Unknown,Transcriptomics,Genomics,Proteomics

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Histone H3.3 and its proteolytically processed form drive a cellular senescence program

ABSTRACT: In this study, we have uncovered novel proteolytic processing of the histone H3 tail in senescence models in primary fibroblasts and melanocytes. Cleavage of H3 tail occurs at two distinct residues and is mediated by Cathepsin L. We show that variant H3.3 is preferentially cleaved, and that cleaved histones are associated with chromatin and incorporated into nucleosomes. We also found that the histone chaperone ASF1a is required for chromatin incorporation of the cleaved histone species. Further, we show that overexpression of cleaved H3.3 induces a senescence program in fibroblasts in the absensence of oncogenic signaling. For the RNA-seq studies, growing IMR90 fibroblasts were compared to cells induced to senesce via oncogene activation or cleaved H3.3 overexpression. Growing controls consist of IMR90 cells infected with empty retroviral construct pBabe and grown under normal conditions for 13 days prior to RNA isolation. For oncogene-induced senescence samples, IMR90s carrying a tamoxifen-inducible H-RasV12 retroviral construct were induced to senesce by addition of 10nM tamoxifen to the media for 8 days. Finally, IMR90s were infected with a retroviral construct expressing the cleaved form of H3.3 with a C-terminal Flag tag. RNA samples form this group were isolated at days 3 (early) and 13 (late) post-infection. In all cases, total RNA samples were isolated using RNeasy kit (Qiagen) and prepared at the Icahn School of Medicine at Mount Sinai Genomics Core Facility for poly A library construction and sequencing on IlluminaHiSeq 2500.

ORGANISM(S): Homo sapiens

SUBMITTER: Zichen Wang

PROVIDER: E-GEOD-55949 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Histone H3.3 and its proteolytically processed form drive a cellular senescence programme.

Duarte Luis F LF Young Andrew R J AR Wang Zichen Z Wu Hsan-Au HA Panda Taniya T Kou Yan Y Kapoor Avnish A Hasson Dan D Mills Nicholas R NR Ma'ayan Avi A Narita Masashi M Bernstein Emily E

Nature communications 20141114

The process of cellular senescence generates a repressive chromatin environment, however, the role of histone variants and histone proteolytic cleavage in senescence remains unclear. Here, using models of oncogene-induced and replicative senescence, we report novel histone H3 tail cleavage events mediated by the protease Cathepsin L. We find that cleaved forms of H3 are nucleosomal and the histone variant H3.3 is the preferred cleaved form of H3. Ectopic expression of H3.3 and its cleavage produ ...[more]

PMID: 25394905

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Project description:Kollarovic2016 - Cell fate decision at G1-S transition This model is described in the article: To senesce or not to senesce: how primary human fibroblasts decide their cell fate after DNA damage. Kollarovic G, Studencka M, Ivanova L, Lauenstein C, Heinze K, Lapytsko A, Talemi SR, Figueiredo AS, Schaber J. Aging (Albany NY) 2016 Jan; Abstract: Excessive DNA damage can induce an irreversible cell cycle arrest, called senescence, which is generally perceived as an important tumour-suppressor mechanism. However, it is unclear how cells decide whether to senesce or not after DNA damage. By combining experimental data with a parameterized mathematical model we elucidate this cell fate decision at the G1-S transition. Our model provides a quantitative and conceptually new understanding of how human fibroblasts decide whether DNA damage is beyond repair and senesce. Model and data imply that the G1-S transition is regulated by a bistable hysteresis switch with respect to Cdk2 activity, which in turn is controlled by the Cdk2/p21 ratio rather than cyclin abundance. We experimentally confirm the resulting predictions that to induce senescence i) in healthy cells both high initial and elevated background DNA damage are necessary and sufficient, and ii) in already damaged cells much lower additional DNA damage is sufficient. Our study provides a mechanistic explanation of a) how noise in protein abundances allows cells to overcome the G1-S arrest even with substantial DNA damage, potentially leading to neoplasia, and b) how accumulating DNA damage with age increasingly sensitizes cells for senescence. This model is hosted on BioModels Database and identified by: BIOMD0000000632. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. 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.

Project description:Hypoxia in stem cell niches and inner core of solid tumors contributes to cellular senescence and differentiation inhibition. It directly increases histone methylationby inhibiting the activities of O2-and α-ketoglutarate (α-KG)-dependent histone lysine demethylases. 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, named senescence-associated heterochromatin foci (SAHF), which are found during oncogene-induced senescence (OIS). This study showed that Raf activation in primary human fibroblasts IMR90 increases mature cathepsin L (CTSL)-mediated cleavage of H3, H2B, and H4. Hypoxia prevented H3 cleavage not by inhibiting CTSL but by increasing H3K18me3 and H3K23me3 nearby cleaved site of H3. Forced expression of cleaved H3 in IMR90 cells induced senescence even under hypoxia, suggesting that hypoxia breaks this positive feedback senescence driving circle by increasing methylated histones. The decrease in methylated histones is necessary for OIS to trigger histone clipping and SAHFs, but hypoxia maintains methylated histones to prevent both. Forced reduction of methylated histones in hypoxic cells using inhibitors of methyl-transferases makes hypoxic conditions unable to prevent OIS from inducing both histone clipping and SAHFs. Reversely forced enhancement of methylated histones in normoxic cells using inhibitors of histone demethylases protected histones from clipping during OIS but failed to block SAHFs. Altogether, the maintenance of methylated histones, especially H3K23me3 and H3K18me3, is sufficient to protect histones from clipping during OIS, but not for inhibiting SAHFs, suggesting that besides inhibiting KDMs, hypoxia adopts other methods to inhibit SAHFs. These findings provide a novel mechanism by which hypoxia affects cell fate by increasing methylated histones that protect histones and chromatin from dramatic epigenetic changes.

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Histone H3.3 and its proteolytically processed form drive a cellular senescence program

Publications

Histone H3.3 and its proteolytically processed form drive a cellular senescence programme.

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