title: The 5' UTR of HIV-1 full-length mRNA and the Tat viral protein modulate the programmed -1 ribosomal frameshift that generates HIV-1 enzymes.
abstract: Translation of the full-length messenger RNA (mRNA) of the human immunodeficiency virus type 1 (HIV-1) generates the precursor of the viral enzymes via a programmed -1 ribosomal frameshift. Here, using dual-luciferase reporters, we investigated whether the highly structured 5' untranslated region (UTR) of this mRNA, which interferes with translation initiation, can modulate HIV-1 frameshift efficiency. We showed that, when the 5' UTR of HIV-1 mRNA occupies the 5' end of the reporter mRNA, HIV-1 frameshift efficiency is increased about fourfold in Jurkat T-cells, compared with a control dual-luciferase reporter with a short unstructured 5' UTR. This increase was related to an interference with cap-dependent translation initiation by the TAR-Poly(A) region at the 5' end of the messenger. HIV-1 mRNA 5' UTR also contains an internal ribosome entry site (IRES), but we showed that, when the cap-dependent initiation mode is available, the IRES is not used or is weakly used. However, when the ribosomes have to use the IRES to translate the dual-luciferase reporter, the frameshift efficiency is comparable to that of the control dual-luciferase reporter. The decrease in cap-dependent initiation and the accompanying increase in frameshift efficiency caused by the 5' UTR of HIV-1 mRNA is antagonized, in a dose-dependent way, by the Tat viral protein. Tat also stimulates the IRES-dependent initiation and decreases the corresponding frameshift efficiency. A model is presented that accounts for the variations in frameshift efficiency depending on the 5' UTR and the presence of Tat, and it is proposed that a range of frameshift efficiencies is compatible with the virus replication.
authors.affiliation: Département de biochimie, Université de Montréal, Montréal, Québec H3T1J4, Canada.
authors.forename: Johanie
authors.initials: J
authors.lastname: Charbonneau
authors.forename: Karine
authors.initials: K
authors.lastname: Gendron
authors.forename: Gerardo
authors.initials: G
authors.lastname: Ferbeyre
authors.forename: Léa
authors.initials: L
authors.lastname: Brakier-Gingras
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics*; D018965:Frameshifting, Ribosomal / Q000235:genetics*; D015967:Gene Expression Regulation, Viral; D023061:Gene Order; D015696:Gene Products, tat / Q000378:metabolism*; D017930:Genes, Reporter; D005822:Genetic Vectors; D057809:HEK293 Cells; D015497:HIV-1 / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D012333:RNA, Messenger / Q000737:chemistry*; D012367:RNA, Viral / Q000737:chemistry*
chemical_list: D020121:5' Untranslated Regions; D015696:Gene Products, tat; D012333:RNA, Messenger; D012367:RNA, Viral