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Abstract
Viral hepatitis causes more deaths than tuberculosis and HIV-1 infection. Most cases are due to chronic infection with hepatitis B virus (HBV), which afflicts >250 million people. Current therapies are rarely curative, and new approaches are needed. Here, we report the discovery (by nuclear magnetic resonance) of a small molecule binder in the hydrophobic pocket in the HBV capsid. This structural element is, in an unknown manner, central in capsid envelopment. Binding of the pocket factor induces a distinct, stable conformation in the capsid, as expected for a signaling switch. This brings not only a new molecular view on the mechanism underlying capsid envelopment, but it also opens a rationale for its inhibition. Viral hepatitis is growing into an epidemic illness, and it is urgent to neutralize the main culprit, hepatitis B virus (HBV), a small-enveloped retrotranscribing DNA virus. An intriguing observation in HB virion morphogenesis is that capsids with immature genomes are rarely enveloped and secreted. This prompted, in 1982, the postulate that a regulated conformation switch in the capsid triggers envelopment. Using solid-state NMR, we identified a stable alternative conformation of the capsid. The structural variations focus on the hydrophobic pocket of the core protein, a hot spot in capsid–envelope interactions. This structural switch is triggered by specific, high-affinity binding of a pocket factor. The conformational change induced by the binding is reminiscent of a maturation signal. This leads us to formulate the “synergistic double interaction” hypothesis, which explains the regulation of capsid envelopment and indicates a concept for therapeutic interference with HBV envelopment.
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The evolution and clinical impact of hepatitis B virus genome diversity. Nat Rev Gastroenterol Hepatol 2020; 17:618-634. [PMID: 32467580 DOI: 10.1038/s41575-020-0296-6] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/20/2020] [Indexed: 02/06/2023]
Abstract
The global burden of hepatitis B virus (HBV) is enormous, with 257 million persons chronically infected, resulting in more than 880,000 deaths per year worldwide. HBV exists as nine different genotypes, which differ in disease progression, natural history and response to therapy. HBV is an ancient virus, with the latest reports greatly expanding the host range of the Hepadnaviridae (to include fish and reptiles) and casting new light on the origins and evolution of this viral family. Although there is an effective preventive vaccine, there is no cure for chronic hepatitis B, largely owing to the persistence of a viral minichromosome that is not targeted by current therapies. HBV persistence is also facilitated through aberrant host immune responses, possibly due to the diverse intra-host viral populations that can respond to host-mounted and therapeutic selection pressures. This Review summarizes current knowledge on the influence of HBV diversity on disease progression and treatment response and the potential effect on new HBV therapies in the pipeline. The mechanisms by which HBV diversity can occur both within the individual host and at a population level are also discussed.
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Ruan J, Ping CY, Sun S, Cheng X, Han PY, Zhang YG, Sun DX. Construction of a replication-competent hepatitis B virus vector carrying secreted luciferase transgene and establishment of new hepatitis B virus replication and expression cell lines. World J Gastroenterol 2019; 25:5961-5972. [PMID: 31660033 PMCID: PMC6815792 DOI: 10.3748/wjg.v25.i39.5961] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 08/08/2019] [Accepted: 09/13/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Previously, we have successfully constructed replication-competent hepatitis B virus (HBV) vectors by uncoupling the P open reading frame (ORF) from the preC/C ORF to carefully design the transgene insertion site to overcome the compact organization of the HBV genome and maintain HBV replication competence. Consequently, the replication-competent HBV vectors carrying foreign genes, including pCH-BsdR, carrying blasticidin resistance gene (399 bp), and pCH-hrGFP, carrying humanized renilla green fluorescent protein gene (720 bp), were successfully obtained. However, the replication efficiency of the former is higher but it is tedious to use, while that of the latter is poor and cannot be quantified. Hence, we need to search for a new reporter gene that is convenient and quantifiable for further research.
AIM To establish a helpful tool for intracellular HBV replication and anti-viral drugs screening studies.
METHODS We utilized the replication-competent HBV viral vectors constructed by our laboratory, combined with the secreted luciferase reporter gene, to construct replication-competent HBV vectors expressing the reporter gene secretory Nanoluc Luciferase (SecNluc). HepG2.TA2-7 cells were transfected with this vector to obtain cell lines with stably secreted HBV particles carrying secNluc reporter gene.
RESULTS The replication-competent HBV vector carrying the SecNluc reporter gene pCH-sNLuc could produce all major viral RNAs and a full set of envelope proteins and achieve high-level secreted luciferase expression. HBV replication intermediates could be produced from this vector. Via transfection with pTRE-sNLuc and selection by hygromycin, we obtained isolated cell clones, named HBV-NLuc-35 cells, which could secrete secNLuc recombinant viruses, and were sensitive to existing anti-HBV drugs. Using differentiated HepaRG cells, it was verified that recombinant HBV possessed infectivity.
CONCLUSION Our research demonstrated that a replication-competent HBV vector carrying a secreted luciferase transgene possesses replication and expression ability, and the established HBV replication and expression cell lines could stably secrete viral particles carrying secNluc reporter gene. More importantly, the cell line and the secreted recombinant viral particles could be used to trace HBV replication or infection.
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Affiliation(s)
- Jie Ruan
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
- Department of Infection and Liver Disease, Shannxi University of Chinese Medicine Affiliated Hospital, Xianyang 712000, Shannxi Province, China
| | - Cai-Yan Ping
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
| | - Shuo Sun
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
| | - Xin Cheng
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
| | - Peng-Yu Han
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
| | - Yin-Ge Zhang
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
| | - Dian-Xing Sun
- The Liver Disease Center of Chinese People’s Liberation Army, the 980th Hospital of Chinese People’s Liberation Army Joint Logistics Support Force, Shijiazhuang 050082, Hebei Province, China
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Heger-Stevic J, Zimmermann P, Lecoq L, Böttcher B, Nassal M. Hepatitis B virus core protein phosphorylation: Identification of the SRPK1 target sites and impact of their occupancy on RNA binding and capsid structure. PLoS Pathog 2018; 14:e1007488. [PMID: 30566530 PMCID: PMC6317823 DOI: 10.1371/journal.ppat.1007488] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 01/03/2019] [Accepted: 11/27/2018] [Indexed: 12/19/2022] Open
Abstract
Hepatitis B virus (HBV) replicates its 3 kb DNA genome through capsid-internal reverse transcription, initiated by assembly of 120 core protein (HBc) dimers around a complex of viral pregenomic (pg) RNA and polymerase. Following synthesis of relaxed circular (RC) DNA capsids can be enveloped and secreted as stable virions. Upon infection of a new cell, however, the capsid disintegrates to release the RC-DNA into the nucleus for conversion into covalently closed circular (ccc) DNA. HBc´s interactions with nucleic acids are mediated by an arginine-rich C terminal domain (CTD) with intrinsically strong non-specific RNA binding activity. Adaptation to the changing demands for nucleic acid binding during the viral life cycle is thought to involve dynamic phosphorylation / dephosphorylation events. However, neither the relevant enzymes nor their target sites in HBc are firmly established. Here we developed a bacterial coexpression system enabling access to definably phosphorylated HBc. Combining Phos-tag gel electrophoresis, mass spectrometry and mutagenesis we identified seven of the eight hydroxy amino acids in the CTD as target sites for serine-arginine rich protein kinase 1 (SRPK1); fewer sites were phosphorylated by PKA and PKC. Phosphorylation of all seven sites reduced nonspecific RNA encapsidation as drastically as deletion of the entire CTD and altered CTD surface accessibility, without major structure changes in the capsid shell. The bulk of capsids from human hepatoma cells was similarly highly, yet non-identically, phosphorylated as by SRPK1. While not proving SRPK1 as the infection-relevant HBc kinase the data suggest a mechanism whereby high-level HBc phosphorylation principally suppresses RNA binding whereas one or few strategic dephosphorylation events enable selective packaging of the pgRNA/polymerase complex. The tools developed in this study should greatly facilitate the further deciphering of the role of HBc phosphorylation in HBV infection and its evaluation as a potential new therapeutic target.
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Affiliation(s)
- Julia Heger-Stevic
- University Hospital Freiburg, Department of Medicine II / Molecular Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Biological Faculty, University of Freiburg, Freiburg, Germany
| | - Peter Zimmermann
- University Hospital Freiburg, Department of Medicine II / Molecular Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Biological Faculty, University of Freiburg, Freiburg, Germany
| | - Lauriane Lecoq
- Institut de Biologie et Chimie des Protéines, University of Lyon1, Lyon, France
| | - Bettina Böttcher
- Department of Biochemistry, Biocenter, University of Würzburg, Würzburg, Germany
| | - Michael Nassal
- University Hospital Freiburg, Department of Medicine II / Molecular Biology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Budzinska MA, Shackel NA, Urban S, Tu T. Cellular Genomic Sites of Hepatitis B Virus DNA Integration. Genes (Basel) 2018; 9:E365. [PMID: 30037029 PMCID: PMC6071206 DOI: 10.3390/genes9070365] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/12/2018] [Accepted: 07/12/2018] [Indexed: 12/14/2022] Open
Abstract
Infection with the Hepatitis B Virus (HBV) is one of the strongest risk-factors for liver cancer (hepatocellular carcinoma, HCC). One of the reported drivers of HCC is the integration of HBV DNA into the host cell genome, which may induce pro-carcinogenic pathways. These reported pathways include: induction of chromosomal instability; generation of insertional mutagenesis in key cancer-associated genes; transcription of downstream cancer-associated cellular genes; and/or formation of a persistent source of viral protein expression (particularly HBV surface and X proteins). The contribution of each of these specific mechanisms towards carcinogenesis is currently unclear. Here, we review the current knowledge of specific sites of HBV DNA integration into the host genome, which sheds light on these mechanisms. We give an overview of previously-used methods to detect HBV DNA integration and the enrichment of integration events in specific functional and structural cellular genomic sites. Finally, we posit a theoretical model of HBV DNA integration during disease progression and highlight open questions in the field.
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Affiliation(s)
| | - Nicholas A Shackel
- Centenary Institute, University of Sydney, Sydney NSW 2050, Australia.
- South Western Sydney Clinical School, University of New South Wales, Liverpool NSW 2170, Australia.
- Gastroenterology, Liverpool Hospital, Liverpool NSW 2170, Australia.
| | - Stephan Urban
- Department of Infectious Diseases, Molecular Virology, Heidelberg Hospital University, D-69120 Heidelberg, Germany.
- German Center for Infection Research (DZIF), Partner Site Heidelberg, D-69120 Heidelberg, Germany.
| | - Thomas Tu
- Department of Infectious Diseases, Molecular Virology, Heidelberg Hospital University, D-69120 Heidelberg, Germany.
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Schreiner S, Nassal M. A Role for the Host DNA Damage Response in Hepatitis B Virus cccDNA Formation-and Beyond? Viruses 2017; 9:v9050125. [PMID: 28531167 PMCID: PMC5454437 DOI: 10.3390/v9050125] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/16/2017] [Accepted: 05/18/2017] [Indexed: 12/12/2022] Open
Abstract
Chronic hepatitis B virus (HBV) infection puts more than 250 million people at a greatly increased risk to develop end-stage liver disease. Like all hepadnaviruses, HBV replicates via protein-primed reverse transcription of a pregenomic (pg) RNA, yielding an unusually structured, viral polymerase-linked relaxed-circular (RC) DNA as genome in infectious particles. Upon infection, RC-DNA is converted into nuclear covalently closed circular (ccc) DNA. Associating with cellular proteins into an episomal minichromosome, cccDNA acts as template for new viral RNAs, ensuring formation of progeny virions. Hence, cccDNA represents the viral persistence reservoir that is not directly targeted by current anti-HBV therapeutics. Eliminating cccDNA will thus be at the heart of a cure for chronic hepatitis B. The low production of HBV cccDNA in most experimental models and the associated problems in reliable cccDNA quantitation have long hampered a deeper understanding of cccDNA molecular biology. Recent advancements including cccDNA-dependent cell culture systems have begun to identify select host DNA repair enzymes that HBV usurps for RC-DNA to cccDNA conversion. While this list is bound to grow, it may represent just one facet of a broader interaction with the cellular DNA damage response (DDR), a network of pathways that sense and repair aberrant DNA structures and in the process profoundly affect the cell cycle, up to inducing cell death if repair fails. Given the divergent interactions between other viruses and the DDR it will be intriguing to see how HBV copes with this multipronged host system.
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Affiliation(s)
- Sabrina Schreiner
- Institute of Virology, Technische Universität München/Helmholtz Zentrum München, Ingolstädter Landstr. 1, Neuherberg, D-85764 Munich, Germany.
| | - Michael Nassal
- Dept. of Internal Medicine II/Molecular Biology, University Hospital Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.
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Tu T, Budzinska MA, Shackel NA, Urban S. HBV DNA Integration: Molecular Mechanisms and Clinical Implications. Viruses 2017; 9:v9040075. [PMID: 28394272 PMCID: PMC5408681 DOI: 10.3390/v9040075] [Citation(s) in RCA: 231] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 02/06/2023] Open
Abstract
Chronic infection with the Hepatitis B Virus (HBV) is a major cause of liver-related morbidity and mortality. One peculiar observation in cells infected with HBV (or with closely‑related animal hepadnaviruses) is the presence of viral DNA integration in the host cell genome, despite this form being a replicative dead-end for the virus. The frequent finding of somatic integration of viral DNA suggests an evolutionary benefit for the virus; however, the mechanism of integration, its functions, and the clinical implications remain unknown. Here we review the current body of knowledge of HBV DNA integration, with particular focus on the molecular mechanisms and its clinical implications (including the possible consequences of replication-independent antigen expression and its possible role in hepatocellular carcinoma). HBV DNA integration is likely to influence HBV replication, persistence, and pathogenesis, and so deserves greater attention in future studies.
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Affiliation(s)
- Thomas Tu
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany.
| | - Magdalena A Budzinska
- Centenary Institute, The University of Sydney, Sydney, NSW 2050, Australia.
- Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Nicholas A Shackel
- Centenary Institute, The University of Sydney, Sydney, NSW 2050, Australia.
- Sydney Medical School, The University of Sydney, Sydney, NSW 2006, Australia.
- Liverpool Hospital, Gastroenterology, Sydney, NSW 2170, Australia.
| | - Stephan Urban
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany.
- German Center for Infection Research (DZIF), Heidelberg Partner Site, Im Neuenheimer Feld 345, 69120 Heidelberg, Germany.
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Huang H, Zhou W, Zhu H, Zhou P, Shi X. Baicalin benefits the anti-HBV therapy via inhibiting HBV viral RNAs. Toxicol Appl Pharmacol 2017; 323:36-43. [PMID: 28322895 DOI: 10.1016/j.taap.2017.03.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 03/14/2017] [Accepted: 03/15/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Although current antiviral treatments (nucleoside analogs, NAs) for chronic hepatitis B virus (HBV) infection are effective in suppressing HBV-DNA replication, their clinical outcomes can be compromised by the increasing drug resistance and the inefficiency in promoting HBsAg/HBeAg seroconversion. OBJECTIVES In this study, we will explore possible effects and mechanism of a natural product baicalin (BA) with the anti-HBV efficacy of entecavir (ETV), a first-line anti-HBV drug, in HBV-DNA, HBsAg/HBeAg seroconversion and drug-resistance. METHODS The co-effects of BA and ETV were conducted in wild-type/NA-resistance mutant HBV cell lines and DHBV-infected duckling models. HBV-DNA/RNAs, HBsAg/HBeAg, host factors (hepatocyte nuclear factors) were explored for possible anti-HBV mechanism. RESULTS AND DISCUSSION BA could significantly enhance and reduced HBsAg and HBeAg in hepG2.2.15, a wild-type HBV cell line. Co-treatment of BA and ETV had a more dramatic effect in NA-resistant HBVrtM204V/rtLl80M transfected hepG2 cells. Our study further revealed that BA mainly inhibited the production of HBV RNAs (3.5, 2.4, 2.1kb), the templates for viral proteins and HBV-DNA synthesis. BA blocked HBV RNAs transcription possibly by down-regulating transcription and expression of HBV replication dependent hepatocyte nuclear factors (HNF1α and HNF4α). Thus, BA may benefit the anti-HBV therapy via inhibiting HBV viral RNAs.
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Affiliation(s)
- Hai Huang
- Department of Microbiology and Biopharmacy, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China.
| | - Wei Zhou
- Department of Chemistry, Fudan University, 220 Han Dan Road, Shanghai 200433, China.
| | - Haiyan Zhu
- Department of Microbiology and Biopharmacy, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China.
| | - Pei Zhou
- Department of Microbiology and Biopharmacy, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China.
| | - Xunlong Shi
- Department of Microbiology and Biopharmacy, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China.
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