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Functional interplay between SWI/SNF complexes underlies BRD9 dependency in SMARCB1-mutant cancers [ChIP-seq]

ABSTRACT: Genes encoding subunits of SWI/SNF (BAF) chromatin remodeling complexes are mutated in >20% of cancers. SWI/SNF complexes exist in three distinct families that each contribute to regulation of transcription, although the functional interactions between the families are not well understood. Rhabdoid tumors constitute an informative model system as these highly aggressive cancers are driven by inactivation of a single SWI/SNF subunit, SMARCB1, which is present in two SWI/SNF families (cBAF and PBAF) but not in the third (GBAF/ncBAF). We and others have shown that BRD9, a therapeutically targetable member of ncBAF, is essential specifically in SMARCB1-deficient cancers, suggesting key functional relationships between SMARCB1-containing complexes and BRD9/ncBAF. However, the mechanistic underpinnings of these relationships are poorly understood. Here, we demonstrate that genomic binding of BRD9 is largely dependent upon SMARCB1 such that the absence of SMARCB1 results in significantly reduced BRD9 binding. At select sites, however, we show that SMARCB1-loss results in gain of BRD9 binding and BRD9-dependent accessibility. We find that this gain is associated with expression of genes promoting cell migration. Our results define relationships between SWI/SNF complex families, elucidate mechanisms by which SMARCB1 loss drives oncogenesis, and provide mechanistic insight into the synthetic-lethal relationship between SMARCB1 and BRD9.

ORGANISM(S): Homo sapiens

PROVIDER: GSE210633 | GEO | 2023/07/14

REPOSITORIES: GEO

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Functional interplay between SWI/SNF complexes underlies BRD9 dependency in SMARCB1-mutant cancers [RNA-seq]

Project description:Genes encoding subunits of SWI/SNF (BAF) chromatin remodeling complexes are mutated in >20% of cancers. SWI/SNF complexes exist in three distinct families that each contribute to regulation of transcription, although the functional interactions between the families are not well understood. Rhabdoid tumors constitute an informative model system as these highly aggressive cancers are driven by inactivation of a single SWI/SNF subunit, SMARCB1, which is present in two SWI/SNF families (cBAF and PBAF) but not in the third (GBAF/ncBAF). We and others have shown that BRD9, a therapeutically targetable member of ncBAF, is essential specifically in SMARCB1-deficient cancers, suggesting key functional relationships between SMARCB1-containing complexes and BRD9/ncBAF. However, the mechanistic underpinnings of these relationships are poorly understood. Here, we demonstrate that genomic binding of BRD9 is largely dependent upon SMARCB1 such that the absence of SMARCB1 results in significantly reduced BRD9 binding. At select sites, however, we show that SMARCB1-loss results in gain of BRD9 binding and BRD9-dependent accessibility. We find that this gain is associated with expression of genes promoting cell migration. Our results define relationships between SWI/SNF complex families, elucidate mechanisms by which SMARCB1 loss drives oncogenesis, and provide mechanistic insight into the synthetic-lethal relationship between SMARCB1 and BRD9.

2023-07-14 | GSE210635 | GEO

Functional interplay between SWI/SNF complexes underlies BRD9 dependency in SMARCB1-mutant cancers [CUT & RUN]

2023-07-14 | GSE210634 | GEO

Functional interplay between SWI/SNF complexes underlies BRD9 dependency in SMARCB1-mutant cancers [ATAC-seq]

2023-07-14 | GSE210632 | GEO

BRD9 defines a novel SWI/SNF sub-complex and constitutes a specific vulnerability in malignant rhabdoid tumors [ChIP-seq]

Project description:Bromodomain-containing protein 9 (BRD9) was recently identified to be associated with the chromatin remodeling SWI/SNF(BAF) complex, yet its function within the complex has remained unclear. Here, using genome-scale CRISPR-Cas9 screens, we found that BRD9 constitutes a specific vulnerability in highly malignant pediatric rhabdoid tumors, which are driven by inactivating mutations of SMARCB1 subunit of SWI/SNF complexes. Surprisingly, we found that BRD9 does not belong to the previously identified BAF or PBAF complexes, but instead is found exclusively in a novel of SWI/SNF sub-complex. We show that BRD9-containing complexes lack SMARCB1, which had previously been considered a core subunit present in all SWI/SNF variants. We recently demonstrated that both SMARCB1-containing and ARID1A-containing SWI/SNF complexes preferentially function at enhancers, but here we show that BRD9-containing complexes are located at active promoters as well as enhancers. We show that loss of SMARCB1, as observed in rhabdoid tumors, results in increased BRD9 interaction with SWI/SNF core subunit SMARCC1, consistent with competition between SMARCB1 and BRD9 in the formation of SWI/SNF complexes. Underlying the dependency, we demonstrate that BRD9, via its DUF3512 domain, is essential for maintaining the integrity of its sub-complex, which predominates in the absence of SMARCB1. Taken together, our results reveal a BRD9-containing SWI/SNF subcomplex which is required for the survival of SMARCB1-mutant rhabdoid tumors.

2019-03-14 | GSE120234 | GEO

BRD9 defines a novel SWI/SNF sub-complex and constitutes a specific vulnerability in malignant rhabdoid tumors [RNA-seq]

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BRD9 defines a novel SWI/SNF sub-complex and constitutes a specific vulnerability in malignant rhabdoid tumors [RNA-seq 2]

2019-03-14 | GSE125775 | GEO

A non-canonical SWI/SNF complex underlies synthetic lethality in cancers driven by BAF complex perturbation

Project description:Mammalian SWI/SNF chromatin remodeling complexes exist in three distinct, final-form assemblies: canonical BAF (cBAF), PBAF, and a newly characterized non-canonical complex, ncBAF. However, their complex-specific targeting on chromatin, functions and roles in disease remain largely unknown. Here, we comprehensively map complex assemblies on chromatin and find that ncBAF uniquely localizes to CTCF sites and promoters. We identified ncBAF subunits as major synthetic lethalities specific to human synovial sarcoma and malignant rhabdoid tumor, which share in common cBAF complex perturbation. Chemical and biological depletion of the BRD9 subunit of ncBAF rapidly attenuates SS and MRT cell proliferation. Notably, in cBAF-perturbed cancers, ncBAF complexes retain localization to CTCF sites and promoters, and maintain gene expression at retained mSWI/SNF sites to support cell proliferation in a manner distinct from fusion oncoprotein-mediated targeting. Taken together, these findings unmask the unique targeting and function of ncBAF complexes and present new cancer-specific therapeutic targets.

2018-11-06 | PXD011103 | Pride

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

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

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2024-01-21 | PXD046273 | Pride