Project description:Mammalian genomes contain several billion base pairs of DNA which are packaged in chromatin fibers. At selected gene loci, cohesin complexes have been proposed to arrange chromatin fibers into higher-order structures, but it is poorly understood how cohesin performs this task, how important this function is for determining the structure of chromosomes, and how this process is regulated to allow changes in gene expression. Here we show that the cohesin release factor Wapl controls chromatin structure and gene regulation at numerous loci throughout the mouse genome. Conditional deletion of the Wapl gene leads to stable accumulation of cohesin on chromatin, chromatin compaction, altered gene expression, cell cycle delay, chromosome segregation defects and embryonic lethality. In Wapl deficient chromosomes, cohesin accumulates in an axial domain, similar to how condensins form a M-bM-^@M-^\scaffoldM-bM-^@M-^] in mitotic chromosomes. We propose that Wapl controls chromatin structure and gene regulation by determining the residence time with which cohesin binds to DNA. 4 biological replicates for each genotype (Wapl +/F; Wapl -/F) treated with/without 4-OHT =16 samples
Project description:Mammalian genomes contain several billion base pairs of DNA which are packaged in chromatin fibers. At selected gene loci, cohesin complexes have been proposed to arrange chromatin fibers into higher-order structures, but it is poorly understood how cohesin performs this task, how important this function is for determining the structure of chromosomes, and how this process is regulated to allow changes in gene expression. Here we show that the cohesin release factor Wapl controls chromatin structure and gene regulation at numerous loci throughout the mouse genome. Conditional deletion of the Wapl gene leads to stable accumulation of cohesin on chromatin, chromatin compaction, altered gene expression, cell cycle delay, chromosome segregation defects and embryonic lethality. In Wapl deficient chromosomes, cohesin accumulates in an axial domain, similar to how condensins form a “scaffold” in mitotic chromosomes. We propose that Wapl controls chromatin structure and gene regulation by determining the residence time with which cohesin binds to DNA. ChIP-Seq using two different antibodies (CTCF, Smc3); one (CTCF) and two (Smc3) replicates; two different genotypes (Wapl +/delta, Wapl -/delta). The control sample is a single-replicate INPUT for each genotype.
Project description:SETMAR/Metnase is a naturally occurring fusion protein that consists of a histone-lysine methyltransferase domain and an HsMar1 transposase. To elucidate the biological role of SETMAR, it is crucial to identify genomic targets to which SETMAR specifically binds and link these sites to the regulation of gene expression. Herein, we mapped the genomic landscape of SETMAR in a near-haploid human leukemia cell line (HAP1) in order to identify on-target and off-target binding sites at high resolution and to elucidate their role in terms of gene expression. Our analysis revealed a perfect correlation between SETMAR and inverted tandem repeats (ITRs) of HsMar1 transposon remnants, which are considered as natural target sites for SETMAR chromosome binding. However, we did not detect any untargeted events at non-ITR sequences, calling into question previously proposed off-target binding sites. We identified sequence fidelity of the ITR motif as a key factor for determining the binding affinity of SETMAR for chromosomes, as higher ITR fidelity resulted in increased affinity for chromatin and stronger repression of SETMAR-bound gene loci. These associations highlight how SETMAR’s chromatin binding fine-tune gene regulatory networks in human tumour cells.
Project description:In budding yeast, telomeres and the mating type (HM) loci are found in a heterochromatin-like silent structure initiated by Rap1 and extended by the interaction of Sir (Silencing Information Regulator) proteins with histones. Binding data demonstrate that both the H3 and H4 N terminal domains required for silencing in vivo interact directly with Sir3 and Sir4 in vitro. The role of H4 lysine 16 deacetylation is well established in Sir3 protein recruitment, however that of the H3 N terminal tail has remained unclear. In order to characterize the role of H3 in silent chromatin formation and compare it to H4 we have generated comprehensive high resolution genome-wide binding maps of heterochromatin proteins. We find that H4 lysine 16 deacetylation is required for the recruitment and spreading of heterochromatin proteins at all telomeres and HM loci. In contrast the H3 N terminus is required for neither recruitment nor spreading of Sir proteins. Instead, deletion of the H3 tail leads to increased accessibility within heterochromatin of an ectopic bacterial dam methylase and the decreased mobility of an HML heterochromatic fragment in sucrose gradients. These findings indicate an altered chromatin structure. We propose that Sir proteins recruited by the H4 tail then interact with the H3 tail to form a higher order silent chromatin structure.
Project description:Mammalian genomes contain several billion base pairs of DNA which are packaged in chromatin fibers. At selected gene loci, cohesin complexes have been proposed to arrange chromatin fibers into higher-order structures, but it is poorly understood how cohesin performs this task, how important this function is for determining the structure of chromosomes, and how this process is regulated to allow changes in gene expression. Here we show that the cohesin release factor Wapl controls chromatin structure and gene regulation at numerous loci throughout the mouse genome. Conditional deletion of the Wapl gene leads to stable accumulation of cohesin on chromatin, chromatin compaction, altered gene expression, cell cycle delay, chromosome segregation defects and embryonic lethality. In Wapl deficient chromosomes, cohesin accumulates in an axial domain, similar to how condensins form a “scaffold” in mitotic chromosomes. We propose that Wapl controls chromatin structure and gene regulation by determining the residence time with which cohesin binds to DNA.
Project description:Mammalian genomes contain several billion base pairs of DNA which are packaged in chromatin fibers. At selected gene loci, cohesin complexes have been proposed to arrange chromatin fibers into higher-order structures, but it is poorly understood how cohesin performs this task, how important this function is for determining the structure of chromosomes, and how this process is regulated to allow changes in gene expression. Here we show that the cohesin release factor Wapl controls chromatin structure and gene regulation at numerous loci throughout the mouse genome. Conditional deletion of the Wapl gene leads to stable accumulation of cohesin on chromatin, chromatin compaction, altered gene expression, cell cycle delay, chromosome segregation defects and embryonic lethality. In Wapl deficient chromosomes, cohesin accumulates in an axial domain, similar to how condensins form a “scaffold” in mitotic chromosomes. We propose that Wapl controls chromatin structure and gene regulation by determining the residence time with which cohesin binds to DNA.
Project description:The packaging of DNA into chromatin plays an important role in transcriptional regulation and nuclear processes. Brahma related gene-1 SMARCA4 (also known as BRG1), the essential ATPase subunit of the mammalian SWI/SNF chromatin remodeling complex, uses the energy from ATP hydrolysis to disrupt nucleosomes at target regions. Although the transcriptional role of SMARCA4 at gene promoters is well-studied, less is known about its role in higher-order genome organization. SMARCA4 knockdown in human mammary epithelial MCF-10A cells resulted in 176 up-regulated genes, including many related to lipid and calcium metabolism, and 1292 down-regulated genes, some of which encode extracellular matrix (ECM) components that can exert mechanical forces and affect nuclear structure. ChIP-seq analysis of SMARCA4 localization and SMARCA4-bound super-enhancers demonstrated extensive binding at intergenic regions. Furthermore, Hi-C analysis showed extensive SMARCA4-mediated alterations in higher-order genome organization at multiple resolutions. First, SMARCA4 knockdown resulted in clustering of intra- and inter- sub-telomeric regions, demonstrating a novel role for SMARCA4 in telomere organization. SMARCA4 binding was enriched at TAD (Topologically Associating Domain) boundaries, and SMARCA4 knockdown resulted in weakening of TAD boundary strength. Taken together, these findings provide a dynamic view of SMARCA4-dependent changes in higher-order chromatin organization and gene expression, identifying SMARCA4 as a novel component of chromatin organization. Hi-C and RNA-seq experiments were conducted in MCF-10A shSCRAM and shSMARCA4 cells. SMARCA4 ChIP-seq was conducted in wildtype MCF-10A cells.
Project description:Higher order chromatin structure establishes domains that organize the genome and coordinate gene expression. However, the molecular mechanisms controlling transcription of individual loci within a topological domain (TAD) are not fully understood. The cystic fibrosis transmembrane conductance regulator (CFTR) gene provides a paradigm for investigating these mechanisms. CFTR occupies a TAD bordered by CTCF/cohesin binding sites within which are cell-type-selective cis-regulatory elements for the locus. We showed previously that intronic and extragenic enhancers, when occupied by specific transcription factors, are recruited to the CFTR promoter by a looping mechanism to drive gene expression. Here we use a combination of CRISPR/Cas9 editing of cis-regulatory elements and siRNA-mediated depletion of architectural proteins to determine the relative contribution of structural elements and enhancers to the higher order structure and expression of the CFTR locus. We found the boundaries of the CFTR TAD are conserved among diverse cell types and are dependent on CTCF and cohesin complex. Removal of an upstream CTCF-binding insulator alters the interaction profile, but has little effect on CFTR expression. Within the TAD, intronic enhancers recruit cell-type selective transcription factors and deletion of a pivotal enhancer element dramatically decreases CFTR expression, but has minor effect on its 3D structure. Examination of open chromatin region in Caco2 (colorectal adenocarcinoma cells), HBE (primary human bronchial epithelial cells), and primary adult human epididymis cells