Saccharomyces cerevisiae
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA285367 | ENA |
REPOSITORIES: ENA
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Project description:Nucleosome arrays begin at nucleosome-free promoter regions (NFRs) and regulate gene expression. Reconstituting such organization throughout a genome with purified proteins is a critical challenge in establishing biochemical mechanisms for chromosome assembly. Here we establish a four-step hierarchical building plan for yeast genomic nucleosome organization using only purified components: genomic DNA, histones, site-specific organizing factors Abf1 and Reb1, and the chromatin remodelers RSC, ISW2, INO80, and ISW1a. First, RSC makes NFRs by translating promoter poly(dA:dT) tracts into directional nucleosome removal. Second, +1 nucleosomes are positioned by INO80 at most genes potentially involving DNA shape, or by ISW2 using gene-specific Abf1 and Reb1. Third, INO80 or ISW2 create arrays with wide spacing. Fourth, ISW1a tightens the spacing and creates properly positioned arrays. We conclude that entire genomes use a simple set of rules and proteins, without transcription, to build a common chromatin architecture. In this study, nucleosomes were assembled using Salt Gradient Dialysis (SGD) on yeast genomic DNA library. Assembled nucleosomes were either left untreated (labelled as "SGD", control), treated with whole cell extract (WCE), mutant extracts (rsc3ts WCE, isw1 isw2 chd1 WCE), purified remodelers; singly or in combinations (RSC, ISW1a, ISW1b, ISW2, INO80, CHD1, SWI/SNF), combinations of mutant extracts and chromatin remodelers or combination of General Regulatory Factors (Abf1, Reb1) and chromatin remodelers. The resulting nucleosome positions were mapped genome-wide using MNase-(anti-H3-ChIP)-Seq.
2016-08-14 | E-GEOD-72106 | biostudies-arrayexpress
Project description:We report change in the nucleosome occupancy and accessibility upon deletion of ATP-dependent chromatin remodellers (ISW1, ISW2 & CHD1) in Saccharomyces cerevisiae.
2024-02-08 | GSE220880 | GEO
Project description:We addressed the roles of three nucleosome spacing enzymes (ISW1, ISW2 and CHD1) in specifying chromatin organization in S. cerevisiae.
2016-02-17 | GSE69400 | GEO
Project description:Most yeast genes have a nucleosome-depleted region (NDR) at the promoter and an array of regularly spaced nucleosomes phased relative to the transcription start site. We have examined the interplay between RSC (a conserved essential SWI/SNF-type complex that determines NDR size) and the ISW1, CHD1 and ISW2 nucleosome spacing enzymes in chromatin organization and transcription, using isogenic strains lacking all combinations of these enzymes. The contributions of these remodelers to chromatin organization are largely combinatorial, distinct and non-redundant, supporting a model in which the +1 nucleosome is positioned by RSC and then used as a reference nucleosome by the spacing enzymes. Defective chromatin organization correlates with altered RNA polymerase II (Pol II) distribution. RSC-depleted cells exhibit low levels of elongating Pol II and high levels of terminating Pol II, consistent with defects in both termination and initiation, suggesting that RSC facilitates both. Cells lacking both ISW1 and CHD1 show the opposite Pol II distribution, suggesting elongation and termination defects. These cells have extremely disrupted chromatin, with high levels of close-packed di-nucleosomes near the 5’-ends of genes. We propose that ISW1 and CHD1 facilitate Pol II elongation by separating close-packed nucleosomes and by eliminating long linkers to prevent cryptic initiation.
2019-01-16 | GSE117514 | GEO
Project description:Arrays of regularly spaced nucleosomes dominate chromatin and are often phased, i.e., aligned at reference sites like active promoters. How distances between nucleosomes and distances between phasing sites and nucleosomes are determined remained unclear, specifically, the role of ATP dependent chromatin remodelers in it. Here, we used a genome-wide reconstitution system to probe how yeast remodelers generate phased nucleosome arrays. We find that remodelers bear a structural element named the ‘ruler’ that sets nucleosome spacing, in the order Chd1 < ISW1a < ISW2 < INO80. Structure-based mutagenesis confirmed the functional significance of the ruler element in INO80. Differences in the ruler elements of different remodelers explain the observed nucleosome array features. More generally, we propose that remodelers use their rulers to regulate the direction of nucleosome sliding in response to nucleosome density and environment, leading to nucleosome positioning relative to other nucleosomes, DNA bound factors or DNA sequence elements.
2020-02-10 | GSE140614 | GEO
Project description:Chromatin remodelers are ATP-dependent enzymes that reorganize nucleosomes within all eukaryotic genomes. The Chd1 remodeler specializes in shifting nucleosomes into evenly spaced arrays, a defining characteristic of chromatin in gene bodies that blocks spurious transcription initiation. Linked to some forms of autism and commonly mutated in prostate cancer, Chd1 is essential for maintaining pluripotency in stem cells. Here we report a complex of yeast Chd1 bound to a nucleosome in a nucleotide-free state, determined by cryo-electron microscopy (cryo-EM) to 2.6 Å resolution. The structure shows a bulge of the DNA tracking strand where the ATPase motor engages the nucleosome, consistent with an initial stage in DNA translocation. Unlike other remodeler-nucleosome complexes, nucleosomal DNA compensates for the remodeler-induced bulge with a bulge of the complementary DNA strand one helical turn downstream from the ATPase motor. Unexpectedly, the structure also reveals an N-terminal binding motif, called ChEx, which binds on the exit-side acidic patch of the nucleosome. The ChEx motif can displace a LANA-based peptide from the acidic patch, which suggests a means by which Chd1 remodelers may block competing chromatin remodelers from acting on the opposite side of the nucleosome.
2022-02-23 | PXD025287 | Pride
Project description:The positioning of nucleosomes within the coding regions of eukaryotic genes is aligned with respect to transcriptional start sites. This organization is likely to influence many genetic processes, requiring access to the underlying DNA. Here we show that the combined action of Isw1 and Chd1 nucleosome spacing enzymes is required to maintain this organization. In the absence of these enzymes regular positioning of the majority of nucleosomes is lost. Exceptions include the region upstream of the promoter, the +1 nucleosome and a subset of locations distributed throughout coding regions where other factors are likely to be involved. These observations indicated that ATP-dependent remodeling enzymes are responsible for directing the positioning of the majority of nucleosomes within the Saccharomyces cerevisiae genome. Examination of nucleosome positioning in mutants of snf2-related enzymes Other data used in this study are provided in GEO Series GSE31301 and GSE31833.
2011-09-16 | E-GEOD-31015 | biostudies-arrayexpress
Project description:The positioning of nucleosomes within the coding regions of eukaryotic genes is aligned with respect to transcriptional start sites. This organization is likely to influence many genetic processes, requiring access to the underlying DNA. Here we show that the combined action of Isw1 and Chd1 nucleosome spacing enzymes is required to maintain this organization. In the absence of these enzymes regular positioning of the majority of nucleosomes is lost. Exceptions include the region upstream of the promoter, the +1 nucleosome and a subset of locations distributed throughout coding regions where other factors are likely to be involved. These observations indicated that ATP-dependent remodeling enzymes are responsible for directing the positioning of the majority of nucleosomes within the Saccharomyces cerevisiae genome.
2011-09-02 | GSE31833 | GEO
Project description:The positioning of nucleosomes within the coding regions of eukaryotic genes is aligned with respect to transcriptional start sites. This organization is likely to influence many genetic processes, requiring access to the underlying DNA. Here we show that the combined action of Isw1 and Chd1 nucleosome spacing enzymes is required to maintain this organization. In the absence of these enzymes regular positioning of the majority of nucleosomes is lost. Exceptions include the region upstream of the promoter, the +1 nucleosome and a subset of locations distributed throughout coding regions where other factors are likely to be involved. These observations indicated that ATP-dependent remodeling enzymes are responsible for directing the positioning of the majority of nucleosomes within the Saccharomyces cerevisiae genome.
2011-09-16 | GSE31015 | GEO
Project description:Chromatin remodelers influence genetic processes by altering nucleosome occupancy, positioning, and composition. In vitro, yeast ISWI and CHD remodelers require > 20 bp of extranucleosomal DNA for remodeling, but linker DNA in S. cerevisiae averages < 20 bp. To resolve this paradox, we have mapped the genomic distributions of the yeast Isw1, Isw2, and Chd1 remodelers at base-pair resolution. Surprisingly, remodelers are highly enriched at promoter nucleosome depleted regions (5' NDRs), where they bind to regions of extended linker DNA. Remodelers are also enriched in the bodies of genes displaying high nucleosome turnover. We hypothesize that remodelers bind but do not act at 5' NDRs, remaining in physical proximity to gene bodies, where they act on regions of transient nucleosome depletion following transcriptional elongation. We have analyzed the dynamics of yeast ISWI and CHD chromatin remodeler genomic association at base-pair resolution using native chromatin immunoprecipitation followed by sequencing (N-ChIP-seq).
2013-03-01 | E-GEOD-39430 | biostudies-arrayexpress