Project description:The S. cerevisiae genome is the most well-characterized eukaryotic genome and one of the simplest in terms of identifying open reading frames (ORFs), yet its primary annotation has been updated continually in the decade since its initial release in 1996 (Goffeau et al., 1996). The Saccharomyces Genome Database (SGD; www.yeastgenome.org) (Hirschman et al., 2006), the community-designated repository for this reference genome, strives to ensure that the S. cerevisiae annotation is as accurate and useful as possible. At SGD, the S. cerevisiae genome sequence and annotation are treated as a working hypothesis, which must be repeatedly tested and refined. In this paper, in celebration of the tenth anniversary of the completion of the S. cerevisiae genome sequence, we discuss the ways in which the S. cerevisiae sequence and annotation have changed, consider the multiple sources of experimental and comparative data on which these changes are based, and describe our methods for evaluating, incorporating and documenting these new data.
Project description:Specific histone modifications play important roles in chromatin functions such as activation or repression of gene transcription. These participation must occur as a dynamic process, however, most of histone modification state maps reported to date only provide static pictures linking certain modification with active or silenced states. This study focused on the global histone modification variation that occurs in response to transcriptional reprogramming produced by a physiological perturbation in yeast. We have performed genome-wide chromatin immunoprecipitation analysis for eight specific histone modifications before and after of a saline stress. The most striking change is a quick deacetylation of lysines 9 and 14 of H3 and lysine 8 of H4 associated to repression of genes. Genes that are activated increase the acetylation levels at these same sites, but this acetylation process of activated genes seems minor quantitatively to that of the deacetylation of repressed genes. The observed changes in tri-methylation of lysines 4, 36 and 79 of H3 and also di-methylation of lysine 79 of H3 are much more moderate than those of acetylation. Additionally, we have produced new genome-wide maps for six histone modifications at more than five times higher resolution of previous available data and analyzed for the first time in S. cerevisiae genome wide profiles of two more, acetylation of lysine 8 of H4 and di-methylation of lysine 79 of H3. In this research we have shown that dynamic of acetylation state of histones during activation or repression of transcription is a process much quicker than methylation and therefore the changes produced in the acetylation may affect methylation but the reverse path is not possible.
Project description:Specific histone modifications play important roles in chromatin functions such as activation or repression of gene transcription. These participation must occur as a dynamic process, however, most of histone modification state maps reported to date only provide static pictures linking certain modification with active or silenced states. This study focused on the global histone modification variation that occurs in response to transcriptional reprogramming produced by a physiological perturbation in yeast. We have performed genome-wide chromatin immunoprecipitation analysis for eight specific histone modifications before and after of a saline stress. The most striking change is a quick deacetylation of lysines 9 and 14 of H3 and lysine 8 of H4 associated to repression of genes. Genes that are activated increase the acetylation levels at these same sites, but this acetylation process of activated genes seems minor quantitatively to that of the deacetylation of repressed genes. The observed changes in tri-methylation of lysines 4, 36 and 79 of H3 and also di-methylation of lysine 79 of H3 are much more moderate than those of acetylation. Additionally, we have produced new genome-wide maps for six histone modifications at more than five times higher resolution of previous available data and analyzed for the first time in S. cerevisiae genome wide profiles of two more, acetylation of lysine 8 of H4 and di-methylation of lysine 79 of H3. In this research we have shown that dynamic of acetylation state of histones during activation or repression of transcription is a process much quicker than methylation and therefore the changes produced in the acetylation may affect methylation but the reverse path is not possible. The experiments described in this study compare ChIP with a histone modification antibody to a control ChIP with a core histone antibody. Budding yeast samples were analyzed in exponential growing conditions (YPD) or after 10 minutes of 0.4M NaCl stress. For each experiment 1 or 2 biological replicates were performed.