Inhibitors of HIV-1 Tat-mediated transactivation.

The transactivation responsive (TAR) RNA is the 5'-leader sequence of the HIV-1 mRNA genome and interacts with the Tat protein during transcription. Tat and the positive transcription elongation factor (P-TEFb) complex bind to TAR to promote efficient transcription of the full-length HIV genome. In the absence of the TAR.Tat.P-TEFb interaction, viral transcription is inefficient, which makes this RNA-protein complex an important target for therapeutic intervention of HIV replication. Inhibitors of HIV-1 transactivation mainly target: 1) TAR RNA, 2) Tat protein and 3) Tat.P-TEFb complex. 1) Compounds against TAR RNA are the most numerous: besides cationic peptides, which were initially developed, recent advances in TAR binding inhibitors include oligonucleotide based-agents and small molecules. Specific research efforts are currently underway to increase cellular uptake. 2) By targeting the Tat protein, both transactivation and other Tat-mediated intra/extracellular functions are affected. Various biopolymeric drugs are reported to effectively inhibit Tat activity. In addition, Tat-targeted antibodies have recently been developed. 3) Intracellular proteins have been discovered to disrupt Tat.P-TEFb interaction, raising the chance of inhibiting HIV-1 transcription via novel mechanisms.