Cyclins are positive regulatory subunits of the cyclin-dependent kinases (CDKs), and thereby play an essential role in the control of the cell cycle, notably via their destruction during cell division. Could be involved at the G2/M (mitosis or meiosis) transition. G2/M cyclins accumulate steadily during G2 and are abruptly destroyed at mitosis. Interacts with the CDK1 and CDK2 protein kinases. The N-terminal destruction box (D-box) probably acts as a recognition signal for degradation via the ubiquitin-proteasome pathway. Ubiquitinated, leading to its degradation. Belongs to the cyclin family. Cyclin AB subfamily.