BACKGROUND
Cell cycle events are regulated by the sequential activation and deactivation of cyclin dependent kinases (Cdks), and by proteolysis of cyclins. Regulatory proteins involved in these processes include the Cdc (cell division control) family of proteins, such as Cdc2 p34, Cdc4, 6, 14, 16, 25, 27, 34, 37 and 45. Members of the Cdc25 family of protein tyrosine phosphatases function as mitotic activators by dephosphorylating Cdc2 p34 on regulatory tyrosine residues. Cdc6 and Cdc45 are involved in the initiation of DNA replication. Cdc37 facilitates Cdk4/cyclin D1 complex formation and forms a stable complex with HSP 90. Cdc34 is essential for the G1 to S phase transition. Cdc16 and Cdc27 are components of the anaphase-promoting complex, which ubiquitinates cyclin B to degrade the cyclin B/Cdk complex. Cdc14a phosphatase plays a role in the regulation of the centrosome cycle, mitosis, and cytokinesis, thereby influencing chromosome partitioning and genomic stability in human cells.