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MSWI/SNF functional genomic characterization of SMARCB1 mutants in SMARCB1-null and heterozygous settings

ABSTRACT: Chromatin remodeling complexes regulate gene expression by shifting, evicting, and exchanging nucleosomes along the chromosomes of eukaryotic organisms. The mammalian SWI/SNF chromatin remodeling complex (mSWI/SNF or BAF) is mutated in over 20% of human cancers and loss of the SMARCB1 gene, encoding the BAF47 protein subunit, results in one of the most aggressive and lethal pediatric cancers. An accumulation of point mutations occurs at the C-terminal end of the protein, for which the functional ramifications are unknown. We previously demonstrated that reintroduction of SMARCB1 in SMARCB1-null malignant rhabdoid tumor cells results in a genome-wide increase of mSWI/SNF complex occupancy coupled with activation of PRC2-repressed genes. Here, we study the functional consequences that these point mutations exert on mSWI/SNF complex activity in SMARCB1-deficient tumor cells and extend this investigation to a CRISPR/Cas9-mediated SMARCB1-heterozygous mutant induced pluripotent stem cell. Intriguingly, we observe that the mutant complexes bind similarly to wild-type SMARCB1 complexes at enhancers throughout the genome but often fail to transcriptionally activate nearby genes in a cis-regulatory manner.

ORGANISM(S): Homo sapiens

PROVIDER: GSE124903 | GEO | 2019/11/21

REPOSITORIES: GEO

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mSWI/SNF functional genomic characterization of SMARCB1 mutants in SMARCB1-null and heterozygous settings

Project description:mSWI/SNF functional genomic characterization of SMARCB1 mutants in SMARCB1-null and heterozygous settings

| PRJNA514244 | ENA

SMARCB1-mediated SWI/SNF complex function is essential for enhancer regulation [primary tissue_ChIP-seq]

Project description:SMARCB1 (SNF5/INI1/BAF47), a core subunit of the SWI/SNF (BAF) chromatin remodeling complex, is inactivated in nearly all pediatric rhabdoid tumors. These aggressive cancers are among the most genomically stable, suggesting an epigenetic mechanism by which SMARCB1 loss drives transformation. Here, we show that despite indistinguishable mutational landscapes, human RTs show distinct enhancer H3K27ac signatures, which reveal remnants of differentiation programs. We show that SMARCB1 is required for the integrity of SWI/SNF complexes and that its loss alters enhancer targeting markedly impairing SWI/SNF binding to typical enhancers, particularly those required for differentiation, while maintaining SWI/SNF binding at super-enhancers. We show that these retained super-enhancers are essential for rhabdoid tumor survival, including some that are shared across all subtypes, such as SPRY1, and other lineage-specific super-enhancers like SOX2 in brain-derived RTs. Taken together, our findings reveal a novel chromatin-based epigenetic mechanism underlying the tumor suppressive activity of SMARCB1.

2016-11-21 | GSE71502 | GEO

SMARCB1-mediated SWI/SNF complex function is essential for enhancer regulation [cell line_RNA-seq]

2016-11-21 | GSE71505 | GEO

SMARCB1-mediated SWI/SNF complex function is essential for enhancer regulation [cell line_ChIP-seq]

2016-11-21 | GSE71504 | GEO

SMARCB1-mediated SWI/SNF complex function is essential for enhancer regulation [primary tissue_RNA-seq]

2016-11-21 | GSE71503 | GEO

Transcriptional response to Smarcb1 re-expression in murine derived Smarcb1 deficient p53 null tumors

Project description:SMARCB1 (Snf5/Ini1/Baf47) is a potent tumor suppressor, the loss of which serves as the diagnostic feature in Malignant Rhabdoid Tumors (MRT) and Atypical Teratoid/Rhabdoid Tumors (AT/RT), two highly aggressive forms of pediatric neoplasms. Here, we restore Smarcb1 expression in cells derived from Smarcb1-deficient tumors which developed in Smarcb1-heterozygous p53-/- mice. Profiling Smarcb1 dependent gene expression we find genes which are dependent on Smarcb1 expression to be enriched for ECM and cell adhesion functions. We identify Igfbp7, which is related to the insulin-like growth factor binding proteins family, as a downstream target of Smarcb1 transcriptional activity, and show that re-introduction of Igfbp7 alone can hinder tumor development. Two cancer cell lines, 167 and 365, derived from Smarcb1-deficient tumors which developed in Smarcb1-heterozygous p53-/- mice were re-infected with a retro-viral vector for Smarcb1 re-expression or an empty retro-viral vector as control. Total-RNA was collected 3 days post infection so as to enrich for direct targets of Smarcb1 transcriptionaly regulated genes

2013-12-31 | E-GEOD-46017 | biostudies-arrayexpress

SMARCB1 is required for widespread BAF complex-mediated activation of enhancers and bivalent promoters [RNA-Seq]

Project description:BAF complex perturbations contribute to over 20% of human cancer, yet the mechanisms by which these alterations drive oncogenesis remain poorly understood. The driving role for BAF complex mutations in cancer was first documented in malignant rhabdoid tumor (MRT), an aggressive pediatric cancer in which loss of SMARCB1 (also known as BAF47, INI1, hSNF5), a core BAF complex subunit, is the hallmark genetic alteration. We find that loss of BAF47 destabilizes the biochemical affinity of BAF complexes on chromatin without significantly impairing complex integrity or subunit composition. Rescue of BAF47 in BAF47-deficient sarcoma cell lines results in global increases in BAF complex occupancy, which mediates a major gain in enhancer activation. In addition, we find BAF47 targets BAF complexes to bivalent promoters, resolving bivalency to activation through opposition of polycomb-mediated repression. These findings demonstrate collaborative gene activation by the BAF complex through distinct mechanisms, highlighting specific BAF complex functions that are coopted or abated to drive human cancers and developmental disorders.

2017-09-25 | GSE90633 | GEO

SMARCB1 is required for widespread BAF complex-mediated activation of enhancers and bivalent promoters [Hi-C]

2017-09-25 | GSE90632 | GEO

SMARCB1 is required for widespread BAF complex-mediated activation of enhancers and bivalent promoters [ChIP-Seq]

2017-09-25 | GSE90631 | GEO

A quality control factor for chromatin complexes is synthetic lethal in SMARCB1-mutant cancers

Project description:While oncogenes can potentially be inhibited with small molecules, the loss of tumor suppressors is more common and is problematic because the tumor suppressor proteins are no longer present to be targeted. Notable examples include SMARCB1-mutant cancers, which are highly lethal malignancies driven by the inactivation of a subunit of SWI/SNF chromatin remodeling complexes. To generate mechanistic insight into the consequences of SMARCB1 mutation and to identify vulnerabilities, we contributed 14 SMARCB1-mutant cell lines to a near genome-wide CRISPR screen as part of the Cancer Dependency Map Project1-3. Here, we report that the little-studied gene DDB1-CUL4 Associated Factor 5 (DCAF5) is required for the survival of SMARCB1-mutant cancers. We show that DCAF5 serves a quality control function for SWI/SNF complexes and promotes degradation of incompletely assembled SWI/SNF complexes in the absence of SMARCB1. Upon depletion of DCAF5, SMARCB1-deficient SWI/SNF complexes re-accumulate, bind to target loci, and restore SWI/SNF-mediated gene expression to levels sufficient to reverse the cancer state, including in vivo. Consequently, cancer results not from the loss of SMARCB1 function per se but rather from DCAF5-mediated degradation of SWI/SNF complexes. These data indicate that therapeutic targeting of ubiquitin-mediated quality control factors may effectively reverse the malignant state of some cancers driven by disruption of tumor suppressor complexes.

2024-01-21 | PXD046275 | Pride

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