InterPro domain: IPR028367

Cyclin C can regulate both cell cycle progression and gene transcription: cyclin C forms complexes with Cdk8 and induces the transcription of Cdk1. TheCdk8-cyclin C complex is a component of the RNA polymerase II holoenzyme, where it functions as a kinase that phosphorylates the C-terminal domain, and can alsorepress transcription by phosphorylating the Cdk7-cyclin H subunits of the general transcription initiator factor TFIIH [ 1 ]. The Cdk7-cyclin H complex can activate many other cyclin-Cdk complexes directly involved in cell cycle progression, such as Cdk2, Cdk4, and Cdc2 (Cdk1) [ 2 ].

This entry represents cyclin C family, which includes cyclins C and yeast RNA polymerase II holoenzyme cyclin-like subunit (also known as Ssn8/Srb11).

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 [ 3 , 4 ].

1. TFIIH is negatively regulated by cdk8-containing mediator complexes. Nature 407, 102-6
2. Reciprocal activation by cyclin-dependent kinases 2 and 7 is directed by substrate specificity determinants outside the T loop. Mol. Cell. Biol. 21, 88-99
3. A kinase-cyclin pair in the RNA polymerase II holoenzyme. Nature 374, 193-6
4. Temporal regulation of RNA polymerase II by Srb10 and Kin28 cyclin-dependent kinases. Mol. Cell 2, 43-53