Similar Datasets
Project description:The recurrent mutation of histone variant H3.3 at glycine-34 (H3.3G34) defines a type of pediatric glioma. Characteristic changes to the epigenome associated with the disease are thought to be the consequence of altered methylation of the adjacent lysine-36 (K36) residue, but the complexity of this regulatory pathway in humans, combined with a multi-component disease etiology, has limited our understanding of how H3.3G34 mutations contribute to oncogenesis. Here we use Neurospora crassa to show that the most common mutation associated with this tumor, glycine to arginine (G34R), drives aberrant heterochromatin formation and abnormal growth by inhibiting the H3K36 methyltransferase ASH1. Inactivation of ASH1, either directly or with H3G34R, drives spurious intergenic DNA methylation, redistribution of H3K27 methylation, and derepression of silent genes. We provide evidence that these defects are largely due to aberrant activity of RNA polymerase II (RNAPII)-associated SET-2, and propose targeted SET-2 inhibition as a therapeutic strategy for H3.3G34R gliomas.
2022-10-19 | GSE134445 | GEO
Project description:The recurrent mutation of histone variant H3.3 at glycine-34 (H3.3G34) defines a type of pediatric glioma. Characteristic changes to the epigenome associated with the disease are thought to be the consequence of altered methylation of the adjacent lysine-36 (K36) residue, but the complexity of this regulatory pathway in humans, combined with a multi-component disease etiology, has limited our understanding of how H3.3G34 mutations contribute to oncogenesis. Here we use Neurospora crassa to show that the most common mutation associated with this tumor, glycine to arginine (G34R), drives aberrant heterochromatin formation and abnormal growth by inhibiting the H3K36 methyltransferase ASH1. Inactivation of ASH1, either directly or with H3G34R, drives spurious intergenic DNA methylation, redistribution of H3K27 methylation, and derepression of silent genes. We provide evidence that these defects are largely due to aberrant activity of RNA polymerase II (RNAPII)-associated SET-2, and propose targeted SET-2 inhibition as a therapeutic strategy for H3.3G34R gliomas.
2022-10-19 | GSE134451 | GEO
Project description:The recurrent mutation of histone variant H3.3 at glycine-34 (H3.3G34) defines a type of pediatric glioma. Characteristic changes to the epigenome associated with the disease are thought to be the consequence of altered methylation of the adjacent lysine-36 (K36) residue, but the complexity of this regulatory pathway in humans, combined with a multi-component disease etiology, has limited our understanding of how H3.3G34 mutations contribute to oncogenesis. Here we use Neurospora crassa to show that the most common mutation associated with this tumor, glycine to arginine (G34R), drives aberrant heterochromatin formation and abnormal growth by inhibiting the H3K36 methyltransferase ASH1. Inactivation of ASH1, either directly or with H3G34R, drives spurious intergenic DNA methylation, redistribution of H3K27 methylation, and derepression of silent genes. We provide evidence that these defects are largely due to aberrant activity of RNA polymerase II (RNAPII)-associated SET-2, and propose targeted SET-2 inhibition as a therapeutic strategy for H3.3G34R gliomas.
2022-10-19 | GSE134449 | GEO
Project description:Ash1 is a Trithorax group protein that possesses H3K36-specific histone methyltransferase activity, which antagonizes Polycomb silencing. Here we report the identification of two Ash1 complex subunits, Mrg15 and Nurf55. In vitro, Mrg15 stimulates the enzymatic activity of Ash1. In vivo, Mrg15 is recruited by Ash1 to their common targets, and Mrg15 reinforces Ash1 chromatin association and facilitates the proper deposition of H3K36me2. To dissect the functional role of Mrg15 in the context of the Ash1 complex, we identify an Ash1 point mutation (Ash1-R1288A) that displays a greatly attenuated interaction with Mrg15. Knock-in flies bearing this mutation display multiple homeotic transformation phenotypes, and these phenotypes are partially rescued by overexpressing the Mrg15-Nurf55 fusion protein, which stabilizes the association of Mrg15 with Ash1. In summary, Mrg15 is a subunit of the Ash1 complex, a stimulator of Ash1 enzymatic activity and a critical regulator of the TrxG protein function of Ash1 in Drosophila.
| S-EPMC5696344 | biostudies-literature
Project description:Ash1 is a classic Trithorax group protein possessing an H3K36-specific histone methyltransferase activity. Ash1 plays a critical role in antagonizing Polycomb silencing and its loss-of-function mutations lead to inactivation of certain Hox genes and homeotic transformation. Here, we report the purification of Ash1 complex with the identification of two novel subunits, Mrg15 and Nurf55. Interestingly, Mrg15 stimulates the enzymatic activity of Ash1 in vitro, and such stimulation is independent of the chromo domain of Mrg15. In vivo, Mrg15 is recruited by Ash1 to their common target genes and Mrg15 is essential for the proper deposition of H3K36me2 at these regions.
2017-10-04 | GSE93100 | GEO
Project description:Methylation of histone H3 at lysine 36 (H3K36me), a widely-distributed chromatin mark, largely results from association of the lysine methyltransferase (KMT) SET-2 with RNA polymerase II (RNAPII), but most eukaryotes also have additional H3K36me KMTs that act independently of RNAPII. These include the orthologs of ASH1, which are conserved in animals, plants, and fungi but whose function and control are poorly understood. We found that Neurospora crassa has just two H3K36 KMTs, ASH1 and SET-2, and were able to explore the function and distribution of each enzyme independently. While H3K36me deposited by SET-2 marks active genes, inactive genes are modified by ASH1 and its activity is critical for their repression. ASH1-marked chromatin can be further modified by methylation of H3K27, and ASH1 catalytic activity modulates the accumulation of H3K27me2/3 both positively and negatively. These findings provide new insight into ASH1 function, H3K27me2/3 establishment, and repression in facultative heterochromatin.
| S-EPMC6251624 | biostudies-literature
Project description:Tuberous sclerosis complex (TSC) is an autosomal dominant tumor-suppressor gene syndrome caused by inactivating mutations in either TSC1 or TSC2, and the TSC protein complex is an essential regulator of mTOR complex 1 (mTORC1). Patients with TSC develop hypomelanotic macules (white spots), but the molecular mechanisms underlying their formation are not fully characterized. Using human primary melanocytes and a highly pigmented melanoma cell line, we demonstrate that reduced expression of either TSC1 or TSC2 causes reduced pigmentation through mTORC1 activation, which results in hyperactivation of glycogen synthase kinase 3? (GSK3?), followed by phosphorylation of and loss of ?-catenin from the nucleus, thereby reducing expression of microphthalmia-associated transcription factor (MITF), and subsequent reductions in tyrosinase and other genes required for melanogenesis. Genetic suppression or pharmacological inhibition of this signaling cascade at multiple levels restored pigmentation. Importantly, primary melanocytes isolated from hypomelanotic macules from 6 patients with TSC all exhibited reduced TSC2 protein expression, and 1 culture showed biallelic mutation in TSC2, one of which was germline and the second acquired in the melanocytes of the hypomelanotic macule. These findings indicate that the TSC/mTORC1/AKT/GSK3?/?-catenin/MITF axis plays a central role in regulating melanogenesis. Interventions that enhance or diminish mTORC1 activity or other nodes in this pathway in melanocytes could potentially modulate pigment production.
| S-EPMC5199706 | biostudies-literature
Project description:Overexpression of the histone methyltransferase MMSET in t(4;14)+ multiple myeloma patients is believed to be the driving factor in the pathogenesis of this subtype of myeloma. MMSET catalyzes dimethylation of lysine 36 on histone H3 (H3K36me2), and its overexpression causes a global increase in H3K36me2, redistributing this mark in a broad, elevated level across the genome. Here, we demonstrate that an increased level of MMSET also induces a global reduction of lysine 27 trimethylation on histone H3 (H3K27me3). Despite the net decrease in H3K27 methylation, specific genomic loci exhibit enhanced recruitment of the EZH2 histone methyltransferase and become hypermethylated on this residue. These effects likely contribute to the myeloma phenotype since MMSET-overexpressing cells displayed increased sensitivity to EZH2 inhibition. Furthermore, we demonstrate that such MMSET-mediated epigenetic changes require a number of functional domains within the protein, including PHD domains that mediate MMSET recruitment to chromatin. In vivo, targeting of MMSET by an inducible shRNA reversed histone methylation changes and led to regression of established tumors in athymic mice. Together, our work elucidates previously unrecognized interplay between MMSET and EZH2 in myeloma oncogenesis and identifies domains to be considered when designing inhibitors of MMSET function.
| S-EPMC4154646 | biostudies-literature
Project description:UnlabelledTransdifferentiation of hepatic stellate cells (HSCs) to a myofibroblast-like phenotype is the pivotal event in liver fibrosis. The dramatic change in phenotype associated with transdifferentiation is underpinned by a global change in gene expression. Orchestrated changes in gene expression take place at the level of chromatin packaging which is regulated by enzymatic activity of epigenetic regulators that in turn affect histone modifications. Using expression profiling of epigenetic regulators in quiescent and activated primary HSCs we found a number of histone methyltransferases including MLL1, MLL5, Set1 and ASH1 to be highly up-regulated during transdifferentiation of HSCs. All of these histone methyltransferases regulate methylation of lysine 4 of histone H3, which is a signature of actively transcribed genes. We therefore postulated that one or more of these enzymes may be involved in positively influencing expression of profibrogenic genes.ConclusionWe find that ASH1 directly binds to the regulatory regions of alpha smooth muscle actin (αSMA), collagen I, tissue inhibitor of metalloproteinase-1 (TIMP1) and transforming growth factor beta1 (TGFβ1) in activated HSCs while depletion of ASH1 caused broad suppression of fibrogenic gene expression. We also discovered that MeCP2 positively regulates ASH1 expression and therefore identify ASH1 as a key transcriptional activator component of the MeCP2 epigenetic relay pathway that orchestrates coordinated induction of multiple profibrogenic genes.
| S-EPMC3430805 | biostudies-literature
Project description:Members of the Polycomb group of repressors and trithorax group of activators maintain heritable states of transcription by modifying nucleosomal histones or remodeling chromatin. Although tremendous progress has been made toward defining the biochemical activities of Polycomb and trithorax group proteins, much remains to be learned about how they interact with each other and the general transcription machinery to maintain on or off states of gene expression. The trithorax group protein Kismet (KIS) is related to the SWI/SNF and CHD families of chromatin remodeling factors. KIS promotes transcription elongation, facilitates the binding of the trithorax group histone methyltransferases ASH1 and TRX to active genes, and counteracts repressive methylation of histone H3 on lysine 27 (H3K27) by Polycomb group proteins. Here, we sought to clarify the mechanism of action of KIS and how it interacts with ASH1 to antagonize H3K27 methylation in Drosophila. We present evidence that KIS promotes transcription elongation and counteracts Polycomb group repression via distinct mechanisms. A chemical inhibitor of transcription elongation, DRB, had no effect on ASH1 recruitment or H3K27 methylation. Conversely, loss of ASH1 function had no effect on transcription elongation. Mutations in kis cause a global reduction in the di- and tri-methylation of histone H3 on lysine 36 (H3K36) - modifications that antagonize H3K27 methylation in vitro. Furthermore, loss of ASH1 significantly decreases H3K36 dimethylation, providing further evidence that ASH1 is an H3K36 dimethylase in vivo. These and other findings suggest that KIS antagonizes Polycomb group repression by facilitating ASH1-dependent H3K36 dimethylation.
| S-EPMC3787758 | biostudies-literature