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‐dependent recruitment of the cyclinT1/CDK9 complex (P‐TEFb) to the transacting element (TAR) RNA. Tat interaction with the cyclinT1, the regulatory partner of CDK9, results in a specific recruitment of the heterodimer CycT1/CDK9 complex to TAR, whereby it promotes transcription elongation of the HIV‐1 LTR‐mediated transcription. Using the yeast two‐hybrid protein interaction assay we analyzed the binding between cyclinT1 and CDK9. Moreover, using a modified three‐hybrid yeast interaction system, we analyzed the recruitment of CycT1 to the Tat/TAR complex. The data presented here demonstrated that distinct domains of cyclinT1 interact with CDK9 and Tat/TAR in vivo. These findings will be instrumental for the designing of proper dominant‐negative P‐TEFb components capable to interfere with Tat function. J. Cell. Biochem. Suppl. 36: 247–253, 2001. © 2001 Wiley‐Liss, Inc.

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