Activation of the Interferon-βPromoter During Hepatitis C Virus RNA Replication

Abstract

In this study we examined the impact of hepatitis C virus (HCV) RNA replication on the innate antiviral response of the host cell. Replication of an HCV subgenomic replicon stimulated the activation of the interferon (IFN)-beta promoter and the production of IFN in human hepatoma cells. Using a variety of functional assays, we found that HCV RNA replication induced the activation and DNA-binding activity of NFkappaB and interferon regulatory factor (IRF)-1. In addition, microscopy experiments revealed a higher frequency of cells containing the nuclear-localized, active form of IRF-3 in HCV replicon cultures versus control cultures. Consistent with these observations, cells harboring the HCV replicon exhibited high basal level expression of a subset of IFN-stimulated antiviral genes. Our results indicate that HCV RNA replication can stimulate cellular antiviral programs that contribute to the assembly and activation of the IFN-beta enhanceosome complex and initiation of the antiviral state. Stable HCV RNA replication in the face of the host antiviral response suggests that HCV may encode one or more proteins capable of overcoming specific antiviral processes, thereby supporting persistent infection.

Gene expression associated with interferon alfa antiviral activity in an HCV replicon cell line

“…Interestingly, Fredricksen et al 36 has reported that HCV replicon can activate IFN-␤ promoter and IFN-␤ production. 36 Using RT-PCR, we did not see increased IFN-␤ mRNA expression in FCA1 cells (data not shown). There may be differences among different HCV replicon cell lines.…”

Control of antiviral defenses through hepatitis C virus disruption of retinoic acid-inducible gene-I signaling

“…Analysis of stained cells was conducted in the University of Texas Southwestern Medical Center Pathogen Imaging Facility by using a Zeiss Axiovert or Zeiss Pascal LSM confocal microscope and AXIOVISION software. Electrophoretic mobility-shift analysis of NF-B DNA binding activity was conducted on nuclear extracts prepared from cultures of 4 ϫ 10 5 cells as described (4). RNA Analysis.…”

“…Recent studies have shown that the processes of RIG-I signaling and the actions of IRF-3 and NF-B initiate host defenses that limit HCV RNA replication (1,3,4). The single-stranded RNA genome of HCV encodes a 3,010-aa polyprotein that is posttranslationally processed into the mature structural proteins (core, E1 and E2), p7, and the nonstructural (NS) proteins NS2-NS5B (5), of which the NS3-NS5B proteins are sufficient to support viral RNA replication (Fig.…”

Effector genes of interferon action against hepatitis C virus

“…The reason for this is not clear, but could be related to a priming effect rendered by a low level of IFN production within the replicon cells, as has been shown in other studies. 17 The gene lists presented by Zhu et al 13 show that, overall, IFN induced a pattern of ISG expression in Huh7 HCV replicon cells that is consistent with the actions of ISGF3. What the investigators may have overlooked is that known STAT3 target genes, such as p21(waf1), myc, pim-1, cyclin D1, and others 5 were not part of this list.…”

“…22 The involvement of dsRNA and IRF pathways in ISG signaling events that limit HCV RNA replication has also been shown in studies of the HCV replicon system. 10,17,24 Thus, control of HCV infection and replication is likely to involve a spectrum of ISGs whose expression is determined through complex virus-host interactions that regulate IFN-dependent and IFN-independent signaling pathways.…”