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Abdelwahed AH, Heineman BD, Wu GY. Novel Approaches to Inhibition of HBsAg Expression from cccDNA and Chromosomal Integrants: A Review. J Clin Transl Hepatol 2023; 11:1485-1497. [PMID: 38161502 PMCID: PMC10752814 DOI: 10.14218/jcth.2023.00067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 07/19/2023] [Accepted: 08/16/2023] [Indexed: 01/03/2024] Open
Abstract
Hepatitis B virus (HBV) is a widely prevalent liver infection that can cause acute or chronic hepatitis. Although current treatment modalities are highly effective in the suppression of viral levels, they cannot eliminate the virus or achieve definitive cure. This is a consequence of the complex nature of HBV-host interactions. Major challenges to achieving sustained viral suppression include the presence of a high viral burden from the HBV DNA and hepatitis B surface antigen (HBsAg), the presence of reservoirs for HBV replication and antigen production, and the HBV-impaired innate and adaptive immune response of the host. Those therapeutic methods include cell entry inhibitors, HBsAg inhibitors, gene editing approaches, immune-targeting therapies and direct inhibitors of covalently closed circular DNA (cccDNA). Novel approaches that target these key mechanisms are now being studied in preclinical and clinical phases. In this review article, we provide a comprehensive review on mechanisms by which HBV escapes elimination from current treatments, and highlight new agents to achieve a definitive HBV cure.
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Affiliation(s)
- Ahmed H. Abdelwahed
- Department of Medicine, Division of Gastroenterology-Hepatology, University of Connecticut Health Center, Farmington, CT, USA
| | - Brent D. Heineman
- Department of Medicine, Division of Gastroenterology-Hepatology, University of Connecticut Health Center, Farmington, CT, USA
| | - George Y. Wu
- Department of Medicine, Division of Gastroenterology-Hepatology, University of Connecticut Health Center, Farmington, CT, USA
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2
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Moon IY, Kim JW. Methylation profile of hepatitis B virus is not influenced by interferon α in human liver cancer cells. Mol Med Rep 2021; 24:715. [PMID: 34396432 PMCID: PMC8383030 DOI: 10.3892/mmr.2021.12354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 07/12/2021] [Indexed: 12/17/2022] Open
Abstract
Interferon (IFN) α is used for the treatment of chronic hepatitis B virus (HBV) infection, but the molecular mechanisms underlying its antiviral effect have not been fully elucidated. Epigenetic modifications regulate the transcriptional activity of covalently closed circular DNA (cccDNA) in cells with chronic HBV infection. IFN‑α has been shown to modify cccDNA‑bound histones, but it is not known whether the anti‑HBV effect of IFN‑α involves methylation of cccDNA. The present study aimed to determine whether IFN‑α induced methylation of HBV cccDNA in a cell‑based model in which HepG2 cells were directly infected with wild‑type HBV virions. Methylation status of HBV cccDNA was assessed using global DNA methylation ELISA assay, methylation‑specific PCR and bisulfite sequencing. IFN‑α suppressed HBV DNA and RNA transcripts, but methylation profiles were similar between the control and IFN‑α treated groups. Chromatin immunoprecipitation results revealed binding of DNA methyltransferases (DNMT) 3A and DNMT3B to HBV cccDNA and treatment with IFN‑α suppressed the recruitment of DNMT3B to cccDNA. Taken together, these results suggest that IFN‑α does not induce methylation of HBV cccDNA. Therefore, it was concluded that methylation is unlikely to contribute to the anti‑HBV effect of IFN‑α in HepG2 cells, and that alternative mechanisms need to be sought to enhance cccDNA methylation as a novel therapy against HBV.
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Affiliation(s)
- In Young Moon
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Jin-Wook Kim
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul 03080, Republic of Korea
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3
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Nowak I, Sarshad AA. Argonaute Proteins Take Center Stage in Cancers. Cancers (Basel) 2021; 13:cancers13040788. [PMID: 33668654 PMCID: PMC7918559 DOI: 10.3390/cancers13040788] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 02/09/2021] [Accepted: 02/10/2021] [Indexed: 12/16/2022] Open
Abstract
Simple Summary The dysregulation of RNA interference (RNAi) has often been observed in cancers, where the main focus of research has been on the small RNA molecules directing RNAi. In this review, we focus on the activity of Argonaute proteins, central components of RNAi, in tumorigenesis, and also highlight their potential applications in grading tumors and anti-cancer therapies. Abstract Argonaute proteins (AGOs) play crucial roles in RNA-induced silencing complex (RISC) formation and activity. AGOs loaded with small RNA molecules (miRNA or siRNA) either catalyze endoribonucleolytic cleavage of target RNAs or recruit factors responsible for translational silencing and target destabilization. miRNAs are well characterized and broadly studied in tumorigenesis; nevertheless, the functions of the AGOs in cancers have lagged behind. Here, we discuss the current state of knowledge on the role of AGOs in tumorigenesis, highlighting canonical and non-canonical functions of AGOs in cancer cells, as well as the biomarker potential of AGO expression in different of tumor types. Furthermore, we point to the possible application of the AGOs in development of novel therapeutic approaches.
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Affiliation(s)
- Iwona Nowak
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden;
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Aishe A. Sarshad
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden;
- Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, 405 30 Gothenburg, Sweden
- Correspondence:
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Zhu A, Liao X, Li S, Zhao H, Chen L, Xu M, Duan X. HBV cccDNA and Its Potential as a Therapeutic Target. J Clin Transl Hepatol 2019; 7:258-262. [PMID: 31608218 PMCID: PMC6783673 DOI: 10.14218/jcth.2018.00054] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 04/02/2019] [Accepted: 07/10/2019] [Indexed: 12/13/2022] Open
Abstract
Chronic hepatitis B virus infection continues to be a major health burden worldwide. It can cause various degrees of liver damage and is strongly associated with the development of liver cirrhosis and hepatocellular carcinoma. Covalently closed circular DNA in the nucleus of infected cells cannot be disabled by present therapies which may lead to HBV persistence and relapse. In this review, we summarized the current knowledge on hepatitis B virus covalently closed circular DNA and its potential role as a therapeutic target.
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Affiliation(s)
- Anjing Zhu
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Xinzhong Liao
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Shuang Li
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Hang Zhao
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Limin Chen
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Min Xu
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
| | - Xiaoqiong Duan
- Institute of Blood Transfusion, Chinese Academy of Medical Sciences and Peking Union Medical College, Chengdu, China
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5
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Moon IY, Choi JH, Chung JW, Jang ES, Jeong SH, Kim JW. MicroRNA‑20 induces methylation of hepatitis B virus covalently closed circular DNA in human hepatoma cells. Mol Med Rep 2019; 20:2285-2293. [PMID: 31257511 PMCID: PMC6691198 DOI: 10.3892/mmr.2019.10435] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 05/22/2019] [Indexed: 02/06/2023] Open
Abstract
Methylation was suggested to suppress the transcriptional activity of hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) in hepatocytes. This may be associated with its low replicative activity during the inactive stage of chronic HBV infection; however, the exact mechanisms of methylation in HBV infection remain unknown. We have previously shown that short hairpin RNAs induced the methylation of the HBV genome in hepatoma cell lines. We also reported that the microRNA (miR) 17–92 cluster negatively regulates HBV replication in human hepatoma cells. In addition, miR-20a, a member of the miR 17–92 cluster, has sequence homology with the short hairpin RNA that induces HBV methylation. In the present study, we investigated whether miR-20a can function as an endogenous effector of HBV DNA methylation. The results indicated that overexpression of miR-20a could suppress the replicative activity of HBV and increased the degree of methylation of HBV cccDNA in the HepAD38 hepatoma cell line. Argonaute (AGO)1 and AGO2, effectors of the RNA-induced silencing complex, were detected in the nucleus of HepAD38 cells; however, only AGO2 was bound to HBV cccDNA. In addition, intranuclear AGO2 was determined to be bound with miR-20a. In conclusion, miR-20a may be loaded onto AGO2, prior to its translocation into the nucleus, inducing the methylation of HBV DNA in human hepatoma cells, leading to the suppression of HBV replication.
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Affiliation(s)
- In Young Moon
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Jae Hee Choi
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Jung Wha Chung
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Eun Sun Jang
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Sook-Hyang Jeong
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
| | - Jin-Wook Kim
- Department of Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi 13620, Republic of Korea
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6
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Patchsung M, Settayanon S, Pongpanich M, Mutirangura D, Jintarith P, Mutirangura A. Alu siRNA to increase Alu element methylation and prevent DNA damage. Epigenomics 2018; 10:175-185. [PMID: 29336607 DOI: 10.2217/epi-2017-0096] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Global DNA hypomethylation promoting genomic instability leads to cancer and deterioration of human health with age. AIM To invent a biotechnology that can reprogram this process. METHODS We used Alu siRNA to direct Alu interspersed repetitive sequences methylation in human cells. We evaluated the correlation between DNA damage and Alu methylation levels. RESULTS We observed an inverse correlation between Alu element methylation and endogenous DNA damage in white blood cells. Cells transfected with Alu siRNA exhibited high Alu methylation levels, increased proliferation, reduced endogenous DNA damage and improved resistance to DNA damaging agents. CONCLUSION Alu methylation stabilizes the genome by preventing accumulation of DNA damage. Alu siRNA could be useful for evaluating reprograming of the global hypomethylation phenotype in cancer and aging cells.
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Affiliation(s)
- Maturada Patchsung
- Inter-Department Program of Biomedical Sciences, Faculty of Graduate School, Chulalongkorn University, Bangkok, Thailand
| | - Sirapat Settayanon
- Program of Medical Science, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Monnat Pongpanich
- Department of Mathematics & Computer Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.,Center for Excellence in Molecular Genetics of Cancer & Human Diseases, Chulalongkorn University, Bangkok, Thailand
| | - Dharm Mutirangura
- Center for Excellence in Molecular Genetics of Cancer & Human Diseases, Chulalongkorn University, Bangkok, Thailand
| | - Pornrutsami Jintarith
- Omics Sciences & Bioinformatics Center, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Apiwat Mutirangura
- Center for Excellence in Molecular Genetics of Cancer & Human Diseases, Chulalongkorn University, Bangkok, Thailand.,Department of Tropical Nutrition & Food Science, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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Zhong C, Lu H, Han T, Tan X, Li P, Huang J, Xie Q, Hou Z, Qu T, Jiang Y, Wang S, Xu L, Zhong Y, Huang T. CpG methylation participates in regulation of hepatitis B virus gene expression in host sperm and sperm-derived embryos. Epigenomics 2017; 9:123-125. [PMID: 27919171 DOI: 10.2217/epi-2016-0129] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
AIM This study was undertaken to investigate relationship between hepatitis B virus (HBV) CpG methylation and HBV gene transcription in sperm and sperm-derived embryos. METHODS HBV-infected patient sperm and HBV plasmid-transfected donor sperm were subjected to interspecific in vitro fertilization, methylation-specific PCR, bisulfite sequencing PCR, reverse transcription PCR and real-time quantitative PCR. RESULTS Positive methylation bands for CpG islands II and III in the HBV genome were observed in patient sperm but not in controls, and methylation percentages of CpG sites varied among different patient sperm samples. After fertilization, CpG sites were highly demethylated in embryos. Transcriptional levels of HBV X and S genes increased with decrease in CpG site methylation percentages. CONCLUSION HBV CpG sites can be methylated in patient sperm before maturation. Methylation of CpG islands II and III participates in transcriptional regulation of HBV X and S genes, respectively, in sperm and sperm-derived embryos.
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Affiliation(s)
- ChengYao Zhong
- Faculty of Science & Engineering, Paul Sabatier University-Toulouse III, Toulouse 31062, France
| | - Hui Lu
- Research Center for Reproductive Medicine, Shantou University Medical College, Shantou 515041, China
| | - TingTing Han
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - XiaoFang Tan
- Research Center for Reproductive Medicine, Shantou University Medical College, Shantou 515041, China
| | - PengHao Li
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - JiHua Huang
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - QingDong Xie
- Research Center for Reproductive Medicine, Shantou University Medical College, Shantou 515041, China
| | - ZhiWei Hou
- Key Laboratory of Birth Defects & Reproductive Health of the National Health & Family Planning Commission, Chongqing Population & Family Planning Science & Technology Research Institute, Chongqing 400020, China
| | - Ting Qu
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - Yang Jiang
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - Sheng Wang
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - Lan Xu
- The First Affiliated Hospital, Shantou University Medical College, Shantou 515041, China
| | - Ying Zhong
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
| | - TianHua Huang
- Jinxin Research Institute for Reproductive Medicine & Genetics, Chengdu Jinjiang Hospital for Maternal & Child Health Care, Chengdu 610066, China
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8
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Ceniceros-Ojeda EA, Rodríguez-Negrete EA, Rivera-Bustamante RF. Two Populations of Viral Minichromosomes Are Present in a Geminivirus-Infected Plant Showing Symptom Remission (Recovery). J Virol 2016. [PMID: 26792752 DOI: 10.1128/jvi.02385-2315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
UNLABELLED Geminiviruses are important plant pathogens characterized by circular, single-stranded DNA (ssDNA) genomes. However, in the nuclei of infected cells, viral double-stranded DNA (dsDNA) associates with host histones to form a minichromosome. In phloem-limited geminiviruses, the characterization of viral minichromosomes is hindered by the low concentration of recovered complexes due to the small number of infected cells. Nevertheless, geminiviruses are both inducers and targets of the host posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) machinery. We have previously characterized a "recovery" phenomenon observed in pepper plants infected with pepper golden mosaic virus (PepGMV) that is associated with a reduction of viral DNA and RNA levels, the presence of virus-related siRNAs, and an increase in the levels of viral DNA methylation. Initial micrococcal nuclease-based assays pinpointed the presence of different viral chromatin complexes in symptomatic and recovered tissues. Using the pepper-PepGMV system, we developed a methodology to obtain a viral minichromosome-enriched fraction that does not disturb the basic chromatin structural integrity, as evaluated by the detection of core histones. Using this procedure, we have further characterized two populations of viral minichromosomes in PepGMV-infected plants. After further purification using sucrose gradient sedimentation, we also observed that minichromosomes isolated from symptomatic tissue showed a relaxed conformation (based on their sedimentation rate), are associated with a chromatin activation marker (H3K4me3), and present a low level of DNA methylation. The minichromosome population obtained from recovered tissue, on the other hand, sedimented as a compact structure, is associated with a chromatin-repressive marker (H3K9me2), and presents a high level of DNA methylation. IMPORTANCE Viral minichromosomes have been reported in several animal and plant models. However, in the case of geminiviruses, there has been some recent discussion about the importance of this structure and the significance of the epigenetic modifications that it can undergo during the infective cycle. Major problems in this type of studies are the low concentration of these complexes in an infected plant and the asynchronicity of infected cells along the process; therefore, the complexes isolated in a given moment usually represent a mixture of cells at different infection stages. The recovery process observed in PepGMV-infected plants and the isolation procedure described here provide two distinct populations of minichromosomes that will allow a more precise characterization of the modifications of viral DNA and its host proteins associated along the infective cycle. This structure could be also an interesting model to study several processes involving plant chromatin.
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Affiliation(s)
- Esther Adriana Ceniceros-Ojeda
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del IPN, Cinvestav-Irapuato, Irapuato, Guanajuato, Mexico
| | | | - Rafael Francisco Rivera-Bustamante
- Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del IPN, Cinvestav-Irapuato, Irapuato, Guanajuato, Mexico
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9
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Two Populations of Viral Minichromosomes Are Present in a Geminivirus-Infected Plant Showing Symptom Remission (Recovery). J Virol 2016; 90:3828-3838. [PMID: 26792752 DOI: 10.1128/jvi.02385-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/16/2016] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED Geminiviruses are important plant pathogens characterized by circular, single-stranded DNA (ssDNA) genomes. However, in the nuclei of infected cells, viral double-stranded DNA (dsDNA) associates with host histones to form a minichromosome. In phloem-limited geminiviruses, the characterization of viral minichromosomes is hindered by the low concentration of recovered complexes due to the small number of infected cells. Nevertheless, geminiviruses are both inducers and targets of the host posttranscriptional gene silencing (PTGS) and transcriptional gene silencing (TGS) machinery. We have previously characterized a "recovery" phenomenon observed in pepper plants infected with pepper golden mosaic virus (PepGMV) that is associated with a reduction of viral DNA and RNA levels, the presence of virus-related siRNAs, and an increase in the levels of viral DNA methylation. Initial micrococcal nuclease-based assays pinpointed the presence of different viral chromatin complexes in symptomatic and recovered tissues. Using the pepper-PepGMV system, we developed a methodology to obtain a viral minichromosome-enriched fraction that does not disturb the basic chromatin structural integrity, as evaluated by the detection of core histones. Using this procedure, we have further characterized two populations of viral minichromosomes in PepGMV-infected plants. After further purification using sucrose gradient sedimentation, we also observed that minichromosomes isolated from symptomatic tissue showed a relaxed conformation (based on their sedimentation rate), are associated with a chromatin activation marker (H3K4me3), and present a low level of DNA methylation. The minichromosome population obtained from recovered tissue, on the other hand, sedimented as a compact structure, is associated with a chromatin-repressive marker (H3K9me2), and presents a high level of DNA methylation. IMPORTANCE Viral minichromosomes have been reported in several animal and plant models. However, in the case of geminiviruses, there has been some recent discussion about the importance of this structure and the significance of the epigenetic modifications that it can undergo during the infective cycle. Major problems in this type of studies are the low concentration of these complexes in an infected plant and the asynchronicity of infected cells along the process; therefore, the complexes isolated in a given moment usually represent a mixture of cells at different infection stages. The recovery process observed in PepGMV-infected plants and the isolation procedure described here provide two distinct populations of minichromosomes that will allow a more precise characterization of the modifications of viral DNA and its host proteins associated along the infective cycle. This structure could be also an interesting model to study several processes involving plant chromatin.
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10
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Recent advance of the hepatitis B virus inhibitors: a medicinal chemistry overview. Future Med Chem 2016; 7:587-607. [PMID: 25921400 DOI: 10.4155/fmc.15.19] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hepatitis B Virus (HBV) is one of the most prevalent viral infections of human worldwide. The therapies are limited in the clinical context because of negative side effects of interferons and the development of viral resistance to the nucleoside/nucleotide inhibitors. In this review, we summarize the recent advances in design and development of potent anti-HBV inhibitors from natural sources and synthetic compounds, targeting different steps in the life cycle of HBV. We attempt to emphasize the major structural modifications, mechanisms of action and computer-aided docking analysis of novel potent inhibitors that need to be addressed in the future to design potent anti-HBV molecules.
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11
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Qian F, Li M, Zhu CW. Impact of antiviral agents on levels of hepatitis B virus covalently closed circular DNA. Shijie Huaren Xiaohua Zazhi 2015; 23:3495-3504. [DOI: 10.11569/wcjd.v23.i22.3495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Chronic hepatitis caused by hepatitis B virus (HBV) infection remains an incurable disease at present, which is mainly because the approved antiviral agents, such as interferon-alpha and nucleos(t)ide analogues, cannot effectively eradicate intrahepatic hepatitis B virus covalently closed circular DNA (cccDNA). And thus a suboptimal efficacy of antiviral agents and relapse after therapy occur very commonly. Therefore, novel drugs and treatment strategies remain to be developed on the basis of further theoretical and clinical research of HBV infection to achieve the ultimate goal of eradication of HBV cccDNA in the future. In this paper, we discuss multiple agents and therapeutic regimens influencing cccDNA levels, in order to help clinicians comprehensively understand the present situation in the research of the clearance of HBV cccDNA.
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12
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Transcription of hepatitis B virus covalently closed circular DNA is regulated by CpG methylation during chronic infection. PLoS One 2014; 9:e110442. [PMID: 25337821 PMCID: PMC4206413 DOI: 10.1371/journal.pone.0110442] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Accepted: 09/12/2014] [Indexed: 02/07/2023] Open
Abstract
The persistence of hepatitis B virus (HBV) infection is maintained by the nuclear viral covalently closed circular DNA (cccDNA), which serves as transcription template for viral mRNAs. Previous studies suggested that cccDNA contains methylation-prone CpG islands, and that the minichromosome structure of cccDNA is epigenetically regulated by DNA methylation. However, the regulatory effect of each CpG island methylation on cccDNA activity remains elusive. In the present study, we analyzed the distribution of CpG methylation within cccDNA in patient samples and investigated the impact of CpG island methylation on cccDNA-driven virus replication. Our study revealed the following observations: 1) Bisulfite sequencing of cccDNA from chronic hepatitis B patients indicated that CpG island I was seldom methylated, 2) CpG island II methylation was correlated to the low level of serum HBV DNA in patients, and in vitro methylation studies confirmed that CpG island II methylation markedly reduced cccDNA transcription and subsequent viral core DNA replication, 3) CpG island III methylation was associated with low serum HBsAg titers, and 4) Furthermore, we found that HBV genotype, HBeAg positivity, and patient age and liver fibrosis stage were also relevant to cccDNA CpG methylation status. Therefore, we clearly demonstrated that the status of cccDNA methylation is connected to the biological behavior of HBV. Taken together, our study provides a complete profile of CpG island methylation within HBV cccDNA and new insights for the function of CpG methylation in regulating HBV cccDNA transcription.
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13
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Li LC. Chromatin remodeling by the small RNA machinery in mammalian cells. Epigenetics 2013; 9:45-52. [PMID: 24149777 DOI: 10.4161/epi.26830] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Chromatin states, quite different from changes in DNA sequence, can impact fundamental cellular processes such as determination of cell identity and development of disease. However, how chromatin states are established and regulated remain to be fully elucidated. In several lower eukaryotes, the small RNA machinery comprised of small RNA and its partners, the Argonaute proteins, is known to play important roles in the establishment of heterochromatin and silencing of repetitive sequences. In mammalian cells, however, the nuclear function of the small RNA machinery is largely unknown. Emerging evidence suggests that components of the small RNA pathway interact with chromatin to regulate nuclear events, including gene transcription and alternative splicing. In addition, these endogenous mechanisms are being exploited to target specific genomic loci for manipulation of gene expression and splicing events. In this review, I summarize current understanding of chromatin remodeling by small RNAs in mammalian cells and highlight recent efforts to map genome-wide interactions between RNAi-related factors and chromatin.
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Affiliation(s)
- Long-Cheng Li
- Department of Urology and Helen Diller Family Comprehensive Cancer Center; University of California; San Francisco, CA USA
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