Terrestrial plants have C-to-U RNA editing in the transcripts of plastids and mitochondria. Target specificity for more than several hundred editing sites are governed by PLS (PPR, Long and Short) class Pentatricopeptide repeat (PPR) proteins with additional C-terminal domains. Half of these PPR proteins have DYW (Asparagine (D), Tyrosine (Y) and Tryptophan (W)) domains, which most likely harbour cytidine deaminase activity. The other half of them, E+ subclass and E subclass proteins, contain only partial or DYW domain, respectively. Missing DYW domains in the E and E+ subclass PPR proteins are likely to be complemented by other DYW containing proteins. All target sites of so far characterized E+ subclass PPR proteins show defects in dyw2 mutants, suggesting that the DYW2 protein complements the missing DYW domains in the E+ subclass PPR proteins. Here we report two novel RNA editing factors, MEF46 and MEF47, which belong to E+ and E subclass, respectively. The defective editing site in mef46, nad5-1958, overlaps with the affected sites in dyw2 mutants, while that in mef47, nad3-64 and ccmC-614 do not, further supporting the specific functional connection between E+ subclass PPR proteins and DYW2.

中文翻译：

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MEF46 和 MEF47 是线粒体 nad 转录物中 RNA 编辑位点的新型特异性因子

陆生植物在质体和线粒体的转录物中具有 C-to-U RNA 编辑。数百个编辑位点的目标特异性受 PLS（PPR、长和短）类五肽重复 (PPR) 蛋白和额外的 C 端域控制。这些 PPR 蛋白中有一半具有 DYW（天冬酰胺 (D)、酪氨酸 (Y) 和色氨酸 (W)）结构域，它们很可能具有胞苷脱氨酶活性。另一半，E+ 亚类和 E 亚类蛋白质，分别只包含部分或 DYW 结构域。E 和 E+ 亚类 PPR 蛋白中缺失的 DYW 结构域可能会被其他含有 DYW 的蛋白质补充。迄今为止表征的 E+ 亚类 PPR 蛋白的所有靶位点都显示出 dyw2 突变体的缺陷，这表明 DYW2 蛋白补充了 E+ 亚类 PPR 蛋白中缺失的 DYW 结构域。在这里，我们报告了两个新的 RNA 编辑因子 MEF46 和 MEF47，它们分别属于 E+ 和 E 子类。mef46 中的缺陷编辑位点 nad5-1958 与 dyw2 突变体中的受影响位点重叠，而 mef47 中的 nad3-64 和 ccmC-614 则没有，进一步支持 E+ 亚类 PPR 蛋白和 DYW2 之间的特定功能联系。