FIGURE 3.

DNA damage-sensing model. The clamp loader Rad17-RFC2–5 forms an ATP-dependent complex with the 9-1-1 sliding clamp, in which Rad17 interacts with Rad1, and loads the 9-1-1 complex onto DNA via opening the Rad1-Rad9 interface. The αII1–βII2 loop in hRad9 and the αI2–βI7 loop in hRad1 are proposed to detect some types of DNA lesions. The DNA damage recognition then leads to conformational changes that facilitate the ring closure and ATP hydrolysis, in turn stimulating the dissociation of Rad17-RFC2–5 clamp loader from the 9-1-1 clamp and ultimately triggering further DNA repair.