A human primary T-lymphocyte-derived human immunodeficiency virus type 1 Tat-associated kinase phosphorylates the C-terminal domain of RNA polymerase II and induces CAK activity.
Tat protein mediates transactivation of human immunodeficiency virus type 1 (HIV-1), which results in more-efficient transcript elongation. Since phosphorylation of C-terminal domain (CTD) of RNA polymerase II correlates with its enhanced processivity, we studied the properties of a Tat-associated CTD kinase derived from mitogenically stimulated human primary T lymphocytes (TTK). TTK binds to full-length Tat and specifically phosphorylates CTD and CDK2. This dual kinase activity is characteristic of CDK-activating kinase (CAK). The CTD kinase activity is induced upon mitogenic stimulation of primary T lymphocytes. Fractionation of T-cell lysate demonstrates that Tat-associated CTD kinase activity elutes in two peaks. About 60% of Tat-associated CTD kinase copurifies with CDK2 kinase activity and contains the CAK components CDK7 and cyclin H. The rest of Tat-associated kinase is free of CDK2 kinase activity and the CAK components and thus may represent a novel CTD kinase. The kinase activities of TTK are blocked by the adenosine analog 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DRB) as well as by the kinase inhibitor H8 at concentrations known to block transcript elongation. Importantly, the Tat-associated kinase markedly induced CAK. We suggest that the mechanism of Tat-mediated processive transcription of the HIV-1 promoter includes a Tat-associated CAK activator.
Nekhai
S
S
Department of Biochemistry and Molecular Biology, George Washington University School of Medicine, Washington, D.C. 20037, USA.
Shukla
R R
RR
Kumar
A
A
D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000302:isolation & purification / Q000378:metabolism; D004789:Enzyme Activation; D015696:Gene Products, tat / Q000378:metabolism*; D015497:HIV-1 / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D008213:Lymphocyte Activation; D010766:Phosphorylation; D042925:Positive Transcriptional Elongation Factor B; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D012319:RNA Polymerase II / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology / Q000821:virology*; D054322:tat Gene Products, Human Immunodeficiency Virus; D000095043:Cyclin-Dependent Kinase-Activating Kinase
D015696:Gene Products, tat; D054322:tat Gene Products, Human Immunodeficiency Virus; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II; D000095043:Cyclin-Dependent Kinase-Activating Kinase