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: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.
Project description:The composition of chromatin remodeling complexes dictates how these enzymes control transcriptional programs and cellular identity. Here, we investigate the composition of SWI/SNF complexes in embryonic stem cells (ESCs). In contrast to differentiated cells, ESCs have a biased incorporation of certain paralogous SWI/SNF subunits, with low levels of Brm, BAF170 and ARID1B. Upon differentiation, the expression of these subunits increases, resulting in a higher diversity of compositionally distinct SWI/SNF enzymes. We also identify Brd7 as a novel component of the PBAF complex in both ESCs and differentiated cells. Using shRNA-mediated depletion of Brg1, we show that SWI/SNF can function as both a repressor and an activator in pluripotent cells, regulating expression of developmental modifiers and signaling components such as Nodal, ADAMTS1, Bmi-1, CRABP1 and TRH. Knock-down studies of PBAF-specific Brd7 and of a signature subunit within the BAF complex, ARID1A, show that these two sub-complexes affect SWI/SNF target genes differentially, in some cases even antagonistically. This may be due to their different biochemical properties. Finally, we examine the role of SWI/SNF in regulating its target genes during differentiation. We find that SWI/SNF affects recruitment of components of the pre-initiation complex in a promoter-specific manner, to modulate transcription positively or negatively. Taken together, our results provide insight into the function of compositionally diverse SWI/SNF enzymes that underlie their inherent gene-specific mode of action. R1 ESCs were infected in duplicates with shRNA targeting Brg1 or GLUT4 (as a control). Knockdown of Brg1 mRNA affected Brg1 protein levels efficiently. RNA was isolated 67 hours post-infection and analyzed using microarrays.
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.