Project description:Alterations in the function of transcriptional regulators can orchestrate oncogenic programs that are critical for the transformation and survival of cancer cells. Here we show that the BAF chromatin remodeling complex, which is mutated in over 20% of human tumors, interacts with EWSR1, a member of the FET family of proteins containing prion-like domains that are frequent partners in oncogenic fusions with transcription factors. In Ewing sarcoma, characterized by the EWS-FLI1 fusion, we find that the BAF complex is recruited by EWS-FLI1 to tumor specific enhancers at GGAA microsatellite repeats and contributes to the activation of target genes. This process depends on tyrosine residues that are necessary for the aggregation properties of the EWSR1 prion-like domain and is a neomorphic feature of EWS-FLI1 compared to the wild type ETS transcription factor FLI1. Furthermore, fusion of short fragments of the EWSR1 prion-like domain to FLI1 is sufficient to recapitulate EWS-FLI1-mediated gene expression. Our studies demonstrate that the aggregation properties of prion-like domains can retarget chromatin regulatory complexes to establish and maintain oncogenic gene expression and proliferation.
Project description:Alterations in the function of transcriptional regulators can orchestrate oncogenic programs that are critical for the transformation and survival of cancer cells. Here we show that the BAF chromatin remodeling complex, which is mutated in over 20% of human tumors, interacts with EWSR1, a member of the FET family of proteins containing prion-like domains that are frequent partners in oncogenic fusions with transcription factors. In Ewing sarcoma, characterized by the EWS-FLI1 fusion, we find that the BAF complex is recruited by EWS-FLI1 to tumor specific enhancers at GGAA microsatellite repeats and contributes to the activation of target genes. This process depends on tyrosine residues that are necessary for the aggregation properties of the EWSR1 prion-like domain and is a neomorphic feature of EWS-FLI1 compared to the wild type ETS transcription factor FLI1. Furthermore, fusion of short fragments of the EWSR1 prion-like domain to FLI1 is sufficient to recapitulate EWS-FLI1-mediated gene expression. Our studies demonstrate that the aggregation properties of prion-like domains can retarget chromatin regulatory complexes to establish and maintain oncogenic gene expression and proliferation.
Project description:Alterations in the function of transcriptional regulators can orchestrate oncogenic programs that are critical for the transformation and survival of cancer cells. Here we show that the BAF chromatin remodeling complex, which is mutated in over 20% of human tumors, interacts with EWSR1, a member of the FET family of proteins containing prion-like domains that are frequent partners in oncogenic fusions with transcription factors. In Ewing sarcoma, characterized by the EWS-FLI1 fusion, we find that the BAF complex is recruited by EWS-FLI1 to tumor specific enhancers at GGAA microsatellite repeats and contributes to the activation of target genes. This process depends on tyrosine residues that are necessary for the aggregation properties of the EWSR1 prion-like domain and is a neomorphic feature of EWS-FLI1 compared to the wild type ETS transcription factor FLI1. Furthermore, fusion of short fragments of the EWSR1 prion-like domain to FLI1 is sufficient to recapitulate EWS-FLI1-mediated gene expression. Our studies demonstrate that the aggregation properties of prion-like domains can retarget chromatin regulatory complexes to establish and maintain oncogenic gene expression and proliferation.
Project description:Chromosomal rearrangements resulting in the fusion of TMRPSS2, an androgen-regulated gene, and the ETS family transcription factor ERG occur in over half of prostate cancers. However, the mechanism by which ERG promotes oncogenic gene expression and proliferation remains incompletely understood. Here, we identify a binding interaction between ERG and the mammalian SWI/SNF (BAF) ATP-dependent chromatin remodeling complex, which is conserved among other ETS factors, including ETV1, ETV4, and ETV5. We find that ERG drives genome-wide retargeting of BAF complexes in a manner dependent on binding of ERG to the ETS DNA motif. Moreover, ERG requires intact BAF complexes for chromatin occupancy and BAF complex ATPase activity for target gene regulation. In a prostate organoid model, BAF complexes are required for ERG-mediated basal-to-luminal transition, a hallmark of ERG activity in prostate cancer. These observations suggest a fundamental interdependence between ETS transcription factors and BAF chromatin remodeling complexes in cancer.
Project description:Chromosomal rearrangements resulting in the fusion of TMRPSS2, an androgen-regulated gene, and the ETS family transcription factor ERG occur in over half of prostate cancers. However, the mechanism by which ERG promotes oncogenic gene expression and proliferation remains incompletely understood. Here, we identify a binding interaction between ERG and the mammalian SWI/SNF (BAF) ATP-dependent chromatin remodeling complex, which is conserved among other ETS factors, including ETV1, ETV4, and ETV5. We find that ERG drives genome-wide retargeting of BAF complexes in a manner dependent on binding of ERG to the ETS DNA motif. Moreover, ERG requires intact BAF complexes for chromatin occupancy and BAF complex ATPase activity for target gene regulation. In a prostate organoid model, BAF complexes are required for ERG-mediated basal-to-luminal transition, a hallmark of ERG activity in prostate cancer. These observations suggest a fundamental interdependence between ETS transcription factors and BAF chromatin remodeling complexes in cancer.
Project description:Resolution and formation of facultative heterochromatin is essential to development, reprogramming, and oncogenesis. The mechanisms underlying these changes are poorly understood due to difficulty with interrogating heterochromatin dynamics and structure in vivo. BAF (mSWI/SNF) ATP-dependent chromatin remodeling complexes are known to promote chromatin accessibility. As the function of topoisomerase IIa (TOP2A) is largely dependent on BAF complexes in embryonic stem (ES) cells, we tested whether TOP2 was involved in BAF-mediated resolution of heterochromatin by performing ATAC-seq on ES cells treated with the TOP2 inhibitor ICRF-193, Brg1 (the primary ATPase subunit of esBAF complexes) conditional knockout cells, and Baf53a (a non-catalytic subunit dispensable for in vitro remodeling) conditional knockout cells. We found that TOP2 synergizes with BAF complexes genome-wide to resolve facultative heterochromatin to accessible chromatin at a large number of regulatory elements.
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.