Association of HIV-1 Tat with the cellular protein, Purα, is mediated by RNA

The interaction between two regulatory proteins plays a crucial role in the control of several biological events, including gene transcription. In this report, we demonstrate that the interaction between the cellular sequence-specific single-stranded DNA binding protein Pur alpha and the HIV type 1 (HIV-1) Tat protein is mediated by specific ribonucleic acids. The region of Tat that is important for its interaction with Pur alpha includes the region demonstrated to bind Tat's viral RNA target, TAR. A 10-nucleotide CC-rich consensus sequence identified in RNAs associated with Pur alpha derived from human U-87MG cells plays an important role in the Pur alpha:Tat interaction as examined by an in vitro reconstitution assay. Furthermore, expression of the Pur alpha-associated RNA in these cells enhances transcriptional activation of the HIV-1 promoter by Tat and Pur alpha.