1
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Butt BG, Fischer D, Rep AR, Schauflinger M, Read C, Böck T, Hirner M, Wienen F, Graham SC, von Einem J. Human cytomegalovirus deploys molecular mimicry to recruit VPS4A to sites of virus assembly. PLoS Pathog 2024; 20:e1012300. [PMID: 38900818 PMCID: PMC11218997 DOI: 10.1371/journal.ppat.1012300] [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: 04/28/2024] [Revised: 07/02/2024] [Accepted: 05/28/2024] [Indexed: 06/22/2024] Open
Abstract
The AAA-type ATPase VPS4 is recruited by proteins of the endosomal sorting complex required for transport III (ESCRT-III) to catalyse membrane constriction and membrane fission. VPS4A accumulates at the cytoplasmic viral assembly complex (cVAC) of cells infected with human cytomegalovirus (HCMV), the site where nascent virus particles obtain their membrane envelope. Here we show that VPS4A is recruited to the cVAC via interaction with pUL71. Sequence analysis, deep-learning structure prediction, molecular dynamics and mutagenic analysis identify a short peptide motif in the C-terminal region of pUL71 that is necessary and sufficient for the interaction with VPS4A. This motif is predicted to bind the same groove of the N-terminal VPS4A Microtubule-Interacting and Trafficking (MIT) domain as the Type 2 MIT-Interacting Motif (MIM2) of cellular ESCRT-III components, and this viral MIM2-like motif (vMIM2) is conserved across β-herpesvirus pUL71 homologues. However, recruitment of VPS4A by pUL71 is dispensable for HCMV morphogenesis or replication and the function of the conserved vMIM2 during infection remains enigmatic. VPS4-recruitment via a vMIM2 represents a previously unknown mechanism of molecular mimicry in viruses, extending previous observations that herpesviruses encode proteins with structural and functional homology to cellular ESCRT-III components.
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Affiliation(s)
- Benjamin G. Butt
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Daniela Fischer
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
| | - Alison R. Rep
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Clarissa Read
- Central Facility for Electron Microscopy, Ulm University, Ulm, Germany
| | - Thomas Böck
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
| | - Manuel Hirner
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
| | - Frederik Wienen
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
| | - Stephen C. Graham
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Jens von Einem
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
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2
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Lučin P, Mahmutefendić Lučin H, Blagojević Zagorac G. Cytomegaloviruses reorganize endomembrane system to intersect endosomal and amphisome-like egress pathway. Front Cell Dev Biol 2023; 11:1328751. [PMID: 38178873 PMCID: PMC10766366 DOI: 10.3389/fcell.2023.1328751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 12/08/2023] [Indexed: 01/06/2024] Open
Affiliation(s)
- Pero Lučin
- Department of Physiology, Immunology and Pathophysiology, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
- University North, University Center Varaždin, Varaždin, Croatia
| | - Hana Mahmutefendić Lučin
- Department of Physiology, Immunology and Pathophysiology, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
- University North, University Center Varaždin, Varaždin, Croatia
| | - Gordana Blagojević Zagorac
- Department of Physiology, Immunology and Pathophysiology, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
- University North, University Center Varaždin, Varaždin, Croatia
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3
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Klupp BG, Mettenleiter TC. The Knowns and Unknowns of Herpesvirus Nuclear Egress. Annu Rev Virol 2023; 10:305-323. [PMID: 37040797 DOI: 10.1146/annurev-virology-111821-105518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
Nuclear egress of herpesvirus capsids across the intact nuclear envelope is an exceptional vesicle-mediated nucleocytoplasmic translocation resulting in the delivery of herpesvirus capsids into the cytosol. Budding of the (nucleo)capsid at and scission from the inner nuclear membrane (INM) is mediated by the viral nuclear egress complex (NEC) resulting in a transiently enveloped virus particle in the perinuclear space followed by fusion of the primary envelope with the outer nuclear membrane (ONM). The dimeric NEC oligomerizes into a honeycomb-shaped coat underlining the INM to induce membrane curvature and scission. Mutational analyses complemented structural data defining functionally important regions. Questions remain, including where and when the NEC is formed and how membrane curvature is mediated, vesicle formation is regulated, and directionality is secured. The composition of the primary enveloped virion and the machinery mediating fusion of the primary envelope with the ONM is still debated. While NEC-mediated budding apparently follows a highly conserved mechanism, species and/or cell type-specific differences complicate understanding of later steps.
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Affiliation(s)
- Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems, Germany
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4
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Martin C, Ligat G, Malnou CE. The Yin and the Yang of extracellular vesicles during viral infections. Biomed J 2023:100659. [PMID: 37690583 DOI: 10.1016/j.bj.2023.100659] [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: 07/25/2023] [Revised: 09/04/2023] [Accepted: 09/05/2023] [Indexed: 09/12/2023] Open
Abstract
The role of extracellular vesicles (EVs) as key players in the intercellular communication is a subject of growing interest in all areas of physiology and pathophysiology, and the field of viral infections is no exception to the rule. In this review, we focus on the current state of knowledge and remaining gaps regarding the entanglement of viruses and EVs during infections. These two entities share many similarities, mainly due to their intricated biogenesis pathways that are in constant interaction. EVs can promote the replication and dissemination of viruses within the organism, through the dysregulation of their cargo and the modulation of the innate and adaptive immune response that occurs upon infection, but they can also promote the mitigation of viral infections. Here, we will examine how viruses hijack EV biogenesis pathways and describe the consequences of dysregulated EV secretion during viral infections, beneficial or not for viruses, revealing the duality of their possible effects.
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Affiliation(s)
- Charlène Martin
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, UPS, Toulouse, France
| | - Gaëtan Ligat
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, UPS, Toulouse, France
| | - Cécile E Malnou
- Institut Toulousain des Maladies Infectieuses et Inflammatoires (Infinity), Université de Toulouse, INSERM, CNRS, UPS, Toulouse, France.
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5
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Rivera-Cuevas Y, Carruthers VB. The multifaceted interactions between pathogens and host ESCRT machinery. PLoS Pathog 2023; 19:e1011344. [PMID: 37141275 PMCID: PMC10159163 DOI: 10.1371/journal.ppat.1011344] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023] Open
Abstract
The Endosomal Sorting Complex Required for Transport (ESCRT) machinery consists of multiple protein complexes that coordinate vesicle budding away from the host cytosol. ESCRTs function in many fundamental cellular processes including the biogenesis of multivesicular bodies and exosomes, membrane repair and restoration, and cell abscission during cytokinesis. Work over the past 2 decades has shown that a diverse cohort of viruses critically rely upon host ESCRT machinery for virus replication and envelopment. More recent studies reported that intracellular bacteria and the intracellular parasite Toxoplasma gondii benefit from, antagonize, or exploit host ESCRT machinery to preserve their intracellular niche, gain resources, or egress from infected cells. Here, we review how intracellular pathogens interact with the ESCRT machinery of their hosts, highlighting the variety of strategies they use to bind ESCRT complexes using short linear amino acid motifs like those used by ESCRTs to sequentially assemble on target membranes. Future work exposing new mechanisms of this molecular mimicry will yield novel insight of how pathogens exploit host ESCRT machinery and how ESCRTs facilitate key cellular processes.
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Affiliation(s)
- Yolanda Rivera-Cuevas
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Vern B. Carruthers
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
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6
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Wu J, Zhao Y, Chen Q, Chen Y, Gu J, Mao L. Enterovirus A71 Promotes Exosome Secretion by the Nonstructural Protein 3A Interacting with Rab27a. Microbiol Spectr 2023; 11:e0344622. [PMID: 36790212 PMCID: PMC10101103 DOI: 10.1128/spectrum.03446-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 01/27/2023] [Indexed: 02/16/2023] Open
Abstract
Exosomes are small membrane-bound vesicles which are intraluminal vesicles (ILVs) secreted to the extracellular space after multivesicular bodies (MVBs) fuse with the plasma membrane. Although it is known that exosomes play a multitude of roles during viral infection, the mechanism that regulates their secretion during viral infection is unknown. Here, we found that enterovirus A71 (EV-A71) infection increased exosome secretion both in vivo and in vitro. Importantly, the expression of nonstructural protein 3A was sufficient to promote exosome secretion, while a mutation affecting the amino acid 18 position abrogated this effect, without changing the size of exosomes in vivo or in vitro. Transmission electron microscopy (TEM) analysis revealed that 3A decreases the number of MVBs and ILVs in vivo and in vitro, which suggested 3A may boost the fusion between MVBs and the plasma membrane. Furthermore, we demonstrated that an interaction between 3A and the small GTPase protein, Rab27a, protected Rab27a from ubiquitination, resulted in increasing exosome release. Data indicated a novel mechanism by which EV-A71 3A modifies exosome secretion during viral infection. IMPORTANCE Research has shown that viral infection impacts exosome secretion, but its regulation mechanisms remain poorly understood. Nonstructural protein 3A of EV-A71 interacts with many host factors and is involved in the remodeling of cellular membranes. In this investigation, we applied exogenous expression of 3A protein for exploring its regulation on exosome secretion and utilized immunoprecipitation combined with proteomics approaches to identify 3A-interacting factors. Our results demonstrate that 3A protein upregulates the release of the exosomes and that the 3A mutant strain of EV-A71 induce less exosome release compared with the EV-A71 wild type. Viral 3A protein interacts with the host factor Rab27a to prevent it from being ubiquitinated, which in turn improves exosome secretion both in vitro and in vivo. EV-A71 3A protein is a novel viral factor in the control of exosome production.
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Affiliation(s)
- Jing Wu
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
| | - Yuxue Zhao
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
| | - Qiaoqiao Chen
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
| | - Yiwen Chen
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
| | - Jiaqi Gu
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
| | - Lingxiang Mao
- Department of Laboratory Medicine, Affiliated Kunshan Hospital of Jiangsu University, Kunshan, Jiangsu, China
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7
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Mosher BS, Kowalik TF, Yurochko AD. Overview of how HCMV manipulation of host cell intracellular trafficking networks can promote productive infection. FRONTIERS IN VIROLOGY 2022. [DOI: 10.3389/fviro.2022.1026452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human cytomegalovirus (HCMV) is a significant cause of morbidity and mortality in the immunocompromised and developing fetuses. Infection has also been linked to chronic inflammatory diseases, cardiovascular disease, and the development of certain cancers. The wide range of pathologies associated with HCMV infection is attributable to the broad cellular tropism of the virus where infection affects every organ system. Like other viruses, HCMV must tailor host cells to support productive infection. In particular, HCMV dedicates many resources and various strategies to manipulate host intracellular trafficking networks to facilitate various aspects of infection across all infected cell types. The dysregulation of host intracellular trafficking networks allows the virus to translocate to the host cell nucleus for genome replication, facilitate nuclear import/export of viral proteins and immature virions, subvert the host immune response, form new organelles for progeny virion assembly, maturation and egress, and promote cellular migration and viral spread. However, due to their complex nature, many aspects of these processes are not well-studied. New research and omics-based technologies have recently begun to elucidate the extent to which HCMV dysregulates host cell trafficking machinery. Here we review the variety of strategies HCMV utilizes to dysregulate intracellular trafficking networks to promote productive infection.
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8
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Turner DL, Mathias RA. The human cytomegalovirus decathlon: Ten critical replication events provide opportunities for restriction. Front Cell Dev Biol 2022; 10:1053139. [PMID: 36506089 PMCID: PMC9732275 DOI: 10.3389/fcell.2022.1053139] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Accepted: 11/10/2022] [Indexed: 11/27/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that can cause severe disease in immunocompromised individuals, transplant recipients, and to the developing foetus during pregnancy. There is no protective vaccine currently available, and with only a limited number of antiviral drug options, resistant strains are constantly emerging. Successful completion of HCMV replication is an elegant feat from a molecular perspective, with both host and viral processes required at various stages. Remarkably, HCMV and other herpesviruses have protracted replication cycles, large genomes, complex virion structure and complicated nuclear and cytoplasmic replication events. In this review, we outline the 10 essential stages the virus must navigate to successfully complete replication. As each individual event along the replication continuum poses as a potential barrier for restriction, these essential checkpoints represent potential targets for antiviral development.
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Affiliation(s)
- Declan L. Turner
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
| | - Rommel A. Mathias
- Department of Microbiology, Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia,Department of Biochemistry and Molecular Biology, Monash University, Melbourne, VIC, Australia,*Correspondence: Rommel A. Mathias,
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9
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Host Cell Signatures of the Envelopment Site within Beta-Herpes Virions. Int J Mol Sci 2022; 23:ijms23179994. [PMID: 36077391 PMCID: PMC9456339 DOI: 10.3390/ijms23179994] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/22/2022] [Accepted: 08/24/2022] [Indexed: 11/26/2022] Open
Abstract
Beta-herpesvirus infection completely reorganizes the membrane system of the cell. This system is maintained by the spatiotemporal arrangement of more than 3000 cellular proteins that continuously adapt the configuration of membrane organelles according to cellular needs. Beta-herpesvirus infection establishes a new configuration known as the assembly compartment (AC). The AC membranes are loaded with virus-encoded proteins during the long replication cycle and used for the final envelopment of the newly formed capsids to form infectious virions. The identity of the envelopment membranes is still largely unknown. Electron microscopy and immunofluorescence studies suggest that the envelopment occurs as a membrane wrapping around the capsids, similar to the growth of phagophores, in the area of the AC with the membrane identities of early/recycling endosomes and the trans-Golgi network. During wrapping, host cell proteins that define the identity and shape of these membranes are captured along with the capsids and incorporated into the virions as host cell signatures. In this report, we reviewed the existing information on host cell signatures in human cytomegalovirus (HCMV) virions. We analyzed the published proteomes of the HCMV virion preparations that identified a large number of host cell proteins. Virion purification methods are not yet advanced enough to separate all of the components of the rich extracellular material, including the large amounts of non-vesicular extracellular particles (NVEPs). Therefore, we used the proteomic data from large and small extracellular vesicles (lEVs and sEVs) and NVEPs to filter out the host cell proteins identified in the viral proteomes. Using these filters, we were able to narrow down the analysis of the host cell signatures within the virions and determine that envelopment likely occurs at the membranes derived from the tubular recycling endosomes. Many of these signatures were also found at the autophagosomes, suggesting that the CMV-infected cell forms membrane organelles with phagophore growth properties using early endosomal host cell machinery that coordinates endosomal recycling.
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10
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Flomm FJ, Soh TK, Schneider C, Wedemann L, Britt HM, Thalassinos K, Pfitzner S, Reimer R, Grünewald K, Bosse JB. Intermittent bulk release of human cytomegalovirus. PLoS Pathog 2022; 18:e1010575. [PMID: 35925870 PMCID: PMC9352052 DOI: 10.1371/journal.ppat.1010575] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 05/06/2022] [Indexed: 01/24/2023] Open
Abstract
Human Cytomegalovirus (HCMV) can infect a variety of cell types by using virions of varying glycoprotein compositions. It is still unclear how this diversity is generated, but spatio-temporally separated envelopment and egress pathways might play a role. So far, one egress pathway has been described in which HCMV particles are individually enveloped into small vesicles and are subsequently exocytosed continuously. However, some studies have also found enveloped virus particles inside multivesicular structures but could not link them to productive egress or degradation pathways. We used a novel 3D-CLEM workflow allowing us to investigate these structures in HCMV morphogenesis and egress at high spatio-temporal resolution. We found that multiple envelopment events occurred at individual vesicles leading to multiviral bodies (MViBs), which subsequently traversed the cytoplasm to release virions as intermittent bulk pulses at the plasma membrane to form extracellular virus accumulations (EVAs). Our data support the existence of a novel bona fide HCMV egress pathway, which opens the gate to evaluate divergent egress pathways in generating virion diversity.
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Affiliation(s)
- Felix J. Flomm
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | - Timothy K. Soh
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | | | - Linda Wedemann
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | - Hannah M. Britt
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, London, United Kingdom
| | | | | | - Kay Grünewald
- Centre for Structural Systems Biology, Hamburg, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
- University of Hamburg, Department of Chemistry, Hamburg, Germany
| | - Jens B. Bosse
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
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11
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Complexities of JC Polyomavirus Receptor-Dependent and -Independent Mechanisms of Infection. Viruses 2022; 14:v14061130. [PMID: 35746603 PMCID: PMC9228512 DOI: 10.3390/v14061130] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 05/19/2022] [Accepted: 05/20/2022] [Indexed: 02/05/2023] Open
Abstract
JC polyomavirus (JCPyV) is a small non-enveloped virus that establishes lifelong, persistent infection in most of the adult population. Immune-competent patients are generally asymptomatic, but immune-compromised and immune-suppressed patients are at risk for the neurodegenerative disease progressive multifocal leukoencephalopathy (PML). Studies with purified JCPyV found it undergoes receptor-dependent infectious entry requiring both lactoseries tetrasaccharide C (LSTc) attachment and 5-hydroxytryptamine type 2 entry receptors. Subsequent work discovered the major targets of JCPyV infection in the central nervous system (oligodendrocytes and astrocytes) do not express the required attachment receptor at detectable levels, virus could not bind these cells in tissue sections, and viral quasi-species harboring recurrent mutations in the binding pocket for attachment. While several research groups found evidence JCPyV can use novel receptors for infection, it was also discovered that extracellular vesicles (EVs) can mediate receptor independent JCPyV infection. Recent work also found JCPyV associated EVs include both exosomes and secretory autophagosomes. EVs effectively present a means of immune evasion and increased tissue tropism that complicates viral studies and anti-viral therapeutics. This review focuses on JCPyV infection mechanisms and EV associated and outlines key areas of study necessary to understand the interplay between virus and extracellular vesicles.
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12
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Wedemann L, Flomm FJ, Bosse JB. The unconventional way out-Egress of HCMV through multiviral bodies. Mol Microbiol 2022; 117:1317-1323. [PMID: 35607767 DOI: 10.1111/mmi.14946] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 05/18/2022] [Accepted: 05/21/2022] [Indexed: 12/14/2022]
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus and the leading cause of congenital disabilities as well as a significant cause of disease in immunocompromised patients. The envelopment and egress of HCMV particles is an essential step of the viral life cycle as it determines viral spread and potentially tropism. Here we review the current literature on HCMV envelopment and egress with a particular focus on the role of virus-containing multivesicular body-like vesicles for virus egress and spread. We discuss the difficulties of determining the cellular provenance of these structures in light of viral redistribution of cellular marker proteins and provide potential paths to illuminate their genesis. Finally, we discuss how divergent egress pathways could result in virions of different tropisms.
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Affiliation(s)
- Linda Wedemann
- Centre for Structural Systems Biology, Hamburg, Germany.,Hannover Medical School, Institute of Virology, Hannover, Germany.,Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany.,Leibniz-Institute of Virology, Hamburg, Germany
| | - Felix J Flomm
- Centre for Structural Systems Biology, Hamburg, Germany.,Hannover Medical School, Institute of Virology, Hannover, Germany.,Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany.,Leibniz-Institute of Virology, Hamburg, Germany
| | - Jens B Bosse
- Centre for Structural Systems Biology, Hamburg, Germany.,Hannover Medical School, Institute of Virology, Hannover, Germany.,Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany.,Leibniz-Institute of Virology, Hamburg, Germany
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13
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Liu B, Ma Y, Huang Y, Liu Z, Ruan Q, Qi Y. Inhibition of Human Cytomegalovirus Particle Maturation by Activation of Liver X Receptor. Front Microbiol 2022; 13:846386. [PMID: 35330771 PMCID: PMC8940258 DOI: 10.3389/fmicb.2022.846386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 01/24/2022] [Indexed: 12/03/2022] Open
Abstract
Human cytomegalovirus (HCMV), a herpesvirus family member, is a large, complex enveloped virus. The activation of liver X receptor (LXR) can significantly inhibit the replication of HCMV and weaken the virulence of progeny virus (unpublished data). Our results showed activated LXR affected some important viral protein expression and reduced cholesterol content in HCMV infected cells and virus particles. To further clarify the influence of activated LXR on HCMV replication, HCMV assembly and maturation processes were studied by transmission electron microscopy (TEM) in HCMV infected foreskin fibroblasts treated with LXR agonist GW3965. Results showed that activated LXR could reduce the envelope integrity of maturating virions. The functional stage of activated LXR on viral envelope integrity was mainly at virus assembly compartment (VAC) mediated envelopment but not structurally complete virus nucleocapsid formation and the egress of nucleocapsid from the nucleus to the cytoplasm mediated by nuclear egress complex. Reduced cholesterol synthesis and viral protein expression might interfere with the VAC-mediated envelopment. The nucleocapsid and tegument proteins enter the VAC area for the secondary envelope, which was interfered with and resulted in the defective particle, thereby affecting the amount and infectivity of the mature virus. The results indicate that inhibition of HCMV maturation is one mechanism of activated LXR inhibiting virus replication in infected cells.
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Affiliation(s)
- Bingnan Liu
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yanping Ma
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Yujing Huang
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Zhongyang Liu
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Qiang Ruan
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
| | - Ying Qi
- Virology Laboratory, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Pediatrics, Shengjing Hospital of China Medical University, Shenyang, China.,Department of Obstetrics and Gynecology, Shengjing Hospital of China Medical University, Shenyang, China
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14
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Tyl MD, Betsinger CN, Cristea IM. Virus-host protein interactions as footprints of human cytomegalovirus replication. Curr Opin Virol 2022; 52:135-147. [PMID: 34923282 PMCID: PMC8844139 DOI: 10.1016/j.coviro.2021.11.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 11/24/2021] [Indexed: 02/03/2023]
Abstract
Human cytomegalovirus (HCMV) is a pervasive β-herpesvirus that causes lifelong infection. The lytic replication cycle of HCMV is characterized by global organelle remodeling and dynamic virus-host interactions, both of which are necessary for productive HCMV replication. With the advent of new technologies for investigating protein-protein and protein-nucleic acid interactions, numerous critical interfaces between HCMV and host cells have been identified. Here, we review temporal and spatial virus-host interactions that support different stages of the HCMV replication cycle. Understanding how HCMV interacts with host cells during entry, replication, and assembly, as well as how it interfaces with host cell metabolism and immune responses promises to illuminate processes that underlie the biology of infection and the resulting pathologies.
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Affiliation(s)
- Matthew D. Tyl
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA
| | - Cora N. Betsinger
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA
| | - Ileana M. Cristea
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ 08544, USA,Corresponding author and lead contact: Ileana M. Cristea, 210 Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Princeton, NJ 08544, Tel: 6092589417, Fax: 6092584575,
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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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Furey C, Astar H, Walsh D. Human Cytomegalovirus Exploits TACC3 To Control Microtubule Dynamics and Late Stages of Infection. J Virol 2021; 95:e0082121. [PMID: 34191581 PMCID: PMC8387038 DOI: 10.1128/jvi.00821-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Accepted: 06/25/2021] [Indexed: 01/23/2023] Open
Abstract
While it is well established that microtubules (MTs) facilitate various stages of virus replication, how viruses actively control MT dynamics and functions remains less well understood. Recent work has begun to reveal how several viruses exploit End-Binding (EB) proteins and their associated microtubule plus-end tracking proteins (+TIPs), in particular to enable loading of viral particles onto MTs for retrograde transport during early stages of infection. Distinct from other viruses studied to date, at mid- to late stages of its unusually protracted replication cycle, human cytomegalovirus (HCMV) increases the expression of all three EB family members. This occurs coincident with the formation of a unique structure, termed the assembly compartment (AC), which serves as a Golgi-derived MT organizing center. Together, the AC and distinct EB proteins enable HCMV to increase the formation of dynamic and acetylated microtubule subsets to regulate distinct aspects of the viral replication cycle. Here, we reveal that HCMV also exploits EB-independent +TIP pathways by specifically increasing the expression of transforming acidic coiled coil protein 3 (TACC3) to recruit the MT polymerase, chTOG, from initial sites of MT nucleation in the AC out into the cytosol, thereby increasing dynamic MT growth. Preventing TACC3 increases or depleting chTOG impaired MT polymerization, resulting in defects in early versus late endosome organization in and around the AC as well as defects in viral trafficking and spread. Our findings provide the first example of a virus that actively exploits EB-independent +TIP pathways to regulate MT dynamics and control late stages of virus replication. IMPORTANCE Diverse viruses rely on host cell microtubule networks to transport viral particles within the dense cytoplasmic environment and to control the broader architecture of the cell to facilitate their replication. However, precisely how viruses regulate the dynamic behavior and function of microtubule filaments remains poorly defined. We recently showed that the assembly compartment (AC) formed by human cytomegalovirus (HCMV) acts as a Golgi-derived microtubule organizing center. Here, we show that at mid- to late stages of infection, HCMV increases the expression of transforming acidic coiled coil protein 3 (TACC3) to control the localization of the microtubule polymerase, chTOG. This, in turn, enables HCMV to generate dynamic microtubule subsets that organize endocytic vesicles in and around the AC and facilitate the transport of new viral particles released into the cytosol. Our findings reveal the first instance of viral targeting of TACC3 to control microtubule dynamics and virus spread.
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Affiliation(s)
- Colleen Furey
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Helen Astar
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Derek Walsh
- Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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Marcelić M, Lučin HM, Begonja AJ, Zagorac GB, Lisnić VJ, Lučin P. Endosomal Phosphatidylinositol-3-Phosphate-Associated Functions Are Dispensable for Establishment of the Cytomegalovirus Pre-Assembly Compartment but Essential for the Virus Growth. Life (Basel) 2021; 11:859. [PMID: 34440603 PMCID: PMC8398575 DOI: 10.3390/life11080859] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/16/2021] [Accepted: 08/20/2021] [Indexed: 01/20/2023] Open
Abstract
Murine cytomegalovirus (MCMV) initiates the stepwise establishment of the pre-assembly compartment (pre-AC) in the early phase of infection by the expansion of the early endosome (EE)/endosomal recycling compartment (ERC) interface and relocation of the Golgi complex. We depleted Vps34-derived phosphatidylinositol-3-phosphate (PI(3)P) at EEs by VPS34-IN1 and inhibited PI(3)P-associated functions by overexpression of 2xFYVE- and p40PX PI(3)P-binding modules to assess the role of PI(3)P-dependent EE domains in the pre-AC biogenesis. We monitored the accumulation of Rab10 and Evectin-2 in the inner pre-AC and the relocation of GM130-positive cis-Golgi organelles to the outer pre-AC by confocal microscopy. Although PI(3)P- and Vps34-positive endosomes build a substantial part of pre-AC, the PI(3)P depletion and the inhibition of PI(3)P-associated functions did not prevent the establishment of infection and progression through the early phase. The PI(3)P depletion in uninfected and MCMV-infected cells rapidly dispersed PI(3)P-bond proteins and reorganized EEs, including ablation of EE-to-ERC transport and relocation of Rab11 endosomes. The PI(3)P depletion one hour before pre-AC initiation and overexpression of 2xFYVE and p40PX domains neither prevented Rab10- and Evectin-2 accumulation, nor Golgi unlinking and relocation. These data demonstrate that PI(3)P-dependent functions, including the Rab11-dependent EE-to-ERC route, are dispensable for pre-AC initiation. Nevertheless, the virus growth was drastically reduced in PI(3)P-depleted cells, indicating that PI(3)P-associated functions are essential for the late phase of infection.
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Affiliation(s)
- Marina Marcelić
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (M.M.); (H.M.L.); (G.B.Z.)
| | - Hana Mahmutefendić Lučin
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (M.M.); (H.M.L.); (G.B.Z.)
- University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
| | - Antonija Jurak Begonja
- Department of Biotechnology, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia;
| | - Gordana Blagojević Zagorac
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (M.M.); (H.M.L.); (G.B.Z.)
- University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
| | - Vanda Juranić Lisnić
- Center for Proteomics, Department of Histology and Embryology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia;
| | - Pero Lučin
- Department of Physiology and Immunology, Faculty of Medicine, University of Rijeka, 51000 Rijeka, Croatia; (M.M.); (H.M.L.); (G.B.Z.)
- University North, University Center Varaždin, Jurja Križanića 31b, 42000 Varaždin, Croatia
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Prazoles Targeting Tsg101 Inhibit Release of Epstein-Barr Virus following Reactivation from Latency. J Virol 2021; 95:e0246620. [PMID: 33853959 DOI: 10.1128/jvi.02466-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Epstein-Barr virus (EBV) is a ubiquitous herpesvirus responsible for several diseases, including cancers of lymphoid and epithelial cells. EBV cancers typically exhibit viral latency; however, the production and release of EBV through its lytic phase are essential for cancer development. Antiviral agents that specifically target EBV production do not currently exist. Previously, we reported that the proton pump inhibitor tenatoprazole, which blocks the interaction of ubiquitin with the ESCRT-1 factor Tsg101, inhibits production of several enveloped viruses, including EBV. Here, we show that three structurally distinct prazoles impair mature particle formation postreactivation and identify the impact on stages of replication. The prazoles did not impair expression of lytic genes representative of the different kinetic classes but interfered with capsid maturation in the nucleus as well as virion transport from the nucleus. Replacement of endogenous Tsg101 with a mutant Tsg101 refractory to prazole-mediated inhibition rescued EBV release. These findings directly implicate Tsg101 in EBV nuclear egress and identify prazoles as potential therapeutic candidates for conditions that rely on EBV replication, such as chronic active EBV infection and posttransplant lymphoproliferative disorders. IMPORTANCE Production of virions is necessary for the ubiquitous Epstein-Barr virus (EBV) to persist in humans and can set the stage for development of EBV cancers in at-risk individuals. In our attempts to identify inhibitors of the EBV lytic phase, we previously found that a prazole proton pump inhibitor, known to block the interaction of ubiquitin with the ESCRT-1 factor Tsg101, blocks production of EBV. We now find that three structurally distinct prazoles impair maturation of EBV capsids and virion transport from the nucleus and, by interfering with Tsg101, prevent EBV release from lytically active cells. Our findings not only implicate Tsg101 in EBV production but also identify widely used prazoles as candidates to prevent development of posttransplant EBV lymphomas.
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Ilaprazole and other novel prazole-based compounds that bind Tsg101 inhibit viral budding of HSV-1/2 and HIV from cells. J Virol 2021; 95:JVI.00190-21. [PMID: 33731460 PMCID: PMC8139698 DOI: 10.1128/jvi.00190-21] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In many enveloped virus families, including HIV and HSV, a crucial, yet unexploited, step in the viral life cycle is releasing particles from the infected cell membranes. This release process is mediated by host ESCRT complex proteins, which are recruited by viral structural proteins and provides the mechanical means for membrane scission and subsequent viral budding. The prazole drug, tenatoprazole, was previously shown to bind to ESCRT complex member Tsg101 and to quantitatively block the release of infectious HIV-1 from cells in culture. In this report we show that tenatoprazole and a related prazole drug, ilaprazole, effectively block infectious Herpes Simplex Virus (HSV)-1/2 release from Vero cells in culture. By electron microscopy, we found that both prazole drugs block the transit of HSV particles through the cell nuclear membrane resulting in their accumulation in the nucleus. Ilaprazole also quantitatively blocks the release of HIV-1 from 293T cells with an EC50 of 0.8-1.2 μM, which is much more potent than tenatoprazole. Our results indicate that prazole-based compounds may represent a class of drugs with potential to be broad-spectrum antiviral agents against multiple enveloped viruses, by interrupting cellular Tsg101 interaction with maturing virus, thus blocking the budding process that releases particles from the cell.ImportanceThese results provide the basis for the development of drugs that target enveloped virus budding that can be used ultimately to control multiple virus infections in humans.
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20
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Jeon H, Kang SK, Lee MJ, Park C, Yoo SM, Kang YH, Lee MS. Rab27b regulates extracellular vesicle production in cells infected with Kaposi's sarcoma-associated herpesvirus to promote cell survival and persistent infection. J Microbiol 2021; 59:522-529. [PMID: 33877577 DOI: 10.1007/s12275-021-1108-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 01/08/2023]
Abstract
Extracellular vesicles (EVs) play a crucial role in cell-to-cell communication. EVs and viruses share several properties related to their structure and the biogenesis machinery in cells. EVs from virus-infected cells play a key role in virus spread and suppression using various loading molecules, such as viral proteins, host proteins, and microRNAs. However, it remains unclear how and why viruses regulate EV production inside host cells. The purpose of this study is to investigate the molecular mechanisms underlying EV production and their roles in Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells. Here, we found that KSHV induced EV production in human endothelial cells via Rab-27b upregulation. The suppression of Rab27b expression in KSHV-infected cells enhanced cell death by increasing autophagic flux and autolysosome formation. Our results indicate that Rab27b regulates EV biogenesis to promote cell survival and persistent viral infection during KSHV infection, thereby providing novel insights into the crucial role of Rab-27b in the KSHV life cycle.
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Affiliation(s)
- Hyungtaek Jeon
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Su-Kyung Kang
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Myung-Ju Lee
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Changhoon Park
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Seung-Min Yoo
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
- Eulji Biomedical Science Research Institute, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Yun Hee Kang
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
- Eulji Biomedical Science Research Institute, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea
| | - Myung-Shin Lee
- Department of Microbiology and Immunology, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea.
- Eulji Biomedical Science Research Institute, Eulji University School of Medicine, Daejeon, 34824, Republic of Korea.
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21
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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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22
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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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23
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Why Cells and Viruses Cannot Survive without an ESCRT. Cells 2021; 10:cells10030483. [PMID: 33668191 PMCID: PMC7995964 DOI: 10.3390/cells10030483] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 02/19/2021] [Accepted: 02/21/2021] [Indexed: 12/15/2022] Open
Abstract
Intracellular organelles enwrapped in membranes along with a complex network of vesicles trafficking in, out and inside the cellular environment are one of the main features of eukaryotic cells. Given their central role in cell life, compartmentalization and mechanisms allowing their maintenance despite continuous crosstalk among different organelles have been deeply investigated over the past years. Here, we review the multiple functions exerted by the endosomal sorting complex required for transport (ESCRT) machinery in driving membrane remodeling and fission, as well as in repairing physiological and pathological membrane damages. In this way, ESCRT machinery enables different fundamental cellular processes, such as cell cytokinesis, biogenesis of organelles and vesicles, maintenance of nuclear–cytoplasmic compartmentalization, endolysosomal activity. Furthermore, we discuss some examples of how viruses, as obligate intracellular parasites, have evolved to hijack the ESCRT machinery or part of it to execute/optimize their replication cycle/infection. A special emphasis is given to the herpes simplex virus type 1 (HSV-1) interaction with the ESCRT proteins, considering the peculiarities of this interplay and the need for HSV-1 to cross both the nuclear-cytoplasmic and the cytoplasmic-extracellular environment compartmentalization to egress from infected cells.
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24
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The Interplay between ESCRT and Viral Factors in the Enveloped Virus Life Cycle. Viruses 2021; 13:v13020324. [PMID: 33672541 PMCID: PMC7923801 DOI: 10.3390/v13020324] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 02/08/2021] [Accepted: 02/12/2021] [Indexed: 12/13/2022] Open
Abstract
Viruses are obligate parasites that rely on host cellular factors to replicate and spread. The endosomal sorting complexes required for transport (ESCRT) system, which is classically associated with sorting and downgrading surface proteins, is one of the host machineries hijacked by viruses across diverse families. Knowledge gained from research into ESCRT and viruses has, in turn, greatly advanced our understanding of many other cellular functions in which the ESCRT pathway is involved, e.g., cytokinesis. This review highlights the interplay between the ESCRT pathway and the viral factors of enveloped viruses with a special emphasis on retroviruses.
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25
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Turner DL, Korneev DV, Purdy JG, de Marco A, Mathias RA. The host exosome pathway underpins biogenesis of the human cytomegalovirus virion. eLife 2020; 9:e58288. [PMID: 32910773 PMCID: PMC7556872 DOI: 10.7554/elife.58288] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 08/26/2020] [Indexed: 02/07/2023] Open
Abstract
Human Cytomegalovirus (HCMV) infects over half the world's population, is a leading cause of congenital birth defects, and poses serious risks for immuno-compromised individuals. To expand the molecular knowledge governing virion maturation, we analysed HCMV virions using proteomics, and identified a significant proportion of host exosome constituents. To validate this acquisition, we characterized exosomes released from uninfected cells, and demonstrated that over 99% of the protein cargo was subsequently incorporated into HCMV virions during infection. This suggested a common membrane origin, and utilization of host exosome machinery for virion assembly and egress. Thus, we selected a panel of exosome proteins for knock down, and confirmed that loss of 7/9 caused significantly less HCMV production. Saliently, we report that VAMP3 is essential for viral trafficking and release of infectious progeny, in various HCMV strains and cell types. Therefore, we establish that the host exosome pathway is intrinsic for HCMV maturation, and reveal new host regulators involved in viral trafficking, virion envelopment, and release. Our findings underpin future investigation of host exosome proteins as important modulators of HCMV replication with antiviral potential.
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Affiliation(s)
- Declan L Turner
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash UniversityVictoriaAustralia
| | - Denis V Korneev
- School of Biological Sciences, Monash UniversityVictoriaAustralia
| | - John G Purdy
- Department of Immunobiology and BIO5 Institute, University of ArizonaTucsonUnited States
| | - Alex de Marco
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash UniversityVictoriaAustralia
- ARC Centre of Excellence in Advanced Molecular Imaging, Monash UniversityVictoriaAustralia
- University of WarwickCoventryUnited Kingdom
| | - Rommel A Mathias
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash UniversityVictoriaAustralia
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash UniversityVictoriaAustralia
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26
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Streck NT, Zhao Y, Sundstrom JM, Buchkovich NJ. Human Cytomegalovirus Utilizes Extracellular Vesicles To Enhance Virus Spread. J Virol 2020; 94:e00609-20. [PMID: 32522858 PMCID: PMC7394901 DOI: 10.1128/jvi.00609-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/01/2020] [Indexed: 12/12/2022] Open
Abstract
Human cytomegalovirus (HCMV) manipulates cellular processes associated with secretory pathways within an infected cell to facilitate efficient viral replication. However, little is known about how HCMV infection alters the surrounding cellular environment to promote virus spread to uninfected cells. Extracellular vesicles (EVs) are key signaling molecules that are commonly altered in numerous disease states. Previous reports have shown that viruses commonly alter EVs, which can significantly impact infection. This study finds that HCMV modulates EV biogenesis machinery through upregulation of the endosomal sorting complex required for transport (ESCRT) proteins. This regulation appears to increase the activity of EV biogenesis, since HCMV-infected fibroblasts have increased vesicle release and altered vesicle size compared to EVs from uninfected cells. EVs generated through ESCRT-independent pathways are also beneficial to virus spread in fibroblasts, as treatment with the EV inhibitor GW4869 slowed the efficiency of HCMV spread. Importantly, the transfer of EVs purified from HCMV-infected cells enhanced virus spread. This suggests that HCMV modulates the EV pathway to transfer proviral signals to uninfected cells that prime the cellular environment for incoming infection and enhance the efficiency of virus spread.IMPORTANCE Human cytomegalovirus (HCMV) is a herpesvirus that leads to serious health consequences in neonatal or immunocompromised patients. Clinical management of infection in these at-risk groups remains a serious concern even with approved antiviral therapies available. It is necessary to increase our understanding of the cellular changes that occur during infection and their importance to virus spread. This may help to identify new targets during infection that will lead to the development of novel treatment strategies. Extracellular vesicles (EVs) represent an important method of intercellular communication in the human host. This study finds that HCMV manipulates this pathway to increase the efficiency of virus spread to uninfected cells. This finding defines a new layer of host manipulation induced by HCMV infection that leads to enhanced virus spread.
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Affiliation(s)
- Nicholas T Streck
- Department of Microbiology & Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Yuanjun Zhao
- Department of Ophthalmology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Jeffrey M Sundstrom
- Department of Ophthalmology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Nicholas J Buchkovich
- Department of Microbiology & Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
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27
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Extracellular Vesicles in Viral Infections of the Nervous System. Viruses 2020; 12:v12070700. [PMID: 32605316 PMCID: PMC7411781 DOI: 10.3390/v12070700] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 06/19/2020] [Accepted: 06/25/2020] [Indexed: 02/07/2023] Open
Abstract
Almost all types of cells release extracellular vesicles (EVs) into the extracellular space. EVs such as exosomes and microvesicles are membrane-bound vesicles ranging in size from 30 to 1000 nm in diameter. Under normal conditions, EVs mediate cell to cell as well as inter-organ communication via the shuttling of their cargoes which include RNA, DNA and proteins. Under pathological conditions, however, the number, size and content of EVs are found to be altered and have been shown to play crucial roles in disease progression. Emerging studies have demonstrated that EVs are involved in many aspects of viral infection-mediated neurodegenerative diseases. In the current review, we will describe the interactions between EV biogenesis and the release of virus particles while also reviewing the role of EVs in various viral infections, such as HIV-1, HTLV, Zika, CMV, EBV, Hepatitis B and C, JCV, and HSV-1. We will also discuss the potential uses of EVs and their cargoes as biomarkers and therapeutic vehicles for viral infections.
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Badierah RA, Uversky VN, Redwan EM. Dancing with Trojan horses: an interplay between the extracellular vesicles and viruses. J Biomol Struct Dyn 2020; 39:3034-3060. [DOI: 10.1080/07391102.2020.1756409] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Raied A. Badierah
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
- Molecular Diagnostic Laboratory, King Abdulaziz University Hospital, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Vladimir N. Uversky
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
- Laboratory of New Methods in Biology, Institute for Biological Instrumentation, Russian Academy of Sciences, Federal Research Center ‘Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences’, Pushchino, Moscow Region, Russia
| | - Elrashdy M. Redwan
- Biological Science Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
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Abstract
The human betaherpesviruses, human cytomegalovirus (HCMV; species Human betaherpesvirus 5) and human herpesviruses 6A, 6B, and 7 (HHV-6A, -6B, and -7; species Human betaherpesviruses 6A, 6B, and 7) are highly prevalent and can cause severe disease in immune-compromised and immune-naive populations in well- and under-developed communities. Herpesvirus virion assembly is an intricate process that requires viral orchestration of host systems. In this review, we describe recent advances in some of the many cellular events relevant to assembly and egress of betaherpesvirus virions. These include modifications of host metabolic, immune, and autophagic/recycling systems. In addition, we discuss unique aspects of betaherpesvirus virion structure, virion assembly, and the cellular pathways employed during virion egress.
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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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Dynamin Is Required for Efficient Cytomegalovirus Maturation and Envelopment. J Virol 2018; 92:JVI.01418-18. [PMID: 30282704 DOI: 10.1128/jvi.01418-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 09/22/2018] [Indexed: 12/17/2022] Open
Abstract
Cytomegalovirus secondary envelopment occurs in a virus-induced cytoplasmic assembly compartment (vAC) generated via a drastic reorganization of the membranes of the secretory and endocytic systems. Dynamin is a eukaryotic GTPase that is implicated in membrane remodeling and endocytic membrane fission events; however, the role of dynamin in cellular trafficking of viruses beyond virus entry is only partially understood. Mouse embryonic fibroblasts (MEF) engineered to excise all three isoforms of dynamin were infected with mouse cytomegalovirus (MCMV-K181). Immediate-early (IE1; m123) viral protein was detected in these triple dynamin knockout (TKO) cells, as well as in mock-induced parental MEF, at early times postinfection, although levels were reduced in TKO cells, indicating that virus entry was affected but not eliminated. Levels of IE1 protein and another viral early protein (m04) were normalized by 48 h postinfection; however, late protein (m55; gB) expression was reduced in infected TKO cells compared to parental MEF. Ultrastructural analysis revealed intact stages of nuclear virus maturation in both cases with equivalent numbers of nucleocapsids containing packaged viral DNA (C-capsids), indicating successful viral DNA replication, capsid assembly, and genome packaging. Most importantly, severe defects in virus envelopment were visualized in TKO cells but not in parental cells. Dynamin inhibitor (dynasore)-treated MEF showed a phenotype similar to TKO cells upon mouse cytomegalovirus infection, confirming the role of dynamin in late maturation processes. In summary, dynamin-mediated endocytic pathways are critical for the completion of cytoplasmic stages of cytomegalovirus maturation.IMPORTANCE Viruses are known to exploit specific cellular functions at different stages of their life cycle in order to replicate, avoid immune recognition by the host and to establish a successful infection. Cytomegalovirus (CMV)-infected cells are characterized by a prominent cytoplasmic inclusion (virus assembly compartment [vAC]) that is the site of virus maturation and envelopment. While endocytic membranes are known to be the functional components of vAC, knowledge of specific endocytic pathways implicated in CMV maturation and envelopment is lacking. We show here that dynamin, which is an integral part of host endocytic machinery, is largely dispensable for early stages of CMV infection but is required at a late stage of CMV maturation. Studies on dynamin function in CMV infection will help us understand the host-virus interaction pathways amenable to targeting by conventional small molecules, as well as by newer generation nucleotide-based therapeutics (e.g., small interfering RNA, CRISPR/CAS gRNA, etc.).
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Arii J, Watanabe M, Maeda F, Tokai-Nishizumi N, Chihara T, Miura M, Maruzuru Y, Koyanagi N, Kato A, Kawaguchi Y. ESCRT-III mediates budding across the inner nuclear membrane and regulates its integrity. Nat Commun 2018; 9:3379. [PMID: 30139939 PMCID: PMC6107581 DOI: 10.1038/s41467-018-05889-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/28/2018] [Indexed: 11/30/2022] Open
Abstract
Vesicle-mediated nucleocytoplasmic transport is a nuclear pore-independent mechanism for the nuclear export of macromolecular complexes, but the molecular basis for this transport remains largely unknown. Here we show that endosomal sorting complex required for transport-III (ESCRT-III) is recruited to the inner nuclear membrane (INM) during the nuclear export of herpes simplex virus 1 (HSV-1). Scission during HSV-1 budding through the INM is prevented by depletion of ESCRT-III proteins. Interestingly, in uninfected human cells, the depletion of ESCRT-III proteins induces aberrant INM proliferation. Our results show that HSV-1 expropriates the ESCRT-III machinery in infected cells for scission of the INM to produce vesicles containing progeny virus nucleocapsids. In uninfected cells, ESCRT-III regulates INM integrity by downregulating excess INM. The endosomal sorting complex required for transport-III (ESCRT-III) has been implicated in the packaging of HIV and HSV-1 viruses in the cytoplasm. Here the authors show that ESCRT-III proteins are required for the transport of HSV-1 nucleocapsids from nucleoplasm to cytosol through the nuclear envelope and confirm that the same mechanism is also used for the nucleocytoplasmic transport of RNP in Drosophila cells.
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Affiliation(s)
- Jun Arii
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Mizuki Watanabe
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Fumio Maeda
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Noriko Tokai-Nishizumi
- Microscope Core Laboratory, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Takahiro Chihara
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.,Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan
| | - Masayuki Miura
- Department of Genetics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Yuhei Maruzuru
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Naoto Koyanagi
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Akihisa Kato
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan
| | - Yasushi Kawaguchi
- Division of Molecular Virology, Department of Microbiology and Immunology, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan. .,Department of Infectious Disease Control, International Research Center for Infectious Diseases, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, 108-8639, Japan.
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Close WL, Glassbrook JE, Gurczynski SJ, Pellett PE. Infection-Induced Changes Within the Endocytic Recycling Compartment Suggest a Roadmap of Human Cytomegalovirus Egress. Front Microbiol 2018; 9:1888. [PMID: 30186245 PMCID: PMC6113367 DOI: 10.3389/fmicb.2018.01888] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 07/27/2018] [Indexed: 12/22/2022] Open
Abstract
Human cytomegalovirus (HCMV) is an important pathogen in developing fetuses, neonates, and individuals with compromised immune systems. Gaps in our understanding of the mechanisms required for virion assembly stand in the way of development of antivirals targeting late stages of viral replication. During infection, HCMV causes a dramatic reorganization of the host endosecretory system, leading to the formation of the cytoplasmic virion assembly complex (cVAC), the site of virion assembly. As part of cVAC biogenesis, the composition and behavior of endosecretory organelles change. To gain more comprehensive understanding of the impact HCMV infection has on components of the cellular endocytic recycling compartment (ERC), we used previously published transcriptional and proteomic datasets to predict changes in the directionality of ERC trafficking. We identified infection-associated changes in gene expression that suggest shifts in the balance between endocytic and exocytic recycling pathways, leading to formation of a secretory trap within the cVAC. Conversely, there was a corresponding shift favoring outbound secretory vesicle trafficking, indicating a potential role in virion egress. These observations are consistent with previous studies describing sequestration of signaling molecules, such as IL-6, and the synaptic vesicle-like properties of mature HCMV virions. Our analysis enabled development of a refined model incorporating old and new information related to the behavior of the ERC during HCMV replication. While limited by the paucity of integrated systems-level data, the model provides an informed basis for development of experimentally testable hypotheses related to mechanisms involved in HCMV virion maturation and egress. Information from such experiments will provide a robust roadmap for rational development of novel antivirals for HCMV and related viruses.
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Affiliation(s)
- William L. Close
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - James E. Glassbrook
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - Stephen J. Gurczynski
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Philip E. Pellett
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
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Identification of Host Factors Involved in Human Cytomegalovirus Replication, Assembly, and Egress Using a Two-Step Small Interfering RNA Screen. mBio 2018; 9:mBio.00716-18. [PMID: 29946045 PMCID: PMC6020295 DOI: 10.1128/mbio.00716-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
As obligate intracellular parasites, viruses are completely dependent on host factors for replication. Assembly and egress of complex virus particles, such as human cytomegalovirus (HCMV), are likely to require many host factors. Despite this, relatively few have been identified and characterized. This study describes a novel high-throughput, two-step small interfering RNA (siRNA) screen, which independently measures virus replication and virus production. By combining data from replication and virus production, multiple candidate genes were identified in which knockdown resulted in substantial loss of virus production with limited effect on primary replication, suggesting roles in later stages such as virus assembly and egress. Knockdown of the top candidates, ERC1, RAB4B, COPA, and COPB2, caused profound loss of virus production. Despite COPA and COPB2 being reported to function in the same complex, knockdown of these genes produced distinct phenotypes. Furthermore, knockdown of COPA caused increased expression of viral late genes despite substantial inhibition of viral DNA replication. This suggests that efficient viral genome replication is not required for late gene expression. Finally, we show that RAB4B relocates to the viral assembly compartment following infection with HCMV and knockdown of RAB4B reduces the release of intact virion particles, suggesting that it plays a role in virion assembly and egress. This study demonstrates a powerful high-throughput screen for identification of host-virus interactions, identifies multiple host genes associated with HCMV assembly and egress, and uncovers potentially independent functions for coatomer components COPA and COPB2 during infection. Human cytomegalovirus infection is a significant cause of disease in immunocompromised populations, individuals with heart disease, and recipients of solid organ and bone marrow transplants. HCMV is also the leading cause of infectious congenital birth defects. The majority of antivirals in clinical use target components of the virus to specifically inhibit replication. However, a major drawback of this approach is the emergence of resistance. An alternative approach is to target host factors that the virus requires for successful infection. In this study, multiple host factors were identified that were found to be essential for the production of newly infectious human cytomegalovirus. Identifying which host genes are necessary for virus replication extends our understanding of how viruses replicate and how cells function and provides potential targets for novel antivirals.
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Nonenvelopment Role for the ESCRT-III Complex during Human Cytomegalovirus Infection. J Virol 2018; 92:JVI.02096-17. [PMID: 29618648 DOI: 10.1128/jvi.02096-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Accepted: 03/28/2018] [Indexed: 12/27/2022] Open
Abstract
Secondary envelopment of human cytomegalovirus (HCMV) occurs through a mechanism that is poorly understood. Many enveloped viruses utilize the endosomal sorting complexes required for transport (ESCRTs) for viral budding and envelopment. Although there are conflicting reports on the role of the ESCRT AAA ATPase protein VPS4 in HCMV infection, VPS4 may act in an envelopment role similar to its function during other viral infections. Because VPS4 is normally recruited by the ESCRT-III complex, we hypothesized that ESCRT-III subunits would also be required for HCMV infection. We investigated the role of ESCRT-III, the core ESCRT scission complex, during the late stages of infection. We show that inducible expression of dominant negative ESCRT-III subunits during infection blocks endogenous ESCRT function but does not inhibit virus production. We also show that HCMV forms enveloped intracellular and extracellular virions in the presence of dominant negative ESCRT-III subunits, suggesting that ESCRT-III is not involved in the envelopment of HCMV. We also found that as with ESCRT-III, inducible expression of a dominant negative form of VPS4A did not inhibit the envelopment of virions or reduce virus titers. Thus, HCMV does not require the ESCRTs for secondary envelopment. However, we found that ESCRT-III subunits are required for efficient virus spread. This suggests a role for ESCRT-III during the spread of HCMV that is independent of viral envelopment.IMPORTANCE Human cytomegalovirus (HCMV) is a prevalent opportunistic pathogen in the human population. For neonatal and immunocompromised patients, HCMV infection can cause severe and possibly life-threatening complications. It is important to define the mechanisms of the viral replication cycle in order to identify potential targets for new therapies. Secondary envelopment, or acquisition of the membrane envelope, of HCMV is a mechanism that needs further study. Using an inducible fibroblast system to carefully control for the toxicity associated with blocking ESCRT-III function, this study determines that the ESCRT proteins are not required for viral envelopment. However, the study does discover a nonenvelopment role for the ESCRT-III complex in the efficient spread of the virus. Thus, this study advances our understanding of an important process essential for the replication of HCMV.
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Interaction of Human Cytomegalovirus Tegument Proteins ppUL35 and ppUL35A with Sorting Nexin 5 Regulates Glycoprotein B (gpUL55) Localization. J Virol 2018; 92:JVI.00013-18. [PMID: 29444945 DOI: 10.1128/jvi.00013-18] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 02/07/2018] [Indexed: 12/13/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a widespread human pathogen that causes asymptomatic infection in healthy individuals but poses a serious threat to immunocompromised patients. During the late phase of HCMV infection, the viral capsid is transported to the cytoplasmic viral assembly center (cVAC), where it is enclosed by the tegument protein layer and the viral envelope. The cVAC consists of circularly arranged vesicles from the trans-Golgi and endosomal networks. The HCMV gene UL35 encodes ppUL35 and its shorter form, ppUL35A. We have previously shown that the UL35 gene is involved in HCMV assembly, but it is unknown how UL35 proteins regulate viral assembly. Here we show that sorting nexin 5 (SNX5), a component of the retromer and part of the retrograde transport pathway, interacts with UL35 proteins. Expression of wild-type proteins but not mutants defective in SNX5 binding resulted in the cellular redistribution of the cation-independent mannose-6-phosphate receptor (CI-M6PR), indicating that UL35 proteins bind and negatively regulate SNX5 to modulate cellular transport pathways. Furthermore, binding of UL35 proteins to SNX5 was required for efficient viral replication and for transport of the most abundant HCMV glycoprotein B (gB; gpUL55) to the cVAC. These results indicate that ppUL35 and ppUL35A control the localization of the essential gB through the regulation of a retrograde transport pathway. Thus, this work is the first to define a molecular interaction between a tegument protein and a vesicular transport factor to regulate glycoprotein localization.IMPORTANCE Human cytomegalovirus is ubiquitously present in the healthy population, but reactivation or reinfection can cause serious, life-threatening infections in immunocompromised patients. For completion of its lytic cycle, human cytomegalovirus induces formation of an assembly center where mature virus particles are formed from multiple viral proteins. Viral glycoproteins use separate vesicular pathways for transport to the assembly center, which are incompletely understood. Our research identified a viral structural protein which affects the localization of one of the major glycoproteins. We could link this change in glycoprotein localization to an interaction of the structural protein with a cellular protein involved in regulation of vesicle transport. This increases our understanding of how the virus intersects into cellular regulatory pathways to enhance its own replication.
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Insight into the Roles of E3 Ubiquitin Ligase c-Cbl, ESCRT Machinery, and Host Cell Signaling in Kaposi's Sarcoma-Associated Herpesvirus Entry and Trafficking. J Virol 2018; 92:JVI.01376-17. [PMID: 29167336 DOI: 10.1128/jvi.01376-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) in vitro infection of dermal endothelial cells begins with its binding to host cell surface receptor molecules such as heparan sulfate (HS), integrins (α3β1, αVβ3, and αVβ5), xCT, and EphA2 receptor tyrosine kinase (EphA2R). These initial events initiate dynamic host protein-protein interactions involving a multimolecular complex of receptors, signal molecules (focal adhesion kinase [FAK], Src, phosphatidylinositol 3-kinase [PI3-K], and RhoA-GTPase), adaptors (c-Cbl, CIB1, Crk, p130Cas, and GEF-C3G), actin, and myosin II light chain that lead to virus entry via macropinocytosis. Here we discuss how KSHV hijacks c-Cbl, an E3 ubiquitin ligase, to monoubiquitinate the receptors and actin, which acts like a marker for trafficking (similar to zip codes), resulting in the recruitment of the members of the host endosomal sorting complexes required for transport (ESCRT) Hrs, Tsg101, EAP45, and the CHMP5 and -6 proteins (zip code readers) recognizing the ubiquitinated protein and adaptor machinery to traffic through the different endosomal compartments in the cytoplasm to initiate the macropinocytic process and infection.
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Close WL, Anderson AN, Pellett PE. Betaherpesvirus Virion Assembly and Egress. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1045:167-207. [PMID: 29896668 DOI: 10.1007/978-981-10-7230-7_9] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Virions are the vehicle for cell-to-cell and host-to-host transmission of viruses. Virions need to be assembled reliably and efficiently, be released from infected cells, survive in the extracellular environment during transmission, recognize and then trigger entry of appropriate target cells, and disassemble in an orderly manner during initiation of a new infection. The betaherpesvirus subfamily includes four human herpesviruses (human cytomegalovirus and human herpesviruses 6A, 6B, and 7), as well as viruses that are the basis of important animal models of infection and immunity. Similar to other herpesviruses, betaherpesvirus virions consist of four main parts (in order from the inside): the genome, capsid, tegument, and envelope. Betaherpesvirus genomes are dsDNA and range in length from ~145 to 240 kb. Virion capsids (or nucleocapsids) are geometrically well-defined vessels that contain one copy of the dsDNA viral genome. The tegument is a collection of several thousand protein and RNA molecules packed into the space between the envelope and the capsid for delivery and immediate activity upon cellular entry at the initiation of an infection. Betaherpesvirus envelopes consist of lipid bilayers studded with virus-encoded glycoproteins; they protect the virion during transmission and mediate virion entry during initiation of new infections. Here, we summarize the mechanisms of betaherpesvirus virion assembly, including how infection modifies, reprograms, hijacks, and otherwise manipulates cellular processes and pathways to produce virion components, assemble the parts into infectious virions, and then transport the nascent virions to the extracellular environment for transmission.
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Affiliation(s)
- William L Close
- Department of Microbiology & Immunology, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Ashley N Anderson
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Philip E Pellett
- Department of Biochemistry, Microbiology, & Immunology, Wayne State University School of Medicine, Detroit, MI, USA.
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Quantitative membrane proteomics reveals a role for tetraspanin enriched microdomains during entry of human cytomegalovirus. PLoS One 2017; 12:e0187899. [PMID: 29121670 PMCID: PMC5679760 DOI: 10.1371/journal.pone.0187899] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 10/27/2017] [Indexed: 12/15/2022] Open
Abstract
Human cytomegalovirus (HCMV) depends on and modulates multiple host cell membrane proteins during each stage of the viral life cycle. To gain a global view of the impact of HCMV-infection on membrane proteins, we analyzed HCMV-induced changes in the abundance of membrane proteins in fibroblasts using stable isotope labeling with amino acids (SILAC), membrane fractionation and protein identification by two-dimensional liquid chromatography and tandem mass spectrometry. This systematic approach revealed that CD81, CD44, CD98, caveolin-1 and catenin delta-1 were down-regulated during infection whereas GRP-78 was up-regulated. Since CD81 downregulation was also observed during infection with UV-inactivated virus we hypothesized that this tetraspanin is part of the viral entry process. Interestingly, additional members of the tetraspanin family, CD9 and CD151, were also downregulated during HCMV-entry. Since tetraspanin-enriched microdomains (TEM) cluster host cell membrane proteins including known CMV receptors such as integrins, we studied whether TEMs are required for viral entry. When TEMs were disrupted with the cholesterol chelator methyl-β-cylcodextrin, viral entry was inhibited and this inhibition correlated with reduced surface levels of CD81, CD9 and CD151, whereas integrin levels remained unchanged. Furthermore, simultaneous siRNA-mediated knockdown of multiple tetraspanins inhibited viral entry whereas individual knockdown had little effect suggesting essential, but redundant roles for individual tetraspanins during entry. Taken together, our data suggest that TEM act as platforms for receptors utilized by HCMV for entry into cells.
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Liu L, Zhou Q, Xie Y, Zuo L, Zhu F, Lu J. Extracellular vesicles: novel vehicles in herpesvirus infection. Virol Sin 2017; 32:349-356. [PMID: 29116589 PMCID: PMC6704204 DOI: 10.1007/s12250-017-4073-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/09/2017] [Indexed: 12/12/2022] Open
Abstract
Herpesviruses are remarkable pathogens that have evolved multiple mechanisms to evade host immunity, ensuring their proliferation and egress. Among these mechanisms, herpesviruses utilize elaborate extracellular vesicles, including exosomes, for the intricate interplay between infected host and recipient cells. Herpesviruses incorporate genome expression products and direct cellular products into exosomal cargoes. These components alter the content and function of exosomes released from donor cells, thus affecting the downstream signalings of recipient cells. In this way, herpesviruses hijack exosomal pathways to ensure their survival and persistence, and exosomes are emerging as critical mediators for virus infection-associated intercellular communication and microenvironment alteration. In this review, the function and effects of exosomes in herpesvirus infection will be discussed, so that we will have a better understanding about the pathogenesis of herpesviruses.
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Affiliation(s)
- Lingzhi Liu
- The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, 410080, China
- Cancer Research Institute, Central South University, Changsha, 410078, China
- Department of Microbiology, School of Basic Medical Science, Central South University, Changsha, 410078, China
| | - Quan Zhou
- Faculty of Chemical, Environmental and Biological Science and Technology, Dalian University of Technology, Dalian, 116024, China
| | - Yan Xie
- The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, 410080, China
- Cancer Research Institute, Central South University, Changsha, 410078, China
- Department of Microbiology, School of Basic Medical Science, Central South University, Changsha, 410078, China
| | - Lielian Zuo
- The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, 410080, China
- Cancer Research Institute, Central South University, Changsha, 410078, China
- Department of Microbiology, School of Basic Medical Science, Central South University, Changsha, 410078, China
| | - Fanxiu Zhu
- The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, 410080, China
- Department of Biological Science, Florida State University, Tallahassee, 32306, USA
| | - Jianhong Lu
- The Key Laboratory of Carcinogenesis of the Chinese Ministry of Health, Xiangya Hospital, Central South University, Changsha, 410080, China.
- Cancer Research Institute, Central South University, Changsha, 410078, China.
- Department of Microbiology, School of Basic Medical Science, Central South University, Changsha, 410078, China.
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Giovannone AJ, Reales E, Bhattaram P, Fraile-Ramos A, Weimbs T. Monoubiquitination of syntaxin 3 leads to retrieval from the basolateral plasma membrane and facilitates cargo recruitment to exosomes. Mol Biol Cell 2017; 28:2843-2853. [PMID: 28814500 PMCID: PMC5638587 DOI: 10.1091/mbc.e17-07-0461] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 08/09/2017] [Accepted: 08/11/2017] [Indexed: 01/02/2023] Open
Abstract
Monoubiquitination of Stx3 leads to efficient endocytosis from the basolateral plasma membrane and trafficking into the multivesicular body/exosomal pathway. Stx3 plays a role in cargo recruitment into exosomes. This pathway is exploited by HCMV for virion excretion. Syntaxin 3 (Stx3), a SNARE protein located and functioning at the apical plasma membrane of epithelial cells, is required for epithelial polarity. A fraction of Stx3 is localized to late endosomes/lysosomes, although how it traffics there and its function in these organelles is unknown. Here we report that Stx3 undergoes monoubiquitination in a conserved polybasic domain. Stx3 present at the basolateral—but not the apical—plasma membrane is rapidly endocytosed, targeted to endosomes, internalized into intraluminal vesicles (ILVs), and excreted in exosomes. A nonubiquitinatable mutant of Stx3 (Stx3-5R) fails to enter this pathway and leads to the inability of the apical exosomal cargo protein GPRC5B to enter the ILV/exosomal pathway. This suggests that ubiquitination of Stx3 leads to removal from the basolateral membrane to achieve apical polarity, that Stx3 plays a role in the recruitment of cargo to exosomes, and that the Stx3-5R mutant acts as a dominant-negative inhibitor. Human cytomegalovirus (HCMV) acquires its membrane in an intracellular compartment and we show that Stx3-5R strongly reduces the number of excreted infectious viral particles. Altogether these results suggest that Stx3 functions in the transport of specific proteins to apical exosomes and that HCMV exploits this pathway for virion excretion.
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Affiliation(s)
- Adrian J Giovannone
- Department of Molecular, Cellular, and Developmental Biology and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Elena Reales
- Department of Molecular, Cellular, and Developmental Biology and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Pallavi Bhattaram
- Department of Molecular, Cellular, and Developmental Biology and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106
| | - Alberto Fraile-Ramos
- Departamento de Biología Celular, Facultad de Medicina, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Thomas Weimbs
- Department of Molecular, Cellular, and Developmental Biology and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106
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Abstract
The release of membrane-bound vesicles from cells is being increasingly recognized as a mechanism of intercellular communication. Extracellular vesicles (EVs) or exosomes are produced by virus-infected cells and are thought to be involved in intercellular communication between infected and uninfected cells. Viruses, in particular oncogenic viruses and viruses that establish chronic infections, have been shown to modulate the production and content of EVs. Viral microRNAs, proteins and even entire virions can be incorporated into EVs, which can affect the immune recognition of viruses or modulate neighbouring cells. In this Review, we discuss the roles that EVs have during viral infection to either promote or restrict viral replication in target cells. We will also discuss our current understanding of the molecular mechanisms that underlie these roles, the potential consequences for the infected host and possible future diagnostic applications.
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Herpesviruses hijack host exosomes for viral pathogenesis. Semin Cell Dev Biol 2017; 67:91-100. [PMID: 28456604 DOI: 10.1016/j.semcdb.2017.03.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 03/23/2017] [Accepted: 03/29/2017] [Indexed: 02/06/2023]
Abstract
Herpesviruses are remarkable pathogens possessing elaborate mechanisms to seize various host cellular components for immune evasion, replication, and virion egress. As viruses are dependent upon their hosts, investigating this intricate interplay has revealed that the exosome pathway is utilised by alpha (Herpes Simplex Virus 1), beta (Human Cytomegalovirus, and Human Herpesvirus 6) and gamma (Epstein-Barr Virus, and Kaposi Sarcoma-associated Herpesvirus) herpesviruses. Virions and exosomes share similar properties and functions. For example, exosomes are small membranous nanovesicles (30-150nm) released from cells that contain proteins, DNA, and various coding and non-coding RNA species. Given exosomes can shuttle various molecular cargo from a donor to recipient cell, they serve as important vehicles facilitating cell-cell communication. Therefore, exploitation by herpesviruses impacts several aspects of infection including: i) acquisition of molecular machinery for secondary envelopment and viral assembly, ii) export of immune-related host proteins from infected cells, iii) enhancing infection in surrounding cells via transfer of viral proteins, mRNA and miRNA, and iv) regulation of viral protein expression to promote persistence. Studying the dichotomy that exists between host exosomes and herpesviruses has two benefits. Firstly, it will reveal the precise pathogenic mechanisms viruses have evolved, generating knowledge for antiviral development. Secondly, it will shed light upon fundamental exosome characteristics that remain unknown, including cargo selection, protein trafficking, and non-canonical biogenesis.
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Inhibition of endocytic pathways impacts cytomegalovirus maturation. Sci Rep 2017; 7:46069. [PMID: 28406138 PMCID: PMC5390266 DOI: 10.1038/srep46069] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 03/08/2017] [Indexed: 12/18/2022] Open
Abstract
Endocytic processes are critical for cellular entry of several viruses; however, the role of endocytosis in cellular trafficking of viruses beyond virus entry is only partially understood. Here, we utilized two laboratory strains (AD169 and Towne) of human cytomegalovirus (HCMV), which are known to use cell membrane fusion rather than endocytosis to enter fibroblasts, in order to study a post-entry role of endocytosis in HCMV life cycle. Upon pharmacological inhibition of dynamin-2 or clathrin terminal domain (TD) ligand association, these strains entered the cells successfully based on the expression of immediate early viral protein. However, both the inhibitors significantly reduced the growth rates and final virus yields of viruses without inhibiting the expression of early to late viral proteins. Clathrin accumulated in the cytoplasmic virus assembly compartment (vAC) of infected cells co-localizing with virus tegument protein pp150 and the formation of vAC was compromised upon endocytic inhibition. Transmission electron micrographs (TEM) of infected cells treated with endocytosis inhibitors showed intact nuclear stages of nucleocapsid assembly but the cytoplasmic virus maturation was greatly compromised. Thus, the data presented here implicate endocytic pathways in HCMV maturation and egress.
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Tabata T, Petitt M, Fang-Hoover J, Zydek M, Pereira L. Persistent Cytomegalovirus Infection in Amniotic Membranes of the Human Placenta. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:2970-2986. [PMID: 27638253 DOI: 10.1016/j.ajpath.2016.07.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 06/25/2016] [Accepted: 07/14/2016] [Indexed: 12/24/2022]
Abstract
Human cytomegalovirus (HCMV) is the leading viral cause of birth defects, including microcephaly, neurological deficits, hearing impairment, and vision loss. We previously reported that epithelial cells in amniotic membranes of placentas from newborns with intrauterine growth restriction and underlying congenital HCMV infection contain viral proteins in cytoplasmic vesicles. Herein, we immunostained amniotic membranes from 51 placentas from symptomatic and asymptomatic congenital infection with HCMV DNA in amniotic fluid and/or newborn saliva, intrauterine growth restriction, preterm deliveries, and controls. We consistently observed HCMV proteins in amniotic epithelial cells (AmEpCs) from infected placentas, sometimes with aberrant morphology. Primary AmEpCs isolated from mid-gestation placentas infected with pathogenic VR1814 proliferated and released infectious progeny for weeks, producing higher virus titers than late-gestation cells that varied by donor. In contrast to intact virion assembly compartments in differentiated retinal pigment epithelial cells, infected AmEpCs made dispersed multivesicular bodies. Primary AmEpCs and explants of amniochorionic membranes from mid-gestation placentas formed foci of infection, and interferon-β production was prolonged. Infected AmEpCs up-regulated anti-apoptotic proteins survivin and Bcl-xL by mechanisms dependent and independent of the activated STAT3. Amniotic membranes naturally expressed both survivin and Bcl-xL, indicating that fetal membranes could foster persistent viral infection. Our results suggest strengthening innate immune responses and reducing viral functions could suppress HCMV infection in the fetal compartment.
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Affiliation(s)
- Takako Tabata
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, San Francisco, California
| | - Matthew Petitt
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, San Francisco, California
| | - June Fang-Hoover
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, San Francisco, California
| | - Martin Zydek
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, San Francisco, California
| | - Lenore Pereira
- Department of Cell and Tissue Biology, School of Dentistry, University of California, San Francisco, San Francisco, California.
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Kim YJ, Kim ET, Kim YE, Lee MK, Kwon KM, Kim KI, Stamminger T, Ahn JH. Consecutive Inhibition of ISG15 Expression and ISGylation by Cytomegalovirus Regulators. PLoS Pathog 2016; 12:e1005850. [PMID: 27564865 PMCID: PMC5001722 DOI: 10.1371/journal.ppat.1005850] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 08/08/2016] [Indexed: 11/18/2022] Open
Abstract
Interferon-stimulated gene 15 (ISG15) encodes an ubiquitin-like protein that covalently conjugates protein. Protein modification by ISG15 (ISGylation) is known to inhibit the replication of many viruses. However, studies on the viral targets and viral strategies to regulate ISGylation-mediated antiviral responses are limited. In this study, we show that human cytomegalovirus (HCMV) replication is inhibited by ISGylation, but the virus has evolved multiple countermeasures. HCMV-induced ISG15 expression was mitigated by IE1, a viral inhibitor of interferon signaling, however, ISGylation was still strongly upregulated during virus infection. RNA interference of UBE1L (E1), UbcH8 (E2), Herc5 (E3), and UBP43 (ISG15 protease) revealed that ISGylation inhibits HCMV growth by downregulating viral gene expression and virion release in a manner that is more prominent at low multiplicity of infection. A viral regulator pUL26 was found to interact with ISG15, UBE1L, and Herc5, and be ISGylated. ISGylation of pUL26 regulated its stability and inhibited its activities to suppress NF-κB signaling and complement the growth of UL26-null mutant virus. Moreover, pUL26 reciprocally suppressed virus-induced ISGylation independent of its own ISGylation. Consistently, ISGylation was more pronounced in infections with the UL26-deleted mutant virus, whose growth was more sensitive to IFNβ treatment than that of the wild-type virus. Therefore, pUL26 is a viral ISG15 target that also counteracts ISGylation. Our results demonstrate that ISGylation inhibits HCMV growth at multiple steps and that HCMV has evolved countermeasures to suppress ISG15 transcription and protein ISGylation, highlighting the importance of the interplay between virus and ISGylation in productive viral infection. Type I IFN response is a front-line defense against virus infection. Activation of type I IFN signaling leads to expression of a subset of cellular proteins encoded by interferon-stimulated genes (ISGs). ISG15 encodes an ubiquitin-like protein that is covalently conjugated to protein lysine residues. ISG15 modification (ISGylation) of a protein causes changes of protein function. ISGylation is known to inhibit the replication of many viruses, although pro-viral effects of ISGylation are also reported. Given that ISG15 and the enzymes involved in ISGylation are strongly induced upon virus infection, understanding the interplay between virus and ISGylation is an important issue in virus-host interaction. Nevertheless, viral substrates of ISG15 and viral strategies to regulate ISGylation-mediated antiviral responses are limited to only a few examples. In this study we demonstrate that ISGylation suppresses human cytomegalovirus (HCMV) infection but the virus is armed with countermeasures that consecutively reduce ISG15 transcription and protein ISGylation. Interestingly, a viral ISG15 target is found to inhibit ISGylation. This study highlights that ISGylation is a critical innate immune response against HCMV infection and interfering with ISG15-mediated anti-viral immunity is critical for productive viral infection.
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Affiliation(s)
- Ye Ji Kim
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Eui Tae Kim
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Young-Eui Kim
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Myoung Kyu Lee
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Ki Mun Kwon
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
| | - Keun Il Kim
- Department of Biological Sciences, Sookmyung Women's University, Seoul, Republic of Korea
| | - Thomas Stamminger
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Schlossgarten, Erlangen, Germany
| | - Jin-Hyun Ahn
- Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea
- * E-mail:
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Herpes Simplex Virus Capsid Localization to ESCRT-VPS4 Complexes in the Presence and Absence of the Large Tegument Protein UL36p. J Virol 2016; 90:7257-7267. [PMID: 27252536 PMCID: PMC4984650 DOI: 10.1128/jvi.00857-16] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 05/24/2016] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED UL36p (VP1/2) is the largest protein encoded by herpes simplex virus 1 (HSV-1) and resides in the innermost layer of tegument, the complex protein layer between the capsid and envelope. UL36p performs multiple functions in the HSV life cycle, including a critical but unknown role in capsid cytoplasmic envelopment. We tested whether UL36p is essential for envelopment because it is required to engage capsids with the cellular ESCRT/Vps4 apparatus. A green fluorescent protein (GFP)-fused form of the dominant negative ATPase Vps4-EQ was used to irreversibly tag ESCRT envelopment sites during infection by UL36p-expressing and UL36-null HSV strains. Using fluorescence microscopy and scanning electron microscopy, we quantitated capsid/Vps4-EQ colocalization and examined the ultrastructure of the corresponding viral assembly intermediates. We found that loss of UL36p resulted in a two-thirds reduction in the efficiency of capsid/Vps4-EQ association but that the remaining UL36p-null capsids were still able to engage the ESCRT envelopment apparatus. It appears that although UL36p helps to couple HSV capsids to the ESCRT pathway, this is likely not the sole reason for its absolute requirement for envelopment. IMPORTANCE Envelopment of the HSV capsid is essential for the assembly of an infectious virion and requires the complex interplay of a large number of viral and cellular proteins. Critical to envelope assembly is the virally encoded protein UL36p, whose function is unknown. Here we test the hypothesis that UL36p is essential for the recruitment of cellular ESCRT complexes, which are also known to be required for envelopment.
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Protein-Protein Interactions Suggest Novel Activities of Human Cytomegalovirus Tegument Protein pUL103. J Virol 2016; 90:7798-810. [PMID: 27334581 PMCID: PMC4988140 DOI: 10.1128/jvi.00097-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 06/14/2016] [Indexed: 12/19/2022] Open
Abstract
UNLABELLED Human cytomegalovirus (HCMV) is an enveloped double-stranded DNA virus that causes severe disease in newborns and immunocompromised patients. During infection, the host cell endosecretory system is remodeled to form the cytoplasmic virion assembly complex (cVAC). We and others previously identified the conserved, multifunctional HCMV virion tegument protein pUL103 as important for cVAC biogenesis and efficient secondary envelopment. To help define its mechanisms of action and predict additional functions, we used two complementary methods, coimmunoprecipitation (co-IP) and proximity biotinylation (BioID), to identify viral and cellular proteins that interact with pUL103. By using the two methods in parallel and applying stringent selection criteria, we identified potentially high-value interactions of pUL103 with 13 HCMV and 18 cellular proteins. Detection of the previously identified pUL103-pUL71 interaction, as well as verification of several interactions by reverse co-IP, supports the specificity of our screening process. As might be expected for a tegument protein, interactions were identified that suggest distinct roles for pUL103 across the arc of lytic infection, including interactions with proteins involved in cellular antiviral responses, nuclear activities, and biogenesis and transport of cytoplasmic vesicles. Further analysis of some of these interactions expands our understanding of the multifunctional repertoire of pUL103: we detected HCMV pUL103 in nuclei of infected cells and identified an ALIX-binding domain within the pUL103 sequence. IMPORTANCE Human cytomegalovirus (HCMV) is able to reconfigure the host cell machinery to establish a virion production factory, the cytoplasmic virion assembly complex (cVAC). cVAC biogenesis and operation represent targets for development of novel HCMV antivirals. We previously showed that the HCMV tegument protein pUL103 is required for cVAC biogenesis. Using pUL103 as bait, we investigated viral and cellular protein-protein interactions to identify and understand the range of pUL103 functions. We found that pUL103 interacts with cellular antiviral defense systems and proteins involved in organelle biogenesis and transport of cytoplasmic vesicles and is present in infected cell nuclei. These results expand our understanding of the functional repertoire of pUL103 to include activities that extend from the earliest stages of infection through virion assembly and egress.
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Goulidaki N, Alarifi S, Alkahtani SH, Al-Qahtani A, Spandidos DA, Stournaras C, Sourvinos G. RhoB is a component of the human cytomegalovirus assembly complex and is required for efficient viral production. Cell Cycle 2016; 14:2748-63. [PMID: 26114383 DOI: 10.1080/15384101.2015.1066535] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Human Cytomegalovirus (HCMV), an ubiquitous β-herpesvirus, is a significant pathogen that causes medically severe diseases in immunocompromised individuals and in congenitally infected neonates. RhoB belongs to the family of Rho GTPases, which regulates diverse cellular processes. Rho proteins are implicated in the entry and egress from the host cell of mainly α- and γ-herpesviruses, whereas β-herpesviruses are the least studied in this regard. Here, we studied the role of RhoB GTPase during HCMV lytic infection. Microscopy analysis, both in fixed and live infected cells showed that RhoB was translocated to the assembly complex/compartment (AC) of HCMV, a cytoplasmic zone in infected cells where many viral structural proteins are known to accumulate and assembly of new virions takes place. Furthermore, RhoB was localized at the AC even when the expression of the late HCMV AC proteins was inhibited. At the very late stages of infection, cellular projections were formed containing RhoB and HCMV virions, potentially contributing to the successful viral spread. Interestingly, the knockdown of RhoB in HCMV-infected cells resulted in a significant reduction of the virus titer and could also affect the accumulation of AC viral proteins at this subcellular compartment. RhoB knockdown also affected actin fibers' structure. Actin reorganization was observed at late stages of infection originating from the viral AC and surrounding the cellular projections, implying a potential interplay between RhoB and actin during HCMV assembly and egress. In conclusion, our results demonstrate for the first time that RhoB is a constituent of the viral AC and is required for HCMV productive infection.
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Affiliation(s)
- Nektaria Goulidaki
- a Laboratory of Virology ; Medical School ; University of Crete ; Heraklion, Crete , Greece
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50
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Human Cytomegalovirus pUL93 Is Required for Viral Genome Cleavage and Packaging. J Virol 2015; 89:12221-5. [PMID: 26401033 DOI: 10.1128/jvi.02382-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 09/16/2015] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus (HCMV) pUL93 is essential for virus growth, but its precise function in the virus life cycle is unknown. Here, we characterize a UL93 stop mutant virus (UL93st-TB40/E-BAC) to demonstrate that the absence of this protein does not restrict viral gene expression; however, cleavage of viral DNA into unit-length genomes as well as genome packaging is abolished. Thus, pUL93 is required for viral genome cleavage and packaging.
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