Table 1.

The different known members of the CDK family, their regulating cyclin partners (except CDK5) and their general functions.

	Cyclin/Regulating Partners	Functions	Reference
CDK1	Cyclin B1	Cell-cycle regulation—promotes G2/M transition, regulates G1 progress and G1/S transition	[4,5]
CDK2	Cyclins A/D1/E1	Cell-cycle regulation—G1/S transition, exit from S-phase; initiation of DNA synthesis	[6]
CDK4	Cyclin D	Cell-cycle regulation—G1-phase transition; partial phosphorylation of Rb with CDK6	[7]
CDK5	p35/p39	All aspects of neuronal physiology; immune response; angiogenesis; myogenesis; melanogenesis and regulation of insulin levels	[6,8,9]
CDK6	Cyclin D	Cell-cycle regulation—G1-phase transition; partial phosphorylation of Rb with CDK4	[7]
CDK7	Cyclin H	CDK Activating Kinase (CAK)—phosphorylates cell-cycle regulating kinases; transcription regulation—S5 phosphorylation on RNAP II CTD to initiate transcription initiation	[10]
CDK8	Cyclin C/Med12/Med13	Part of Mediator Complex (MC), regulates the phosphorylation transcription factors, their activity and turn-over	[11]
CDK9	Cyclins T1/T2a/T2b	Positive regulation of transcription elongation	[12]
CDK10	Cyclin M	Cell-cycle regulation and tumor suppressor	[13,14]
CDK12	Cyclin K	Positive regulation of transcription elongation	[15,16]
CDK13	Cyclin K	Positive regulation of transcription elongation	[15,17]
CDK14	Cyclin Y	Regulation of cell-cycle, proliferation, migration and invasion	[18]
CDK15	Unknown	Inhibits apoptosis by phosphorylating Survivin on T34	[19]
CDK16	Cyclin Y	Promotes proliferation in medulloblastoma, prostate, breast, melanoma and cervical cancers, inhibits apoptosis by down-regulating the tumor suppressor p27 in NSCLC	[20,21,22]
CDK17	Unknown	Down-regulation causes poor prognosis in glioma. Unknown functions	[23]
CDK18	Cyclins A2 and E	Negative regulator of cell migration and adhesion, prevents the accumulation of DNA damage and genome instability	[24,25,26]
CDK19	Cyclin C	CDK8 homolog, part of Mediator Complex (MC), promotes proliferation and mitotic gene expression in the absence of CDK8 expression, negative regulation of NOTCH signaling	[11]
CDK20	Cyclin H and CK2 (generic CDK20); KCNIP2 and SNAPIN (cardiac CDK20)	Cell-cycle regulator (generic CDK20) and promotes cell survival (cardiac CDK20)	[27]
CDK21	Unknown	Regulates spermatogonial proliferation and meiosis progression and germ line cell activation in testis; unknown function in cancer	[28]