Human eukaryotic translation initiation factor 4G (eIF4G) possesses two separate and independent binding sites for eIF4A
Human eukaryotic translation initiation factor 4G (eIF4G) possesses two separate and independent binding sites for eIF4A
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DOI：
10.1128/mcb.17.12.6940
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发表时间：
1997-12-01
影响因子：
5.3
通讯作者：
Sonenberg, N
中科院分区：
文献类型：
--
作者：
Imataka, H;Sonenberg, N
哺乳动物翻译起始因子 4F (eIF4F) 由三个亚基组成：eIF4A、eIF4E 和 eIF4G。 eIF4G 直接与 eIF4A 和 eIF4E 相互作用，eIF4E 的结合位点包含在 eIF4G 的氨基末端三分之一处，而 eIF4A 的结合位点被映射到分子的羧基末端三分之一处，这里我们表明，人类 eIF4G 在中间三分之一处拥有两个独立的 eIF4A 结合域（氨基酸 [aa] 478 至 883）和 分子的羧基末端第三位（氨基酸 884 至 1404），eIF4G 中间部分的氨基酸序列在酵母和人类之间非常保守，我们表明中间结构域中保守氨基酸片段的突变会消除或减少 eIF4A 结合以及 eIF3 结合，此外，羧基末端中存在单独且不重叠的 eIF4A 结合结构域 eIF4G 的第三个氨基酸（氨基酸 1045 至 1404）不存在于酵母中。 eIF4G 的 C 端三分之二区域（氨基酸 457 至 1404）包含两个 eIF4A 结合位点，是刺激翻译所必需的。没有一个 eIF4A 结合域单独激活翻译。与 eIF4G 相比，人 p97（一种与 eIF4G 同源的翻译抑制剂）仅通过氨基端近端区域结合 eIF4A，即 与 eIF4G 的中间结构域同源。
Mammalian translation initiation factor 4F (eIF4F) consists of three subunits, eIF4A, eIF4E, and eIF4G. eIF4G interacts directly with both eIF4A and eIF4E, The binding site for eIF4E is contained in the aminoterminal third of eIF4G, while the binding site for eIF4A was mapped to the carboxy-terminal third of the molecule, Here we show that human eIF4G possesses two separate eIF4A binding domains in the middle third (amino acids [aa] 478 to 883) and carboxy-terminal third (aa 884 to 1404) of the molecule, The amino acid sequence of the middle portion of eIF4G is well conserved between yeasts and humans, We show that mutations of conserved amino acid stretches in the middle domain abolish or reduce eIF4A binding as well as eIF3 binding, In addition, a separate and nonoverlapping eIF4A binding domain exists in the carboxy-terminal third (aa 1045 to 1404) of eIF4G, which is not present in yeast. The C-terminal two-thirds region (aa 457 to 1404) of eIF4G, containing both eIF4A binding sites, is required for stimulating translation, Neither one of the eIF4A binding domains alone activates translation, In contrast to eIF4G, human p97, a translation inhibitor with homology to eIF4G, binds eIF4A only through the amino-terminal proximal region, which is homologous to the middle domain of eIF4G.