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Benning FMC, Jenni S, Garcia CY, Nguyen TH, Zhang X, Chao LH. Helical reconstruction of VP39 reveals principles for baculovirus nucleocapsid assembly. Nat Commun 2024; 15:250. [PMID: 38177118 PMCID: PMC10767040 DOI: 10.1038/s41467-023-44596-y] [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: 06/22/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
Baculoviruses are insect-infecting pathogens with wide applications as biological pesticides, in vitro protein production vehicles and gene therapy tools. Its cylindrical nucleocapsid, which encapsulates and protects the circular double-stranded viral DNA encoding proteins for viral replication and entry, is formed by the highly conserved major capsid protein VP39. The mechanism for VP39 assembly remains unknown. We use electron cryomicroscopy to determine a 3.2 Å helical reconstruction of an infectious nucleocapsid of Autographa californica multiple nucleopolyhedrovirus, revealing how dimers of VP39 assemble into a 14-stranded helical tube. We show that VP39 comprises a distinct protein fold conserved across baculoviruses, which includes a Zinc finger domain and a stabilizing intra-dimer sling. Analysis of sample polymorphism shows that VP39 assembles in several closely-related helical geometries. This VP39 reconstruction reveals general principles for baculoviral nucleocapsid assembly.
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Affiliation(s)
- Friederike M C Benning
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - Simon Jenni
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, 02115, USA
| | - Coby Y Garcia
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, 02114, USA
- Harvard College, Cambridge, MA, 02138, USA
| | - Tran H Nguyen
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Xuewu Zhang
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Luke H Chao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, 02114, USA.
- Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA.
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2
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Benning FMC, Jenni S, Garcia CY, Nguyen TH, Zhang X, Chao LH. Helical reconstruction of VP39 reveals principles for baculovirus nucleocapsid assembly. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.15.545104. [PMID: 37398449 PMCID: PMC10312762 DOI: 10.1101/2023.06.15.545104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Baculoviruses are insect-infecting pathogens with wide applications as biological pesticides, in vitro protein production vehicles and gene therapy tools. Its cylindrical nucleocapsid, which encapsulates and protects the circular double-stranded viral DNA encoding proteins for viral replication and entry, is formed by the highly conserved major capsid protein VP39. The mechanism for VP39 assembly remains unknown. We determined a 3.2 Å electron cryomicroscopy helical reconstruction of an infectious nucleocapsid of Autographa californica multiple nucleopolyhedrovirus, revealing how dimers of VP39 assemble into a 14-stranded helical tube. We show that VP39 comprises a unique protein fold conserved across baculoviruses, which includes a Zinc finger domain and a stabilizing intra-dimer sling. Analysis of sample polymorphism revealed that VP39 assembles in several closely-related helical geometries. This VP39 reconstruction reveals general principles for baculoviral nucleocapsid assembly.
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Affiliation(s)
- Friederike M. C. Benning
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Simon Jenni
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Coby Y. Garcia
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Harvard College, Cambridge, MA 02138, USA
| | - Tran H. Nguyen
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Xuewu Zhang
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Luke H. Chao
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
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3
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Behrens RT, Sherer NM. Retroviral hijacking of host transport pathways for genome nuclear export. mBio 2023; 14:e0007023. [PMID: 37909783 PMCID: PMC10746203 DOI: 10.1128/mbio.00070-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023] Open
Abstract
Recent advances in the study of virus-cell interactions have improved our understanding of how viruses that replicate their genomes in the nucleus (e.g., retroviruses, hepadnaviruses, herpesviruses, and a subset of RNA viruses) hijack cellular pathways to export these genomes to the cytoplasm where they access virion egress pathways. These findings shed light on novel aspects of viral life cycles relevant to the development of new antiviral strategies and can yield new tractable, virus-based tools for exposing additional secrets of the cell. The goal of this review is to summarize defined and emerging modes of virus-host interactions that drive the transit of viral genomes out of the nucleus across the nuclear envelope barrier, with an emphasis on retroviruses that are most extensively studied. In this context, we prioritize discussion of recent progress in understanding the trafficking and function of the human immunodeficiency virus type 1 Rev protein, exemplifying a relatively refined example of stepwise, cooperativity-driven viral subversion of multi-subunit host transport receptor complexes.
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Affiliation(s)
- Ryan T. Behrens
- Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, Wisconsin, USA
| | - Nathan M. Sherer
- McArdle Laboratory for Cancer Research and Carbone Cancer Center, University of Wisconsin, Madison, Wisconsin, USA
- Institute for Molecular Virology, University of Wisconsin, Madison, Wisconsin, USA
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4
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Eren E, Watts NR, Randazzo D, Palmer I, Sackett DL, Wingfield PT. Structural basis of microtubule depolymerization by the kinesin-like activity of HIV-1 Rev. Structure 2023; 31:1233-1246.e5. [PMID: 37572662 PMCID: PMC10592302 DOI: 10.1016/j.str.2023.07.009] [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: 08/17/2022] [Revised: 04/07/2023] [Accepted: 07/18/2023] [Indexed: 08/14/2023]
Abstract
HIV-1 Rev is an essential regulatory protein that transports unspliced and partially spliced viral mRNAs from the nucleus to the cytoplasm for the expression of viral structural proteins. During its nucleocytoplasmic shuttling, Rev interacts with several host proteins to use the cellular machinery for the advantage of the virus. Here, we report the 3.5 Å cryo-EM structure of a 4.8 MDa Rev-tubulin ring complex. Our structure shows that Rev's arginine-rich motif (ARM) binds to both the acidic surfaces and the C-terminal tails of α/β-tubulin. The Rev-tubulin interaction is functionally homologous to that of kinesin-13, potently destabilizing microtubules at sub-stoichiometric levels. Expression of Rev in astrocytes and HeLa cells shows that it can modulate the microtubule cytoskeleton within the cellular environment. These results show a previously undefined regulatory role of Rev.
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Affiliation(s)
- Elif Eren
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Norman R Watts
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Davide Randazzo
- Light Imaging Section, Office of Science and Technology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ira Palmer
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Dan L Sackett
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Paul T Wingfield
- Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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5
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Spittler D, Indorato RL, Boeri Erba E, Delaforge E, Signor L, Harris SJ, Garcia-Saez I, Palencia A, Gabel F, Blackledge M, Noirclerc-Savoye M, Petosa C. Binding stoichiometry and structural model of the HIV-1 Rev/importin β complex. Life Sci Alliance 2022; 5:5/10/e202201431. [PMID: 35995566 PMCID: PMC9396022 DOI: 10.26508/lsa.202201431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 11/24/2022] Open
Abstract
HIV-1 Rev mediates the nuclear export of intron-containing viral RNA transcripts and is essential for viral replication. Rev is imported into the nucleus by the host protein importin β (Impβ), but how Rev associates with Impβ is poorly understood. Here, we report biochemical, mutational, and biophysical studies of the Impβ/Rev complex. We show that Impβ binds two Rev monomers through independent binding sites, in contrast to the 1:1 binding stoichiometry observed for most Impβ cargos. Peptide scanning data and charge-reversal mutations identify the N-terminal tip of Rev helix α2 within Rev's arginine-rich motif (ARM) as a primary Impβ-binding epitope. Cross-linking mass spectrometry and compensatory mutagenesis data combined with molecular docking simulations suggest a structural model in which one Rev monomer binds to the C-terminal half of Impβ with Rev helix α2 roughly parallel to the HEAT-repeat superhelical axis, whereas the other monomer binds to the N-terminal half. These findings shed light on the molecular basis of Rev recognition by Impβ and highlight an atypical binding behavior that distinguishes Rev from canonical cellular Impβ cargos.
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Affiliation(s)
- Didier Spittler
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Rose-Laure Indorato
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Elisabetta Boeri Erba
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Elise Delaforge
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Luca Signor
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Simon J Harris
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Isabel Garcia-Saez
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Andrés Palencia
- Institute for Advanced Biosciences, Structural Biology of Novel Targets in Human Diseases, INSERM U1209, CNRS UMR5309, Université Grenoble Alpes, Grenoble, France
| | - Frank Gabel
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Martin Blackledge
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Marjolaine Noirclerc-Savoye
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
| | - Carlo Petosa
- Université Grenoble Alpes, Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA), Centre National de la Recherche Scientifique (CNRS), Institut de Biologie Structurale, Grenoble, France
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6
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Mazinani M, Rahbarizadeh F. CAR-T cell potency: from structural elements to vector backbone components. Biomark Res 2022; 10:70. [PMID: 36123710 PMCID: PMC9487061 DOI: 10.1186/s40364-022-00417-w] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 09/07/2022] [Indexed: 12/03/2022] Open
Abstract
Chimeric antigen receptor (CAR) T cell therapy, in which a patient’s own T lymphocytes are engineered to recognize and kill cancer cells, has achieved remarkable success in some hematological malignancies in preclinical and clinical trials, resulting in six FDA-approved CAR-T products currently available in the market. Once equipped with a CAR construct, T cells act as living drugs and recognize and eliminate the target tumor cells in an MHC-independent manner. In this review, we first described all structural modular of CAR in detail, focusing on more recent findings. We then pointed out behind-the-scene elements contributing to CAR expression and reviewed how CAR expression can be drastically affected by the elements embedded in the viral vector backbone.
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Affiliation(s)
- Marzieh Mazinani
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-111, Tehran, Iran
| | - Fatemeh Rahbarizadeh
- Department of Medical Biotechnology, Faculty of Medical Sciences, Tarbiat Modares University, P.O. Box 14115-111, Tehran, Iran. .,Research and Development Center of Biotechnology, Tarbiat Modares University, Tehran, Iran.
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7
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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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8
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Knoener R, Evans E, Becker JT, Scalf M, Benner B, Sherer NM, Smith LM. Identification of host proteins differentially associated with HIV-1 RNA splice variants. eLife 2021; 10:e62470. [PMID: 33629952 PMCID: PMC7906601 DOI: 10.7554/elife.62470] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 01/27/2021] [Indexed: 12/12/2022] Open
Abstract
HIV-1 generates unspliced (US), partially spliced (PS), and completely spliced (CS) classes of RNAs, each playing distinct roles in viral replication. Elucidating their host protein 'interactomes' is crucial to understanding virus-host interplay. Here, we present HyPR-MSSV for isolation of US, PS, and CS transcripts from a single population of infected CD4+ T-cells and mass spectrometric identification of their in vivo protein interactomes. Analysis revealed 212 proteins differentially associated with the unique RNA classes, including preferential association of regulators of RNA stability with US and PS transcripts and, unexpectedly, mitochondria-linked proteins with US transcripts. Remarkably, >80 of these factors screened by siRNA knockdown impacted HIV-1 gene expression. Fluorescence microscopy confirmed several to co-localize with HIV-1 US RNA and exhibit changes in abundance and/or localization over the course of infection. This study validates HyPR-MSSV for discovery of viral splice variant protein interactomes and provides an unprecedented resource of factors and pathways likely important to HIV-1 replication.
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Affiliation(s)
- Rachel Knoener
- Department of Chemistry, University of WisconsinMadisonUnited States
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of WisconsinMadisonUnited States
| | - Edward Evans
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of WisconsinMadisonUnited States
| | - Jordan T Becker
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of WisconsinMadisonUnited States
| | - Mark Scalf
- Department of Chemistry, University of WisconsinMadisonUnited States
| | - Bayleigh Benner
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of WisconsinMadisonUnited States
| | - Nathan M Sherer
- McArdle Laboratory for Cancer Research and Institute for Molecular Virology, University of WisconsinMadisonUnited States
| | - Lloyd M Smith
- Department of Chemistry, University of WisconsinMadisonUnited States
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9
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Abstract
The human immunodeficiency virus type 1 (HIV-1) proteome is expressed from alternatively spliced and unspliced genomic RNAs. However, HIV-1 RNAs that are not fully spliced are perceived by the host machinery as defective and are retained in the nucleus. During late infection, HIV-1 bypasses this regulatory mechanism by expression of the Rev protein from a fully spliced mRNA. Once imported into the nucleus, Rev mediates the export of unprocessed HIV-1 RNAs to the cytoplasm, leading to the production of the viral progeny. While regarded as a canonical RNA export factor, Rev has also been linked to HIV-1 RNA translation, stabilization, splicing and packaging. However, Rev's functions beyond RNA export have remained poorly understood. Here, we revisit this paradigmatic protein, reviewing recent data investigating its structure and function. We conclude by asking: what remains unknown about this enigmatic viral protein?
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Affiliation(s)
| | - Aino Järvelin
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Alfredo Castello
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
- MRC-University of Glasgow Centre for Virus Research, University of Glasgow, 464 Bearsden Road, Glasgow G61 1QH, UK
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10
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O'Carroll IP, Fan L, Kroupa T, McShane EK, Theodore C, Yates EA, Kondrup B, Ding J, Martin TS, Rein A, Wang YX. Structural Mimicry Drives HIV-1 Rev-Mediated HERV-K Expression. J Mol Biol 2020; 432:166711. [PMID: 33197463 DOI: 10.1016/j.jmb.2020.11.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 11/09/2020] [Accepted: 11/09/2020] [Indexed: 10/23/2022]
Abstract
Expression of the Human Endogenous Retrovirus Type K (HERV-K), the youngest and most active HERV, has been associated with various cancers and neurodegenerative diseases. As in all retroviruses, a fraction of HERV-K transcripts is exported from the nucleus in unspliced or incompletely spliced forms to serve as templates for translation of viral proteins. In a fraction of HERV-K loci (Type 2 proviruses), nuclear export of the unspliced HERV-K mRNA appears to be mediated by a cis-acting signal on the mRNA, the RcRE, and the protein Rec-these are analogous to the RRE-Rev system in HIV-1. Interestingly, the HIV-1 Rev protein is able to mediate the nuclear export of the HERV-K RcRE, contributing to elevated HERV-K expression in HIV-infected patients. We aimed to understand the structural basis for HIV Rev-HERV-K RcRE recognition. We examined the conformation of the RcRE RNA in solution using small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). We found that the 433-nt long RcRE can assume folded or extended conformations as observed by AFM. SAXS analysis of a truncated RcRE variant revealed an "A"-shaped topological structure similar to the one previously reported for the HIV-1 RRE. The effect of the overall topology was examined using several deletion variants. SAXS and biochemical analyses demonstrated that the "A" shape is necessary for efficient Rev-RcRE complex formation in vitro and nuclear export activity in cell culture. The findings provide insight into the mechanism of HERV-K expression and a structural explanation for HIV-1 Rev-mediated expression of HERV-K in HIV-infected patients. IMPORTANCE: Expression of the human endogenous retrovirus type K (HERV-K) has been associated with various cancers and autoimmune diseases. Nuclear export of both HIV-1 and HERV-K mRNAs is dependent on the interaction between a small viral protein (Rev in HIV-1 and Rec in HERV-K) and a region on the mRNA (RRE in HIV-1 and RcRE in HERV-K). HIV-1 Rev is able to mediate the nuclear export of RcRE-containing HERV-K mRNAs, which contributes to elevated production of HERV-K proteins in HIV-infected patients. We report the solution conformation of the RcRE RNA-the first three-dimensional topological structure for a HERV molecule-and find that the RcRE resembles the HIV-1 nuclear export signal, RRE. The finding reveals the structural basis for the increased HERV-K expression observed in HIV-infected patients. Elevated HERV expression, mediated by HIV infection or other stressors, can have various HERV-related biological consequences. The findings provide structural insight for regulation of HERV-K expression.
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Affiliation(s)
- Ina P O'Carroll
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA.
| | - Lixin Fan
- Basic Science Program, Frederick National Laboratory for Cancer Research, SAXS Core Facility of the National Cancer Institute, Frederick, MD 21702, USA
| | - Tomáš Kroupa
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Erin K McShane
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Christophe Theodore
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Elizabeth A Yates
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Benjamin Kondrup
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Jienyu Ding
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Tyler S Martin
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Alan Rein
- HIV Dynamics and Replication Program, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Yun-Xing Wang
- Protein-Nucleic Acid Interaction Section, Structural Biophysics Laboratory, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
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11
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Wang Z, Ji X, Hao Y, Hong K, Ma L, Li D, Shao Y. Premature Stop Codon at Residue 101 within HIV-1 Rev Does Not Influence Viral Replication of Clade BC but Severely Reduces Viral Fitness of Clade B. Virol Sin 2019; 35:181-190. [PMID: 31828587 DOI: 10.1007/s12250-019-00179-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Accepted: 10/17/2019] [Indexed: 11/26/2022] Open
Abstract
HIV-1 Rev is an accessory protein that plays a key role in nuclear exportation, stabilization, and translation of the viral mRNAs. Rev of HIV-1 clade BC often shows a truncation of 16 AAs due to a premature stop codon at residue 101. This stop codon presents the highest frequency in clade BC and the lowest frequency in clade B. In order to discover the potential biological effect of this truncation on Rev activity and virus replication of clade BC, we constructed Rev expression vectors of clade BC with or without 16 AAs within C-terminal separately, and replaced the stop codon by Q in a CRF07_BC infectious clone. We found that 16 AAs truncation had no effect on expression and activity of Rev in clade BC. Also, the mutation from the stop codon to Q had no effect on virus replication of clade BC. Next, to investigate the effect of this truncation on Rev activity and replication capacity of clade B, Rev expression vectors of clade B carrying or lacking 16 AAs in C-terminal were constructed respectively, and residue Q at position 101 within Rev was substituted by the stop codon in a clade B infectious clone. It was found that 16 AAs truncation significantly down-regulated Rev expression and impaired clade B Rev activity. Furthermore, a Q-to-stop codon substitution within Rev significantly reduced viral replication fitness of clade B. These results indicate that the premature stop codon at residue 101 within Rev exerts diverse impact on viral replication among different HIV-1 clades.
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Affiliation(s)
- Zheng Wang
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China.
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China.
| | - Xiaolin Ji
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
| | - Yanling Hao
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
| | - Kunxue Hong
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
| | - Liying Ma
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
| | - Dan Li
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China
| | - Yiming Shao
- State Key Laboratory of Infectious Diseases Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Chinese Center for Disease Control and Prevention, Beijing, 102206, China.
- Division of Research of Virology and Immunology, National Center for AIDS/STD Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, 102206, China.
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12
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Pabis M, Corsini L, Vincendeau M, Tripsianes K, Gibson TJ, Brack-Werner R, Sattler M. Modulation of HIV-1 gene expression by binding of a ULM motif in the Rev protein to UHM-containing splicing factors. Nucleic Acids Res 2019; 47:4859-4871. [PMID: 30892606 PMCID: PMC6511859 DOI: 10.1093/nar/gkz185] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 03/04/2019] [Accepted: 03/18/2019] [Indexed: 12/01/2022] Open
Abstract
The HIV-1 protein Rev is essential for virus replication and ensures the expression of partially spliced and unspliced transcripts. We identified a ULM (UHM ligand motif) motif in the Arginine-Rich Motif (ARM) of the Rev protein. ULMs (UHM ligand motif) mediate protein interactions during spliceosome assembly by binding to UHM (U2AF homology motifs) domains. Using NMR, biophysical methods and crystallography we show that the Rev ULM binds to the UHMs of U2AF65 and SPF45. The highly conserved Trp45 in the Rev ULM is crucial for UHM binding in vitro, for Rev co-precipitation with U2AF65 in human cells and for proper processing of HIV transcripts. Thus, Rev-ULM interactions with UHM splicing factors contribute to the regulation of HIV-1 transcript processing, also at the splicing level. The Rev ULM is an example of viral mimicry of host short linear motifs that enables the virus to interfere with the host molecular machinery.
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Affiliation(s)
- Marta Pabis
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
| | - Lorenzo Corsini
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
| | - Michelle Vincendeau
- Institute of Virology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Research Unit Cellular Signal Integration, Helmholtz Zentrum München, Neuherberg, 85 764, Germany
| | - Konstantinos Tripsianes
- CEITEC - Central European Institute of Technology, Masaryk University, Brno 62 500, Czech Republic
| | | | - Ruth Brack-Werner
- Institute of Virology, Helmholtz Zentrum München, Neuherberg 85 764, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München, Neuherberg 85 764, Germany.,Center for Integrated Protein Science Munich, Department Chemie, TU München, Garching 85748, Germany
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13
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Jayaraman B, Fernandes JD, Yang S, Smith C, Frankel AD. Highly Mutable Linker Regions Regulate HIV-1 Rev Function and Stability. Sci Rep 2019; 9:5139. [PMID: 30914719 PMCID: PMC6435700 DOI: 10.1038/s41598-019-41582-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 03/05/2019] [Indexed: 11/12/2022] Open
Abstract
HIV-1 Rev is an essential viral regulatory protein that facilitates the nuclear export of intron-containing viral mRNAs. It is organized into structured, functionally well-characterized motifs joined by less understood linker regions. Our recent competitive deep mutational scanning study confirmed many known constraints in Rev’s established motifs, but also identified positions of mutational plasticity, most notably in surrounding linker regions. Here, we probe the mutational limits of these linkers by testing the activities of multiple truncation and mass substitution mutations. We find that these regions possess previously unknown structural, functional or regulatory roles, not apparent from systematic point mutational approaches. Specifically, the N- and C-termini of Rev contribute to protein stability; mutations in a turn that connects the two main helices of Rev have different effects in different contexts; and a linker region which connects the second helix of Rev to its nuclear export sequence has structural requirements for function. Thus, Rev function extends beyond its characterized motifs, and is tuned by determinants within seemingly plastic portions of its sequence. Additionally, Rev’s ability to tolerate many of these massive truncations and substitutions illustrates the overall mutational and functional robustness inherent in this viral protein.
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Affiliation(s)
- Bhargavi Jayaraman
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, 94158, USA
| | - Jason D Fernandes
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, 94158, USA.,UCSC Genomics Institute/Howard Hughes Medical Institute, University of Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Shumin Yang
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, 94158, USA.,School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Cynthia Smith
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, 94158, USA
| | - Alan D Frankel
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, CA, 94158, USA.
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14
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Dearborn AD, Eren E, Watts NR, Palmer IW, Kaufman JD, Steven AC, Wingfield PT. Structure of an RNA Aptamer that Can Inhibit HIV-1 by Blocking Rev-Cognate RNA (RRE) Binding and Rev-Rev Association. Structure 2018; 26:1187-1195.e4. [PMID: 30017564 DOI: 10.1016/j.str.2018.06.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 04/24/2018] [Accepted: 05/31/2018] [Indexed: 12/30/2022]
Abstract
HIV-1 Rev protein mediates nuclear export of unspliced and partially spliced viral RNAs for production of viral genomes and structural proteins. Rev assembles on a 351-nt Rev response element (RRE) within viral transcripts and recruits host export machinery. Small (<40-nt) RNA aptamers that compete with the RRE for Rev binding inhibit HIV-1 viral replication. We determined the X-ray crystal structure of a potential anti-HIV-1 aptamer that binds Rev with high affinity (Kd = 5.9 nM). The aptamer is structurally similar to the RRE high-affinity site but forms additional contacts with Rev unique to its sequence. Exposed bases of the aptamer interleave with the guanidinium groups of two arginines of Rev, forming stacking interactions and hydrogen bonds. The aptamer also obstructs an oligomerization interface of Rev, blocking Rev self-assembly. We propose that this aptamer can inhibit HIV-1 replication by interfering with Rev-RRE, Rev-Rev, and possibly Rev-host protein interactions.
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Affiliation(s)
- Altaira D Dearborn
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Elif Eren
- The Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Norman R Watts
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Ira W Palmer
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Joshua D Kaufman
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Alasdair C Steven
- The Laboratory of Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA
| | - Paul T Wingfield
- The Protein Expression Laboratory, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD 20892, USA.
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15
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Heymann JB. Single particle reconstruction and validation using Bsoft for the map challenge. J Struct Biol 2018; 204:90-95. [PMID: 29981840 DOI: 10.1016/j.jsb.2018.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 06/12/2018] [Accepted: 07/04/2018] [Indexed: 11/18/2022]
Abstract
The Bsoft package is aimed at processing electron micrographs for the determination of the three-dimensional structures of biological specimens. Recent advances in hardware allow us to solve structures to near atomic resolution using single particle analysis (SPA). The Map Challenge offered me an opportunity to test the ability of Bsoft to produce reconstructions from cryo-electron micrographs at the best resolution. I also wanted to understand what needed to be done to work towards full automation with validation. Here, I present two cases for the Map Challenge using Bsoft: ß-galactosidase and GroEL. I processed two independent subsets in each case with resolution-limited alignment. In both cases the reconstructions approached the expected resolution within a few iterations of alignment. I further validated the results by coherency-testing: i.e., that the reconstructions from real particles give better resolutions than reconstructions from the same number of aligned noise images. The key operations requiring attention for full automation are: particle picking, faster accurate alignment, proper mask generation, appropriate map sharpening, and understanding the amount of data needed to reach a desired resolution.
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Affiliation(s)
- J Bernard Heymann
- Laboratory for Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, NIH, Bethesda, MD 20892, United States.
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16
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Watts NR, Eren E, Zhuang X, Wang YX, Steven AC, Wingfield PT. A new HIV-1 Rev structure optimizes interaction with target RNA (RRE) for nuclear export. J Struct Biol 2018; 203:102-108. [PMID: 29605570 DOI: 10.1016/j.jsb.2018.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 03/27/2018] [Accepted: 03/28/2018] [Indexed: 02/06/2023]
Abstract
HIV-1 Rev mediates the nuclear export of unspliced and partially-spliced viral transcripts for the production of progeny genomes and structural proteins. In this process, four (or more) copies of Rev assemble onto a highly-structured 351-nt region in such viral transcripts, the Rev response element (RRE). How this occurs is not known. The Rev assembly domain has a helical-hairpin structure which associates through three (A-A, B-B and C-C) interfaces. The RRE has the topology of an upper-case letter A, with the two known Rev binding sites mapping onto the legs of the A. We have determined a crystal structure for the Rev assembly domain at 2.25 Å resolution, without resort to either mutations or chaperones. It shows that B-B dimers adopt an arrangement reversed relative to that previously reported, and join through a C-C interface to form tetramers. The new subunit arrangement shows how four Rev molecules can assemble on the two sites on the RRE to form the specificity checkpoint, and how further copies add through A-A interactions. Residues at the C-C interface, specifically the Pro31-Trp45 axis, are a potential target for intervention.
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Affiliation(s)
- Norman R Watts
- Protein Expression Laboratory, NIAMS, NIH, Bethesda, MD 20892, USA
| | - Elif Eren
- Laboratory of Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USA
| | - Xiaolei Zhuang
- Protein Expression Laboratory, NIAMS, NIH, Bethesda, MD 20892, USA
| | - Yun-Xing Wang
- Structural Biophysics Laboratory, NCI, NIH, Frederick, MD 21702, USA
| | - Alasdair C Steven
- Laboratory of Structural Biology Research, NIAMS, NIH, Bethesda, MD 20892, USA
| | - Paul T Wingfield
- Protein Expression Laboratory, NIAMS, NIH, Bethesda, MD 20892, USA.
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17
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Heymann JB. Guidelines for using Bsoft for high resolution reconstruction and validation of biomolecular structures from electron micrographs. Protein Sci 2017; 27:159-171. [PMID: 28891250 DOI: 10.1002/pro.3293] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/12/2022]
Abstract
Cryo-electron microscopy (cryoEM) is becoming popular as a tool to solve biomolecular structures with the recent availability of direct electron detectors allowing automated acquisition of high resolution data. The Bsoft software package, developed over 20 years for analyzing electron micrographs, offers a full workflow for validated single particle analysis with extensive functionality, enabling customization for specific cases. With the increasing use of cryoEM and its automation, proper validation of the results is a bigger concern. The three major validation approaches, independent data sets, resolution-limited processing, and coherence testing, can be incorporated into any Bsoft workflow. Here, the main workflow is divided into four phases: (i) micrograph preprocessing, (ii) particle picking, (iii) particle alignment and reconstruction, and (iv) interpretation. Each of these phases represents a conceptual unit that can be automated, followed by a check point to assess the results. The aim in the first three phases is to reconstruct one or more validated maps at the best resolution possible. Map interpretation then involves identification of components, segmentation, quantification, and modeling. The algorithms in Bsoft are well established, with future plans focused on ease of use, automation and institutionalizing validation.
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Affiliation(s)
- J Bernard Heymann
- Laboratory for Structural Biology Research, National Institute of Arthritis, Musculoskeletal and Skin Diseases, NIH, Bethesda, Maryland, 20892
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18
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Zhuang X, Watts NR, Palmer IW, Kaufman JD, Dearborn AD, Trenbeath JL, Eren E, Steven AC, Rader C, Wingfield PT. Chimeric rabbit/human Fab antibodies against the hepatitis Be-antigen and their potential applications in assays, characterization, and therapy. J Biol Chem 2017; 292:16760-16772. [PMID: 28842495 DOI: 10.1074/jbc.m117.802272] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 08/15/2017] [Indexed: 01/05/2023] Open
Abstract
Hepatitis B virus (HBV) infection afflicts millions worldwide, causing cirrhosis and liver cancer. HBV e-antigen (HBeAg), a clinical marker for disease severity, is a soluble variant of the viral capsid protein. HBeAg is not required for viral replication but is implicated in establishing immune tolerance and chronic infection. The structure of recombinant e-antigen (rHBeAg) was recently determined, yet to date, the exact nature and quantitation of HBeAg still remain uncertain. Here, to further characterize HBeAg, we used phage display to produce a panel of chimeric rabbit/human monoclonal antibody fragments (both Fab and scFv) against rHBeAg. Several of the Fab/scFv, expressed in Escherichia coli, had unprecedentedly high binding affinities (Kd ∼10-12 m) and high specificity. We used Fab/scFv in the context of an enzyme-linked immunosorbent assay (ELISA) for HBeAg quantification, which we compared with commercially available kits and verified with seroconversion panels, the WHO HBeAg standard, rHBeAg, and patient plasma samples. We found that the specificity and sensitivity are superior to those of existing commercial assays. To identify potential fine differences between rHBeAg and HBeAg, we used these Fabs in microscale immunoaffinity chromatography to purify HBeAg from individual patient plasmas. Western blotting and MS results indicated that rHBeAg and HBeAg are essentially structurally identical, although HBeAg from different patients exhibits minor carboxyl-terminal heterogeneity. We discuss several potential applications for the humanized Fab/scFv.
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Affiliation(s)
| | | | | | | | | | - Joni L Trenbeath
- Department of Transfusion Medicine, Warren Grant Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, and
| | - Elif Eren
- Laboratory of Structural Biology Research, NIAMS, National Institutes of Health, Bethesda, Maryland 20892
| | - Alasdair C Steven
- Laboratory of Structural Biology Research, NIAMS, National Institutes of Health, Bethesda, Maryland 20892
| | - Christoph Rader
- the Department of Immunology and Microbiology, The Scripps Research Institute, Jupiter, Florida 33458
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19
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Nuclear Export Signal Masking Regulates HIV-1 Rev Trafficking and Viral RNA Nuclear Export. J Virol 2017; 91:JVI.02107-16. [PMID: 27852860 DOI: 10.1128/jvi.02107-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 11/14/2016] [Indexed: 12/28/2022] Open
Abstract
HIV-1's Rev protein forms a homo-oligomeric adaptor complex linking viral RNAs to the cellular CRM1/Ran-GTP nuclear export machinery through the activity of Rev's prototypical leucine-rich nuclear export signal (NES). In this study, we used a functional fluorescently tagged Rev fusion protein as a platform to study the effects of modulating Rev NES identity, number, position, or strength on Rev subcellular trafficking, viral RNA nuclear export, and infectious virion production. We found that Rev activity was remarkably tolerant of diverse NES sequences, including supraphysiological NES (SNES) peptides that otherwise arrest CRM1 transport complexes at nuclear pores. Rev's ability to tolerate a SNES was both position and multimerization dependent, an observation consistent with a model wherein Rev self-association acts to transiently mask the NES peptide(s), thereby biasing Rev's trafficking into the nucleus. Combined imaging and functional assays also indicated that NES masking underpins Rev's well-known tendency to accumulate at the nucleolus, as well as Rev's capacity to activate optimal levels of late viral gene expression. We propose that Rev multimerization and NES masking regulates Rev's trafficking to and retention within the nucleus even prior to RNA binding. IMPORTANCE HIV-1 infects more than 34 million people worldwide causing >1 million deaths per year. Infectious virion production is activated by the essential viral Rev protein that mediates nuclear export of intron-bearing late-stage viral mRNAs. Rev's shuttling into and out of the nucleus is regulated by the antagonistic activities of both a peptide-encoded N-terminal nuclear localization signal and C-terminal nuclear export signal (NES). How Rev and related viral proteins balance strong import and export activities in order to achieve optimal levels of viral gene expression is incompletely understood. We provide evidence that multimerization provides a mechanism by which Rev transiently masks its NES peptide, thereby biasing its trafficking to and retention within the nucleus. Targeted pharmacological disruption of Rev-Rev interactions should perturb multiple Rev activities, both Rev-RNA binding and Rev's trafficking to the nucleus in the first place.
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