title: The 5'-untranslated region of the mouse mammary tumor virus mRNA exhibits cap-independent translation initiation.
abstract: 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.
authors.affiliation: Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Pontificia Universidad Católica de Chile, Marcoleta 391, Chile.
authors.forename: Maricarmen
authors.initials: M
authors.lastname: Vallejos
authors.forename: Pablo
authors.initials: P
authors.lastname: Ramdohr
authors.forename: Fernando
authors.initials: F
authors.lastname: Valiente-Echeverría
authors.forename: Karla
authors.initials: K
authors.lastname: Tapia
authors.forename: Felipe E
authors.initials: FE
authors.lastname: Rodriguez
authors.forename: Fernando
authors.initials: F
authors.lastname: Lowy
authors.forename: J Pablo
authors.initials: JP
authors.lastname: Huidobro-Toro
authors.forename: John A
authors.initials: JA
authors.lastname: Dangerfield
authors.forename: Marcelo
authors.initials: M
authors.lastname: López-Lastra
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D002460:Cell Line; D006801:Humans; D049409:Luciferases, Firefly / Q000032:analysis / Q000235:genetics; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D010442:Peptide Chain Initiation, Translational; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012315:RNA Caps / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000737:chemistry; D012367:RNA, Viral / Q000737:chemistry*; D011817:Rabbits; D014982:Xenopus laevis; D054321:rev Gene Products, Human Immunodeficiency Virus / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D029543:Nucleocytoplasmic Transport Proteins; D012315:RNA Caps; D012333:RNA, Messenger; D012367:RNA, Viral; D054321:rev Gene Products, Human Immunodeficiency Virus; C514860:rev protein, Human Immunodeficiency Virus-1; D049409:Luciferases, Firefly