Department of Biochemistry, The University of Western Ontario, London, ON N6A 3K7, Canada.
Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA.
G3 (Bethesda). 2021 Sep 27;11(10). doi: 10.1093/g3journal/jkab218.
Mistranslation, the misincorporation of an amino acid not specified by the "standard" genetic code, occurs in all organisms. tRNA variants that increase mistranslation arise spontaneously and engineered tRNAs can achieve mistranslation frequencies approaching 10% in yeast and bacteria. Interestingly, human genomes contain tRNA variants with the potential to mistranslate. Cells cope with increased mistranslation through multiple mechanisms, though high levels cause proteotoxic stress. The goal of this study was to compare the genetic interactions and the impact on transcriptome and cellular growth of two tRNA variants that mistranslate at a similar frequency but create different amino acid substitutions in Saccharomyces cerevisiae. One tRNA variant inserts alanine at proline codons whereas the other inserts serine for arginine. Both tRNAs decreased growth rate, with the effect being greater for arginine to serine than for proline to alanine. The tRNA that substituted serine for arginine resulted in a heat shock response. In contrast, heat shock response was minimal for proline to alanine substitution. Further demonstrating the significance of the amino acid substitution, transcriptome analysis identified unique up- and down-regulated genes in response to each mistranslating tRNA. Number and extent of negative synthetic genetic interactions also differed depending upon type of mistranslation. Based on the unique responses observed for these mistranslating tRNAs, we predict that the potential of mistranslation to exacerbate diseases caused by proteotoxic stress depends on the tRNA variant. Furthermore, based on their unique transcriptomes and genetic interactions, different naturally occurring mistranslating tRNAs have the potential to negatively influence specific diseases.
错译，即掺入“标准”遗传密码未指定的氨基酸，发生在所有生物体中。增加错译的 tRNA 变体自发出现，工程化 tRNA 可使酵母和细菌中的错译频率接近 10%。有趣的是，人类基因组包含有潜在错译能力的 tRNA 变体。细胞通过多种机制来应对错译增加，但高水平的错译会导致蛋白毒性应激。本研究的目的是比较两种在相似频率下发生错译但在酿酒酵母中产生不同氨基酸取代的 tRNA 变体的遗传相互作用和对转录组及细胞生长的影响。一种 tRNA 变体在脯氨酸密码子处插入丙氨酸，而另一种 tRNA 变体将精氨酸插入丝氨酸。两种 tRNA 变体都降低了生长速度，精氨酸突变为丝氨酸的效果大于脯氨酸突变为丙氨酸。将丝氨酸插入精氨酸的 tRNA 导致了热休克反应。相比之下，脯氨酸突变为丙氨酸的替代物导致的热休克反应则很小。进一步证明了氨基酸取代的重要性，转录组分析鉴定了每种错译 tRNA 响应的独特上调和下调基因。负合成遗传相互作用的数量和程度也取决于错译的类型。基于这些错译 tRNA 观察到的独特反应，我们预测错译加剧蛋白毒性应激引起的疾病的可能性取决于 tRNA 变体。此外，基于它们独特的转录组和遗传相互作用，不同的天然存在的错译 tRNA 有可能对特定疾病产生负面影响。
