A novel cytoprotective function for the DNA repair protein Ku in regulating p53 mRNA translation and function.

Ku heterodimer is a DNA binding protein with a prominent role in DNA repair. Here, we investigate whether and how Ku impacts the DNA damage response by acting as a post-transcriptional regulator of gene expression. We show that Ku represses p53 protein synthesis and p53-mediated apoptosis by binding to a bulged stem-loop structure within the p53 5' UTR However, Ku-mediated translational repression of the p53 mRNA is relieved after genotoxic stress. The underlying mechanism involves Ku acetylation which disrupts Ku-p53 mRNA interactions. These results suggest that Ku-mediated repression of p53 mRNA translation constitutes a novel mechanism linking DNA repair and mRNA translation.