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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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Zhang Y, Liu H, Yi R, Yan T, He Y, Zhao Y, Liu J. Hepatitis B virus whole-X and X protein play distinct roles in HBV-related hepatocellular carcinoma progression. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2016; 35:87. [PMID: 27255760 PMCID: PMC4891919 DOI: 10.1186/s13046-016-0366-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 05/25/2016] [Indexed: 01/30/2023]
Abstract
Background The role of HBV X protein (HBx) in the development of hepatocellular carcinoma (HCC) has been well studied. However, little is known about the molecular functions of HBV whole-X protein (HBwx), a protein fused with HBx and upstream 56 amino acid, in HCC. In current study, the molecular functions of HBwx in HCC pathogenesis has been investigated, as well as comparison between HBwx and HBx. Methods Expression of HBwx and HBx in 50 HCC tissues was examined by immunohistochemistry. Their tumor-forming abilities were evaluated by an animal model and colony formation assay. Migration and invasion were detected by transwell assay and subcellular localization was tracked by GFP fluorescence. Cell proliferation, cell cycle and apoptosis were detected by CCK8 and FCM. Protein level was determined by Western blotting. Results HBwx was present in 72 % (36/50) of the liver tumor tissues and mainly expressed in the nucleus and deposited in the cytoplasm surrounding karyotheca. HBwx showed a promoting effect on tumorigenesis and growth in vivo and in vitro as well as cell migration and invasion, whilst such effect is compromised compared with that of HBx. Further analysis demonstrated differences in cell proliferation, cell cycle and cell apoptosis between cells expressing HBwx and those expressing HBx. Additionally, it was confirmed that RKIP-p-ERK pathway was involved in HBwx-related tumor formation. Conclusion HBwx, with the extra 56 amino acids, is closely related with hepatocarcinogenesis, while displays different biological functions from HBx.
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Affiliation(s)
- Yu Zhang
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China.,Department of Gastroenterology, Xi'an Central Hospital, Xi'an, 710003, Shaanxi Province, China
| | - Hongli Liu
- Xi'an Eighth Hospital Affiliated to Xi'an Jiaotong University Health Science Center, Xi'an, 710061, Shaanxi Province, China.
| | - Ruitian Yi
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China
| | - Taotao Yan
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China
| | - Yingli He
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China
| | - Yingren Zhao
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China.
| | - Jinfeng Liu
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China.
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Zhang Y, Liu J, Liu H, He Y, Yi R, Niu Y, Chen T, Yang Q, Zhao Y. Comparative study of the different activities of hepatitis B virus whole-X protein and HBx in hepatocarcinogenesis by proteomics and bioinformatics analysis. Arch Virol 2015; 160:1645-56. [PMID: 25913689 DOI: 10.1007/s00705-015-2421-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 04/04/2015] [Indexed: 01/30/2023]
Abstract
The hepatitis B virus (HBV) whole-X gene comprises the HBV X gene and the 168-bp region immediately upstream. Although the functions of HBx in hepatocarcinogenesis are well known, the activity of the HBV whole-X protein (HBwx), with 56 additional amino acids, has not yet been explored. In this study, proteomic and bioinformatic analysis was done to determine the protein interaction profiles of HBwx and HBx and to describe their functions in carcinogenesis. A total of 203 proteins were identified that interacted with HBwx, of which 149 were unique, the rest interacting also with HBx, and 73% (148/203) of these proteins are involved in carcinogenesis. Gene ontology (GO) analysis showed that HBwx- and HBx-interacting proteins are involved in different processes, the former mainly in biosynthetic processes (glycolysis, cell-cycle functions, and protein folding), and the latter mainly in localization, viral transcription, biological adhesion and angiogenesis. Pathway networks analysis revealed that proteins interacting with HBx participate mainly in oxidative phosphorylation, localization, the cytoskeleton, and cell adhesion. In contrast, more-specific functional analysis showed that proteins interacting with HBwx are involved in apoptosis and survival, cell-cycle functions, glycolysis, and gluconeogenesis (Pathway Maps); to cellular macromolecular complex assembly, protein folding and mRNA metabolic process (GO Processes); and to regulation of protein folding in the endoplasmic reticulum and cytoplasm, transcription, cell cycle G2-M and cytoskeleton rearrangement (Process Networks). In conclusion, this study shows that HBwx functions in carcinogenesis in a way that is different from that of HBx.
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Affiliation(s)
- Yu Zhang
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an, 710061, Shaanxi Province, China
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4
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Zhang Y, Liu H, Cui M, Liu J, Yi R, Niu Y, Chen T, Zhao Y. Effect of the HBV whole-X gene on the expression of hepatocellular carcinoma associated proteins. JOURNAL OF MICROBIOLOGY, IMMUNOLOGY, AND INFECTION = WEI MIAN YU GAN RAN ZA ZHI 2014; 49:335-43. [PMID: 25311406 DOI: 10.1016/j.jmii.2014.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 07/15/2014] [Indexed: 12/13/2022]
Abstract
BACKGROUND The hepatitis B virus (HBV) pre-X gene resides upstream of the HBV X gene, and together they form the HBV whole-X gene. Although it has been evident that the HBV whole-X protein is involved in the development of hepatocellular carcinoma, its biological role and molecular mechanism remain largely unknown. METHODS In this study, we subcloned the HBV whole-X gene and constructed a HBV whole-X expressing vector. After transfection of the HBV whole-X gene into HL-7702 cells, the profile of the differential cellular protein composition in the cells was analyzed by using two-dimensional electrophoresis coupled to matrix-assisted laser desorption/ionization-time of flight mass spectrometry. RESULTS The results showed that 18 major proteins were differentially expressed in the cells transfected with or without the HBV whole-X gene. The expression of these genes was further confirmed by reverse transcription-polymerase chain reaction and Western blot analysis. CONCLUSION Our findings provide a new insight into the investigation of the pathological role that the HBV whole-X gene plays in the development of hepatocellular carcinoma and may lead to the design of novel strategies for the treatment of this disease.
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Affiliation(s)
- Yu Zhang
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Hongli Liu
- Shaanxi Provincial Infectious Diseases Hospital, Xi'an 710061, Shaanxi Province, China; Xi'an Eighth Hospital Affiliated to Xi'an Jiaotong University Health Science Center, Xi'an 710061, Shaanxi Province, China
| | - Meiling Cui
- Zhengzhou Sixth People's Hospital, Zhengzhou 450061, He'nan Province, China
| | - Jinfeng Liu
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Ruitian Yi
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Yinghua Niu
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Tianyan Chen
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China
| | - Yingren Zhao
- Department of Infectious Diseases, First Affiliated Hospital of Medical College, Xi'an Jiaotong University, Xi'an 710061, Shaanxi Province, China.
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Pollicino T, Saitta C, Raimondo G. Hepatocellular carcinoma: the point of view of the hepatitis B virus. Carcinogenesis 2011; 32:1122-32. [PMID: 21665892 DOI: 10.1093/carcin/bgr108] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Teresa Pollicino
- Department of Internal Medicine, Unit of Clinical and Molecular Hepatology, University Hospital of Messina, Via Consolare Valeria, Messina, Italy.
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6
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Liou W, Sung YJ, Tao MH, Lo SJ. Morphogenesis of the hepatitis B virion and subviral particles in the liver of transgenic mice. J Biomed Sci 2007; 15:311-6. [DOI: 10.1007/s11373-007-9221-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2007] [Accepted: 10/30/2007] [Indexed: 11/29/2022] Open
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7
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Kremsdorf D, Soussan P, Paterlini-Brechot P, Brechot C. Hepatitis B virus-related hepatocellular carcinoma: paradigms for viral-related human carcinogenesis. Oncogene 2006; 25:3823-33. [PMID: 16799624 DOI: 10.1038/sj.onc.1209559] [Citation(s) in RCA: 206] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
As discussed in detail in other chapters of this review, chronic hepatitis B (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC). Most HCCs complicate the evolution of an active or inactive cirrhosis. However, some tumors occur on livers with minimal histological changes; the prevalence of such cases varies from one geographical region to the other, being much higher in the southern half of Africa (around 40% of HCCs) than in Asia, America and Europe, where at least 90% of HCCs are associated with the cirrhosis. This heterogeneity is probably a reflection of different environmental and genetic factors. This review will summarize the current knowledge on the mechanisms involved in HBV-related liver carcinogenesis. It will show in particular how viruses can be viewed as tools to discover and dissect new cellular pathways involved in cancer development and emphasize the potential synergistic effects between HBV and hepatitis C virus, as well as between viral infections and other environmental factors, such as alcohol.
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Bréchot C, Gozuacik D, Murakami Y, Paterlini-Bréchot P. Molecular bases for the development of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Semin Cancer Biol 2000; 10:211-31. [PMID: 10936070 DOI: 10.1006/scbi.2000.0321] [Citation(s) in RCA: 221] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hepatocellular carcinoma (HCC) is the most common histological form of primary liver cancer; the tumor cells having retained features of hepatocytic differentiation. It is important to emphasize the heterogeneity of the histological background on which the tumor develops. Most HCCs complicate the evolution of an active or inactive cirrhosis. However, some tumors occur on livers with minimal histological changes; the prevalence of such cases varies from one geographical region to the other; being much higher in the southern half of Africa (around 40% of HCCs) than in Asia, America and Europe, where at least 90% of HCCs are associated in the cirrhosis. This heterogeneity is probably a reflection of different environmental and genetic factors. A large number of epidemiological and molecular studies have indeed clearly demonstrated the prime importance of environmental factors to the development of primary liver cancers in humans. Chronic hepatitis B (HBV) and C (HCV) infections are major risk factors. This review will mainly analyse the impact of chronic HBV infection but it is important to emphasize the potential synergistic effects between HBV and HCV, as well as between viral infections and other environmental factors, such as alcohol, chemical carcinogens (see review by Dr Wogan) and other, still poorly defined, hormonal factors which may account for the higher incidence of the tumor in man. Finally the review by Dr Buendia highlights the emerging issue of liver-cancer genetics.
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MESH Headings
- Apoptosis
- Carcinoma, Hepatocellular/pathology
- Carcinoma, Hepatocellular/virology
- Cell Cycle
- DNA, Viral/analysis
- Genome, Viral
- Hepatitis B Surface Antigens/analysis
- Hepatitis B virus/genetics
- Hepatitis B, Chronic/genetics
- Hepatitis B, Chronic/pathology
- Hepatitis B, Chronic/virology
- Hepatitis C, Chronic/genetics
- Hepatitis C, Chronic/pathology
- Hepatitis C, Chronic/virology
- Humans
- Liver Neoplasms/pathology
- Liver Neoplasms/virology
- Transcription, Genetic/genetics
- Tumor Cells, Cultured/drug effects
- Virus Integration
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Affiliation(s)
- C Bréchot
- Liver unit and INSERM U370, CNR Pasteur/Necker Institute, Paris, France.
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9
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Zhong S, Chan JY, Yeo W, Tam JS, Johnson PJ. Frequent integration of precore/core mutants of hepatitis B virus in human hepatocellular carcinoma tissues. J Viral Hepat 2000; 7:115-23. [PMID: 10760041 DOI: 10.1046/j.1365-2893.2000.00209.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The development of hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) frequently follows persistent HBV infection and may arise in individuals who are hepatitis B e antigen (HBeAg) negative, indicating the possible presence of precore/core mutants. It is unclear whether precore/core mutants are associated with tumour development or are selected for after chromosomal integration of the wild-type viral DNA. We studied the status and sequence variation of the precore/core region of HBV in 56 patients with HBV-associated HCC and in various corresponding non-tumour tissues by Southern blot analysis, polymerase chain reaction and direct sequencing. Southern blot showed that integrated HBV DNA existed in 43 of 56 HCC tissues. Sequence analysis revealed mutations in 65% of the HCC (26/40) and 45% (14/31) of the corresponding non-tumour tissues. The mutation at nucleotide (nt) 1896, known to prevent HBeAg synthesis, was detected in 40% (16/40) of the tumours and in 35.4% (11/31) of the non-tumour tissues. Other mutations were found at nt 1899 (eight of 40 in HCC; three of 31 in non-tumour tissues), nt 1898 (seven of 40 in HCC; two of 31 in non-tumour tissues), nt 1912 (seven of 40 in HCC; none of 31 in non-tumour tissues) and nt 1886 (three of 40 in HCC; none of 31 in non-tumour tissues). To determine whether this finding merely reflected the prevalence of such mutants in this geographical region, HBV DNA from the sera of patients (also in this region) with acute and chronic hepatitis were sequenced. The nt 1896 mutant was found in 5.6% (one of 18) of patients with acute hepatitis B and in 22.8% (nine of 35) of patients with chronic hepatitis B. However, the nt 1898 mutation was not found in any of these sera. The precore/core mutant was observed with increasing frequency from acute hepatitis to chronic hepatitis, non-tumour and HCC, and this difference in frequency was significant between HCC and acute hepatitis B groups (P < 0.01), suggesting that the precore/core mutant or hepatocytes harbouring this mutant may be under immune selection and that such mutations may facilitate integration and subsequent tumour development.
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Affiliation(s)
- S Zhong
- Department of Clinical Oncology, Sir Y. K. Pao Centre for Cancer, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong
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10
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Abstract
The core promoter (CP) of hepatitis B virus (HBV) plays a central role in HBV replication and morphogenesis, directing the transcription of both species of 3.5 kb mRNA: pregenomic (pg) RNA and precore (pre-C) mRNA. The CP overlaps the 3' end of the X open-reading frame (ORF) and the 5' end of the pre-C/C ORF. The major functional elements of the CP are the upper regulatory region (URR) and the basic core promoter (BCP). The BCP is sufficient for accurate initiation of both pre-C mRNA and pgRNA transcription. It contains four AT-rich regions and the initiators for pre-C mRNA and pgRNA transcription. The upstream regulatory region consists of the negative regulatory element and the core upstream regulatory sequence. Co-operative interaction of various liver-enriched and ubiquitous transcription factors is necessary for liver-specific expression from the CP. These factors bind to the CP. Sequence conservation within the CP is crucial for maintaining active viral replication, and variation may contribute to the persistence of HBV within the host, leading to chronic infection and, ultimately, hepatocarcinogenesis. The most frequently described mutations within this region are an A to T transversion at position 1762 together with a G to A transition at position 1764. This double mutant is accompanied by a reduced level of hepatitis B e antigen (HBeAg) expression. Deletions, insertions and duplications occur within the CP.
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Affiliation(s)
- A Kramvis
- Medical Research Council/CANSA/University Molecular Hepatology Research Unit, Department of Medicine, University of the Witwatersrand, Johannesburg, South Africa
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11
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Abstract
The existence of HBV as quasispecies is thought to be favoured by the infidelity of HBV RT, which would account for the emergence of the many natural mutants with point substitutions. RT infidelity may also underlie the hypermutation phenomenon. Indeed, the oft-reported point mutation in the preC gene that leads to failure of HBeAg synthesis may be driven by a hypermutation-related mechanism. The presence of mutants with deletions and insertions involving single nucleotides and oligonucleotides at specific positions in the genome, and of mutants with deletions of even longer stretches particularly in the C gene, suggests that other mutagenic mechanisms operate. Candidates include slippage during mispairing between template and progeny DNA strand, the action of cellular topoisomerase I, and gene splicing using alternative donor and acceptor sites. Natural substitutions, deletions or insertions involving the Cp/ENII locus in the X gene can significantly alter the extent of viral replicative activity. Similar mutations occurring at other locations of Cp/ENII, and at B-cell epitope sites of the S gene are associated with failure to detect serological markers of HBV infection. HBV variation can also arise from recombination between coinfecting strains. S gene mutations that become evident following HBIG administration and HBV vaccination are all point substitutions, as are mutations in functional RT domains of the P gene after treatment with viral RT-inhibitory drugs. Widespread and long-term use of prophylactic and therapeutic agents may potentially generate serologically occult HBV variants that might become difficult to eradicate.
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Affiliation(s)
- S L Ngui
- Section of Hepatology, Rush-Presbyterian-St. Luke's Medical Centre, 1725 West Harrison, Chicago, Illinois 60612, USA
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12
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Kramvis A, Kew MC, Bukofzer S. Hepatitis B virus precore mutants in serum and liver of Southern African Blacks with hepatocellular carcinoma. J Hepatol 1998; 28:132-41. [PMID: 9537850 DOI: 10.1016/s0168-8278(98)80212-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND/AIM The aim of this study was to sequence the precore region of HBV isolated from serum and tumorous and non-tumorous liver tissue from patients with hepatocellular carcinoma to identify mutations that might play a role in malignant transformation. METHODS HBV DNA was extracted from 62 sera, 14 tumorous and 12 non-tumorous liver tissue samples of patients with hepatocellular carcinoma, amplified by the polymerase chain reaction and sequenced directly. RESULTS Thirty-nine patients were HBeAg-negative and 23 HBeAg-positive. Missense mutations were present predominantly in HBeAg-negative sera. The most common missense mutation, a guanine to thymine transversion, occurred at nucleotide 1862 in the bulge of the encapsidation signal; it was more prevalent in HBeAg-negative (10/39) than in HBeAg-positive patients (1/23) (p = 0.03). Mutations known to prevent HBeAg synthesis were detected in seven sera; five with an 1896 stop-codon mutation, one with an 1817 nonsense mutation, and one with a frameshift mutation caused by an insertion between 1838 and 1839. Missense mutations and deletions were present more often in tumorous tissue derived from HBsAg-negative patients. In the tumours missense mutations occurred at position 1862 and 1899, and the deletions affected direct repeat 1 and/or the encapsidation signal and included the x gene stop-codon. CONCLUSIONS The 1862 mutation, and other missense mutations and deletions detected in the precore gene, may disrupt HBV DNA replication and/or signal peptide cleavage leading to HBeAg-negativity. Disruption of viral replication may promote integration of unencapsidated replicative intermediates and hence contribute to hepatocarcinogenesis.
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Affiliation(s)
- A Kramvis
- Medical Research Council, Department of Medicine, University of the Witwatersrand, Johannesburg, South Africa
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13
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Brechot C. Hepatitis B and C viruses and primary liver cancer. BAILLIERE'S CLINICAL GASTROENTEROLOGY 1996; 10:335-73. [PMID: 8864037 DOI: 10.1016/s0950-3528(96)90010-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The data presented indicate that viral agents (namely, HBV and HCV) are major environmental aetiological factors for human primary liver cancer. It is important to elucidate the molecular mechanisms further because HCC is one of the few examples of virus-related human cancers. In addition, the available evidence points to the possibility of at least partial prevention of the tumour by large-scale vaccination.
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Affiliation(s)
- C Brechot
- INSERM U370 and Liver Unit, CHU Necker, Paris, France
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14
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Bock CT, Schwinn S, Schröder CH, Velhagen I, Zentgraf H. Localization of hepatitis B virus core protein and viral DNA at the nuclear membrane. Virus Genes 1996; 12:53-63. [PMID: 8879121 DOI: 10.1007/bf00370001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
An early step in the replication of the hepatitis B virus (HBV) genome is the transport of the viral DNA into the nucleus of the infected cell. So far only little is known about the events and mechanisms at the nuclear membrane required for entry of the viral genome into the nucleus. Using a hepatoblastoma cell line that constitutively produces hepatitis B virions and in so doing displays intracellular viral amplification, we showed that nonparticulated HBV core protein is associated with nuclear membrane pore complexes. Additionally, viral DNA has been detected firmly attached to the nuclear membrane. Small amounts of viral core protein, as well as viral DNA, were detectable within the cell nucleus. However, core particles could not be shown at the nuclear membrane or within the nuclei of these cells. Our observations on localization of HBV DNA and core protein at the nuclear membrane thus provide a suggestion for further examinations of the transfer of the viral genome from the cytoplasm into the nucleus of the infected cell.
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Affiliation(s)
- C T Bock
- German Cancer Research Centre, Applied Tumor Virology, Heidelberg, FRG
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15
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Bock CT, Schwinn S, Zentgraf H. Diheteroduplex formation using gold labeled single-stranded PCR fragments and its application in electron microscopy. Chromosoma 1995; 103:653-7. [PMID: 7587588 DOI: 10.1007/bf00357692] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Heteroduplex analysis is commonly used to map homologous sequences in DNA:DNA or DNA:RNA hybrids in spread preparations by electron microscopy. However, the standard procedures are not suitable to detect the orientation of a fragment with a defined sequence in a hybrid molecule. Here, we describe an alternative protocol for the visualization of DNA:DNA "diheteroduplex" structures based on digoxigenin/anti-digoxigenin gold labeling that allows determination of the position and orientation of a fragment. Single-stranded polymerase chain reaction (PCR) generated fragments labeled at their 3' ends are hybridized to double-stranded plasmid DNA. Electron microscopy of spread preparations visualizes the gold label and, in combination with morphometric measurements, it is possible to determine the position and orientation of the fragment with the diheteroduplex molecule.
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Affiliation(s)
- C T Bock
- German Cancer Research Center, Heidelberg, Germany
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16
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Bock CT, Schranz P, Schröder CH, Zentgraf H. Hepatitis B virus genome is organized into nucleosomes in the nucleus of the infected cell. Virus Genes 1994; 8:215-29. [PMID: 7975268 DOI: 10.1007/bf01703079] [Citation(s) in RCA: 142] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hepatitis B virus (HBV) nucleoprotein complexes were isolated from nuclei of the human hepatoblastoma cell line HepG2.2.15. Under conditions of physiological ionic strength, the complexes sedimented at a rate corresponding to about 82 S. They contained viral DNA, histone, and nonhistone proteins. For DNA a circular, covalently closed structure was shown both by CsCl gradient centrifugation and electron microscopy. Spread preparations revealed the typical "beads-on-a-string" appearance of nucleosomally organized DNA. The average number of nucleosomes was 18, resulting in a biochemical repeat unit of HBV chromatin of approximately 180 base pairs of DNA. This value was confirmed by experiments analyzing the structure of the HBV chromatin by the use of micrococcal nuclease. Electron microscopy demonstrated that exposure to high ionic strength conditions resulted in removal of nucleosomes from the complexes, but also revealed proteinaceous structures remaining bound to viral DNA molecules. The nature of these residual proteins is discussed. Since native nucleoprotein complexes could be precipitated with HBV-core antibodies, core protein appeared to be one of the nonhistone proteins.
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Affiliation(s)
- C T Bock
- German Cancer Research Centre, Heidelberg, FRG
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17
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Galle PR, Hagelstein J, Kommerell B, Volkmann M, Schranz P, Zentgraf H. In vitro experimental infection of primary human hepatocytes with hepatitis B virus. Gastroenterology 1994; 106:664-73. [PMID: 8119538 DOI: 10.1016/0016-5085(94)90700-5] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND/AIMS Studies on the interaction of hepatitis B virus (HBV) with its host cell require a suitable tissue culture system. This study used primary adult hepatocytes from healthy human liver tissue to establish productive infection in vitro. METHODS Hepatocytes were inoculated overnight with HBV. Production of viral proteins was assessed by radioimmunoassay and by [35S]methionine labeling, and production of viral DNA was assessed by Southern blotting and endogenous polymerase assay. RESULTS Secretion of high levels of hepatitis B surface antigen (HBsAg) and low levels of hepatitis B virus e antigen (HBeAg) into the medium was detectable 6 days after infection and reached maximum values after 12 days. Metabolic labeling showed production of viral proteins to be a result of de novo synthesis. The appearance of single-stranded HBV DNA in the cytoplasm of infected cells, typically present in immature cores, indicated viral replication. HBV DNA containing particles possessing an active viral DNA polymerase could be immunoprecipitated from the medium 12 days after infection. An antiserum specific for the preS1 region of the viral envelope was capable to block infection. Presence of dimethyl sulfoxide in the medium greatly improved the yield of viral proteins. CONCLUSIONS Primary adult human liver cells are competent for infection with HBV.
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Affiliation(s)
- P R Galle
- Department of Internal Medicine, University of Heidelberg, Germany
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18
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Clementi M, Manzin A, Paolucci S, Menzo S, Bangarelli P, Carloni G, Bearzi I. Hepatitis B virus preC mutants in human hepatocellular carcinoma tissues. RESEARCH IN VIROLOGY 1993; 144:297-301. [PMID: 8210712 DOI: 10.1016/s0923-2516(06)80044-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A comparative analysis of preC sequences of hepatitis B virus (HBV) in human hepatoma (hepatocellular carcinoma; HCC) tissues and non-tumoral liver samples from HCC patients was performed. Ten out of 17 HCC tissue samples exhibited an amino acid substitution at the level of the distal cysteine residue of the HBV preC region, while generation of a TAG translational stop codon was observed in 4 of these samples. Interestingly, substitution of the distal cysteine residue was not observed in non-tumoral liver (available from 8 of the 17 patients), thus suggesting either that a selection among different HBV variants occurs in HCC cells, or that modifications to the conformation and stability of the HBV capsid protein may play a role in the process of selection and escape of transformed liver cells.
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Affiliation(s)
- M Clementi
- Institute of Microbiology, University of Ancona, Italy
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19
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Lamberts C, Nassal M, Velhagen I, Zentgraf H, Schröder CH. Precore-mediated inhibition of hepatitis B virus progeny DNA synthesis. J Virol 1993; 67:3756-62. [PMID: 8510204 PMCID: PMC237739 DOI: 10.1128/jvi.67.7.3756-3762.1993] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The capacities to induce the synthesis of hepatitis B virus (HBV) unit-length DNA were compared for two HBV DNAs with an overall sequence diversity of about 10%. They had been cloned from serum (DNA2) and from a hepatocellular carcinoma (DNA4), respectively. As a major difference, DNA4 carries a translational stop signal preventing the synthesis of precore protein. Progeny DNA yields obtained after transfection with respective pregenome transcription units allocated DNA2 to a low-replicator and DNA4 to a high-replicator phenotype. Cotransfection of DNA2 interfered with progeny DNA synthesis induced by DNA4. By mutual exchange of restriction fragments, the region on the viral genome responsible for the differing replicator phenotypes was confined to a sequence comprising the 3'-terminal part of the X gene, core promoter, encapsidation signal epsilon, precore/core gene, and 5'-terminal part of the pol gene. Point mutations in DNA2 abolishing proper expression of the precore gene strongly enhanced the yield of progeny DNA, whereas cotransfection of a precore expression plasmid with DNA4 or with the mutated DNA2 substantially lowered the amount of progeny DNA. Hence, precore expression acts as an inhibitory principle for HBV replication. The same stop mutation as in DNA4 has been found to arise frequently in virus carriers. Loss of precore expression and concomitant conversion to a more severe hepatitis, as observed in the course of a chronic infection, thus can be explained by a relaxation of replication-level control.
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Affiliation(s)
- C Lamberts
- Angewandte Tumorvirologie, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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20
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Manzin A, Menzo S, Bagnarelli P, Varaldo PE, Bearzi I, Carloni G, Galibert F, Clementi M. Sequence analysis of the hepatitis B virus pre-C region in hepatocellular carcinoma [HCC] and nontumoral liver tissues from HCC patients. Virology 1992; 188:890-5. [PMID: 1316686 DOI: 10.1016/0042-6822(92)90548-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We investigated whether replication-competent pre-C/C defective mutants of hepatitis B virus (HBV) are detectable in primary human hepatocellular carcinoma (HCC) tissues from patients of a geographic area endemic for such mutants. DNAs extracted from formalin-fixed paraffin-embedded HCC samples were checked for the presence of specific HBV DNA sequences using the polymerase chain reaction (PCR). Amplified pre-C regions from nine HCC samples were directly sequenced as were samples of nontumoral liver tissues from five of these patients. The data show that hypervariable distal pre-C sequences were present in all nine HCC samples; this high variability was dependent on point mutations, which led to amino acid substitutions in nearly all cases. Interestingly, seven of the nine HBV DNA-positive samples from HCC tissues (but not samples from peritumoral liver tissue) showed mutations leading to amino acid substitution at the level of a distal cysteine residue. No mutation generating a translationally defective pre-C/C region was detectable in the tumor samples. Otherwise, in four of the six nontumoral liver tissues available from the same patients, a pre-C sequence with an in-frame TAG stop codon was detectable, although in three cases as a component of mixed population.
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Affiliation(s)
- A Manzin
- Institute of Microbiology, University of Ancona Medical School, Italy
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21
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Löchelt M, Zentgraf H, Flügel RM. Construction of an infectious DNA clone of the full-length human spumaretrovirus genome and mutagenesis of the bel 1 gene. Virology 1991; 184:43-54. [PMID: 1651600 DOI: 10.1016/0042-6822(91)90820-2] [Citation(s) in RCA: 132] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
An infectious and full-length molecular clone of genomic human spumaretrovirus (HSRV) DNA was constructed. The infectivity of the pHSRV13 clone was demonstrated after transfection into susceptible cells by passage of HSRV-specific cytopathic effects as a cell-free culture supernatant, by electron microscopy of HSRV particles in pHSRV13 DNA-transfected cells, by detection of HSRV transcripts, and by identification of HSRV-encoded proteins with Env- and Bel-specific antisera in indirect immunofluorescence assays and in protein blotting. The predominant HSRV protein detected in immunoblots by both Bel 1- and Bel 2-specific antisera had an apparent molecular weight of 56 kDa and corresponds to Bet. The amino-terminus of Bet is encoded by part of a Bel 1-specific RNA and the larger Bet domain by an RNA species from the bel 2 gene (Muranyi, W., and Flügel, R. M. J. Virology 65, 727-735, 1991). HSRV-specific proteins of 36 and 43 kDa reacted with Bel 1 and Bel 2 antisera, consistent with the values calculated for the bel 1 and bel 2 gene products, respectively. Deletion mutagenesis of the transcriptional HSRV-specific trans-activator bel 1 and the bet genes completely abolished the infectivity of the pHSRV13 clone. The defect in RNA, protein, and virion synthesis was trans-complemented by cotransfection of an expression clone harboring the complete bel coding region. This result demonstrates that the bel 1 gene is required for viral replication. It remains to be determined whether other HSRV gene products, like bet that share a common region with bel 1, contributed to the defect observed.
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Affiliation(s)
- M Löchelt
- Institut für Virusforschung, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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22
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Hilger C, Velhagen I, Zentgraf H, Schröder CH. Diversity of hepatitis B virus X gene-related transcripts in hepatocellular carcinoma: a novel polyadenylation site on viral DNA. J Virol 1991; 65:4284-91. [PMID: 1649331 PMCID: PMC248866 DOI: 10.1128/jvi.65.8.4284-4291.1991] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
RNA was isolated from tissue of two patients with hepatocellular carcinoma developed on the background of a chronic hepatitis B virus infection. For identification and characterization of 3' ends of X gene open reading frame (ORF)-related transcripts, RNA was reverse transcribed into cDNA and subjected to polymerase chain reaction. Cloned amplification products from tumor tissue of one patient represented an approximately even distribution of transcripts terminating at the established poly(A) signal (standard transcripts) and of truncated transcripts terminating at a CATAAA poly(A) signal within the 3' end region of X gene ORF (truncated transcripts). Amplified cDNA from tumor tissue of the second patient could be attributed mainly to the standard type of transcripts, whereas cDNA from the nontumor tissue of the same patient could be assigned to four groups of transcripts: (i) standard transcripts, (ii) transcripts with internal deletions affecting the 3' end of the X gene, (iii) truncated transcripts, and (iv) hybrid transcripts displaying 5' sequences from the X gene ORF fused to cellular sequences.
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Affiliation(s)
- C Hilger
- Institut für Virusforschung/ATV, Deutsches Krebsforschungszentrum, Heidelberg, Germany
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23
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Klein R, Schröder CH, Zentgraf H. Expression of the X protein of hepatitis B virus in insect cells using recombinant baculoviruses. Virus Genes 1991; 5:157-74. [PMID: 2058090 DOI: 10.1007/bf00571930] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The baculovirus system was used to express the X protein of human hepatitis B virus (HBV). The X open reading frames (X ORFs) from cloned viral DNA of the HBV subtypes ayw and adr were introduced into the genome of Autographa californica nuclear polyhedrosis virus (AcNPV). The HBV-DNA of subtype adr derived from a hepatocellular carcinoma contains an X ORF and a 5' extended preX/X ORF, which were both used to construct X recombinant baculoviruses. Infection of Sf9 insect cells with these recombinant viruses yielded large amounts of the respective X proteins. They were identified by a set of mouse monoclonal antibodies directed against different epitopes of the ayw X protein using immunoblotting techniques. A subpopulation of the X protein expressed is modified, thus raising the molecular weight from the expected size of 17 kD to 21 kD. Indirect immunofluorescence and immunoelectron microscopy was performed to characterize the subcellular distribution of the X protein expressed in Sf9 cells. Data are presented that it accumulates as large globular structures within the cytoplasm and the nucleus of the infected cells.
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Affiliation(s)
- R Klein
- Institute for Virus Research, German Cancer Research Center, Heidelberg, FRG
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24
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25
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Liang XH, Loncarevic IF, Tang ZY, Yu YQ, Zentgraf H, Schröder CH. Resection of hepatocellular carcinoma: oligocentric origin of recurrent and multinodular tumours. J Gastroenterol Hepatol 1991; 6:77-80. [PMID: 1653057 DOI: 10.1111/j.1440-1746.1991.tb01150.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The structure of integrated hepatitis B virus (HBV) DNA was analysed to determine the origin of recurrent and multinodular hepatocellular carcinoma (HCC). In 5 cases, recurrent tumours were compared with the respective primary tumours, all of which had chromosomally integrated viral DNA. In only one of these cases, an identical HBV DNA integration pattern was found, indicating a monocentric origin of primary and secondary tumour. In all other cases a polycentric origin was deduced. Particular features observed were: (i) the apparent absence of integrated viral DNA in a recurrent tumour; and (ii) an integration pattern identical to that of the primary tumour and a distinct new pattern in two different foci of multinodular recurrent HCC. For multinodular primary HCC one case was analysed and found to be of independent origin.
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Affiliation(s)
- X H Liang
- Liver Cancer Institute, Shanghai Medical University, People's Republic of China
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26
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Schröder CH, Zentgraf H. Hepatitis B virus related hepatocellular carcinoma: chronicity of infection--the opening to different pathways of malignant transformation? BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1032:137-56. [PMID: 2175655 DOI: 10.1016/0304-419x(90)90001-h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- C H Schröder
- Institut für Virusforschung, Deutsches Krebsforschungszentrum, Heidelberg, F.R.G
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27
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Schranz P, Zentgraf H, Schröder CH. Integrated defective replication units of hepatitis B virus. Virus Genes 1990; 4:367-74. [PMID: 1962978 DOI: 10.1007/bf00570031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Stable transformants of the human hepatoma cell line HepG2 were established that constitutively transcribe a DNA unit consisting of a stretch of hepatitis B virus DNA and of nonviral DNA conferring resistance to neomycin. Previously it had been shown that upon cotransfection of such transformants with replication-competent HBV DNA, transcripts of such units become reverse transcribed, demonstrating that DNA constructs can function as defective replication units. Transformed cell lines stably transcribing the defective replication units could be shown to use the transcriptional starts for the viral pregenome and for the large core antigen at a ratio of 9:1. Upon the induction of replicative processes in the transformed cells by transfection with replication-competent wild type (wt) DNA, defective pregenomes transcribed from the integrated state became included in the pool of replicating nucleic acids.
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Affiliation(s)
- P Schranz
- Institut für Virusforschung, Deutsches Krebsforschungszentrum, Heidelberg, FRG
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28
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Loncarevic IF, Zentgraf H, Schröder CH. Sequence of a replication competent hepatitis B virus genome with a preX open reading frame. Nucleic Acids Res 1990; 18:4940. [PMID: 2395664 PMCID: PMC332005 DOI: 10.1093/nar/18.16.4940] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Affiliation(s)
- I F Loncarevic
- Institut für Virusforschung, Deutsches Krebsforschungszentrum, Heidelberg, FRG
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29
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Schranz P, Zentgraf H, Loncarević IF, Niepmann M, Schröder CH. Defective replication units of hepatitis B virus. J Virol 1990; 64:1851-4. [PMID: 2157068 PMCID: PMC249328 DOI: 10.1128/jvi.64.4.1851-1854.1990] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Templates for the synthesis of defective hepatitis B virus RNA pregenomes were constructed. Viral sequences in these constructs were replaced by the neomycin resistance gene. Deletions spanned up to 80% of the genome and did not include the cohesive end region. The size of the defective replication units was reduced up to half of the wild-type unit length. After cotransfection with replication competent wild-type DNA, defective pregenomes became included into the pool of replicating viral nucleic acids. A natural template for a defective pregenome was derived from the integrated state in a hepatocellular carcinoma. Owing to a deletion, this unit was devoid of the hepatitis B virus enhancer.
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Affiliation(s)
- P Schranz
- Institut für Virusforschung, Deutsches Krebsforschungszentrum, Heidelberg, Federal Republic of Germany
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