HEXIM is a transcriptional regulator that functions as a general RNA polymerase II transcription inhibitor. In cooperation with 7SK snRNA it sequesters P-TEFb in a large inactive 7SK snRNP complex preventing RNA polymerase II phosphorylation and subsequent transcriptional elongation. HEXIM may also regulate NF-kappa-B, ESR1, NR3C1 and CIITA-dependent transcriptional activity.
Hexamethylene bisacetamide-inducible proteins (HEXIMs) are transcriptional regulators that function as general RNA polymerase II transcription inhibitors. HEXIMs, aided by the 7SK snRNA, sequester positive transcriptional elongation factor b (P-TEFb) into a large inactive 7SK snRNP complex [PUBMED:14580347, PUBMED:15713661]. This prevents P-TEFb from phosphorylating RNA polymerase II and blocks subsequent transcriptional elongation.
Ouchida R, Kusuhara M, Shimizu N, Hisada T, Makino Y, Morimoto C, Handa H, Ohsuzu F, Tanaka H;, Genes Cells. 2003;8:95-107.: Suppression of NF-kappaB-dependent gene expression by a hexamethylene bisacetamide-inducible protein HEXIM1 in human vascular smooth muscle cells. PUBMED:12581153 EPMC:12581153 .
Yik JH, Chen R, Nishimura R, Jennings JL, Link AJ, Zhou Q;, Mol Cell. 2003;12:971-982.: Inhibition of P-TEFb (CDK9/Cyclin T) kinase and RNA polymerase II transcription by the coordinated actions of HEXIM1 and 7SK snRNA. PUBMED:14580347 EPMC:14580347 .
Dames SA, Schonichen A, Schulte A, Barboric M, Peterlin BM, Grzesiek S, Geyer M;, Proc Natl Acad Sci U S A. 2007;104:14312-14317.: Structure of the Cyclin T binding domain of Hexim1 and molecular basis for its recognition of P-TEFb. PUBMED:17724342 EPMC:17724342.