elF4B and elF4G Jointly Stimulate elF4A ATPase and Unwinding Activities by Modulation of the elF4A Conformational Cycle
elF4B and elF4G Jointly Stimulate elF4A ATPase and Unwinding Activities by Modulation of the elF4A Conformational Cycle
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DOI：
10.1016/j.jmb.2013.09.027
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发表时间：
2014-01-09
影响因子：
5.6
通讯作者：
Klostermeier, Dagmar
中科院分区：
文献类型：
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作者：
Andreou, Alexandra Zoi;Klostermeier, Dagmar
真核翻译起始因子 4A (eIF4A) 是一种参与翻译起始的 DEAD-box 蛋白。作为一种 ATP 依赖性 RNA 解旋酶，它被认为可以解析 mRNA 5'-非翻译区的二级结构元件，从而实现核糖体扫描。辅助蛋白可增强 eF4A 的 RNA 刺激的 ATP 酶和 ATP 依赖性解旋酶活性，但其潜在机制仍不清楚。在这里，我们剖析了 eF4B 和 eF4G 对 eF4A RNA 依赖性 ATP 酶和 RNA 解旋酶活性以及 eF4A 构象的影响。我们首次证明酵母 eF4B 与其哺乳动物对应物一样，可以刺激 eF4A 的 RNA 解旋，尽管它不影响 eF4A 构象。 eF4G 中间结构域增强了这种刺激作用，并在 ATP 和 RNA 存在的情况下促进闭合 eF4A 构象的形成。 eF4A 的闭合状态已被推断，但之前尚未通过实验观察到。 eF4B 和 eF4G 共同刺激 eF4A 的 ATP 水解和 RNA 解旋，并有利于闭合 eF4A 构象异构体的形成。我们的结果揭示了 eF4B 和 eF4G 在 mRNA 扫描过程中协同刺激 eF4A 解旋酶活性的独特功能。 (C) 2013 Elsevier Ltd. 保留所有权利。
Eukaryotic translation initiation factor 4A (eIF4A) is a DEAD-box protein that participates in translation initiation. As an ATP-dependent RNA helicase, it is thought to resolve secondary structure elements from the 5 '-untranslated region of mRNAs to enable ribosome scanning. The RNA-stimulated ATPase and ATP-dependent helicase activities of elF4A are enhanced by auxiliary proteins, but the underlying mechanisms are still largely unknown. Here, we have dissected the effect of elF4B and elF4G on elF4A RNA-dependent ATPase- and RNA helicase activities and on elF4A conformation. We show for the first time that yeast elF4B, like its mammalian counterpart, can stimulate RNA unwinding by elF4A, although it does not affect the elF4A conformation. The elF4G middle domain enhances this stimulatory effect and promotes the formation of a closed elF4A conformation in the presence of ATP and RNA. The closed state of elF4A has been inferred but has not been observed experimentally before. elF4B and elF4G jointly stimulate ATP hydrolysis and RNA unwinding by elF4A and favor the formation of the closed elF4A conformer. Our results reveal distinct functions of elF4B and elF4G in synergistically stimulating the elF4A helicase activity in the mRNA scanning process. (C) 2013 Elsevier Ltd. All rights reserved.