Expression studies of the HCV-1a core+1 open reading frame in mammalian cells

Virus Res. 2008 May;133(2):123-35. doi: 10.1016/j.virusres.2007.10.019. Epub 2008 Feb 19.


The hepatitis C virus (HCV) genome possesses an open reading frame overlapping the core gene in the +1 frame (core+1 ORF). Initial studies, mainly in rabbit reticulocyte lysates, indicated that the HCV-1 core+1 ORF is expressed by a -2/+1 frameshift at codons 8-11 during translation elongation of the viral polyprotein, resulting in a protein known as alternative reading frame protein (ARFP), frameshift (F), or core+1. However, subsequent investigation, based on reporter constructs carrying portions of the core+1 ORF, suggested the function of alternative mechanisms for core+1 expression in mammalian cells, including translation initiation from internal codons 85/87 or 26. Because results from these studies have been variable, we sought to re-evaluate expression of the core+1 ORF using constructs carrying the complete core+1 coding sequence fused to GFP or LUC. We showed here that codons 85/87 serve as the predominant initiation sites for internal translation initiation of core+1 ORF in Huh-7 and Huh-7/T7 mammalian cells, which support nuclear or cytoplasmic transcription, respectively. We also showed that internal translation initiation can occur concomitantly with the expression of the core+1/F protein that is produced artificially in Huh-7 or naturally in Huh-7/T7 cells. Furthermore, translation of core+1 ORF is not significantly affected by the presence of the HCV IRES element. The core+1/S-GFP protein is cytoplasmic and exhibits an ER distribution similar to that of the core+1/F-GFP protein.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cell Line, Tumor
  • Codon
  • Codon, Initiator*
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Hepacivirus / metabolism*
  • Humans
  • Luciferases / genetics
  • Luciferases / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Open Reading Frames / genetics
  • Open Reading Frames / physiology*
  • Plasmids
  • Protein Biosynthesis*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Transfection
  • Viral Core Proteins / chemistry
  • Viral Core Proteins / genetics
  • Viral Core Proteins / metabolism*


  • Codon
  • Codon, Initiator
  • Recombinant Fusion Proteins
  • Viral Core Proteins
  • hepatitis C protein F, Hepatitis C virus
  • Green Fluorescent Proteins
  • Luciferases