Histone Variant Research Articles

HSV-1 exploits host heterochromatin for nuclear egress.

Herpes simplex virus (HSV-1) progeny form in the nucleus and exit to successfully infect other cells. Newly formed capsids navigate complex chromatin architecture to reach the inner nuclear membrane (INM) and egress. Here, we demonstrate by transmission electron microscopy (TEM) that HSV-1 capsids traverse heterochromatin associated with trimethylation on histone H3 lysine 27 (H3K27me3) and the histone variant macroH2A1. Through chromatin profiling during infection, we revealed global redistribution of these marks whereby massive host genomic regions bound by macroH2A1 and H3K27me3 correlate with decreased host transcription in active compartments. We found that the loss of these markers resulted in significantly lower viral titers but did not impact viral genome or protein accumulation. Strikingly, we discovered that loss of macroH2A1 or H3K27me3 resulted in nuclear trapping of capsids. Finally, by live-capsid tracking, we quantified this decreased capsid movement. Thus, our work demonstrates that HSV-1 takes advantage of the dynamic nature of host heterochromatin formation during infection for efficient nuclear egress.

A long non-coding RNA essential for early embryonic development improves SCNT efficiency in goats.

Although abundant long non-coding RNAs (lncRNAs) have been found to be highly expressed in early embryos, the functions and mechanisms of most lncRNAs in regulating embryonic development remain unclear. This study was conducted to identify the key lncRNAs during embryonic genome activation (EGA) for promoting embryonic development after somatic cell nuclear transfer (SCNT) in goats. We screened and characterized lncRNAs from transcriptome data of in vitro-fertilized, 2-cell (IVF-2c) and 8-cell embryos (IVF-8c) and 8-cell SCNT embryos (SCNT-8c). We obtained 12 differentially expressed lncRNAs that were highly expressed in IVF-8c embryos compared to IVF-2c, and less expressed in SCNT-8c embryos. After target gene prediction, expression verification, and functional deletion experiments, we found that the expression level of lncRNA3720 affected the early embryonic development in goats. We cloned full length lncRNA3720 and over-expressed it in goat fetal fibroblasts (GFFs). We identified histone variants by analyzing the transcriptome data from both GFFs and embryos. Gene annotation of the gene library and literature search revealed that histone variants may have important roles in early embryo development, so we selected them as the potential target genes for lncRNA3720. Lastly, we compensated for the low expression of lncRNA3720 in SCNT embryos by microinjection, and showed that the development rate and quality of SCNT embryos was significantly improved. We speculate that lncRNA3720 is a key promoter of embryonic development in goats by interacting with histone variants.

Histone variants shape chromatin states in Arabidopsis.

How different intrinsic sequence variations and regulatory modifications of histones combine in nucleosomes remain unclear. To test the importance of histone variants in the organization of chromatin we investigated how histone variants and histone modifications assemble in the Arabidopsis thaliana genome. We showed that a limited number of chromatin states divide euchromatin and heterochromatin into several subdomains. We found that histone variants are as significant as histone modifications in determining the composition of chromatin states. Particularly strong associations were observed between H2A variants and specific combinations of histone modifications. To study the role of H2A variants in organizing chromatin states we determined the role of the chromatin remodeler DECREASED IN DNA METHYLATION (DDM1) in the organization of chromatin states. We showed that the loss of DDM1 prevented the exchange of the histone variant H2A.Z to H2A.W in constitutive heterochromatin, resulting in significant effects on the definition and distribution of chromatin states in and outside of constitutive heterochromatin. We thus propose that dynamic exchanges of histone variants control the organization of histone modifications into chromatin states, acting as molecular landmarks.

Histone variants shape chromatin states in Arabidopsis

How different intrinsic sequence variations and regulatory modifications of histones combine in nucleosomes remain unclear. To test the importance of histone variants in the organization of chromatin we investigated how histone variants and histone modifications assemble in the Arabidopsis thaliana genome. We showed that a limited number of chromatin states divide euchromatin and heterochromatin into several subdomains. We found that histone variants are as significant as histone modifications in determining the composition of chromatin states. Particularly strong associations were observed between H2A variants and specific combinations of histone modifications. To study the role of H2A variants in organizing chromatin states we determined the role of the chromatin remodeler DECREASED IN DNA METHYLATION (DDM1) in the organization of chromatin states. We showed that the loss of DDM1 prevented the exchange of the histone variant H2A.Z to H2A.W in constitutive heterochromatin, resulting in significant effects on the definition and distribution of chromatin states in and outside of constitutive heterochromatin. We thus propose that dynamic exchanges of histone variants control the organization of histone modifications into chromatin states, acting as molecular landmarks.

H3.3B controls aortic dissection progression by regulating vascular smooth muscle cells phenotypic transition and vascular inflammation

Aortic dissection is a devastating cardiovascular disease with a high lethality. Histone variants maintain the genomic integrity and play important roles in development and diseases. However, the role of histone variants in aortic dissection has not been well identified. In the present study, H3f3b knockdown reduced the synthetic genes expression of VSMCs, while overexpressing H3f3b exacerbated the cellular immune response of VSMCs induced by inflammatory cytokines. Combined RNA-seq and ChIP-seq analyses revealed that histone variant H3.3B directly bound to the genes related to extracellular matrix, VSMC synthetic phenotype, cytokine responses and TGFβ signaling pathway, and regulated their expressions. In addition, VSMC-specific H3f3b knockin aggravated aortic dissection development in mice, while H3f3b knockout significantly reduced the incidence of aortic dissection. In term of mechanisms, H3.3B regulated Spp1 and Ccl2 genes, inducing the apoptosis of VSMCs and recruiting macrophages. This study demonstrated the vital roles of H3.3B in phenotypic transition of VSMCs, loss of media VSMCs, and vascular inflammation in aortic dissection.

Spontaneous histone exchange between nucleosomes

The nucleosome is the fundamental gene-packing unit in eukaryotes. Nucleosomes comprise ∼147bp DNA wrapped around an octameric histone protein core composed of two H2A-H2B dimers and one (H3-H4)2 tetramer. The strong yet flexible DNA-histone interactions are the physical basis of the dynamic regulation of genes packaged in chromatin. The dynamic nature of DNA-histone interactions also implies thatnucleosomes dissociate DNA-histone contacts both transiently and repeatedly. This kinetic instability may lead to spontaneous nucleosome disassembly or histone exchange between nucleosomes. At high nucleosome concentrations, nucleosome-nucleosome collisions and subsequent histone exchange would be a more likely event, where nucleosomes could act as their own histone chaperone. This spontaneous histone exchange could serve as a mechanism for maintaining overall chromatin stability, although it has never been reported. Here we employed three-color single-molecule FRET (smFRET) to demonstrate that histone H2A-H2B dimers are exchanged spontaneously between nucleosomes on a time scale of a few tens of seconds at a physiological nucleosome concentration. We show that the rate of histone exchange increases at a higher monovalent salt concentration, with histone-acetylated nucleosomes, and in the presence of histone chaperone Nap1, while it remains unchanged at a higher temperature, and decreases upon DNA methylation. These results support the notion of histone exchange via transient and repetitive partial disassembly of the nucleosome and corroborate spontaneous histone diffusion in a compact chromatin context, modulating the local concentrations of histone modifications and variants.

Involvement of the H3.3 Histone Variant in the Epigenetic Regulation of Gene Expression in the Nervous System, in Both Physiological and Pathological Conditions.

All the cells of an organism contain the same genome. However, each cell expresses only a minor fraction of its potential and, in particular, the genes encoding the proteins necessary for basal metabolism and the proteins responsible for its specific phenotype. The ability to use only the right and necessary genes involved in specific functions depends on the structural organization of the nuclear chromatin, which in turn depends on the epigenetic history of each cell, which is stored in the form of a collection of DNA and protein modifications. Among these modifications, DNA methylation and many kinds of post-translational modifications of histones play a key role in organizing the complex indexing of usable genes. In addition, non-canonical histone proteins (also known as histone variants), the synthesis of which is not directly linked with DNA replication, are used to mark specific regions of the genome. Here, we will discuss the role of the H3.3 histone variant, with particular attention to its loading into chromatin in the mammalian nervous system, both in physiological and pathological conditions. Indeed, chromatin modifications that mark cell memory seem to be of special importance for the cells involved in the complex processes of learning and memory.

MsaH2A.W is identified response to salt tolerance in Miscanthus sacchariflorus

AbstractMiscanthus is a perennial forage plant with great potential for high stress tolerance and biomass yield. It has strong adaptability for growing in saline land and avoids competition with grain crops in arable lands. However, little is known about the underlying genetic basis of Miscanthus adaptation to salt stress. Two diploid species of the genus Miscanthus, Miscanthus sinensis and Miscanthus sacchariflorus, were the focus of this study. The transcriptome variations of these varieties and their hybrid were analysed using RNA‐seq technology under salt treatment. The number of differentially expressed genes in M. sinensis was much higher than that in M. sacchariflorus and their hybrid under salt stress, which indicated that M. sacchariflorus and their hybrid require less transcriptional variation. In addition, most salt‐tolerant genes in the enriched salt‐tolerant pathways were induced in the roots of M. sinensis and constitutively highly expressed in the roots of M. sacchariflorus and their hybrid under salt stress. According to this expression pattern of known salt‐tolerant genes, a histone variant gene MsaH2A.W of M. sacchariflorus was mined and consequently proved for the first time that it could enhance the salt tolerance of transgenic Arabidopsis plants. Overall, this study provides valuable genetic resources for studying the underlying genetic basis of salt stress resistance in Miscanthus. Identification of the salt tolerance gene MsaH2A.W can promote the genetic improvement and molecular breeding of salt‐resistant species.

Histone exchange sensors reveal variant specific dynamics in mouse embryonic stem cells

Eviction of histones from nucleosomes and their exchange with newly synthesized or alternative variants is a central epigenetic determinant. Here, we define the genome-wide occupancy and exchange pattern of canonical and non-canonical histone variants in mouse embryonic stem cells by genetically encoded exchange sensors. While exchange of all measured variants scales with transcription, we describe variant-specific associations with transcription elongation and Polycomb binding. We found considerable exchange of H3.1 and H2B variants in heterochromatin and repeat elements, contrasting the occupancy and little exchange of H3.3 in these regions. This unexpected association between H3.3 occupancy and exchange of canonical variants is also evident in active promoters and enhancers, and further validated by reduced H3.1 dynamics following depletion of H3.3-specific chaperone, HIRA. Finally, analyzing transgenic mice harboring H3.1 or H3.3 sensors demonstrates the vast potential of this system for studying histone exchange and its impact on gene expression regulation in vivo.

Promoter-proximal nucleosomes attenuate RNA polymerase II transcription through TFIID

A nucleosome is typically positioned with its proximal edge (NPE) ∼50bp downstream from the transcription start site of metazoan RNA polymerase II promoters. This+1 nucleosome has distinctive characteristics, including the presence of variant histone types and trimethylation of histone H3 at lysine 4. To address the role of these features in transcription complex assembly, we generated templates with four different promoters and nucleosomes located at a variety of downstream positions, which were transcribed invitro using HeLa nuclear extracts. Two promoters lacked TATA elements, but all supported strong initiation from a single transcription start site. In contrast to results with minimal invitro systems based on the TATA-binding protein (TBP), TATA promoter templates with a+51 NPE were transcriptionally inhibited in extracts; activity continuously increased as the nucleosome was moved downstream to+100. Inhibition was much more pronounced for the TATA-less promoters:+51 NPE templates were inactive, and substantial activity was only seen with the+100 NPE templates. Substituting the histone variants H2A.Z, H3.3, or both did not eliminate the inhibition. However, addition of excess TBP restored activity on nucleosomal templates with TATA promoters, even with an NPE at+20. Remarkably, nucleosomal templates with histone H3 trimethylated at lysine 4 are active with an NPE at+51 for both TATA and TATA-less promoters. Our results strongly suggest that the+1 nucleosome interferes with promoter recognition by TFIID. This inhibition can be overcome with TBP alone at TATA promoters or through positive interactions with histone modifications and TFIID.

Nerve Injury-Induced γH2AX Reduction in Primary Sensory Neurons Is Involved in Neuropathic Pain Processing.

Phosphorylation of the serine 139 of the histone variant H2AX (γH2AX) is a DNA damage marker that regulates DNA damage response and various diseases. However, whether γH2AX is involved in neuropathic pain is still unclear. We found the expression of γH2AX and H2AX decreased in mice dorsal root ganglion (DRG) after spared nerve injury (SNI). Ataxia telangiectasia mutated (ATM), which promotes γH2AX, was also down-regulated in DRG after peripheral nerve injury. ATM inhibitor KU55933 decreased the level of γH2AX in ND7/23 cells. The intrathecal injection of KU55933 down-regulated DRG γH2AX expression and significantly induced mechanical allodynia and thermal hyperalgesia in a dose-dependent manner. The inhibition of ATM by siRNA could also decrease the pain threshold. The inhibition of dephosphorylation of γH2AX by protein phosphatase 2A (PP2A) siRNA partially suppressed the down-regulation of γH2AX after SNI and relieved pain behavior. Further exploration of the mechanism revealed that inhibiting ATM by KU55933 up-regulated extracellular-signal regulated kinase (ERK) phosphorylation and down-regulated potassium ion channel genes, such as potassium voltage-gated channel subfamily Q member 2 (Kcnq2) and potassium voltage-gated channel subfamily D member 2 (Kcnd2) in vivo, and KU559333 enhanced sensory neuron excitability in vitro. These preliminary findings imply that the down-regulation of γH2AX may contribute to neuropathic pain.

DIPG-35. IDENTIFYING DRIVER-SPECIFIC VULNERABILITIES IN PAEDIATRIC HIGH GRADE GLIOMA SUBTYPES

Abstract Paediatric high-grade gliomas (pHGGs) are incurable malignant brain tumours and a leading cause of cancer-related death in children. The majority of pHGGs carry lysine-to-methionine (K27M) or glycine-to-arginine/valine (G34R/V) mutations in histone variants H3.1 or H3.3. Moreover, histone mutations associate with different anatomical locations and co-segregating mutations defining distinct tumour subtypes within pHGG. However whether these co-occuring mutations can act as drivers to modify tumour phenotypes and drug sensitivities is currently unknown. In order to functionally evaluate the role of partner alterations and to identify new therapeutic targets, we developed in vivo tumour models of pHGG subtypes using in utero electroporation (IUE) in combination with piggyBac transposon and CRISPR technology. We also established ex vivo glioma stem cell (GSCs) lines from mouse models with different co-segregating mutations, able to engraft in syngeneic immune-competent mice. Then, we performed transcriptome analysis and drug screening identifying selective pharmacological vulnerabilities. Our approach represents a preclinical platform to evaluate subtype-specific precision therapies identifying new pathways involved in brain tumour initiation, progression and maintenance.

DIPG-21. LINKING DETERMINATION OF CELL FATE IN THE DEVELOPING CENTRAL NERVOUS SYSTEM TO DIFFUSE MIDLINE GLIOMA

Abstract Diffuse midline glioma, K27-altered (DMG) is a treatment resistant, uniformly fatal cancer that arises predominantly in children. Next-generation sequencing has revealed that the majority of patients with DMG harbor K27M mutations in canonical histone variants H3.1 and H3.3, leading to global epigenetic dysregulation and an oligodendrocyte precursor cell (OPC) transcriptional profile. DLX2 is a homeobox transcription factor that directly represses OPC cell fate and promotes a GABAergic interneuron cell fate during neurogenesis. We identified DLX2 occupancy of early (Olig2, Nkx2.2) and late (Myt1, Plp1) genes required in OPC differentiation in vivo. Co-expression of DLX2 to target sequences reduced reporter gene expression in vitro. The Dlx1/Dlx2 double knockout (DKO) mouse showed increases in Olig2, Nkx2.2, and Plp-1 expression in vivo. Transient over-expression of a Dlx2-GFP construct into murine DMG cells resulted in significant increased expression of Gad1/2 isoforms and decreased Olig2 and Nkx2.2, global restoration of H3K27me3, as well as a reduction in migration, invasion, and colony formation in vitro. An RNAseq database containing 45 human DMG cell lines showed an inverse correlation between DLX2 expression and OLIG1/2. Cell fate changes in DLX2high/OLIG1/2low cell lines were evaluated by knockout of DLX2 using CRISPR/Cas9. Concurrently, OLIG1/2high/DLX2low expressing cell lines underwent stable transfection of an DLX2-mCherry overexpression construct. Successful alteration of DLX2 expression was confirmed by qPCR and immunoblot in knockout and overexpressing human DMG cell lines. Analysis of histone H3 marks (K27me3, K27ac), K27M, and OPC signature genes will be presented along with comparison of altered OPC genes from the Dlx1/Dlx2 DKO mouse as determined by RNAseq. The manipulation of DLX2 expression in human DMG cells both in vitro and in vivo provides a model system for assessing the contribution of a homeobox transcription factor required for neurogenesis to cell fate regulation and effects on tumorigenicity in DMG.

DIPG-48. DIPG THROUGH THE LOOKING GLASS

Abstract Diffuse intrinsic pontine glioma (DIPG) has a peculiar pathogenesis with canonical Histone variants H3.1/H3.2 wherein Lysine 27 (H3K27) is substituted to methionine (H3K27M). It is restricted to pons and affects young children whereas non canonical H3.3 mutations result in tumours across the midline and affects older children. This discrepancy in the spatiotemporal distribution provides cues to target DIPG. Based on altered neuronal signalling which is a hallmark of cancer, a deeper understanding of neuron tumour interaction may unravel numerous new targets. One such target is light. The restriction of specific spectrum of light may hinder the progression and even the development of tumours in young children. It provides a lucrative therapeutic option which can be implemented merely by blocking a certain spectrum of light with glasses in an otherwise baffling disease. It warrants a deeper understanding of the light exposure on DIPG tumour progression.

Reduced histone gene copy number disrupts Drosophila Polycomb function.

The chromatin of animal cells contains two types of histones: canonical histones that are expressed during S phase of the cell cycle to package the newly replicated genome, and variant histones with specialized functions that are expressed throughout the cell cycle and in non-proliferating cells. Determining whether and how canonical and variant histones cooperate to regulate genome function is integral to understanding how chromatin-based processes affect normal and pathological development. Here, we demonstrate that variant histone H3.3 is essential for Drosophila development only when canonical histone gene copy number is reduced, suggesting that coordination between canonical H3.2 and variant H3.3 expression is necessary to provide sufficient H3 protein for normal genome function. To identify genes that depend upon, or are involved in, this coordinate regulation we screened for heterozygous chromosome 3 deficiencies that impair development of flies bearing reduced H3.2 and H3.3 gene copy number. We identified two regions of chromosome 3 that conferred this phenotype, one of which contains the Polycomb gene, which is necessary for establishing domains of facultative chromatin that repress master regulator genes during development. We further found that reduction in Polycomb dosage decreases viability of animals with no H3.3 gene copies. Moreover, heterozygous Polycomb mutations result in de-repression of the Polycomb target gene Ubx and cause ectopic sex combs when either canonical or variant H3 gene copy number is reduced. We conclude that Polycomb-mediated facultative heterochromatin function is compromised when canonical and variant H3 gene copy number falls below a critical threshold.

Histone variant HTB4 delays leaf senescence by epigenetic control of Ib bHLH transcription factor-mediated iron homeostasis.

Leaf senescence is an orderly process regulated by multiple internal factors and diverse environmental stresses including nutrient deficiency. Histone variants are involved in regulating plant growth and development. However, their functions and underlying regulatory mechanisms in leaf senescence remain largely unclear. Here, we found that H2B histone variant HTB4 functions as a negative regulator of leaf senescence. Loss of function of HTB4 led to early leaf senescence phenotypes that were rescued by functional complementation. RNA-seq analysis revealed that several Ib subgroup basic helix-loop-helix (bHLH) transcription factors (TFs) involved in iron (Fe) homeostasis, including bHLH038, bHLH039, bHLH100, and bHLH101, were suppressed in the htb4 mutant, thereby compromising the expressions of FERRIC REDUCTION OXIDASE 2 (FRO2) and IRON-REGULATED TRANSPORTER (IRT1), two important components of the Fe uptake machinery. Chromatin immunoprecipitation-quantitative polymerase chain reaction analysis revealed that HTB4 could bind to the promoter regions of Ib bHLH TFs and enhance their expression by promoting the enrichment of the active mark H3K4me3 near their transcriptional start sites. Moreover, overexpression of Ib bHLH TFs or IRT1 suppressed the premature senescence phenotype of the htb4 mutant. Our work established a signaling pathway, HTB4-bHLH TFs-FRO2/IRT1-Fe homeostasis, which regulates the onset and progression of leaf senescence.

Bee Venom Induces the Interaction between Phosphorylated Histone Variant, H2AX, and the Intracellular Site of beta-Actin in Liver and Breast Cancer Cells.

Bee venom is a natural mixture and candidate anti-cancer agent with selective cytotoxic effect on some cancer cells. However, the cellular mechanisms of how bee venom selectively targets cancer cells remain elusive. The aim of this study was to reveal the genotoxic effect of bee venom in concordance with the location of β-actin protein throughout the nucleus or/and cytoplasm. For this aim, the level of H2AX phosphorylation (γH2AX) and intracellular location of β-actin were assessed by immunofluorescence in liver (HEPG2) and metastatic breast (MDA-MB-231) cancer cell lines compared to normal fibroblasts (NIH3T3) after bee venom treatment. Colocalisation profiles of γH2AX and β-actin in each cell line were also analysed. The results showed that the levels of γH2AX staining decreased in normal cells but increased in cancer cells. The majority of β-actin was localised within the cytoplasm of normal cells after bee venom treatment, but it was mostly accumulated within the nucleus in cancer cells. Colocalisation of β-actin and γH2AX both in nucleus and cytoplasm was induced in each cancer cell by different patterns. The results showed that normal and cancerous cells had different responses against bee venom, and suggested that bee venom induced a cellular response by the interaction between γH2AX and β-actin.

Sex‐specific accumulation and therapeutic effect of the histone variant H2A.Z in Alzheimer’s disease

AbstractBackgroundThere is growing evidence that dysregulation of gene expression plays a role in cognitive deficits and neuropathology in Alzheimer’s disease (AD), thus prompting interest in epigenetic factors as mechanisms of neurodegeneration and memory loss. Here, we assess the therapeutic potential of the histone variant H2A.Z. H2A.Z is a memory suppressor that is actively removed from DNA during learning to promote gene expression and memory formation. The memory‐suppressive effects of H2A.Z are further supported by our finding that H2A.Z levels increase in the aged brain and may act as a prelude to age‐related memory decline. We hypothesize that H2A.Z also accumulates in AD and that targeted depletion of H2A.Z is an effective therapy for memory impairment.MethodsTo characterize H2A.Z levels in the AD brain, we assessed genome wide (ChIP‐seq) and site‐specific (ChIP‐qPCR) binding of H2A.Z to DNA as well as mRNA expression of genes encoding H2A.Z in both the human post‐mortem and 5xFAD mouse hippocampus. To directly test the therapeutic potential of H2A.Z depletion, adeno‐associated virus (AAV) vector containing short hairpin RNA against H2A.Z was delivered in the hippocampus of 5xFAD mice and memory was assessed using object location and contextual fear conditioning tasks.ResultsConsistent with the hypothesis that H2A.Z accumulates in the AD brain, binding of H2A.Z increased at several memory and AD‐related genes in the human and 5xFAD female hippocampus. Interestingly, this effect was sex specific, as H2A.Z binding decreased in the male hippocampus across species. Similarly, mRNA expression of genes encoding H2A.Z increased in the human and 5xFAD female hippocampus. This female‐specific increase in H2A.Z was paralleled by the remediation of memory impairment following H2A.Z depletion in 5xFAD females but not males.ConclusionOur data are the first demonstration of histone variants as regulators of AD‐related memory impairment. The sex‐specific changes in H2A.Z generalize across species and provide promising support for H2A.Z depletion as a therapeutic strategy for AD in females.

Reduced YAP1 and FOLR1 in gliomas predict better response to chemotherapeutics

Gliomas harbouring mutations in IDH1 (isocitrate dehydrogenase 1) are characterized by greater sensitivity to chemotherapeutics. These mutants also exhibit diminished levels of transcriptional coactivator YAP1 (yes-associated protein 1). Enhanced DNA damage in IDH1 mutant cells, as evidenced by γH2AX formation (phosphorylation of histone variant H2A.X) and ATM (serine/threonine kinase; ataxia telangiectasia mutated) phosphorylation, was accompanied by reduced FOLR1 (folate receptor 1) expression. Diminished FOLR1, concomitant with heightened γH2AX levels, was also observed in patient-derived IDH1 mutant glioma tissues. Chromatin immunoprecipitation, overexpression of mutant YAP1, and treatment with YAP1-TEAD (TEA domain transcription factors) complex inhibitor verteporfin demonstrated regulation of FOLR1 expression by YAP1 and its partner transcription factor TEAD2. TCGA (The Cancer Genome Atlas) data analysis demonstrated better patient survival with reduced FOLR1 expression. Depletion of FOLR1 rendered IDH1 wild-type gliomas more susceptible to temozolomide-mediated death. Despite heightened DNA damage, IDH1 mutants exhibited reduced levels of IL6 (interleukin 6) and IL8 (interleukin 8) – pro-inflammatory cytokines known to be associated with persistent DNA damage. While both FOLR1 and YAP1 influenced DNA damage, only YAP1 was involved in regulating IL6 and IL8. ESTIMATE and CIBERSORTx analyses revealed the association between YAP1 expression and immune cell infiltration in gliomas. By identifying the influence of YAP1-FOLR1 link in DNA damage, our findings suggest that simultaneous depletion of both could amplify the potency of DNA damaging agents, while concomitantly reducing the release of inflammatory mediators and potentially affecting immune modulation. This study also highlights the novel role of FOLR1 as a probable prognostic marker in gliomas, predicting responsiveness to temozolomide and other DNA damaging agents.

MacroH2A2 antagonizes epigenetic programs of stemness in glioblastoma

Self-renewal is a crucial property of glioblastoma cells that is enabled by the choreographed functions of chromatin regulators and transcription factors. Identifying targetable epigenetic mechanisms of self-renewal could therefore represent an important step toward developing effective treatments for this universally lethal cancer. Here we uncover an epigenetic axis of self-renewal mediated by the histone variant macroH2A2. With omics and functional assays deploying patient-derived in vitro and in vivo models, we show that macroH2A2 shapes chromatin accessibility at enhancer elements to antagonize transcriptional programs of self-renewal. macroH2A2 also sensitizes cells to small molecule-mediated cell death via activation of a viral mimicry response. Consistent with these results, our analyses of clinical cohorts indicate that high transcriptional levels of this histone variant are associated with better prognosis of high-grade glioma patients. Our results reveal a targetable epigenetic mechanism of self-renewal controlled by macroH2A2 and suggest additional treatment approaches for glioblastoma patients.