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Kumar V. HBx protein as a therapeutic target for functional cure of hepatitis B virus infection. Virology 2025; 604:110438. [PMID: 39908774 DOI: 10.1016/j.virol.2025.110438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2024] [Revised: 01/22/2025] [Accepted: 01/24/2025] [Indexed: 02/07/2025]
Abstract
Hepatitis B virus (HBV) is a major cause of acute and chronic liver disease and represents a major public health problem worldwide. Current antiviral therapies with nucleos(t)ide analogues can effectively suppressing viremia but are not curative, and have little or no impact upon the HBV cccDNA minichromosome or the portions of integrated HBV DNA. Several alternative therapeutic strategies targeted at viral components and life cycle are under intense investigation. This article highlights the reasons for considering HBx as a therapeutic target as this may allow targeting of both virus and disease. Recent studies focused at HBx have led to the identification of several new pharmacological agents and development of some novel therapeutic approaches that now deserve to be taken to the next level for better management of hepatitis B. Besides, new therapies could be combined with other established therapies, to provide a functional cure from hepatitis B infection.
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Affiliation(s)
- Vijay Kumar
- Department of Molecular and Cellular Medicine, Institute of Liver and Biliary Sciences, New Delhi, India.
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Bai T, Mai RY, Tang ZH, Wang XB, Chen J, Ye JZ, Wei M, Zhang B, Li K, Gu ZM, Wu FX, Li LQ. Ubiquitination of P53 Regulated by Ubiquitin-Specific Protease 14 Delays the Invasion of Hepatitis B Virus and the Development of Hepatitis. Viral Immunol 2024; 37:432-439. [PMID: 39601371 DOI: 10.1089/vim.2024.0066] [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] [Indexed: 11/29/2024] Open
Abstract
This study aims to explore the mechanism underlying the role of ubiquitin-specific protease 14 (USP14) in regulating P53 expression and influencing the development of hepatitis B. The animal and cell models of hepatitis B were constructed. The mRNA and protein expression of USP14, mouse double minute 2 (MDM2), and P53 were detected by western blot and qPCR. The USP14 overexpression vector was constructed. The pathological changes of liver tissue were detected by HE and Masson staining. Protein immunoprecipitation was used to detect the interaction between MDM2 and P53, as well as between MDM2 and USP14. The ubiquitination levels of P53 after USP14 overexpression were detected. qPCR and western blot were used to detect the expression of MDM2, Bcl-2, P53, Bax, and Caspase-1 in vivo and in vitro. Compared with the control group, the model group showed increased cell proliferation, increased expression of MDM2 and Bcl-2 in cells and liver tissue, and decreased expression of P53, Bax, and Caspase-1. Compared with the model group, overexpression of USP14 resulted in a decrease in MDM2 expression and an increase in P53 expression. After transfection with the USP14 overexpression plasmid, cell proliferation was inhibited, and the expression of MDM2 and Bcl-2 was decreased in cells and liver tissue, while the expression of P53, Bax, and Caspase-1 was increased. In the model of hepatitis B, USP14 upregulation downregulated MDM2 and promoted P53 deubiquitination to delay the invasion of hepatitis B virus and the development of hepatitis.
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Affiliation(s)
- Tao Bai
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Rong-Yun Mai
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Zhi-Hong Tang
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Xiao-Bo Wang
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Jie Chen
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Jia-Zhou Ye
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Meng Wei
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Bin Zhang
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Kai Li
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Zhao-Min Gu
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Fei-Xiang Wu
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
| | - Le-Qun Li
- Hepatobiliary Pancreatic Splenic Surgery, Guangxi Medical University Cancer Hospital, Nanning, China
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Shi L, Fang X, Du L, Yang J, Xue J, Yue X, Xie D, Hui Y, Meng K. An E3 ligase TRIM1 promotes colorectal cancer progression via K63-linked ubiquitination and activation of HIF1α. Oncogenesis 2024; 13:16. [PMID: 38769340 PMCID: PMC11106307 DOI: 10.1038/s41389-024-00517-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 05/06/2024] [Accepted: 05/10/2024] [Indexed: 05/22/2024] Open
Abstract
Accumulating studies have shown that E3 ligases play crucial roles in regulating cellular biological processes and signaling pathways during carcinogenesis via ubiquitination. Tripartite-motif (TRIM) ubiquitin E3 ligases consist of over 70 members. However, the clinical significance and their contributions to tumorigenesis remain largely unknown. In this study, we analyzed the RNA-sequencing expression of TRIM E3 ligases in colorectal cancer (CRC) and identified 10 differentially expressed genes, among which TRIM1 expression predicted poor prognosis of CRC patients. We demonstrated that TRIM1 expression is positively associated with CRC pathological stages, and higher expression is positively correlated with infiltrating levels of immune cells and immunotherapy biomarkers. TRIM1 expression promotes the proliferation and migration of colorectal cancer cells in vitro and in vivo. Transcriptional analysis showed that TRIM1 is responsible for metabolism promotion and immune suppression. Mechanistically, we found that TRIM1 binds HIF1α and mediates its K63-linked ubiquitination, which is required for HIF1α nuclear translocation and subsequent activation. Ubiquitination occurs at Lys214 in the loop between the two PAS domains of HIF1α, and mutation of Lys214 severely disturbs the function of HIF1α. Besides, HIF1α ubiquitination enhances its binding with proteins involved in cellular trafficking and nucleocytoplasmic transport pathway. Collectively, our results indicate TRIM1's role in predicting prognosis and reveal how TRIM1 functions to upregulate HIF1α expression and promote tumor cell proliferation.
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Affiliation(s)
- Liuliu Shi
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
- Hubei Key Laboratory of Embryonic Stem Cell Research, School of Basic Medicine, Hubei University of Medicine, Shiyan, China
- Hubei Provincial Clinical Research Center for Umbilical Cord Blood Hematopoietic Stem Cells, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Xianglan Fang
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Lijie Du
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
- Hubei Key Laboratory of Embryonic Stem Cell Research, School of Basic Medicine, Hubei University of Medicine, Shiyan, China
- Hubei Provincial Clinical Research Center for Umbilical Cord Blood Hematopoietic Stem Cells, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Jin Yang
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Juan Xue
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Xiaokai Yue
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China
| | - Duoshuang Xie
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China.
| | - Yuanjian Hui
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China.
- Department of General Surgery, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China.
| | - Kun Meng
- Institute of Infection and Immunity, Department of Infection Control, School of Public Health, Affiliated Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China.
- Hubei Key Laboratory of Embryonic Stem Cell Research, School of Basic Medicine, Hubei University of Medicine, Shiyan, China.
- Hubei Provincial Clinical Research Center for Umbilical Cord Blood Hematopoietic Stem Cells, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei, China.
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Kong X, Liu Z, Zhang R, Xie F, Liang R, Zhang Y, Yu L, Yang W, Li X, Chen Q, Li B, Hong Y, Li M, Xia X, Gu L, Fu L, Li X, Shen Y, Wu T, Yu C, Li W. JMJD2D stabilises and cooperates with HBx protein to promote HBV transcription and replication. JHEP Rep 2023; 5:100849. [PMID: 37701334 PMCID: PMC10494471 DOI: 10.1016/j.jhepr.2023.100849] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 06/16/2023] [Accepted: 07/01/2023] [Indexed: 09/14/2023] Open
Abstract
Background & Aims HBV infection is a global health burden. Covalently closed circular DNA (cccDNA) transcriptional regulation is a major cause of poor cure rates of chronic hepatitis B (CHB) infection. Herein, we evaluated whether targeting host factors to achieve functional silencing of cccDNA may represent a novel strategy for the treatment of HBV infection. Methods To evaluate the effects of Jumonji C domain-containing (JMJD2) protein subfamily JMJD2A-2D proteins on HBV replication, we used lentivirus-based RNA interference to suppress the expression of isoforms JMJD2A-2D in HBV-infected cells. JMJD2D-knockout mice were generated to obtain an HBV-injected model for in vivo experiments. Co-immunoprecipitation and ubiquitylation assays were used to detect JMJD2D-HBx interactions and HBx stability modulated by JMJD2D. Chromatin immunoprecipitation assays were performed to investigate JMJD2D-cccDNA and HBx-cccDNA interactions. Results Among the JMJD2 family members, JMJD2D was significantly upregulated in mouse livers and human hepatoma cells. Downregulation of JMJD2D inhibited cccDNA transcription and HBV replication. Molecularly, JMJD2D sustained HBx stability by suppressing the TRIM14-mediated ubiquitin-proteasome degradation pathway and acted as a key co-activator of HBx to augment HBV replication. The JMJD2D-targeting inhibitor, 5C-8-HQ, suppressed cccDNA transcription and HBV replication. Conclusion Our study clarified the mechanism by which JMJD2D regulates HBV transcription and replication and identified JMJD2D as a potential diagnostic biomarker and promising drug target against CHB, and HBV-associated hepatocarcinoma. Impact and implications HBV cccDNA is central to persistent infection and is a major obstacle to healing CHB. In this study, using cellular and animal HBV models, JMJD2D was found to stabilise and cooperate with HBx to augment HBV transcription and replication. This study reveals a potential novel translational target for intervention in the treatment of chronic hepatitis B infection.
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Affiliation(s)
- Xu Kong
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Zuofeng Liu
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatology, Affiliated Hospital of Panzhihua University, Panzhihua, China
| | - Ruyi Zhang
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Fu’an Xie
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Rubing Liang
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Yong Zhang
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Lingling Yu
- Department of Cardiology, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, China
| | - Wensheng Yang
- Department of Pathology, Chenggong Hospital of Xiamen University, Xiamen, China
| | - Xi Li
- College of Arts and Sciences, Boston University, Boston, MA, USA
| | - Qiang Chen
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Bei Li
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Yilin Hong
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Ming Li
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
- Key Laboratory of Natural Medicine Research and Developing, Xiamen Medicine Research Institute, Xiamen, China
| | - Xiaogang Xia
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Lingwei Gu
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Management, Jiang Xia Blood Technology Co., Ltd., Shanghai, China
| | - Lijuan Fu
- Department of Infectious Diseases, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
| | - Xiaohua Li
- Department of Surgery, Affiliated Fuzhou First Hospital of Fujian Medical University, Fuzhou, China
| | - Ye Shen
- Department of Management, Jiang Xia Blood Technology Co., Ltd., Shanghai, China
| | - Ting Wu
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
| | - Chundong Yu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, China
| | - Wengang Li
- Cancer Research Center, School of Medicine, Xiamen University, Xiamen, China
- Department of Hepatobiliary Surgery, Xiang’an Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, China
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Kar A, Samanta A, Mukherjee S, Barik S, Biswas A. The HBV web: An insight into molecular interactomes between the hepatitis B virus and its host en route to hepatocellular carcinoma. J Med Virol 2023; 95:e28436. [PMID: 36573429 DOI: 10.1002/jmv.28436] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 11/26/2022] [Accepted: 12/23/2022] [Indexed: 12/28/2022]
Abstract
Hepatitis B virus (HBV) is a major aetiology associated with the development and progression of hepatocellular carcinoma (HCC), the most common primary liver malignancy. Over the past few decades, direct and indirect mechanisms have been identified in the pathogenesis of HBV-associated HCC which include altered signaling pathways, genome integration, mutation-induced genomic instability, chromosomal deletions and rearrangements. Intertwining of the HBV counterparts with the host cellular factors, though well established, needs to be systemized to understand the dynamics of host-HBV crosstalk and its consequences on HCC progression. Existence of a vast array of protein-protein and protein-nucleic acid interaction databases has led to the uncoiling of the compendia of genes/gene products associated with these interactions. This review covers the existing knowledge about the HBV-host interplay and brings it down under one canopy emphasizing on the HBV-host interactomics; and thereby highlights new strategies for therapeutic advancements against HBV-induced HCC.
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Affiliation(s)
- Arpita Kar
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
| | - Abhisekh Samanta
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
| | - Soumyadeep Mukherjee
- Department of In Vitro Carcinogenesis and Cellular Chemotherapy, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
| | - Subhasis Barik
- Department of In Vitro Carcinogenesis and Cellular Chemotherapy, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
| | - Avik Biswas
- Department of Signal Transduction and Biogenic Amines, Chittaranjan National Cancer Institute, Kolkata, West Bengal, India
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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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Van Damme E, Vanhove J, Severyn B, Verschueren L, Pauwels F. The Hepatitis B Virus Interactome: A Comprehensive Overview. Front Microbiol 2021; 12:724877. [PMID: 34603251 PMCID: PMC8482013 DOI: 10.3389/fmicb.2021.724877] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 08/17/2021] [Indexed: 12/19/2022] Open
Abstract
Despite the availability of a prophylactic vaccine, chronic hepatitis B (CHB) caused by the hepatitis B virus (HBV) is a major health problem affecting an estimated 292 million people globally. Current therapeutic goals are to achieve functional cure characterized by HBsAg seroclearance and the absence of HBV-DNA after treatment cessation. However, at present, functional cure is thought to be complicated due to the presence of covalently closed circular DNA (cccDNA) and integrated HBV-DNA. Even if the episomal cccDNA is silenced or eliminated, it remains unclear how important the high level of HBsAg that is expressed from integrated HBV DNA is for the pathology. To identify therapies that could bring about high rates of functional cure, in-depth knowledge of the virus' biology is imperative to pinpoint mechanisms for novel therapeutic targets. The viral proteins and the episomal cccDNA are considered integral for the control and maintenance of the HBV life cycle and through direct interaction with the host proteome they help create the most optimal environment for the virus whilst avoiding immune detection. New HBV-host protein interactions are continuously being identified. Unfortunately, a compendium of the most recent information is lacking and an interactome is unavailable. This article provides a comprehensive review of the virus-host relationship from viral entry to release, as well as an interactome of cccDNA, HBc, and HBx.
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Affiliation(s)
- Ellen Van Damme
- Janssen Research & Development, Janssen Pharmaceutical Companies, Beerse, Belgium
| | - Jolien Vanhove
- Janssen Research & Development, Janssen Pharmaceutical Companies, Beerse, Belgium.,Early Discovery Biology, Charles River Laboratories, Beerse, Belgium
| | - Bryan Severyn
- Janssen Research & Development, Janssen Pharmaceutical Companies, Springhouse, PA, United States
| | - Lore Verschueren
- Janssen Research & Development, Janssen Pharmaceutical Companies, Beerse, Belgium
| | - Frederik Pauwels
- Janssen Research & Development, Janssen Pharmaceutical Companies, Beerse, Belgium
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Proulx J, Borgmann K, Park IW. Role of Virally-Encoded Deubiquitinating Enzymes in Regulation of the Virus Life Cycle. Int J Mol Sci 2021; 22:ijms22094438. [PMID: 33922750 PMCID: PMC8123002 DOI: 10.3390/ijms22094438] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 01/21/2023] Open
Abstract
The ubiquitin (Ub) proteasome system (UPS) plays a pivotal role in regulation of numerous cellular processes, including innate and adaptive immune responses that are essential for restriction of the virus life cycle in the infected cells. Deubiquitination by the deubiquitinating enzyme, deubiquitinase (DUB), is a reversible molecular process to remove Ub or Ub chains from the target proteins. Deubiquitination is an integral strategy within the UPS in regulating survival and proliferation of the infecting virus and the virus-invaded cells. Many viruses in the infected cells are reported to encode viral DUB, and these vial DUBs actively disrupt cellular Ub-dependent processes to suppress host antiviral immune response, enhancing virus replication and thus proliferation. This review surveys the types of DUBs encoded by different viruses and their molecular processes for how the infecting viruses take advantage of the DUB system to evade the host immune response and expedite their replication.
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Affiliation(s)
- Jessica Proulx
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (J.P.); (K.B.)
| | - Kathleen Borgmann
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, Fort Worth, TX 76107, USA; (J.P.); (K.B.)
| | - In-Woo Park
- Department of Microbiology, Immunology and Genetics, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
- Correspondence: ; Tel.: +1-(817)-735-5115; Fax: +1-(817)-735-2610
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Cao H, Chen X, Wang Z, Wang L, Xia Q, Zhang W. The role of MDM2-p53 axis dysfunction in the hepatocellular carcinoma transformation. Cell Death Discov 2020; 6:53. [PMID: 32595984 PMCID: PMC7305227 DOI: 10.1038/s41420-020-0287-y] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 05/24/2020] [Accepted: 05/28/2020] [Indexed: 12/12/2022] Open
Abstract
Liver cancer is the second most frequent cause of cancer-related death globally. The main histological subtype is hepatocellular carcinoma (HCC), which is derived from hepatocytes. According to the epidemiologic studies, the most important risk factors of HCC are chronic viral infections (HBV, HCV, and HIV) and metabolic disease (metabolic syndrome). Interestingly, these carcinogenic factors that contributed to HCC are associated with MDM2-p53 axis dysfunction, which presented with inactivation of p53 and overactivation of MDM2 (a transcriptional target and negative regulator of p53). Mechanically, the homeostasis of MDM2-p53 feedback loop plays an important role in controlling the initiation and progression of HCC, which has been found to be dysregulated in HCC tissues. To maintain long-term survival in hepatocytes, hepatitis viruses have lots of ways to destroy the defense strategies of hepatocytes by inducing TP53 mutation and silencing, promoting MDM2 overexpression, accelerating p53 degradation, and stabilizing MDM2. As a result, genetic instability, chronic ER stress, oxidative stress, energy metabolism switch, and abnormalities in antitumor genes can be induced, all of which might promote hepatocytes' transformation into hepatoma cells. In addition, abnormal proliferative hepatocytes and precancerous cells cannot be killed, because of hepatitis viruses-mediated exhaustion of Kupffer cells and hepatic stellate cells (HSCs) and CD4+T cells by disrupting their MDM2-p53 axis. Moreover, inefficiency of hepatic immune response can be further aggravated when hepatitis viruses co-infected with HIV. Unlike with chronic viral infections, MDM2-p53 axis might play a dual role in glucolipid metabolism of hepatocytes, which presented with enhancing glucolipid catabolism, but promoting hepatocyte injury at the early and late stages of glucolipid metabolism disorder. Oxidative stress, fatty degeneration, and abnormal cell growth can be detected in hepatocytes that were suffering from glucolipid metabolism disorder, and all of which could contribute to HCC initiation. In this review, we focus on the current studies of the MDM2-p53 axis in HCC, and specifically discuss the impact of MDM2-p53 axis dysfunction by viral infection and metabolic disease in the transformation of normal hepatocytes into hepatoma cells. We also discuss the therapeutic avenues and potential targets that are being developed to normalize the MDM2-p53 axis in HCC.
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Affiliation(s)
- Hui Cao
- Department of Liver Diseases, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200030 China
| | - Xiaosong Chen
- Department of Liver Surgery, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, 200127 China
| | - Zhijun Wang
- Department of Traditional Chinese Medicine, Putuo People’s Hospital Affiliated to Tongji University, Shanghai, China
| | - Lei Wang
- Department of Liver Diseases, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200030 China
| | - Qiang Xia
- Department of Liver Surgery, Renji Hospital, School of Medicine, Shanghai Jiaotong University, Shanghai, 200127 China
| | - Wei Zhang
- Department of Liver Diseases, Longhua Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai, 200030 China
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Chromatin remodelling factor BAF155 protects hepatitis B virus X protein (HBx) from ubiquitin-independent proteasomal degradation. Emerg Microbes Infect 2020; 8:1393-1405. [PMID: 31533543 PMCID: PMC6758689 DOI: 10.1080/22221751.2019.1666661] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
HBx is a short-lived protein whose rapid turnover is mainly regulated by ubiquitin-dependent proteasomal degradation pathways. Our prior work identified BAF155 to be one of the HBx binding partners. Since BAF155 has been shown to stabilize other members of the SWI/SNF chromatin remodelling complex by attenuating their proteasomal degradation, we proposed that BAF155 might also contribute to stabilizing HBx protein in a proteasome-dependent manner. Here we report that BAF155 protected hepatitis B virus X protein (HBx) from ubiquitin-independent proteasomal degradation by competing with the 20S proteasome subunit PSMA7 to bind to HBx. BAF155 was found to directly interact with HBx via binding of its SANT domain to the HBx region between amino acid residues 81 and 120. Expression of either full-length BAF155 or SANT domain increased HBx protein levels whereas siRNA-mediated knockdown of endogenous BAF155 reduced HBx protein levels. Increased HBx stability and steady-state level by BAF155 were attributable to inhibition of ubiquitin-independent and PSMA7-mediated protein degradation. Consequently, overexpression of BAF155 enhanced the transcriptional transactivation function of HBx, activated protooncogene expression and inhibited hepatoma cell clonogenicity. These results suggest that BAF155 plays important roles in ubiquitin-independent degradation of HBx, which may be related to the pathogenesis and carcinogenesis of HBV-associated HCC.
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11
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Kong F, You H, Kong D, Zheng K, Tang R. The interaction of hepatitis B virus with the ubiquitin proteasome system in viral replication and associated pathogenesis. Virol J 2019; 16:73. [PMID: 31146743 PMCID: PMC6543661 DOI: 10.1186/s12985-019-1183-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 05/20/2019] [Indexed: 12/21/2022] Open
Abstract
Background The ubiquitin proteasome system (UPS) regulates the expression levels of cellular proteins by ubiquitination of protein substrates followed by their degradation via the proteasome. As a highly conserved cellular degradation mechanism, the UPS affects a variety of biological processes and participates in viral propagation. Main body During hepatitis B virus (HBV) infection, the UPS is shown to act as a double-edged sword in viral pathogenesis. On the one hand, the UPS acts as a host defense mechanism to selectively recognize HBV proteins as well as special cellular proteins that favor the viral life cycle and induces their ubiquitin-dependent proteasomal degradation to limit HBV infection. On the other hand, the HBV has evolved to subvert the UPS function for its own advantage. Moreover, in the infected hepatocytes, certain cellular proteins that are dependent on the UPS are involved in abnormal biological processes which are mediated by HBV. Conclusion The molecular interaction of HBV with the UPS to modulate viral propagation and pathogenesis is summarized in the review. Considering the important role of the UPS in HBV infection, a better understanding of the HBV-UPS interaction could provide novel insight into the mechanisms that are involved in viral replication and pathogenesis and help to develop potential treatment strategies targeting the UPS.
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Affiliation(s)
- Fanyun Kong
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China
| | - Hongjuan You
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China
| | - Delong Kong
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China
| | - Kuiyang Zheng
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China.,National Demonstration Center for Experimental Basic Medical Sciences Education, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China
| | - Renxian Tang
- Jiangsu Key Laboratory of Immunity and Metabolism, Department of Pathogenic Biology and Immunology, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China. .,National Demonstration Center for Experimental Basic Medical Sciences Education, Xuzhou Medical University, Xuzhou, 221004, Jiangsu, China.
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12
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Tornesello ML, Annunziata C, Tornesello AL, Buonaguro L, Buonaguro FM. Human Oncoviruses and p53 Tumor Suppressor Pathway Deregulation at the Origin of Human Cancers. Cancers (Basel) 2018; 10:213. [PMID: 29932446 PMCID: PMC6071257 DOI: 10.3390/cancers10070213] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 06/19/2018] [Accepted: 06/22/2018] [Indexed: 12/18/2022] Open
Abstract
Viral oncogenesis is a multistep process largely depending on the complex interplay between viruses and host factors. The oncoviruses are capable of subverting the cell signaling machinery and metabolic pathways and exploit them for infection, replication, and persistence. Several viral oncoproteins are able to functionally inactivate the tumor suppressor p53, causing deregulated expression of many genes orchestrated by p53, such as those involved in apoptosis, DNA stability, and cell proliferation. The Epstein⁻Barr virus (EBV) BZLF1, the high-risk human papillomavirus (HPV) E6, and the hepatitis C virus (HCV) NS5 proteins have shown to directly bind to and degrade p53. The hepatitis B virus (HBV) HBx and the human T cell lymphotropic virus-1 (HTLV-1) Tax proteins inhibit p53 activity through the modulation of p300/CBP nuclear factors, while the Kaposi's sarcoma herpesvirus (HHV8) LANA, vIRF-1 and vIRF-3 proteins have been shown to destabilize the oncosuppressor, causing a decrease in its levels in the infected cells. The large T antigen of the Merkel cell polyomavirus (MCPyV) does not bind to p53 but significantly reduces p53-dependent transcription. This review describes the main molecular mechanisms involved in the interaction between viral oncoproteins and p53-related pathways as well as in the development of therapeutic strategies targeting such interactions.
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Affiliation(s)
- Maria Lina Tornesello
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", via Mariano Semmola, 80131 Napoli, Italy.
| | - Clorinda Annunziata
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", via Mariano Semmola, 80131 Napoli, Italy.
| | - Anna Lucia Tornesello
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", via Mariano Semmola, 80131 Napoli, Italy.
| | - Luigi Buonaguro
- Cancer Immunomodulation Unit, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", via Mariano Semmola, 80131 Napoli, Italy.
| | - Franco Maria Buonaguro
- Molecular Biology and Viral Oncology Unit, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", via Mariano Semmola, 80131 Napoli, Italy.
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13
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Azer SA. MDM2-p53 Interactions in Human Hepatocellular Carcinoma: What Is the Role of Nutlins and New Therapeutic Options? J Clin Med 2018; 7:64. [PMID: 29584707 PMCID: PMC5920438 DOI: 10.3390/jcm7040064] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 03/22/2018] [Accepted: 03/23/2018] [Indexed: 12/18/2022] Open
Abstract
Human hepatocellular carcinoma (HCC) is the fifth most common cancer and is associated with poor prognosis worldwide. The molecular mechanisms underlying the pathogenesis of HCC have been an area of continuing interest, and recent studies using next generation sequencing (NGS) have revealed much regarding previously unsettled issues. Molecular studies using HCC samples have been mainly targeted with the aim to identify the fundamental mechanisms contributing to HCC and identify more effective treatments. In response to cellular stresses (e.g., DNA damage or oncogenes), activated p53 elicits appropriate responses that aim at DNA repair, genetic stability, cell cycle arrest, and the deletion of DNA-damaged cells. On the other hand, the murine double minute 2 (MDM2) oncogene protein is an important cellular antagonist of p53. MDM2 negatively regulates p53 activity through the induction of p53 protein degradation. However, current research has shown that the mechanisms underlying MDM2-p53 interactions are more complex than previously thought. Microarray data have added new insight into the transcription changes in HCC. Recently, Nutlin-3 has shown potency against p53-MDM2 binding and the enhancement of p53 stabilization as well as an increment of p53 cellular accumulation with potential therapeutic effects. This review outlines the molecular mechanisms involved in the p53-MDM2 pathways, the biological factors influencing these pathways, and their roles in the pathogenesis of HCC. It also discusses the action of Nutlin-3 treatment in inducing growth arrest in HCC and elaborates on future directions in research in this area. More research on the biology of p53-MDM2 interactions may offer a better understanding of these mechanisms and discover new biomarkers, sensitive prognostic indicators as well as new therapeutic interventions in HCC.
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Affiliation(s)
- Samy A Azer
- Professor of Medical Education and Gastroenterologist, The Chair of Curriculum Development and Research Unit, College of Medicine, King Saud University, Riyadh 11461, Saudi Arabia.
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14
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Yeom S, Kim SS, Jeong H, Jang KL. Hepatitis B virus X protein activates E3 ubiquitin ligase Siah-1 to control virus propagation via a negative feedback loop. J Gen Virol 2017; 98:1774-1784. [PMID: 28714848 DOI: 10.1099/jgv.0.000856] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The seven in absentia homologue 1 (Siah-1) protein is an E3 ubiquitin ligase that induces ubiquitin-dependent proteasomal degradation of HBx, the principal regulatory protein of hepatitis B virus (HBV); however, its role in HBV propagation remains unknown. Here, we found that HBx upregulates Siah-1 levels in HepG2 but not in Hep3B cells, in which p53 is absent. For this effect, HBx sequentially activated ataxia telangiectasia mutated kinase and checkpoint kinase 2 via phosphorylation at the Ser-1981 and Thr-68 residues, respectively, which led to the activation of p53 via phosphorylation at the Ser-15 and Ser-20 residues. As a result, HBx was heavily ubiquitinated by Siah-1 and degraded by the ubiquitin-proteasome system in HepG2 cells, whereas this effect was marginal or undetectable in Hep3B cells. Knock-down of p53 in HepG2 cells downregulated Siah-1 levels and subsequently upregulated HBx levels, whereas ectopic p53 expression in Hep3B cells upregulated Siah-1 levels and subsequently downregulated HBx levels. In addition, Siah-1 knock-down impaired the ubiquitination and proteasomal degradation of HBx in HepG2 cells, whereas ectopic Siah-1 expression induced ubiquitin-dependent proteasomal degradation of HBx in Hep3B cells. The effects of HBx on p53 and Siah-1 were exactly reproduced in a 1.2-mer HBV replicon system, mimicking the natural course of HBV infection. In particular, Siah-1 knock-down upregulated the levels of HBx derived from the HBV replicon, resulting in an increase in HBV production. In conclusion, HBx modulates its own protein level via a negative feedback loop involving p53 and Siah-1 to control HBV propagation.
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Affiliation(s)
- Sujeong Yeom
- Department of Microbiology, College of Natural Science, Pusan National University, Busan 46241, Republic of Korea
| | - Soo Shin Kim
- Department of Microbiology, College of Natural Science, Pusan National University, Busan 46241, Republic of Korea
| | - Hyerin Jeong
- Department of Microbiology, College of Natural Science, Pusan National University, Busan 46241, Republic of Korea
| | - Kyung Lib Jang
- Department of Microbiology, College of Natural Science, Pusan National University, Busan 46241, Republic of Korea
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15
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Su ZJ, Cao JS, Wu YF, Chen WN, Lin X, Wu YL, Lin X. Deubiquitylation of hepatitis B virus X protein (HBx) by ubiquitin-specific peptidase 15 (USP15) increases HBx stability and its transactivation activity. Sci Rep 2017; 7:40246. [PMID: 28074857 PMCID: PMC5225491 DOI: 10.1038/srep40246] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 12/05/2016] [Indexed: 02/07/2023] Open
Abstract
Hepatitis B virus X protein (HBx) plays important roles in viral replication and the development of hepatocellular carcinoma. HBx is a rapid turnover protein and ubiquitin-proteasome pathway has been suggested to influence HBx stability as treatment with proteasome inhibitors increases the levels of HBx protein and causes accumulation of the polyubiquitinated forms of HBx. Deubiquitinases (DUBs) are known to act by removing ubiquitin moieties from proteins and thereby reverse their stability and/or activity. However, no information is available regarding the involvement of DUBs in regulation of ubiquitylation-dependent proteasomal degradation of HBx protein. This study identified the deubiquitylating enzyme USP15 as a critical regulator of HBx protein level. USP15 was found to directly interact with HBx via binding to the HBx region between amino acid residues 51 and 80. USP15 increased HBx protein levels in a dose-dependent manner and siRNA-mediated knockdown of endogenous USP15 reduced HBx protein levels. Increased HBx stability and steady-state level by USP15 were attributable to reduced HBx ubiquitination and proteasomal degradation. Importantly, the transcriptional transactivation function of HBx is enhanced by overexpression of USP15. These results suggest that USP15 plays an essential role in stabilizing HBx and subsequently affects the biological function of HBx.
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Affiliation(s)
- Zhi-Jun Su
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China.,Department of Infectious Diseases, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou, China
| | - Jia-Shou Cao
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Yan-Fang Wu
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Wan-Nan Chen
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Xinjian Lin
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China
| | - Yun-Li Wu
- Fujian Key Laboratory of Tumor Microbiology, Fujian Medical University, Fuzhou, China
| | - Xu Lin
- Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, Fuzhou, China.,Department of Infectious Diseases, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Quanzhou, China
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16
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Zhao J, Wu J, Cai H, Wang D, Yu L, Zhang WH. E3 Ubiquitin Ligase Siah-1 is Down-regulated and Fails to Target Natural HBx Truncates for Degradation in Hepatocellular Carcinoma. J Cancer 2016; 7:418-426. [PMID: 26918055 PMCID: PMC4749362 DOI: 10.7150/jca.13019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 11/14/2015] [Indexed: 01/05/2023] Open
Abstract
Hepatocellular carcinoma (HCC) is a common worldwide malignancy with high morbidity and mortality. Hepatitis B viral (HBV)-encoded X protein (HBx) and natural HBx variants play important roles in HBV-associated HCC development. HBx is an unstable protein that can be degraded in vivo. Our previous study found that the E3 ubiquitin ligase Siah-1 could target HBx for poly-ubiquitylation and proteasomal degradation and attenuate the transcriptional activity of HBx. However, in HCC patients, high expression levels of HBx and HBx variants are frequently observed and are associated with HCC progression. The mechanism underlying their up-regulation is largely unknown. In this study, we screened for Siah-1 mutations in 270 HCC samples and 9 HCC cell lines, and examined Siah-1 mRNA and protein expression in a subset of paired HCC specimens. Our results demonstrate that Siah-1 is highly conserved, as no somatic mutation was identified, with the exception of one synonymous transition from G to A at codon 67. Both the mRNA and protein levels of Siah-1 were significantly down-regulated in HCC tissues compared with their adjacent normal counterparts. We constructed three natural HBx truncates that were identified in our HCC cases. We found that Siah-1 failed to decrease the stability of these HBx variants and was unable to inhibit the transcriptional activity of these HBx truncates at heat shock elements (HSEs). Moreover, Siah-1 had weaker association with three HBx mutants than full length HBx. Therefore, our findings suggest that down-regulation of Siah-1, but not its mutations, and natural HBx variants resistant to Siah-1-induced degradation may be a novel mechanism for HCC development.
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Affiliation(s)
- Jing Zhao
- 1. Department of General Surgery, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Jing Wu
- 2. Department of Infectious Diseases, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200040, China
| | - Hao Cai
- 3. The State Key Laboratory of Genetics Engineering, Fudan University, Shanghai 200433, China
| | - Dan Wang
- 3. The State Key Laboratory of Genetics Engineering, Fudan University, Shanghai 200433, China
| | - Long Yu
- 3. The State Key Laboratory of Genetics Engineering, Fudan University, Shanghai 200433, China
| | - Wen-Hong Zhang
- 2. Department of Infectious Diseases, Huashan Hospital, Shanghai Medical College, Fudan University, Shanghai 200040, China
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17
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Geng M, Xin X, Bi LQ, Zhou LT, Liu XH. Molecular mechanism of hepatitis B virus X protein function in hepatocarcinogenesis. World J Gastroenterol 2015; 21:10732-10738. [PMID: 26478665 PMCID: PMC4600575 DOI: 10.3748/wjg.v21.i38.10732] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 06/24/2015] [Accepted: 09/02/2015] [Indexed: 02/06/2023] Open
Abstract
Many factors are considered to contribute to hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC), including products of HBV, HBV integration and mutation, and host susceptibility. HBV X protein (HBx) can interfere with several signaling pathways associated with cell proliferation and invasion, and HBx C-terminal truncation has been suggested to impact the development of HCC. This review focuses on the pathological functions of HBx in HBV-induced hepatocarcinogenesis. As a transactivator, HBx can affect regulatory non-coding RNAs (ncRNAs), including microRNAs and long ncRNAs. HBx is also involved in epigenetic modification and DNA repair. HBx interacts with various signal-transduction pathways, such as the p53, Wnt, and nuclear factor-κB pathways. We conclude that HBx hastens the development of hepatoma.
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18
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Yuan Y, Tian C, Gong Q, Shang L, Zhang Y, Jin C, He F, Wang J. Interactome map reveals phospholipid scramblase 1 as a novel regulator of hepatitis B virus x protein. J Proteome Res 2014; 14:154-63. [PMID: 25365352 DOI: 10.1021/pr500943x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
HBV X protein plays crucial roles during viral infection and hepatocellular carcinoma (HCC) development through interaction with various host factors. Here, we mapped the interactome of HBx using a yeast two-hybrid screen. Nine human proteins were identified as novel interacting partners of HBx, one of which is phospholipid scramblase 1 (PLSCR1). PLSCR1 is an interferon-inducible protein that mediates antiviral activity against DNA and RNA viruses. However, the molecular mechanisms of PLSCR1 activity against HBV remain unclear. Here, we reported that PLSCR1 promotes HBx degradation by a proteasome- and ubiquitin-dependent mechanism. Furthermore, we found that PLSCR1 inhibits HBx-mediated cell proliferation. After HBV infection, the protein level of PLSCR1 in plasma is elevated, and chronic hepatitis B patients with low plasma levels of PLSCR1 have a high risk of developing HCC. These results suggest that the nuclear trafficking of PLSCR1 mediates the antiviral activity and anticarcinogenesis against HBV by regulating HBx stability.
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Affiliation(s)
- Yanzhi Yuan
- State Key Laboratory of Proteomics, Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing 102206, China
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19
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Xie N, Chen X, Zhang T, Liu B, Huang C. Using proteomics to identify the HBx interactome in hepatitis B virus: how can this inform the clinic? Expert Rev Proteomics 2013; 11:59-74. [PMID: 24308553 DOI: 10.1586/14789450.2014.861745] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Hepatitis B virus (HBV) is a small and enveloped DNA virus, of which chronic infection is the main risk factor of liver cirrhosis and hepatocellular carcinoma. Hepatitis B virus X protein (HBx) is a multifunctional protein encoded by HBV genome, which have significant effects on HBV replication and pathogenesis. Through directly interacting with cellular proteins, HBx is capable to promote HBV replication, regulate transcription of host genes, disrupt protein degradation, modulate signaling pathway, manipulate cell death and deregulate cell cycle. In this review, we briefly discuss the diversified effects of HBx-interactome and their potential clinical significances.
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Affiliation(s)
- Na Xie
- The State Key Laboratory of Biotherapy, West China Hospital of Sichuan University, Chengdu, 610041, P.R. China
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20
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Lu JW, Yang WY, Tsai SM, Lin YM, Chang PH, Chen JR, Wang HD, Wu JL, Jin SLC, Yuh CH. Liver-specific expressions of HBx and src in the p53 mutant trigger hepatocarcinogenesis in zebrafish. PLoS One 2013; 8:e76951. [PMID: 24130815 PMCID: PMC3793937 DOI: 10.1371/journal.pone.0076951] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/29/2013] [Indexed: 02/07/2023] Open
Abstract
Hepatocarcinogenesis is a multistep process that starts from fatty liver and transitions to fibrosis and, finally, into cancer. Many etiological factors, including hepatitis B virus X antigen (HBx) and p53 mutations, have been implicated in hepatocarcinogenesis. However, potential synergistic effects between these two factors and the underlying mechanisms by which they promote hepatocarcinogenesis are still unclear. In this report, we show that the synergistic action of HBx and p53 mutation triggers progressive hepatocellular carcinoma (HCC) formation via src activation in zebrafish. Liver-specific expression of HBx in wild-type zebrafish caused steatosis, fibrosis and glycogen accumulation. However, the induction of tumorigenesis by HBx was only observed in p53 mutant fish and occurred in association with the up-regulation and activation of the src tyrosine kinase pathway. Furthermore, the overexpression of src in p53 mutant zebrafish also caused hyperplasia, HCC, and sarcomatoid HCC, which were accompanied by increased levels of the signaling proteins p-erk, p-akt, myc, jnk1 and vegf. Increased expression levels of lipogenic factors and the genes involved in lipid metabolism and glycogen storage were detected during the early stages of hepatocarcinogenesis in the HBx and src transgenic zebrafish. The up-regulation of genes involved in cell cycle regulation, tumor progression and other molecular hallmarks of human liver cancer were found at later stages in both HBx and src transgenic, p53 mutant zebrafish. Together, our study demonstrates that HBx and src overexpression induced hepatocarcinogenesis in p53 mutant zebrafish. This phenomenon mimics human HCC formation and provides potential in vivo platforms for drug screening for therapies for human liver cancer.
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Affiliation(s)
- Jeng-Wei Lu
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
- Department of Life Sciences, National Central University, Jhongli City, Taoyuan, Taiwan
| | - Wan-Yu Yang
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
| | - Su-Mei Tsai
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
| | - Yueh-Min Lin
- Department of Pathology, Changhua Christian Hospital, Changhua City, Changhua County, Taiwan
- Department of Medical Technology, Jen-Teh Junior College of Medicine, Nursing and Management, Hou-Loung Town, Miaoli County, Taiwan
| | - Pen-Heng Chang
- Department of Veterinary Medicine, National Taiwan University, Taipei, Taiwan
| | - Jim-Ray Chen
- Department of Pathology, Chang Gung Memorial Hospital, Keelung, Taiwan
- College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Horng-Dar Wang
- Institute of Biotechnology, National Tsing Hua University, Hsinchu, Taiwan
| | - Jen-Leih Wu
- Institute of Cellular and Organismic Biology, Academia Sinica, Nangang District, Taipei, Taiwan
| | | | - Chiou-Hwa Yuh
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
- Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan
- * E-mail:
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21
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Shin GC, Ahn SH, Choi HS, Lim KH, Choi DY, Kim KP, Kim KH. Hepatocystin/80K-H inhibits replication of hepatitis B virus through interaction with HBx protein in hepatoma cell. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1569-81. [PMID: 23644164 DOI: 10.1016/j.bbadis.2013.04.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 04/11/2013] [Accepted: 04/25/2013] [Indexed: 02/07/2023]
Abstract
Hepatitis B virus (HBV) X protein (HBx) is a key player in HBV replication as well as HBV-induced hepatocellular carcinoma (HCC). However, the pathogenesis of HBV infection and the mechanisms of host-virus interactions are still elusive. In this study, a combination of affinity purification and mass spectrometry was applied to identify the host factors interacting with HBx in hepatoma cells. Thirteen proteins were identified as HBx binding partners. Among them, we first focused on determining the functional significance of the interaction between HBx and hepatocystin. A physical interaction between HBx and hepatocystin was confirmed by co-immunoprecipitation and Western blotting. Immunocytochemistry demonstrated that HBx and hepatocystin colocalized in the hepatoma cells. Domain mapping of both proteins revealed that the HBx C-terminus (amino acids 110-154) was responsible for binding to the mannose 6-phosphate receptor homology domain (amino acids, 419-525) of hepatocystin. Using translation and proteasome inhibitors, we found that hepatocystin overexpression accelerated HBx degradation via a ubiquitin-independent proteasome pathway. We demonstrated that this effect was mediated by an interaction between both proteins using a HBx deletion mutant. Hepatocystin overexpression significantly inhibited HBV DNA replication and expression of HBs antigen concomitant with HBx degradation. Using the hepatocystin mutant constructs that bind HBx, we also confirmed that hepatocystin inhibited HBx-dependent HBV replication. In conclusion, we demonstrated for the first time that hepatocystin functions as a chaperon-like molecule by accelerating HBx degradation, and thereby inhibits HBV replication. Our results suggest that inducing hepatocystin may provide a novel therapeutic approach to control HBV infection.
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Affiliation(s)
- Gu-Choul Shin
- Department of Pharmacology, Konkuk University School of Medicine, Seoul, Republic of Korea
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22
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Kapoor NR, Ahuja R, Shukla SK, Kumar V. The HBx protein of hepatitis B virus confers resistance against nucleolar stress and anti-cancer drug-induced p53 expression. FEBS Lett 2013; 587:1287-92. [PMID: 23507139 DOI: 10.1016/j.febslet.2013.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 02/28/2013] [Accepted: 03/03/2013] [Indexed: 12/28/2022]
Abstract
The nucleolus is a stress sensor associated with cell cycle progression and a viral target. However, the role of the nucleolus during hepatitis B virus infection has not been studied. Here we show that under nucleolar stress, the HBx oncoprotein down-regulates p53 and p21(waf1) levels by disrupting the interaction between ribosomal protein L11 and MDM2. Further, HBx inhibited Act D-mediated down-regulation of proliferative factors such as c-Myc and cyclin E and revived RNA pol I-dependent transcription under these conditions. Importantly, HBx also countered the action of anticancer drug Paclitaxel suggesting its possible role in drug resistance. Thus, HBx not only can facilitate cell proliferation under stress conditions but can confer resistance against anticancer drugs.
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Affiliation(s)
- Neetu Rohit Kapoor
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
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Wang W, Zhou D, Wei J, Wu Z, Cheng X, Sun Q, Xie H, Zhou L, Zheng S. Hepatitis B virus X protein inhibits p53-mediated upregulation of mitofusin-2 in hepatocellular carcinoma cells. Biochem Biophys Res Commun 2012; 421:355-60. [DOI: 10.1016/j.bbrc.2012.04.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 04/03/2012] [Indexed: 02/07/2023]
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24
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Zhao J, Wang C, Wang J, Yang X, Diao N, Li Q, Wang W, Xian L, Fang Z, Yu L. E3 ubiquitin ligase Siah-1 facilitates poly-ubiquitylation and proteasomal degradation of the hepatitis B viral X protein. FEBS Lett 2011; 585:2943-50. [PMID: 21878328 DOI: 10.1016/j.febslet.2011.08.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2011] [Revised: 07/23/2011] [Accepted: 08/09/2011] [Indexed: 11/15/2022]
Abstract
Hepatitis B viral X protein (HBx) is a multifunctional transactivator and implicated in hepatitis B virus (HBV) replication and hepatocarcinogenesis. HBx can be ubiquitinated and degraded through ubiquitin-proteasome pathway. However, the E3 ubiquitin ligase regulating HBx ubiquitin-dependent degradation is still unknown. In this study, we identified Siah-1 as a novel E3 ubiquitin ligase for HBx, which interacted with HBx and facilitated HBx poly-ubiquitylation and proteasomal degradation. Co-expression of Siah-1 attenuated the transcriptional transactivation of HBx on glucocorticoid response element (GRE), heat shock response element (HSE) and cAMP response element (CRE) signal pathways. Moreover, Siah-1 participated in p53-mediated HBx degradation. Therefore, Siah-1 may play important roles in ubiquitin-dependent degradation of HBx and may be involved in suppressing the progression of hepatocellular carcinoma (HCC).
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Affiliation(s)
- Jing Zhao
- State Key Laboratory of Genetic Engineering, Institute of Genetics, Shanghai, PR China
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25
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Abstract
Chronic hepatitis B virus (HBV) infection has been identified as a major risk factor in hepatocellular carcinoma (HCC), which is one of the most common cancers worldwide. The pathogenesis of HBV-mediated hepatocarcinogenesis is, however, incompletely understood. Evidence suggests that the HBV X protein (HBx) plays a crucial role in HCC development. HBx is a multifunctional regulator that modulates transcription, signal transduction, cell cycle progression, apoptosis, protein degradation pathways, and genetic stability through interaction with host factors. This review describes the current state of knowledge of the molecular pathogenesis of HBV-induced HCC, with a focus on the role of HBx in hepatocarcinogenesis.
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Affiliation(s)
- Sue-Ann Ng
- University of New South Wales, Sydney, Australia.
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26
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Kido T, Ou JHJ, Lau YFC. The X-linked tumor suppressor TSPX interacts and promotes degradation of the hepatitis B viral protein HBx via the proteasome pathway. PLoS One 2011; 6:e22979. [PMID: 21829568 PMCID: PMC3146538 DOI: 10.1371/journal.pone.0022979] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 07/08/2011] [Indexed: 01/05/2023] Open
Abstract
Hepatitis B virus (HBV) infection is a major risk for hepatocellular carcinoma (HCC), and it is a serious global health problem with two billion people exposed to it worldwide. HBx, an essential factor for viral replication and a putative oncoprotein encoded by the HBV genome, has been shown to promote oncogenic properties at multiple sites in HBV-infected liver cells. The expression level of HBx closely associates with the development and progression of HCC, therefore the mechanism(s) regulating the stability of HBx is important in oncogenesis of HBV-infected cells. We demonstrate that the X-linked tumor suppressor TSPX enhances the degradation of HBx through the ubiquitin-proteasome pathway. TSPX interacts with both HBx and a proteasome 19S lid subunit RPN3 via its C-terminal acidic tail. Most importantly, over-expression of RPN3 protects HBx from, and hence acts as a negative regulator for, proteasome-dependent degradation. TSPX abrogates the RPN3-depedent stabilization of HBx, suggesting that TSPX and RPN3 act competitively in regulation of HBx stability. Since mutation and/or epigenetic repression of X-located tumor suppressor gene(s) could significantly predispose males to human cancers, our data suggest that TSPX-induced HBx degradation could play key role(s) in hepatocarcinogenesis among HBV-infected HCC patients.
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Affiliation(s)
- Tatsuo Kido
- Division of Cell and Developmental Genetics, Department of Medicine, Veterans Affairs Medical Center, University of California San Francisco, San Francisco, California, United States of America
| | - Jing-Hsiung James Ou
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Yun-Fai Chris Lau
- Division of Cell and Developmental Genetics, Department of Medicine, Veterans Affairs Medical Center, University of California San Francisco, San Francisco, California, United States of America
- * E-mail:
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27
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Shukla R, Yue J, Siouda M, Gheit T, Hantz O, Merle P, Zoulim F, Krutovskikh V, Tommasino M, Sylla BS. Proinflammatory cytokine TNF-α increases the stability of hepatitis B virus X protein through NF-κB signaling. Carcinogenesis 2011; 32:978-85. [PMID: 21459755 DOI: 10.1093/carcin/bgr057] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hepatitis B virus (HBV) X protein (HBx) is a key player in HBV-induced hepatocellular carcinoma (HCC). HBx interacts with several cell signaling molecules, leading to activation of various transcription factors including nuclear factor-kappaB (NF-κB). Activated NF-κB signaling is implicated in many human cancers including HCC. Here, we present evidence that the NF-κB signaling activator, tumor necrosis factor (TNF)-α, induces the accumulation of HBx in cells by increasing protein stability due to reduced proteasomal degradation. The effects of TNF-α on HBx protein stability are mediated via activated NF-κB effector kinases IKKα and IKKβ and p65. The non-IKK-phosphorylable p65-S534A mutant did not induce HBx protein stability; hence, phosphorylation of p65 by IKK is a key step in TNF-α-induced stabilization of HBx. Phospho-p65 showed higher affinity to HBx compared with the non-phosphorylable p65 mutant, suggesting that the interaction of phospho-p65 with HBx might be important for HBx stabilization. We also show that the increased level of HBx in cells cooperates with TNF-α toward activation of NF-κB and expression of NF-κB-regulated genes, indicating a positive feedback loop between HBx and NF-κB signaling. Overall, our study provides evidence for interplay between HBx and NF-κB signaling, which may account for HBV-mediated liver carcinogenesis.
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Affiliation(s)
- Ruchi Shukla
- Infections and Cancer Biology Group, International Agency for Research on Cancer, 150 cours Albert-Thomas, 69372 Lyon Cedex 08, France
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28
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Gong Q, He S. Advances in understanding the biological roles of HBx. Shijie Huaren Xiaohua Zazhi 2010; 18:3656-3661. [DOI: 10.11569/wcjd.v18.i34.3656] [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
Hepatitis B virus (HBV) is the leading cause of liver cancer. Globally, there are over 350 million individuals chronically infected with HBV, and approximately 25% of these individuals will develop hepatocellular carcinoma (HCC). HBV is the prototype virus of the hepadnavirus family. The genome of HBV is circular and contains four open reading frames (ORFs). The HBx protein encoded by the X region of HBV is a multifunctional regulatory protein that possesses a wide transactivation activity and plays critical roles in regulating intracellular signal transduction, viral replication and transcription, cell proliferation and apoptosis, protein degradation, and heredity stability of hepatocytes. Due to its important roles in the development of chronic liver diseases, the research on the HBx protein has become a hot topic in recent years. In this paper, we will summarize the latest advances in understanding the biological roles of the HBx protein.
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29
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Wang JJ, Zheng Y, Sun L, Wang L, Yu PB, Dong JH, Zhang L, Xu J, Shi W, Ren YC. TP53 codon 72 polymorphism and colorectal cancer susceptibility: a meta-analysis. Mol Biol Rep 2010; 38:4847-53. [PMID: 21140221 DOI: 10.1007/s11033-010-0619-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 11/26/2010] [Indexed: 02/07/2023]
Abstract
Colorectal cancer constitutes a significant proportion of the global burden of cancer morbidity and mortality. A number of studies have been conducted to explore whether TP53 codon 72 polymorphism is associated with colorectal cancer susceptibility. However, controversial results were obtained. In order to derive a more precise estimation of the relationship, we systematically searched Medline, Google scholar, and Ovid database for studies reported before May 2010. A total of 3603 colorectal cancer cases and 5524 controls were included. TP53 codon 72 polymorphism was not associated with colorectal cancer risk in all genetic models (for dominant model: OR = 0.99, 95% CI: 0.86-1.15; for recessive model: OR = 1.00, 95% CI: 0.81-1.23; for Arg/Pro vs. Arg/Arg: OR = 1.00, 95% CI: 0.87-1.15; for Pro/Pro vs. Arg/Arg: OR = 0.97, 95% CI: 0.76-1.25). In the subgroup analyses by ethnic groups and sources of controls, no significant associations were found in all models. Taken together, this meta-analysis suggested that the biologically usefulness of TP53 codon 72 polymorphism as a selection marker in colorectal cancer susceptibility may be very limited.
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Affiliation(s)
- Jing-Jun Wang
- Department of Center for Disease Control and Prevention of Shaanxi Province, 3 Jiandong Road, 710043 Xi'an, Shaanxi, People's Republic of China
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30
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Wang L, He G, Zhang P, Wang X, Jiang M, Yu L. Interplay between MDM2, MDMX, Pirh2 and COP1: the negative regulators of p53. Mol Biol Rep 2010; 38:229-36. [PMID: 20333547 DOI: 10.1007/s11033-010-0099-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 03/16/2010] [Indexed: 12/17/2022]
Abstract
MDM2, Pirh2 and COP1 are important E3 ubiquitin ligases, which directly interact with p53 and target p53 for proteasome-mediated degradation. MDMX, the MDM2 homologous protein, inhibits p53-mediated transcription activity. The interplay between MDM2, MDMX, Pirh2 and COP1 has not been reported, except the interaction between MDM2 and MDMX. Here, we reported that there were interactions between these four proteins independently of p53. The protein levels of MDM2, MDMX, Pirh2 and COP1 changed when any two of them were co-transfected. Our data also showed that the integrity of MDM2 RING finger domain was crucial for its ability to elevate the protein levels of COP1 and Pirh2. Any two of these four proteins could inhibit p53-mediated transcriptional activity synergistically. Furthermore, COP1 inhibited MDM2 self-ubiquitination and interfered with MDMX ubiquitination by MDM2. Our results suggest that MDM2, MDMX, Pirh2 and COP1 might inhibit p53 activity synergistically in vivo.
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Affiliation(s)
- Lan Wang
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, 200433, People's Republic of China
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