In addition, we demonstrated that nickel exposure trigger the reduction of GADD45A-mediated DNA repair by impairing the physical interactions between GADD45A and proliferating cell nuclear antigen or xeroderma pigmentosum G. Notably, in the GADD45A-knockdown system, the levels of unrepaired DNA photoproducts were higher than wild-type cells, elucidating the importance of GADD45A in the nickel-associated inhibition of DNA repair.
Furthermore, ectopic expression of USP7 promoted the UV-induced proliferating cell nuclear antigen (PCNA) monoubiquitination in Polη-proficient but not in Polη-deficient XPV (Xeroderma pigmentosum variant) cells, suggesting that USP7 facilitates UV-induced PCNA monoubiquitination by stabilizing Polη.
We analyzed 13 polymorphisms in seven DNA repair genes belonging to different repair pathways [X-ray repair cross-complementing group 1 (XRCC1): 26304C>T, 26651A>G, 28152A>G; xeroderma pigmentosum-D (XPD): 23591A>G, 35931A>C; excision repair complementing defective in Chinese hamster, group 1 (ERCC1): 19007C>T; XRCC3: 4541T>C, 17893A>G, 18067C>T; proliferating cell nuclear antigen (PCNA): 6084G>C; ERCC4: 30028C>T, 30147A>G; and XRCC2-31479A>G] in 317 incident bladder cancer patients and 317 controls.