improved synthesis of 26: Iodination of 2′-deoxy-2′-fluorocytidine (28) provided the 5-iodo derivative 29 in 58% yield. This compound was then smoothly converted into 5-(3-aminopropynyl) derivative 30. Hydrogenation afforded 5-(3-aminopropyl) derivative 31 which was phosphorylated directly with POCl 3 /PPi to afford 26 in 37% yield. Coupling of the 5′-triphosphate 26 with succinic anhydride yielded succinylated derivative 32 in 36% yield.

References

1. Tarasow, T. M.; Eaton, B. E. Biopolymers 1998, 48, 29.

2. Eaton, B. E.; Pieken, W. A. Annu. Rev. Biochem . 1995, 64, 837.

3. Eaton, B. E. Curr. Opin. Chem. Biol . 1997, 1, 10.

4. Dewey, T. M.; Mundt, A. A.; Crouch, G. J.; Zyzniewski, M. C., Eaton, B. E. J. Am. Chem. Soc . 1995, 32, 8475.

5. Aurup, H.; Williams, D. M.; Eckstein, F. Biochemistry 1992, 31, 9637.

6. Sakthivel, K.; Barbas III, C. F. Angew. Chem. Int . Ed. 1998, 37, 2872.

7. Padilla, R.; Sousa, R. Nucleic Acids Res . 1999, 27, 1561.

8. Asakura, J.; Robins, M. J. J. Org. Chem . 1990, 55, 4928.

9. Hobbs, F. W.,Jr. J. Org. Chem . 1989, 54, 3420.

10. Kovácz, T; Ötvös, L. Tetrahedron Lett. 1988, 29, 4525.

11. Ludwig, J.; Eckstein, F. J. Org. Chem . 1989, 54, 631.

12. Nyilas, A. Tetrahedron Lett . 1997, 38, 2517.

13. Dyer, R. L.; Jones, A. S.; Walker, R. T. in Nucleic Acid Chemistry ; Townsend, L. B. and Tipson, R. T., Ed.; John Wiley & Sons, Inc., New, York, 1991; p. 79.

Synthesis of 5-Imidazoleacetic Acid 2′-deoxy-5′-triphosphate Uridine

5-dintrophenylimidazoleacetic acid 2′-deoxy uridine nucleoside (80 mg) was dissolved in 5 ml of triethylphosphate while stirring under argon, and the reaction mixture was cooled to 0° C. Phosphorous oxychloride (1.8 eq, 22 ml) was added to the reaction mixture at 0° C., three more aliquots were added over the course of 48 hours at room temperature. The reaction mixture was then diluted with anhydrous MeCN (5 ml) and cooled to 0° C., followed by the addition of tributylamine (0.65 ml) and tributylammonium pyrophosphate (4.0 eq, 0.24 g). After 45 minutes, the reaction was quenched with 10 ml aq. methyl amine for four hours. After co-evaporation with MeOH (3×), purified material on DEAE Sephadex followed by RP chromatography to afford 15 mg of triphosphate.

Synthesis of 2′-(N-lysyl)-amino-2′-deoxy-cytidine Triphosphate

2′-(N-lysyl)-amino-2′-deoxy cytidine (0.180 g, 0.22 mmol) was dissolved in triethyl phosphate (2.00 ml) under Ar. The solution was cooled to 0° C. in an ice bath. Phosphorus oxychloride (99.999%, 3 eq., 0.0672 mL) was added to the solution and the reaction was stirred for two hours at 0° C. Tributylammonium pyrophosphate (4 eq., 0.400 g) was dissolved in 3.42 mL of acetonitrile and tribuytylamine (0.165 mL).

Acetonitrile (1 mL) was added to the monophosphate solution followed by the pyrophosphate solution which was added dropwise. The resulting solution was clear. The reaction was allowed to warm up to room temperature. After stirring for 45 minutes, methylamine (5 mL) was added and the reaction and stirred at room temperature for 2 hours. A biphasic mixture appeared (little beads at the bottom of the flask). TLC (7:1:2 iPrOH:NH 4 OH:H 2 O) showed the appearance of triphosphate material. The solution was concentrated, dissolved in water and loaded on a newly prepared DEAE Sephadex A-25 column. The column was washed with a gradient up to 0.6 M TEAB buffer and the product eluted off in fractions 90-95. The fractions were analyzed by ion exchange HPLC. Each fraction showed one triphosphate peak that eluted at ˜4.000 minutes. The fractions were combined and pumped down from methanol to remove buffer salt to yield 15.7 mg of product.

Synthesis of 2′-deoxy-2′-(L-histidine)amino Cytidine Triphosphate

2′-[N-Fmoc, N imid -dinitrophenyl-histidyl]amino-2′-cytidine (0.310 g, 4.04 mmol) was dissolved in triethyl phosphate (3 ml) under Ar. The solution was cooled to 0° C. Phosphorus oxychloride (1.8 eq., 0.068 mL) was added to the solution and stored overnight in the freezer. The next morning TLC (10% MeOH in CH 2 Cl 2 ) showed significant starting material, one more equivalent of POCl 3 was added. After two hours, TLC still showed starting material. Tributylamine (0.303 mL) and Tributylammonium pyrophosphate (4 eq., 0.734 g) dissolved in 6.3 mL of acetonitrile (added dropwise) were added to the monophosphate solution. The reaction was allowed to warm up to room temperature. After stirring for 15 min, methylamine (10 mL) was added at room temperature and stirring continued for 2 hours. TLC (7:1:2 iPrOH:NH 4 OH:H 2 O) showed the appearance of triphosphate material. The solution was concentrated, dissolved in water and loaded on a DEAE Sephadex A-25 column. The column was washed with a gradient up to 0.6 M TEAB buffer and the product eluted off in fractions 170-179. The fractions were analyzed by ion exchange HPLC. Each fraction showed one triphosphate peak that eluted at ˜6.77 minutes. The fractions were combined and pumped down from methanol to remove buffer salt to afford 17 mg of product.

Screening for Novel Enzymatic Nucleic Acid Molecule Motifs Using Modified NTPs (Class I Motif)

Our initial pool contained 3×10 14 individual sequences of 2′-amino-dCTP/2′-amino-dUTP RNA. We optimized transcription conditions in order to increase the amount of RNA product by inclusion of methanol and lithium chloride. 2′-amino-2′-deoxynucleotides do not interfere with the reverse transcription and amplification steps of selection and confer nuclease resistance. We designed the pool to have two binding arms complementary to the substrate, separated by the random 40 nucleotide region. The 16-mer substrate had two domains, 5 and 10 nucleotides long, that bind the pool, separated by an unpaired guanosine. On the 5′ end of the substrate was a biotin attached by a C18 linker. This enabled us to link the substrate to a NeutrAvidin™ resin in a column format. The desired reaction would be cleavage at the unpaired G upon addition of magnesium cofactor followed by dissociation from the column due to instability of the 5 base pair helix. A detailed protocol follows:

Enzymatic nucleic acid molecule Pool Prep: The initial pool DNA was prepared by converting the following template oligonucleotides into double-stranded DNA by filling in with taq polymerase. (template=5′-ACC CTC ACT AAA GGC CGT (N) 40 GGT TGC ACA CCT TTC-3′ (SEQ ID NO. 1523); primer 1=5′-CAC TTA GCA TTA ACC CTC ACT AAA GGC CGT-3′ (SEQ ID NO. 1515); primer 2=5′-TAA TAC GAC TCA CTA TAG GAA AGG TGT GCA ACC-3′ (SEQ ID NO. 1516)). All DNA oligonucleotides were synthesized by Operon technologies. Template oligos were purified by denaturing PAGE and Sep-pak chromatography columns (Waters). RNA substrate oligos were using standard solid phase chemistry and purified by denaturing PAGE followed by ethanol precipitation. Substrates for in vitro cleavage assays were 5′-end labeled with gamma- 32 P-ATP and T4 polynucleotide kinase followed by denaturing PAGE purification and ethanol precipitation.

5 nmole of template, 10 nmole of each primer and 250 U taq polymerase were incubated in a 10 ml volume with 1×PCR buffer (10 mM tris-HCl (pH 8.3), 1.5 mM MgCl 2 , 50 mM KCl) and 0.2 mM each dNTP as follows: 94° C., 4 minutes; (94° C., 1 min; 42° C., 1 min; 72° C., 2 min) through four cycles; and then 72° C., for 10 minutes. The product was analyzed on 2% Separide T agarose gel for size and then was extracted twice with buffered phenol, then chloroform-isoamyl alcohol, and ethanol precipitated. The initial RNA pool was made by transcription of 500 pmole (3×10 14 molecules) of this DNA as follows. Template DNA was added to 40 mM tris-HCl (pH 8.0),12 mM MgCl 2 , 5 mM dithiothreitol (DTT), 1 mM spermidine, 0.002% triton X-100, 1 mM LiCi, 4% PEG-8000, 10% methanol, 2 mM ATP, 2 mM GTP, 2 mM 2′-amino-dCTP, 2 mM 2′-amino-dUTP, 5 U/ml inorganic pyrophosphatase, and 5 U/μl T7 RNA polymerase at room temperature for a total volume of 1 ml. A separate reaction contained a trace amount of alpha- 32 P-GTP for detection. Transcriptions were incubated at 37° C. for 2 hours followed by addition of equal volume STOP buffer (94% formamide, 20 mM EDTA, 0.05% bromophenol blue). The resulting RNA was purified by 6% denaturing PAGE gel, Sep-pak™ chromatography, and ethanol precipitated.

INITIAL SELECTION: 2 nmole of 16 mer 5′-biotinylated substrate (Biotin-C18 linker-5′-GCC GUG GGU UGC ACA C-3′ (SEQ ID NO: 1493) was linked to 200 μl UltraLink Immobilized NeutrAvidin™ resin (400 μl slurry, Pierce) in binding buffer (20 mM NaPO 4 (pH 7.5), 150 mM NaCl) for 30 minutes at room temperature. The resulting substrate column was washed with 2 ml binding buffer followed by 2 ml column buffer (50 mM tris-HCl (pH 8.5), 100 mM NaCl, 50 mM KCl). The flow was capped off and 1000 pmole of initial pool RNA in 200 μl column buffer was added to the column and incubated 30 minutes at room temperature. The column was uncapped and washed with 2 ml column buffer, then capped off. 200 μl elution buffer (=column buffer+25 mM MgCl 2 ) was added to the column and allowed to incubate 30 minutes at room temperature. The column was uncapped and eluent collected followed by three 200 μl elution buffer washes. The eluent/washes were ethanol precipitated using glycogen as carrier and rehydrated in 50 μl sterile H 2 O. The eluted RNA was amplified by standard reverse transcription/PCR amplification techniques. 5-31 μl RNA was incubated with 20 pmol of primer 1 in 14 μl volume 90° for 3 min then placed on ice for 1 minute. The following reagent were added (final concentrations noted): 1×PCR buffer, 1 mM each dNTP, 2 U/μl RNase Inhibitor, 10 U/μl SuperScript™ II reverse transcriptase. The reaction was incubated 42° for 1 hour followed by 95° for 5 min in order to inactivate the reverse transcriptase. The volume was then increased to 100 μl by adding water and reagents for PCR: 1×PCR buffer, 20 pmol primer 2, and 2.5 U taq DNA polymerase. The reaction was cycled in a Hybaid thermocycler: 94°, 4 min; (94° C., 30 sec; 54° C., 30 sec; 72° C., 1 min)×25; 72° C., 5 min. Products were analyzed on agarose gel for size and ethanol precipitated. One-third to one-fifth of the PCR DNA was used to transcribe the next generation, in 100 μl volume, as described above. Subsequent rounds used 20 pmol RNA for the column with 40 pmol substrate.

TWO COLUMN SELECTION: At generation 8 (G8), the column selection was changed to the two column format. 200 pmoles of 22 mer 5′-biotinylated substrate (Biotin-C18 linker-5′-GCC GUG GGU UGC ACA CCU UUC C-3′ (SEQ ID NO: 1481)-C18 linker-thiol modifier C6 S-S-inverted abasic′) was used in the selection column as described above. Elution was in 200 μl elution buffer followed by a 1 ml elution buffer wash. The 1200 μl eluent was passed through a product trap column by gravity. The product trap column was prepared as follows: 200 pmol 16 mer 5′-biotinylated “product” (5′-GGU UGC ACA CCU UUC C-3′ (SEQ ID NO: 1521)-C18 linker-biotin′) was linked to the column as described above and the column was equilibrated in elution buffer. Eluent from the product column was precipitated as previously described. The products were amplified as above only with 2.5-fold more volume and 100 pmol each primer. 100 μl of the PCR reaction was used to do a cycle course; the remaining fraction was amplified the minimal number of cycles needed for product. After 3 rounds (G11), there was visible activity in a single turnover cleavage assay. By generation 13, 45% of the substrate was cleaved a hours; k obs of the pool was 0.037 min −1 in 25 mM MgCl 2 . We subcloned and sequenced generation 13; the pool was still very diverse. Since our goal was a enzymatic nucleic acid molecule that would work in a physiological environment, we decided to change selection presure rather than exhaustively catalog G13.

Reselection of the N40 pool was started from G12 DNA. Part of the G12 DNA was subjected to hypermutagenic PCR (Vartanian et al., 1996 , Nucleic Acids Research 24, 2627-2631) to introduce a 10% per position mutation frequency and was designated N40H. At round 19, part of the DNA was hypermutagenized again, giving N40M and N40HM (a total of 4 parallel pools). The column substrates remained the same; buffers were changed and temperature of binding and elution was raised to 37° C. Column buffer was replaced by physiological buffer (50 mM tris-HCl (pH 7.5), 140 mM KCl, 10 mM NaCl) and elution buffer was replaced by 1 mM Mg buffer (physiological buffer +1 mM MgCl 2 ). Amount of time allowed for the pool to bind the column was eventually reduced to 10 min and elution time was gradually reduced from 30 min to 20 sec. Between rounds 18 and 23, k obs for the N40 pool stayed relatively constant at 0.035-0.04 min −1 . Generation 22 from each of the 4 pools was cloned and sequenced.

CLONING AND SEQUENCING: Generations 13 and 22 were cloned using Novagen's Perfectly Blunt™ Cloning kit (pT7Blue-3 vector) following the kit protocol. Clones were screened for insert by PCR amplification using vector-specific primers. Positive clones were sequenced using ABI Prism 7700 sequence detection system and vector-specific primer. Sequences were aligned using MacVector software; two-dimensional folding was performed using Mulfold software (Zuker, 1989 , Science 244, 48-52; Jaeger et al., 1989 , Biochemistry 86, 7706-7710; Jaeger et al., 1989, R. F. Doolittle ed., Methods in Enzymology , 183, 281-306). Individual clone transcription units were constructed by PCR amplification with 50 pmol each primer 1 and primer 2 in 1×PCR buffer, 0.2 mM each dNTP, and 2.5 U of taq polymerase in 100 μl volume cycled as follows: 94° C., 4 min; (94° C., 30 sec; 54° C., 30 sec; 72° C., 1 min)×20; 72° C., 5 min. Transcription units were ethanol precipitated, rehydrated in 30 μl H2O, and 10 μl was transcribed in 100 μl volume and purified as previously described.

Thirty-six clones from each pool were sequenced and were found to be variations of the same consensus motif. Unique clones were assayed for activity in 1 mM MgCl 2 and physiological conditions; nine clones represented the consensus sequence and were used in subsequent experiments. There were no mutations that significantly increased activity; most of the mutations were in regions believed to be duplex, based on the proposed secondary structure. In order to make the motif shorter, we deleted the 3′-terminal 25 nucleotides necessary to bind the primer for amplification. The measured rates of the full length and truncated molecules were both 0.04 min −1 ; thus we were able reduce the size of the motif from 86 to 61 nucleotides. The molecule was shortened even further by truncating base pairs in the stem loop structures as well as the substrate recognition arms to yield a 48 nucleotide molecule. In addition, many of the ribonucleotides were replaced with 2O-methyl modified nucleotides to stabilize the molecule. An example of the new motif is given in FIG. 4 . Those of ordinary skill in the art will recognize that the molecule is not limited to the chemical modifications shown in the figure and that it represents only one possible chemically modified molecule.

Kinetic Analysis

Single turnover kinetics were performed with trace amounts of 5′- 32 P-labeled substrate and 10-1000 nM pool of enzymatic nucleic acid molecule. 2x substrate in 1x buffer and 2x pool/enzymatic nucleic acid molecule in 1x buffer were incubated separately 90° for 3 min followed by equilibration to 37° for 3 min. Equal volume of 2x substrate was added to pool/enzymatic nucleic acid molecule at t 0 and the reaction was incubated at 37° C. Time points were quenched in 1.2 vol STOP buffer on ice. Samples were heated to 90° C. for 3 min prior to separation on 15% sequencing gels. Gels were imaged using a PhosphorImager and quantitated using ImageQuant™ software (Molecular Dynamics). Curves were fit to double-exponential decay in most cases, although some of the curves required linear fits.

STABILITY: Serum stability assays were performed as previously described (Beigelman et al., 1995 , J. Biol. Chem . 270, 25702-25708). 1 μg of 5′- 32 P-labeled synthetic enzymatic nucleic acid molecule was added to 13 μl cold and assayed for decay in human serum. Gels and quantitation were as described in kinetics section.

SUBSTRATE REQUIREMENTS: Table XVII outlines the substrate requirements for Class I motif. Substrates maintained Watson-Crick or wobble base pairing with mutant Class I constructs. Activity in single turnover kinetic assay is shown relative to wild type Class I and 22 mer substrate (50 mM Tris-HCL (pH 7.5), 140 mM KCl, 10 mM NaCl, 1 mM MgCl 2 , 100 nM ribozyme, 5 nM substrate, 37° C.).

RANDOM REGION MUTATION ALIGNMENT: Table XVII outlines the random region alignment of 134 clones from generation 22 (1.×=N40, 2.×=N40M, 3.×=N40H, 4.×=N40HM). The number of copies of each mutant is in parenthesis in the table, deviations from consensus are shown. Mutations that maintain base pair U19:A34 are shown in italic. Activity in single turnover kinetic assay is shown relative to the G22 pool rate (50 mM Tris-HCL pH 7.5, 140 mM KCl, 10 mM NaCl, 1 mM MgCl 2 , 100 nM ribozyme, trace substrate, 37° C.).

STEM TRUNCATION AND LOOP REPLACEMENT ANALYSIS: FIG. 16 shows a representation of Class I ribozyme stem truncation and loop replacement analysis. The K re1 is compared to a 61 mer Class I ribozyme measured as described above. FIG. 17 shows examples of Class I ribozymes with truncated stem(s) and/or non-nucleotide linker replaced loop structures.

Inhibition of HCV Using Class I (Amberzme) Motif

During HCV infection, viral RNA is present as a potential target for enzymatic nucleic acid molecule cleavage at several processes: uncoating, translation, RNA replication and packaging. Target RNA may be more or less accessible to enzymatic nucleic acid molecule cleavage at any one of these steps. Although the association between the HCV initial ribosome entry site (IRES) and the translation apparatus is mimicked in the HCV 5′UTR/luciferase reporter system (example 9), these other viral processes are not represented in the OST7 system. The resulting RNA/protein complexes associated with the target viral RNA are also absent. Moreover, these processes may be coupled in an HCV-infected cell which could further impact target RNA accessibility. Therefore, we tested whether enzymatic nucleic acid molecules designed to cleave the HCV 5′UTR could effect a replicating viral system.

Recently, Lu and Wimmer characterized an HCV-poliovirus chimera in which the poliovirus IRES was replaced by the IRES from HCV (Lu & Wimmer, 1996 , Proc. Natl. Acad. Sci. USA . 93, 1412-1417). Poliovirus (PV) is a positive strand RNA virus like HCV, but unlike HCV is non-enveloped and replicates efficiently in cell culture. The HCV-PV chimera expresses a stable, small plaque phenotype relative to wild type PV.

The capability of the new enzymatic nucleic acid molecule motifs to inhibit HCV RNA intracellularly was tested using a dual reporter system that utilizes both firefly and Renilla luciferase (FIG. 5 ). A number of enzymatic nucleic acid molecules having the new class I motif (Amberzyme) were designed and tested (Table XIII). The Amberzyme ribozymes were targeted to the 5′ HCV UTR region, which when cleaved, would prevent the translation of the transcript into luciferase. OST-7 cells were plated at 12,500 cells per well in black walled 96-well plates (Packard) in medium DMEM containing 10% fetal bovine serum, 1% pen/strep, and 1% L-glutamine and incubated at 37° C. overnight. A plasmid containing T7 promoter expressing 5′ HCV UTR and firefly luciferase (T7C1-341 (Wang et al., 1993 , J. of Virol . 67, 3338-3344)) was mixed with a pRLSV40 Renilla control plasmid (Promega Corporation) followed by enzymatic nucleic acid molecule, and cationic lipid to make a 5×concentration of the reagents (T7C1-341 (4 μg/ml), pRLSV40 renilla luciferase control (6 μg/ml), enzymatic nucleic acid molecule (250 nM), transfection reagent (28.5 μg/ml).

The complex mixture was incubated at 37° C. for 20 minutes. The media was removed from the cells and 120 μl of Opti-mem media was added to the well followed by 30 μl of the 5×complex mixture. 150 μl of Opti-mem was added to the wells holding the untreated cells. The complex mixture was incubated on OST-7 cells for 4 hours, lysed with passive lysis buffer (Promega Corporation) and luminescent signals were quantified using the Dual Luciferase Assay Kit using the manufacturer's protocol (Promega Corporation). The data shown in FIG. 6 is a dose curve of enzymatic nucleic acid molecule targeting site 146 of the HCV RNA and is presented as a ratio between the firefly and Renilla luciferase fluorescence. The enzymatic nucleic acid molecule was able to reduce the quantity of HCV RNA at all enzymatic nucleic acid molecule concentrations yielding an IC 50 of approximately 5 nM. Other sites were also efficacious (FIG. 7 ), in particular enzymatic nucleic acid molecules targeting sitesl33, 209, and 273 were also able to reduce HCV RNA compared to the irrelevant (IRR) controls.

Cleavage of Substrates Using Completely Modified class I (Amberzvme) Enzymatic Nucleic Acid Molecule

The ability of an enzymatic nucleic acid, which is modified at every 2′ position to cleave a target RNA was tested to determine if any ribonucleotide positions are necessary in the Amberzyme motif. Enzymatic nucleic acid molecules were constructed with 2′-O-methyl, and 2′-amino (NH 2 ) nucleotides and included no ribonucleotides (Table XIII; gene name: no ribo) and kinetic analysis was performed as described in example 13. 100 nM enzymatic nucleic acid was mixed with trace amounts of substrate in the presence of 1 mM MgCl 2 at physiological conditions (37° C.). The Amberzyme with no ribonucleotide present in it has a K rel of 0.13 compared to the enzymatic nucleic acid with a few ribonucleotides present in the molecule shown in Table XIII (ribo). This shows that Amberzyme enzymatic nucleic acid molecule may not require the presence of 2′-OH groups within the molecule for activity.

Substrate Recognition Rules for Class II (Zinzyme) Enzymatic Nucleic Acid Molecules

Class II (zinzyme) ribozymes were tested for their ability to cleave base-paired substrates with all sixteen possible combinations of bases immediately 5′ and 3′ proximal to the bulged cleavage site G. Ribozymes were identical in all remaining positions of their 7 base pair binding arms. Activity was assessed at two and twenty-four hour time points under standard reaction conditions [20 mM HEPES pH 7.4, 140 mM KCl, 10 mM NaCl, 1 mM MgCl 2 , 1 mM CaCi 2 —37° C.]. FIG. 10 shows the results of this study. Base paired substrate UGG (not shown in the figure) cleaved as poorly as CGG shown in the figure. The figure shows the cleavage site substrate triplet in the 5′-3′ direction and 2 and 24 hour time points are shown top to bottom respectively. The results indicate the cleavage site triplet is most active with a 5′-Y-G-H-3′ (where Y is C or U and H is A, C or U with cleavage between G and H); however activity is detected particularly with the 24 hour time point for most paired substrates. All positions outside of the cleavage triplet were found to tolerate any base pairings (data not shown).

All possible mispairs immediately 5′ and 3′ proximal to the bulged cleavage site G were tested to a class II ribozyme designed to cleave a 5′-C-G-C -3′. It was observed the 5′ and 3′ proximal sites are as active with G:U wobble pairs, in addition, the 5′ proximal site will tolerate a mismatch with only a slight reduction in activity [data not shown].

Screening for Novel Enzymatic Nucleic Acid Molecule Motifs (Class II Motifs)

The selections were initiated with pools of >10 14 modified RNA's of the following sequence: 5′-GGGAGGAGGAAGUGCCU-(N) 35 -UGCCGCGCUCGCUCCCAGUCC-3′ (SEQ ID NO: 1524). The RNA was enzymatically generated using the mutant T7 Y639F RNA polymerase prepared by Rui Souza (1997 , Biochemistry 36(44):13718-28). The following modified NTP's were incorporated: 2′-deoxy-2′-fluoro-adenine triphosphate, 2′-deoxy-2′-fluoro-uridine triphosphate or 2′-deoxy-2′-fluoro-5-[(N-imidazole-4acetyl)propyl amine] uridine triphosphate, and 2′-deoxy-2′-amino-cytidine triphosphate; natural guanidine triphosphate was used in all selections so that alpha— 32 P-GTP could be used to label pool RNA's. RNA pools were purified by denaturing gel electrophoresus 8% polyacrilamide 7 M Urea.

The following target RNA (resin A) was synthesized and coupled to lodoacetyl Ultralink™ resin (Pierce) by the supplier's procedure: 5′ -b-L-GGACUGGGAGCGAGCGCGGCGCAGGCACUGAAG-L-S-B-3′ (SEQ ID NO: 1496); where b is biotin (Glenn Research cat# 10-1953-nn), L is polyethylene glycol spacer (Glenn Research cat# 10-1918-nn), S is thiol-modifier C6 S-S (Glenn Research cat# 10-1936-nn), B is a standard inverted deoxy abasic.

RNA pools were added to 100 ul of 5 uM Resin A in the buffer A (20 mM HEPES pH 7.4, 140 mM KCL, 10 mM NaCl) and incubated at 22° C. for 5 minutes. The temperature was then raised to 37° C. for 10 minutes. The resin was washed with 5 ml buffer A. Reaction was triggered by the addition of buffer B(20 mM HEPES pH 7.4, 140 mM KCL, 10 mM NaCl, 1 mM MgCl 2 , 1 mM CaCl 2 ). Incubation proceeded for 20 minutes in the first generation and was reduced progressively to 1 minute in the final generations; with 13 total generations. The reaction eluant was collected in 5 M NaCl to give a final concentration of 2 M NaCl. To this was added 100 μl of 50% slurry Ultralink NeutraAvidin™ (Pierce). Binding of cleaved biotin product to the avidin resin was allowed by 20 minute incubation at 22° C. The resin was subsequently washed with 5 ml of 20 mM HEPES pH 7.4, 2 M NaCl. Desired RNA's were removed by a 1.2 ml denaturing wash 1M NaCl, 10 M Urea at 94° C. over 10 minutes. RNA's were double precipitated in 0.3 M sodium acetate to remove Cl − ions inhibitory to reverse transcription. Standard protocols of reverse transcription and PCR amplification were performed. RNA's were again transcribed with the modified NTP's described above. After 13 generations cloning and sequencing provided 14 sequences which were able to cleave the target substrate. Six sequences were characterized to determine secondary structure and kinetic cleavage rates. The structures and kinetic data are given in FIG. 8 . The sequences of eight other enzymatic nucleic acid molecule sequences are given in Table XIV. The size, sequence, and chemical compositions of these molecules can be modified as described under example 13 or using other techniques well known in the art.

Nucleic Acid Catalyst Engineering

Sequence, chemical and structural variants of Class I and Class II enzymatic nucleic acid molecule can be engineered and re-engineered using the techniques shown in this application and known in the art. For example, the size of class I and class II enzymatic nucleic acid molecules can, be reduced or increased using the techniques known in the art (Zaug et al., 1986 , Nature , 324, 429; Ruffnier et al., 1990 , Biochem ., 29, 10695; Beaudry et al., 1990 , Biochem ., 29, 6534; McCall et al., 1992 , Proc. Natl. Acad. Sci., USA ., 89, 5710; Long et al., 1994, supra; Hendry et al., 1994 , BBA 1219, 405; Benseler et al., 1993 , JACS , 115, 8483; Thompson et al., 1996 , Nucl. Acids Res ., 24, 4401; Michels et al., 1995 , Biochem ., 34, 2965; Been et al., 1992 , Biochem ., 31, 11843; Guo et al., 1995 , EMBO. J ., 14, 368; Pan et al., 1994 , Biochem ., 33, 9561; Cech, 1992 , Curr. Op. Struc. Bio ., 2, 605; Sugiyama et al., 1996 , FEBS Lett ., 392, 215; Beigelman et al., 1994 , Bioorg. Med. Chem ., 4, 1715; Santoro et al., 1997 , PNAS 94, 4262; all are incorporated in their totality by reference herein), to the extent that the overall catalytic activity of the ribozyme is not significantly decreased.

Further rounds of in vitro selection strategies described herein and variations thereof can be readily used by a person skilled in the art to evolve additional nucleic acid catalysts and such new catalysts are within the scope of the instant invention.

Activity of Class II (Zinzyme) Nucleic Acid Catalysts to Inhibit HER2 Gene Expression

HER2 (also known as neu, erbB2 and c-erbB2) is an oncogene that encodes a 185-kDa transmembrane tyrosine kinase receptor. HER2 is a member of the epidermal growth factor receptor (EGFR) family and shares partial homology with other family members. In normal adult tissues HER2 expression is low. However, HER2 is overexpressed in at least 25-30% of breast (McGuire & Greene, 1989) and ovarian cancers (Berchuck, et al., 1990). Furthermore, overexpression of HER2 in malignant breast tumors has been correlated with increased metastasis, chemoresistance and poor survival rates (Slamon et al., 1987 Science 235: 177-182). Because HER2 expression is high in aggressive human breast and ovarian cancers, but low in normal adult tissues, it is an attractive target for ribozyme-mediated therapy (Thompson et al., supra).

Cell Culture Review

The greatest HER2 specific effects have been observed in cancer cell lines that express high levels of HER2 protein (as measured by ELISA). Specifically, in one study that treated five human breast cancer cell lines with the HER2 antibody (anti-erbB2-sFv), the greatest inhibition of cell growth was seen in three cell lines (MDA-MB-361, SKBR-3 and BT-474) that express high levels of HER2 protein. No inhibition of cell growth was observed in two cell lines (MDA-MB-231 and MCF-7) that express low levels of HER2 protein (Wright et al., 1997). Another group successfully used SKBR-3 cells to show HER2 antisense oligonucleotide-mediated inhibition of. HER2 protein expression and HER2 RNA knockdown (Vaughn et al., 1995). Other groups have also demonstrated a decrease in the levels of HER2 protein, HER2 mRNA and/or cell proliferation in cultured cells using anti-HER2 ribozymes or antisense molecules (Suzuki, T. et al., 1997; Weichen, et al., 1997; Czubayko, F. et al., 1997; Colomer, et al., 1994; Betram et al., 1994). Because cell lines that express higher levels of HER2 have been more sensitive to anti-HER2 agents, we prefer using several medium to high expressing cell lines, including SKBR-3 and T47D, for ribozyme screens in cell culture.

A variety of endpoints have been used in cell culture models to look at HER2-mediated effects after treatment with anti-HER2 agents. Phenotypic endpoints include inhibition of cell proliferation, apoptosis assays and reduction of HER2 protein expression. Because overexpression of HER2 is directly associated with increased proliferation of breast and ovarian tumor cells, a proliferation endpoint for cell culture assays will preferably be used as the primary screen. There are several methods by which this endpoint can be measured. Following treatment of cells with ribozymes, cells are allowed to grow (typically 5 days) after which either the cell viability, the incorporation of [ 3 H] thymidine into cellular DNA and/or the cell density can be measured. The assay of cell density is very straightforward and can be done in a 96-well format using commercially available fluorescent nucleic acid stains (such as Syto® 13 or CyQuant®). The assay using CyQuant® is described herein and is currently being employed to screen 100 ribozymes targeting HER2 (details below).

As a secondary, confirmatory endpoint a ribozyme-mediated decrease in the level of HER2 protein expression can be evaluated using a HER2-specific ELISA.

Validation of Cell Lines and Ribozyme Treatment Conditions

Two human breast cancer cell lines (T47D and SKBR-3) that are known to express medium to high levels of HER2 protein, respectively, were considered for ribozyme screening. In order to validate these cell lines for HER2-mediated sensitivity, both cell lines were treated with the HER2 specific antibody, Herceptin® (Genentech) and its effect on cell proliferation was determined. Herceptin® was added to cells at concentrations ranging from 0-8 μM in medium containing either no serum (OptiMem), 0.1% or 0.5% FBS and efficacy was determined via cell proliferation. Maximal inhibition of proliferation (˜50%) in both cell lines was observed after addition of Herceptin® at 0.5 nM in medium containing 0.1% or no FBS. The fact that both cell lines are sensitive to an anti-HER2 agent (Herceptin®) supports their use in experiments testing anti-HER2 ribozymes.

Prior to ribozyme screening, the choice of the optimal lipid(s) and conditions for ribozyme delivery was determined empirically for each cell line. Applicant has established a panel of cationic lipids (lipids as described in PCT application W099/05094) that can be used to deliver ribozymes to cultured cells and are very useful for cell proliferation assays that are typically 3-5 days in length. (Additional description of useful lipids is provided above, and those skilled in the art are also familiar with a variety of lipids that can be used for delivery of oligonucleotide to cells in culture.) Initially, this panel of lipid delivery vehicles was screened in SKBR-3 and T47D cells using previously established control oligonucleotides. Specific lipids and conditions for optimal delivery were selected for each cell line based on these screens. These conditions were used to deliver HER2 specific ribozymes to cells for primary (inhibition of cell proliferation) and secondary (decrease in HER2 protein) efficacy endpoints.

Primary Screen: Inhibition of Cell Proliferation

Although optimal ribozyme delivery conditions were determined for two cell lines, the SKBR-3 cell line was used for the initial screen because it has the higher level of HER2 protein, and thus should be most susceptible to a HER2-specific ribozyme. Follow-up studies can be carried out in T47D cells to confirm delivery and activity results as necessary.

Ribozyme screens were be performed using an automated, high throughput 96-well cell proliferation assay. Cell proliferation was measured over a 5-day treatment period using the nucleic acid stain CyQuant® for determining cell density. The growth of cells treated with ribozyme/lipid complexes were compared to both untreated cells and to cells treated with Scrambled-arm Attenuated core Controls (SAC; FIG. 11 ). SACs can no longer bind to the target site due to the scrambled arm sequence and have nucleotide changes in the core that greatly diminish ribozyme cleavage. These SACs are used to determine non-specific inhibition of cell growth caused by ribozyme chemistry (i.e. multiple 2′O-Me modified nucleotides, a single 2′C-allyl uridine, 4 phosphorothioates and a 3′ inverted abasic). Lead ribozymes are chosen from the primary screen based on their ability to inhibit cell proliferation in a specific manner. Dose response assays are carried out on these leads and a subset was advanced into a secondary screen using the level of HER2 protein as an endpoint.

Secondary Screen: Decrease in HER2 Protein

A secondary screen that measures the effect of anti-HER2 ribozymes on HER2 protein levels is used to affirm preliminary findings. A robust HER2 ELISA for both T47D and SKBR-3 cells has been established and is available for use as an additional endpoint.

Ribozyme Mechanism Assays

A Taqman® assay for measuring the ribozyme-mediated decrease in HER2 RNA has also been established. This assay is based on PCR technology and can measure in real time the production of HER2 mRNA relative to a standard cellular MRNA such as GAPDH. This RNA assay is used to establish proof that lead ribozymes are working through an RNA cleavage mechanism and result in a decrease in the level of HER2 mRNA, thus leading to a decrease in cell surface HER2 protein receptors and a subsequent decrease in tumor cell proliferation.

Animal Models

Evaluating the efficacy of anti-HER2 agents in animal models is an important prerequisite to human clinical trials. As in cell culture models, the most HER2 sensitive mouse tumor xenografts are those derived from human breast carcinoma cells that express high levels of HER2 protein. In a recent study, nude mice bearing BT-474 xenografts were sensitive to the anti-HER2 humanized monoclonal antibody Herceptin®, resulting in an 80% inhibition of tumor growth at a 1 mg kg dose (ip, 2x week for 4-5 weeks). Tumor eradication was observed in 3 of 8 mice treated in this manner (Baselga et al., 1998). This same study compared the efficacy of Herceptin® alone or in combination with the commonly used chemotherapeutics, paclitaxel or doxorubicin. Although, all three anti-HER2 agents caused modest inhibition of tumor growth, the greatest antitumor activity was produced by the combination of Herceptin® and paclitaxel (93% inhibition of tumor growth vs 35% with paclitaxel alone). The above studies provide proof that inhibition of HER2 expression by anti-HER2 agents causes inhibition of tumor growth in animals. Lead anti-HER2 ribozymes chosen from in vitro assays are further tested in mouse xenograft models. Ribozymes are first tested alone and then in combination with standard chemotherapies.

Animal Model Development

Three human breast tumor cell lines (T47D, SKBR-3 and BT-474) were characterized to establish their growth curves in mice. These three cell lines have been implanted into the mammary papillae of both nude and SClD mice and primary tumor volumes are being measured 3 times per week. Growth characteristics of these tumor lines using a Matrigel implantation format can also be established. In addition, the use of two other breast cell lines that have been engineered to express high levels of HER2 can also be used. The tumor cell line(s) and implantation method that supports the most consistent and reliable tumor growth is used in animal studies testing the lead HER2 ribozyme(s). Ribozyme are administered by daily subcutaneous injection or by continuous subcutaneous infusion from Alzet mini osmotic pumps beginning 3 days after tumor implantation and continuing for the duration of the study. Group sizes of at least 10 animals are employed. Efficacy is determined by statistical comparison of tumor volume of ribozyme-treated animals to a control group of animals treated with saline alone. Because the growth of these tumors is generally slow (45-60 days), an initial endpoint will be the time in days it takes to establish an easily measurable primary tumor (i.e. 50-100 mm 3 ) in the presence or absence of ribozyme treatment.

Clinical Summary

Overview

Breast cancer is a common cancer in women and also occurs in men to a lesser degree. The incidence of breast cancer in the United States is ˜180,000 cases per year and ˜46,000 die each year of the disease. In addition, 21,000 new cases of ovarian cancer per year lead to ˜13,000 deaths (data from Hung et al., 1995 and the Surveillance, Epidemiology and End Results Program, NCI). Ovarian cancer is a potential secondary indication for anti-HER2 ribozyme therapy.

A full review of breast cancer is given in the NCI PDQ for Breast Cancer. A brief overview is given here. Breast cancer is evaluated or “staged” on the basis of tumor size, and whether it has spread to lymph nodes and/or other parts of the body. In Stage I breast cancer, the cancer is no larger than 2 centimeters and has not spread outside of the breast. In Stage II, the patient's tumor is 2-5 centimeters but cancer may have spread to the axillary lymph nodes. By Stage III, metastasis to the lymph nodes is typical, and tumors are ≧5 centimeters. Additional tissue involvement (skin, chest wall, ribs, muscles etc.) may also be noted. Once cancer has spread to additional organs of the body, it is classed as Stage IV.

Almost all breast cancers (>90%) are detected at Stage I or II, but 31% of these are already lymph node positive. The 5-year survival rate for node negative patients (with standard surgery/radiation/chemotherapy /hormone regimens) is 97%; however, involvement of the lymph nodes reduces the 5-year survival to only 77%. Involvement of other organs (≧Stage III) drastically reduces the overall survival, to 22% at 5 years. Thus, chance of recovery from breast cancer is highly dependent on early detection. Because up to 10% of breast cancers are hereditary, those with a family history are considered to be at high risk for breast cancer and should be monitored very closely.

Therapy

Breast cancer is highly treatable and often curable when detected in the early stages. (For a complete review of breast cancer treatments, see the NCI PDQ for Breast Cancer.) Common therapies include surgery, radiation therapy, chemotherapy and hormonal therapy. Depending upon many factors, including the tumor size, lymph node involvement and location of the lesion, surgical removal varies from lumpectomy (removal of the tumor and some surrounding tissue) to mastectomy (removal of the breast, lymph nodes and some or all of the underlying chest muscle). Even with successful surgical resection, as many as 21% of the patients may ultimately relapse (10-20 years). Thus, once local disease is controlled by surgery, adjuvant radiation treatments, chemotherapies and/or hormonal therapies are typically used to reduce the rate of recurrence and improve survival. The therapy regimen employed depends not only on the stage of the cancer at its time of removal, but other variables such the type of cancer (ductal or lobular), whether lymph nodes were involved and removed, age and general health of the patient and if other organs are involved.

Common chemotherapies include various combinations cytotoxic drugs to kill the cancer cells. These drugs include paclitaxel (Taxol), docetaxel, cisplatin, methotrexate, cyclophosphamide, doxorubin, fluorouracil etc. Significant toxicities are associated with these cytotoxic therapies. Well-characterized toxicities include nausea and vomiting, myelosuppression, alopecia and mucosity. Serious cardiac problems are also associated with certain of the combinations, e.g. doxorubin and paclitaxel, but are less common.

Testing for estrogen and progesterone receptors helps to determine whether certain anti-hormone therapies might be helpful in inhibiting tumor growth. If either or both receptors are present, therapies to interfere with the action of the hormone ligands, can be given in combination with chemotherapy and are generally continued for several years. These adjuvant therapies are called SERMs, selective estrogen receptor modulators, and they can give beneficial estrogen-like effects on bone and lipid metabolism while antagonizing estrogen in reproductive tissues. Tamoxifen is one such compound. The primary toxic effect associated with the use of tamoxifen is a 2 to 7-fold increase in the rate of endometrial cancer. Blood clots in the legs and lung and the possibility of stroke are additional side effects. However, tamoxifen has been determined to reduce breast cancer incidence by 49% in high-risk patients and an extensive, somewhat controversial, clinical study is underway to expand the prophylactic use of tamoxifen. Another SERM, raloxifene, was also shown to reduce the incidence of breast cancer in a large clinical trial where it was being used to treat osteoporosis. In additional studies, removal of the ovaries and/or drugs to keep the ovaries from working are being tested.

Bone marrow transplantation is being studied in clinical trials for breast cancers that have become resistant to traditional chemotherapies or where >3 lymph nodes are involved. Marrow is removed from the patient prior to high-dose chemotherapy to protect it from being destroyed, and then replaced after the chemotherapy. Another type of “transplant” involves the exogenous treatment of peripheral blood stem cells with drugs to kill cancer cells prior to replacing the treated cells in the bloodstream.

One biological treatment, a humanized monoclonal anti-HER2 antibody, Herceptin® (Genentech) has been approved by the FDA as an additional treatment for HER2 positive tumors. Herceptin® binds with high affinity to the extracellular domain of HER2 and thus blocks its signaling action. Herceptin® can be used alone or in combination with chemotherapeutics (i.e. paclitaxel, docetaxel, cisplatin, etc.) (Pegram, et al., 1998). In Phase III studies, Herceptin® significantly improved the response rate to chemotherapy as well as improving the time to progression (Ross & Fletcher, 1998). The most common side effects attributed to Herceptin® are fever and chills, pain, asthenia, nausea, vomiting, increased cough, diarrhea, headache, dyspnea, infection, rhinitis, and insomnia. Herceptin® in combination with chemotherapy (paclitaxel) can lead to cardiotoxicity (Sparano, 1999), leukopenia, anemia, diarrhea, abdominal pain and infection.

HER2 Protein Levels for Patient Screening and as a Potential Endpoint

Because elevated HER2 levels can be detected in at least 30% of breast cancers, breast cancer patients can be pre-screened for elevated HER2 prior to admission to initial clinical trials testing an anti-HER2 ribozyme. Initial HER2 levels can be determined (by ELISA) from tumor biopsies or resected tumor samples.

During clinical trials, it may be possible to monitor circulating HER2 protein by ELISA (Ross and Fletcher, 1998). Evaluation of serial blood/serum samples over the course of the anti-HER2 ribozyme treatment period could be useful in determining early indications of efficacy. In fact, the clinical course of Stage IV breast cancer was correlated with shed HER2 protein fragment following a dose-intensified paclitaxel monotherapy. In all responders, the HER2 serum level decreased below the detection limit (Luftner et al.).

Two cancer-associated antigens, CA27.29 and CA15.3, can also be measured in the serum. Both of these glycoproteins have been used as diagnostic markers for breast cancer. CA27.29 levels are higher than CA15.3 in breast cancer patients; the reverse is true in healthy individuals. Of these two markers, CA27.29 was found to better discriminate primary cancer from healthy subjects. In addition, a statistically significant and direct relationship was shown between CA27.29 and large vs small tumors and node postive vs node negative disease (Gion, et al., 1999). Moreover, both cancer antigens were found to be suitable for the detection of possible metastases during follow-up (Rodriguez de Paterna et al., 1999). Thus, blocking breast tumor growth may be reflected in lower CA27.29 and/or CA15.3 levels compared to a control group. FDA submissions for the use of CA27.29 and CA1 5.3 for monitoring metastatic breast cancer patients have been filed (reviewed in Beveridge, 1999). Fully automated methods for measurement of either of these markers are commercially available.

References

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Applicant has designed, synthesized and tested several class II (zinzyme) ribozymes targeted against HER2 RNA (see for example Tables XV and XVI) in cell proliferation assays.

Proliferation assay: The model proliferation assay used in the study requires a cell-plating density of 2000 cells/well in 96-well plates and at least 2 cell doublings over a 5-day treatment period. To calculate cell density for proliferation assays, the FIPS (fluoro-imaging processing system) method well known in the art was used. This method allows for cell density measurements after nucleic acids are stained with CyQuant® dye, and has the advantage of accurately measuring cell densities over a very wide range 1,000-100,000 cells/well in 96-well format.

Ribozymes (50-200 nM) were delivered in the presence of cationic lipid at 2.0 μg/mL and inhibition of proliferation was determined on day S post-treatment. Two full ribozyme screens were completed resulting in the selection of 14 ribozymes. Class II (zinzyme) ribozymes against sites, 314 (RPI No. 18653), 443 (RPI No. 18680), 597 (RPI No. 18697), 659 (RPI No. 18682), 878 (RPI Nos. 18683 and 18654), 881 (RPI Nos. 18684 and 18685) 934 (RPI No. 18651), 972 (RPI No. 18656, 19292, 19727, and 19728), 1292 (RPI No. 18726), 1541 (RPI No. 18687), 2116 (RPI No. 18729), 2932 (RPI No. 18678), 2540 (RPI No. 18715), and 3504 (RPI No. 18710) caused inhibition of proliferation ranging from 25-80% as compared to a scrambled control ribozyme. An example of results from a cell culture assay is shown in FIG. 11 . Referring to FIG. 11, Class II ribozymes targeted against HER2 RNA are shown to cause significant inhibition of proliferation of cells. This shows that ribozymes, for instance the Class II (zinzyme) ribozymes are capable of inhibiting HER2 gene expression in mammalian cells.

Reduction of Ribose Residues in Class II (Zinzyme) Nucleic Acid Catalysts

Class II (zinzyme) nucleic acid catalysts were tested for their activity as a function ribonucleotide content. A Zinzyme having no ribonucleotide residue (ie., no 2′-OH group at the 2′ position of the nucleotide sugar) against the K-Ras site 521 was designed. This molecules were tested utilizing the chemistry shown in FIG. 18 a . The in vitro catalytic activity zinzyme construct was not significantly effected (the cleavage rate reduced only 10 fold).

The Kras zinzyme shown in FIG. 18 a was tested in physiological buffer with the divalent concentrations as indicated in the legend (high NaCl is an altered monovalent condition shown) of FIG. 19 . The 1 mM Ca ++ condition yielded a rate of 0.005 min −1 while the 1 mM Mg ++ condition yielded a rate of 0.002 min −1 . The ribose containing wild type yields a rate of 0.05 min −1 while substrate in the absence of zinzyme demonstrates less than 2% degradation at the longest time point under reaction conditions shown. This illustrates a well-behaved cleavage reaction done by a non-ribose containing catalyst with only a 10-fold reduced cleavage as compared to ribonucleotide-containing zinzyme and vastly above non-catalyzed degradation.

A more detailed investigation into the role of ribose positions in the Class II (zinzyme) motif was carried out in the context of the HER2 site 972 (Applicant has further designed a fully modified Zinzyme as shown in FIG. 18 b targeting the HER2 RNA site 972). FIG. 20 is a diagram of the alternate formats tested and their relative rates of catalysis. The effect of substitution of ribose G for the 2′-O-methyl C-2′-O-methyl A in the loop of Zinzyme was insignificant when assayed with the Kras target but showed a modest rate enhancement in the HER2 assays. The activity of all Zinzyme motifs, including the fully stabilized “0 ribose” are well above background noise level degradation. Zinzyme with only two ribose positions are sufficient to restore “wild-type” activity. Motifs containing 3, 4 or 5 ribose positions demonstrated a greater extent of cleavage and profiles almost identical to the 2 ribose motif. Applicant has thus demonstrated that a Zinzyme with no ribonucleotides present at any position can catalyze efficient RNA cleavage activity. Thus, Zinzyme enzymatic nucleic acid molecules do not require the presence of 2′-OH group within the molecule for catalytic activity.

Activity of Reduced Ribose Containing Class II (Zinzyme) Nucleic Acid Catalysts to Inhibit HER2 Gene Expression

A cell proliferation assay for testing reduced ribo class II (zinzyme) nucleic acid catalysts (100-200 nM) targeting HER2 site 972 was performed as described in example 19. Single ribonucleotide containing Zinzyme (RPI No 19728) showed cell proliferation inhibition of between 37% and 67%, and fully stabilized non-ribonucleotide containing Zinzyme (RPI No. 19727) showed cell proliferation inhibition of between 38% and 65% compared to scrambled attenuated controls. The seven-ribonucleotide Zinzyme (RPI No. 19292) demonstrated the same level of inhibition as the single ribo/non-ribo derivatives. These results indicate significant inhibition of HER2 gene expression using stabilized Class II (zinzyme) motifs, including one ribo and non-ribo containing nucleic acid catalysts.

Applications

The use of NTP's described in this invention have several research and commercial applications. These modified nucleotide triphosphates can be used for in vitro selection (evolution) of oligonucleotides with novel functions. Examples of in vitro selection protocols are incorporated herein by reference (Joyce, 1989 , Gene , 82, 83-87; Beaudry et al., 1992 , Science 257, 635-641; Joyce, 1992 , Scientific American 267, 90-97; Breaker et al., 1994 , TIBTECH 12, 268; Bartel et al., 1993 , Science 261:1411-1418; Szostak, 1993 , TIBS 17, 89-93; Kumar et al., 1995 , FASEB J ., 9, 1183; Breaker, 1996 , Curr. Op. Biotech ., 7, 442).

Additionally, these modified nucleotide triphosphates can be employed to generate modified oligonucleotide combinatorial chemistry libraries. Several references for this technology exist (Brenner et al., 1992 , PNAS 89, 5381-5383, Eaton, 1997 , Curr. Opin. Chem. Biol . 1, 10-16).

Diagnostic Uses

Enzymatic nucleic acid molecules of this invention may be used as diagnostic tools to examine genetic drift and mutations within diseased cells or to detect the presence of specific RNA in a cell. The close relationship between enzymatic nucleic acid molecule activity and the structure of the target RNA allows the detection of mutations in any region of the molecule which alters the base-pairing and three-dimensional structure of the target RNA. By using multiple enzymatic nucleic acid molecules described in this invention, one may map nucleotide changes which are important to RNA structure and function in vitro, as well as in cells and tissues. Cleavage of target RNAs with enzymatic nucleic acid molecules may be used to inhibit gene expression and define the role (essentially) of specified gene products in the progression of disease. In this manner, other genetic targets may be defined as important mediators of the disease. These experiments will lead to better treatment of the disease progression by affording the possibility of combinational therapies (e.g., multiple enzymatic nucleic acid molecules targeted to different genes, enzymatic nucleic acid molecules coupled with known small molecule inhibitors, radiation or intermittent treatment with combinations of enzymatic nucleic acid molecules and/or other chemical or biological molecules). Other in vitro uses of enzymatic nucleic acid molecules of this invention are well known in the art, and include detection of the presence of mRNAs associated with related conditions. Such RNA is detected by determining the presence of a cleavage product after treatment with a enzymatic nucleic acid molecule using standard methodology.

In a specific example, enzymatic nucleic acid molecules which can cleave only wild-type or mutant forms of the target RNA are used for the assay. The first enzymatic nucleic acid molecule is used to identify wild-type RNA present in the sample and the second enzymatic nucleic acid molecule will be used to identify mutant RNA in the sample. As reaction controls, synthetic substrates of both wild-type and mutant RNA will be cleaved by both enzymatic nucleic acid molecules to demonstrate the relative enzymatic nucleic acid molecule efficiencies in the reactions and the absence of cleavage of the “non-targeted” RNA species. The cleavage products from the synthetic substrates will also serve to generate size markers for the analysis of wild type and mutant RNAs in the sample population. Thus each analysis can involve two enzymatic nucleic acid molecules, two substrates and one unknown sample which can be combined into six reactions. The presence of cleavage products can be determined using an RNAse protection assay so that full-length and cleavage fragments of each RNA can be analyzed in one lane of a polyacrylamide gel. It is not absolutely required to quantify the results to gain insight into the expression of mutant RNAs and putative risk of the desired phenotypic changes in target cells. The expression of mRNA whose protein product is implicated in the development of the phenotype is adequate to establish risk. If probes of comparable specific activity are used for both transcripts, then a qualitative comparison of RNA levels will be adequate and will decrease the cost of the initial diagnosis. Higher mutant form to wild-type ratios will be correlated with higher risk whether RNA levels are compared qualitatively or quantitatively.

Additional Uses

Potential usefulness of sequence-specific enzymatic nucleic acid molecules of the instant invention can have many of the same applications for the study of RNA that DNA restriction endonucleases have for the study of DNA (Nathans et al., 1975 Ann. Rev. Biochem . 44:273). For example, the pattern of restriction fragments can be used to establish sequence relationships between two related RNAs, and large RNAs could be specifically cleaved to fragments of a size more useful for study. The ability to engineer sequence specificity of the enzymatic nucleic acid molecule is ideal for cleavage of RNAs of unknown sequence. Applicant describes the use of nucleic acid molecules to down-regulate gene expression of target genes in bacterial, microbial, fungal, viral, and eukaryotic systems including plant, or mammalian cells.

All patents and publications mentioned in the specification are indicative of the levels of skill of those skilled in the art to which the invention pertains. All U.S. patents and published patent applications cited in this disclosure are incorporated by reference to the same extent as if each reference had been incorporated by reference in its entirety individually.

One skilled in the art would readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The methods and compositions described herein as presently representative. of preferred embodiments are exemplary and are not intended as limitations on the scope of the invention. Changes therein and other uses will occur to those skilled in the art, which are encompassed within the spirit of the invention, are defined by the scope of the claims.

It will be readily apparent to one skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention. Thus, such additional embodiments are within the scope of the present invention and the following claims.

The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments, optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the description and the appended claims.

In addition, where features or aspects of the invention are described in terms of Markush groups or other grouping of alternatives, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group or other group.

Thus, additional embodiments are within the scope of the invention and within the following claims