Nucleosome maps in S. cerevisiae at varying phosphate concentrations
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ABSTRACT:
ORGANISM(S): Saccharomyces cerevisiae
PROVIDER: GSE26392 | GEO | 2011/08/01
SECONDARY ACCESSION(S): PRJNA136841
REPOSITORIES: GEO
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Project description:Genome wide maps of nucleosome occupancy in yeast have been produced through deep sequencing of nuclease-protected DNA. These maps have been obtained from crosslinked chromatin in vivo at varying phosphate concentrations (no phoshate and 10mM phosphate concentration). Here, we analyze these maps in combination with existing TF binding data (Harbison et al., Nature, 2004, 431(7004):99-104), and with new gene expression experiments reported here (GSE26770). We also confirm previous conclusions that the intrinsic,sequence dependent binding of nucleosomes helps determine the localization of TF binding sites. High-throughput sequencing of yeast nucleosomal DNA at varying phosphate concentration. Yeast S. cerevisiae (strain: PHO4-MYC::TRP1; CBF1-3HA::LEU2) in log phase was grown in PNB medium with no phosphate for 3 hours and then shifted to various phosphate concentration (0mM and 10 mM) for 80 minutes. After micrococcal nuclease treatment, reverse crosslink and gel purification mononucleosome were isolated. The sequencing by Illumina Solexa following manufacturer protocol has provided mononucleosomal maps in yeast genome (Oct. 2003 SGD/sacSer1 genome release) at two phosphate concentrations (starvation and normal).
2011-08-01 | E-GEOD-26392 | biostudies-arrayexpress
Project description:Binding of transcription factors to DNA is a key regulatory step in the control of gene expression. DNA sequences with high affinity for transcription factors occur more frequently in the genome than instances of genes bound or regulated by these factors. How specific gene regulation is achieved by transcription factors remains unclear. We used genome-wide approaches to study how trans factors shape the binding and regulatory landscape of Pho4, a budding yeast transcription factor that activates gene expression in response to phosphate limitation. In no phosphate (0mM phosphate) medium, Pho4 is transported into the nucleus and activates transcription of a set of genes (PHO) that are necessary for cell survival in phosphate limited environment. In high phosphate (10mM phosphate) medium, Pho4 is transported outside of the nucleus and the transcription program of PHO genes are turned off. Here we examined the transcription profiling of S. cerevisiae (W303) in various strains treated in media with 10mM or 0mM inorganic phosphate, to study the the transcription activation by Pho4 its cooperative binding factor Pho2, and its competitive binding factor Cbf1.
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Project description:Transcription factors (TF) binding is key to understanding and characterizing the effect of genetic variability on phenotypic differences. Here, we used a novel scalable ChIP-seq approach to annotate the regulatory landscape of the maize genome with binding data from 104 leaf TFs. TF binding regions co-localized with open chromatin regions, with ~70% of TF binding nearby genes. TF binding sites are evolutionarily conserved and show enrichment for GWAS-hits, cis-expression QTLs. Furthermore, the regulatory network shows characteristics of real-word networks such as scale-free topology and larger modularity than random graphs. Finally, machine-learning analyses reveal that sequence preferences are alike within TF families, and that TF co-localization is key for TF binding specificity. Our comprehensive TF-DNA interaction approach provides the starting point to decipher the gene regulatory system in plant leaves.
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Project description:The binding and contribution of transcription factors (TF) to cell specific gene expression is often deduced from open-chromatin measurements to avoid cost and labour intensive TF ChIP-seq assays.It is important to develop reliable and fast computational methods for accurate TF binding prediction in open-chromatin regions (OCRs). Here, we report a novel segmentation-based method, TEPIC, to predict TF binding by combining sets of OCRs with position weight matrices.TEPIC can be applied to various open-chromatin data, e.g. DNaseI-seq and NOMe-seq, using either peaks or footprints as input.In addition to open-chromatin data, also Histone-Marks (HMs) can be used in TEPIC to identify candidate TF binding sites.TEPIC computes TF affinities and uses open-chromatin/HM signal intensity as quantitative measures of TF binding strength.Using machine learning techniques, we show that incorporating low affinity binding sites improves our ability to explain gene expression variability compared to the standard presence/absence classification of binding sites.Further, we show that both footprints and peaks capture essential TF binding events and lead to a good prediction performance.In our application, gene-based scores computed by TEPIC with one open-chromatin assay nearly reach the quality of several TF ChIP-seq datasets.Finally, we show that these scores correctly predict known transcriptional regulators as illustrated by the application to novel DNaseI-seq and NOMe-seq data for primary human hepatocytes and CD4+ T-cells, respectively.
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Project description:Binding of transcription factors to DNA is a key regulatory step in the control of gene expression. DNA sequences with high affinity for transcription factors occur more frequently in the genome than instances of genes bound or regulated by these factors. How specific gene regulation is achieved by transcription factors remains unclear. We used genome-wide approaches to study how trans factors shape the binding and regulatory landscape of Pho4, a budding yeast transcription factor that activates gene expression in response to phosphate limitation. In no phosphate (0mM phosphate) medium, Pho4 is transported into the nucleus and activates transcription of a set of genes (PHO) that are necessary for cell survival in phosphate limited environment. In high phosphate (10mM phosphate) medium, Pho4 is transported outside of the nucleus and the transcription program of PHO genes are turned off. Here we examined the transcription profiling of S. cerevisiae (W303) in various strains treated in media with 10mM or 0mM inorganic phosphate, to study the the transcription activation by Pho4 its cooperative binding factor Pho2, and its competitive binding factor Cbf1. (I) To infer how much Pho4 itself, Pho2 itself, and the interaction between Pho2 and Pho4 contribute to transcriptional activation in response to Pi starvation, we applied mutant cycle analysis to compare wild type, pho2Δ, pho4Δ and pho2Δ pho4Δ strains in both 10 mM and 0 mM Pi conditions. Mutant cycle analysis is a cyclic comparison among all various mutants. For example, by comparing pho2Δ and pho2Δ pho4Δ, we can directly infer the contribution from Pho4 alone to gene activation. And by comparing wild type and pho2Δ, we can infer the contribution from Pho2 alone together with that from the interaction between Pho2 and Pho4. (II) Compare two strains or one strain in two treatments in multiple replicates with dye-swap method. wt no vs high Pi, to identify genes that are induced in response to Pi starvation. cbf1Δ vs wt in high Pi, to identify the influence of Cbf1 on gene expression in high Pi condition. cbf1Δpho4Δ vs wt in high Pi, to identify the influence of Cbf1 on gene expression that is mediated through Pho4, in high Pi condition. rtg3Δtye7Δ vs wt in high Pi, to identify the influence of Rtg3 and Tye7 on gene expression in high Pi condition. pho80Δ vs pho80Δpho4Δ, to identify the genes that are activated Pho4 when Pho4 is fully nuclear localized. pho80Δcbf1Δ vs pho80Δcbf1Δpho4Δ, to identify the influence of Cbf1 on gene expression that is mediated through Pho4, when Pho4 is fully nuclear localized.
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