Intracellular dynamism of transcription factors and signal cross-talk in the stress response in yeast

a）硫氧还蛋白在酵母Yap 1转录因子调控中的作用。酿酒酵母，并且它调节许多编码抗氧化酶的基因的表达。当酵母细胞暴露于氧化应激时，Yap 1集中在细胞核中。我们发现，如果硫氧还蛋白，巯基二硫键氧化还原酶，被破坏，Yap 1是组成性集中在细胞核中。如果硫氧还蛋白被破坏（trx 1 △/trx 2 △），则细胞内谷胱甘肽含量增加，然而，这样的突变体显示出对氧化应激的敏感性增加，即使细胞内谷胱甘肽水平很高。B）谷胱甘肽在酵母热激应激反应中的作用。酿酒酵母细胞被转移到更高的温度，因此细胞内的氧化水平增加。此外，我们还发现，expr ...更多信息 热休克增加了编码谷胱甘肽合成酶的GSH 1和GSH 2的分泌，细胞内谷胱甘肽含量也增加。在gsh 1突变体中，热激处理诱导呼吸功能障碍率高。这些结果表明，在热休克下谷胱甘肽的产生增加保护线粒体DNA免受氧化损伤。在该微生物的基因组序列数据库中的酵母酿酒酵母基因组中发现了三种谷胱甘肽过氧化物酶（GPx）同源物。我们破坏了这些同源基因中的每一个，并分析了每个基因产物的功能。GPX 3基因在大肠杆菌中组成型表达，gpx 3 △突变体对氧化应激反应敏感。与此相反，GPX 2基因的表达诱导氧化应激在Yap 1依赖的方式。对硫氧还蛋白过氧化物酶突变体（tsal△）的表型分析表明，GPX 2基因产物可能是硫氧还蛋白过氧化物酶的后备系统。少

a)Role of thioredoxin in regulation of Yap1 transcription factor in Saccharomyces cerevisiae.Yap1 is an AP-1-like, b-Zip transcription factor in S. cerevisiae, and it regulates the expression of many genes encoding antioxidant enzymes. Yap1 is concentrated in the nucleus when the yeast cells are exposed to oxidative stress. We found that Yap1 is constitutively concentrated in the nucleus if thioredoxin, a thiol-disulfide oxidoreductase, was disrupted. Intracellular glutathione contents are increased if thioredoxin was destroyed (trx1△/trx2△), however, such a mutant showed increased sensitivity to oxidative stress even though intracellular glutathione levels are high. This was presumably due to the lack of thioredoxin.b)Role of glutathione in heat shock stress response in yeast.We found that oxygen respiration rate is increased if the yeast S. cerevisiae cells are shifted to higher temperature, and consequently intracellular oxidation level was increased. Additionally we found that expr … More ession of GSH1 and GSH2, both encoding glutathione-synthesizing enzymes, is increased by heat shock, and intracellular glutathione contents are also increased. In a gsh1 mutant, heat shock treatment induced the respiration deficiency at high rate. These results suggest that the increased production of glutathione under heat shock protects mitochondrial DNA from oxidative damage.c)Genetic analysis of glutathione peroxidase in S. cerevisiae.Three glutathione peroxidase (GPx) homologs were found in the yeast S.cerevisiae genome in the genome sequence database of this microorganism. We disrupted each of these homolog genes, and analyzed the function of each gene product. The GPX3 gene was found to be constitutively expressed, and the gpx3△ mutant was hypersensitive to oxidative stress. On the contrary, expression of the GPX2 gene was induced by oxidative stress in a Yap1-dependent fashion. Based on the analysis of the phenotype of a thioredoxin peroxidase mutant (tsal△), the GPX2 gene product was likely to function as a backup system for the thioredoxin peroxidase. Less