Haghighat A, Sonenberg N
Department of Biochemistry and McGill Cancer Center, Faculty of Medicine, McGill University, Montreal, Quebec, Canada H3G 1Y6.
J Biol Chem. 1997 Aug 29;272(35):21677-80. doi: 10.1074/jbc.272.35.21677.
The cap structure, m7GpppN, is present at the 5'-end of all eukaryotic cellular (except organellar) mRNAs. Initiation of translation is mediated by the multisubunit initiation factor eIF4F, which binds the cap structure via its eIF4E subunit and facilitates the binding of mRNA to ribosomes. Here, we used recombinant proteins to reconstitute the cap recognition activity of eIF4F in vitro. We demonstrate that the interaction of eIF4E with the mRNA 5'-cap structure is dramatically enhanced by eIF4G, as determined by a UV-induced cross-linking assay. Furthermore, assembly of the eIF4F complex at the cap structure, as well as ATP hydrolysis, is shown to be a requisite for the cross-linking of another initiation factor, eIF4B, to the cap structure. In addition, the stimulatory effect of eIF4G on the cap recognition of eIF4E is inhibited by the translational repressor, 4E-BP1. These results suggest that eIF4E initially interacts with the mRNA cap structure as part of the eIF4F complex.
帽结构m7GpppN存在于所有真核细胞（细胞器mRNA除外）mRNA的5'端。翻译起始由多亚基起始因子eIF4F介导，该因子通过其eIF4E亚基结合帽结构，并促进mRNA与核糖体的结合。在此，我们使用重组蛋白在体外重建eIF4F的帽识别活性。通过紫外线诱导的交联试验确定，我们证明eIF4G显著增强了eIF4E与mRNA 5'帽结构的相互作用。此外，eIF4F复合物在帽结构处的组装以及ATP水解被证明是另一个起始因子eIF4B与帽结构交联的必要条件。此外，翻译抑制因子4E-BP1抑制了eIF4G对eIF4E帽识别的刺激作用。这些结果表明，eIF4E最初作为eIF4F复合物的一部分与mRNA帽结构相互作用。
