InterPro domain: IPR043198

Cyclins are eukaryotic proteins that play an active role in controlling nuclear cell division cycles, and regulate cyclin dependent kinases (CDKs) [ 1 ].

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 [ 2 , 3 ].

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 [ 4 ].
• Cyclin L is a transcriptional regulator involved in the regulation of RNA polymerase II transcription and participating in regulating the pre-mRNA splicing process [ 5 , 6 ].
• Cyclin Q (also known as Cyclin M) consists of cyclin-related protein FAM58A [ 7 ].
• Cyclin-T2 is a regulatory subunit of the cyclin-dependent kinase pair (CDK9/cyclin T) complex [ 8 ].
• Cyclin-H from vertebrates, mcs2 from fission yeast and Ccl1 from budding yeasts are cyclins that play a role in cell cycle [ 9 ].
• Cyclin-T associates with CDK9 which are subunits of the positive-transcription elongation factor (P-TEFb) [ 10 ].

1. Cell cycle regulation and neural differentiation. Oncogene 22, 5208-19
2. A kinase-cyclin pair in the RNA polymerase II holoenzyme. Nature 374, 193-6
3. Temporal regulation of RNA polymerase II by Srb10 and Kin28 cyclin-dependent kinases. Mol. Cell 2, 43-53
4. TFIIH is negatively regulated by cdk8-containing mediator complexes. Nature 407, 102-6
5. Cyclin L is an RS domain protein involved in pre-mRNA splicing. J. Biol. Chem. 277, 25465-73
6. Characterization of cyclin L1 as an immobile component of the splicing factor compartment. FASEB J. 21, 3142-52
7. CDK10/cyclin M is a protein kinase that controls ETS2 degradation and is deficient in STAR syndrome. Proc. Natl. Acad. Sci. U.S.A. 110, 19525-30
8. Analysis of the effect of natural sequence variation in Tat and in cyclin T on the formation and RNA binding properties of Tat-cyclin T complexes. J. Virol. 73, 5777-86
9. Phosphorylation by PKA potentiates retinoic acid receptor alpha activity by means of increasing interaction with and phosphorylation by cyclin H/cdk7. Proc. Natl. Acad. Sci. U.S.A. 103, 9548-53
10. Cyclin K functions as a CDK9 regulatory subunit and participates in RNA polymerase II transcription. J. Biol. Chem. 274, 34527-30