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HMGB2 orchestrates the chromatin landscape of senescence-associated secretory phenotype gene loci.

ABSTRACT: Cellular senescence is a stable cell growth arrest that is characterized by silencing of proliferation-promoting genes through compaction of individual chromosomes into senescence-associated heterochromatin foci (SAHF). Paradoxically, senescence is also accompanied by increased expression of certain secreted factors such as cytokines and chemokines, known as senescence-associated secretory phenotype (SASP). How SASP genes are excluded from SAHF-mediated global gene silencing remains unclear. Here we report that HMGB2 orchestrates the chromatin landscape of SASP gene loci. HMGB2 preferentially localizes to SASP gene loci during senescence. Loss of HMGB2 during senescence blunts SASP gene expression by allowing for spreading of repressive heterochromatin into SASP gene loci. This correlated with incorporation of SASP gene loci into SAHF. Our results establish HMGB2 as a novel master regulator that orchestrates SASP through preventing heterochromatin spreading to allow for exclusion of SASP gene loci from a global heterochromatin environment during senescence.

ORGANISM(S): Homo sapiens

PROVIDER: GSE85057 | GEO | 2016/10/11

SECONDARY ACCESSION(S): PRJNA336027

REPOSITORIES: GEO

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Homo sapiens

Project description:HMGB2 orchestrates the chromatin landscape of senescence-associated secretory phenotype gene loci.

| PRJNA336027 | ENA

Independence of Repressive Histone Marks and Chromatin Compaction during Senescent Heterochromatic Layer Formation

Project description:The expansion of repressive epigenetic marks has been implicated in heterochromatin formation during embryonic development, but the general applicability of this mechanism is unclear. Here we show that nuclear rearrangement of repressive histone marks H3K9me3 and H3K27me3 into non-overlapping structural layers characterizes senescence-associated heterochromatic foci (SAHF) formation in human fibroblasts. However, the global landscape of these repressive marks remains unchanged upon SAHF formation, suggesting that in somatic cells heterochromatin can be formed through the spatial repositioning of pre-existing repressively marked histones. This model is reinforced by the correlation of pre-senescent replication timing with both the subsequent layered structure of SAHFs and the global landscape of the repressive marks, allowing us to integrate microscopic and genomic information. Furthermore, modulation of SAHF structure does not affect the occupancy of these repressive marks nor vice versa. These experiments reveal that high-order heterochromatin formation and epigenetic remodeling of the genome can be discrete events. Profile comparison of normal growing (control) and Ras-induced senescent IMR90 cells.

2012-06-30 | E-GEOD-38460 | biostudies-arrayexpress

DNMT1 drives 4D genome rewiring during oncogene induced senescence

Project description:While, transcriptional and epigenetic changes associated senescence processes are well studied, the 3D chromatin changes associated with it remains elusive. In this study, we have generated genome wide chromatin interaction maps (Hi-C), epigenetic (ChIP-Seq), replication-timing and gene expression (RNA-Seq) profiles from replication induced (RS) and oncogene induced (OIS) senescent cells. As senescence associated heterochromatin foci (SAHFs) differentiates both RS and OIS nuclei, we identified the regions that constitute SAHFs and called them Senescence Associated Heterochromatin Domains (SAHDs). Further, screening of candidate factors for SAHF induction allowed us to identify DNMT1 as a novel component that induces SAHFs by stimulation of HMGA2 expression. DNMT1 depletion does not reverse the senescence process, however, instead, depleted cells transition to a 3D genome conformation akin to that of cells in replicative senescence, suggesting that acute senescence induction (OIS) involves SAHF formation in addition to the RS-dependent 3D genome rewiring.

2020-03-27 | GSE130306 | GEO

Redistribution of the Lamin B1 genomic binding profile affects spatial rearrangement of heterochromatic domains and gene expression during senescence

Project description:Senescence is a stress responsive form of stable cell cycle exit. Senescent cells have a distinct gene expression profile, which is often accompanied by the spatial redistribution of heterochromatin into senescence-associated heterochromatic foci (SAHFs). Studying a key component of the nuclear lamina, lamin B1 (LMNB1), we report dynamic alterations in its genomic profile and their implications for SAHF formation and gene regulation during senescence. Genome-wide mapping reveals that LMNB1 is depleted during senescence, preferentially from the central regions of lamina-associated domains (LADs), which are enriched for H3K9me3. LMNB1 knockdown facilitates the spatial relocalization of perinuclear H3K9me3, thus promoting SAHF formation, which is inhibited by ectopic LMNB1 expression. Furthermore, despite the global reduction in LMNB1 protein levels, LMNB1 binding increases during senescence in a small subset of gene-rich regions where H3K27me3 also increases and gene expression becomes repressed. These results suggest that LMNB1 may contribute to senescence in at least two ways due to its uneven genomewide redistribution: firstly through the spatial re-organization of chromatin and, secondly, through gene repression. ChIP-seq for Lamin B1 in Growing and Ras Induced Senescence

2013-08-22 | E-GEOD-49341 | biostudies-arrayexpress

HMGB2 in endocrine resistant breast cancer

Project description:HMGB2 and ER ChIPseq was investigated in the MCF-7 endocrine sensitive and LY2 endocrine resistant cell lines upon treatment with Tamoxifen.

2014-09-18 | E-MTAB-1865 | biostudies-arrayexpress

Independence of Repressive Histone Marks and Chromatin Compaction during Senescent Heterochromatic Layer Formation (mRNA)

Project description:The expansion of repressive epigenetic marks has been implicated in heterochromatin formation during embryonic development, but the general applicability of this mechanism is unclear. Here we show that nuclear rearrangement of repressive histone marks H3K9me3 and H3K27me3 into non-overlapping structural layers characterizes senescence-associated heterochromatic foci (SAHF) formation in human fibroblasts. However, the global landscape of these repressive marks remains unchanged upon SAHF formation, suggesting that in somatic cells heterochromatin can be formed through the spatial repositioning of pre-existing repressively marked histones. This model is reinforced by the correlation of pre-senescent replication timing with both the subsequent layered structure of SAHFs and the global landscape of the repressive marks, allowing us to integrate microscopic and genomic information. Furthermore, modulation of SAHF structure does not affect the occupancy of these repressive marks nor vice versa. These experiments reveal that high-order heterochromatin formation and epigenetic remodeling of the genome can be discrete events. mRNA expression profiles were compared between normal growing (control) and Ras-induced senescent IMR90 cells. Each includes 5 biological replicates.

2012-07-08 | E-GEOD-38410 | biostudies-arrayexpress

Topological demarcation by HMGB2 is disrupted early upon senescence entry and induces CTCF clustering across cell types [DROP-seq]

Project description:Ageing-relevant processes, like cellular senescence, are characterized by complex, often stochastic, effects giving rise to heterogeneous cell populations. We hypothesized that entry into senescence by different primary human cells can be triggered by one early molecular event affecting the spatial organization of chromosomes. To test this, we combined whole-genome chromosome conformation capture, population and single-cell transcriptomics, super-resolution imaging, and functional analyses applied on proliferating and replicatively-senescent populations from three distinct human cell types. We found a number of genes involved in DNA conformation maintenance being suppressed upon senescence across cell types. Of these, the abundant HMGB1 and HMGB2 nuclear factors are quantitatively removed from cell nuclei before typical senescence markers appear, and mark a subset of topologically-associating domain (TAD) boundaries. Their loss coincides with obvious reorganization of chromatin interactions via the dramatic spatial clustering of CTCF foci. HMGB2 knock-down recapitulates this senescence-induced CTCF clustering, while also affecting insulation at TAD boundaries. We accordingly propose that HMGB-mediated deregulation of chromosome conformation constitutes a primer for the ensuing senescent program across cell types.

2018-04-25 | GSE102090 | GEO

HMGB2 is important for liver regeneration through transient accumulation of lipid droplets in hepatocytes

Project description:Liver regeneration is an well orchestrated compensatory process that regulated by multiple factors. We recently reported the importance of chromatin protein, a high-mobility group box 2 (HMGB2) in mouse liver regeneration, however, it’s molecular mechanism is not yet understood. In this study, we aimed to study how HMGB2 regulates hepatocyte proliferation during liver regeneration. Wild-type (WT) and HMGB2-knockout (KO) mice were 70% partial hepatectomized (PHx), and liver tissues were analyzed by microarray, immunohistochemistry, qPCR and western blotting. In vivo experimental findings were confirmed by in vitro experiments using HMGB2 gene knockdown in combination with de novo lipogenesis model. In WT mouse, HMGB2-positive hepatocytes were co-localized with cell proliferation markers, whereas, hepatocyte proliferation was significantly decreased in HMGB2-KO mice. Oil red-O staining detected the transient accumulation of lipid droplets at 12-24 h in WT mouse livers, however, decreased amount of lipid droplets were found in HMGB2-KO mouse livers, and it was prolonged until 36 h. Microarray, immunohistochemistry and qPCR results were demonstrated that lipid metabolism related genes were significantly decreased in HMGB2-KO mouse livers. In vitro experiments demonstrated that decreased lipid droplets in HMGB2-knockdown cells correlated with decreased cell proliferation activity. HMGB2 is involved in the regulation of liver regeneration through transient accumulation of lipid droplets in hepatocytes.

2023-10-14 | GSE244551 | GEO

A 5’ Sequence of Human HMGB2 Gene for Transcriptional Targeting of Glioblastoma

Project description:Achievement of specific tumor cell targeting remains a challenge for glioma gene therapy. We report here the identification and characterization of a 5’ sequence of human HMGB2 gene for transcriptional targeting to glioblastoma. We performed microarray analysis and found HMGB2 as one of the genes that had a low level of expression in normal human astrocytes, but was significantly up-regulated in glioblastoma cells. Real-time PCR quantification revealed increase in HMBG2 expression level in glioblastoma tissues and cells between 11 to 79 fold over that in normal human brain tissue. With progressive truncation of a 5’-upstream sequence of the HMGB2 gene, we identified a 500-bp fragment that displayed a high transcriptional activity in glioblastoma cells, but a low activity in normal brain cells. Using the sequence to drive the expression of the herpes simplex virus thymidine kinase gene in the context of a baculoviral vector, glioblastoma cells died in the presence of ganciclovir, whereas normal human astrocytes and neurons were not affected. We further confirmed that after intra-tumor injection, the baculoviral vector effectively suppressed the growth of human glioblastoma cells in a mouse xenograft model. Our results suggest that the 5’-upstream sequence of the HMGB2 gene can be used as an efficient, tumor-selective promoter in targeted vectors for glioblastoma gene therapy. U251 cells (n=3) genes level expression were compared to that of normal astrocytes (n=3) to find overexpressed genes in glioblastoma. Highly expressed genes were compared to those found in the litterature. This was selected to clone promoters of highly expressed genes in glioblastomas

2008-12-31 | E-GEOD-12305 | biostudies-arrayexpress

Spatiotemporal expression of HMGB2 regulates cell proliferation and hepatocyte size during liver regeneration

Project description:Liver regeneration is an extraordinarily complex process involving a variety of factors; however, the role of chromatin protein in hepatocyte proliferation is largely unknown. In this study, we investigated the functional role of high-mobility group box 2 (HMGB2), a chromatin protein in liver regeneration using wild-type and HMGB2-knockout (KO) mice. Liver tissues were sampled after 70% partial hepatectomy (PHx), and analyzed by immunohistochemistry using various markers of cell proliferation, including Ki-67, PCNA, cyclin D1, cyclin B1, EdU and pH3S10. In WT mice, hepatocyte proliferation was strongly correlated with the spatiotemporal expression of HMGB2; however, cell proliferation was significantly delayed in hepatocytes of HMGB2-KO mice. Quantitative PCR demonstrated that cyclin D1 and cyclin B1 mRNAs were significantly decreased in HMGB2-KO mice livers. Interestingly, hepatocyte size was significantly larger in HMGB2-KO mice at 36-72 h after PHx, and these results suggest that hepatocyte hypertrophy appeared in parallel with delayed cell proliferation. In vitro experiments demonstrated that cell proliferation was significantly decreased in HMGB2-KO cells. A significant delay in cell proliferation was also found in HMGB2-siRNA transfected cells. In summary, spatiotemporal expression of HMGB2 is important for regulation of hepatocyte proliferation and cell size during liver regeneration.

2022-04-03 | GSE199944 | GEO

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