Project description:Nucleosomes in all eukaryotes examined to date adopt a characteristic architecture within genes and play fundamental roles in regulating transcription, yet the identity and precise roles of many of the trans-acting factors responsible for the establishment and maintenance of this organization remain to be identified. We profiled a compendium of 50 yeast strains carrying conditional alleles or complete deletions of genes involved in transcriptional regulation, histone biology and chromatin remodeling, as well as compounds that target transcription and histone deacetylases, to assess their respective roles in nucleosome positioning and transcription. We find that nucleosome patterning in genes is affected by many factors including the CAF-1 complex, Spt10 and Spt21, in addition to previously reported remodeler ATPases and histone chaperones. Disruption of these factors or reductions in histone levels led genic nucleosomes to assume positions more consistent with their intrinsic sequence preferences, with pronounced and specific shifts of the +1 nucleosome relative to the transcription start site. These shifts of +1 nucleosomes appear to have functional consequences, as several affected genes in Ino80 mutants exhibited altered expression responses. Our parallel expression profiling compendium revealed extensive transcription changes in intergenic and antisense regions, most of which occur in regions with altered nucleosome occupancy and positioning. We show that the nucleosome-excluding transcription factors Reb1, Abf1, Tbf1, and Rsc3 suppress cryptic transcripts at their target promoters, while a combined analysis of nucleosome and expression profiles identified 36 novel transcripts that are normally repressed by Tup1/Cyc8. Our data confirm and extend the roles of chromatin remodelers and chaperones as major determinants of genic nucleosome positioning and these data provide a valuable resource for future studies. We examined 50 single-gene loss-of-function strains, comprised of gene deletions (del) and temperature-sensitive (ts) or tetracycline promoter-shutoff (tet) alleles. These genes were selected based on their known or potential role in nucleosome biology and include remodeler ATPases and chaperones, histones and histone modifiers, transcription and elongation factors, and components of RNA polymerase I and II. The compendium also includes 4 compounds targeting transcription and histone deacetylases, as well as a histone depletion time course performed with a strain in which H4 gene expression is exclusively under the control of a GAL1 promoter. Genome-wide nucleosome occupancy profiles were generated using Affymetrix Tiling arrays with probes spaced every 4 bp [PMID:16569694], or next-generation sequencing. Identically prepared samples for each strain and treatment were analyzed on the same tiling arrays for strand-specific expression differences. Each compendium condition was compared to a matched wild-type (WT) reference grown in parallel.

Project description:Title : Characterization of genes differentially expressed in roots of transgenic arabidopsis lines expressing the p25 protein of beet necrotic yellow vein virus. Biological question : Rhizomania ("crazy root") is a severe disease of sugar beet caused by beet necrotic yellow vein virus (BNYVV), which is transmitted by the soil-inhabiting fungus Polymyxa betae. Symptoms of virus infection are characterized by a constricted tap root and a massive proliferation of fine rootlets that often undergo necrosis. BNYVV RNA-3 encodes a 25 kDa (p25) which is an important determinant of leaf symptom phenotype. It also governs BNYVV invasion of the plant root system and induction of rootlet proliferation in sugar beet. In order to obtain a better understanding of molecular aspects of disease development in roots and to characterize specific host genes involved in response to viral infection, transgenic Arabidopsis overexpressors of p25 viral protein was obtained and better characterized. It was shown that transgenic plants that efficiently expressed p25 protein produced more lateral roots. Comparative analysis (microarray) was performed between wild type Arabidopsis roots and transgenic Arabidopsis roots expressing p25 protein, in order to identify Arabidopsis genes differentially expressed in response to p25 viral protein. Experiment description: Seeds were surface sterilized, chilled at 4C for 4 days, and then germinated and grown on square Petri plates containing sterilized Murashige and Skoog (MS) medium with 1% sucrose. Such stock plates were arranged vertically in plastic racks and placed into growth chamber. After 5 days, plants were transferred carefully onto fresh MS medium big round plates. On each plate, 60 Wild Type (WT) plantlets were transferred on the half right of the plate, and 60 transgenic plantlets (B, E or T lines) were transferred on the half left of the plate. Plates were arranged horizontally and placed into growth chamber. Experiment 1 : 5 plates containing WT0A control plants and B0A transgenic plants. Experiment 2 : 5 plates containing WT1 control plants and B transgenic plants. 5 plates containing WT2 control plants and E transgenic plants. 5 plates containing WT3 control plants and T transgenic plants. Plants were harvested after 7 days (experiment 1) or 12 days (experiment 2), and WT roots or transgenic roots were pooled and conserved at -80C.

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Analysis of nucleosome occupancy in yeast using a whole genome tiling array

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