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Open Access Research

Expression of an IRF-3 fusion protein and mouse estrogen receptor, inhibits hepatitis C viral replication in RIG-I-deficient Huh 7.5 cells

Luyu Yao1, Xiaobo Yan4, Huijia Dong2, David R Nelson3, Chen Liu2 and Xiaoyu Li1*

Author Affiliations

1 Division of Gastroenterology and Hepatology, Department of Medicine, University of Florida-Jacksonville, FL 32206, USA

2 Department of Pathology, University of Florida-Gainesville, FL 32610, USA

3 Department of Medicine, University of Florida-Gainesville, FL 32610, USA

4 Department of Neurology, Second University Affiliated Hospital, Harbin Medical University, Harbin, 150081, China

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Virology Journal 2011, 8:445  doi:10.1186/1743-422X-8-445

Published: 21 September 2011

Abstract

Interferon Regulatory Factor-3 (IRF-3) plays a central role in the induction of interferon (IFN) production and succeeding interferon-stimulated genes (ISG) expression en route for restraining hepatitis C virus (HCV) infection. Here, we established a stable Huh7.5-IRF3ER cell line expressing a fusion protein of IRF-3 and mouse estrogen receptor (ER) to examine IFN production and anti-HCV effects of IRF-3 in retinoic acid inducible-gene-I (RIG-I) deficient Huh 7.5 cells. Homodimerization of the IRF-3ER fusion protein was detected by Western blotting after treatment with the estrogen receptor agonist 4-hydrotamoxifen (4-HT) in Huh7.5-IRF3ER cells. Expression of IFN-α, IFN-β, and their inhibitory effects on HCV replication were demonstrated by real-time polymerase chain reaction (PCR). Peak expression of IFN-α and IFN-β was achieved 24-hours post 4-HT treatment, coinciding with the appearance of phosphorylated signal transducer and activator of transcription (STAT) proteins. Additionally, HCV viral replication declined in time-dependent fashion. In previous studies, a novel IFN-mediated pathway regulating expression of 1-8U and heterogeneous nuclear ribonucleoprotein M (hnRNP M) inhibited HCV internal ribosomal entry site (IRES)-dependent translation. When expression of ISGs such as 1-8U and hnRNP M were measured in 4-HT-treated Huh7.5-IRF3ER cells, both genes were positively regulated by activation of the IRF-3ER fusion protein. In conclusion, the anti-HCV effects of IRF-3ER homodimerization inhibited HCV RNA replication as well as HCV IRES-dependent translation in Huh7.5-IRF3ER cells. The results of this study indicate that IRF-3ER homodimerization is a key step to restore IFN expression in Huh7.5-IRF3ER cells and in achieving its anti-HCV effects.