Cyclin E2 is a member of the cyclin E family that can associate with and activate Cdk2. It is essential for the control of the cell cycle at the late G1 and early S phase. Cyclin E2 associates with Cdk2 in a functional kinase complex that is inhibited by both p27 (Kip1) and p21 (Cip1). Cyclin E2 is high expressed in adult testis, thymus and brain. Abnormally high levels of cyclin E expression have frequently been observed in human cancers.