Cyclin-A2 RxL substrate-binding groove (CCNA2 RxL groove)

The Cyclin A RxL substrate-binding groove, also known as the hydrophobic patch or recruitment site, is a specialized protein-protein interaction surface located on Cyclin A2 (CCNA2). This groove is characterized by a conserved MRAIL sequence that recognizes and binds to the RxL (Arg-x-Leu) motif found in various cell cycle substrates and regulators, including E2F1, p21, and p27 (nih.gov, 1.1.1, 1.1.2). By facilitating these interactions, the groove enables the Cyclin A-CDK2 complex to phosphorylate specific targets required for DNA replication during S-phase and the subsequent transition into mitosis (wikipedia.org, 1.3.1). In many cancers, particularly those with RB1 or TP53 mutations, the G1-S checkpoint is compromised, leading to dysregulated and high E2F activity (biorxiv.org, 1.2.4). Therapeutic targeting of this groove with macrocyclic peptides or small molecules, such as CID-078, competitively inhibits substrate recruitment, paradoxically hyperactivating E2F1 and inducing mitotic catastrophe (cancer.gov, 1.2.3). This mechanism provides a synthetic lethal approach for treating E2F-driven malignancies like small-cell lung cancer while maintaining a therapeutic window relative to normal cells (nih.gov, 1.2.1).

Other names

Hydrophobic patchCyclin-binding groove (CBG)Recruitment siteCy-motif binding siteMRAIL motif

Competitive inhibition of RxL-motif substrate binding to Cyclin A2, leading to E2F1 hyperactivation and disruption of the Cyclin B-Myt1 interaction, which triggers the spindle assembly checkpoint and apoptotic cell death.