Spt6 regulates intragenic and antisense transcription, nucleosome positioning, and histone modifications genome-wide in fission yeast [ChIP-seq]
ABSTRACT: Spt6 is a highly conserved histone chaperone that interacts directly with both RNA polymerase II and histones to regulate gene expression. To gain a comprehensive understanding of the requirements for this critical factor, we have performed genome-wide analyses of transcription, chromatin structure, and histone modifications in an S. pombe spt6 mutant. Our results demonstrate several dramatic changes to transcription and chromatin structure in the spt6 mutant, including an elevation of antisense transcripts at over 70 percent of all genes and general loss of the +1 nucleosome. Furthermore, Spt6 is required for the trimethylation of histone H3 on lysines 4 and 36, marks associated with active transcription. Taken together, our results indicate that Spt6 is critical for the accuracy of transcription and the integrity of chromatin, likely via its direct interactions with RNA polymerase II and histones. ChIP-seq experiments were performed on wild type and spt6-1 strains on the following proteins: RNA polymerase II (Rpb1), Paf1 Complex (Ctr9), COMPASS (Swd1), Set2, Spt6, histones H2B and H3, histone modifications H3K4me3 and H3K36me3. Experiments were performed in replicates and matching inputs were also sequenced.
Project description:Spt6 is a highly conserved histone chaperone that interacts directly with both RNA polymerase II and histones to regulate gene expression. To gain a comprehensive understanding of the requirements for this critical factor, we have performed genome-wide analyses of transcription, chromatin structure, and histone modifications in an S. pombe spt6 mutant. Our results demonstrate several dramatic changes to transcription and chromatin structure in the spt6 mutant, including an elevation of antisense transcripts at over 70 percent of all genes and general loss of the +1 nucleosome. Furthermore, Spt6 is required for the trimethylation of histone H3 on lysines 4 and 36, marks associated with active transcription. Taken together, our results indicate that Spt6 is critical for the accuracy of transcription and the integrity of chromatin, likely via its direct interactions with RNA polymerase II and histones. MNase-seq experiments were performed on wild type and spt6-1 strains in replicate at two different MNase concentrations
Project description:Spt6 is a highly conserved histone chaperone that interacts directly with both RNA polymerase II and histones to regulate gene expression. To gain a comprehensive understanding of the requirements for this critical factor, we have performed genome-wide analyses of transcription, chromatin structure, and histone modifications in an S. pombe spt6 mutant. Our results demonstrate several dramatic changes to transcription and chromatin structure in the spt6 mutant, including an elevation of antisense transcripts at over 70 percent of all genes and general loss of the +1 nucleosome. Furthermore, Spt6 is required for the trimethylation of histone H3 on lysines 4 and 36, marks associated with active transcription. Taken together, our results indicate that Spt6 is critical for the accuracy of transcription and the integrity of chromatin, likely via its direct interactions with RNA polymerase II and histones. RNA-seq experiments were performed on wild type and spt6-1 strains in replicate
Project description:The FACT complex and Spt6 are conserved histone chaperones that are recruited to the open reading frames of transcribed genes. In this study, we provide evidence that FACT interaction with acetylated H3 tail is important for its localization to the coding sequences. Pol II CTD kinase Kin28 additionally stimulates FACT recruitment to a subset of genes. Pol II occupancies in the 5’ ends of transcribed genes are greatly reduced on depleting FACT, whereas reduced occupancies at the 3’ ends were observed upon Spt6 depletion indicating that these factors modulate Pol II progression through distinct regions of transcribed coding sequences. While FACT is largely responsible for reassembling histones, we uncover a role for Spt6 in promoting histone eviction in addition to widely-accepted role for Spt6 in histone reassembly. Consistent with their localization in the coding regions, simultaneously impairing FACT and Spt6 function severely dampens histone eviction and impairs transcription genome-wide. ChIP-chip experiments to measure Spt16 occupancies in WT and kin28as mutant, as well Rpb3 and histone H3 occupancies in undepleted or depleted cells for Spt16 and Spt6, and also in the strain lacking Spt6 tandem SH2 domain Overall design: The WT and mutant strains were grown in Synthetic complete and cells were induced for Gcn4 by treating with Sulfometuron methyl for 30 minutes and processed for chromatin immunoprecipitation using antibodies again Myc, Rpb3 or histone H3.
Project description:Histone chaperones affect chromatin structure and gene expression through interaction with histones and RNA polymerase II (PolII). Here, we report that the histone chaperone Spt6 counteracts H3K27me3, an epigenetic mark deposited by the Polycomb Repressive Complex 2 (PRC2) and associated with transcriptional repression. We found that Spt6 is required for proper engagement and function of the H3K27 demethylase KDM6A (UTX) on muscle genes and regulates muscle gene expression and cell differentiation. ChIP-Seq experiments revealed an extensive genome-wide overlap of Spt6, PolII and KDM6A at transcribed regions that are devoid of H3K27me3. Mammalian cells and zebrafish embryos with reduced Spt6 display increased H3K27me3 and diminished expression of the master regulator MyoD, resulting in myogenic differentiation defects. As a confirmation for an antagonistic relationship between Spt6 and H3K27me3, inhibition of PRC2 permits MyoD re-expression in myogenic cells with reduced Spt6. Our data indicate that, through cooperation with PolII and KDM6A, Spt6 orchestrates removal of H3K27me3, thus effectively controlling developmental gene expression and cell differentiation. Examination of Spt6 and KDM6A levels in a skeletal muscle cells at various developmental stages
Project description:Heterochromatin contains repressively modified histones and replicates late in S phase of the cell cycle. Besides the shortage in replication origins, little is known about replication timing regulation in silenced regions. In Drosophila polytene cells, late replication results in under-replication and decreased DNA copy number in heterochromatic regions of the genome. The Suppressor of Under-replication (SUUR) protein controls this feature – in its absence the DNA polytenization level in most silenced regions is restored, however the repressive histone marks are lost. We hypothesized that SUUR regulates the re-establishment of repressive histone pattern during replication which results in delayed replication completion of heterochromatin. Measuring DNA copy number in mutants with disrupted repressive pathways, we found that under-replication is directly linked to repressive histone marks supply. DamID-seq and ChIP-seq experiments revealed that SuUR mutation does not affect the establishment of heterochromatin domains. Here, we identified a novel SUUR protein interaction (CG12018) that supports SUUR association with replication complex. SUUR loads onto replication forks shortly after the origin firing and participates in chromatin maintenance rather than its establishment. Thus, our findings provide comprehensive evidence that late replication in Drosophila is caused by the time-consuming process of replication-coupled repressive chromatin renewal. Examination of H3K27me3 histone modification in 3 cell types in presence or absence of SuUR mutation.
Project description:Post-translational modifications of histones determines cell lineage- or signal-specific gene expression. Depending on the type and combination of modifications, histones bind to functionally distinct effector proteins ('readers') that control gene activation or silencing. The current pharmacological modulation of the epigenome aims to control gene expression by regulation of the enzymes that catalyze post-translational histone modifications. Here we present a novel pharmacological approach that targets gene expression by interfering with the function of histone ?readers?. We describe the impact of a synthetic compound that selectively occupies the acetylated histone-binding pocket of the Bromodomain and Extra Terminal domain (BET) family of proteins and prevents their interaction with acetylated histones. The bromodomain blocking compound suppresses the expression of a specific subset of key inflammatory genes in activated macrophages and confers protection against LPS-induced septic shock in vivo. Our findings suggest that small molecules specifically targeting histone 'readers' can serve as a new generation of drugs to treat immune diseases. Microarray, ChIP-qPCR and ChIP-seq examination of control, 1H LPS stimulated bone-marrow-derived macrophages in the presence/absence of acetylated histone mimic in mouse.
Project description:This model is described in the article:
Kinetics of histone gene expression during early development of Xenopus laevis.
Koster JG, Destrée OH and Westerhoff HV. J Theor Biol.
1988 Nov 21;135(2):139-67. PMID: 3267765
Using literature data for transcriptional and translational rate constants, gene copy numbers, DNA concentrations, and stability constants, we have calculated the expected concentrations of histones and histone mRNA during embryogenesis of Xenopus laevis. The results led us to conclude that: (i) for X. laevis the gene copy number of the histone genes is too low to ensure the synthesis of sufficient histones during very early development, inheritance from the oocyte of either histone protein or histone mRNA (but not necessarily both) is necessary; (ii) from the known storage of histones in the oocyte and the rates of histone synthesis determined by Adamson and Woodland (1977), there would be sufficient histones to structure the newly synthesized DNA up to gastrulation but not thereafter (these empirical rates of histone synthesis may be underestimates); (iii) on the other hand, the amount of H3 mRNA recently observed during early embryogenesis (Koster, 1987, Koster et al., 1988) could direct a higher and sufficient synthesis of H3 protein, also after gastrulation. We present a quantitative model that accounts both for the observed H3 mRNA concentration as a function of time during embryogenesis and for the synthesis of sufficient histones to structure the DNA throughout early embryogenesis. The model suggests that X. laevis exhibits a major (i.e. some 14-fold) reduction in transcription of histone genes approximately 11 hours after fertilization. This reduction could be due to a decrease in the number of transcribed histone genes, a decreased rate constant of transcription with continued transcription of all the histone genes, and/or a reduction in the time during the cell cycle in which histone mRNA synthesis takes place. Alternatively, the histone mRNA stability might decrease approximately 16-fold 11 hours after fertilization.
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Project description:The histone acetyltransferase Sas2 is part of the SAS-I complex and acetylates lysine 16 of histone H4 (H4 K16Ac) in the genome of Saccharomyces cerevisiae. Sas2-mediated H4 K16Ac is strongest over the coding region of genes with low expression. However, it is unclear how Sas2-mediated acetylation is incorporated into chromatin. Our previous work has shown physical interactions of SAS with the histone chaperones CAF-I and Asf1, suggesting a link between SAS-I mediated acetylation and chromatin assembly. Here, we find that Sas2-dependent H4 K16Ac in bulk histones requires passage of the cells through the S-phase of the cell cycle, and the rate of increase in H4 K16Ac depends on both CAF-I and Asf1, whereas steady-state levels and genome-wide distribution of H4 K16Ac shows only mild changes in their absence. Furthermore, H4 K16Ac is deposited in chromatin at genes upon repression, and this deposition requires the histone chaperone Spt6, but not CAF-I, Asf1, HIR or Rtt106. Altogether, our data indicate that Spt6 controls H4 K16Ac levels by incorporating K16-unacetylated H4 in strongly transcribed genes. Upon repression, Spt6 association is decreased, resulting in less deposition of K16-unacetylated and therefore in a concomitant increase of H4 K16Ac that is recycled during transcription.
Project description:Regulatory T cells (Treg) contribute to the crucial immunological processes of self-tolerance and immune homeostasis. However, the mechanisms underlying Treg function and cell fate decisions to differentiate between Treg and conventional T cells (Tconv) remain to be fully elucidated, especially at the histone modification level. Covalent modifications of histones establish and maintain chromatin structure, and regulate gene transcription events by facilitating access to cis-elements by trans-acting factors during mammalian development and cellular differentiation. We aimed to investigate the role of the methylation form of histone modification as related to Treg function and phenotype. High-resolution maps of the genome-wide distribution of monomethylated histone H3 lysine 4, H3K4me1, and the trimethylated form H3K4me3 were generated for human activated conventional CD4+CD25+FOXP3- T cells (aTconv) and CD4+CD25+FOXP3+ regulatory T cells (Treg) by sequencing using the Solexa 1G Genetic Analyzer. We found 2115 H3K4me3 regions corresponding to proximal promoter regions; the genes associated with these regions in Treg cells included the crucial transcription factor forkhead box P3 (FOXP3) and the chemokine receptor CCR7. We also identified 41024 Treg cell type-specific H3K4me1 regions. The majority of the H3K4me1 regions differing between the Treg and aTconv cells were located at promoter-distal sites, some of which were selected and consolidated to further examine enhancer activity in in vitro reporter gene assays. The findings from our study provide a comprehensive genome-wide dataset of lineage-specific H3K4me1 and H3K4me3 patterns in Treg and aTconv cells, which may control the differentiation decision, lineage commitment and cell type-specific gene regulation. This basic principle is likely not confined to the two closely-related T cell populations, but may apply generally to somatic cell lineages in adult organisms. Genome-wide distribution of monomethylated histone H3 lysine 4, H3K4me1, and the trimethylated form H3K4me3 in human activated conventional CD4+CD25+FOXP3- T cells (aTconv) and CD4+CD25+FOXP3+ regulatory T cells (Treg) (5 samples in total)
Project description:The nuclear receptor Peroxisome Proliferator Activator Receptor (PPAR ) is the target of antidiabetic thiazolidinedione drugs, which improve insulin resistance but have side-effects that limit widespread use. PPAR is required for adipocyte differentiation, but is also expressed in other cell types, notably macrophages, where it influences atherosclerosis, insulin resistance, and inflammation. A central question is whether PPAR binding in macrophages occurs at the same or different genomic locations compared to adipocytes. Here, utilizing chromatin immunoprecipitation and high throughput sequencing (ChIP-seq), we demonstrate that PPAR cistromes in adipocytes and macrophages are predominantly cell type specific. In macrophages, PPAR colocalizes with the hematopoietic transcription factor PU.1 in areas of open chromatin and histone acetylation, near a distinct set of immune genes in addition to a number of metabolic genes shared with adipocytes. In adipocytes, the macrophage-unique binding regions are marked with repressive histone modifications, typically associated with local chromatin compaction and gene silencing. PPAR , when introduced into cells that are neither macrophages nor adipocytes, bound only to regions depleted of repressive histone modifications, where it increased DNA accessibility, enhanced histone acetylation, and induced gene expression. Thus, the cell-specificity of PPAR function is regulated by cell-specific chromatin accessibility, histone marks, and transcription factors. Genomic occupancy profiled by high throughput sequencing (ChIP-seq) from mouse macrophages for PPARgamma, PU.1, C/EBPbeta, H3K9Ace; and from 3T3-L1 adipocytes for PPARgamma and H3K9Ace Masking file used to subtract input bias areas prior to generating final peak lists is linked below.