Project description:The eukaryotic genome is organized into chromatin, which constitutes the physiological template for DNA-dependent processes including replication, recombination, repair and transcription. Chromatin mediated transcription regulation involves histone modifications, chromatin remodeling and DNA methylation. However, the precise biological function of non-histone chromatin-associated proteins is still unclear. The high mobility group proteins are the most abundant non-histone chromatin-associated proteins. Here we combined proteomic, ChIP-seq and transcriptome data to decipher the mechanism of transcriptional regulation mediated by the high mobility group AT-hook protein 2 (HMGA2). We showed that HMGA2-induced transcription requires H2AX phosphorylation at S139 (H2AXS139ph; γ-H2AX), mediated by the kinase ataxia telangiectasia mutated (ATM). Furthermore, we demonstrated the relevance of this mechanism within the biological context of TGFB1-signaling. Our results link H2AXS139ph, a marker for DNA damage, to transcription, which is a new function for this histone modification. The interplay between HMGA2, ATM and H2AX is a novel mechanism of transcription initiation.
Project description:The eukaryotic genome is organized into chromatin, which constitutes the physiological template for DNA-dependent processes including replication, recombination, repair and transcription. Chromatin mediated transcription regulation involves histone modifications, chromatin remodeling and DNA methylation. However, the precise biological function of non-histone chromatin-associated proteins is still unclear. The high mobility group proteins are the most abundant non-histone chromatin-associated proteins. Here we combined proteomic, ChIP-seq and transcriptome data to decipher the mechanism of transcriptional regulation mediated by the high mobility group AT-hook protein 2 (HMGA2). We showed that HMGA2-induced transcription requires H2AX phosphorylation at S139 (H2AXS139ph; γ-H2AX), mediated by the kinase ataxia telangiectasia mutated (ATM). Furthermore, we demonstrated the relevance of this mechanism within the biological context of TGFB1-signaling. Our results link H2AXS139ph, a marker for DNA damage, to transcription, which is a new function for this histone modification. The interplay between HMGA2, ATM and H2AX is a novel mechanism of transcription initiation. Chip-seq data of HMGA2, H2AXS139ph and ATM obtained from Mouse embryonic Fibroblast cells in wt and Ko of Hmga2
Project description:The eukaryotic genome is organized into chromatins, the physiological template for DNA-dependent processes including replication, recombination, repair, and transcription. Chromatin-mediated transcription regulation involves DNA methylation, chromatin remodeling, and histone modifications. However, chromatin also contains non-histone chromatin-associated proteins, of which the high-mobility group (HMG) proteins are the most abundant. Although it is known that HMG proteins induce structural changes of chromatin, the processes underlying transcription regulation by HMG proteins are poorly understood. Here we decipher the molecular mechanism of transcription regulation mediated by the HMG AT-hook 2 protein (HMGA2). We combined proteomic, ChIP-seq, and transcriptome data to show that HMGA2-induced transcription requires phosphorylation of the histone variant H2AX at S139 (H2AXS139ph; γ-H2AX) mediated by the protein kinase ataxia telangiectasia mutated (ATM). Furthermore, we demonstrate the biological relevance of this mechanism within the context of TGFβ1 signaling. The interplay between HMGA2, ATM, and H2AX is a novel mechanism of transcription initiation. Our results link H2AXS139ph to transcription, assigning a new function for this DNA damage marker. Controlled chromatin opening during transcription may involve intermediates with DNA breaks that may require mechanisms that ensure the integrity of the genome.
Project description:Phosphorylation of the histone variant H2AX forms γ-H2AX that marks DNA double-strand break (DSB). Here we generated the sequencing-based maps of H2AX and γ-H2AX positioning in resting and proliferating cells before and after ionizing irradiation. Genome-wide locations of possible endogenous and exogenous DSBs were identified based on γ-H2AX distribution in dividing cancer cells without irradiation and that in resting cells upon irradiation, respectively. γ-H2AX-enriched regions of endogenous origin in replicating cells included telomeres and active transcription start sites, apparently reflecting replication- and transcription-mediated stress during rapid cell division. Surprisingly, H2AX itself, prior to phosphorylation, was specifically located at these endogenous hotspots. This phenomenon was only observed in dividing cancer cells but not in resting cells. Endogenous H2AX was concentrated on the transcription start site of actively transcribed genes but was irrelevant to pausing of RNA polymerase II (pol II), which precisely coincided with γ-H2AX of endogenous origin. γ-H2AX enrichment upon irradiation also coincided with actively transcribed regions, but unlike endogenous γ-H2AX, it extended into the gene body and was not specifically concentrated on the pausing site of pol II. Subtelomeres were not responsive to external DNA damage. Our findings provide insight into DNA repair programs of cancer and may have implications for cancer therapy.
Project description:Phosphorylation of the histone variant H2AX forms γ-H2AX, which serves as a marker of DNA repair response. Here we provide ChIP-seq-based maps of histone H2AX, γ-H2AX, H2AZ, INO80, SRCAP, and RNA polymerase II in activated T cells. Matched data for H2AX and γ-H2AX in resting T cells and Jurkat cancer T cells are available in GSE25577.
Project description:Phosphorylation of histone H2AX is an early response to DNA damage in eukaryotes. In Saccharomyces cerevisiae, DNA damage or replication fork stalling results in histone H2A phosphorylation to yield gamma-H2A (yeast gamma-H2AX) in a Mec1 (ATR)- and Tel1 (ATM)- dependent manner. Here, we describe the genome-wide location analysis of gamma-H2A as a strategy to identify loci prone to engage the Mec1 and Tel1 pathways. Remarkably, gamma-H2A enrichment overlaps with loci prone to replication fork stalling and is caused by the action of Mec1 and Tel1, indicating that these loci are prone to breakage. Moreover, about half the sites enriched for gamma-H2A map to repressed protein-coding genes, and histone deacetylases are necessary for formation of gamma-H2A at these loci. Finally, our work indicates that high resolution mapping of gamma-H2AX is a fruitful route to map fragile sites in eukaryotic genomes.
Project description:Phosphorylation of the histone variant H2AX forms M-NM-3-H2AX that marks DNA double-strand break (DSB). Here we generated the sequencing-based maps of H2AX and M-NM-3-H2AX positioning in resting and proliferating cells before and after ionizing irradiation. Genome-wide locations of possible endogenous and exogenous DSBs were identified based on M-NM-3-H2AX distribution in dividing cancer cells without irradiation and that in resting cells upon irradiation, respectively. M-NM-3-H2AX-enriched regions of endogenous origin in replicating cells included telomeres and active transcription start sites, apparently reflecting replication- and transcription-mediated stress during rapid cell division. Surprisingly, H2AX itself, prior to phosphorylation, was specifically located at these endogenous hotspots. This phenomenon was only observed in dividing cancer cells but not in resting cells. Endogenous H2AX was concentrated on the transcription start site of actively transcribed genes but was irrelevant to pausing of RNA polymerase II (pol II), which precisely coincided with M-NM-3-H2AX of endogenous origin. M-NM-3-H2AX enrichment upon irradiation also coincided with actively transcribed regions, but unlike endogenous M-NM-3-H2AX, it extended into the gene body and was not specifically concentrated on the pausing site of pol II. Subtelomeres were not responsive to external DNA damage. Our findings provide insight into DNA repair programs of cancer and may have implications for cancer therapy. Profiles of H2AX and gamma-H2AX in normal resting and cancer T cells with and without ionizing irradiation.
Project description:In Saccharomyces cerevisiae, a single double-strand break (DSB) triggers extensive phosphorylation of histone H2A (known as gammaH2AX) over 50 kb on either side of the DSB. This modification is carried out by either of yeastM-^Rs checkpoint kinases, the ATM homolog, Tel1, or the ATR homolog, Mec1. In G1-arrested cells, where there is very little 5M-^R to 3M-^R processing of DSB ends, only Tel1 promotes this modification. We have recently described a second modification gammaH2B - the phosphorylation of the C terminal T129 locus of histone H2B which is also carried out by both Mec1 and Tel1 kinases. To understand in detail how gamma-H2AX and gamma-H2B spread along the chromosome from a DSB we have undertaken a high-density analysis of their occupancy where there is a DSB on three different chromosomes. gamma-H2AX and gamma-H2B modifications are similar, but there is a marked absence of gamma-H2B near telomeres. We find that there is reduced gamma-H2AX and gamma-H2B modification over strongly transcribed regions, even taking into account the reduced histone occupancy of these genes. When transcription of the galactose-regulated genes GAL1, GAL10, GAL7 are turned off by the addition of glucose, gamma-H2AX is restored within 5 min; when these genes are again induced, gamma-H2AX is rapidly lost. Regions more distal to the GAL genes have markedly reduced gamma-H2AX levels that rise rapidly when transcription is repressed, suggesting that transcription acts as a barrier to the propagation of gamma-H2AX away from the DSB. The restoration of gamma-H2AX in transcribed regions can be carried out by either Mec1 or Tel1, even 7 h after break induction, suggesting that Tel1 remains associated with damaged chromosomes for an extended time. In addition, we show that gamma-H2AX can be transferred in trans, to regions unlinked to the DSB that lie in close proximity the DSB. Specifically, if a DSB is generated 14 kb from CEN2, gamma-H2AX is transferred to regions around all the other centromeres, in keeping with observed close proximity of all centromere-adjacent chromosome arms. This transfer can be observed even in the absence of formaldehyde crosslinking of the samples.
Project description:DNA double strand breaks (DSBs) in B lymphocytes are thought to arise stochastically during replication (S phase) or as a result of targeted DNA damage by activation induced cytidine deaminase (AID) in G1. Here we identify a novel class of recurrent, early replicating and AID independent DNA lesions, termed early replication fragile sites (ERFS), by genome-wide localization of DNA repair proteins DNA double strand breaks (DSBs) in B lymphocytes are thought to arise stochastically during replication (S phase) or as a result of targeted DNA damage by activation induced cytidine deaminase (AID) in G1. Here we identify a novel class of recurrent, early replicating and AID independent DNA lesions, termed early replication fragile sites (ERFS), by genome-wide localization of DNA repair proteins DNA double strand breaks (DSBs) in B lymphocytes are thought to arise stochastically during replication (S phase) or as a result of targeted DNA damage by activation induced cytidine deaminase (AID) in G1. Here we identify a novel class of recurrent, early replicating and AID independent DNA lesions, termed early replication fragile sites (ERFS), by genome-wide localization of DNA repair proteins RPA, SMC5, gamma-H2AX, and BRCA1 in B cells subjected to replication stress. Protein-DNA association for four DNA damage response proteins (RPA, SMC5, g-H2AX, BRCA1), BrdU incorporation, and gene transcription in B lymphocytes with and without hydroxyurea treatment were examined.
Project description:Mutant ataxin-1 (Atxn1), which causes spinocerebellar ataxia type 1 (SCA1), binds to and impairs the function of high mobility group box 1 (HMGB1), a critical nuclear protein that regulates DNA architectural changes essential for DNA damage repair and transcription. In this study, we established that transgenic or virus vector-mediated supplementation of HMGB1 ameliorates motor dysfunction and elongates lifespan in mutant Atxn1 knock-in (Atxn1-KI) mice. We identified mitochondrial DNA damage repair by HMGB1 as a novel molecular basis for this effect, in addition to the mechanisms already associated with HMGB1 function, such as nuclear DNA damage repair and nuclear transcription. The dysfunction and the improvement of mitochondrial DNA damage repair functions are tightly associated with the exacerbation and rescue, respectively, of symptoms, supporting the involvement of mitochondrial DNA quality control by HMGB1 in SCA1 pathology. Moreover, we show that the rescue of Purkinje cell dendrites and dendritic spines by HMGB1 could be downstream effects. Although extracellular HMGB1 triggers inflammation mediated by toll-like receptor and receptor for advanced glycation end products, upregulation of intracellular HMGB1 does not induce such side effects. Thus, viral delivery of HMGB1 is a candidate approach by which to modify the disease progression of SCA1 even after its onset.