AN ASSESSMENT OF THE ANTISENSE PROPERTIES OF RNASE H-COMPETENT AND STERIC-BLOCKING OLIGOMERS

The antisense activity and gene specificity of two classes of oligonuc leotides (ONs) were directly compared in a highly controlled assay. On e class of ONs has been proposed to act by targeting the degradation o f specific RNAs through an RNase H-mediated mechanism and consists of C-5 propynyl pyrimidine phosphorothioate ONs (propyne-S-ON). The secon d class of antisense agents has been proposed to function by stericall y blocking target RNA formation, transport or translation and includes sugar modified (2'-O-allyl) ONs and peptide nucleic acids (PNAs). Usi ng a CV-1 cell based microinjection assay, we targeted antisense agent s representing both classes to various cloned sequences localized with in the SV40 large T antigen RNA. We determined the propyne-S-ON was th e most potent and gene-specific agent of the two classes which likely reflected its ability to allow RNase H cleavage of its target. The RNA oligomer inhibited T Ag expression via an antisense mechanism, but wa s less effective than the propyne-S-ON; the lack of potency may have b een due in part to the PNAs slow kinetics of RNA association. interest ingly, unlike the 2'-O-allyl ON, the antisense activity of the PNA was not restricted to the 5' untranslated region of the T Ag RNA. Based o n these findings we conclude that PNAs could be effective antisense ag ents with additional chemical modification that will lead to more rapi d association with their RNA target.