Cyclin E–cyclin-dependent kinase 2 complex (Cyclin E–CDK2)

The **Cyclin E–cyclin-dependent kinase 2 complex** is a heterodimeric enzyme composed of Cyclin E (primarily isoforms E1 or E2) and CDK2, which plays a central role in driving the cell cycle through the G1/S phase transition[1][2][4]. Upon complex formation and phosphorylation of CDK2 on Thr160 by CDK-activating kinase (CAK), the active complex phosphorylates substrates including RB family proteins, CDC6, Cdt1, and others involved in DNA replication, centrosome duplication, and chromatin remodeling[1][4]. The Cyclin E–CDK2 complex is tightly regulated and peaks during late G1, enabling S phase entry by inactivating RB and facilitating E2F-dependent transcription[2][4]. Overactivity or dysregulation (commonly via cyclin E overexpression) is implicated in oncogenesis, where the complex drives aberrant proliferation and correlates with poor prognosis in various cancers[3][2]. It is considered a validated but challenging target for therapeutic intervention, with several ATP-competitive CDK inhibitors in development, though selectivity and toxicity remain key hurdles[6]. The complex is found primarily in the cell nucleus but also localizes to centrosomes, and its activity is modulated by endogenous CDK inhibitors such as p21^Cip1^ and p27^Kip1^[1][2].

Other names

Cyclin E/CDK2CCNE1–CDK2 complexE-type cyclin–CDK2cyclin E1–CDK2cyclin E2–CDK2

ATP-competitive kinase inhibition (by small molecules) Disruption of Cyclin–CDK interface (rare approach; largely preclinical) Inhibition of CDK2 phosphorylation activity, which blocks cell cycle progression from G1 to S phase