Evidence for the Translation Initiation of Leaderless mRNAs by the Intact 70 S Ribosome without Its Dissociation into Subunits in Eubacteria

Tsuyoshi Udagawa, Yoshihiro Shimizu, Takuya Ueda

Research output: Contribution to journalArticle

82 Citations (Scopus)

Abstract

In eubacteria, the dissociation of the 70 S ribosome into the 30 S and 50 S subunits is the essential first step for the translation initiation of canonical mRNAs that possess 5′-leader sequences. However, a number of leaderless mRNAs that start with the initiation codon have been identified in some eubacteria. These have been shown to be translated efficiently in vivo. Here we investigated the process by which leaderless mRNA translation is initiated by using a highly reconstituted cell-free translation system from Escherichia coli. We found that leaderless mRNAs bind preferentially to 70 S ribosomes and that the leaderless mRNA·70 S·fMet-tRNA complex can transit from the initiation to the elongation phase even in the absence of initiation factors (IFs). Moreover, leaderless mRNA translation proceeds more efficiently if the intact 70 S ribosome is involved compared with the 30 S subunit. Furthermore, excess amounts of IF3 inhibit leaderless mRNA translation, probably because it promotes the disassembly of the 70 S ribosome into subunits. Finally, excess amounts of fMet-tRNA facilitate the IF-independent translation of leaderless mRNA. These observations strongly suggest that leaderless mRNA translation is initiated by the assembled 70 S ribosome and thereby bypasses the dissociation process.

Original languageEnglish
Pages (from-to)8539-8546
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number10
DOIs
Publication statusPublished - 2004 Mar 5
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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