Moll Isabella, Hirokawa Go, Kiel Michael C, Kaji Akira, Bläsi Udo
Max F. Perutz Laboratories, Department of Microbiology and Genetics, University Department at the Vienna Biocenter, Dr Bohrgasse 9/4, 1030 Vienna, Austria.
Nucleic Acids Res. 2004 Jun 23;32(11):3354-63. doi: 10.1093/nar/gkh663. Print 2004.
It is generally accepted that translation in bacteria is initiated by 30S ribosomal subunits. In contrast, several lines of rather indirect in vitro evidence suggest that 70S monosomes are capable of initiating translation of leaderless mRNAs, starting with the A of the initiation codon. In this study, we demonstrate the proficiency of dedicated 70S ribosomes in in vitro translation of leaderless mRNAs. In support, we show that a natural leaderless mRNA can be translated with crosslinked 70S wild-type ribosomes. Moreover, we report that leaderless mRNA translation continues under conditions where the prevalence of 70S ribosomes is created in vivo, and where translation of bulk mRNA ceases. These studies provide in vivo as well as direct in vitro evidence for a 70S initiation pathway of a naturally occurring leaderless mRNA, and are discussed in light of their significance for bacterial growth under adverse conditions and their evolutionary implications for translation.
人们普遍认为细菌中的翻译由30S核糖体亚基起始。相比之下，一些相当间接的体外证据表明70S单体能够起始无领导mRNA的翻译，从起始密码子的A开始。在本研究中，我们证明了专用70S核糖体在体外翻译无领导mRNA方面的能力。作为支持，我们表明天然无领导mRNA可以用交联的70S野生型核糖体进行翻译。此外，我们报告在体内产生70S核糖体占优势且大量mRNA翻译停止的条件下，无领导mRNA的翻译仍在继续。这些研究提供了体内以及天然无领导mRNA的70S起始途径的直接体外证据，并根据它们在不利条件下对细菌生长的意义及其对翻译的进化影响进行了讨论。
