Ontology highlight
ABSTRACT:
PROVIDER: PRJNA665281 | ENA |
REPOSITORIES: ENA
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Project description:Polycomb-repressive complex 1 (PRC1) has a constraining influence on 3D genome organization, mediating localized and chromosome-wide clustering of target loci. Polycomb-bound regions form transcriptionally repressive chromatin domains independent of topologically associating domains (TADs). Several subunits of PRC1 have the capacity to form biomolecular condensates through liquid-liquid phase separation (LLPS) in vitro and when tagged and over-expressed in cells. Here, we use 1,6 hexandiol (1,6-HD), which disrupts liquid-like condensates, to examine the role of endogenous PRC1 biomolecular condensates on local and chromosome-wide clustering of PRC1-bound loci. Using imaging and chromatin immunoprecipitation combined with deep sequencing (ChIP-seq) analyses, we show that PRC1-mediated localized chromatin compaction and clustering of targeted genomic loci at megabase and tens of megabase scales can be reversibly disrupted by the addition and subsequent removal of 1,6-HD to mouse embryonic stem cells (mESCs). Decompaction and dispersal of polycomb domains and clusters cannot be solely attributable to the reduction of PRC1 binding following 1,6-HD treatment as the addition of 2,5-HD has similar effects despite this alcohol not perturbing PRC1-mediated clustering, at least at the sub-megabase and megabase scales. These results suggest that weak, hydrophobic interactions between PRC1 molecules characteristic of liquid condensates do have a role in polycomb-mediated genome organization.
2023-02-13 | GSE224930 | GEO
Project description:Chromatin is partitioned into distinct topological domains in an activity-dependent manner, with topological boundaries limiting the interaction between adjacent domains. Recent studies support the concept that several well-established nuclear compartments are assembled as ribonucleoprotein condensates. Here we ask whether the physical processes driving the assembly of the nuclear condensates play any role in three-dimensional chromatin architecture. We report that the insulation of approximately 20% of topological boundaries in human embryonic stem cells is substantially weakened following brief treatment with 1,6-hexanediol, a chemical known to disrupt several nuclear condensates. The disrupted boundaries are characterized by a high level of transcription, striking spatial clustering, and the augmented presence of transcription units widely expressed in diverse cell types. These topological boundary regions tend to be spatially associated, even inter-chromosomally, and segregate with nuclear speckles. These observations reveal a previously unappreciated mode of genome organization mediated by conserved boundary elements harboring widely-expressed transcription units and associated transcriptional condensates.
2022-06-15 | GSE195561 | GEO
Project description:Compartmentalization is an essential feature of eukaryotic life and is achieved both via membrane-bound organelles, such as mitochondria, and membrane-less biomolecular condensates, such as the nucleolus. Known biomolecular condensates typically exhibit liquid-like properties and are visualized by microscopy on the scale of ~1µm. They have been studied mostly by microscopy, examining select individual proteins. So far, several dozen biomolecular condensates are known, serving a multitude of functions, for example, in the regulation of transcription, RNA processing or signalling and their malfunction can cause diseases. However, it remains unclear to what extent biomolecular condensates are utilized in cellular organization and at what length scale they typically form. Here we examine native cytoplasm from Xenopus egg extract on a global scale with quantitative proteomics, filtration, size exclusion and dilution experiments. These assays reveal that at least 18% of the proteome is organized into mesoscale biomolecular condensates at the scale of ~100nm and appear to be stabilized by RNA or gelation. We confirmed mesoscale sizes via imaging below the diffraction limit by investigating protein permeation into porous substrates with defined pore sizes. Our results show that eukaryotic cytoplasm organizes extensively via biomolecular condensates, but at surprisingly short length scales.
2023-11-02 | GSE232651 | GEO
Project description:Liquid-liquid phase separation (LLPS) contributes to the spatial and functional segregation of molecular processes within the cell nucleus. However, the role played by LLPS in chromatin folding in living cells remains unclear. Here, using stochastic optical reconstruction microscopy (STORM) and Hi-C techniques, we studied the effects of 1,6-hexanediol (1,6-HD)- mediated LLPS disruption/modulation on higher-order chromatin organization in living cells. We found that 1,6-HD treatment caused the enlargement of nucleosome clutches and their more uniform distribution in the nuclear space. At a megabase-scale, chromatin underwent moderate but irreversible perturbations that resulted in the partial mixing of A and B compartments. The removal of 1,6-HD from the culture medium did not allow chromatin to acquire initial configurations, and resulted in more compact repressed chromatin than in untreated cells. 1,6-HD treatment also weakened enhancer-promoter interactions and TAD insulation but did not considerably affect CTCF-dependent loops. Our results suggest that 1,6-HD-sensitive LLPS plays a limited role in chromatin spatial organization by constraining its folding patterns and facilitating compartmentalization at different levels.
2021-03-22 | GSE138543 | GEO
Project description:Chromatin is partitioned into distinct topological domains in an activity-dependent manner, with topological boundaries limiting the interaction between adjacent domains. Recent studies support the concept that several well-established nuclear compartments are assembled as ribonucleoprotein condensates. Here we ask whether the physical processes driving the assembly of the nuclear condensates play any role in three-dimensional chromatin architecture. We report that the insulation of approximately 20% of topological boundaries in human embryonic stem cells is substantially weakened following brief treatment with 1,6-hexanediol, a chemical known to disrupt several nuclear condensates. The disrupted boundaries are characterized by a high level of transcription, striking spatial clustering, and the augmented presence of transcription units widely expressed in diverse cell types. These topological boundary regions tend to be spatially associated, even inter-chromosomally, and segregate with nuclear speckles. These observations reveal a previously unappreciated mode of genome organization mediated by conserved boundary elements harboring widely-expressed transcription units and associated transcriptional condensates.
2022-06-15 | GSE195563 | GEO
Project description:Chromatin is partitioned into distinct topological domains in an activity-dependent manner, with topological boundaries limiting the interaction between adjacent domains. Recent studies support the concept that several well-established nuclear compartments are assembled as ribonucleoprotein condensates. Here we ask whether the physical processes driving the assembly of the nuclear condensates play any role in three-dimensional chromatin architecture. We report that the insulation of approximately 20% of topological boundaries in human embryonic stem cells is substantially weakened following brief treatment with 1,6-hexanediol, a chemical known to disrupt several nuclear condensates. The disrupted boundaries are characterized by a high level of transcription, striking spatial clustering, and the augmented presence of transcription units widely expressed in diverse cell types. These topological boundary regions tend to be spatially associated, even inter-chromosomally, and segregate with nuclear speckles. These observations reveal a previously unappreciated mode of genome organization mediated by conserved boundary elements harboring widely-expressed transcription units and associated transcriptional condensates.
2022-06-15 | GSE195562 | GEO
Project description:Chromatin is partitioned into distinct topological domains in an activity-dependent manner, with topological boundaries limiting the interaction between adjacent domains. Recent studies support the concept that several well-established nuclear compartments are assembled as ribonucleoprotein condensates. Here we ask whether the physical processes driving the assembly of the nuclear condensates play any role in three-dimensional chromatin architecture. We report that the insulation of approximately 20% of topological boundaries in human embryonic stem cells is substantially weakened following brief treatment with 1,6-hexanediol, a chemical known to disrupt several nuclear condensates. The disrupted boundaries are characterized by a high level of transcription, striking spatial clustering, and the augmented presence of transcription units widely expressed in diverse cell types. These topological boundary regions tend to be spatially associated, even inter-chromosomally, and segregate with nuclear speckles. These observations reveal a previously unappreciated mode of genome organization mediated by conserved boundary elements harboring widely-expressed transcription units and associated transcriptional condensates.
2022-06-15 | GSE195565 | GEO
Project description:Cell identity is orchestrated through an interplay between transcription factor (TF) action and genome architecture. The mechanisms used by TFs to shape three-dimensional (3D) genome organization remain incompletely understood. Here we present evidence that the lineage-instructive TF CEBPA drives extensive chromatin compartment switching and promotes the formation of long-range chromatin hubs during induced B cell to macrophage transdifferentiation. A large intrinsically disordered region (IDR) enables CEBPA to undergo in vitro phase separation and to co-condense with transcriptional partners, which is at least partially mediated by aromatic residues. Furthermore, CEBPA forms visible nuclear condensates in transdifferentiating B cells that co-localize with co-activator condensates and recover rapidly upon photobleaching. Finally, native CEBPA-expressing cell types such as primary granulocyte-macrophage progenitors (GMPs), liver cells and trophectoderm cells also reveal nuclear CEBPA condensates and long-range 3D chromatin hubs at CEBPA-bound regions. These findings support a model in which CEBPA acts as a 3D genome structural organizer and suggest that this effect is mediated at least in part by its phase-separation capacity.
2023-07-24 | GSE221167 | GEO
Project description:Some transcription factors (TFs) can form liquid-liquid phase separated (LLPS) condensates. However, the function of these TF condensates in 3D genome organization and gene regulation remains elusive. In response to methionine (met) starvation in budding yeast, Met4 and a few sequence-specific co-activators, including Met32, induce a set of genes involved in met biosynthesis. Here, we show that the endogenous Met4 and Met32 form puncta-like structures that significantly overlap in yeast nuclei upon met depletion. Recombinant Met4 and Met32 form mixed droplets with LLPS properties in vitro. In relation to chromatin, Met4 puncta co-localize with target genes, and at least a subset of these target genes are clustered in 3D in a Met4-dependent manner. A MET3pr-GFP reporter inserted near several native Met4 binding sites becomes co-localized with Met4 puncta and displays enhanced transcriptional activity. A Met4 variant with a partial truncation of an intrinsically disordered region (IDR) shows less puncta formation, and this mutant selectively reduces the reporter activity near Met4 binding sites to the basal level. Overall, these results support a model where Met4 and co-activators form condensates to bring multiple target genes into a vicinity with higher local TF concentrations, which facilitates a strong response to met depletion (-met).
2024-01-08 | GSE252384 | GEO
Project description:Hox genes are essential regulators of embryonic development. They are activated in a temporal sequence following their topological order within their genomic clusters. Subsequently, states of activity are fine-tuned and maintained to translate into domains of progressively overlapping gene products. While the mechanisms underlying such temporal and spatial progressions begin to be understood, many of their aspects remain unclear. We have systematically analyzed the 3D chromatin organization of Hox clusters in vivo, during their activation using high-resolution circular chromosome conformation capture (4C-seq). Initially, Hox clusters are organized as single 3D chromatin compartments decorated with bivalent chromatin marks. Their progressive transcriptional activation is associated with a dynamic bi-modal 3D organization, whereby the genes switch one after the other, from an inactive to an active 3D compartment. These local 3D dynamics occur within a larger constitutive framework of interactions within the surrounding Topological Associated Domains, which confirms previous results that regulation of this process in primarily cluster intrinsic. The local step-wise progression in time can be stopped and memorized at various body levels and hence it may accounts for the various chromatin architectures previously described at different anterior to posterior body levels for the same embryo at a later stage. ChIP-seq samples (H3K4me3 and H3K27me3) from mouse ES cells and mouse embryonic stage E8.5 pre-somitic mesoderm. Data based on 4 biological samples.
2014-04-28 | E-GEOD-54955 | biostudies-arrayexpress