Epigenome characterization at single base-pair resolution
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ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae
PROVIDER: GSE30551 | GEO | 2011/10/27
SECONDARY ACCESSION(S): PRJNA144469
REPOSITORIES: GEO
Similar Datasets
Project description:We have combined standard micrococcal (MNase) digestion of nuclei with a modified protocol for construction paired-end DNA sequencing libraries to map both nucleosomes and subnucleosome-sized particles at single base-pair resolution throughout the budding yeast genome. We found that partially unwrapped nucleosomes and subnucleosome-sized particles can occupy the same position within a cell population, suggesting dynamic behavior. By varying the time of MNase digestion, we have been able to observe changes that reflect differential sensitivity of particles, including eviction of nucleosomes. Our protocol and mapping method provide a general strategy for characterizing full epigenomes. We used micrococcal nuclease mapping, chromatin immunoprecipitation and paired-end sequencing to determine the structure of yeast centromeres at single base-pair resolution.
2011-10-26 | E-GEOD-30551 | biostudies-arrayexpress
Project description:The nucleosome plays a central role in genome regulation. Traditional methods for mapping nucleosomes depend on the resistance of the nucleosome core to micrococcal nuclease (MNase). However, the lengths of the protected DNA fragments are heterogeneous, limiting the accuracy of nucleosome position information. To resolve this problem, we removed residual linker DNA by simultaneous digestion of yeast chromatin with MNase and exonuclease III (ExoIII). Paired-end sequencing of mono-nucleosomes revealed not only core particles (145-147 bp), but also intermediate particles in which ~8 bp project from one side (154 bp) or both sides (161 bp) of the nucleosome core. We term these particles "pseudo-chromatosomes" because they are present in yeast lacking linker histone. They are also observed after MNase-ExoIII digestion of chromatin reconstituted using recombinant core histones. We propose that the pseudo-chromatosome provides a DNA framework to facilitate H1 binding. Comparison of budding yeast nucleosome sequences obtained using micrococcal nuclease (MNase-seq) and MNase + exonuclease III (ExoIII) (MNase-ExoIII-seq): wild type cells and hho1-null cells. Nucleosome sequences from native chromatin and H1-depleted chromatin from mouse liver. Nucleosome sequences from a plasmid reconstituted into nucleosomes using recombinant yeast histones or native chicken erythrocyte histones.
2015-09-23 | E-GEOD-65889 | biostudies-arrayexpress
Project description:Nucleosome is the basic structural unit of chromatin, and its dynamics plays critical roles in the regulation of genome functions. However, how the nucleosome structure is regulated by histone variants in vivo is still largely uncharacterized. Here, by employing Micrococcal nuclease (MNase) digestion of crosslinked chromatin followed by chromatin immunoprecipitation (ChIP) and paired-end sequencing (MNase-X-ChIP-seq), we mapped genome-wide unwrapping states of nucleosomes containing histone variant H2A.Z in mouse embryonic stem (ES) cells. We found that H2A.Z is enriched with unwrapped nucleosomes. Interestingly, the function of +1 H2A.Z nucleosome in transcriptional regulation is correlated with the unwrapping states. We further showed that H2A.Z nucleosomes adjacent the CTCF binding sites (CBS) may adopt an open conformation. We confirmed the unwrapping state of H2A.Z nucleosomes under native condition by re-ChIP of H2A.Z after CTCF CUT&RUN in mouse ES cells. Importantly, we found that depletion of H2A.Z results in increased CTCF binding, indicating dynamic competition between the unwrapped H2A.Z nucleosomal intermediates and CTCF at the CBS. Taken together, our results showed that histone variant H2A.Z regulates transcription and CTCF binding through modulating the nucleosome unwrapping.
2020-04-27 | GSE146082 | GEO
Project description:Background: Analysis of the effect that chromatin structure has on the expression patterns of eukaryotic genes has recently expanded knowledge of the complex influence genome accessibility has on genome function. Interlaced with regular nucleosomal patterning are other mobile and labile sub-nucleosomal-sized protein structures bound to the genome such as transcription factors (TF), initiation complexes, and modified nucleosomes. Results: We present chromatin structure maps of the A. thaliana Col-0 wild-type (in vitro cell culture) combining differential micrococcal nuclease (MNase) digestion and analysis by paired-end next-generation sequencing with RNASeq data to provide insight into the sensitive genomic regions and variable DNA-bound particle size related to transcriptional activity. The landscape of sub-nucleosomal sized particles (subNSPs) has been investigated, revealing the DNA-binding complex positioning genome-wide. We observe the dynamic changes in the distribution of these complexes surrounding genomic features, particularly at transcription start sites (TSS). Differential digestion reveals the presence of MNase-sensitive smaller particles and a labile -1 nucleosome upstream of the TSS of active genes. These changes correlate with gene expression differences resulting from different environmental conditions of light- or dark growth both globally and locally, and a complex profile of bound particles is directly visualised. Conclusions: Analysis of the A. thaliana genome reveals that resolution of chromatin particle size by differential MNase digestion allows detection of the sensitive features in chromatin structure that have hereto been obfuscated. The concomitant analysis of transcript levels reveals the impact of transient extrinsic factors in modifying the sub- nucleosomal landscape in association with transcriptional changes, giving insight into the binding of transcription-associated factors.
2017-08-21 | GSE94377 | GEO
Project description:Chromatin mapping using micrococcal nuclease (MNase) has been the standard tool for mapping nucleosomes for >40 years. When coupled with DNA sequencing, MNase-seq can provide base-pair-resolution nucleosome maps. However, determining nucleosome occupancy using MNase-seq has been hampered by its aggressive endo-/exo-nuclease activities, whereby cleavages within linker regions produce oligo- and mono-nucleosomes whereas cleavages within nucleosomes destroy them. Here we introduce a theoretical framework for predicting nucleosome occupancies and an experimental protocol with appropriate spike-in normalization that confirms our theory and provides accurate occupancy levels over an MNase digestion time-course. As expected, DNaseI hypersensitive sites and transcription units are digested by MNase at elevated rates, and the apparent deficiency of nucleosomes at 3’ ends of Drosophila genes is an artifact of MNase preference for AT-rich DNA. Surprisingly, we observed no overall differences between Drosophila euchromatin and heterochromatin, which implies that heterochromatin compaction does not render nucleosomal DNA less accessible than euchromatin.
2019-08-27 | GSE128689 | GEO
Project description:In this study we developed MPE-seq, a method for the genome-wide characterization of chromatin that involves the digestion of nuclei with methidiumpropyl-EDTA-Fe(II) [MPE-Fe(II)] followed by massively parallel sequencing. Like micrococcal nuclease (MNase), MPE-Fe(II) preferentially cleaves the linker DNA between nucleosomes. We also performed MNase-seq as a comparison. We further performed ChIP-seq using chromatin samples obtained by MPE-Fe(II) or MNase digestion of nuclei.
2015-06-16 | GSE69098 | GEO
Project description:Nucleosomes are the most basic units of chromatin and are regulators of genome integrity and gene expression. The fundamental mechanism how nucleosomes are dynamically regulated is one of the main questions in chromatin organization; most of the study has, however, focused on its positioning. Here we performed HiLo-MNase-seq, which involves limit and partial digestion of chromatin by micrococcal nuclease (MNase) to identify the positioning of nucleosome array along with the kinetics of MNase digestion. We identified a subset of unique nucleosomes with fast digestion kinetics at the transcription factor binding sites that have been characterized as nucleosome depleted regions (NDRs). By inhibiting RNA polymerase II, we also showed that those nucleosomes changed its sensitivity to MNase in a context-dependent manner. These findings implicated a self-reinforcing regulatory network involving nucleosomes, Pol II, and transcription factors for fine-tuning of gene expression.
2020-02-01 | GSE77526 | GEO
Project description:Eukaryotic chromosomal DNA is assembled into regularly spaced nucleosomes, which play a central role in gene regulation by determining accessibility of control regions. The nucleosome contains ~147 bp of DNA wrapped ~1.7 times around a central core histone octamer. The linker histone, H1, binds both to the nucleosome, sealing the DNA coils, and to the linker DNA between nucleosomes, directing chromatin folding. Micrococcal nuclease (MNase) digests the linker to yield the chromatosome, containing H1 and ~160 bp, and then converts it to a core particle, containing ~147 bp and no H1. Sequencing of nucleosomal DNA obtained after MNase digestion (MNase-seq) generates genome-wide nucleosome maps that are important for understanding gene regulation. We present an improved MNase-seq method involving simultaneous digestion with exonuclease III, which removes linker DNA. Remarkably, we discovered two novel intermediate particles containing 154 or 161 bp, corresponding to 7 bp protruding from one or both sides of the nucleosome core. These particles are detected in yeast lacking H1 and in H1-depleted mouse chromatin. They can be reconstituted in vitro using purified core histones and DNA. We propose that these "proto-chromatosomes" are fundamental chromatin subunits, which include the H1 binding site and influence nucleosome spacing independently of H1.
2015-09-23 | GSE65889 | GEO
Project description:The classic view of nucleosome organization at active promoters is that two well-positioned nucleosomes flank a nucleosome-depleted region (NDR). However, this view has been recently challenged by contradictory reports as to whether a distinct set of wider (≳150 bp) NDRs instead contain unusually unstable Micrococcal Nuclease-sensitive “fragile” particles, thought to be nucleosomal because of their size. To determine the composition of fragile particles we introduce CUT&RUN.ChIP, in which targeted nuclease cleavage and release is followed by chromatin immunoprecipitation. We find that fragile particles represent the occupancy and action of the RSC nucleosome remodeler acting on dynamically unwrapped nucleosomal intermediates. We also find that general regulatory factors (GRFs) bind to partially unwrapped nucleosomal intermediates at NDRs. We propose that RSC-engagement and its action cause nucleosomes to unravel, and subsequent binding of GRFs constitute a dynamic cycle of nucleosome deposition and clearance at the subset of wide Pol II promoter NDRs.
2018-12-22 | GSE116853 | GEO
Project description:Micrococcal nuclease (MNase) is commonly used to map nucleosomes genome-wide, but nucleosome maps are affected by the degree of digestion. It has been proposed that many yeast promoters are not nucleosome-free but occupied by easily digested, unstable, “fragile” nucleosomes. We analyzed the histone content of all MNase-sensitive complexes by MNase-ChIP-seq and Sonication-ChIP-seq. We find that yeast promoters are predominantly bound by non-histone protein complexes, with little evidence for fragile nucleosomes. We do detect MNase-sensitive nucleosomes elsewhere in the genome, including transcription termination sites. However, they have high A/T-content, suggesting that MNase sensitivity does not indicate instability, but the preference of MNase for A/T-rich DNA, such that A/T-rich nucleosomes are digested faster than G/C-rich nucleosomes. We confirm our observations by analyzing ChIP-exo, chemical mapping and ATAC-seq data from other laboratories. Thus, histone ChIP-seq experiments are essential to distinguish nucleosomes from other DNA-binding proteins that protect against MNase.
2016-12-15 | GSE83123 | GEO