Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0017, Japan.
Nucleic Acids Res. 2012 Apr;40(8):3653-62. doi: 10.1093/nar/gkr1226. Epub 2011 Dec 19.
Class II transfer RNAs (tRNAs), including tRNA(Leu) and tRNA(Ser), have an additional stem and loop structure, the long variable arm (V-arm). Here, we describe Class II tRNAs with a unique anticodon corresponding to neither leucine nor serine. Because these tRNAs are specifically conserved among the nematodes, we have called them 'nematode-specific V-arm-containing tRNAs' (nev-tRNAs). The expression of nev-tRNA genes in Caenorhabditis elegans was confirmed experimentally. A comparative sequence analysis suggested that the nev-tRNAs derived phylogenetically from tRNA(Leu). In vitro aminoacylation assays showed that nev-tRNA(Gly) and nev-tRNA(Ile) are only charged with leucine, which is inconsistent with their anticodons. Furthermore, the deletion and mutation of crucial determinants for leucylation in nev-tRNA led to a marked loss of activity. An in vitro translation analysis showed that nev-tRNA(Gly) decodes GGG as leucine instead of the universal glycine code, indicating that nev-tRNAs can be incorporated into ribosomes and participate in protein biosynthesis. Our findings provide the first example of unexpected tRNAs that do not consistently obey the general translation rules for higher eukaryotes.
II 类转移 RNA（tRNA），包括 tRNA（Leu）和 tRNA（Ser），具有额外的茎环结构，即长可变臂（V 臂）。在这里，我们描述了一类具有独特反密码子的 II 类 tRNA，它既不对应亮氨酸也不对应丝氨酸。由于这些 tRNA 在线虫中特异性保守，我们将它们称为“线虫特异性含 V 臂 tRNA”（nev-tRNA）。在秀丽隐杆线虫中，nev-tRNA 基因的表达已通过实验得到证实。比较序列分析表明，nev-tRNA 从 tRNA（Leu）进化而来。体外氨酰化实验表明，nev-tRNA（Gly）和 nev-tRNA（Ile）只能被亮氨酸酰化，这与它们的反密码子不一致。此外，nev-tRNA 中亮氨酸酰化关键决定因素的缺失和突变导致活性显著丧失。体外翻译分析表明，nev-tRNA（Gly）将 GGG 解码为亮氨酸，而不是通用的甘氨酸密码子，这表明 nev-tRNA 可以被整合到核糖体中并参与蛋白质生物合成。我们的研究结果提供了第一个非预期的 tRNA 的例子，这些 tRNA 并不始终遵循真核生物的一般翻译规则。
