Discoveries of Tat-TAR interaction inhibitors for HIV-1.

A major problem associated with anti-HIV-1 treatment is rapid emergence of drug-resistant strains. Accordingly, a compelling need is to discover anti-HIV drugs against alternative viral targets in addition to HIV-1 RT, PR, IN and CCR5. One such target is the interaction between HIV Trans-activator of transcription (Tat) protein and Trans Activation Responsive region (TAR) RNA. An arginine-rich motif (ARM) of Tat recognizing both the base sequence and the active conformation of TAR RNA three-base bulge region as well as newly elucidated TAR RNA inactive conformation are important for the specific Tat-TAR interaction. According to the possible binding modes, the inhibitors have been mainly divided into two classes: (1) Compounds binding directly to TAR RNA either to the TAR RNA three-base bulge region alone or to the three-base bulge together with the lower and upper-stem/Loop region. (2) Compounds binding directly to Tat protein with high affinity, thus potently inhibiting HIV-1. They both block Tat trans-activation in the formation of the Tat/TAR complex to exert antiviral activity in primary human cells. Recent researches also focus on the drugs targeting specificity of Tat and TAR by such new assays as capillary electrophoresis and quartz crystal microbalance. Cell-based reporter systems are established for high-throughput screening of novel compounds that interfere with Tat transactivation. The identification of dominant-negative mutants also finds wide application in this field. The Tat-TAR interaction is an important target in efforts to develop anti-HIV gene therapy or potential therapeutic antiviral agents for the treatment of HIV-1 infections.