Oxidation of phenylalanyl-tRNA synthetase positively regulates translational quality control
Oxidation of phenylalanyl-tRNA synthetase positively regulates translational quality control
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DOI：
10.1073/pnas.1901634116
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
R. Steiner;A. Kyle;M. Ibba
中科院分区：
文献类型：
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作者：
R. Steiner;A. Kyle;M. Ibba
在不利的生长条件下，翻译质量控制的调节对于维持细胞内稳态至关重要。翻译质量控制通过氨酰-tRNA合成酶（阿尔斯）的校对来维持，其确保同源氨酰-tRNA被提供给核糖体用于蛋白质合成。我们的研究结果表明，在氧化应激下，苯丙氨酰-tRNA合成酶的全局构象变化正调节质量控制，提高校对率。这些结果表明，翻译机器能够快速和积极地应对环境挑战，以保持蛋白质合成的准确性。遗传密码的准确翻译部分地由氨酰-tRNA合成酶（阿尔斯）校对机制维持，所述校对机制确保同源氨基酸与转移RNA（tRNA）的正确连接。在环境压力，如氧化应激，阿尔斯校对的需求被改变细胞质氨基酸的可用性的变化。例如，氧化应激增加细胞毒性酪氨酸异构体的水平，非同源氨基酸通常被苯丙氨酰-tRNA合成酶（PheRS）的校对活性排除在翻译之外。在这里，我们表明，氧化的PheRS诱导构象变化，产生部分非结构化的蛋白质。这种构象变化不影响Phe或Tyr活化或PheRS的氨酰化活性。然而，在体外和离体分析表明，校正活性水解Tyr-tRNAPhe的氧化应激过程中增加，而同源Phe-tRNAPhe氨酰化活性不变。在HPX−中，缺乏活性氧清除酶并积累细胞内H2 O2的大肠杆菌，我们发现PheRS校正增加了11%，从而提供了潜在的保护，防止有害的细胞质间-Tyr积累。这些研究结果表明，在氧化应激反应中，PheRS校对是积极的调节，没有负面影响的酶的管家活动的翻译。我们的研究结果还表明，虽然在某些条件下，质量控制和误译的损失可能是有益的，但增加校对为细胞提供了一种机制，使其在氧化应激期间对环境变化做出适当的反应。
Significance Regulation of translational quality control during adverse growth conditions is critical to maintain cellular homeostasis. Translational quality control is maintained by proofreading by the aminoacyl-tRNA synthetases (aaRS), which ensure that cognate aminoacyl-tRNAs are provided to the ribosome for protein synthesis. Our findings now show that under oxidative stress a global conformational change in the phenylalanyl-tRNA synthetase positively regulates quality control by increasing the rate of proofreading. These results demonstrate that the translational machinery is able to rapidly and positively respond to environmental challenges to maintain the accuracy of protein synthesis. Accurate translation of the genetic code is maintained in part by aminoacyl-tRNA synthetases (aaRS) proofreading mechanisms that ensure correct attachment of a cognate amino acid to a transfer RNA (tRNA). During environmental stress, such as oxidative stress, demands on aaRS proofreading are altered by changes in the availability of cytoplasmic amino acids. For example, oxidative stress increases levels of cytotoxic tyrosine isomers, noncognate amino acids normally excluded from translation by the proofreading activity of phenylalanyl-tRNA synthetase (PheRS). Here we show that oxidation of PheRS induces a conformational change, generating a partially unstructured protein. This conformational change does not affect Phe or Tyr activation or the aminoacylation activity of PheRS. However, in vitro and ex vivo analyses reveal that proofreading activity to hydrolyze Tyr-tRNAPhe is increased during oxidative stress, while the cognate Phe-tRNAPhe aminoacylation activity is unchanged. In HPX−, Escherichia coli that lack reactive oxygen-scavenging enzymes and accumulate intracellular H2O2, we found that PheRS proofreading is increased by 11%, thereby providing potential protection against hazardous cytoplasmic m-Tyr accumulation. These findings show that in response to oxidative stress, PheRS proofreading is positively regulated without negative effects on the enzyme’s housekeeping activity in translation. Our findings also illustrate that while the loss of quality control and mistranslation may be beneficial under some conditions, increased proofreading provides a mechanism for the cell to appropriately respond to environmental changes during oxidative stress.