Use of Catalytic DNA in Target Validation and Therapeutics

Abstract

RNA is a relatively amenable target for nucleic-acid-based gene suppression, because it is transcribed in a single-stranded form from its parent double-helical DNA. The unpaired bases of this polynucleotide are therefore in theory available for hybridization by other complementary single-stranded nucleic acids such as antisense reagents. Where these hybridization events impair the ability of the RNA to function, for example, in translation, they can bring about suppression of the genes’ expression. Probably the most common mechanism for oligonucleotide-based suppression is heteroduplex-mediated induction of RNase H, which digests the RNA component of the hybrid, leaving the DNA to bind to other target molecules (1). In an alternative strategy, catalytic RNA such as the hammerhead ribozyme, which has its own built-in RNA cleavage activity, can be used to bind and destroy target RNA (2). These have the advantage of being independent of RNase H; however, they lack the natural chemical and biological stability possessed by the antisense DNA oligonucleotide (ON). Although it is possible to manufacture biologically active RNA, its relative fragility in this environment makes it difficult to administer in a direct delivery mode. For this and other reasons, most ribozyme applications rely on transgenic production of RNA in vivo within the context of a gene therapy.