Histone 3 Lysine 9 Methylating Enzyme G9a Regulates Transcriptional Expression of Nuclear Receptors and Cytochrome P450 Genes in HepaRG Cells

Abstract

Histone modification transcriptionally regulate gene expression. Cytochrome P450 genes are studied extensively in terms of regulation of expression through histone modification. Histone 3 lysine 4 (H3K4) and Histone 3 lysine 27 (H3K27) methylation are studied extensively in regulation of P450 gene expression. Another histone modification Histone 3 lysine 9 methylation, is well known for transcriptional repression of genes but not studies well in regulation of nuclear receptors and cytochrome P450 gene expression. In this study, the role of histone methyl transferase G9a, which is responsible for mono and di‐methylation of histone 3 lysine 9 residue, was studied in regulation of drug metabolizing enzymes and nuclear receptors. We treated HepaRG cell with small interfering RNA to selectively knockdown EHMT2 mRNA and using adenovirus, G9a was overexpressed to study the effect on nuclear receptors CAR (NR1I3), PXR (NR1I2), AHR and heterodimer partner RXRα along with the selected drug metabolizing cytochrome P450 genes. In pathological conditions such as steatosis, the expression of nuclear receptors and cytochrome P450 genes is affected along with G9a in a mice model treated with high fat diet. In this study, we treated HepaRG cells with fatty acids to induce steatosis. In conclusion we observed that loss of G9a shown to decrease mRNA expression of nuclear receptors and cytochrome P450 genes whereas overexpression of G9a increased expression of nuclear receptors CAR (NR1I3), PXR (NR1I2)and selected drug metabolizing enzymes CYP1A2, CYP2B6, CYP2C9, CYP3A4 etc. In fatty acid treated cells overexpression of G9a was observed to prevent fatty acid mediated down regulation of nuclear receptor CAR (NR1I3) and drug metabolizing enzyme genes CYP2C19, CYP2C8 and CYP3A4.Support or Funding InformationThis project work was funded by Boehringer Ingelheim Pharmaceuticals