Publications by authors named "David R McGivern"

35 Publications

Chitinase 3-like 1 is a profibrogenic factor overexpressed in the aging liver and in patients with liver cirrhosis.

Proc Natl Acad Sci U S A 2021 Apr;118(17)

Hepatic Pathogenesis Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892;

Older age at the time of infection with hepatitis viruses is associated with an increased risk of liver fibrosis progression. We hypothesized that the pace of fibrosis progression may reflect changes in gene expression within the aging liver. We compared gene expression in liver specimens from 54 adult donors without evidence of fibrosis, including 36 over 40 y old and 18 between 18 and 40 y old. (), which encodes chitinase-like protein YKL-40/CHI3L1, was identified as the gene with the greatest age-dependent increase in expression in liver tissue. We investigated the cellular source of CHI3L1 in the liver and its function using liver tissue specimens and in vitro models. expression was significantly higher in livers of patients with cirrhosis of diverse etiologies compared with controls represented by patients who underwent liver resection for hemangioma. The highest intrahepatic expression was observed in cirrhosis due to hepatitis D virus, followed by hepatitis C virus, hepatitis B virus, and alcohol-induced cirrhosis. In situ hybridization of messenger RNA (mRNA) identified hepatocytes as the major producers of CHI3L1 in normal liver and in cirrhotic tissue, wherein hepatocytes adjacent to fibrous septa showed higher expression than did those in more distal areas. In vitro studies showed that recombinant CHI3L1 promotes proliferation and activation of primary human hepatic stellate cells (HSCs), the major drivers of liver fibrosis. These findings collectively demonstrate that CHI3L1 promotes liver fibrogenesis through a direct effect on HSCs and support a role for CHI3L1 in the increased susceptibility of aging livers to fibrosis progression.
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http://dx.doi.org/10.1073/pnas.2019633118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092404PMC
April 2021

Stimulator of interferon genes (STING) is an essential proviral host factor for human rhinovirus species A and C.

Proc Natl Acad Sci U S A 2020 11 15;117(44):27598-27607. Epub 2020 Oct 15.

Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;

Human rhinoviruses (RVs) are positive-strand RNA viruses that cause respiratory tract disease in children and adults. Here we show that the innate immune signaling protein STING is required for efficient replication of members of two distinct RV species, RV-A and RV-C. The host factor activity of STING was identified in a genome-wide RNA interference (RNAi) screen and confirmed in primary human small airway epithelial cells. Replication of RV-A serotypes was strictly dependent on STING, whereas RV-B serotypes were notably less dependent. Subgenomic RV-A and RV-C RNA replicons failed to amplify in the absence of STING, revealing it to be required for a step in RNA replication. STING was expressed on phosphatidylinositol 4-phosphate (PI4P)-enriched membranes and was enriched in RV-A16 compared with RV-B14 replication organelles isolated in isopycnic gradients. The host factor activity of STING was species-specific, as murine STING (mSTING) did not rescue RV-A16 replication in STING-deficient cells. This species specificity mapped primarily to the cytoplasmic, ligand-binding domain of STING. Mouse-adaptive mutations in the RV-A16 2C protein allowed for robust replication in cells expressing mSTING, suggesting a role for 2C in recruiting STING to RV-A replication organelles. Palmitoylation of STING was not required for RV-A16 replication, nor was the C-terminal tail of STING that mediates IRF3 signaling. Despite co-opting STING to promote its replication, interferon signaling in response to STING agonists remained intact in RV-A16 infected cells. These data demonstrate a surprising requirement for a key host mediator of innate immunity to DNA viruses in the life cycle of a small pathogenic RNA virus.
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http://dx.doi.org/10.1073/pnas.2014940117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7959528PMC
November 2020

Prevalence and Impact of Hepatitis E Virus Infection Among Persons With Chronic Hepatitis B Living in the US and Canada.

Open Forum Infect Dis 2019 May 9;6(5):ofz175. Epub 2019 Apr 9.

UNC Liver Center, Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

Background: Patients with chronic hepatitis B virus (HBV) may experience spontaneous biochemical flares of liver disease activity. This study aimed to determine (i) the prevalence of prior and possible acute hepatitis E virus (HEV) infection among persons with chronic HBV and (ii) whether HEV infection is associated with liver disease flares among persons with chronic HBV.

Methods: Serum from a random sample of 600 adults in the Hepatitis B Research Network Cohort Study was tested for HEV RNA and anti-HEV IgM and IgG. Logistic regression models were used to estimate crude and adjusted odds ratios of anti-HEV prevalence for participant characteristics.

Results: Anti-HEV IgG and IgM seroprevalence was 28.5% and 1.7%, respectively. No participants had detectable HEV RNA. Of the 10 anti-HEV IgM+ participants, only 1 had elevated serum ALT at seroconversion. The odds of anti-HEV seropositivity (IgG+ or IgM+) were higher in older participants, males, Asians, less educated people, and those born outside the United States and Canada.

Conclusions: Acute HEV infection is a rare cause of serum ALT flares among persons with chronic HBV. The high seroprevalence of anti-HEV IgG among the chronic HBV patients is strongly associated with various demographic factors in this largely Asian American cohort.
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http://dx.doi.org/10.1093/ofid/ofz175DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6527087PMC
May 2019

Near-Neighbor Interactions in the NS3-4A Protease of HCV Impact Replicative Fitness of Drug-Resistant Viral Variants.

J Mol Biol 2019 05 30;431(12):2354-2368. Epub 2019 Apr 30.

Department of Computational Biology and Applied Algorithmics, Max Planck Institute for Informatics, Saarbrücken, Germany; Department of Internal Medicine 1, Goethe University Hospital Frankfurt, Frankfurt a.M., Germany. Electronic address:

A variety of amino acid substitutions in the NS3-4A protease of the hepatitis C virus lead to protease inhibitor (PI) resistance. Many of these significantly impair the replication fitness of the resistant variants in a genotype- and subtype-dependent manner, a critical factor in determining the probability with which resistant variants will persist. However, the underlying molecular mechanisms are unknown. Here, we present a novel residue-interaction network approach to determine how near-neighbor interactions of PI resistance mutations in NS3-4A can impact protease functional sites dependent on their genomic background. We constructed subtype-specific consensus residue networks for subtypes 1a and 1b from protease structure ensembles combined with biological properties of protein residues and evolutionary amino acid conservation. By applying local and global network topology analysis and visual exploration, we characterize PI resistance-associated sites and outline differences in near-neighbor interactions. We find local residue-interaction patterns and features at protease functional sites that are subtype specific. The noncovalent bonding patterns indicate higher fitness costs conferred by PI resistance mutations in a subtype 1b genomic background and explain the prevalence of Q80K and R155K in subtype 1a. Based on local residue interactions, we predict a subtype-specific role for the protease residue NS3-Q80 in molecular mechanisms related to the assembly of infectious virus particles that is supported by experimental data on the capacity of Q80K variants to replicate and produce infectious virus in subtype 1a and 1b cell culture.
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http://dx.doi.org/10.1016/j.jmb.2019.04.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6554042PMC
May 2019

Evolutionary pathways to NS5A inhibitor resistance in genotype 1 hepatitis C virus.

Antiviral Res 2018 10 3;158:45-51. Epub 2018 Aug 3.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA; Division of Infectious Diseases, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. Electronic address:

Direct-acting antivirals (DAAs) targeting NS5A are broadly effective against hepatitis C virus (HCV) infections, but sustained virological response rates are generally lower in patients infected with genotype (gt)-1a than gt-1b viruses. The explanation for this remains uncertain. Here, we adopted a highly accurate, ultra-deep primer ID sequencing approach to intensively study serial changes in the NS5A-coding region of HCV in gt-1a- and gt-1b-infected subjects receiving a short course of monotherapy with the NS5A inhibitor, elbasvir. Low or undetectable levels of viremia precluded on-treatment analysis in gt-1b-infected subjects, but variants with the resistance-associated substitution (RAS) Y93H in NS5A dominated rebounding virus populations following cessation of treatment. These variants persisted until the end of the study, two months later. In contrast, while Y93H emerged in multiple lineages and became dominant in subjects with gt-1a virus, these haplotypes rapidly decreased in frequency off therapy. Substitutions at Q30 and L31 emerged in distinctly independent lineages at later time points, ultimately coming to dominate the virus population off therapy. Consistent with this, cell culture studies with gt-1a and gt-1b reporter viruses and replicons demonstrated that Y93H confers a much greater loss of replicative fitness in gt-1a than gt-1b virus, and that L31M/V both compensates for the loss of fitness associated with Q30R (but not Y93H) and also boosts drug resistance. These observations show how differences in the impact of RASs on drug resistance and replicative fitness influence the evolution of gt-1a and gt-1b viruses during monotherapy with an antiviral targeting NS5A.
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http://dx.doi.org/10.1016/j.antiviral.2018.07.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6146077PMC
October 2018

An Efficient, Large-Scale Survey of Hepatitis C Viremia in the Democratic Republic of the Congo Using Dried Blood Spots.

Clin Infect Dis 2018 01;66(2):254-260

Abbott Laboratories, Abbott Park, Illinois.

Background: Efficient viral load testing is needed for hepatitis C (HCV) surveillance and diagnosis. HCV viral load testing using dried blood spots (DBSs), made with a single drop of finger-prick whole blood on filter paper, is a promising alternative to traditional serum- or plasma-based approaches.

Methods: We adapted the Abbott Molecular m2000 instrument for high-throughput HCV viremia testing using DBSs with simple specimen processing and applied these methods to estimate the national burden of infection in the Democratic Republic of the Congo (DRC). We tested DBSs collected during the 2013-2014 DRC Demographic and Health Survey, including 1309 adults ≥40 years of age. HCV-positive samples underwent targeted sequencing, genotyping, and phylogenetic analyses.

Results: This high-throughput screening approach reliably identified HCV RNA extracted from DBSs prepared using whole blood, with a 95% limit of detection of 1196 (95% confidence interval [CI], 866-2280) IU/mL for individual 6-mm punches and 494 (95% CI, 372-1228) IU/mL for larger 12-mm punches. Fifteen infections were identified among samples from the DRC Demographic and Health Survey; the weighted country-wide prevalence of HCV viremia was 0.9% (95% CI, 0.3%-1.6%) among adults ≥40 years of age and 0.7% (95% CI, .6%-.8%) among human immunodeficiency virus-infected subjects. All successfully genotyped cases were due to genotype 4 infection.

Conclusions: DBS-based HCV testing represents a useful tool for the diagnosis and surveillance of HCV viremia and can easily be incorporated into specimen referral systems. Among adults ≥40 years of age in the DRC, 100000-200000 may have active infection and be eligible for treatment.
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http://dx.doi.org/10.1093/cid/cix771DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5850542PMC
January 2018

NLRX1 promotes immediate IRF1-directed antiviral responses by limiting dsRNA-activated translational inhibition mediated by PKR.

Nat Immunol 2017 Dec 2;18(12):1299-1309. Epub 2017 Oct 2.

Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

NLRX1 is unique among the nucleotide-binding-domain and leucine-rich-repeat (NLR) proteins in its mitochondrial localization and ability to negatively regulate antiviral innate immunity dependent on the adaptors MAVS and STING. However, some studies have suggested a positive regulatory role for NLRX1 in inducing antiviral responses. We found that NLRX1 exerted opposing regulatory effects on viral activation of the transcription factors IRF1 and IRF3, which might potentially explain such contradictory results. Whereas NLRX1 suppressed MAVS-mediated activation of IRF3, it conversely facilitated virus-induced increases in IRF1 expression and thereby enhanced control of viral infection. NLRX1 had a minimal effect on the transcription of IRF1 mediated by the transcription factor NF-kB and regulated the abundance of IRF1 post-transcriptionally by preventing translational shutdown mediated by the double-stranded RNA (dsRNA)-activated kinase PKR and thereby allowed virus-induced increases in the abundance of IRF1 protein.
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http://dx.doi.org/10.1038/ni.3853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690873PMC
December 2017

NS5A inhibitors unmask differences in functional replicase complex half-life between different hepatitis C virus strains.

PLoS Pathog 2017 Jun 8;13(6):e1006343. Epub 2017 Jun 8.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

Hepatitis C virus (HCV) RNA is synthesized by the replicase complex (RC), a macromolecular assembly composed of viral non-structural proteins and cellular co-factors. Inhibitors of the HCV NS5A protein block formation of new RCs but do not affect RNA synthesis by pre-formed RCs. Without new RC formation, existing RCs turn over and are eventually lost from the cell. We aimed to use NS5A inhibitors to estimate the half-life of the functional RC of HCV. We compared different cell culture-infectious strains of HCV that may be grouped based on their sensitivity to lipid peroxidation: robustly replicating, lipid peroxidation resistant (LPOR) viruses (e.g. JFH-1 or H77D) and more slowly replicating, lipid peroxidation sensitive (LPOS) viruses (e.g. H77S.3 and N.2). In luciferase assays, LPOS HCV strains declined under NS5A inhibitor therapy with much slower kinetics compared to LPOR HCV strains. This difference in rate of decline was not observed for inhibitors of the NS5B RNA-dependent RNA polymerase suggesting that the difference was not simply a consequence of differences in RNA stability. In further analyses, we compared two isoclonal HCV variants: the LPOS H77S.3 and the LPOR H77D that differ only by 12 amino acids. Differences in rate of decline between H77S.3 and H77D following NS5A inhibitor addition were not due to amino acid sequences in NS5A but rather due to a combination of amino acid differences in the non-structural proteins that make up the HCV RC. Mathematical modeling of intracellular HCV RNA dynamics suggested that differences in RC stability (half-lives of 3.5 and 9.9 hours, for H77D and H77S.3, respectively) are responsible for the different kinetics of antiviral suppression between LPOS and LPOR viruses. In nascent RNA capture assays, the rate of RNA synthesis decline following NS5A inhibitor addition was significantly faster for H77D compared to H77S.3 indicating different half-lives of functional RCs.
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http://dx.doi.org/10.1371/journal.ppat.1006343DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5464671PMC
June 2017

Hepatitis C Virus Indirectly Disrupts DNA Damage-Induced p53 Responses by Activating Protein Kinase R.

mBio 2017 04 25;8(2). Epub 2017 Apr 25.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA

Many DNA tumor viruses promote cellular transformation by inactivating the critically important tumor suppressor protein p53. In contrast, it is not known whether p53 function is disrupted by hepatitis C virus (HCV), a unique, oncogenic RNA virus that is the leading infectious cause of liver cancer in many regions of the world. Here we show that HCV-permissive, liver-derived HepG2 cells engineered to constitutively express microRNA-122 (HepG2/miR-122 cells) have normal p53-mediated responses to DNA damage and that HCV replication in these cells potently suppresses p53 responses to etoposide, an inducer of DNA damage, or nutlin-3, an inhibitor of p53 degradation pathways. Upregulation of p53-dependent targets is consequently repressed within HCV-infected cells, with potential consequences for cell survival. Despite this, p53 function is not disrupted by overexpression of the complete HCV polyprotein, suggesting that altered p53 function may result from the host response to viral RNA replication intermediates. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated ablation of double-stranded RNA (dsRNA)-activated protein kinase R (PKR) restored p53 responses while boosting HCV replication, showing that p53 inhibition results directly from viral activation of PKR. The hepatocellular abundance of phosphorylated PKR is elevated in HCV-infected chimpanzees, suggesting that PKR activation and consequent p53 inhibition accompany HCV infection These findings reveal a feature of the host response to HCV infection that may contribute to hepatocellular carcinogenesis. Chronic infection with hepatitis C virus (HCV) is the leading cause of liver cancer in most developed nations. However, the mechanisms whereby HCV infection promotes carcinogenesis remain unclear. Here, we demonstrate that HCV infection inhibits the activation of p53 following DNA damage. Contrary to previous reports, HCV protein expression is insufficient to inhibit p53. Rather, p53 inhibition is mediated by cellular protein kinase R (PKR), which is activated by HCV RNA replication and subsequently suppresses global protein synthesis. These results redefine our understanding of how HCV infection influences p53 function. We speculate that persistent disruption of p53-mediated DNA damage responses may contribute to hepatocellular carcinogenesis in chronically infected individuals.
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http://dx.doi.org/10.1128/mBio.00121-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5405228PMC
April 2017

Chronic hepatitis C infection-induced liver fibrogenesis is associated with M2 macrophage activation.

Sci Rep 2016 12 21;6:39520. Epub 2016 Dec 21.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

The immuno-pathogenic mechanisms of chronic hepatitis C virus (HCV) infection remain to be elucidated and pose a major hurdle in treating or preventing chronic HCV-induced advanced liver diseases such as cirrhosis. Macrophages are a major component of the inflammatory milieu in chronic HCV-induced liver disease, and are generally derived from circulating inflammatory monocytes; however very little is known about their role in liver diseases. To investigate the activation and role of macrophages in chronic HCV-induced liver fibrosis, we utilized a recently developed humanized mouse model with autologous human immune and liver cells, human liver and blood samples and cell culture models of monocyte/macrophage and/or hepatic stellate cell activation. We showed that M2 macrophage activation was associated with liver fibrosis during chronic HCV infection in the livers of both humanized mice and patients, and direct-acting antiviral therapy attenuated M2 macrophage activation and associated liver fibrosis. We demonstrated that supernatant from HCV-infected liver cells activated human monocytes/macrophages with M2-like phenotypes. Importantly, HCV-activated monocytes/macrophages promoted hepatic stellate cell activation. These results suggest a critical role for M2 macrophage induction in chronic HCV-associated immune dysregulation and liver fibrosis.
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http://dx.doi.org/10.1038/srep39520DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5175173PMC
December 2016

MAVS-dependent host species range and pathogenicity of human hepatitis A virus.

Science 2016 09 15;353(6307):1541-1545. Epub 2016 Sep 15.

Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27517, USA. Department of Medicine, University of North Carolina, Chapel Hill, NC 27517, USA.

Hepatotropic viruses are important causes of human disease, but the intrahepatic immune response to hepatitis viruses is poorly understood because of a lack of tractable small- animal models. We describe a murine model of hepatitis A virus (HAV) infection that recapitulates critical features of type A hepatitis in humans. We demonstrate that the capacity of HAV to evade MAVS-mediated type I interferon responses defines its host species range. HAV-induced liver injury was associated with interferon-independent intrinsic hepatocellular apoptosis and hepatic inflammation that unexpectedly resulted from MAVS and IRF3/7 signaling. This murine model thus reveals a previously undefined link between innate immune responses to virus infection and acute liver injury, providing a new paradigm for viral pathogenesis in the liver.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5068972PMC
http://dx.doi.org/10.1126/science.aaf8325DOI Listing
September 2016

How do persistent infections with hepatitis C virus cause liver cancer?

Curr Opin Virol 2015 Oct 29;14:101-8. Epub 2015 Sep 29.

Division of Infectious Diseases, Department of Medicine, and Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

Persistent infection with hepatitis C virus (HCV) is associated with an increased risk of hepatocellular carcinoma (HCC). Cancer typically develops in a setting of chronic hepatic inflammation and advanced fibrosis or cirrhosis, and such tissue represents a pre-neoplastic 'cancer field'. However, not all persistent infections progress to HCC and a combination of viral and host immune factors likely contributes to carcinogenesis. HCV may disrupt cellular pathways involved in detecting and responding to DNA damage, potentially adding to the risk of cancer. Efforts to unravel how HCV promotes HCC are hindered by lack of a robust small animal model, but a better understanding of molecular mechanisms could identify novel biomarkers for early detection and allow for development of improved therapies.
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http://dx.doi.org/10.1016/j.coviro.2015.09.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4628866PMC
October 2015

Ribavirin Contributes to Hepatitis C Virus Suppression by Augmenting pDC Activation and Type 1 IFN Production.

PLoS One 2015 14;10(8):e0135232. Epub 2015 Aug 14.

Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

Ribavirin is used as a component of combination therapies for the treatment of chronic hepatitis C virus (HCV) infection together with pegylated interferon and/or direct-acting antiviral drugs. Its mechanism of action, however, is not clear. Direct antiviral activity and immunomodulatory functions have been implicated. Plasmacytoid dendritic cells (pDCs) are the principal source of type 1 interferon during viral infection. The interaction of pDCs with HCV-infected hepatocytes is the subject of intense recent investigation, but the effect of ribavirin on pDC activation has not been evaluated. In this study we showed that ribavirin augments toll-like receptors 7 and 9-mediated IFNα/β expression from pDCs and up-regulated numerous interferon-stimulated genes. Using the H77S.3 HCV infection and replication system, we showed that ribavirin enhanced the ability of activated pDCs to inhibit HCV replication, correlated with elevated induction of IFNα. Our findings provide novel evidence that ribavirin contributes to HCV inhibition by augmenting pDCs-derived type 1 IFN production.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0135232PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4537094PMC
May 2016

Protease Inhibitors Block Multiple Functions of the NS3/4A Protease-Helicase during the Hepatitis C Virus Life Cycle.

J Virol 2015 May 4;89(10):5362-70. Epub 2015 Mar 4.

Astex Pharmaceuticals, Cambridge, United Kingdom.

Unlabelled: Hepatitis C virus (HCV) NS3 is a multifunctional protein composed of a protease domain and a helicase domain linked by a flexible linker. Protease activity is required to generate viral nonstructural (NS) proteins involved in RNA replication. Helicase activity is required for RNA replication, and genetic evidence implicates the helicase domain in virus assembly. Binding of protease inhibitors (PIs) to the protease active site blocks NS3-dependent polyprotein processing but might impact other steps of the virus life cycle. Kinetic analyses of antiviral suppression of cell culture-infectious genotype 1a strain H77S.3 were performed using assays that measure different readouts of the viral life cycle. In addition to the active-site PI telaprevir, we examined an allosteric protease-helicase inhibitor (APHI) that binds a site in the interdomain interface. By measuring nucleotide incorporation into HCV genomes, we found that telaprevir inhibits RNA synthesis as early as 12 h at high but clinically relevant concentrations. Immunoblot analyses showed that NS5B abundance was not reduced until after 12 h, suggesting that telaprevir exerts a direct effect on RNA synthesis. In contrast, the APHI could partially inhibit RNA synthesis, suggesting that the allosteric site is not always available during RNA synthesis. The APHI and active-site PI were both able to block virus assembly soon (<12 h) after drug treatment, suggesting that they rapidly engage with and block a pool of NS3 involved in assembly. In conclusion, PIs and APHIs can block NS3 functions in RNA synthesis and virus assembly, in addition to inhibiting polyprotein processing.

Importance: The NS3/4A protease of hepatitis C virus (HCV) is an important antiviral target. Currently, three PIs have been approved for therapy of chronic hepatitis C, and several others are in development. NS3-dependent cleavage of the HCV polyprotein is required to generate the mature nonstructural proteins that form the viral replicase. Inhibition of protease activity can block RNA replication by preventing expression of mature replicase components. Like many viral proteins, NS3 is multifunctional, but how PIs affect stages of the HCV life cycle beyond polyprotein processing has not been well studied. Using cell-based assays, we show here that PIs can directly inhibit viral RNA synthesis and also block a late stage in virus assembly/maturation at clinically relevant concentrations.
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http://dx.doi.org/10.1128/JVI.03188-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4442512PMC
May 2015

miR-122 stimulates hepatitis C virus RNA synthesis by altering the balance of viral RNAs engaged in replication versus translation.

Cell Host Microbe 2015 Feb 5;17(2):217-28. Epub 2015 Feb 5.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27517, USA; Department of Microbiology & Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27517, USA; Division of Infectious Diseases, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27517, USA. Electronic address:

The liver-specific microRNA, miR-122, stabilizes hepatitis C virus (HCV) RNA genomes by recruiting host argonaute 2 (AGO2) to the 5' end and preventing decay mediated by exonuclease Xrn1. However, HCV replication requires miR-122 in Xrn1-depleted cells, indicating additional functions. We show that miR-122 enhances HCV RNA levels by altering the fraction of HCV genomes available for RNA synthesis. Exogenous miR-122 increases viral RNA and protein levels in Xrn1-depleted cells, with enhanced RNA synthesis occurring before heightened protein synthesis. Inhibiting protein translation with puromycin blocks miR-122-mediated increases in RNA synthesis, but independently enhances RNA synthesis by releasing ribosomes from viral genomes. Additionally, miR-122 reduces the fraction of viral genomes engaged in protein translation. Depleting AGO2 or PCBP2, which binds HCV RNA in competition with miR-122 and promotes translation, eliminates miR-122 stimulation of RNA synthesis. Thus, by displacing PCBP2, miR-122 reduces HCV genomes engaged in translation while increasing the fraction available for RNA synthesis.
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http://dx.doi.org/10.1016/j.chom.2014.12.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326553PMC
February 2015

Regulation of the hepatitis C virus RNA replicase by endogenous lipid peroxidation.

Nat Med 2014 Aug 27;20(8):927-35. Epub 2014 Jul 27.

1] Department of Medicine, Division of Infectious Diseases, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. [2] Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. [3] Department of Microbiology and Immunology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

Oxidative tissue injury often accompanies viral infection, yet there is little understanding of how it influences virus replication. We show that multiple hepatitis C virus (HCV) genotypes are exquisitely sensitive to oxidative membrane damage, a property distinguishing them from other pathogenic RNA viruses. Lipid peroxidation, regulated in part through sphingosine kinase-2, severely restricts HCV replication in Huh-7 cells and primary human hepatoblasts. Endogenous oxidative membrane damage lowers the 50% effective concentration of direct-acting antivirals in vitro, suggesting critical regulation of the conformation of the NS3-4A protease and the NS5B polymerase, membrane-bound HCV replicase components. Resistance to lipid peroxidation maps genetically to transmembrane and membrane-proximal residues within these proteins and is essential for robust replication in cell culture, as exemplified by the atypical JFH1 strain of HCV. Thus, the typical, wild-type HCV replicase is uniquely regulated by lipid peroxidation, providing a mechanism for attenuating replication in stressed tissue and possibly facilitating long-term viral persistence.
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http://dx.doi.org/10.1038/nm.3610DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4126843PMC
August 2014

Mechanisms of hepatocarcinogenesis in chronic hepatitis C.

Hepat Oncol 2014 Jun 9;1(3):293-307. Epub 2014 Sep 9.

Lineberger Comprehensive Cancer Center & Division of Infectious Diseases, Department of Medicine, University of North Carolina, Chapel Hill, NC 27599-7295, USA.

Infection with hepatitis C virus (HCV) is a major risk factor for hepatocellular carcinoma. The genetic changes that drive cancer development are heterogeneous and how chronic hepatitis C promotes the initiation of hepatocellular carcinoma is incompletely understood. Cancer typically arises in the setting of advanced fibrosis and/or cirrhosis where chronic immune-mediated inflammation over decades promotes hepatocyte turnover providing selective pressure that favors the malignant phenotype. As well as contributions of unresolved inflammation to carcinogenesis, evidence from transgenic mice with liver-specific expression of viral sequences suggests that some HCV-encoded proteins may directly promote cancer. Numerous studies suggest roles for HCV proteins in subversion of cellular pathways that normally act to suppress tumorigenesis. Here, we review the mechanisms by which persistent HCV infection might promote cancer in addition to the procarcinogenic effects of inflammatory liver disease.
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http://dx.doi.org/10.2217/hep.14.7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6095168PMC
June 2014

Kinetic analyses reveal potent and early blockade of hepatitis C virus assembly by NS5A inhibitors.

Gastroenterology 2014 Aug 22;147(2):453-62.e7. Epub 2014 Apr 22.

Departments of Medicine and Microbiology and Immunology and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Electronic address:

Background & Aims: All-oral regimens combining different classes of direct-acting antivirals (DAA) are highly effective for treatment of patients with chronic hepatitis C. NS5A inhibitors will likely form a component of future interferon-sparing treatment regimens. However, despite their potential, the detailed mechanism of action of NS5A inhibitors is unclear. To study their mechanisms, we compared their kinetics of antiviral suppression with those of other classes of DAA, using the hepatitis C virus genotype 1a cell culture-infectious virus H77S.3.

Methods: We performed detailed kinetic analyses of specific steps in the hepatitis C virus life cycle using cell cultures incubated with protease inhibitors, polymerase inhibitors, or NS5A inhibitors. Assays were designed to measure active viral RNA synthesis and steady-state RNA abundance, polyprotein synthesis, virion assembly, and infectious virus production.

Results: Despite their high potency, NS5A inhibitors were slow to inhibit viral RNA synthesis compared with protease or polymerase inhibitors. By 24 hours after addition of an NS5A inhibitor, polyprotein synthesis was reduced <50%, even at micromolar concentrations. In contrast, inhibition of virus release by NS5A inhibitors was potent and rapid, with onset of inhibition as early as 2 hours. Cells incubated with NS5A inhibitors were rapidly depleted of intracellular infectious virus and RNA-containing hepatitis C virus particles, indicating a block in virus assembly.

Conclusions: DAAs that target NS5A rapidly inhibit intracellular assembly of genotype 1a virions. They also inhibit formation of functional replicase complexes, but have no activity against preformed replicase, thereby resulting in slow shut-off of viral RNA synthesis.
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http://dx.doi.org/10.1053/j.gastro.2014.04.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4107048PMC
August 2014

Class A scavenger receptor 1 (MSR1) restricts hepatitis C virus replication by mediating toll-like receptor 3 recognition of viral RNAs produced in neighboring cells.

PLoS Pathog 2013 23;9(5):e1003345. Epub 2013 May 23.

Division of Infectious Diseases, Department of Medicine, and the Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.

Persistent infections with hepatitis C virus (HCV) may result in life-threatening liver disease, including cirrhosis and cancer, and impose an important burden on human health. Understanding how the virus is capable of achieving persistence in the majority of those infected is thus an important goal. Although HCV has evolved multiple mechanisms to disrupt and block cellular signaling pathways involved in the induction of interferon (IFN) responses, IFN-stimulated gene (ISG) expression is typically prominent in the HCV-infected liver. Here, we show that Toll-like receptor 3 (TLR3) expressed within uninfected hepatocytes is capable of sensing infection in adjacent cells, initiating a local antiviral response that partially restricts HCV replication. We demonstrate that this is dependent upon the expression of class A scavenger receptor type 1 (MSR1). MSR1 binds extracellular dsRNA, mediating its endocytosis and transport toward the endosome where it is engaged by TLR3, thereby triggering IFN responses in both infected and uninfected cells. RNAi-mediated knockdown of MSR1 expression blocks TLR3 sensing of HCV in infected hepatocyte cultures, leading to increased cellular permissiveness to virus infection. Exogenous expression of Myc-MSR1 restores TLR3 signaling in MSR1-depleted cells with subsequent induction of an antiviral state. A series of conserved basic residues within the carboxy-terminus of the collagen superfamily domain of MSR1 are required for binding and transport of dsRNA, and likely facilitate acidification-dependent release of dsRNA at the site of TLR3 expression in the endosome. Our findings reveal MSR1 to be a critical component of a TLR3-mediated pattern recognition receptor response that exerts an antiviral state in both infected and uninfected hepatocytes, thereby limiting the impact of HCV proteins that disrupt IFN signaling in infected cells and restricting the spread of HCV within the liver.
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http://dx.doi.org/10.1371/journal.ppat.1003345DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3662657PMC
December 2013

Liver injury and disease pathogenesis in chronic hepatitis C.

Curr Top Microbiol Immunol 2013 ;369:263-88

Department of Medicine, The University of North Carolina, Chapel Hill, NC 27599-7292, USA.

Chronic hepatitis C virus (HCV) infection is a leading cause of liver-specific morbidity and mortality in humans, including progressive liver fibrosis, cirrhosis, and hepatocellular carcinoma. It has also been associated with altered function in other organs, including those of the endocrine, hematopoietic, and nervous systems. Disease results from both direct regulation of cellular metabolism and signaling pathways by viral proteins as well as indirect consequences of the host response to HCV infection, including inflammatory responses stemming from immune recognition of the virus. Recent in vitro studies have begun to reveal molecular mechanisms responsible for virus-induced changes in cell metabolism and cellular kinase cascades that culminate in pathologic consequences in the liver, such as steatosis, insulin resistance, and carcinogenesis. Here we discuss how these findings may be relevant to disease pathogenesis in patients, and suggest future directions in the field.
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http://dx.doi.org/10.1007/978-3-642-27340-7_11DOI Listing
August 2013

Competing and noncompeting activities of miR-122 and the 5' exonuclease Xrn1 in regulation of hepatitis C virus replication.

Proc Natl Acad Sci U S A 2013 Jan 17;110(5):1881-6. Epub 2012 Dec 17.

Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7292, USA.

Hepatitis C virus (HCV) replication is dependent on microRNA 122 (miR-122), a liver-specific microRNA that recruits Argonaute 2 to the 5' end of the viral genome, stabilizing it and slowing its decay both in cell-free reactions and in infected cells. Here we describe the RNA degradation pathways against which miR-122 provides protection. Transfected HCV RNA is degraded by both the 5' exonuclease Xrn1 and 3' exonuclease exosome complex, whereas replicating RNA within infected cells is degraded primarily by Xrn1 with no contribution from the exosome. Consistent with this, sequencing of the 5' and 3' ends of RNA degradation intermediates in infected cells confirmed that 5' decay is the primary pathway for HCV RNA degradation. Xrn1 knockdown enhances HCV replication, indicating that Xrn1 decay and the viral replicase compete to set RNA abundance within infected cells. Xrn1 knockdown and miR-122 supplementation have equal, redundant, and nonadditive effects on the rate of viral RNA decay, indicating that miR-122 protects HCV RNA from 5' decay. Nevertheless, Xrn1 knockdown does not rescue replication of a viral mutant defective in miR-122 binding, indicating that miR-122 has additional yet uncharacterized function(s) in the viral life cycle.
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http://dx.doi.org/10.1073/pnas.1213515110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3562843PMC
January 2013

Is hepatitis C virus carcinogenic?

Gastroenterology 2012 May;142(6):1274-8

Lineberger Comprehensive Cancer Center, Center for Translational Research, Inflammatory Diseases Institute, Department of Medicine, The University of North Carolina at Chapel Hill, Chapel Hill 27599-7292, USA.

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http://dx.doi.org/10.1053/j.gastro.2012.01.045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4422399PMC
May 2012

Model systems for hepatitis C research: the cup half empty?

Gastroenterology 2011 Sep 23;141(3):806-9. Epub 2011 Jul 23.

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http://dx.doi.org/10.1053/j.gastro.2011.07.028DOI Listing
September 2011

Hepatitis C virus infection causes cell cycle arrest at the level of initiation of mitosis.

J Virol 2011 Aug 15;85(16):7989-8001. Epub 2011 Jun 15.

Division of Infectious Diseases, Department of Medicine, Center for Translational Research, Inflammatory Diseases Institute, Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7295, USA.

Chronic infection with the hepatitis C virus (HCV) is associated with increased risk for hepatocellular carcinoma (HCC). Chronic immune-mediated inflammation is likely to be an important factor in the development of HCV-associated HCC, but direct effects of HCV infection on the host cell cycle may also play a role. Although overexpression studies have revealed multiple interactions between HCV-encoded proteins and host cell cycle regulators and tumor suppressor proteins, the relevance of these observations to HCV-associated liver disease is not clear. We determined the net effect of these interactions on regulation of the cell cycle in the context of virus infection. Flow cytometry of HCV-infected carboxyfluorescein succinimidyl ester-labeled hepatoma cells indicated a slowdown in proliferation that correlated with abundance of viral antigen. A decrease in the proportions of infected cells in G(1) and S phases with an accumulation of cells in G(2)/M phase was observed, compared to mock-infected controls. Dramatic decreases in markers of mitosis, such as phospho-histone H3, in infected cells suggested a block to mitotic entry. In common with findings described in the published literature, we observed caspase 3 activation, suggesting that cell cycle arrest is associated with apoptosis. Differences were observed in patterns of cell cycle disturbance and levels of apoptosis with different strains of HCV. However, the data suggest that cell cycle arrest at the interface of G(2) and mitosis is a common feature of HCV infection.
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http://dx.doi.org/10.1128/JVI.00280-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3147967PMC
August 2011

Protease inhibitor-resistant hepatitis C virus mutants with reduced fitness from impaired production of infectious virus.

Gastroenterology 2011 Feb 4;140(2):667-75. Epub 2010 Nov 4.

Division of Infectious Diseases, Department of Medicine, Inflammatory Diseases Institute, and the Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.

Background & Aims: Several small molecule inhibitors of the hepatitis C virus (HCV) nonstructural protein (NS) 3/4A protease have advanced successfully to clinical trials. However, the selection of drug-resistant mutants is a significant issue with protease inhibitors (PIs). A variety of amino acid substitutions in the protease domain of NS3 can lead to PI resistance. Many of these significantly impair the replication fitness of HCV RNA replicons. However, it is not known whether these mutations also adversely affect infectious virus assembly and release, processes in which NS3 also participates.

Methods: We studied the impact of 25 previously identified PI-resistance mutations on the capacity of genotype 1a H77S RNA to replicate in cell culture and produce infectious virus.

Results: Most PI-resistance mutations resulted in moderate loss of replication competence, although several (V36A/L/M, R109K, and D168E) showed fitness comparable to wild type, whereas others (S138T and A156V) were severely impaired both in RNA replication and infectious virus production. Although reductions in RNA replication capacity correlated with decreased yields of infectious virus for most mutations, a subset of mutants (Q41R, F43S, R155T, A156S, and I170A/T) showed greater impairment in their ability to produce virus than predicted from reductions in RNA replication capacity. Detailed examination of the I170A mutant showed no defect in release of virus from cells and no significant difference in specific infectivity of extracellular virus particles.

Conclusions: Replicon-based assays might underestimate the loss of fitness caused by PI-resistance mutations, because some mutations in the NS3 protease domain specifically impair late steps in the viral life cycle that involve intracellular assembly of infectious virus.
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http://dx.doi.org/10.1053/j.gastro.2010.10.056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3155954PMC
February 2011

Roles of the respiratory syncytial virus trailer region: effects of mutations on genome production and stress granule formation.

Virology 2010 Oct 10;406(2):241-52. Epub 2010 Aug 10.

Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, USA.

The 5' extragenic trailer region of respiratory syncytial virus (RSV) is known to be necessary for genome replication, but is more than three times the length of the 3' leader replication promoter, raising the possibility that trailer might play an additional role in viral replication. To examine this, mutant recombinant viruses were constructed in which the trailer region was truncated or substituted with leader-complement sequence. This analysis showed that the complete trailer increased promoter activity, facilitating genome production and viral multiplication. In addition, trailer-containing viruses did not induce stress granules, whereas the leader-complement virus mutant did, resulting in poor multi-cycle viral growth. These data demonstrate that although the RSV trailer does not contain a unique essential sequence, it augments virus growth by enabling optimal genome production. In addition, a sequence at the 5' terminal end of the trailer region allows RSV to subvert stress granule formation.
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http://dx.doi.org/10.1016/j.virol.2010.07.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2971657PMC
October 2010

Evidence that the polymerase of respiratory syncytial virus initiates RNA replication in a nontemplated fashion.

Proc Natl Acad Sci U S A 2010 Jun 17;107(22):10226-31. Epub 2010 May 17.

Division of Pathology and Neuroscience, University of Dundee Medical School, Dundee DD1 9SY, United Kingdom.

RNA virus polymerases must initiate replicative RNA synthesis with extremely high accuracy to maintain their genome termini and to avoid generating defective genomes. For the single-stranded negative-sense RNA viruses, it is not known how this accuracy is achieved. To investigate this question, mutations were introduced into the 3' terminal base of a respiratory syncytial virus (RSV) template, and the RNA products were examined to determine the impact of the mutation. To perform the assay, RNA replication was reconstituted using a modified minireplicon system in which replication was limited to a single step. Importantly, this system allowed analysis of RSV RNA generated intracellularly, but from a defined template that was not subject to selection by replication. Sequence analysis of RNA products generated from templates containing 1U-C and 1U-A substitutions showed that, in both cases, replication products were initiated with a nontemplated, WT A residue, rather than a templated G or U residue, indicating that the polymerase selects the terminal NTP independently of the template. Examination of a template in which the position 1 nucleotide was deleted supported these findings. This mutant directed efficient replication at approximately 60% of WT levels, and its product was found to be initiated at the WT position (-1 relative to the template) with a WT A residue. These findings show that the RSV replicase selects ATP and initiates at the correct position, independently of the first nucleotide of the template, suggesting a mechanism by which highly accurate replication initiation is achieved.
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http://dx.doi.org/10.1073/pnas.0913065107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890450PMC
June 2010

Requirement of cellular DDX3 for hepatitis C virus replication is unrelated to its interaction with the viral core protein.

J Gen Virol 2010 Jan 30;91(Pt 1):122-32. Epub 2009 Sep 30.

MRC Virology Unit, Institute of Virology, University of Glasgow, Church Street, Glasgow G11 5JR, UK.

The cellular DEAD-box protein DDX3 was recently shown to be essential for hepatitis C virus (HCV) replication. Prior to that, we had reported that HCV core binds to DDX3 in yeast-two hybrid and transient transfection assays. Here, we confirm by co-immunoprecipitation that this interaction occurs in cells replicating the JFH1 virus. Consistent with this result, immunofluorescence staining of infected cells revealed a dramatic redistribution of cytoplasmic DDX3 by core protein to the virus assembly sites around lipid droplets. Given this close association of DDX3 with core and lipid droplets, and its involvement in virus replication, we investigated the importance of this host factor in the virus life cycle. Mutagenesis studies located a single amino acid in the N-terminal domain of JFH1 core that when changed to alanine significantly abrogated this interaction. Surprisingly, this mutation did not alter infectious virus production and RNA replication, indicating that the core-DDX3 interaction is dispensable in the HCV life cycle. Consistent with previous studies, siRNA-led knockdown of DDX3 lowered virus production and RNA replication levels of both WT JFH1 and the mutant virus unable to bind DDX3. Thus, our study shows for the first time that the requirement of DDX3 for HCV replication is unrelated to its interaction with the viral core protein.
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http://dx.doi.org/10.1099/vir.0.015909-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885062PMC
January 2010

Impaired replication of hepatitis C virus containing mutations in a conserved NS5B retinoblastoma protein-binding motif.

J Virol 2009 Aug 20;83(15):7422-33. Epub 2009 May 20.

Center for Hepatitis Research, Institute for Human Infections and Immunity, and Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-0610, USA.

Hepatitis C virus (HCV) downregulates the retinoblastoma tumor suppressor protein (Rb), a central cell cycle regulator which is also targeted by oncoproteins expressed by DNA tumor viruses. HCV genome replication is also enhanced in proliferating cells. Thus, it is possible that HCV interactions with host cell cycle regulators, such as Rb, have evolved to modify the intracellular environment to promote viral replication. To test this hypothesis and to determine the impact of viral regulation of Rb on HCV replication, we constructed infectious viral genomes containing mutations in the Rb-binding motif of NS5B which ablate the ability of HCV to regulate Rb. These genomes underwent replication in transfected cells but produced variably reduced virus yields. One mutant, L314A, was severely compromised for replication and rapidly mutated to L314V, thereby restoring both Rb regulation and replication competence. Another mutant, C316A, also failed to downregulate Rb abundance and produced virus yields that were about one-third that of virus with the wild-type (wt) NS5B sequence. Despite this loss of replication competence, purified NS5B-C316A protein was two- to threefold more active than wt NS5B in cell-free polymerase and replicase assays. Although small interfering RNA knockdown of Rb did not rescue the replication fitness of these mutants, we conclude that the defect in replication fitness is not due to defective polymerase or replicase function and is more likely to result from the inability of the mutated NS5B to optimally regulate Rb abundance and thereby modulate host gene expression.
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http://dx.doi.org/10.1128/JVI.00262-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2708619PMC
August 2009

Tumor suppressors, chromosomal instability, and hepatitis C virus-associated liver cancer.

Annu Rev Pathol 2009 ;4:399-415

The Center for Hepatitis Research, Institute for Human Infections and Immunity, Sealy Center for Cancer Cell Biology, Galveston, TX 77555, USA.

Hepatitis C virus (HCV) is the only known RNA virus with an exclusively cytoplasmic life cycle that is associated with cancer. The mechanisms by which it causes cancer are unclear, but chronic immune-mediated inflammation and associated oxidative chromosomal DNA damage probably play a role. Compelling data suggest that the path to hepatocellular carcinoma in chronic hepatitis C shares some important features with the mechanisms of transformation employed by DNA tumor viruses. Interactions of viral proteins with key regulators of the cell cycle, the retinoblastoma-susceptibility protein, p53, and possibly DDX5 and DDX3 lead to enhanced cellular proliferation and may also compromise multiple cell-cycle checkpoints that maintain genomic integrity, thus setting the stage for carcinogenesis. Dysfunctional DNA damage and mitotic spindle checkpoints resulting from these interactions may promote chromosomal instability and leave the hepatocyte unable to control DNA damage caused by oxidative stress mediated by HCV proteins, alcohol, and immune-mediated inflammation.
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http://dx.doi.org/10.1146/annurev.pathol.4.110807.092202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4422400PMC
May 2009