Dynamic Interplay between Cockayne Syndrome Protein B and Poly(ADP-Ribose) Polymerase 1 during Oxidative DNA Damage Repair.

Oxidative stress contributes to numerous diseases, including cancer. CSB is an ATP-dependent chromatin remodeler critical for oxidative stress relief. PARP1 is the major sensor for DNA breaks and fundamental for efficient single-strand break repair. DNA breaks activate PARP1, leading to the synthesis of poly(ADP-ribose) (PAR) on itself and neighboring proteins, which is crucial for the recruitment of DNA repair machinery. CSB and PARP1 interact; however, how CSB mechanistically participates in oxidative DNA damage repair mediated by PARP1 remains unclear. Using chromatin immunoprecipitation followed by quantitative PCR, we found that CSB and PARP1 facilitate each other's chromatin association during the onset of oxidative stress, and that CSB facilitates PARP1 removal when the level of chromatin-bound CSB increases. Furthermore, by monitoring chromatin PAR levels using Western blot analysis, we found that CSB sustains the DNA damage signal initiated by PARP1, and may prevent PARP1 overactivation by facilitating DNA repair. By assaying cell viability in response to oxidative stress, we further demonstrate that PARP1 regulation by CSB is a major CSB function in oxidatively-stressed cells. Together, our study uncovers a dynamic interplay between CSB and PARP1 that is critical for oxidative stress relief.