The HIV transactivator TAT binds to the CDK-activating kinase and activates the phosphorylation of the carboxy-terminal domain of RNA polymerase II.
The human immunodeficiency virus encodes the transcriptional transactivator Tat, which binds to the transactivation response (TAR) RNA stem-loop in the viral long terminal repeat (LTR) and increases rates of elongation rather than initiation of transcription by RNA polymerase II (Pol II). In this study, we demonstrate that Tat binds directly to the cyclin-dependent kinase 7 (CDK7), which leads to productive interactions between Tat and the CDK-activating kinase (CAK) complex and between Tat and TFIIH. Tat activates the phosphorylation of the carboxy-terminal domain (CTD) of Pol II by CAK in vitro. The ability of CAK to phosphorylate the CTD can be inhibited specifically by a CDK7 pseudosubstrate peptide that also inhibits transcriptional activation by Tat in vitro and in vivo. We conclude that the phosphorylation of the CTD by CAK is essential for Tat transactivation. Our data identify a cellular protein that interacts with the activation domain of Tat, demonstrate that this interaction is critical for the function of Tat, and provide a mechanism by which Tat increases the processivity of Pol II.
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Howard Hughes Medical Institute, Department of Medicine, University of California at San Francisco, San Franscisco, California USA.
Okamoto
H
H
Fujinaga
K
K
Meyer
J
J
Chamberlin
H
H
Morgan
D O
DO
Peterlin
B M
BM
D000818:Animals; D002460:Cell Line; D018844:Cyclin-Dependent Kinases; D015696:Gene Products, tat / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008956:Models, Chemical; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D018411:Spodoptera; D013379:Substrate Specificity; D051758:Transcription Factor TFIIH; D014157:Transcription Factors / Q000378:metabolism; D019473:Transcription Factors, TFII; D015533:Transcriptional Activation; D014162:Transfection; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D015696:Gene Products, tat; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II; D000095043:Cyclin-Dependent Kinase-Activating Kinase