RNA-sequence-mediated gene regulation in HIV-1.

The quantity and quality of human immunodeficiency virus type 1 (HIV-1) gene expression is controlled in large part by the action of two small nuclear viral regulatory proteins termed Tat and Rev. Tat is unique among transcriptional trans-activators in that it acts via a structured RNA target sequence, termed TAR, to induce high levels of transcription from the HIV-1 long terminal repeat promoter element. The activity of the viral Rev protein is also unprecedented in that this protein functions to induce the nuclear export of a specific class of viral RNA species that are otherwise sequestered in the nucleus by the action of cellular factors. Like Tat, Rev also interacts with a highly specific cis-acting target sequence termed, in this case, the Rev Response Element. In this review, I provide an outline of our current understanding of the roles and mechanisms of action of these two novel RNA-sequence-dependent regulatory proteins.