Project description:H3 ChIP and input DNA were hybridized to Affymetrix GeneChip S. cerevisiae Tiling 1.0R Array Genome-wide mapping of nucleosomes generated by micrococcal nuclease (MNase) suggests that yeast promoter and terminator regions are very depleted of nucleosomes, predominantly because their DNA sequences intrinsically disfavor nucleosome formation. However, MNase has strong DNA sequence specificity that favors cleavage at promoters and terminators and accounts for some of the correlation between occupancy patterns of nucleosomes assembled in vivo and in vitro. Using an improved method for measuring nucleosome occupancy in vivo that does not involve MNase, we confirm that promoter regions are strongly depleted of nucleosomes, but find that terminator regions are much less depleted than expected. Unlike at promoter regions, nucleosome occupancy at terminators is strongly correlated with the orientation of and distance to adjacent genes. In addition, nucleosome occupancy at terminators is strongly affected by growth conditions, indicating that it is not primarily determined by intrinsic histone-DNA interactions. Rapid removal of RNA polymerase II (Pol II) causes increased nucleosome occupancy at terminators, strongly suggesting a transcription-based mechanism of nucleosome depletion. However, the distinct behavior of terminator regions and their corresponding coding regions suggests that nucleosome depletion at terminators is not simply associated with passage of Pol II, but rather involves a distinct mechanism linked to 3’ end formation.
Project description:Iron is an essential cofactor for enzymes involved in numerous cellular processes. We analyzed the metabolomes and transcriptomes of yeast grown in iron-rich and iron-poor media to determine which biosynthetic processes are altered when iron availability falls.
Project description:Transcriptional profiling of P. gingivalis cells comparing cells grown under iron replete conditions to that grown under iron depleted conditions
Project description:Regulation of iron acquisition genes is critical for microbial survival under both iron-limiting conditions (to acquire essential iron) and iron-replete conditions (to limit iron toxicity). In fungi, iron acquisition genes are repressed under iron-replete conditions by a conserved GATA transcriptional regulator. Here we investigate the role of this transcription factor, Sre1, in the cellular responses of the fungal pathogen Histoplasma capsulatum to iron. We showed that cells in which SRE1 levels were diminished by RNA interference were unable to repress siderophore biosynthesis and utilization genes in the presence of abundant iron, and thus produced siderophores even under iron-replete conditions. Mutation of a GATA-containing consensus site found in the promoters of these genes also resulted in inappropriate gene expression under iron-replete conditions. Microarray analysis comparing control and SRE1-depleted strains under conditions of iron limitation or abundance revealed both iron-responsive genes and Sre1-dependent genes, which comprised distinct but overlapping sets. Iron-responsive genes included putative oxidoreductases, metabolic and mitochondrial enzymes, superoxide dismutase, and nitrosative-stress response genes; Sre1-dependent genes were of diverse function. Genes regulated by iron levels and Sre1 included all of the siderophore biosynthetic genes, a gene involved in reductive iron acquisition, an iron-responsive transcription factor, and two catalases. Based on transcriptional profiling and phenotypic analyses, we conclude that Sre1 plays a critical role in the regulation of both traditional iron-responsive genes and iron-independent pathways such as regulation of cell morphology. These data highlight the evolving realization that the effect of Sre1 orthologs on fungal biology extends beyond the iron regulon.
Project description:In this study we focus on two Saccharomyces cerevisiae strains with varying production of heterologous α-amylase and we compare the metabolic fluxes and transcriptional regulation at aerobic and anaerobic conditions, in particular with the objective to identify the final electron acceptor for protein folding. We found that anaerobic conditions showed high amount of amylase productions when comparing to aerobic conditions and the genome-scale transcriptional analysis suggested that genes related to the endoplasmic reticulum (ER), lipid synthesis and stress responses were generally up-regulated at anaerobic conditions. Moreover, we proposed a model for the electron transfer from ER to the final electron acceptor, fumarate under anaerobic conditions.