Coactivator condensation at super-enhancers links phase separation and gene control (RNA-Seq)
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE112807 | GEO | 2018/04/07
REPOSITORIES: GEO
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Project description:Super-enhancers (SEs) are clusters of enhancers that cooperatively assemble a high density of transcriptional apparatus to drive robust expression of genes with prominent roles in cell identity. We recently proposed that a phase-separated multi-molecular assembly underlies the formation and function of SEs. Here, we demonstrate that the SE-enriched factors BRD4 and MED1 form nuclear puncta that occur at SEs and exhibit properties of liquid-like condensates. Disruption of BRD4 and MED1 puncta by 1,6-hexanediol is accompanied by a loss of BRD4 and MED1 at SEs and a loss of RNAPII from SE-driven genes. We find that the intrinsically disordered regions (IDRs) of BRD4 and MED1 are sufficient to form phase-separated droplets in vitro and the MED1 IDR promotes phase separation in living cells. The MED1 IDR droplets are capable of compartmentalizing BRD4 and other transcriptional machinery in nuclear extracts. These results support the idea that SEs form phase-separated condensates that compartmentalize the transcription apparatus at key genes, provide insights into the role of cofactor IDRs in this process, and offer new insights into mechanisms involved in control of key cell identity genes.
2018-04-07 | GSE112806 | GEO
Project description:HIPPO-YAP/TAZ signaling has been implicated in supratentorial ependymoma formation from neural progenitor cells (NPC) in the brain, however, the underlying mechanisms to trigger the neural progenitor cell transformation remains elusive. Here, we uncover that patient-derived tumorigenic YAP-fusion proteins (YAP-MAMLD1 and C11ORF95-YAP) promote ependymoma tumorigenesis through forming liquid-liquid phase-separated condensates. Intrinsically disordered regions (IDR) in the fusion proteins promote oligomerization of YAP-transcriptional co-activators and self-assembly of nuclear puncta-like membrane-less organelles. Phase separation of YAP-fusion proteins further facilitates the compartmentalization of transcriptional coactivators, BRD4 and MED1, resulting in pervasive enhancer landscape changes and exclusion of transcriptional repressors such as PRC2 complexes. YAP-fusion proteins-induced nuclear puncta recruit RNA polymerase II to promote transcriptional bursting of multiple oncogenic pathways. Moreover, we show that IDR-mediated phase separation is necessary for YAP-fusion protein-induced tumor formation. Distinct YAP fusion-proteins identified in other human tumors also encompass IDR features. Together, our data suggest that IDR-mediated phase separation is an integral component of YAP-fusion protein-induced tumorigenesis and might serve as a therapeutic target in supratentorial ependymoma.
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Project description:HIPPO-YAP/TAZ signaling has been implicated in supratentorial ependymoma formation from neural progenitor cells (NPC) in the brain, however, the underlying mechanisms to trigger the neural progenitor cell transformation remains elusive. Here, we uncover that patient-derived tumorigenic YAP-fusion proteins (YAP-MAMLD1 and C11ORF95-YAP) promote ependymoma tumorigenesis through forming liquid-liquid phase-separated condensates. Intrinsically disordered regions (IDR) in the fusion proteins promote oligomerization of YAP-transcriptional co-activators and self-assembly of nuclear puncta-like membrane-less organelles. Phase separation of YAP-fusion proteins further facilitates the compartmentalization of transcriptional coactivators, BRD4 and MED1, resulting in pervasive enhancer landscape changes and exclusion of transcriptional repressors such as PRC2 complexes. YAP-fusion proteins-induced nuclear puncta recruit RNA polymerase II to promote transcriptional bursting of multiple oncogenic pathways. Moreover, we show that IDR-mediated phase separation is necessary for YAP-fusion protein-induced tumor formation. Distinct YAP fusion-proteins identified in other human tumors also encompass IDR features. Together, our data suggest that IDR-mediated phase separation is an integral component of YAP-fusion protein-induced tumorigenesis and might serve as a therapeutic target in supratentorial ependymoma.
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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).
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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).
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Project description:Development of cancer is intimately associated with genetic abnormalities that target proteins with intrinsically disordered regions (IDRs). In human hematological malignancies, recurrent chromosomal translocation of nucleoporin (NUP98 or NUP214) generates an aberrant chimera that invariably retains nucleoporin?s IDR, tandemly dispersed phenylalanine-and-glycine (FG) repeats. However, it remains elusive how unstructured IDRs contribute to oncogenesis. We show that IDR harbored within NUP98-HOXA9, a homeodomain-containing transcription factor (TF) chimera recurrently detected in leukemias, is essential for establishing liquid-liquid phase separation (LLPS) puncta of chimera and for inducing leukemic transformation. Strikingly, LLPS of NUP98-HOXA9 not only promotes chromatin occupancy of chimera TFs but is also required for formation of a broad, ?super-enhancer?-like binding pattern, typically seen at a battery of leukemogenic genes, potentiating their transcriptional activation. Artificial HOX chimera (FUS-HOXA9), created by replacing NUP98?s FG repeats with an unrelated LLPS-forming IDR of FUS, had similar enhancement effects on chimera?s genome-wide binding and target gene activation. Hi-C mapping further demonstrated that phase-separated NUP98-HOXA9 induces CTCF-independent chromatin looping enriched at proto-oncogenes. Together, this report describes a proof-of-principle example wherein cancer acquires mutation to establish oncogenic TF condensates via phase separation, which simultaneously enhances their genomic targeting and induces organization of aberrant three-dimensional chromatin structure during tumorous transformation. As LLPS-competent molecules are frequently implicated in diseases, this mechanism can potentially be generalized to many malignant and pathological settings.
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Project description:Development of cancer is intimately associated with genetic abnormalities that target proteins with intrinsically disordered regions (IDRs). In human hematological malignancies, recurrent chromosomal translocation of nucleoporin (NUP98 or NUP214) generates an aberrant chimera that invariably retains nucleoporin?s IDR, tandemly dispersed phenylalanine-and-glycine (FG) repeats. However, it remains elusive how unstructured IDRs contribute to oncogenesis. We show that IDR harbored within NUP98-HOXA9, a homeodomain-containing transcription factor (TF) chimera recurrently detected in leukemias, is essential for establishing liquid-liquid phase separation (LLPS) puncta of chimera and for inducing leukemic transformation. Strikingly, LLPS of NUP98-HOXA9 not only promotes chromatin occupancy of chimera TFs but is also required for formation of a broad, ?super-enhancer?-like binding pattern, typically seen at a battery of leukemogenic genes, potentiating their transcriptional activation. Artificial HOX chimera (FUS-HOXA9), created by replacing NUP98?s FG repeats with an unrelated LLPS-forming IDR of FUS, had similar enhancement effects on chimera?s genome-wide binding and target gene activation. Hi-C mapping further demonstrated that phase-separated NUP98-HOXA9 induces CTCF-independent chromatin looping enriched at proto-oncogenes. Together, this report describes a proof-of-principle example wherein cancer acquires mutation to establish oncogenic TF condensates via phase separation, which simultaneously enhances their genomic targeting and induces organization of aberrant three-dimensional chromatin structure during tumorous transformation. As LLPS-competent molecules are frequently implicated in diseases, this mechanism can potentially be generalized to many malignant and pathological settings.
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Project description:TAZ promotes cell proliferation, development, and tumorigenesis by regulating target gene transcription. However, how TAZ orchestrates the transcriptional responses remains poorly defined. Here we demonstrate that TAZ forms nuclear condensates via liquid-liquid phase separation to compartmentalize its DNA binding co-factor TEAD4, the transcription co-activators BRD4 and MED1 and the transcription elongation factor CDK9 for activation of gene expression. TAZ, but not its paralog YAP, forms phase-separated droplets in vitro and liquid-like nuclear condensates in cells and tissues, and this ability is negatively regulated by Hippo signaling via LATS-mediated phosphorylation and mediated by the coiled-coil domain. Deletion of the TAZ coiled-coil domain or substitution with the YAP coiled-coil domain does not affect the interaction with its partners, but prevents its phase separation and more importantly, its ability to induce expression of TAZ-specific target genes. Thus, our study has identified a novel mechanism for the transcriptional activation by TAZ and demonstrated for the first time that pathway-specific transcription factors also engage the phase separation mechanism for efficient and specific transcription activation.
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