Transcription profiling by array of eight pairs of closely related strains using pair-wise two-colour microarray analysis
ABSTRACT: To examine whether naturally occurring duplications are altering gene expression we chose eight pairs of closely related strains (less than 150 SNPS between each pair) that contained at least one unshared duplication and performed pair-wise two-colour microarray analysis.
Project description:Fission yeast in high glucose media preferentially uses fermentation for energy production, even under aerobic conditions, an analogous metabolic programme, aerobic glycolysis, is a hallmark of cancer and enables the proliferation of tumor cells. Fission yeast, unlike budding yeast, requires mitochondrial genomes and oxidative phosphorylation for survival, mitochondrial inheritance, genome organisation and RNA processing are strikingly different between the two yeasts, and S. pombe mitochondria resemble more the human mitochondria. However, mitochondrial biology and respiratory control is poorly understood in fission yeast. In this study, we used microarrays to profile gene expression before and at six time points after the shift from fermentative to respiratory medium. Cells were grown in yeast extract based media with 3% glucose to early exponential phase (time point 0), then the carbon source was changed to 3% glycerol, 0.1% glucose. Transcript levels were monitored by microarrays at several time points after the switch (0.2, 0.5, 1, 2; 04 and 24 hours). Sample from each time point is hybrydized with sample of all pooled time points. Experiment was repeated twice with the dye swap.
Project description:Retrograde response was widely studied in budding yeast but the main transcription factors that transmit it (RTG1,2 and 3) are not conserved in other organisms, thus it is interesting to study how communication between mitochondria and nucleus evolved in distantly related fission yeast, and which are the common aspects of this conserved pathway between yeast and higher organisms.To analyse any retrograde response in fission yeast, we inhibited the electron transport chain activity by antimycin A and studied cellular gene expression changes by microarrays. Cells treated with antimycin A in fermentative medium (YE with 3% glucose), showed the same growth rate as untreated cells, but they reached a lower biomass in stationary phase. Antimycin A treated cells consumed glucose at a faster rate and produced more ethanol, indicating that the energy metabolism was shifted even more towards fermentation. We analyzed the transcriptomes of antimycin A-treated cells to untreated control cells during early exponential growth phase (OD 0.5).
Project description:Target of Rapamycin Complex 1 (TORC1) signaling promotes growth and ageing. Inhibition of TORC1 leads to a down-regulation of factors that stimulate protein translation, which in turn contributes to longevity. TORC1-dependent post-transcriptional regulation of protein translation has been well studied, while analogous transcriptional regulation is less understood. Here we screened fission yeast deletion mutants for resistance to Torin1, which inhibits TORC1 and cell growth. Cells lacking the GATA transcription factor Gaf1 (gaf1Δ) grew normally even in high doses of Torin1. The gaf1Δ mutation shortened the chronological lifespan of non-dividing cells and diminished the longevity triggered by Torin1 treatment. Expression profiling and genome-wide binding experiments showed that, upon TORC1 inhibition, Gaf1 directly up-regulated genes for small-molecule metabolic pathways and indirectly repressed genes for protein translation. Surprisingly, Gaf1 bound to, and down-regulated the tRNA genes, so also functions as a transcription factor for genes transcribed by RNA polymerase III. Thus, Gaf1 controls the transcription of both coding and tRNA genes to inhibit translation and growth downstream of TORC1.
Project description:Spt6 is a conserved factor, critically required for several transcription and chromatin related processes. We now show that Spt6 and its binding partner, Iws1, are required for heterochromatic silencing in Schizosaccharomyces pombe. Our studies demonstrate that Spt6 is required for silencing of all heterochromatic loci and that an spt6 mutant has an unusual combination of heterochromatic phenotypes compared to previously studied silencing mutants. Unexpectedly, we find normal nucleosome positioning over heterochromatin and normal levels of histone H3K9 dimethylation. However, we also find greatly reduced levels of H3K9 trimethylation, elevated levels of H3K14 acetylation, and reduced recruitment of several silencing factors. Our evidence suggests that Spt6 plays a role at both the transcriptional and post-transcriptional levels; in an spt6 mutant, RNA polymerase II (RNAPII) occupancy at the pericentric regions is only modestly increased, while production of small interfering RNAs (siRNAs) is lost. Taken together, our results suggest that Spt6 is required for multiple steps in heterochromatic silencing by controlling chromatin, transcriptional, and post-transcriptional processes.
Project description:The SAGA complex is a conserved multifunctional coactivator known to play broad roles in eukaryotic transcription. To gain new insights into its functions, we have performed biochemical and genetic analyses of SAGA in the fission yeast, Schizosaccharomyces pombe. Purification of the S. pombe SAGA complex showed that its subunit composition is identical to that of Saccharomyces cerevisiae. Analysis of S. pombe SAGA mutants revealed that SAGA has two opposing roles regulating sexual differentiation. First, in nutrient rich conditions, the SAGA histone acetyltransferase, Gcn5, represses ste11+, which encodes the master regulator of the mating pathway. In contrast, the SAGA subunit Spt8 is required for the induction of ste11+ upon nutrient starvation. Chromatin immunoprecipitation experiments suggest that these regulatory effects are direct, as SAGA is physically associated with the ste11+ promoter independent of nutrient levels. Genetic tests suggest that nutrient levels do cause a switch in SAGA function, as spt8? suppresses gcn5? with respect to ste11+ derepression in rich medium, whereas the opposite relationship, gcn5? suppression of spt8?, occurs during starvation. Thus, SAGA plays distinct roles in the control of the switch from proliferation to differentiation in S. pombe through the dynamic and opposing activities of Gcn5 and Spt8.