Function
Cyclin (CYC) activates CYC-dependent kinase (CDK) thus acting in the control of the cell cycle. The CYC name derives from the fact that different CYCs are expressed during different phases of the cell cycle. Among the CYCs:
- CYCA is active in the S phase
- CYCB1 is essential for the control of the cell cycle at the G2/M (mitosis) transition.
- CYCC is active in the G0/G1 phase transition[1].br />
- CYCD regulates the transition from G1 to S.[2]
- CYCE and its CDK partner are key regulators of DNA synthesis and of mitosis.[3]
- CYCK and its CDK12 partner regulate the expression of DNA-damage response genes and thus protect cells from genomic instability.[4]
- CYCT and its CDK9 partner regulate gene expression.[5]
- Viral CYC could be involved in oncogenic events associated with the cyclin-encoding viruses.[6]
See also Intrinsically Disordered Protein.
Relevance
Overexpression of CYCD1 and its catalytic partner CDK4 is seen in human cancer[7]. Overexpression of CYCH and its catalytic partner CDK7 is seen in breast cancer[8].
Structural highlights
All cyclins have an all-α helix fold and share an identical ca. 100 residue domain called 'cyclin box' which binds CDK. .[9]
3D Structures of Cyclin
Cyclin 3D structures