IGF2BP1 enhances HCV IRES-mediated translation initiation via the 3'UTR.
The positive-strand RNA genome of the Hepatitis C virus (HCV) contains an internal ribosome entry site (IRES) in the 5'untranslated region (5'UTR) and structured sequence elements within the 3'UTR, but no poly(A) tail. Employing a limited set of initiation factors, the HCV IRES coordinates the 5'cap-independent assembly of the 43S pre-initiation complex at an internal initiation codon located in the IRES sequence. We have established a Huh7 cell-derived in vitro translation system that shows a 3'UTR-dependent enhancement of 43S pre-initiation complex formation at the HCV IRES. Through the use of tobramycin (Tob)-aptamer affinity chromatography, we identified the Insulin-like growth factor-II mRNA-binding protein 1 (IGF2BP1) as a factor that interacts with both, the HCV 5'UTR and 3'UTR. We report that IGF2BP1 specifically enhances translation at the HCV IRES, but it does not affect 5'cap-dependent translation. RNA interference against IGF2BP1 in HCV replicon RNA-containing Huh7 cells reduces HCV IRES-mediated translation, whereas replication remains unaffected. Interestingly, we found that endogenous IGF2BP1 specifically co-immunoprecipitates with HCV replicon RNA, the ribosomal 40S subunit, and eIF3. Furthermore eIF3 comigrates with IGF2BP1 in 80S ribosomal complexes when a reporter mRNA bearing both the HCV 5'UTR and HCV 3'UTR is translated. Our data suggest that IGF2BP1, by binding to the HCV 5'UTR and/or HCV 3'UTR, recruits eIF3 and enhances HCV IRES-mediated translation.
Weinlich
Susan
S
Institute of Biochemistry and Biotechnology, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany.
Hüttelmaier
Stefan
S
Schierhorn
Angelika
A
Behrens
Sven-Erik
SE
Ostareck-Lederer
Antje
A
Ostareck
Dirk H
DH
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002478:Cells, Cultured; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism; D016679:Genome, Viral; D016174:Hepacivirus / Q000235:genetics* / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism / Q000821:virology; D006801:Humans; D016366:Open Reading Frames; D010442:Peptide Chain Initiation, Translational; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D012093:Replicon; D012270:Ribosomes / Q000378:metabolism
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D039621:Eukaryotic Initiation Factor-3; C406144:IGF2BP1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012367:RNA, Viral; D016601:RNA-Binding Proteins