Cell cycle associated protein capable of promoting cell proliferation through the activation of CDK2 at the G1/S phase transition. Interacts with CDK2. Ubiquitously expressed with highest expression in the mammary gland and large intestine. Highly expressed in cancer tissues and cancer cell lines. During cell cycle progression expression is high in G1/S, low in the middle of S phase, and increases again in S/G2 phase. Belongs to the cullin family.