Convergent transcription induces dynamic DNA methylation at disiRNA loci
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ABSTRACT:
ORGANISM(S): Neurospora crassa
PROVIDER: GSE47666 | GEO | 2013/08/01
SECONDARY ACCESSION(S): PRJNA207075
REPOSITORIES: GEO
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Project description:Cytosine methylation of DNA is an important epigenetic gene silencing mechanism in plants, fungi, and animals. In the filamentous fungus Neurospora crassa, nearly all known DNA methylations occur in transposon relics and repetitive sequences, and DNA methylation does not depend on the canonical RNAi pathway. disiRNAs are Dicer-independent small non-coding RNAs that arise from gene-rich part of the Neurospora genome. Here we describe a new type of DNA methylation that is associated with the disiRNA loci. Unlike the known DNA methylation in Neurospora, disiRNA loci DNA methylation (DLDM) is highly dynamic and is regulated by an on/off mechanism. Surprisingly, some of the DLDM is independent of the known DNA methyltransferase. At least in disi47, disiRNA production appears to rely on pol II directed transcription. Importantly, DLDM is triggered by convergent transcription and enriched in promoter regions. Together, our results establish a new mechanism that triggers DNA methylation. Two small RNA library were generated from Neurospora wild type (FGSC4200) and wc-2 KO mutant
2013-08-01 | E-GEOD-47666 | biostudies-arrayexpress
Project description:Heterochromatin is a specialized form of chromatin that restricts access to DNA and inhibits genetic processes, including transcription and recombination. In Neurospora crassa, constitutive heterochromatin is characterized by trimethylation of lysine 9 on histone H3, hypoacetylation of histones, and DNA methylation. Here we explore whether the conserved histone demethylase, lysine-specific demethylase 1 (LSD1), regulates heterochromatin in Neurospora, and if so, how. Though LSD1 is implicated in heterochromatin regulation, its function is inconsistent across different systems; orthologs of LSD1 have been shown to either promote or antagonize heterochromatin expansion by removing H3K4me or H3K9me respectively. We identify three members of the Neurospora LSD complex (LSDC): LSD1, PHF1, and BDP-1, and strains deficient for any exhibit variable spreading of heterochromatin and establishment of new heterochromatin domains dispersed across the genome. Heterochromatin establishment outside of canonical domains in Neurospora share the unusual characteristic of DNA methylation-dependent H3K9me3; typically, H3K9me3 establishment is independent of DNA methylation. Consistent with this, the hyper-H3K9me3 phenotype of LSD1 knock-out strains is dependent on the presence of DNA methylation, as well as HCHC-mediated histone deacetylation, suggesting spreading is dependent on some feedback mechanism. Altogether, our results suggest LSD1 works in opposition to HCHC to maintain proper heterochromatin boundaries.
2021-07-21 | PXD017300 | Pride
Project description:Both RNAi-dependent and -independent mechanisms have been implicated in the establishment of heterochromatin domains, which may be stabilized by feedback loops involving chromatin proteins and modifications of histones and DNA. Neurospora crassa sports features of heterochromatin found in higher eukaryotes, namely cytosine methylation (5mC), methylation of histone H3 lysine9 (H3K9me) and HETEROCHROMATIN PROTEIN-1 (HP1), and provides a model to investigate heterochromatin establishment and maintenance. We mapped the distribution of HP1, 5mC, H3K9me3 and H3K4me2 at 100bp-resolution and explored their interplay. HP1, H3K9me3 and DNA methylation were extensively colocalized and defined 44 heterochromatic domains on linkage group VII, all relics of repeat-induced point mutation (RIP). Interestingly, the centromere was found in a striking ~350kb heterochromatic domain with no detectable H3K4me2. 5mC was not found in genes, in contrast to the situation in plants and animals. H3K9me3 is required for HP1 localization and DNA methylation. Here, we show that localization of H3K9me3 is independent of 5mC or HP1 at virtually all heterochromatin regions. In addition, we observed complete restoration of DNA methylation patterns after depletion and reintroduction of the H3K9 methylation machinery, indicating that the signals for de novo heterochromatin formation lie upstream of H3K9 methylation. These data show that A:T rich RIPâd DNA efficently directs methylation of H3K9, which in turn, directs methylation of associated cytosines. Immunoprecipitation experiments using antibodies to 5mC, H3K9me3, epitope-tagged HP1, and H3K4me2 were performed. The immunoprecipitate fraction was labeled with Cy5 and the total input was labeled with Cy3. Samples were hybridized to a N. crassa LGVII tiling path microarray.
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Project description:Both RNAi-dependent and -independent mechanisms have been implicated in the establishment of heterochromatin domains, which may be stabilized by feedback loops involving chromatin proteins and modifications of histones and DNA. Neurospora crassa sports features of heterochromatin found in higher eukaryotes, namely cytosine methylation (5mC), methylation of histone H3 lysine9 (H3K9me) and HETEROCHROMATIN PROTEIN-1 (HP1), and provides a model to investigate heterochromatin establishment and maintenance. We mapped the distribution of HP1, 5mC, H3K9me3 and H3K4me2 at 100bp-resolution and explored their interplay. HP1, H3K9me3 and DNA methylation were extensively colocalized and defined 44 heterochromatic domains on linkage group VII, all relics of repeat-induced point mutation (RIP). Interestingly, the centromere was found in a striking ~350kb heterochromatic domain with no detectable H3K4me2. 5mC was not found in genes, in contrast to the situation in plants and animals. H3K9me3 is required for HP1 localization and DNA methylation. Here, we show that localization of H3K9me3 is independent of 5mC or HP1 at virtually all heterochromatin regions. In addition, we observed complete restoration of DNA methylation patterns after depletion and reintroduction of the H3K9 methylation machinery, indicating that the signals for de novo heterochromatin formation lie upstream of H3K9 methylation. These data show that A:T rich RIP’d DNA efficently directs methylation of H3K9, which in turn, directs methylation of associated cytosines.
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Project description:Histone methylations play a major role in regulating the chromatin state and gene expression, yet little is known about their involvement in differential gene expression and function of memory CD8 T cells. Here, we report a genome-wide analysis of two histone H3 methylations (H3K4me3 and H3K27me3) and gene expression in naïve, central (TCM) and effector (TEM) memory CD8 T cells. Analysis of 16,314 annotated genes in CD8 T cell subsets revealed that gene expression were positively correlated with the levels of H3K4me3 and negatively correlated with the levels of H3K27me3 in these gene loci. The correlation between differential H3K4me3 orH3K27me3 levels with gene expressions in memory CD8 T cells displayed four distinct modes: repressive, active, poised, and bivalent, reflecting their complex regulation and different function of these genes. Furthermore, accessible chromatin states of different gene loci were preferentially influenced by different histone modifications as demonstrated here high levels of H3K9ac found in active gene loci without high levels of H3K4me3. These findings reveal a histone methylation based complex regulation of differential gene expression in memory CD8 T cells. Thus, change of chromatin structure mediated by histone methylation may serve a fundamental basis for the rapid transcriptional response of memory CD8 T cells. genome-wide analysis of two histone H3 methylations (H3K4me3 and H3K27me3) in naïve, central (TCM) and effector (TEM) memory CD8 T cells.
2009-06-12 | E-GEOD-12616 | biostudies-arrayexpress
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Project description:Histone methylations play a major role in regulating the chromatin state and gene expression, yet little is known about their involvement in differential gene expression and function of memory CD8 T cells. Here, we report a genome-wide analysis of two histone H3 methylations (H3K4me3 and H3K27me3) and gene expression in naïve, central (TCM) and effector (TEM) memory CD8 T cells. Analysis of 16,314 annotated genes in CD8 T cell subsets revealed that gene expression were positively correlated with the levels of H3K4me3 and negatively correlated with the levels of H3K27me3 in these gene loci. The correlation between differential H3K4me3 orH3K27me3 levels with gene expressions in memory CD8 T cells displayed four distinct modes: repressive, active, poised, and bivalent, reflecting their complex regulation and different function of these genes. Furthermore, accessible chromatin states of different gene loci were preferentially influenced by different histone modifications as demonstrated here high levels of H3K9ac found in active gene loci without high levels of H3K4me3. These findings reveal a histone methylation based complex regulation of differential gene expression in memory CD8 T cells. Thus, change of chromatin structure mediated by histone methylation may serve a fundamental basis for the rapid transcriptional response of memory CD8 T cells. Keywords: Histone methylations, chromatin state, CD8 memory T cells
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