Grill S, Moll I, Hasenöhrl D, Gualerzi C O, Bläsi U
Institute of Microbiology and Genetics, Vienna Biocenter, University of Vienna, Austria.
FEBS Lett. 2001 Apr 27;495(3):167-71. doi: 10.1016/s0014-5793(01)02378-x.
Sequence determinants and structural features of the RNA govern mRNA-ribosome interaction in bacteria. However, ribosomal recruitment to leaderless mRNAs, which start directly with the AUG start codon and do not bear a Shine-Dalgarno sequence like canonical mRNAs, does not appear to rely on 16S rRNA-mRNA interactions. Here, we have studied the effects of translation initiation factors IF2 and IF3 on 30S initiation at a 5'-terminal AUG and at a competing downstream canonical ribosome binding site. We show that IF2 affects the forward kinetics of 30S initiation complex formation at the 5'-terminal AUG as well as the stability of these complexes. Moreover, the IF2:IF3 molar ratio was found to play a decisive role in translation initiation of a leaderless mRNA both in vitro and in vivo indicating that the translational efficiency of an mRNA is not only intrinsically determined but can be altered depending on the availability of components of the translational machinery.
RNA的序列决定因素和结构特征决定了细菌中mRNA与核糖体的相互作用。然而，核糖体募集到无帽mRNA（直接以AUG起始密码子开始，不像典型mRNA那样具有Shine-Dalgarno序列）似乎并不依赖于16S rRNA与mRNA的相互作用。在这里，我们研究了翻译起始因子IF2和IF3对5'-末端AUG以及竞争性下游典型核糖体结合位点处30S起始的影响。我们表明，IF2影响5'-末端AUG处30S起始复合物形成的正向动力学以及这些复合物的稳定性。此外，发现IF2与IF3的摩尔比在体外和体内无帽mRNA的翻译起始中都起着决定性作用，这表明mRNA的翻译效率不仅由其内在决定，还可根据翻译机器组件的可用性而改变。
