Project description:Skin-specific Eda signaling promotes skin appendage development through NF-kB mediated gene transcription. We find that Eda triggers the formation of a novel SWI/SNF complex in which RelB is recruited through a linker protein, Tfg, to interact with the BAF45d component in SWI/SNF (BAF) chromatin remodeling complex. BAF component BAF250a is particularly enriched in skin appendages, and epidermal knockout (cKO) of BAF250a impairs skin appendage development, resulting in phenotypes similar to those of Eda-deficient mouse models. We further reveal that Eda signaling is predominantly mediated by the p50/RelB subclass of NF-kB in both human keratinocytes and mouse skin. Consistent with the phenotype of BAF250a cKO mice, downregulation of RelB, Tfg, or BAF45d arrests the growth of Meibomian gland germs in organ cultures. Transcription profiling consistently identifies several target genes regulated by Eda, RelB and SWI/SNF. In particular, we show that both RelB and SWI/SNF are indispensable for transcription of Eda target Ltb. Chromatin remodeling SWI/SNF recruited to specific gene loci by Eda-activated RelB thus provides a mediation model between an initiation signal and gene activation in organogenesis.
Project description:Mammalian SWI/SNF/BAF chromatin remodeling complexes influence cell lineage determination. While the contribution of mammalian SWI/SNF/BAF complexes in neural progenitor cell (NPC) proliferation and differentiation has been reported, little is known about the transcriptional profiles that determine neurogenesis or gliogenesis. Here we report that BCL7A is a modulator of the SWI/SNF/BAF complex and stimulates the genome-wide occupancy of the ATPase BRG1. We demonstrate that BCL7A is dispensable for SWI/SNF/BAF complex integrity, whereas it is essential to regulate Notch/Wnt pathway and mitochondrial bioenergetics in differentiating NPCs. Together, our findings uncover the unique mechanistic contribution of BCL7A-containing SWI/SNF/BAF complex in mitochondria-driven NPC commitment, thereby providing a better understanding of the cell-intrinsic transcriptional processes that connect metabolism, neuronal morphogenesis and cognitive flexibility.
Project description:Mammalian SWI/SNF/BAF chromatin remodeling complexes influence cell lineage determination. While the contribution of mammalian SWI/SNF/BAF complexes in neural progenitor cell (NPC) proliferation and differentiation has been reported, little is known about the transcriptional profiles that determine neurogenesis or gliogenesis. Here we report that BCL7A is a modulator of the SWI/SNF/BAF complex and stimulates the genome-wide occupancy of the ATPase BRG1. We demonstrate that BCL7A is dispensable for SWI/SNF/BAF complex integrity, whereas it is essential to regulate Notch/Wnt pathway and mitochondrial bioenergetics in differentiating NPCs. Together, our findings uncover the unique mechanistic contribution of BCL7A-containing SWI/SNF/BAF complex in mitochondria-driven NPC commitment, thereby providing a better understanding of the cell-intrinsic transcriptional processes that connect metabolism, neuronal morphogenesis and cognitive flexibility.
Project description:Mammalian SWI/SNF/BAF chromatin remodeling complexes influence cell lineage determination. While the contribution of mammalian SWI/SNF/BAF complexes in neural progenitor cell (NPC) proliferation and differentiation has been reported, little is known about the transcriptional profiles that determine neurogenesis or gliogenesis. Here we report that BCL7A is a modulator of the SWI/SNF/BAF complex and stimulates the genome-wide occupancy of the ATPase BRG1. We demonstrate that BCL7A is dispensable for SWI/SNF/BAF complex integrity, whereas it is essential to regulate Notch/Wnt pathway and mitochondrial bioenergetics in differentiating NPCs. Together, our findings uncover the unique mechanistic contribution of BCL7A-containing SWI/SNF/BAF complex in mitochondria-driven NPC commitment, thereby providing a better understanding of the cell-intrinsic transcriptional processes that connect metabolism, neuronal morphogenesis and cognitive flexibility.
Project description:The SWI/SNF family of ATP-dependent chromatin remodeling complexes are implicated in multiple DNA damage response mechanisms and frequently mutated in cancer. The BAF and PBAF complexes are two major types of SWI/SNF complexes that are functionally distinguished by their exclusive subunits. Accumulating evidence suggests that double-strand breaks (DSBs) in transcriptionally active DNA are preferentially repaired by a dedicated homologous recombination pathway. We show that different BAF and PBAF subunits promote homologous recombination and are rapidly recruited to DSBs in a transcription-dependent manner. The PBAF complex promotes RNA polymerase II eviction near DNA damage to rapidly initiate transcriptional silencing, while the BAF complex helps to maintain this transcriptional silencing. Furthermore, ARID1A-containing BAF complexes promote RNaseH1 and RAD52 recruitment to facilitate R-loop resolution and DNA repair. Our results highlight how multiple SWI/SNF complexes perform different functions to enable DNA repair in the context of actively transcribed genes.
Project description:The SWI/SNF (or BAF) complex is an essential chromatin remodeler that regulates DNA accessibility at developmental genes and enhancers. SWI/SNF subunits are among the most frequently mutated genes in cancer and neurodevelopmental disorders. These mutations are often heterozygous loss-of-function alleles, indicating a dosage-sensitive role for SWI/SNF subunits in chromatin regulation. However, the molecular mechanisms that regulate SWI/SNF subunit dosage to ensure proper complex assembly remain largely unexplored. We performed a genome-wide CRISPR KO screen, using epigenome editing in mouse embryonic stem cells, and identified Mlf2 and Rbm15 as regulators of SWI/SNF complex activity. First, we show that MLF2, a poorly characterized chaperone protein, regulates a subset of SWI/SNF target genes by promoting its chromatin remodeling activity. Rapid degradation of MLF2 reduces chromatin accessibility at sites that depend on high levels of SWI/SNF binding to maintain open chromatin. Next, we find that RBM15, part of the m6A RNA methylation writer complex, controls m6A modifications on specific SWI/SNF mRNAs to regulate protein levels of these subunits. Misregulation of m6A methylation causes overexpression of core SWI/SNF subunits leading to the assembly of incomplete complexes lacking the catalytic ATPase/ARP subunits. These data indicate that targeting modulators of SWI/SNF complex assembly may offer a potent therapeutic strategy for diseases associated with impaired chromatin remodeling.
Project description:The SWI/SNF (or BAF) complex is an essential chromatin remodeler that regulates DNA accessibility at developmental genes and enhancers. SWI/SNF subunits are among the most frequently mutated genes in cancer and neurodevelopmental disorders. These mutations are often heterozygous loss-of-function alleles, indicating a dosage-sensitive role for SWI/SNF subunits in chromatin regulation. However, the molecular mechanisms that regulate SWI/SNF subunit dosage to ensure proper complex assembly remain largely unexplored. We performed a genome-wide CRISPR KO screen, using epigenome editing in mouse embryonic stem cells, and identified Mlf2 and Rbm15 as regulators of SWI/SNF complex activity. First, we show that MLF2, a poorly characterized chaperone protein, regulates a subset of SWI/SNF target genes by promoting its chromatin remodeling activity. Rapid degradation of MLF2 reduces chromatin accessibility at sites that depend on high levels of SWI/SNF binding to maintain open chromatin. Next, we find that RBM15, part of the m6A RNA methylation writer complex, controls m6A modifications on specific SWI/SNF mRNAs to regulate protein levels of these subunits. Misregulation of m6A methylation causes overexpression of core SWI/SNF subunits leading to the assembly of incomplete complexes lacking the catalytic ATPase/ARP subunits. These data indicate that targeting modulators of SWI/SNF complex assembly may offer a potent therapeutic strategy for diseases associated with impaired chromatin remodeling.
Project description:Mammalian SWI/SNF (mSWI/SNF) ATP-dependent chromatin remodeling complexes are large, multisubunit molecular machines that play vital roles in regulating genomic architecture and are frequently disrupted in human cancer and developmental disorders. To date, the organization and pathway of assembly of these chromatin regulators remain unknown, presenting a major barrier to structural and functional determination. Here we elucidate the architecture and assembly pathway of three different classes of mammalian SWI/SNF complexes: canonical BAF, PBAF, and a newly defined complex, ncBAF, and define the requirement of each subunit for complex formation and stability. Using affinity purification of endogenous complexes from mammalian and Drosophila cells coupled with cross linking-mass spectrometry, we uncover three distinct and evolutionarily conserved modules, their organization, and the temporal incorporation of these modules into each complete mSWI/SNF complex class.
Project description:Mammalian SWI/SNF (mSWI/SNF) ATP-dependent chromatin remodeling complexes are large, multisubunit molecular machines that play vital roles in regulating genomic architecture and are frequently disrupted in human cancer and developmental disorders. To date, the organization and pathway of assembly of these chromatin regulators remain unknown, presenting a major barrier to structural and functional determination. Here we elucidate the architecture and assembly pathway of three different classes of mammalian SWI/SNF complexes: canonical BAF, PBAF, and a newly defined complex, ncBAF, and define the requirement of each subunit for complex formation and stability. Using affinity purification of endogenous complexes from mammalian and Drosophila cells coupled with cross linking-mass spectrometry, we uncover three distinct and evolutionarily conserved modules, their organization, and the temporal incorporation of these modules into each complete mSWI/SNF complex class.
Project description:Every known SWI/SNF chromatin-remodeling complex incorporates an ARID DNA binding domain-containing subunit. Despite being a ubiquitous component of the complex, physiological roles for this domain remain undefined. Here we show that disruption of ARID1a-DNA binding in mice results in embryonic lethality, with mutant embryos manifesting prominent defects in the heart and extraembryonic vasculature. The DNA binding defective mutant ARID1a subunit is stably expressed and capable of assembling into a SWI/SNF complex with chromatin remodeling activity, but promoter occupancy by ARID1a-containing, SWI/SNF complexes (BAF-A) is impaired. Depletion of ARID domain-dependent, BAF-A associations at THROMBOSPONDIN 1 (THBS1) led to the concomitant upregulation of this anti-angiogenic protein. Using a THBS1 promoter-reporter gene, we further show that BAF-A directly regulates THBS1 promoter activity in an ARID domain-dependent manner. Our data not only demonstrate that ARID-DNA interactions are physiologically relevant in higher eukaryotes, but also indicate these interactions can facilitate SWI/SNF binding to target sites in vivo. These findings support the model wherein cooperative interactions among intrinsic subunit-chromatin interaction domains and sequence-specific transcription factors drive SWI/SNF recruitment.