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Bianca C, Sidhartha E, Tiribelli C, El-Khobar KE, Sukowati CHC. Role of hepatitis B virus in development of hepatocellular carcinoma: Focus on covalently closed circular DNA. World J Hepatol 2022; 14:866-884. [PMID: 35721287 PMCID: PMC9157711 DOI: 10.4254/wjh.v14.i5.866] [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] [Received: 11/30/2021] [Revised: 01/31/2022] [Accepted: 04/25/2022] [Indexed: 02/06/2023] Open
Abstract
Chronic infection with hepatitis B virus (HBV) remains a major global health problem, especially in developing countries. It may lead to prolonged liver damage, fibrosis, cirrhosis, and hepatocellular carcinoma. Persistent chronic HBV infection is related to host immune response and the stability of the covalently closed circular DNA (cccDNA) in human hepatocytes. In addition to being essential for viral transcription and replication, cccDNA is also suspected to play a role in persistent HBV infections or hepatitis relapses since cccDNA is very stable in non-dividing human hepatocytes. Understanding the pathogenicity and oncogenicity of HBV components would be essential in the development of new diagnostic tools and treatment strategies. This review summarizes the role and molecular mechanisms of HBV cccDNA in hepatocyte transformation and hepatocarcinogenesis and current efforts to its detection and targeting.
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Affiliation(s)
- Claryssa Bianca
- Department of Biomedicine, Indonesia International Institute for Life Sciences, Jakarta 13210, Indonesia
| | - Elizabeth Sidhartha
- Department of Biomedicine, Indonesia International Institute for Life Sciences, Jakarta 13210, Indonesia
| | - Claudio Tiribelli
- Centro Studi Fegato, Fondazione Italiana Fegato ONLUS, Trieste 34149, Italy
| | - Korri Elvanita El-Khobar
- Eijkman Center for Molecular Biology, National Research and Innovation Agency (BRIN), Jakarta 10340, Indonesia
| | - Caecilia H C Sukowati
- Centro Studi Fegato, Fondazione Italiana Fegato ONLUS, Trieste 34149, Italy
- Eijkman Center for Molecular Biology, National Research and Innovation Agency (BRIN), Jakarta 10340, Indonesia
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Wang J, Huang H, Liu Y, Chen R, Yan Y, Shi S, Xi J, Zou J, Yu G, Feng X, Lu F. HBV Genome and Life Cycle. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1179:17-37. [PMID: 31741332 DOI: 10.1007/978-981-13-9151-4_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chronic hepatitis B virus (HBV) infection remains to be a serious threat to public health and is associated with many liver diseases including chronic hepatitis B (CHB), liver cirrhosis, and hepatocellular carcinoma. Although nucleos(t)ide analogues (NA) and pegylated interferon-α (Peg-IFNα) have been confirmed to be efficient in inhibiting HBV replication, it is difficult to eradicate HBV and achieve the clinical cure of CHB. Therefore, long-term therapy has been recommended to CHB treatment under the current antiviral therapy. In this context, the new antiviral therapy targeting one or multiple critical steps of viral life cycle may be an alternative approach in future. In the last decade, the functional receptor [sodium-taurocholate cotransporting polypeptide (NTCP)] of HBV entry into hepatocytes has been discovered, and the immature nucleocapsids containing the non- or partially reverse-transcribed pregenomic RNA, the nucleocapsids containing double-strand linear DNA (dslDNA), and the empty particles devoid of any HBV nucleic acid have been found to be released into circulation, which have supplemented the life cycle of HBV. The understanding of HBV life cycle may offer a new instruction for searching the potential antiviral targets, and the new viral markers used to monitor the efficacy of antiviral therapy for CHB patients in the future.
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Affiliation(s)
- Jie Wang
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Hongxin Huang
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Yongzhen Liu
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Ran Chen
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Ying Yan
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Shu Shi
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Jingyuan Xi
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Jun Zou
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Guangxin Yu
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Xiaoyu Feng
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China
| | - Fengmin Lu
- Department of Microbiology & Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, P.R. China.
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Potential use of serum HBV RNA in antiviral therapy for chronic hepatitis B in the era of nucleos(t)ide analogs. Front Med 2017; 11:502-508. [PMID: 29170915 DOI: 10.1007/s11684-017-0590-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Accepted: 09/22/2017] [Indexed: 01/05/2023]
Abstract
Although the efficacy of nucleos(t)ide analogue (NA) has been confirmed for treatment of chronic hepatitis B, long-term therapy has been recommended due to the high frequency of off-therapy viral DNA rebound and disease relapse. In this review, the RNA virion-like particles of hepatitis B virus (HBV) are integrated into the life cycle of HBV replication, and the potential significance of serum HBV RNA is systematically described. The production of HBV RNA virion-like particles should not be blocked by NA; in this regard, serum HBV RNA is found to be a suitable surrogate marker for the activity of intrahepatic covalently closed circular DNA (cccDNA), particularly among patients receiving NA therapy. Therefore, the concept of virological response is redefined as persistent loss of serum HBV DNA and HBV RNA. In contrast to hepatitis B surface antigen (HBsAg) that can originate from either the cccDNA or the integrated HBV DNA fragment, serum HBV RNA, with pregenomic RNA origination, can only be transcribed from cccDNA. Therefore, the loss of serum HBV RNA would likely be a promising predicator for safe drug discontinuation. The clinical status of consistent loss of serum HBV RNA accompanied with low serum HBsAg levels might be implicated as a "para-functional cure," a status nearly close to the functional cure of chronic hepatitis B, to distinguish the "functional cure" characterized as serum HBsAg loss with or without anti-HBs seroconversion.
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4
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Patel AG, Flatten KS, Peterson KL, Beito TG, Schneider PA, Perkins AL, Harki DA, Kaufmann SH. Immunodetection of human topoisomerase I-DNA covalent complexes. Nucleic Acids Res 2016; 44:2816-26. [PMID: 26917015 PMCID: PMC4824114 DOI: 10.1093/nar/gkw109] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 02/15/2016] [Indexed: 12/29/2022] Open
Abstract
A number of established and investigational anticancer drugs slow the religation step of DNA topoisomerase I (topo I). These agents induce cytotoxicity by stabilizing topo I-DNA covalent complexes, which in turn interact with advancing replication forks or transcription complexes to generate lethal lesions. Despite the importance of topo I-DNA covalent complexes, it has been difficult to detect these lesions within intact cells and tumors. Here, we report development of a monoclonal antibody that specifically recognizes covalent topo I-DNA complexes, but not free topo I or DNA, by immunoblotting, immunofluorescence or flow cytometry. Utilizing this antibody, we demonstrate readily detectable topo I-DNA covalent complexes after treatment with camptothecins, indenoisoquinolines and cisplatin but not nucleoside analogues. Topotecan-induced topo I-DNA complexes peak at 15-30 min after drug addition and then decrease, whereas indotecan-induced complexes persist for at least 4 h. Interestingly, simultaneous staining for covalent topo I-DNA complexes, phospho-H2AX and Rad51 suggests that topotecan-induced DNA double-strand breaks occur at sites distinct from stabilized topo I-DNA covalent complexes. These studies not only provide new insight into the action of topo I-directed agents, but also illustrate a strategy that can be applied to study additional topoisomerases and their inhibitors in vitro and in vivo.
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Affiliation(s)
- Anand G Patel
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA
| | - Karen S Flatten
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Kevin L Peterson
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Thomas G Beito
- Department of Immunology, Mayo Clinic, Rochester, MN 55905, USA
| | - Paula A Schneider
- Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
| | - Angela L Perkins
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Daniel A Harki
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Scott H Kaufmann
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA Division of Oncology Research, Mayo Clinic, Rochester, MN 55905, USA
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Mosesso P, Pepe G, Ottavianelli A, Schinoppi A, Cinelli S. Cytogenetic evidence that DNA topoisomerase II is not involved in radiation induced chromsome-type aberrations. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2015; 793:14-8. [PMID: 26520368 DOI: 10.1016/j.mrgentox.2015.06.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 06/09/2015] [Indexed: 11/17/2022]
Abstract
ICRF-187 (Cardioxane™, Chiron) is a catalytic inhibitor of DNA topoisomerase II (Topo II), proposed to act by blocking Topo II-mediated DNA cleavage without stabilizing DNA-Topo II-"cleavable complexes". In this study ICRF-187 was used to evaluate the potential involvement of DNA topoisomerase II in the formation of the radiation-induced chromosome-type aberrations in the G0 phase of the cell cycle in human lymphocytes from three healthy male donors. This is based on many evidences that DNA topoisomerases are involved in DNA recombination, mainly of illegitimate type (non-homologous) both in vitro and in vivo. The results obtained clearly indicated that ICRF-187 did not induce per se any chromosomal damage. When challenged with the non-catalytic Topo II poison VP-16 (etoposide), which acts by stabilizing the "cleavable complex" generating "protein concealed" DSB's and thus chromosomal aberrations, it completely abolished the significant induction of chromosome-type aberrations and formation of dicentric chromosomes. This indicates that ICRF-187 acts effectively as catalytic inhibitor of Topo II. On the other hand, when X-ray treatments were challenged with ICRF-187 using experimental conditions as for VP-16 treatments, no modification of the incidence of chromosome-type aberrations and dicentric chromosomes was observed. On this basis, we conclude that Topo II is not involved in the formation of X-ray-induced chromosome-type aberrations and dicentric chromosomes in human lymphocytes in the G0 phase of the cell cycle.
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Affiliation(s)
- P Mosesso
- Dipartimento di Scienze Ecologiche e Biologiche, Università degli Studi della Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy.
| | - G Pepe
- Dipartimento di Scienze Ecologiche e Biologiche, Università degli Studi della Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy
| | - A Ottavianelli
- Dipartimento di Scienze Ecologiche e Biologiche, Università degli Studi della Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy
| | - A Schinoppi
- Dipartimento di Scienze Ecologiche e Biologiche, Università degli Studi della Tuscia, Largo dell'Università s.n.c., 01100 Viterbo, Italy
| | - S Cinelli
- Research Toxicology Centre, Via Tito Speri 12/14, 00040, Pomezia, Roma, Italy
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Tong HV, Thomas Bock C, Velavan TP. Genetic insights on host and hepatitis B virus in liver diseases. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2014; 762:65-75. [PMID: 25475418 DOI: 10.1016/j.mrrev.2014.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 06/16/2014] [Accepted: 06/17/2014] [Indexed: 02/08/2023]
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Lim L, Tran BM, Vincan E, Locarnini S, Warner N. HBV-related hepatocellular carcinoma: the role of integration, viral proteins and miRNA. Future Virol 2012. [DOI: 10.2217/fvl.12.113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The development of hepatocellular carcinoma during chronic hepatitis B infection is a multifactorial process thought to be a consequence of several direct and indirect mechanisms. In this review we discuss how viral proteins and cycles of ongoing liver damage and regeneration, coupled with HBV DNA integration and aberrant miRNA expression may enhance the risk for the development of hepatocellular carcinoma.
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Affiliation(s)
- Lucy Lim
- Victorian Infectious Diseases Reference Laboratories, North Melbourne, Victoria, Australia
- Austin Liver Transplant Unit, Heidelberg, Victoria, Australia
| | - Bang Manh Tran
- Victorian Infectious Diseases Reference Laboratories, North Melbourne, Victoria, Australia
- Cancer Biology Laboratory, Department of Anatomy & Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Elizabeth Vincan
- Victorian Infectious Diseases Reference Laboratories, North Melbourne, Victoria, Australia
- Cancer Biology Laboratory, Department of Anatomy & Neuroscience, The University of Melbourne, Parkville, Victoria, Australia
| | - Stephen Locarnini
- Victorian Infectious Diseases Reference Laboratories, North Melbourne, Victoria, Australia
| | - Nadia Warner
- Victorian Infectious Diseases Reference Laboratories, North Melbourne, Victoria, Australia
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Datta S, Chatterjee S, Veer V, Chakravarty R. Molecular biology of the hepatitis B virus for clinicians. J Clin Exp Hepatol 2012; 2:353-65. [PMID: 25755457 PMCID: PMC3940099 DOI: 10.1016/j.jceh.2012.10.003] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 10/12/2012] [Indexed: 02/08/2023] Open
Abstract
Hepatitis B virus (HBV) infection is one of the major global health problems, especially in economically under-developed or developing countries. HBV infection can lead to a number of clinical outcomes including chronic infection, cirrhosis and liver cancer. It ranks among the top 10 causes of death, being responsible for around 1 million deaths every year. Despite the availability of a highly efficient vaccine and potent antiviral agents, HBV infection still remains a significant clinical problem, particularly in those high endemicity areas where vaccination of large populations has not been possible due to economic reasons. Although HBV is among the smallest viruses in terms of virion and genome size, it has numerous unique features that make it completely distinct from other DNA viruses. It has a partially double stranded DNA with highly complex genome organization, life cycle and natural history. Remarkably distinct from other DNA viruses, it uses an RNA intermediate called pregenomic RNA (pgRNA) and reverse transcriptase for its genome replication. Genome replication is accomplished by a complex mechanism of primer shifting facilitated by direct repeat sequences encoded in the genome. Further, the genome has evolved in such a manner that every single nucleotide of the genome is used for either coding viral proteins or used as regulatory regions or both. Moreover, it utilizes internal in-frame translation initiation codons, as well as different reading frames from the same RNA to generate different proteins with diverse functions. HBV also shows considerable genetic variability which has been related with clinical outcomes, replication potential, therapeutic response etc. This review aims at reviewing fundamental events of the viral life cycle including viral replication, transcription and translation, from the molecular standpoint, as well as, highlights the clinical relevance of genetic variability of HBV.
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Key Words
- AUG, translation start codon
- BCP, basal core promoter
- CHB, chronic hepatitis B infection
- DR, direct repeat
- EBP, enhancer binding protein
- EN, enhancer
- ER, endoplasmic reticulum
- HBV, hepatitis B virus
- HBsAg
- HCC, hepatocellular cancer
- Hepadnavirus
- IL, interleukin
- LEF, liver enriched factors
- LHB, large envelope protein
- MHBs, middle hepatitis B surface antigen
- MHR, major hydrophilic region
- ORF, open reading frames
- PC, precore
- RT, reverse transcriptase
- SHBs, small hepatitis B surface antigen
- TGF-α, transforming growth factor-α
- TNF-α, tumor necrosis factor-α
- TP, terminal protein
- WHV, woodchuck hepatitis virus
- cccDNA, covalently closed circular
- dGMP, deoxyguanosine monophosphate
- genotype
- pHSA, poly-human serum albumin
- pgRNA
- pgRNA, pregenomic RNA
- rcDNA
- rcDNA, relaxed circular DNA
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Affiliation(s)
| | | | - Vijay Veer
- Defence Research Laboratory Tezpur, Tezpur, Assam, India
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10
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Affiliation(s)
- Ying-Qian Liu
- a School of Pharmacy, Lanzhou University , Lanzhou, 730000 , PR China
| | - Zhen-Ling Liu
- b State Key Laboratory of Applied Organic Chemistry, Lanzhou Universitry , Lanzhou, 730000 , PR China
| | - Xuan Tian
- b State Key Laboratory of Applied Organic Chemistry, Lanzhou Universitry , Lanzhou, 730000 , PR China
| | - Liu Yang
- c Analytic Center of Environment Engineering , Environmental and Municipal Engineering School, Lanzhou Jiaotong Universitry , Lanzhou, 730000 , PR China
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Liver cell transformation in chronic HBV infection. Viruses 2009; 1:630-646. [PMID: 21994562 PMCID: PMC3185520 DOI: 10.3390/v1030630] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 10/26/2009] [Accepted: 10/29/2009] [Indexed: 12/20/2022] Open
Abstract
Epidemiological studies have provided overwhelming evidence for a causal role of chronic HBV infection in the development of hepatocellular carcinoma (HCC), but the molecular mechanisms underlying virally-induced tumorigenesis remain largely debated. In the absence of a dominant oncogene encoded by the HBV genome, indirect roles have been proposed, including insertional activation of cellular oncogenes by HBV DNA integration, induction of genetic instability by viral integration or by the regulatory protein HBx, and long term effects of viral proteins in enhancing immune-mediated liver disease. In this chapter, we discuss different models of HBV-mediated liver cell transformation based on animal systems of hepadnavirus infection as well as functional studies in hepatocyte and hepatoma cell lines. These studies might help identifying the cellular effectors connecting HBV infection and liver cell transformation.
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Chemin I, Zoulim F. Hepatitis B virus induced hepatocellular carcinoma. Cancer Lett 2009; 286:52-9. [PMID: 19147276 DOI: 10.1016/j.canlet.2008.12.003] [Citation(s) in RCA: 142] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 11/21/2008] [Accepted: 12/02/2008] [Indexed: 12/11/2022]
Abstract
A number of risk factors appear to play a role in Hepatocellularcinoma (HCC), HBV infection being one of the most important. Chronic inflammation and cytokines are key determinants in the development of fibrosis and liver cell proliferation. HBV DNA integration and/or expression of HBV proteins may have a direct effect on cellular functions. Occult hepatitis B virus infection is characterized by persistence of HBV DNA in hepatitis B surface antigen-negative individuals. There are evidences that occult HBV is a risk factor for the development of HCC and that the potential mechanisms whereby overt HBV might induce tumour formation are mostly maintained.
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Affiliation(s)
- I Chemin
- INSERM, U871, 69003 Lyon, France.
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Affiliation(s)
- Stephan Günther
- Bernhard-Nocht-Institute of Tropical Medicine, Hamburg, Germany.
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Abstract
AIM: To examine the serum from black African patients with acute hepatitis B to ascertain if integrants of viral DNA can be detected in fragments of cellular DNA leaking from damaged hepatocytes into the circulation.
METHODS: DNA was extracted from the sera of five patients with uncomplicated acute hepatitis B and one with fulminant disease. Two subgenomic PCRs designed to amplify the complete genome of HBV were used and the resulting amplicons were cloned and sequenced.
RESULTS: HBV and chromosomal DNA were amplified from the sera of all the patients. In one patient with uncomplicated disease, HBV DNA was integrated into host chromosome 7 q11.23 in the WBSCR1 gene. The viral DNA comprised 200 nucleotides covering the S and X genes in opposite orientation, with a 1 169 nucleotide deletion. The right virus/host junction was situated at nucleotide 1 774 in the cohesive overlap region of the viral genome, at a preferred topoisomerase I cleavage motif. The chromosomal DNA was not rearranged. The patient made a full recovery and seroconverted to anti-HBs- and anti-HBe-positivity. Neither HBV nor chromosomal DNA could be amplified from his serum at that time.
CONCLUSION: Integration of viral DNA into chromosomal DNA may occur rarely during acute hepatitis B and, with clonal propagation of the integrant, might play a role in hepatocarcinogenesis.
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Affiliation(s)
- Gerald C Kimbi
- Department of Medicine, University of the Witwatersrand Medical School, 7 York Road, Parktown 2193, Johannesburg, South Africa
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Merle P. [Epidemiology, natural history and pathogenesis of hepatocellular carcinoma]. Cancer Radiother 2005; 9:452-7. [PMID: 16226912 DOI: 10.1016/j.canrad.2005.09.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/05/2005] [Indexed: 10/25/2022]
Abstract
Hepatocellular carcinoma is one of the most prevalent tumors worldwide and its incidence is increasing due to hepatitis C virus infection. Other etiologic factors are hepatitis B virus infection, alcoholic liver disease and hemochromatosis. This tumor mainly develops in cirrhotic livers that are true precancerous states. Although mechanisms of hepatocarcinogenesis remain badly known, some signaling pathways are frequently deregulated: inactivation of the p53 tumor suppressor factor in 25% of HCC, activation of the Wnt signaling and the telomerase immortalization enzyme in most of tumors. Hepatitis viruses play a direct oncogenic role by interaction between viral proteins and cellular ones, which control cell homeostasis, or by integration of hepatitis B virus genome into the host genome. Furthermore, hepatitis viruses play an indirect oncogenic role by chronic inflammation and hepatocyte regeneration related to viral hepatopathy. In a near future, a better understanding of virus-specific oncogenic mechanisms should allow us to set up innovative preventive and curative therapeutic strategies.
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Affiliation(s)
- P Merle
- Service d'hépatogastroentérologie, hôpital de l'Hôtel-Dieu, Inserm U271, 69003 Lyon, France.
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Momosaki S, Hsia CC, Nakashima Y, Kojiro M, Tabor E. Integration of hepatitis B virus containing mutations in the core promoter/X gene in patients with hepatocellular carcinoma. Dig Liver Dis 2003; 35:795-800. [PMID: 14674670 DOI: 10.1016/s1590-8658(03)00462-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED Integration of hepatitis B virus is thought to be an essential step in hepatitis B virus associated hepatocarcinogenesis. Mutations at nucleotides 1762 and 1764 in the hepatitis B virus, within a sequence encoding both the core promoter gene and the X gene, have been found frequently in patients with hepatocellular carcinoma. However, integration of these mutant sequences has not been reported to date. METHODS A 228-base pair segment of the hepatitis B virus core promoter gene was amplified from hepatocellular carcinomas and adjacent non-tumourous liver tissue by nested PCR and sequenced. Integration of hepatitis B virus into human genomic DNA was investigated using the 'genome walking' method. RESULTS Point mutations were found in both hepatitis B virus nucleotides 1762 and 1764 in 8 of 14 hepatocellular carcinoma tissues (57%) and in 11 of 14 adjacent non-tumourous liver tissues (79%). Three patients were evaluated using the 'genome walking' method; all were found to have hepatitis B virus DNA integrated in their hepatocellular carcinoma (two patients) and/or in their non-tumourous liver tissue (three patients). Integration occurred in all tissues near host genomic sites that are prone to integration. Hepatitis B virus was integrated at or near the hepatitis B virus DR1 site in all samples, and all contained truncated X gene sequences that have been reported to be capable of producing fusion transcripts with transactivation potential. CONCLUSIONS Integrated hepatitis B virus DNA containing core promoter mutations at nucleotides 1762 and 1764 was found in hepatocellular carcinoma and/or adjacent non-tumourous liver tissue of three patients. These findings leave open the possibility that insertional mutagenesis or transactivation by fusion transcripts resulting from hepatitis B virus integration could play a role in hepatocarcinogenesis in some patients.
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Affiliation(s)
- S Momosaki
- Division of Emerging and Transfusion Transmitted Diseases, Food and Drug Administration, Center for Biologics Evaluation and Research, 1401 Rockville Pike, HFM-300, Rockville, MD 20852-1448, USA
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MESH Headings
- Carcinoma, Hepatocellular/etiology
- Carcinoma, Hepatocellular/genetics
- Carcinoma, Hepatocellular/pathology
- Carcinoma, Hepatocellular/prevention & control
- Carcinoma, Hepatocellular/virology
- Cell Adhesion/genetics
- Cell Transformation, Neoplastic
- Cell Transformation, Viral
- Chronic Disease
- Genes, cdc
- Genes, p53
- Growth Substances/physiology
- Hepacivirus/pathogenicity
- Hepatitis B virus/pathogenicity
- Hepatitis B, Chronic/complications
- Hepatitis B, Chronic/virology
- Hepatitis C, Chronic/complications
- Hepatitis C, Chronic/virology
- Humans
- Liver Diseases/complications
- Liver Diseases/pathology
- Liver Neoplasms/etiology
- Liver Neoplasms/genetics
- Liver Neoplasms/pathology
- Liver Neoplasms/prevention & control
- Liver Neoplasms/virology
- Neoplasm Invasiveness/genetics
- Neoplasm Metastasis
- Neovascularization, Pathologic/genetics
- Precancerous Conditions/complications
- Precancerous Conditions/pathology
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Abstract
Camptothecin analogues and derivatives appear to exert their antitumour activity by binding to topoisomerase I and have shown significant activity against a broad range of tumours. In general, camptothecins are not substrates for either the multidrug-resistance P-glycoprotein or the multidrug-resistance-associated protein (MRP). Because of manageable toxicity and encouraging activity against solid tumours, camptothecins offer promise in the clinical management of human tumours. This review illustrates the proposed mechanism(s) of action of camptothecins and presents a concise overview of current camptothecin therapy, including irinotecan and topotecan, and novel analogues undergoing clinical trails, such as exatecan (DX-8951f), IDEC-132 (9-aminocamptothecin), rubitecan (9-nitrocamptothecin), lurtotecan (GI-147211C), and the recently developed homocamptothecins diflomotecan (BN-80915) and BN-80927.
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Affiliation(s)
- Hulya Ulukan
- Division of Pharmaceutics, College of Pharmacy, The Ohio State University, Columbus, Ohio 43210-1291, USA
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Abstract
Hepatitis B virus (HBV) is at the origin of severe liver diseases like chronic active hepatitis, liver cirrhosis and hepatocellular carcinoma. There are some groups of patients with high risk of generation of HBV mutants: infected infants, immunosuppressed individuals (including hemodialysis patients), patients treated with interferon and lamivudine for chronic HBV infection. These groups are the target for molecular investigations reviewed in this paper. The emergence of lamivudine- or other antiviral-resistant variants, rises concern regarding long term use of these drugs. Infection or immunization with one HBV subtype confers immunity to all subtypes. However, reinfection or reactivation of latent HBV infection with HBV mutants have been reported in patients undergoing transplant and those infected with HIV. Mutations of the viral genome which are not replicative incompetent can be selected in further course of infection or under prolonged antiviral treatment and might maintain the liver disease. Four open reading frames (ORF) which are called S-gene, C-gene, X-gene and P-gene were identified within the HBV genome. Mutations may affect each of the ORFs. Mutated S-genes were described to be responsible for HBV-infections in successfully vaccinated persons, mutated C-genes were found to provoke severe chronic liver diseases, mutated X-genes could cause serious medical problems in blood donors by escaping the conventional test systems and mutated P-genes were considered to be the reason for chemotherapeutic drug resistance. This paper reviews molecular, immunological and clinical aspects of the HBV mutants.
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Affiliation(s)
- C Kreutz
- International Technology for Evaluation of Clinical Pharmacology, Paris, France.
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21
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Burda MR, Günther S, Dandri M, Will H, Petersen J. Structural and functional heterogeneity of naturally occurring hepatitis B virus variants. Antiviral Res 2001; 52:125-38. [PMID: 11672822 DOI: 10.1016/s0166-3542(01)00177-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Most organisms have developed sophisticated machineries to preserve their genomic integrity. On the contrary hepatitis B virus (HBV), like a lot of other viruses can undergo rapid and drastic sequence changes, especially if the virus has to cope with natural or therapy induced antiviral mechanisms in the host. Here, we try to summarize possible implications for the molecular pathogenesis of HBV based on the extensive research on the genetic variants of HBV.
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Affiliation(s)
- M R Burda
- Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Martinistr. 52, 20251 Hamburg, Germany
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22
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Abstract
Chronic hepatitis B virus (HBV) infection is a major global cause of hepatocellular carcinoma (HCC). Individuals who are chronic carriers have a greater than 100-fold increased relative risk of developing the tumour. Several mechanisms of HBV-induced HCC have been proposed. Integration of HBV DNA into the genome of hepatocytes occurs commonly, although integration at cellular sites that are important for regulation of hepatocyte proliferation appears to be a rare event. Functions of the HBx protein are also potentially oncogenic. These include transcriptional activation of cellular growth regulatory genes, modulation of apoptosis and inhibition of nucleotide excision repair of damaged cellular DNA. The effects of HBx are mediated by interaction with cellular proteins and activation of cell signalling pathways. Variations in HBV genome sequences may be important in hepatocarcinogenesis, although their significance has not yet been completely elucidated. Necroinflammatory hepatic disease, which often accompanies chronic HBV infection, may contribute indirectly to hepatocyte transformation in a number of ways, including by facilitating HBV DNA integration, predisposing to the acquisition of cellular mutations and generating mutagenic oxygen reactive species. Although HCC is a malignancy with a poor prognosis, the availability of an effective vaccine against HBV infection, and its inclusion in the Expanded Programme of Immunization of many countries, augurs well for the eventual elimination of HBV-associated HCC.
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Affiliation(s)
- P Arbuthnot
- Department of Molecular Medicine and Haematology and Molecular Hepatology Research Unit, Department of Medicine, University of the Witwatersrand Medical School, 7 York Road, Parktown 2193, South Africa
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23
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Abstract
Chronic hepatitis B virus (HBV) infection is a major global cause of hepatocellular carcinoma (HCC). Individuals who are chronic carriers have a greater than 100-fold increased relative risk of developing the tumour. Several mechanisms of HBV-induced HCC have been proposed. Integration of HBV DNA into the genome of hepatocytes occurs commonly, although integration at cellular sites that are important for regulation of hepatocyte proliferation appears to be a rare event. Functions of the HBx protein are also potentially oncogenic. These include transcriptional activation of cellular growth regulatory genes, modulation of apoptosis and inhibition of nucleotide excision repair of damaged cellular DNA. The effects of HBx are mediated by interaction with cellular proteins and activation of cell signalling pathways. Variations in HBV genome sequences may be important in hepatocarcinogenesis, although their significance has not yet been completely elucidated. Necroinflammatory hepatic disease, which often accompanies chronic HBV infection, may contribute indirectly to hepatocyte transformation in a number of ways, including by facilitating HBV DNA integration, predisposing to the acquisition of cellular mutations and generating mutagenic oxygen reactive species. Although HCC is a malignancy with a poor prognosis, the availability of an effective vaccine against HBV infection, and its inclusion in the Expanded Programme of Immunization of many countries, augurs well for the eventual elimination of HBV-associated HCC.
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Affiliation(s)
- Patrick Arbuthnot
- Department of Molecular Medicine and Haematology, University of the Witwatersrand Medical School7 York Road, Parktown 2193, South Africa
- Molecular Hepatology Research Unit, Department of Medicine, University of the Witwatersrand Medical School7 York Road, Parktown 2193, South Africa
| | - Michael Kew
- Molecular Hepatology Research Unit, Department of Medicine, University of the Witwatersrand Medical School7 York Road, Parktown 2193, South Africa
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24
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Abstract
Topoisomerase I is a ubiquitous and essential enzyme in multicellular organisms. It is involved in multiple DNA transactions including DNA replication, transcription, chromosome condensation and decondensation, and probably DNA recombination. Besides its activity of DNA relaxation necessary to eliminate torsional stresses associated with these processes, topoisomerase I may have other functions related to its interaction with other cellular proteins. Topoisomerase I is the target of the novel anticancer drugs, the camptothecins. Recently a broad range of physiological and environmentally-induced DNA modifications have also been shown to poison topoisomerases. This review summarizes the various factors that enhance or suppress top1 cleavage complexes and discusses the significance of such effects. We also review the different mechanisms that have been proposed for the repair of topoisomerase I-mediated DNA lesions.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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25
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Zoulim F. Therapy of chronic hepatitis B virus infection: inhibition of the viral polymerase and other antiviral strategies. Antiviral Res 1999; 44:1-30. [PMID: 10588330 DOI: 10.1016/s0166-3542(99)00056-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Chronic hepatitis B infection remains a major public health problem worldwide. The hepatitis B virus belongs to the family of hepadnaviruses that replicate their DNA genome via a reverse transcription pathway. The chronicity of infection in infected hepatocytes is maintained by the persistence of the viral covalently closed circular DNA. The main strategies to combat chronic HBV infection rely on the stimulation of the specific antiviral immune response and on the inhibition of viral replication. While the prolonged administration of reverse transcriptase inhibitors is most often associated with a control of viral replication rather than eradication, it may select for resistant mutants. The search for new viral targets is therefore mandatory to design combination strategies to prevent the emergence of resistant mutants and eventually clear viral infection.
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26
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Abstract
Mammalian DNA topoisomerase I is a multifunctional enzyme which is essential for embryonal development. In addition to its classical DNA nicking-closing activities which are needed for relaxation of supercoiled DNA, topoisomerase I can phosphorylate certain splicing factors. The enzyme is also involved in transcriptional regulation through its ability to associate with other proteins in the TFIID-, and possibly TFIIH-, transcription complexes, and is implicated in the recognition of DNA lesions. Finally, topoisomerase I is a recombinase which can mediate illegitimate recombination. A crucial reaction intermediate during relaxation of DNA is the formation of a DNA-topoisomerase I complex (the cleavable complex) where topoisomerase I is covalently linked to a 3 -end of DNA thereby creating a single stranded DNA break. Cleavable complexes are also formed in the vicinity of DNA lesions and in the presence of the antitumor agent, camptothecin. While formation of cleavable complexes may be necessary for the initial stages of the DNA damage response, these complexes are also potentially dangerous to the cell due to their ability to mediate illegitimate recombination, which can lead to genomic instability and oncogenesis. Thus the levels and stability of these complexes have to be strictly regulated. This is obtained by maintaining the enzyme levels relatively constant, by limiting the stability of the cleavable complexes through physical interaction with the oncogene suppressor protein p53 and by degradation of the topoisomerase I by the proteasome system. Emerging evidence suggest that these regulatory functions are perturbed in tumor cells, explaining at the same time why topoisomerase I activities so often are increased in certain human tumors, and why these cells are sensitized to the cytotoxic effects of camptothecins.
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Affiliation(s)
- A K Larsen
- Institut Gustave-Roussy, Laboratory of Biology and Pharmacology of DNA Topoisomerases 39, Rue Camille Desmoulins, Villejuif, 94805, France.
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27
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Günther S, Fischer L, Pult I, Sterneck M, Will H. Naturally occurring variants of hepatitis B virus. Adv Virus Res 1999; 52:25-137. [PMID: 10384235 DOI: 10.1016/s0065-3527(08)60298-5] [Citation(s) in RCA: 189] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- S Günther
- Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Universität Hamburg, Federal Republic of Germany.
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28
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Pourquier P, Jensen AD, Gong SS, Pommier Y, Rogler CE. Human DNA topoisomerase I-mediated cleavage and recombination of duck hepatitis B virus DNA in vitro. Nucleic Acids Res 1999; 27:1919-25. [PMID: 10101202 PMCID: PMC148402 DOI: 10.1093/nar/27.8.1919] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this study, we report that eukaryotic topoisomerase I (top1) can linearize the open circular DNA of duck hepatitis B virus (DHBV). Using synthetic oligonucleotides mimicking the three-strand flap DR1 region of the DHBV genome, we found that top1 cleaves the DNA plus strand in a suicidal manner, which mimics the linearization of the virion DNA. We also report that top1 can cleave the DNA minus strand at specific sites and can linearize the minus strand via a non-homologous recombination reaction. These results are consistent with the possibility that top1 can act as a DNA endo-nuclease and strand transferase and play a role in the circularization, linearization and possibly integration of viral replication intermediates.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Building 37, Room 5D02, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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29
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Gong SS, Jensen AD, Chang CJ, Rogler CE. Double-stranded linear duck hepatitis B virus (DHBV) stably integrates at a higher frequency than wild-type DHBV in LMH chicken hepatoma cells. J Virol 1999; 73:1492-502. [PMID: 9882355 PMCID: PMC103974 DOI: 10.1128/jvi.73.2.1492-1502.1999] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Integration of hepadnavirus DNAs into host chromosomes can have oncogenic consequences. Analysis of host-viral DNA junctions of DHBV identified the terminally duplicated r region of the viral genome as a hotspot for integration. Since the r region is present on the 5' and 3' ends of double-stranded linear (DSL) hepadnavirus DNAs, these molecules have been implicated as integration precursors. We have produced a LMH chicken hepatoma cell line (LMH 66-1 DSL) which replicates exclusively DSL duck hepatitis B virus (DHBV) DNA. To test whether linear DHBV DNAs integrate more frequently than the wild type open circular DHBV DNAs, we have characterized the integration frequency in LMH 66-1 DSL cells by using a subcloning approach. This approach revealed that 83% of the LMH 66-1 DSL subclones contained new integrations, compared to only 16% of subclones from LMH-D2 cells replicating wild-type open circular DHBV DNA. Also, a higher percentage of the LMH 66-1 DSL subclones contained two or more new integrations. Mathematical analysis suggests that the DSL DHBV DNAs integrated stably once every three generations during subcloning whereas wild-type DHBV integrated only once every four to five generations. Cloning and sequencing of new integrations confirmed the r region as a preferred integration site for linear DHBV DNA molecules. One DHBV integrant was associated with a small deletion of chromosomal DNA, and another DHBV integrant occurred in a telomeric repeat sequence.
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Affiliation(s)
- S S Gong
- Marion Bessin Liver Research Center, Department of Medicine, The Jack and Pearl Resnick Campus of the Albert Einstein College of Medicine, Bronx, New York 10461, USA
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30
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Laskus T, Radkowski M, Wang LF, Nowicki M, Rakela J. Detection and sequence analysis of hepatitis B virus integration in peripheral blood mononuclear cells. J Virol 1999; 73:1235-8. [PMID: 9882326 PMCID: PMC103945 DOI: 10.1128/jvi.73.2.1235-1238.1999] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A PCR-based technique was used to detect hepatitis B virus (HBV) integration in peripheral blood mononuclear cells from patients with chronic hepatitis B. Integrated HBV DNA sequences, with virus-cell junctions located in the cohesive region between direct repeat 1 (DR1) and DR2, were found in 2 of 10 studied patients.
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Affiliation(s)
- T Laskus
- Division of Gastroenterology and Hepatology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213, USA.
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31
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Pantazis P, Han Z, Chatterjee D, Wyche J. Water-insoluble camptothecin analogues as potential antiviral drugs. J Biomed Sci 1999; 6:1-7. [PMID: 9933736 DOI: 10.1007/bf02256417] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
In addition to being causative agents of infectious diseases in animals and humans, DNA viruses have served as models for the study of eukaryotic molecular mechanisms including replication and transcription. Studies of DNA virus functions utilizing cell-free systems and virus-infected cells in culture, in the presence of the anticancer drug camptothecin (CPT), have demonstrated that CPT is a potent inhibitor of replication, transcription and packaging of double-stranded DNA-containing adenoviruses, papovaviruses and herpesviruses, and the single- stranded DNA-containing autonomous parvoviruses. CPT inhibits viral functions by inhibiting topoisomer- ase I, a host cell enzyme required for initiation and completion of the viral functions. These findings indicate that CPT analogues could be developed for use as potent drugs against DNA viruses.
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Affiliation(s)
- P Pantazis
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, R.I., USA.
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32
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Pommier Y, Pourquier P, Fan Y, Strumberg D. Mechanism of action of eukaryotic DNA topoisomerase I and drugs targeted to the enzyme. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1400:83-105. [PMID: 9748515 DOI: 10.1016/s0167-4781(98)00129-8] [Citation(s) in RCA: 422] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
DNA topoisomerase I is essential for cellular metabolism and survival. It is also the target of a novel class of anticancer drugs active against previously refractory solid tumors, the camptothecins. The present review describes the topoisomerase I catalytic mechanisms with particular emphasis on the cleavage complex that represents the enzyme's catalytic intermediate and the site of action for camptothecins. Roles of topoisomerase I in DNA replication, transcription and recombination are also reviewed. Because of the importance of topoisomerase I as a chemotherapeutic target, we review the mechanisms of action of camptothecins and the other topoisomerase I inhibitors identified to date.
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Affiliation(s)
- Y Pommier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, Bethesda, MD 20892-4255, USA.
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33
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Abstract
DNA topoisomerase I is a nuclear enzyme which catalyzes the conversion of the DNA topology by introducing single-strand breaks into the DNA molecule. This enzyme represents a novel and distinct molecule target for cancer therapy by antitopoisomerase drugs belonging to the campthotecin series of antineoplastics. As many tumors can acquire resistance to drug treatment and become refractary to the chemotherapy it is very important to investigate the mechanisms involved in such a drug resistance for circumventing the phenomenon. This article describes the role of topoisomerase I in cell functions and the methods used to assess its in vitro catalytic activity. It reviews the mechanisms of cytotoxicity of the most specific antitopoisomerase I drugs by considering also the phenomenon of drug resistance. Some factors useful to drive the future perspectives in the development of new topoisomerase I inhibitors are also evidenced and discussed.
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Affiliation(s)
- R E Parchment
- Division of Hematology-Oncology, The Barbara Ann Karmanos Cancer Institute, Wayne State University, 3900 John R., Detroit, MI, U.S.A
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34
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D'Ugo E, Bruni R, Argentini C, Giuseppetti R, Rapicetta M. Identification of scaffold/matrix attachment region in recurrent site of woodchuck hepatitis virus integration. DNA Cell Biol 1998; 17:519-27. [PMID: 9655245 DOI: 10.1089/dna.1998.17.519] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Scaffold or matrix attachment regions (S/MARs) are noncoding genomic DNA sequences displaying in vitro selective binding affinity for nuclear scaffold. They have been reported to be involved in the physical attachment of genomic DNA to the nuclear scaffold, and thus in the organization of the chromatin in functional loops or domains, and in the regulation of gene expression. In this work, we report the identification of an S/MAR in a woodchuck chromosomal locus, named b3n, previously described as a recurrent site of woodchuck hepatitis virus (WHV) DNA integration in woodchuck hepatocellular carcinoma (HCC). The 4.3-kb sequence of this locus contains several Alu-like repeats and a gag-like coding region with frameshift mutations. Computer analysis revealed the presence of a region with unusually high AT content, typical of most S/MARs, and of specific motifs (A boxes, T boxes, topoisomerase II sites, and unwinding elements) overlapping or in proximity to the region with high AT content, predicting that b3n might contain an S/MAR. Fragments of the b3n locus were isolated by conventional and inverse PCR techniques. In in vitro binding experiments with both heterologous and autologous scaffold preparations, a 592-bp fragment spanning the region rich in S/MAR features showed marked scaffold affinity, which was specific when autologous scaffolds were used. The presence of an S/MAR at the b3n locus and its nature as a recurrent WHV integration site in HCC suggest the involvement of S/MAR elements in some of the mechanisms leading to liver oncogenesis.
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Affiliation(s)
- E D'Ugo
- Laboratory of Virology, Istituto Superiore di Sanità, Rome, Italy
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35
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Meima R, Haan GJ, Venema G, Bron S, de Jong S. Sequence specificity of illegitimate plasmid recombination in Bacillus subtilis: possible recognition sites for DNA topoisomerase I. Nucleic Acids Res 1998; 26:2366-73. [PMID: 9580687 PMCID: PMC147579 DOI: 10.1093/nar/26.10.2366] [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: 02/07/2023] Open
Abstract
Previous work in our group indicated that structural plasmid instability in Bacillus subtilis is often caused by illegitimate recombination between non-repeated sequences, characterized by a relatively high AT content. Recently we developed a positive selection vector for analysis of plasmid recombination events in B. subtilis which enables measurement of recombination frequencies without interference of selective growth differences of cells carrying wild-type or deleted plasmids. Here we have used this system to further analyse the sequence specificity of illegitimate plasmid recombination events and to assess the role of the host-encoded DNA topoisomerase I enzyme in this process. Several lines of evidence suggest that single-strand DNA nicks introduced by DNA topoisomerase I are a major source of plasmid deletions in pGP100. First, strains overproducing DNA topoisomerase I showed increased levels of plasmid deletion. Second, these deletions occurred predominantly (>90% of the recombinants) between non-repeated DNA sequences, the majority of which resemble potential DNA topoisomerase I target sites. Sequence alignment of 66 deletion end-points confirmed the previously reported high AT content and, most importantly, revealed a highly conserved C residue at position -4 relative to the site of cleavage at both deletion termini. Based on these genetic data we propose the following putative consensus cleavage site for DNA topoisomerase I of B.subtilis: 5'-A/TCATA/TTAA/TA/TA-3'.
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Affiliation(s)
- R Meima
- Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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36
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Laskus T, Radkowski M, Nowicki M, Wang LF, Vargas H, Rakela J. Association between hepatitis B virus core promoter rearrangements and hepatocellular carcinoma. Biochem Biophys Res Commun 1998; 244:812-4. [PMID: 9535748 DOI: 10.1006/bbrc.1998.8249] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Hepatitis B virus (HBV) is the major etiological agent of hepatocellular carcinoma (HCC). Whether any particular viral variants are associated with HCC is unknown. We studied 53 Gambian patients with HCC and 33 HBsAg positive controls. A functional part of HBV core promoter and whole precore region were sequenced directly and/or after cloning. HBV DNA was amplified from sera from 27 HCC patients and in all controls. Fourteen (52%) patients and 12 (36%) controls (NS) were found to harbor an HBV strain with G to A transition mutation at position 1896 leading to HBeAg negative phenotype. Nine (33%) HCC patients and 2 (6%) controls (p < 0.01) harbored a mixture of wild type and HBV strains with deletions/insertions; strong consensus sequences for topoisomerase I breakage were located in the vicinity of these changes. In Africa, HCC is associated with HBV strains that have deletions/insertions in the HBV core promoter region.
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Affiliation(s)
- T Laskus
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pennsylvania, USA
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37
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Pourquier P, Pilon AA, Kohlhagen G, Mazumder A, Sharma A, Pommier Y. Trapping of mammalian topoisomerase I and recombinations induced by damaged DNA containing nicks or gaps. Importance of DNA end phosphorylation and camptothecin effects. J Biol Chem 1997; 272:26441-7. [PMID: 9334220 DOI: 10.1074/jbc.272.42.26441] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We used purified mammalian topoisomerases I (top1) and oligonucleotides containing a unique top1 cleavage site to study top1-mediated cleavage and recombination in the presence of nicks and short gaps mimicking DNA damage. In general, top1 cleavage was not induced opposite to the nicks, and nicks upstream from the top1 cleavage site suppressed top1 activity. Irreversible top1 cleavage complexes ("suicide products" or "aborted complexes") were produced in DNA containing nicks or short gaps just opposite to the normal top1 cleavage site. Camptothecin enhanced the formation of the aborted top1 complexes only for nicks downstream from the cleavage site. These aborted (suicide) complexes can mediate DNA recombination and promote illegitimate recombination by catalyzing the ligation of nonhomologous DNA fragments (acceptors). We report for the first time that top1-mediated recombination is greatly enhanced by the presence of a phosphate at the 5' terminus of the top1 aborted complex (donor DNA). By contrast, phosphorylation of the 3' terminus of the gap did not affect recombination. At concentrations that strongly enhanced inhibition of intramolecular religation, resulting in an increase of top1 cleavable complexes, camptothecin did not reduce recombination (intermolecular religation). Nicks or gaps with 5'-phosphate termini would be expected to be produced directly by ionizing radiations or by processing of abasic sites and DNA lesions induced by carcinogens or drugs used in cancer chemotherapy. Thus, these results further demonstrate that DNA damage can efficiently trap top1-cleavable complexes and enhance top1-mediated DNA recombination.
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Affiliation(s)
- P Pourquier
- Laboratory of Molecular Pharmacology, Division of Basic Sciences, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA
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38
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Fourel G, Ringeisen F, Flajolet M, Tronche F, Pontoglio M, Tiollais P, Buendia MA. The HNF1/HNF4-dependent We2 element of woodchuck hepatitis virus controls viral replication and can activate the N-myc2 promoter. J Virol 1996; 70:8571-83. [PMID: 8970982 PMCID: PMC190950 DOI: 10.1128/jvi.70.12.8571-8583.1996] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Transcriptional activation of myc family proto-oncogenes through the insertion of viral sequences is the predominant mechanism by which woodchuck hepatitis virus (WHV) induces liver tumors in chronically infected animals. The main target is N-myc2, a functional retroposon of the N-myc gene, but c-myc and N-myc are also marginally involved. Here we identify a major, liver-specific regulatory element in the WHV genome (We2) which efficiently activates the N-myc2 promoter in cultured hepatoma cells. In the context of the episomal viral genome, We2 governs the production of pregenomic RNA and thus plays a central role in the control of viral replication. We2 activity is primarily controlled by the liver-enriched HNF1 and HNF4 transcription factors, although NF1 and Oct proteins were also shown to bind in a central region. The expression of HNF1 and HNF4 appears to be maintained in woodchuck tumors. Thus, We2 is a prime candidate for controlling myc gene cis activation during WHV-induced hepatocarcinogenesis.
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Affiliation(s)
- G Fourel
- Unité de Recombinaison et Expression Génétique, INSERM U163, Institut Pasteur, Paris, France
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39
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Yang W, Mason WS, Summers J. Covalently closed circular viral DNA formed from two types of linear DNA in woodchuck hepatitis virus-infected liver. J Virol 1996; 70:4567-75. [PMID: 8676483 PMCID: PMC190393 DOI: 10.1128/jvi.70.7.4567-4575.1996] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We found that livers from woodchucks chronically infected with woodchuck hepatitis virus (WHV) contained covalently closed circular DNA (cccDNA) molecules with deletions and insertions indicative of their formation from linear viral DNA by nonhomologous recombination, as we previously described for the duck hepatitis B virus (W. Yang and J. Summers, J. Virol. 69:4029-4036, 1995). However, evidence for two different types of linear precursors was obtained by analysis of the recombination joints in WHV cccDNA. Type 1 linear precursors possessed the structural properties that correspond to those of in situ-primed linear DNA molecules, which constitute between 7 and 20% of all viral DNA replicative intermediates synthesized in the liver. Type 2 linear precursors are hypothetical species of linear DNAs with a terminal duplication of the cohesive-end region, between DR1 and DR2. This type of linear DNA has not been previously described and was not detected among the DNA species present in nucleocapsids. A fraction of cccDNAs formed from both type 1 and type 2 linear DNAs are predicted to be functional for further DNA synthesis, and some evidence for the formation of two or more generations of cccDNA from linear DNA was observed.
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MESH Headings
- Animals
- Base Sequence
- Chromosome Mapping
- Chronic Disease
- DNA Transposable Elements
- DNA, Circular/analysis
- DNA, Circular/chemistry
- DNA, Viral/analysis
- DNA, Viral/chemistry
- Defective Viruses/genetics
- Hepatitis B/pathology
- Hepatitis B/veterinary
- Hepatitis B/virology
- Hepatitis B Virus, Woodchuck/genetics
- Hepatitis, Viral, Animal/pathology
- Hepatitis, Viral, Animal/virology
- Liver/pathology
- Liver/virology
- Marmota
- Molecular Sequence Data
- Nucleic Acid Conformation
- Recombination, Genetic
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Affiliation(s)
- W Yang
- Department of Cell Biology, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA
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40
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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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41
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Zhu J, Schiestl RH. Topoisomerase I involvement in illegitimate recombination in Saccharomyces cerevisiae. Mol Cell Biol 1996; 16:1805-12. [PMID: 8657156 PMCID: PMC231167 DOI: 10.1128/mcb.16.4.1805] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Chromosome aberrations may cause cancer and many heritable diseases. Topoisomerase I has been suspected of causing chromosome aberrations by mediating illegitimate recombination. The effects of deletion and of overexpression of the topoisomerase I gene on illegitimate recombination in the yeast Saccharomyces cerevisiae have been studied. Yeast transformations were carried out with DNA fragments that did not have any homology to the genomic DNA. The frequency of illegitimate integration was 6- to 12-fold increased in a strain overexpressing topoisomerase I compared with that in isogenic control strains. Hot spot sequences [(G/C)(A/T)T] for illegitimate integration target sites accounted for the majority of the additional events after overexpression of topoisomerase I. These hot spot sequences correspond to sequences previously identified in vitro as topoisomerase I preferred cleavage sequences in other organisms. Furthermore, such hot spot sequences were found in 44% of the integration events present in the TOP1 wild-type strain and at a significantly lower frequency in the top1delta strain. Our results provide in vivo evidence that a general eukaryotic topoisomerase I enzyme nicks DNA and ligates nonhomologous ends, leading to illegitimate recombination.
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Affiliation(s)
- J Zhu
- Department of Molecular and Cellular Toxicology, Harvard School of Public Health, Boston, Massachusetts 02115, USA
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42
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Gong SS, Jensen AD, Rogler CE. Loss and acquisition of duck hepatitis B virus integrations in lineages of LMH-D2 chicken hepatoma cells. J Virol 1996; 70:2000-7. [PMID: 8627726 PMCID: PMC190029 DOI: 10.1128/jvi.70.3.2000-2007.1996] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Hepatocellular carcinoma is the culmination of a series of genetic events which progressively alter the phenotype of a hepatocyte toward malignancy. Hepadnaviral DNA integrations are agents of genetic change which can promote the process of hepatocarcinogenesis. We previously characterized episomally derived duck hepatitis B virus (DHBV) integrations in LMH-D2 cells that replicate wild-type DHBV. In an effort to understand how integrations function as agents of progressive genetic change, we have studied integrations of DHBV DNA in three lineages of LMH-D2 cells through three generations of subclones. Our data have established several features of the integration process. First, single and multiple integrations occur continuously through successive cell generations. Second, the integration frequency can vary dramatically in subclones of the same cell line. Third, integrations can be lost from successive generations of cells and loss of an integration can be accompanied by loss of cellular DNA associated with the integration. Finally, certain subclones which acquire greater plating efficiency have been distinguished by unique new integration patterns. These results provide a basis for DHBV integrations to function as activators of protooncogenes, as well as agents of the loss of tumor suppressor genes during hepatocellular carcinogenesis.
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Affiliation(s)
- S S Gong
- Marion Bessin Liver Research Center, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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43
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Aratani Y, Andoh T, Koyama H. Effects of DNA topoisomerase inhibitors on nonhomologous and homologous recombination in mammalian cells. Mutat Res 1996; 362:181-91. [PMID: 8596537 DOI: 10.1016/0921-8777(95)00049-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To study the involvement of DNA topoisomerases in recombination in mammalian cells, we used gene transfer assays to examine the effects of DNA topoisomerase inhibitors on nonhomologous (illegitimate) and homologous recombination. The assays were performed by transfecting adenine phosphoribosyltransferase-deficient (APRT-) CHO cells with plasmids carrying the wild-type or mutant aprt genes and by treating the cells with the inhibitors, followed by subsequent cultivation to select for APRT-positive (APRT+) colonies. Treatments with DNA topoisomerase II inhibitors such as VP-16, VM-26, ICRF-193 resulted in a 3- to 5-fold stimulation of integration of both closed-circular and linearized plasmids carrying the wild-type aprt gene into the recipient genome through nonhomologous recombination. The same treatments also increased 6- to 9-fold and 3-fold the number of APRT+ recombinant colonies that were generated by cotransfecting two closed-circular plasmids with nonoverlapping defective aprt genes and their linearized equivalents, respectively. However, this cotransfection assay involved intrinsically nonhomologous recombination processes; normalization of the frequencies by dividing them with those of the above nonhomologous recombination revealed 2-fold enhancement of homologous recombination events between the circular mutant genes but not between the linear ones. In contrast, DNA topoisomerase I inhibitor, camptothecin, showed no such effect on either recombination. From these results, we discuss the function of DNA topoisomerases on recombination in mammalian cells.
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Affiliation(s)
- Y Aratani
- Kihara Institute for Biolgical Research, Yokohama City University, Japan
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44
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Gong SS, Jensen AD, Wang H, Rogler CE. Duck hepatitis B virus integrations in LMH chicken hepatoma cells: identification and characterization of new episomally derived integrations. J Virol 1995; 69:8102-8. [PMID: 7494330 PMCID: PMC189762 DOI: 10.1128/jvi.69.12.8102-8108.1995] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
While the cytoplasmic phase of the hepadnavirus replication cycle is well understood, very little is known about the nuclear phase. In contrast to retroviruses, proviral integration is not required for hepadnavirus replication; however, some of the viral DNAs in the nucleus are diverted into an integration pathway. Under certain conditions these integrations function as carcinogenic agents. In order to study the integration process, we have utilized LMH-D2 cells, which replicate wild-type duck hepatitis B virus (DHBV), to develop the first protocol to detect and characterize integrations of DHBV originating from episomal viral DNAs. Contrary to expectations, our results showed that stable new integrations are readily detectable in subclones of LMH-D2 cells. Complete characterization of one integration revealed a single-genome-length integrant with the structure of double-stranded linear (DSL) DHBV DNAs which are produced by in situ priming during viral replication. The integration contained a terminal redundancy of 6 bp from the r region of the virus DNA minus strand as well as a direct repeat of 70 bp of cellular DNA. On the basis of the structure of the integrant and the cellular DNA target site, we propose a molecular model for the integration mechanism that has some similarities to that of retroviruses. Identification of DSL hepadnavirus DNA integration suggests the possibility that modified DSL viral DNAs may be the precursors to a class of simple, unrearranged hepadnavirus integrations.
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Affiliation(s)
- S S Gong
- Marion Bessin Liver Research Center, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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45
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Pommier Y, Jenkins J, Kohlhagen G, Leteurtre F. DNA recombinase activity of eukaryotic DNA topoisomerase I; effects of camptothecin and other inhibitors. Mutat Res 1995; 337:135-45. [PMID: 7565862 DOI: 10.1016/0921-8777(95)00019-g] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
DNA oligonucleotides containing a strong topoisomerase I cleavage site were used to study the DNA cleavage and strand transferase activities of calf thymus topoisomerase I (top1) in the absence and presence of camptothecin. A partially single-stranded oligonucleotide with only two nucleotides on the 3' side of the cleavage site (positions +1 and +2) was cleaved at the same position as the corresponding duplex oligonucleotide. However, cleavage in the absence of camptothecin was more pronounced than in the duplex oligonucleotide and was only partially reversible in the presence of 0.5 M NaCl, consistent with release of the dinucleotide 3' to the top1 break. Another reaction took place generating a larger DNA fragment which resulted from religation (strand transfer) of the 5'-hydroxyl terminus of the non-scissile DNA strand to the 3' end of the top1-linked oligonucleotide after loss of the +1 and +2 nucleotides. Top1 religation activity appeared efficient since only the last 5' base of the single-stranded DNA acceptor was complementary to the 3' tail of the donor DNA. Religation was not detectable with a double-stranded DNA acceptor, which is consistent with the persistence of top1-induced DNA double-strand breaks in camptothecin-treated cells. Camptothecin and other top1 inhibitors enhanced cleavage in both the partially single-stranded and the duplex oligonucleotides, indicating that they did not inhibit the induction of top1-mediated DNA cleavage but primarily blocked the religation step of the enzyme catalytic cycle. The top1 DNA strand transferase activity was reversibly inhibited by camptothecin and several derivatives, as well as saintopin. These results are discussed in terms of camptothecin-induced DNA recombinations.
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Affiliation(s)
- Y Pommier
- Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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46
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Takahashi H, Matsuda M, Kojima A, Sata T, Andoh T, Kurata T, Nagashima K, Hall WW. Human immunodeficiency virus type 1 reverse transcriptase: enhancement of activity by interaction with cellular topoisomerase I. Proc Natl Acad Sci U S A 1995; 92:5694-8. [PMID: 7539924 PMCID: PMC41763 DOI: 10.1073/pnas.92.12.5694] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
A number of studies have suggested that topoisomerase I (topo I) activity may be important in human immunodeficiency virus type 1 (HIV-1) replication. Specifically it has been reported that purified virus particles have topo I activity and that inhibitors of this enzyme can inhibit virus replication in vitro. We have investigated a possible association of HIV-1 gag proteins with topo I activity. We found that whereas the gag-encoded proteins by themselves do not have activity, the nucleocapsid protein p15 can interact with and enhance the activity of cellular topo I. Furthermore it could be demonstrated that topo I markedly enhanced HIV-1 reverse transcriptase activity in vitro and that this could be inhibited by the topo I-specific inhibitor camptothecin. The findings suggest that cellular topo I plays an important role in the reverse transcription of HIV-1 RNA and that the recruitment of this enzyme may be an important step in virus replication.
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Affiliation(s)
- H Takahashi
- Department of Pathology, National Institute of Health, Tokyo, Japan
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47
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Feitelson MA, Duan LX, Guo J, Blumberg BS. X region deletion mutants associated with surface antigen-positive hepatitis B virus infections. Gastroenterology 1995; 108:1810-9. [PMID: 7768387 DOI: 10.1016/0016-5085(95)90144-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND/AIMS The finding of antibodies against the polymerase of hepatitis B virus in renal dialysis patients before the incubation phase of infection implies underlying virus replication. Hence, the aim of the study was to test for virus during infection. METHODS Viremia was assayed in virus-infected and control patients using the polymerase chain reaction and Southern blotting. RESULTS Six months before the appearance of surface antigen, most patients had detectable core region, but few patients were X region positive. Three months after surface antigen appeared, most carriers had detectable core and X products. Three years after surface antigen appeared, 5 of 8 carriers with persistent hepatitis B e antigen and 1 of 8 carriers with corresponding antibody had these products. Cloning and sequencing showed deletions within the X/precore region of viral DNA. CONCLUSIONS Infection with X region mutants precedes that of wild-type virus, and they reappear after wild-type virus is eliminated in carriers.
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Affiliation(s)
- M A Feitelson
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania, USA
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48
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Gupta M, Fujimori A, Pommier Y. Eukaryotic DNA topoisomerases I. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1262:1-14. [PMID: 7772596 DOI: 10.1016/0167-4781(95)00029-g] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- M Gupta
- Laboratory of Molecular Pharmacology, National Cancer Institute, National Institute of Health, Bethesda, MD 20892-4255, USA
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49
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Wei Y, Etiemble J, Fourel G, Vitvitski-Trepo L, Buendia MA. Hepadna virus integration generates virus-cell cotranscripts carrying 3' truncated X genes in human and woodchuck liver tumors. J Med Virol 1995; 45:82-90. [PMID: 7714496 DOI: 10.1002/jmv.1890450116] [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: 01/26/2023]
Abstract
Integration of the human and woodchuck hepatitis B viruses (HBV and WHV) in host chromosomes has been implicated in the development of hepatocellular carcinoma by different cis- and trans-acting mechanisms. The structure and coding capacity of abundant HBV and WHV transcripts of abnormal sizes produced from integrated viral sequences in one human and two woodchuck liver tumors were examined. Analysis of cDNA clones revealed in all cases hybrid virus-cell transcripts containing sequences of the viral surface gene, the viral enhancer, and different truncated versions of the viral X transactivator. Cotranscribed cellular sequences showing no significant coding function provided the signals for transcription termination. In two transcripts, the HBX and WHX genes truncated at carboxy terminal positions conserved transcriptional trans-acting capacity in transient transfection assays. These results lend support to the hypothesis that the integrated hepadnavirus X transactivator might participate in the development of woodchuck as well as human liver tumors by a common trans-acting mechanism.
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MESH Headings
- Amino Acid Sequence
- Animals
- Carcinoma, Hepatocellular/virology
- Gene Library
- Genes, Regulator/genetics
- Hepatitis B Virus, Woodchuck/genetics
- Hepatitis B virus/genetics
- Humans
- Liver Neoplasms/virology
- Marmota
- Molecular Sequence Data
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- RNA, Neoplasm/analysis
- RNA, Neoplasm/genetics
- RNA, Viral/analysis
- RNA, Viral/genetics
- Restriction Mapping
- Trans-Activators/genetics
- Transcription, Genetic/genetics
- Transcriptional Activation/genetics
- Viral Regulatory and Accessory Proteins
- Virus Integration
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Affiliation(s)
- Y Wei
- Unité de Recombinaison et Expression Génétique, INSERM U.163, Institut Pasteur, Paris, France
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50
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Tsuei DJ, Chen PJ, Lai MY, Chen DS, Yang CS, Chen JY, Hsu TY. Inverse polymerase chain reaction for cloning cellular sequences adjacent to integrated hepatitis B virus DNA in hepatocellular carcinomas. J Virol Methods 1994; 49:269-84. [PMID: 7868645 DOI: 10.1016/0166-0934(94)90142-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Integration of hepatitis B virus (HBV) DNA is found in most HBV-related human hepatocellular carcinomas (HCCs). In the past, construction of genomic libraries was mainly employed to study the role of viral integration. However, large amounts of tissue DNA and a laborious screening procedures were required. Inverse polymerase chain reaction (IPCR) is based on the simple procedures of digestion of DNA with restriction enzymes and circularization of cleavage products before amplification using primers synthesized in the opposite orientations to those normally employed for PCR. This technique allows the in vitro amplification of DNA flanking a region of known sequence. By employing this method, starting from nanograms of hepatoma DNA, two adjacent cellular sequences were cloned from 11 HBV integrants in three HCCs. The original configurations in the chromosomes were further confirmed. One of the flanking cellular sequences was identified as the human 28S rRNA gene, the other was not found homologous to any known human sequences. This method appears to be practical and can be improved further to clone more flanking cellular sequences, especially in early and small HCCs.
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Affiliation(s)
- D J Tsuei
- Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei
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