ANTISENSE 2'-O-ALKYL OLIGORIBONUCLEOTIDES ARE EFFICIENT INHIBITORS OFREVERSE TRANSCRIPTION

Reverse transcription is one step of the retroviral development which can be inhibited by antisense oligonucleotides complementary to the RN A template. 2'-O-Alkyl oligoribonucleotides are of interest due to the ir nuclease resistance, and to the high stability of the hybrids they form with RNA. Oligonucleotides, either fully or partly modified with 2'-O-alkyl residues, were targeted to an RNA template to prevent cDNA synthesis by the Avian Myeloblastosis Virus reverse transcriptase (AMV RT). Fully-modified 2'-O-allyl 17mers were able to specifically block reverse transcription via an RNase H-independent mechanism, with effi ciencies comparable to those observed with phosphodiester (PO) and pho sphorothioate oligonucleotides. Sandwich 2'-O-alkyl/PO/2'-O-alkyl olig onucleotides, supposed to combine the properties of 2'-O-alkyl modific ations (physical blocking of the RT) to those of the PO window (RNase H-mediated cleavage of the RNA) were quasi-stoichiometric inhibitors w hen adjacent to the primer, but remained without any effect when non-a djacent. They were not able to compete with the polymerase and inhibit ed reverse transcription only through RNase H-mediated cleavage of the target.