Nucleosomal DNA has topological memory
Ontology highlight
ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae
PROVIDER: GSE228623 | GEO | 2023/06/05
REPOSITORIES: GEO
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2014-11-21 | E-GEOD-62265 | biostudies-arrayexpress
Project description:Goal of this project was the identification of chromatin interacting proteins whose binding is differentially regulated by various combinatorial chromatin modifications found in different chromatin states such as promoters, enhancers and heterochromatin. To achieve this, recombinant modified nucleosomes representing different chromatin states were assembled from canonical histones, H2A.Z and modified ligated H3/H4 histone proteins and biotinylated nucleosomal DNAs. Assembled nucleosomes were immobilized on streptavidin-coated beads via biotinylated di-nucleosomal 601 DNA and used for nucleosome affinity purifications to identify proteins regulated by chromatin modifications from SILAC-labelled HeLaS3 nuclear extracts (Arg10 and Lys8). SILAC affinity purifications were carried out in "forward" (heavy extract on modified nucleosome and light extract on unmodified nucleosome) and "reverse" (light extract on modified nucleosome and heavy extract on unmodified nucleosome) label-swap experiments and protein abundances were quantified by MaxQuant. Initial trial experiments with biotinylated mono-, di- and tetra- 601 nucleosomes are also deposited along with the data for the di-nucleosome experiments. See also: Bartke et al., 2010. Nucleosome-interacting proteins regulated by DNA and histone methylation. Cell 143, 470–484; doi:10.1016/j.cell.2010.10.012. The H4K20me2 samples from this experiment were previously deposited with identifier PXD009281. These were published in: Nakamura et al., 2019. H4K20me0 recognition by BRCA1-BARD1 directs homologous recombination to sister chromatids. Nature Cell Biology 21, 311–318; doi: 10.1038/s41556-019-0282-9.
2023-12-12 | PXD018966 | Pride
Project description:Goal of this project was the identification of chromatin interacting proteins whose binding is differentially regulated by di-methylation of lysine 20 on histone H4 (H4K20me2). To achieve this unodified and H4K20me2-modified histone H4 were generated by native chemical ligation and assembled into recombinant di-nucleosomes. The di-nucleosomes were immobilized on streptavidin-coated beads via the biotinylated di-nucleosomal DNA and used for nucleosome affinity purifications to identify proteins regulated by H4K20me2 from SILAC-labelled HeLaS3 nuclear extracts (Arg10 and Lys8). SILAC affinity purifications were carried out in "forward" (heavy extract on modified nucleosome and light extract on unmodified nucleosome) and "reverse" (light extract on modified nucleosome and heavy extract on unmodified nucleosome) label-swap experiments and protein abundances were quantified by MaxQuant.
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Project description:Chemical modification of histone proteins by methylation plays a central role in chromatin regulation by recruiting epigenetic ‘readers’ via specialized binding domains. Depending on the degree of methylation, the exact modified amino acid, and the associated reader proteins histone methylations are involved in the regulation of all DNA-based processes, such as transcription, DNA replication, and DNA repair. We have previously established a method that allows the unbiased identification of nuclear proteins which binding to nucleosomes is regulated by the presence of specific histone modifications (1,2). The method is based on an in-vitro reconstitution of semi-synthetic nucleosomes bearing a predefined set of histone modifications which are subsequently used as baits for affinity purification pull-down experiments with nuclear extracts followed by identification and quantification of nucleosome-interacting proteins using LC-MS/MS. Here we provide a representative set of label-free MS results for nucleosome pull-down affinity purification experiments performed using unmodified as well as H3K4me3- and H3K9me3-modified di-nucleosomes and nuclear extract obtained from HeLa S3 cells. 1. Bartke T, Vermeulen M, Xhemalce B, Robson SC, Mann M, Kouzarides T (2010) Nucleosome-interacting proteins regulated by DNA and histone methylation. Cell 143:470-484 2. Makowski MM, Gräwe C, Foster BM, Nguyen NV, Bartke T, Vermeulen M (2018) Global profiling of protein-DNA and protein-nucleosome binding affinities using quantitative mass spectrometry. Nat Commun 9:1653
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Project description:Characteristic features of chromatin states are not limited to particular epigenetic modifications but include other regulatory cues, such as linker DNA length, typically ranging from around 35-55 bp in most eu- and heterochromatin domains (Valouev et al, 2011; Voong et al., 2016, Cell) to over 200 bp in nucleosome-depleted regions (NDRs) found at active enhancers and promoters (Schones et al, 2008; Hansen He et al, 2010). To investigate whether and how the nucleosome linker DNA affects chromatin recognition by nuclear proteins we performed a set of affinity purifications using di-nucleosomes incorporating different DNA linkers. Here, we investigated the effect of a 200 bp di-nucleosome linker DNA represented by scrambled DNA or SV40 promoter DNA sequence on the nuclear protein binding to di-nucleosome decorated with promoter-associated modifications, including H3K4me3K9acK14acK18acK23acK27ac, H4K5acK8acK12acK16acK20me2 and histone variant H2A.Z Below is a description (modifications and linker) of di-nucleosomes used in pull-downs with HeLa nuclear extracts followed by label-free MS: 1. H3K4me3-5ac,H4K20me2-4ac, H2AZ, 50bp linker 2. H3K4me3-5ac,H4K20me2-4ac, H2AZ, 200bp scrambled DNA linker 3. H3K4me3-5ac,H4K20me2-4ac, H2AZ, 200bp SV40 promoter DNA linker 4. Unmod. H3&H4, 50bp linker 5. Unmod. H3&H4, 200bp scrambled DNA linker 6. Unmod. H3&H4, 200bp SV40 promoter DNA linker
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Project description:N6-methyldeoxyadenosine (6mA or m6dA) was shown more than 40 years ago to exist in simple eukaryotes, yet functional studies have been limited. Recent investigations in multiple eukaryotes suggest 6mA as a potential DNA epigenetic mark that plays regulatory roles in gene regulation. Here we use Tetrahymena thermophila as a model to examine the effects of 6mA on nucleosome positioning. We have employed independent methods to identify genome-wide 6mA distribution, which revealed the enrichment after transcription start sites with a periodic pattern and a mutually exclusive relationship with the positions of nucleosomes. The exclusive distribution pattern of 6mA and nucleosome can be recapitulated by in vitro nucleosome assembly on native Tetrahymena genomic DNA, but not on DNA without 6mA. Model DNA containing artificially installed 6mA resists nucleosome assembling compared to unmodified DNA in vitro. Computational simulation revealed that 6mA increases dsDNA rigidity, which disfavors nucleosome wrapping. Knockout of a potential 6mA methyltransferase disturbs the nucleosome positioning in Tetrahymena, leading to the transcriptome-wide change of gene expression. These findings uncover a new mechanism by which DNA 6mA assists to shape the chromatin topology in order to stabilize gene expression.
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2014-12-04 | GSE59523 | GEO