Project description:During cancer development, mutations promote gene expression changes that cause transformation. Leukemia is frequently associated with aberrant HOXA expression driven by translocations in nucleoporin genes or KMT2A, and mutations in NPM1. How disparate mutations converge on this regulatory pathway is not understood. Here we demonstrate that mutant NPM1 (NPM1c) forms nuclear condensates in multiple human cell lines, mouse models, and primary patient samples. We show NPM1c phase separation is necessary and sufficient to recruit NUP98 and KMT2A to condensates. Through extensive mutagenesis and pharmacological destabilization of phase separation, we find that NPM1c condensates are necessary for regulating gene expression, promoting in vivo expansion, and maintaining the undifferentiated leukemic state. Finally, we show that nucleoporin and KMT2A fusion proteins form condensates that are biophysically indistinguishable from NPM1c condensates. Together, these data define a new condensate underlying leukemias that we term coordinating bodies (C-bodies), and propose C-bodies as a therapeutic vulnerability.
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.
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.
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.
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.
Project description:This study investigates the role of SMXL7 protein condensates in regulating gene expression and chromatin organization in the model plant Arabidopsis thaliana. The researchers found that SMXL7 forms phase-separated nuclear condensates that sequester transcription factors and histone demethylases, thereby repressing gene expression. These condensates also associate with and modulate levels of the repressive histone mark H3K27me3, influencing higher-order chromatin structure. The findings reveal a novel mechanism linking plant hormone signaling to epigenetic regulation and nuclear architecture, with implications for understanding how plants control development in response to environmental cues. This work provides new insights into the functions of biomolecular condensates in transcriptional control and hormone signaling in plants.
Project description:This study investigates the role of SMXL7 protein condensates in regulating gene expression and chromatin organization in the model plant Arabidopsis thaliana. The researchers found that SMXL7 forms phase-separated nuclear condensates that sequester transcription factors and histone demethylases, thereby repressing gene expression. These condensates also associate with and modulate levels of the repressive histone mark H3K27me3, influencing higher-order chromatin structure. The findings reveal a novel mechanism linking plant hormone signaling to epigenetic regulation and nuclear architecture, with implications for understanding how plants control development in response to environmental cues. This work provides new insights into the functions of biomolecular condensates in transcriptional control and hormone signaling in plants.
Project description:This study investigates the role of SMXL7 protein condensates in regulating gene expression and chromatin organization in the model plant Arabidopsis thaliana. The researchers found that SMXL7 forms phase-separated nuclear condensates that sequester transcription factors and histone demethylases, thereby repressing gene expression. These condensates also associate with and modulate levels of the repressive histone mark H3K27me3, influencing higher-order chromatin structure. The findings reveal a novel mechanism linking plant hormone signaling to epigenetic regulation and nuclear architecture, with implications for understanding how plants control development in response to environmental cues. This work provides new insights into the functions of biomolecular condensates in transcriptional control and hormone signaling in plants.