Repression of Interferon Regulatory Factor 1 by Hepatitis C Virus Core Protein Results in Inhibition of Antiviral and Immunomodulatory Genes

Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena, 299 Rome 00161, Italy. .
Journal of Virology (Impact Factor: 4.44). 02/2007; 81(1):202-14. DOI: 10.1128/JVI.01011-06
Source: PubMed


Hepatitis C virus (HCV) proteins are known to interfere at several levels with both innate and adaptive responses of the host.
A key target in these effects is the interferon (IFN) signaling pathway. While the effects of nonstructural proteins are well
established, the role of structural proteins remains controversial. We investigated the effect of HCV structural proteins
on the expression of interferon regulatory factor 1 (IRF-1), a secondary transcription factor of the IFN system responsible
for inducing several key antiviral and immunomodulatory genes. We found substantial inhibition of IRF-1 expression in cells
expressing the entire HCV replicon. Suppression of IRF-1 synthesis was mainly mediated by the core structural protein and
occurred at the transcriptional level. The core protein in turn exerted a transcriptional repression of several interferon-stimulated
genes, targets of IRF-1, including interleukin-15 (IL-15), IL-12, and low-molecular-mass polypeptide 2. These data recapitulate
in a unifying mechanism, i.e., repression of IRF-1 expression, many previously described pathogenetic effects of HCV core
protein and suggest that HCV core-induced IRF-1 repression may play a pivotal role in establishing persistent infection by
dampening an effective immune response.

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    • "The Huh-7 cells carrying the Sfl HCV full-length replicon (genotype 1b) were obtained from Dr. R. Bartenschlager. The 21-5, 21-7 and 22-6 clones are cell lines that stably replicates the HCV replicon and were passaged as described [43-45]. HCV replicon cells were cultured in complete DMEM supplemented with 10% FCS, antibiotics, 1× non-essential amino acids, and 250 μg/ml (21-5, 21-7) and 500 μg/ml (22-6) G418. "
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    ABSTRACT: Infections with hepatitis C virus (HCV) progress to chronic phase in 80% of patients. To date, the effect produced by HCV on the expression of microRNAs (miRs) involved in the interferon-β (IFN-β) antiviral pathway has not been explored in details. Thus, we compared the expression profile of 24 selected miRs in IFN-β-treated Huh-7 cells and in three different clones of Huh-7 cells carrying a self-replicating HCV RNA which express all viral proteins (HCV replicon system). The expression profile of 24 selected miRs in IFN-β-treated Huh-7 cells and in HCV replicon 21-5 clone with respect to Huh-7 parental cells was analysed by real-time PCR. To exclude clone specific variations, the level of 16 out of 24 miRs, found to be modulated in 21-5 clone, was evaluated in two other HCV replicon clones, 22-6 and 21-7. Prediction of target genes of 3 miRs, confirmed in all HCV clones, was performed by means of miRGator program. The gene dataset obtained from microarray analysis of HCV clones was farther used to validate target prediction. The expression profile revealed that 16 out of 24 miRs were modulated in HCV replicon clone 21-5. Analysis in HCV replicon clones 22-6 and 21-7 indicated that 3 out of 16 miRs, (miR-128a, miR-196a and miR-142-3p) were modulated in a concerted fashion in all three HCV clones. Microarray analysis revealed that 37 out of 1981 genes, predicted targets of the 3 miRs, showed an inverse expression relationship with the corresponding miR in HCV clones, as expected for true targets. Classification of the 37 genes by Panther System indicated that the dataset contains genes involved in biological processes that sustain HCV replication and/or in pathways potentially implicated in the control of antiviral response by HCV infection. The present findings reveal that 3 IFN-β-regulated miRs and 37 genes, which are likely their functional targets, were commonly modulated by HCV in three replicon clones. The future use of miR inhibitors or mimics and/or siRNAs might be useful for the development of diagnostic and therapeutic strategies aimed at the recovering of protective innate responses in HCV infections.
    Full-text · Article · Oct 2011 · BMC Genomics
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    • "The core protein interferes with IFN signalling and the antiviral response (Gale & Foy, 2005; Melen et al., 2004), for example by binding to the SH2 domain of signal transducers and activators of transcription (STAT) 1 (Lin et al., 2006b). Furthermore, the core protein can downregulate the transcription of IRF1 (Ciccaglione et al., 2007). In addition, the E1 and NS5A proteins have been shown to block the activation of PKR, leading to a reduced IFN-induced Fig. 3. HCV protein expression interferes with transcription factor binding to ISRE and NF-kB REs on the CXCL10 promoter. "
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    ABSTRACT: The hepatitis C virus (HCV) non-structural (NS) 3/4A protein complex inhibits the retinoic acid inducible gene I (RIG-I) pathway by proteolytically cleaving mitochondria-associated CARD-containing adaptor protein Cardif, and this leads to reduced production of beta interferon (IFN-beta). This study examined the expression of CCL5 (regulated upon activation, normal T-cell expressed and secreted, or RANTES), CXCL8 (interleukin 8) and CXCL10 (IFN-gamma-activated protein 10, or IP-10) chemokine genes in osteosarcoma cell lines that inducibly expressed NS3/4A, NS4B, core-E1-E2-p7 and the entire HCV polyprotein. Sendai virus (SeV)-induced production of IFN-beta, CCL5, CXCL8 and CXCL10 was downregulated by the NS3/4A protein complex and by the full-length HCV polyprotein. Expression of NS3/4A and the HCV polyprotein reduced the binding of interferon regulatory factors (IRFs) 1 and 3 and, to a lesser extent, nuclear factor (NF)-kappaB (p65/p50) to their respective binding elements on the CXCL10 promoter during SeV infection. Furthermore, binding of IRF1 and IRF3 to the interferon-stimulated response element-like element, and of c-Jun and phosphorylated c-Jun to the activator protein 1 element of the CXCL8 promoter, was reduced when NS3/4A and the HCV polyprotein were expressed. In cell lines expressing NS3/4A and the HCV polyprotein, the subcellular localization of mitochondria was changed, and this was kinetically associated with the partial degradation of endogenous Cardif. These results indicate that NS3/4A alone or as part of the HCV polyprotein disturbs the expression of IRF1- and IRF3-regulated genes, as well as affecting mitogen-activated protein kinase kinase- and NF-kappaB-regulated genes.
    Preview · Article · Mar 2008 · Journal of General Virology
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    • "To overcome these restrictions, selectable HCV replicons in human hepatoma-derived Huh7 cells, which contain self-replicating HCV RNA and express all viral proteins, were developed [3-6]. These systems have been largely used for the study of HCV translation and RNA replication revealing important processes of virus-host interactions [7-12]. HCV proteins have been proposed to be involved in a wide range of activities, including cell signaling, transcriptional modulation, transformation, apoptosis, oxidative stress, membrane rearrangement, vesicular trafficking and immune response [13-21]. "
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    ABSTRACT: Hepatitis C virus (HCV) RNA synthesis and protein expression affect cell homeostasis by modulation of gene expression. The impact of HCV replication on global cell transcription has not been fully evaluated. Thus, we analysed the expression profiles of different clones of human hepatoma-derived Huh-7 cells carrying a self-replicating HCV RNA which express all viral proteins (HCV replicon system). First, we compared the expression profile of HCV replicon clone 21-5 with both the Huh-7 parental cells and the 21-5 cured (21-5c) cells. In these latter, the HCV RNA has been eliminated by IFN-alpha treatment. To confirm data, we also analyzed microarray results from both the 21-5 and two other HCV replicon clones, 22-6 and 21-7, compared to the Huh-7 cells. The study was carried out by using the Applied Biosystems (AB) Human Genome Survey Microarray v1.0 which provides 31,700 probes that correspond to 27,868 human genes. Microarray analysis revealed a specific transcriptional program induced by HCV in replicon cells respect to both IFN-alpha-cured and Huh-7 cells. From the original datasets of differentially expressed genes, we selected by Venn diagrams a final list of 38 genes modulated by HCV in all clones. Most of the 38 genes have never been described before and showed high fold-change associated with significant p-value, strongly supporting data reliability. Classification of the 38 genes by Panther System identified functional categories that were significantly enriched in this gene set, such as histones and ribosomal proteins as well as extracellular matrix and intracellular protein traffic. The dataset also included new genes involved in lipid metabolism, extracellular matrix and cytoskeletal network, which may be critical for HCV replication and pathogenesis. Our data provide a comprehensive analysis of alterations in gene expression induced by HCV replication and reveal modulation of new genes potentially useful for selection of antiviral targets.
    Full-text · Article · Feb 2008 · BMC Genomics
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