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Cross EM, Marin O, Ariawan D, Aragão D, Cozza G, Di Iorio E, Forwood JK, Alvisi G. Structural determinants of phosphorylation-dependent nuclear transport of HCMV DNA polymerase processivity factor UL44. FEBS Lett 2024; 598:199-209. [PMID: 38158756 DOI: 10.1002/1873-3468.14797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/08/2023] [Accepted: 12/11/2023] [Indexed: 01/03/2024]
Abstract
Human cytomegalovirus DNA polymerase processivity factor UL44 is transported into the nucleus by importin (IMP) α/β through a classical nuclear localization signal (NLS), and this region is susceptible to cdc2-mediated phosphorylation at position T427. Whilst phosphorylation within and close to the UL44 NLS regulates nuclear transport, the details remain elusive, due to the paucity of structural information regarding the role of negatively charged cargo phosphate groups. We addressed this issue by studying the effect of UL44 T427 phosphorylation on interaction with several IMPα isoforms by biochemical and structural approaches. Phosphorylation decreased UL44/IMPα affinity 10-fold, and a comparative structural analysis of UL44 NLS phosphorylated and non-phosphorylated peptides complexed with mouse IMPα2 revealed the structural rearrangements responsible for phosphorylation-dependent inhibition of UL44 nuclear import.
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Affiliation(s)
- Emily M Cross
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, Australia
- Diamond Light Source, Didcot, UK
| | - Oriano Marin
- Department of Biomedical Sciences, University of Padova, Italy
| | - Daryl Ariawan
- Dementia Research Centre, Macquarie University, Sydney, Australia
| | | | - Giorgio Cozza
- Department of Molecular Medicine, University of Padua, Italy
| | - Enzo Di Iorio
- Department of Molecular Medicine, University of Padua, Italy
| | - Jade K Forwood
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, Australia
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Alvisi G, Manaresi E, Cross EM, Hoad M, Akbari N, Pavan S, Ariawan D, Bua G, Petersen GF, Forwood J, Gallinella G. Importin α/β-dependent nuclear transport of human parvovirus B19 nonstructural protein 1 is essential for viral replication. Antiviral Res 2023; 213:105588. [PMID: 36990397 DOI: 10.1016/j.antiviral.2023.105588] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 03/08/2023] [Accepted: 03/25/2023] [Indexed: 03/30/2023]
Abstract
Human parvovirus B19 (B19V) is a major human pathogen causing a variety of diseases, characterized by a selective tropism to human progenitor cells in bone marrow. In similar fashion to all Parvoviridae members, the B19V ssDNA genome is replicated within the nucleus of infected cells through a process which involves both cellular and viral proteins. Among the latter, a crucial role is played by non-structural protein (NS)1, a multifunctional protein involved in genome replication and transcription, as well as modulation of host gene expression and function. Despite the localization of NS1 within the host cell nucleus during infection, little is known regarding the mechanism of its nuclear transport pathway. In this study we undertake structural, biophysical, and cellular approaches to characterize this process. Quantitative confocal laser scanning microscopy (CLSM), gel mobility shift, fluorescence polarization and crystallographic analysis identified a short sequence of amino acids (GACHAKKPRIT-182) as the classical nuclear localization signal (cNLS) responsible for nuclear import, mediated in an energy and importin (IMP) α/β-dependent fashion. Structure-guided mutagenesis of key residue K177 strongly impaired IMPα binding, nuclear import, and viral gene expression in a minigenome system. Further, treatment with ivermectin, an antiparasitic drug interfering with the IMPα/β dependent nuclear import pathway, inhibited NS1 nuclear accumulation and viral replication in infected UT7/Epo-S1 cells. Thus, NS1 nuclear transport is a potential target of therapeutic intervention against B19V induced disease.
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Affiliation(s)
- Gualtiero Alvisi
- Department of Molecular Medicine, University of Padova, 35121, Padova, Italy.
| | - Elisabetta Manaresi
- Department of Pharmacy and Biotechnology, University of Bologna, 40138, Bologna, Italy
| | - Emily M Cross
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
| | - Mikayla Hoad
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
| | - Nasim Akbari
- Department of Molecular Medicine, University of Padova, 35121, Padova, Italy
| | - Silvia Pavan
- Department of Molecular Medicine, University of Padova, 35121, Padova, Italy
| | - Daryl Ariawan
- Dementia Research Centre, Macquarie University, Sydney, NSW, 2109, Australia
| | - Gloria Bua
- Department of Pharmacy and Biotechnology, University of Bologna, 40138, Bologna, Italy
| | - Gayle F Petersen
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
| | - Jade Forwood
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, 2650, Australia
| | - Giorgio Gallinella
- Department of Pharmacy and Biotechnology, University of Bologna, 40138, Bologna, Italy
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Functional diversity: update of the posttranslational modification of Epstein-Barr virus coding proteins. Cell Mol Life Sci 2022; 79:590. [PMID: 36376593 DOI: 10.1007/s00018-022-04561-2] [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: 06/10/2022] [Revised: 08/26/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022]
Abstract
Epstein-Barr virus (EBV), a human oncogenic herpesvirus with a typical life cycle consisting of latent phase and lytic phase, is associated with many human diseases. EBV can express a variety of proteins that enable the virus to affect host cell processes and evade host immunity. Additionally, these proteins provide a basis for the maintenance of viral infection, contribute to the formation of tumors, and influence the occurrence and development of related diseases. Posttranslational modifications (PTMs) are chemical modifications of proteins after translation and are very important to guarantee the proper biological functions of these proteins. Studies in the past have intensely investigated PTMs of EBV-encoded proteins. EBV regulates the progression of the latent phase and lytic phase by affecting the PTMs of its encoded proteins, which are critical for the development of EBV-associated human diseases. In this review, we summarize the PTMs of EBV-encoded proteins that have been discovered and studied thus far with focus on their effects on the viral life cycle.
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Cryo-EM Structure and Functional Studies of EBNA1 Binding to the Family of Repeats and Dyad Symmetry Elements of Epstein-Barr Virus oriP. J Virol 2022; 96:e0094922. [PMID: 36037477 PMCID: PMC9472633 DOI: 10.1128/jvi.00949-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Epstein-Barr nuclear antigen 1 (EBNA1) is a multifunctional viral-encoded DNA-binding protein essential for Epstein-Barr virus (EBV) DNA replication and episome maintenance. EBNA1 binds to two functionally distinct elements at the viral origin of plasmid replication (oriP), termed the dyad symmetry (DS) element, required for replication initiation and the family of repeats (FR) required for episome maintenance. Here, we determined the cryo-electron microscopy (cryo-EM) structure of the EBNA1 DNA binding domain (DBD) from amino acids (aa) 459 to 614 and its interaction with two tandem sites at the DS and FR. We found that EBNA1 induces a strong DNA bending angle in the DS, while the FR is more linear. The N-terminal arm of the DBD (aa 444 to 468) makes extensive contact with DNA as it wraps around the minor groove, with some conformational variation among EBNA1 monomers. Mutation of variable-contact residues K460 and K461 had only minor effects on DNA binding but had abrogated oriP-dependent DNA replication. We also observed that the AT-rich intervening DNA between EBNA1 binding sites in the FR can be occupied by the EBNA1 AT hook, N-terminal domain (NTD) aa 1 to 90 to form a Zn-dependent stable complex with EBNA1 DBD on a 2×FR DNA template. We propose a model showing EBNA1 DBD and NTD cobinding at the FR and suggest that this may contribute to the oligomerization of viral episomes important for maintenance during latent infection. IMPORTANCE EBV latent infection is causally linked to diverse cancers and autoimmune disorders. EBNA1 is the viral-encoded DNA binding protein required for episomal maintenance during latent infection and is consistently expressed in all EBV tumors. The interaction of EBNA1 with different genetic elements confers different viral functions, such as replication initiation at DS and chromosome tethering at FR. Here, we used cryo-EM to determine the structure of the EBNA1 DNA-binding domain (DBD) bound to two tandem sites at the DS and at the FR. We also show that the NTD of EBNA1 can interact with the AT-rich DNA sequence between tandem EBNA1 DBD binding sites in the FR. These results provide new information on the mechanism of EBNA1 DNA binding at DS and FR and suggest a higher-order oligomeric structure of EBNA1 bound to FR. Our findings have implications for targeting EBNA1 in EBV-associated disease.
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Hoad M, Roby JA, Forwood JK. Structural characterization of the porcine adeno-associated virus Po1 capsid protein binding to the nuclear trafficking protein importin alpha. FEBS Lett 2021; 595:2793-2804. [PMID: 34661283 DOI: 10.1002/1873-3468.14209] [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: 08/30/2021] [Revised: 10/11/2021] [Accepted: 10/11/2021] [Indexed: 11/05/2022]
Abstract
Adeno-associated viruses (AAVs) are key vectors for gene therapy; thus, many aspects of their cell transduction pathway have been revealed in detail. However, the specific mechanisms AAV virions use to enter the host nucleus remain largely unresolved. We therefore aimed to reveal the structural interactions between the AAV capsid (Cap) protein and the nuclear transport protein importin alpha (IMPα). A putative nuclear localization sequence (NLS) in the virion protein 1 capsid protein of the porcine AAV Po1 was identified. This region was complexed with IMPα and a structure solved at 2.26 Å. This is the first time that an NLS of AAV Cap complexed with IMPα has been determined structurally. Our results support the findings that AAV capsids enter the nucleus through binding the nuclear import adapter IMPα.
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Affiliation(s)
- Mikayla Hoad
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia
| | - Justin A Roby
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia
| | - Jade K Forwood
- School of Dentistry and Medical Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia
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Li J, Guo Y, Deng Y, Hu L, Li B, Deng S, Zhong J, Xie L, Shi S, Hong X, Zheng X, Cai M, Li M. Subcellular Localization of Epstein-Barr Virus BLLF2 and Its Underlying Mechanisms. Front Microbiol 2021; 12:672192. [PMID: 34367081 PMCID: PMC8339435 DOI: 10.3389/fmicb.2021.672192] [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: 02/25/2021] [Accepted: 05/24/2021] [Indexed: 11/13/2022] Open
Abstract
Epstein-Barr virus (EBV), the pathogen of several human malignancies, encodes many proteins required to be transported into the nucleus for viral DNA reproduction and nucleocapsids assembly in the lytic replication cycle. Here, fluorescence microscope, mutation analysis, interspecies heterokaryon assays, co-immunoprecipitation assay, RNA interference, and Western blot were performed to explore the nuclear import mechanism of EBV encoded BLLF2 protein. BLLF2 was shown to be a nucleocytoplasmic shuttling protein neither by a chromosomal region maintenance 1 (CRM1)- nor by a transporter associated with antigen processing (TAP)-dependent pathway. Yet, BLLF2's two functional nuclear localization signals (NLSs), NLS1 (16KRQALETVPHPQNRGR31) and NLS2 (44RRPRPPVAKRRRFPR58), were identified, whereas the predicted NES was nonfunctional. Finally, BLLF2 was proven to transport into the nucleus via a Ran-dependent and importin β1-dependent pathway. This mechanism may contribute to a more extensive insight into the assembly and synthesis of EBV virions in the nucleus, thus affording a new direction for the treatment of viruses.
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Affiliation(s)
- Jingjing Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China.,Department of Oncology, Affiliated Hospital of Weifang Medical University, Weifang, China
| | - Yingjie Guo
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Yangxi Deng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Li Hu
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Bolin Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Shenyu Deng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Jiayi Zhong
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Li Xie
- Centralab, Shenzhen Center for Chronic Disease Control, Shenzhen, China
| | - Shaoxuan Shi
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Xuejun Hong
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Xuelong Zheng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Mingsheng Cai
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Meili Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
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Jiang L, Xie C, Lung HL, Lo KW, Law GL, Mak NK, Wong KL. EBNA1-targeted inhibitors: Novel approaches for the treatment of Epstein-Barr virus-associated cancers. Am J Cancer Res 2018; 8:5307-5319. [PMID: 30555548 PMCID: PMC6276081 DOI: 10.7150/thno.26823] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Accepted: 08/14/2018] [Indexed: 12/11/2022] Open
Abstract
Epstein-Barr virus (EBV) infects more than 90% of humans worldwide and establishes lifelong latent infection in the hosts. It is closely associated with endemic forms of a wide range of human cancers and directly contributes to the formation of some. Despite its critical role in cancer development, no EBV- or EBV latent protein-targeted therapy is available. The EBV-encoded latent protein, Epstein-Barr nuclear antigen 1 (EBNA1), is expressed in all EBV-associated tumors and acts as the only latent protein in some of these tumors. This versatile protein functions in the maintenance, replication, and segregation of the EBV genome and can therefore serve as an attractive therapeutic target to treat EBV-associated cancers. In the last decades, efforts have been made for designing specific EBNA1 inhibitors to decrease EBNA1 expression or interfere with EBNA1-dependent functions. In this review, we will briefly introduce the salient features of EBNA1, summarize its functional domains, and focus on the recent developments in the identification and design of EBNA1 inhibitors related to various EBNA1 domains as well as discuss their comparative merits.
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Constructing TC-1-GLUC-LMP2 Model Tumor Cells to Evaluate the Anti-Tumor Effects of LMP2-Related Vaccines. Viruses 2018; 10:v10040145. [PMID: 29570629 PMCID: PMC5923439 DOI: 10.3390/v10040145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 03/21/2018] [Accepted: 03/22/2018] [Indexed: 12/20/2022] Open
Abstract
Epstein-Barr virus (EBV) is related to a variety of malignant tumors, and its encoded protein, latent membrane protein 2 (LMP2), is an effective target antigen that is widely used to construct vector vaccines. However, the model cells carrying LMP2 have still not been established to assess the oncolytic effect of LMP2-related vaccines at present. In this study, TC-1-GLUC-LMP2 tumor cells were constructed as target cells to evaluate the anti-tumor effects of LMP2-assosiated vaccines. The results showed that both LMP2 and Gaussia luciferase (GLuc) genes could be detected by polymerase chain reaction (PCR) and reverse transcription-polymerase chain reaction (RT-PCR) in TC-1-GLUC-LMP2 cells. Western blot results showed that the LMP2 and Gaussia luciferase proteins were stably expressed in tumor cells for at least 30 generations. We mixed 5 × 104 LMP2-specific mouse splenic lymphocytes with 5 × 103 TC-1-GLUC-LMP2 target cells and found that the target cells were killed as the specific killing effect was obviously enhanced by the increased quantities of LMP2-peptide stimulated spleens. Furthermore, the tumor cells could not be observed in the mice inoculated TC-1-GLUC-LMP2 cells after being immunized with vaccine-LMP2, while the vaccine-NULL immunized mice showed that tumor volume gradually grew with increased inoculation time. These results indicated that the TC-1-GLUC-LMP2 cells stably expressing LMP2 and GLuc produced tumors in mice, and that the LMP2-specific cytotoxic T lymphocyte (CTL) effectively killed the cells in vitro and in vivo, suggesting that TC-1-GLUC-LMP2 cells can be used as model cells to assess the immune and antitumor effects of LMP2-related vaccines.
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Nemes K, Gellért Á, Almási A, Vági P, Sáray R, Kádár K, Salánki K. Phosphorylation regulates the subcellular localization of Cucumber Mosaic Virus 2b protein. Sci Rep 2017; 7:13444. [PMID: 29044170 PMCID: PMC5647415 DOI: 10.1038/s41598-017-13870-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 10/03/2017] [Indexed: 11/27/2022] Open
Abstract
The 2b protein of Cucumber mosaic virus has a role in nearly all steps of the viral cycle including cell-to-cell movement, symptom induction and suppression of antiviral RNA silencing. Previous studies demonstrated the presence of 2b protein in the nucleus and in cytoplasm as well. Phosphorylation site of 2b protein is conserved in all CMV isolates, including proposed constitute motifs for casein kinase II and cyclin-dependent kinase 2. To discern the impact of 2b protein phosphorylation, we created eight different mutants to mimic the non-phosporylated (serine to alanine) as well as the phosphorylated state (serine to aspartic acid) of the protein. We compared these mutants to the wild-type (Rs-CMV) virus in terms of symptom induction, gene silencing suppressor activity as well as in cellular localization. Here, in this study we confirmed the phosphorylation of 2b protein in vivo, both in infected N. benthamiana and in infiltrated patches. Mutants containing aspartic acid in the phosphorylation site accumulated only in the cytoplasm indicating that phosphorylated 2b protein could not enter the nucleus. We identified a conserved dual phosphorylation switch in CMV 2b protein, which equilibrates the shuttling of the 2b protein between the nucleus and the cytoplasm, and regulates the suppressor activity of the 2b protein.
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Affiliation(s)
- Katalin Nemes
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Ákos Gellért
- Institute for Veterinary Medical Research, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Asztéria Almási
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Pál Vági
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Plant Anatomy, Eötvös Loránd University, Faculty of Sciences, Budapest, Hungary
| | - Réka Sáray
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Katalin Kádár
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary
| | - Katalin Salánki
- Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary.
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Nakada R, Matsuura Y. Crystal structure of importin-α bound to the nuclear localization signal of Epstein-Barr virus EBNA-LP protein. Protein Sci 2017; 26:1231-1235. [PMID: 28383161 DOI: 10.1002/pro.3173] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 04/01/2017] [Accepted: 04/03/2017] [Indexed: 11/09/2022]
Abstract
Epstein-Barr virus EBNA-LP protein is a transcriptional coactivator of EBNA2. Efficient nuclear localization of EBNA-LP is essential for cooperation with EBNA2. Here, we report the crystal structure of the nuclear import adaptor importin-α1 bound to the nuclear localization signal (NLS) of EBNA-LP that shows EBNA-LP residues 44-RRVRRR-49 binding to the major NLS-binding site at the P0-P5 positions. In contrast to previously characterized classical NLSs that invariably have a basic residue [either lysine (in the vast majority of cases) or arginine] at the P2 position, the EBNA-LP NLS is unique in that it has valine at the P2 position. The loss of the critical P2 lysine (or arginine) is compensated by arginine at the P0 position in the EBNA-LP NLS.
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Affiliation(s)
- Ryohei Nakada
- Division of Biological Science, Graduate School of Science, Nagoya University, Japan
| | - Yoshiyuki Matsuura
- Division of Biological Science, Graduate School of Science, Nagoya University, Japan.,Structural Biology Research Center, Graduate School of Science, Nagoya University, Japan
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