Project description:Clustering of multiple transcription factor binding sites (TFBSs) for the same TF has proved to be a pervasive feature of cis-regulatory elements in eukaryotic genome. However, contribution of binding sites within the homotypic clusters of TFBSs (HCTs) to TF binding and target gene expression remains to be understood. Here, we characterize the CHD4 enhancers that harbor unique functional ZNF410 HCTs genome-wide. We uncover that ZNF410 controls chromatin accessibility and activity of the CHD4 enhancer regions. We demonstrate that ZNF410 binds to the HCTs in a collaborative fashion, further conferring transcriptional activation. Especially, three ZNF410 motifs (sub-HCTs) located at 3´ end of the distal enhancer act as “switch motifs” to control the chromatin accessibility and enhancer activity. Mechanistically, SWI/SNF complex is selectively required to mediate cooperative ZNF410 binding for CHD4 expression. Together, our findings expose a complex functional hierarchy of homotypic clustered motifs, which cooperates to fine-tune target gene expression.
Project description:Clustering of multiple transcription factor binding sites (TFBSs) for the same TF has proved to be a pervasive feature of cis-regulatory elements in eukaryotic genome. However, contribution of binding sites within the homotypic clusters of TFBSs (HCTs) to TF binding and target gene expression remains to be understood. Here, we characterize the CHD4 enhancers that harbor unique functional ZNF410 HCTs genome-wide. We uncover that ZNF410 controls chromatin accessibility and activity of the CHD4 enhancer regions. We demonstrate that ZNF410 binds to the HCTs in a collaborative fashion, further conferring transcriptional activation. Especially, three ZNF410 motifs (sub-HCTs) located at 3´ end of the distal enhancer act as “switch motifs” to control the chromatin accessibility and enhancer activity. Mechanistically, SWI/SNF complex is selectively required to mediate cooperative ZNF410 binding for CHD4 expression. Together, our findings expose a complex functional hierarchy of homotypic clustered motifs, which cooperates to fine-tune target gene expression.
Project description:Clustering of multiple transcription factor binding sites (TFBSs) for the same TF has proved to be a pervasive feature of cis-regulatory elements in eukaryotic genome. However, contribution of binding sites within the homotypic clusters of TFBSs (HCTs) to TF binding and target gene expression remains to be understood. Here, we characterize the CHD4 enhancers that harbor unique functional ZNF410 HCTs genome-wide. We uncover that ZNF410 controls chromatin accessibility and activity of the CHD4 enhancer regions. We demonstrate that ZNF410 binds to the HCTs in a collaborative fashion, further conferring transcriptional activation. Especially, three ZNF410 motifs (sub-HCTs) located at 3´ end of the distal enhancer act as “switch motifs” to control the chromatin accessibility and enhancer activity. Mechanistically, SWI/SNF complex is selectively required to mediate cooperative ZNF410 binding for CHD4 expression. Together, our findings expose a complex functional hierarchy of homotypic clustered motifs, which cooperates to fine-tune target gene expression.
Project description:Here we performed transcriptional profiling of the prostate cancer cell lines LNCaP and 22Rv1 comparing non-targeting siRNA treatment versus siRNAs targeting SWI/SNF complex proteins (SMARCA2, SMARCA4, and SMARCB1). Goal was to determine the effect of SWI/SNF knockdown on gene expression in prostate cancer. Two-condition experiment: non-targeting siRNA versus SWI/SNF-siRNA treated cells. Three SWI/SNF proteins were targeted: SMARCA2, SMARCA4, and SMARB1. Biological replicates: 1 control replicate, 2 treatment replicates per SWI/SNF protein. Technical replicates: 1 replicate per SWI/SNF protein. Cell lines: 22Rv1 and LNCaP.
Project description:A systems understanding of nuclear organization and events is critical for determining how cells divide, differentiate and respond to stimuli and for identifying the causes of diseases. Chromatin remodeling complexes such as SWI/SNF have been implicated in a wide variety of cellular processes including gene expression, nuclear organization, centromere function and chromosomal stability, and mutations in SWI/SNF components have been linked to several types of cancer. To better understand the biological processes in which chromatin remodeling proteins participate we globally mapped binding regions for several components of the SWI/SNF complex throughout the human genome using ChIP-Seq. SWI/SNF components were found to lie near regulatory elements integral to transcription (e.g. 5M-bM-^@M-^Y ends, RNA Polymerases II and III and enhancers) as well as regions critical for chromosome organization (e.g. CTCF, lamins and DNA replication origins). To further elucidate the association of SWI/SNF subunits with each other as well as with other nuclear proteins we also analyzed SWI/SNF immunoprecipitated complexes by mass spectrometry. Individual SWI/SNF factors are associated with their own family members as well as with cellular constituents such as nuclear matrix proteins, key transcription factors and centromere components implying a ubiquitous role in gene regulation and nuclear function. We find an overrepresentation of both SWI/SNF-associated regions and proteins in cell cycle and chromosome organization. Taken together the results from our ChIP and immunoprecipitation experiments suggest that SWI/SNF facilitates gene regulation and genome function more broadly and through a greater diversity of interactions than previously appreciated. ChIP-Seq analysis of the SWI/SNF subunits Ini1, Brg1, BAF155 and BAF170 in HeLa S3 cells
Project description:Somatic progenitors suppress differentiation to maintain tissue self-renewal. While epigenetic regulators of DNA and histone modifications can support such repression, a role for nuclear actin-like proteins is unclear. In epidermis, ACTL6a/BAF53A was found enriched in progenitors and down-regulated during differentiation. Conditional ACTL6a deletion abolished epidermal self-renewal and induced terminal differentiation, whereas ectopically expressed ACTL6a suppressed differentiation. Among known activators of epidermal differentiation, KLF4 was found to control 227 genes also regulated by ACTL6a. ACTL6a loss upregulated KLF4 and its target genes, effects that were blocked by KLF4 depletion. Among multiple ACTL6a-interacting epigenetic regulators, the SWI/SNF complex was required for KLF4 activation and differentiation. In progenitors, ACTL6a loss led to enhanced SWI/SNF binding to the promoters of KLF4 and other differentiation genes. ACTL6a thus maintains the undifferentiated progenitor state, in part by suppressing SWI/SNF complex-enabled induction of KLF4. Gene expression analysis: To identify the gene set controlled by ACTL6a in human keratinocyte. Total RNA was isolated in biologic duplicate from cells with ACTL6a loss as compared to controls, and hybridized to Affymetrix HG-U133 2.0 Plus arrays.
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.