Role for p53 in the Recovery of Transcription and Protection Against Apoptosis Induced by Ultraviolet Light

We have previously suggested that the inhibition of RNA polymerase II-mediated transcription after exposure to UV light promotes the accumulation of p53 and the induction of apoptosis (Oncogene 13, 823-831). However, it was not clear whether p53 induction was contributing to apoptosis. Here we report that apoptosis is triggered at lower UV doses in p53-deficient Li-Fraumeni syndrome (LFS) and human papillomavirus (HPV) E6 expressing fibroblasts than in normal cells, suggesting that p53 can be protective against UV-induced apoptosis. There is no significant difference in the effect of UV-irradiation on the cell cycle distribution of normal and primary LFS fibroblasts. Importantly, the recovery of nascent mRNA synthesis in all p53-deficient fibroblasts is significantly impaired compared with control cells after exposure to relevant doses of UV light. Taken together, our results suggest that wild-type p53 can protect cells against UV-induced apoptosis by facilitating the recovery of transcription. Furthermore, we suggest that the capacity of cells to recover transcription after genotoxic damage is an important determinant of sensitivity to apoptosis.