1
|
Ricciardi-Jorge T, da Rocha EL, Gonzalez-Kozlova E, Rodrigues-Luiz GF, Ferguson BJ, Sweeney T, Irigoyen N, Mansur DS. PKR-mediated stress response enhances dengue and Zika virus replication. mBio 2023; 14:e0093423. [PMID: 37732809 PMCID: PMC10653888 DOI: 10.1128/mbio.00934-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/01/2023] [Indexed: 09/22/2023] Open
Abstract
IMPORTANCE One of the fundamental features that make viruses intracellular parasites is the necessity to use cellular translational machinery. Hence, this is a crucial checkpoint for controlling infections. Here, we show that dengue and Zika viruses, responsible for nearly 400 million infections every year worldwide, explore such control for optimal replication. Using immunocompetent cells, we demonstrate that arrest of protein translations happens after sensing of dsRNA and that the information required to avoid this blocking is contained in viral 5'-UTR. Our work, therefore, suggests that the non-canonical translation described for these viruses is engaged when the intracellular stress response is activated.
Collapse
Affiliation(s)
- Taissa Ricciardi-Jorge
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
- The Pirbright Institute, Woking, United Kingdom
| | - Edroaldo Lummertz da Rocha
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
| | - Edgar Gonzalez-Kozlova
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
- Icahn School of Medicine, New York, USA
| | - Gabriela Flavia Rodrigues-Luiz
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
| | - Brian J. Ferguson
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Nerea Irigoyen
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Daniel Santos Mansur
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
| |
Collapse
|
2
|
Shiner B, Huybrechts K, Gui J, Rozema L, Forehand J, Watts BV, Jiang T, Hoyt JE, Esteves J, Schnurr PP, Ray K, Gradus JL. Comparative Effectiveness of Direct-Acting Antivirals for Posttraumatic Stress Disorder in Veterans Affairs Patients With Hepatitis C Virus Infection. Am J Epidemiol 2022; 191:1614-1625. [PMID: 35689641 PMCID: PMC9989349 DOI: 10.1093/aje/kwac104] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 05/26/2022] [Accepted: 06/08/2022] [Indexed: 01/29/2023] Open
Abstract
We recently conducted an exploratory study that indicated that several direct-acting antivirals (DAAs), highly effective medications for hepatitis C virus (HCV) infection, were also associated with improvement in posttraumatic stress disorder (PTSD) among a national cohort of US Department of Veterans Affairs (VA) patients treated between October 1, 1999, and September 30, 2019. Limiting the same cohort to patients with PTSD and HCV, we compared the associations of individual DAAs with PTSD symptom improvement using propensity score weighting. After identifying patients who had available baseline and endpoint PTSD symptom data as measured with the PTSD Checklist (PCL), we compared changes over the 8-12 weeks of DAA treatment. The DAAs most prescribed in conjunction with PCL measurement were glecaprevir/pibrentasvir (GLE/PIB; n = 54), sofosbuvir/velpatasvir (SOF/VEL; n = 54), and ledipasvir/sofosbuvir (LDV/SOF; n = 145). GLE/PIB was superior to LDV/SOF, with a mean difference in improvement of 7.3 points on the PCL (95% confidence interval (CI): 1.1, 13.6). The mean differences in improvement on the PCL were smaller between GLE/PIB and SOF/VEL (3.0, 95% CI: -6.3, 12.2) and between SOF/VEL and LDV/SOF (4.4, 95% CI: -2.4, 11.2). While almost all patients were cured of HCV (92.5%) regardless of the agent received, PTSD outcomes were superior for those receiving GLE/PIB compared with those receiving LDV/SOF, indicating that GLE/PIB may merit further investigation as a potential PTSD treatment.
Collapse
Affiliation(s)
- Brian Shiner
- Correspondence to Dr. Brian Shiner, VA Medical Center, 215 N. Main Street, White River Junction, VT 05009 (e-mail: )
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
3
|
Lozano-Sepulveda SA, Bautista-Osorio E, Merino-Mascorro JA, Varela-Rey M, Muñoz-Espinosa LE, Cordero-Perez P, Martinez-Chantar ML, Rivas-Estilla AM. S-adenosyl-L-methionine modifies antioxidant-enzymes, glutathione-biosynthesis and methionine adenosyltransferases-1/2 in hepatitis C virus-expressing cells. World J Gastroenterol 2016; 22:3746-3757. [PMID: 27076759 PMCID: PMC4814737 DOI: 10.3748/wjg.v22.i14.3746] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 02/14/2016] [Accepted: 03/02/2016] [Indexed: 02/06/2023] Open
Abstract
AIM: To elucidate the mechanism(s) by which S-adenosyl-L-methionine (SAM) decreases hepatitis C virus (HCV) expression.
METHODS: We examined the effects of SAM on viral expression using an HCV subgenomic replicon cell culture system. Huh7 HCV-replicon cells were treated with 1 mmol/L SAM for different times (24-72 h), then total RNA and proteins were isolated. cDNA was synthesized and real time-PCR was achieved to quantify HCV-RNA, superoxide dismutase 1 and 2 (SOD-1, SOD-2) catalase, thioredoxin 1, methionine adenosyltransferase 1A and 2A (MAT1A, MAT2A) expression, and GAPDH and RPS18 as endogenous genes. Expression of cellular and viral protein was evaluated by western-blot analysis using antibodies vs HCV-NS5A, SOD-1, SOD-2, catalase, thioredoxin-1, MAT1A, MAT2A, GAPDH and actin. Total glutathione levels were measured at different times by Ellman’s recycling method (0-24 h). Reactive oxidative species (ROS) levels were quantified by the dichlorofluorescein assay (0-48 h); Pyrrolidin dithiocarbamate (PDTC) was tested as an antioxidant control and H2O2 as a positive oxidant agent.
RESULTS: SAM exposition decreased HCV-RNA levels 50%-70% compared to non-treated controls (24-72 h). SAM induced a synergic antiviral effect with standard IFN treatment but it was independent of IFN signaling. In addition, 1 mmol/L SAM exposition did not modify viral RNA stability, but it needs cellular translation machinery in order to decrease HCV expression. Total glutathione levels increased upon SAM treatment in HCV-replicon cells. Transcriptional antioxidant enzyme expression (SOD-1, SOD-2 and thioredoxin-1) was increased at different times but interestingly, there was no significant change in ROS levels upon SAM treatment, contrary to what was detected with PDTC treatment, where an average 40% reduction was observed in exposed cells. There was a turnover from MAT1A/MAT2A, since MAT1A expression was increased (2.5 fold-times at 48 h) and MAT2A was diminished (from 24 h) upon SAM treatment at both the transcriptional and translational level.
CONCLUSION: A likely mechanism(s) by which SAM diminish HCV expression could involve modulating antioxidant enzymes, restoring biosynthesis of glutathione and switching MAT1/MAT2 turnover in HCV expressing cells.
Collapse
|
4
|
Govea-Salas M, Rivas-Estilla AM, Rodríguez-Herrera R, Lozano-Sepúlveda SA, Aguilar-Gonzalez CN, Zugasti-Cruz A, Salas-Villalobos TB, Morlett-Chávez JA. Gallic acid decreases hepatitis C virus expression through its antioxidant capacity. Exp Ther Med 2015; 11:619-624. [PMID: 26893656 DOI: 10.3892/etm.2015.2923] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 09/25/2015] [Indexed: 01/16/2023] Open
Abstract
Gallic acid (GA) is a natural phenolic compound that possesses various biological effects, including antioxidant, anti-inflammatory, antibiotic, anticancer, antiviral and cardiovascular protection activities. In addition, numerous studies have reported that antioxidants possess antiviral activities. Hepatitis C virus (HCV) is one of the most important causes of chronic liver diseases worldwide, but until recently, only a small number of antiviral agents had been developed against HCV. Therefore, the present study investigated whether GA exhibits an anti-HCV activity. The effects of GA on HCV expression were examined using a subgenomic HCV replicon cell culture system that expressed HCV nonstructural proteins (NSs). In addition, GA cytotoxicity was evaluated at concentrations between 100-600 mg/ml using an MTT assay. Huh-7 replicon cells were incubated with 300 mg/ml GA for different times, and the HCV-RNA and protein levels were measured by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. Pyrrolidine dithiocarbamate (PDTC) was used as an antioxidant control and reactive oxygen species (ROS) production was measured during the exposure. The results indicated that GA did not produce a statistically significant cytotoxicity in parental and HCV replicon cells. Furthermore, GA downregulated the expression levels of NS5A-HCV protein (~55%) and HCV-RNA (~50%) in a time-dependent manner compared with the levels in untreated cells. Notably, GA treatment decreased ROS production at the early time points of exposure in cells expressing HCV proteins. Similar results were obtained upon PDTC exposure. These findings suggest that the antioxidant capacity of GA may be involved in the downregulation of HCV replication in hepatoma cells.
Collapse
Affiliation(s)
- Mayela Govea-Salas
- Food Research Department, School of Chemical Sciences, Autonomous University of Coahuila, Saltillo Unit, Saltillo, Coahuila 25260, México; Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo Leon 66450, México
| | - Ana Maria Rivas-Estilla
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo Leon 66450, México
| | - Raul Rodríguez-Herrera
- Food Research Department, School of Chemical Sciences, Autonomous University of Coahuila, Saltillo Unit, Saltillo, Coahuila 25260, México
| | - Sonia A Lozano-Sepúlveda
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo Leon 66450, México
| | - Cristobal N Aguilar-Gonzalez
- Food Research Department, School of Chemical Sciences, Autonomous University of Coahuila, Saltillo Unit, Saltillo, Coahuila 25260, México
| | - Alejandro Zugasti-Cruz
- Food Research Department, School of Chemical Sciences, Autonomous University of Coahuila, Saltillo Unit, Saltillo, Coahuila 25260, México
| | - Tanya B Salas-Villalobos
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo Leon 66450, México
| | - Jesus Antonio Morlett-Chávez
- Food Research Department, School of Chemical Sciences, Autonomous University of Coahuila, Saltillo Unit, Saltillo, Coahuila 25260, México; Clinical Laboratory Department, General Hospital Zone No. 2, Mexican Social Security Institute, Saltillo, Coahuila 25017, México
| |
Collapse
|
5
|
Wang X, Zhang H, Abel AM, Nelson E. Protein kinase R (PKR) plays a pro-viral role in porcine reproductive and respiratory syndrome virus (PRRSV) replication by modulating viral gene transcription. Arch Virol 2015; 161:327-33. [DOI: 10.1007/s00705-015-2671-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/31/2015] [Indexed: 01/01/2023]
|
6
|
Emerging roles of interferon-stimulated genes in the innate immune response to hepatitis C virus infection. Cell Mol Immunol 2014; 13:11-35. [PMID: 25544499 PMCID: PMC4712384 DOI: 10.1038/cmi.2014.127] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 11/21/2014] [Accepted: 11/22/2014] [Indexed: 12/14/2022] Open
Abstract
Infection with hepatitis C virus (HCV), a major viral cause of chronic liver disease, frequently progresses to steatosis and cirrhosis, which can lead to hepatocellular carcinoma. HCV infection strongly induces host responses, such as the activation of the unfolded protein response, autophagy and the innate immune response. Upon HCV infection, the host induces the interferon (IFN)-mediated frontline defense to limit virus replication. Conversely, HCV employs diverse strategies to escape host innate immune surveillance. Type I IFN elicits its antiviral actions by inducing a wide array of IFN-stimulated genes (ISGs). Nevertheless, the mechanisms by which these ISGs participate in IFN-mediated anti-HCV actions remain largely unknown. In this review, we first outline the signaling pathways known to be involved in the production of type I IFN and ISGs and the tactics that HCV uses to subvert innate immunity. Then, we summarize the effector mechanisms of scaffold ISGs known to modulate IFN function in HCV replication. We also highlight the potential functions of emerging ISGs, which were identified from genome-wide siRNA screens, in HCV replication. Finally, we discuss the functions of several cellular determinants critical for regulating host immunity in HCV replication. This review will provide a basis for understanding the complexity and functionality of the pleiotropic IFN system in HCV infection. Elucidation of the specificity and the mode of action of these emerging ISGs will also help to identify novel cellular targets against which effective HCV therapeutics can be developed.
Collapse
|
7
|
Emerging roles of interferon-stimulated genes in the innate immune response to hepatitis C virus infection. Cell Mol Immunol 2014; 11:218-20. [PMID: 25544499 DOI: 10.1038/cmi.2014.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 01/03/2014] [Accepted: 01/06/2014] [Indexed: 12/16/2022] Open
Abstract
Infection with hepatitis C virus (HCV), a major viral cause of chronic liver disease, frequently progresses to steatosis and cirrhosis, which can lead to hepatocellular carcinoma. HCV infection strongly induces host responses, such as the activation of the unfolded protein response, autophagy and the innate immune response. Upon HCV infection, the host induces the interferon (IFN)-mediated frontline defense to limit virus replication. Conversely, HCV employs diverse strategies to escape host innate immune surveillance. Type I IFN elicits its antiviral actions by inducing a wide array of IFN-stimulated genes (ISGs). Nevertheless, the mechanisms by which these ISGs participate in IFN-mediated anti-HCV actions remain largely unknown. In this review, we first outline the signaling pathways known to be involved in the production of type I IFN and ISGs and the tactics that HCV uses to subvert innate immunity. Then, we summarize the effector mechanisms of scaffold ISGs known to modulate IFN function in HCV replication. We also highlight the potential functions of emerging ISGs, which were identified from genome-wide siRNA screens, in HCV replication. Finally, we discuss the functions of several cellular determinants critical for regulating host immunity in HCV replication. This review will provide a basis for understanding the complexity and functionality of the pleiotropic IFN system in HCV infection. Elucidation of the specificity and the mode of action of these emerging ISGs will also help to identify novel cellular targets against which effective HCV therapeutics can be developed.
Collapse
|
8
|
Downregulation of inducible nitric oxide synthase (iNOS) expression is implicated in the antiviral activity of acetylsalicylic acid in HCV-expressing cells. Arch Virol 2014; 159:3321-8. [PMID: 25106115 DOI: 10.1007/s00705-014-2201-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 07/30/2014] [Indexed: 12/30/2022]
Abstract
Previously, we described that acetylsalicylic acid (ASA) decreases HCV expression, but the mechanisms involved have not been clearly established. We evaluated the participation of inducible nitric oxide synthase (iNOS) in the regulation of HCV-RNA induced by ASA. Huh7 cells expressing non-structural HCV proteins were exposed to 4 mM ASA and incubated at the same times we reported HCV downregulation (24-72 h), and iNOS mRNA and protein levels were then measured by real-time PCR and Western blot, respectively. Nitric oxide levels were measured at the same time. Inhibition of iNOS mRNA by small interfering RNAs (siRNA) and activation of the iNOS gene promoter by ASA treatment were evaluated. In Huh7 replicon cells treated with ASA, we found decreased levels of iNOS mRNA, iNOS protein and nitrosylated protein levels at 48-72 h. ASA exposure also reduced the transactivation of the iNOS promoter in HCV replicon cells at 48 h, and this was partly due to the decrease in the affinity of transcription factor C/EBP-β for its binding site in the iNOS promoter. siRNA silencing of iNOS decreased HCV-RNA expression (65 %) and potentiated the antiviral effect (80 %) of ASA compared with control cells. ASA reduces iNOS expression by downregulating promoter activity, mRNA and protein levels at the same time that it decreases HCV expression. These findings suggest that the antiviral activity of ASA is mediated partially through the modulation of iNOS.
Collapse
|
9
|
Au HHT, Jan E. Novel viral translation strategies. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 5:779-801. [PMID: 25045163 PMCID: PMC7169809 DOI: 10.1002/wrna.1246] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 05/03/2014] [Accepted: 05/08/2014] [Indexed: 01/06/2023]
Abstract
Viral genomes are compact and encode a limited number of proteins. Because they do not encode components of the translational machinery, viruses exhibit an absolute dependence on the host ribosome and factors for viral messenger RNA (mRNA) translation. In order to recruit the host ribosome, viruses have evolved unique strategies to either outcompete cellular transcripts that are efficiently translated by the canonical translation pathway or to reroute translation factors and ribosomes to the viral genome. Furthermore, viruses must evade host antiviral responses and escape immune surveillance. This review focuses on some recent major findings that have revealed unconventional strategies that viruses utilize, which include usurping the host translational machinery, modulating canonical translation initiation factors to specifically enhance or repress overall translation for the purpose of viral production, and increasing viral coding capacity. The discovery of these diverse viral strategies has provided insights into additional translational control mechanisms and into the viral host interactions that ensure viral protein synthesis and replication. WIREs RNA 2014, 5:779–801. doi: 10.1002/wrna.1246 This article is categorized under:
Translation > Translation Mechanisms Translation > Translation Regulation
Collapse
Affiliation(s)
- Hilda H T Au
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
| | | |
Collapse
|
10
|
Karamichali E, Foka P, Tsitoura E, Kalliampakou K, Kazazi D, Karayiannis P, Georgopoulou U, Mavromara P. HCV NS5A co-operates with PKR in modulating HCV IRES-dependent translation. INFECTION GENETICS AND EVOLUTION 2014; 26:113-22. [PMID: 24815730 DOI: 10.1016/j.meegid.2014.04.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/15/2014] [Accepted: 04/19/2014] [Indexed: 12/11/2022]
Abstract
Translation initiation of the Hepatitis C virus (HCV) genome is driven by an internal ribosome entry site (IRES), located within the 5' non-coding region. Several studies have suggested that different cellular non canonical proteins or viral proteins can regulate the HCV IRES activity. However, the role of the viral proteins on HCV translation remains controversial. In this report, we confirmed previous studies showing that NS5A down-regulates IRES activity in HepG2 but not in Huh7 cells suggesting that the NS5A effect on HCV IRES is cell-type dependent. Additionally, we provide strong evidence that activated PKR up-regulates the IRES activity while silencing of endogenous PKR had the opposite effect. Furthermore, we present data indicating that the NS5A-mediated inhibitory effect on IRES-dependent translation could be linked with the PKR inactivation. Finally, we show that NS5A from GBV-C but not from GBV-B down-regulates HCV IRES activity in the absence or the presence of PKR over expression. Notably, HCV and GBV-C but not GBV-B NS5A contains a previously identified PKR interacting protein domain.
Collapse
Affiliation(s)
- Eirini Karamichali
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece; University of Patras, School of Health Sciences, Department of Pharmacy, Greece
| | - Pelagia Foka
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece
| | - Eliza Tsitoura
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece
| | | | - Dorothea Kazazi
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece
| | - Peter Karayiannis
- Molecular Virology/Microbiology, University of Nicosia Medical School, Cyprus
| | | | - Penelope Mavromara
- Molecular Virology Laboratory, Hellenic Pasteur Institute, Athens, Greece.
| |
Collapse
|
11
|
Nandakumar R, Finsterbusch K, Lipps C, Neumann B, Grashoff M, Nair S, Hochnadel I, Lienenklaus S, Wappler I, Steinmann E, Hauser H, Pietschmann T, Kröger A. Hepatitis C virus replication in mouse cells is restricted by IFN-dependent and -independent mechanisms. Gastroenterology 2013; 145:1414-23.e1. [PMID: 23973921 DOI: 10.1053/j.gastro.2013.08.037] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 08/10/2013] [Accepted: 08/14/2013] [Indexed: 01/01/2023]
Abstract
BACKGROUND & AIMS Current treatment strategies for hepatitis C virus (HCV) infection include pegylated interferon (IFN)-alfa and ribavirin. Approximately 50% of patients control HCV infection after treatment, but the broad range of patients' outcomes and responses to treatment, among all genotypes, indicates a role for host factors. Although the IFN system is important in limiting HCV replication, the virus has evolved mechanisms to circumvent the IFN response. However, direct, IFN-independent antiviral processes also might help control HCV replication. We examined the role of IFN-independent responses against HCV replication. METHODS We analyzed replication of the subgenomic JFH1 replicon in embryonic fibroblasts and primary hepatocytes from mice with disruptions in genes encoding factors in the IFN-dependent and alternative antiviral pathways (signal transducers and activators of transcription 1 [STAT1], protein kinase R, interferon regulatory factors (IRF) IRF-1, IRF-3, IRF-5, IRF-7, mitochondrial antiviral signaling molecule [MAVS], and IFN receptor [IFNAR]). We also assessed the effects of expression of these factors by mouse primary hepatocytes on HCV replication. RESULTS In addition to IRF-3- and IFN-mediated antiviral responses, IFN-independent, but IRF-1- and IRF-5-dependent mechanisms, restrict HCV replication in mouse embryonic fibroblasts. In primary hepatocytes these IFN-independent require MAVS and IRF-1. CONCLUSIONS HCV replication is limited by interferon-mediated pathways as well pathways that are independent of type I IFNs. IRF1 and IRF5 control IFN-independent signaling events that lead to antiviral responses. We observed antiviral roles of IRF1 and IRF5 that were IFN-independent and cell-type specific. These mechanisms are important in controlling viruses that interfere with the IFN signaling because cells retain the ability to induce functional but local antiviral states through expression of interferon-stimulated genes.
Collapse
Affiliation(s)
- Ramya Nandakumar
- Research Group Innate Immunity and Infection, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Interferon and ribavirin combination treatment synergistically inhibit HCV internal ribosome entry site mediated translation at the level of polyribosome formation. PLoS One 2013; 8:e72791. [PMID: 24009705 PMCID: PMC3751885 DOI: 10.1371/journal.pone.0072791] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 07/12/2013] [Indexed: 12/20/2022] Open
Abstract
Purpose Although chronic hepatitis C virus (HCV) infection has been treated with the combination of interferon alpha (IFN-α) and ribavirin (RBV) for over a decade, the mechanism of antiviral synergy is not well understood. We aimed to determine the synergistic antiviral mechanisms of IFN-α and RBV combination treatment using HCV cell culture. Methods The antiviral efficacy of IFN-α, RBV alone and in combination was quantitatively measured using HCV infected and replicon cell culture. Direct antiviral activity of these two drugs at the level of HCV internal ribosome entry site (IRES) mediated translation in Huh-7 cell culture was investigated. The synergistic antiviral effect of IFN-α and RBV combination treatment was verified using both the CalcuSyn Software and MacSynergy Software. Results RBV combination with IFN-α efficiently inhibits HCV replication cell culture. Our results demonstrate that IFN-α, interferon lambda (IFN-λ) and RBV each inhibit the expression of HCV IRES-GFP and that they have a minimal effect on the expression of GFP in which the translation is not IRES dependent. The combination treatments of RBV along with IFN-α or IFN-λ were highly synergistic with combination indexes <1. We show that IFN-α treatment induce levels of PKR and eIF2α phosphorylation that prevented ribosome loading of the HCV IRES-GFP mRNA. Silencing of PKR expression in Huh-7 cells prevented the inhibitory effect of IFN-α on HCV IRES-GFP expression. RBV also blocked polyribosome loading of HCV-IRES mRNA through the inhibition of cellular IMPDH activity, and induced PKR and eIF2α phosphorylation. Knockdown of PKR or IMPDH prevented RBV induced HCV IRES-GFP translation. Conclusions We demonstrated both IFN-α and RBV inhibit HCV IRES through prevention of polyribosome formation. The combination of IFN-α and RBV treatment synergistically inhibits HCV IRES translation via using two different mechanisms involving PKR activation and depletion of intracellular guanosine pool through inhibition of IMPDH.
Collapse
|
13
|
Watanabe T, Hiasa Y, Tokumoto Y, Hirooka M, Abe M, Ikeda Y, Matsuura B, Chung RT, Onji M. Protein kinase R modulates c-Fos and c-Jun signaling to promote proliferation of hepatocellular carcinoma with hepatitis C virus infection. PLoS One 2013; 8:e67750. [PMID: 23844083 PMCID: PMC3699507 DOI: 10.1371/journal.pone.0067750] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 05/22/2013] [Indexed: 12/22/2022] Open
Abstract
Double-stranded RNA-activated protein kinase R (PKR) is known to be upregulated by hepatitis C virus (HCV) and overexpressed in hepatocellular carcinoma (HCC). However, the precise roles of PKR in HCC with HCV infection remain unclear. Two HCV replicating cell lines (JFH-1 and H77s), generated by transfection of Huh7.5.1 cells, were used for experiments reported here. PKR expression was modulated with siRNA and a PKR expression plasmid, and cancer-related genes were assessed by real-time PCR and Western blotting; cell lines were further analyzed using a proliferation assay. Modulation of genes by PKR was also assessed in 34 human HCC specimens. Parallel changes in c-Fos and c-Jun gene expression with PKR were observed. Levels of phosphorylated c-Fos and c-Jun were upregulated by an increase of PKR, and were related to levels of phosphorylated JNK1 and Erk1/2. DNA binding activities of c-Fos and c-Jun also correlated with PKR expression, and cell proliferation was dependent on PKR-modulated c-Fos and c-Jun expression. Coordinate expression of c-Jun and PKR was confirmed in human HCC specimens with HCV infection. PKR upregulated c-Fos and c-Jun activities through activation of Erk1/2 and JNK1, respectively. These modulations resulted in HCC cell proliferation with HCV infection. These findings suggest that PKR-related proliferation pathways could be an attractive therapeutic target.
Collapse
Affiliation(s)
- Takao Watanabe
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Yoichi Hiasa
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
- * E-mail:
| | - Yoshio Tokumoto
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Masashi Hirooka
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Masanori Abe
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Yoshio Ikeda
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Bunzo Matsuura
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| | - Raymond T. Chung
- Gastrointestinal Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Morikazu Onji
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Toon, Ehime, Japan
| |
Collapse
|
14
|
Rivas-Estilla AM, Bryan-Marrugo OL, Trujillo-Murillo K, Pérez-Ibave D, Charles-Niño C, Pedroza-Roldan C, Ríos-Ibarra C, Ramírez-Valles E, Ortiz-López R, Islas-Carbajal MC, Nieto N, Rincón-Sánchez AR. Cu/Zn superoxide dismutase (SOD1) induction is implicated in the antioxidative and antiviral activity of acetylsalicylic acid in HCV-expressing cells. Am J Physiol Gastrointest Liver Physiol 2012; 302:G1264-73. [PMID: 22442156 DOI: 10.1152/ajpgi.00237.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We evaluated the participation of oxidative stress in the negative regulation of hepatitis C virus (HCV)-RNA induced by acetylsalicylic acid (ASA). We used the HCV subgenomic replicon cell system that stably expresses HCV-nonstructural proteins (Huh7 HCV replicon cells) and the parental cell line. Cells were exposed to 4 mM ASA at different times (12-72 h), and pyrrolidine dithiocarbamate (PDTC) was used as an antioxidant control. Reactive oxygen species (ROS) production, oxidized protein levels, cytosolic superoxide dismutase (Cu/Zn-SOD), and glutathione peroxidase (GPx) activity were measured to evaluate oxidative stress. In addition, viral RNA and prostaglandin (PGE(2)) levels were determined. We observed that ASA treatment decreased ROS production and oxidized protein levels in a time-dependent fashion in both parental and HCV replicon cells with a greater extent in the latter. Similar results were found with PDTC exposure. Average GPx activity was decreased, whereas a striking increase was observed in average cytosolic SOD activity at 48 and 72 h in both cells exposed to ASA, compared with untreated cells. HCV replicon cells showed higher levels of Cu/Zn-SOD expression (mRNA and protein) with ASA treatment (48 and 72 h), whereas NS5A protein levels showed decreased expression. In addition, we found that inhibition of SOD1 expression reversed the effect of ASA. Interestingly, PDTC downregulated HCV-RNA expression (55%) and PGE(2) (60%) levels, imitating ASA exposure. These results suggest that ASA treatment could reduce cellular oxidative stress markers and modify Cu/Zn-SOD expression, a phenomenon that may contribute to the mechanisms involved in HCV downregulation.
Collapse
Affiliation(s)
- Ana María Rivas-Estilla
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo León, México.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Minisini R, Giarda P, Grossi G, Bitetto D, Toniutto P, Falleti E, Avellini C, Occhino G, Fabris C, Pirisi M. Early activation of interferon-stimulated genes in human liver allografts: relationship with acute rejection and histological outcome. J Gastroenterol 2011; 46:1307-15. [PMID: 21789480 DOI: 10.1007/s00535-011-0440-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Accepted: 06/19/2011] [Indexed: 02/04/2023]
Abstract
BACKGROUND Innate immunity mechanisms have been shown to play a paramount role in organ transplantation. Our aim was to investigate the hypothesis that activation of the interferon system may affect clinically relevant outcomes, such as acute rejection and/or early fibrosis progression, after liver transplantation. METHODS We studied 71 consecutive recipients (57 males; 25 with hepatitis C) who underwent two per protocol graft biopsies: the first, within 60 days after the transplant operation (median 24) and the second, after 1 year. The mRNA expression for five interferon-stimulated genes (Mx1, OAS2, PKR, IRF7A, IFI16) was measured on the first biopsy specimens. The main outcome measures were acute rejection during the first post-transplant year and fibrosis progression at the second biopsy. RESULTS On multivariate analysis, the independent predictors of gene expression were hepatitis C (Mx1, OAS2, PKR and IFI16), donor age (IFI16) and recipient gender (IRF7A) (P < .05 for all). During the first post-transplant year, 19/71 patients (27%) had acute cellular rejection. At multivariate analysis, acute cellular rejection was independently predicted by high IRF7A mRNA expression. At the end of follow-up, 25 patients had some degree of fibrosis (F2 or higher in seven cases). On multivariate analysis, hepatitis C etiology, recipient age, and OAS2 overexpression were independent predictors of early fibrosis progression. CONCLUSIONS In the early postoperative period of liver transplantation, interferon-stimulated gene activation is dependent on hepatitis C recurrence (the main factor responsible for early fibrosis progression) and donor age, and is related to the risk of acute cellular rejection.
Collapse
Affiliation(s)
- Rosalba Minisini
- Department of Clinical and Experimental Medicine, Università del Piemonte Orientale A. Avogadro, Via G. Solaroli 17, 28100 Novara, Italy.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Poat B, Hazari S, Chandra PK, Gunduz F, Alvarez X, Balart LA, Garry RF, Dash S. Intracellular expression of IRF9 Stat fusion protein overcomes the defective Jak-Stat signaling and inhibits HCV RNA replication. Virol J 2010; 7:265. [PMID: 20939906 PMCID: PMC2964675 DOI: 10.1186/1743-422x-7-265] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Accepted: 10/12/2010] [Indexed: 01/05/2023] Open
Abstract
Interferon alpha (IFN-α) binds to a cell surface receptor that activates the Jak-Stat signaling pathway. A critical component of this pathway is the translocation of interferon stimulated gene factor 3 (a complex of three proteins Stat1, Stat2 and IRF9) to the nucleus to activate antiviral genes. A stable sub-genomic replicon cell line resistant to IFN-α was developed in which the nuclear translocation of Stat1 and Stat2 proteins was prevented due to the lack of phosphorylation; whereas the nuclear translocation of IRF9 protein was not affected. In this study, we sought to overcome defective Jak-Stat signaling and to induce an antiviral state in the IFN-α resistant replicon cell line by developing a chimera IRF9 protein fused with the trans activating domain (TAD) of either a Stat1 (IRF9-S1C) or Stat2 (IRF9-S2C) protein. We show here that intracellular expression of fusion proteins using the plasmid constructs of either IRF9-S1C or IRF9-S2C, in the IFN-α resistant cells, resulted in an increase in Interferon Stimulated Response Element (ISRE) luciferase promoter activity and significantly induced HLA-1 surface expression. Moreover, we show that transient transfection of IRF9-S1C or IRF9-S2C plasmid constructs into IFN-α resistant replicon cells containing sub-genomic HCV1b and HCV2a viruses resulted in an inhibition of viral replication and viral protein expression independent of IFN-α treatment. The results of this study indicate that the recombinant fusion proteins of IRF9-S1C, IRF9-S2C alone, or in combination, have potent antiviral properties against the HCV in an IFN-α resistant cell line with a defective Jak-Stat signaling.
Collapse
Affiliation(s)
- Bret Poat
- Department of Pathology and Laboratory Medicine, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA-70112, USA
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Rojas M, Arias CF, López S. Protein kinase R is responsible for the phosphorylation of eIF2alpha in rotavirus infection. J Virol 2010; 84:10457-66. [PMID: 20631127 PMCID: PMC2950594 DOI: 10.1128/jvi.00625-10] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 07/07/2010] [Indexed: 11/20/2022] Open
Abstract
The eukaryotic initiation translation factor 2 (eIF2) represents a key point in the regulation of protein synthesis. This factor delivers the initiator Met-tRNA to the ribosome, a process that is conserved in all eukaryotic cells. Many types of stress reduce global translation by triggering the phosphorylation of the α subunit of eIF2, which reduces the formation of the preinitiation translation complexes. Early during rotavirus infection, eIF2α becomes phosphorylated, and even under these conditions viral protein synthesis is not affected, while most of the cell protein synthesis is blocked. Here, we found that the kinase responsible for the phosphorylation of eIF2α in rotavirus-infected cells is PKR, since in mouse embryonic fibroblasts deficient in the kinase domain of PKR, or in MA104 cells where the expression of PKR was knocked down by RNA interference, eIF2α was not phosphorylated upon rotavirus infection. The viral component responsible for the activation of PKR seems to be viral double-stranded RNA, which is found in the cytoplasm of infected cells, outside viroplasms. Taken together, these results suggest that rotaviruses induce the PKR branch of the interferon system and have evolved a mechanism to translate its proteins, surpassing the block imposed by eIF2α phosphorylation.
Collapse
MESH Headings
- Animals
- Cell Line
- Cells, Cultured
- Enzyme Activation
- Eukaryotic Initiation Factor-2/genetics
- Eukaryotic Initiation Factor-2/metabolism
- Gene Knockdown Techniques
- Host-Pathogen Interactions/physiology
- Macaca mulatta
- Mice
- Mice, Knockout
- Mutant Proteins/antagonists & inhibitors
- Mutant Proteins/genetics
- Mutant Proteins/metabolism
- Phosphorylation
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Ribosome Subunits, Small, Eukaryotic/virology
- Rotavirus/genetics
- Rotavirus/pathogenicity
- Rotavirus/physiology
- Rotavirus Infections/metabolism
- Transfection
- Viral Proteins/biosynthesis
- eIF-2 Kinase/antagonists & inhibitors
- eIF-2 Kinase/deficiency
- eIF-2 Kinase/genetics
- eIF-2 Kinase/metabolism
Collapse
Affiliation(s)
- Margarito Rojas
- Departamento de Génetica del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM, Cuernavaca, Morelos 62210, México
| | - Carlos F. Arias
- Departamento de Génetica del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM, Cuernavaca, Morelos 62210, México
| | - Susana López
- Departamento de Génetica del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, UNAM, Cuernavaca, Morelos 62210, México
| |
Collapse
|
18
|
Rosenfeld AB, Racaniello VR. Components of the multifactor complex needed for internal initiation by the IRES of hepatitis C virus in Saccharomyces cerevisiae. RNA Biol 2010; 7:596-605. [PMID: 20935471 DOI: 10.4161/rna.7.5.13096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Interaction between the 40S ribosomal subunit and the IRES of hepatitis C virus (HCV) is thought to be independent of initiation proteins, while joining of the 60S ribosomal subunit, and initiation of translation is dependent upon components of the translation machinery. An established in vivo functional assay for internal initiation mediated by the HCV IRES was used to identify proteins needed for IRES dependent translation in Saccharomyces cerevisiae strains possessing alterations of the translation machinery. Internal initiation dependent upon the HCV IRES was abrogated in strains lacking eIF5B, and reduced in strains with altered eIF3, either lacking the Hcr1p subunit, a component of eIF3 not previously known to interact with HCV RNA, or possessing an amino acid change in the Rpg1p subunit. The HCV RNA-induced conformational change in the 40S subunit might affect positioning of eIF3 and lead to different interactions between the ribosome, eIF3, and the multifactor complex. HCV IRES dependent initiation was unaffected in strains in which the concentration of the initiating tRNA was reduced. Alteration of the δ subunit of eIF2B, which leads to inefficient recycling, or substitution of aspartic acid for serine 51 of eIF2α had no effect on internal initiation. Production of human Pkr inhibited HCV IRES dependent initiation in yeast. The synthesis of Pkr in yeast is known to result in high levels of eIF2α phosphorylation, increased Gcn4p synthesis, and reduced ribosomal protein production. These alterations may explain the effect of Pkr synthesis on HCV IRES dependent initiation in yeast.
Collapse
Affiliation(s)
- Amy B Rosenfeld
- Department of Microbiology, Columbia University College of Physicians & Surgeons, New York, NY, USA.
| | | |
Collapse
|
19
|
Abstract
The dicistrovirus is a positive-strand single-stranded RNA virus that possesses two internal ribosome entry sites (IRES) that direct translation of distinct open reading frames encoding the viral structural and nonstructural proteins. Through an unusual mechanism, the intergenic region (IGR) IRES responsible for viral structural protein expression mimics a tRNA to directly recruit the ribosome and set the ribosome into translational elongation. In this study, we explored the mechanism of host translational shutoff in Drosophila S2 cells infected by the dicistrovirus, cricket paralysis virus (CrPV). CrPV infection of S2 cells results in host translational shutoff concomitant with an increase in viral protein synthesis. CrPV infection resulted in the dissociation of eukaryotic translation initiation factor 4G (eIF4G) and eIF4E early in infection and the induction of deIF2alpha phosphorylation at 3 h postinfection, which lags after the initial inhibition of host translation. Forced dephosphorylation of deIF2alpha by overexpression of dGADD34, which activates protein phosphatase I, did not prevent translational shutoff nor alter virus production, demonstrating that deIF2alpha phosphorylation is dispensable for host translational shutoff. However, premature induction of deIF2alpha phosphorylation by thapsigargin treatment early in infection reduced viral protein synthesis and replication. Finally, translation mediated by the 5' untranslated region (5'UTR) and the IGR IRES were resistant to impairment of eIF4F or eIF2 in translation extracts. These results support a model by which the alteration of the deIF4F complex contribute to the shutoff of host translation during CrPV infection, thereby promoting viral protein synthesis via the CrPV 5'UTR and IGR IRES.
Collapse
|
20
|
Paytubi S, Wang X, Lam YW, Izquierdo L, Hunter MJ, Jan E, Hundal HS, Proud CG. ABC50 promotes translation initiation in mammalian cells. J Biol Chem 2009; 284:24061-73. [PMID: 19570978 DOI: 10.1074/jbc.m109.031625] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ABC50 is an ATP-binding cassette (ABC) protein, which, unlike most ABC proteins, does not possess membrane-spanning domains. ABC50 interacts with eukaryotic initiation factor 2 (eIF2), which plays a key role in translation initiation and its control. ABC50 binds to ribosomes, and this interaction requires both the N-terminal domain and at least one ABC domain. Knockdown of ABC50 by RNA interference impaired translation of both cap-dependent and -independent reporters, consistent with a positive role for ABC50 in the function of eIF2, which is required for both types of translation initiation. Mutation of the Walker box A or B motifs in both ABC regions of ABC50 yielded a mutant protein that exerted a dominant-interfering phenotype with respect to protein synthesis and translation initiation. Importantly, although dominant-interfering mutants of ABC50 impaired cap-dependent translation, translation driven by certain internal ribosome entry segments was not inhibited. ABC50 is located in the cytoplasm and nucleoplasm but not in the nucleolus. Thus, ABC50 is not likely to be directly involved in early ribosomal biogenesis, unlike some other ABC proteins. Taken together, the present data show that ABC50 plays a key role in translation initiation and has functions that are distinct from those of other non-membrane ABC proteins.
Collapse
Affiliation(s)
- Sonia Paytubi
- Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
21
|
Kang JI, Kwon SN, Park SH, Kim YK, Choi SY, Kim JP, Ahn BY. PKR protein kinase is activated by hepatitis C virus and inhibits viral replication through translational control. Virus Res 2009; 142:51-6. [PMID: 19189853 DOI: 10.1016/j.virusres.2009.01.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 01/09/2009] [Accepted: 01/09/2009] [Indexed: 02/05/2023]
Abstract
Hepatitis C virus (HCV) infection is currently treated with IFNalpha-based therapy but little is known how IFNalpha inhibits HCV replication. We show here that HCV JFH1 infection of human hepatoma Huh-7 cells leads to the activation of IFN-inducible protein kinase PKR and phosphorylation of the translation initiation factor eIF2alpha. Compared to a control cell HCV replication was significantly elevated in a PKR-knockdown cell, giving rise to a 10-fold higher viral titer, and was less sensitive to IFNalpha treatment. Conversely, transient expression of PKR inhibited HCV replication in a kinase-dependent manner with concomitant increase of eIF2alpha phosphorylation. Further, expression of a phospho-mimetic eIF2alpha mutant moderately inhibited HCV replication. Together, these results demonstrate that PKR is activated by HCV infection and plays a critical antiviral role through inhibition of viral protein translation.
Collapse
Affiliation(s)
- Ju-Il Kang
- School of Life Sciences & Biotechnology, Korea University, 5-1 Anamdong, Seoul 136-701, Republic of Korea
| | | | | | | | | | | | | |
Collapse
|
22
|
Terenin IM, Dmitriev SE, Andreev DE, Shatsky IN. Eukaryotic translation initiation machinery can operate in a bacterial-like mode without eIF2. Nat Struct Mol Biol 2008; 15:836-41. [PMID: 18604219 DOI: 10.1038/nsmb.1445] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2008] [Accepted: 05/14/2008] [Indexed: 02/07/2023]
Abstract
Unlike bacteria, a specialized eukaryotic initiation factor (eIF)-2, in the form of the ternary complex eIF2-GTP-Met-tRNA(i) (Met), is used to deliver the initiator tRNA to the ribosome in all eukaryotic cells. Here we show that the hepatitis C virus (HCV) internal ribosome entry site (IRES) can direct translation without eIF2 and its GTPase-activating protein eIF5. In addition to the general eIF2- and eIF5-dependent pathway of 80S complex assembly, the HCV IRES makes use of a bacterial-like pathway requiring as initiation factors only eIF5B (an analog of bacterial IF2) and eIF3. The switch from the conventional eukaryotic mode of translation initiation to the eIF2-independent mechanism occurs when eIF2 is inactivated by phosphorylation under stress conditions.
Collapse
Affiliation(s)
- Ilya M Terenin
- A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia
| | | | | | | |
Collapse
|
23
|
Trujillo-Murillo K, Rincón-Sánchez AR, Martínez-Rodríguez H, Bosques-Padilla F, Ramos-Jiménez J, Barrera-Saldaña HA, Rojkind M, Rivas-Estilla AM. Acetylsalicylic acid inhibits hepatitis C virus RNA and protein expression through cyclooxygenase 2 signaling pathways. Hepatology 2008; 47:1462-72. [PMID: 18393288 DOI: 10.1002/hep.22215] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
UNLABELLED It has been reported that salicylates (sodium salicylate and aspirin) inhibit the replication of flaviviruses, such as Japanese encephalitis virus and dengue virus. Therefore, we considered it important to test whether acetylsalicylic acid (ASA) had anti-hepatitis C virus (HCV) activity. To this end, we examined the effects of ASA on viral replication and protein expression, using an HCV subgenomic replicon cell culture system. We incubated Huh7 replicon cells with 2-8 mM ASA for different times and measured HCV-RNA and protein levels by northern blot, real-time polymerase chain reaction, and western analysis, respectively. We found that ASA had a suppressive effect on HCV-RNA and protein levels (nearly 58%). ASA-dependent inhibition of HCV expression was not mediated by the 5'-internal ribosome entry site or 3'-untranslated regions, as determined by transfection assays using bicistronic constructs containing these regulatory regions. However, we found that HCV-induced cyclooxygenase 2 (COX-2) messenger RNA and protein levels and activity and these effects were down-regulated by ASA, possibly by a nuclear factor kappa B-independent mechanism. We also observed that the ASA-dependent inhibition of viral replication was due in part to inhibition of COX-2 and activation of p38 and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) mitogen-activated protein kinases (MAPKs). Inhibition of these kinases by SB203580 and U0126, respectively, and by short interfering RNA silencing of p38 and MEK1 MAPK prevented the antiviral effect of ASA. Taken together, our findings suggest that the anti-HCV effect of ASA in the Huh7 replicon cells is due to its inhibitory effect on COX-2 expression, which is mediated in part by the activation of MEK1/2/p38 MAPK. CONCLUSION These findings suggest the possibility that ASA could be an excellent adjuvant in the treatment of chronic HCV infection.
Collapse
Affiliation(s)
- Karina Trujillo-Murillo
- Department of Biochemistry, School of Medicine and University Hospital, Autonomous University of Nuevo Leon, Monterrey, Nuevo Leon, Mexico
| | | | | | | | | | | | | | | |
Collapse
|
24
|
Pestova TV, de Breyne S, Pisarev AV, Abaeva IS, Hellen CUT. eIF2-dependent and eIF2-independent modes of initiation on the CSFV IRES: a common role of domain II. EMBO J 2008; 27:1060-72. [PMID: 18337746 DOI: 10.1038/emboj.2008.49] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 02/21/2008] [Indexed: 02/05/2023] Open
Abstract
Specific interactions of the classical swine fever virus internal ribosomal entry site (IRES) with 40S ribosomal subunits and eukaryotic translation initiation factor (eIF)3 enable 43S preinitiation complexes containing eIF3 and eIF2-GTP-Met-tRNA(iMet) to bind directly to the initiation codon, yielding 48S initiation complexes. We report that eIF5B or eIF5B/eIF3 also promote Met-tRNA(iMet) binding to IRES-40S complexes, forming 48S complexes that can assemble elongation-competent ribosomes. Although 48S complexes assembled both by eIF2/eIF3- and eIF5B/eIF3-mediated Met-tRNA(iMet) recruitment were destabilized by eIF1, dissociation of 48S complexes formed with eIF2 could be out-competed by efficient subunit joining. Deletion of IRES domain II, which is responsible for conformational changes induced in 40S subunits by IRES binding, eliminated the sensitivity of 48S complexes assembled by eIF2/eIF3- and eIF5B/eIF3-mediated mechanisms to eIF1-induced destabilization. However, 48S complexes formed by the eIF5B/eIF3-mediated mechanism on the truncated IRES could not undergo efficient subunit joining, as reported previously for analogous complexes assembled with eIF2, indicating that domain II is essential for general conformational changes in 48S complexes, irrespective of how they were assembled, that are required for eIF5-induced hydrolysis of eIF2-bound GTP and/or subunit joining.
Collapse
Affiliation(s)
- Tatyana V Pestova
- Department of Microbiology and Immunology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA.
| | | | | | | | | |
Collapse
|
25
|
Trujillo-Murillo K, Alvarez-Martínez O, Garza-Rodríguez L, Martínez-Rodríguez H, Bosques-Padilla F, Ramos-Jiménez J, Barrera-Saldaña H, Rincón-Sánchez AR, Rivas-Estilla AM. Additive effect of ethanol and HCV subgenomic replicon expression on COX-2 protein levels and activity. J Viral Hepat 2007; 14:608-17. [PMID: 17697012 DOI: 10.1111/j.1365-2893.2006.00837.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The mechanisms by which alcohol exacerbates liver injury in patients with hepatitis C are unknown. We used the hepatitis C virus (HCV) subgenomic replicon cell system to evaluate the effect of ethanol on HCV replication and viral protein synthesis. Our results demonstrate that alcohol stimulates HCV replicon expression at both HCV-RNA and protein levels. Furthermore, we observed that ethanol treatment showed an additive effect in cyclooxygenase-2 (COX-2) protein expression and activity already induced by HCV viral proteins, and in turn increased HCV viral expression. Our results suggest that COX-2 activity is involved in ethanol-induced HCV-RNA and NS5A protein expression, because acetylsalicylic acid (ASA), a COX-1/2 inhibitor, blocked this induction and downregulated COX-2 protein expression and activity. Therefore, we suggest that ethanol increases HCV replication expression, at least in part, by upregulating a key cellular regulator of oxidative stress pathway known as COX-2 or its products.
Collapse
Affiliation(s)
- K Trujillo-Murillo
- Department of Biochemistry, School of Medicine, UANL, Monterrey, Nuevo León, México
| | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Tokumoto Y, Hiasa Y, Horiike N, Michitaka K, Matsuura B, Chung RT, Onji M. Hepatitis C virus expression and interferon antiviral action is dependent on PKR expression. J Med Virol 2007; 79:1120-7. [PMID: 17596833 DOI: 10.1002/jmv.20902] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Interferon (IFN)-inducible double-stranded RNA-activated protein kinase (PKR) is thought to play a key antiviral role against hepatitis C virus (HCV). However, demonstrating the importance of PKR expression on HCV protein synthesis in the presence or absence of IFN has proven difficult in vivo. In the present experiment, full-length HCV constructs were transiently transfected into two cell lines stably expressing T7 RNA polymerase. HCV expression was monitored under conditions of upregulated or downregulated PKR expression. In addition, IFN was monitored during downregulation of PKR. HCV expression effectively increased PKR expression, as well as that of its regulated proteins. PKR was obviously knocked down by PKR-specific siRNA, which resulted in significantly increased HCV core protein levels. Conversely, over-expression of PKR significantly suppressed HCV core levels in both cell lines. Furthermore, IFN induced high levels of PKR, whereas downregulation of PKR reversed IFN's antiviral effects and increased HCV core levels. Based on these results, it appears that HCV protein expression is directly dependent on PKR expression. PKR is antiviral toward HCV and responsible for IFN's effect against HCV.
Collapse
Affiliation(s)
- Yoshio Tokumoto
- Department of Gastroenterology and Metabology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, Japan
| | | | | | | | | | | | | |
Collapse
|
27
|
Fillebeen C, Muckenthaler M, Andriopoulos B, Bisaillon M, Mounir Z, Hentze MW, Koromilas AE, Pantopoulos K. Expression of the subgenomic hepatitis C virus replicon alters iron homeostasis in Huh7 cells. J Hepatol 2007; 47:12-22. [PMID: 17399844 DOI: 10.1016/j.jhep.2007.01.035] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 12/06/2006] [Accepted: 01/02/2007] [Indexed: 12/21/2022]
Abstract
BACKGROUND/AIMS Infection with hepatitis C virus (HCV) is associated with alterations in body iron homeostasis by poorly defined mechanisms. To seek for molecular links, we employed an established cell culture model for viral replication, and assessed how the expression of an HCV subgenomic replicon affects iron metabolism in host Huh7 hepatoma cells. METHODS The expression of iron metabolism genes and parameters defining the cellular iron status were analyzed and compared between parent and replicon Huh7 cells. RESULTS By using the IronChip microarray platform, we observed replicon-induced changes in expression profiles of iron metabolism genes. Notably, ceruloplasmin mRNA and protein expression were decreased in replicon cells. In addition, transferrin receptor 1 (TfR1) was also downregulated, while ferroportin levels were elevated, resulting in reduced iron uptake and increased iron release capacity of replicon cells. These responses were associated with an iron-deficient phenotype, manifested in decreased levels of the "labile iron pool" and concomitant induction of IRE-binding activity and IRP2 expression. Furthermore, hemin-treated replicon cells exhibited a defect in retaining iron. The clearance of the replicon by prolonged treatment with interferon-alpha only partially reversed the iron-deficient phenotype but almost completely restored the capacity of cured cells to retain iron. CONCLUSIONS We propose that Huh7 cells undergo genetic reprogramming to permit subgenomic viral replication that results in reduction of intracellular iron levels. This response may provide a mechanism to bypass iron-mediated inactivation of the viral RNA polymerase NS5B.
Collapse
Affiliation(s)
- Carine Fillebeen
- Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital, 3755 Cote-Ste-Catherine Road, Montreal, Que., Canada H3T 1E2
| | | | | | | | | | | | | | | |
Collapse
|
28
|
MacCallum PR, Jack SC, Egan PA, McDermott BT, Elliott RM, Chan SW. Cap-dependent and hepatitis C virus internal ribosome entry site-mediated translation are modulated by phosphorylation of eIF2alpha under oxidative stress. J Gen Virol 2006; 87:3251-3262. [PMID: 17030858 DOI: 10.1099/vir.0.82051-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Chronic hepatitis C is often associated with oxidative stress. Hepatitis C virus (HCV) utilizes an internal ribosome entry site (IRES) element for translation, in contrast to cap-dependent translation of the majority of cellular proteins. To understand how virus translation is modulated under oxidative stress, HCV IRES-mediated translation was compared with cap-dependent translation using a bicistronic reporter construct and hydrogen peroxide (H2O2) as a stress inducer. In H2O2-sensitive HeLa cells, H2O2 repressed translation in a time- and dose-dependent manner, concomitant with the kinetics of eIF2alpha phosphorylation. A phosphomimetic of eIF2alpha, which mimics the structure of the phosphorylated eIF2alpha, was sufficient to repress translation in the absence of H2O2. In H2O2-resistant HepG2 cells, H2O2 activated both HCV IRES-mediated and cap-dependent translation, associated with an increased level of phospho-eIF2alpha. It was postulated that H2O2 might stimulate translation in HepG2 cells via an eIF2alpha-independent mechanism, whereas the simultaneous phosphorylation of eIF2alpha repressed part of the translational activities. Indeed, the translational repression was released in the presence of a non-phosphorylatable mutant, eIF2alpha-SA, resulting in further enhancement of both translational activities after exposure to H2O2. In HuH7 cells, which exhibited an intermediate level of sensitivity towards H2O2, both HCV IRES-mediated and cap-dependent translational activities were upregulated after treatment with various doses of H2O2, but the highest level of induction was achieved with a low level of H2O2, which may represent the physiological level of H2O2. At this level, the HCV IRES-mediated translation was preferentially upregulated compared with cap-dependent translation.
Collapse
Affiliation(s)
- Paul R MacCallum
- Faculty of Life Sciences, The University of Manchester, Jackson's Mill, PO Box 88, Sackville Street, Manchester M60 1QD, UK
| | - Samantha C Jack
- Faculty of Life Sciences, The University of Manchester, Jackson's Mill, PO Box 88, Sackville Street, Manchester M60 1QD, UK
| | - Philip A Egan
- Faculty of Life Sciences, The University of Manchester, Jackson's Mill, PO Box 88, Sackville Street, Manchester M60 1QD, UK
| | - Benjamin T McDermott
- Faculty of Life Sciences, The University of Manchester, Jackson's Mill, PO Box 88, Sackville Street, Manchester M60 1QD, UK
| | - Richard M Elliott
- Centre for Biomolecular Sciences, School of Biology, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK
| | - Shiu-Wan Chan
- Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, UK
- Faculty of Life Sciences, The University of Manchester, Jackson's Mill, PO Box 88, Sackville Street, Manchester M60 1QD, UK
| |
Collapse
|
29
|
Xiong Z, Liu E, Yan Y, Silver RT, Yang F, Chen IH, Chen Y, Verstovsek S, Wang H, Prchal J, Yang XF. An unconventional antigen translated by a novel internal ribosome entry site elicits antitumor humoral immune reactions. THE JOURNAL OF IMMUNOLOGY 2006; 177:4907-16. [PMID: 16982933 PMCID: PMC3902139 DOI: 10.4049/jimmunol.177.7.4907] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Self-tumor Ags that elicit antitumor immune responses in responses to IFN-alpha stimulation remain poorly defined. We screened a human testis cDNA library with sera from three polycythemia vera patients who responded to IFN-alpha and identified a novel Ag, MPD6. MPD6 belongs to the group of cryptic Ags without conventional genomic structure and is encoded by a cryptic open reading frame located in the 3'-untranslated region of myotrophin mRNA. MPD6 elicits IgG Ab responses in a subset of polycythemia vera patients, as well as patients with chronic myelogenous leukemia and prostate cancer, suggesting that it is broadly immunogenic. The expression of myotrophin-MPD6 transcripts was up-regulated in some tumor cells, but only slightly increased in K562 cells in response to IFN-alpha treatment. By using bicistronic reporter constructs, we showed that the translation of MPD6 was mediated by a novel internal ribosome entry site (IRES) upstream of the MPD6 reading frame. Furthermore, the MPD6-IRES-mediated translation, but not myotrophin-MPD6 transcription, was significantly up-regulated in response to IFN-alpha stimulation. These findings demonstrate that a novel IRES-mediated mechanism may be responsible for the translation of unconventional self-Ag MPD6 in responsive to IFN-alpha stimulation. The eliciting antitumor immune response against unconventional Ag MPD6 in patients with myeloproliferative diseases suggests MPD6 as a potential target of novel immunotherapy.
Collapse
MESH Headings
- Amino Acid Sequence
- Antigens, Neoplasm/chemistry
- Antigens, Neoplasm/physiology
- Antigens, Neoplasm/ultrastructure
- Blotting, Northern
- Blotting, Western
- Enzyme-Linked Immunosorbent Assay
- Gene Library
- Humans
- Intercellular Signaling Peptides and Proteins/genetics
- Intercellular Signaling Peptides and Proteins/immunology
- Interferon-gamma/immunology
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/immunology
- Male
- Molecular Sequence Data
- Polycythemia Vera/immunology
- Prostatic Neoplasms/immunology
- Protein Biosynthesis
- Protein Structure, Secondary
- RNA, Messenger/analysis
- Reverse Transcriptase Polymerase Chain Reaction
- Ribosomes/chemistry
- Ribosomes/genetics
- Ribosomes/ultrastructure
- Testis/physiology
Collapse
Affiliation(s)
- Zeyu Xiong
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Enli Liu
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
| | - Yan Yan
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Richard T. Silver
- Department of Medicine, New York Presbyterian-Weill Cornell Medical Center, New York, NY 10021
| | - Fan Yang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Irene H. Chen
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Yangyang Chen
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Srdan Verstovsek
- Department of Leukemia, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Hong Wang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
| | - Josef Prchal
- Department of Medicine, University of Utah School of Medicine, Salt Lake City, UT 84112
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
| | - Xiao-Feng Yang
- Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140
- Address correspondence and reprint requests to Dr. Xiao-Feng Yang, Department of Pharmacology, Temple University School of Medicine, 3420 North Broad Street, Philadelphia, PA 19140.
| |
Collapse
|
30
|
Berlanga JJ, Baass A, Sonenberg N. Regulation of poly(A) binding protein function in translation: Characterization of the Paip2 homolog, Paip2B. RNA (NEW YORK, N.Y.) 2006; 12:1556-68. [PMID: 16804161 PMCID: PMC1524897 DOI: 10.1261/rna.106506] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The 5' cap and 3' poly(A) tail of eukaryotic mRNAs act synergistically to enhance translation. This synergy is mediated via interactions between eIF4G (a component of the eIF4F cap binding complex) and poly(A) binding protein (PABP). Paip2 (PABP-interacting protein 2) binds PABP and inhibits translation both in vitro and in vivo by decreasing the affinity of PABP for polyadenylated RNA. Here, we describe the functional characteristics of Paip2B, a Paip2 homolog. A full-length brain cDNA of Paip2B encodes a protein that shares 59% identity and 80% similarity with Paip2 (Paip2A), with the highest conservation in the two PABP binding domains. Paip2B acts in a manner similar to Paip2A to inhibit translation of capped and polyadenylated mRNAs both in vitro and in vivo by displacing PABP from the poly(A) tail. Also, similar to Paip2A, Paip2B does not affect the translation mediated by the internal ribosome entry site (IRES) of hepatitis C virus (HCV). However, Paip2A and Paip2B differ with respect to both mRNA and protein distribution in different tissues and cell lines. Paip2A is more highly ubiquitinated than is Paip2B and is degraded more rapidly by the proteasome. Paip2 protein degradation may constitute a primary mechanism by which cells regulate PABP activity in translation.
Collapse
Affiliation(s)
- Juan José Berlanga
- Department of Biochemistry and McGill Cancer Center, McGill University, Montréal, Québec, Canada.
| | | | | |
Collapse
|
31
|
Chang KS, Cai Z, Zhang C, Sen GC, Williams BRG, Luo G. Replication of hepatitis C virus (HCV) RNA in mouse embryonic fibroblasts: protein kinase R (PKR)-dependent and PKR-independent mechanisms for controlling HCV RNA replication and mediating interferon activities. J Virol 2006; 80:7364-74. [PMID: 16840317 PMCID: PMC1563689 DOI: 10.1128/jvi.00586-06] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2006] [Accepted: 05/09/2006] [Indexed: 12/11/2022] Open
Abstract
Hepatitis C virus (HCV) infection causes chronic hepatitis and is currently treated with alpha interferon (IFN-alpha)-based therapies. The underlying mechanisms of chronic HCV infection and IFN-based therapies, however, have not been defined. Protein kinase R (PKR) was implicated in the control of HCV replication and mediation of IFN-induced antiviral response. In this report, we demonstrate that a subgenomic RNA replicon of genotype 2a HCV replicated efficiently in mouse embryonic fibroblasts (MEFs), as determined by cell colony formation efficiency and the detection of HCV proteins and both positive- and negative-strand RNAs. Additionally, the subgenomic HCV RNA was found to replicate more efficiently in the PKR knockout (PKR(-/-)) MEF than in the wild-type (PKR(+/+)) MEF. The knockdown expression of PKR by specific small interfering RNAs significantly enhanced the level of HCV RNA replication, suggesting that PKR is involved in the control of HCV RNA replication. The level of ISG56 (p56) was induced by HCV RNA replication, indicating the activation of PKR-independent antiviral pathways. Furthermore, IFN-alpha/beta inhibited HCV RNA replication in PKR(-/-) MEFs as efficiently as in PKR(+/+) MEFs. These findings demonstrate that PKR-independent antiviral pathways play important roles in controlling HCV replication and mediating IFN-induced antiviral effect. Our findings also provide a foundation for the development of transgenic mouse models of HCV replication and set a stage to further define the roles of cellular genes in the establishment of chronic HCV infection and the mediation of intracellular innate antiviral response by using MEFs derived from diverse gene knockout animals.
Collapse
Affiliation(s)
- Kyung-Soo Chang
- Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536-0298, USA
| | | | | | | | | | | |
Collapse
|
32
|
Lancaster AM, Jan E, Sarnow P. Initiation factor-independent translation mediated by the hepatitis C virus internal ribosome entry site. RNA (NEW YORK, N.Y.) 2006; 12:894-902. [PMID: 16556939 PMCID: PMC1440913 DOI: 10.1261/rna.2342306] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The hepatitis C viral mRNA initiates translation using an internal ribosome entry site (IRES) located in the 5' noncoding region of the viral genome. At physiological magnesium ion concentrations, the HCV IRES forms a binary complex with the 40S ribosomal subunit, recruits initiation factor eIF3 and the ternary eIF2/GTP/Met-tRNA(i)Met complex, and joins 60S subunits to assemble translation-competent 80S ribosomes. Here we show that in the presence of 5 mM MgCl2, the HCV IRES can initiate translation by an alternative mechanism that does not require known initiation factors. Specifically, the HCV IRES was shown to initiate translation in a reconstituted system consisting only of purified 40S and 60S subunits, elongation factors, and aminoacylated tRNAs at high magnesium concentration. Analyses of assembled complexes supported a mechanism by which preformed 80S ribosomes can assemble directly on the HCV IRES at high cation concentrations. This mechanism is reminiscent of that employed by the divergent IRES elements in the Dicistroviridae, exemplified by the cricket paralysis virus, which mediates initiation of protein synthesis without initiator tRNA.
Collapse
Affiliation(s)
- Alissa M Lancaster
- Department of Microbiology and Immunology, Stanford University School of Medicine, California 94305, USA
| | | | | |
Collapse
|
33
|
Parato KA, Senger D, Forsyth PAJ, Bell JC. Recent progress in the battle between oncolytic viruses and tumours. Nat Rev Cancer 2005; 5:965-76. [PMID: 16294217 DOI: 10.1038/nrc1750] [Citation(s) in RCA: 406] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In the past 5 years, the field of oncolytic virus research has matured significantly and is moving past the stage of being a laboratory novelty into a new era of preclinical and clinical trials. What have recent anticancer trials of oncolytic viruses taught us about this exciting new line of therapeutics?
Collapse
Affiliation(s)
- Kelley A Parato
- Centre for Cancer Therapeutics, Ottawa Health Research Institute, 503 Smyth Road, Ottawa, Ontario, Canada K1H 8L6
| | | | | | | |
Collapse
|
34
|
Svitkin YV, Pause A, Lopez-Lastra M, Perreault S, Sonenberg N. Complete translation of the hepatitis C virus genome in vitro: membranes play a critical role in the maturation of all virus proteins except for NS3. J Virol 2005; 79:6868-81. [PMID: 15890926 PMCID: PMC1112104 DOI: 10.1128/jvi.79.11.6868-6881.2005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We developed an in vitro translation extract from Krebs-2 cells that translates the entire open reading frame of the hepatitis C virus (HCV) strain H77 and properly processes the viral protein precursors when supplemented with canine microsomal membranes (CMMs). Translation of the C-terminal portion of the viral polyprotein in this system is documented by the synthesis of NS5B. Evidence for posttranslational modification of the viral proteins, the N-terminal glycosylation of E1 and the E2 precursor (E2-p7), and phosphorylation of NS5A is presented. With the exception of NS3, efficient generation of all virus-specific proteins is CMM dependent. A time course of the appearance of HCV products indicates that the viral polyprotein is cleaved cotranslationally. A competitive inhibitor of the NS3 protease inhibited accumulation of NS3, NS4B, NS5A, and NS5B, but not that of NS2 or structural proteins. CMMs also stabilized HCV mRNA during translation. Finally, the formyl-[35S]methionyl moiety of the initiator tRNA(Met) was incorporated exclusively into the core protein portion of the polyprotein, demonstrating that translation initiation in this system occurs with high fidelity.
Collapse
Affiliation(s)
- Yuri V Svitkin
- Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6.
| | | | | | | | | |
Collapse
|
35
|
Fillebeen C, Rivas-Estilla AM, Bisaillon M, Ponka P, Muckenthaler M, Hentze MW, Koromilas AE, Pantopoulos K. Iron inactivates the RNA polymerase NS5B and suppresses subgenomic replication of hepatitis C Virus. J Biol Chem 2005; 280:9049-57. [PMID: 15637067 DOI: 10.1074/jbc.m412687200] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Clinical data suggest that iron is a negative factor in chronic hepatitis C; however, the molecular mechanisms by which iron modulates the infectious cycle of hepatitis C virus (HCV) remain elusive. To explore this, we utilized cells expressing a HCV replicon as a well-established model for viral replication. We demonstrate that iron administration dramatically inhibits the expression of viral proteins and RNA, without significantly affecting its translation or stability. Experiments with purified recombinant HCV RNA polymerase (NS5B) revealed that iron binds specifically and with high affinity (apparent Kd: 6 and 60 microM for Fe2+ and Fe3+, respectively) to the protein's Mg2+-binding pocket, thereby inhibiting its enzymatic activity. We propose that iron impairs HCV replication by inactivating NS5B and that its negative effects in chronic hepatitis C may be primarily due to attenuation of antiviral immune responses. Our data provide a direct molecular link between iron and HCV replication.
Collapse
Affiliation(s)
- Carine Fillebeen
- Lady Davis Institute for Medical Research, Sir Mortimer B Davis Jewish General Hospital, 3755 Cote-Sainte-Catherine Road, Montreal, Quebec H3T 1E2, Canada
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Fimia GM, Evangelisti C, Alonzi T, Romani M, Fratini F, Paonessa G, Ippolito G, Tripodi M, Piacentini M. Conventional protein kinase C inhibition prevents alpha interferon-mediated hepatitis C virus replicon clearance by impairing STAT activation. J Virol 2004; 78:12809-16. [PMID: 15542633 PMCID: PMC525020 DOI: 10.1128/jvi.78.23.12809-12816.2004] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Accepted: 06/23/2004] [Indexed: 12/17/2022] Open
Abstract
Hepatitis C virus (HCV) has evolved complex strategies to evade host immune responses and establish chronic infection. The only treatment available for HCV infections, alpha interferon (IFN-alpha), is effective in a limited percentage of patients. The mechanisms by which IFN-alpha interferes with the HCV life cycle and the reasons for limited effectiveness of IFN-alpha therapy have not yet been fully elucidated. Using a cell-based HCV replication system and specific kinase inhibitors, we examined the role played by various signaling pathways in the IFN-alpha-mediated HCV clearance. We reported that conventional protein kinase C (cPKC) activity is important for the effectiveness of IFN-alpha treatment. In cells treated with a cPKC-specific inhibitor, IFN-alpha failed to induce an efficient HCV RNA degradation. The lack of cPKC activity leads to a broad reduction of IFN-alpha-stimulated gene expression due to a significant impairment of STAT1 and STAT3 tyrosine phosphorylation. Thus, modulation of cPKC function by either host or viral factors could influence the positive outcome of IFN-alpha-mediated antiviral therapies.
Collapse
Affiliation(s)
- Gian Maria Fimia
- Gene Expression Laboratory, National Institute for Infectious Diseases "L. Spallanzani" IRCCS, Via Portuense 292, 00149 Rome, Italy
| | | | | | | | | | | | | | | | | |
Collapse
|
37
|
|
38
|
Vyas J, Elia A, Clemens MJ. Inhibition of the protein kinase PKR by the internal ribosome entry site of hepatitis C virus genomic RNA. RNA (NEW YORK, N.Y.) 2003; 9:858-870. [PMID: 12810919 PMCID: PMC1370452 DOI: 10.1261/rna.5330503] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2003] [Accepted: 04/10/2003] [Indexed: 05/24/2023]
Abstract
Translation of the hepatitis C genome is mediated by internal ribosome entry on the structurally complex 5' untranslated region of the large viral RNA. Initiation of protein synthesis by this mechanism is independent of the cap-binding factor eIF4E, but activity of the initiator Met-tRNA(f)-binding factor eIF2 is still required. HCV protein synthesis is thus potentially sensitive to the inhibition of eIF2 activity that can result from the phosphorylation of the latter by the interferon-inducible, double-stranded RNA-activated protein kinase PKR. Two virally encoded proteins, NS5A and E2, have been shown to reduce this inhibitory effect of PKR by impairing the activation of the kinase. Here we present evidence for a third viral strategy for PKR inhibition. A region of the viral RNA comprising part of the internal ribosome entry site (IRES) is able to bind to PKR in competition with double-stranded RNA and can prevent autophosphorylation and activation of the kinase in vitro. The HCV IRES itself has no PKR-activating ability. Consistent with these findings, cotransfection experiments employing a bicistronic reporter construct and wild-type PKR indicate that expression of the protein kinase is less inhibitory towards HCV IRES-driven protein synthesis than towards cap-dependent protein synthesis. These data suggest a dual function for the viral IRES, with both a structural role in promoting initiation complex formation and a regulatory role in preventing inhibition of initiation by PKR.
Collapse
Affiliation(s)
- Jashmin Vyas
- Translational Control Group, Department of Basic Medical Sciences, St. George's Hospital Medical School, London SW17 0RE, UK
| | | | | |
Collapse
|