Meier F, Suter B, Grosjean H, Keith G, Kubli E
EMBO J. 1985 Mar;4(3):823-7. doi: 10.1002/j.1460-2075.1985.tb03704.x.
The 'in vivo' decoding properties of four tRNAHis isoacceptors, two from Drosophila melanogaster and two from brewer's yeast, were studied after their microinjection, along with turnip yellow mosaic virus (TYMV) coat protein mRNA, into Xenopus laevis oocytes. The two Drosophila isoacceptors are identical besides containing either a guanosine (G) or the hypermodified nucleoside queuosine (Q) in the wobble position. The brewer's yeast isoacceptors differ by four bases in the anticodon stem, and by one base in the amino acceptor stem. Our results show that, under competing 'in vivo' conditions, the Drosophila tRNAHis with the anticodon GUG clearly prefers the histidine codon CAC to the codon CAU, whereas little preference is observed for the tRNAHis with the anticodon QUG for the codon CAU, and no preference for either codon by the two yeast isoacceptors. Hence, it can be concluded that the presence of the Q-base clearly affects the choice of the codon. This is the first demonstration of an 'in vivo' codon preference by tRNA isoacceptors differing in the modification of the wobble base during the elongation step of protein synthesis. These results imply that one function of the Q-base is at the translational level.
将来自黑腹果蝇的两种和酿酒酵母的两种共四种组氨酸异源接受体tRNA与芜菁黄花叶病毒（TYMV）外壳蛋白mRNA一起显微注射到非洲爪蟾卵母细胞中后，对它们的“体内”解码特性进行了研究。这两种果蝇异源接受体除了在摆动位置分别含有一个鸟苷（G）或超修饰核苷queuosine（Q）外，其余部分相同。酿酒酵母的异源接受体在反密码子茎上有四个碱基不同，在氨基接受茎上有一个碱基不同。我们的结果表明，在竞争性的“体内”条件下，反密码子为GUG的果蝇组氨酸tRNA明显更倾向于组氨酸密码子CAC而非CAU，而反密码子为QUG的组氨酸tRNA对密码子CAU几乎没有偏好，两种酵母异源接受体对这两个密码子均无偏好。因此，可以得出结论，Q碱基的存在明显影响密码子的选择。这是首次证明在蛋白质合成延伸步骤中，摆动碱基修饰不同的tRNA异源接受体在“体内”对密码子有偏好。这些结果表明Q碱基的一个功能在翻译水平上。
