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The Unique, the Known, and the Unknown of Spumaretrovirus Assembly. Viruses 2021; 13:v13010105. [PMID: 33451128 PMCID: PMC7828637 DOI: 10.3390/v13010105] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 01/08/2021] [Accepted: 01/10/2021] [Indexed: 12/22/2022] Open
Abstract
Within the family of Retroviridae, foamy viruses (FVs) are unique and unconventional with respect to many aspects in their molecular biology, including assembly and release of enveloped viral particles. Both components of the minimal assembly and release machinery, Gag and Env, display significant differences in their molecular structures and functions compared to the other retroviruses. This led to the placement of FVs into a separate subfamily, the Spumaretrovirinae. Here, we describe the molecular differences in FV Gag and Env, as well as Pol, which is translated as a separate protein and not in an orthoretroviral manner as a Gag-Pol fusion protein. This feature further complicates FV assembly since a specialized Pol encapsidation strategy via a tripartite Gag-genome–Pol complex is used. We try to relate the different features and specific interaction patterns of the FV Gag, Pol, and Env proteins in order to develop a comprehensive and dynamic picture of particle assembly and release, but also other features that are indirectly affected. Since FVs are at the root of the retrovirus tree, we aim at dissecting the unique/specialized features from those shared among the Spuma- and Orthoretrovirinae. Such analyses may shed light on the evolution and characteristics of virus envelopment since related viruses within the Ortervirales, for instance LTR retrotransposons, are characterized by different levels of envelopment, thus affecting the capacity for intercellular transmission.
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Dupont A, Glück IM, Ponti D, Stirnnagel K, Hütter S, Perrotton F, Stanke N, Richter S, Lindemann D, Lamb DC. Identification of an Intermediate Step in Foamy Virus Fusion. Viruses 2020; 12:v12121472. [PMID: 33371254 PMCID: PMC7766700 DOI: 10.3390/v12121472] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/13/2020] [Accepted: 12/17/2020] [Indexed: 12/20/2022] Open
Abstract
Viral glycoprotein-mediated membrane fusion is an essential step for productive infection of host cells by enveloped viruses; however, due to its rarity and challenges in detection, little is known about the details of fusion events at the single particle level. Here, we have developed dual-color foamy viruses (FVs) composed of eGFP-tagged prototype FV (PFV) Gag and mCherry-tagged Env of either PFV or macaque simian FV (SFVmac) origin that have been optimized for detection of the fusion process. Using our recently developed tracking imaging correlation (TrIC) analysis, we were able to detect the fusion process for both PFV and SFVmac Env containing virions. PFV Env-mediated fusion was observed both at the plasma membrane as well as from endosomes, whereas SFVmac Env-mediated fusion was only observed from endosomes. PFV Env-mediated fusion was observed to happen more often and more rapidly than as for SFVmac Env. Strikingly, using the TrIC method, we detected a novel intermediate state where the envelope and capsids are still tethered but separated by up to 400 nm before final separation of Env and Gag occurred.
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Affiliation(s)
- Aurélie Dupont
- Department of Chemistry, Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany; (A.D.); (I.M.G.); (D.P.); (F.P.)
- Center for Nano Science (CENS), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
- LIPhy, University Grenoble Alpes, CNRS, F-38000 Grenoble, France
| | - Ivo M. Glück
- Department of Chemistry, Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany; (A.D.); (I.M.G.); (D.P.); (F.P.)
- Center for Nano Science (CENS), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
| | - Dorothee Ponti
- Department of Chemistry, Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany; (A.D.); (I.M.G.); (D.P.); (F.P.)
- Center for Nano Science (CENS), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
| | - Kristin Stirnnagel
- Medical Faculty “Carl Gustav Carus”, Institute of Virology, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (K.S.); (S.H.); (N.S.); (S.R.)
- CRTD/DFG-Center for Regenerative Therapies, Technische Universität Dresden, Fetscherstr. 105, 01307 Dresden, Germany
| | - Sylvia Hütter
- Medical Faculty “Carl Gustav Carus”, Institute of Virology, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (K.S.); (S.H.); (N.S.); (S.R.)
- CRTD/DFG-Center for Regenerative Therapies, Technische Universität Dresden, Fetscherstr. 105, 01307 Dresden, Germany
| | - Florian Perrotton
- Department of Chemistry, Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany; (A.D.); (I.M.G.); (D.P.); (F.P.)
| | - Nicole Stanke
- Medical Faculty “Carl Gustav Carus”, Institute of Virology, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (K.S.); (S.H.); (N.S.); (S.R.)
- CRTD/DFG-Center for Regenerative Therapies, Technische Universität Dresden, Fetscherstr. 105, 01307 Dresden, Germany
| | - Stefanie Richter
- Medical Faculty “Carl Gustav Carus”, Institute of Virology, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (K.S.); (S.H.); (N.S.); (S.R.)
- CRTD/DFG-Center for Regenerative Therapies, Technische Universität Dresden, Fetscherstr. 105, 01307 Dresden, Germany
| | - Dirk Lindemann
- Medical Faculty “Carl Gustav Carus”, Institute of Virology, Technische Universität Dresden, Fetscherstr. 74, 01307 Dresden, Germany; (K.S.); (S.H.); (N.S.); (S.R.)
- CRTD/DFG-Center for Regenerative Therapies, Technische Universität Dresden, Fetscherstr. 105, 01307 Dresden, Germany
- Correspondence: (D.L.); (D.C.L.)
| | - Don C. Lamb
- Department of Chemistry, Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany; (A.D.); (I.M.G.); (D.P.); (F.P.)
- Center for Nano Science (CENS), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
- Nanosystems Initiative München (NIM), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
- Center for Integrated Protein Science (CIPSM), Ludwig Maximilians-Universität München, Butenandtstraße 5-13, 81377 München, Germany
- Correspondence: (D.L.); (D.C.L.)
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Lnc-RP5 Regulates the miR-129-5p/Notch1/PFV Internal Promoter Axis to Promote the Expression of the Prototype Foamy Virus Transactivator Tas. Virol Sin 2019; 35:73-82. [PMID: 31637632 DOI: 10.1007/s12250-019-00168-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 08/28/2019] [Indexed: 10/25/2022] Open
Abstract
Prototype foamy virus (PFV) is a unique retrovirus that infects animals and humans and does not cause clinical symptoms. Long noncoding RNAs (lncRNAs) are believed to exert multiple regulatory functions during viral infections. Previously, we utilized RNA sequencing (RNA-seq) to characterize and identify the lncRNA lnc-RP5-1086D14.3.1-1:1 (lnc-RP5), which is markedly decreased in PFV-infected cells. However, little is known about the function of lnc-RP5 during PFV infection. In this study, we identified lnc-RP5 as a regulator of the PFV transcriptional transactivator (Tas). Lnc-RP5 enhanced the activity of the PFV internal promoter (IP). The expression of PFV Tas was found to be promoted by lnc-RP5. Moreover, miR-129-5p was found to be involved in the lnc-RP5-mediated promotion of PFV IP activity, while the Notch1 protein suppressed the activity of PFV IP and the expression of Tas. Our results demonstrate that lnc-RP5 promotes the expression of PFV Tas through the miR-129-5p/Notch1/PFV IP axis. This work provides evidence that host lncRNAs can manipulate PFV replication by employing miRNAs and proteins during an early viral infection.
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Liu Y, Betts MJ, Lei J, Wei G, Bao Q, Kehl T, Russell RB, Löchelt M. Mutagenesis of N-terminal residues of feline foamy virus Gag reveals entirely distinct functions during capsid formation, particle assembly, Gag processing and budding. Retrovirology 2016; 13:57. [PMID: 27549192 PMCID: PMC4994201 DOI: 10.1186/s12977-016-0291-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 08/04/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Foamy viruses (FVs) of the Spumaretrovirinae subfamily are distinct retroviruses, with many features of their molecular biology and replication strategy clearly different from those of the Orthoretroviruses, such as human immunodeficiency, murine leukemia, and human T cell lymphotropic viruses. The FV Gag N-terminal region is responsible for capsid formation and particle budding via interaction with Env. However, the critical residues or motifs in this region and their functional interaction are currently ill-defined, especially in non-primate FVs. RESULTS Mutagenesis of N-terminal Gag residues of feline FV (FFV) reveals key residues essential for either capsid assembly and/or viral budding via interaction with the FFV Env leader protein (Elp). In an in vitro Gag-Elp interaction screen, Gag mutations abolishing particle assembly also interfered with Elp binding, indicating that Gag assembly is a prerequisite for this highly specific interaction. Gradient sedimentation analyses of cytosolic proteins indicate that wild-type Gag is mostly assembled into virus capsids. Moreover, proteolytic processing of Gag correlates with capsid assembly and is mostly, if not completely, independent from particle budding. In addition, Gag processing correlates with the presence of packaging-competent FFV genomic RNA suggesting that Pol encapsidation via genomic RNA is a prerequisite for Gag processing. Though an appended heterogeneous myristoylation signal rescues Gag particle budding of mutants unable to form capsids or defective in interacting with Elp, it fails to generate infectious particles that co-package Pol, as evidenced by a lack of Gag processing. CONCLUSIONS Changes in proteolytic Gag processing, intracellular capsid assembly, particle budding and infectivity of defined N-terminal Gag mutants highlight their essential, distinct and only partially overlapping roles during viral assembly and budding. Discussion of these findings will be based on a recent model developed for Gag-Elp interactions in prototype FV.
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Affiliation(s)
- Yang Liu
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany.,Center for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Matthew J Betts
- CellNetworks, Bioquant, University of Heidelberg, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany
| | - Janet Lei
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany.,Department of Oncology, University of Oxford, Oxford, UK
| | - Guochao Wei
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany
| | - Qiuying Bao
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany.,Biology Department, East China Normal University, Shanghai, China
| | - Timo Kehl
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany
| | - Robert B Russell
- CellNetworks, Bioquant, University of Heidelberg, Im Neuenheimer Feld 267, 69120, Heidelberg, Germany.,Biochemie Zentrum Heidelberg (BZH), Im Neuenheimer Feld 328, 69120, Heidelberg, Germany
| | - Martin Löchelt
- Department of Molecular Diagnostics of Oncogenic Infections, Research Program Infection and Cancer, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120, Heidelberg, Germany.
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Hamann MV, Müllers E, Reh J, Stanke N, Effantin G, Weissenhorn W, Lindemann D. The cooperative function of arginine residues in the Prototype Foamy Virus Gag C-terminus mediates viral and cellular RNA encapsidation. Retrovirology 2014; 11:87. [PMID: 25292281 PMCID: PMC4198681 DOI: 10.1186/s12977-014-0087-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 09/23/2014] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND One unique feature of the foamy virus (FV) capsid protein Gag is the absence of Cys-His motifs, which in orthoretroviruses are irreplaceable for multitude functions including viral RNA genome recognition and packaging. Instead, FV Gag contains glycine-arginine-rich (GR) sequences at its C-terminus. In case of prototype FV (PFV) these are historically grouped in three boxes, which have been shown to play essential functions in genome reverse transcription, virion infectivity and particle morphogenesis. Additional functions for RNA packaging and Pol encapsidation were suggested, but have not been conclusively addressed. RESULTS Here we show that released wild type PFV particles, like orthoretroviruses, contain various cellular RNAs in addition to viral genome. Unlike orthoretroviruses, the content of selected cellular RNAs in capsids of PFV vector particles was not altered by viral genome encapsidation. Deletion of individual GR boxes had only minor negative effects (2 to 4-fold) on viral and cellular RNA encapsidation over a wide range of cellular Gag to viral genome ratios examined. Only the concurrent deletion of all three PFV Gag GR boxes, or the substitution of multiple arginine residues residing in the C-terminal GR box region by alanine, abolished both viral and cellular RNA encapsidation (>50 to >3,000-fold reduced), independent of the viral production system used. Consequently, those mutants also lacked detectable amounts of encapsidated Pol and were non-infectious. In contrast, particle release was reduced to a much lower extent (3 to 20-fold). CONCLUSIONS Taken together, our data provides the first identification of a full-length PFV Gag mutant devoid in genome packaging and the first report of cellular RNA encapsidation into PFV particles. Our results suggest that the cooperative action of C-terminal clustered positively charged residues, present in all FV Gag proteins, is the main viral protein determinant for viral and cellular RNA encapsidation. The viral genome independent efficiency of cellular RNA encapsidation suggests differential packaging mechanisms for both types of RNAs. Finally, this study indicates that analogous to orthoretroviruses, Gag - nucleic acid interactions are required for FV capsid assembly and efficient particle release.
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Affiliation(s)
- Martin V Hamann
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Erik Müllers
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany. .,Present address: Department of Cell and Molecular Biology, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Juliane Reh
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Nicole Stanke
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
| | - Gregory Effantin
- Univ. Grenoble Alpes, UVHCI, F-38000, Grenoble, France. .,CNRS, UVHCI, F-38000, Grenoble, France.
| | - Winfried Weissenhorn
- Univ. Grenoble Alpes, UVHCI, F-38000, Grenoble, France. .,CNRS, UVHCI, F-38000, Grenoble, France.
| | - Dirk Lindemann
- Institute of Virology, Medical Faculty "Carl Gustav Carus", Technische Universität Dresden, Fetscherstr. 74, 01307, Dresden, Germany. .,CRTD/DFG-Center for Regenerative Therapies Dresden - Cluster of Excellence, Technische Universität Dresden, Fetscherstr. 105, 01307, Dresden, Germany.
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