The Pentatricopeptide Repeat Protein PGR3 Is Required for the Translation of petL and ndhG by Binding Their 5′ UTRs
The Pentatricopeptide Repeat Protein PGR3 Is Required for the Translation of petL and ndhG by Binding Their 5′ UTRs
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DOI：
10.1093/pcp/pcaa180
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发表时间：
2021-01-13
影响因子：
4.9
通讯作者：
Shikanai, Toshiharu
中科院分区：
文献类型：
--
作者：
Higashi, Haruka;Kato, Yoshinobu;Shikanai, Toshiharu
PGR 3是一种P类五肽重复序列（PPR）蛋白，其是petL操纵子RNA的稳定和petL基因在质体中的翻译所必需的。尽管PGR 3在质体中发挥重要作用，但关键问题仍未得到解答，包括PGR 3蛋白如何促进翻译以及PGR 3激活哪种质体mRNA翻译。在这里，我们表明，PGR 3促进翻译从ndhG，除了petL，通过结合到他们的5 '非翻译区（UTR）。pgr3突变体的核糖体分析和RNA测序显示，petL和ndhG的翻译被特异性抑制。利用体内受PPR蛋白保护的小RNA片段，我们探测了PGR 3向petL和ndhG的5'UTR的募集。推测的PGR 3结合的RNA片段本身可能通过强二级结构抑制翻译，从而阻断核糖体的进入。然而，PGR 3结合拮抗作用并促进体外从petL和ndhG的蛋白质合成。对PGR 3三维结构的预测表明，第26位PPR基序在靶RNA结合中起重要作用。我们的数据显示了质体RNA结合蛋白的特异性，并提供了一个翻译控制的机制。
PGR3 is a P-class pentatricopeptide repeat (PPR) protein required for the stabilization of petL operon RNA and the translation of the petL gene in plastids. Irrespective of its important roles in plastids, key questions have remained unanswered, including how PGR3 protein promotes translation and which plastid mRNA PGR3 activates the translation. Here, we show that PGR3 facilitates the translation from ndhG, in addition to petL, through binding to their 5 ' untranslated regions (UTRs). Ribosome profiling and RNA sequencing in pgr3 mutants revealed that translation from petL and ndhG was specifically suppressed. Harnessing small RNA fragments protected by PPR proteins in vivo, we probed the PGR3 recruitment to the 5' UTRs of petL and ndhG. The putative PGR3-bound RNA segments per se repress the translation possibly with a strong secondary structure and thereby block ribosomes' access. However, the PGR3 binding antagonizes the effects and facilitates the protein synthesis from petL and ndhG in vitro. The prediction of the 3-dimensional structure of PGR3 suggests that the 26th PPR motif plays important roles in target RNA binding. Our data show the specificity of a plastidic RNA-binding protein and provide a mechanistic insight into translational control.