Nucleosomes stabilize ssRNA-dsDNA triple helices in human cells
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE114900 | GEO | 2019/02/18
REPOSITORIES: GEO
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Project description:Nucleosomes stabilize ssRNA-dsDNA triple helices in human cells
| PRJNA473000 | ENA
Project description:Chromatin architectural proteins interact with nucleosomes to modulate chromatin accessibility and higher-order chromatin structure. While these proteins are almost certainly important for gene regulation they have been studied far less than the core histone proteins. Here we describe the genomic distributions and functional roles of two chromatin architectural proteins: histone H1 and the high mobility group protein HMGD1, in Drosophila S2 cells. Using ChIP-seq, biochemical and gene specific approaches, we find that HMGD1 binds to highly accessible regulatory chromatin and active promoters. In contrast, H1 is primarily associated with heterochromatic regions marked with repressive histone marks. However, the ratio of HMGD1 to H1 is better correlated with chromatin accessibility, gene expression and nucleosome spacing variation than either protein alone suggesting a competitive mechanism between these proteins. Indeed, we show that HMGD1 and H1 compensate each other’s absence by binding reciprocally to chromatin resulting in changes to nucleosome repeat length and distinct gene expression patterns. Collectively our data suggest that dynamic and mutually exclusive binding of H1 and HMGD1 to nucleosomes and linker sequences may control the fluid chromatin structure that is required for transcriptional regulation. This study thus provides a framework to further study the interplay between chromatin architectural proteins and epigenetics in gene regulation. ChIP-seq of HMGD1 and Histone H1 bound nucleosomes as well as MNase-seq of total nucleosome in Drosophila S2 cells
2013-12-01 | E-GEOD-49526 | biostudies-arrayexpress
Project description:Nuc-MS characterizes histone modifications and variants directly from intact
endogenous mono-nucleosomes. Preserving whole nucleosome particles enables
precise interrogation of their protein content, as for H3.3-containing nucleosomes which
had 6-fold co-enrichment of variant H2A.Z over bulk chromatin. Moreover, Nuc-MS
showed co-occurrence of oncogenic H3.3K27M with euchromatic marks (e.g., H4K16ac
and >40-fold enrichment of H3K79me2). By capturing the entire epigenetic landscape,
Nuc-MS provides a new, quantitative readout of nucleosome-level biology.
2020-04-06 | MSV000085238 | MassIVE
Project description:The structural complexity of nucleosomes underlies their functional versatility. Here we report a new type of complexity – nucleosome fragility, manifested as high sensitivity to micrococcal nuclease, in contrast to the common presumption that nucleosomes are similar in resistance to MNase digestion. Using differential MNase digestion of chromatin and high-throughput sequencing, we have identified a special group of nucleosomes termed fragile nucleosomes throughout the yeast genome, nearly one thousand of which are at previously determined “nucleosome free” loci. Nucleosome fragility is broadly implicated in multiple chromatin processes, including transcription, translocation and replication, in correspondence to specific physiological states of cells. In the environmental-stress-response genes, the presence of fragile nucleosomes prior to the occurrence of environmental changes suggests that nucleosome fragility poises genes for swift up-regulation in response to the environmental changes. We propose that nucleosome fragility underscores distinct functional statuses of the chromatin and provides a new dimension for portraying the landscape of genome organization. Comparing nucleosome occupancy under different MNase digestion levels and growth conditions.
2011-01-24 | E-GEOD-26412 | biostudies-arrayexpress
Project description:Nucleosome remodeling factors regulate the occupancy and positioning of nucleosomes genome-wide through ATP-driven DNA translocation. While many nucleosomes are well- and consistently positioned, some nucleosomes and nucleosome-like structures are more sensitive to nuclease digestion or transitory in nature. To better understand the role of nucleosome remodeling factors in generating and clearing these alternative nucleosome structures, we depleted murine embryonic stem cells of the remodeler ATPases BRG1 and SNF2H then performed MNase-seq in murine embryonic stem cells. We performed MNase-seq under high- and low-MNase conditions to assess the effects of nucleosome remodeling factors on nuclease-sensitive or “fragile” nucleosome occupancy. In parallel, we gel-extracted MNase-digested fragments to enrich for another alternative nucleosome structure, the overlapping dinucleosome. Overlapping dinucleosomes are composed of two canonical nucleosomes, asymmetrically lacking one H2A:H2B dimer and wrapped by ~250 bp of DNA. In vitro studies of nucleosome remodeling have suggested that the collision of adjacent nucleosomes by nucleosome sliding can stimulate formation of overlapping dinucleosomes. Using these methods, we were able to identify fragile nucleosomes and overlapping dinucleosomes near transcription start sites and gene-distal DNaseI hypersensitive sites in mouse embryonic stem cells, among other loci. We find that BRG1 consistently stimulates occupancy of fragile nucleosomes but represses occupancy of overlapping dinucleosomes through its nucleosome remodeling function, while SNF2H expression slightly increases fragile nucleosome occupancy.
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Project description:Histone octamers are thought to be a rigid part of nucleosomes that shape chromatin and block cellular machinery from accessing DNA. ATP-dependent chromatin remodelers like ISW2 mobilize nucleosomes to provide DNA access. We find evidence for histone octamer distortion preceding DNA being moved into nucleosomes and processive movement of the ATPase motor of ISW2 on nucleosomal DNA. DNA entering nucleosome is uncoupled from the ATPase activity of ISW2 and alterations of the histone octamer structure mediated by ISW2 by deletion of the SANT domain from the C-terminus of the Isw2 catalytic subunit. We also find that restricting histone movement by chemical crosslinking traps remodeling intermediates resembling those seen by loss of the SANT domain, further supporting the importance of changes in histone octamer structure early in ISW2 remodeling. Transient octamer distortions are stabilized by H3-H4 tetramer disulfide crosslinking, thereby linking intrinsic histone octamer flexibility to chromatin remodeling.
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2011-12-28 | E-MTAB-721 | biostudies-arrayexpress
Project description:The structural complexity of nucleosomes underlies their functional versatility. Here we report a new type of complexity – nucleosome fragility, manifested as high sensitivity to micrococcal nuclease, in contrast to the common presumption that nucleosomes are similar in resistance to MNase digestion. Using differential MNase digestion of chromatin and high-throughput sequencing, we have identified a special group of nucleosomes termed fragile nucleosomes throughout the yeast genome, nearly one thousand of which are at previously determined “nucleosome free” loci. Nucleosome fragility is broadly implicated in multiple chromatin processes, including transcription, translocation and replication, in correspondence to specific physiological states of cells. In the environmental-stress-response genes, the presence of fragile nucleosomes prior to the occurrence of environmental changes suggests that nucleosome fragility poises genes for swift up-regulation in response to the environmental changes. We propose that nucleosome fragility underscores distinct functional statuses of the chromatin and provides a new dimension for portraying the landscape of genome organization.
2011-01-24 | GSE26412 | GEO
Project description:Nucleosomes are the primary unit of chromatin structure and inhibit key intracellular interactions which regulate how eukaryotic genetic information is read, including transcription factor (TF) binding to DNA. In theory, the sterics of nucleosome-DNA interactions could inhibit TF binding to all nucleosome-bound DNA. In reality, however, nucleosome inhibition of TF binding is variable both across a genome and even within a single nucleosome. Prior studies have demonstrated that nucleosome occupancy, nucleosome positioning, TF binding site (TFBS) affinity & TFBS location can each influence TF targeting in vivo, however, this work has been largely correlative and no study has dissected collective from individual contributions of these important variables. Therefore, to address this deficiency, we have mapped genome-wide changes in chromatin structure and TF binding following experimental nucleosome depletion. Heuristic modeling of results confirmed that chromatin specification of TF targeting is a multivariate, context-specific, process, with most informative features originating from additive interactions between cis and trans variables. Additionally, we found compelling evidence that nucleosomes serve to inhibit intra-genic TF binding, as evidenced by an increasing number of sub-optimal TFBS occupied following nucleosome depletion. The majority of these conditional loci were located within open reading frames and parallel transcriptome analysis revealed their occurrence was linked to generation of intragenic cryptic transcripts. Together results support the idea that chromatin structure has evolved to coordinate specification of regulatory factor targeting & gene expression. Findings have functional relevance to emerging datasets on genetic and epigenetic variation in human disease states.
2021-11-01 | GSE90669 | GEO