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Hypoxia increases the methylated histones to prevent histone clipping and redistribution of heterochromatin during Raf-induced senescence.

ABSTRACT: Hypoxia increases histone methylation by inhibiting O2- and a-ketoglutarate-dependent histone lysine demethylases (KDMs). This study is the first to demonstrate how the hypoxic increment of methylated histones cross-talks with other epigenetic changes, such as histone clipping, and heterochromatin redistribution (senescence-associated heterochromatin foci, SAHF) found during oncogene-induced senescence (OIS). Raf activation in primary human fibroblasts IMR90 increased cathepsin L (CTSL)-mediated clipping of histone 3 (H3), H2B and H4 at H3 A21/T22, H2B T19/K20, and H4 G11/K12, respectively. Hypoxia protected H3 from CTSL by increasing histone methylation, especially at H3K23me3 without reducing the activity of CTSL. The maintenance of methylated histones is sufficient for protecting histones from CTSL, not sufficient but necessary for inhibiting SAHFs. Expression of cleaved H3 induces senescence even under hypoxia, suggesting that hypoxia disrupts this positive feedback loop of OIS by increasing histone methylation. Thus, hypoxia protects histones and chromatin from dramatic epigenetic changes by increasing histone methylation. These observations suggest that the OIS process increases the accessibility of chromatin, which hypoxic conditions inhibited.

ORGANISM(S): Homo sapiens

PROVIDER: GSE234895 | GEO | 2024/01/22

REPOSITORIES: GEO

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Project description:This model is described in the article: Kinetics of histone gene expression during early development of Xenopus laevis. Koster JG, Destrée OH and Westerhoff HV. J Theor Biol. 1988 Nov 21;135(2):139-67. PMID: 3267765 Abstract: Using literature data for transcriptional and translational rate constants, gene copy numbers, DNA concentrations, and stability constants, we have calculated the expected concentrations of histones and histone mRNA during embryogenesis of Xenopus laevis. The results led us to conclude that: (i) for X. laevis the gene copy number of the histone genes is too low to ensure the synthesis of sufficient histones during very early development, inheritance from the oocyte of either histone protein or histone mRNA (but not necessarily both) is necessary; (ii) from the known storage of histones in the oocyte and the rates of histone synthesis determined by Adamson and Woodland (1977), there would be sufficient histones to structure the newly synthesized DNA up to gastrulation but not thereafter (these empirical rates of histone synthesis may be underestimates); (iii) on the other hand, the amount of H3 mRNA recently observed during early embryogenesis (Koster, 1987, Koster et al., 1988) could direct a higher and sufficient synthesis of H3 protein, also after gastrulation. We present a quantitative model that accounts both for the observed H3 mRNA concentration as a function of time during embryogenesis and for the synthesis of sufficient histones to structure the DNA throughout early embryogenesis. The model suggests that X. laevis exhibits a major (i.e. some 14-fold) reduction in transcription of histone genes approximately 11 hours after fertilization. This reduction could be due to a decrease in the number of transcribed histone genes, a decreased rate constant of transcription with continued transcription of all the histone genes, and/or a reduction in the time during the cell cycle in which histone mRNA synthesis takes place. Alternatively, the histone mRNA stability might decrease approximately 16-fold 11 hours after fertilization. This model originates from BioModels Database: A Database of Annotated Published Models. It is copyright (c) 2005-2011 The BioModels.net Team. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information. In summary, you are entitled to use this encoded model in absolutely any manner you deem suitable, verbatim, or with modification, alone or embedded it in a larger context, redistribute it, commercially or not, in a restricted way or not.. To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.

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Hypoxia increases the methylated histones to prevent histone clipping and redistribution of heterochromatin during Raf-induced senescence.

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