Essential for the control of the cell cycle at the G2/M (mitosis) transition. Interacts with the CDC2 protein kinase to form a serine/threonine kinase holoenzyme complex also known as maturation promoting factor (MPF). The cyclin subunit imparts substrate specificity to the complex. Binds HEI10. Interacts with catalytically active RALBP1 and CDC2 during mitosis to form an endocytotic complex during interphase. Interacts with CCNF; interaction is required for nuclear localization. Interacts with CDK5RAP3. Interacts with RFPL4A and UBE2A. Interacts with INCA1. Accumulates steadily during G2 and is abruptly destroyed at mitosis. Ubiquitinated by the SCF(NIPA) complex during interphase, leading to its destruction. Not ubiquitinated during G2/M phases (By similarity). Phosphorylated by PLK1 at Ser-123 on centrosomes during prophase: phosphorylation by PLK1 does not cause nuclear import. Phosphorylation at Ser-137 was also reported to be mediated by PLK1 but Ser-123 seems to be the primary phosphorylation site (By similarity). Belongs to the cyclin family. Cyclin AB subfamily.