Inhibition of p300-HAT results in a reduced histone acetylation and down-regulation of gene expression in cardiac myocytes.

AIMS: Histone acetylation plays an important role in cardiogenesis, but the underlying mechanism is unclear. In this study, we investigated the relationship between histone hypo-acetylation and the expression of cardiac-specific genes to explore the underlying mechanisms. MAIN
METHODS: Cardiac-specific genes that physically interacted with p300 protein in mouse hearts were analyzed using chromatin immunoprecipitation (ChIP) assays. The cultured mouse neonatal cardiac myocytes were treated with curcumin with different concentrations and durations. The changes of histone acetyltransferase (HAT) activities, histone acetylation, cardiac-specific genes expression, and structure of chromatin were assessed by ELISA, Western blotting, quantitative RT-PCR, and ChIP assays, respectively. KEY
FINDINGS: Results from the ChIP assay showed that GATA4, Nkx2.5, and Mef2c physically interacted with p300 protein. After treatment with 30 μM curcumin for 24h, the HAT activities of cardiac myocytes were inhibited significantly. And the acetylation of whole histone H3 was reduced by 0.3983-fold compared to control groups (P<0.05). Accordingly, the expression of cardiac-specific genes, GATA4, Nkx2.5, and Mef2c, were significantly down-regulated. Acetylation of histone H3 bound with promoter regions of these genes was significantly reduced. SIGNIFICANCE: p300 interacts with cardiac-specific genes, GATA4, Nkx2.5 and Mef2c, and inhibition of p300-HAT by curcumin down-regulates their expression through the inhibition of histone H3 acetylation in the promoter regions. This finding indicates that p300-HAT mediated histone H3 acetylation plays an important role in the regulation of cardiac gene expression, which is a novel mechanism of epigenetic regulation in the heart during the development and in case of some congenital heart diseases.