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Thiyagarajah K, Basic M, Hildt E. Cellular Factors Involved in the Hepatitis D Virus Life Cycle. Viruses 2023; 15:1687. [PMID: 37632029 PMCID: PMC10459925 DOI: 10.3390/v15081687] [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: 06/30/2023] [Revised: 07/30/2023] [Accepted: 08/01/2023] [Indexed: 08/27/2023] Open
Abstract
Hepatitis D virus (HDV) is a defective RNA virus with a negative-strand RNA genome encompassing less than 1700 nucleotides. The HDV genome encodes only for one protein, the hepatitis delta antigen (HDAg), which exists in two forms acting as nucleoproteins. HDV depends on the envelope proteins of the hepatitis B virus as a helper virus for packaging its ribonucleoprotein complex (RNP). HDV is considered the causative agent for the most severe form of viral hepatitis leading to liver fibrosis/cirrhosis and hepatocellular carcinoma. Many steps of the life cycle of HDV are still enigmatic. This review gives an overview of the complete life cycle of HDV and identifies gaps in knowledge. The focus is on the description of cellular factors being involved in the life cycle of HDV and the deregulation of cellular pathways by HDV with respect to their relevance for viral replication, morphogenesis and HDV-associated pathogenesis. Moreover, recent progress in antiviral strategies targeting cellular structures is summarized in this article.
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Affiliation(s)
| | | | - Eberhard Hildt
- Paul-Ehrlich-Institute, Department of Virology, D-63225 Langen, Germany; (K.T.); (M.B.)
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Stephenson-Tsoris S, Liang TJ. Hepatitis Delta Virus-Host Protein Interactions: From Entry to Egress. Viruses 2023; 15:1530. [PMID: 37515216 PMCID: PMC10383234 DOI: 10.3390/v15071530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 07/04/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023] Open
Abstract
Hepatitis delta virus (HDV) is the smallest known human virus and causes the most severe form of human viral hepatitis, yet it is still not fully understood how the virus replicates and how it interacts with many host proteins during replication. This review aims to provide a systematic review of all the host factors currently known to interact with HDV and their mechanistic involvement in all steps of the HDV replication cycle. Finally, we discuss implications for therapeutic development based on our current knowledge of HDV-host protein interactions.
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Affiliation(s)
- Susannah Stephenson-Tsoris
- Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
| | - T Jake Liang
- Liver Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
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Chiou WC, Lu HF, Chen JC, Lai YH, Chang MF, Huang YL, Tien N, Huang C. Identification of a novel interaction site between the large hepatitis delta antigen and clathrin that regulates the assembly of genotype III hepatitis delta virus. Virol J 2022; 19:163. [PMID: 36253859 PMCID: PMC9578201 DOI: 10.1186/s12985-022-01866-3] [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] [Received: 02/24/2022] [Accepted: 08/17/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Hepatitis delta virus (HDV), a satellite virus of hepatitis B virus (HBV), is a small, defective RNA virus strongly associated with the most severe form of hepatitis and progressive chronic liver disease and cirrhosis. Chronic hepatitis D, resulting from HBV/HDV coinfection, is considered to be the most severe form of viral hepatitis and affects 12-20 million people worldwide. Involved in the endocytosis and exocytosis of cellular and viral proteins, clathrin contributes to the pathogenesis and morphogenesis of HDV. Previously, we demonstrated that HDV-I and -II large hepatitis delta antigens (HDAg-L) possess a putative clathrin box that interacts with clathrin heavy chain (CHC) and supports HDV assembly. METHODS Virus assembly and vesicular trafficking of HDV virus-like particles (VLPs) were evaluated in Huh7 cells expressing HDV-I, -II and -III HDAg-L and hepatitis B surface antigen (HBsAg). To elucidate the interaction motif between HDAg-L and CHC, site-directed mutagenesis was performed to introduce mutations into HDAg-L and CHC and analyzed using coimmunoprecipitation or pull-down assays. RESULTS Comparable to HDV-I virus-like particles (VLPs), HDV-III VLPs were produced at a similar level and secreted into the medium via clathrin-mediated post-Golgi vesicular trafficking. Mutation at F27 or E33 of CHC abolished the binding of CHC to the C-terminus of HDV-III HDAg-L. Mutation at W207 of HDV-III HDAg-L inhibited its association with CHC and interfered with HDV-III VLP formation. We elucidated mechanism of the binding of HDV-III HDAg-L to CHC and confirmed the pivotal role of clathrin binding in the assembly of genotype III HDV. CONCLUSIONS A novel W box which was identified at the C terminus of HDV-III HDAg-L is known to differ from the conventional clathrin box but also interacts with CHC. The novel W box of HDAg-L constitutes a new molecular target for anti-HDV-III therapeutics.
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Affiliation(s)
- Wei-Chung Chiou
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Linong St., Beitou District, Taipei, 11221, Taiwan
| | - Hsu-Feng Lu
- Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung, 41354, Taiwan.,Department of Laboratory Medicine, China Medical University Hospital, Taichung, 40402, Taiwan
| | - Jui-Chieh Chen
- Department of Biochemical Science and Technology, National Chiayi University, Chiayi, 60004, Taiwan
| | - Yu-Heng Lai
- Department of Chemistry, Chinese Culture University, Taipei, 11114, Taiwan
| | - Ming-Fu Chang
- Institute of Biochemistry and Molecular Biology, School of Medicine, National Taiwan University, Taipei, 10051, Taiwan
| | - Yuan-Li Huang
- Department of Medical Laboratory Science and Biotechnology, Asia University, Taichung, 41354, Taiwan
| | - Ni Tien
- Department of Laboratory Medicine, China Medical University Hospital, Taichung, 40402, Taiwan
| | - Cheng Huang
- Department of Biotechnology and Laboratory Science in Medicine, National Yang Ming Chiao Tung University, No. 155, Sec. 2, Linong St., Beitou District, Taipei, 11221, Taiwan.
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Zi J, Gao X, Du J, Xu H, Niu J, Chi X. Multiple Regions Drive Hepatitis Delta Virus Proliferation and Are Therapeutic Targets. Front Microbiol 2022; 13:838382. [PMID: 35464929 PMCID: PMC9022428 DOI: 10.3389/fmicb.2022.838382] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/11/2022] [Indexed: 12/02/2022] Open
Abstract
Hepatitis Delta Virus (HDV) is the smallest mammalian single-stranded RNA virus. It requires host cells and hepatitis B virus (HBV) to complete its unique life cycle. The present review summarizes the specific regions on hepatitis D antigen (HDAg) and hepatitis B surface antigen (HBsAg) that drive HDV to utilize host cell machinery system to produce three types of RNA and two forms of HDAg, and hijack HBsAg for its secretion and de novo entry. Previously, interferon-α was the only recommended therapy for HDV infection. In recent years, some new therapies targeting these regions, such as Bulevirtide, Lonafarnib, Nucleic acid polymers have appeared, with better curative effects and fewer adverse reactions.
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Affiliation(s)
- Jun Zi
- Gene Therapy Laboratory, Center for Pathogen Biology and Infectious Diseases, First Hospital of Jilin University, Changchun, China
| | - Xiuzhu Gao
- Department of Hepatology, Center for Pathogen Biology and Infectious Diseases, First Hospital of Jilin University, Changchun, China
| | - Juan Du
- Institute of Virology and AIDS Research, First Hospital of Jilin University, Changchun, China
| | - Hongqin Xu
- Department of Hepatology, Center for Pathogen Biology and Infectious Diseases, First Hospital of Jilin University, Changchun, China
| | - Junqi Niu
- Department of Hepatology, Center for Pathogen Biology and Infectious Diseases, First Hospital of Jilin University, Changchun, China
| | - Xiumei Chi
- Gene Therapy Laboratory, Center for Pathogen Biology and Infectious Diseases, First Hospital of Jilin University, Changchun, China
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Zhou J, Li J, Li H, Zhang Y, Dong W, Jin Y, Yan Y, Gu J, Zhou J. The serine-48 residue of nucleolar phosphoprotein nucleophosmin-1 plays critical role in subcellular localization and interaction with porcine circovirus type 3 capsid protein. Vet Res 2021; 52:4. [PMID: 33413620 PMCID: PMC7792357 DOI: 10.1186/s13567-020-00876-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 12/03/2020] [Indexed: 12/25/2022] Open
Abstract
The transport of circovirus capsid protein into nucleus is essential for viral replication in infected cell. However, the role of nucleolar shuttle proteins during porcine circovirus 3 capsid protein (PCV3 Cap) import is still not understood. Here, we report a previously unidentified nucleolar localization signal (NoLS) of PCV3 Cap, which hijacks the nucleolar phosphoprotein nucleophosmin-1 (NPM1) to facilitate nucleolar localization of PCV3 Cap. The NoLS of PCV3 Cap and serine-48 residue of N-terminal oligomerization domain of NPM1 are essential for PCV3 Cap/NPM1 interaction. In addition, charge property of serine-48 residue of NPM1 is critical for nucleolar localization and interaction with PCV3 Cap. Taken together, our findings demonstrate for the first time that NPM1 interacts with PCV3 Cap and is responsible for its nucleolar localization.
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Affiliation(s)
- Jianwei Zhou
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Juan Li
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Haimin Li
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Ying Zhang
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Weiren Dong
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Yulan Jin
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Yan Yan
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Jinyan Gu
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China.
| | - Jiyong Zhou
- MOA Key Laboratory of Animal Virology, Center of Veterinary Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China. .,Collaborative Innovation Center and State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University, Hangzhou, PR China.
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6
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Lucifora J, Delphin M. Current knowledge on Hepatitis Delta Virus replication. Antiviral Res 2020; 179:104812. [PMID: 32360949 DOI: 10.1016/j.antiviral.2020.104812] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/20/2020] [Accepted: 04/25/2020] [Indexed: 12/14/2022]
Abstract
Hepatitis B Virus (HBV) that infects liver parenchymal cells is responsible for severe liver diseases and co-infection with Hepatitis Delta Virus (HDV) leads to the most aggressive form of viral hepatitis. Even tough being different for their viral genome (relaxed circular partially double stranded DNA for HBV and circular RNA for HDV), HBV and HDV are both maintained as episomes in the nucleus of infected cells and use the cellular machinery for the transcription of their viral RNAs. We propose here an update on the current knowledge on HDV replication cycle that may eventually help to identify new antiviral targets.
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Affiliation(s)
- Julie Lucifora
- INSERM, U1052, Cancer Research Center of Lyon (CRCL), Université de Lyon (UCBL1), CNRS UMR_5286, France.
| | - Marion Delphin
- INSERM, U1052, Cancer Research Center of Lyon (CRCL), Université de Lyon (UCBL1), CNRS UMR_5286, France
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Mou C, Wang M, Pan S, Chen Z. Identification of Nuclear Localization Signals in the ORF2 Protein of Porcine Circovirus Type 3. Viruses 2019; 11:v11121086. [PMID: 31766638 PMCID: PMC6950156 DOI: 10.3390/v11121086] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 11/18/2019] [Accepted: 11/19/2019] [Indexed: 11/16/2022] Open
Abstract
Porcine circovirus type 3 (PCV3) contains two major open reading frames (ORFs) and the ORF2 gene encodes the major structural capsid protein. In this study, nuclear localization of ORF2 was demonstrated by fluorescence observation and subcellular fractionation assays in ORF2-transfected PK-15 cells. The subcellular localization of truncated ORF2 indicated that the 38 N-terminal amino acids were responsible for the nuclear localization of ORF2. The truncated and site-directed mutagenesis of this domain were constructed, and the results demonstrated that the basic amino acid residues at positions 8-32 were essential for the strict nuclear localization. The basic motifs 8RRR-R-RRR16 and 16RRRHRRR22 were further shown to be the key functional nucleolar localization signals that guide PCV3 ORF2 into nucleoli. Furthermore, sequence analysis showed that the amino acids of PCV3 nuclear localization signals were highly conserved. Overall, this study provides insight into the biological and functional characteristics of the PCV3 ORF2 protein.
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Affiliation(s)
- Chunxiao Mou
- College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China; (C.M.); (S.P.)
| | - Minmin Wang
- College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China; (C.M.); (S.P.)
| | - Shuonan Pan
- College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China; (C.M.); (S.P.)
| | - Zhenhai Chen
- College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China; (C.M.); (S.P.)
- Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou 225009, China
- Joint International Research Laboratory of Agriculture and Agri-Product Safety, the Ministry of Education of China, Yangzhou University, Yangzhou 225009, China
- Correspondence: ; Tel.: +86-182-5274-7459 or +86-514-8979-8271; Fax: 0514-8797-2218
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Lobaina Y, Perera Y. Implication of B23/NPM1 in Viral Infections, Potential Uses of B23/NPM1 Inhibitors as Antiviral Therapy. Infect Disord Drug Targets 2019; 19:2-16. [PMID: 29589547 DOI: 10.2174/1871526518666180327124412] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 01/08/2018] [Accepted: 02/12/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND B23/nucleophosmin (B23/NPM1) is an abundant multifunctional protein mainly located in the nucleolus but constantly shuttling between the nucleus and cytosol. As a consequence of its constitutive expression, intracellular dynamics and binding capacities, B23/NPM1 interacts with multiple cellular factors in different cellular compartments, but also with viral proteins from both DNA and RNA viruses. B23/NPM1 influences overall viral replication of viruses like HIV, HBV, HCV, HDV and HPV by playing functional roles in different stages of viral replication including nuclear import, viral genome transcription and assembly, as well as final particle formation. Of note, some virus modify the subcellular localization, stability and/or increases B23/NPM1 expression levels on target cells, probably to foster B23/NPM1 functions in their own replicative cycle. RESULTS This review summarizes current knowledge concerning the interaction of B23/NPM1 with several viral proteins during relevant human infections. The opportunities and challenges of targeting this well-conserved host protein as a potentially new broad antiviral treatment are discussed in detail. Importantly, although initially conceived to treat cancer, a handful of B23/NPM1 inhibitors are currently available to test on viral infection models. CONCLUSION As B23/NPM1 partakes in key steps of viral replication and some viral infections remain as unsolved medical needs, an appealing idea may be the expedite evaluation of B23/NPM1 inhibitors in viral infections. Furthermore, worth to be addressed is if the up-regulation of B23/NPM1 protein levels that follows persistent viral infections may be instrumental to the malignant transformation induced by virus like HBV and HCV.
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Affiliation(s)
- Yadira Lobaina
- Therapeutic Hepatitis B Vaccine Group, Vaccine Division, Biomedical Research Direction, Center for Genetic Engineering and Biotechnology, Havana, CP 10600, Cuba
| | - Yasser Perera
- Molecular Oncology Group, Pharmaceuticals Division, Biomedical Research Direction, Center for Genetic Engineering and Biotechnology, Havana, CP 10600, Cuba
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Terrier O, Carron C, De Chassey B, Dubois J, Traversier A, Julien T, Cartet G, Proust A, Hacot S, Ressnikoff D, Lotteau V, Lina B, Diaz JJ, Moules V, Rosa-Calatrava M. Nucleolin interacts with influenza A nucleoprotein and contributes to viral ribonucleoprotein complexes nuclear trafficking and efficient influenza viral replication. Sci Rep 2016; 6:29006. [PMID: 27373907 PMCID: PMC4931502 DOI: 10.1038/srep29006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 06/09/2016] [Indexed: 01/18/2023] Open
Abstract
Influenza viruses replicate their single-stranded RNA genomes in the nucleus of infected cells and these replicated genomes (vRNPs) are then exported from the nucleus to the cytoplasm and plasma membrane before budding. To achieve this export, influenza viruses hijack the host cell export machinery. However, the complete mechanisms underlying this hijacking remain not fully understood. We have previously shown that influenza viruses induce a marked alteration of the nucleus during the time-course of infection and notably in the nucleolar compartment. In this study, we discovered that a major nucleolar component, called nucleolin, is required for an efficient export of vRNPs and viral replication. We have notably shown that nucleolin interacts with the viral nucleoprotein (NP) that mainly constitutes vRNPs. Our results suggest that this interaction could allow vRNPs to "catch" the host cell export machinery, a necessary step for viral replication.
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Affiliation(s)
- Olivier Terrier
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Coralie Carron
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Benoît De Chassey
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Julia Dubois
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Aurélien Traversier
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Thomas Julien
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
- VirNext, Faculté de Médecine RTH Laennec, Université Lyon 1, Lyon, France
| | - Gaëlle Cartet
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Anaïs Proust
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
- VirNext, Faculté de Médecine RTH Laennec, Université Lyon 1, Lyon, France
| | - Sabine Hacot
- Centre de Recherche en Cancérologie de Lyon, UMR Inserm 1052 CNRS 5286, Centre Léon Bérard, Lyon, France and Université de Lyon, Lyon, France
| | - Denis Ressnikoff
- CIQLE, Centre d’imagerie quantitative Lyon-Est, Université Claude Bernard Lyon 1, Lyon, France
| | - Vincent Lotteau
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Bruno Lina
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
- Hospices Civils de Lyon, Laboratory of Virology, Lyon, France
| | - Jean-Jacques Diaz
- Centre de Recherche en Cancérologie de Lyon, UMR Inserm 1052 CNRS 5286, Centre Léon Bérard, Lyon, France and Université de Lyon, Lyon, France
| | - Vincent Moules
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
- VirNext, Faculté de Médecine RTH Laennec, Université Lyon 1, Lyon, France
| | - Manuel Rosa-Calatrava
- Virologie et Pathologie Humaine - Team VirPath - Université Claude Bernard Lyon 1 - Hospices Civils de Lyon, Lyon, France
- CIRI, International Center for Infectiology Research, Inserm U1111, CNRS UMR5308, ENS Lyon, Université Claude Bernard Lyon 1, Lyon, France
- VirNext, Faculté de Médecine RTH Laennec, Université Lyon 1, Lyon, France
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Yu YTC, Chien SC, Chen IY, Lai CT, Tsay YG, Chang SC, Chang MF. Surface vimentin is critical for the cell entry of SARS-CoV. J Biomed Sci 2016; 23:14. [PMID: 26801988 PMCID: PMC4724099 DOI: 10.1186/s12929-016-0234-7] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 01/12/2016] [Indexed: 01/19/2023] Open
Abstract
Background Severe acute respiratory syndrome coronavirus (SARS-CoV) caused a global panic due to its high morbidity and mortality during 2002 and 2003. Soon after the deadly disease outbreak, the angiotensin-converting enzyme 2 (ACE2) was identified as a functional cellular receptor in vitro and in vivo for SARS-CoV spike protein. However, ACE2 solely is not sufficient to allow host cells to become susceptible to SARS-CoV infection, and other host factors may be involved in SARS-CoV spike protein-ACE2 complex. Results A host intracellular filamentous cytoskeletal protein vimentin was identified by immunoprecipitation and LC-MS/MS analysis following chemical cross-linking on Vero E6 cells that were pre-incubated with the SARS-CoV spike protein. Moreover, flow cytometry data demonstrated an increase of the cell surface vimentin level by 16.5 % after SARS-CoV permissive Vero E6 cells were treated with SARS-CoV virus-like particles (VLPs). A direct interaction between SARS-CoV spike protein and host surface vimentin was further confirmed by far-Western blotting. In addition, antibody neutralization assay and shRNA knockdown experiments indicated a vital role of vimentin in cell binding and uptake of SARS-CoV VLPs and the viral spike protein. Conclusions A direct interaction between vimentin and SARS-CoV spike protein during viral entry was observed. Vimentin is a putative anti-viral drug target for preventing/reducing the susceptibility to SARS-CoV infection.
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Affiliation(s)
- Yvonne Ting-Chun Yu
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
| | - Ssu-Chia Chien
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
| | - I-Yin Chen
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan. .,Institute of Microbiology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
| | - Chia-Tsen Lai
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
| | - Yeou-Guang Tsay
- Institute of Biochemistry and Molecular Biology, School of Life Sciences, National Yang-Ming University, Taipei, 112, Taiwan.
| | - Shin C Chang
- Institute of Microbiology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
| | - Ming-Fu Chang
- Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, First Section, Taipei, 100, Taiwan.
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Abstract
The nucleolus is the largest nuclear organelle and is the primary site of ribosome subunit biogenesis in eukaryotic cells. It is assembled around arrays of ribosomal DNA genes, forming specific chromosomal features known as nucleolar organizing regions (NORs) which are the sites of ribosomal DNA transcription. While the nucleolus main activity involve different steps of ribosome biogenesis, the presence of proteins with no obvious relationship with ribosome subunit production suggests additional functions for the nucleolus, such as regulation of mitosis, cell cycle progression, stress response and biogenesis of multiple ribonucleoprotein complexes. The many novel factors and separate classes of proteins identified within the nucleolus support this view that the nucleolus may perform additional functions beyond its known role in ribosome subunit biogenesis. Here we review our knowledge of the nucleolar functions and will provide a detailed picture of how the nucleolus is involved in many cellular pathways.
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Affiliation(s)
- David P. Bazett-Jones
- Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario Canada
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12
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Abstract
This work reviews specific related aspects of hepatitis delta virus (HDV) reproduction, including virion structure, the RNA genome, the mode of genome replication, the delta antigens, and the assembly of HDV using the envelope proteins of its helper virus, hepatitis B virus (HBV). These topics are considered with perspectives ranging from a history of discovery through to still-unsolved problems. HDV evolution, virus entry, and associated pathogenic potential and treatment of infections are considered in other articles in this collection.
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Affiliation(s)
- John M Taylor
- Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111
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13
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Mendes M, Pérez-Hernandez D, Vázquez J, Coelho AV, Cunha C. Proteomic changes in HEK-293 cells induced by hepatitis delta virus replication. J Proteomics 2013; 89:24-38. [PMID: 23770296 DOI: 10.1016/j.jprot.2013.06.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/21/2013] [Accepted: 06/04/2013] [Indexed: 02/07/2023]
Abstract
UNLABELLED Hepatitis delta virus (HDV) infection greatly increases the risk of hepatocellular carcinoma in hepatitis B virus chronically infected patients. HDV is highly dependent on host factors for accomplishment of the replication cycle. However, these factors are largely unknown and the mechanisms involved in the pathogenicity of the virus still remain elusive. Here, we made use of the HEK-293 cell line, which was engineered in order to mimic HDV replication. Five different proteomes were analyzed and compared using a MS-based quantitative proteomics approach by (18)O/(16)O stable isotope labeling. About 3000 proteins were quantified and 89 found to be differentially expressed as a consequence HDV RNA replication. The down-regulation of p53 , HSPE, and ELAV as well as the up-regulation of Transportin 1 , EIF3D, and Cofilin 1 were validated by Western blot. A systems biology approach was additionally used to analyze altered pathways and networks. The G2/M DNA damage checkpoint and pyruvate metabolism were among the most affected pathways, and Cancer was the most likely disease associated to HDV replication. Western blot analysis allowed identifying 14-3-3 σ interactor as down-regulated protein acting in the G2/M cell cycle control checkpoint. This evidence supports deregulation of G2/M checkpoint as a possible mechanism involved in the promotion of HDV associated hepatocellular carcinoma. BIOLOGICAL SIGNIFICANCE This manuscript provides a description of changes observed in the cellular proteome that arise as result of expression of the hepatitis delta virus (HDV) antigen as well as virus genome replication. Using a systems biology approach cancer was found to be the most probable disease associated with HDV replication. Additionally, results show that HDV alters the regulation of G2/M cell cycle control checkpoint. Taken together, our data provide new insights into probable mechanisms associated with the increased incidence of hepatocellular carcinoma observed in HDV infected patients.
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Affiliation(s)
- Marta Mendes
- Unidade de Microbiologia Médica, Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal
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14
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Affiliation(s)
- Mark O. J. Olson
- Dept. Biochemistry, University of Mississippi Medical Center, North State St. 2500, Jackson, 39216 Mississippi USA
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15
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Casaca A, Fardilha M, da Cruz E Silva E, Cunha C. In Vivo Interaction of the Hepatitis Delta Virus Small Antigen with the ELAV-Like Protein HuR. Open Virol J 2011; 5:12-21. [PMID: 21660185 PMCID: PMC3109592 DOI: 10.2174/1874357901105010012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 10/27/2010] [Accepted: 11/04/2010] [Indexed: 01/05/2023] Open
Abstract
The small and large delta antigens (S-HDAg and L-HDAg, respectively) represent two forms of the only protein encoded by the hepatitis delta virus (HDV) RNA genome. Consequently, HDV relies, at a large extent, on the host cell machinery for replication and transcription. Until now, only a limited number of cellular proteins were identified as S-HDAg or L-HDAg partners being involved in the modulation of the virus life cycle. In an attempt to identify cellular S-HDAg-binding proteins we made use of a yeast two-hybrid approach to screen a human liver cDNA library. We were able to identify HuR, a ubiquitously expressed protein involved in RNA stabilization, as an S-HDAg partner both in vitro and in vivo. HuR was found to be overexpressed and colocalize with HDAg in human hepatoma cells. siRNA knockdown of HuR mRNA resulted in inhibition of S-HDAg and L-HDAg expression.
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Affiliation(s)
- Ana Casaca
- Unidade de Biologia Molecular, Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa. Rua da Junqueira 100, 1349-008 Lisboa, Portugal
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16
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Upregulation of the chemokine (C-C motif) ligand 2 via a severe acute respiratory syndrome coronavirus spike-ACE2 signaling pathway. J Virol 2010; 84:7703-12. [PMID: 20484496 DOI: 10.1128/jvi.02560-09] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus (SARS-CoV) was identified to be the causative agent of SARS with atypical pneumonia. Angiotensin-converting enzyme 2 (ACE2) is the major receptor for SARS-CoV. It is not clear whether ACE2 conveys signals from the cell surface to the nucleus and regulates expression of cellular genes upon SARS-CoV infection. To understand the pathogenesis of SARS-CoV, human type II pneumocyte (A549) cells were incubated with the viral spike protein or with SARS-CoV virus-like particles containing the viral spike protein to examine cytokine modulation in lung cells. Results from oligonucleotide-based microarray, real-time PCR, and enzyme-linked immunosorbent assays indicated an upregulation of the fibrosis-associated chemokine (C-C motif) ligand 2 (CCL2) by the viral spike protein and the virus-like particles. The upregulation of CCL2 by SARS-CoV spike protein was mainly mediated by extracellular signal-regulated kinase 1 and 2 (ERK1/2) and AP-1 but not the IkappaBalpha-NF-kappaB signaling pathway. In addition, Ras and Raf upstream of the ERK1/2 signaling pathway were involved in the upregulation of CCL2. Furthermore, ACE2 receptor was activated by casein kinase II-mediated phosphorylation in cells pretreated with the virus-like particles containing spike protein. These results indicate that SARS-CoV spike protein triggers ACE2 signaling and activates fibrosis-associated CCL2 expression through the Ras-ERK-AP-1 pathway.
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17
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Interaction of host cellular proteins with components of the hepatitis delta virus. Viruses 2010; 2:189-212. [PMID: 21994607 PMCID: PMC3185554 DOI: 10.3390/v2010189] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 01/13/2010] [Accepted: 01/14/2010] [Indexed: 12/18/2022] Open
Abstract
The hepatitis delta virus (HDV) is the smallest known RNA pathogen capable of propagation in the human host and causes substantial global morbidity and mortality. Due to its small size and limited protein coding capacity, HDV is exquisitely reliant upon host cellular proteins to facilitate its transcription and replication. Remarkably, HDV does not encode an RNA-dependent RNA polymerase which is traditionally required to catalyze RNA-templated RNA synthesis. Furthermore, HDV lacks enzymes responsible for post-transcriptional and -translational modification, processes which are integral to the HDV life cycle. This review summarizes the known HDV-interacting proteins and discusses their significance in HDV biology.
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18
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Hepatitis delta virus RNA replication. Viruses 2009; 1:818-31. [PMID: 21994571 PMCID: PMC3185533 DOI: 10.3390/v1030818] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Revised: 11/03/2009] [Accepted: 11/03/2009] [Indexed: 12/12/2022] Open
Abstract
Hepatitis delta virus (HDV) is a distant relative of plant viroids in the animal world. Similar to plant viroids, HDV replicates its circular RNA genome using a double rolling-circle mechanism. Nevertheless, the production of hepatitis delta antigen (HDAg), which is indispensible for HDV replication, is a unique feature distinct from plant viroids, which do not encode any protein. Here the HDV RNA replication cycle is reviewed, with emphasis on the function of HDAg in modulating RNA replication and the nature of the enzyme involved.
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19
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Cao D, Haussecker D, Huang Y, Kay MA. Combined proteomic-RNAi screen for host factors involved in human hepatitis delta virus replication. RNA (NEW YORK, N.Y.) 2009; 15:1971-9. [PMID: 19776158 PMCID: PMC2764473 DOI: 10.1261/rna.1782209] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Human hepatitis delta virus (HDV) is the only animal virus known to replicate its RNA genome using a host polymerase because its only virally encoded proteins, the small and large hepatitis delta antigens (HDAg-S and HDAg-L), lack polymerase activity. Although this makes HDV an ideal model system to study RNA-directed transcription in mammalian cells, little is known about the host factors involved in its replication. To comprehensively identify such host factors, we created a stable cell line carrying a functional FLAG-HDAg-S. Anti-Flag immunopurification and mass spectrometry identified >100 proteins associated with FLAG-HDAg-S, many of which had predicted roles in RNA metabolism. The biological relevance of this screen was strongly supported by the identification of nine out of the 12 subunits of the RNA polymerase II complex thought to mediate HDV replication. To further investigate the significance of these factors for HDV replication, we selected 65 proteins to look for factors that would also affect the accumulation of HDV RNA following siRNA knockdown. Fifteen and three factors were found to regulate HDV RNA accumulation negatively and positively, respectively, upon RNAi knockdown. Our results provide a valuable resource for future research to advance our mechanistic understanding of HDV replication and RNA-directed transcription in mammalian cells.
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20
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Abstract
Hepatitis delta virus (HDV) is a subviral agent dependent upon hepatitis B virus (HBV). HDV uses the envelope proteins of HBV to achieve assembly and infection of target cells. Otherwise, the replication of the RNA genome of HDV is totally different from that of its helper virus, and involves redirection of host polymerase activity. This chapter is concerned with recent developments in our understanding of the genome replication process.
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Affiliation(s)
- John M Taylor
- Fox Chase Cancer Center, Philadelphia, Pennsylvania, USA
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21
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Clathrin-mediated post-Golgi membrane trafficking in the morphogenesis of hepatitis delta virus. J Virol 2009; 83:12314-24. [PMID: 19793827 DOI: 10.1128/jvi.01044-09] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Clathrin is involved in the endocytosis and exocytosis of cellular proteins and the process of virus infection. We have previously demonstrated that large hepatitis delta antigen (HDAg-L) functions as a clathrin adaptor, but the detailed mechanisms of clathrin involvement in the morphogenesis of hepatitis delta virus (HDV) are not clear. In this study, we found that clathrin heavy chain (CHC) is a key determinant in the morphogenesis of HDV. HDAg-L with a single amino acid substitution at the clathrin box retained nuclear export activity but failed to interact with CHC and to assemble into virus-like particles. Downregulation of CHC function by a dominant-negative mutant or by short hairpin RNA reduced the efficiency of HDV assembly, but not the secretion of hepatitis B virus subviral particles. In addition, the coexistence of a cell-permeable peptide derived from the C terminus of HDAg-L significantly interfered with the intracellular transport of HDAg-L. HDAg-L, small HBsAg, and CHC were found to colocalize with the trans-Golgi network and were highly enriched on clathrin-coated vesicles. Furthermore, genotype II HDV, which assembles less efficiently than genotype I HDV does, has a putative clathrin box in its HDAg-L but interacted only weakly with CHC. The assembly efficiency of the various HDV genotypes correlates well with the CHC-binding activity of their HDAg-Ls and coincides with the severity of disease outcome. Thus, the clathrin box and the nuclear export signal at the C terminus of HDAg-L are potential new molecular targets for HDV therapy.
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22
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Abstract
Viruses are intracellular pathogens that have to usurp some of the cellular machineries to provide an optimal environment for their own replication. An increasing number of reports reveal that many viruses induce modifications of nuclear substructures including nucleoli, whether they replicate or not in the nucleus of infected cells. Indeed, during infection of cells with various types of human viruses, nucleoli undergo important morphological modifications. A large number of viral components traffic to and from the nucleolus where they interact with different cellular and/or viral factors, numerous host nucleolar proteins are redistributed in other cell compartments or are modified and some cellular proteins are delocalised in the nucleolus of infected cells. Well‐documented studies have established that several of these nucleolar modifications play a role in some steps of the viral cycle, and also in fundamental cellular pathways. The nucleolus itself is the place where several essential steps of the viral cycle take place. In other cases, viruses divert host nucleolar proteins from their known functions in order to exert new unexpected role(s). Copyright © 2009 John Wiley & Sons, Ltd.
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Affiliation(s)
- Anna Greco
- Université de Lyon, Lyon F-69003, France.
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23
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Han Z, Alves C, Gudima S, Taylor J. Intracellular localization of hepatitis delta virus proteins in the presence and absence of viral RNA accumulation. J Virol 2009; 83:6457-63. [PMID: 19369324 PMCID: PMC2698582 DOI: 10.1128/jvi.00008-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2009] [Accepted: 04/11/2009] [Indexed: 02/08/2023] Open
Abstract
Hepatitis delta virus (HDV) encodes one protein, hepatitis delta antigen (deltaAg), a 195-amino-acid RNA binding protein essential for the accumulation of HDV RNA-directed RNA transcripts. It has been accepted that deltaAg localizes predominantly to the nucleolus in the absence of HDV genome replication while in the presence of replication, deltaAg facilitates HDV RNA transport to the nucleoplasm and helps redirect host RNA polymerase II (Pol II) to achieve transcription and accumulation of processed HDV RNA species. This study used immunostaining and confocal microscopy to evaluate factors controlling the localization of deltaAg in the presence and absence of replicating and nonreplicating HDV RNAs. When deltaAg was expressed in the absence of full-length HDV RNAs, it colocalized with nucleolin, a predominant nucleolar protein. With time, or more quickly after induced cell stress, there was a redistribution of both deltaAg and nucleolin to the nucleoplasm. Following expression of nonreplicating HDV RNAs, deltaAg moved to the nucleoplasm, but nucleolin was unchanged. When deltaAg was expressed along with replicating HDV RNA, it was found predominantly in the nucleoplasm along with Pol II. This localization was insensitive to inhibitors of HDV replication, suggesting that the majority of deltaAg in the nucleoplasm reflects ribonucleoprotein accumulation rather than ongoing transcription. An additional approach was to reevaluate several forms of deltaAg altered at specific locations considered to be essential for protein function. These studies provide evidence that deltaAg does not interact directly with either Pol II or nucleolin and that forms of deltaAg which support replication are also capable of prior nucleolar transit.
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Affiliation(s)
- Ziying Han
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111-2497, USA
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24
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Mota S, Mendes M, Freitas N, Penque D, Coelho AV, Cunha C. Proteome analysis of a human liver carcinoma cell line stably expressing hepatitis delta virus ribonucleoproteins. J Proteomics 2008; 72:616-27. [PMID: 19136081 DOI: 10.1016/j.jprot.2008.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/03/2008] [Accepted: 12/04/2008] [Indexed: 01/26/2023]
Abstract
Hepatitis delta virus (HDV) infects human hepatocytes already infected with the hepatitis B virus increasing about ten fold the risk of cirrhosis and fulminant hepatitis. The lack of an appropriate cell culture system capable of supporting virus replication has so far impaired the detailed investigation of the HDV biology including the identification of host factors involved in pathogenesis. Here, we made use of a HDV cDNA stably transfected cell line, Huh7-D12, in a proteomic approach to identify the changes in the protein expression profiles in human liver cells that arise as a consequence of HDV replication. Total protein extracts from Huh7-D12 cells and of the corresponding non transfected human liver carcinoma cell line, Huh7, were separated by 2-DE. Differentially expressed spots were identified by MALDI-TOF followed by database searching. We identified 23 differentially expressed proteins of which 15 were down regulated and 8 up regulated in Huh7-D12 cells. These proteins were found to be involved in different cellular pathways. The down regulation of the histone H1-binding protein and of triosephosphate isomerase was confirmed by Real time PCR, and the up regulation of the La protein and lamin A/C was validated by western blot.
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Affiliation(s)
- Sérgio Mota
- Unidade de Biologia Molecular, Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Rua da Junqueira 96, Lisbon, Portugal
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25
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Emmott E, Dove BK, Howell G, Chappell LA, Reed ML, Boyne JR, You JH, Brooks G, Whitehouse A, Hiscox JA. Viral nucleolar localisation signals determine dynamic trafficking within the nucleolus. Virology 2008; 380:191-202. [PMID: 18775548 PMCID: PMC7103397 DOI: 10.1016/j.virol.2008.05.032] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 05/22/2008] [Accepted: 05/30/2008] [Indexed: 02/08/2023]
Abstract
Localisation of both viral and cellular proteins to the nucleolus is determined by a variety of factors including nucleolar localisation signals (NoLSs), but how these signals operate is not clearly understood. The nucleolar trafficking of wild type viral proteins and chimeric proteins, which contain altered NoLSs, were compared to investigate the role of NoLSs in dynamic nucleolar trafficking. Three viral proteins from diverse viruses were selected which localised to the nucleolus; the coronavirus infectious bronchitis virus nucleocapsid (N) protein, the herpesvirus saimiri ORF57 protein and the HIV-1 Rev protein. The chimeric proteins were N protein and ORF57 protein which had their own NoLS replaced with those from ORF57 and Rev proteins, respectively. By analysing the sub-cellular localisation and trafficking of these viral proteins and their chimeras within and between nucleoli using confocal microscopy and photo-bleaching we show that NoLSs are responsible for different nucleolar localisations and trafficking rates.
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Affiliation(s)
- Edward Emmott
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Brian K. Dove
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Gareth Howell
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Lucy A. Chappell
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Mark L. Reed
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - James R. Boyne
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Jae-Hwan You
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
| | - Gavin Brooks
- School of Pharmacy, University of Reading, Reading, UK
| | - Adrian Whitehouse
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - Julian A. Hiscox
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, LS2 9JT, Leeds, England, UK
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
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26
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Goić B, Bustamante J, Miquel A, Alvarez M, Vera MI, Valenzuela PDT, Burzio LO. The nucleoprotein and the viral RNA of infectious salmon anemia virus (ISAV) are localized in the nucleolus of infected cells. Virology 2008; 379:55-63. [PMID: 18632128 DOI: 10.1016/j.virol.2008.05.036] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 03/21/2008] [Accepted: 05/30/2008] [Indexed: 11/20/2022]
Abstract
The infectious salmon anemia virus (ISAV), which belongs to the new genus Isavirus of the Orthomyxoviridae family, is an important pathogen of the salmon farming industry. Indirect immunofluorescence assays carried out with monoclonal antibodies specific for the nucleoprotein (NP) reveal differential staining of sub-cellular compartments in infected cells. Particularly interesting was the staining of the nucleolus, which showed co-localization with nucleolin in CHSE-214, EPC and SHK-1 cells infected with ISAV. These results were confirmed by co-immunoprecipitation studies showing an interaction between NP and nucleolin. In addition, in situ hybridization carried out with probes specific for each of the 8 RNA segments of ISAV showed that the genomic as well as the anti-genomic strands were also localized in the nucleolus. These results suggest a role of the nucleolus in the replication and/or in the packaging of the ISAV genome.
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27
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ERK1/2-mediated phosphorylation of small hepatitis delta antigen at serine 177 enhances hepatitis delta virus antigenomic RNA replication. J Virol 2008; 82:9345-58. [PMID: 18632853 DOI: 10.1128/jvi.00656-08] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The small hepatitis delta virus (HDV) antigen (SHDAg) plays an essential role in HDV RNA double-rolling-circle replication. Several posttranslational modifications (PTMs) of HDAgs, including phosphorylation, acetylation, and methylation, have been characterized. Among the PTMs, the serine 177 residue of SHDAg is a phosphorylation site, and its mutation preferentially abolishes HDV RNA replication from antigenomic RNA to genomic RNA. Using coimmunoprecipitation analysis, the cellular kinases extracellular signal-related kinases 1 and 2 (ERK1/2) are found to be associated with the Flag-tagged SHDAg mutant (Ser-177 replaced with Cys-177). In an in vitro kinase assay, serine 177 of SHDAg was phosphorylated directly by either Flag-ERK1 or Flag-ERK2. Activation of endogenous ERK1/2 by a constitutively active MEK1 (hemagglutinin-AcMEK1) increased phosphorylation of SHDAg at Ser-177; this phosphorylation was confirmed by immunoblotting using an antibody against phosphorylated S177 and mass spectrometric analysis. Interestingly, we found an increase in the HDV replication from antigenomic RNA to genomic RNA but not in that from genomic RNA to antigenomic RNA. The Ser-177 residue was critical for SHDAg interaction with RNA polymerase II (RNAPII), the enzyme proposed to regulate antigenomic RNA replication. These results demonstrate the role of ERK1/2-mediated Ser-177 phosphorylation in modulating HDV antigenomic RNA replication, possibly through RNAPII regulation. The results may shed light on the mechanisms of HDV RNA replication.
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28
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Reyes-Reyes EM, Akiyama SK. Cell-surface nucleolin is a signal transducing P-selectin binding protein for human colon carcinoma cells. Exp Cell Res 2008; 314:2212-23. [PMID: 18504038 PMCID: PMC2504360 DOI: 10.1016/j.yexcr.2008.03.016] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 03/18/2008] [Accepted: 03/19/2008] [Indexed: 01/02/2023]
Abstract
We have previously shown that P-selectin binding to Colo-320 human colon carcinoma cells induces specific activation of the alpha(5)beta(1) integrin with a concomitant increase of cell adhesion and spreading on fibronectin substrates in a phosphatidylinositol 3-kinase (PI3-K) and p38 MAPK-dependent manner. Here, we identified by affinity chromatography and characterized nucleolin as a P-selectin receptor on Colo-320 cells. Nucleolin mAb D3 significantly decreases the Colo-320 cell adhesion to immobilized P-selectin-IgG-Fc. Moreover, nucleolin becomes clustered at the external side of the plasma membrane of living, intact cells when bound to cross-linked P-selectin-IgG-Fc chimeric protein. We have also found P-selectin binding to Colo-320 cells induces tyrosine phosphorylation specifically of cell-surface nucleolin and formation of a signaling complex containing cell-surface nucleolin, PI3-K and p38 MAPK. Using siRNA approaches, we have found that both P-selectin binding to Colo-320 cells and formation of the P-selectin-mediated p38 MAPK/PI3-K signaling complex require nucleolin expression. These results show that nucleolin (or a nucleolin-like protein) is a signaling receptor for P-selectin on Colo-320 cells and suggest a mechanism for linkage of nucleolin to P-selectin-induced signal transduction pathways that regulate the adhesion and the spreading of Colo-320 on fibronectin substrates.
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Affiliation(s)
- E. Merit Reyes-Reyes
- Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
| | - Steven K. Akiyama
- Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA
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29
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Transcription factor YY1 and its associated acetyltransferases CBP and p300 interact with hepatitis delta antigens and modulate hepatitis delta virus RNA replication. J Virol 2008; 82:7313-24. [PMID: 18480431 DOI: 10.1128/jvi.02581-07] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Hepatitis delta virus (HDV) is a pathogenic RNA virus with a plant viroid-like genome structure. HDV encodes two isoforms of delta antigen (HDAg), the small and large forms of HDAg (SHDAg and LHDAg), which are essential for HDV RNA replication and virion assembly, respectively. Replication of HDV RNA depends on host cellular transcription machinery, and the exact molecular mechanism for HDV RNA replication is still unclear. In this study, we demonstrated that both isoforms of HDAg interact with transcription factor YY1 (Yin Yang 1) in vivo and in vitro. Their interaction domains were identified as the middle region encompassing the RNA binding domain of HDAg and the middle GA/GK-rich region and the C-terminal zinc-finger region of YY1. Results of sucrose gradient centrifugation analysis indicated the cosedimentation of the majority of SHDAg and a portion of the LHDAg with YY1 and its associated acetyltransferases CBP (CREB-binding protein) and p300 as a large nuclear complex in vivo. Furthermore, exogenous expression of YY1 or CBP/p300 in HDV RNA replication system showed an enhancement of HDV RNA replication. Interestingly, the acetyltransferase activity of p300 is important for this enhancement. Moreover, SHDAg could be acetylated in vivo, and treatment with cellular deacetylase inhibitor elevated the replication of HDV RNA and acetylation of SHDAg. All together, our results reveal that HDAg interacts with cellular transcription factor YY1 and its associated acetyltransferases CBP and p300 in a large nuclear complex, which in turn modulates the replication of HDV RNA.
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30
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Degenhardt RF, Bonham-Smith PC. Arabidopsis ribosomal proteins RPL23aA and RPL23aB are differentially targeted to the nucleolus and are disparately required for normal development. PLANT PHYSIOLOGY 2008; 147:128-42. [PMID: 18322146 PMCID: PMC2330296 DOI: 10.1104/pp.107.111799] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Accepted: 02/26/2008] [Indexed: 05/19/2023]
Abstract
Protein synthesis is catalyzed by the ribosome, a two-subunit enzyme comprised of four ribosomal RNAs and, in Arabidopsis (Arabidopsis thaliana), 81 ribosomal proteins (r-proteins). Plant r-protein genes exist as families of multiple expressed members, yet only one r-protein from each family is incorporated into any given ribosome, suggesting that many r-protein genes may be functionally redundant or development/tissue/stress specific. Here, we characterized the localization and gene-silencing phenotypes of a large subunit r-protein family, RPL23a, containing two expressed genes (RPL23aA and RPL23aB). Live cell imaging of RPL23aA and RPL23aB in tobacco with a C-terminal fluorescent-protein tag demonstrated that both isoforms accumulated in the nucleolus; however, only RPL23aA was targeted to the nucleolus with an N-terminal fluorescent protein tag, suggesting divergence in targeting efficiency of localization signals. Independent knockdowns of endogenous RPL23aA and RPL23aB transcript levels using RNA interference determined that an RPL23aB knockdown did not alter plant growth or development. Conversely, a knockdown of RPL23aA produced a pleiotropic phenotype characterized by growth retardation, irregular leaf and root morphology, abnormal phyllotaxy and vasculature, and loss of apical dominance. Comparison to other mutants suggests that the phenotype results from reduced ribosome biogenesis, and we postulate a link between biogenesis, microRNA-target degradation, and maintenance of auxin homeostasis. An additional RNA interference construct that coordinately silenced both RPL23aA and RPL23aB demonstrated that this family is essential for viability.
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Affiliation(s)
- Rory F Degenhardt
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2.
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Lee CZ, Sheu JC. Histone H1e interacts with small hepatitis delta antigen and affects hepatitis delta virus replication. Virology 2008; 375:197-204. [PMID: 18314153 DOI: 10.1016/j.virol.2008.02.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2007] [Revised: 01/12/2008] [Accepted: 02/08/2008] [Indexed: 12/13/2022]
Abstract
Hepatitis delta virus (HDV) encodes two isoforms of delta antigens (HDAgs). The small form of HDAg (SHDAg) is required for HDV RNA replication, while the large form of HDAg (LHDAg) is required for viral assembly. Using tandem affinity purification method combined with mass spectrometry, we found that linker histone H1e bound to SHDAg. The binding domain of SHDAg to histone H1e was mapped to the N-terminal 67 amino acids. Oligomerization of SHDAg was required for its interaction with histone H1e. LHDAg barely bound to histone H1e and was masked at N-terminus. The binding domain of histone H1e to SHDAg was mapped to its central globular domain. HDV replication was inhibited by N- or C-terminal deletion mutants of histone H1e and was rescued by wild-type histone H1e. We conclude that histone H1e plays a significant role in HDV replication through forming protein complex with SHDAg.
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Affiliation(s)
- Cha-Ze Lee
- Division of Gastroenterology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
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Changes in the proteome of Huh7 cells induced by transient expression of hepatitis D virus RNA and antigens. J Proteomics 2008; 71:71-9. [PMID: 18541475 DOI: 10.1016/j.jprot.2007.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 12/13/2007] [Accepted: 12/14/2007] [Indexed: 02/06/2023]
Abstract
Hepatitis delta virus (HDV) infection of human hepatocytes infected with the hepatitis B virus (HBV) is associated with increased liver damage and risk of fulminant disease. Although considerable progress has been made towards the elucidation of the mechanisms of HDV replication and pathogenesis, little is still known about the host factors involved in the different steps of the replication cycle. Here, we made use of a proteomic approach to analyse the global alterations in protein expression that arise in human hepatocytes separately transfected with each of the HDV components. Huh7 cells were transiently transfected with plasmids that code for the small delta antigen (S-HDAg), large delta antigen (L-HDAg), genomic RNA (gRNA), and antigenomic RNA (agRNA), respectively. Total protein extracts were separated by 2-DE and differentially expressed spots were identified by MALDI-TOF followed by database searching. We identified 32 proteins known to be involved in different pathways namely nucleic acid metabolism, protein metabolism, transport, signal transduction, apoptosis, and cell growth. Moreover, the down regulation of hnRNP D, HSP105, and triosephosphate isomerase was further confirmed by Real time PCR.
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Nucleolar targeting of hepatitis delta antigen abolishes its ability to initiate viral antigenomic RNA replication. J Virol 2007; 82:692-9. [PMID: 17989182 DOI: 10.1128/jvi.01155-07] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Hepatitis delta virus (HDV) is a small RNA virus that contains one 1.7-kb single-stranded circular RNA of negative polarity. The HDV particle also contains two isoforms of hepatitis delta antigen (HDAg), small (SHDAg) and large HDAg. SHDAg is required for the replication of HDV, which is presumably carried out by host RNA-dependent RNA polymerases. The localization and the HDAg and host RNA polymerase responsible for HDV replication remain important issues to be addressed. In this study, using recombinant SHDAg fused with a heterologous nucleolar localization sequence (NoLS) to confine its subcellular localization in nucleoli, we aimed to study the effect of SHDAg subcellular localization on HDV RNA replication. The initiation of genomic RNA synthesis from antigenomic template was hardly detectable when SHDAg was fused with the NoLS motif and localized mainly in nucleoli. In contrast, the initiation of antigenomic RNA synthesis was not affected. Drug treatment to release a SHDAg-NoLS mutant from nucleoli could partially restore the replication of HDV genomic RNA from antigenomic RNA. This also recovered the cointeraction between SHDAg and RNA polymerase II. These data strongly suggest that nuclear polymerase (RNA polymerase II) is involved in the synthesis of genomic RNA and that the synthesis of antigenomic RNA can occur in nucleoli. Our results support the idea that the replication of HDV genomic RNA or antigenomic RNA is likely to be carried out by different machineries in different subcellular localizations.
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Alves C, Freitas N, Cunha C. Characterization of the nuclear localization signal of the hepatitis delta virus antigen. Virology 2007; 370:12-21. [PMID: 17897693 DOI: 10.1016/j.virol.2007.07.034] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Revised: 06/05/2007] [Accepted: 07/31/2007] [Indexed: 12/18/2022]
Abstract
The delta antigen (HDAg) is the only protein encoded by the hepatitis delta virus (HDV) RNA genome. The HDAg contains an RNA binding domain, a dimerization domain, and a nuclear localization signal (NLS). The nuclear import of HDV RNPs is thought to be one of the first tasks of the HDAg during the HDV replication cycle. Using c-myc-PK fusions with several regions of the HDAg in transfection assays in Huh7 cells, we found that the HDAg NLS consists of a single stretch of 10 amino acids, EGAPPAKRAR, located in positions 66-75. Deletion and mutation analysis of this region showed that both the acidic glutamic acid residue at position 66 and the basic arginine residue at position 75 are essential for promoting nuclear import.
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Affiliation(s)
- Carolina Alves
- Unidade de Biologia Molecular, Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 96 1349-008 Lisboa, Portugal
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Huang C, Chang SC, Yu IC, Tsay YG, Chang MF. Large hepatitis delta antigen is a novel clathrin adaptor-like protein. J Virol 2007; 81:5985-94. [PMID: 17376909 PMCID: PMC1900268 DOI: 10.1128/jvi.02809-06] [Citation(s) in RCA: 33] [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
Clathrin-mediated endocytosis is a common pathway for viral entry, but little is known about the direct association of viral protein with clathrin in the cytoplasm. In this study, a putative clathrin box known to be conserved in clathrin adaptors was identified at the C terminus of the large hepatitis delta antigen (HDAg-L). Similar to clathrin adaptors, HDAg-L directly interacted with the N terminus of the clathrin heavy chain through the clathrin box. HDAg-L is a nucleocytoplasmic shuttle protein important for the assembly of hepatitis delta virus (HDV). Here, we demonstrated that brefeldin A and wortmannin, inhibitors of clathrin-mediated exocytosis and endosomal trafficking, respectively, specifically blocked HDV assembly but had no effect on the assembly of the small surface antigen of hepatitis B virus. In addition, cytoplasm-localized HDAg-L inhibited the clathrin-mediated endocytosis of transferrin and the degradation of epidermal growth factor receptor. These results indicate that HDAg-L is a new clathrin adaptor-like protein, and it may be involved in the maturation and pathogenesis of HDV coinfection or superinfection with hepatitis B virus through interaction with clathrin.
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Affiliation(s)
- Cheng Huang
- Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, No. 1, Jen-Ai Road, First Section, Taipei, Taiwan
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Abstract
The nucleolus is a dynamic subnuclear structure that is crucial to the successful functioning of a cell. Its functions include ribosomal RNA synthesis, cell growth and cell-cycle control as well as responding to cellular stress. Recent studies show that the nucleolus is not a steady-state structure but instead is made up of numerous protein–protein and protein–nucleic-acid interactions that are constantly changing in response to the metabolic conditions of the cell. Many different viruses target the nucleolus to disrupt host-cell function and to recruit cellular proteins to aid in virus replication. The study of viral-protein trafficking to the nucleolus and the interaction of viral proteins with nucleolar proteins is providing many insights into the cell biology of the nucleolus. Because the nucleolus is fundamental to the life cycle of many viruses, disrupting the interaction between the nucleolus and the virus could lead to the design of novel therapeutic strategies.
RNA viruses, particularly positive-strand RNA viruses, interact with the nucleolus to usurp host-cell functions and recruit nucleolar proteins to facilitate virus replication. Here, Julian Hiscox reviews the latest data on RNA-virus interactions with this dynamic subnuclear structure. The nucleolus is a dynamic subnuclear structure with roles in ribosome subunit biogenesis, mediation of cell-stress responses and regulation of cell growth. The proteome and structure of the nucleolus are constantly changing in response to metabolic conditions. RNA viruses interact with the nucleolus to usurp host-cell functions and recruit nucleolar proteins to facilitate virus replication. Investigating the interactions between RNA viruses and the nucleolus will facilitate the design of novel anti-viral therapies, such as recombinant vaccines and therapeutic molecular interventions, and also contribute to a more detailed understanding of the cell biology of the nucleolus.
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Affiliation(s)
- Julian A Hiscox
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, Garstang Building, University of Leeds, Leeds, LS2 9JT, UK.
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Abstract
The nucleolus is the most prominent compartment in the nucleus and known as the site for ribosome biogenesis in eucaryotes. In contrast, there is no such equivalent structure for ribosome synthesis in procaryotes. This raises two concerns that how does the nucleolus evolve and that whether the nucleolus remains playing a single role in ribosome biogenesis along the evolution. Increasing data support new nucleolus functions, including signal recognition particle assembly, small RNA modification, telomerase maturation, cell-cycle and aging control, and cell stress sensor. Multiple functions of the nucleolus possibly result from the plurifunctionality of nucleolar proteins, such as nucleolin and Nopp140. Proteomic analyses of human and Arabidopsis nucleolus lead a remarkable progress in understanding the evolution and new functions of nucleoli. In this review, we present a brief history of nucleolus research and new concepts and unresolved questions. Also, we introduce hepatitis D virus for studying the communication between the nucleolus and other subnuclear compartments, and Caenorhabditis elegans for the role of nucleolus in the development and the epistatic control of nucleologenesis.
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Affiliation(s)
- Szecheng J Lo
- Department of Life Science, Graduate Institute of Basic Medical Science, 259, Wen-Hwa 1st Road, Chang Gung University, TaoYuan 333.
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Abstract
HDV replicates its circular RNA genome using a double rolling-circle mechanism and transcribes a hepatitis delta antigen-encodeing mRNA from the same RNA template during its life cycle. Both processes are carried out by RNA-dependent RNA synthesis despite the fact that HDV does not encode an RNA-dependent RNA polymerase (RdRP). Cellular RNA polymerase II has long been implicated in these processes. Recent findings, however, have shown that the syntheses of genomic and antigenomic RNA strands have different metabolic requirements, including sensitives to alpha-amanitin and the site of synthesis. Evidence is summarized here for the involvement of other cellular polymerases, probably pol I, in the synthesis of antigenomic RNA strand. The ability of mammalian cells to replicate HDV RNA implies that RNA-dependent RNA synthesis was preserved throughout evolution.
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Affiliation(s)
- T B Macnaughton
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles 90033, USA
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Huang WH, Chen CW, Wu HL, Chen PJ. Post-translational modification of delta antigen of hepatitis D virus. Curr Top Microbiol Immunol 2006; 307:91-112. [PMID: 16903222 DOI: 10.1007/3-540-29802-9_5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The hepatitis delta virus (HDV) genome has only one open reading frame, which encodes the viral small delta antigen. After RNA editing, the same open reading frame is extended 19 amino acids at the carboxyl terminus and encodes the large delta antigen. These two viral proteins escort the HDV genome through different cellular compartments for the complicated phases of replication, transcription and, eventually, the formation of progeny virions. To orchestrate these events, the delta antigens have to take distinct cues to traffic to the right compartments and make correct molecular contacts. In eukaryotes, post-translational modification (PTM) is a major mechanism of dictating the multiple functions of a single protein. Multiple PTMs, including phosphorylation, isoprenylation, acetylation, and methylation, have been identified on hepatitis delta antigens. In this chapter we review these PTMs and discuss their functions in regulating and coordinating the life cycle of HDV.
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Affiliation(s)
- W H Huang
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, and Hepatitis Research Center, National Taiwan University Hospital, Taipei
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Greco-Stewart VS, Thibault CSL, Pelchat M. Binding of the polypyrimidine tract-binding protein-associated splicing factor (PSF) to the hepatitis delta virus RNA. Virology 2006; 356:35-44. [PMID: 16938326 DOI: 10.1016/j.virol.2006.06.040] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2006] [Revised: 04/04/2006] [Accepted: 06/09/2006] [Indexed: 12/17/2022]
Abstract
The hepatitis delta virus (HDV) has a very limited protein coding capacity and must rely on host proteins for its replication. A ribonucleoprotein complex was detected following UV cross-linking between HeLa nuclear proteins and an RNA corresponding to the right terminal stem-loop domain of HDV genomic RNA. Mass spectrometric analysis of the complex revealed the polypyrimidine tract-binding protein-associated splicing factor (PSF) as a novel HDV RNA-interacting protein. Co-immunoprecipitation demonstrated the interaction between HDV RNA and PSF both in vitro in HeLa nuclear extract and in vivo within HeLa cells containing both polarities of the HDV genome. Analysis of the binding of various HDV-derived RNAs to purified, recombinant PSF further confirmed the specificity of the interaction and revealed that PSF directly binds to the terminal stem-loop domains of both polarities of HDV RNA. Our findings provide evidence of the involvement of a host mRNA processing protein in the HDV life cycle.
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Affiliation(s)
- Valerie S Greco-Stewart
- Department of Biochemistry, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Room 4223A, Ottawa, ON, Canada K1H 8M5
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Tate A, Isotani S, Bradley MJ, Sikes RA, Davis R, Chung LWK, Edlund M. Met-Independent Hepatocyte Growth Factor-mediated regulation of cell adhesion in human prostate cancer cells. BMC Cancer 2006; 6:197. [PMID: 16869958 PMCID: PMC1559714 DOI: 10.1186/1471-2407-6-197] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Accepted: 07/25/2006] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Prostate cancer cells communicate reciprocally with the stromal cells surrounding them, inside the prostate, and after metastasis, within the bone. Each tissue secretes factors for interpretation by the other. One stromally-derived factor, Hepatocyte Growth Factor (HGF), was found twenty years ago to regulate invasion and growth of carcinoma cells. Working with the LNCaP prostate cancer progression model, we found that these cells could respond to HGF stimulation, even in the absence of Met, the only known HGF receptor. The new HGF binding partner we find on the cell surface may help to clarify conflicts in the past literature about Met expression and HGF response in cancer cells. METHODS We searched for Met or any HGF binding partner on the cells of the PC3 and LNCaP prostate cancer cell models, using HGF immobilized on agarose beads. By using mass spectrometry analyses and sequencing we have identified nucleolin protein as a novel HGF binding partner. Antibodies against nucleolin (or HGF) were able to ameliorate the stimulatory effects of HGF on met-negative prostate cancer cells. Western blots, RT-PCR, and immunohistochemistry were used to assess nucleolin levels during prostate cancer progression in both LNCaP and PC3 models. RESULTS We have identified HGF as a major signaling component of prostate stromal-conditioned media (SCM) and have implicated the protein nucleolin in HGF signal reception by the LNCaP model prostate cancer cells. Antibodies that silence either HGF (in SCM) or nucleolin (on the cell surfaces) eliminate the adhesion-stimulatory effects of the SCM. Likewise, addition of purified HGF to control media mimics the action of SCM. C4-2, an LNCaP lineage-derived, androgen-independent human prostate cancer cell line, responds to HGF in a concentration-dependent manner by increasing its adhesion and reducing its migration on laminin substratum. These HGF effects are not due to shifts in the expression levels of laminin-binding integrins, nor can they be linked to expression of the known HGF receptor Met, as neither LNCaP nor clonally-derived C4-2 sub-line contain any detectable Met protein. Even in the absence of Met, small GTPases are activated, linking HGF stimulation to membrane protrusion and integrin activation. Membrane-localized nucelolin levels increase during cancer progression, as modeled by both the PC3 and LNCaP prostate cancer progression cell lines. CONCLUSION We propose that cell surface localized nucleolin protein may function in these cells as a novel HGF receptor. Membrane localized nucleolin binds heparin-bound growth factors (including HGF) and appears upregulated during prostate cancer progression. Antibodies against nucleolin are able to ameliorate the stimulatory effects of HGF on met-negative prostate cancer cells. HGF-nucleolin interactions could be partially responsible for the complexity of HGF responses and met expression reported in the literature.
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Affiliation(s)
- Amanda Tate
- Department of Urology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - Shuji Isotani
- Department of Urology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - Michael J Bradley
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Robert A Sikes
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Rodney Davis
- Department of Urology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - Leland WK Chung
- Department of Urology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
| | - Magnus Edlund
- Department of Urology and Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA, USA
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You J, Dove BK, Enjuanes L, DeDiego ML, Alvarez E, Howell G, Heinen P, Zambon M, Hiscox JA. Subcellular localization of the severe acute respiratory syndrome coronavirus nucleocapsid protein. J Gen Virol 2005; 86:3303-3310. [PMID: 16298975 DOI: 10.1099/vir.0.81076-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The coronavirus nucleocapsid (N) protein is a viral RNA-binding protein with multiple functions in terms of virus replication and modulating cell signalling pathways. N protein is composed of three distinct regions containing RNA-binding motif(s), and appropriate signals for modulating cell signalling. The subcellular localization of severe acute respiratory syndrome coronavirus (SARS-CoV) N protein was studied. In infected cells, SARS-CoV N protein localized exclusively to the cytoplasm. In contrast to the avian coronavirus N protein, overexpressed SARS-CoV N protein remained principally localized to the cytoplasm, with very few cells exhibiting nucleolar localization. Bioinformatic analysis and deletion mutagenesis coupled to confocal microscopy and live-cell imaging, revealed that SARS-CoV N protein regions I and III contained nuclear localization signals and region II contained a nucleolar retention signal. However, cytoplasmic localization was directed by region III and was the dominant localization signal in the protein.
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Affiliation(s)
- Jaehwan You
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, Leeds LS2 9JT, UK
| | - Brian K Dove
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, Leeds LS2 9JT, UK
| | - Luis Enjuanes
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB, CSIC), Campus Univ. Autonoma, 3 Darwin Street, Cantoblanco, 28049 Madrid, Spain
| | - Marta L DeDiego
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB, CSIC), Campus Univ. Autonoma, 3 Darwin Street, Cantoblanco, 28049 Madrid, Spain
| | - Enrique Alvarez
- Department of Molecular and Cell Biology, Centro Nacional de Biotecnología (CNB, CSIC), Campus Univ. Autonoma, 3 Darwin Street, Cantoblanco, 28049 Madrid, Spain
| | - Gareth Howell
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Paul Heinen
- Health Protection Agency, London NW9 5HT, UK
| | | | - Julian A Hiscox
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
- Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, Garstang Building, University of Leeds, Leeds LS2 9JT, UK
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Wang YH, Chen YH, Lu JH, Tsai HJ. A 23-amino acid motif spanning the basic domain targets zebrafish myogenic regulatory factor myf5 into nucleolus. DNA Cell Biol 2005; 24:651-60. [PMID: 16225396 DOI: 10.1089/dna.2005.24.651] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Myf5 is a nuclear protein and one of the basic helix-loop-helix (bHLH) myogenic factors that play an important role in muscle specification and differentiation. The motif responsible for the nuclear translocation of Myf5 was unknown. Using on-line monitoring of EGFP (enhanced green fluorescent protein)-tagged zebrafish Myf5 translocation, we demonstrated that Myf5-EGFP protein resided in the nucleoplasm and nucleolus of zebrafish fibroblast cell lines (ZEM2S and ZF4), mammalian nonmuscle cell line (COS1), and muscle cell lines (RD and C2C12). In contrast, zebrafish MyoD-EGFP was localized in the nucleus but did not condense in the nucleolus. Using indirect immunofluorescent staining, we determined that zebrafish Myf5 was colocalized with nucleophosmin/B23, a nucleolus protein. Deletion analysis revealed that amino acid residues 60 to 82 (60KRKASTVDRRRAATMRERRRLKK82) of Myf5 were sufficient and necessary for nucleolus targeting. A GST pulldown assay followed by Western analysis showed that nucleolin/C23 could be pulled down specifically by GST-Myf5, but not by GST-MyoD. Based on these findings, we propose that the distinct functions of Myf5 and MyoD may result from their differential binding affinity to nucleolin/C23.
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Affiliation(s)
- Yun-Hsin Wang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan, Republic of China.
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Lai MMC. RNA replication without RNA-dependent RNA polymerase: surprises from hepatitis delta virus. J Virol 2005; 79:7951-8. [PMID: 15956541 PMCID: PMC1143735 DOI: 10.1128/jvi.79.13.7951-7958.2005] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Michael M C Lai
- Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, 2011 Zonal Ave., HMR503C, Los Angeles, California 90033, USA.
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Wang YH, Chang SC, Huang C, Li YP, Lee CH, Chang MF. Novel nuclear export signal-interacting protein, NESI, critical for the assembly of hepatitis delta virus. J Virol 2005; 79:8113-20. [PMID: 15956556 PMCID: PMC1143724 DOI: 10.1128/jvi.79.13.8113-8120.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The process of host factor-mediated nucleocytoplasmic transport is critical for diverse cellular events in eukaryotes and the life cycle of viruses. We have previously identified a chromosome region maintenance 1-independent nuclear export signal (NES) at the C terminus of the large form of hepatitis delta antigen (HDAg), designated NES(HDAg-L) that is required for the assembly of hepatitis delta virus (HDV) (C.-H. Lee et al., J. Biol. Chem. 276:8142-8148, 2001). To look for interacting proteins of the NES(HDAg-L), yeast two-hybrid screening was applied using the GAL4-binding domain fused to the NES(HDAg-L) as bait. Among the positive clones, one encodes a protein, designated NESI [NES(HDAg-L) interacting protein] that specifically interacted with the wild-type NES(HDAg-L) but not with the export/package-defective HDAg-L mutant, NES*(HDAg-L), in which Pro-205 has been replaced by Ala. Northern blot analysis revealed NESI as the gene product of a 1.9-kb endogenous mRNA transcript that is present predominantly in human liver tissue. NESI consists of 467 amino acid residues and bears a putative actin-binding site and a bipartite nuclear localization signal. Specific interaction between HDAg-L and NESI was further confirmed by coimmunoprecipitation and immunofluorescence staining. Overexpression of antisense NESI RNAs inhibited the expression of NESI and abolished HDAg-L-mediated nuclear export and assembly of HDV genomic RNA. These data indicate a critical role of NESI in the assembly of HDV through interaction with HDAg-L.
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Affiliation(s)
- Yun-Hsin Wang
- Institute of Biochemistry and Molecular Biology, National Taiwan University College of Medicine, No. 1, Jen-Ai Road, First Section, Taipei 100, Taiwan
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Russo G, Cuccurese M, Monti G, Russo A, Amoresano A, Pucci P, Pietropaolo C. Ribosomal protein L7a binds RNA through two distinct RNA-binding domains. Biochem J 2005; 385:289-99. [PMID: 15361074 PMCID: PMC1134697 DOI: 10.1042/bj20040371] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The human ribosomal protein L7a is a component of the major ribosomal subunit. We previously identified three nuclear-localization-competent domains within L7a, and demonstrated that the domain defined by aa (amino acids) 52-100 is necessary, although not sufficient, to target the L7a protein to the nucleoli. We now demonstrate that L7a interacts in vitro with a presumably G-rich RNA structure, which has yet to be defined. We also demonstrate that the L7a protein contains two RNA-binding domains: one encompassing aa 52-100 (RNAB1) and the other encompassing aa 101-161 (RNAB2). RNAB1 does not contain any known nucleic-acid-binding motif, and may thus represent a new class of such motifs. On the other hand, a specific region of RNAB2 is highly conserved in several other protein components of the ribonucleoprotein complex. We have investigated the topology of the L7a-RNA complex using a recombinant form of the protein domain that encompasses residues 101-161 and a 30mer poly(G) oligonucleotide. Limited proteolysis and cross-linking experiments, and mass spectral analyses of the recombinant protein domain and its complex with poly(G) revealed the RNA-binding region.
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Affiliation(s)
- Giulia Russo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Monica Cuccurese
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Gianluca Monti
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
| | - Annapina Russo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Angela Amoresano
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
| | - Pietro Pucci
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
- ‡CEINGE Biotecnologie Avanzate S.C.a.r.l., Via Comunale Margherita 482 Napoli, I-80145 Italy
| | - Concetta Pietropaolo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
- To whom correspondence should be addressed (email )
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Joo EJ, ten Dam GB, van Kuppevelt TH, Toida T, Linhardt RJ, Kim YS. Nucleolin: acharan sulfate-binding protein on the surface of cancer cells. Glycobiology 2005; 15:1-9. [PMID: 15329357 PMCID: PMC1237021 DOI: 10.1093/glycob/cwh132] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Glycosaminoglycans (GAGs) are complex polysaccharides that participate in the regulation of physiological processes through the interactions with a wide variety of proteins. Acharan sulfate (AS), isolated from the giant African snail Achatina fulica, primarily consists of the repeating disaccharide structure alpha-D-N-acetylglucosaminyl (1-->4) 2-sulfoiduronic acid. Exogenous AS was injected subcutaneously near the tumor tissue in C57BL/6 mice that had been implanted with Lewis lung carcinoma cells (LLCs). The location of AS in the tumor was assessed by staining of sectioned tissues with alcian blue and periodic acid-Schiff (PAS) reagent. In vitro assays indicated binding of cells to 50 microg/ml AS (or heparin) after a 5-h incubation. Immunofluorescence assays, using anti-AS antibody, detected AS at the cell surface. The outer-surface of LLCs were next biotinylated to identify the AS-binding proteins. Biotinylated cells were lysed, and the lysates were fractionated on the AS affinity column using a stepwise salt gradient (0, 0.1, 0.3, 0.5, 0.7, 1.0, and 2.0 M). The fractions were analyzed by SDS-PAGE with silver staining and western blotting. We focused on the proteins with high affinity for AS (eluting at 1 M NaCl) and detected only two bands by western blotting. ESI Q-TOF MS analysis of one of these bands, molecular weight approximately 110 kDa, showed it to be nucleolin. A phosphorylated form of nucleolin on the surface of cells acts as a cell surface receptor for a variety of ligands, including growth factors (i.e., basic fibroblast growth factor) and chemokines (i.e., midkine). These results show that nucleolin is one of several AS-binding proteins and suggest that AS might demonstrate its tumor growth inhibitory activity by binding the nucleolin receptor protein on the surface of cancer cells.
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Key Words
- as-binding protein
- biotinylation
- lewis lung carcinoma
- nucleolin
- as, acharan sulfate
- bsa, bovine serum albumin
- caps, 3-[cyclohexylamino]-1-propanesulfonic acid
- dmem, dulbecco’s modified eagle medium
- d-pbs, dulbecco’s phosphate buffered saline
- edta, ethylenediamine tetraacetic acid
- elisa, enzyme-linked immunosorbent assay
- esi q-tof ms, electrospray ionization quadrupole timeof- flight mass spectrometry
- fgf, fibroblast growth factor
- fitc, fluorescein isothiocyanate
- gag, glycosaminoglycan
- hrp, horseradish peroxidase
- llc, lewis lung carcinoma
- ms/ms, tandem mass spectrometry
- mtt, methylthiazol-2-yl-2,5-diphenyltetrazolium bromide
- pas, periodic acid-schiff
- pvdf, polyvinylidene difluoride
- sds-page, sodium dodecyl sulfate-polyacrylamide gel electrophoresis
- vsv, vesicular stromatitis virus
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Affiliation(s)
- Eun Ji Joo
- Natural Products Research Institute, College of Pharmacy, Seoul National University, 28 Yeonkun-Dong, Jongno-Ku, Seoul 110-460, Korea
| | - Gerdy B. ten Dam
- Department of Biochemistry, NCMLS, UMC Nijmegen, 6500 HB Nijmegen, The Netherlands
| | | | - Toshihiko Toida
- Graduate School of Pharmaceutical Science, Chiba University, Chiba 263-8522, Japan; and
| | - Robert J. Linhardt
- Department of Chemistry and Chemical Biology, Biology and Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180
| | - Yeong Shik Kim
- Natural Products Research Institute, College of Pharmacy, Seoul National University, 28 Yeonkun-Dong, Jongno-Ku, Seoul 110-460, Korea
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Ning B, Shih C. Nucleolar localization of human hepatitis B virus capsid protein. J Virol 2004; 78:13653-68. [PMID: 15564475 PMCID: PMC533942 DOI: 10.1128/jvi.78.24.13653-13668.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Accepted: 08/12/2004] [Indexed: 01/02/2023] Open
Abstract
Wild-type human hepatitis B virus (HBV) exhibits selective export of virions containing mature genomes. In contrast, changing an isoleucine to a leucine at amino acid 97 (I97L) of the HBV core antigen (HBcAg) causes it to release immature genomes. To elucidate the structure-function relationship of HBcAg at amino acid 97, we systematically replaced the isoleucine residue at this position with 18 other amino acids via mutagenesis. Twelve of the 18 mutants exhibited no significant phenotype, while five new mutants displayed strong phenotypes. The I97D mutant had a near lethal phenotype, the I97P mutant exhibited a significantly reduced level of virion secretion, and the I97G mutant lacked the full-length relaxed circular form of viral DNA. The tip of the spike of the capsid particle is known to contain a predominant B-cell epitope. However, the recognition of this exposed epitope by an anti-HBc antibody appeared to be affected by the I97E mutation or by histidine tagging at the C terminus of mutant HBcAg, which is presumably in the capsid interior. Surprisingly, the nuclear HBcAg of mutants I97E and I97W, produced from either a replicon or an expression vector, was found to be colocalized with nucleolin and B23 at a frequency of nearly 100% by confocal immunofluorescence microscopy. In contrast, this colocalization occurred with wild-type HBcAg only to a limited extent. We also noted that nucleolin-colocalizing cells were often binucleated or apoptotic, suggesting that the presence of HBcAg in the nucleolus may perturb cytokinesis. The mechanism of this phenomenon and its potential involvement in liver pathogenesis are discussed. To our knowledge, this is the first report of nucleolar HBcAg in culture.
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Affiliation(s)
- Bo Ning
- Department of Pathology, WHO Collaborating Center for Tropical Diseases and Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
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Samuilova O, Krogerus C, Pöyry T, Hyypiä T. Specific interaction between human parechovirus nonstructural 2A protein and viral RNA. J Biol Chem 2004; 279:37822-31. [PMID: 15226313 DOI: 10.1074/jbc.m314203200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The functional properties of the nonstructural 2A protein are variable among different picornaviruses. The 2A protein of the human parechovirus 1 (HPEV1) has been shown to lack the proteolytic activity found in many other picornaviruses, but no particular function has been identified for HPEV1 2A. To obtain information about the role of HPEV1 2A in the viral life cycle, the protein was expressed in Escherichia coli. A polyclonal antibody was then raised against the protein and employed to investigate its subcellular localization in the infected cells by immunofluorescence microscopy. Typically, a diffuse cytoplasmic staining pattern, concentrated to the perinuclear area, was observed in the infected cells. However, at late stages of infection some infected cells also exhibited diffuse nuclear staining. Viral RNA, visualized by fluorescent in situ hybridization, partly colocalized with 2A in the perinuclear region. Three experimental approaches including Northwestern blot, UV cross-linking, and gel retardation demonstrated that 2A possesses RNA binding activity. Competition experiments with various single-stranded RNA molecules addressed the specificity of 2A binding. These studies revealed that the 2A protein bound RNA corresponding to the 3'-untranslated region (UTR) of the viral genome with highest affinity. At the N- and C-terminal ends of the protein, two regions, necessary for RNA binding, were identified by mutagenesis. In addition, we demonstrated that 2A has affinity to double-stranded RNA containing 3'UTR(+)-3'UTR(-). In conclusion, our experiments showed that HPEV1 2A binds to viral 3'UTR RNA, a feature that could be important for the function of the protein during HPEV1 replication.
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Affiliation(s)
- Olga Samuilova
- Department of Virology, Haartman Institute, University of Helsinki, P. O. Box 21, FIN-00014 Helsinki, Finland.
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Abstract
Betanodavirus greasy grouper (Epinephelus tauvina) nervous necrosis viruses (GGNNV) protein alpha, a virus capsid protein, was detected in both nucleolus and cytoplasm of infected cells of Asian sea bass (SB) and transfected cells of SB and Cos-7 with pcDNA3.1/RNA2. To study its subcellular localization, ORF of protein alpha with 338 aa was fused with enhanced green fluorescent protein (EGFP) gene and was detected in transfected cells in the absence of other viral proteins. In both SB and Cos-7 cells, protein alpha was found to localize EGFP to the nucleolus and cytoplasm. Deletion mutants of protein alpha indicated that N-terminal 43 amino acid residues were required to import EGFP-alpha protein into the nucleolus. Further deletions within the 43 amino acid backbone, EGFP/33aa(1-33) and EGFP/30aa(14-43), localized to the nucleolus, suggesting that the 20 amino acids from 14 to 33 of protein alpha were the domain of nucleolus localization. To further determine the nucleolus targeting sequence, deletion mutations within the 20 amino acids of protein alpha were constructed. It was found that the deletion of (23)RRR(25), (29)RRR(31), or (23)RRRANNRRR(31) prevented the accumulation of EGFP fusion proteins into the nucleolus, demonstrating that (23)RRRANNRRR(31) contain the signal required for nucleolar localization. A similar distribution pattern of localization of protein alpha and its deletion mutants in SB and Cos-7 cells suggested that N-terminal residues of protein alpha (23)RRRANNRRR(31) constitute a nucleolus localization signal that functions in both fish and mammalian cells.
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Affiliation(s)
- Yan Xiang Guo
- Temasek Life Sciences Laboratory, The National University of Singapore, 117604, Singapore
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