GATA-1: one TEF customer

摘要

The precise patterns of gene expression in cells and organisms are regulated primarily at the level of transcription through recruitment of RNA polymerase II (RNAPII). Although transcriptional initiation has received the most attention, it is clear that for certain genes, elongation of nascent transcripts is the critical step. Positive transcription elongation factor b (P-TEFb), the major effector of transcriptional elongation, is composed of a cyclin-dependent kinase, Cdk9, and its associated cyclins (cyclins Tl and T2; reviewed in Price,1 Peterlin and Price, and Price). P-TEFb issubject to complex regulation by both positively acting factors, including the bromodo-main protein Brd4 and a number of recruiting proteins, and negative factors that include the HEXIM1 and HEXIM2 proteins and 7SK snRNA. The principal targets of this kinase are serine residues in the C-terminal domain of RNAP II.