CDK-activating kinases(CAKs) are multisubunit proteins that phosphorylate and thus activate certain cyclin-dependent protein kinases in the regulation of cell cycle progression. Cyclin dependent kinase7(CDK7) gene is mapped to chromosome 2p15-cen. CDK7 functions in both cyclin binding and T-loop phosphorylation and that these 2 steps of CDK1 activation are mutually dependent.