May be involved in the control of the cell cycle at the G1/S (start) and G2/M (mitosis) transitions. Interacts with the CDK1 and the CDK2 protein kinases to form a serine/threonine kinase holoenzyme complex. The cyclin subunit imparts substrate specificity to the complex (By similarity). Present in eggs and early embryos but cannot be detected in late embryos. Belongs to the cyclin family. Cyclin AB subfamily.