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A Constitutive Heterochromatic Region Shapes Genome Organization and Impacts Gene Expression in Neurospora crassa [ChIP-Seq]

ABSTRACT: Genome organization is essential for proper function, including gene expression. In metazoan genome organization, chromatin loops and Topologically Associated Domains (TADs) facilitate local gene clustering, while chromosomes form distinct nuclear territories characterized by compartmentalization of silent heterochromatin at the nuclear periphery and active euchromatin in the nucleus center. A similar hierarchical organization occurs in the fungus Neurospora crassa where its seven chromosomes form a Rabl conformation, where heterochromatic centromeres and telomeres independently cluster at the nuclear membrane, while interspersed heterochromatic loci in Neurospora aggregate across megabases of linear genomic distance for forming TAD-like structures. However, the role of individual heterochromatic loci in normal genome organization and function is unknown. Here, we examined the genome organization of a Neurospora strain harboring a ~41 kilobase facultative (temporarily silent) heterochromatic region deletion, as well as the genome organization of a strain deleted of a ~110 kilobase permanently silent constitutive heterochromatic region. While the facultative heterochromatin deletion had little effect on local chromatin structure, the constitutive heterochromatin deletion altered local TAD-like structures, gene expression, and the predicted 3D genome structure by qualitatively repositioning genes into the nucleus center. Our work elucidates the role of individual heterochromatic regions for genome organization and function.

ORGANISM(S): Neurospora crassa

PROVIDER: GSE269228 | GEO | 2024/06/10

REPOSITORIES: GEO

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A Constitutive Heterochromatic Region Shapes Genome Organization and Impacts Gene Expression in Neurospora crassa [Hi-C]

Project description:Genome organization is essential for proper function, including gene expression. In metazoan genome organization, chromatin loops and Topologically Associated Domains (TADs) facilitate local gene clustering, while chromosomes form distinct nuclear territories characterized by compartmentalization of silent heterochromatin at the nuclear periphery and active euchromatin in the nucleus center. A similar hierarchical organization occurs in the fungus Neurospora crassa where its seven chromosomes form a Rabl conformation, where heterochromatic centromeres and telomeres independently cluster at the nuclear membrane, while interspersed heterochromatic loci in Neurospora aggregate across megabases of linear genomic distance for forming TAD-like structures. However, the role of individual heterochromatic loci in normal genome organization and function is unknown. Here, we examined the genome organization of a Neurospora strain harboring a ~41 kilobase facultative (temporarily silent) heterochromatic region deletion, as well as the genome organization of a strain deleted of a ~110 kilobase permanently silent constitutive heterochromatic region. While the facultative heterochromatin deletion had little effect on local chromatin structure, the constitutive heterochromatin deletion altered local TAD-like structures, gene expression, and the predicted 3D genome structure by qualitatively repositioning genes into the nucleus center. Our work elucidates the role of individual heterochromatic regions for genome organization and function.

2024-06-10 | GSE269229 | GEO

A Constitutive Heterochromatic Region Shapes Genome Organization and Impacts Gene Expression in Neurospora crassa [RNA-Seq]

2024-06-10 | GSE269230 | GEO

Histone deacetylation and cytosine methylation are required for the normal compartmentalization of heterochromatin in the genome organization of Neurospora crassa [ChIP-Seq]

Project description:Chromosomes must correctly fold in eukaryotic nuclei for proper genome function. Eukaryotic organisms hierarchically organize their genomes: in the fungus Neurospora crassa, chromatin fiber loops compact into Topologically Associated Domain (TAD)-like structures that are anchored by heterochromatic region aggregates. However, insufficient information exists on how histone post-translational modifications, including acetylation, impact genome organization. In Neurospora, the HCHC (HDA-1, CDP-2, HP1, CHAP) complex deacetylates heterochromatic regions including centromeres: loss of individual HCHC members increases centromeric acetylation and cytosine methylation. Here, we evaluate the role of the HCHC complex on genome organization using chromosome conformation capture with high-throughput sequencing (Hi-C) in Δcdp-2 or Δchap deletion strains. CDP-2 loss increases interactions between intra- and inter-chromosomal heterochromatic regions, while removal of CHAP decreases heterochromatic region compaction. Individual HCHC mutants exhibit different histone PTM patterns genome-wide: in Dcdp-2, heterochromatic H4K16 acetylation is increased, yet some heterochromatic regions lose H3K9 trimethylation, which locally increases inter-heterochromatin contacts; CHAP loss produces minimal acetylation changes but increases H3K9me3 enrichment in heterochromatin. Furthermore, deletion of the DIM-2 DNA methyltransferase in a Δcdp-2 background causes extensive genome disorder, as heterochromatic-euchromatic contacts increase despite additional H3K9me3 enrichment. Our results highlight how enhanced cytosine methylation ensures heterochromatic compartmentalization when silenced regions are acetylated.

2023-07-03 | GSE232933 | GEO

Histone deacetylation and cytosine methylation are required for the normal compartmentalization of heterochromatin in the genome organization of Neurospora crassa [Hi-C]

2023-07-03 | GSE232934 | GEO

HiC of Wild Type Neurospora crassa and mutants deficient in heterochromatin formation

Project description:Eukaryotic genomes are organized into chromatin domains with distinct three-dimensional arrangements resulting from nucleic acid and protein factor interactions within the physical constraints of the nucleus. It is of obvious interest to determine interactions between various chromosomal regions defined by these nuclear constraints, and to identify important factors that limit the interactions. We used chromosome conformation capture (3C) followed by high-throughput sequencing (HiC) to improve our understanding of Neurospora crassa genome organization and to examine if known components of heterochromatin machinery influence nuclear organization. In heterochromatin establishment, DIM-5 tri-methylates histone H3 on lysine 9 (H3K9me3), and this mark is subsequently bound by Heterochromatin Protein-1 (HP1). NUP-6 is required to target DIM-5 to incipient A:T rich DNA and the dim-3 mutant of NUP-6 is deficient in DIM-5 localization. We performed HiC on chromatin from wildtype, Δdim-5, Δhpo, and dim-3 strains. The genome configuration of wild type nuclei revealed strong intra- and inter-chromosomal associations between both constitutive and facultative heterochromatic domains, with the strongest interactions among the centromeres, telomeres and interspersed heterochromatin. We found that loss of the H3K9me3 mark, as well as loss of HP1, minimally altered the chromatin organization found at these strongly interacting heterochromatic regions. Surprisingly, dim-3 chromatin was highly disorganized suggesting NUP-6 plays key role(s) in genome structure. Thus, our datasets suggest that while heterochromatic regions are critical to defining the genome conformation in Neurospora, non-canonical protein factors may play a key role in maintaining this organization.

2016-05-19 | GSE71024 | GEO

Neurospora crassa genome organization requires subtelomeric facultative heterochromatin

Project description:Facultative heterochromatin in the filamentous fungus Neurospora crassa is identified by the repressive histone mark H3K27me3 and is primarily subtelomeric, while constitutive heterochromatin, marked by the DIM-5-catalzyed H3K9me3, is found at centromeres, telomeres, and smaller dispersed regions. In strains lacking constitutive heterochromatin (e.g., Δdim-5), H3K27me2/3 relocalizes to the regions formerly marked by H3K9me3. H3K27me3 is catalyzed by the SET-7 histone methyltransferase subunit of the Polycomb Repressive Complex 2 (PRC2); another PRC2 member, Neurospora p55 (NPF) regulates subtelomeric H3K27me2/3. Despite the de-repression of >70 genes, a Δset-7 strain has no distinguishable phenotype. To investigate the facultative heterochromatin contribution to genome organization, we performed high-throughput “chromosome conformation capture” (Hi-C) on mutants with impacted H3K27me2/3 deposition. A Δset-7 strain has decreased inter-/intra-subtelomeric contacts among others; this pattern is mirrored in a Δnpf strain, which lacks subtelomeric H3K27me3. In a Δset-7 strain, telomere bundles were often uncoupled from the nuclear membrane and de-repressed genes were subtelomeric. The chromosome conformation of a Δset-7;Δdim-5 double mutant was similar to Δset-7, suggesting that facultative heterochromatin relocalization does not compensate for H3K9me3 loss and rescue the Neurospora genome organization in strains with defective constitutive heterochromatin.

2016-10-27 | GSE82222 | GEO

Neurospora crassa

Project description:Neurospora crassa genome organization requires subtelomeric facultative heterochromatin

| PRJNA324378 | ENA

IMITATION SWITCH is required for normal chromatin structure and gene repression in PRC2 target domains

Project description:Polycomb Group (PcG) proteins are part of an epigenetic cell memory system that plays essential roles in multicellular development, stem cell biology, X-chromosome inactivation, and cancer. In animals, plants, and many fungi, Polycomb Repressive Complex 2 (PRC2) catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) to assemble transcriptionally repressed facultative heterochromatin. PRC2 is structurally and functionally conserved in the model fungus Neurospora crassa, and recent work in this organism has generated insights into PRC2 control and function. To identify new components of the facultative heterochromatin pathway, we performed a targeted screen of Neurospora deletion strains lacking individual ATP-dependent chromatin remodeling enzymes. We found the Neurospora homolog of IMITATION SWITCH (ISW) is critical for normal transcriptional repression, nucleosome organization, and establishment of typical histone methylation patterns in facultative heterochromatin domains. We also found that stable interaction between PRC2 and chromatin depends on ISW. A functional ISW ATPase domain is required for gene repression and H3K27 methylation. ISW homologs interact with accessory proteins to form multiple complexes with distinct functions. Using proteomics and molecular approaches, we identified three distinct Neurospora ISW-containing complexes. A triple mutant lacking three ISW-accessory factors and disrupting multiple ISW complexes led to widespread upregulation of PRC2 target genes and altered H3K27 methylation patterns, similar to an ISW-deficient strain. Taken together, our data show that ISW is a key component of the facultative heterochromatin pathway in Neurospora and that distinct ISW complexes perform an apparently overlapping role to regulate chromatin structure and gene repression at PRC2 target domains.

2021-01-05 | GSE150758 | GEO

Interplay of pericentromeric genome organization and chromatin landscape regulates the expression of Drosophila melanogaster heterochromatic genes [5C]

Project description:Transcription of genes residing within constitutive heterochromatin is paradoxical to the tenets of epigenetic code. Regulatory mechanisms of Drosophila melanogaster heterochromatic gene transcription remain largely unknown. We investigated the contribution of pericentromeric genome organization and heterochromatic factors in orchestrating heterochromatic gene expression. Using 5C-seq, we characterized the pericentromeric TADs in Drosophila melanogaster. Het TAD borders are enriched in nuclear matrix attachment regions while the intra-TAD interactions are mediated by various insulator binding proteins. Heterochromatic genes of similar expression levels cluster into Het TADs, indicating transcriptional co-regulation. HP1a or Su(var)3-9 RNAi results in perturbation of global pericentromeric TAD organization but the expression of the heterochromatic genes is minimally affected. A subset of active heterochromatic genes has been shown to have combination of HP1a/H3K9me3 with H3K36me3 at their exons. Consequently, knock-down of dMES-4 (H3K36 methyl transferase) downregulates expression of the heterochromatic genes. Furthermore, dADD1, present near the TSS of the active heterochromatic genes, is likely to regulate the heterochromatic gene expression in the presence of HP1a or H3K9me3 marks. Therefore, our findings provide mechanistic insights into the interplay of chromatin interactions and the combination of heterochromatic factors (HP1a, H3K9me3, dMES-4 and dADD1) in regulating heterochromatic gene expression.

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