Translation quality control is critical for bacterial responses to amino acid stress
Translation quality control is critical for bacterial responses to amino acid stress
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DOI：
10.1073/pnas.1525206113
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发表时间：
2016-02-23
影响因子：
11.1
通讯作者：
Ibba, Michael
中科院分区：
文献类型：
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作者：
Bullwinkle, Tammy J.;Ibba, Michael
基因表达依赖于质量控制来准确传递遗传信息。防止翻译过程中氨基酸误结合错误的一种机制是通过氨基酰-tRNA合成酶编辑错酰化的tRNA。在没有编辑的情况下，生长受到暴露在过量的非同源氨基酸底物和其他压力下的限制，但这些生理效应是否仅仅是错误翻译的结果尚不清楚。为了探索翻译质量控制是否影响蛋白质合成以外的细胞过程，我们使用了一株在Tyr-tRNA(Phe)编辑方面存在缺陷的大肠杆菌。在没有编辑的情况下，氨基酰化tRNA(Phe)的细胞水平在氨基酸胁迫期间升高，而在相同的生长条件下，野生型菌株的这些水平下降。在编辑缺陷菌株中，在氨基酸胁迫下，氨基酰化tRNA(Phe)水平的增加导致PHEL前导肽的持续合成和PHEA转录的减弱。因此，在没有编辑的情况下，苯丙氨酸生物合成操纵子的激活对苯丙氨酸限制变得不太敏感。除了提高氨基酰化tRNA水平外，没有编辑还降低了细胞中脱酰化tRNA(Phe)的数量。这种脱酰化tRNA的减少伴随着第二信使四磷酸鸟苷的合成减少，并在氨基酸应激期间有限地诱导编辑缺陷细胞中严格依赖反应的基因表达。这些数据表明，单一的质量控制机制，编辑错酰化的氨基酰-tRNAs，为维持翻译的准确性和确定转录反应对氨基酸胁迫的敏感性提供了一个关键的检查点。
Gene expression relies on quality control for accurate transmission of genetic information. One mechanism that prevents amino acid misincorporation errors during translation is editing of misacylated tRNAs by aminoacyl-tRNA synthetases. In the absence of editing, growth is limited upon exposure to excess noncognate amino acid substrates and other stresses, but whether these physiological effects result solely from mistranslation remains unclear. To explore if translation quality control influences cellular processes other than protein synthesis, an Escherichia coli strain defective in Tyr-tRNA(Phe) editing was used. In the absence of editing, cellular levels of aminoacylated tRNA(Phe) were elevated during amino acid stress, whereas in the wild-type strain these levels declined under the same growth conditions. In the editing-defective strain, increased levels of aminoacylated tRNA(Phe) led to continued synthesis of the PheL leader peptide and attenuation of pheA transcription under amino acid stress. Consequently, in the absence of editing, activation of the phenylalanine biosynthetic operon becomes less responsive to phenylalanine limitation. In addition to raising aminoacylated tRNA levels, the absence of editing lowered the amount of deacylated tRNA(Phe) in the cell. This reduction in deacylated tRNA was accompanied by decreased synthesis of the second messenger guanosine tetraphosphate and limited induction of stringent response-dependent gene expression in editing-defective cells during amino acid stress. These data show that a single quality-control mechanism, the editing of misacylated aminoacyl-tRNAs, provides a critical checkpoint both for maintaining the accuracy of translation and for determining the sensitivity of transcriptional responses to amino acid stress.