Cyclin Dependent Kinase 20 (CDK20)

The cyclin-dependent protein kinases (CDKs) that regulate cell cycle transitions are themselves regulated by inhibitory and activating phosphorylation. CDK-activating kinases (CAKs) phosphorylate conserved threonine residues such as thr161 in CDC2 and thr160 in CDK2. CCRK/p42 is a monomeric CAK that specifically phosphorylates CDK2 thr160 and functions as a CDK2-activating kinase. p42 expression in multiple cell lines originating from many tissue types, including osteogenic sarcoma, breast adenocarcinoma, lung fibroblast, myoblast, and lymphocyte. p42 levels showed no cell-cycle stage fluctuation in double thymidine block synchronized HeLa cells. p42 localized to the nucleus. Gel filtration of HeLa cell extracts demonstrated that p42 exists primarily as a monomer.