Hepatitis C Virus Viral Proteins Research Articles

HCV 5-Methylcytosine Enhances Viral RNA Replication through Interaction with m5C Reader YBX1.

Hepatitis C virus (HCV) is a positive-stranded RNA virus that mainly causes chronic hepatitis, cirrhosis and hepatocellular carcinoma. Recently we confirmed m5C modifications within NS5A gene of HCV RNA genome. However, the roles of the m5C modification and its interaction with host proteins in regulating HCV's life cycle, remain unexplored. Here, we demonstrate that HCV infection enhances the expression of the host m5C reader YBX1 through the transcription factor MAX. YBX1 acts as an m5C reader, recognizing the m5C-modified NS5A C7525 site in the HCV RNA genome and significantly enhancing HCV RNA stability. This m5C-modification is also required for YBX1 colocalization with lipid droplets and HCV Core protein. Moreover, YBX1 facilitates HCV RNA replication, as well as viral assembly/budding. The tryptophan residue at position 65 (W65) of YBX1 is critical for these functions. Knockout of YBX1 or the application of YBX1 inhibitor SU056 suppresses HCV RNA replication and viral protein translation. To our knowledge, this is the first report demonstrating that the interaction between host m5C reader YBX1 and HCV RNA m5C methylation facilitates viral replication. Therefore, hepatic-YBX1 knockdown holds promise as a potential host-directed strategy for HCV therapy.

Hepatitis C Virus Down-Regulates the Expression of Ribonucleotide Reductases to Promote Its Replication.

Ribonucleotide reductases (RRs or RNRs) catalyze the reduction of the OH group on the 2nd carbon of ribose, reducing four ribonucleotides (NTPs) to the corresponding deoxyribonucleotides (dNTPs) to promote DNA synthesis. Large DNA viruses, such as herpesviruses and poxviruses, could benefit their replication through increasing dNTPs via expression of viral RRs. Little is known regarding the relationship between cellular RRs and RNA viruses. Mammalian RRs contain two subunits of ribonucleotide reductase M1 polypeptide (RRM1) and two subunits of ribonucleotide reductase M2 polypeptide (RRM2). In this study, expression of cellular RRMs, including RRM1 and RRM2, is found to be down-regulated in hepatitis C virus (HCV)-infected Huh7.5 cells and Huh7 cells with HCV subgenomic RNAs (HCVr). As expected, the NTP/dNTP ratio is elevated in HCVr cells. Compared with that of the control Huh7 cells with sh-scramble, the NTP/dNTP ratio of the RRM-knockdown cells is elevated. Knockdown of RRM1 or RRM2 increases HCV replication in HCV replicon cells. Moreover, inhibitors to RRMs, including Didox, Trimidox and hydroxyurea, enhance HCV replication. Among various HCV viral proteins, the NS5A and/or NS3/4A proteins suppress the expression of RRMs. When these are taken together, the results suggest that HCV down-regulates the expression of RRMs in cultured cells to promote its replication.

Regulatory Role of Ribonucleotide Reductase Subunit M2 in Hepatocyte Growth and Pathogenesis of Hepatitis C Virus.

Hepatitis C virus (HCV) frequently causes chronic infection in the human liver, which may progress to advanced hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. HCV primarily infects highly differentiated quiescent hepatocytes and can modulate cell cycle-regulatory genes and proliferation pathways, which ultimately contribute to persistent infection and pathogenesis. On the other hand, several studies have shown differential regulation of HCV RNA and viral protein expression levels, depending on the proliferation state of hepatocytes and the phase of the cell cycle. HCV typically requires factors provided by host cells for efficient and persistent viral replication. Previously, we found that HCV infection upregulates the expression of ribonucleotide reductase subunit M2 (RRM2) in quiescent hepatocytes. RRM2 is a rate-limiting protein that catalyzes de novo synthesis of deoxyribonucleotide triphosphates, and its expression is highly regulated during various phases of the cell cycle. RRM2 functions as a pro-viral factor essential for HCV RNA synthesis, but its functional role in HCV-induced liver diseases remains unknown. Here, we present a comprehensive review of the role of the hepatocyte cell cycle, in correlation with RRM2 expression, in the regulation of HCV replication. We also discuss the potential relevance of this protein in the pathogenesis of HCV, particularly in the development of hepatocellular carcinoma.

Integrated analysis to study the interplay between post-translational modifications (PTM) in hepatitis C virus proteins and hepatocellular carcinoma (HCC) development

Many PTMs dysregulation is known to be the major cause of many cancers including HCV induced HCC. PTMs of hepatitis C virus (HCV) regions NS3/4A, NS5A and NS5B are crucial for proper protein functions and replication that directly affect the generation of infectious virus particles and completion of its life cycle. In this study, we have performed comprehensive analysis of PTMs within HCV non-structural proteins (NS3/4A, NS5A and NS5B) through bioinformatics analysis to examine post-translational crosstalk between phosphorylation, palmitoylation, methylation, acetylation and ubiquitination sites in selected viral proteins. Our analysis has revealed many highly putative PTMs sites that are also conserved among major genotypes conferring the importance of these sites. We have also analysed viral 3D structures in their modified and unmodified forms to address extent and signatures of structural changes upon PTM. This study provides evidence that PTMs induce significant conformational changes and make viral proteins more stable. To find the potential role of PTMs in HCV induced HCC, docking analysis between selected viral proteins and p38-MAPK has been performed which also confirms their strong association with HCV induced HCC. The major findings proposed that PTMs at specific sites of HCV viral proteins could dysregulate specific pathways that cause the development of HCC.

Unlike for cellular mRNAs and other viral internal ribosome entry sites (IRESs), the eIF3 subunit e is not required for the translational activity of the HCV IRES

Viruses depend on the host cell translation machinery for their replication, and one common strategy is the presence of internal ribosome entry sites (IRESs) in the viral RNAs, using different sets of host translation initiation factors. The hepatitis C virus (HCV) IRES binds eukaryotic translation initiation factor 3 (eIF3), but the exact functional role of the eIF3 complex and of its subunits remains to be precisely defined. Toward this goal, here we focused on eIF3 subunit e. We used an in vitro assay combining a ribosome-depleted rabbit reticulocyte lysate and ribosomes prepared from HeLa or Huh-7.5 cells transfected with either control or eIF3e siRNAs. eIF3e silencing reduced translation mediated by the 5'UTR of various cellular genes and HCV-like IRESs. However, this effect was not observed with the bona fide HCV IRES. Silencing of eIF3e reduced the intracellular levels of the c, d, and l subunits of eIF3 and their association with the eIF3 core subunit a. A pulldown analysis of eIF3 subunits associated with the HCV IRES disclosed similar effects and that the a subunit is critical for binding to the HCV IRES. Carrying out HCV infections of control and eIF3e-silenced Huh-7.5 cells, we found that in agreement with the in vitro findings, eIF3e silencing does not reduce HCV replication and viral protein expression. We conclude that unlike for host cellular mRNAs, the entire eIF3 is not required for HCV RNA translation, favoring viral expression under conditions of low eIF3e levels.

A Cell Culture Model for Persistent HCV Infection.

Chronic hepatitis C virus (HCV) infection affects millions of humans throughout the globe, causing liver disease and hepatocellular carcinoma. Persistence of the virus in the infected host can last for decades as a result of a faulty immune response that fails to clear the virus while constituting a major player in viral pathogenesis. In addition to evading immune responses, HCV has evolved intracellular survival strategies that enable persistent replication without directly killing the host cell.After the generation of cell culture infection models for HCV, the knowledge about this virus and host-virus interactions acquired in the last decade has been greatly increased. Interestingly, persistent infection can also be established in cell culture. This model recapitulates persistent HCV RNA replication and viral protein expression as well as infectious progeny virus assembly and secretion and may be used to study not only these aspects of the virus replication cycle but also to study host-virus interactions in a model of prolonged HCV infection. In this chapter, we describe a methodology to generate persistently HCV-infected cultures and to monitor viral load and progeny virus production. Also, we provide generic protocols to study the impact of chemical compounds and host-targeting shRNAs to illustrate the applications of this model in the study of HCV infection in cell culture.

Identification and functional analysis of a core gene module associated with hepatitis C virus-induced human hepatocellular carcinoma progression.

Hepatitis C virus (HCV)-induced human hepatocellular carcinoma (HCC) progression may be due to a complex multi-step processes. The developmental mechanism of these processes is worth investigating for the prevention, diagnosis and therapy of HCC. The aim of the present study was to investigate the molecular mechanism underlying the progression of HCV-induced hepatocarcinogenesis. First, the dynamic gene module, consisting of key genes associated with progression between the normal stage and HCC, was identified using the Weighted Gene Co-expression Network Analysis tool from R language. By defining those genes in the module as seeds, the change of co-expression in differentially expressed gene sets in two consecutive stages of pathological progression was examined. Finally, interaction pairs of HCV viral proteins and their directly targeted proteins in the identified module were extracted from the literature and a comprehensive interaction dataset from yeast two-hybrid experiments. By combining the interactions between HCV and their targets, and protein-protein interactions in the Search Tool for the Retrieval of Interacting Genes database (STRING), the HCV-key genes interaction network was constructed and visualized using Cytoscape software 3.2. As a result, a module containing 44 key genes was identified to be associated with HCC progression, due to the dynamic features and functions of those genes in the module. Several important differentially co-expressed gene pairs were identified between non-HCC and HCC stages. In the key genes, cyclin dependent kinase 1 (CDK1), NDC80, cyclin A2 (CCNA2) and rac GTPase activating protein 1 (RACGAP1) were shown to be targeted by the HCV nonstructural proteins NS5A, NS3 and NS5B, respectively. The four genes perform an intermediary role between the HCV viral proteins and the dysfunctional module in the HCV key genes interaction network. These findings provided valuable information for understanding the mechanism of HCV-induced HCC progression and for seeking drug targets for the therapy and prevention of HCC.

The Absence of HCV RNA and NS5A Protein in Peripheral Blood Mononuclear Cells Is a Prognostic Tool for Sustained Virological Response.

Hepatitis C Virus (HCV) infection is a major health concern worldwide. The presence of both HCV viral RNA and NS5A proteins in peripheral blood mononuclear cells (PBMCs) indicate the efficacy of the treatment during sustained virological response (SVR) and end of treatment response (ETR). The main objective of this study was to detect the absence or presence of HCV RNA and NS5A proteins in PBMCs. Blood samples were taken from selected patients (Islamabad, Pakistan) before treatment, at ETR, and during SVR. Two hundred HCV responders to pegylated IFN-α-2a plus ribavirin were selected. HCV RNA was extracted from the patients to determine the viral load by reverse transcription (RT)-polymerase chain reaction before treatment. Out of 200 patients, 152 (76%) and 48 (24%) achieved positive and negative ETR, respectively. Among ETR patients, 134 (88.2%) showed SVR, whereas 18 (11.8%) displayed relapse. The male to female ratio was 92:108 with mean age of 37.4 years. Among 152 ETR-positive patients, 29 (19%) patients' PBMCs were positive for HCV RNA and 27 (17.8%) were positive for NS55A proteins. Patients having HCV RNA in PBMCs showed higher relapse frequency compared with patients lacking it. Similarly, patients having NS5A protein showed significantly higher relapse frequency compared with patients lacking it. All PBMC-positive samples were of genotype 3a. In addition, patients with positive NS5A in their PBMCs showed greater risk of relapse compared with patients having HCV RNA. We conclude that the absence of both viral HCV and proteins can be used as an indicator for diagnosis of SVR in the future.

Metformin activates type I interferon signaling against HCV via activation of adenosine monophosphate-activated protein kinase.

Activation of the type I interferon (IFN) signaling pathway is essential for the eradication of hepatitis C virus (HCV). Metformin can activate adenosine monophosphate-activated protein kinase (AMPK) to reduce insulin resistance. Cross talks between AMPK and IFN signaling remain unclear. To understand the influence of metformin on the type I IFN signaling pathway and HCV infection, the full-length HCV replicon OR6 cells and the infectious HCV clones JFH1 were used to assess the anti-HCV effect of the insulin sensitizers, metformin and pioglitazone. Immunofluorescence staining and the immunoblotting of HCV viral protein demonstrated that metformin, but not pioglitazone, inhibited HCV replication in OR-6 and JFH-1-infected Huh 7.5.1 cells. Immunoblotting data showed that metformin activated the phosphorylation of STAT-1 and STAT-2 in OR-6 and JFH-1 infected Huh 7.5.1 cells. Metformin enhanced the phosphorylation of AMPK, and the metformin-activated IFN signaling was down-regulated by AMPK inhibitor. After treatment of AMPK inhibitor, the level of HCV core protein decreased by metformin can be rescued. In conclusion, metformin activates type I interferon signaling and inhibits the replication of HCV via activation of AMPK.

Development of an Aryloxazole Class of Hepatitis C Virus Inhibitors Targeting the Entry Stage of the Viral Replication Cycle.

Reliance on hepatitis C virus (HCV) replicon systems and protein-based screening assays has led to treatments that target HCV viral replication proteins. The model does not encompass other viral replication cycle steps such as entry, processing, assembly and secretion, or viral host factors. We previously applied a phenotypic high-throughput screening platform based on an infectious HCV system and discovered an aryloxazole-based anti-HCV hit. Structure-activity relationship studies revealed several compounds exhibiting EC50 values below 100 nM. Lead compounds showed inhibition of the HCV pseudoparticle entry, suggesting a different mode of action from existing HCV drugs. Hit 7a and lead 7ii both showed synergistic effects in combination with existing HCV drugs. In vivo pharmacokinetics studies of 7ii showed high liver distribution and long half-life without obvious hepatotoxicity. The lead compounds are promising as preclinical candidates for the treatment of HCV infection and as molecular probes to study HCV pathogenesis.

Immune modulation by the hepatitis C virus core protein.

Hepatitis C virus (HCV) infection is currently the most important cause of chronic viral hepatitis in the world and one of the most frequent indications for liver transplantation. HCV uses different strategies to evade the innate and adaptive immune response, and this evasion plays a key role in determining viral persistence. Several HCV viral proteins have been described as immune modulators. In this review, we will focus on the effect of HCV nucleocapsid core protein in the function of immune cells and its correlation with the findings observed in HCV chronically infected patients. Effects on immune cell function related to both extracellular and intracellular HCV core localization will be considered. This review provides an updated perspective on the mechanisms involved in HCV evasion related to one single HCV protein, which could become a key tool in the development of new antiviral strategies able to control and/or eradicate HCV infection.

Hepatitis C Virus-Associated Cancers.

Most hepatitis C virus (HCV) infection results in persistent infection. Significant portion of chronic HCV-infected patients develop hepatocellular carcinoma (HCC). Chronic hepatitis C is also associated with extrahepatic manifestations, including cryoglobulinemia, lymphoma, insulin resistance, type 2 diabetes, and neurological disorders. The molecular mechanisms of how HCV infection causes liver cancer are largely unknown. HCV replication or viral proteins may perturb cellular hemostasis and induce the generation of reactive oxygen species (ROS); viral components or viral replication products act as agonist to trigger innate immune response and cause chronic inflammation. Within the liver, non-hepatocytes such as hepatic stellate cell (HSC) are activated upon HCV infection to provide the major source of extracellular proteins and play important roles in fibrogenesis. With the great achievements of HCV treatment, especially the direct-acting antivirals (DAAs) against HCV, HCV eradication is possible. However, until now there are only very limited data on the effect of DAA-based anti-HCV treatment on HCC patients.

Small acid, big hopes: a rosy outlook for formic acid attracts chemical companies

We aimed to investigate regulation of signal transducer and activator of transcription 3 (STAT3) and suppressor of cytokine signaling 3 (SOCS3) by interferon alpha (IFN-α) and to analyze the relationship between STAT3 and SOCS3 during hepatitis C virus (HCV) infection. Changes in STAT3 and SOCS3 were analyzed at both mRNA and protein levels in human hepatoma cells infected with HCV (J6/JFH1). At 72 h of HCV infection, STAT3 expression was decreased with sustained phosphorylation, and IFN-α increased such decrease and phosphorylation. HCV increased SOCS3 expression, while IFN-α impaired such increase, indicating different regulation of STAT3 and SOCS3 by IFN-α. IFN-α-induced expression and phosphorylation of upstream kinases of the JAK/STAT pathway, Tyk2 and Jak1, were suppressed by HCV. Moreover, knockdown of STAT3 by RNA interference led to decreases in HCV RNA replication and viral protein expression, without affecting either the expression of Tyk2 and Jak1 or the SOCS3 induction in response to IFN-α. These results show that IFN-α antagonizes STAT3 and SOCS3 signaling triggered by HCV and that STAT3 regulation correlates inversely with SOCS3 induction by IFN-α, which may be important in better understanding the complex interplay between IFN-α and signal molecules during HCV infection.

Interferon alpha antagonizes STAT3 and SOCS3 signaling triggered by hepatitis C virus

We aimed to investigate regulation of signal transducer and activator of transcription 3 (STAT3) and suppressor of cytokine signaling 3 (SOCS3) by interferon alpha (IFN-α) and to analyze the relationship between STAT3 and SOCS3 during hepatitis C virus (HCV) infection. Changes in STAT3 and SOCS3 were analyzed at both mRNA and protein levels in human hepatoma cells infected with HCV (J6/JFH1). At 72h of HCV infection, STAT3 expression was decreased with sustained phosphorylation, and IFN-α increased such decrease and phosphorylation. HCV increased SOCS3 expression, while IFN-α impaired such increase, indicating different regulation of STAT3 and SOCS3 by IFN-α. IFN-α-induced expression and phosphorylation of upstream kinases of the JAK/STAT pathway, Tyk2 and Jak1, were suppressed by HCV. Moreover, knockdown of STAT3 by RNA interference led to decreases in HCV RNA replication and viral protein expression, without affecting either the expression of Tyk2 and Jak1 or the SOCS3 induction in response to IFN-α. These results show that IFN-α antagonizes STAT3 and SOCS3 signaling triggered by HCV and that STAT3 regulation correlates inversely with SOCS3 induction by IFN-α, which may be important in better understanding the complex interplay between IFN-α and signal molecules during HCV infection.

Inducible CYP4F12 enhances Hepatitis C virus infection via association with viral nonstructural protein 5B

Hepatitis C virus (HCV) nonstructural protein 5B (NS5B) functions as an RNA-dependent RNA polymerase in the HCV replication complex derived from the endoplasmic reticulum in hepatic cells. In this study, NS5B was used as bait in a yeast two-hybrid assay to screen a human liver cDNA library. We confirmed that CYP4F12, a member of the cytochrome P450 superfamily, interacted with NS5B. Furthermore, overexpression of CYP4F12 facilitated HCV replication. In contrast, knockdown of CYP4F12 by specific shRNA decreased HCV replication and viral protein expression. Moreover, our results demonstrated that HCV infection increased the binding of the transcription factor SREBP1 to the CYP4F12 promoter and activated the promoter activity, which indicated that HCV infection increased the expression of CYP4F12 through the SREBP1 pathway. Our results showed that HCV infection induced expression of CYP4F12 protein, which bound to the HCV replication complex to facilitate viral replication.

Inhibition of STAT Pathway Impairs Anti-Hepatitis C Virus Effect of Interferon Alpha

Background/Aims: Signal transducer and activator of transcription (STAT) pathway plays an important role in antiviral efficacy of interferon alpha (IFN-α). IFN-α is the main therapeutic against hepatitis C virus (HCV) infection. We explored effects of IFN-α on HCV replication and antiviral gene expression by targeting STAT. Methods: In response to IFN-α, STAT status, HCV replication, and antiviral gene expression were analyzed in human hepatoma Huh7.5.1 cells before and after cell culture-derived HCV infection. Results: IFN-α treatment induced expression and phosphorylation of STAT1 and STAT2 in Huh7.5.1 cells. Pretreatment of Huh7.5.1 cells with a mAb to IFN alpha receptor (IFNAR) 2 decreased IFN-α-dependent phosphorylation of STAT1 and STAT2, whereas pretreatment with an IFNAR1 mAb increased such phosphorylation, suggesting that IFNAR mediates IFN-α-triggered STAT signaling. During HCV infection, STAT1 and STAT2 phosphorylation could be rescued by IFN-α and IFN-α-induced phosphorylation of STAT1 and STAT2 was impaired. Inhibition of STAT pathway by Jak inhibitor I significantly enhanced HCV RNA replication and viral protein expression. Antiviral genes coding for IFN regulatory factor 9 and IFN-stimulated gene 15 were up-regulated by IFN-α during HCV infection but such up-regulation was abrogated by Jak inhibitor I. Conclusion: These results establish that activation of STAT pathway is essential for anti-HCV efficacy of IFN-α. Impairment of IFN-α-triggered STAT signaling by HCV may account for evading IFN-α response.

Dominating expression of negative regulatory factors downmodulates major histocompatibility complex Class-II expression on dendritic cells in chronic hepatitis C infection.

To elucidate the molecular mechanisms leading to development of functionally impaired dendritic cells (DCs) in chronic hepatitis C (CHC) patients infected with genotype 3 virus. This prospective study was conducted on the cohorts of CHC individuals identified as responders or non-responders to antiviral therapy. Myeloid DCs were isolated from the peripheral blood of each subject using CD1c (BDCA1)(+) DC isolation Kit. Monocytes from healthy donor were cultured with DC growth factors such as IL-4 and GM-CSF either in the presence or absence of hepatitis C virus (HCV) viral proteins followed by LPS stimulation. Phenotyping was done by flowcytometry and gene expression profiling was evaluated by real-time PCR. Non-responders [sustained virological response (SVR)-ve] to conventional antiviral therapy had significantly higher expression of genes associated with interferon responsive element such as IDO1 and PD-L1 (6-fold) and negative regulators of JAK-STAT pathway such as SOCS (6-fold) as compared to responders (SVR+ve) to antiviral therapy. The down-regulated genes in non-responders included factors involved in antigen processing and presentation mainly belonging to major histocompatibility complex (MHC) Class-II family as HLA-DP, HLA-DQ (2-fold) and superoxide dismutase (2-fold). Cells grown in the presence of HCV viral proteins had genes down-regulated for factors involved in innate response, interferon signaling, DC maturation and co-stimulatory signaling to T-cells, while the genes for cytokine signaling and Toll-like receptors (4-fold) were up-regulated as compared to cells grown in absence of viral proteins. Underexpressed MHC class-II genes and upregulated negative regulators in non-responders indicate diminished capacity to present antigen and may constitute mechanism of functionally defective state of DCs.

Quantitative Proteomics Analysis of the Hepatitis C Virus Replicon High-Permissive and Low-Permissive Cell Lines

Chronic hepatitis C virus (HCV) infection is one of the leading causes of severe hepatitis. The molecular mechanisms underlying HCV replication and pathogenesis remain unclear. The development of the subgenome replicon model system significantly enhanced study of HCV. However, the permissiveness of the HCV subgenome replicon greatly differs among different hepatoma cell lines. Proteomic analysis of different permissive cell lines might provide new clues in understanding HCV replication. In this study, to detect potential candidates that might account for the differences in HCV replication. Label-free and iTRAQ labeling were used to analyze the differentially expressed protein profiles between Huh7.5.1 wt and HepG2 cells. A total of 4919 proteins were quantified in which 114 proteins were commonly identified as differentially expressed by both quantitative methods. A total of 37 differential proteins were validated by qRT-PCR. The differential expression of Glutathione S-transferase P (GSTP1), Ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCHL1), carboxylesterase 1 (CES1), vimentin, Proteasome activator complex subunit1 (PSME1), and Cathepsin B (CTSB) were verified by western blot. And over-expression of CTSB or knock-down of vimentin induced significant changes to HCV RNA levels. Additionally, we demonstrated that CTSB was able to inhibit HCV replication and viral protein translation. These results highlight the potential role of CTSB and vimentin in virus replication.

Hepatitis C virus upregulates B-cell receptor signaling: a novel mechanism for HCV-associated B-cell lymphoproliferative disorders.

B-cell receptor (BCR) signaling is essential for the development of B cells and has a critical role in B-cell neoplasia. Increasing evidence indicates an association between chronic hepatitis C virus (HCV) infection and B-cell lymphoma, however, the mechanisms by which HCV causes B-cell lymphoproliferative disorder are still unclear. Herein, we demonstrate the expression of HCV viral proteins in B cells of HCV-infected patients and show that HCV upregulates BCR signaling in human primary B cells. HCV nonstructural protein NS3/4A interacts with CHK2 and downregulates its activity, modulating HuR posttranscriptional regulation of a network of target mRNAs associated with B-cell lymphoproliferative disorders. Interestingly, the BCR signaling pathway was found to have the largest number of transcripts with increased association with HuR and was upregulated by NS3/4A. Our study reveals a previously unidentified role of NS3/4A in regulation of host BCR signaling during HCV infection, contributing to a better understanding of the molecular mechanisms underlying HCV-associated B-cell lymphoproliferative disorders.

Abstract LB-035: Hepatitis C virus NS3/4A hijacks the host B-cell receptor signaling pathway

Abstract B-cell receptor (BCR) signaling is critical for the development of normal B-cells and B-cell lymphoma. Increasing epidemiological evidence indicates an association between chronic hepatitis C virus (HCV) infection and B-cell lymphoma, however, the mechanisms by which HCV causes B-cell lymphoproliferative disorder are still unclear. Herein, we demonstrate the expression of HCV viral proteins in B-cells of HCV-infected patients and show that HCV up-regulates BCR signaling in human primary B-cells. HCV nonstructural protein NS3/4A interacts with CHK2 and down-regulates its activity, modulating HuR posttranscriptional regulation of a network of target mRNAs associated with B-cell lymphoproliferative disorders. Strikingly, the BCR signaling pathway was found to have the largest number of transcripts with increased association with HuR and up-regulated by NS3/4A. Our study reveals a previously unidentified role of NS3/4A in regulation of host BCR signaling during HCV infection, lending further insight into the molecular mechanisms underlying HCV-associated B-cell lymphoproliferative disorders. Citation Format: Bojie Dai, Ari Landon, Simone Houng, Ronald B. Gartenhaus. Hepatitis C virus NS3/4A hijacks the host B-cell receptor signaling pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-035. doi:10.1158/1538-7445.AM2015-LB-035