Alanyl-tRNA Synthetase Quality Control Prevents Global Dysregulation of the Escherichia coli Proteome
Alanyl-tRNA Synthetase Quality Control Prevents Global Dysregulation of the Escherichia coli Proteome
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DOI：
10.1128/mbio.02921-19
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发表时间：
2019-11-01
期刊：
影响因子：
6.4
通讯作者：
Ibba, Michael
中科院分区：
文献类型：
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作者：
Kelly, Paul;Backes, Nicholas;Ibba, Michael
在遗传物质的复制、转录和翻译过程中，已经进化出了防止错误的机制，其中翻译错误是最常见的。蛋白质合成的错误可以发生在两个步骤，在tRNA氨基酰化和核糖体解码。蛋白质质谱分析的最新进展表明，先前关于翻译错误的报道可能低估了这些事件的频率，而且大多数翻译错误发生在核糖体解码期间，这表明氨基酰化错误在进化上的耐受性较低。尽管有这种解释，但有证据表明，一些氨基酰化错误可能受到调节，从而对细胞有益，而其他错误显然是有害的。在这里，我们表明，虽然已经提出调控的Thr-to-Ser取代可能是有益的，但有一个阈值，超过这个阈值，这些错误是有害的。相反，我们发现alanyl-tRNA合成酶（AlaRS）介导的错误不能很好地耐受，并诱导全局应激反应，导致大肠杆菌蛋白质组的严重扰动，对适应性和生存能力产生潜在的灾难性影响。对Ala误译的容忍度似乎比其他翻译错误要低得多，这与先前报道的针对误充tRNA（Ala）的多种校对机制一致。这些结果证明了氨基酰基- trna校对在优化细胞适应性方面的重要作用，并表明误译的任何潜在有益影响可能仅限于特定的氨基酸取代。蛋白质合成中的错误历来被认为对细胞有害。虽然有许多报道认为翻译错误是后果性的，但越来越多的证据表明，一些误译事件是可以容忍的，甚至是有益的。利用两种误译模型，我们比较了这些事件在大肠杆菌中的直接表型效应。这项工作提供了对特定误翻译事件的耐受性阈值的见解，这些事件先前被预测为对蛋白质组完整性大致中性。此外，这些数据揭示了误译的影响超出了一般的未展开的应激反应，导致全局翻译重编程。
Mechanisms have evolved to prevent errors in replication, transcription, and translation of genetic material, with translational errors occurring most frequently. Errors in protein synthesis can occur at two steps, during tRNA aminoacylation and ribosome decoding. Recent advances in protein mass spectrometry have indicated that previous reports of translational errors have potentially underestimated the frequency of these events, but also that the majority of translational errors occur during ribosomal decoding, suggesting that aminoacylation errors are evolutionarily less tolerated. Despite that interpretation, there is evidence that some aminoacylation errors may be regulated, and thus provide a benefit to the cell, while others are clearly detrimental. Here, we show that while it has been suggested that regulated Thr-to-Ser substitutions may be beneficial, there is a threshold beyond which these errors are detrimental. In contrast, we show that errors mediated by alanyl-tRNA synthetase (AlaRS) are not well tolerated and induce a global stress response that leads to gross perturbation of the Escherichia coli proteome, with potentially catastrophic effects on fitness and viability. Tolerance for Ala mistranslation appears to be much lower than with other translational errors, consistent with previous reports of multiple proofreading mechanisms targeting mischarged tRNA(Ala). These results demonstrate the essential role of aminoacyl-tRNA proofreading in optimizing cellular fitness and suggest that any potentially beneficial effects of mistranslation may be confined to specific amino acid substitutions.IMPORTANCE Errors in protein synthesis have historically been assumed to be detrimental to the cell. While there are many reports that translational errors are consequential, there is a growing body of evidence that some mistranslation events may be tolerated or even beneficial. Using two models of mistranslation, we compare the direct phenotypic effects of these events in Escherichia coli. This work provides insight into the threshold for tolerance of specific mistranslation events that were previously predicted to be broadly neutral to proteome integrity. Furthermore, these data reveal the effects of mistranslation beyond the general unfolded stress response, leading to global translational reprogramming.