Transcriptional regulator which functions as a general RNA polymerase II transcription inhibitor. In cooperation with 7SK snRNA sequesters P-TEFb in a large inactive 7SK snRNP complex preventing RNA polymerase II phosphorylation and subsequent transcriptional elongation. May also regulate NF-kappa-B, ESR1, NR3C1 and CIITA-dependent transcriptional activity. Homooligomer and heterooligomer with HEXIM2; probably dimeric. Component of the 7SK snRNP complex at least composed of P-TEFb (composed of CDK9 and CCNT1/cyclin-T1), HEXIM1, HEXIM2, BCDIN3, SART3 proteins and 7SK and U6 snRNAs. Interacts with the N-CoR complex through NCOR1. Interacts with ESR1 and NR3C1. May interact with NF-kappa-B through RELA. Up-regulated by HMBA (hexamethylene bisacetamide). Down-regulated by estrogen. Ubiquitously expressed with higher expression in placenta. HEXIM1 and HEXIM2 are differentially expressed. Expressed in endocrine tissues. Belongs to the HEXIM family. Note: This description may include information from UniProtKB.
Protein type: Motility/polarity/chemotaxis; Transcription factor
Molecular Function: cyclin-dependent protein kinase inhibitor activity; protein binding; snRNA binding
Biological Process: negative regulation of cyclin-dependent protein kinase activity; negative regulation of transcription from RNA polymerase II promoter; negative regulation of transcription, DNA-dependent