The roles of p53, DNA repair, and oxidative stress in ultraviolet C induction of proliferating cell nuclear antigen expression

The expression of proliferating cell nuclear antigen (PCNA) promoter was moderately induced in UV-irradiated, quiescent human and rodent cells. The induction was independent of tumor suppressor gene p53, because the PCNA expression was UV-inducible in the subclones of human fibroblasts in which the activity of p53 was abrogated by human papilloma virus E6. Furthermore, the induction did not depend on DNA repair, since PCNA was UV inducible in UVL-10 and xrs-6 cells, in which nucleotide excision repair and double-stranded repair, respectively, are largely compromised. However, the induction was inhibited by antioxidant N-acetylcysteine. The role of oxidative stress observed here is consistent with the previous finding that the proximal AP-1 site is critical to the UV inducibility of PCNA promoter.