title: Eukaryotic translation initiation factor 4E availability controls the switch between cap-dependent and internal ribosomal entry site-mediated translation.
abstract: Translation of m7G-capped cellular mRNAs is initiated by recruitment of ribosomes to the 5' end of mRNAs via eukaryotic translation initiation factor 4F (eIF4F), a heterotrimeric complex comprised of a cap-binding subunit (eIF4E) and an RNA helicase (eIF4A) bridged by a scaffolding molecule (eIF4G). Internal translation initiation bypasses the requirement for the cap and eIF4E and occurs on viral and cellular mRNAs containing internal ribosomal entry sites (IRESs). Here we demonstrate that eIF4E availability plays a critical role in the switch from cap-dependent to IRES-mediated translation in picornavirus-infected cells. When both capped and IRES-containing mRNAs are present (as in intact cells or in vitro translation extracts), a decrease in the amount of eIF4E associated with the eIF4F complex elicits a striking increase in IRES-mediated viral mRNA translation. This effect is not observed in translation extracts depleted of capped mRNAs, indicating that capped mRNAs compete with IRES-containing mRNAs for translation. These data explain numerous reported observations where viral mRNAs are preferentially translated during infection.
authors.affiliation: Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6.
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Svitkin
authors.forename: Barbara
authors.initials: B
authors.lastname: Herdy
authors.forename: Mauro
authors.initials: M
authors.lastname: Costa-Mattioli
authors.forename: Anne-Claude
authors.initials: AC
authors.lastname: Gingras
authors.forename: Brian
authors.initials: B
authors.lastname: Raught
authors.forename: Nahum
authors.initials: N
authors.lastname: Sonenberg
mesh_terms: D000818:Animals; D002460:Cell Line; D002474:Cell-Free System; D004686:Encephalomyocarditis virus / Q000235:genetics; D039562:Eukaryotic Initiation Factor-4F / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D011485:Protein Binding; D014176:Protein Biosynthesis; D021381:Protein Transport; D012315:RNA Caps / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D039562:Eukaryotic Initiation Factor-4F; D012315:RNA Caps; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012367:RNA, Viral