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首页> 外文期刊>Molecular and Cellular Biology >Functional dissection of eukaryotic initiation factor 4F: the 4A subunit and the central domain of the 4G subunit are sufficient to mediate internal entry of 43S preinitiation complexes.
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Functional dissection of eukaryotic initiation factor 4F: the 4A subunit and the central domain of the 4G subunit are sufficient to mediate internal entry of 43S preinitiation complexes.

机译：真核生物起始因子4F的功能解剖：4A亚基和4G亚基的中央结构域足以介导43S预起始复合物的内部进入。

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摘要

Eukaryotic translation is initiated following binding of ribosomes either to the capped 5' end of an mRNA or to an internal ribosomal entry site (IRES) within its 5' nontranslated region. These processes are both mediated by eukaryotic initiation factor 4F (eIF4F), which consists of eIF4A (helicase), eIF4E (cap-binding protein), and eIF4G subunits. Here we present a functional analysis of eIF4F which defines the subunits and subunit domains necessary for its function in initiation mediated by the prototypical IRES element of encephalomyocarditis virus. In an initiation reaction reconstituted in vitro from purified translation components and lacking eIF4A and -4F, IRES-mediated initiation did not require the cap-binding protein eIF4E but was absolutely dependent on eIF4A and the central third of eIF4G. This central domain of eIF4G bound strongly and specifically to a structural element within the encephalomyocarditis virus IRES upstream of the initiation codon in an ATP-independent manner and with the same specificity as eIF4F. The carboxy-terminal third of eIF4G did not bind to the IRES. The central domain of eIF4G was itself UV cross-linked to the IRES and strongly stimulated UV cross-linking of eIF4A to the IRES in conjunction with either eIF4B or with the carboxy-terminal third of eIF4G.
机译：核糖体结合到mRNA的带帽5'端或其5'非翻译区内的内部核糖体进入位点（IRES）后，便开始真核翻译。这些过程均由真核起始因子4F（eIF4F）介导，该因子由eIF4A（解旋酶），eIF4E（帽结合蛋白）和eIF4G亚基组成。在这里，我们介绍了eIF4F的功能分析，该功能定义了由心肌心肌炎病毒的原型IRES元件介导的启动其功能所必需的亚基和亚基域。在由纯化的翻译成分体外重建且缺少eIF4A和-4F的起始反应中，IRES介导的起始不需要结合帽的蛋白质eIF4E，但绝对依赖eIF4A和eIF4G的中央三分之一。 eIF4G的这个中央结构域以不依赖ATP的方式并与eIF4F具有相同的特异性，牢固且特异性地与起始密码子上游的脑心肌炎病毒IRES内的结构元件结合。 eIF4G的羧基末端三分之一未结合IRES。 eIF4G的中央结构域本身是UV交联到IRES的，并与eIF4B或eIF4G的羧基末端三分之一结合在一起，强烈刺激了eIF4A与IRES的UV交联。

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