De Gregorio E, Preiss T, Hentze M W
Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
EMBO J. 1999 Sep 1;18(17):4865-74. doi: 10.1093/emboj/18.17.4865.
Most eukaryotic mRNAs possess a 5' cap structure (m(7)GpppN) and a 3' poly(A) tail which promote translation initiation by binding the eukaryotic translation initiation factor (eIF)4E and the poly(A) binding protein (PABP), respectively. eIF4G can bridge between eIF4E and PABP, and-through eIF3-is thought to establish a link to the small ribosomal subunit. We fused the C-terminal region of human eIF4GI lacking both the eIF4E- and PABP-binding sites, to the IRE binding protein IRP-1. This chimeric protein suffices to direct the translation of the downstream cistron of bicistronic mRNAs bearing IREs in their intercistronic space in vivo. This function is preserved even when translation via the 5' end is inhibited. Deletion analysis defined the conserved central domain (amino acids 642-1091) of eIF4G as an autonomous 'ribosome recruitment core' and implicated eIF4A as a critical binding partner. Our data reveal the sufficiency of the conserved eIF4G ribosome recruitment core to drive productive mRNA translation in living cells. The C-terminal third of eIF4G is dispensable, and may serve as a regulatory domain.
大多数真核生物mRNA具有5'帽结构（m(7)GpppN）和3'多聚腺苷酸尾，它们分别通过结合真核生物翻译起始因子（eIF）4E和多聚腺苷酸结合蛋白（PABP）来促进翻译起始。eIF4G可在eIF4E和PABP之间形成桥梁，并通过eIF3被认为能与小核糖体亚基建立联系。我们将缺失eIF4E和PABP结合位点的人eIF4GI的C末端区域与IRE结合蛋白IRP-1融合。这种嵌合蛋白足以在体内指导双顺反子mRNA下游顺反子的翻译，该双顺反子mRNA在其顺反子间空间带有IRE。即使5'端的翻译被抑制，此功能仍能保留。缺失分析将eIF4G保守的中央结构域（氨基酸642 - 1091）定义为一个自主的“核糖体招募核心”，并表明eIF4A是关键的结合伙伴。我们的数据揭示了保守的eIF4G核糖体招募核心足以驱动活细胞中有成效的mRNA翻译。eIF4G的C末端三分之一是可有可无的，可能作为一个调节结构域。
