A central role for G9a and EZH2 in the epigenetic silencing of cyclooxygenase-2 in idiopathic pulmonary fibrosis

Coward, William R.; Feghali-Bostwick, Carol A.; Jenkins, Gisli; Knox, Alan J.; Pang, Linhua

Abstract

Selective silencing of the cyclooxygenase-2 (COX-2) gene with the loss of the antifibrotic mediator PGE2 contributes to the fibrotic process in idiopathic pulmonary fibrosis (IPF). This study explored the role of G9a- and EZH2-mediated methylation of histone H3 lysine 9 (H3K9me3) and 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 MeCP2, at the COX-2 promoter in lung fibroblasts from IPF patients (F-IPF) compared with fibroblasts from non-fibrotic lungs (F-NL). HP1, EZH2 and MeCP2 in turn were associated with additional repressive chromatin modifiers in F-IPF. G9a and EZH2 inhibitors and siRNAs and Dnmt1 inhibitor markedly reduced H3K9me3 (49-79%), H3K27me3 (44-81%) and DNA methylation (61-97%) at the COX-2 promoter. This was correlated with increased histone H3 and H4 acetylation, resulting in COX-2 mRNA and protein re-expression in F-IPF. 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.

Citation

Coward, W. R., Feghali-Bostwick, C. A., Jenkins, G., Knox, A. J., & Pang, L. (2014). A central role for G9a and EZH2 in the epigenetic silencing of cyclooxygenase-2 in idiopathic pulmonary fibrosis. FASEB Journal, 28(7), 3183-3196. https://doi.org/10.1096/fj.13-241760

• Journal Article Type: Article
• Acceptance Date: Mar 10, 2014
• Online Publication Date: Mar 20, 2014
• Publication Date: 2014-07
• Deposit Date: Feb 1, 2016
• Publicly Available Date: Sep 18, 2019
• Journal: The FASEB Journal
• Print ISSN: 0892-6638
• Electronic ISSN: 1530-6860
• Publisher: Federation of American Society of Experimental Biology (FASEB)
• Peer Reviewed: Peer Reviewed
• Volume: 28
• Issue: 7
• Pages: 3183-3196
• DOI: https://doi.org/10.1096/fj.13-241760
• Public URL: https://nottingham-repository.worktribe.com/output/724551
• Publisher URL: http://www.fasebj.org/content/28/7/3183.full.pdf+html
• Contract Date: Sep 18, 2019