A giant virus genome is densely packaged by stable nucleosomes
Ontology highlight
ABSTRACT:
ORGANISM(S): synthetic construct Marseillevirus marseillevirus Drosophila melanogaster
PROVIDER: GSE193224 | GEO | 2022/09/27
REPOSITORIES: GEO
Similar Datasets
Project description:Human Cytomegalovirus (HCMV) significantly remodels host cell processes and membranes to enable effective production of virus progeny. Nascent capsids exit the nucleus and undergo a final morphogenesis process in the cytoplasm where they associate with tegument and membranes. During this process called secondary envelopment, fully assembled virions are formed which are wrapped inside of host vesicles. Both the origin of the receiving membrane as well as the dynamic organization of the envelopment and exocytosis process are not well understood. Enveloped virus particles can be both found individually wrapped in small vesicles but also as accumulations in multivesicular bodies (MVBs). While individually wrapped particles are believed to exit the cell by exocytosis, it is unclear if particles in MVBs ever leave the cell or are actually targeted for lysosomal degradation. Using a novel correlative light and electron microscopy workflow that allows three-dimensional imaging of whole cells, we present evidence that HCMV capsids can bud into MVBs, generating large intracellular accumulations of enveloped virions. Immunofluorescence and fusion assays suggest that these MVBs are positive for markers of the exosomal pathway. Time-lapse as well as functional live-cell imaging showed that MVBs fuse with the plasma membrane and release patch-like accumulations of virus particles. Our data suggests a so far undescribed envelopment and exocytosis pathway of HCMV, possibly involving the late-endosome/exosome pathway, leading to the intermittent bulk release of virus particles.
2022-06-23 | PXD023444 | Pride
Project description:Nuclear DNA is wrapped around core histones to form nucleosomes, which constrains how transcription factors bind to gene regulatory sequences. Pioneer transcription factors have the special ability to bind target DNA on nucleosomes and initiate gene regulatory events, often leading to a local opening of chromatin. Yet the nucleosomal status of such open chromatin, e.g., at active enhancers, is not clear. Here we develop a combination of low and high levels of MNase digestion along with core histone ChIP-seq to assess the presence of nucleosomes at enhancers and promoters in mouse liver. We find that liver-specific enhancers retain preferentially MNase-accessible nucleosomes, with factors bound, substantially more than ubiquitous enhancers. Furthermore, the pioneer factor FoxA2 is required to keep enhancer nucleosomes accessible in chromatin at active liver genes. Thus, nucleosomes are not exclusively repressive to gene regulation when they are retained with, and exposed by, pioneer factors.
2018-05-30 | GSE71947 | GEO
Project description:Nuclear DNA is wrapped around core histones to form nucleosomes, which constrains how transcription factors bind to gene regulatory sequences. Pioneer transcription factors have the special ability to bind target DNA on nucleosomes and initiate gene regulatory events, often leading to a local opening of chromatin. Yet the nucleosomal configuration of such open chromatin and the basis for chromatin opening is unclear. Here we combine low and high levels of MNase digestion along with core histone ChIP-seq to assess the presence of nucleosomes at enhancers and promoters in mouse liver. We find that the pioneer factor FoxA displaces linker histone H1, thereby keeping enhancer nucleosomes accessible in chromatin and helping other transcription factors bind. MNase-accessible nucleosomes, bound by transcription factors, are retained substantially more at liver-specific enhancers than promoters and tissue-ubiquitous enhancers. Thus, nucleosomes are not exclusively repressive to gene regulation when they are retained with, and exposed by, pioneer factors.
2016-04-08 | GSE77670 | GEO
Project description:The centromere is the genetic locus that organizes the proteinaceous kinetochore and is responsible for attachment of the chromosome to the spindle at mitosis and meiosis. In most eukaryotes, the centromere consists of highly repetitive DNA sequences that are occupied by nucleosomes containing the CenH3 histone variant, whereas in budding yeast, an ~120-bp Centromere DNA Element (CDE) that is sufficient for centromere function is occupied by a single right-handed CenH3 (Cse4) nucleosome. However, these in vivo observations are inconsistent with in vitro evidence for left-handed octameric CenH3 nucleosomes. To help resolve these inconsistencies, we characterized yeast centromeric chromatin at single base-pair resolution. Intact particles containing both Cse4 and H2A are precisely protected from micrococcal nuclease over the entire CDE of all 16 yeast centromeres in both solubilized chromatin and the insoluble kinetochore. Small DNA-binding proteins protect CDEI and CDEIII and delimit the centromeric nucleosome to the ~80-bp CDEII, only enough for a single DNA wrap. As expected for a tripartite organization of centromeric chromatin, loss of Cbf1 protein, which binds to CDEI, both reduces the size of the centromere-protected region and shifts its location towards CDEIII. Surprisingly, Cse4 overproduction caused genome-wide misincorporation of non-functional CenH3-containing nucleosomes that protect ~135 base pairs and are preferentially enriched at sites of high nucleosome turnover. Our detection of two forms of CenH3 nucleosomes in the yeast genome, a singly wrapped particle at the functional centromere and octamer-sized particles on chromosome arms, reconcile seemingly conflicting in vivo and in vitro observations. We used micrococcal nuclease mapping, chromatin immunoprecipitation and paired-end sequencing to determine the structure of yeast centromeres at single base-pair resolution.
2011-12-07 | E-GEOD-28298 | biostudies-arrayexpress
Project description:DDM1/Lsh remodelers allow methylation of DNA wrapped in nucleosomes
| PRJNA380344 | ENA
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:Chromatin is composed of DNA wrapped around nucleosomes, complexes consisting of highly basic proteins called histones. Histone variants are non-canonical variants of histones that have specific functions. The Apicomplexan parasite Toxoplasma gondii possesses conserved histone variants CenH3, H3.3, H2A.Z, H2A.X, as well as the parasite-specific H2B variant, H2BV (or H2B.Z). We surveyed the genome-wide distribution of T. gondii histone variants by chromatin immunoprecipitation coupled with microarray (ChIP-chip) and next generation sequencing (ChIP-seq). Histone variants have specific localisations in chromosomes and in relation to genomic features. Histones H2BV and H2AZ localise to promoter regions with the transcriptional activation mark H3K4me3. Sites where H2BV, H2AZ and H3K4me3 colocalise are enriched in motifs recognised by AP2 transcription factors, particularly in the nucleosome-free region just upstream of the transcription start site. In contrast, histone variants H3.3 and H2AX are largely absent from promoters but enriched in gene bodies. Consistent with previous biochemical work, the majority of H2AX and H2AZ loci do not overlap, suggesting that they are present in different nucleosomes. In addition, the T. gondii homologue of the centromeric histone CenH3 demarcates centromeric chromatin and appears to be part of a unique centromeric histone complex including H3.3 that localises to centromeric chromatin as detected in proteomic analysis of co-immunoprecipitated CenH3 complexes. Together, these data suggest that the position of variant histones demarcates specific functional regions of chromatin and that exchange of histone variants is an important transcriptional regulatory mechanism in T. gondii.
2018-03-01 | GSE104347 | GEO
Project description:Chromatin is composed of DNA wrapped around nucleosomes, complexes consisting of highly basic proteins called histones. Histone variants are non-canonical variants of histones that have specific functions. The Apicomplexan parasite Toxoplasma gondii possesses conserved histone variants CenH3, H3.3, H2A.Z, H2A.X, as well as the parasite-specific H2B variant, H2BV (or H2B.Z). We surveyed the genome-wide distribution of T. gondii histone variants by chromatin immunoprecipitation coupled with microarray (ChIP-chip) and next generation sequencing (ChIP-seq). Histone variants have specific localisations in chromosomes and in relation to genomic features. Histones H2BV and H2AZ localise to promoter regions with the transcriptional activation mark H3K4me3. Sites where H2BV, H2AZ and H3K4me3 colocalise are enriched in motifs recognised by AP2 transcription factors, particularly in the nucleosome-free region just upstream of the transcription start site. In contrast, histone variants H3.3 and H2AX are largely absent from promoters but enriched in gene bodies. Consistent with previous biochemical work, the majority of H2AX and H2AZ loci do not overlap, suggesting that they are present in different nucleosomes. In addition, the T. gondii homologue of the centromeric histone CenH3 demarcates centromeric chromatin and appears to be part of a unique centromeric histone complex including H3.3 that localises to centromeric chromatin as detected in proteomic analysis of co-immunoprecipitated CenH3 complexes. Together, these data suggest that the position of variant histones demarcates specific functional regions of chromatin and that exchange of histone variants is an important transcriptional regulatory mechanism in T. gondii.
2019-04-30 | GSE87834 | GEO
Project description:In mature human sperm, genes of importance for embryo development (i.e. transcription factors) lack DNA methylation and bear nucleosomes with distinctive histone modifications, suggesting the specialized packaging of these developmental genes in the germline. Here, we explored the tractable zebrafish model and found conceptual conservation as well as several new features. Biochemical and mass spectrometric approaches reveal the zebrafish sperm genome packaged in nucleosomes and histone variants (and not protamine), and we find linker histones high and H4K16ac absent - key factors which may contribute to genome condensation. We examined several activating (H3K4me2/3, H3K14ac, H2AFV) and repressing (H3K27me3, H3K36me3, H3K9me3, hypoacetylation) modifications/compositions genome-wide, and find developmental genes packaged in large blocks of chromatin with coincident activating and repressing marks and DNA hypomethylation, revealing complex ‘multivalent’ chromatin. Notably, genes that acquire DNA methylation in the soma (muscle) are enriched in transcription factors for alternative cell fates. Remarkably, we find H3K36me3 located in ‘silent’ developmental gene promoters, and not present at the 3’ ends of coding regions of genes heavily transcribed during sperm maturation, suggesting different rules for H3K36me3 in the germline and soma. We also reveal the chromatin patterns of transposons, rDNA, and tRNAs. Finally, high levels of H3K4me3 and H3K14ac in sperm are correlated with genes activated in embryos prior to the mid-blastula transition (MBT), whereas multivalent genes are correlated with activation at or after MBT. Taken together, gene sets with particular functions in the embryo are packaged by distinctive types of complex and often atypical chromatin in sperm. [DNA profiling]: H3K4me3, H3K4me2, H3K14ac, H3K36me3, H3K27me3, H3K9me3, and H2AFV ChIP-chip in zebrafish sperm; DNA methylation in zebrafish sperm and muscle by MeDIP-chip. (two replicates and dye-swaps for all experiments). Antibodies: H3K4me3 (Abcam ab8580 and Active Motif 39159), H3K4me2 (Abcam ab7766), H3K14Ac (Upstate 07-353), H2AZ (Abcam ab4174), H3K27me3 (Upstate 07-449), H3K9me3 (Active Motif 39161), H3K36me3 (Abcam ab9050), 5-methylcytidine (Eurogentec BI-MECY-1000). Supplementary files: Processed data files reporting calculated enrichment log2 ratio (mean ChIP/mean Input in the log2 ratio). Note: For analysis, "mean Input" from H3K4me3-rep1 ch1, H3K4me2-rep1 ch2, and H3K36me3-rep2 ch1 for all ChIP eluates. [mRNA profiling]: Transcripts in zebrafish mature sperm using zebrafish expression microarray from Agilent. (two replicates)
2011-01-13 | E-GEOD-26609 | biostudies-arrayexpress
Project description:The centromere is the genetic locus that organizes the proteinaceous kinetochore and is responsible for attachment of the chromosome to the spindle at mitosis and meiosis. In most eukaryotes, the centromere consists of highly repetitive DNA sequences that are occupied by nucleosomes containing the CenH3 histone variant, whereas in budding yeast, an ~120-bp Centromere DNA Element (CDE) that is sufficient for centromere function is occupied by a single right-handed CenH3 (Cse4) nucleosome. However, these in vivo observations are inconsistent with in vitro evidence for left-handed octameric CenH3 nucleosomes. To help resolve these inconsistencies, we characterized yeast centromeric chromatin at single base-pair resolution. Intact particles containing both Cse4 and H2A are precisely protected from micrococcal nuclease over the entire CDE of all 16 yeast centromeres in both solubilized chromatin and the insoluble kinetochore. Small DNA-binding proteins protect CDEI and CDEIII and delimit the centromeric nucleosome to the ~80-bp CDEII, only enough for a single DNA wrap. As expected for a tripartite organization of centromeric chromatin, loss of Cbf1 protein, which binds to CDEI, both reduces the size of the centromere-protected region and shifts its location towards CDEIII. Surprisingly, Cse4 overproduction caused genome-wide misincorporation of non-functional CenH3-containing nucleosomes that protect ~135 base pairs and are preferentially enriched at sites of high nucleosome turnover. Our detection of two forms of CenH3 nucleosomes in the yeast genome, a singly wrapped particle at the functional centromere and octamer-sized particles on chromosome arms, reconcile seemingly conflicting in vivo and in vitro observations.
2011-12-07 | GSE28298 | GEO