Inhibition of Tat-mediated transactivation of HIV-1 LTR transcription by polyamide nucleic acid targeted to TAR hairpin element

Tar, an essential human immunodeficiency virus type 1 protein interacts wit h the transactivation response element (TAR) and stimulates transcription f rom the viral long-terminal repeat (LTR). Blockage of Tar-TAR interaction h alts viral transcription and hence replication. We have found that polyamid e nucleic acid (PNA), targeted to the TAR sequences of viral RNA genome is able to prevent Tat-TAR interaction by efficient sequestration of the TAR. Anti-TAR PNA competes for TAR and prevents Tat-mediated stimulation of HIV- 1 LTR transcription in vitro but has no influence on the basal level of tra nscription in the absence of Tar. Using a reporter gene construct pHIV LTR- CAT and pCMV-Tat in cell culture, we have further shown that anti-TAR PNA i s able to block Tat-mediated transactivation of HIV-1 LTR transcription in vivo as judged by the extent of LTR driven CAT gene expression in the absen ce and presence of anti-TAR PNA. Supplementation of 100 nM of anti-TAR PNA into the culture medium further enhances the suppression of transactivation . Nonspecific scrambled PNA had no influence on Tar-TAR interaction and LTR -driven CAT gene expression in cell culture. These results suggest that PNA targeted to the TAR sequence of the viral genome may be a potential inhibi tor of HIV-1 gene expression.