title: Hypoxic stress induces dimethylated histone H3 lysine 9 through histone methyltransferase G9a in mammalian cells.
abstract: Dimethylated histone H3 lysine 9 (H3K9me2) is a critical epigenetic mark for gene repression and silencing and plays an essential role in embryogenesis and carcinogenesis. Here, we investigated the effects of hypoxic stress on H3K9me2 at both global and gene-specific level. We found that hypoxia increased global H3K9me2 in several mammalian cell lines. This hypoxia-induced H3K9me2 was temporally correlated with an increase in histone methyltransferase G9a protein and enzyme activity. The increase in H3K9me2 was significantly mitigated in G9a-/- mouse embryonic stem cells following hypoxia challenge, indicating that G9a was involved in the hypoxia-induced H3K9me2. In addition to the activation of G9a, our results also indicated that hypoxia increased H3K9me2 by inhibiting H3K9 demethylation processes. Hypoxic mimetics, such as deferoxamine and dimethyloxalylglycine, were also found to increase H3K9me2 as well as G9a protein and activity. Finally, hypoxia increased H3K9me2 in the promoter regions of the Mlh1 and Dhfr genes, and these increases temporally correlated with the repression of these genes. Collectively, these results indicate that G9a plays an important role in the hypoxia-induced H3K9me2, which would inhibit the expression of several genes that would likely lead to solid tumor progression.
authors.affiliation: Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987, USA.
authors.forename: Haobin
authors.initials: H
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Yan
authors.forename: Todd L
authors.initials: TL
authors.lastname: Davidson
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Shinkai
authors.forename: Max
authors.initials: M
authors.lastname: Costa
mesh_terms: D000107:Acetylation; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D051379:Mice; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D011496:Protein Methyltransferases; D011499:Protein Processing, Post-Translational; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis / Q000235:genetics; D014162:Transfection
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D006657:Histones; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D013762:Tetrahydrofolate Dehydrogenase; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D000070957:MutL Protein Homolog 1; D008239:Lysine