Cdc5

Cdc5, or Cell Division Cycle 5, is a serine/threonine protein kinase of the polo-like kinase (PLK) family in the budding yeast Saccharomyces cerevisiae. It is encoded by the CDC5 gene and serves as a central regulator of cell cycle progression, coordinating events from the G2/M transition through mitosis and into cytokinesis. Cdc5 localizes to the nucleus and spindle pole bodies and is required for proper spindle formation, chromosome segregation, and cytokinesis. Mutants in CDC5 typically show defects in mitotic entry and progression, underscoring its essential role in cell cycle control.

Functionally, Cdc5 promotes mitotic entry by regulating Cdk1 (Cdc28) activity. It phosphorylates and promotes the inactivation of Swe1 (a Wee1-like kinase) and supports the activation of Mih1 (a Cdc25 homolog), leading to dephosphorylation and activation of Cdk1. Cdc5 also contributes to the activation of the FEAR network (Cdc14 Early Anaphase Release), which releases the Cdc14 phosphatase from the nucleolus during early anaphase and helps coordinate mitotic exit. In addition to these roles in chromosome segregation and mitotic timing, Cdc5 participates in spindle pole body maturation, spindle dynamics, and the organization of the actomyosin contractile apparatus during cytokinesis. Its kinase activity and subcellular localization are tightly regulated throughout the cell cycle.

Cdc5 has homologs in other organisms, reflecting the conserved nature of PLK family kinases. Notable relatives include human PLK1, which shares functional similarities in regulating mitosis and cell division. In yeast research, Cdc5 serves as a model for understanding Polo-like kinase function and regulation, and its study has implications for broader cell cycle control and potential insights into anti-cancer strategies targeting PLKs in higher eukaryotes.