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Hepatitis C virus (HCV) infection represents an important global health problem. Current antiviral therapeutics for HCV have proven inadequate in stemming the disease process. A novel therapeutic strategy involves the use of deoxyribozymes, also known as DNA enzymes or DNAzymes. These catalytic DNA molecules, designed to target and cleave specific RNA sequences, have shown promise in in vitro experimental models for various diseases and may serve as an alternative or adjunct to current HCV drug therapy. We designed and tested several deoxyribozymes that can bind and cleave highly conserved RNA sequences encoding the HCV core protein in in vitro systems. One of these deoxyribozymes reduced the level of our HCV RNA target by 32% and 48% after 24 h of cell exposure when tested in human hepatoma and epithelial cell lines, respectively. As this deoxyribozyme showed significant cleavage activity against HCV core protein target RNA in human cells, it may have potential as a therapeutic candidate for clinical trial in HCV infected patients.

An Azotobacter vinelandii homolog to the Salmonella typhimurium mutS gene was discovered upstream of the fdx4 gene. The product of this gene is much more similar to S. typhimurium MutS than either is to the HexA protein of Streptococcus pneumoniae. An A. vinelandii AmutS mutant strain was shown to have a spontaneous mutation frequency 65-fold greater than that of the wild type.Errors in DNA biosynthesis, chemical damage to DNA, and homologous recombination events can all give rise to mismatches in DNA base pairing. All organisms must therefore have some system for repairing those mismatches. One wellcharacterized repair system is the methyl-directed long-patch mismatch correction system of Escherichia coli (5,14,15). This system relies, in part, on the fact that DNA methylation is a postreplicational event such that the newly synthesized strand (where the repair occurs, if necessary) is unmethylated for a short time. The first component of the system is a 97-kDa protein, MutS, that recognizes and binds to DNA at the site of the mismatch (23,24).In this study, we identified a mutS homolog in the free-living, obligately aerobic diazotroph Azotobacter vinelandii. This organism is increasingly being used for biochemical and genetic characterization of a variety of biological phenomena, in large part because it has an excellent transformation system (17, 18) and undergoes high-frequency reciprocal recombination (21).Studies of DNA replication or repair have not, however, previously been reported for this organism. Here we report the sequence of the A. vinelandii mutS gene and show that deletion of this gene from the A. vinelandii chromosome results in a Mut -phenotype.DNA sequence analysis. We have previously reported the cloning of a 4.8-kb A. vinelandii DNA fragment that contains the fdxA gene and the subcloning of that fragment into pUC9 to form a plasmid designated pML1 (16). Here we determined the nucleotide sequence of the portion of pML1 upstream of the fdx4 gene. Four M13mpl8 derivatives were successfully constructed for sequencing, and the sequencing strategy is shown in Fig. 1. A total of 2,748 bp were sequenced, and the sequences of all fragments were overlapped, in both directions, to minimize sequencing errors. This sequencing strategy revealed a 2,605-bp open reading frame. As shown in Fig. 2

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