Kinase Family CDK

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Kinase Classification: Group CMGC: Family CDK

This large family (21 human genes) contains several cyclin-dependent kinases, which regulate different phases of cell cycle (classical CDKs), as well as other kinases that bind cyclin-like proteins, serve as CDK-Activating Kinases (CAKs), regulate RNA polymerase and splicing, and other functions.

Cell Cycle CDKs

CDK1 (CDC2) The primary cell cycle in all eukaryotic cells

CDK2 An animal-specific variant of CDK1

CDK4 Animal-specific CDK, parter of Cyclin D


These regulate transcription by phosphorylating RNA polymerase II (the mRNA polymerase) on the heptad repeat unit of its C-Terminal Domain (CTD).

CDK7 binds Cyclin H and MAT1 to form the basal transcription factor, TFIIH, serves as a CDK Activating Kinase (CAK)

CDK8 is part of the Mediator transcription complex, binds Cyclin H and interacts with CDK7.

CDK9 complexes with Cyclin T or Cyclin K to make P-TEFb, a CTD kinase involved in transcriptional elongation.

CDK12 (CRK7)


CDK5: a non-cell cycle CDK, ancient, but largely brain-specific in animals.

CDK10 is active in the G2/M phase of cell cycle. Modulates activity of the Ets2 transcription factor.

CDK11 (PITSLRE) is involved in apoptosis

CDK14 (PFTAIRE): Cyclin Y-associated. Mediates cell cycle interaction with Wnt signaling, and roles in late development and cell cycle progression.

CDK16 (PCTAIRE) is implicated in protein trafficking and secretion.

CDK20 (CCRK) is invovled in cilium biology and Hedgehog signaling. Similar to CDK7 and a possible CAK.

Other CDK subfamilies not found in human include CDK-DD1 (Dictyostelium), CDK-plant1 and CDKB (plant-specific), CDK-Smoe1 and CDK-smoe2 (Selaginella-specific). Most of these are very poorly studied.

CDK-Cyclin Interaction Guide

Most CDKs require binding by a Cyclin to be catalytically active. All conserve specific cyclin-interacting motifs (leading to their original names like PSTAIRE and PFTAIRE), though the cyclin partners of some are either unknown or non-existent. CDK5 binds p35 which is a structural analog of cyclins, but not a member of the cyclin family.

CDK Cyclin Phase/Function
CDK1 Cyclin A
CDK1 Cyclin B M phase
CDK2 Cyclin A, C
CDK2 Cyclin E G1/S
CDK4 Cyclin D G1
CDK5 p35 Neuronal Development
CDK7 Cyclin H CAK
CDK8 Cyclin C Transcription
CDK9 Cyclin K, T
CDK10 Cyclin D
CDK11 Cyclin L
CDK12 Cyclin D
CDK14 Cyclin Y
CDK16 Cyclin K? p35
CDK20  ??