Abstract
Recent studies report serine ADP-ribosylation on nucleosomes during the DNA damage response. We unveil histone H3 serine 10 as the primary acceptor residue for chromatin ADP-ribosylation and find that specific histone acetylation marks block this activity. Our results provide a molecular explanation for the well-documented phenomenon of rapid deacetylation at DNA damage sites and support the combinatorial application of PARP and HDAC inhibitors for the treatment of PARP-dependent cancers.