Yeast 18 S rRNA Is Directly Involved in the Ribosomal Response to Stringent AUG Selection during Translation Initiation
Yeast 18 S rRNA Is Directly Involved in the Ribosomal Response to Stringent AUG Selection during Translation Initiation
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DOI：
10.1074/jbc.m110.146662
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发表时间：
2010-10-15
影响因子：
4.8
通讯作者：
Asano, Katsura
中科院分区：
文献类型：
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作者：
Nemoto, Naoki;Singh, Chingakham Ranjit;Asano, Katsura
在真核生物中，40 S核糖体亚基作为起始因子装配的平台，将其自身精确地置于AUG起始密码子上。18 S rRNA的结构排列决定了40 S亚基的整体形状。在这里，我们提出了酵母18 S rRNA功能的遗传评价使用10个点突变改变多核糖体的配置文件。所有的突变体都减少了突变体40 S的丰度，使其限制翻译起始。其中两个分离的突变，G875 A，改变了结合eIF 1和eIF 2的平台结构域的核心，A1193 U，改变了位于P位点tRNA（i）（Met）下方的h31环，显示出AUG选择调节缺陷的表型。提供的证据表明，这些突变减少了与preinitiation复合物的组分的相互作用，从而抑制其在不同步骤的功能。这些结果表明，18 S rRNA突变损害了完整的扫描能力preinitiation复合物，从而改变了40 S亚基响应严格的AUG选择。有趣的是，其中9个突变改变了18 S rRNA的主体/平台结构域，可能影响到60 S亚基的桥梁，但它们不会改变18 S rRNA中间体的水平。在此基础上，我们还讨论了突变体40 S亚基选择性降解的机理。
In eukaryotes, the 40 S ribosomal subunit serves as the platform of initiation factor assembly, to place itself precisely on the AUG start codon. Structural arrangement of the 18 S rRNA determines the overall shape of the 40 S subunit. Here, we present genetic evaluation of yeast 18 S rRNA function using 10 point mutations altering the polysome profile. All the mutants reduce the abundance of the mutant 40 S, making it limiting for translation initiation. Two of the isolated mutations, G875A, altering the core of the platform domain that binds eIF1 and eIF2, and A1193U, changing the h31 loop located below the P-site tRNA(i)(Met), show phenotypes indicating defective regulation of AUG selection. Evidence is provided that these mutations reduce the interaction with the components of the preinitiation complex, thereby inhibiting its function at different steps. These results indicate that the 18 S rRNA mutations impair the integrity of scanning-competent preinitiation complex, thereby altering the 40 S subunit response to stringent AUG selection. Interestingly, nine of the mutations alter the body/platform domains of 18 S rRNA, potentially affecting the bridges to the 60 S subunit, but they do not change the level of 18 S rRNA intermediates. Based on these results, we also discuss the mechanism of the selective degradation of the mutant 40 S subunits.