Distinct regions of cyclinT1 are required for binding to CDK9 and for recruitment to the HIV-1 Tat/TAR complex

Tat-mediated activation of the HIV-1 promoter activity requires Tat-depende nt recruitment of the cyclinT1/CDK9 complex (P-TEFb) to the transacting ele ment (TAR) RNA. Tat interaction with the cyclinT1, the regulatory partner o f CDK9, results in a specific recruitment of the heterodimer CycT1 /CDK9 co mplex to TAR, whereby it promotes transcription elongation of the HIV-1 LTR -mediated transcription. Using the yeast two-hybrid protein interaction ass ay we analyzed the binding between cyclinT1 and CDK9. Moreover, using a mod ified three-hybrid yeast interaction system,m we analyzed the recruitment o f CycT1 to the Tat/TAR complex. The data presented here demonstrated that d istinct domains of cyclinT1 interact with CDK9 and Tat/TAR in vivo. These f indings will be instrumental for the designing of proper dominant-negative P-TEFb components capable to interfere with Tat function. (C) 2001 Wiley-Li ss, Inc.