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MLL4 establishes enhancer-associated condensates to counterbalance Polycomb-mediated nuclear mechanical stress in Kabuki Syndrome [3'UTR RNA-seq]

ABSTRACT: The genetic elements required to tune gene expression are partitioned in active and repressive nuclear condensates. These chromatin compartments include enhancer-associated clusters whose dynamic establishment and functioning depends on multivalent interactions occurring among transcription factors, cofactors and basal transcriptional machinery. However how chromatin modifiers contribute to the assembly of enhancer-associated condensates have not been addressed. We herein defined the non-catalytic function of MLL4 in driving the formation active nuclear condensates and its interplay with Polycomb compartment in determining the nuclear architecture. By interrogating the role of haploinsufficiency of KMT2D in Kabuki Syndrome, we found that MLL4 guides the assembly of enhancer-associated condensates through liquid-liquid phase separation. The loss-of-function of MLL4 impaired the correct chromatin compartmentalization of Polycomb proteins, altering nuclear architecture. By releasing the nuclear mechanical stress through the inhibition of the mechano-sensor ATR, we re-established the mechano-signaling of MSCs and their commitments towards chondrocytes. This study supports the notion that MLL4 contributes to the functional partitioning of chromatin, which is required to determine the structure and the mechanical properties of the nucleus.

ORGANISM(S): Homo sapiens

PROVIDER: GSE135550 | GEO | 2020/09/09

REPOSITORIES: GEO

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MLL4-associated condensates counterbalance Polycomb-mediated nuclear mechanical stress in Kabuki Syndrome

Project description:The genetic elements required to tune gene expression are partitioned in active and repressive nuclear condensates. Chromatin compartments include transcriptional clusters whose dynamic establishment and functioning depends on multivalent interactions occurring among transcription factors, cofactors and basal transcriptional machinery. However how chromatin players contribute to the assembly of transcriptional condensates has not been addressed. By interrogating the effect of KMT2D haploinsufficiency in Kabuki Syndrome, we found that MLL4 contributes in the assembly of transcriptional condensates through liquid-liquid phase separation. MLL4 loss-of-function impaired Polycomb-dependent chromatin compartmentalization, altering nuclear architecture. By releasing the nuclear mechanical stress through the inhibition of the mechano-sensor ATR, we re-established the mechano-signaling of mesenchymal stem cells and their commitment towards chondrocytes both in vitro and in vivo. This study supports the notion that in Kabuki Syndrome the haploinsufficiency of MLL4 causes an altered functional partitioning of chromatin, which determines the architecture and mechanical properties of the nucleus.

2020-09-22 | PXD021616 | Pride

MLL4 establishes enhancer-associated condensates to counterbalance Polycomb-mediated nuclear mechanical stress in Kabuki Syndrome [3'UTR RNA-seq]

Project description:MLL4 establishes enhancer-associated condensates to counterbalance Polycomb-mediated nuclear mechanical stress in Kabuki Syndrome [3'UTR RNA-seq]

| PRJNA559272 | ENA

A mechanically regulated liquid-liquid phase separation of the transcriptional regulator Tono instructs muscle development

Project description:Muscle morphogenesis is a multi-step program, starting with myoblast fusion, followed by myotube-tendon attachment and sarcomere assembly, with subsequent sarcomere maturation, mitochondrial amplification and specialisation. The correct chronological order of these steps requires precise control of the transcriptional regulators and their effectors. How this regulation is achieved during muscle development is not well understood. In a genome-wide RNAi screen inDrosophila, we identified the BTB-zinc finger protein Tono (CG32121) as a muscle-specific transcriptional regulator.tonomutant flight muscles display severe deficits in mitochondria and sarcomere maturation, resulting in uncontrolled contractile forces causing muscle atrophy during development. Tono protein is expressed during sarcomere maturation and localises in distinct condensates in flight muscle nuclei. Interestingly, internal pressure exerted by the maturing sarcomeres deforms the muscle nuclei into elongated shapes and changes the Tono condensates, suggesting that Tono senses the mechanical status of the muscle cells. Indeed, external mechanical pressure on the muscles triggers rapid liquid-liquid phase separation of Tono utilising its BTB domain. Thus, we propose that Tono senses high mechanical pressure to in turn adapt muscle transcription specifically at the sarcomere maturation stage. Consistently,tonomutant muscles display specific defects in a transcriptional switch that represses early muscle differentiation genes and boosts late ones. We hypothesise that a similar mechano-responsive regulation mechanism may control the activity of related BTB-zinc finger proteins that, if mutated, can result in uncontrolled force production in human muscle.

2024-06-30 | GSE270794 | GEO

Dispersal of PRC1 condensates disrupts polycomb chromatin domains and loops

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

Stress-induced nuclear condensation of NELF drives global transcriptional downregulation

Project description:In response to stress, human cells actively downregulate ongoing gene expression programs. Translational downregulation is accompanied by the assembly of stress granules which are cytosolic condensates containing ribosomes and mRNA. Transcriptional downregulation is caused by an increased recruitment of Negative Elongation Factors (NELF) to promoters, inhibiting RNA Pol II elongation. We report here that NELF forms nuclear condensates upon stress which can be recapitulated by liquid-liquid phase separation of recombinant NELF in vitro. Stress leads to rapid dephosphorylation and SUMOylation of NELF in cells facilitating condensate formation driven by intrinsically disordered domains of NELFA and NELFE subunits. Using NELF mutants that do not form condensates we provide evidence that condensation is required for increased recruitment of NELF to downregulated promoters and cellular survival in stress. Thus, our study has uncovered a novel nuclear condensate that is conceptually similar to cytosolic stress granule in downregulating gene expression during stressful conditions.

2021-02-05 | GSE140053 | GEO

Long-distance association of topological boundaries through nuclear condensates (Hi-C)

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

Long-distance association of topological boundaries through nuclear condensates (PRO-Seq)

2022-06-15 | GSE195563 | GEO

Long-distance association of topological boundaries through nuclear condensates (GRO-Seq)

2022-06-15 | GSE195562 | GEO

Long-distance association of topological boundaries through nuclear condensates (ChIP-Seq)

2022-06-15 | GSE195561 | GEO

The MLL3/MLL4 branch of the COMPASS family regulates H3K4 monomethylation at enhancers

Project description:Histone H3 lysine 4 (H3K4) can be mono-, di-, and trimethylated by members of the COMPASS (COMplex of Proteins ASsociated with Set1) family from yeast to human and these modifications can be found at distinct regions of the genome. Monomethylation of histone H3K4 (H3K4me1) is relatively more enriched at metazoan enhancer regions compared to trimethylated histone H3K4 (H3K4me3), which are found at transcription start sites in all eukaryotes. Our recent studies in Drosophila demonstrated that the Trithorax-related (Trr) branch of the COMPASS family regulates enhancer activity and is responsible for the implementation of H3K4me1 at these regions. There are six COMPASS family members in mammals, two of which, MLL3 and MLL4, are most closely related to Drosophila Trr. Here, we use ChIP-seq of this class of COMPASS family members in both human HCT116 cells and mouse embryonic stem cells and find that MLL4 is preferentially found at enhancer regions. MLL3 and MLL4 are frequently mutated in cancer, and indeed, the widely used HCT116 cancer cell line contains inactivating mutations in the MLL3 gene. Using HCT116 cells in which MLL4 has also been knocked out, we demonstrate that MLL4 is a major regulator of H3K4me1 in these cells, with the greatest loss of monomethylation at enhancer regions. Moreover, we found a redundant role between Mll3 and Mll4 in enhancer H3K4 monomethylation in mouse embryonic fibroblast (MEF) cells. These findings suggest that mammalian MLL3/MLL4 function in the regulation of enhancer activity and enhancer-promoter communication during gene expression and that mutations of MLL3 and MLL4 found in cancer could exert their properties through enhancer malfunction. ChIP-Seq in mouse embryonic stem (mES) cells for MLL4. ChIP-seq of MLL4 and p300 in human parental HCT116 cells. ChIP-seq of H3K4me1, H3K4me2 and H3K4me3 in parental HCT116 cells and HCT116 cells with Mll4∆set.

2013-09-30 | E-GEOD-51176 | biostudies-arrayexpress

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