CBP/p300-mediated acetylation of PCNA is required for its chromatin removal and degradation in nucleotide excision repair

PCNA protein, a molecular platform recruiting and coordinating the activity of several DNA transaction factors, appears to be regulated by different post-translational modifications, among which acetylation. In this study, we have identified CBP, as another acetyltransferase (p300 homolog) interacting with PCNA, and found that PCNA is acetylated after UV-induced DNA damage. MS/MS analysis indicated that in vitro, CBP acetylates PCNA at residues Lys 13,14,77 and 80. Expression of PCNA mutated in these residues, resulted in impaired DNA replication and repair, enhanced sensitivity to UV radiation, and activated a DNA damage response. The same mutations prevented removal of chromatin-bound PCNA, and its subsequent proteolytic degradation after DNA damage. Depletion of CBP/p300 in normal fibroblasts prevented PCNA acetylation and degradation, while proteasome inhibition resulted in accumulation of acetylated PCNA. Our results suggest that PCNA acetylation by CBP and p300 is required to link DNA repair synthesis with chromatin removal and degradation of PCNA after DNA damage, to avoid its excessive accumulation, dangerous for genome stability.