The 5'-untranslated region of the mouse mammary tumor virus mRNA exhibits cap-independent translation initiation

Nucleic Acids Res. 2010 Jan;38(2):618-32. doi: 10.1093/nar/gkp890. Epub 2009 Nov 4.


In this study, we demonstrate the identification of an internal ribosome entry site (IRES) within the 5'-untranslated region (5'-UTR) of the mouse mammary tumor virus (MMTV). The 5'-UTR of the full-length mRNA derived from the infectious, complete MMTV genome was cloned into a dual luciferase reporter construct containing an upstream Renilla luciferase gene (RLuc) and a downstream firefly luciferase gene (FLuc). In rabbit reticulocyte lysate, the MMTV 5'-UTR was capable of driving translation of the second cistron. In vitro translational activity from the MMTV 5'-UTR was resistant to the addition of m(7)GpppG cap-analog and cleavage of eIF4G by foot-and-mouth disease virus (FMDV) L-protease. IRES activity was also demonstrated in the Xenopus laevis oocyte by micro-injection of capped and polyadenylated bicistronic RNAs harboring the MMTV-5'-UTR. Finally, transfection assays showed that the MMTV-IRES exhibits cell type-dependent translational activity, suggesting a requirement for as yet unidentified cellular factors for its optimal function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5' Untranslated Regions*
  • Animals
  • Cell Line
  • Humans
  • Luciferases, Firefly / analysis
  • Luciferases, Firefly / genetics
  • Mammary Tumor Virus, Mouse / genetics*
  • Nucleocytoplasmic Transport Proteins / metabolism
  • Oocytes / metabolism
  • Peptide Chain Initiation, Translational*
  • Plasmids / genetics
  • Promoter Regions, Genetic
  • RNA Caps / antagonists & inhibitors
  • RNA, Messenger / chemistry
  • RNA, Viral / chemistry*
  • Rabbits
  • Xenopus laevis
  • rev Gene Products, Human Immunodeficiency Virus / metabolism


  • 5' Untranslated Regions
  • Nucleocytoplasmic Transport Proteins
  • RNA Caps
  • RNA, Messenger
  • RNA, Viral
  • rev Gene Products, Human Immunodeficiency Virus
  • rev protein, Human Immunodeficiency Virus-1
  • Luciferases, Firefly