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Wang J, Yuan X, Wang Y, Zhang Y, Han M, Lu H, Liu S, Zhang Y, Ge F, Liu Y, Cheng J. PreS1BP mediates inhibition of Hepatitis B virus replication by promoting HBx protein degradation. Virus Res 2024; 341:199326. [PMID: 38253259 PMCID: PMC10846407 DOI: 10.1016/j.virusres.2024.199326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 01/07/2024] [Accepted: 01/18/2024] [Indexed: 01/24/2024]
Abstract
BACKGROUND PreS1-binding protein (PreS1BP), recognized as a nucleolar protein and tumor suppressor, influences the replication of various viruses, including vesicular stomatitis virus (VSV) and herpes simplex virus type 1 (HSV-1). Its role in hepatitis B virus (HBV) replication and the underlying mechanisms, however, remain elusive. METHODS We investigated PreS1BP expression levels in an HBV-replicating cell and animal model and analyzed the impact of its overexpression on viral replication metrics. HBV DNA, covalently closed circular DNA (cccDNA), hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg), and HBV RNA levels were assessed in HBV-expressing stable cell lines under varying PreS1BP conditions. Furthermore, co-immunoprecipitation and ubiquitination assays were used to detect PreS1BP- hepatitis B virus X protein (HBx) interactions and HBx stability modulated by PreS1BP. RESULTS Our study revealed a marked decrease in PreS1BP expression in the presence of active HBV replication. Functional assays showed that PreS1BP overexpression significantly inhibited HBV replication and transcription, evidenced by the reduction in HBV DNA, cccDNA, HBsAg, HBcAg, and HBV RNA levels. At the molecular level, PreS1BP facilitated the degradation of HBx in a dose-dependent fashion, whereas siRNA-mediated knockdown of PreS1BP led to an increase in HBx levels. Subsequent investigations uncovered that PreS1BP accelerated HBx protein degradation via K63-linked ubiquitination in a ubiquitin-proteasome system-dependent manner. Co-immunoprecipitation assays further established that PreS1BP enhances the recruitment of the proteasome 20S subunit alpha 3 (PSMA3) for interaction with HBx, thereby fostering its degradation. CONCLUSIONS These findings unveil a previously unidentified mechanism wherein PreS1BP mediates HBx protein degradation through the ubiquitin-proteasome system, consequentially inhibiting HBV replication. This insight positions PreS1BP as a promising therapeutic target for future HBV interventions. Further studies are warranted to explore the clinical applicability of modulating PreS1BP in HBV therapy.
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Affiliation(s)
- Jun Wang
- Peking University Ditan Teaching Hospital, Beijing 100015, China; Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Xiaoxue Yuan
- Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China; The Division of Liver Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Yun Wang
- The Division of Liver Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Yu Zhang
- The Division of Liver Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Ming Han
- Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China; The Division of Liver Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Hongping Lu
- Hebei Utu Pharmaceutical Company Ltd, Shijiazhuang, Hebei Province 052165, China
| | - Shunai Liu
- Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China; The Division of Liver Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Yang Zhang
- Beijing Key Laboratory of Emerging Infectious Diseases, Institute of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, China
| | - Feilin Ge
- Department of Chinese Medicine, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Yan Liu
- Department of Infectious Diseases, The Fifth Medical Center of Chinese PLA General Hospital, Beijing 100039, China.
| | - Jun Cheng
- Peking University Ditan Teaching Hospital, Beijing 100015, China; Hebei Utu Pharmaceutical Company Ltd, Shijiazhuang, Hebei Province 052165, China.
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Hepatitis B Virus X Protein Is Stabilized by the Deubiquitinating Enzyme VCPIP1 in a Ubiquitin-Independent Manner by Recruiting the 26S Proteasome Subunit PSMC3. J Virol 2022; 96:e0061122. [PMID: 35695579 PMCID: PMC9278118 DOI: 10.1128/jvi.00611-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/09/2022] Open
Abstract
Hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) is the sixth most common cancer worldwide, and the viral X protein (HBx) is an etiological factor in HCC development. HBx is a high-turnover protein, but knowledge of the role of deubiquitinating enzymes (DUBs) in maintaining HBx homeostasis is very limited. We used a 74-DUB library-based yeast two-hybrid assay and determined that a novel DUB, valosin-containing protein-interacting protein 1 (VCPIP1), interacted with HBx. VCPIP1 and its C-terminal amino acids 863 to 1221 upregulated the HBx protein expression, with or without HBV infection. Mechanistically, VCPIP1 stabilized HBx protein through a ubiquitin-independent pathway, which was validated by the HBx ubiquitination site mutant plasmid. Coimmunoprecipitation assays demonstrated the potency of VCPIP1 in recruiting 26S proteasome regulatory subunit 6A (PSMC3) and forming a ternary complex with HBx through mutual interaction. In vitro, purified His-tagged PSMC3 protein rescued HBx degradation induced by the 20S proteasome, and in vivo VCPIP1 synergized the mechanism. Functionally, HBx specifically binding to VCPIP1 significantly enhanced the transcriptional transactivation of HBx by activating NF-κB, AP-1, and SP-1 and inhibited hepatoma cell clonogenicity in Huh7 and HepG2 cells. Moreover, we further demonstrated that overexpression of VCPIP1 significantly affected the HBV covalently closed circular DNA (cccDNA) transcription in HBV-infected HepG2-NTCP cells. Altogether, our results indicate a novel mechanism by which VCPIP1 recruits PSMC3 to bind with HBx, stabilizing it in a ubiquitin-independent manner, which might be critical for developing DUB inhibitors in the future. IMPORTANCE HBx is a multifunctional viral oncoprotein that plays an essential role in the viral life cycle and hepatocarcinogenesis. HBx degradation occurs through the ubiquitin-proteasome system (UPS). However, whether novel compartments of the DUBs in the UPS also act in regulating HBx stability is not fully understood. Here, for the first time, we defined VCPIP1 as a novel DUB for preventing HBx degradation by the 20S proteasome in a ubiquitin-independent manner. PSMC3, encoding the 26S proteasome regulatory subunit, directly stabilized HBx through physical binding instead of a common approach in protein degradation, serving as the key downstream effector of VCPIP1 on HBx. Therefore, the ternary binding pattern between VCPIP1, HBx, and PSMC3 is initiated for the first time, which eventually promotes HBx stability and its functions. Our findings provide novel insights into host-virus cross talk by targeting DUBs in the UPS.
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Li W, Li M, Liao D, Lu X, Gu X, Zhang Q, Zhang Z, Li H. Carboxyl-terminal truncated HBx contributes to invasion and metastasis via deregulating metastasis suppressors in hepatocellular carcinoma. Oncotarget 2016; 7:55110-55127. [PMID: 27391153 PMCID: PMC5342405 DOI: 10.18632/oncotarget.10399] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 06/17/2016] [Indexed: 12/11/2022] Open
Abstract
Hepatitis B virus (HBV) X protein (HBx), a trans-regulator, is frequently expressed in truncated form without carboxyl-terminus in hepatocellular carcinoma (HCC), but its functional mechanisms are not fully defined. In this report, we investigated frequency of this natural HBx mutant in HCCs and its functional significance. In 102 HBV-infected patients with HCC, C-terminal truncation of HBx, in contrast to full-length HBx, were more prevalent in tumors (70.6%) rather than adjacent non-tumorous tissues (29.4%) (p = 0.0032). Furthermore, two naturally-occurring HBx variants (HBxΔ31), which have 31 amino acids (aa) deleted (codons 123-125/124-126) at C-terminus were identified in tumors and found that the presence of HBxΔ31 significantly correlated with intrahepatic metastasis. We also show that over-expression of HBxΔ31 enhanced hepatoma cell invasion in vitro and metastasis in vivo compared to full-length HBx. Interestingly, HBxΔ31 exerts this function via down-regulating Maspin, RhoGDIα and CAPZB, a set of putative metastasis-suppressors in HCC, in part, by enhancing the binding of transcriptional repressor, myc-associated zinc finger protein (MAZ) to the promoters through physical association with MAZ. Notably, these HBxΔ31-repressed proteins were also significantly lower expression in a subset of HCC tissues with C-terminal HBx truncation than the adjacent non-tumorous tissues, highlighting the clinical significance of this novel HBxΔ31-driven metastatic molecular cascade. Our data suggest that C-terminal truncation of HBx, particularly breakpoints at 124aa, plays a role in enhancing hepatoma cell invasion and metastasis by deregulating a set of metastasis-suppressors partially through MAZ, thus uncovering a novel mechanism for the progression of HBV-associated hepatocarcinogenesis.
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Affiliation(s)
- Weihua Li
- Department of Gastroenterology, Zhujiang Hospital of Nanfang Medical University, Guangzhou 510280, China
| | - Man Li
- Department of Infectious Disease and Hepatology, Hepatitis Research Room, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Dongjiang Liao
- Pathology Research Room, State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, Guangzhou 510120, China
| | - Xinpeng Lu
- Pathology Research Room, State Key Laboratory of Respiratory Disease, Guangzhou Institute of Respiratory Disease, Guangzhou 510120, China
| | - Xia Gu
- Department of Pathology, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Qianqian Zhang
- Department of Infectious Disease and Hepatology, Hepatitis Research Room, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Zhixiang Zhang
- Department of Infectious Disease and Hepatology, Hepatitis Research Room, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Hui Li
- Department of Infectious Disease and Hepatology, Hepatitis Research Room, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
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Slagle BL, Bouchard MJ. Hepatitis B Virus X and Regulation of Viral Gene Expression. Cold Spring Harb Perspect Med 2016; 6:a021402. [PMID: 26747833 DOI: 10.1101/cshperspect.a021402] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The efficient replication of hepatitis B virus (HBV) requires the HBV regulatory hepatitis B virus X (HBx) protein. The exact contributions of HBx are not fully understood, in part because of the limitations of the assays used for its study. When HBV replication is driven from a plasmid DNA, the contribution of HBx is modest. However, there is an absolute requirement for HBx in assays that recapitulate the infectious virus life cycle. There is much evidence that HBx can contribute directly to HBV replication by acting on viral promoters embedded within protein coding sequences. In addition, HBx may also contribute indirectly by modulating cellular pathways to benefit virus replication. Understanding the mechanism(s) of HBx action during virus replication may provide insight into novel ways to disrupt chronic HBV replication.
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Affiliation(s)
- Betty L Slagle
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030
| | - Michael J Bouchard
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102
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Zhang H, Diab A, Fan H, Mani SKK, Hullinger R, Merle P, Andrisani O. PLK1 and HOTAIR Accelerate Proteasomal Degradation of SUZ12 and ZNF198 during Hepatitis B Virus-Induced Liver Carcinogenesis. Cancer Res 2015; 75:2363-74. [PMID: 25855382 PMCID: PMC4452430 DOI: 10.1158/0008-5472.can-14-2928] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 03/19/2015] [Indexed: 12/11/2022]
Abstract
Elucidating mechanisms of hepatitis B virus (HBV)-mediated hepatocarcinogenesis is needed to gain insights into the etiology and treatment of liver cancer. Cells where HBV is replicating exhibit increased expression of Plk1 kinase and reduced levels of two transcription repression factors, SUZ12 and ZNF198. SUZ12 is an essential subunit of the transcription repressive complex PRC2. ZNF198 stabilizes the transcription repressive complex composed of LSD1, Co-REST, and HDAC1. These two transcription repressive complexes are held together by binding the long noncoding RNA HOTAIR. In this study, we linked these regulatory events mechanistically by showing that Plk1 induces proteasomal degradation of SUZ12 and ZNF198 by site-specific phosphorylation. Plk1-dependent ubiquitination of SUZ12 and ZNF198 was enhanced by expression of HOTAIR, significantly reducing SUZ12 and ZNF198 stability. In cells expressing the HBV X protein (HBx), downregulation of SUZ12 and ZNF198 mediated global changes in histone modifications. In turn, HBx-expressing cells propagated an altered chromatin landscape after cell division, as exemplified by changes in histone modifications of the EpCAM promoter, a target of PRC2 and LSD1/Co-REST/HDAC1 complexes. Notably, liver tumors from X/c-myc bitransgenic mice exhibited downregulation of SUZ12 and ZNF198 along with elevated expression of Plk1, HOTAIR, and EpCAM. Clinically, similar effects were documented in a set of HBV-related liver tumors consistent with the likelihood that downregulation of SUZ12 and ZNF198 leads to epigenetic reprogramming of infected hepatocytes. Because both Plk1 and HOTAIR are elevated in many human cancers, we propose that their combined effects are involved in epigenetic reprogramming associated broadly with oncogenic transformation.
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Affiliation(s)
- Hao Zhang
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Ahmed Diab
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Huitao Fan
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Saravana Kumar Kailasam Mani
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Ronald Hullinger
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Philippe Merle
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
| | - Ourania Andrisani
- Department of Basic Medical Sciences and Purdue Center for Cancer Research, Purdue University,West Lafayette IN 47907, USA, and Centre de Recherche en Cancérologie de Lyon , UMR INSERM 1052 - CNRS 5286 , Lyon Cedex 03, France
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Hepatitis B virus X protein induces EpCAM expression via active DNA demethylation directed by RelA in complex with EZH2 and TET2. Oncogene 2015; 35:715-26. [PMID: 25893293 PMCID: PMC4615262 DOI: 10.1038/onc.2015.122] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 12/16/2022]
Abstract
Chronic hepatitis B virus (HBV) infection is a major risk factor for developing hepatocellular carcinoma (HCC), and HBV X protein (HBx) acts as cofactor in hepatocarcinogenesis. In liver tumors from animals modeling HBx- and HBV-mediated hepatocarcinogenesis, downregulation of chromatin regulating proteins SUZ12 and ZNF198 induces expression of several genes, including epithelial cell adhesion molecule (EpCAM). EpCAM upregulation occurs in HBV-mediated HCCs and hepatic cancer stem cells, by a mechanism not understood. Herein we demonstrate HBx induces EpCAM expression via active DNA demethylation. In hepatocytes, EpCAM is silenced by polycomb repressive complex 2 (PRC2) and ZNF198/LSD1/Co-REST/HDAC1 chromatin-modifying complexes. Cells with stable knockdown of SUZ12, an essential PRC2 subunit, upon HBx expression demethylate a CpG dinucleotide located adjacent to NF-κB/RelA half-site. This NF-κB/RelA site is in a CpG island downstream from EpCAM transcriptional start site (TSS). Chromatin immunoprecipitation (ChIP) assays demonstrate HBx-dependent RelA occupancy of NF-κB half-site, whereas RelA knockdown suppresses CpG demethylation and EpCAM expression. Tumor necrosis factor-α activates RelA, propagating demethylation to nearby CpG sites, shown by sodium bisulfite sequencing. RelA-dependent demethylation occurring upon HBx expression requires methyltrasferase EZH2, TET2 a key factor in cytosine demethylation and inactive DNMT3L, shown by knockdown assays and sodium bisulfite sequencing. Co-immunoprecipitations and sequential ChIP assays demonstrate that RelA in the presence of HBx forms a complex with EZH2, TET2 and DNMT3L, although the role of DNMT3L remains to be understood. Interestingly, the human EpCAM gene also has a CpG island downstream from its TSS, and a NF-κB-binding site flanked by CpGs. HepG2 cells derived from human HCC exhibit demethylation of these NF-κB-flanking CpG sites, and HBV replication propagates demethylation to nearby CpG sites. DLK1, another PRC2 target gene, also upregulated in HBV-mediated HCCs, is demethylated in liver tumors at CpG dinucleotides flanking the NF-κB-binding sequence, supporting that this active DNA demethylation mechanism functions during oncogenic transformation.
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Yamaguchi M. Involvement of regucalcin as a suppressor protein in human carcinogenesis: insight into the gene therapy. J Cancer Res Clin Oncol 2014; 141:1333-41. [PMID: 25230901 DOI: 10.1007/s00432-014-1831-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 09/09/2014] [Indexed: 12/18/2022]
Abstract
Regucalcin, which its gene is located on the X chromosome, plays a multifunctional role as a suppressor protein in cell signal transduction in various types of cells and tissues. The suppression of regucalcin gene expression has been shown to involve in carcinogenesis. Regucalcin gene expression was uniquely downregulated in carcinogenesis of rat liver in vivo, although the expression of other many genes was upregulated, indicating that endogenous regucalcin plays a suppressive role in the development of hepatocarcinogenesis. Overexpression of endogenous regucalcin was found to suppress proliferation of rat cloned hepatoma cells in vitro. Moreover, the regucalcin gene and its protein levels were demonstrated specifically to downregulate in human hepatocellular carcinoma by analysis with multiple gene expression profiles and proteomics. Regucalcin gene expression was also found to suppress in human tumor tissues including kidney, lung, brain, breast and prostate, suggesting that repressed regucalcin gene expression leads to the development of carcinogenesis in various tissues. Regucalcin may play a role as a suppressor protein in carcinogenesis. Overexpression of endogenous regucalcin is suggested to reveal preventive and therapeutic effects on carcinogenesis. Delivery of the regucalcin gene may be a novel useful tool in the gene therapy of carcinogenesis. This review will discuss regarding to an involvement of regucalcin as a suppressor protein in human carcinogenesis in insight into the gene therapy.
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Affiliation(s)
- Masayoshi Yamaguchi
- Department of Hematology and Medical Oncology, Winship Cancer Institute, Emory University School of Medicine, 1365 C Clifton Road NE, Atlanta, GA, 30322, USA,
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Deregulation of epigenetic mechanisms by the hepatitis B virus X protein in hepatocarcinogenesis. Viruses 2013; 5:858-72. [PMID: 23507839 PMCID: PMC3705300 DOI: 10.3390/v5030858] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/12/2013] [Accepted: 03/13/2013] [Indexed: 12/18/2022] Open
Abstract
This review focuses on the significance of deregulation of epigenetic mechanisms by the hepatitis B virus (HBV) X protein in hepatocarcinogenesis and HBV replication. Epigenetic mechanisms, DNA methylation, and specific histone modifications, e.g., trimethylation of H3 on lysine-27 or lysine-4, maintain ‘cellular memory’ by silencing expression of lineage-inducing factors in stem cells and conversely, of pluripotency factors in differentiated cells. The X protein has been reported to induce expression of DNA methyltransferases (DNMTs), likely promoting epigenetic changes during hepatocarcinogenesis. Furthermore, in cellular and animal models of X-mediated oncogenic transformation, protein levels of chromatin modifying proteins Suz12 and Znf198 are down-regulated. Suz12 is essential for the Polycomb Repressive Complex 2 (PRC2) mediating the repressive trimethylation of H3 on lysine-27 (H3K27me3). Znf198, stabilizes the LSD1-CoREST-HDAC complex that removes, via lysine demethylase1 (LSD1), the activating trimethylation of H3 on lysine-4 (H3K4me3). Down-regulation of Suz12 also occurs in liver tumors of woodchucks chronically infected by woodchuck hepatitis virus, an animal model recapitulating HBV-mediated hepatocarcinogenesis in humans. Significantly, subgroups of HBV-induced liver cancer re-express hepatoblast and fetal markers, and imprinted genes, suggesting hepatocyte reprogramming during oncogenic transformation. Lastly, down-regulation of Suz12 and Znf198 enhances HBV replication. Collectively, these observations suggest deregulation of epigenetic mechanisms by HBV X protein influences both the viral cycle and the host cell.
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Rawat S, Clippinger AJ, Bouchard MJ. Modulation of apoptotic signaling by the hepatitis B virus X protein. Viruses 2012; 4:2945-72. [PMID: 23202511 PMCID: PMC3509679 DOI: 10.3390/v4112945] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 10/23/2012] [Accepted: 10/31/2012] [Indexed: 12/18/2022] Open
Abstract
Worldwide, an estimated 350 million people are chronically infected with the Hepatitis B Virus (HBV); chronic infection with HBV is associated with the development of severe liver diseases including hepatitis and cirrhosis. Individuals who are chronically infected with HBV also have a significantly higher risk of developing hepatocellular carcinoma (HCC) than uninfected individuals. The HBV X protein (HBx) is a key regulatory HBV protein that is important for HBV replication, and likely plays a cofactor role in the development of HCC in chronically HBV-infected individuals. Although some of the functions of HBx that may contribute to the development of HCC have been characterized, many HBx activities, and their putative roles during the development of HBV-associated HCC, remain incompletely understood. HBx is a multifunctional protein that localizes to the cytoplasm, nucleus, and mitochondria of HBV‑infected hepatocytes. HBx regulates numerous cellular signal transduction pathways and transcription factors as well as cell cycle progression and apoptosis. In this review, we will summarize reports in which the impact of HBx expression on cellular apoptotic pathways has been analyzed. Although various effects of HBx on apoptotic pathways have been observed in different model systems, studies of HBx activities in biologically relevant hepatocyte systems have begun to clarify apoptotic effects of HBx and suggest mechanisms that could link HBx modulation of apoptotic pathways to the development of HBV-associated HCC.
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Affiliation(s)
- Siddhartha Rawat
- Graduate Program in Molecular and Cellular Biology and Genetics, Drexel University College of Medicine, Philadelphia, PA 19102, USA;
| | - Amy J. Clippinger
- Department of Cancer Biology, Abramson Family Cancer Research Institute, School of Medicine, University of Pennsylvania Philadelphia, PA 19104, USA;
| | - Michael J. Bouchard
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
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Yue X, Yang F, Yang Y, Mu Y, Sun W, Li W, Xu D, Wu J, Zhu Y. Induction of cyclooxygenase-2 expression by hepatitis B virus depends on demethylation-associated recruitment of transcription factors to the promoter. Virol J 2011; 8:118. [PMID: 21401943 PMCID: PMC3066118 DOI: 10.1186/1743-422x-8-118] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 03/14/2011] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND The hepatitis B virus (HBV) is a major etiological factor of inflammation and damage to the liver resulting in hepatocellular carcinoma. Transcription factors play important roles in the disordered gene expression and liver injury caused by HBV. However, the molecular mechanisms behind this observation have not been defined. RESULTS In this study, we observed that circulating prostaglandin (PGE) 2 synthesis was increased in patients with chronic hepatitis B infection, and detected elevated cyclooxygenase (COX)-2 expression in HBV- and HBx-expressing liver cells. Likewise, the association of HBx with C/EBPβ contributed to the induction of COX-2. The COX-2 promoter was hypomethylated in HBV-positive cells, and specific demethylation of CpG dinucleotides within each of the two NF-AT sites in the COX-2 promoter resulted in the increased binding affinity of NF-AT to the cognate sites in the promoter, followed by increased COX-2 expression and PGE2 accumulation. The DNA methylatransferase DNMT3B played a key role in the methylation of the COX-2 promoter, and its decreased binding to the promoter was responsible for the regional demethylation of CpG sites, and for the increased binding of transcription factors in HBV-positive cells. CONCLUSION Our results indicate that upregulation of COX-2 by HBV and HBx is mediated by both demethylation events and recruitment of multiple transcription factors binding to the promoter.
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Affiliation(s)
- Xin Yue
- State Key Laboratory of Virology and College of Life Sciences, Chinese-French Liver Disease Research Institute of Wuhan University (Zhongnan Hospital), Wuhan University, Wuhan 430072, PR China
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Andrisani OM, Studach L, Merle P. Gene signatures in hepatocellular carcinoma (HCC). Semin Cancer Biol 2011; 21:4-9. [PMID: 20851183 PMCID: PMC3030925 DOI: 10.1016/j.semcancer.2010.09.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 09/08/2010] [Accepted: 09/13/2010] [Indexed: 12/25/2022]
Abstract
Primary hepatocellular carcinoma (HCC) is a significant human cancer globally, with poor prognosis. New and efficacious therapy strategies are needed as well as new biomarkers for early detection of at-risk patients. In this review, we discuss select microarray studies of human HCCs, and propose a gene signature that has promise for clinical/translational application. This gene signature combines the proliferation cluster of genes and the hepatic cancer initiating/stem cell gene cluster for identification of HCCs with poor prognosis. Evidence from cell-based assays identifies the existence of a mechanistic link between these two gene clusters, involving the proliferation cluster gene polo-like kinase 1 (PLK1). We propose that PLK1 is a promising therapy target for HCC.
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Affiliation(s)
- Ourania M Andrisani
- Basic Medical Sciences Department and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, United States.
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Studach L, Wang WH, Weber G, Tang J, Hullinger RL, Malbrue R, Liu X, Andrisani O. Polo-like kinase 1 activated by the hepatitis B virus X protein attenuates both the DNA damage checkpoint and DNA repair resulting in partial polyploidy. J Biol Chem 2010; 285:30282-93. [PMID: 20624918 PMCID: PMC2943266 DOI: 10.1074/jbc.m109.093963] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 07/09/2010] [Indexed: 01/21/2023] Open
Abstract
Hepatitis B virus X protein (pX), implicated in hepatocarcinogenesis, induces DNA damage because of re-replication and allows propagation of damaged DNA, resulting in partial polyploidy and oncogenic transformation. The mechanism by which pX allows cells with DNA damage to continue proliferating is unknown. Herein, we show pX activates Polo-like kinase 1 (Plk1) in the G(2) phase, thereby attenuating the DNA damage checkpoint. Specifically, in the G(2) phase of pX-expressing cells, the checkpoint kinase Chk1 was inactive despite DNA damage, and protein levels of claspin, an adaptor of ataxia telangiectasia-mutated and Rad3-related protein-mediated Chk1 phosphorylation, were reduced. Pharmacologic inhibition or knockdown of Plk1 restored claspin protein levels, Chk1 activation, and p53 stabilization. Also, protein levels of DNA repair protein Mre11 were decreased in the G(2) phase of pX-expressing cells but not with Plk1 knockdown. Interestingly, in pX-expressing cells, Mre11 co-immunoprecipitated with transfected Plk1 Polo-box domain, and inhibition of Plk1 increased Mre11 stability in cycloheximide-treated cells. These results suggest that pX-activated Plk1 by down-regulating Mre11 attenuates DNA repair. Importantly, concurrent inhibition of Plk1, p53, and Mre11 increased the number of pX-expressing cells with DNA damage entering mitosis, relative to Plk1 inhibition alone. By contrast, inhibition or knockdown of Plk1 reduced pX-induced polyploidy while increasing apoptosis. We conclude Plk1, activated by pX, allows propagation of DNA damage by concurrently attenuating the DNA damage checkpoint and DNA repair, resulting in polyploidy. We propose this novel Plk1 mechanism initiates pX-mediated hepatocyte transformation.
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Affiliation(s)
- Leo Studach
- From the Departments of Basic Medical Sciences and
| | | | - Gregory Weber
- Biochemistry, Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | - Jiabin Tang
- Biochemistry, Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
| | | | | | - Xiaoqi Liu
- Biochemistry, Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907
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13
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Li C, Jin J. DNA replication licensing control and rereplication prevention. Protein Cell 2010; 1:227-36. [PMID: 21203969 DOI: 10.1007/s13238-010-0032-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Accepted: 01/18/2010] [Indexed: 01/23/2023] Open
Abstract
Eukaryotic DNA replication is tightly restricted to only once per cell cycle in order to maintain genome stability. Cells use multiple mechanisms to control the assembly of the prereplication complex (pre-RC), a process known as replication licensing. This review focuses on the regulation of replication licensing by posttranslational modifications of the licensing factors, including phosphorylation, ubiquitylation and acetylation. These modifications are critical in establishing the pre-RC complexes as well as preventing rereplication in each cell cycle. The relationship between rereplication and diseases, including cancer and virus infection, is discussed as well.
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Affiliation(s)
- Chonghua Li
- Department of Biochemistry and Molecular Biology, The University of Texas Medical School at Houston, Houston, TX 77030, USA
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14
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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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15
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Yang X, Li H, Zhou Z, Wang WH, Deng A, Andrisani O, Liu X. Plk1-mediated phosphorylation of Topors regulates p53 stability. J Biol Chem 2009; 284:18588-92. [PMID: 19473992 PMCID: PMC2707202 DOI: 10.1074/jbc.c109.001560] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Revised: 05/20/2009] [Indexed: 11/06/2022] Open
Abstract
Polo-like kinase 1 (Plk1) overexpression is associated with tumorigenesis by an unknown mechanism. Likewise, Plk1 was suggested to act as a negative regulator of tumor suppressor p53, but the mechanism remains to be determined. Herein, we have identified topoisomerase I-binding protein (Topors), a p53-binding protein, as a Plk1 target. We show that Plk1 phosphorylates Topors on Ser(718) in vivo. Significantly, expression of a Plk1-unphosphorylatable Topors mutant (S718A) leads to a dramatic accumulation of p53 through inhibition of p53 degradation. Topors is an ubiquitin and small ubiquitin-like modifier ubiquitin-protein isopeptide ligase (SUMO E3) ligase. Plk1-mediated phosphorylation of Topors inhibits Topors-mediated sumoylation of p53, whereas p53 ubiquitination is enhanced, leading to p53 degradation. These results demonstrate that Plk1 modulates Topors activity in suppressing p53 function and identify a likely mechanism for the tumorigenic potential of Plk1.
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Affiliation(s)
- Xiaoming Yang
- From the College of Chemistry, Sichuan University, Chengdu 610064, China and
- the Departments of Biochemistry and
| | | | | | - Wen-Horng Wang
- Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907
| | - Anping Deng
- From the College of Chemistry, Sichuan University, Chengdu 610064, China and
| | - Ourania Andrisani
- Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907
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16
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Sung WK, Lu Y, Lee CWH, Zhang D, Ronaghi M, Lee CGL. Deregulated direct targets of the hepatitis B virus (HBV) protein, HBx, identified through chromatin immunoprecipitation and expression microarray profiling. J Biol Chem 2009; 284:21941-21954. [PMID: 19439406 DOI: 10.1074/jbc.m109.014563] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The hepatitis B-X (HBx) protein is strongly associated with hepatocellular carcinoma. It is implicated not to directly cause cancer but to play a role in hepatocellular carcinoma as a co-factor. The oncogenic potential of HBx primarily lies in its interaction with transcriptional regulators resulting in aberrant gene expression and deregulated cellular pathways. Utilizing ultraviolet irradiation to simulate a tumor-initiating event, we integrated chip-based chromatin immunoprecipitation (ChIP-chip) with expression microarray profiling and identified 184 gene targets directly deregulated by HBx. One-hundred forty-four transcription factors interacting with HBx were computationally inferred. We experimentally validated that HBx interacts with some of the predicted transcription factors (pTF) as well as the promoters of the deregulated target genes of these pTFs. Significantly, we demonstrated that the pTF interacts with the promoters of the deregulated HBx target genes and that deregulation by HBx of these HBx target genes carrying the pTF consensus sequences can be reversed using pTF small interfering RNAs. The roles of these deregulated direct HBx target genes and their relevance in cancer was inferred via querying against biogroup/cancer-related microarray databases using web-based NextBio(TM) software. Six pathways, including the Jak-STAT pathway, were predicted to be significantly deregulated when HBx binds indirectly to direct target gene promoters. In conclusion, this study represents the first ever demonstration of the utilization of ChIP-chip to identify deregulated direct gene targets from indirect protein-DNA binding as well as transcriptional factors directly interacting with HBx. Increased knowledge of the gene/transcriptional factor targets of HBx will enhance our understanding of the role of HBx in hepatocellular carcinogenesis and facilitate the design of better strategies in combating hepatitis B virus-associated hepatocellular carcinoma.
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Affiliation(s)
- Wing-Kin Sung
- Departments of Computer Science, Singapore 119077, Singapore; Genome Institute of Singapore, Singapore 138672, Singapore
| | - Yiwei Lu
- Division of Medical Sciences, National Cancer Centre Singapore, Singapore 169610, Singapore
| | - Charlie W H Lee
- Departments of Computer Science, Singapore 119077, Singapore; Genome Institute of Singapore, Singapore 138672, Singapore
| | - Dongwei Zhang
- Division of Medical Sciences, National Cancer Centre Singapore, Singapore 169610, Singapore; Biochemistry, National University of Singapore, Singapore 119077, Singapore
| | - Mostafa Ronaghi
- Department of Biochemistry, Stanford Genome Technology Center, Stanford University, Stanford, California 94305
| | - Caroline G L Lee
- Division of Medical Sciences, National Cancer Centre Singapore, Singapore 169610, Singapore; Biochemistry, National University of Singapore, Singapore 119077, Singapore; Duke-NUS Graduate Medical School, Singapore 169547, Singapore
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17
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Hepatitis B virus X protein modulates apoptosis in primary rat hepatocytes by regulating both NF-kappaB and the mitochondrial permeability transition pore. J Virol 2009; 83:4718-31. [PMID: 19279112 DOI: 10.1128/jvi.02590-08] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The hepatitis B virus (HBV) X protein (HBx) is a multifunctional protein that regulates numerous cellular signal transduction pathways, including those that modulate apoptosis. However, different HBx-dependent effects on apoptosis have been reported; these differences are likely the consequence of the exact conditions and cell types used in a study. Many of the previously reported studies that analyzed HBx regulation of apoptosis were conducted in immortalized or transformed cells, and the alterations that have transformed or immortalized these cells likely impact apoptotic pathways. We examined the effects of HBx on apoptotic pathways in cultured primary rat hepatocytes, a biologically relevant system that mimics normal hepatocytes in the liver. We analyzed the effects of HBx on apoptosis both when HBx was expressed in the absence of other HBV proteins and in the context of HBV replication. HBx stimulation of NF-kappaB inhibited the activation of apoptotic pathways in cultured primary rat hepatocytes. However, when HBx-induced activation of NF-kappaB was blocked, HBx stimulated apoptosis; blocking the activity of the mitochondrial permeability transition pore inhibited HBx activation of apoptosis. These results suggest that HBx can be either proapoptotic or antiapoptotic in hepatocytes, depending on the status of NF-kappaB, and confirm previous studies that link some HBx activities to modulation of the mitochondrial permeability transition pore. Overall, our studies define apoptotic pathways that are regulated by HBx in cultured primary hepatocytes and provide potential mechanisms for the development of HBV-associated liver cancer.
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18
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Rakotomalala L, Studach L, Wang WH, Gregori G, Hullinger RL, Andrisani O. Hepatitis B virus X protein increases the Cdt1-to-geminin ratio inducing DNA re-replication and polyploidy. J Biol Chem 2008; 283:28729-40. [PMID: 18693245 PMCID: PMC2568909 DOI: 10.1074/jbc.m802751200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 07/24/2008] [Indexed: 12/16/2022] Open
Abstract
Hepatitis B virus X protein (pX) is implicated in hepatocellular carcinoma pathogenesis by an unknown mechanism. Employing the tetracycline-regulated pX-expressing 4pX-1 cell line, derived from the murine AML12 hepatocyte cell line, we demonstrate that pX induces partial polyploidy (>4N DNA). Depletion of p53 in 4pX-1 cells increases by 5-fold the polyploid cells in response to pX expression, indicating that p53 antagonizes pX-induced polyploidy. Dual-parameter flow cytometric analyses show pX-dependent bromodeoxyuridine (BrdUrd) incorporation in 4pX-1 cells containing 4N and >4N DNA, suggesting pX induces DNA re-replication. Interestingly, pX increases expression of endogenous replication initiation factors Cdc6 and Cdtl while suppressing geminin expression, a negative regulator of rereplication. In comparison to a geminin knockdown 4pX-1 cell line used as DNA re-replication control, the Cdt1/geminin ratio is greater in 4pX-1 cells expressing pX, indicating that pX promotes DNA re-replication. In support of this conclusion, pX-expressing 4pX-1 cells, similar to the geminin knockdown 4pX-1 cells, continue to incorporate BrdUrd in the G2 phase and exhibit nuclear Cdc6 and MCM5 co-localization and the absence of geminin. In addition, pX expression activates the ATR kinase, the sensor of DNA re-replication, which in turn phosphorylates RAD17 and H2AX. Interestingly, phospho-H2AX-positive and BrdUrd -positive cells progress through mitosis, demonstrating a link between pX-induced DNA re-replication and polyploidy. Our studies high-light a novel function of pX that likely contributes to hepatocellular carcinoma pathogenesis.
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Affiliation(s)
- Lova Rakotomalala
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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19
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Wang WH, Hullinger RL, Andrisani OM. Hepatitis B virus X protein via the p38MAPK pathway induces E2F1 release and ATR kinase activation mediating p53 apoptosis. J Biol Chem 2008; 283:25455-25467. [PMID: 18606816 DOI: 10.1074/jbc.m801934200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Hepatitis B virus (HBV) X protein (pX) is implicated in hepatocellular carcinoma (HCC) pathogenesis by an unknown mechanism. Deletions or mutations of genes involved in the p53 pathway are often associated with HBV-mediated HCC, indicating rescue from p53 apoptosis is a likely mechanism in HBV-HCC pathogenesis. Herein, we determined the mechanism by which pX sensitizes hepatocytes to p53-mediated apoptosis. Although it is well established that the Rb/E2F/ARF pathway stabilizes p53, and the DNA damage-activated ATM/ATR kinases activate p53, the mechanism that coordinates these two pathways has not been determined. We demonstrate that the p38MAPK pathway activated by pX serves this role in p53 apoptosis. Specifically, the activated p38MAPK pathway stabilizes p53 via E2F1-mediated ARF expression, and also activates the transcriptional function of p53 by activating ATR. Knockdown of p53, E2F1, ATR, or p38MAPKalpha abrogates pX-mediated apoptosis, demonstrating that E2F1, ATR, and p38MAPKalpha are all essential in p53 apoptosis in response to pX. Specifically, in response to pX expression, the p38MAPK pathway activates Cdk4 and Cdk2, leading to phosphorylation of Rb, release of E2F1, and transcription of ARF. The p38MAPK pathway also activates ATR, leading to phosphorylation of p53 on Ser-18 and Ser-23, transcription of pro-apoptotic genes Bax, Fas, and Noxa, and apoptosis. In conclusion, pX sensitizes hepatocytes to p53 apoptosis via activation of the p38MAPK pathway, which couples p53 stabilization and p53 activation, by E2F1 induction and ATR activation, respectively.
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Affiliation(s)
- Wen-Horng Wang
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907
| | - Ronald L Hullinger
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907
| | - Ourania M Andrisani
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana 47907.
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20
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Clippinger AJ, Bouchard MJ. Hepatitis B virus HBx protein localizes to mitochondria in primary rat hepatocytes and modulates mitochondrial membrane potential. J Virol 2008; 82:6798-811. [PMID: 18448529 PMCID: PMC2446973 DOI: 10.1128/jvi.00154-08] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 04/22/2008] [Indexed: 12/20/2022] Open
Abstract
Over 350 million people are chronically infected with hepatitis B virus (HBV), and a significant number of chronically infected individuals develop primary liver cancer. HBV encodes seven viral proteins, including the nonstructural X (HBx) protein. The results of studies with immortalized or transformed cells and with HBx-transgenic mice demonstrated that HBx can interact with mitochondria. However, no studies with normal hepatocytes have characterized the precise mitochondrial localization of HBx or the effect of HBx on mitochondrial physiology. We have used cultured primary rat hepatocytes as a model system to characterize the mitochondrial localization of HBx and the effect of HBx expression on mitochondrial physiology. We now show that a fraction of HBx colocalizes with density-gradient-purified mitochondria and associates with the outer mitochondrial membrane. We also demonstrate that HBx regulates mitochondrial membrane potential in hepatocytes and that this function of HBx varies depending on the status of NF-kappaB activity. In primary rat hepatocytes, HBx activation of NF-kappaB prevented mitochondrial membrane depolarization; however, when NF-kappaB activity was inhibited, HBx induced membrane depolarization through modulation of the mitochondrial permeability transition pore. Collectively, these results define potential pathways through which HBx may act in order to modulate mitochondrial physiology, thereby altering many cellular activities and ultimately contributing to the development of HBV-associated liver cancer.
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Affiliation(s)
- Amy J Clippinger
- Graduate Program in Molecular and Cellular Biology and Genetics, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, USA
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21
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Macdonald DC, Nelson M, Bower M, Powles T. Hepatocellular carcinoma, human immunodeficiency virus and viral hepatitis in the HAART era. World J Gastroenterol 2008; 14:1657-63. [PMID: 18350596 PMCID: PMC2695905 DOI: 10.3748/wjg.14.1657] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The incidence of hepatocellular carcinoma (HCC) in patients with human immunodeficiency virus (HIV) is rising. HCC in HIV almost invariably occurs in the context of hepatitis C virus (HCV) or hepatitis B virus (HBV) co-infection and, on account of shared modes of transmission, this occurs in more than 33% and 10% of patients with HIV worldwide respectively. It has yet to be clearly established whether HIV directly accelerates HCC pathogenesis or whether the rising incidence is an epiphenomenon of the highly active antiretroviral therapy (HAART) era, wherein the increased longevity of patients with HIV allows long-term complications of viral hepatitis and cirrhosis to develop. Answering this question will have implications for HCC surveillance and the timing of HCV/HBV therapy, which in HIV co-infection presents unique challenges. Once HCC develops, there is growing evidence that HIV co-infection should not preclude conventional therapeutic strategies, including liver transplantation.
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22
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Kern MA, Breuhahn K, Schuchmann M, Schirmacher P. [Molecular pathogenesis of hepatocellular carcinoma: new therapeutic approaches and predictive pathology]. DER PATHOLOGE 2008; 28:261-8. [PMID: 17605064 DOI: 10.1007/s00292-007-0890-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Hepatocellular carcinoma is one of the most prevalent malignancies worldwide and its incidence is increasing. Multimodal strategies directed towards this carcinoma include primary (e.g. immunisation) and secondary (e.g. antiviral therapy) prevention, surgical approaches, novel specific systemic therapies (targeted therapy), and the treatment of comorbidity (cirrhosis). New molecular approaches are currently under development. These tackle several specific targets, with pathology being challenged in many aspects: experimental evaluation, the development of valid tumor-relevant diagnostic tests as well as morphological evaluation in the context of clinical studies, and finally in routine diagnosis.
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Affiliation(s)
- M A Kern
- Pathologisches Institut, Universität Heidelberg, Im Neuenheimer Feld 220/221, 69120, Heidelberg, Deutschland.
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23
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Li H, Chi CY, Lee S, Andrisani OM. The mitogenic function of hepatitis B virus X protein resides within amino acids 51 to 140 and is modulated by N- and C-terminal regulatory regions. J Virol 2006; 80:10554-64. [PMID: 16920820 PMCID: PMC1641793 DOI: 10.1128/jvi.00661-06] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The hepatitis B virus (HBV) X protein (pX) is implicated in hepatocarcinogenesis by an unknown mechanism. pX variants encoded by HBV genomes found integrated in genomic DNA from liver tumors of patients with hepatocellular carcinoma (HCC) generally lack amino acids 134 to 154. Since deregulation of mitogenic pathways is linked to oncogenic transformation, herein we define the pX region required for mitogenic pathway activation. A series of pX deletions was used to construct tetracycline-regulated pX-expressing cell lines. The activation of the mitogenic pathways by these pX deletions expressed in the constructed cell lines was measured by transient transreporter assays, effects on endogenous cyclin A expression, and apoptosis. Conditional expression of pX51-140 in AML12 clone 4 cell line activates the mitogenic pathways, induces endogenous cyclin A expression, and sensitizes cells to apoptosis, similar to wild-type (WT) pX. By contrast, pX1-115 is inactive, supporting the idea that amino acids 116 to 140 are required for mitogenic pathway activation. Moreover, this pX deletion analysis demonstrates that WT pX function is modulated by two regions spanning amino acids 1 to 78 and 141 to 154. The N-terminal X1-78, expressed via a retroviral vector in WT pX-expressing 4pX-1 cells, coimmunoprecipitates with WT pX, indicating this pX region participates in protein-protein interactions leading to pX oligomerization. Interestingly, pX1-78 interferes with WT pX in mediating mitogenic pathway activation, endogenous gene expression, and apoptosis. The C-terminal pX region spanning amino acids 141 to 154 decreases pX stability, determined by pulse-chase studies of WT pX and pX1-140, suggesting that increased stability of naturally occurring pX variants lacking amino acids 134 to 154 may play a role in HCC development.
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Affiliation(s)
- Huajie Li
- Department of Basic Medical Sciences, Purdue University, 625 Harrison Street, West Lafayette, IN 47907-2026, USA
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24
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Barone M, Spano D, D’Apolito M, Centra M, Lasalandra C, Capasso M, Di Leo A, Volinia S, Arcelli D, Rosso N, Francavilla A, Tiribelli C, Iolascon A. Gene expression analysis in HBV transgenic mouse liver: a model to study early events related to hepatocarcinogenesis. Mol Med 2006; 12:115-23. [PMID: 16953557 PMCID: PMC1578771 DOI: 10.2119/2006-00015.barone] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Accepted: 05/06/2006] [Indexed: 02/05/2023] Open
Abstract
Hepatitis B virus (HBV) is one of the major etiological factors responsible for the development of hepatocellular carcinoma (HCC). We used a transgenic mouse, containing HBV sequences, as a model system to unravel the molecular mechanisms of hepatocarcinogenesis induced by HBV. We chose this animal model because it consistently develops liver cancer after intermediate steps that mimic the natural history of HBV infection in humans. In this study, we focus our attention on the early events leading to liver cancer. We compared the gene expression profile of 3-month-old transgenic mice with that of 3-month-old wild-type (wt) animals. In the transgenic mouse, microarray data analysis showed a total of 45 significantly differentially expressed genes, 25 highly expressed (fold change > or =2; P = 0.0025), and 20 downregulated (fold change < or =0.5; P = 0.0025). These genes belong to several different functional categories such as the regulation of immunological response, transcription, intracellular calcium ion mobilization, regulation of cell cycle and proliferation, NF-kappab signal transduction cascades, and apoptosis. In particular, the upregulation of the antiapoptotic gene NuprI and the downregulation of the proapoptotic gene Bnip3 were found. This observation was supported by an in vitro apoptosis assay that showed downregulation of apoptosis in hepatocytes of HBV transgenic mouse compared with wt mice treated with staurosporine. In conclusion, our experimental approach allowed identification of new genes modulated by HBV and showed that the apoptotic process was deregulated in transgenic mouse hepatocytes. These data shed light on one possible mechanism by which HBV induces hepatocarcinogenesis.
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Affiliation(s)
- Michele Barone
- Sezione di Gastroenterologia, Dipartimento di Emergenza e di Trapianto d’Organo (D.E.T.O.), Università di Bari, Bari, Italia
| | - Daniela Spano
- CEINGE Biotecnologie Avanzate s.c.ra.l., Napoli, Italia
| | - Maria D’Apolito
- Laboratorio di Medicina Molecolare, Dipartimento di Scienze Mediche e del Lavoro, Università di Foggia, Foggia, Italia
| | - Marta Centra
- Laboratorio di Medicina Molecolare, Dipartimento di Scienze Mediche e del Lavoro, Università di Foggia, Foggia, Italia
| | - Carla Lasalandra
- Laboratorio di Medicina Molecolare, Dipartimento di Scienze Mediche e del Lavoro, Università di Foggia, Foggia, Italia
| | - Mario Capasso
- CEINGE Biotecnologie Avanzate s.c.ra.l., Napoli, Italia
| | - Alfredo Di Leo
- Sezione di Gastroenterologia, Dipartimento di Emergenza e di Trapianto d’Organo (D.E.T.O.), Università di Bari, Bari, Italia
| | - Stefano Volinia
- Dipartimento di Morfologia ed Embriologia, Università di Ferrara, Ferrara, Italia
| | - Diego Arcelli
- Dipartimento di Morfologia ed Embriologia, Università di Ferrara, Ferrara, Italia
| | - Natalia Rosso
- Centro Studi Fegato, AREA Science Park, Campus Basovizza Bldg Q, Università di Trieste, Trieste, Italia
| | - Antonio Francavilla
- Sezione di Gastroenterologia, Dipartimento di Emergenza e di Trapianto d’Organo (D.E.T.O.), Università di Bari, Bari, Italia
| | - Claudio Tiribelli
- Centro Studi Fegato, AREA Science Park, Campus Basovizza Bldg Q, Università di Trieste, Trieste, Italia
| | - Achille Iolascon
- CEINGE Biotecnologie Avanzate s.c.ra.l., Napoli, Italia
- Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli, Napoli, Italia
- Address correspondence and reprint requests to Prof Achille Iolascon, Chair of Medical Genetics, University Federico II – Naples, CEINGE Biotecnologie Avanzate s.c.ra.l., Via Comunale Margherita 482, 80145 Napoli, Italy. Phone: +39-0813722897; Fax: +39-0813722804; e-mail:
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25
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Hu Z, Zhang Z, Kim JW, Huang Y, Liang TJ. Altered proteolysis and global gene expression in hepatitis B virus X transgenic mouse liver. J Virol 2006; 80:1405-13. [PMID: 16415018 PMCID: PMC1346956 DOI: 10.1128/jvi.80.3.1405-1413.2006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Hepatitis B virus X (HBX) is essential for the productive infection of hepatitis B virus (HBV) in vivo and has a pleiotropic effect on host cells. We have previously demonstrated that the proteasome complex is a cellular target of HBX, that HBX alters the proteolytic activity of proteasome in vitro, and that inhibition of proteasome leads to enhanced viral replication, suggesting that HBX and proteasome interaction plays a crucial role in the life cycle and pathogenesis of HBV. In the present study, we tested the effect of HBX on the proteasome activities in vivo in a transgenic mouse model in which HBX expression is developmentally regulated by the mouse major urinary promoter in the liver. In addition, microarray analysis was performed to examine the effect of HBX expression on the global gene expression profile of the liver. The results showed that the peptidase activities of the proteasome were reduced in the HBX transgenic mouse liver, whereas the activity of another cellular protease was elevated, suggesting a compensatory mechanism in protein degradation. In the microarray analysis, diverse genes were altered in the HBX mouse livers and the number of genes with significant changes increased progressively with age. Functional clustering showed that a number of genes involved in transcription and cell growth were significantly affected in the HBX mice, possibly accounting for the observed pleiotropic effect of HBX. In particular, insulin-like growth factor-binding protein 1 was down-regulated in the HBX mouse liver. The down-regulation was similarly observed during acute woodchuck hepatitis virus infection. Other changes including up-regulation of proteolysis-related genes may also contribute to the profound alterations of liver functions in HBV infection.
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Affiliation(s)
- Zongyi Hu
- Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases/NIH, Bldg. 10, Rm. 9B16, Bethesda, MD 20892, USA
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Abstract
The heat shock proteins (HSPs) are ubiquitous molecules induced in cells exposed to various stress conditions, including carcinogenesis. The HSP70 and HSP27 among HSPs are of special relevance in human cancer inhibiting apoptosis. The aim of this study is to investigate the expressions of HSP70 and HSP27 in hepatocellular carcinoma (HCC) in association to tumor cell proliferation and apoptosis. We examined the expressions of HSP70 and HSP27 by immunohistochemical staining in 71 cases of HCC, and then related their expressions to clinicopathologic parameters and expressions of p53, Ki-67 and Apotag. HSP70 and HSP27 were frequently stained in the cytoplasm and nuclei of tumor cells, but not in the non-neoplastic hepatocytes. Immunoreactivities of HSP70 and HSP27 were observed in 56.3% and 61.9% of HCCs, respectively. HSP70 immunoreactivity correlated with high Ki-67 labeling indices (LIs) (p=0.0159), large tumor size (p=0.0129), presence of portal vein invasion (p=0.0231), and high tumor stage (p=0.0392). HSP27 immunoreactivity significantly related with the subgroup of HBV-associated HCCs (p=0.0003), but not with the others. Both HSP70 and HSP27 immunoreactivities showed no relation to Apotag LIs or p53 immunoreactivity. In conclusion, expressions of HSP70 and HSP27 may play an important role in hepatocarcinogenesis, and especially HSP70 showed a close relationship to the pathological parameters associated with tumor progression and high Ki-67 LIs. Our results could be additional evidence that HSP70 expressions can contribute to not only hepatocarcinogenesis but also tumor progression by promoting tumor cell proliferation.
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Affiliation(s)
- Mee Joo
- Department of Pathology, Inje University Ilsanpaik Hospital, Goyang, Korea.
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Wilkinson DS, Ogden SK, Stratton SA, Piechan JL, Nguyen TT, Smulian GA, Barton MC. A direct intersection between p53 and transforming growth factor beta pathways targets chromatin modification and transcription repression of the alpha-fetoprotein gene. Mol Cell Biol 2005; 25:1200-12. [PMID: 15657445 PMCID: PMC544019 DOI: 10.1128/mcb.25.3.1200-1212.2005] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We purified the oncoprotein SnoN and found that it functions as a corepressor of the tumor suppressor p53 in the regulation of the hepatic alpha-fetoprotein (AFP) tumor marker gene. p53 promotes SnoN and histone deacetylase interaction at an overlapping Smad binding, p53 regulatory element (SBE/p53RE) in AFP. Comparison of wild-type and p53-null mouse liver tissue by using chromatin immunoprecipitation (ChIP) reveals that the absence of p53 protein correlates with the disappearance of SnoN at the SBE/p53RE and loss of AFP developmental repression. Treatment of AFP-expressing hepatoma cells with transforming growth factor-beta1 (TGF-beta1) induced SnoN transcription and Smad2 activation, concomitant with AFP repression. ChIP assays show that TGF-beta1 stimulates p53, Smad4, P-Smad2 binding, and histone H3K9 deacetylation and methylation, at the SBE/p53RE. Depletion, by small interfering RNA, of SnoN and/or p53 in hepatoma cells disrupted repression of AFP transcription. These findings support a model of cooperativity between p53 and TGF-beta effectors in chromatin modification and transcription repression of an oncodevelopmental tumor marker gene.
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Affiliation(s)
- Deepti S Wilkinson
- Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
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Affiliation(s)
- Michael J Bouchard
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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N/A. N/A. Shijie Huaren Xiaohua Zazhi 2004; 12:938-940. [DOI: 10.11569/wcjd.v12.i4.938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/26/2023] Open
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Szabó E, Páska C, Kaposi Novák P, Schaff Z, Kiss A. Similarities and differences in hepatitis B and C virus induced hepatocarcinogenesis. Pathol Oncol Res 2004; 10:5-11. [PMID: 15029254 DOI: 10.1007/bf02893401] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Accepted: 02/10/2004] [Indexed: 12/16/2022]
Abstract
Hepatocellular carcinoma (HCC), the major manifestation of primary liver cancer, is one of the most frequent and malignant diseases worldwide. Among other environmental factors, hepatitis viruses, as the hepatitis B (HBV) and hepatitis C (HCV) viruses, are to be listed in the etiology of HCC. Both of these viruses cause a wide spectrum of clinical manifestations, ranging from healthy carrier state to acute and chronic hepatitis, cirrhosis and HCC. HBV and HCV are different viruses in structure: HBV contains a DNA genome which replicates through an RNA intermediate and requires an active viral reverse transcriptase (RT) polymerase enzyme, while HCV is an RNA virus which has no RT activity and replicates on the cellular membrane by RNA replication. In this review we discuss how these two biologically diverse viruses use common pathways to induce hepatocarcinogenesis despite their significant structural and viral cycle differences. A summary is also given of several observable common and different features. Direct integration of HBV viral sequences into the host genome increases the genomic instability, which does not occur in HCV infection. However, viral proteins may directly play a significant role in the induction of carcinogenesis by both viruses.
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Affiliation(s)
- Erzsébet Szabó
- 2nd Department of Pathology, Semmelweis University, Budapest, Hungary
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Wang L, Li K, Cheng J, Zhang J, Liu M. Cloning and identification of human gene 5 transactivated by hepatitis B virus X protein. Shijie Huaren Xiaohua Zazhi 2004; 12:74-77. [DOI: 10.11569/wcjd.v12.i1.74] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To explore the new target genes transactivated by HBx, suppression subtractive hybridization (SSH) method and to pave the way for elucidating the pathogenesis mechanism of HBV infection.
METHODS: The mRNA was isolated from HepG2 cells transfected with pcDNA3.1(-)-X and pcDNA3.1(-) empty vector, respectively, using SSH and bioinformatics technique, and the differentially expressed DNA sequence between the two groups was analyzed. The obtained sequences were searched for homologous DNA sequence from GenBank, one of which was a novel gene with unknown function. The new gene with no homology with known genes in this database was confirmed and electric polymerase chain reaction (PCR) was conducted for the cloning of the full-length DNA for the new gene and in conjunction with Kozak role and the exist of polyadenyl signal sequence. The reverse transcription PCR (RT-PCR) was used to amplify the new gene, named as XTP5, from the mRNA of HepG2 cells transfected.
RESULTS: The new gene was cloned in combination of molecular biological and bioinformatics methods.
CONCLUSION: HBx is a potential transactivator. A new gene has been recognized as the new target transactivated by HBx protein. These results pave the way for study on the transactivation of HBx protein.
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Liu Y, Cheng J, Wang L, Wang JJ, Lu YY, Li K. Cloning and identification of human gene 1 transactivated by hepatitis B virus X antigen. Shijie Huaren Xiaohua Zazhi 2003; 11:1107-1113. [DOI: 10.11569/wcjd.v11.i8.1107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To study the transactivation effects of HBxAg, and clone the target genes of HBxAg transactivating effects, in order to help understand the mechanism of pathogenesis of HBxAg.
METHODS Polymerase chain reaction (PCR) was employed to amplify the coding sequence of HBxAg. The hepatoblastoma cell HepG2 was transfected by pcDNA3.1(-) and pcDNA3.1(-)-X, respectively. Total mRNA was purified from the HepG2 cells transfected and suppression subtractive hybridization(SSH) method was used to analyze the differentially expressed DNA sequence between the two groups. The sequences were searched for homologous DNA sequence from GenBank. The new DNA sequence was confirmed and the full-length coding sequence was identified according to the Kozak rule and the existence of polyadenyl signal sequences. Reverse transcription PCR (RT-PCR)was used to amplify the new gene by using mRNA from HepG2 cell as the template. The coding sequence for the new gene was deduced according to the nucleotide sequence.
RESULTS PCR technique was employed to amplify the coding sequence for HBxAg by using pCP10 plasmid containing whole HBV genome as the template. The recombinant plasmid expressing HBxAg was confirmed by restriction enzyme digestion and sequencing. HepG2 cells were transfected with pcDNA3.1(-) and pcDNA3.1(-)-X by lipofectamine, respectively. Total mRNA was purified from transfected HepG2 cell, and suppression subtractive hybridization method was used for the screening and identification of differentially expressed genes by these two cell groups. After sequencing, each DNA sequence was compared with the genes deposited in the GenBank and the new gene with no homology with known genes in this database was identified. Electric polymerase chain reaction was conducted for the cloning of the full-length DNA of the new gene and in conjunction with Kozak rule and the existence of polyadenyl signal sequence. RT-PCR technique was used to amplify the new gene, named as XTP1, from the mRNA of HepG2 cells. The sequence for the XTP1 gene was deposited into GenBank, and the accession number is AF488828.
CONCLUSION A new gene named XTP1 which is transac-tivated by hepatitis B virus X protein has been successfully cloned by molecular biological methods. These results pave the way for the study of the molecular mechanism of HBxAg transactivating effects and the development of new therapy for chronic hepatitis B.
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Affiliation(s)
- Yan Liu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Jun Cheng
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Lin Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Jian-Jun Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Yin-Ying Lu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
| | - Ke Li
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, Beijing 100039, China
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Lu YY, Chen TY, Cheng J, Liang YD, Wang L, Liu Y, Zhang J, Shao Q, Li K, Zhang LX. Cloning of a gene coding for novel mutant of asialoglycoprotein receptor 2 binding to hepatitis B virus X protein in hepatocytes. Shijie Huaren Xiaohua Zazhi 2003; 11:1126-1130. [DOI: 10.11569/wcjd.v11.i8.1126] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM The pathogenesis of HBV-induced malignant transformation is incompletely understood. The X protein of hepatitis B virus (HBxAg) is a multifunctional protein that can influence a variety of signal transduction pathways within the cell and is essential for establishing natural viral infection, it also has been implicated in the development of liver cancer associated with chronic infection. Further understanding of the interaction between HBxAg and proteins in hepatocytes is of great significance for the prevention of the development of hepatocellular carcinoma (HCC).
METHODS HBxAg bait plasmid was constructed by ligating the HBxAg gene with a yeast expression vector pGBKT7, then transformed into yeast AH109 (a type). The transformed yeast cells were amplified and mated with yeast cells Y187(α type) containing liver cDNA library plasmid pCAT2 in 2×YPDA medium. Diploid yeast cells were plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing x-α-gal for selection twice. Plasmid of true positive blue colonies was extracted and analysed by DNA sequencing and blast in GenBank. After the complete sequence of the novel mutant of asialoglycoprotein receptor 2 (ASGPR2) was amplified from the mRNA of HepG2 cell by reverse transcription polymerase chain reaction (RT-PCR) and cloned into pGADT7 vector, the recombined plasmid was translated by using reticulocyte lysate and analysed by immunoprecipitation technique in vitro together with HBxAg.
RESULTS Eighteen genes in forty-one positive colonies were obtained, one of them is a novel mutant of ASGPR2, which is 80 % homologous to natural ASGPR2. The complete sequence of the mutant was amplified from the mRNA of HepG2 cell by RT-PCR successfully. The interaction between HBx and ASGPR2 mutant was further confirmed by immunoprecipitation technique.
CONCLUSION Interaction between HBx and ASGPR2 mutant can be observed in both yeast cell and in vitro.
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Affiliation(s)
- Yin-Ying Lu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Tian-Yan Chen
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Jun Cheng
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Yao-Dong Liang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Lin Wang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Yan Liu
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Jian Zhang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Qing Shao
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Ke Li
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
| | - Ling-Xia Zhang
- Gene Therapy Research Center, Institute of Infectious Diseases, The 302 Hospital of PLA, 100 Xisihuan Zhonglu, Beijing 100039, China
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35
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Hafner A, Brandenburg B, Hildt E. Reconstitution of gene expression from a regulatory-protein-deficient hepatitis B virus genome by cell-permeable HBx protein. EMBO Rep 2003; 4:767-73. [PMID: 12872136 PMCID: PMC1326343 DOI: 10.1038/sj.embor.embor903] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2003] [Revised: 05/13/2003] [Accepted: 06/18/2003] [Indexed: 11/09/2022] Open
Abstract
Various functions are ascribed to the HBx regulatory protein of the hepatitis B virus (HBV). Due to the low expression level of HBx, it has been difficult to correlate spatial and temporal HBx expression levels with specific functions. Based on a novel cell-permeable peptide, known as the translocation motif (TLM), cell-permeable HBx fusion proteins were generated. The TLM-HBx fusion protein is rapidly internalized from the medium into almost all cells, whereas no significant internalization was seen with wild-type HBx. The major fraction of internalized HBx protein moves from the cytoplasm to the nucleus. The cytosolic fraction, however, activates c-RAF1/extracellular-signal-related kinase 2 signalling and causes activation of activator protein 1 (AP1) and nuclear factor-kappaB. The TLM-HBx protein rescues HBV gene expression from an activator-deficient HBV genome. These results indicate that cell-permeable regulatory proteins provide a novel, efficient tool for a clearly defined, dose-dependent analysis of regulatory protein function, without affecting the integrity of the cell, and can be used for the safe reconstitution of virus production from a regulatory-protein-deficient virus genome.
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Affiliation(s)
- Angela Hafner
- Robert Koch-Institut, Nordufer 20,
D-13353 Berlin, Germany
| | | | - Eberhard Hildt
- Robert Koch-Institut, Nordufer 20,
D-13353 Berlin, Germany
- Tel: +49 304547 2528; Fax: +49 304547 2328;
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36
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Bouchard MJ, Puro RJ, Wang L, Schneider RJ. Activation and inhibition of cellular calcium and tyrosine kinase signaling pathways identify targets of the HBx protein involved in hepatitis B virus replication. J Virol 2003; 77:7713-9. [PMID: 12829810 PMCID: PMC161925 DOI: 10.1128/jvi.77.14.7713-7719.2003] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Human hepatitis B virus (HBV) HBx protein is a multifunctional protein that activates cellular signaling pathways and is thought to be essential for viral infection. Woodchuck HBV mutants that lack HBx are unable to replicate in vivo or are severely impaired. HBV replication in HepG2 cells, a human hepatoblastoma cell line, is stimulated 5- to 10-fold by HBx protein. We have utilized the HepG2, HBx-dependent HBV replication system to study the effects of activators and inhibitors of cytosolic calcium and tyrosine kinase signaling pathways on viral replication. By transfecting either a wild-type HBV genome or an HBV genome that does not express HBx and then treating transfected cells with activators or inhibitors of signaling pathways, we identified compounds that either impair wild-type HBV replication or rescue HBx-deficient HBV replication. Geldanamycin or herbimycin A, tyrosine kinase inhibitors, blocked HBV replication. Derivatives of cyclosporine, i.e., cyclosporine A, cyclosporine H, and SDZ NIM811, which block cytosolic calcium signaling and specifically the mitochondrial permeability transition pore (SDZ NIM811), also impaired HBV replication. Treatment of cells with compounds that increase cytosolic calcium levels by a variety of mechanisms rescued replication of an HBx-deficient HBV mutant. Transcription of viral RNA and production of viral capsids were only minimally affected by these treatments. These results define a functional signaling circuit for HBV replication that includes calcium signaling and activation of cytosolic signaling pathways involving Src kinases, and they suggest that these pathways are stimulated by HBx acting on the mitochondrial transition pore.
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Affiliation(s)
- Michael J Bouchard
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA
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Li J, Xu Z, Zheng Y, Johnson DL, Ou JH. Regulation of hepatocyte nuclear factor 1 activity by wild-type and mutant hepatitis B virus X proteins. J Virol 2002; 76:5875-81. [PMID: 12021320 PMCID: PMC136206 DOI: 10.1128/jvi.76.12.5875-5881.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The hepatitis B virus (HBV) core promoter regulates the transcription of two related RNA products named precore RNA and core RNA. Previous studies indicate that a double-nucleotide mutation that occurs frequently during chronic HBV infection converts a nuclear receptor binding site in the core promoter to the binding site of the transcription factor hepatocyte nuclear factor-1 (HNF-1) and specifically suppresses the transcription of the precore RNA. This mutation also changes two codons in the overlapping X protein coding sequence. In this report, we demonstrate that the X protein and its mutant X(mt) can physically bind to HNF-1 both in vitro and in vivo. Further analyses indicate that both X and X(mt) can enhance the gene transactivation and the DNA binding activities of HNF-1. This finding demonstrates for the first time that the X protein can stimulate the DNA binding activity of a homeodomain transcription factor. Interestingly, while both X and X(mt) can stimulate the HNF-1 activities, they differ in their effects: a smaller amount of X(mt) is needed to generate greater transactivation and DNA binding activities of HNF-1. This functional difference between X and X(mt) may have important implications in HBV pathogenesis and is apparently why they have different effects on the core promoter bearing the HNF-1 binding site.
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Affiliation(s)
- Jie Li
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
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38
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Tralhao JG, Roudier J, Morosan S, Giannini C, Tu H, Goulenok C, Carnot F, Zavala F, Joulin V, Kremsdorf D, Bréchot C. Paracrine in vivo inhibitory effects of hepatitis B virus X protein (HBx) on liver cell proliferation: an alternative mechanism of HBx-related pathogenesis. Proc Natl Acad Sci U S A 2002; 99:6991-6. [PMID: 12011457 PMCID: PMC124516 DOI: 10.1073/pnas.092657699] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The role of the hepatitis B virus X protein (HBx) in the pathogenesis of hepatitis B virus (HBV) infection remains unclear. HBx exhibits pleiotropic biological effects, whose in vivo relevance is a matter for debate. In the present report, we have used a combination of HBx-expressing transgenic mice and liver cell transplantation to investigate the in vivo impact of HBx expression on liver cell proliferation and viability in a regenerative context. We show that moderate HBx expression inhibits liver regeneration after partial hepatectomy in HBx-expressing transgenic mice. We also demonstrate that the transplantation of HBx-expressing liver cells, isolated from HBx transgenic mice, is sufficient to inhibit overall recipient liver regeneration after partial hepatectomy. Moreover, the injection of serum samples drawn from HBx-expressing transgenic mice mimicked the inhibitory effect of HBx on liver regeneration. Finally, the incubation of primary rat hepatocytes with the supernatant of HBx-expressing liver cells inhibits cellular DNA synthesis. Taken together, our results demonstrate a paracrine inhibitory effect of HBx on liver cell proliferation and lead us to propose HBV as one of the few viruses implicated in human cancer which act, at least in part, through paracrine biological pathways.
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Affiliation(s)
- J Guilherme Tralhao
- Institut Pasteur-Institut National de la Santé et de la Recherche Médicale Unit 370, Necker Institute, 75015 Paris, France
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39
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Kim JH, Rho HM. Activation of the human transforming growth factor alpha (TGF-alpha) gene by the hepatitis B viral X protein (HBx) through AP-2 sites. Mol Cell Biochem 2002; 231:155-61. [PMID: 11952158 DOI: 10.1023/a:1014477218369] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The HBx protein is known as a transactivator and potential oncogene, and TGF-alpha as a potent mitogen in hepatocellular carcinoma. By assays of serial deletion of the promoter of TGF-alpha gene and the cotransfection of HBx and AP-2 expression vectors, we observed that the HBx significantly activated the promoter activity through AP-2 sites located in the proximal region of the TGF-alpha promoter (-136 to -30). This effect was also observed in the heterologous promoter assay system containing AP-2 sites. The mutation analyses of three AP-2 sites in the promoter revealed that all three AP-2 sites contributed to the activation of the TGF-a gene in the presence of HBx. Accordingly, the mRNA level of TGF-alpha was significantly elevated in the HBx-expressing cell, HepG2-HBx and the HBV-producing cell, HepG2-K8. These results suggest that the HBx protein could increase the mitogenic effect of TGF-alpha by the transactivation of the gene through AP-2 binding sites and consequently, these interactions may accelerate the process of hepatocarcinogenesis.
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Affiliation(s)
- Jun Hwan Kim
- School of Biological Sciences, Seoul National University, Korea
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40
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Pál J, Somogyi C, Szmolenszky A A, Szekeres G, Sípos J, Hegedüs G, Martzinovits I, Molnár J, Németh P. Immunohistochemical assessment and prognostic value of hepatitis B virus X protein in chronic hepatitis and primary hepatocellular carcinomas using anti-HBxAg monoclonal antibody. Pathol Oncol Res 2002; 7:178-84. [PMID: 11692143 DOI: 10.1007/bf03032346] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hepatitis B virus (HBV) is the most meaningful risk factor in chronic hepatitis, cirrhosis and primary hepatocellular carcinoma (PHC). The hepatitis B virus X protein (HBxAg) is a multifunctional protein with many important functions in hepatocellular carcinogenesis. A monoclonal anti-HBxAg antibody was developed in our laboratory and characterized by different methods. Using this antibody HBxAg was detected in formaldehyde fixed paraffin embedded tissue sections of 72 liver biopsies from patients with acute hepatitis, chronic hepatitis, cirrhosis and primary hepatocellular carcinoma. The co-expression of hepatitis B surface antigen (HBsAg), hepatitis B core antigen (HBcAg) and HBxAg was compared. The histological and cytological localization of the detected HBxAg showed a characteristic distribution in different stages of HBV infection. Strong and diffuse nuclear reaction was detected in PHC cases in contrast to the focal, cytoplasmic and nuclear labeling in the acute and chronic B hepatitis cases. Our antibody seems to be a suitable prognostic marker for routine pathohistological diagnosis and for comparative pathological and epidemiological research on the development of PHC.
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Affiliation(s)
- J Pál
- University of Pécs, Faculty of Medicine, Department of Immunology and Biotechnology Szigeti u. 12., Pécs, H-7643, Hungary
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41
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Nijhara R, Jana SS, Goswami SK, Rana A, Majumdar SS, Kumar V, Sarkar DP. Sustained activation of mitogen-activated protein kinases and activator protein 1 by the hepatitis B virus X protein in mouse hepatocytes in vivo. J Virol 2001; 75:10348-58. [PMID: 11581403 PMCID: PMC114609 DOI: 10.1128/jvi.75.21.10348-10358.2001] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2001] [Accepted: 07/30/2001] [Indexed: 12/18/2022] Open
Abstract
Transcriptional activation of diverse cellular genes by the X protein (HBx) of hepatitis B virus (HBV) has been suggested as one of the mechanisms for HBV-associated hepatocellular carcinoma. However, such functions of HBx have been studied using transformed cells in culture and have not been examined in the normal adult hepatocytes, a natural host of HBV. Using an efficient hepatocyte-specific virus-based gene delivery system developed in our laboratory earlier, we studied the HBx action in vivo. We demonstrate that following virosome-mediated delivery of HBx DNA, a large population (>50%) of hepatocytes express the HBx protein in a dose-dependent manner, which induces a significant increase in the activity of extracellular signal-regulated kinases (ERKs) in the livers of HBx-transfected mice. Inhibition of HBx-induced ERK activation following intravenous administration of PD98059, a mitogen-activated protein kinase kinase kinase (MEK) inhibitor, confirmed the requirement for MEK in the activation of ERKs by HBx. Induction of ERK activity by HBx was sustained for up to 30 days. Interestingly, sustained activation of c-Jun N-terminal kinases (JNKs) for up to 30 days was also noted. Such constitutive ERK and JNK activation as a consequence of continued HBx expression also led to sustained stimulation of further downstream events, such as increased levels of c-Jun and c-Fos proteins along with the persistent induction of activator protein 1 binding activity. Taken together, our data suggest a critical role of these molecules in HBx-mediated cell transformation.
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Affiliation(s)
- R Nijhara
- Department of Biochemistry, University of Delhi South Campus, New Delhi-110021, India
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Bouchard M, Giannakopoulos S, Wang EH, Tanese N, Schneider RJ. Hepatitis B virus HBx protein activation of cyclin A-cyclin-dependent kinase 2 complexes and G1 transit via a Src kinase pathway. J Virol 2001; 75:4247-57. [PMID: 11287574 PMCID: PMC114170 DOI: 10.1128/jvi.75.9.4247-4257.2001] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Numerous studies have demonstrated that the hepatitis B virus HBx protein stimulates signal transduction pathways and may bind to certain transcription factors, particularly the cyclic AMP response element binding protein, CREB. HBx has also been shown to promote early cell cycle progression, possibly by functionally replacing the TATA-binding protein-associated factor 250 (TAF(II)250), a transcriptional coactivator, and/or by stimulating cytoplasmic signal transduction pathways. To understand the basis for early cell cycle progression mediated by HBx, we characterized the molecular mechanism by which HBx promotes deregulation of the G0 and G1 cell cycle checkpoints in growth-arrested cells. We demonstrate that TAF(II)250 is absolutely required for HBx activation of the cyclin A promoter and for promotion of early cell cycle transit from G0 through G1. Thus, HBx does not functionally replace TAF(II)250 for transcriptional activity or for cell cycle progression, in contrast to a previous report. Instead, HBx is shown to activate the cyclin A promoter, induce cyclin A-cyclin-dependent kinase 2 complexes, and promote cycling of growth-arrested cells into G1 through a pathway involving activation of Src tyrosine kinases. HBx stimulation of Src kinases and cyclin gene expression was found to force growth-arrested cells to transit through G1 but to stall at the junction with S phase, which may be important for viral replication.
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Affiliation(s)
- M Bouchard
- Department of Microbiology, NYU School of Medicine, New York, New York 10016, USA
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43
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Abstract
Virus infections induce a proinflammatory response including expression of cytokines and chemokines. The subsequent leukocyte recruitment and antiviral effector functions contribute to the first line of defense against viruses. The molecular virus-cell interactions initiating these events have been studied intensively, and it appears that viral surface glycoproteins, double-stranded RNA, and intracellular viral proteins all have the capacity to activate signal transduction pathways leading to the expression of cytokines and chemokines. The signaling pathways activated by viral infections include the major proinflammatory pathways, with the transcription factor NF-kappaB having received special attention. These transcription factors in turn promote the expression of specific inducible host proteins and participate in the expression of some viral genes. Here we review the current knowledge of virus-induced signal transduction by seven human pathogenic viruses and the most widely used experimental models for viral infections. The molecular mechanisms of virus-induced expression of cytokines and chemokines is also analyzed.
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Affiliation(s)
- T H Mogensen
- Department of Medical Microbiology and Immunology, University of Aarhus, DK-8000 Aarhus C, Denmark
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Chang SF, Netter HJ, Hildt E, Schuster R, Schaefer S, Hsu YC, Rang A, Will H. Duck hepatitis B virus expresses a regulatory HBx-like protein from a hidden open reading frame. J Virol 2001; 75:161-70. [PMID: 11119585 PMCID: PMC113909 DOI: 10.1128/jvi.75.1.161-170.2001] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Duck hepatitis B viruses (DHBV), unlike mammalian hepadnaviruses, are thought to lack X genes, which encode transcription-regulatory proteins believed to contribute to the development of hepatocellular carcinoma. A lack of association of chronic DHBV infection with hepatocellular carcinoma development supports this belief. Here, we demonstrate that DHBV genomes have a hidden open reading frame from which a transcription-regulatory protein, designated DHBx, is expressed both in vitro and in vivo. We show that DHBx enhances neither viral protein expression, intracellular DNA synthesis, nor virion production when assayed in the full-length genome context in LMH cells. However, similar to mammalian hepadnavirus X proteins, DHBx activates cellular and viral promoters via the Raf-mitogen-activated protein kinase signaling pathway and localizes primarily in the cytoplasm. The functional similarities as well as the weak sequence homologies of DHBx and the X proteins of mammalian hepadnaviruses strongly suggest a common ancestry of ortho- and avihepadnavirus X genes. In addition, our data disclose similar intracellular localization and transcription regulatory functions of the corresponding proteins, raise new questions as to their presumed role in hepatocarcinogenesis, and imply unique opportunities for deciphering of their still-enigmatic in vivo functions.
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Affiliation(s)
- S F Chang
- Heinrich-Pette-Institut für experimentelle Virologie und Immunologie an der Universität Hamburg, Hamburg, Germany
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