P300‐dependent acetylation of Histone H3 at lysine 56 is required for cardioprotection and DNA damage response

Abstract

Backgroundp300 is important for transcription‐dependent DNA damage repair. Acetylation of Histone H3 at Lysine 56 (AcH3K56) by p300 has been suggested to be important for initiation of DNA damage response.HypothesisAcetyltransferase p300 loss is causally related to reduced DNA damage response during aging and genotoxic stress.Methodsp300 was knocked down in neonatal cardiac myocytes using siRNA and compared to a non‐targeting sequence. Doxorubicin (Dox) was used to model genotoxic stress. Cycloheximide (CY)(5μg/ml) was used to assess p300 stability.ResultsIn cardiac myocytes, DOX caused a p300‐HAT activity dependent rapid and sustained stabilization of p300 protein (3.7±1.9 fold vs. control at 8h; p<0.05). AcH3K56 co localized with p300 after DOX treatment. p300 knockdown increased DOX‐induced myocyte death (26.9±13.5%; p<0.05) and caspase3 cleavage, decreased AcH3K56, blunted phosphorylation of H2AX, ATM, and BRCA1, and reduced phosphorylation and acetylation of p53. Converse effects were seen with activation of p300 by HDAC inhibitors TSA and SAHA (HDACi). Further, p300KD completely abolished HDACi mediated cardioprotection and increase in AcH3K56. This could also explain accelerated aging phenotype of mice with heterozygous p300 loss.ConclusionGenotoxic stress causes a post‐transcriptional stabilization of p300 that is required for the DNA damage response and cardioprotection.The work was supported by NIH R01‐ HL7109, the Florida Heart Research Institute and AHA Pre‐doctoral fellowship to Sumit Jain.