Ochs K, Rust R C, Niepmann M
Institute of Biochemistry, D-35392 Giessen, Germany.
J Virol. 1999 Sep;73(9):7505-14. doi: 10.1128/JVI.73.9.7505-7514.1999.
Most eukaryotic initiation factors (eIFs) are required for internal translation initiation at the internal ribosome entry site (IRES) of picornaviruses. eIF4B is incorporated into ribosomal 48S initiation complexes with the IRES RNA of foot-and-mouth disease virus (FMDV). In contrast to the weak interaction of eIF4B with capped cellular mRNAs and its release upon entry of the ribosomal 60S subunit, eIF4B remains tightly associated with the FMDV IRES during formation of complete 80S ribosomes. Binding of eIF4B to the IRES is energy dependent, and binding of the small ribosomal subunit to the IRES requires the previous energy-dependent association of initiation factors with the IRES. The interaction of eIF4B with the IRES in 48S and 80S complexes is independent of the location of the initiator AUG and thus independent of the mechanism by which the small ribosomal subunit is placed at the actual start codon, either by direct internal ribosomal entry or by scanning. eIF4B does not greatly rearrange its binding to the IRES upon entry of the ribosomal subunits, and the interaction of eIF4B with the IRES is independent of the polypyrimidine tract-binding protein, which enhances FMDV translation.
大多数真核生物起始因子（eIFs）是微小核糖核酸病毒内部核糖体进入位点（IRES）处内部翻译起始所必需的。eIF4B与口蹄疫病毒（FMDV）的IRES RNA一起被纳入核糖体48S起始复合物中。与eIF4B与加帽的细胞mRNA的弱相互作用及其在核糖体60S亚基进入时的释放不同，在完整80S核糖体形成过程中，eIF4B与FMDV IRES保持紧密结合。eIF4B与IRES的结合是能量依赖性的，小核糖体亚基与IRES的结合需要起始因子先前与IRES的能量依赖性结合。eIF4B在48S和80S复合物中与IRES的相互作用独立于起始AUG的位置，因此独立于小核糖体亚基通过直接内部核糖体进入或扫描放置在实际起始密码子处的机制。核糖体亚基进入时，eIF4B与IRES的结合不会发生很大的重排，并且eIF4B与IRES的相互作用独立于增强FMDV翻译的多嘧啶序列结合蛋白。
