Positive transcription elongation factor B phosphorylates hSPT5 and RNA polymerase II carboxyl-terminal domain independently of cyclin-dependent kinase-activating kinase.

阅读量：

作者：

展开

摘要：

The CDK9-cyclin T kinase complex, positive transcription elongation factor b (P-TEFb), stimulates the process of elongation of RNA polymerase (Pol) II during transcription of human immunodeficiency virus. P-TEFb associates with the human immunodeficiency virus Tat protein and with the transactivation response element to form a specific complex, thereby mediating efficient elongation. Here, we show that P-TEFb preferentially phosphorylates hSPT5 as compared with the carboxyl-terminal domain of RNA Pol II in vitro. Phosphorylation of hSPT5 by P-TEFb occurred on threonine and serine residues in its carboxyl-terminal repeat domains. In addition, we provide several lines of evidence that P-TEFb is a CDK-activating kinase (CAK)-independent kinase. For example, CDK9 was not phosphorylated by CAK, whereas CDK2-cyclin A kinase activity was dramatically enhanced by CAK. Therefore, it is likely that P-TEFb participates in regulation of elongation by RNA Pol II by phosphorylation of its substrates, hSPT5 and the CTD of RNA Pol II, in a CAK-independent manner.

展开

关键词：

Transcription Factors Transcriptional Elongation Factors Positive Transcriptional Elongation Factor B DNA Primers RNA Polymerase II Nuclear Proteins Chromosomal Proteins, Non-Histone Base Sequence Phosphorylation Protein-Serine-Threonine Kinases