This entry represents the short highly conserved C-terminal domain of certain bromodomain proteins, notably Brd4. The Brd4 CTD interacts with the cyclin T1 and Cdk9 subunits of positive transcription elongation factor b (pTEFb) complex. Brd4 displaces negative regulators, the HEXIM1 and 7SKsnRNA complex, from pTEFb, thereby transforming it into an active form that can phosphorylate RNA pol II [, ].
Cyclins are eukaryotic proteins that play an active role in controlling nuclear cell division cycles [], and regulate cyclin dependent kinases (CDKs). This entry represents cyclin-T1 and cyclin-T.Cyclin-T associates with CDK9. Both cyclin-T and CDK9 are subunits of the positive-transcription elongation factor (P-TEFb), which facilitates transcription elongation by phosphorylating the carboxy-terminal domain (CTD) of the largest subunit of pol II []. In humans, there are three T-type cyclins: cyclins T1, T2a and T2b. Cyclins T2a and T2b are splice variants of a primary transcript []. Each of the T-type cyclin/CDK9 complexes can phosphorylate the C-terminal domain of the large subunit of RNA polymerase II. However, only human cyclin T1/CDK9 complexes can bind HIV Tat and promote RNA Pol II activation, allowing transcription of viral genes [, , , ].
Cyclins are eukaryotic proteins that play an active role in controlling nuclear cell division cycles, and regulate cyclin dependent kinases (CDKs) [].This entry represents several Cyclin families (C, L, Q, T1, T2, and H/Ccl1) and yeast RNA polymerase II holoenzyme cyclin-like subunit (also known as Ssn8/Srb11).Cyclin C can regulate both cell cycle progression and gene transcription. The Cdk8-cyclin C complex is a component of the RNA polymerase II holoenzyme [].Cyclin L is a transcriptional regulator involved in the regulation of RNA polymerase II transcription and participating in regulating the pre-mRNA splicing process [, ].Cyclin Q (also known as Cyclin M) consists of cyclin-related protein FAM58A [].Cyclin-T2 is a regulatory subunit of the cyclin-dependent kinase pair (CDK9/cyclin T) complex [].Cyclin-H from vertebrates, mcs2 from fission yeast and Ccl1 from budding yeasts are cyclins that play a role in cell cycle [].Cyclin-T associates with CDK9 which are subunits of the positive-transcription elongation factor (P-TEFb) [].Ssn8/Srb11 is a component of the SRB8-11 complex (consists of SRB8, SSN2/SRB9, SSN3/SRB10 and SSN8/SRB11), which is a regulatory module of the mediator complex that is involved in regulation of basal and activated RNA polymerase II-dependent transcription [, ].
