Cell cycle checkpoint control protein RAD9A (RAD9A)

Cell cycle checkpoint control protein RAD9A (commonly known as RAD9A) is a key component of the heterotrimeric RAD9-RAD1-HUS1 (9-1-1) checkpoint clamp, a ring-shaped protein complex that is loaded onto DNA at sites of damage to initiate the DNA damage response and arrest the cell cycle[1][2]. RAD9A structurally resembles proliferating cell nuclear antigen (PCNA) and together with RAD1 and HUS1 forms a PCNA-like sliding clamp that is critical for sensing DNA lesions and coordinating downstream repair pathways[1][2][3]. The 9-1-1 complex is loaded onto DNA by the RAD17-RFC clamp loader and serves as a recruitment platform for mediators of the ATR-CHK1 checkpoint pathway, helping activate cell cycle arrest and DNA repair in response to genotoxic stress[1][2]. RAD9A and the 9-1-1 complex are evolutionarily conserved, with critical roles in genome maintenance, and defects in this complex contribute to cancer susceptibility and therapy resistance[1][2][3]. There is ongoing research on targeting components of the checkpoint pathway—including 9-1-1—for potential cancer therapies that modulate DNA repair and checkpoint signaling[1].

Other names

RAD9hRAD9DNA repair exonuclease rad9 homolog ARAD9 homolog Acell cycle checkpoint control protein RAD9A

Inhibition or disruption impairs DNA damage–induced checkpoint signaling\nPotential for drug-induced checkpoint abrogation enhancing cancer cell sensitivity to DNA-damaging agents[1]