Project description:Excess cysteine (and cystine) is known to be toxic in organisms. Due to the absence of cysteine dioxygenase (involved in degradation of excess cysteine in humans and pathogenic fungi) in non pathogenic fungi such as S. cerevisiae, mechanism of cysteine (and cystine) tolerance is yet to be addressed.
Project description:Prolonged cultivation (>25 generations) of Saccharomyces cerevisiae in aerobic, maltose-limited chemostat cultures led to profound physiological changes. Maltose hypersensitivity was observed when cells from prolonged cultivations were suddenly exposed to excess maltose. This substrate hypersensitivity was evident from massive cell lysis and loss of viability. During prolonged cultivation at a fixed specific growth rate, the affinity for the growth-limiting nutrient (i.e., maltose) increased, as evident from a decreasing residual maltose concentration. Furthermore, the capacity of maltose-dependent proton uptake increased up to 2.5-fold during prolonged cultivation. Genome-wide transcriptome analysis showed that the increased maltose transport capacity was not primarily due to increased transcript levels of maltose-permease genes upon prolonged cultivation. We propose that selection for improved substrate affinity (ratio of maximum substrate consumption rate and substrate saturation constant) in maltose-limited cultures leads to selection for cells with an increased capacity for maltose uptake. At the same time, the accumulative nature of maltose-proton symport in S. cerevisiae leads to unrestricted uptake when maltose-adapted cells are exposed to a substrate excess. These changes were retained after isolation of individual cell lines from the chemostat cultures and nonselective cultivation, indicating that mutations were involved. The observed trade-off between substrate affinity and substrate tolerance may be relevant for metabolic engineering and strain selection for utilization of substrates that are taken up by proton symport. Keywords: Evolution
Project description:Saccharomyces cerevisiae is an excellent microorganism for industrial succinic acid production, but high succinic acid concentration will inhibit the growth of Saccharomyces cerevisiae then reduce the production of succinic acid. Through analysis the transcriptomic data of Saccharomyces cerevisiae with different genetic backgrounds under different succinic acid stress, we hope to find the response mechanism of Saccharomyces cerevisiae to succinic acid.
Project description:In this study, we combined metabolic reconstruction, growth assays, metabolome and transcriptome analyses to obtain a global view of the sulfur metabolic network and of the response to sulfur availability in Brevibacterium aurantiacum. In agreement with the growth of B. aurantiacum in the presence of sulfate and cystine, the metabolic reconstruction showed the presence of a sulfate assimilation pathway and of thiolation pathways that produce cysteine (cysE and cysK) or homocysteine (metX and metY) from sulfide, of at least one gene of the transsulfuration pathway (aecD) and of genes encoding three MetE-type methionine synthases. We also compared the expression profiles of B. aurantiacum ATCC9175 during sulfur starvation and in the presence of sulfate, cystine or methionine plus cystine. In sulfur starvation, 690 genes including 21 genes involved in sulfur metabolism and 29 genes encoding amino acids and peptide transporters were differentially expressed. We also investigated changes in pools of sulfur-containing metabolites and in expression profiles after growth in the presence of sulfate, cystine or methionine plus cystine. The expression of genes involved in sulfate assimilation and cysteine synthesis was repressed in presence of cysteine, while the expression of metX, metY, metE1, metE2 and BL613 encoding a probable cystathionine-γ-synthase decreased in the presence of methionine. We identified three ABC transporters: two stronger transcribed during cysteine limitation and one during methionine depletion. Finally, the expression of genes encoding a methionine γ-lyase, BL929, and a methionine transporter (metPS) was induced in the presence of methionine, in conjunction with a significant increase of volatile sulfur compounds production. Refer to individual Series. This SuperSeries is composed of the following subset Series: GSE25418: BA-Methionine plus Cystine vs Cystine GSE25419: BA-Sulfate vs Cystine GSE25420: BA-Methionine plus Cystine vs Sulfate GSE25421: BA-Sulfate vs Sulfate starvation
Project description:The amino acid cysteine and its oxidized dimeric form cystine are commonly believed to be synonymous in metabolic functions. Cyst(e)ine depletion not only induces amino acid response, but also triggers ferroptosis, a non-apoptotic cell death. Here we report that, unlike general amino acid starvation, cyst(e)ine deprivation triggers ATF4 induction at the transcriptional level. Unexpectedly, it is the shortage of lysosomal cystine, but not the cytosolic cysteine, that elicits the adaptative ATF4 response. The lysosome-nucleus signaling pathway involves the aryl hydrocarbon receptor (AhR) that senses lysosomal cystine via the kynurenine pathway. A blockade of lysosomal cystine efflux attenuates ATF4 induction and sensitizes ferroptosis. To potentiate ferroptosis in cancer, we develop a synthetic mRNA reagent CysRx that converts cytosolic cysteine to lysosomal cystine. CysRx maximizes cancer cell ferroptosis and effectively suppresses tumor growth in vivo. Thus, intracellular nutrient reprogramming has the potential to induce selective ferroptosis in cancer without systematic perturbation.
Project description:The mutant Saccharomyces cerevisiae Y518 generated much more intracellular glutathione (GSH) than its counterpart dose. The RNA-seq based global transcriptome analysis was performed for exploring the potential mechanisms. Statistical analysis indicated that 1125 differentially expressed genes (fold-change>=2.0, FDR<=0.001) were up-regulated and 503 were down-regulated. There were 12 genes involved in glutathione metabolism. Of which GSH1, encodes gamma-glutamine cysteine synthetase, the rate-limiting enzyme in GSH biosynthesis process, was up-regulated. And MET17, encodes cysteine synthase A, an enzyme catalyzes the biosynthesis of one of the precursor amino acids L- cysteine, was also up-regulated. Besides, regulator SKN7 and several genes involved in oxidative stress response (GPX2, CTT1, SOD1, TRX2) were up-regulated. Intracellular ROS level of Y518 was also enhanced compared to that of 2-10515. Our results indicate that up-regulations of GSH1 and MET17 might be associated with the increased intracellular GSH content of the mutant, and up-regulated GSH1 may be caused by increased intracellular ROS level. Saccharomyces cerevisiae mRNA profiles of 24-h wild type 2-10515 and mutant Y518 were generated by deep sequencing using Illumina HiSeqTM 2000