STRUCTURAL ELEMENTS IN YEAST TRANSFER-RNAS REQUIRED FOR HOMOLOGOUS MODIFICATION OF GUANOSINE-26 INTO DIMETHYLGUANOSINE-26 BY THE YEAST TRM1 TRANSFER-RNA-MODIFYING ENZYME
STRUCTURAL ELEMENTS IN YEAST TRANSFER-RNAS REQUIRED FOR HOMOLOGOUS MODIFICATION OF GUANOSINE-26 INTO DIMETHYLGUANOSINE-26 BY THE YEAST TRM1 TRANSFER-RNA-MODIFYING ENZYME
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DOI：
10.1021/bi00198a021
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发表时间：
1994-08-16
期刊：
影响因子：
2.9
通讯作者：
STRABY, KB
中科院分区：
文献类型：
--
作者：
EDQVIST, J;BLOMQVIST, K;STRABY, KB
在真核tRNA中，位于tRNA d -茎和反密码子茎交界处的26位鸟苷（G26）通常被修饰为N-2，N-2-二甲基鸟苷(m（2)(2)G）。虽然G26是m(2)(2)G26生物合成的先决条件，但它不能自给自足地形成二甲基化的G26，因为在极少数情况下真核trna具有未修饰的G26。在酵母中，唯一具有未修饰G26的tRNA物种是tRNA（Asp）。利用该tRNA的体外转录本，以及酵母tRNA(Phe)，一种在体内含有m(2)(2)G26的tRNA，我们研究了酵母酶形成m(2)(2)G26对tRNA序列和结构的要求，即在同源体外系统中。我们现在已经证明，G26在体外也在删除整个反密码子茎和环后有效地二甲基化。我们得出结论，核编码酵母tRNA中的G26与酵母G26修饰酶之间产生相互作用所必需的元件位于tRNA的核心。通过单甲基化G26将G26修饰为m(2)(2)G26， trna中重要的一级和二级结构元件是可变环中至少五个核苷酸的大小以及d -茎中的两个G-C碱基对。这是首次报道酵母修饰酶对核编码trna的最低要求。
In eukaryotic tRNAs, guanosines in position 26 (G26), located at the junction between the D-stem and the anticodon stem of tRNA, are usually modified to N-2,N-2-dimethylguanosine (m(2)(2)G). Although G26 is a prerequisite for biosynthesis of m(2)(2)G26, it is not self-sufficient for the formation of the dimethylated G26, since in exceptional cases eukaryotic tRNAs have an unmodified G26. In the yeast Saccharomyces cerevisiae the only tRNA species with an unmodified G26 is tRNA(Asp). Using in vitro transcripts of this tRNA, as well as of yeast tRNA(Phe), a tRNA containing m(2)(2)G26 in vivo, we have investigated the requirements on tRNA sequences and structures for the formation of m(2)(2)G26 by the yeast enzyme, i.e. in a homologous in vitro system. We have now demonstrated that G26 was efficiently dimethylated in vitro also after deletion of the entire anticodon stem and loop. We conclude that the elements necessary for a productive interaction between G26 in nuclear coded yeast tRNAs and the yeast G26 modifying enzyme are located within the core of the tRNA. For modification of G26 to m(2)(2)G26 via monomethylated G26, important primary and secondary structural elements in the tRNAs are a size of at least five nucleotides in the variable loop together with two G-C base pairs in the D-stem. This is the first case reported where the minimal requirements on nuclear coded tRNAs for a yeast modifying enzyme has been elucidated.