Prévôt Déborah, Décimo Didier, Herbreteau Cécile H, Roux Florence, Garin Jérôme, Darlix Jean-Luc, Ohlmann Théophile
LaboRétro, Inserm Unité de Virologie Humaine (U 412), Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon cedex 07, France.
EMBO J. 2003 Apr 15;22(8):1909-21. doi: 10.1093/emboj/cdg175.
The eukaryotic translation initiation factor eIF4GI binds several proteins and acts as a scaffold to promote preinitiation complex formation on the mRNA molecule (48S). Following mRNA attachment this complex scans along the messenger in a 5' to 3' direction until it locates and recognizes the initiation start codon. By using a combination of retroviral and picornaviral proteases (HIV-2 and L respectively) in the reticulocyte lysate system, we have characterized a 40 amino acid (aa) region of eIF4GI (aa 642-681) that exhibits general RNA-binding properties. Removal of this domain by proteolytic processing followed by translational assays showed virtually no inhibition of internal ribosome entry on the encephalomyocarditis virus, but resulted in drastic impairment of ribosome scanning as demonstrated by studying poliovirus and foot-and-mouth disease virus translation. Based on these findings, we propose that this 40 aa motif of eIF4GI is critical for ribosome scanning.
真核生物翻译起始因子eIF4GI结合多种蛋白质,并作为一个支架来促进在mRNA分子(48S)上形成起始前复合物。mRNA附着后,该复合物沿信使RNA从5'到3'方向扫描,直到找到并识别起始密码子。通过在网织红细胞裂解物系统中使用逆转录病毒和小RNA病毒蛋白酶(分别为HIV-2和L)的组合,我们鉴定了eIF4GI的一个40个氨基酸(aa)的区域(aa 642-681),该区域表现出一般的RNA结合特性。通过蛋白水解处理去除该结构域,随后进行翻译分析,结果表明,脑心肌炎病毒的内部核糖体进入几乎没有受到抑制,但如通过研究脊髓灰质炎病毒和口蹄疫病毒的翻译所表明的,核糖体扫描受到了严重损害。基于这些发现,我们提出eIF4GI的这个40 aa基序对核糖体扫描至关重要。