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Ramakrishnan K, Babu S, Shaji V, Soman S, Leelamma A, Rehman N, Raju R. Hepatitis B Virus Modulated Transcriptional Regulatory Map of Hepatic Cellular MicroRNAs. OMICS : A JOURNAL OF INTEGRATIVE BIOLOGY 2023; 27:581-597. [PMID: 38064540 DOI: 10.1089/omi.2023.0171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2023]
Abstract
Hepatitis B virus (HBV) is an enveloped, hepatotropic, noncytopathic virus with a partially double-stranded DNA genome. It infects hepatocytes and is associated with progression to liver fibrosis and cirrhosis, culminating in hepatocellular carcinoma (HCC), accounting for 55% of total HCC cases. MicroRNAs (miRNAs) regulated by HBV play an important role in these pathologies. Mapping the miRNAs responsive to HBV and HBV-specific proteins, including HBV X protein (HBx) that harbor the majority of HBV-human protein interactions, could aid accelerate the diagnostics and therapeutics innovation against the infection and associated diseases. With this in mind, we used a unique annotation strategy whereby we first amassed 362 mature HBV responsive-human Differentially Expressed miRNAs (HBV-hDEmiRs). The core experimentally-validated messenger RNA targets of the HBV-hDEmiRs were mostly associated with viral infections and hepatic inflammation processes. Moreover, our annotation strategy enabled the characterization of HBx-dependent/independent HBV-hDEmiRs as a tool for evaluation of the impact of HBx as a therapeutic target. Bioinformatics analysis of the HBV-human protein-protein interactome revealed new insights into the transcriptional regulatory network of the HBV-hDEmiRs. We performed a comparative analysis of data on miRNAs gathered from HBV infected cell line studies and from tissue studies of fibrosis, cirrhosis, and HCC. Accordingly, we propose hsa-miR-15a-5p that is downregulated by multiple HBV proteins, including HBx, as a potential biomarker of HBV infection, and its progression to HCC. In all, this study underscores (1) the complexity of miRNA regulation in response to HBV infection and its progression into other liver pathologies and (2) provides a regulatory map of HBV-hDEmiRs and the underlying mechanisms modulating their expression through a cross talk between HBV viral proteins and human transcription factors.
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Affiliation(s)
| | - Sreeranjini Babu
- Centre for Integrative Omics Data Science, Yenepoya (Deemed to be University), Mangalore, India
- Centre for Systems Biology and Molecular Medicine (CSBMM), Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore, Karnataka, India
| | - Vineetha Shaji
- Centre for Integrative Omics Data Science, Yenepoya (Deemed to be University), Mangalore, India
- Centre for Systems Biology and Molecular Medicine (CSBMM), Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore, Karnataka, India
| | - Sowmya Soman
- Centre for Integrative Omics Data Science, Yenepoya (Deemed to be University), Mangalore, India
| | - Anila Leelamma
- Department of Biochemistry, NSS College, Nilamel, Kollam, Kerala, India
| | - Niyas Rehman
- Centre for Integrative Omics Data Science, Yenepoya (Deemed to be University), Mangalore, India
| | - Rajesh Raju
- Centre for Integrative Omics Data Science, Yenepoya (Deemed to be University), Mangalore, India
- Centre for Systems Biology and Molecular Medicine (CSBMM), Yenepoya Research Centre, Yenepoya (Deemed to be University), Deralakatte, Mangalore, Karnataka, India
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Hong Y, Zhang Y, Zhao H, Chen H, Yu QQ, Cui H. The roles of lncRNA functions and regulatory mechanisms in the diagnosis and treatment of hepatocellular carcinoma. Front Cell Dev Biol 2022; 10:1051306. [PMID: 36467404 PMCID: PMC9716033 DOI: 10.3389/fcell.2022.1051306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 11/07/2022] [Indexed: 10/27/2023] Open
Abstract
Hepatocellular carcinoma (HCC) is the most frequent and deadly type of liver cancer. While the underlying molecular mechanisms are poorly understood, it is documented that lncRNAs may play key roles. Many HCC-associated lncRNAs have been linked to HBV and HCV infection, mediating gene expression, cell growth, development, and death. Studying the regulatory mechanisms and biological functions of HCC-related lncRNAs will assist our understanding of HCC pathogenesis as well as its diagnosis and management. Here, we address the potential of dysregulated lncRNAs in HCC as diagnostic and therapeutic biomarkers, and we evaluate the oncogenic or tumor-suppressive properties of these lncRNAs.
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Affiliation(s)
- Yuling Hong
- School of Clinical Medicine, Jining Medical University, Jining, China
| | - Yunxing Zhang
- Jining First People’s Hospital, Jining Medical College, Jining, China
| | - Haibo Zhao
- Jining First People’s Hospital, Jining Medical College, Jining, China
| | - Hailing Chen
- School of Clinical Medicine, Jining Medical University, Jining, China
| | - Qing-Qing Yu
- Jining First People’s Hospital, Jining Medical College, Jining, China
| | - Hongxia Cui
- Jining First People’s Hospital, Jining Medical College, Jining, China
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3
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Martinez MG, Boyd A, Combe E, Testoni B, Zoulim F. Covalently closed circular DNA: The ultimate therapeutic target for curing HBV infections. J Hepatol 2021; 75:706-717. [PMID: 34051332 DOI: 10.1016/j.jhep.2021.05.013] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 05/03/2021] [Accepted: 05/07/2021] [Indexed: 12/16/2022]
Abstract
Current antiviral therapies, such as pegylated interferon-α and nucleos(t)ide analogues, effectively improve the quality of life of patients with chronic hepatitis B. However, they can only control the infection rather than curing infected hepatocytes. Complete HBV cure is hampered by the lack of therapies that can directly affect the viral minichromosome (in the form of covalently closed circular DNA [cccDNA]). Approaches currently under investigation in early clinical trials are aimed at achieving a functional cure, defined as the loss of HBsAg and undetectable HBV DNA levels in serum. However, achieving a complete HBV cure requires therapies that can directly target the cccDNA pool, either via degradation, lethal mutations or functional silencing. In this review, we discuss cutting-edge technologies that could lead to non-cytolytic direct cccDNA targeting and cure of infected hepatocytes.
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Affiliation(s)
| | - Anders Boyd
- Stichting HIV Monitoring, Amsterdam, the Netherlands; Department of Infectious Diseases, Research and Prevention, Public Health Service of Amsterdam, Amsterdam, the Netherlands
| | - Emmanuel Combe
- INSERM U1052, CNRS UMR-5286, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France
| | - Barbara Testoni
- INSERM U1052, CNRS UMR-5286, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France
| | - Fabien Zoulim
- INSERM U1052, CNRS UMR-5286, Cancer Research Center of Lyon (CRCL), Lyon, 69008, France; University of Lyon, Université Claude- Bernard (UCBL), 69008 Lyon, France; Hospices Civils de Lyon (HCL), 69002 Lyon, France.
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Tao S, Pan S, Gu C, Wei L, Kang N, Xie Y, Liu J. Characterization and engineering of broadly reactive monoclonal antibody against hepatitis B virus X protein that blocks its interaction with DDB1. Sci Rep 2019; 9:20323. [PMID: 31889135 PMCID: PMC6937242 DOI: 10.1038/s41598-019-56819-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 12/17/2019] [Indexed: 12/20/2022] Open
Abstract
Hepatitis B virus (HBV) X protein (HBx) plays diverse roles in both viral life cycle and HBV-related carcinogenesis. Its interaction with DNA damage-binding protein 1 (DDB1) was shown to be essential for engendering cellular conditions favorable for optimal viral transcription and replication. Previously, we described a mouse monoclonal antibody against HBx (anti-HBx 2A7) recognizing HBx encoded by representative strains from 7 of 8 known HBV genotypes. In this work, we further characterized 2A7 in order to explore its potential usefulness in HBx-targeting applications. We demonstrated that 2A7 recognizes a linear epitope mapped to L89PKVLHKR96 on HBx, a segment that is highly conserved across genotypes and coincidentally overlaps with the DDB1-interacting segment. HBx-DDB1 binding could be inhibited by 2A7 in vitro, suggesting therapeutic potential. Nucleic acid and amino acid sequences of 2A7 were then obtained, which allowed construction of recombinant antibody and single chain variable fragments (scFv). 2A7-derived recombinant antibody and scFv recapitulate 2A7's HBx-binding capacity and epitope specificity. We also reported preliminary results using cell-penetrating peptide for delivering 2A7 antibody across cell membrane to target intracellular HBx. Anti-HBx 2A7 and 2A7-derived scFv characterized here may give rise to novel HBx-targeting diagnostics and therapeutics for HBV- and HBx-related pathologies.
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Affiliation(s)
- Shuai Tao
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Shaokun Pan
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.,National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
| | - Chenjian Gu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Lili Wei
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Ning Kang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China
| | - Youhua Xie
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.
| | - Jing Liu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS), Department of Microbiology and Parasitology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China. .,Key Laboratory of Medical Epigenetics and Metabolism, Institutes of Biomedical Sciences, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, China.
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Huang SX, Mou JF, Luo Q, Mo QH, Zhou XL, Huang X, Xu Q, Tan XD, Chen X, Liang CQ. Anti-Hepatitis B Virus Activity of Esculetin from Microsorium fortunei In Vitro and In Vivo. Molecules 2019; 24:E3475. [PMID: 31557836 PMCID: PMC6803987 DOI: 10.3390/molecules24193475] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 09/14/2019] [Accepted: 09/24/2019] [Indexed: 02/07/2023] Open
Abstract
Coumarins are widely present in a variety of plants and have a variety of pharmacological activities. In this study, we isolated a coumarin compound from Microsorium fortunei (Moore) Ching; the compound was identified as esculetin by hydrogen and carbon spectroscopy. Its anti-hepatitis B virus (HBV) activity was investigated in vitro and in vivo. In the human hepatocellular liver carcinoma 2.2.15 cell line (HepG2.2.15) transfected with HBV, esculetin effecting inhibited the expression of the HBV antigens and HBV DNA in vitro. Esculetin inhibited the expression of Hepatitis B virus X (HBx) protein in a dose-dependent manner. In the ducklings infected with duck hepatitis B virus (DHBV), the levels of DHBV DNA, duck hepatitis B surface antigen (DHBsAg), duck hepatitis B e-antigen (DHBeAg), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) decreased significantly after esculetin treatment. Summing up the above, the results suggest that esculetin efficiently inhibits HBV replication both in vitro and in vivo, which provides an opportunity for further development of esculetin as antiviral drug.
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Affiliation(s)
- Si-Xin Huang
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Jun-Fei Mou
- Biotechnology Institute, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Qin Luo
- Science Experiment Center, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Qing-Hu Mo
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Xian-Li Zhou
- Biotechnology Institute, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Xiao Huang
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Qing Xu
- Guangxi Key Laboratory of Molecular Medicine in Liver Injury and Repair, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Xiang-Duan Tan
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Xu Chen
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
| | - Cheng-Qin Liang
- College of Pharmacy, Guilin Medical University, Guilin 541004, Guangxi, China.
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Liu J, Jiang J, Mo J, Liu D, Cao D, Wang H, He Y, Wang H. Global DNA 5-Hydroxymethylcytosine and 5-Formylcytosine Contents Are Decreased in the Early Stage of Hepatocellular Carcinoma. Hepatology 2019; 69:196-208. [PMID: 30070373 DOI: 10.1002/hep.30146] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 06/14/2018] [Indexed: 12/22/2022]
Abstract
Methylation of the fifth position of cytosine (5mC) is an important epigenetic modification of DNA. It has been shown that the oxidized derivatives of 5mC, namely 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC), are in dynamic existence and have distinct regulatory functions. In the current study, we investigated whether there are changes in the contents of all three 5mC-oxidized derivatives in the hepatocellular carcinoma (HCC) genome and further explored the underlying mechanisms. We showed that both global genomic 5hmC and 5fC contents were decreased significantly in the very early stage (stage 0, Barcelona Clinic Liver Cancer [BCLC] staging) of HCC compared with those of paratumor tissues. Noteworthily, 5fC content continued to decrease in the late stage (BCLC staging from 0 to A) of HCC. The 5caC content in HCC tissues was below the detection threshold. Hepatitis B virus (HBV) infection was associated with 5mC, 5hmC, or 5fC decrease in HCC; and measurements in cell lines integrated with or without HBV DNA showed consistent results. On the other hand, both the expression level of ten-eleven translocation enzyme 2 (TET2) and α-ketoglutarate content were decreased significantly in HCC. The significantly positive correlations among the expression levels of DNA methylation-related enzymes in paratumor tissues were generally attenuated or even disappeared in HCC tumor tissues. The decreases of both 5hmC and 5fC contents in genomic DNA were associated with poor prognosis of HCC patients. Conclusion: Global 5hmC and 5fC contents were decreased significantly in the very early stage of HCC; the decrease of 5hmC and 5fC was mainly due to the decrease of 5mC and associated with HBV infection, decreased TET enzyme activity, and uncoordinated expression of DNA methylation-related enzymes.
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Affiliation(s)
- Jiao Liu
- National Center for Liver Cancer, Eastern Hepatobiliary Surgery Hospital, Shanghai, People's Republic of China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Jinhua Jiang
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute/Hospital, Shanghai, People's Republic of China
| | - Jiezhen Mo
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Dan Liu
- National Center for Liver Cancer, Eastern Hepatobiliary Surgery Hospital, Shanghai, People's Republic of China
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center of Nanjing University, Nanjing, People's Republic of China
| | - Dan Cao
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute/Hospital, Shanghai, People's Republic of China
| | - Hailin Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, People's Republic of China
| | - Yufei He
- National Center for Liver Cancer, Eastern Hepatobiliary Surgery Hospital, Shanghai, People's Republic of China
| | - Hongyang Wang
- National Center for Liver Cancer, Eastern Hepatobiliary Surgery Hospital, Shanghai, People's Republic of China
- State Key Laboratory of Oncogenes and Related Genes, Shanghai Cancer Institute, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
- International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute/Hospital, Shanghai, People's Republic of China
- State Key Laboratory of Pharmaceutical Biotechnology and MOE Key Laboratory of Model Animals for Disease Study, Model Animal Research Center of Nanjing University, Nanjing, People's Republic of China
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Lv D, Wang Y, Zhang Y, Cui P, Xu Y. Downregulated long non-coding RNA DREH promotes cell proliferation in hepatitis B virus-associated hepatocellular carcinoma. Oncol Lett 2017; 14:2025-2032. [PMID: 28789433 PMCID: PMC5530050 DOI: 10.3892/ol.2017.6436] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 03/23/2017] [Indexed: 02/06/2023] Open
Abstract
The hepatitis B virus X (HBx) protein has been characterized as an oncogene involved in epigenetic modifications during hepatocarcinogenesis; however, the underlying mechanisms are not entirely clear. Long non-coding RNAs (lncRNAs), a type of epigenetic regulator molecules, have also been demonstrated to serve crucial roles in carcinogenesis, including hepatocellular carcinoma (HCC). In the present study, a human lncRNA DREH was identified, which inhibits cell proliferation in vitro and in vivo, and acts as a tumor suppressor in HBx-mediated hepatocarcinogenesis. The study revealed that the expression of DREH was frequently downregulated in hepatitis B virus (HBV)-associated HCC tissues in comparison with adjacent non-cancerous hepatic tissues, and was inversely correlated with HBx mRNA expression in HBV-associated HCC. In addition, the levels of DREH were inversely correlated with hepatitis B surface antigen and tumor size in HCC tissues. The forced expression of HBx in liver cell lines resulted in a significant decrease in the expression of DREH. Furthermore, suppression of DREH expression promotes the proliferation of HCC cells in vitro and in vivo. In conclusion, the present findings support the role of HBx-downregulated lncRNA DREH in tumor suppression in HBV-associated HCC patients. This contributes to a better understanding of epigenetic aberration of deregulated lncRNAs by HBx and the potential development of lncRNA-based targeted approaches for the treatment of HBV-associated HCC.
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Affiliation(s)
- Dong Lv
- Gastroenterology Department, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Yuan Wang
- Third Department of General Surgery, Peking University People's Hospital, Beijing 100044, P.R. China
| | - Ying Zhang
- Gastroenterology Department, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Peilin Cui
- Gastroenterology Department, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Youqing Xu
- Gastroenterology Department, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
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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: 8.6] [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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Hepatitis B virus X protein is capable of down-regulating protein level of host antiviral protein APOBEC3G. Sci Rep 2017; 7:40783. [PMID: 28098260 PMCID: PMC5241686 DOI: 10.1038/srep40783] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/09/2016] [Indexed: 12/17/2022] Open
Abstract
The apolipoprotein B mRNA editing catalytic polypeptide-like (APOBEC) family proteins bind RNA and single-stranded DNA, and create C-to-U base modifications through cytidine deaminase activity. APOBEC3G restricts human immunodeficiency virus 1 (HIV-1) infection by creating hypermutations in proviral DNA, while HIV-1-encoded vif protein antagonizes such restriction by targeting APOBEC3G for degradation. APOBEC3G also inhibits hepatitis B virus (HBV): APOBEC3G co-expression inhibits HBV replication and evidences exist indicating APOBEC3G-mediated HBV hypermutations in patients. HBV encodes a small non-structural X protein (HBx) with a recognized activating effect on HBV life cycle. In this work, we report the discovery that HBx selectively and dose-dependently decreases the protein level of co-expressed APOBEC3G in transfected Huh-7 cells. The effect was shown to take place post-translationally, but does not rely on protein degradation via proteasome or lysosome. Further work demonstrated that intracellular APOBEC3G is normally exported via exosome secretion and inhibition of exosome biogenesis causes retention of intracellular APOBEC3G. Finally, HBx co-expression specifically enhanced externalization of APOBEC3G via exosomes, resulting in decrease of intracellular APOBEC3G protein level. These data suggest the possibility that in addition to other mechanisms, HBx-mediated activation of HBV might also involve antagonizing of intracellular restriction factor APOBEC3G through promotion of its export.
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