The 3'-untranslated region of hepatitis C virus RNA enhances translation from an internal ribosomal entry site.
Translation of most eukaryotic mRNAs and many viral RNAs is enhanced by their poly(A) tails. Hepatitis C virus (HCV) contains a positive-stranded RNA genome which does not have a poly(A) tail but has a stretch of 98 nucleotides (X region) at the 3'-untranslated region (UTR), which assumes a highly conserved stem-loop structure. This X region binds a polypyrimidine tract-binding protein (PTB), which also binds to the internal ribosome entry site (IRES) in HCV 5'-UTR. These RNA-protein interactions may regulate its translation. We generated a set of HCV RNAs differing only in their 3'-UTRs and compared their translation efficiencies. HCV RNA containing the X region was translated three- to fivefold more than the corresponding RNAs without this region. Mutations that abolished PTB binding in the X region reduced, but did not completely abolish, enhancement in translation. The X region also enhanced translation from another unrelated IRES (from encephalomyocarditis virus RNA), but did not affect the 5'-end-dependent translation of globin mRNA in either monocistronic or bicistronic RNAs. It did not appear to affect RNA stability. The free X region added in trans, however, did not enhance translation, indicating that the translational enhancement by the X region occurs only in cis. These results demonstrate that the highly conserved 3' end of HCV RNA provides a novel mechanism for enhancement of HCV translation and may offer a target for antiviral agents.
Howard Hughes Medical Institute, University of Southern California School of Medicine, Los Angeles, California 90033-1054, USA.
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D020413:3' Untranslated Regions / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D004686:Encephalomyocarditis virus / Q000235:genetics; D005814:Genes, Viral / Q000235:genetics; D005914:Globins / Q000235:genetics; D016174:Hepacivirus / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics*; D012270:Ribosomes / Q000378:metabolism / Q000821:virology; D015678:Viral Structural Proteins / Q000235:genetics
D020413:3' Untranslated Regions; D017931:DNA Primers; D012367:RNA, Viral; D015678:Viral Structural Proteins; D005914:Globins; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase