Immature small ribosomal subunits can engage in translation initiation in Saccharomyces cerevisiae
Immature small ribosomal subunits can engage in translation initiation in Saccharomyces cerevisiae
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DOI：
10.1038/emboj.2009.307
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发表时间：
2010-01-06
期刊：
影响因子：
11.4
通讯作者：
Mougin, Annie
中科院分区：
文献类型：
--
作者：
Soudet, Julien;Gelugne, Jean-Paul;Mougin, Annie
一般认为，在酿酒酵母中，未成熟的40 S核糖体亚基不能胜任翻译起始。在这里，我们通过不同的方法表明，在野生型条件下，一部分前40 S颗粒（前SSU）与翻译核糖体复合物。当细胞质20 S前rRNA加工受损时，如在Rio 1 p或Nob 1 p缺失的细胞中，大部分前SSU与翻译核糖体复合物相关。前40 S颗粒装载到mRNA上可能使用经典途径，因为抑制起始因子与20 S前rRNA相互作用。然而，40 S核糖体亚基成熟不需要翻译起始。我们还提供了证据表明，与翻译复合物相关的细胞质20 S前体rRNA通过不去衰变（NGD）途径被翻转，这是一种已知降解核糖体停滞的mRNA的过程。我们提出，20 S前rRNA的细胞质命运是由前SSU加工动力学和NGD机制加载到mRNA上的核糖体样颗粒的传感之间的平衡决定的，NGD机制作为最终的核糖体质量检查点。The EMBO Journal（2010）29，80-92. doi：10.1038/doj.2009.307; 2009年11月5日在线发布
It is generally assumed that, in Saccharomyces cerevisiae, immature 40S ribosomal subunits are not competent for translation initiation. Here, we show by different approaches that, in wild-type conditions, a portion of pre-40S particles (pre-SSU) associate with translating ribosomal complexes. When cytoplasmic 20S pre-rRNA processing is impaired, as in Rio1p- or Nob1p-depleted cells, a large part of pre-SSUs is associated with translating ribosomes complexes. Loading of pre-40S particles onto mRNAs presumably uses the canonical pathway as translation-initiation factors interact with 20S pre-rRNA. However, translation initiation is not required for 40S ribosomal subunit maturation. We also provide evidence suggesting that cytoplasmic 20S pre-rRNAs that associate with translating complexes are turned over by the no go decay (NGD) pathway, a process known to degrade mRNAs on which ribosomes are stalled. We propose that the cytoplasmic fate of 20S pre-rRNA is determined by the balance between pre-SSU processing kinetics and sensing of ribosome-like particles loaded onto mRNAs by the NGD machinery, which acts as an ultimate ribosome quality check point. The EMBO Journal (2010) 29, 80-92. doi: 10.1038/emboj.2009.307; Published online 5 November 2009