G2/M Transition

Together with two B-type cyclins, CCNB1 and CCNB2, Cdc2 (CDK1) regulates the transition from G2 into mitosis. CDK1 can also form complexes with Cyclin A (CCNA1 and CCNA3). CDK1 complexes with A and B type cyclins are activated by dephosphorylation of CDK1 threonine residue T14 and tyrosine residue Y15. Cyclin A:CDK1 and Cyclin B:CDK1 complexes phosphorylate several proteins involved in mitotic spindle formation and function, the breakdown of the nuclear envelope, and chromosome condensation that is necessary for the ~2 meters of DNA to be segregated at mitosis.

Summary from Reactome (R-HSA-69275), read 2026-09-23.