Homologous trans-editing factors with broad tRNA specificity prevent mistranslation caused by serine/threonine misactivation
Homologous trans-editing factors with broad tRNA specificity prevent mistranslation caused by serine/threonine misactivation
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DOI：
10.1073/pnas.1423664112
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发表时间：
2015-05-12
影响因子：
11.1
通讯作者：
Musier-Forsyth, Karin
中科院分区：
文献类型：
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作者：
Liu, Ziwei;Vargas-Rodriguez, Oscar;Musier-Forsyth, Karin
氨基酰-tRNA合成酶(ARs)建立了遗传密码的规则，由此每个氨基酸都连接到一个同源tRNA上。这一过程中的错误会导致误译，这可能会对细胞产生毒性。物种特定要求和环境条件施加的选择性力量可能会形成有助于防止误译的质量控制机制。与细菌Prolyl-tRNA合成酶的编辑结构域同源的一系列编辑因子包括先前描述的分别清除Ala-tRNA(Pro)和Cys-tRNA(Pro)的反式编辑因子ProXp-Ala和YbaK，以及另外三个功能未知的同源物ProXp-x、ProXp-y和ProXp-z。我们进行了230个条件的体内筛选，在这些条件下，大肠杆菌proXp-y缺失菌株在氨基酸水平和特定ARS水平升高的情况下生长。这一筛选结合体外脱酰化试验的结果，揭示了该同源物的丝氨酸和苏氨酸-tRNA脱酰酶功能。副肺结核波氏杆菌ProXp-z在体外也有类似的活性。这些蛋白质现在分别被重新命名为“ProXp-ST1”和“ProXp-ST2”，它们识别多个tRNA作为底物。综上所述，我们的数据表明，这些独立的编辑结构域具有防止一些ARS引起的误翻译错误的能力，这些ARS包括赖氨酰-tRNA合成酶、苏氨酰-tRNA合成酶、丝氨酰-tRNA合成酶和丙氨酰-tRNA合成酶。这些多功能酶的表达很可能为遭受环境压力和其他改变氨基酸库的条件的生物体提供选择性生长优势。
Aminoacyl-tRNA synthetases (ARSs) establish the rules of the genetic code, whereby each amino acid is attached to a cognate tRNA. Errors in this process lead to mistranslation, which can be toxic to cells. The selective forces exerted by species-specific requirements and environmental conditions potentially shape quality-control mechanisms that serve to prevent mistranslation. A family of editing factors that are homologous to the editing domain of bacterial prolyl-tRNA synthetase includes the previously characterized trans-editing factors ProXp-ala and YbaK, which clear Ala-tRNA(Pro) and Cys-tRNA(Pro), respectively, and three additional homologs of unknown function, ProXp-x, ProXp-y, and ProXp-z. We performed an in vivo screen of 230 conditions in which an Escherichia coli proXp-y deletion strain was grown in the presence of elevated levels of amino acids and specific ARSs. This screen, together with the results of in vitro deacylation assays, revealed Ser- and Thr-tRNA deacylase function for this homolog. A similar activity was demonstrated for Bordetella parapertussis ProXp-z in vitro. These proteins, now renamed "ProXp-ST1" and "ProXp-ST2," respectively, recognize multiple tRNAs as substrates. Taken together, our data suggest that these free-standing editing domains have the ability to prevent mistranslation errors caused by a number of ARSs, including lysyl-tRNA synthetase, threonyl-tRNA synthetase, seryl-tRNA synthetase, and alanyl-tRNA synthetase. The expression of these multifunctional enzymes is likely to provide a selective growth advantage to organisms subjected to environmental stresses and other conditions that alter the amino acid pool.