Translation factors promote the formation of two states of the closed-loop mRNP
Translation factors promote the formation of two states of the closed-loop mRNP
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DOI：
10.1038/nature06974
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发表时间：
2008-06-26
期刊：
影响因子：
64.8
通讯作者：
Jacobson, Allan
中科院分区：
文献类型：
--
作者：
Amrani, Nadia;Ghosh, Shubhendu;Jacobson, Allan
大多数真核信使RNA的有效翻译起始和最佳稳定性取决于闭环结构的形成以及59 m（7）G帽和3 ' poly（A）尾之间产生的协同相互作用（1，2）. eIF 4G和Pab 1相互作用的证据支持闭环mRNP的概念（3），但导致其形成和维持的机制事件仍然未知。在这里，我们使用脚趾印和多核糖体分析测定来描绘核糖体定位在启动子AUG密码子和核糖体- mRNA的关联，分别，并发现两个不同的稳定（抗帽类似物）的闭环结构形成在酵母细胞的无细胞提取物的启动过程中。两种形式的完整性都需要mRNA帽和poly（A）尾，以及eIF 4 E、eIF 4G、Pab 1和eIF 3，并且依赖于mRNA和poly（A）尾的长度。第一种结构的形成需要48 S核糖体复合物，而第二种结构需要80 S核糖体和终止因子eRF 3/Sup 35和eRF 1/Sup 45。终止因素的参与与终止事件无关。
Efficient translation initiation and optimal stability of most eukaryotic messenger RNAs depends on the formation of a closed- loop structure and the resulting synergistic interplay between the 59 m (7)G cap and the 3 ' poly( A) tail(1,2). Evidence of eIF4G and Pab1 interaction supports the notion of a closed- loop mRNP(3), but the mechanistic events that lead to its formation and maintenance are still unknown. Here we use toeprinting and polysome profiling assays to delineate ribosome positioning at initiator AUG codons and ribosome - mRNA association, respectively, and find that two distinct stable ( resistant to cap analogue) closed- loop structures are formed during initiation in yeast cell- free extracts. The integrity of both forms requires the mRNA cap and poly( A) tail, as well as eIF4E, eIF4G, Pab1 and eIF3, and is dependent on the length of both the mRNA and the poly( A) tail. Formation of the first structure requires the 48S ribosomal complex, whereas the second requires an 80S ribosome and the termination factors eRF3/ Sup35 and eRF1/ Sup45. The involvement of the termination factors is independent of a termination event.