Reinitiation and other unconventional posttermination events during eukaryotic translation.
Reinitiation and other unconventional posttermination events during eukaryotic translation.
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DOI：
10.1016/j.molcel.2013.05.026
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发表时间：
2013-07-25
期刊：
影响因子：
16
通讯作者：
Pestova, Tatyana V.
中科院分区：
文献类型：
--
作者：
Skabkin, Maxim A.;Skabkina, Olga V.;Hellen, Christopher U. T.;Pestova, Tatyana V.
在核糖体循环过程中，终止后复合体被ABCE1和eRF1解离成60S和tRNA/mRNA相关的40S亚基，之后tRNA/mRNA由eIF1/eIF1A、Ligatin或MCT1/DENR释放。在某些情况下，40s亚基仍然与mRNA相关，并在附近的AUGS重新启动。在这里，我们回顾了使用重组的哺乳动物翻译系统在体外重新启动的情况。EIFS2/3/1/1A和Met-tRNAiMet的存在足以使循环的40S亚基保留在mRNA上，如果终止密码子两侧的mRNA区域是非结构化的，则在上游和下游的AUG处都可以双向扫描和重新启动。3‘方向性的实施还需要eIF4F。值得注意的是，终止后的核糖体并不稳定地锚定在mRNA上，并双向迁移到与P-位点tRNA同源的密码子上。迁移依赖于多肽的释放方式(普鲁霉素和GT；eRF1和GT；eRF1/eRF3)和tRNA的性质，并被eEF2增强。终止后核糖体的流动性表明，一些再启动事件可能涉及80S核糖体，而不是40S亚基。
During ribosome recycling, post-termination complexes are dissociated by ABCE1 and eRF1 into 60S and tRNA/mRNA-associated 40S subunits, after which tRNA/mRNA are released by eIF1/eIF1A, Ligatin or MCT1/DENR. In some instances, 40S subunits remain associated with mRNA and reinitiate at nearby AUGs. Here, we recapitulated reinitiation in vitro using a reconstituted mammalian translation system. The presence of eIFs 2/3/1/1A and Met-tRNAiMet was sufficient for recycled 40S subunits to remain on mRNA, scan bidirectionally and reinitiate both at upstream and downstream AUGs if mRNA regions flanking the stop codon were unstructured. Imposition of 3’-directionality additionally required eIF4F. Strikingly, post-termination ribosomes were not stably anchored on mRNA, and migrated bidirectionally to codons cognate to the P-site tRNA. Migration depended on the mode of peptide release (puromycin>eRF1>eRF1/eRF3), the nature of tRNA, and was enhanced by eEF2. The mobility of post-termination ribosomes suggests that some reinitiation events could involve 80S ribosomes rather than 40S subunits.
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