Project description:The SWI/SNF ATP-dependent chromatin remodeler is a master regulator of the epigenome; controlling pluripotency, cell fate determination and differentiation. There is a sparsity of information on the autoregulation of SWI/SNF, the domains involved and their mode of action. We find a DNA or RNA binding module conserved from yeast to humans located in the C-terminus of the catalytic subunit of SWI/SNF called the AT-hook that positively regulates the chromatin remodeling activity of yeast and mouse SWI/SNF. The AT-hook in yeast SWI/SNF interacts with the SnAC and ATPase domains, which after binding to nucleosome switches to contacting the N-terminus of histone H3. Deletion of the AT-hooks in yeast SWI/SNF and mouse esBAF complexes reduces the remodeling activity of SWI/SNF without affecting complex integrity or its recruitment to nucleosomes. In addition, deletion of the AT-hook impairs the ATPase and nucleosome mobilizing activities of yeast SWI/SNF without disrupting the interactions of the ATPase domain with nucleosomal DNA. The AT-hook is also important in vivo for SWI/SNF-dependent response to amino acid starvation in yeast and for cell lineage priming in mouse embryonic stem cells. In summary, the AT-hook is shown to be an evolutionarily conserved autoregulatory domain of SWI/SNF that positively regulates SWI/SNF both in vitro and in vivo.
Project description:The SWI/SNF complexes play crucial roles in chromatin remodeling, with the protein BDH emerging as a key component in Arabidopsis. Through evolutionary analysis, we demonstrate the conservation of BDH function across mammals, yeast, and plants. Our study reveals that BDH is integral to the stability of the catalytic subcomplex within SWI/SNF assemblies. Furthermore, we elucidate the biological and molecular implications of BDH in Arabidopsis, highlighting its involvement in nucleosomal occupancy regulation. Mutational characterization and transcriptomic analyses underscore BDH's significance, shedding light on its multifaceted role in chromatin dynamics and gene regulation.
Project description:The SWI/SNF complexes play crucial roles in chromatin remodeling, with the protein BDH emerging as a key component in Arabidopsis. Through evolutionary analysis, we demonstrate the conservation of BDH function across mammals, yeast, and plants. Our study reveals that BDH is integral to the stability of the catalytic subcomplex within SWI/SNF assemblies. Furthermore, we elucidate the biological and molecular implications of BDH in Arabidopsis, highlighting its involvement in nucleosomal occupancy regulation. Mutational characterization and transcriptomic analyses underscore BDH's significance, shedding light on its multifaceted role in chromatin dynamics and gene regulation.
Project description:SWI/SNF chromatin remodeling complexes play critical roles in transcription and other chromatin-related processes. The analysis of the two members of this class in Saccharomyces cerevisiae, SWI/SNF and RSC, has heavily contributed to our understanding of these complexes. To understand the in vivo functions of SWI/SNF and RSC in an evolutionarily distant organism, we have characterized these complexes in Schizosaccharomyces pombe. While core components are conserved between the two yeasts, the compositions of S. pombe SWI/SNF and RSC differ from their S. cerevisiae counterparts and in some ways are more similar to metazoan complexes. Furthermore, several of the conserved proteins, including actin-like proteins, are strikingly different between the two yeasts with respect to their requirement for viability. Finally, phenotypic and microarray analyses identified widespread requirements for SWI/SNF and RSC on transcription including strong evidence that SWI/SNF directly represses iron transport genes.
Project description:Studies in yeast and animals have revealed that histone deacetylases (HDACs) often act as components of multiprotein complexes, including chromatin remodeling complexes (CRCs). In our group, we found evidence for the interaction between Arabidopsis HD2C deacetylase and a BRM-containing SWI/SNF chromatin remodeling complex. Moreover, we revealed a novel function of HD2C as a regulator of the heat stress response. HD2C transcript levels were strongly induced in plants subjected to heat treatment and the expression of selected heat-responsive genes was up-regulated in heat-stressed hd2c mutant, suggesting that HD2C acts to down-regulate heat-activated genes. Microarray transcriptome analysis of brm and hd2c mutants identified a subset of commonly regulated heat-responsive genes, and the effect of the double brm hd2c mutation on the expression of these genes was non-additive. Moreover, heat treated hd2c, brm and brm hd2c mutants displayed similar rates of growth retardation. Taken together, our findings suggest that HD2C and BRM act in a common genetic pathway to regulate the Arabidopsis heat stress response. 3-week-old WT (Col-0), hd2c-3, brm-1 and brm-1 hd3c-3 plants were collected before and after 1 hour of heat (38°C) treatment. For each variant, three biological replicates with similar expression levels of selected marker genes, were chosen for microarray analysis.
Project description:The 12-subunit Swi/Snf chromatin remodeling complex is conserved from yeast to humans. It functions to alter nucleosome positions by either sliding nucleosomes on DNA or evicting histones. Interestingly, 20% of all human cancers carry mutations in subunits of the Swi/Snf complex. Many of these mutations cause protein instability and loss, resulting in partial Swi/Snf complexes. Although several studies have shown that histone acetylation and activator-dependent recruitment of Swi/Snf regulate its function, it is less well understood how subunits regulate stability and function of the complex. Using functional proteomic and genomic approaches, we have assembled the network architecture of yeast Swi/Snf. In addition, we find that subunits of the Swi/Snf complex regulate occupancy of the catalytic subunit Snf2, thereby modulating gene transcription. Our findings have direct bearing on how cancer-causing mutations in orthologous subunits of human Swi/Snf may lead to aberrant regulation of gene expression by this complex.
Project description:The 12-subunit Swi/Snf chromatin remodeling complex is conserved from yeast to humans. It functions to alter nucleosome positions by either sliding nucleosomes on DNA or evicting histones. Interestingly, 20% of all human cancers carry mutations in subunits of the Swi/Snf complex. Many of these mutations cause protein instability and loss, resulting in partial Swi/Snf complexes. Although several studies have shown that histone acetylation and activator-dependent recruitment of Swi/Snf regulate its function, it is less well understood how subunits regulate stability and function of the complex. Using functional proteomic and genomic approaches, we have assembled the network architecture of yeast Swi/Snf. In addition, we find that subunits of the Swi/Snf complex regulate occupancy of the catalytic subunit Snf2, thereby modulating gene transcription. Our findings have direct bearing on how cancer-causing mutations in orthologous subunits of human Swi/Snf may lead to aberrant regulation of gene expression by this complex.
Project description:Studies in yeast and animals have revealed that histone deacetylases (HDACs) often act as components of multiprotein complexes, including chromatin remodeling complexes (CRCs). In our group, we found evidence for the interaction between Arabidopsis HD2C deacetylase and a BRM-containing SWI/SNF chromatin remodeling complex. Moreover, we revealed a novel function of HD2C as a regulator of the heat stress response. HD2C transcript levels were strongly induced in plants subjected to heat treatment and the expression of selected heat-responsive genes was up-regulated in heat-stressed hd2c mutant, suggesting that HD2C acts to down-regulate heat-activated genes. Microarray transcriptome analysis of brm and hd2c mutants identified a subset of commonly regulated heat-responsive genes, and the effect of the double brm hd2c mutation on the expression of these genes was non-additive. Moreover, heat treated hd2c, brm and brm hd2c mutants displayed similar rates of growth retardation. Taken together, our findings suggest that HD2C and BRM act in a common genetic pathway to regulate the Arabidopsis heat stress response.
Project description:The nucleosome remodeling complex RSC functions throughout the yeast genome to set the positions of -1 and +1 nucleosomes and thereby determines the widths of nucleosome-depleted regions (NDRs). The related complex SWI/SNF participates in nucleosome remodeling/eviction and promoter activation at certain yeast genes, including those activated by transcription factor Gcn4, but does not appear to function broadly in establishing NDRs. By analyzing the large cohort of Gcn4-induced genes in mutants lacking the catalytic subunits of SWI/SNF or RSC, we uncovered cooperation between these remodelers in evicting nucleosomes from different locations in the promoter and in repositioning the +1 nucleosome downstream to produce wider NDRs, highly depleted of nucleosomes, during transcriptional activation. SWI/SNF also functions on par with RSC at the most highly transcribed constitutively expressed genes, suggesting general cooperation by these remodelers for maximal transcription. SWI/SNF and RSC occupancies are greatest at the most highly expressed genes, consistent with their cooperative functions in nucleosome remodeling and transcriptional activation. Thus, SWI/SNF acts comparably to RSC in forming wide, nucleosome-free NDRs to achieve high-level transcription, but only at the most highly expressed genes exhibiting the greatest SWI/SNF occupancies.
Project description:Aberrant forms of the SWI/SNF chromatin remodeling complex are associated with human disease. Loss of the Snf5 subunit of SWI/SNF is a driver mutation in pediatric rhabdoid cancers and forms aberrant sub-complexes that are not well characterized. We determined the effects of loss of Snf5 on the composition, nucleosome binding, recruitment and remodeling activities of yeast SWI/SNF. The Snf5 subunit interacts with the ATPase domain of Snf2 and forms a submodule consisting of Snf5, Swp82 and Taf14 as shown by mapping SWI/SNF subunit interactions by crosslinking-mass spectrometry and subunit deletion followed by immunoaffinity chromatography. Snf5 promoted binding of the Snf2 ATPase domain to nucleosomal DNA, enhanced its catalytic activity and facilitated nucleosome remodeling. Snf5 was required for acidic transcription factors to recruit SWI/SNF to chromatin. RNA-seq analysis suggested that both the recruitment and catalytic functions mediated by Snf5 are required for SWI/SNF regulation of gene expression.