Nucleosome profiles in strains with different numbers of nucleosomes at HML and HMR
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ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae
PROVIDER: GSE136897 | GEO | 2019/09/06
REPOSITORIES: GEO
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Project description:Nucleosome profiles in strains with different numbers of nucleosomes at HML and HMR
| PRJNA564006 | ENA
Project description:Nucleosomes in active chromatin are dynamic, but whether they have distinct structural conformations is unknown. To identify nucleosomes with alternative structures genome-wide, we used H4S47C-anchored cleavage mapping, which revealed that nucleosomes at 5% of budding yeast nucleosome positions have asymmetric histone-DNA interactions. These asymmetric interactions are enriched at nucleosome positions that flank promoters. Micrococcal nuclease (MNase) sequence-based profiles of asymmetric nucleosome positions revealed a corresponding asymmetry in MNase protection near the dyad axis, suggesting that the loss of DNA contacts around H4S47 is accompanied by protection of the DNA from MNase. Chromatin immunoprecipitation mapping of selected nucleosome remodelers indicated that asymmetric nucleosomes are bound by the RSC chromatin remodeling complex, which is required for maintaining nucleosomes at asymmetric positions. These results imply that the asymmetric nucleosome-RSC complex is a metastable intermediate representing partial unwrapping and protection of nucleosomal DNA on one side of the dyad axis during chromatin remodeling. We have analyzed the chromatin landscape of the yeast genome using paired-end MNase-seq and the chromatin binding of yeast remodelers Swr1, Ino80 and RSC at base-pair resolution using native chromatin immunoprecipitation followed by sequencing (N-ChIP-seq).
2014-12-04 | E-GEOD-59523 | biostudies-arrayexpress
Project description:Nucleosomes in active chromatin are dynamic, but whether they have distinct structural conformations is unknown. To identify nucleosomes with alternative structures genome-wide, we used H4S47C-anchored cleavage mapping, which revealed that nucleosomes at 5% of budding yeast nucleosome positions have asymmetric histone-DNA interactions. These asymmetric interactions are enriched at nucleosome positions that flank promoters. Micrococcal nuclease (MNase) sequence-based profiles of asymmetric nucleosome positions revealed a corresponding asymmetry in MNase protection near the dyad axis, suggesting that the loss of DNA contacts around H4S47 is accompanied by protection of the DNA from MNase. Chromatin immunoprecipitation mapping of selected nucleosome remodelers indicated that asymmetric nucleosomes are bound by the RSC chromatin remodeling complex, which is required for maintaining nucleosomes at asymmetric positions. These results imply that the asymmetric nucleosome-RSC complex is a metastable intermediate representing partial unwrapping and protection of nucleosomal DNA on one side of the dyad axis during chromatin remodeling.
2014-12-04 | GSE59523 | GEO
Project description:The precise mechanisms governing sequence-dependent positioning of nucleosomes on DNA remain unknown in detail. Existing algorithms, taking into account the sequence-dependent deformability of DNA and its interactions with the histone globular domains, predict rotational setting of only 65% of human nucleosomes mapped in vivo. To uncover novel factors responsible for the nucleosome positioning, we analyzed potential involvement of the histone N-tails in this process. To this aim, we reconstituted the H2A/H4 N-tailless nucleosomes on human BRCA1 DNA (~100 kb) and compared their positions and sequences with those of the wild-type nucleosomes. In the case of H2A tailless nucleosomes, the AT content of DNA sequences is changed locally at superhelical location (SHL) ±4, while maintaining the same rotational setting as their wild-type counterparts. Conversely, the H4 tailless nucleosomes display widespread changes of the AT content near SHL ±1 and SHL ±2, where the H4 N-tails interact with DNA. Furthermore, a substantial number of H4 tailless nucleosomes exhibit rotational setting opposite to that of the wild-type nucleosomes. Thus, our findings strongly suggest that the histone N-tails are operative in selection of nucleosome positions, which may have wide-ranging implications for epigenetic modulation of chromatin states.
2024-01-03 | GSE252427 | GEO
Project description:Retroviral integration is catalyzed by a tetramer of integrase (IN) assembled on viral DNA ends in a stable complex, known as the intasome. How the intasome interfaces with chromosomal DNA, which exists in the form of nucleosomal arrays, is currently unknown. Here we show that the prototype foamy virus (PFV) intasome is proficient at stable capture of nucleosomes as targets for integration. Single-particle cryo-electron microscopy (EM) reveals a multivalent intasome-nucleosome interface involving both gyres of nucleosomal DNA and one H2A-H2B heterodimer. While the histone octamer remains intact, the DNA is lifted from the surface of the H2A-H2B heterodimer to allow integration at strongly preferred superhelix location (SHL) ±3.5 positions. Amino acid substitutions disrupting these contacts impinge on the ability of the intasome to engage nucleosomes in vitro and redistribute viral integration sites on the genomic scale. Our findings elucidate the molecular basis for nucleosome capture by the viral DNA recombination machinery and the underlying nucleosome plasticity that allows integration. Genomic positions of integration sites of WT and mutant PFV vectors in HT1080 cells were determined using ligation-mediated PCR and next generation sequencing. Integration sites of purified recombinant PFV intasome into deproteinized human genomic DNA were used as a reference dataset.
2015-06-10 | E-GEOD-67730 | biostudies-arrayexpress
Project description:Plant and animal centromeres comprise megabases of highly repeated satellite sequences, yet centromere function can be specified epigenetically on single-copy DNA by the presence of nucleosomes containing a centromere-specific variant of histone H3 (cenH3). We determined the positions of cenH3 nucleosomes in rice (Oryza sativa), which has centromeres composed of both the 155-bp CentO repeat and single-copy non-CentO sequences. We find that cenH3 nucleosomes protect 90-100 bp of DNA from micrococcal nuclease digestion, sufficient for only a single wrap of DNA around the cenH3 nucleosome core. cenH3 nucleosomes are translationally phased with 155-bp periodicity on CentO repeats, but not on non-CentO sequences. CentO repeats have a ~10-bp periodicity in WW dinucleotides and in micrococcal nuclease cleavage, providing evidence for rotational phasing of cenH3 nucleosomes on CentO, and suggesting that satellites evolve for translational and rotational stabilization of centromeric nucleosomes. Examination of measured size of rice centromere nucleosome
2013-11-06 | E-GEOD-50755 | biostudies-arrayexpress
Project description:Background: Repair of DNA damage requires chromatin remodeling to permit removal of the lesions. How nucleosomes are remodelled to initiate repair of DNA damage remains largely unknown. Here, we describe how chromatin is altered during repair of UV-induced DNA damage at the level of the linear organisation of nucleosomes. Results: Using MNase-seq, we identified a subset of nucleosomes in the genome that are remodelled in UV-damaged wild-type yeast cells. We mapped the genomic location of these nucleosomes, showing that they contain the histone variant H2A.Z. The remodelling observed is consistent with histone exchange or eviction at these positions. This depends on the yeast SWI/SNF global genome nucleotide excision repair (GG-NER) chromatin-remodelling complex. Remarkably, we found that in the absence of DNA damage, the GG-NER complex occupies chromatin at nucleosome free regions separating adjacent nucleosomes. This establishes the nucleosome structure at these genomic locations, which we refer to as GG-NER complex binding sites (GCBS’s). We observed that these sites are frequently located precisely at certain boundary regions that delineate chromasomally interacting domains (CIDs). These boundaries define chromosomal domains of higher-order nucleosome-nucleosome interaction. We demonstrate that the GG-NER complex redistributes following remodelling of these nucleosomes after DNA damage taking up genomic positions located within the CIDs. This permits the efficient removal of DNA damage at these sites. Conclusions: We argue that organising DNA repair in the genome as described may define origins of DNA repair that greatly reduces the genomic search space for DNA damage recognition, thus ensuring the efficient repair of damage in chromatin.
2018-12-06 | E-MTAB-6569 | biostudies-arrayexpress
Project description:Nucleosome positioning is both active and passive and regulates access to the genome for replication, transcription and repair. Here we report that Mit1, a subunit of the fission yeast SHREC complex similar to Mi-2/NuRD, regulates transcription at regions of heterochromatin by positioning nucleosomes to preclude access to RNA Polymerase II. Purified Mit1 is a nucleosome remodeling factor capable of mobilizing histone octamers on short DNA fragments and requires ATP hydrolysis and chromatin tethering domains to remodel nucleosomes and silence transcription. We propose that SHREC is recruited to heterochromatin to mobilize nucleosomes onto unfavorable positions to prevent spurious transcription within heterochromatin.
2014-04-08 | GSE46649 | GEO
Project description:Nucleosome positioning is both active and passive and regulates access to the genome for replication, transcription and repair. Here we report that Mit1, a subunit of the fission yeast SHREC complex similar to Mi-2/NuRD, regulates transcription at regions of heterochromatin by positioning nucleosomes to preclude access to RNA Polymerase II. Purified Mit1 is a nucleosome remodeling factor capable of mobilizing histone octamers on short DNA fragments and requires ATP hydrolysis and chromatin tethering domains to remodel nucleosomes and silence transcription. We propose that SHREC is recruited to heterochromatin to mobilize nucleosomes onto unfavorable positions to prevent spurious transcription within heterochromatin. M-bM-^@M-^C RNA samples were prepared from biological duplicates of WT and mit1M-bM-^HM-^F::NatMX6 fission yeast to compare transcript levels using the Affymetrix GeneChip S.pombe Tiling 1.0FR microarray.
2014-04-08 | E-GEOD-46649 | biostudies-arrayexpress
Project description:Hybrid incompatibility between Drosophila melanogaster and D. simulans is caused by a lethal interaction of the proteins encoded by the Hmr and Lhr genes. In D. melanogaster the loss of HMR results in mitotic defects, an increase in transcription of transposable elements and a deregulation of heterochromatic genes. To investigate the molecular mechanisms that mediate HMRs function, we measured genome-wide localization of HMR in D. melanogaster by chromatin immunoprecipitation. Interestingly, we find HMR localizing to genomic insulator sites that can be classified into two groups. One group that belongs to the gypsy class of insulators and another one that separates HP1a binding regions from active promoters. The activity of these promoters is strongly affected in Hmr mutant flies. Our data provide a novel link between HMR and insulator proteins and suggest a key role for genome organization in the formation of species.
2017-01-31 | GSE86106 | GEO