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Massaro L, De Sanctis S, Franchini V, Regalbuto E, Alfano G, Focaccetti C, Benvenuto M, Cifaldi L, Sgura A, Berardinelli F, Marinaccio J, Barbato F, Rossi E, Nardozi D, Masuelli L, Bei R, Lista F. Study of genotoxic and cytotoxic effects induced in human fibroblasts by exposure to pulsed and continuous 1.6 GHz radiofrequency. Front Public Health 2024; 12:1419525. [PMID: 39145180 PMCID: PMC11323689 DOI: 10.3389/fpubh.2024.1419525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Accepted: 07/18/2024] [Indexed: 08/16/2024] Open
Abstract
Background The widespread use of radiofrequency (RF) sources, ranging from household appliances to telecommunications devices and military equipment, raises concerns among people and regulatory agencies about the potential health risks of RF exposure. Consequently, several in vitro and in vivo studies have been done to investigate the biological effects, in particular non-thermal, of this non-ionizing radiation. To date, this issue is still being debated due to the controversial results that have been reported. Furthermore, the impact of different RF signal modulations on biological systems remains poorly investigated. The present in vitro study aims to evaluate the cytotoxicity and genotoxicity of continuous or pulsed 1.6 GHz RF in human dermal fibroblasts (HDF). Methods HDF cultures were exposed to continuous and pulsed 1.6 GHz RF, for 2 h, with Specific Absorption Rate (SAR) of 0.4 W/kg. The potential biological effects of 1.6 GHz RF on HDF were assessed with a multi-methodological approach, analyzing the effects on cell cycle, ultrastructure, protein expression, mitotic spindle, CREST stained micronuclei, chromosome segregation and γ-H2AX/53BP1 foci. Results 1.6 GHz RF exposure modified proteins expression and morphology of HDF. Specifically, the expression of different heat-shock proteins (HSP) (i.e., HSP-90, HSP-60, and HSP-25) and phospho-AKT were affected. In addition, both continuous and pulsed RF modified the cytoskeletal organization in HDF and increased the number of lysosomes, while the formation of autophagosomes was observed only after pulsed RF exposure. Mitotic spindle anomalies were also found after exposure. However, no significant effect was observed on cell cycle, chromosome segregation, CREST-stained micronuclei and γ-H2AX/53BP1 foci. Conclusion The results of the present study show the absence of genotoxic damage in 1.6 GHz RF exposed HDF and, although mitotic spindle alterations were observed, they did not have an aneugenic effect. On the other hand, changes in some proteins expression and cell ultrastructure in exposed HDF suggest that RF can potentially induce cell alterations at the morphological and molecular levels.
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Affiliation(s)
- Luca Massaro
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
- Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy
| | - Stefania De Sanctis
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
| | - Valeria Franchini
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
| | - Elisa Regalbuto
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
| | - Gaetano Alfano
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
| | - Chiara Focaccetti
- Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy
| | - Monica Benvenuto
- Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy
| | - Loredana Cifaldi
- Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy
| | - Antonella Sgura
- Department of Science, University of Rome “Roma Tre”, Rome, Italy
| | | | | | - Federica Barbato
- Department of Science, University of Rome “Roma Tre”, Rome, Italy
| | - Erica Rossi
- Department of Science, University of Rome “Roma Tre”, Rome, Italy
| | - Daniela Nardozi
- Department of Experimental Medicine, University of Rome “Sapienza”, Rome, Italy
| | - Laura Masuelli
- Department of Experimental Medicine, University of Rome “Sapienza”, Rome, Italy
| | - Roberto Bei
- Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata”, Rome, Italy
| | - Florigio Lista
- Radiobiology Section, Defence Center for Biotechnologies, Defence Institute for Biomedical Sciences, Rome, Italy
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2
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Draganova EB, Wang H, Wu M, Liao S, Vu A, Gonzalez-Del Pino GL, Zhou ZH, Roller RJ, Heldwein EE. The universal suppressor mutation restores membrane budding defects in the HSV-1 nuclear egress complex by stabilizing the oligomeric lattice. PLoS Pathog 2024; 20:e1011936. [PMID: 38227586 PMCID: PMC10817169 DOI: 10.1371/journal.ppat.1011936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/26/2024] [Accepted: 01/01/2024] [Indexed: 01/18/2024] Open
Abstract
Nuclear egress is an essential process in herpesvirus replication whereby nascent capsids translocate from the nucleus to the cytoplasm. This initial step of nuclear egress-budding at the inner nuclear membrane-is coordinated by the nuclear egress complex (NEC). Composed of the viral proteins UL31 and UL34, NEC deforms the membrane around the capsid as the latter buds into the perinuclear space. NEC oligomerization into a hexagonal membrane-bound lattice is essential for budding because NEC mutants designed to perturb lattice interfaces reduce its budding ability. Previously, we identified an NEC suppressor mutation capable of restoring budding to a mutant with a weakened hexagonal lattice. Using an established in-vitro budding assay and HSV-1 infected cell experiments, we show that the suppressor mutation can restore budding to a broad range of budding-deficient NEC mutants thereby acting as a universal suppressor. Cryogenic electron tomography of the suppressor NEC mutant lattice revealed a hexagonal lattice reminiscent of wild-type NEC lattice instead of an alternative lattice. Further investigation using x-ray crystallography showed that the suppressor mutation promoted the formation of new contacts between the NEC hexamers that, ostensibly, stabilized the hexagonal lattice. This stabilization strategy is powerful enough to override the otherwise deleterious effects of mutations that destabilize the NEC lattice by different mechanisms, resulting in a functional NEC hexagonal lattice and restoration of membrane budding.
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Affiliation(s)
- Elizabeth B. Draganova
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Hui Wang
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
- Department of Bioengineering, UCLA, Los Angeles, California, United States of America
- California NanoSystems Institute, UCLA, Los Angeles, California, United States of America
| | - Melanie Wu
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Shiqing Liao
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
- California NanoSystems Institute, UCLA, Los Angeles, California, United States of America
| | - Amber Vu
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Gonzalo L. Gonzalez-Del Pino
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Z. Hong Zhou
- Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles (UCLA), Los Angeles, California, United States of America
- Department of Bioengineering, UCLA, Los Angeles, California, United States of America
- California NanoSystems Institute, UCLA, Los Angeles, California, United States of America
| | - Richard J. Roller
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
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3
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Kicuntod J, Häge S, Lösing J, Kopar S, Muller YA, Marschall M. An antiviral targeting strategy based on the inducible interference with cytomegalovirus nuclear egress complex. Antiviral Res 2023; 212:105557. [PMID: 36796541 DOI: 10.1016/j.antiviral.2023.105557] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/09/2023] [Accepted: 02/13/2023] [Indexed: 02/16/2023]
Abstract
The nucleocytoplasmic capsid egress of herpesviruses like the human cytomegalovirus (HCMV) is based on a uniquely regulated process. The core nuclear egress complex (NEC) of HCMV, represented by the pUL50-pUL53 heterodimer, is able to oligomerize and thus to build hexameric lattices. Recently, we and others validated the NEC as a novel target for antiviral strategies. So far, the experimental targeting approaches included the development of NEC-directed small molecules, cell-penetrating peptides and NEC-directed mutagenesis. Our postulate states that an interference with the hook-into-groove interaction of pUL50-pUL53 prevents NEC formation and strictly limits viral replication efficiency. Here, we provide an experimental proof-of-concept of the antiviral strategy: the inducible intracellular expression of a NLS-Hook-GFP construct exerted a pronounced level of antiviral activity. The data provide evidence for the following points: (i) generation of a primary fibroblast population with inducible NLS-Hook-GFP expression showed nuclear localization of the construct, (ii) interaction between NLS-Hook-GFP and the viral core NEC was found specific for cytomegaloviruses but not for other herpesviruses, (iii) construct overexpression exerted a strong antiviral activity against three strains of HCMV, (iv) confocal imaging demonstrated the interference with NEC nuclear rim formation in HCMV-infected cells, and (v) quantitative nuclear egress assay confirmed the block of viral nucleocytoplasmic transition and, consequently, an inhibitory effect onto viral cytoplasmic virion assembly complex (cVAC). Combined, data confirmed that the specific interference with protein-protein interaction of the HCMV core NEC represents an efficient antiviral targeting strategy.
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Affiliation(s)
- Jintawee Kicuntod
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Josephine Lösing
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Serli Kopar
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Yves A Muller
- Division of Biotechnology, Department of Biology, FAU, Erlangen, Germany.
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
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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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Thorsen MK, Draganova EB, Heldwein EE. The nuclear egress complex of Epstein-Barr virus buds membranes through an oligomerization-driven mechanism. PLoS Pathog 2022; 18:e1010623. [PMID: 35802751 PMCID: PMC9299292 DOI: 10.1371/journal.ppat.1010623] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 07/20/2022] [Accepted: 05/28/2022] [Indexed: 11/21/2022] Open
Abstract
During replication, herpesviral capsids are translocated from the nucleus into the cytoplasm by an unusual mechanism, termed nuclear egress, that involves capsid budding at the inner nuclear membrane. This process is mediated by the viral nuclear egress complex (NEC) that deforms the membrane around the capsid. Although the NEC is essential for capsid nuclear egress across all three subfamilies of the Herpesviridae, most studies to date have focused on the NEC homologs from alpha- and beta- but not gammaherpesviruses. Here, we report the crystal structure of the NEC from Epstein-Barr virus (EBV), a prototypical gammaherpesvirus. The structure resembles known structures of NEC homologs yet is conformationally dynamic. We also show that purified, recombinant EBV NEC buds synthetic membranes in vitro and forms membrane-bound coats of unknown geometry. However, unlike other NEC homologs, EBV NEC forms dimers in the crystals instead of hexamers. The dimeric interfaces observed in the EBV NEC crystals are similar to the hexameric interfaces observed in other NEC homologs. Moreover, mutations engineered to disrupt the dimeric interface reduce budding. Putting together these data, we propose that EBV NEC-mediated budding is driven by oligomerization into membrane-bound coats. Herpesviruses, which infect most of the world’s population for life, translocate their capsids from the nucleus, where they are formed, into the cytoplasm, where they mature into infectious virions, by an unusual mechanism, termed nuclear egress. During nuclear budding, an early step in this process, the inner nuclear membrane is deformed around the capsid by the complex of two viral proteins termed the nuclear egress complex (NEC). The NEC is conserved across all three subfamilies of Herpesviruses and essential for nuclear egress. However, most studies to date have focused on the NEC homologs from alpha- and betaherpesviruses while less is known about the NEC from gammaherpesviruses. Here, we determined the crystal structure of the NEC from Epstein-Barr virus (EBV), a prototypical gammaherpesvirus, and investigated its membrane budding properties in vitro. Our data show that the ability to vesiculate membranes by forming membrane-bound coats and the structure are conserved across the NEC homologs from all three subfamilies. However, the EBV NEC may employ a distinct membrane-budding mechanism due to its structural flexibility and the ability to form coats of different geometry.
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Affiliation(s)
- Michael K. Thorsen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Graduate Program in Cellular, Molecular, and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Elizabeth B. Draganova
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- Graduate Program in Cellular, Molecular, and Developmental Biology, Graduate School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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6
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‘Come Together’—The Regulatory Interaction of Herpesviral Nuclear Egress Proteins Comprises both Essential and Accessory Functions. Cells 2022; 11:cells11111837. [PMID: 35681532 PMCID: PMC9180862 DOI: 10.3390/cells11111837] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 02/01/2023] Open
Abstract
Herpesviral nuclear egress is a fine-tuned regulatory process that defines the nucleocytoplasmic release of viral capsids. Nuclear capsids are unable to traverse via nuclear pores due to the fact of their large size; therefore, herpesviruses evolved to develop a vesicular transport pathway mediating the transition across the two leaflets of the nuclear membrane. The entire process involves a number of regulatory proteins, which support the local distortion of the nuclear envelope. In the case of the prototype species of β-Herpesvirinae, the human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the core proteins pUL50 and pUL53 that oligomerize, form capsid docking lattices and mediate multicomponent assembly with NEC-associated viral and cellular proteins. The NEC-binding principle is based on the hook-into-groove interaction through an N-terminal hook-like pUL53 protrusion that embraces an α-helical pUL50 binding groove. Thus far, the function and characteristics of herpesviral core NECs have been well studied and point to the groove proteins, such as pUL50, as the multi-interacting, major determinants of NEC formation and egress. This review provides closer insight into (i) sequence and structure conservation of herpesviral core NEC proteins, (ii) experimentation on cross-viral core NEC interactions, (iii) the essential functional roles of hook and groove proteins for viral replication, (iv) an establishment of assay systems for NEC-directed antiviral research and (v) the validation of NEC as putative antiviral drug targets. Finally, this article provides new insights into the conservation, function and antiviral targeting of herpesviral core NEC proteins and, into the complex regulatory role of hook and groove proteins during the assembly, egress and maturation of infectious virus.
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7
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Sanchez V, Britt W. Human Cytomegalovirus Egress: Overcoming Barriers and Co-Opting Cellular Functions. Viruses 2021; 14:v14010015. [PMID: 35062219 PMCID: PMC8778548 DOI: 10.3390/v14010015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 12/11/2022] Open
Abstract
The assembly of human cytomegalovirus (HCMV) and other herpesviruses includes both nuclear and cytoplasmic phases. During the prolonged replication cycle of HCMV, the cell undergoes remarkable changes in cellular architecture that include marked increases in nuclear size and structure as well as the reorganization of membranes in cytoplasm. Similarly, significant changes occur in cellular metabolism, protein trafficking, and cellular homeostatic functions. These cellular modifications are considered integral in the efficient assembly of infectious progeny in productively infected cells. Nuclear egress of HCMV nucleocapsids is thought to follow a pathway similar to that proposed for other members of the herpesvirus family. During this process, viral nucleocapsids must overcome structural barriers in the nucleus that limit transit and, ultimately, their delivery to the cytoplasm for final assembly of progeny virions. HCMV, similar to other herpesviruses, encodes viral functions that co-opt cellular functions to overcome these barriers and to bridge the bilaminar nuclear membrane. In this brief review, we will highlight some of the mechanisms that define our current understanding of HCMV egress, relying heavily on the current understanding of egress of the more well-studied α-herpesviruses, HSV-1 and PRV.
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Affiliation(s)
- Veronica Sanchez
- Department of Pediatrics, University of Alabama School of Medicine, Birmingham, AL 35294, USA;
- Correspondence:
| | - William Britt
- Department of Pediatrics, University of Alabama School of Medicine, Birmingham, AL 35294, USA;
- Department of Microbiology, University of Alabama School of Medicine, Birmingham, AL 35294, USA
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8
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Häge S, Büscher N, Pakulska V, Hahn F, Adrait A, Krauter S, Borst EM, Schlötzer-Schrehardt U, Couté Y, Plachter B, Marschall M. The Complex Regulatory Role of Cytomegalovirus Nuclear Egress Protein pUL50 in the Production of Infectious Virus. Cells 2021; 10:3119. [PMID: 34831342 PMCID: PMC8625744 DOI: 10.3390/cells10113119] [Citation(s) in RCA: 6] [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: 10/07/2021] [Revised: 11/04/2021] [Accepted: 11/05/2021] [Indexed: 11/30/2022] Open
Abstract
The regulation of the nucleocytoplasmic release of herpesviral capsids is defined by the process of nuclear egress. Due to their large size, nuclear capsids are unable to traverse via nuclear pores, so that herpesviruses evolved to develop a vesicular transport pathway mediating their transition through both leaflets of the nuclear membrane. This process involves regulatory proteins, which support the local distortion of the nuclear envelope. For human cytomegalovirus (HCMV), the nuclear egress complex (NEC) is determined by the pUL50-pUL53 core that initiates multicomponent assembly with NEC-associated proteins and capsids. Hereby, pUL50 serves as a multi-interacting determinant that recruits several viral and cellular factors by direct and indirect contacts. Recently, we generated an ORF-UL50-deleted recombinant HCMV in pUL50-complementing cells and obtained first indications of putative additional functions of pUL50. In this study, we produced purified ΔUL50 particles under both complementing (ΔUL50C) and non-complementing (ΔUL50N) conditions and performed a phenotypical characterization. Findings were as follows: (i) ΔUL50N particle preparations exhibited a clear replicative defect in qPCR-based infection kinetics compared to ΔUL50C particles; (ii) immuno-EM analysis of ΔUL50C did not reveal major changes in nuclear distribution of pUL53 and lamin A/C; (iii) mass spectrometry-based quantitative proteomics showed a large concordance of protein contents in the NIEP fractions of ΔUL50C and ΔUL50N particles, but virion fraction was close to the detection limit for ΔUL50N; (iv) confocal imaging of viral marker proteins of immediate early (IE) and later phases of ΔUL50N infection indicated a very low number of cells showing an onset of viral lytic protein expression; and, finally (v) quantitative measurements of encapsidated genomes provided evidence for a substantial reduction in the DNA contents in ΔUL50N compared to ΔUL50C particles. In summary, the results point to a complex and important regulatory role of the HCMV nuclear egress protein pUL50 in the maturation of infectious virus.
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Affiliation(s)
- Sigrun Häge
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Nicole Büscher
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Victoria Pakulska
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Friedrich Hahn
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
| | - Annie Adrait
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Steffi Krauter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School (MHH), 30625 Hannover, Germany;
| | | | - Yohann Couté
- Institut National de la Santé et de la Recherche Médicale (INSERM), University Grenoble Alpes, CEA, UMR BioSanté U1292, CNRS, CEA, FR2048, 38000 Grenoble, France; (V.P.); (A.A.); (Y.C.)
| | - Bodo Plachter
- Institute for Virology and Forschungszentrum für Immuntherapie, University Medical Center of the Johannes Gutenberg-University Mainz, 55131 Mainz, Germany; (N.B.); (S.K.); (B.P.)
| | - Manfred Marschall
- Institute for Clinical and Molecular Virology, Friedrich-Alexander University of Erlangen-Nürnberg (FAU), 91054 Erlangen, Germany;
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Thorsen MK, Lai A, Lee MW, Hoogerheide DP, Wong GCL, Freed JH, Heldwein EE. Highly Basic Clusters in the Herpes Simplex Virus 1 Nuclear Egress Complex Drive Membrane Budding by Inducing Lipid Ordering. mBio 2021; 12:e0154821. [PMID: 34425706 PMCID: PMC8406295 DOI: 10.1128/mbio.01548-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/28/2021] [Indexed: 02/01/2023] Open
Abstract
During replication of herpesviruses, capsids escape from the nucleus into the cytoplasm by budding at the inner nuclear membrane. This unusual process is mediated by the viral nuclear egress complex (NEC) that deforms the membrane around the capsid by oligomerizing into a hexagonal, membrane-bound scaffold. Here, we found that highly basic membrane-proximal regions (MPRs) of the NEC alter lipid order by inserting into the lipid headgroups and promote negative Gaussian curvature. We also find that the electrostatic interactions between the MPRs and the membranes are essential for membrane deformation. One of the MPRs is phosphorylated by a viral kinase during infection, and the corresponding phosphomimicking mutations block capsid nuclear egress. We show that the same phosphomimicking mutations disrupt the NEC-membrane interactions and inhibit NEC-mediated budding in vitro, providing a biophysical explanation for the in vivo phenomenon. Our data suggest that the NEC generates negative membrane curvature by both lipid ordering and protein scaffolding and that phosphorylation acts as an off switch that inhibits the membrane-budding activity of the NEC to prevent capsid-less budding. IMPORTANCE Herpesviruses are large viruses that infect nearly all vertebrates and some invertebrates and cause lifelong infections in most of the world's population. During replication, herpesviruses export their capsids from the nucleus into the cytoplasm by an unusual mechanism in which the viral nuclear egress complex (NEC) deforms the nuclear membrane around the capsid. However, how membrane deformation is achieved is unclear. Here, we show that the NEC from herpes simplex virus 1, a prototypical herpesvirus, uses clusters of positive charges to bind membranes and order membrane lipids. Reducing the positive charge or introducing negative charges weakens the membrane deforming ability of the NEC. We propose that the virus employs electrostatics to deform nuclear membrane around the capsid and can control this process by changing the NEC charge through phosphorylation. Blocking NEC-membrane interactions could be exploited as a therapeutic strategy.
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Affiliation(s)
- Michael K. Thorsen
- Department of Molecular Biology and Microbiology, Graduate Program in Cellular, Molecular and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Alex Lai
- Department of Chemistry and Chemical Biology and National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York, USA
| | - Michelle W. Lee
- Department of Bioengineering, Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, USA
| | - David P. Hoogerheide
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Gerard C. L. Wong
- Department of Bioengineering, Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California, USA
| | - Jack H. Freed
- Department of Chemistry and Chemical Biology and National Biomedical Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York, USA
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Graduate Program in Cellular, Molecular and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
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Herpesvirus Regulation of Selective Autophagy. Viruses 2021; 13:v13050820. [PMID: 34062931 PMCID: PMC8147283 DOI: 10.3390/v13050820] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 04/28/2021] [Accepted: 04/29/2021] [Indexed: 12/18/2022] Open
Abstract
Selective autophagy has emerged as a key mechanism of quality and quantity control responsible for the autophagic degradation of specific subcellular organelles and materials. In addition, a specific type of selective autophagy (xenophagy) is also activated as a line of defense against invading intracellular pathogens, such as viruses. However, viruses have evolved strategies to counteract the host’s antiviral defense and even to activate some proviral types of selective autophagy, such as mitophagy, for their successful infection and replication. This review discusses the current knowledge on the regulation of selective autophagy by human herpesviruses.
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11
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Mechanism of Nuclear Lamina Disruption and the Role of pUS3 in HSV-1 Nuclear Egress. J Virol 2021; 95:JVI.02432-20. [PMID: 33658339 PMCID: PMC8139644 DOI: 10.1128/jvi.02432-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpes simplex virus capsid envelopment at the nuclear membrane is coordinated by nuclear egress complex (NEC) proteins, pUL34 and pUL31, and is accompanied by alteration in the nuclear architecture and local disruption of nuclear lamina. Here, we examined the role of capsid envelopment in the changes of the nuclear architecture by characterizing HSV-1 recombinants that do not form capsids. Typical changes in nuclear architecture and disruption of the lamina were observed in the absence of capsids, suggesting that disruption of the nuclear lamina occurs prior to capsid envelopment. Surprisingly, in the absence of capsid envelopment, lamin A/C becomes concentrated at the nuclear envelope in a pUL34-independent and cell type-specific manner, suggesting that ongoing nuclear egress may be required for the dispersal of lamins observed in wild-type infection. Mutation of virus-encoded protein kinase, pUS3, on a wild-type virus background has been shown to cause accumulation of perinuclear enveloped capsids, formation of NEC aggregates, and exacerbated lamina disruption. We observed that mutation of US3 in the absence of capsids results in identical NEC aggregation and lamina disruption phenotypes, suggesting that they do not result from accumulation of perinuclear virions. TEM analysis revealed that, in the absence of capsids, NEC aggregates correspond to multi-folded nuclear membrane structures, suggesting that pUS3 may control NEC self-association and membrane deformation. To determine the significance of the pUS3 nuclear egress function for virus growth, the replication of single and double UL34 and US3 mutants was measured, showing that the significance of pUS3 nuclear egress function is cell-type specific.ImportanceThe nuclear lamina is an important player in infection by viruses that replicate in the nucleus. Herpesviruses alter the structure of the nuclear lamina to facilitate transport of capsids from the nucleus to the cytoplasm and use both viral and cellular effectors to disrupt the protein-protein interactions that maintain the lamina. Here we explore the role of capsid envelopment and the virus-encoded protein kinase, pUS3, in the disruption of lamina structure. We show that capsid envelopment is not necessary for the lamina disruption, or for US3 mutant phenotypes, including exaggerated lamina disruption, that accompany nuclear egress. These results clarify the mechanisms behind alteration of nuclear lamina structure and support a function for pUS3 in regulating the aggregation state of the nuclear egress machinery.
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12
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Host and Viral Factors Involved in Nuclear Egress of Herpes Simplex Virus 1. Viruses 2021; 13:v13050754. [PMID: 33923040 PMCID: PMC8146395 DOI: 10.3390/v13050754] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/20/2021] [Accepted: 04/23/2021] [Indexed: 12/14/2022] Open
Abstract
Herpes simplex virus 1 (HSV-1) replicates its genome and packages it into capsids within the nucleus. HSV-1 has evolved a complex mechanism of nuclear egress whereby nascent capsids bud on the inner nuclear membrane to form perinuclear virions that subsequently fuse with the outer nuclear membrane, releasing capsids into the cytosol. The viral-encoded nuclear egress complex (NEC) plays a crucial role in this vesicle-mediated nucleocytoplasmic transport. Nevertheless, similar system mediates the movement of other cellular macromolecular complexes in normal cells. Therefore, HSV-1 may utilize viral proteins to hijack the cellular machinery in order to facilitate capsid transport. However, little is known about the molecular mechanisms underlying this phenomenon. This review summarizes our current understanding of the cellular and viral factors involved in the nuclear egress of HSV-1 capsids.
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13
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Lee CP, Chen MR. Conquering the Nuclear Envelope Barriers by EBV Lytic Replication. Viruses 2021; 13:702. [PMID: 33919628 PMCID: PMC8073350 DOI: 10.3390/v13040702] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Revised: 04/14/2021] [Accepted: 04/14/2021] [Indexed: 12/14/2022] Open
Abstract
The nuclear envelope (NE) of eukaryotic cells has a highly structural architecture, comprising double lipid-bilayer membranes, nuclear pore complexes, and an underlying nuclear lamina network. The NE structure is held in place through the membrane-bound LINC (linker of nucleoskeleton and cytoskeleton) complex, spanning the inner and outer nuclear membranes. The NE functions as a barrier between the nucleus and cytoplasm and as a transverse scaffold for various cellular processes. Epstein-Barr virus (EBV) is a human pathogen that infects most of the world's population and is associated with several well-known malignancies. Within the nucleus, the replicated viral DNA is packaged into capsids, which subsequently egress from the nucleus into the cytoplasm for tegumentation and final envelopment. There is increasing evidence that viral lytic gene expression or replication contributes to the pathogenesis of EBV. Various EBV lytic proteins regulate and modulate the nuclear envelope structure in different ways, especially the viral BGLF4 kinase and the nuclear egress complex BFRF1/BFRF2. From the aspects of nuclear membrane structure, viral components, and fundamental nucleocytoplasmic transport controls, this review summarizes our findings and recently updated information on NE structure modification and NE-related cellular processes mediated by EBV.
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Affiliation(s)
- Chung-Pei Lee
- School of Nursing, National Taipei University of Nursing and Health Sciences, Taipei 112303, Taiwan;
| | - Mei-Ru Chen
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei 100233, Taiwan
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14
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Houen G, Trier NH. Epstein-Barr Virus and Systemic Autoimmune Diseases. Front Immunol 2021; 11:587380. [PMID: 33488588 PMCID: PMC7817975 DOI: 10.3389/fimmu.2020.587380] [Citation(s) in RCA: 153] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Accepted: 11/19/2020] [Indexed: 12/11/2022] Open
Abstract
Epstein-Barr Virus (EBV) is an extremely successful human herpes virus, which infects essentially all human beings at some time during their life span. EBV infection and the associated immune response results in production of antibodies (seroconversion), which occurs mainly during the first years of life, but may also happen during adolescence or later in life. Infection of adolescents can result in infectious mononucleosis, an acute serious condition characterized by massive lymphocytosis. Transmission of EBV mainly occurs through saliva but can rarely be spread through semen or blood, e.g. through organ transplantations and blood transfusions. EBV transmission through oral secretions results in infection of epithelial cells of the oropharynx. From the epithelial cells EBV can infect B cells, which are the major reservoir for the virus, but other cell types may also become infected. As a result, EBV can shuttle between different cell types, mainly B cells and epithelial cells. Moreover, since the virus can switch between a latent and a lytic life cycle, EBV has the ability to cause chronic relapsing/reactivating infections. Chronic or recurrent EBV infection of epithelial cells has been linked to systemic lupus erythematosus and Sjögren’s syndrome, whereas chronic/recurrent infection of B cells has been associated with rheumatoid arthritis, multiple sclerosis and other diseases. Accordingly, since EBV can shuttle between epithelial cells and B cells, the systemic autoimmune diseases often occur as overlapping syndromes with symptoms and characteristic autoantibodies (e.g. antinuclear antibodies and rheumatoid factors) reflecting epithelial and/or B cell infection.
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Affiliation(s)
- Gunnar Houen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Odense, Denmark.,Department of Neurology, Rigshospitalet, Glostrup, Denmark
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15
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Wang P, Deng Y, Guo Y, Xu Z, Li Y, Ou X, Xie L, Lu M, Zhong J, Li B, Hu L, Deng S, Peng T, Cai M, Li M. Epstein-Barr Virus Early Protein BFRF1 Suppresses IFN-β Activity by Inhibiting the Activation of IRF3. Front Immunol 2020; 11:513383. [PMID: 33391252 PMCID: PMC7774019 DOI: 10.3389/fimmu.2020.513383] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 09/15/2020] [Indexed: 12/13/2022] Open
Abstract
Epstein-Barr virus (EBV) is the causative agent of infectious mononucleosis that is closely associated with several human malignant diseases, while type I interferon (IFN-I) plays an important role against EBV infection. As we all know, EBV can encode some proteins to inhibit the production of IFN-I, but it’s not clear whether other proteins also take part in this progress. EBV early lytic protein BFRF1 is shown to be involved in viral maturation, however, whether BFRF1 participates in the host innate immune response is still not well known. In this study, we found BFRF1 could down-regulate sendai virus-induced IFN-β promoter activity and mRNA expression of IFN-β and ISG54 during BFRF1 plasmid transfection and EBV lytic infection, but BFRF1 could not affect the promoter activity of NF-κB or IRF7. Specifically, BFRF1 could co-localize and interact with IKKi. Although BFRF1 did not interfere the interaction between IKKi and IRF3, it could block the kinase activity of IKKi, which finally inhibited the phosphorylation, dimerization, and nuclear translocation of IRF3. Taken together, BFRF1 may play a critical role in disrupting the host innate immunity by suppressing IFN-β activity during EBV lytic cycle.
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Affiliation(s)
- Ping Wang
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, 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, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Yingjie Guo
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Zuo Xu
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Yiwen Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Xiaowen Ou
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, 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
| | - Manjiao Lu
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, 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, 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, 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, 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, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Tao Peng
- State Key Laboratory of Respiratory Diseases, Sino-French Hoffmann Institute, Guangzhou Medical University, Guangzhou, China.,South China Vaccine Corporation Limited, Guangzhou, China
| | - Mingsheng Cai
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, 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, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
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16
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Gonnella R, Dimarco M, Farina GA, Santarelli R, Valia S, Faggioni A, Angeloni A, Cirone M, Farina A. BFRF1 protein is involved in EBV-mediated autophagy manipulation. Microbes Infect 2020; 22:585-591. [PMID: 32882412 DOI: 10.1016/j.micinf.2020.08.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/06/2020] [Accepted: 08/25/2020] [Indexed: 12/28/2022]
Abstract
Viral egress and autophagy are two mechanisms that seem to be strictly connected in Herpesviruses's biology. Several data suggest that the autophagic machinery facilitates the egress of viral capsids and thus the production of new infectious particles. In the Herpesvirus family, viral nuclear egress is controlled and organized by a well conserved group of proteins named Nuclear Egress Complex (NEC). In the case of EBV, NEC is composed by BFRF1 and BFLF2 proteins, although the alterations of the nuclear host cell architecture are mainly driven by BFRF1, a multifunctional viral protein anchored to the inner nuclear membrane of the host cell. BFRF1 shares a peculiar distribution with several nuclear components and with them it strictly interacts. In this study, we investigated the possible role of BFRF1 in manipulating autophagy, pathway that possibly originates from nucleus, regulating the interplay between autophagy and viral egress.
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Affiliation(s)
- Roberta Gonnella
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | - Marzia Dimarco
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | | | - Roberta Santarelli
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | - Sandro Valia
- Dep. Molecular Medicine University of Rome "La Sapienza", Italy
| | - Alberto Faggioni
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | - Antonio Angeloni
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | - Mara Cirone
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy
| | - Antonella Farina
- Dep. Experimental Medicine University of Rome "La Sapienza", Laboratory Affiliated to Istituto Pasteur Italia fondazione Cenci-Bolognetti, Italy; Dep. Molecular Medicine University of Rome "La Sapienza", Italy; Boston University School of Medicine, Boston, MA, USA.
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17
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Andrews RJ, O’Leary CA, Moss WN. A survey of RNA secondary structural propensity encoded within human herpesvirus genomes: global comparisons and local motifs. PeerJ 2020; 8:e9882. [PMID: 32974099 PMCID: PMC7487152 DOI: 10.7717/peerj.9882] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 08/16/2020] [Indexed: 12/13/2022] Open
Abstract
There are nine herpesviruses known to infect humans, of which Epstein-Barr virus (EBV) is the most widely distributed (>90% of adults infected). This ubiquitous virus is implicated in a variety of cancers and autoimmune diseases. Previous analyses of the EBV genome revealed numerous regions with evidence of generating unusually stable and conserved RNA secondary structures and led to the discovery of a novel class of EBV non-coding (nc)RNAs: the stable intronic sequence (sis)RNAs. To gain a better understanding of the roles of RNA structure in EBV biology and pathogenicity, we revisit EBV using recently developed tools for genome-wide motif discovery and RNA structural characterization. This corroborated previous results and revealed novel motifs with potential functionality; one of which has been experimentally validated. Additionally, since many herpesviruses increasingly rival the seroprevalence of EBV (VZV, HHV-6 and HHV-7 being the most notable), analyses were expanded to include all sequenced human Herpesvirus RefSeq genomes, allowing for genomic comparisons. In total 10 genomes were analyzed, for EBV (types 1 and 2), HCMV, HHV-6A, HHV-6B, HHV-7, HSV-1, HSV-2, KSHV, and VZV. All resulting data were archived in the RNAStructuromeDB (https://structurome.bb.iastate.edu/herpesvirus) to make them available to a wide array of researchers.
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Affiliation(s)
- Ryan J. Andrews
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States of America
| | - Collin A. O’Leary
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States of America
| | - Walter N. Moss
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, United States of America
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18
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Abstract
During viral replication, herpesviruses utilize a unique strategy, termed nuclear egress, to translocate capsids from the nucleus into the cytoplasm. This initial budding step transfers a newly formed capsid from within the nucleus, too large to fit through nuclear pores, through the inner nuclear membrane to the perinuclear space. The perinuclear enveloped virion must then fuse with the outer nuclear membrane to be released into the cytoplasm for further maturation, undergoing budding once again at the trans-Golgi network or early endosomes, and ultimately exit the cell non-lytically to spread infection. This first budding process is mediated by two conserved viral proteins, UL31 and UL34, that form a heterodimer called the nuclear egress complex (NEC). This review focuses on what we know about how the NEC mediates capsid transport to the perinuclear space, including steps prior to and after this budding event. Additionally, we discuss the involvement of other viral proteins in this process and how NEC-mediated budding may be regulated during infection.
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Affiliation(s)
- Elizabeth B Draganova
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Michael K Thorsen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
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19
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The Human Cytomegalovirus Transmembrane Protein pUL50 Induces Loss of VCP/p97 and Is Regulated by a Small Isoform of pUL50. J Virol 2020; 94:JVI.00110-20. [PMID: 32321808 DOI: 10.1128/jvi.00110-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 04/10/2020] [Indexed: 11/20/2022] Open
Abstract
The human cytomegalovirus (HCMV) UL50 gene encodes a transmembrane protein, pUL50, which acts as a core component of the nuclear egress complex (NEC) for nucleocapsids. Recently, pUL50 has been shown to have NEC-independent activities: downregulation of IRE1 to repress the unfolded protein response and degradation of UBE1L to inhibit the protein ISG15 modification pathway. Here, we demonstrate that a 26-kDa N-terminal truncated isoform of pUL50 (UL50-p26) is expressed from an internal methionine at amino acid position 199 and regulates the activity of pUL50 to induce the loss of valosin-containing protein (VCP/p97). A UL50(M199V) mutant virus expressing pUL50(M199V) but not UL50-p26 showed delayed growth at a low multiplicity of infection. There was also delayed accumulation of the viral immediate early 2 (IE2) protein in the mutant virus, and this correlated with the reduced expression of VCP/p97, which promotes IE2 expression. Infection with mutant virus did not significantly alter ISGylation levels. In transient expression assays, pUL50 induced VCP/p97 loss posttranscriptionally, and this was dependent on the presence of its transmembrane domain. In contrast, UL50-p26 did not destabilize VCP/p97 but, rather, inhibited pUL50-mediated VCP/p97 loss and the associated major IE gene suppression. Both pUL50 and UL50-p26 interacted with VCP/p97, although UL50-p26 did so more weakly than pUL50. UL50-p26 interacted with pUL50, and this interaction was much stronger than the pUL50 self-interaction. Furthermore, UL50-p26 was able to interfere with the pUL50-VCP/p97 interaction. Our study newly identifies UL50-p26 expression during HCMV infection and suggests a regulatory role for UL50-p26 in blocking pUL50-mediated VCP/p97 loss by associating with pUL50.IMPORTANCE Targeting the endoplasmic reticulum (ER) by viral proteins may affect ER-associated protein homeostasis. During human cytomegalovirus (HCMV) infection, pUL50 targets the ER through its transmembrane domain and moves to the inner nuclear membrane (INM) to form the nuclear egress complex (NEC), which facilitates capsid transport from the nucleus to the cytoplasm. Here, we demonstrate that pUL50 induces the loss of valosin-containing protein (VCP/p97), which promotes the expression of viral major immediate early gene products, in a manner dependent on its membrane targeting but that a small isoform of pUL50 is expressed to negatively regulate this pUL50 activity. This study reports a new NEC-independent function of pUL50 and highlights the fine regulation of pUL50 activity by a smaller isoform for efficient viral growth.
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20
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Hung CH, Chiu YF, Wang WH, Chen LW, Chang PJ, Huang TY, Lin YJ, Tsai WJ, Yang CC. Interaction Between BGLF2 and BBLF1 Is Required for the Efficient Production of Infectious Epstein-Barr Virus Particles. Front Microbiol 2020; 10:3021. [PMID: 32038519 PMCID: PMC6993569 DOI: 10.3389/fmicb.2019.03021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 12/17/2019] [Indexed: 11/13/2022] Open
Abstract
BGLF2 is a tegument protein of the Epstein-Barr virus (EBV). This study finds that BGLF2 is expressed in the late stage of the EBV lytic cycle. Microscopic investigations reveal that BGLF2 is present in both the nucleus and the cytoplasm and colocalized with BBLF1 and gp350 at juxtanuclear regions in the cytoplasm. This study also finds that the basic KKK69 motif of BGLF2 and acidic DYEE31 motif of BBLF1 are crucial for the interaction between BGLF2 and BBLF1, which is required for the recruitment of BGLF2 to the BBLF1 that is anchored on the trans-Golgi-network (TGN). In addition, BGLF2 in a density gradient is co-sedimented with un-enveloped capsids, revealing that BGLF2 associates with the EBV capsid before the final envelopment. The knockout of BGLF2 expression is demonstrated to reduce the numbers of infectious virions that are released into the culture medium, but they do not affect the expression of lytic proteins and viral DNA replication. The production of infectious viral particles by a BGLF2-knockout mutant can be rescued by exogenously expressed BGLF2 but only partially rescued by BGLF2-3KA, which is a mutant with reduced ability to interact with BBLF1 but does not affect its ability to activate the MAPK pathway and the expression of the EBV lytic proteins, suggesting that the interaction of BGLF2 with BBLF1 is important to the efficient production of infectious viral particles during the maturation. The results of this study improve our understanding of how BGLF2 promotes EBV viral production.
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Affiliation(s)
- Chien-Hui Hung
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan, Taiwan.,Division of Infectious Diseases, Chang Gung Memorial Hospital Chiayi Branch, Chiayi, Taiwan
| | - Ya-Fang Chiu
- Department of Microbiology and Immunology, Chang-Gung University, Taoyuan, Taiwan.,Research Center for Emerging Viral Infections, Chang-Gung University, Taoyuan, Taiwan.,Department of Medical Laboratory, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Wen-Hung Wang
- Division of Infectious Disease, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Lee-Wen Chen
- Department of Respiratory Care, Chang-Gung University of Science and Technology, Chiayi, Taiwan
| | - Pey-Jium Chang
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan, Taiwan
| | - Tsung-Yu Huang
- Division of Infectious Diseases, Chang Gung Memorial Hospital Chiayi Branch, Chiayi, Taiwan
| | - Ying-Ju Lin
- Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan
| | - Wan-Ju Tsai
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan, Taiwan
| | - Chia-Ching Yang
- Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Taoyuan, Taiwan
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21
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Functional Identification and Characterization of the Nuclear Egress Complex of a Gammaherpesvirus. J Virol 2019; 93:JVI.01422-19. [PMID: 31554685 DOI: 10.1128/jvi.01422-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 09/17/2019] [Indexed: 01/29/2023] Open
Abstract
The herpesvirus nuclear egress complex (NEC) is composed of two viral proteins. They play key roles in mediating the translocation of capsids from the nucleus to the cytoplasm by facilitating the budding of capsids into the perinuclear space (PNS). The NEC of alphaherpesvirus can induce the formation of virion-like vesicles from the nuclear membrane in the absence of other viral proteins. However, whether the NEC of gammaherpesvirus harbors the ability to do so in mammalian cells remains to be determined. In this study, we first constructed open reading frame 67 (ORF67)-null and ORF69-null mutants of murine gammaherpesvirus 68 (MHV-68) and demonstrated that both ORF67 and ORF69 play critical roles in nuclear egress and hence viral lytic replication. Biochemical and bioimaging analyses showed that ORF67 and ORF69 interacted with each other and were sufficient to induce the formation of virion-like vesicles from the nuclear membrane in mammalian cells. Thus, we designated ORF67 and ORF69 components of MHV-68 NEC. Furthermore, we identified amino acids critical for mediating the interaction between ORF67 and ORF69 through homology modeling and verified their function in nuclear egress, providing insights into the molecular basis of NEC formation in gammaherpesviruses.IMPORTANCE Increasing amounts of knowledge indicate that the nuclear egress complex (NEC) is critical for the nuclear egress of herpesvirus capsids, which can be viewed as a vesicle-mediated transport pathway through the nuclear membrane. In this study, we identified open reading frame 67 (ORF67) and ORF69 as components of the NEC in murine gammaherpesvirus 68 (MHV-68) and demonstrated that they efficiently induce virion-like vesicles from the nuclear membrane in mammalian cells. This is the first time that the NEC of a gammaherpesvirus has been found to demonstrate such an essential characteristic. In addition, we identified amino acids critical for mediating the interaction between ORF67 and ORF69 as well as nuclear egress. Notably, these amino acids are conserved in Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), providing a structural basis to design antigammaherpesvirus drugs.
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22
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Abstract
The Herpesviridae are structurally complex DNA viruses whose capsids undergo primary envelopment at the inner nuclear membrane and secondary envelopment at organelles in the cytoplasm. In both locations, there is evidence that envelope formation and scission involve the participation of multiple viral proteins and also the cellular ESCRT apparatus. It nevertheless appears that the best-understood viral strategies for ESCRT recruitment, those adopted by the retroviruses and many other families of enveloped RNA viruses, are not utilized by the Herpesviridae, at least during envelopment in the cytoplasm. Thus, although a large number of herpesvirus proteins have been assigned roles in envelopment, there is a dearth of candidates for the acquisition of the ESCRT complex and the control of envelope scission. This review summarizes our current understanding of ESCRT association by enveloped viruses, examines what is known of herpesvirus ESCRT utilization in the nucleus and cytoplasm, and identifies candidate cellular and viral proteins that could link enveloping herpesviruses to cellular ESCRT components.
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23
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Martinez T, Shapiro M, Bhaduri-McIntosh S, MacCarthy T. Evolutionary effects of the AID/APOBEC family of mutagenic enzymes on human gamma-herpesviruses. Virus Evol 2019; 5:vey040. [PMID: 30792902 PMCID: PMC6371749 DOI: 10.1093/ve/vey040] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The human gamma-herpesviruses, Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus, establish lifelong latency in B cells and are associated with multiple malignancies. Virus-host coevolution often drive changes in both host immunity and in the viral genome. We consider one host immune mechanism, the activation-induced deaminase (AID)/APOBEC family of cytidine deaminases, that induces mutations in viral DNA. AID, the ancestral gene in the family has a conserved role in somatic hypermutation, a key step in antibody affinity maturation. The APOBEC3 subfamily, of which there are seven genes in human, have evolved antiviral functions and have diversified in terms of their expression pattern, subcellular localization, and DNA mutation motifs (hotspots). In this study, we investigated how the human gamma-herpesviruses have evolved to avoid the action of the AID/APOBEC enzymes and determine if these enzymes are contributing to the ongoing evolution of the viruses. We used computational methods to evaluate observed versus expected frequency of AID/APOBEC hotspots in viral genomes and found that the viruses have evolved to limit the representation of AID and certain APOBEC3 motifs. At the same time, the remaining hotspots were highly likely to cause amino acid changes, suggesting prolonged evolutionary pressure of the enzymes on the viruses. To study current hypermutation, as opposed to historical mutation processes, we also analyzed putative mutations derived from alignments of published viral genomes and found again that AID and APOBEC3 appear to target the genome most frequently. New protein variants resulting from AID/APOBEC activity may have important consequences in health, including vaccine development (epitope evolution) and host immune evasion.
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Affiliation(s)
- Teresa Martinez
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - Maxwell Shapiro
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - Sumita Bhaduri-McIntosh
- Division of Infectious Diseases, Department of Pediatrics, University of Florida, Gainesville, FL, USA
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL, USA
| | - Thomas MacCarthy
- Department of Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
- Laufer Center for Physical and Quantitative Biology, Stony Brook University, Stony Brook, NY, USA
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24
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Encyclopedia of EBV-Encoded Lytic Genes: An Update. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1045:395-412. [DOI: 10.1007/978-981-10-7230-7_18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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25
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Coghill AE, Pfeiffer RM, Proietti C, Hsu WL, Chien YC, Lekieffre L, Krause L, Teng A, Pablo J, Yu KJ, Lou PJ, Wang CP, Liu Z, Chen CJ, Middeldorp J, Mulvenna J, Bethony J, Hildesheim A, Doolan DL. Identification of a Novel, EBV-Based Antibody Risk Stratification Signature for Early Detection of Nasopharyngeal Carcinoma in Taiwan. Clin Cancer Res 2018; 24:1305-1314. [PMID: 29301829 DOI: 10.1158/1078-0432.ccr-17-1929] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 10/10/2017] [Accepted: 12/18/2017] [Indexed: 12/14/2022]
Abstract
Background Epstein-Barr virus (EBV) is necessary for the development of nasopharyngeal carcinoma (NPC). By adulthood, approximately 90% of individuals test EBV-positive, but only a fraction develop cancer. Factors that identify which individuals are most likely to develop disease, including differential antibody response to the virus, could facilitate detection at early stages when treatment is most effective.Methods We measured anti-EBV IgG and IgA antibody responses in 607 Taiwanese individuals. Antibodies were measured using a custom protein microarray targeting 199 sequences from 86 EBV proteins. Variation in response patterns between NPC cases and controls was used to develop an antibody-based risk score for predicting NPC. The overall accuracy [area under the curve (AUC)] of this risk score, and its performance relative to currently used biomarkers, was evaluated in two independent Taiwanese cohorts.Findings Levels of 60 IgA and 73 IgG anti-EBV antibodies differed between stage I/IIa NPC cases and controls (P < 0.0002). Risk prediction analyses identified antibody targets that best discriminated NPC status-BXLF1, LF2,BZLF1, BRLF1, EAd, BGLF2, BPLF1, BFRF1, and BORF1. When combined with currently used VCA/EBNA1 IgA biomarkers, the resulting risk score predicted NPC with 93% accuracy (95% CI, 87%-98%) in the general Taiwanese population, a significant improvement beyond current biomarkers alone (82%; 95% CI, 75%-90%, P ≤ 0.01). This EBV-based risk score also improved NPC prediction in genetically high-risk families (89%; 95% CI, 82%-96%) compared with current biomarkers (78%; 95% CI, 66%-90%, P ≤ 0.03).Interpretation We identified NPC-related differences in 133 anti-EBV antibodies and developed a risk score using this microarray dataset that targeted immune responses against EBV proteins from all stages of the viral life cycle, significantly improving the ability to predict NPC. Clin Cancer Res; 24(6); 1305-14. ©2017 AACR.
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Affiliation(s)
- Anna E Coghill
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland.
| | - Ruth M Pfeiffer
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland
| | - Carla Proietti
- Queensland Institute of Medical Research, Brisbane, Australia.,Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Wan-Lun Hsu
- Genomics Research Center, Academica Sinica, Taipei, Taiwan.,Graduate Institute of Epidemiology and Prevention Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | - Yin-Chu Chien
- Genomics Research Center, Academica Sinica, Taipei, Taiwan.,National Institute of Cancer Research, National Health Research Institute, Miaoli, Taiwan
| | - Lea Lekieffre
- Queensland Institute of Medical Research, Brisbane, Australia
| | - Lutz Krause
- Queensland Institute of Medical Research, Brisbane, Australia
| | - Andy Teng
- Antigen Discovery Inc., Irvine, California
| | | | - Kelly J Yu
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland
| | - Pei-Jen Lou
- Department of Otolaryngology, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | - Cheng-Ping Wang
- Department of Otolaryngology, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | - Zhiwei Liu
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland
| | - Chien-Jen Chen
- Genomics Research Center, Academica Sinica, Taipei, Taiwan.,Graduate Institute of Epidemiology and Prevention Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan
| | | | - Jason Mulvenna
- Queensland Institute of Medical Research, Brisbane, Australia
| | - Jeff Bethony
- Department of Microbiology, Immunology, and Tropical Medicine, George Washington University Medical Center, Washington, District of Columbia
| | - Allan Hildesheim
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland
| | - Denise L Doolan
- Queensland Institute of Medical Research, Brisbane, Australia. .,Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
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26
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Bailer SM. Venture from the Interior-Herpesvirus pUL31 Escorts Capsids from Nucleoplasmic Replication Compartments to Sites of Primary Envelopment at the Inner Nuclear Membrane. Cells 2017; 6:cells6040046. [PMID: 29186822 PMCID: PMC5755504 DOI: 10.3390/cells6040046] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 01/29/2023] Open
Abstract
Herpesviral capsid assembly is initiated in the nucleoplasm of the infected cell. Size constraints require that newly formed viral nucleocapsids leave the nucleus by an evolutionarily conserved vescular transport mechanism called nuclear egress. Mature capsids released from the nucleoplasm are engaged in a membrane-mediated budding process, composed of primary envelopment at the inner nuclear membrane and de-envelopment at the outer nuclear membrane. Once in the cytoplasm, the capsids receive their secondary envelope for maturation into infectious virions. Two viral proteins conserved throughout the herpesvirus family, the integral membrane protein pUL34 and the phosphoprotein pUL31, form the nuclear egress complex required for capsid transport from the infected nucleus to the cytoplasm. Formation of the nuclear egress complex results in budding of membrane vesicles revealing its function as minimal virus-encoded membrane budding and scission machinery. The recent structural analysis unraveled details of the heterodimeric nuclear egress complex and the hexagonal coat it forms at the inside of budding vesicles to drive primary envelopment. With this review, I would like to present the capsid-escort-model where pUL31 associates with capsids in nucleoplasmic replication compartments for escort to sites of primary envelopment thereby coupling capsid maturation and nuclear egress.
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Affiliation(s)
- Susanne M. Bailer
- Institute for Interfacial Engineering and Plasma Technology IGVP, University of Stuttgart, Stuttgart 70174, Germany;
- Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart 70569, Germany;
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27
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Yadav S, Libotte F, Buono E, Valia S, Farina G, Faggioni A, Farina A. EBV early lytic protein BFRF1 alters emerin distribution and post-translational modification. Virus Res 2017; 232:113-122. [DOI: 10.1016/j.virusres.2017.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/11/2017] [Accepted: 02/22/2017] [Indexed: 12/20/2022]
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28
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Farina A, Peruzzi G, Lacconi V, Lenna S, Quarta S, Rosato E, Vestri AR, York M, Dreyfus DH, Faggioni A, Morrone S, Trojanowska M, Farina GA. Epstein-Barr virus lytic infection promotes activation of Toll-like receptor 8 innate immune response in systemic sclerosis monocytes. Arthritis Res Ther 2017; 19:39. [PMID: 28245863 PMCID: PMC5331713 DOI: 10.1186/s13075-017-1237-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 01/16/2017] [Indexed: 01/15/2023] Open
Abstract
Background Monocytes/macrophages are activated in several autoimmune diseases, including systemic sclerosis (scleroderma; SSc), with increased expression of interferon (IFN)-regulatory genes and inflammatory cytokines, suggesting dysregulation of the innate immune response in autoimmunity. In this study, we investigated whether the lytic form of Epstein-Barr virus (EBV) infection (infectious EBV) is present in scleroderma monocytes and contributes to their activation in SSc. Methods Monocytes were isolated from peripheral blood mononuclear cells (PBMCs) depleted of the CD19+ cell fraction, using CD14/CD16 negative-depletion. Circulating monocytes from SSc and healthy donors (HDs) were infected with EBV. Gene expression of innate immune mediators were evaluated in EBV-infected monocytes from SSc and HDs. Involvement of Toll-like receptor (TLR)8 in viral-mediated TLR8 response was investigated by comparing the TLR8 expression induced by infectious EBV to the expression stimulated by CL075/TLR8/agonist-ligand in the presence of TLR8 inhibitor in THP-1 cells. Results Infectious EBV strongly induced TLR8 expression in infected SSc and HD monocytes in vitro. Markers of activated monocytes, such as IFN-regulated genes and chemokines, were upregulated in SSc- and HD-EBV-infected monocytes. Inhibiting TLR8 expression reduced virally induced TLR8 in THP-1 infected cells, demonstrating that innate immune activation by infectious EBV is partially dependent on TLR8. Viral mRNA and proteins were detected in freshly isolated SSc monocytes. Microarray analysis substantiated the evidence of an increased IFN signature and altered level of TLR8 expression in SSc monocytes carrying infectious EBV compared to HD monocytes. Conclusion This study provides the first evidence of infectious EBV in monocytes from patients with SSc and links EBV to the activation of TLR8 and IFN innate immune response in freshly isolated SSc monocytes. This study provides the first evidence of EBV replication activating the TLR8 molecular pathway in primary monocytes. Immunogenicity of infectious EBV suggests a novel mechanism mediating monocyte inflammation in SSc, by which EBV triggers the innate immune response in infected cells. Electronic supplementary material The online version of this article (doi:10.1186/s13075-017-1237-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Antonella Farina
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA.,Department of Experimental Medicine, Sapienza University, Rome, Italy
| | | | - Valentina Lacconi
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA
| | - Stefania Lenna
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA
| | - Silvia Quarta
- Department of Clinical Medicine, Sapienza University, Rome, Italy
| | - Edoardo Rosato
- Department of Clinical Medicine, Sapienza University, Rome, Italy
| | | | - Michael York
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA
| | | | - Alberto Faggioni
- Department of Experimental Medicine, Sapienza University, Rome, Italy
| | - Stefania Morrone
- Department of Experimental Medicine, Sapienza University, Rome, Italy
| | - Maria Trojanowska
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA
| | - G Alessandra Farina
- Rheumatology, Boston University School of Medicine, Arthritis Center, 72 E. Concord Street, E-5, Boston, MA, 02118, USA.
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29
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Lye MF, Wilkie AR, Filman DJ, Hogle JM, Coen DM. Getting to and through the inner nuclear membrane during herpesvirus nuclear egress. Curr Opin Cell Biol 2017; 46:9-16. [PMID: 28086162 DOI: 10.1016/j.ceb.2016.12.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/10/2016] [Accepted: 12/21/2016] [Indexed: 12/16/2022]
Abstract
Herpesviruses, like most DNA viruses, replicate and package their genomes into capsids in the host cell nucleus. Capsids then transit to the cytoplasm in a fascinating process called nuclear egress, which includes several unusual steps: Movement of capsids from the nuclear interior to the periphery, disruption of the nuclear lamina, capsid budding through the inner nuclear membrane, and fusion of enveloped particles with the outer nuclear membrane. Here, we review recent advances and emerging questions relating to herpesvirus nuclear egress, emphasizing controversies regarding mechanisms for capsid trafficking to the nuclear periphery, and implications of recent structures of the two-subunit, viral nuclear egress complex for the process, particularly at the step of budding through the inner nuclear membrane.
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Affiliation(s)
- Ming F Lye
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Ave., Boston, MA 02052, United States
| | - Adrian R Wilkie
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Ave., Boston, MA 02052, United States
| | - David J Filman
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Ave., Boston, MA 02052, United States
| | - James M Hogle
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Ave., Boston, MA 02052, United States
| | - Donald M Coen
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 250 Longwood Ave., Boston, MA 02052, United States.
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30
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Roller RJ, Baines JD. Herpesvirus Nuclear Egress. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2017; 223:143-169. [PMID: 28528443 DOI: 10.1007/978-3-319-53168-7_7] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Herpesviruses assemble and package their genomes into capsids in the nucleus, but complete final assembly of the mature virion in the cell cytoplasm. This requires passage of the genome-containing capsid across the double-membrane nuclear envelope. Herpesviruses have evolved a mechanism that relies on a pair of conserved viral gene products to shuttle the capsids from the nucleus to the cytoplasm by way of envelopment and de-envelopment at the inner and outer nuclear membranes, respectively. This complex process requires orchestration of the activities of viral and cellular factors to alter the architecture of the nuclear membrane, select capsids at the appropriate stage for egress, and accomplish efficient membrane budding and fusion events. The last few years have seen major advances in our understanding of the membrane budding mechanism and helped clarify the roles of viral and cellular proteins in the other, more mysterious steps. Here, we summarize and place into context this recent research and, hopefully, clarify both the major advances and major gaps in our understanding.
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Affiliation(s)
- Richard J Roller
- Department of Microbiology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Joel D Baines
- Kenneth F. Burns Chair in Veterinary Medicine, School of Veterinary Medicine, Skip Bertman Drive, Louisiana State University, Baton Rouge, LA, USA.
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31
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Kuan MI, O'Dowd JM, Fortunato EA. The absence of p53 during Human Cytomegalovirus infection leads to decreased UL53 expression, disrupting UL50 localization to the inner nuclear membrane, and thereby inhibiting capsid nuclear egress. Virology 2016; 497:262-278. [PMID: 27498409 PMCID: PMC5026620 DOI: 10.1016/j.virol.2016.07.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/18/2016] [Accepted: 07/19/2016] [Indexed: 01/10/2023]
Abstract
Our electron microscopy study (Kuan et al., 2016) found HCMV nuclear capsid egress was significantly reduced in p53 knockout cells (p53KOs), correlating with inhibited formation of infoldings of the inner nuclear membrane (IINMs). Molecular examination of these phenomena has found p53KOs expressed UL97 and phosphorylated lamins, however the lamina failed to remodel. The nuclear egress complex (NEC) protein UL50 was expressed in almost all cells. UL50 re-localized to the inner nuclear membrane (INM) in ~90% of wt cells, but only ~35% of p53KOs. UL53 expression was significantly reduced in p53KOs, and cells lacking UL50 nuclear staining, expressed no UL53. Re-introduction of p53 into p53KOs largely recovered UL53 positivity and UL50 nuclear re-localization. Nuclear rim located UL50/53 puncta, which co-localized with the major capsid protein, were largely absent in p53KOs. We believe these puncta were IINMs. In the absence of p53, UL53 expression was inhibited, disrupting formation of the NEC/IINMs, and reducing functional virion secretion.
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Affiliation(s)
- Man I Kuan
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - John M O'Dowd
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - Elizabeth A Fortunato
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA.
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32
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The Ubiquitin Ligase Itch and Ubiquitination Regulate BFRF1-Mediated Nuclear Envelope Modification for Epstein-Barr Virus Maturation. J Virol 2016; 90:8994-9007. [PMID: 27466427 DOI: 10.1128/jvi.01235-16] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 07/19/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The cellular endosomal sorting complex required for transport (ESCRT) was recently found to mediate important morphogenesis processes at the nuclear envelope (NE). We previously showed that the Epstein-Barr virus (EBV) BFRF1 protein recruits the ESCRT-associated protein Alix to modulate NE structure and promote EBV nuclear egress. Here, we uncover new cellular factors and mechanisms involved in this process. BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. BFRF1 is ubiquitinated, and elimination of possible ubiquitination by either lysine mutations or fusion of a deubiquitinase hampers NE-derived vesicle formation and virus maturation. While it interacts with multiple Nedd4-like ubiquitin ligases, BFRF1 preferentially binds Itch ligase. We show that Itch associates with Alix and BFRF1 and is required for BFRF1-induced NE vesicle formation. Our data demonstrate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE and EBV maturation, uncovering novel regulatory mechanisms of nuclear egress of viral nucleocapsids. IMPORTANCE The nuclear envelope (NE) of eukaryotic cells not only serves as a transverse scaffold for cellular processes, but also as a natural barrier for most DNA viruses that assemble their nucleocapsids in the nucleus. Previously, we showed that the cellular endosomal sorting complex required for transport (ESCRT) machinery is required for the nuclear egress of EBV. Here, we further report the molecular interplay among viral BFRF1, the ESCRT adaptor Alix, and the ubiquitin ligase Itch. We found that BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. The lysine residues and the ubiquitination of BFRF1 regulate the formation of BFRF1-induced NE-derived vesicles and EBV maturation. During the process, a ubiquitin ligase, Itch, preferably associates with BFRF1 and is required for BFRF1-induced NE vesicle formation. Therefore, our data indicate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE, suggesting novel regulatory mechanisms for ESCRT-mediated NE modulation.
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33
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Affiliation(s)
- Ya-Fang Chiu
- McArdle Laboratory for Cancer Research, University of Wisconsin–Madison, Madison, Wisconsin 53705;
- Morgridge Institute for Research, Madison, Wisconsin 53715
- Research Center for Emerging Viral Infections and Department of Microbiology and Immunology, Chang Gung University, Taoyuan 33302, Taiwan
- Department of Medical Laboratory, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan
| | - Bill Sugden
- McArdle Laboratory for Cancer Research, University of Wisconsin–Madison, Madison, Wisconsin 53705;
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34
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Bigalke JM, Heldwein EE. Have NEC Coat, Will Travel: Structural Basis of Membrane Budding During Nuclear Egress in Herpesviruses. Adv Virus Res 2016; 97:107-141. [PMID: 28057257 DOI: 10.1016/bs.aivir.2016.07.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Herpesviruses are unusual among enveloped viruses because they bud twice yet acquire a single envelope. Furthermore, unlike other DNA viruses that replicate in the nucleus, herpesviruses do not exit it by passing through the nuclear pores or by rupturing the nuclear envelope. Instead, herpesviruses have a complex mechanism of nuclear escape whereby nascent capsids bud at the inner nuclear membrane to form perinuclear virions that subsequently fuse with the outer nuclear membrane, releasing capsids into the cytosol. This makes them some of the very few known viruses that bud into the nuclear envelope. The envelope acquired during nuclear budding does not end up in the mature viral particle but instead allows the capsid to translocate from the nucleus into the cytosol. The viral nuclear egress complex (NEC) is a critical player in the nuclear egress, yet its function and mechanism have remained enigmatic. Recent studies have demonstrated that the NEC buds membranes without the help of other proteins by forming a honeycomb coat, which established the NEC as the first virally encoded budding machine that operates at the nuclear, as opposed to cytoplasmic, membrane. This review discusses our current understanding of the NEC budding mechanism, with the emphasis on studies that illuminated the structure of the NEC coat and its role in capsid budding during herpesvirus nuclear escape.
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Affiliation(s)
- J M Bigalke
- Tufts University School of Medicine, Boston, MA, United States
| | - E E Heldwein
- Tufts University School of Medicine, Boston, MA, United States.
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35
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Kuan MI, O'Dowd JM, Chughtai K, Hayman I, Brown CJ, Fortunato EA. Human Cytomegalovirus nuclear egress and secondary envelopment are negatively affected in the absence of cellular p53. Virology 2016; 497:279-293. [PMID: 27498410 DOI: 10.1016/j.virol.2016.07.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/10/2016] [Accepted: 07/19/2016] [Indexed: 01/10/2023]
Abstract
Human Cytomegalovirus (HCMV) infection is compromised in cells lacking p53, a transcription factor that mediates cellular stress responses. In this study we have investigated compromised functional virion production in cells with p53 knocked out (p53KOs). Infectious center assays found most p53KOs released functional virions. Analysis of electron micrographs revealed modestly decreased capsid production in infected p53KOs compared to wt. Substantially fewer p53KOs displayed HCMV-induced infoldings of the inner nuclear membrane (IINMs). In p53KOs, fewer capsids were found in IINMs and in the cytoplasm. The deficit in virus-induced membrane remodeling within the nucleus of p53KOs was mirrored in the cytoplasm, with a disproportionately smaller number of capsids re-enveloped. Reintroduction of p53 substantially recovered these deficits. Overall, the absence of p53 contributed to inhibition of the formation and function of IINMs and re-envelopment of the reduced number of capsids able to reach the cytoplasm.
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Affiliation(s)
- Man I Kuan
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - John M O'Dowd
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - Kamila Chughtai
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - Ian Hayman
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - Celeste J Brown
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA
| | - Elizabeth A Fortunato
- Department of Biological Sciences and Center for Reproductive Biology, University of Idaho, Moscow, ID, USA.
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36
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Abstract
Most DNA viruses replicate in the nucleus and exit it either by passing through the nuclear pores or by rupturing the nuclear envelope. Unusually, herpesviruses have evolved a complex mechanism of nuclear escape whereby nascent capsids bud at the inner nuclear membrane to form perinuclear virions that subsequently fuse with the outer nuclear membrane, releasing capsids into the cytosol. Although this general scheme is accepted in the field, the players and their roles are still debated. Recent studies illuminated critical mechanistic features of this enigmatic process and uncovered surprising parallels with a novel cellular nuclear export process. This review summarizes our current understanding of nuclear egress in herpesviruses, examines the experimental evidence and models, and outlines outstanding questions with the goal of stimulating new research in this area.
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Affiliation(s)
- Janna M Bigalke
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111;
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111;
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37
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Changotra H, Turk SM, Artigues A, Thakur N, Gore M, Muggeridge MI, Hutt-Fletcher LM. Epstein-Barr virus glycoprotein gM can interact with the cellular protein p32 and knockdown of p32 impairs virus. Virology 2016; 489:223-32. [PMID: 26773383 DOI: 10.1016/j.virol.2015.12.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 12/23/2015] [Accepted: 12/29/2015] [Indexed: 02/08/2023]
Abstract
The Epstein-Barr virus glycoprotein complex gMgN has been implicated in assembly and release of fully enveloped virus, although the precise role that it plays has not been elucidated. We report here that the long predicted cytoplasmic tail of gM is not required for complex formation and that it interacts with the cellular protein p32, which has been reported to be involved in nuclear egress of human cytomegalovirus and herpes simplex virus. Although redistribution of p32 and colocalization with gM was not observed in virus infected cells, knockdown of p32 expression by siRNA or lentivirus-delivered shRNA recapitulated the phenotype of a virus lacking expression of gNgM. A proportion of virus released from cells sedimented with characteristics of virus lacking an intact envelope and there was an increase in virus trapped in nuclear condensed chromatin. The observations suggest the possibility that p32 may also be involved in nuclear egress of Epstein-Barr virus.
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Affiliation(s)
- Harish Changotra
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Susan M Turk
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Antonio Artigues
- Department of Biochemistry, University of Kansas Medical Center, Kansas City, KS, USA
| | - Nagendra Thakur
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Mindy Gore
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Martin I Muggeridge
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA
| | - Lindsey M Hutt-Fletcher
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology and Feist-Weiller Cancer Center, Louisiana State University Health Sciences Center, Shreveport, LA, USA.
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Traylen C, Ramasubramanyan S, Zuo J, Rowe M, Almohammad R, Heesom K, Sweet SMM, Matthews DA, Sinclair AJ. Identification of Epstein-Barr Virus Replication Proteins in Burkitt's Lymphoma Cells. Pathogens 2015; 4:739-51. [PMID: 26529022 PMCID: PMC4693162 DOI: 10.3390/pathogens4040739] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 10/20/2015] [Accepted: 10/23/2015] [Indexed: 12/11/2022] Open
Abstract
The working model to describe the mechanisms used to replicate the cancer-associated virus Epstein-Barr virus (EBV) is partly derived from comparisons with other members of the Herpes virus family. Many genes within the EBV genome are homologous across the herpes virus family. Published transcriptome data for the EBV genome during its lytic replication cycle show extensive transcription, but the identification of the proteins is limited. We have taken a global proteomics approach to identify viral proteins that are expressed during the EBV lytic replication cycle. We combined an enrichment method to isolate cells undergoing EBV lytic replication with SILAC-labeling coupled to mass-spectrometry and identified viral and host proteins expressed during the EBV lytic replication cycle. Amongst the most frequently identified viral proteins are two components of the DNA replication machinery, the single strand DNA binding protein BALF2, DNA polymerase accessory protein BMRF1 and both subunits of the viral ribonucleoside-diphosphate reductase enzyme (BORF2 and BaRF1). An additional 42 EBV lytic cycle proteins were also detected. This provides proteomic identification for many EBV lytic replication cycle proteins and also identifies post-translational modifications.
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Affiliation(s)
- Chris Traylen
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK.
| | | | - Jianmin Zuo
- School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham B15 2TT, UK.
| | - Martin Rowe
- School of Cancer Sciences and Centre for Human Virology, University of Birmingham College of Medical and Dental Sciences, Edgbaston, Birmingham B15 2TT, UK.
| | - Rajaei Almohammad
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK.
| | - Kate Heesom
- School of Cellular and Molecular Medicine, University of Bristol, Medical Sciences Building, Bristol BS8 1TD, UK.
| | - Steve M M Sweet
- Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, UK.
| | - David A Matthews
- School of Cellular and Molecular Medicine, University of Bristol, Medical Sciences Building, Bristol BS8 1TD, UK.
| | - Alison J Sinclair
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK.
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Abstract
Glycoproteins are critical to virus entry, to spread within and between hosts and can modify the behavior of cells. Many viruses carry only a few, most found in the virion envelope. EBV makes more than 12, providing flexibility in how it colonizes its human host. Some are dedicated to getting the virus through the cell membrane and on toward the nucleus of the cell, some help guide the virus back out and on to the next cell in the same or a new host. Yet others undermine host defenses helping the virus persist for a lifetime, maintaining a presence that is mostly tolerated and serves to perpetuate EBV as one of the most common infections of man.
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Affiliation(s)
- Lindsey M Hutt-Fletcher
- Department of Microbiology & Immunology, Feist-Weiller Cancer Center and Center for Molecular & Tumor Virology, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, LA 71130, USA; Tel.: +1 318 675 4948
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40
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Hennig T, O'Hare P. Viruses and the nuclear envelope. Curr Opin Cell Biol 2015; 34:113-21. [PMID: 26121672 DOI: 10.1016/j.ceb.2015.06.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 06/05/2015] [Accepted: 06/08/2015] [Indexed: 10/23/2022]
Abstract
Viruses encounter and manipulate almost all aspects of cell structure and metabolism. The nuclear envelope (NE), with central roles in cell structure and genome function, acts and is usurped in diverse ways by different viruses. It can act as a physical barrier to infection that must be overcome, as a functional barrier that restricts infection by various mechanisms and must be counteracted or indeed as a positive niche, important or even essential for virus infection or production of progeny virions. This review summarizes virus-host interactions at the NE, highlighting progress in understanding the replication of viruses including HIV-1, Influenza, Herpes Simplex, Adenovirus and Ebola, and molecular insights into hitherto unknown functional pathways at the NE.
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Affiliation(s)
- Thomas Hennig
- Section of Virology, Faculty of Medicine, Imperial College, London W2 1PG, United Kingdom
| | - Peter O'Hare
- Section of Virology, Faculty of Medicine, Imperial College, London W2 1PG, United Kingdom.
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41
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Gammaherpesvirus Tegument Protein ORF33 Is Associated With Intranuclear Capsids at an Early Stage of the Tegumentation Process. J Virol 2015; 89:5288-97. [PMID: 25717105 DOI: 10.1128/jvi.00079-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 02/13/2015] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Herpesvirus nascent capsids, after assembly in the nucleus, must acquire a variety of tegument proteins during maturation. However, little is known about the identity of the tegument proteins that are associated with capsids in the nucleus or the molecular mechanisms involved in the nuclear egress of capsids into the cytoplasm, especially for the two human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), due to a lack of efficient lytic replication systems. Murine gammaherpesvirus 68 (MHV-68) is genetically related to human gammaherpesviruses and serves as an excellent model to study the de novo lytic replication of gammaherpesviruses. We have previously shown that open reading frame 33 (ORF33) of MHV-68 is a tegument protein of mature virions and is essential for virion assembly and egress. However, it remains unclear how ORF33 is incorporated into virions. In this study, we first show that the endogenous ORF33 protein colocalizes with capsid proteins at discrete areas in the nucleus during viral infection. Cosedimentation analysis as well as an immunoprecipitation assay demonstrated that ORF33 is associated with both nuclear and cytoplasmic capsids. An immunogold labeling experiment using an anti-ORF33 monoclonal antibody revealed that ORF33-rich areas in the nucleus are surrounded by immature capsids. Moreover, ORF33 is associated with nucleocapsids prior to primary envelopment as well as with mature virions in the cytoplasm. Finally, we show that ORF33 interacts with two capsid proteins, suggesting that nucleocapsids may interact with ORF33 in a direct manner. In summary, we identified ORF33 to be a tegument protein that is associated with intranuclear capsids prior to primary envelopment, likely through interacting with capsid proteins in a direct manner. IMPORTANCE Morphogenesis is an essential step in virus propagation that leads to the generation of progeny virions. For herpesviruses, this is a complicated process that starts in the nucleus. Although the process of capsid assembly and genome packaging is relatively well understood, how capsids acquire tegument (the layer between the capsid and the envelope in a herpesvirus virion) and whether the initial tegumentation process takes place in the nucleus remain unclear. We previously showed that ORF33 of MHV-68 is a tegument protein and functions in both the nuclear egress of capsids and final virion maturation in the cytoplasm. In the present study, we show that ORF33 is associated with intranuclear capsids prior to primary envelopment and identify novel interactions between ORF33 and two capsid proteins. Our work provides new insights into the association between tegument proteins and nucleocapsids at an early stage of the virion maturation process for herpesviruses.
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42
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Schulz KS, Klupp BG, Granzow H, Passvogel L, Mettenleiter TC. Herpesvirus nuclear egress: Pseudorabies Virus can simultaneously induce nuclear envelope breakdown and exit the nucleus via the envelopment-deenvelopment-pathway. Virus Res 2015; 209:76-86. [PMID: 25678269 DOI: 10.1016/j.virusres.2015.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 02/01/2015] [Accepted: 02/02/2015] [Indexed: 12/19/2022]
Abstract
Herpesvirus replication takes place in the nucleus and in the cytosol. After entering the cell, nucleocapsids are transported to nuclear pores where viral DNA is released into the nucleus. After gene expression and DNA replication new nucleocapsids are assembled which have to exit the nucleus for virion formation in the cytosol. Since nuclear pores are not wide enough to allow passage of the nucleocapsid, nuclear egress occurs by vesicle-mediated transport through the nuclear envelope. To this end, nucleocapsids bud at the inner nuclear membrane (INM) recruiting a primary envelope which then fuses with the outer nuclear membrane (ONM). In the absence of this regulated nuclear egress, mutants of the alphaherpesvirus pseudorabies virus have been described that escape from the nucleus after virus-induced nuclear envelope breakdown. Here we review these exit pathways and demonstrate that both can occur simultaneously under appropriate conditions.
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Affiliation(s)
- Katharina S Schulz
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Harald Granzow
- Institute of Infectology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Lars Passvogel
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, 17493 Greifswald-Insel Riems, Germany.
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43
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Farina A, Santarelli R, Bloise R, Gonnella R, Granato M, Bei R, Modesti A, Cirone M, Bengtsson L, Angeloni A, Faggioni A. KSHV ORF67 encoded lytic protein localizes on the nuclear membrane and alters emerin distribution. Virus Res 2013; 175:143-50. [PMID: 23623980 DOI: 10.1016/j.virusres.2013.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 03/28/2013] [Accepted: 04/01/2013] [Indexed: 11/18/2022]
Abstract
p29, a newly identified Kaposi's sarcoma-associated herpesvirus (KSHV) protein, is the product of ORF67, the positional homolog of the conserved herpesvirus protein UL34. Like its homologues in other herpesviruses, p29 is expressed early during viral lytic cycle, and is localized on the nuclear rim. Upon chemical induction of viral replication in primary effusion lymphoma cells, p29 interacts with p33, encoded by ORF69, the positional homolog of the conserved herpesvirus protein UL31, and both proteins colocalize on the nuclear membrane. IFA and biochemical analysis of infected or transfected cells showed that p29 expression resulted in delocalization and hyperphosphorylation of emerin, whereas other nuclear lamin associated proteins, such as LUMA, LB1 and LBR were not affected. Mislocalization of emerin was robustly increased upon combined expression of p29 and p33, suggesting that emerin destabilization might represent the first step in nuclear lamina disassembling, a process necessary for nucleocapsid maturation.
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Affiliation(s)
- Antonella Farina
- Istituto Pasteur Fondazione Cenci Bolognetti, Dipartimento di Medicina Sperimentale, Sapienza Università di Roma, Italy.
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44
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Luitweiler EM, Henson BW, Pryce EN, Patel V, Coombs G, McCaffery JM, Desai PJ. Interactions of the Kaposi's Sarcoma-associated herpesvirus nuclear egress complex: ORF69 is a potent factor for remodeling cellular membranes. J Virol 2013; 87:3915-29. [PMID: 23365436 PMCID: PMC3624222 DOI: 10.1128/jvi.03418-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 01/18/2013] [Indexed: 12/17/2022] Open
Abstract
All herpesviruses encode a complex of two proteins, referred to as the nuclear egress complex (NEC), which together facilitate the exit of assembled capsids from the nucleus. Previously, we showed that the Kaposi's sarcoma-associated herpesvirus (KSHV) NEC specified by the ORF67 and ORF69 genes when expressed in insect cells using baculoviruses for protein expression forms a complex at the nuclear membrane and remodels these membranes to generate nuclear membrane-derived vesicles. In this study, we have analyzed the functional domains of the KSHV NEC proteins and their interactions. Site-directed mutagenesis of gammaherpesvirus conserved residues revealed functional domains of these two proteins, which in many cases abolish the formation of the NEC and remodeling of nuclear membranes. Small in-frame deletions within ORF67 in all cases result in loss of the ability of the mutant protein to induce cellular membrane proliferation as well as to interact with ORF69. Truncation of the C terminus of ORF67 that resides in the perinuclear space does not impair the functions of ORF67; however, deletion of the transmembrane domain of ORF67 produces a protein that cannot induce membrane proliferation but can still interact with ORF69 in the nucleus and can be tethered to the nuclear membrane by virtue of its interaction with the wild-type-membrane-anchored ORF67. In-frame deletions in ORF69 have varied effects on NEC formation, but all abolish remodeling of nuclear membranes into circular structures. One mutant interacts with ORF67 as well as the wild-type protein but cannot function in membrane curvature and fission events that generate circular vesicles. These studies genetically confirm that ORF67 is required for cellular membrane proliferation and that ORF69 is the factor required to remodel these duplicated membranes into circular-virion-size vesicles. Furthermore, we also investigated the NEC encoded by Epstein-Barr virus (EBV). The EBV complex comprised of BFRF1 and BFLF2 was visualized at the nuclear membrane using autofluorescent protein fusions. BFRF1 is a potent inducer of membrane proliferation; however, BFLF2 cannot remodel these membranes into circular structures. What was evident is the superior remodeling activity of ORF69, which could convert the host membrane proliferations induced by BFRF1 into circular structures.
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Affiliation(s)
- Eric M. Luitweiler
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins
| | - Brandon W. Henson
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins
| | - Erin N. Pryce
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Varun Patel
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins
| | - Gavin Coombs
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - J. Michael McCaffery
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Prashant J. Desai
- Viral Oncology Program, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins
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45
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Characterization of conserved region 2-deficient mutants of the cytomegalovirus egress protein pM53. J Virol 2012; 86:12512-24. [PMID: 22993161 DOI: 10.1128/jvi.00471-12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Dominant-negative (DN) mutants are powerful tools for studying essential protein-protein interactions. A systematic genetic screen of the essential murine cytomegalovirus (MCMV) protein pM53 identified the accumulation of inhibitory mutations within conserved region 2 (CR2) and CR4. The strong inhibitory potential of these CR4 mutants is characterized by a particular phenotype. The DN effect of the small insertion mutations in CR2 was too weak to analyze (M. Popa, Z. Ruzsics, M. Lötzerich, L. Dölken, C. Buser, P. Walther, and U. H. Koszinowski, J. Virol. 84:9035-9046, 2010); therefore, the present study describes the construction of M53 alleles lacking CR2 (either completely or partially) and subsequent examination of the DN effect on MCMV replication upon conditional expression. Overexpression of CR2-deficient pM53 inhibited virus production by about 10,000-fold. This was due to interference with capsid export from the nucleus and viral genome cleavage/packaging. In addition, the fate of the nuclear envelopment complex in the presence of DN pM53 overexpression was analyzed. The CR2 mutants were able to bind to pM50, albeit to a lesser extent than the wild-type protein, and relocalized the wild-type nuclear envelope complex in infected cells. Unlike the CR4 DN, the CR2 DN mutants did not affect the stability of pM50.
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46
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Lee CP, Liu PT, Kung HN, Su MT, Chua HH, Chang YH, Chang CW, Tsai CH, Liu FT, Chen MR. The ESCRT machinery is recruited by the viral BFRF1 protein to the nucleus-associated membrane for the maturation of Epstein-Barr Virus. PLoS Pathog 2012; 8:e1002904. [PMID: 22969426 PMCID: PMC3435242 DOI: 10.1371/journal.ppat.1002904] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Accepted: 07/30/2012] [Indexed: 12/11/2022] Open
Abstract
The cellular endosomal sorting complex required for transport (ESCRT) machinery participates in membrane scission and cytoplasmic budding of many RNA viruses. Here, we found that expression of dominant negative ESCRT proteins caused a blockade of Epstein-Barr virus (EBV) release and retention of viral BFRF1 at the nuclear envelope. The ESCRT adaptor protein Alix was redistributed and partially colocalized with BFRF1 at the nuclear rim of virus replicating cells. Following transient transfection, BFRF1 associated with ESCRT proteins, reorganized the nuclear membrane and induced perinuclear vesicle formation. Multiple domains within BFRF1 mediated vesicle formation and Alix recruitment, whereas both Bro and PRR domains of Alix interacted with BFRF1. Inhibition of ESCRT machinery abolished BFRF1-induced vesicle formation, leading to the accumulation of viral DNA and capsid proteins in the nucleus of EBV-replicating cells. Overall, data here suggest that BFRF1 recruits the ESCRT components to modulate nuclear envelope for the nuclear egress of EBV.
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Affiliation(s)
- Chung-Pei Lee
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
- Center of General Education, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan
| | - Po-Ting Liu
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Hsiu-Ni Kung
- Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Mei-Tzu Su
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Huey-Huey Chua
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Yu-Hsin Chang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chou-Wei Chang
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ching-Hwa Tsai
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Fu-Tong Liu
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- Department of Dermatology, School of Medicine, University of California, Davis, California, United States of America
| | - Mei-Ru Chen
- Graduate Institute and Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
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47
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Nuclear actin and lamins in viral infections. Viruses 2012; 4:325-47. [PMID: 22590674 PMCID: PMC3347030 DOI: 10.3390/v4030325] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Revised: 02/20/2012] [Accepted: 02/21/2012] [Indexed: 12/11/2022] Open
Abstract
Lamins are the best characterized cytoskeletal components of the cell nucleus that help to maintain the nuclear shape and participate in diverse nuclear processes including replication or transcription. Nuclear actin is now widely accepted to be another cytoskeletal protein present in the nucleus that fulfills important functions in the gene expression. Some viruses replicating in the nucleus evolved the ability to interact with and probably utilize nuclear actin for their replication, e.g., for the assembly and transport of capsids or mRNA export. On the other hand, lamins play a role in the propagation of other viruses since nuclear lamina may represent a barrier for virions entering or escaping the nucleus. This review will summarize the current knowledge about the roles of nuclear actin and lamins in viral infections.
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48
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Structural determinants for nuclear envelope localization and function of pseudorabies virus pUL34. J Virol 2011; 86:2079-88. [PMID: 22156520 DOI: 10.1128/jvi.05484-11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Herpesvirus proteins pUL34 and pUL31 form a complex at the inner nuclear membrane (INM) which is necessary for efficient nuclear egress. Pseudorabies virus (PrV) pUL34 is a type II membrane protein of 262 amino acids (aa). The transmembrane region (TM) is predicted to be located between aa 245 and 261, leaving only one amino acid in the C terminus that probably extends into the perinuclear space. It is targeted to the nuclear envelope in the absence of other viral proteins, pointing to intrinsic localization motifs, and shows structural similarity to cellular INM proteins like lamina-associated polypeptide (Lap) 2ß and Emerin. To investigate which domains of pUL34 are relevant for localization and function, we constructed chimeric proteins by replacing parts of pUL34 with regions of cellular INM proteins. First the 18 C-terminal amino acids encompassing the TM were exchanged with TM regions and C-terminal domains of Lap2ß and Emerin or with the first TM region of the polytopic lamin B receptor (LBR), including the nine following amino acids. All resulting chimeric proteins complemented the replication defect of PrV-ΔUL34, demonstrating that the substitution of the TM and the extension of the C-terminal domain does not interfere with the function of pUL34. Complementation was reduced but not abolished when the C-terminal 50 aa were replaced by corresponding Lap2ß sequences (pUL34-LapCT50). However, replacing the C-terminal 100 aa (pUL34-LapCT100) resulted in a nonfunctional protein despite continuing pUL31 binding, pointing to an important functional role of this region. The replacement of the N-terminal 100 aa (pUL34-LapNT100) had no effect on nuclear envelope localization but abrogated pUL31 binding and function.
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49
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Reconstitution of the Kaposi's sarcoma-associated herpesvirus nuclear egress complex and formation of nuclear membrane vesicles by coexpression of ORF67 and ORF69 gene products. J Virol 2011; 86:594-8. [PMID: 22013050 DOI: 10.1128/jvi.05988-11] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Kaposi's sarcoma-associated herpesvirus nuclear egress complex is composed of two proteins, ORF67 and ORF69. In this study, we have recapitulated the KSHV complex by coexpression of these two proteins in insect cells using expression from recombinant baculoviruses. The proteins form a complex at the nuclear membrane as judged by live-cell analysis of protein fusions tagged with green fluorescent protein (GFP) and mCherry. Ultrastructural analysis of infected cells showed that ORF67 expression results in reduplication of the nuclear membrane. When the two proteins are expressed together, numerous virion-size nuclear membrane-derived vesicles were evident at the nuclear margins.
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50
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Intragenic and extragenic suppression of a mutation in herpes simplex virus 1 UL34 that affects both nuclear envelope targeting and membrane budding. J Virol 2011; 85:11615-25. [PMID: 21900173 DOI: 10.1128/jvi.05730-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Late in infection herpesviruses move DNA-filled capsids from the nucleus to the cytoplasm by enveloping DNA-containing capsids at the inner nuclear membrane (INM) and deenveloping them at the outer nuclear membrane. This process requires two conserved herpesvirus proteins, pUL31 and pUL34. Interaction between pUL34 and pUL31 is essential for targeting both proteins to the nuclear envelope (NE), and sequences that mediate the targeting interaction have been mapped in both proteins. Here, we show that a mutation in the INM-targeting domain of pUL34 fails to support production of infectious virus or plaque formation. The mutation results in multiple defects, including impaired interaction between pUL34 and pUL31, poor NE targeting of pUL34, and misregulated, capsid-independent budding of the NE. The mutant defects in virus production, plaque formation, and pUL31 interaction can be suppressed by other mutations in the INM-targeting domain of pUL31 and by additional mutations in the pUL34 coding sequence.
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