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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Ribosomal shunting mediated by a translational enhancer element that base pairs to 18S rRNA
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Ribosomal shunting mediated by a translational enhancer element that base pairs to 18S rRNA

机译：由与18S rRNA碱基配对的翻译增强子介导的核糖体分流

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摘要

In eukaryotes, 40S ribosomal subunits move from their recruitment site on the mRNA to the initiation codon by an as yet poorly understood process. One postulated mechanism involves ribosomal shunting, in which ribosomal subunits completely bypass regions of the 5' leader. For some mRNAs, shunting has been shown to require various mRNA elements, some of which are thought to base pair to 18S rRNA; however, the role of base pairing has not yet been tested directly. In earlier studies, we demonstrated that a short mRNA element in the 5' leader of the Gtx homeodomain mRNA functioned as a ribosomal recruitment site by base pairing to the 18S rRNA. Using a model system to assess translation in transfected cells, we now show that this intermolecular interaction also facilitates ribosomal shunting across two types of obstacles: an upstream AUG codon in excellent context or a stable hairpin structure. Highly efficient shunting occurred when multiple Gtx elements were present upstream of the obstacles, and a single Gtx element was present downstream. Shunting was less efficient, however, when the multiple Gtx elements were present only upstream of the obstacles. In addition, control experiments with mRNAs lacking the upstream elements showed that these results could not be attributed to recruitment by the single downstream element. Experiments in yeast in which the mRNA elements and 18S rRNA sequences were both mutated indicated that shunting required an intact complementary match. The data obtained by this model system provide direct evidence that ribosomal shunting can be mediated by mRNA-rRNA base pairing, a finding that may have general implications for mechanisms of ribosome movement.
机译：在真核生物中，40S核糖体亚基通过一个尚不为人所知的过程从其在mRNA的募集位点移动到起始密码子。一种假定的机制涉及核糖体分流，其中核糖体亚基完全绕过5'前导区。对于某些mRNA，分流已显示需要各种mRNA元件，其中一些被认为与18S rRNA碱基配对。但是，碱基配对的作用尚未经过直接测试。在较早的研究中，我们证明了Gtx同源域mRNA 5'末端的短mRNA元件通过与18S rRNA碱基配对而充当核糖体募集位点。使用模型系统评估转染细胞中的翻译，我们现在表明，这种分子间的相互作用还促进了核糖体分流跨越两种类型的障碍：优良环境中的上游AUG密码子或稳定的发夹结构。当障碍物上游存在多个Gtx元素，而下游存在单个Gtx元素时，会发生高效分流。但是，当多个Gtx元素仅出现在障碍物的上游时，调车效率较低。另外，具有缺乏上游元件的mRNA的对照实验表明，这些结果不能归因于单个下游元件的募集。酵母中的mRNA元素和18S rRNA序列均发生突变的实验表明，分流需要完整的互补匹配。通过该模型系统获得的数据提供了直接的证据，表明核糖体分流可以通过mRNA-rRNA碱基配对来介导，这一发现可能对核糖体的运动机制具有普遍意义。

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