Phosphorothioate oligonucleotides block reverse transcription by the Rnase H activity associated with the HIV-1 polymerase.

We demonstrate the degradation of RNA bound to an antisense oligonucleotide by a reverse transcriptase enzyme-associated RNase H activity. We found that phosphorothioate oligonucleotides inhibit the RNase H activity by binding to AMV RT, rather than to the template RNA, whereas the RNase H activity of HIV-1 RT is not affected by the antisense phosphorothioate oligonucleotide. Selective inhibition of HIV-1 gene expression involves the degradation of the template RNA bound to the antisense phosphorothioate oligonucleotide by the RNase H activity associated with the HIV-1 polymerase.