Cap-dependent translation without base-by-base scanning of an messenger ribonucleic acid

Nucleic Acids Res. 2012 Aug;40(15):7541-51. doi: 10.1093/nar/gks471. Epub 2012 May 25.


'Ribosome scanning' is the generally accepted mechanism for explaining how a ribosome finds an initiation codon located far removed from the ribosome recruiting site (cap structure). However, the molecular characteristics of ribosome scanning along 5' untranslated regions (UTRs) remain obscure. Herein, using a rabbit reticulocyte lysate (RRL) system and artificial ribonucleic acid (RNA) constructs composed of a capped leader RNA and an uncapped reporter RNA annealed through a double-stranded RNA (dsRNA) bridge, we show that the ribosome can efficiently bypass a stable, dsRNA region without melting the structure. The insertion of an upstream open reading frame in the capped leader RNA impaired the translation of reporter RNA, indicating that a ribosome associated with the 5'-end explores the regions upstream of the dsRNA bridge in search of the initiation codon. These data indicate that a ribosome may skip part(s) of an messenger RNA 5'UTR without thoroughly scanning it.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions*
  • Open Reading Frames
  • Protein Biosynthesis*
  • RNA Caps / metabolism*
  • RNA, Double-Stranded / metabolism
  • RNA, Messenger / chemistry


  • 5' Untranslated Regions
  • RNA Caps
  • RNA, Double-Stranded
  • RNA, Messenger