Project description:Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation as nucleosomes modulate DNA access by their positioning along the genome. A cell population nucleosome map requires two observables: nucleosome positions along the DNA (“Where?”) and nucleosome occupancies across the population (“In how many cells?”). All available genome-wide nucleosome mapping techniques are yield methods as they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or non-nucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby crossvalidating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9 bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (± SD). Depending on nucleosome position calling procedures, there are 57-60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but with increased presence of the nucleosome-evicting RSC chromatin remodeling complex there and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
Project description:Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation as nucleosomes modulate DNA access by their positioning along the genome. A cell population nucleosome map requires two observables: nucleosome positions along the DNA (“Where?”) and nucleosome occupancies across the population (“In how many cells?”). All available genome-wide nucleosome mapping techniques are yield methods as they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or non-nucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby crossvalidating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9 bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (± SD). Depending on nucleosome position calling procedures, there are 57-60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but with increased presence of the nucleosome-evicting RSC chromatin remodeling complex there and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
Project description:Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation as nucleosomes modulate DNA access by their positioning along the genome. A cell population nucleosome map requires two observables: nucleosome positions along the DNA (“Where?”) and nucleosome occupancies across the population (“In how many cells?”). All available genome-wide nucleosome mapping techniques are yield methods as they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or non-nucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby crossvalidating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9 bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (± SD). Depending on nucleosome position calling procedures, there are 57-60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but with increased presence of the nucleosome-evicting RSC chromatin remodeling complex there and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
Project description:Mapping of nucleosomes, the basic DNA packaging unit in eukaryotes, is fundamental for understanding genome regulation as nucleosomes modulate DNA access by their positioning along the genome. A cell population nucleosome map requires two observables: nucleosome positions along the DNA (“Where?”) and nucleosome occupancies across the population (“In how many cells?”). All available genome-wide nucleosome mapping techniques are yield methods as they score either nucleosomal (e.g., MNase-seq, chemical cleavage-seq) or non-nucleosomal (e.g., ATAC-seq) DNA but lose track of the total DNA population for each genomic region. Therefore, they only provide nucleosome positions and maybe compare relative occupancies between positions but cannot measure absolute nucleosome occupancy, which is the fraction of all DNA molecules occupied at a given position and time by a nucleosome. Here, we established two orthogonal and thereby crossvalidating approaches to measure absolute nucleosome occupancy across the Saccharomyces cerevisiae genome via restriction enzymes and DNA methyltransferases. The resulting high-resolution (9 bp) map shows uniform absolute occupancies. Most nucleosome positions are occupied in most cells: 97% of all nucleosomes called by chemical cleavage-seq have a mean absolute occupancy of 90 ± 6% (± SD). Depending on nucleosome position calling procedures, there are 57-60,000 nucleosomes per yeast cell. The few low absolute occupancy nucleosomes do not correlate with highly transcribed gene bodies, but with increased presence of the nucleosome-evicting RSC chromatin remodeling complex there and are enriched upstream of highly transcribed or regulated genes. Our work provides a quantitative method and reference frame in absolute terms for future chromatin studies.
Project description:MNase-seq Experiments from Calorie Restricted and Non-Restricted Yeast from WT, ISW2DEL and ISW2K215R strains We used MNase-seq to study genome-wide nucleosome positions under Calorie Restricted and Non-restricted Saccharomyces cerevisiae
Project description:The relationship between chromatin structure and transposable element (TE) integration is a fundamental question as nucleosomes can either mediate or inhibit TE insertion. The Ty1 element in Saccharomyces cerevisiae preferentially inserts upstream of RNA Polymerase III-transcribed genes, in a manner coincident with nucleosome positioning. Ty1 insertion positions have largely been inferred from nucleosome occupancy maps, but this approach is imperfect. Nucleosome occupancy maps are typically generated from wild-type Saccharomyces cerevisiae cells grown in standard conditions. Many Ty1 studies rely on a galactose-inducible expression system and it is not yet known if Ty1 overexpression from the GAL1 promoter itself alters nucleosome organization under inducing conditions. Here, we used a galactose-inducible Ty1 expression system and genome-wide MNase-seq to determine whether Ty1 donor plasmid transformation and overexpression alter nucleosome occupancy. We find that changes in carbon source do not substantially alter genome-wide nucleosome organization. In contrast, galactose induction of Ty1 expression revealed time-dependent changes in nucleosome occupancy. Nucleosome organization is unchanged across pre-induction, 6-hour galactose exposure, and post-induction repressing conditions, but nucleosome occupancy shifted at 12 and 24 hours, with changes evident at both Pol II and tRNA genes. We also found that Ty1 integration events are rare at early time points, emerge by 12 hours, and accumulate substantially by 24 hours. Ty1 preferentially targets nucleosomal DNA, but prolonged induction shifts insertion positions relative to nucleosomes. We also find that Ty1 preferentially targets nucleosomal DNA that lies in close proximity to histones, with this preference showing time-dependent shifts during induction.
Project description:We determined nucleosome positions genome-wide in diploid Saccharomyces species undergoing early stages of synchronous meiosis. This study sought to assess if meiotic DNA double-strand break formation occurred preferentially in promoter nucleosome-depleted regions in other Saccharomyces species, as it does in S. cerevisiae SK1 (Pan et al. 2011 Cell 144:719-731).
Project description:Saccharomyces cerevisiae is an excellent microorganism for industrial succinic acid production, but high succinic acid concentration will inhibit the growth of Saccharomyces cerevisiae then reduce the production of succinic acid. Through analysis the transcriptomic data of Saccharomyces cerevisiae with different genetic backgrounds under different succinic acid stress, we hope to find the response mechanism of Saccharomyces cerevisiae to succinic acid.
Project description:This experiment aims to map nucleosome positions and comparison of the same in WT NORMAL GROWTH vs WT-NUTRIENT STARVATION/isw1∆2∆ MUTANT/rsc4-∆4 MUTANT in Saccharomyces cerevisiae using a custom designed tiling array on Agilent plat form. The corresponding platform is submitted to GEO under Geo-ID GPL15842. 60mer probes with variable tiling density were designed for all the genes transcribed by RNA polymerase III. Each gene is tiled along with its 1kb downstream and upstream region with the exceptions of RPR1, SCR1, RDN5(1-6) and SNR52. Mononucleosomal DNA and size matched naked DNA was competitively hybridized to the array. Data was extracted and normalized log ratios were calculated using Agilent sofware. Normalized log2 ratio data was used in MLM to detection nucleosome positions.