Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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High-throughput sequencing reveals a simple model of nucleosome energetics

ABSTRACT: We use nucleosome maps obtained by high-throughput sequencing to study sequence specificity of intrinsic histone-DNA interactions. In contrast with previous approaches, we employ an analogy between a classical one-dimensional fluid of finite-size particles in an arbitrary external potential and arrays of DNA-bound histone octamers. We derive an analytical solution to infer free energies of nucleosome formation directly from nucleosome occupancies measured in high-throughput experiments. The sequence-specific part of free energies is then captured by fitting them to a sum of energies assigned to individual nucleotide motifs. We have developed hierarchical models of increasing complexity and spatial resolution, establishing that nucleosome occupancies can be explained by systematic differences in mono- and dinucleotide content between nucleosomal and linker DNA sequences, with periodic dinucleotide distributions and longer sequence motifs playing a secondary role. Furthermore, similar sequence signatures are exhibited by control experiments in which genomic DNA is either sonicated or digested with micrococcal nuclease in the absence of nucleosomes, making it possible that current predictions based on highthroughput nucleosome positioning maps are biased by experimental artifacts. Included are raw (eland) and mapped (wig) reads. The mapped reads are provided in eland and wiggle formats, and the raw reads are included in the eland file. This series includes only Mnase control data. The sonicated control is part of this already published accession, as is a in vitro nucleosome map: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE15188 We also studied data (in vitro and in vivo maps as well as a model) from http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE13622 and from: http://www.ncbi.nlm.nih.gov/sra/?term=SRA001023

ORGANISM(S): Escherichia coli

SUBMITTER: George Locke

PROVIDER: E-GEOD-23712 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:We used high density oligonucleotide arrays to measure the relative expression levels of >39,000 genes and ESTs in the NOD mouse (a murine model of T1D and other autoimmune conditions), four NOD-derived diabetes resistant congenic strains and two nondiabetic control strains. Owing to the importance of T cells in the development of T1D we decided to target two organs, the spleen and thymus. We profiled gene expression in thymi from four week old female mice and spleens from three month old female mice. For each of the 14 strain-tissue combinations (7 strains x 2 tissues) we performed two independent replicate experiments, making the total number of hybridizations performed 28. In each case, an RNA population from a pool of two or three organs was generated to minimize the chances of within strain variation masking genuine variation between the strains. To minimize any variation introduced during target preparation, all samples within a given replicate group were processed in parallel. Three samples from group two (spleen: B10.H2g7_S2 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=gsm594 (GSM594); thymus: B10.H2g7_T2 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=gsm608 (GSM608), B10.H2g7 Idd3_T2 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=gsm609 (GSM609)) and one from group one (spleen B10.H2g7_S1 http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=gsm587 (GSM587) failed a preliminary quality control check. Consequently, the steps involved in preparing labelled cRNA from the initial starting material had to be repeated for these four samples at a later date. A subsequent comparison of the variation seen between samples within the same replicate group (samples processed in parallel) versus samples in distinct replicate groups (samples processed at different times) revealed that the variation between the two groups (i.e. owing to independent sample preparation) was higher than the small amount of variation between the closely matched strains. Ignoring the variability introduced during sample preparation was therefore likely to result in spurious changes being detected and genuine strain-specific differences in gene expression being masked. Consequently, we decided to exclude the four samples that had had to be prepared independently owing to failing initial quality control. Keywords = NOD, diabetes, congenic Keywords: other

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High-throughput sequencing reveals a simple model of nucleosome energetics

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