p34 cdc-2 nuclear protein

p34(Cdc2) kinase is a an essential nuclear protein for mitosis in human cells. During the prophase/metaphase transition the inactive phosphorylated form of p34(cdc2) is dephosphorylated to make the active form of the protein. This dephosphorylation is performed by the p80(cdc25) dual-specificity phosphatase. The regulatory subunit of p34(cdc2) is cyclin B, a 47-52 kDa protein. The p34(cdc2) protein is the catalytic subunit of the M phase-promoting factor (MPF) which is intracellular factor responsible for entry into M phase. Three mechanisms are responsible for the activitation of MPF at the onset of mitosis: binding of p34(cdc2) to cyclin B, a series of phosphorylation/dephosphorylation events on the two subunits and translocation of the complex to the nucleus or microtubules.