Differences in the expression of the hepatitis C virus core+1 open reading frame between a nuclear and a cytoplasmic expression system.

Abstract

The hepatitis C virus (HCV) genome possesses an open reading frame (ORF) overlapping the core gene at +1 nucleotide (core+1 ORF). Initial in vitro studies suggested that the core+1 ORF is translated by a ribosomal -2/+1 frameshift mechanism during elongation of the viral polyprotein. Recent studies, however, based on transfection of mammalian cells with reporter constructs have shown that translation of the core+1 ORF is mediated from internal core+1 codons. To resolve the apparent discrepancies associated with the mechanism of core+1 translation, we examined the expression of the HCV-1 and HCV-1a (H) core+1 ORF in a cytoplasmic transcription system based on Huh-7/T7 cells that constitutively synthesize the T7 RNA polymerase in comparison to that in Huh-7 cells. We showed that the efficiency of both the -2/+1 and -1/+2 frameshift events operating at the HCV-1 core codons 8-11 is significantly enhanced in the Huh-7/T7 cytoplasmic transcription system and is dependent on the presence of the consecutive adenine (A) residues within core codons 8-11. In contrast, internal translation initiation at core+1 codons 85/87 occurs in both the nuclear and cytoplasmic transcription systems and is not repressed by the ribosomal frameshifting event. Finally, although core+1 codons 85/87 is the most efficient site for internal initiation of core+1 translation, it may not be unique, as additional internal core+1 codon(s) appear to drive translation at low levels.

• Authors: Niki Vassilaki, Katerina I Kalliampakou, Penelope Mavromara
• Journal: The Journal of general virology (J Gen Virol) Vol. 89 Issue Pt 1 Pg. 222-231 (Jan 2008) ISSN: 0022-1317 [Print] England
• PMID: 18089746 (Publication Type: Journal Article)

Chemical References

• Codon
• Viral Core Proteins

Topics

• Amino Acid Sequence
• Base Sequence
• Carcinoma, Hepatocellular (virology)
• Cell Line
• Cell Nucleus (virology)
• Codon (genetics)
• Cytoplasm (virology)
• Gene Expression Regulation, Viral
• Hepacivirus (genetics)
• Humans
• Liver Neoplasms (virology)
• Molecular Sequence Data
• Mutagenesis, Insertional
• Mutagenesis, Site-Directed
• Open Reading Frames
• Plasmids
• Promoter Regions, Genetic
• Transfection
• Viral Core Proteins (chemistry, genetics)