1
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McCoullough LC, Sadauskas T, Sozzi V, Mak KY, Mason H, Littlejohn M, Revill PA. The in vitro replication phenotype of hepatitis B virus (HBV) splice variants Sp3 and Sp9 and their impact on wild-type HBV replication. J Virol 2024; 98:e0153823. [PMID: 38501924 PMCID: PMC11019940 DOI: 10.1128/jvi.01538-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 02/22/2024] [Indexed: 03/20/2024] Open
Abstract
Prior to nuclear export, the hepatitis B virus (HBV) pregenomic RNA may be spliced by the host cell spliceosome to form shorter RNA sequences known as splice variants. Due to deletions in the open reading frames, splice variants may encode novel fusion proteins. Although not essential for HBV replication, the role of splice variants and their novel fusion proteins largely remains unknown. Some splice variants and their encoded novel fusion proteins have been shown to impair or promote wild-type HBV replication in vitro, and although splice variants Sp3 and Sp9 are two of the most common splice variants identified to date, their in vitro replication phenotype and their impact on wild-type HBV replication are unclear. Here, we utilize greater than genome-length Sp3 and Sp9 constructs to investigate their replication phenotype in vitro, and their impact on wild-type HBV replication. We show that Sp3 and Sp9 were incapable of autonomous replication, which was rescued by providing the polymerase and core proteins in trans. Furthermore, we showed that Sp3 had no impact on wild-type HBV replication, whereas Sp9 strongly reduced wild-type HBV replication in co-transfection experiments. Knocking out Sp9 novel precore-surface and core-surface fusion protein partially restored replication, suggesting that these proteins contributed to suppression of wild-type HBV replication, providing further insights into factors regulating HBV replication in vitro. IMPORTANCE The role of hepatitis B virus (HBV) splice variants in HBV replication and pathogenesis currently remains largely unknown. However, HBV splice variants have been associated with the development of hepatocellular carcinoma, suggesting a role in HBV pathogenesis. Several in vitro co-transfection studies have shown that different splice variants have varying impacts on wild-type HBV replication, perhaps contributing to viral persistence. Furthermore, all splice variants are predicted to produce novel fusion proteins. Sp1 hepatitis B splice protein contributes to liver disease progression and apoptosis; however, the function of other HBV splice variant novel fusion proteins remains largely unknown. We show that Sp9 markedly impairs HBV replication in a cell culture co-transfection model, mediated by expression of Sp9 novel fusion proteins. In contrast, Sp3 had no effect on wild-type HBV replication. Together, these studies provide further insights into viral factors contributing to regulation of HBV replication.
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Affiliation(s)
- Laura C. McCoullough
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Tomas Sadauskas
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Vitina Sozzi
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Kai Yan Mak
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Hugh Mason
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Margaret Littlejohn
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Infectious Diseases, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
| | - Peter A. Revill
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Infectious Diseases, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
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2
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Dobrica MO, Varghese CS, Harris JM, Ferguson J, Magri A, Arnold R, Várnai C, Parish JL, McKeating JA. CTCF regulates hepatitis B virus cccDNA chromatin topology. J Gen Virol 2024; 105. [PMID: 38175123 DOI: 10.1099/jgv.0.001939] [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] [Indexed: 01/05/2024] Open
Abstract
Hepatitis B Virus (HBV) is a small DNA virus that replicates via an episomal covalently closed circular DNA (cccDNA) that serves as the transcriptional template for viral mRNAs. The host protein, CCCTC-binding factor (CTCF), is a key regulator of cellular transcription by maintaining epigenetic boundaries, nucleosome phasing, stabilisation of long-range chromatin loops and directing alternative exon splicing. We previously reported that CTCF binds two conserved motifs within Enhancer I of the HBV genome and represses viral transcription, however, the underlying mechanisms were not identified. We show that CTCF depletion in cells harbouring cccDNA-like HBV molecules and in de novo infected cells resulted in an increase in spliced transcripts, which was most notable in the abundant SP1 spliced transcript. In contrast, depletion of CTCF in cell lines with integrated HBV DNA had no effect on the abundance of viral transcripts and in line with this observation there was limited evidence for CTCF binding to viral integrants, suggesting that CTCF-regulation of HBV transcription is specific to episomal cccDNA. Analysis of HBV chromatin topology by Assay for Transposase Accessible Chromatin Sequencing (ATAC-Seq) revealed an accessible region spanning Enhancers I and II and the basal core promoter (BCP). Mutating the CTCF binding sites within Enhancer I resulted in a dramatic rearrangement of chromatin accessibility where the open chromatin region was no longer detected, indicating loss of the phased nucleosome up- and down-stream of the HBV enhancer/BCP. These data demonstrate that CTCF functions to regulate HBV chromatin conformation and nucleosomal positioning in episomal maintained cccDNA, which has important consequences for HBV transcription regulation.
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Affiliation(s)
- Mihaela Olivia Dobrica
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Present address: Institute of Biochemistry of the Romanian Academy, Bucharest, Romania
| | - Christy Susan Varghese
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | | | - Jack Ferguson
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- Present address: Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK
| | - Andrea Magri
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Roland Arnold
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Csilla Várnai
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Joanna L Parish
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
- National Institute for Health and Care Research (NIHR) Birmingham Biomedical Research Centre, Oxford, UK
| | - Jane A McKeating
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, Oxford, UK
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3
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Xu X, Zhang L, Ye G, Shi J, Peng Y, Xin F, Lin Y, Wu Q, Lin X, Chen W. Hepatitis B doubly spliced protein (HBDSP) promotes hepatocellular carcinoma cell apoptosis via ETS1/GATA2/YY1-mediated p53 transcription. J Virol 2023; 97:e0108723. [PMID: 37929990 PMCID: PMC10688342 DOI: 10.1128/jvi.01087-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 09/26/2023] [Indexed: 11/07/2023] Open
Abstract
IMPORTANCE Hepatitis B virus (HBV) spliced variants are associated with viral persistence or pathogenicity. Hepatitis B doubly spliced protein (HBDSP), which has been previously reported as a pleiotropic transactivator protein, can potentially serve as an HBV virulence factor. However, the underlying mechanisms of HBDSP in HBV-associated liver diseases remain to be elucidated. In this study, we revealed that HBDSP promotes cellular apoptosis and induces wt-p53-dependent apoptotic signaling pathway in wt-p53 hepatocellular cells by transactivating p53 transcription, and increases the release of HBV progeny. Therefore, HBDSP may promote the HBV particles release through wt-p53-dependent hepatocellular apoptosis. Our findings suggest that blocking HBDSP-induced wt-p53-dependent apoptosis might have therapeutic values for chronic hepatitis B.
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Affiliation(s)
- Xiazhen Xu
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Lu Zhang
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Guiying Ye
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Jiajian Shi
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Yibin Peng
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Fan Xin
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Yi Lin
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Qiong Wu
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Xu Lin
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Wannan Chen
- Key Laboratory of Gastrointestinal Cancer (Fujian Medical University), Ministry of Education, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
- Fujian Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
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4
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Villanueva RA, Loyola A. Pre- and Post-Transcriptional Control of HBV Gene Expression: The Road Traveled towards the New Paradigm of HBx, Its Isoforms, and Their Diverse Functions. Biomedicines 2023; 11:1674. [PMID: 37371770 DOI: 10.3390/biomedicines11061674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 06/04/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
Hepatitis B virus (HBV) is an enveloped DNA human virus belonging to the Hepadnaviridae family. Perhaps its main distinguishable characteristic is the replication of its genome through a reverse transcription process. The HBV circular genome encodes only four overlapping reading frames, encoding for the main canonical proteins named core, P, surface, and X (or HBx protein). However, pre- and post-transcriptional gene regulation diversifies the full HBV proteome into diverse isoform proteins. In line with this, hepatitis B virus X protein (HBx) is a viral multifunctional and regulatory protein of 16.5 kDa, whose canonical reading frame presents two phylogenetically conserved internal in-frame translational initiation codons, and which results as well in the expression of two divergent N-terminal smaller isoforms of 8.6 and 5.8 kDa, during translation. The canonical HBx, as well as the smaller isoform proteins, displays different roles during viral replication and subcellular localizations. In this article, we reviewed the different mechanisms of pre- and post-transcriptional regulation of protein expression that take place during viral replication. We also investigated all the past and recent evidence about HBV HBx gene regulation and its divergent N-terminal isoform proteins. Evidence has been collected for over 30 years. The accumulated evidence simply strengthens the concept of a new paradigm of the canonical HBx, and its smaller divergent N-terminal isoform proteins, not only during viral replication, but also throughout cell pathogenesis.
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Affiliation(s)
| | - Alejandra Loyola
- Centro Ciencia & Vida, Fundación Ciencia & Vida, Santiago 8580702, Chile
- Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago 7510602, Chile
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5
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Kremsdorf D, Lekbaby B, Bablon P, Sotty J, Augustin J, Schnuriger A, Pol J, Soussan P. Alternative splicing of viral transcripts: the dark side of HBV. Gut 2021; 70:2373-2382. [PMID: 34535538 DOI: 10.1136/gutjnl-2021-324554] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 09/06/2021] [Indexed: 02/06/2023]
Abstract
Regulation of alternative splicing is one of the most efficient mechanisms to enlarge the proteomic diversity in eukaryotic organisms. Many viruses hijack the splicing machinery following infection to accomplish their replication cycle. Regarding the HBV, numerous reports have described alternative splicing events of the long viral transcript (pregenomic RNA), which also acts as a template for viral genome replication. Alternative splicing of HBV pregenomic RNAs allows the synthesis of at least 20 spliced variants. In addition, almost all these spliced forms give rise to defective particles, detected in the blood of infected patients. HBV-spliced RNAs have long been unconsidered, probably due to their uneasy detection in comparison to unspliced forms as well as for their dispensable role during viral replication. However, recent data highlighted the relevance of these HBV-spliced variants through (1) the trans-regulation of the alternative splicing of viral transcripts along the course of liver disease; (2) the ability to generate defective particle formation, putative biomarker of the liver disease progression; (3) modulation of viral replication; and (4) their intrinsic propensity to encode for novel viral proteins involved in liver pathogenesis and immune response. Altogether, tricky regulation of HBV alternative splicing may contribute to modulate multiple viral and cellular processes all along the course of HBV-related liver disease.
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Affiliation(s)
- Dina Kremsdorf
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France
| | - Bouchra Lekbaby
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France
| | - Pierre Bablon
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France
| | - Jules Sotty
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France
| | - Jérémy Augustin
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France
| | - Aurélie Schnuriger
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France.,Assistance Publique - Hôpitaux de Paris, Département de Virologie, GHU Paris-Est, Paris, France
| | - Jonathan Pol
- Institut National de la Santé et de la Recherche Médicale U1138, Centre de Recherche des Cordeliers, Université de Paris, Sorbonne Université, Paris, France.,Metabolomics ann Cell Biology Platforms, Gustave Roussy Cancer Campus, Villejuif, France
| | - Patrick Soussan
- Institut National de la Santé et de la Recherche Médicale U938, Centre de Recherche de Saint Antoine, Sorbonne Université-Faculté Saint Antoine, Paris, France .,Assistance Publique - Hôpitaux de Paris, Département de Virologie, GHU Paris-Est, Paris, France
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6
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Lim CS, Sozzi V, Littlejohn M, Yuen LK, Warner N, Betz-Stablein B, Luciani F, Revill PA, Brown CM. Quantitative analysis of the splice variants expressed by the major hepatitis B virus genotypes. Microb Genom 2021; 7:mgen000492. [PMID: 33439114 PMCID: PMC8115900 DOI: 10.1099/mgen.0.000492] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 11/23/2020] [Indexed: 12/13/2022] Open
Abstract
Hepatitis B virus (HBV) is a major human pathogen that causes liver diseases. The main HBV RNAs are unspliced transcripts that encode the key viral proteins. Recent studies have shown that some of the HBV spliced transcript isoforms are predictive of liver cancer, yet the roles of these spliced transcripts remain elusive. Furthermore, there are nine major HBV genotypes common in different regions of the world, these genotypes may express different spliced transcript isoforms. To systematically study the HBV splice variants, we transfected human hepatoma cells, Huh7, with four HBV genotypes (A2, B2, C2 and D3), followed by deep RNA-sequencing. We found that 13-28 % of HBV RNAs were splice variants, which were reproducibly detected across independent biological replicates. These comprised 6 novel and 10 previously identified splice variants. In particular, a novel, singly spliced transcript was detected in genotypes A2 and D3 at high levels. The biological relevance of these splice variants was supported by their identification in HBV-positive liver biopsy and serum samples, and in HBV-infected primary human hepatocytes. Interestingly the levels of HBV splice variants varied across the genotypes, but the spliced pregenomic RNA SP1 and SP9 were the two most abundant splice variants. Counterintuitively, these singly spliced SP1 and SP9 variants had a suboptimal 5' splice site, supporting the idea that splicing of HBV RNAs is tightly controlled by the viral post-transcriptional regulatory RNA element.
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Affiliation(s)
- Chun Shen Lim
- Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Vitina Sozzi
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Margaret Littlejohn
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Lilly K.W. Yuen
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Nadia Warner
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
| | - Brigid Betz-Stablein
- Systems Medicine, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
- Present address: Dermatology Research Centre, Diamantina Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Fabio Luciani
- Systems Medicine, School of Medical Sciences, Faculty of Medicine, University of New South Wales, Sydney, New South Wales, Australia
| | - Peter A. Revill
- Victorian Infectious Diseases Reference Laboratory, Royal Melbourne Hospital at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Victoria, Australia
| | - Chris M. Brown
- Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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7
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Su ZJ, Cao JS, Wu YF, Chen WN, Lin X, Wu YL, Lin X. Deubiquitylation of hepatitis B virus X protein (HBx) by ubiquitin-specific peptidase 15 (USP15) increases HBx stability and its transactivation activity. Sci Rep 2017; 7:40246. [PMID: 28074857 PMCID: PMC5225491 DOI: 10.1038/srep40246] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/05/2016] [Indexed: 02/07/2023] Open
Abstract
Hepatitis B virus X protein (HBx) plays important roles in viral replication and the development of hepatocellular carcinoma. HBx is a rapid turnover protein and ubiquitin-proteasome pathway has been suggested to influence HBx stability as treatment with proteasome inhibitors increases the levels of HBx protein and causes accumulation of the polyubiquitinated forms of HBx. Deubiquitinases (DUBs) are known to act by removing ubiquitin moieties from proteins and thereby reverse their stability and/or activity. However, no information is available regarding the involvement of DUBs in regulation of ubiquitylation-dependent proteasomal degradation of HBx protein. This study identified the deubiquitylating enzyme USP15 as a critical regulator of HBx protein level. USP15 was found to directly interact with HBx via binding to the HBx region between amino acid residues 51 and 80. USP15 increased HBx protein levels in a dose-dependent manner and siRNA-mediated knockdown of endogenous USP15 reduced HBx protein levels. Increased HBx stability and steady-state level by USP15 were attributable to reduced HBx ubiquitination and proteasomal degradation. Importantly, the transcriptional transactivation function of HBx is enhanced by overexpression of USP15. These results suggest that USP15 plays an essential role in stabilizing HBx and subsequently affects the biological function of HBx.
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Affiliation(s)
- Zhi-Jun Su
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China.,Department of Infectious Diseases, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou, China
| | - Jia-Shou Cao
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Yan-Fang Wu
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Wan-Nan Chen
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Xinjian Lin
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Yun-Li Wu
- Fujian Key Laboratory of Tumor Microbiology, Fujian Medical University, Fuzhou, China
| | - Xu Lin
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China.,Department of Infectious Diseases, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou, China
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8
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Hepatitis B virus spliced variants are associated with an impaired response to interferon therapy. Sci Rep 2015; 5:16459. [PMID: 26585041 PMCID: PMC4653653 DOI: 10.1038/srep16459] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 10/14/2015] [Indexed: 02/08/2023] Open
Abstract
During hepatitis B virus (HBV) replication, spliced HBV genomes and splice-generated proteins have been widely described, however, their biological and clinical significance remains to be defined. Here, an elevation of the proportion of HBV spliced variants in the sera of patients with chronic hepatitis B (CHB) is shown to correlate with an impaired respond to interferon-α (IFN-α) therapy. Transfection of the constructs encoding the three most dominant species of spliced variants into cells or ectopic expression of the two major spliced protein including HBSP and N-terminal-truncated viral polymerase protein result in strong suppression of IFN-α signaling transduction, while mutation of the major splicing-related sites of HBV attenuates the viral anti-IFN activities in both cell and mouse models. These results have associated the productions of HBV spliced variants with the failure response to IFN therapy and illuminate a novel mechanism where spliced viral products are employed to resist IFN-mediated host defense.
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9
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Bouton C, Geldreich A, Ramel L, Ryabova LA, Dimitrova M, Keller M. Cauliflower mosaic virus Transcriptome Reveals a Complex Alternative Splicing Pattern. PLoS One 2015; 10:e0132665. [PMID: 26162084 PMCID: PMC4498817 DOI: 10.1371/journal.pone.0132665] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 06/18/2015] [Indexed: 12/23/2022] Open
Abstract
The plant pararetrovirus Cauliflower mosaic virus (CaMV) uses alternative splicing to generate several isoforms from its polycistronic pregenomic 35S RNA. This pro-cess has been shown to be essential for infectivity. Previous works have identified four splice donor sites and a single splice acceptor site in the 35S RNA 5' region and suggested that the main role of CaMV splicing is to downregulate expression of open reading frames (ORFs) I and II. In this study, we show that alternative splicing is a conserved process among CaMV isolates. In Cabb B-JI and Cabb-S isolates, splicing frequently leads to different fusion between ORFs, particularly between ORF I and II. The corresponding P1P2 fusion proteins expressed in E. coli interact with viral proteins P2 and P3 in vitro. However, they are detected neither during infection nor upon transient expression in planta, which suggests rapid degradation after synthesis and no important biological role in the CaMV infectious cycle. To gain a better understanding of the functional relevance of 35S RNA alternative splicing in CaMV infectivity, we inactivated the previously described splice sites. All the splicing mutants were as pathogenic as the corresponding wild-type isolate. Through RT-PCR-based analysis we demonstrate that CaMV 35S RNA exhibits a complex splicing pattern, as we identify new splice donor and acceptor sites whose selection leads to more than thirteen 35S RNA isoforms in infected turnip plants. Inactivating splice donor or acceptor sites is not lethal for the virus, since disrupted sites are systematically rescued by the activation of cryptic and/or seldom used splice sites. Taken together, our data depict a conserved, complex and flexible process, involving multiple sites, that ensures splicing of 35S RNA.
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Affiliation(s)
- Clément Bouton
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
| | - Angèle Geldreich
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
| | - Laëtitia Ramel
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
| | - Lyubov A. Ryabova
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
| | - Maria Dimitrova
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
- * E-mail: (MD); (MK)
| | - Mario Keller
- Institut de Biologie Moléculaire des Plantes du CNRS, Université de Strasbourg, Strasbourg, France
- * E-mail: (MD); (MK)
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10
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Wang YL, Liou GG, Lin CH, Chen ML, Kuo TM, Tsai KN, Huang CC, Chen YL, Huang LR, Chou YC, Chang C. The inhibitory effect of the hepatitis B virus singly-spliced RNA-encoded p21.5 protein on HBV nucleocapsid formation. PLoS One 2015; 10:e0119625. [PMID: 25785443 PMCID: PMC4364729 DOI: 10.1371/journal.pone.0119625] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 01/20/2015] [Indexed: 12/29/2022] Open
Abstract
Hepatitis B virus (HBV) is the smallest DNA virus and the major cause of acute and chronic hepatitis. The 3.2 kb HBV viral genome generates four major species of unspliced viral transcript as well as several alternatively spliced RNAs. A 2.2 kb singly-spliced RNA is the most abundant spliced RNA and is widely expressed among all HBV genotypes. The expression of the singly-spliced RNA, as well as that of its encoded protein HBSP, is strongly associated with hepatopathology during HBV infection. Here, we report a novel inhibitory role of a p21.5 protein, which is encoded by a 2.2 kb singly-spliced RNA, in the modulation of HBV replication. We show that overexpression of the singly-spliced RNA is able to efficiently inhibit HBV replication. Furthermore, a mutation in the ATG start codon of the precore region completely abolishes the inhibitory effect of the singly-spliced RNA, indicating that a viral protein (p21.5) derived from the singly-spliced RNA is the mediator of the inhibition. Furthermore, p21.5 is able to form a homodimer that interacts with core dimers forming hybrid viral assembly components. Sucrose gradient fractionation revealed that co-expression of p21.5 resulted in a spread distribution pattern of core proteins ranging from low to high sucrose densities. When compared with p22, p21.5 is almost ten times more efficient at destabilizing HBV nucleocapsid assembly in Huh7 cells overexpressing either p21.5 or p22 protein. Moreover, in vivo expression of p21.5 protein by tail vein injection was found to decrease the amount of nucleocapsid in the livers of HBV-expressing BALB/c mice. In conclusion, our study reveals that the HBV 2.2 kb singly-spliced RNA encodes a 21.5 kDa viral protein that significantly interferes with the assembly of nucleocapsids during HBV nucleocapsid formation. These findings provide a possible strategy for elimination of HBV particles inside cells.
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Affiliation(s)
- Yi-Ling Wang
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Gan-Guang Liou
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Chao-Hsiung Lin
- Institute of Biomedical Informatics, National Yang-Ming University, Taipei, Taiwan
| | - Mong-Liang Chen
- Center for Molecular Medicine, China Medical University and Hospital, Taichung, Taiwan
| | - Tzer-Min Kuo
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Kuen-Nan Tsai
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Chien-Choao Huang
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Ya-Ling Chen
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Li-Rung Huang
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
| | - Yu-Chi Chou
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
- * E-mail: (CC); (YCC)
| | - Chungming Chang
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Miaoli, Taiwan
- * E-mail: (CC); (YCC)
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Liu W, Lin YT, Yan XL, Ding YL, Wu YL, Chen WN, Lin X. Hepatitis B virus core protein inhibits Fas-mediated apoptosis of hepatoma cells via regulation of mFas/FasL and sFas expression. FASEB J 2014; 29:1113-23. [PMID: 25466893 DOI: 10.1096/fj.14-263822] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hepatitis B virus core protein (HBc) has been implicated in hepatocarcinogenesis through several mechanisms. Resistance of hepatitis B virus (HBV)-infected hepatocytes to apoptosis is considered one of the major contributors to the progression of chronic hepatitis to cirrhosis and ultimately to hepatocellular carcinoma. The Fas receptor/ligand (Fas/FasL) system plays a prominent role in hepatocyte death during HBV infection. Here we report that HBc mediates resistance of hepatoma cells to agonistic anti-Fas antibody (CH11)-induced apoptosis. When HBc was introduced into human hepatoma cells, the cells became resistant to CH11 cytotoxicity in a p53-dependent manner. HBc significantly down-regulated the expression of p53, total Fas, and membrane-bound Fas at the mRNA and protein levels and reduced FasL mRNA expression. In contrast, HBc up-regulated the expression of soluble forms of Fas by increasing Fas alternative mRNA splicing. Mechanistically, HBc-mediated Fas alternative mRNA splicing was associated with up-regulation of polypyrimidine tract-binding protein 1 and down-regulation of Fas-activated serine/threonine kinase. These results indicated that HBc may prevent hepatocytes from Fas-induced apoptosis by the dual effects of reducing the expression of the proapoptotic form of Fas and enhancing the expression of the antiapoptotic form of the receptor, which may contribute to the survival and persistence of infected hepatocytes during chronic infection.
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Affiliation(s)
- Wei Liu
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Yan-Ting Lin
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Xiao-Li Yan
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Ya-Lan Ding
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Yun-Li Wu
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Wan-Nan Chen
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
| | - Xu Lin
- *Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Minhou, China; and Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Minhou, China
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Ajiro M, Zheng ZM. Oncogenes and RNA splicing of human tumor viruses. Emerg Microbes Infect 2014; 3:e63. [PMID: 26038756 PMCID: PMC4185361 DOI: 10.1038/emi.2014.62] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 06/29/2014] [Accepted: 06/29/2014] [Indexed: 02/07/2023]
Abstract
Approximately 10.8% of human cancers are associated with infection by an oncogenic virus. These viruses include human papillomavirus (HPV), Epstein–Barr virus (EBV), Merkel cell polyomavirus (MCV), human T-cell leukemia virus 1 (HTLV-1), Kaposi's sarcoma-associated herpesvirus (KSHV), hepatitis C virus (HCV) and hepatitis B virus (HBV). These oncogenic viruses, with the exception of HCV, require the host RNA splicing machinery in order to exercise their oncogenic activities, a strategy that allows the viruses to efficiently export and stabilize viral RNA and to produce spliced RNA isoforms from a bicistronic or polycistronic RNA transcript for efficient protein translation. Infection with a tumor virus affects the expression of host genes, including host RNA splicing factors, which play a key role in regulating viral RNA splicing of oncogene transcripts. A current prospective focus is to explore how alternative RNA splicing and the expression of viral oncogenes take place in a cell- or tissue-specific manner in virus-induced human carcinogenesis.
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Affiliation(s)
- Masahiko Ajiro
- Tumor Virus RNA Biology Section, Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Frederick, MD 21702, USA
| | - Zhi-Ming Zheng
- Tumor Virus RNA Biology Section, Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research, National Cancer Institute, National Institutes of Health , Frederick, MD 21702, USA
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