Purification of a Tat-associated kinase reveals a TFIIH complex that modulates HIV-1 transcription.

The Tat protein is a transcriptional activator which is required for efficient human immunodeficiency virus 1 (HIV-1) gene expression Tat stimulates HIV-1 transcriptional elongation by increasing the processivity of RNA polymerase II. To address whether Tat-mediated effects on HIV-1 gene expression are due to modulation in the phosphorylation of the ...
RNA polymerase II C-terminal domain (CTD), we developed a purification protocol to identify cellular kinases that are capable of binding to Tat and hyperphosphorylating the RNA polymerase II CTD. A 600 kDa protein complex with these properties was isolated, and specific components were identified using peptide microsequence analysis. This analysis indicated that proteins comprising the multi-subunit TFIIH complex, in addition to several novel factors, were associated with Tat using both in vitro and in vivo analysis. The Tat-associated kinase bound to the activation domain of Tat, and its ability to hyperphosphorylate RNA polymerase II was markedly stimulated by Tat. Furthermore, the addition of the Tat-associated kinase to in vitro transcription assays stimulated the ability of Tat to activate HIV-1 transcription. These results define a cellular kinase complex whose activity is modulated by Tat to result in activation of HIV-1 trancription.
Mesh Terms:
Cyclin-Dependent Kinases, Dichlororibofuranosylbenzimidazole, Gene Expression Regulation, Viral, Gene Products, tat, HIV-1, Neoplasm Proteins, Nucleic Acid Synthesis Inhibitors, Phosphorylation, Positive Transcriptional Elongation Factor B, Protein Binding, Protein-Serine-Threonine Kinases, RNA Polymerase II, Sequence Analysis, Transcription Factor TFIIH, Transcription Factors, Transcription Factors, TFII, Transcription, Genetic, tat Gene Products, Human Immunodeficiency Virus
EMBO J.
Date: May. 15, 1997
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