Inhibition of HIV-1 replication by foldback triple-helix forming oligonucleotides

Replication of retroviral RNA into double-stranded DNA is catalyzed by reverse transcriptase (RT). The polypurine tract (PPT) serves as a primer for plus-strand DNA synthesis and is highly conserved among HIV-1. The PPT region is a possible target for triple-helix formation. Here, we show the effects of triple-helix formation by analyses of melting temperature and gel shift using a foldback triplex-forming-oligonucleotides (FTFOs). We found that the FTFOs containing phosphorothioate groups at the 3'- and 5'-ends, or inside the hairpin loop, exhibited greater exonuclease resistance than the unmodified FTFOs. Several triplex oligonucleotides have thermal stability. The abilities of the FTFOs (DsDG-37) containing the guanosine in place of the cytidine in the third Hoogsteen base-pairing strand to inhibit HIV-1 replications were examined. The FTFOs (DsDG-37) inhibit the replication of HIV-1 more efficiently than the FTFOs (DsD-37) indicating sequence-specific inhibition of HIV-1 replication.