As a substrate of FBXW7, cyclin E, a nuclear protein that interacts with and activates cyclin-dependent kinase 2 (CDK2) to phosphorylate proteins, facilitates G1/S phase transition and is degraded at the boundary of the S/G2 phase, whereas the overexpression of cyclin E has been detected in human cancer cells associated with cell cycle deregulation and chromosome instability (CIN) (161, 162). Here, CDK2 is linked to cervical squamous intraepithelial neoplasia.