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Romero S, Unchwaniwala N, Evans EL, Eliceiri KW, Loeb DD, Sherer NM. Live Cell Imaging Reveals HBV Capsid Translocation from the Nucleus To the Cytoplasm Enabled by Cell Division. mBio 2023; 14:e0330322. [PMID: 36809075 PMCID: PMC10127671 DOI: 10.1128/mbio.03303-22] [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: 11/29/2022] [Accepted: 01/17/2023] [Indexed: 02/23/2023] Open
Abstract
Hepatitis B virus (HBV) capsid assembly is traditionally thought to occur predominantly in the cytoplasm, where the virus gains access to the virion egress pathway. To better define sites of HBV capsid assembly, we carried out single cell imaging of HBV Core protein (Cp) subcellular trafficking over time under conditions supporting genome packaging and reverse transcription in Huh7 hepatocellular carcinoma cells. Time-course analyses including live cell imaging of fluorescently tagged Cp derivatives showed Cp to accumulate in the nucleus at early time points (~24 h), followed by a marked re-distribution to the cytoplasm at 48 to 72 h. Nucleus-associated Cp was confirmed to be capsid and/or high-order assemblages using a novel dual label immunofluorescence strategy. Nuclear-to-cytoplasmic re-localization of Cp occurred predominantly during nuclear envelope breakdown in conjunction with cell division, followed by strong cytoplasmic retention of Cp. Blocking cell division resulted in strong nuclear entrapment of high-order assemblages. A Cp mutant, Cp-V124W, predicted to exhibit enhanced assembly kinetics, also first trafficked to the nucleus to accumulate at nucleoli, consistent with the hypothesis that Cp's transit to the nucleus is a strong and constitutive process. Taken together, these results provide support for the nucleus as an early-stage site of HBV capsid assembly, and provide the first dynamic evidence of cytoplasmic retention after cell division as a mechanism underpinning capsid nucleus-to-cytoplasm relocalization. IMPORTANCE Hepatitis B virus (HBV) is an enveloped, reverse-transcribing DNA virus that is a major cause of liver disease and hepatocellular carcinoma. Subcellular trafficking events underpinning HBV capsid assembly and virion egress remain poorly characterized. Here, we developed a combination of fixed and long-term (>24 h) live cell imaging technologies to study the single cell trafficking dynamics of the HBV Core Protein (Cp). We demonstrate that Cp first accumulates in the nucleus, and forms high-order structures consistent with capsids, with the predominant route of nuclear egress being relocalization to the cytoplasm during cell division in conjunction with nuclear membrane breakdown. Single cell video microscopy demonstrated unequivocally that Cp's localization to the nucleus is constitutive. This study represents a pioneering application of live cell imaging to study HBV subcellular transport, and demonstrates links between HBV Cp and the cell cycle.
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Affiliation(s)
- Sofia Romero
- McArdle Laboratory for Cancer Research (Department of Oncology), University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Carbone Cancer Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Nuruddin Unchwaniwala
- McArdle Laboratory for Cancer Research (Department of Oncology), University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Carbone Cancer Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Edward L. Evans
- Laboratory for Optical and Computational Instrumentation, Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Morgridge Institute for Research, Madison, Wisconsin, USA
| | - Kevin W. Eliceiri
- Laboratory for Optical and Computational Instrumentation, Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Morgridge Institute for Research, Madison, Wisconsin, USA
| | - Daniel D. Loeb
- McArdle Laboratory for Cancer Research (Department of Oncology), University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
- Carbone Cancer Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
| | - Nathan M. Sherer
- McArdle Laboratory for Cancer Research (Department of Oncology), University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
- Institute for Molecular Virology, University of Wisconsin-Madison, Madison, Wisconsin, USA
- Carbone Cancer Center, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin, USA
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CRM1-spike-mediated nuclear export of hepatitis B virus encapsidated viral RNA. Cell Rep 2022; 38:110472. [PMID: 35263598 DOI: 10.1016/j.celrep.2022.110472] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 01/23/2022] [Accepted: 02/10/2022] [Indexed: 11/20/2022] Open
Abstract
Hepatitis B virus (HBV) is a global pathogen. We report here that the cellular CRM1 machinery can mediate nuclear export of entire HBV core (HBc) particles containing encapsidated viral RNAs. Two CRM1-mediated nuclear export signals (NESCRM1) cluster at the conformationally flexible spike tips of HBc particles. Mutant NESCRM1 capsids exhibit strongly reduced associations with CRM1 and nucleoporin358 in vivo. CRM1 and NXF1 machineries mediate nuclear export of HBc particles independently. Inhibition of nuclear export has pleiotropic consequences, including nuclear accumulation of HBc particles, a significant reduction of encapsidated viral RNAs in the cytoplasm but not in the nucleus, and barely detectable viral DNA. We hypothesize an HBV life cycle where encapsidation of the RNA pregenome can initiate early in the nucleus, whereas DNA genome maturation occurs mainly in the cytoplasm. We identified a druggable target for HBV by blocking its intracellular trafficking.
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Pastor F, Shkreta L, Chabot B, Durantel D, Salvetti A. Interplay Between CMGC Kinases Targeting SR Proteins and Viral Replication: Splicing and Beyond. Front Microbiol 2021; 12:658721. [PMID: 33854493 PMCID: PMC8040976 DOI: 10.3389/fmicb.2021.658721] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 03/04/2021] [Indexed: 12/27/2022] Open
Abstract
Protein phosphorylation constitutes a major post-translational modification that critically regulates the half-life, intra-cellular distribution, and activity of proteins. Among the large number of kinases that compose the human kinome tree, those targeting RNA-binding proteins, in particular serine/arginine-rich (SR) proteins, play a major role in the regulation of gene expression by controlling constitutive and alternative splicing. In humans, these kinases belong to the CMGC [Cyclin-dependent kinases (CDKs), Mitogen-activated protein kinases (MAPKs), Glycogen synthase kinases (GSKs), and Cdc2-like kinases (CLKs)] group and several studies indicate that they also control viral replication via direct or indirect mechanisms. The aim of this review is to describe known and emerging activities of CMGC kinases that share the common property to phosphorylate SR proteins, as well as their interplay with different families of viruses, in order to advance toward a comprehensive knowledge of their pro- or anti-viral phenotype and better assess possible translational opportunities.
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Affiliation(s)
- Florentin Pastor
- International Center for Infectiology Research (CIRI), INSERM U1111, CNRS UMR5308, Université de Lyon (UCBL1), Lyon, France
| | - Lulzim Shkreta
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Benoit Chabot
- Department of Microbiology and Infectious Diseases, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - David Durantel
- International Center for Infectiology Research (CIRI), INSERM U1111, CNRS UMR5308, Université de Lyon (UCBL1), Lyon, France
| | - Anna Salvetti
- International Center for Infectiology Research (CIRI), INSERM U1111, CNRS UMR5308, Université de Lyon (UCBL1), Lyon, France
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Nuclear Import of Adeno-Associated Viruses Imaged by High-Speed Single-Molecule Microscopy. Viruses 2021; 13:v13020167. [PMID: 33499411 PMCID: PMC7911914 DOI: 10.3390/v13020167] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/21/2021] [Accepted: 01/21/2021] [Indexed: 12/15/2022] Open
Abstract
Understanding the detailed nuclear import kinetics of adeno-associated virus (AAV) through the nuclear pore complex (NPC) is essential for the application of AAV capsids as a nuclear delivery instrument as well as a target for drug development. However, a comprehensive understanding of AAV transport through the sub-micrometer NPCs in live cells calls for new techniques that can conquer the limitations of conventional fluorescence microscopy and electron microscopy. With recent technical advances in single-molecule fluorescence microscopy, we are now able to image the entire nuclear import process of AAV particles and also quantify the transport dynamics of viral particles through the NPCs in live human cells. In this review, we initially evaluate the necessity of single-molecule live-cell microscopy in the study of nuclear import for AAV particles. Then, we detail the application of high-speed single-point edge-excitation sub-diffraction (SPEED) microscopy in tracking the entire process of nuclear import for AAV particles. Finally, we summarize the major findings for AAV nuclear import by using SPEED microscopy.
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Hepatitis B virus Core protein nuclear interactome identifies SRSF10 as a host RNA-binding protein restricting HBV RNA production. PLoS Pathog 2020; 16:e1008593. [PMID: 33180834 PMCID: PMC7707522 DOI: 10.1371/journal.ppat.1008593] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 12/01/2020] [Accepted: 10/04/2020] [Indexed: 12/11/2022] Open
Abstract
Despite the existence of a preventive vaccine, chronic infection with Hepatitis B virus (HBV) affects more than 250 million people and represents a major global cause of hepatocellular carcinoma (HCC) worldwide. Current clinical treatments, in most of cases, do not eliminate viral genome that persists as a DNA episome in the nucleus of hepatocytes and constitutes a stable template for the continuous expression of viral genes. Several studies suggest that, among viral factors, the HBV core protein (HBc), well-known for its structural role in the cytoplasm, could have critical regulatory functions in the nucleus of infected hepatocytes. To elucidate these functions, we performed a proteomic analysis of HBc-interacting host-factors in the nucleus of differentiated HepaRG, a surrogate model of human hepatocytes. The HBc interactome was found to consist primarily of RNA-binding proteins (RBPs), which are involved in various aspects of mRNA metabolism. Among them, we focused our studies on SRSF10, a RBP that was previously shown to regulate alternative splicing (AS) in a phosphorylation-dependent manner and to control stress and DNA damage responses, as well as viral replication. Functional studies combining SRSF10 knockdown and a pharmacological inhibitor of SRSF10 phosphorylation (1C8) showed that SRSF10 behaves as a restriction factor that regulates HBV RNAs levels and that its dephosphorylated form is likely responsible for the anti-viral effect. Surprisingly, neither SRSF10 knock-down nor 1C8 treatment modified the splicing of HBV RNAs but rather modulated the level of nascent HBV RNA. Altogether, our work suggests that in the nucleus of infected cells HBc interacts with multiple RBPs that regulate viral RNA metabolism. Our identification of SRSF10 as a new anti-HBV restriction factor offers new perspectives for the development of new host-targeted antiviral strategies. Chronic infection with Hepatitis B virus (HBV) affects more than 250 million of people world-wide and is a major global cause of liver cancer. Current treatments lead to a significant reduction of viremia in patients. However, viral clearance is rarely obtained and the persistence of the HBV genome in the hepatocyte’s nucleus generates a stable source of viral RNAs and subsequently proteins which play important roles in immune escape mechanisms and liver disease progression. Therapies aiming at efficiently and durably eliminating viral gene expression are still required. In this study, we identified the nuclear partners of the HBV Core protein (HBc) to understand how this structural protein, responsible for capsid assembly in the cytoplasm, could also regulate viral gene expression. The HBc interactome was found to consist primarily of RNA-binding proteins (RBPs). One of these RBPs, SRSF10, was demonstrated to restrict HBV RNA levels and a drug, able to alter its phosphorylation, behaved as an antiviral compound capable of reducing viral gene expression. Altogether, this study sheds new light on novel regulatory functions of HBc and provides information relevant for the development of antiviral strategies aiming at preventing viral gene expression.
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Diab A, Foca A, Zoulim F, Durantel D, Andrisani O. The diverse functions of the hepatitis B core/capsid protein (HBc) in the viral life cycle: Implications for the development of HBc-targeting antivirals. Antiviral Res 2017; 149:211-220. [PMID: 29183719 DOI: 10.1016/j.antiviral.2017.11.015] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 11/08/2017] [Accepted: 11/17/2017] [Indexed: 12/14/2022]
Abstract
Virally encoded proteins have evolved to perform multiple functions, and the core protein (HBc) of the hepatitis B virus (HBV) is a perfect example. While HBc is the structural component of the viral nucleocapsid, additional novel functions for the nucleus-localized HBc have recently been described. These results extend for HBc, beyond its structural role, a regulatory function in the viral life cycle and potentially a role in pathogenesis. In this article, we review the diverse roles of HBc in HBV replication and pathogenesis, emphasizing how the unique structure of this protein is key to its various functions. We focus in particular on recent advances in understanding the significance of HBc phosphorylations, its interaction with host proteins and the role of HBc in regulating the transcription of host genes. We also briefly allude to the emerging niche for new direct-acting antivirals targeting HBc, known as Core (protein) Allosteric Modulators (CAMs).
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Affiliation(s)
- Ahmed Diab
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA; INSERM U1052, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, Université Claude-Bernard (UCBL), UMR_S1052, UCBL, 69008, Lyon, France
| | - Adrien Foca
- INSERM U1052, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, Université Claude-Bernard (UCBL), UMR_S1052, UCBL, 69008, Lyon, France
| | - Fabien Zoulim
- INSERM U1052, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, Université Claude-Bernard (UCBL), UMR_S1052, UCBL, 69008, Lyon, France; Hepato-Gastroenterology Unit, Croix-Rousse Hospital, Hospices Civils de Lyon (HCL), 69002, Lyon, France; Labex DEVweCAN, 69008, Lyon, France
| | - David Durantel
- INSERM U1052, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, Université Claude-Bernard (UCBL), UMR_S1052, UCBL, 69008, Lyon, France; Hepato-Gastroenterology Unit, Croix-Rousse Hospital, Hospices Civils de Lyon (HCL), 69002, Lyon, France.
| | - Ourania Andrisani
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN, 47907, USA.
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7
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Nuclear Import of Hepatitis B Virus Capsids and Genome. Viruses 2017; 9:v9010021. [PMID: 28117723 PMCID: PMC5294990 DOI: 10.3390/v9010021] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 01/17/2017] [Accepted: 01/17/2017] [Indexed: 02/07/2023] Open
Abstract
Hepatitis B virus (HBV) is an enveloped pararetrovirus with a DNA genome, which is found in an up to 36 nm-measuring capsid. Replication of the genome occurs via an RNA intermediate, which is synthesized in the nucleus. The virus must have thus ways of transporting its DNA genome into this compartment. This review summarizes the data on hepatitis B virus genome transport and correlates the finding to those from other viruses.
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Chen C, Wang JCY, Pierson EE, Keifer DZ, Delaleau M, Gallucci L, Cazenave C, Kann M, Jarrold MF, Zlotnick A. Importin β Can Bind Hepatitis B Virus Core Protein and Empty Core-Like Particles and Induce Structural Changes. PLoS Pathog 2016; 12:e1005802. [PMID: 27518410 PMCID: PMC4982637 DOI: 10.1371/journal.ppat.1005802] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 07/11/2016] [Indexed: 02/06/2023] Open
Abstract
Hepatitis B virus (HBV) capsids are found in many forms: immature single-stranded RNA-filled cores, single-stranded DNA-filled replication intermediates, mature cores with relaxed circular double-stranded DNA, and empty capsids. A capsid, the protein shell of the core, is a complex of 240 copies of core protein. Mature cores are transported to the nucleus by a complex that includes both importin α and importin β (Impα and Impβ), which bind to the core protein's C-terminal domains (CTDs). Here we have investigated the interactions of HBV core protein with importins in vitro. Strikingly, empty capsids and free core protein can bind Impβ without Impα. Cryo-EM image reconstructions show that the CTDs, which are located inside the capsid, can extrude through the capsid to be bound by Impβ. Impβ density localized on the capsid exterior near the quasi-sixfold vertices, suggested a maximum of 30 Impβ per capsid. However, examination of complexes using single molecule charge-detection mass spectrometry indicate that some complexes include over 90 Impβ molecules. Cryo-EM of capsids incubated with excess Impβ shows a population of damaged particles and a population of "dark" particles with internal density, suggesting that Impβ is effectively swallowed by the capsids, which implies that the capsids transiently open and close and can be destabilized by Impβ. Though the in vitro complexes with great excess of Impβ are not biological, these results have implications for trafficking of empty capsids and free core protein; activities that affect the basis of chronic HBV infection.
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Affiliation(s)
- Chao Chen
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Joseph Che-Yen Wang
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Elizabeth E. Pierson
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States of America
| | - David Z. Keifer
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Mildred Delaleau
- Universite de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Lara Gallucci
- Universite de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Christian Cazenave
- Universite de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Michael Kann
- Universite de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
- CHU de Bordeaux, Bordeaux, France
| | - Martin F. Jarrold
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States of America
| | - Adam Zlotnick
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, United States of America
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States of America
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
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Blondot ML, Bruss V, Kann M. Intracellular transport and egress of hepatitis B virus. J Hepatol 2016; 64:S49-S59. [PMID: 27084037 DOI: 10.1016/j.jhep.2016.02.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 01/27/2016] [Accepted: 02/03/2016] [Indexed: 12/23/2022]
Abstract
Hepatitis B virus (HBV) replicates its genomic information in the nucleus via transcription and therefore has to deliver its partially double stranded DNA genome into the nucleus. Like other viruses with a nuclear replication phase, HBV genomes are transported inside the viral capsids first through the cytoplasm towards the nuclear envelope. Following the arrival at the nuclear pore, the capsids are transported through, using classical cellular nuclear import pathways. The arrest of nuclear import at the nucleoplasmic side of the nuclear pore is unique, however, and is where the capsids efficiently disassemble leading to genome release. In the latter phase of the infection, newly formed nucleocapsids in the cytosol have to move to budding sites at intracellular membranes carrying the three viral envelope proteins. Capsids containing single stranded nucleic acid are not enveloped, in contrast to empty and double stranded DNA containing capsids. A small linear domain in the large envelope protein and two areas on the capsid surface have been mapped, where point mutations strongly block nucleocapsid envelopment. It is possible that these domains are involved in the envelope--with capsid interactions driving the budding process. Like other enveloped viruses, HBV also uses the cellular endosomal sorting complexes required for transport (ESCRT) machinery for catalyzing budding through the membrane and away from the cytosol.
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Affiliation(s)
- Marie-Lise Blondot
- Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Volker Bruss
- Institute for Virology, Helmholtz Zentrum München, Technische Universität Muenchen, Neuherberg, Germany
| | - Michael Kann
- Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France; CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France; CHU de Bordeaux, Bordeaux, France.
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10
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Deroubaix A, Osseman Q, Cassany A, Bégu D, Ragues J, Kassab S, Lainé S, Kann M. Expression of viral polymerase and phosphorylation of core protein determine core and capsid localization of the human hepatitis B virus. J Gen Virol 2014; 96:183-195. [PMID: 25274856 DOI: 10.1099/vir.0.064816-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Biopsies from patients show that hepadnaviral core proteins and capsids - collectively called core - are found in the nucleus and cytoplasm of infected hepatocytes. In the majority of studies, cytoplasmic core localization is related to low viraemia while nuclear core localization is associated with high viral loads. In order to better understand the molecular interactions leading to core localization, we analysed transfected hepatoma cells using immune fluorescence microscopy. We observed that expression of core protein in the absence of other viral proteins led to nuclear localization of core protein and capsids, while expression of core in the context of the other viral proteins resulted in a predominantly cytoplasmic localization. Analysis of which viral partner was responsible for cytoplasmic retention indicated that the HBx, surface proteins and HBeAg had no impact but that the viral polymerase was the major determinant. Further analysis revealed that ϵ, an RNA structure to which the viral polymerase binds, was essential for cytoplasmic retention. Furthermore, we showed that core protein phosphorylation at Ser 164 was essential for the cytoplasmic core localization phenotype, which is likely to explain differences observed between individual cells.
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Affiliation(s)
- Aurélie Deroubaix
- Hepatitis Virus Diversity Research Programme, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg 2193, South Africa.,CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Quentin Osseman
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Aurélia Cassany
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Dominique Bégu
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Jessica Ragues
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Somar Kassab
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
| | - Sébastien Lainé
- CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,Université Montpellier 1, CPBS, UMR 5236 CNRS, Montpellier, France
| | - Michael Kann
- Univ. de Bordeaux, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France.,CHU de Bordeaux, Bordeaux, France.,CNRS, Microbiologie Fondamentale et Pathogénicité, UMR 5234, Bordeaux, France
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11
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Shi KD, Hwang SG, Choi JH, Hwang IJ, Yoon JH, Kim KI, Kwon CI, Hong SP, Park PW, Rim KS. [Hepatitis B core antigen expression pattern predicts response to lamivudine therapy in patients with chronic hepatitis B]. THE KOREAN JOURNAL OF HEPATOLOGY 2008; 14:197-205. [PMID: 18617767 DOI: 10.3350/kjhep.2008.14.2.197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUNDS/AIMS Negative hepatitis B core antigen (HBcAg) staining in hepatocytes is indicative of viral replication by an active immune response. HBcAg is expressed mainly in the cytoplasm in patients with active hepatitis and hepatocyte regeneration, and mainly in the nuclei of hepatocytes in patients with minimal liver injury in the absence of hepatocyte regeneration. The aim of this study was to elucidate whether the existence and expression pattern of HBcAg predicts the response to antiviral treatment. METHODS The study involved 58 patients with biopsy-proven chronic hepatitis B who were treated with lamivudine. Hepatitis B e antigen (HBeAg), antibody to HBeAg, hepatitis B virus DNA, and alanine aminotransferase in serum were recorded every 3 months. The inflammation grade and the fibrosis stage of chronic hepatitis were scored from 0 to 4 according to lobular inflammation, portal inflammation, periportal inflammation, and fibrosis. RESULTS The 58 patients included 49(84%) HBcAg-positive patients, with HBcAg staining confined to the cytoplasm in 15(31%) and in both cytoplasm and nuclei in 34(69%). The grade of lobular inflammation and the total histology score were significantly higher in patients with cytoplasmic expression of HBcAg than in HBcAg-negative patients (lobular inflammation: 2.9 vs 2.1, P=0.02; total histology score: 12.2 vs 10.3, P=0.04). The virologic responses at 3, 6, 9, and 12 months differed significantly between the cytoplasmic and mixed expression groups (P<0.01). CONCLUSIONS The expression pattern of HBcAg (including its possible absence) before initial therapy appears to predict the response to antiviral treatment.
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Affiliation(s)
- Kyeh Dong Shi
- Department of Gastroenterology and Hepatology, Bundang CHA Hospital, College of Medicine, Pochon CHA University, Seongnam, Korea
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12
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Yeh CT, Tang JH, Hsu CW, Chen YC, Chang ML, Lin CY. Expression of hepatitis B virus nuclear core antigen in young cirrhotic patients is associated with an unfavourable long-term outcome. J Viral Hepat 2008; 15:839-48. [PMID: 18647234 DOI: 10.1111/j.1365-2893.2008.01017.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
The aim of this case control study was to investigate the clinical significance of hepatitis B virus nuclear core antigen (HBcAg) in young cirrhotic patients. Fifteen cirrhotic patients with nuclear HBcAg in the liver biopsies were included. Their clinicopathological parameters as well as the core gene sequences were compared with those of a sex- and age-matched (1 to 2) control group. The mean follow-up periods were 124 +/- 80 and 102 +/- 43 months, respectively. Expression of nuclear HBcAg in cirrhotic liver was significantly associated with higher aspartate aminotransferase levels (P = 0.001), alanine aminotransferase levels (P < 0.001), and alpha-fetoprotein levels (P = 0.002), as well as a shorter duration to develop hepatocellular carcinoma or liver decompensation (Kaplan-Meier method, P = 0.044). Sequence analysis revealed mutations on the nuclear localization signal (NLS) of core protein in five cirrhotic patients with nuclear HBcAg (Q171K in four and Q179K in one patients). Site-directed mutagenesis experiments demonstrated that both the Q171K and Q179K mutation enhanced nuclear localization of the core protein. In conclusion, expression of nuclear HBcAg in young cirrhotic patients was associated with more severe hepatitis activities as well as an unfavourable long-term outcome. Mutations on the NLS of core protein were selected in some patients with nuclear HBcAg.
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Affiliation(s)
- C-T Yeh
- Department of Gastroenterology, Liver Cancer Research Centre, Chang Gung Memorial Hospital, Taipei, Taiwan.
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13
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Roingeard P, Lu SL, Sureau C, Freschlin M, Arbeille B, Essex M, Romet-Lemonne JL. Immunocytochemical and electron microscopic study of hepatitis B virus antigen and complete particle production in hepatitis B virus DNA transfected HepG2 cells. Hepatology 1990; 11:277-85. [PMID: 2407629 DOI: 10.1002/hep.1840110219] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The relationship between the presence of hepatitis B virus antigens, their localization and hepatitis B virus replication was studied in different clones of cultured HepG2 hepatoblastoma cells transfected with cloned hepatitis B virus DNA. Intracellular hepatitis B virus antigens were detected by immunofluorescence. The production of these antigens was evaluated in the culture media by enzyme-linked immunoassay. Hepatitis B virus DNA was detected using dot-blot hybridization. Three types of HBcAg staining were observed in transfected HepG2 cells: (a) cells with nuclear HBcAg, (b) cells with cytoplasmic HBcAg and (c) cells with both nuclear and cytoplasmic HBcAg. Cell types b and c also expressed hepatitis B virus DNA in their culture media. Our results suggest that cytoplasmic HBcAg may be more involved than nuclear HBcAg in hepatitis B virus replication. The site of hepatitis B virus formation in hepatocytes was studied by electron microscopic examination of a specific hepatitis B virus producer clone, thereby allowing detection of intracellular Dane particles more easily than liver biopsy samples from infected patients. Dane particles and HBsAg filaments were found in large, dilated structures probably related to the endoplasmic reticulum. Budding of core particles into cisternae of endoplasmic reticulum-related structures appears to be a possible mechanism for hepatitis B virus formation; our results suggest that the exocytosis of cisternae to extracellular spaces may be a mechanism for release of hepatitis B virus particles.
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Affiliation(s)
- P Roingeard
- Department of Cancer Biology, Harvard School of Public Health, Boston, Massachusetts 02115
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14
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Theilmann L, Hofmann WJ, Pfaff E. Isolation and characterization of cytoplasmic and nuclear particles of hepatitis B virus. Virus Res 1989; 14:225-34. [PMID: 2623942 DOI: 10.1016/0168-1702(89)90003-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The properties of hepatitis B virus (HBV) core particles from liver tissue of two patients with acute HBV infection were investigated. Cores were isolated from cytoplasm and nuclear fractions by centrifugation and two thirds of the cores were located in the cytoplasm. In all properties examined cores isolated from the cytoplasm or nucleus were the same. The cores had a density of 1.38 g/ml and had the same DNA and protein content when analyzed by Southern blotting and by Western blotting with C-specific antisera. Cores from both subcellular fractions had endogenous polymerase activity. We conclude that core particles with identical properties are found in both the cytoplasm and nucleus of cells during acute infection.
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Affiliation(s)
- L Theilmann
- Department of Medicine, University of Heidelberg, F.R.G
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15
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Infection chronique a virus de l'hepatite B. Aspects cliniques, biologiques et histologiques : A propos de 30 Cas. Med Mal Infect 1989. [DOI: 10.1016/s0399-077x(89)80226-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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