Cyclin

spinqualitylabelsall models Cyclin T1 (green) complex with CDK9 (cyan) and TRIS (PDB entry 3blh) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D 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 CYCA2 regulates DNA replication and mitotic entry. 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. CYCCCL1 controls the phosphorylation of RNA polymerase II largest subunit and mRNA transcription CYCD regulates the transition from G1 to S. CYCE and its CDK partner are key regulators of DNA synthesis and of mitosis. CYCF is the substrate recognition component of the Skp1-Cul1-F-box E3 ubiquitin ligase complex CYCH is highly expressed in ovarian cancer CYCK and its CDK12 partner regulate the expression of DNA-damage response genes and thus protect cells from genomic instability. CYCT and its CDK9 partner regulate gene expression. Viral CYC could be involved in oncogenic events associated with the cyclin-encoding viruses. See also Intrinsically Disordered Protein. Relevance Overexpression of CYCD1 and its catalytic partner CDK4 is seen in human cancer. Overexpression of CYCH and its catalytic partner CDK7 is seen in breast cancer. Structural highlights All cyclins have an all-α helix fold and share an identical ca. 100 residue domain called 'cyclin box' which binds CDK. Two 5 α-helix cyclin boxes are shown. 3D Structures of Cyclin Cyclin 3D structures

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