Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.26 (GSK)
 6,788 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID: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. 931 22

Activation of the HIV-1 promoter by the virally encoded Tat protein is characterized by efficient processive transcription, mediated by host cell factors that are tethered to the promoter with the Tat-TAR RNA complex. Importantly, viral gene activation has been shown to be stimulated in mitogenically induced cells, although the link between cell cycle regulation and viral gene activation is unclear. We reported a Tat-associated CAK/CTD kinase from mitogenically induced primary human T-cells (TTK) (S. Nekhai et al., 1997, J. Virol. 71, 7436-7441). Here, biological activity of the kinase has been studied by direct microinjection at the individual-cell level. The TTK-dependent Tat response is maximal during G1 phase as shown by co-injection with Tat protein in cells synchronized at the various stages of the cell cycle. The cell cycle dependence of the Tat response was confirmed by inhibiting G0 --> G1 progression with the expression of dominant negative mutant Ras(Asn17) or the cyclin-dependent kinase CDK4. The results support a mechanism whereby transactivation of the HIV promoter is regulated by cell growth signal transduction pathways that target the Tat cofactor.
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PMID:Cell cycle-dependent stimulation of the HIV-1 promoter by Tat-associated CAK activator. 1063 11