Abstract：
The toxicity of non-proteinogenic amino acids has been known for decades. Numerous reports describe their antimicrobial/anticancer potential. However, these molecules are often toxic to the host as well; thus, a synthetic lethality approach that reduces the dose of these toxins while maintaining toxicity can be beneficial. Here we investigate synthetic lethality between toxic amino acids, the retrograde pathway, and molecular chaperones. In Saccharomyces cerevisiae, mitochondrial retrograde (RTG) pathway activation induces transcription of RTG-target genes to replenish alpha-ketoglutarate and its downstream product glutamate; both metabolites are required for arginine and lysine biosynthesis. We previously reported that tolerance of canavanine, a toxic arginine derivative, requires an intact RTG pathway, and low-dose canavanine exposure reduces the expression of RTG-target genes. Here we show that only a few of the examined chaperone mutants are sensitive to sublethal doses of canavanine. To predict synthetic lethality potential between RTG-target genes and chaperones, we measured the expression of RTG-target genes in canavanine-sensitive and canavanine-tolerant chaperone mutants. Most RTG-target genes were induced in all chaperone mutants starved for arginine; the same trend was not observed under lysine starvation. Canavanine exposure under arginine starvation attenuated and even reversed RTG-target-gene expression in the tested chaperone mutants. Importantly, under nearly all tested genetic and pharmacological conditions, the expression of IDH1 and/or IDH2 was induced. In agreement, idh1 and idh2 mutants are sensitive to canavanine and thialysine and show synthetic growth inhibition with chaperone mutants. Overall, we show that inhibiting molecular chaperones, RTG-target genes, or both can sensitize cells to low doses of toxic amino acids.
摘要：
非蛋白氨基酸的毒性已经知道了几十年。许多报道描述了它们的抗微生物/抗癌潜力。然而,这些分子通常对宿主也是有毒的；因此，在保持毒性的同时减少这些毒素剂量的合成致死方法可能是有益的。在这里，我们研究了有毒氨基酸之间的合成致死性，逆行途径，和分子伴侣。在酿酒酵母中，线粒体逆行（RTG）途径的激活诱导RTG靶基因的转录，以补充α-酮戊二酸及其下游产物谷氨酸；两种代谢物都是精氨酸和赖氨酸生物合成所必需的。我们以前报道过对canavanine的耐受性，一种有毒的精氨酸衍生物,需要完整的RTG通路,和低剂量的canavanine暴露减少RTG靶基因的表达。在这里，我们表明只有少数被检查的伴侣突变体对亚致死剂量的canavanine敏感。为了预测RTG靶基因和伴侣之间的合成致死潜力，我们测量了RTG靶基因在对刀豆氨酸敏感和对刀豆氨酸耐受的伴侣突变体中的表达。在所有缺乏精氨酸的伴侣突变体中诱导了大多数RTG靶基因；在赖氨酸饥饿下没有观察到相同的趋势。在精氨酸饥饿下暴露于Canavanine会减弱甚至逆转测试的伴侣突变体中的RTG靶基因表达。重要的是,在几乎所有测试的遗传和药理条件下，诱导了IDH1和/或IDH2的表达。在协议中,idh1和idh2突变体对canavanine和thialysine敏感，并显示与伴侣突变体的合成生长抑制。总的来说,我们证明了抑制分子伴侣，RTG靶基因，或者两者都能使细胞对低剂量的有毒氨基酸敏感。
