Competitive and Noncompetitive Binding of eIF4B, eIF4A, and the Poly(A) Binding Protein to Wheat Translation Initiation Factor eIFiso4G
Competitive and Noncompetitive Binding of eIF4B, eIF4A, and the Poly(A) Binding Protein to Wheat Translation Initiation Factor eIFiso4G
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DOI：
10.1021/bi1008529
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发表时间：
2010-09-28
期刊：
影响因子：
2.9
通讯作者：
Gallie, Daniel R.
中科院分区：
文献类型：
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作者：
Cheng, Shijun;Gallie, Daniel R.
真核翻译起始因子 4G (eIF4G) 的功能是组织起始因子的组装，这些起始因子是将 40S 核糖体亚基募集到 mRNA 中并与聚腺苷酸结合蛋白 (PABP) 相互作用。许多真核生物表达两种高度相似的 eIF4G 亚型。 eIFiso4G 是植物中的两种亚型之一，具有高度差异性且尺寸异常小。与动物和酵母 eIF4G 不同，植物 eIF4G 蛋白的结构域组织很大程度上未知。因此，人们对植物 eIF4G 与其他真核生物中 eIF4G 的保守性知之甚少。在这项研究中，我们发现 eIFiso4G 与其他 eIF4G 蛋白相似，因为 eIF4A 和 PABP 存在相互作用域，并且我们首次鉴定了 eIF4B 的相互作用域。与之前的报道相反，在 eIFiso4G 中发现了两个 eIF4A 结合域，其数量和结构与动物 eIF4G 相似。然而，eIFiso4G 结构域的组织确实有所不同，因为 N 端 eIF4A 结合结构域与 eIF4B 和 PABP 结合结构域重叠。此外，eIF4B 和 PABP 结合域重叠。在 C 端 eIF4A 结合域不存在的情况下，PABP 和 eIF4B 与 eIF4A 竞争结合 eIFiso4G，但当两个 eIF4A 结合域都存在时，PABP 和 eIF4B 不会与 eIF4A 竞争结合 eIFiso4G，这表明在 eIF4B 或 PABP 存在的情况下，C 端 eIF4A 相互作用域起到稳定 eIF4A 与 eIFiso4G 结合的作用。 eIF4B 和 PABP 之间也观察到与 eIFiso4G 的竞争性结合。这些观察结果揭示了 C 端 eIF4A 结合结构域在维持多个伙伴蛋白与 eIFiso4G 相互作用方面的重要功能，尽管其大小和结构域组织存在很大差异。
Eukaryotic translation initiation factor 4G (eIF4G) functions to organize the assembly of initiation factors required for the recruitment of a 40S ribosomal subunit to an mRNA and for interacting with the poly(A) binding protein (PABP). Many eukaryotes express two highly similar eIF4G isoforms. eIFiso4G, one of two isoforms in plants, is highly divergent and unusually small in size. Unlike animal and yeast eIF4G, the domain organization of plant eIF4G proteins is largely unknown. Consequently, little is known about the conservation of plant eIF4G with those in other eukaryotes. In this study, we show that eIFiso4G is similar to other eIF4G proteins in that there are interaction domains for eIF4A and PABP and we identify, for the first time, the interaction domain for eIF4B. In contrast to previous reports, two eIF4A binding domains in eIFiso4G were identified, similar in number and organization to those of animal eIF4G. The eIFiso4G domain organization does differ, however, in that the N-terminal eIF4A binding domain overlaps with the eIF4B and PABP binding domains. Moreover, the eIF4B and PABP binding domains overlap. PABP and eIF4B compete with eIF4A for binding eIFiso4G in the absence of the C-terminal eIF4A binding domain but not when both eIF4A binding domains are present, suggesting that the C-terminal eIF4A interaction domain functions to stabilize the association of eIF4A with eIFiso4G in the presence of eIF4B or PABP. Competitive binding to eIFiso4G was also observed between eIF4B and PABP. These observations reveal an important function of the C-terminal eIF4A binding domain in maintaining the interaction of multiple partner proteins with eIFiso4G despite the substantial divergence in its size and domain organization.