Cdc2CDK1

Cdc2CDK1, also known as CDK1, is a highly conserved serine/threonine protein kinase that drives cell cycle progression in eukaryotic cells. It is a catalytic subunit of the cyclin-dependent kinase (CDK) family and plays a central role in initiating and coordinating mitosis and, in some organisms, meiosis. In humans and many other species, CDK1 is commonly referred to as p34CDC2 and forms an essential complex with one of the B-type cyclins (notably cyclin B1) to create the maturation-promoting factor (MPF) that triggers mitotic entry.

Activation and regulation of CDK1 depend on multiple layers. The CDK1–cyclin B complex becomes active when cyclin B accumulates during late interphase and when inhibitory phosphates are removed. Inhibitory phosphorylation occurs at Thr14 and Tyr15 by Wee1 family kinases, while activation is achieved by the dual-specificity phosphatase Cdc25 (e.g., Cdc25C) that dephosphorylates these sites. Once activated, CDK1 phosphorylates a broad set of substrates to promote chromosome condensation, nuclear envelope breakdown, spindle formation, and centrosome maturation. CDK1 activity is tightly reduced during mitotic exit as cyclin B is degraded by the anaphase-promoting complex/cyclosome (APC/C), leading to inactivation of MPF and progression into cytokinesis and G1.

CDK1 is essential for cell division and is highly conserved across eukaryotes. Its proper regulation ensures timely mitotic entry, fidelity of chromosome segregation, and coordination with other cell cycle checkpoints.