title: A central role for G9a and EZH2 in the epigenetic silencing of cyclooxygenase-2 in idiopathic pulmonary fibrosis.
abstract: Selective silencing of the cyclooxygenase-2 (COX-2) gene with the loss of the antifibrotic mediator prostaglandin E2 contributes to the fibrotic process in idiopathic pulmonary fibrosis (IPF). This study explored the role of G9a- and enhancer of zeste homolog 2 (EZH2)-mediated methylation of histone H3 lysine 9 (H3K9me3) and histone H3 lysine 27 (H3K27me3) in COX-2 silencing in IPF. Chromatin immunoprecipitation (ChIP) and re-ChIP assays demonstrated marked increases in H3K9me3, H3K27me3, and DNA methylation, together with their respective modifying enzymes G9a, EZH2, and DNA methyltransferases (Dnmts) and respective binding proteins heterochromatin protein 1 (HP1), polycomb protein complex 1 (PRC1) and methyl CpG binding protein 2 (MeCP2), at the COX-2 promoter in lung fibroblasts from patients with IPF (F-IPFs) compared with fibroblasts from nonfibrotic lungs. HP1, EZH2, and MeCP2 in turn were associated with additional repressive chromatin modifiers in F-IPFs. G9a and EZH2 inhibitors and small interfering RNAs and the Dnmt1 inhibitor markedly reduced H3K9me3 (49-79%), H3K27me3 (44-81%), and DNA methylation (61-97%) at the COX-2 promoter. These reductions were correlated with increased histone H3 and H4 acetylation, resulting in COX-2 mRNA and protein reexpression in F-IPFs. Our results support a central role for G9a- and EZH2-mediated histone hypermethylation and a model of bidirectional, mutually reinforcing, and interdependent crosstalk between histone hypermethylation and DNA methylation in COX-2 epigenetic silencing in IPF.-Coward, W. R., Feghali-Bostwick, C. A., Jenkins, G., Knox, A. J., Pang, L. A central role for G9a and EZH2 in the epigenetic silencing of cyclooxygenase-2 in idiopathic pulmonary fibrosis.
authors.affiliation: Division of Respiratory Medicine and Nottingham Respiratory Biomedical Research Unit, University of Nottingham, City Hospital, Nottingham, UK; and.
authors.forename: William R
authors.initials: WR
authors.lastname: Coward
authors.affiliation: Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Feghali-Bostwick
authors.affiliation: Division of Respiratory Medicine and Nottingham Respiratory Biomedical Research Unit, University of Nottingham, City Hospital, Nottingham, UK; and.
authors.forename: Gisli
authors.initials: G
authors.lastname: Jenkins
authors.affiliation: Division of Respiratory Medicine and Nottingham Respiratory Biomedical Research Unit, University of Nottingham, City Hospital, Nottingham, UK; and.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Knox
authors.affiliation: Division of Respiratory Medicine and Nottingham Respiratory Biomedical Research Unit, University of Nottingham, City Hospital, Nottingham, UK; and linhua.pang@nottingham.ac.uk.
authors.forename: Linhua
authors.initials: L
authors.lastname: Pang
mesh_terms: D000107:Acetylation; D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation / Q000379:methods; D051546:Cyclooxygenase 2 / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D020868:Gene Silencing / Q000502:physiology*; D006649:Histocompatibility Antigens / Q000235:genetics / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000235:genetics* / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D063151:Polycomb Repressive Complex 2 / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D055815:Young Adult
chemical_list: D006649:Histocompatibility Antigens; D006657:Histones; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; C445405:EHMT2 protein, human; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; D011495:Histone-Lysine N-Methyltransferase; D063151:Polycomb Repressive Complex 2
keywords: DNA methylation; antifibrotic gene; histone deacetylation; histone hypermethylation; lung fibroblasts