<p>Cyclin B was first identified in the Xenopus oocyte as a component of the maturation promoting factor (MPF) and is evolutionarily conserved throughout eukaryotes. The progress through mitosis is regulated by the presence of cyclin B. Cyclin B associates with Cdc2 and forms the primary kinase present during mitosis (MPF=M-phase/maturation promoting factor) [<cite idref="PUB00034781"/>].</p> <p>During anaphase cyclin B is degraded. Mitotic cyclins contain a nine-residue sequence, the destruction box, that is recognised by ubiquitinating enzymes. The anaphase-promoting complex (APC) directs the polyubiquitination of cyclin B, marking them for degradation by the proteasome. This degradation of cyclin B appears to regulate the cells progression out of mitosis and into G1 [<cite idref="PUB00034782"/>].</p> Cyclin B, G2/mitotic-specific