Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
Genes Cells. 2020 Oct;25(10):651-662. doi: 10.1111/gtc.12801. Epub 2020 Aug 27.
Saccharomyces cerevisiae cells activate the Rim101 pathway to adapt to alkaline and salt stresses. On activation of this pathway, the transcription factor Rim101 undergoes proteolytic activation and regulates the expression of responsive genes. We found Rim101 to be a short-lived protein with a half-life of approximately 15 min. Its rapid turnover was supposedly mediated by the ubiquitin-proteasome system. Excess accumulation of the processed active Rim101 through its over-expression conferred tolerance to both alkaline and salt stresses in yeast cells; in contrast, it had detrimental effects under cadmium stress condition. Cadmium ion inhibited proteolytic activation of Rim101, implying reciprocal interaction between the Rim101 pathway and cadmium stress. Our results showed yeast cells to be equipped with two protective systems to prevent overaccumulation of the processed active Rim101; Rim101 processing is inhibited when Rim101 level is high, and turnover of processed Rim101 is accelerated when it is abundant. Collectively, the results confirmed the flexible aspect of stress response in yeast cell; the cells not only prevent excess activation of one stress-responsive pathway but also facilitate its attenuation to cope with other environmental stresses.
酿酒酵母细胞通过激活 Rim101 途径来适应碱性和盐胁迫。在该途径被激活后，转录因子 Rim101 经历蛋白水解激活，并调节响应基因的表达。我们发现 Rim101 是一种半衰期约为 15 分钟的短寿命蛋白。其快速周转可能是由泛素-蛋白酶体系统介导的。通过过度表达积累过多的加工活性 Rim101，赋予酵母细胞对碱性和盐胁迫的耐受性；相比之下，在镉胁迫条件下，它会产生不利影响。镉离子抑制 Rim101 的蛋白水解激活，这意味着 Rim101 途径和镉胁迫之间存在相互作用。我们的研究结果表明，酵母细胞配备了两种保护系统，以防止加工活性 Rim101 的过度积累；当 Rim101 水平较高时，Rim101 加工被抑制，而当它丰富时，加工后的 Rim101 的周转率会加快。总的来说，这些结果证实了酵母细胞中应激反应的灵活性；细胞不仅防止一种应激反应途径的过度激活，还促进其衰减以应对其他环境应激。
