Biochemical Impact of p300-Mediated Acetylation of Replication Protein A: Implications for DNA Metabolic Pathway Choice

Replication Protein A (RPA), a single-stranded DNA (ssDNA) binding protein, is vital for various aspects of genome maintenance such as replication, recombination, repair and cell cycle checkpoint activation. Binding of RPA to ssDNA protects it from degradation by cellular nucleases, prevents secondary structure formation and illegitimate recombination. In our current study, we identified the acetyltransferase p300 to be capable of acetylating the 70kDa subunit of RPA in vitro and within cells. The acetylation status of RPA was increased specifically during the G1/S phase of the cell cycle and also following exposure to UV-induced damage. Furthermore, we were able to specifically identify RPA directly associated with the replication fork during the S phase and UV damage to be acetylated. Based on these observations, we evaluated the impact of lysine acetylation on the biochemical properties of RPA. Investigation of binding properties of RPA revealed that acetylation of RPA increased its binding affinity to ssDNA compared to unmodified RPA. The improvement in binding efficiency was a function of DNA length with the greatest increases observed on shorter length ssDNA oligomers. Furthermore, the mechanism of acetylated RPAs’ increased affinity for ssDNA was shown to be a function of a slower rate of dissociation compared to the unmodified form of the RPA. Our findings demonstrate that p300-dependent, site-specific acetylation enhances RPA’s DNA binding properties, potentially regulating its function during various DNA transactions.