Poly(ADP-ribose) Polymerase 1 Modulates Interaction of the Nucleotide Excision Repair Factor XPC-RAD23B with DNA via Poly(ADP-ribosyl)ation.

Poly(ADP-ribosyl)ation is a reversible post-translational modification that plays an essential role in many cellular processes, including regulation of DNA repair. Cellular DNA damage response by the synthesis of poly(ADP-ribose) (PAR) is mediated mainly by poly(ADP-ribose) polymerase 1 (PARP1). The XPC-RAD23B complex is one of the key factors of nucleotide excision repair participating in the primary DNA damage recognition. By using several biochemical approaches, we have analyzed the influence of PARP1 and PAR synthesis on the interaction of XPC-RAD23B with damaged DNA. Free PAR binds to XPC-RAD23B with an affinity that depends on the length of the poly(ADP-ribose) strand and competes with DNA for protein binding. Using (32)P-labeled NAD(+) and immunoblotting, we also demonstrate that both subunits of the XPC-RAD23B are poly(ADP-ribosyl)ated by PARP1. The efficiency of XPC-RAD23B PARylation depends on DNA structure and increases after UV irradiation of DNA. Therefore, our study clearly shows that XPC-RAD23B is a target of poly(ADP-ribosyl)ation catalyzed by PARP1, which can be regarded as a universal regulator of DNA repair processes.