The human Cyclin E2 gene encodes a 404 amino acid protein that is most closely related to Cyclin E. Cyclin E2 mRNA levels peaks at the G1 / S transition. Cyclin E2 associates with Cdk2 in a functional kinase complex that is inhibited by both p27 (Kip1) and p21 (Cip1). Cyclin E2 / Cdk2 phosphorylates histone H1 in vitro. G1 cyclin E controls the initiation of DNA synthesis by activating CDK2. Abnormally high levels of cyclin E expression have frequently been observed in human cancers. Unlike Cy