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Williams ZH, Imedio AD, Gaucherand L, Lee DC, Mostafa SM, Phelan JP, Coffin JM, Johnson WE. Recombinant origin and interspecies transmission of a HERV-K(HML-2)-related primate retrovirus with a novel RNA transport element. eLife 2024; 13:e80216. [PMID: 39037763 PMCID: PMC11379458 DOI: 10.7554/elife.80216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/20/2024] [Indexed: 07/23/2024] Open
Abstract
HERV-K(HML-2), the youngest clade of human endogenous retroviruses (HERVs), includes many intact or nearly intact proviruses, but no replication competent HML-2 proviruses have been identified in humans. HML-2-related proviruses are present in other primates, including rhesus macaques, but the extent and timing of HML-2 activity in macaques remains unclear. We have identified 145 HML-2-like proviruses in rhesus macaques, including a clade of young, rhesus-specific insertions. Age estimates, intact open reading frames, and insertional polymorphism of these insertions are consistent with recent or ongoing infectious activity in macaques. 106 of the proviruses form a clade characterized by an ~750 bp sequence between env and the 3' long terminal repeat (LTR), derived from an ancient recombination with a HERV-K(HML-8)-related virus. This clade is found in Old World monkeys (OWM), but not great apes, suggesting it originated after the ape/OWM split. We identified similar proviruses in white-cheeked gibbons; the gibbon insertions cluster within the OWM recombinant clade, suggesting interspecies transmission from OWM to gibbons. The LTRs of the youngest proviruses have deletions in U3, which disrupt the Rec Response Element (RcRE), required for nuclear export of unspliced viral RNA. We show that the HML-8-derived region functions as a Rec-independent constitutive transport element (CTE), indicating the ancestral Rec-RcRE export system was replaced by a CTE mechanism.
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Affiliation(s)
| | | | - Lea Gaucherand
- Molecular Microbiology Program, Tufts University Graduate School of Biomedical Sciences, Boston, United States
| | - Derek C Lee
- Department of Biology, Boston College, Boston, United States
| | - Salwa Mohd Mostafa
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, United States
| | - James P Phelan
- Molecular Microbiology Program, Tufts University Graduate School of Biomedical Sciences, Boston, United States
| | - John M Coffin
- Molecular Microbiology Program, Tufts University Graduate School of Biomedical Sciences, Boston, United States
- Department of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, United States
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2
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Jackson PEH, Dzhivhuho G, Rekosh D, Hammarskjold ML. Sequence and Functional Variation in the HIV-1 Rev Regulatory Axis. Curr HIV Res 2021; 18:85-98. [PMID: 31906839 DOI: 10.2174/1570162x18666200106112842] [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] [Received: 10/09/2019] [Revised: 11/22/2019] [Accepted: 12/02/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND To complete its replication cycle, HIV-1 requires the nucleocytoplasmic export of intron-containing viral mRNAs. This process is ordinarily restricted by the cell, but HIV overcomes the block by means of a viral protein, Rev, and an RNA secondary structure found in all unspliced and incompletely spliced viral mRNAs called the Rev Response Element (RRE). In vivo activity of the Rev-RRE axis requires Rev binding to the RRE, oligomerization of Rev to form a competent ribonucleoprotein complex, and recruitment of cellular factors including Crm1 and RanGTP in order to export the targeted transcript. Sequence variability is observed among primary isolates in both Rev and the RRE, and the activity of both can be modulated through relatively small sequence changes. Primary isolates show differences in Rev-RRE activity and a few studies have found a correlation between lower Rev-RRE activity and slower progression of clinical disease. Lower Rev-RRE activity has also been associated with the evasion of cytotoxic T lymphocyte mediated killing. CONCLUSION The HIV-1 Rev-RRE regulatory axis is an understudied mechanism by which viral adaptation to diverse immune milieus may take place. There is evidence that this adaptation plays a role in HIV pathogenesis, particularly in immune evasion and latency, but further studies with larger sample sizes are warranted.
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Affiliation(s)
- Patrick E H Jackson
- Division of Infectious Diseases and International Health, School of Medicine, University of Virginia, Charlottesville, Virginia United States.,Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, Virginia, United States
| | - Godfrey Dzhivhuho
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, Virginia, United States.,Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, Virginia, United States
| | - David Rekosh
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, Virginia, United States.,Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, Virginia, United States
| | - Marie-Louise Hammarskjold
- Myles H. Thaler Center for HIV and Human Retrovirus Research, University of Virginia, Charlottesville, Virginia, United States.,Department of Microbiology, Immunology, and Cancer Biology, School of Medicine, University of Virginia, Charlottesville, Virginia, United States
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3
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García-de-Gracia F, Gaete-Argel A, Riquelme-Barrios S, Pereira-Montecinos C, Rojas-Araya B, Aguilera P, Oyarzún-Arrau A, Rojas-Fuentes C, Acevedo ML, Chnaiderman J, Valiente-Echeverría F, Toro-Ascuy D, Soto-Rifo R. CBP80/20-dependent translation initiation factor (CTIF) inhibits HIV-1 Gag synthesis by targeting the function of the viral protein Rev. RNA Biol 2021; 18:745-758. [PMID: 33103564 PMCID: PMC8078705 DOI: 10.1080/15476286.2020.1832375] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/25/2020] [Accepted: 09/30/2020] [Indexed: 02/07/2023] Open
Abstract
Translation initiation of the human immunodeficiency virus type-1 (HIV-1) full-length RNA has been shown to occur through cap-dependent and IRES-driven mechanisms. Previous studies suggested that the nuclear cap-binding complex (CBC) rather than eIF4E drives cap-dependent translation of the full-length RNA and we have recently reported that the CBC subunit CBP80 supports the function of the viral protein Rev during nuclear export and translation of this viral transcript. Ribosome recruitment during CBC-dependent translation of cellular mRNAs relies on the activity CBP80/20 translation initiation factor (CTIF), which bridges CBP80 and the 40S ribosomal subunit through interactions with eIF3g. Here, we report that CTIF inhibits HIV-1 and HIV-2 Gag synthesis from the full-length RNA. Our results indicate that CTIF associates with HIV-1 Rev through its N-terminal domain and is recruited onto the full-length RNA ribonucleoprotein complex in order to interfere with Gag synthesis. We also demonstrate that CTIF induces the cytoplasmic accumulation of Rev impeding the association of the viral protein with CBP80. We finally show that Rev interferes with the association of CTIF with CBP80 indicating that CTIF and Rev compete for the CBC subunit.
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Affiliation(s)
- Francisco García-de-Gracia
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Aracelly Gaete-Argel
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Sebastián Riquelme-Barrios
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Camila Pereira-Montecinos
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Bárbara Rojas-Araya
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Paulina Aguilera
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Aarón Oyarzún-Arrau
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Cecilia Rojas-Fuentes
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Mónica L. Acevedo
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Jonás Chnaiderman
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Fernando Valiente-Echeverría
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Daniela Toro-Ascuy
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Ricardo Soto-Rifo
- Laboratory of Molecular and Cellular Virology, Virology Program, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile
- HIV/AIDS Workgroup, Faculty of Medicine, Universidad de Chile, Santiago, Chile
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4
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Gales JP, Kubina J, Geldreich A, Dimitrova M. Strength in Diversity: Nuclear Export of Viral RNAs. Viruses 2020; 12:E1014. [PMID: 32932882 PMCID: PMC7551171 DOI: 10.3390/v12091014] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/03/2020] [Accepted: 09/09/2020] [Indexed: 12/11/2022] Open
Abstract
The nuclear export of cellular mRNAs is a complex process that requires the orchestrated participation of many proteins that are recruited during the early steps of mRNA synthesis and processing. This strategy allows the cell to guarantee the conformity of the messengers accessing the cytoplasm and the translation machinery. Most transcripts are exported by the exportin dimer Nuclear RNA export factor 1 (NXF1)-NTF2-related export protein 1 (NXT1) and the transcription-export complex 1 (TREX1). Some mRNAs that do not possess all the common messenger characteristics use either variants of the NXF1-NXT1 pathway or CRM1, a different exportin. Viruses whose mRNAs are synthesized in the nucleus (retroviruses, the vast majority of DNA viruses, and influenza viruses) exploit both these cellular export pathways. Viral mRNAs hijack the cellular export machinery via complex secondary structures recognized by cellular export factors and/or viral adapter proteins. This way, the viral transcripts succeed in escaping the host surveillance system and are efficiently exported for translation, allowing the infectious cycle to proceed. This review gives an overview of the cellular mRNA nuclear export mechanisms and presents detailed insights into the most important strategies that viruses use to export the different forms of their RNAs from the nucleus to the cytoplasm.
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Affiliation(s)
- Jón Pol Gales
- Institut de Biologie Moléculaire des Plantes, The French National Center for Scientific Research (CNRS) UPR2357, Université de Strasbourg, F-67084 Strasbourg, France; (J.P.G.); (J.K.); (A.G.)
| | - Julie Kubina
- Institut de Biologie Moléculaire des Plantes, The French National Center for Scientific Research (CNRS) UPR2357, Université de Strasbourg, F-67084 Strasbourg, France; (J.P.G.); (J.K.); (A.G.)
- SVQV UMR-A 1131, INRAE, Université de Strasbourg, F-68000 Colmar, France
| | - Angèle Geldreich
- Institut de Biologie Moléculaire des Plantes, The French National Center for Scientific Research (CNRS) UPR2357, Université de Strasbourg, F-67084 Strasbourg, France; (J.P.G.); (J.K.); (A.G.)
| | - Maria Dimitrova
- Institut de Biologie Moléculaire des Plantes, The French National Center for Scientific Research (CNRS) UPR2357, Université de Strasbourg, F-67084 Strasbourg, France; (J.P.G.); (J.K.); (A.G.)
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5
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Mougel M, Akkawi C, Chamontin C, Feuillard J, Pessel-Vivares L, Socol M, Laine S. NXF1 and CRM1 nuclear export pathways orchestrate nuclear export, translation and packaging of murine leukaemia retrovirus unspliced RNA. RNA Biol 2020; 17:528-538. [PMID: 31918596 PMCID: PMC7237160 DOI: 10.1080/15476286.2020.1713539] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/16/2019] [Accepted: 12/18/2019] [Indexed: 10/25/2022] Open
Abstract
Cellular mRNAs are exported from the nucleus as fully spliced RNAs. Proofreading mechanisms eliminate unprocessed and irregular pre-mRNAs to control the quality of gene expression. Retroviruses need to export partially spliced and unspliced full-length RNAs to the cytoplasm where they serve as templates for protein synthesis and/or as encapsidated RNA in progeny viruses. Genetically complex retroviruses such as HIV-1 use Rev-equivalent proteins to export intron-retaining RNA from the nucleus using the cellular CRM1-driven nuclear export machinery. By contrast, genetically simpler retroviruses such as murine leukaemia virus (MLV) recruit the NXF1 RNA export machinery. In this study, we reveal for the first time that MLV hijacks both NXF1 and CRM1-dependent pathways to achieve optimal replication capacity. The CRM1-pathway marks the MLV full-length RNA (FL RNA) for packaging, while NXF1-driven nuclear export is coupled to translation. Thus, the cytoplasmic function of the viral RNA is determined early in the nucleus. Depending on the nature of ribonucleoprotein complex formed on FL RNA cargo in the nucleus, the FL RNA will be addressed to the translation machinery sites or to the virus-assembly sites at the plasma membrane.
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Affiliation(s)
- M. Mougel
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - C. Akkawi
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - C. Chamontin
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - J. Feuillard
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - L. Pessel-Vivares
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - M. Socol
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
| | - S. Laine
- Team R2D2: Retroviral RNA Dynamics and Delivery, IRIM, UMR9004, CNRS, University of Montpellier, Montpellier, FranceG
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6
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Rekosh D, Hammarskjold ML. Intron retention in viruses and cellular genes: Detention, border controls and passports. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1470. [PMID: 29508942 DOI: 10.1002/wrna.1470] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 01/04/2018] [Accepted: 01/24/2018] [Indexed: 02/06/2023]
Abstract
Intron retention (IR), where one or more introns remain in the RNA after splicing, was long thought to be rare in mammalian cells, albeit common in plants and some viruses. Largely due to the development of better methods for RNA analysis, it has now been recognized that IR is much more common than previously thought and that this mechanism is likely to play an important role in mammalian gene regulation. To date, most publications and reviews about IR have described the resulting mRNAs as "dead end" products, with no direct consequence for the proteome. However, there are also many reports of mRNAs with retained introns giving rise to alternative protein isoforms. Although this was originally revealed in viral systems, there are now numerous examples of bona fide cellular proteins that are translated from mRNAs with retained introns. These new isoforms have sometimes been shown to have important regulatory functions. In this review, we highlight recent developments in this area and the research on viruses that led the way to the realization of the many ways in which mRNAs with retained introns can be regulated. This article is categorized under: RNA Processing > Splicing Mechanisms RNA Processing > Splicing Regulation/Alternative Splicing RNA Export and Localization > Nuclear Export/Import RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.
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Affiliation(s)
- David Rekosh
- The Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia.,Department of Microbiology, University of Venda, Thohoyandou, South Africa
| | - Marie-Louise Hammarskjold
- The Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia.,Department of Microbiology, University of Venda, Thohoyandou, South Africa
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7
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Pocock GM, Zimdars LL, Yuan M, Eliceiri KW, Ahlquist P, Sherer NM. Diverse activities of viral cis-acting RNA regulatory elements revealed using multicolor, long-term, single-cell imaging. Mol Biol Cell 2017; 28:476-487. [PMID: 27903772 PMCID: PMC5341730 DOI: 10.1091/mbc.e16-08-0612] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 11/22/2016] [Accepted: 11/23/2016] [Indexed: 02/06/2023] Open
Abstract
Cis-acting RNA structural elements govern crucial aspects of viral gene expression. How these structures and other posttranscriptional signals affect RNA trafficking and translation in the context of single cells is poorly understood. Herein we describe a multicolor, long-term (>24 h) imaging strategy for measuring integrated aspects of viral RNA regulatory control in individual cells. We apply this strategy to demonstrate differential mRNA trafficking behaviors governed by RNA elements derived from three retroviruses (HIV-1, murine leukemia virus, and Mason-Pfizer monkey virus), two hepadnaviruses (hepatitis B virus and woodchuck hepatitis virus), and an intron-retaining transcript encoded by the cellular NXF1 gene. Striking behaviors include "burst" RNA nuclear export dynamics regulated by HIV-1's Rev response element and the viral Rev protein; transient aggregations of RNAs into discrete foci at or near the nuclear membrane triggered by multiple elements; and a novel, pulsiform RNA export activity regulated by the hepadnaviral posttranscriptional regulatory element. We incorporate single-cell tracking and a data-mining algorithm into our approach to obtain RNA element-specific, high-resolution gene expression signatures. Together these imaging assays constitute a tractable, systems-based platform for studying otherwise difficult to access spatiotemporal features of viral and cellular gene regulation.
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MESH Headings
- Active Transport, Cell Nucleus/physiology
- Cell Nucleus/metabolism
- Gene Expression Regulation, Viral
- Gene Products, rev/metabolism
- Genes, env/physiology
- HIV-1
- Mason-Pfizer monkey virus
- Molecular Imaging/methods
- RNA Processing, Post-Transcriptional/physiology
- RNA, Messenger/metabolism
- RNA, Viral
- Regulatory Sequences, Nucleic Acid/genetics
- Regulatory Sequences, Nucleic Acid/physiology
- Regulatory Sequences, Ribonucleic Acid/genetics
- Regulatory Sequences, Ribonucleic Acid/physiology
- Single-Cell Analysis/methods
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Affiliation(s)
- Ginger M Pocock
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706
| | - Laraine L Zimdars
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
| | - Ming Yuan
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706
- Department of Statistics, University of Wisconsin-Madison, Madison, WI 53706
| | - Kevin W Eliceiri
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706
- Laboratory for Optical and Computational Instrumentation and Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI 53706
| | - Paul Ahlquist
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI 53706
- Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, WI 53706
| | - Nathan M Sherer
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of Wisconsin-Madison, Madison, WI 53706
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8
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Ferrer M, Henriet S, Chamontin C, Lainé S, Mougel M. From Cells to Virus Particles: Quantitative Methods to Monitor RNA Packaging. Viruses 2016; 8:v8080239. [PMID: 27556480 PMCID: PMC4997601 DOI: 10.3390/v8080239] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/16/2016] [Accepted: 08/16/2016] [Indexed: 02/07/2023] Open
Abstract
In cells, positive strand RNA viruses, such as Retroviridae, must selectively recognize their full-length RNA genome among abundant cellular RNAs to assemble and release particles. How viruses coordinate the intracellular trafficking of both RNA and protein components to the assembly sites of infectious particles at the cell surface remains a long-standing question. The mechanisms ensuring packaging of genomic RNA are essential for viral infectivity. Since RNA packaging impacts on several essential functions of retroviral replication such as RNA dimerization, translation and recombination events, there are many studies that require the determination of RNA packaging efficiency and/or RNA packaging ability. Studies of RNA encapsidation rely upon techniques for the identification and quantification of RNA species packaged by the virus. This review focuses on the different approaches available to monitor RNA packaging: Northern blot analysis, ribonuclease protection assay and quantitative reverse transcriptase-coupled polymerase chain reaction as well as the most recent RNA imaging and sequencing technologies. Advantages, disadvantages and limitations of these approaches will be discussed in order to help the investigator to choose the most appropriate technique. Although the review was written with the prototypic simple murine leukemia virus (MLV) and complex human immunodeficiency virus type 1 (HIV-1) in mind, the techniques were described in order to benefit to a larger community.
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Affiliation(s)
- Mireia Ferrer
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Simon Henriet
- Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen 5018, Norway.
| | - Célia Chamontin
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Sébastien Lainé
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
| | - Marylène Mougel
- CPBS, CNRS, Université de Montpellier, 1919 Route de Mende, Montpellier 34293, France.
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9
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Pessel-Vivares L, Houzet L, Lainé S, Mougel M. Insights into the nuclear export of murine leukemia virus intron-containing RNA. RNA Biol 2016; 12:942-9. [PMID: 26158194 DOI: 10.1080/15476286.2015.1065375] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
The retroviral genome consists of an intron-containing transcript that has essential cytoplasmic functions in the infected cell. This viral transcript can escape splicing, circumvent the nuclear checkpoint mechanisms and be transported to the cytoplasm by hijacking the host machinery. Once in the cytoplasm, viral unspliced RNA acts as mRNA to be translated and as genomic RNA to be packaged into nascent viruses. The murine leukemia virus (MLV) is among the first retroviruses discovered and is classified as simple Retroviridae due to its minimal encoding capacity. The oncogenic and transduction abilities of MLV are extensively studied, whereas surprisingly the crucial step of its nuclear export has remained unsolved until 2014. Recent work has revealed the recruitment by MLV of the cellular NXF1/Tap-dependent pathway for export. Unconventionally, MLV uses of Tap to export both spliced and unspliced viral RNAs. Unlike other retroviruses, MLV does not harbor a unique RNA signal for export. Indeed, multiple sequences throughout the MLV genome appear to promote export of the unspliced MLV RNA. We review here the current understanding of the export mechanism and highlight the determinants that influence MLV export. As the molecular mechanism of MLV export is elucidated, we will gain insight into the contribution of the export pathway to the cytoplasmic fate of the viral RNA.
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Affiliation(s)
- Lucie Pessel-Vivares
- a CNRS, UM; CPBS ; Montpellier , France.,b Department of Infectious Diseases ; King's College London ; London , UK
| | - Laurent Houzet
- c Inserm U1085-IRSET; Université de Rennes 1; Structure Fédérative Recherche Biosit ; Rennes , France
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10
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HIV-1 and M-PMV RNA Nuclear Export Elements Program Viral Genomes for Distinct Cytoplasmic Trafficking Behaviors. PLoS Pathog 2016; 12:e1005565. [PMID: 27070420 PMCID: PMC4829213 DOI: 10.1371/journal.ppat.1005565] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Accepted: 03/21/2016] [Indexed: 12/15/2022] Open
Abstract
Retroviruses encode cis-acting RNA nuclear export elements that override nuclear retention of intron-containing viral mRNAs including the full-length, unspliced genomic RNAs (gRNAs) packaged into assembling virions. The HIV-1 Rev-response element (RRE) recruits the cellular nuclear export receptor CRM1 (also known as exportin-1/XPO1) using the viral protein Rev, while simple retroviruses encode constitutive transport elements (CTEs) that directly recruit components of the NXF1(Tap)/NXT1(p15) mRNA nuclear export machinery. How gRNA nuclear export is linked to trafficking machineries in the cytoplasm upstream of virus particle assembly is unknown. Here we used long-term (>24 h), multicolor live cell imaging to directly visualize HIV-1 gRNA nuclear export, translation, cytoplasmic trafficking, and virus particle production in single cells. We show that the HIV-1 RRE regulates unique, en masse, Rev- and CRM1-dependent "burst-like" transitions of mRNAs from the nucleus to flood the cytoplasm in a non-localized fashion. By contrast, the CTE derived from Mason-Pfizer monkey virus (M-PMV) links gRNAs to microtubules in the cytoplasm, driving them to cluster markedly to the centrosome that forms the pericentriolar core of the microtubule-organizing center (MTOC). Adding each export element to selected heterologous mRNAs was sufficient to confer each distinct export behavior, as was directing Rev/CRM1 or NXF1/NXT1 transport modules to mRNAs using a site-specific RNA tethering strategy. Moreover, multiple CTEs per transcript enhanced MTOC targeting, suggesting that a cooperative mechanism links NXF1/NXT1 to microtubules. Combined, these results reveal striking, unexpected features of retroviral gRNA nucleocytoplasmic transport and demonstrate roles for mRNA export elements that extend beyond nuclear pores to impact gRNA distribution in the cytoplasm.
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11
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Pilkington GR, Purzycka KJ, Bear J, Le Grice SFJ, Felber BK. Gammaretrovirus mRNA expression is mediated by a novel, bipartite post-transcriptional regulatory element. Nucleic Acids Res 2014; 42:11092-106. [PMID: 25190459 PMCID: PMC4176177 DOI: 10.1093/nar/gku798] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Post-transcriptional regulatory mechanisms of several complex and simple retroviruses and retroelements have been elucidated, with the exception of the gammaretrovirus family. We found that, similar to the other retroviruses, gag gene expression of MuLV and XMRV depends on post-transcriptional regulation mediated via an RNA sequence overlapping the pro-pol open reading frame, termed the Post-Transcriptional Element (PTE). PTE function can be replaced by heterologous RNA export elements, e.g. CTE of simian type D retroviruses. Alternatively, Gag particle production is achieved using an RNA/codon optimized gag gene. PTE function is transferable and can replace HIV Rev-RRE-regulated expression of HIV gag. Analysis of PTE by SHAPE revealed a highly structured RNA comprising seven stem-loop structures, with the 5′ and 3′ stem-loops forming an essential bipartite signal. MuLV and XMRV PTE share 98% identity and have highly similar RNA structures, with changes mostly located to single-stranded regions. PTE identification strongly suggests that all retroviruses and retroelements share common strategies of post-transcriptional gene regulation to produce Gag. Expression depends on complex RNA structures embedded within retroviral mRNA, in coding regions or the 3′ untranslated region. These specific structures serve as recognition signals for either cellular or viral proteins.
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Affiliation(s)
- Guy R Pilkington
- Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Katarzyna J Purzycka
- RT Biochemistry Section, Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, 61-704, Poland
| | - Jenifer Bear
- Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Stuart F J Le Grice
- RT Biochemistry Section, Drug Resistance Program, National Cancer Institute at Frederick, Frederick, MD 21702, USA
| | - Barbara K Felber
- Human Retrovirus Pathogenesis Section, Vaccine Branch, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, USA
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