title: Impairment of interferon regulatory factor-3 activation by hepatitis C virus core protein basic amino acid region 1.
abstract: Interferon regulatory factor-3 (IRF-3), a key transcriptional factor in the type I interferon system, is frequently impaired by hepatitis C virus (HCV), in order to establish persistent infection. However, the exact mechanism by which the virus establishes persistent infection has not been fully understood yet. The present study aimed to investigate the effects of various HCV proteins on IRF-3 activation, and elucidate the underlying mechanisms. To achieve this, full-length HCV and HCV subgenomic constructs corresponding to structural and each of the nonstructural proteins were transiently transfected into HepG2 cells. IFN-β induction, plaque formation, and IRF-3 dimerization were elicited by Newcastle disease virus (NDV) infection. The expressions of IRF-3 homodimer and its monomer, Ser386-phosphorylated IRF-3, and HCV core protein were detected by immunofluorescence and western blotting. IFN-β mRNA expression was quantified by real-time PCR (RT-PCR), and IRF-3 activity was measured by the levels of IRF-3 dimerization and phosphorylation, induced by NDV infection or polyriboinosinic:polyribocytidylic acid [poly(I:C)]. Switching of the expression of the complete HCV genome as well as the core proteins, E1, E2, and NS2, suppressed IFN-β mRNA levels and IRF-3 dimerization, induced by NDV infection. Our study revealed a crucial region of the HCV core protein, basic amino acid region 1 (BR1), to inhibit IRF-3 dimerization as well as its phosphorylation induced by NDV infection and poly (I:C), thus interfering with IRF-3 activation. Therefore, our study suggests that rescue of the IRF-3 pathway impairment may be an effective treatment for HCV infection.
authors.affiliation: Department of Microbiology and Cell Biology, The Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Tokyo 156-0057, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Inoue
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tsukiyama-Kohara
authors.forename: Chiho
authors.initials: C
authors.lastname: Matsuda
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Yoneyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Fujita
authors.forename: Shusuke
authors.initials: S
authors.lastname: Kuge
authors.forename: Makoto
authors.initials: M
authors.lastname: Yoshiba
authors.forename: Michinori
authors.initials: M
authors.lastname: Kohara
mesh_terms: D021581:Active Transport, Cell Nucleus; D024361:Amino Acids, Basic; D002467:Cell Nucleus / Q000378:metabolism; D016679:Genome, Viral; D056945:Hep G2 Cells; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism*; D006526:Hepatitis C / Q000276:immunology* / Q000821:virology*; D006801:Humans; D050838:Interferon Regulatory Factor-3 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016899:Interferon-beta / Q000276:immunology; D055503:Protein Multimerization; D014758:Viral Core Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017361:Viral Nonstructural Proteins / Q000378:metabolism; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
chemical_list: D024361:Amino Acids, Basic; D050838:Interferon Regulatory Factor-3; D016899:Interferon-beta; D014758:Viral Core Proteins; D017361:Viral Nonstructural Proteins; C494232:IRF3 protein, human; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases