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Levanova AA, Poranen MM. Utilization of Bacteriophage phi6 for the Production of High-Quality Double-Stranded RNA Molecules. Viruses 2024; 16:166. [PMID: 38275976 PMCID: PMC10818839 DOI: 10.3390/v16010166] [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: 12/24/2023] [Revised: 01/12/2024] [Accepted: 01/18/2024] [Indexed: 01/27/2024] Open
Abstract
Double-stranded RNA (dsRNA) molecules are mediators of RNA interference (RNAi) in eukaryotic cells. RNAi is a conserved mechanism of post-transcriptional silencing of genes cognate to the sequences of the applied dsRNA. RNAi-based therapeutics for the treatment of rare hereditary diseases have recently emerged, and the first sprayable dsRNA biopesticide has been proposed for registration. The range of applications of dsRNA molecules will likely expand in the future. Therefore, cost-effective methods for the efficient large-scale production of high-quality dsRNA are in demand. Conventional approaches to dsRNA production rely on the chemical or enzymatic synthesis of single-stranded (ss)RNA molecules with a subsequent hybridization of complementary strands. However, the yield of properly annealed biologically active dsRNA molecules is low. As an alternative approach, we have developed methods based on components derived from bacteriophage phi6, a dsRNA virus encoding RNA-dependent RNA polymerase (RdRp). Phi6 RdRp can be harnessed for the enzymatic production of high-quality dsRNA molecules. The isolated RdRp efficiently synthesizes dsRNA in vitro on a heterologous ssRNA template of any length and sequence. To scale up dsRNA production, we have developed an in vivo system where phi6 polymerase complexes produce target dsRNA molecules inside Pseudomonas cells.
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Affiliation(s)
- Alesia A. Levanova
- Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, 00014 Helsinki, Finland;
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2
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Heymann JB. Structural Studies of Bacteriophage Φ6 and Its Transformations during Its Life Cycle. Viruses 2023; 15:2404. [PMID: 38140645 PMCID: PMC10747372 DOI: 10.3390/v15122404] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 12/01/2023] [Accepted: 12/04/2023] [Indexed: 12/24/2023] Open
Abstract
From the first isolation of the cystovirus bacteriophage Φ6 from Pseudomonas syringae 50 years ago, we have progressed to a better understanding of the structure and transformations of many parts of the virion. The three-layered virion, encapsulating the tripartite double-stranded RNA (dsRNA) genome, breaches the cell envelope upon infection, generates its own transcripts, and coopts the bacterial machinery to produce its proteins. The generation of a new virion starts with a procapsid with a contracted shape, followed by the packaging of single-stranded RNA segments with concurrent expansion of the capsid, and finally replication to reconstitute the dsRNA genome. The outer two layers are then added, and the fully formed virion released by cell lysis. Most of the procapsid structure, composed of the proteins P1, P2, P4, and P7 is now known, as well as its transformations to the mature, packaged nucleocapsid. The outer two layers are less well-studied. One additional study investigated the binding of the host protein YajQ to the infecting nucleocapsid, where it enhances the transcription of the large RNA segment that codes for the capsid proteins. Finally, I relate the structural aspects of bacteriophage Φ6 to those of other dsRNA viruses, noting the similarities and differences.
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Affiliation(s)
- J. Bernard Heymann
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr., Bethesda, MD 20892, USA; ; Tel.: +1-301-846-6924
- National Cryo-EM Program, Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick, MD 21701, USA
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3
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Gottlieb P, Alimova A. Discovery and Classification of the φ6 Bacteriophage: An Historical Review. Viruses 2023; 15:1308. [PMID: 37376608 DOI: 10.3390/v15061308] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/30/2023] [Accepted: 05/28/2023] [Indexed: 06/29/2023] Open
Abstract
The year 2023 marks the fiftieth anniversary of the discovery of the bacteriophage φ6. The review provides a look back on the initial discovery and classification of the lipid-containing and segmented double-stranded RNA (dsRNA) genome-containing bacteriophage-the first identified cystovirus. The historical discussion describes, for the most part, the first 10 years of the research employing contemporary mutation techniques, biochemical, and structural analysis to describe the basic outline of the virus replication mechanisms and structure. The physical nature of φ6 was initially controversial as it was the first bacteriophage found that contained segmented dsRNA, resulting in a series of early publications that defined the unusual genomic quality. The technology and methods utilized in the initial research (crude by current standards) meant that the first studies were quite time-consuming, hence the lengthy period covered by this review. Yet when the data were accepted, the relationship to the reoviruses was apparent, launching great interest in cystoviruses, research that continues to this day.
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Affiliation(s)
- Paul Gottlieb
- Department of Molecular, Cellular and Biomedical Sciences, The City University of New York School of Medicine, New York, NY 10031, USA
| | - Aleksandra Alimova
- Department of Molecular, Cellular and Biomedical Sciences, The City University of New York School of Medicine, New York, NY 10031, USA
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4
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Gottlieb P, Alimova A. Heterologous RNA Recombination in the Cystoviruses φ6 and φ8: A Mechanism of Viral Variation and Genome Repair. Viruses 2022; 14:v14112589. [PMID: 36423198 PMCID: PMC9697746 DOI: 10.3390/v14112589] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 11/15/2022] [Accepted: 11/18/2022] [Indexed: 11/23/2022] Open
Abstract
Recombination and mutation of viral genomes represent major mechanisms for viral evolution and, in many cases, moderate pathogenicity. Segmented genome viruses frequently undergo reassortment of the genome via multiple infection of host organisms, with influenza and reoviruses being well-known examples. Specifically, major genomic shifts mediated by reassortment are responsible for radical changes in the influenza antigenic determinants that can result in pandemics requiring rapid preventative responses by vaccine modifications. In contrast, smaller mutational changes brought about by the error-prone viral RNA polymerases that, for the most part, lack a replication base mispairing editing function produce small mutational changes in the RNA genome during replication. Referring again to the influenza example, the accumulated mutations-known as drift-require yearly vaccine updating and rapid worldwide distribution of each new formulation. Coronaviruses with a large positive-sense RNA genome have long been known to undergo intramolecular recombination likely mediated by copy choice of the RNA template by the viral RNA polymerase in addition to the polymerase-based mutations. The current SARS-CoV-2 origin debate underscores the importance of understanding the plasticity of viral genomes, particularly the mechanisms responsible for intramolecular recombination. This review describes the use of the cystovirus bacteriophage as an experimental model for recombination studies in a controlled manner, resulting in the development of a model for intramolecular RNA genome alterations. The review relates the sequence of experimental studies from the laboratory of Leonard Mindich, PhD at the Public Health Research Institute-then in New York City-and covers a period of approximately 12 years. Hence, this is a historical scientific review of research that has the greatest relevance to current studies of emerging RNA virus pathogens.
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5
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Gottlieb P, Alimova A. RNA Packaging in the Cystovirus Bacteriophages: Dynamic Interactions during Capsid Maturation. Int J Mol Sci 2022; 23:ijms23052677. [PMID: 35269819 PMCID: PMC8910881 DOI: 10.3390/ijms23052677] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 02/16/2022] [Accepted: 02/23/2022] [Indexed: 12/10/2022] Open
Abstract
The bacteriophage family Cystoviridae consists of a single genus, Cystovirus, that is lipid-containing with three double-stranded RNA (ds-RNA) genome segments. With regard to the segmented dsRNA genome, they resemble the family Reoviridae. Therefore, the Cystoviruses have long served as a simple model for reovirus assembly. This review focuses on important developments in the study of the RNA packaging and replication mechanisms, emphasizing the structural conformations and dynamic changes during maturation of the five proteins required for viral RNA synthesis, P1, P2, P4, P7, and P8. Together these proteins constitute the procapsid/polymerase complex (PC) and nucleocapsid (NC) of the Cystoviruses. During viral assembly and RNA packaging, the five proteins must function in a coordinated fashion as the PC and NC undergo expansion with significant position translation. The review emphasizes this facet of the viral assembly process and speculates on areas suggestive of additional research efforts.
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6
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Konevtsova OV, Roshal DS, Podgornik R, Rochal SB. Irreversible and reversible morphological changes in the φ6 capsid and similar viral shells: symmetry and micromechanics. SOFT MATTER 2020; 16:9383-9392. [PMID: 32945317 DOI: 10.1039/d0sm01338b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Understanding the physicochemical processes occurring in viruses during their maturation is of fundamental importance since only mature viruses can infect host cells. Here we consider the irreversible and reversible morphological changes that occur with the dodecahedral φ6 procapsid during the sequential packaging of 3 RNA segments forming the viral genome. It is shown that the dodecahedral shape of all the four observed capsid states is perfectly reproduced by a sphere radially deformed by only two irreducible spherical harmonics with icosahedral symmetry and wave numbers l = 6 and l = 10. The rotation of proteins around the 3-fold axes at the Procapsid → Intermediate 1 irreversible transformation is in fact also well described with the shear field containing only two irreducible harmonics with the same two wave numbers. The high stability of the Intermediate 1 state is discussed and the shapes of the Intermediate 2 state and Capsid (reversibly transforming back to the Intermediate 1 state) are shown to be mainly due to the isotropic pressure that the encapsidated RNA segments exert on the shell walls. The hidden symmetry of the capsid and the physicochemical features of the in vitro genome extraction from the viral shell are also elucidated.
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Affiliation(s)
- Olga V Konevtsova
- Physics Faculty, Southern Federal University, Rostov-on-Don, Russia.
| | - Daria S Roshal
- Physics Faculty, Southern Federal University, Rostov-on-Don, Russia.
| | - Rudolf Podgornik
- Department of Theoretical Physics, JoŽef Stefan Institute, SI-1000 Ljubljana, Slovenia and Department of Physics, Faculty of Mathematics and Physics, University of Ljubljana, SI-1000 Ljubljana, Slovenia and School of Physical Sciences and Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Sergei B Rochal
- Physics Faculty, Southern Federal University, Rostov-on-Don, Russia.
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7
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San Martín C. Virus Maturation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1215:129-158. [DOI: 10.1007/978-3-030-14741-9_7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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8
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Borodavka A, Desselberger U, Patton JT. Genome packaging in multi-segmented dsRNA viruses: distinct mechanisms with similar outcomes. Curr Opin Virol 2018; 33:106-112. [PMID: 30145433 PMCID: PMC6289821 DOI: 10.1016/j.coviro.2018.08.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/31/2018] [Accepted: 08/01/2018] [Indexed: 12/20/2022]
Abstract
Segmented double-stranded (ds)RNA viruses share remarkable similarities in their replication strategy and capsid structure. During virus replication, positive-sense single-stranded (+)RNAs are packaged into procapsids, where they serve as templates for dsRNA synthesis, forming progeny particles containing a complete equimolar set of genome segments. How the +RNAs are recognized and stoichiometrically packaged remains uncertain. Whereas bacteriophages of the Cystoviridae family rely on specific RNA-protein interactions to select appropriate +RNAs for packaging, viruses of the Reoviridae instead rely on specific inter-molecular interactions between +RNAs that guide multi-segmented genome assembly. While these families use distinct mechanisms to direct +RNA packaging, both yield progeny particles with a complete set of genomic dsRNAs.
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Affiliation(s)
- Alexander Borodavka
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Ulrich Desselberger
- Department of Medicine, Addenbrooke's Hospital, University of Cambridge, Cambridge CB2 0QQ, UK
| | - John T Patton
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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9
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Abstract
Double-stranded RNA viruses infect a wide spectrum of hosts, including animals, plants, fungi, and bacteria. Yet genome replication mechanisms of these viruses are conserved. During the infection cycle, a proteinaceous capsid, the polymerase complex, is formed. An essential component of this capsid is the viral RNA polymerase that replicates and transcribes the enclosed viral genome. The polymerase complex structure is well characterized for many double-stranded RNA viruses. However, much less is known about the hierarchical molecular interactions that take place in building up such complexes. Using the bacteriophage Φ6 self-assembly system, we obtained novel insights into the processes that mediate polymerase subunit incorporation into the polymerase complex for generation of functional structures. The results presented pave the way for the exploitation and engineering of viral self-assembly processes for biomedical and synthetic biology applications. An understanding of viral assembly processes at the molecular level may also facilitate the development of antivirals that target viral capsid assembly. Double-stranded RNA (dsRNA) viruses package several RNA-dependent RNA polymerases (RdRp) together with their dsRNA genome into an icosahedral protein capsid known as the polymerase complex. This structure is highly conserved among dsRNA viruses but is not found in any other virus group. RdRp subunits typically interact directly with the main capsid proteins, close to the 5-fold symmetric axes, and perform viral genome replication and transcription within the icosahedral protein shell. In this study, we utilized Pseudomonas phage Φ6, a well-established virus self-assembly model, to probe the potential roles of the RdRp in dsRNA virus assembly. We demonstrated that Φ6 RdRp accelerates the polymerase complex self-assembly process and contributes to its conformational stability and integrity. We highlight the role of specific amino acid residues on the surface of the RdRp in its incorporation during the self-assembly reaction. Substitutions of these residues reduce RdRp incorporation into the polymerase complex during the self-assembly reaction. Furthermore, we determined that the overall transcription efficiency of the Φ6 polymerase complex increased when the number of RdRp subunits exceeded the number of genome segments. These results suggest a mechanism for RdRp recruitment in the polymerase complex and highlight its novel role in virion assembly, in addition to the canonical RNA transcription and replication functions.
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10
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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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11
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Sun Z, El Omari K, Sun X, Ilca SL, Kotecha A, Stuart DI, Poranen MM, Huiskonen JT. Double-stranded RNA virus outer shell assembly by bona fide domain-swapping. Nat Commun 2017; 8:14814. [PMID: 28287099 PMCID: PMC5355851 DOI: 10.1038/ncomms14814] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/26/2017] [Indexed: 12/30/2022] Open
Abstract
Correct outer protein shell assembly is a prerequisite for virion infectivity in many multi-shelled dsRNA viruses. In the prototypic dsRNA bacteriophage φ6, the assembly reaction is promoted by calcium ions but its biomechanics remain poorly understood. Here, we describe the near-atomic resolution structure of the φ6 double-shelled particle. The outer T=13 shell protein P8 consists of two alpha-helical domains joined by a linker, which allows the trimer to adopt either a closed or an open conformation. The trimers in an open conformation swap domains with each other. Our observations allow us to propose a mechanistic model for calcium concentration regulated outer shell assembly. Furthermore, the structure provides a prime exemplar of bona fide domain-swapping. This leads us to extend the theory of domain-swapping from the level of monomeric subunits and multimers to closed spherical shells, and to hypothesize a mechanism by which closed protein shells may arise in evolution. Double-shelled bacteriophage φ6 is a well-studied model system used to understand assembly of dsRNA viruses. Here the authors report a near-atomic resolution cryo-EM structure of φ6 and propose a model for the structural transitions occurring in the outer shell during genome packaging.
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Affiliation(s)
- Zhaoyang Sun
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Kamel El Omari
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Xiaoyu Sun
- Department of Biosciences, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Serban L Ilca
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Abhay Kotecha
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - David I Stuart
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Minna M Poranen
- Department of Biosciences, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
| | - Juha T Huiskonen
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.,Department of Biosciences, University of Helsinki, Viikinkaari 9, Helsinki 00014, Finland
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12
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Alphonse S, Ghose R. Cystoviral RNA-directed RNA polymerases: Regulation of RNA synthesis on multiple time and length scales. Virus Res 2017; 234:135-152. [PMID: 28104452 PMCID: PMC5476504 DOI: 10.1016/j.virusres.2017.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 01/04/2017] [Accepted: 01/09/2017] [Indexed: 12/18/2022]
Abstract
Role of the RNA polymerase in the cystoviral life-cycle. Spatio-temporal regulation of RNA synthesis in cystoviruses. Emerging role of conformational dynamics in polymerase function.
P2, an RNA-directed RNA polymerase (RdRP), is encoded on the largest of the three segments of the double-stranded RNA genome of cystoviruses. P2 performs the dual tasks of replication and transcription de novo on single-stranded RNA templates, and plays a critical role in the viral life-cycle. Work over the last few decades has yielded a wealth of biochemical and structural information on the functional regulation of P2, on its role in the spatiotemporal regulation of RNA synthesis and its variability across the Cystoviridae family. These range from atomic resolution snapshots of P2 trapped in functionally significant states, in complex with catalytic/structural metal ions, polynucleotide templates and substrate nucleoside triphosphates, to P2 in the context of viral capsids providing structural insight into the assembly of supramolecular complexes and regulatory interactions therein. They include in vitro biochemical studies using P2 purified to homogeneity and in vivo studies utilizing infectious core particles. Recent advances in experimental techniques have also allowed access to the temporal dimension and enabled the characterization of dynamics of P2 on the sub-nanosecond to millisecond timescale through measurements of nuclear spin relaxation in solution and single molecule studies of transcription from seconds to minutes. Below we summarize the most significant results that provide critical insight into the role of P2 in regulating RNA synthesis in cystoviruses.
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Affiliation(s)
- Sébastien Alphonse
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY 10031, United States.
| | - Ranajeet Ghose
- Department of Chemistry and Biochemistry, The City College of New York, New York, NY 10031, United States; Graduate Programs in Biochemistry, The Graduate Center of CUNY, New York, NY 10016, United States; Graduate Programs in Chemistry, The Graduate Center of CUNY, New York, NY 10016, United States; Graduate Programs in Physics, The Graduate Center of CUNY, New York, NY 10016, United States.
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13
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Hanhijärvi KJ, Ziedaite G, Bamford DH, Hæggström E, Poranen MM. Single-molecule measurements of viral ssRNA packaging. RNA (NEW YORK, N.Y.) 2017; 23:119-129. [PMID: 27803153 PMCID: PMC5159644 DOI: 10.1261/rna.057471.116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 10/27/2016] [Indexed: 06/06/2023]
Abstract
Genome packaging of double-stranded RNA (dsRNA) phages has been widely studied using biochemical and molecular biology methods. We adapted the existing in vitro packaging system of one such phage for single-molecule experimentation. To our knowledge, this is the first attempt to study the details of viral RNA packaging using optical tweezers. Pseudomonas phage φ6 is a dsRNA virus with a tripartite genome. Positive-sense (+) single-stranded RNA (ssRNA) genome precursors are packaged into a preformed procapsid (PC), where negative strands are synthesized. We present single-molecule measurements of the viral ssRNA packaging by the φ6 PC. Our data show that packaging proceeds intermittently in slow and fast phases, which likely reflects differences in the unfolding of the RNA secondary structures of the ssRNA being packaged. Although the mean packaging velocity was relatively low (0.07-0.54 nm/sec), packaging could reach 4.62 nm/sec during the fast packaging phase.
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Affiliation(s)
| | - Gabija Ziedaite
- Department of Biosciences, University of Helsinki, Helsinki 00014, Finland
| | - Dennis H Bamford
- Department of Biosciences, University of Helsinki, Helsinki 00014, Finland
- Institute of Biotechnology, University of Helsinki, Helsinki 00014, Finland
| | - Edward Hæggström
- Department of Physics, University of Helsinki, Helsinki 00014, Finland
| | - Minna M Poranen
- Department of Biosciences, University of Helsinki, Helsinki 00014, Finland
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14
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Oikonomou CM, Chang YW, Jensen GJ. A new view into prokaryotic cell biology from electron cryotomography. Nat Rev Microbiol 2016; 14:205-20. [PMID: 26923112 PMCID: PMC5551487 DOI: 10.1038/nrmicro.2016.7] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electron cryotomography (ECT) enables intact cells to be visualized in 3D in an essentially native state to 'macromolecular' (∼4 nm) resolution, revealing the basic architectures of complete nanomachines and their arrangements in situ. Since its inception, ECT has advanced our understanding of many aspects of prokaryotic cell biology, from morphogenesis to subcellular compartmentalization and from metabolism to complex interspecies interactions. In this Review, we highlight how ECT has provided structural and mechanistic insights into the physiology of bacteria and archaea and discuss prospects for the future.
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Affiliation(s)
- Catherine M Oikonomou
- Howard Hughes Medical Institute; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125, USA
| | - Yi-Wei Chang
- Howard Hughes Medical Institute; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125, USA
| | - Grant J Jensen
- Howard Hughes Medical Institute; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125, USA
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15
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Alimova A, Wei H, Katz A, Spatz L, Gottlieb P. The ϕ6 cystovirus protein P7 becomes accessible to antibodies in the transcribing nucleocapsid: a probe for viral structural elements. PLoS One 2015; 10:e0122160. [PMID: 25799314 PMCID: PMC4370446 DOI: 10.1371/journal.pone.0122160] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 02/15/2015] [Indexed: 01/01/2023] Open
Abstract
Protein P7 is a component of the cystovirus viral polymerase complex. In the unpackaged procapsid, the protein is situated in close proximity to the viral directed RNA polymerase, P2. Cryo-electron microscopy difference maps from the species ϕ6 procapsid have demonstrated that P7 and P2 likely interact prior to viral RNA packaging. The location of P7 in the post-packaged nucleocapsid (NC) remains unknown. P7 may translocate closer to the five-fold axis of a filled procapsid but this has not been directly visualized. We propose that monoclonal antibodies (Mabs) can be selected that serve as probe- reagents for viral assembly and structure. A set of Mabs have been isolated that recognize and bind to the ϕ6 P7. The antibody set contains five unique Mabs, four of which recognize a linear epitope and one which recognizes a conformational epitope. The four unique Mabs that recognize a linear epitope display restricted utilization of Vκ and VH genes. The restricted genetic range among 4 of the 5 antibodies implies that the antibody repertoire is limited. The limitation could be the consequence of a paucity of exposed antigenic sites on the ϕ6 P7 surface. It is further demonstrated that within ϕ6 nucleocapsids that are primed for early-phase transcription, P7 is partially accessible to the Mabs, indicating that the nucleocapsid shell (protein P8) has undergone partial disassembly exposing the protein’s antigenic sites.
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Affiliation(s)
- Alexandra Alimova
- Sophie Davis School of Biomedical Education, City College of New York, New York, NY 10031, United States of America
| | - Hui Wei
- Sophie Davis School of Biomedical Education, City College of New York, New York, NY 10031, United States of America
| | - Al Katz
- Department of Physics, City College of New York, New York, NY 10031, United States of America
| | - Linda Spatz
- Sophie Davis School of Biomedical Education, City College of New York, New York, NY 10031, United States of America
| | - Paul Gottlieb
- Sophie Davis School of Biomedical Education, City College of New York, New York, NY 10031, United States of America
- * E-mail:
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16
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Abstract
As they mature, many capsids undergo massive conformational changes that transform their stability, reactivity, and capacity for DNA. In some cases, maturation proceeds via one or more intermediate states. These structures represent local minima in a rich energy landscape that combines contributions from subunit folding, association of subunits into capsomers, and intercapsomer interactions. We have used scanning calorimetry and cryo-electron microscopy to explore the range of capsid conformations accessible to bacteriophage HK97. To separate conformational effects from those associated with covalent cross-linking (a stabilization mechanism of HK97), a cross-link-incompetent mutant was used. The mature capsid Head I undergoes an endothermic phase transition at 60°C in which it shrinks by 7%, primarily through changes in its hexamer conformation. The transition is reversible, with a half-life of ~3 min; however, >50% of reverted capsids are severely distorted or ruptured. This observation implies that such damage is a potential hazard of large-scale structural changes such as those involved in maturation. Assuming that the risk is lower for smaller changes, this suggests a rationalization for the existence of metastable intermediates: that they serve as stepping stones that preserve capsid integrity as it switches between the radically different conformations of its precursor and mature states. Large-scale conformational changes are widespread in virus maturation and infection processes. These changes are accompanied by the release of conformational free energy as the virion (or fusogenic glycoprotein) switches from a precursor state to its mature state. Each state corresponds to a local minimum in an energy landscape. The conformational changes in capsid maturation are so radical that the question arises of how maturing capsids avoid being torn apart. Offering proof of principle, severe damage is inflicted when a bacteriophage HK97 capsid reverts from the (nonphysiological) state that it enters when heated past 60°C. We suggest that capsid proteins have been selected in part by the criterion of being able to avoid sustaining collateral damage as they mature. One way of achieving this—as with the HK97 capsid—involves breaking the overall transition down into several smaller steps in which the risk of damage is reduced.
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17
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Electrostatic interactions drive the self-assembly and the transcription activity of the Pseudomonas phage ϕ6 procapsid. J Virol 2014; 88:7112-6. [PMID: 24719418 DOI: 10.1128/jvi.00467-14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Assembly of an empty procapsid is a crucial step in the formation of many complex viruses. Here, we used the self-assembly system of the double-stranded RNA bacteriophage ϕ6 to study the role of electrostatic interactions in a scaffolding-independent procapsid assembly pathway. We demonstrate that ϕ6 procapsid assembly is sensitive to salt at both the nucleation and postnucleation steps. Furthermore, we observed that the salt sensitivity of ϕ6 procapsid-directed transcription is reversible.
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18
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Sun X, Pirttimaa MJ, Bamford DH, Poranen MM. Rescue of maturation off-pathway products in the assembly of Pseudomonas phage φ 6. J Virol 2013; 87:13279-86. [PMID: 24089550 PMCID: PMC3838280 DOI: 10.1128/jvi.02285-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 09/23/2013] [Indexed: 12/30/2022] Open
Abstract
Many complex viruses use an assembly pathway in which their genome is packaged into an empty procapsid which subsequently matures into its final expanded form. We utilized Pseudomonas phage 6, a well-established virus assembly model, to probe the plasticity of the procapsid maturation pathway. The 6 packaging nucleoside triphosphatase (NTPase), which powers sequential translocation of the three viral genomic single-stranded RNA molecules to the procapsid during capsid maturation, is part of the mature 6 virion but may spontaneously be dissociated from the procapsid shell. We demonstrate that the dissociation of NTPase subunits results in premature capsid expansion, which is detected as a change in the sedimentation velocity and as defects in RNA packaging and transcription activity. However, this dead-end conformation of the procapsids was rescued by the addition of purified NTPase hexamers, which efficiently associated on the NTPase-deficient particles and subsequently drove their contraction to the compact naive conformation. The resulting particles regained their biological and enzymatic activities, directing them into a productive maturation pathway. These observations imply that the maturation pathways of complex viruses may contain reversible steps that allow the rescue of the off-pathway conformation in an overall unidirectional virion assembly pathway. Furthermore, we provide direct experimental evidence that particles which have different physical properties (distinct sedimentation velocities and conformations) display different stages of the genome packaging program and show that the transcriptional activity of the 6 procapsids correlates with the number of associated NTPase subunits.
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Affiliation(s)
- Xiaoyu Sun
- Department of Biosciences
- Institute of Biotechnology, University of Helsinki, Viikki Biocenter, Helsinki, Finland
| | - Markus J. Pirttimaa
- Department of Biosciences
- Institute of Biotechnology, University of Helsinki, Viikki Biocenter, Helsinki, Finland
| | - Dennis H. Bamford
- Department of Biosciences
- Institute of Biotechnology, University of Helsinki, Viikki Biocenter, Helsinki, Finland
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19
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Using cryoEM Reconstruction and Phase Extension to Determine Crystal Structure of Bacteriophage ϕ6 Major Capsid Protein. Protein J 2013; 32:635-40. [DOI: 10.1007/s10930-013-9526-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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20
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Lagerstedt I, Moore WJ, Patwardhan A, Sanz-García E, Best C, Swedlow JR, Kleywegt GJ. Web-based visualisation and analysis of 3D electron-microscopy data from EMDB and PDB. J Struct Biol 2013; 184:173-81. [PMID: 24113529 PMCID: PMC3898923 DOI: 10.1016/j.jsb.2013.09.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 09/24/2013] [Accepted: 09/25/2013] [Indexed: 11/25/2022]
Abstract
The Protein Data Bank in Europe (PDBe) has developed web-based tools for the visualisation and analysis of 3D electron microscopy (3DEM) structures in the Electron Microscopy Data Bank (EMDB) and Protein Data Bank (PDB). The tools include: (1) a volume viewer for 3D visualisation of maps, tomograms and models, (2) a slice viewer for inspecting 2D slices of tomographic reconstructions, and (3) visual analysis pages to facilitate analysis and validation of maps, tomograms and models. These tools were designed to help non-experts and experts alike to get some insight into the content and assess the quality of 3DEM structures in EMDB and PDB without the need to install specialised software or to download large amounts of data from these archives. The technical challenges encountered in developing these tools, as well as the more general considerations when making archived data available to the user community through a web interface, are discussed.
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Affiliation(s)
- Ingvar Lagerstedt
- Protein Data Bank in Europe, European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SD, United Kingdom
| | - William J. Moore
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
| | - Ardan Patwardhan
- Protein Data Bank in Europe, European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SD, United Kingdom
| | - Eduardo Sanz-García
- Protein Data Bank in Europe, European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SD, United Kingdom
| | - Christoph Best
- Protein Data Bank in Europe, European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SD, United Kingdom
| | - Jason R. Swedlow
- Centre for Gene Regulation and Expression, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, United Kingdom
| | - Gerard J. Kleywegt
- Protein Data Bank in Europe, European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton CB10 1SD, United Kingdom
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21
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El Omari K, Sutton G, Ravantti J, Zhang H, Walter T, Grimes J, Bamford D, Stuart D, Mancini E. Plate tectonics of virus shell assembly and reorganization in phage φ8, a distant relative of mammalian reoviruses. Structure 2013; 21:1384-95. [PMID: 23891291 PMCID: PMC3737474 DOI: 10.1016/j.str.2013.06.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 06/26/2013] [Accepted: 06/27/2013] [Indexed: 01/07/2023]
Abstract
The hallmark of a virus is its capsid, which harbors the viral genome and is formed from protein subunits, which assemble following precise geometric rules. dsRNA viruses use an unusual protein multiplicity (120 copies) to form their closed capsids. We have determined the atomic structure of the capsid protein (P1) from the dsRNA cystovirus Φ8. In the crystal P1 forms pentamers, very similar in shape to facets of empty procapsids, suggesting an unexpected assembly pathway that proceeds via a pentameric intermediate. Unlike the elongated proteins used by dsRNA mammalian reoviruses, P1 has a compact trapezoid-like shape and a distinct arrangement in the shell, with two near-identical conformers in nonequivalent structural environments. Nevertheless, structural similarity with the analogous protein from the mammalian viruses suggests a common ancestor. The unusual shape of the molecule may facilitate dramatic capsid expansion during phage maturation, allowing P1 to switch interaction interfaces to provide capsid plasticity.
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Affiliation(s)
- Kamel El Omari
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
| | - Geoff Sutton
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
| | - Janne J. Ravantti
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, Biocenter 2, P.O. Box 56, 00014 Helsinki, Finland
| | - Hanwen Zhang
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
| | - Thomas S. Walter
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
| | - Jonathan M. Grimes
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
- Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| | - Dennis H. Bamford
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, Biocenter 2, P.O. Box 56, 00014 Helsinki, Finland
| | - David I. Stuart
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
- Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK
| | - Erika J. Mancini
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Headington, Oxford OX3 7BN, UK
- Corresponding author
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22
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Nemecek D, Boura E, Wu W, Cheng N, Plevka P, Qiao J, Mindich L, Heymann JB, Hurley JH, Steven AC. Subunit folds and maturation pathway of a dsRNA virus capsid. Structure 2013; 21:1374-83. [PMID: 23891288 PMCID: PMC3742642 DOI: 10.1016/j.str.2013.06.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 06/08/2013] [Accepted: 06/14/2013] [Indexed: 12/24/2022]
Abstract
The cystovirus ϕ6 shares several distinct features with other double-stranded RNA (dsRNA) viruses, including the human pathogen, rotavirus: segmented genomes, nonequivalent packing of 120 subunits in its icosahedral capsid, and capsids as compartments for transcription and replication. ϕ6 assembles as a dodecahedral procapsid that undergoes major conformational changes as it matures into the spherical capsid. We determined the crystal structure of the capsid protein, P1, revealing a flattened trapezoid subunit with an α-helical fold. We also solved the procapsid with cryo-electron microscopy to comparable resolution. Fitting the crystal structure into the procapsid disclosed substantial conformational differences between the two P1 conformers. Maturation via two intermediate states involves remodeling on a similar scale, besides huge rigid-body rotations. The capsid structure and its stepwise maturation that is coupled to sequential packaging of three RNA segments sets the cystoviruses apart from other dsRNA viruses as a dynamic molecular machine.
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Affiliation(s)
- Daniel Nemecek
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
- Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Evzen Boura
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
- Institute of Organic Chemistry and Biochemistry AS CR, v.v.i., Flemingovo nam. 2. 16600 Prague 6, Czech Republic
| | - Weimin Wu
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
| | - Naiqian Cheng
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
| | - Pavel Plevka
- Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
- Department of Biological Sciences, Purdue University, 915 W. State Street, West Lafayette, IN 47907
| | - Jian Qiao
- Department of Microbiology, Public Health Research Institute Center, University of Medicine and Dentistry of New Jersey, 225 Warren Street, Newark, NJ 07103
| | - Leonard Mindich
- Department of Microbiology, Public Health Research Institute Center, University of Medicine and Dentistry of New Jersey, 225 Warren Street, Newark, NJ 07103
| | - J. Bernard Heymann
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
| | - James H. Hurley
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
| | - Alasdair C. Steven
- National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, 50 South Dr, Bethesda, MD 20892
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23
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Guerrero-Ferreira RC, Wright ER. Cryo-electron tomography of bacterial viruses. Virology 2013; 435:179-86. [PMID: 23217626 DOI: 10.1016/j.virol.2012.08.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 08/08/2012] [Accepted: 08/19/2012] [Indexed: 01/15/2023]
Abstract
Bacteriophage particles contain both simple and complex macromolecular assemblages and machines that enable them to regulate the infection process under diverse environmental conditions with a broad range of bacterial hosts. Recent developments in cryo-electron tomography (cryo-ET) make it possible to observe the interactions of bacteriophages with their host cells under native-state conditions at unprecedented resolution and in three-dimensions. This review describes the application of cryo-ET to studies of bacteriophage attachment, genome ejection, assembly and egress. Current topics of investigation and future directions in the field are also discussed.
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Affiliation(s)
- Ricardo C Guerrero-Ferreira
- Division of Pediatric Infectious Diseases, Emory University School of Medicine, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA
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24
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Protein P7 of the cystovirus φ6 is located at the three-fold axis of the unexpanded procapsid. PLoS One 2012; 7:e47489. [PMID: 23077625 PMCID: PMC3471842 DOI: 10.1371/journal.pone.0047489] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
The objective of this study was to determine the location of protein P7, the RNA packaging factor, in the procapsid of the φ6 cystovirus. A comparison of cryo-electron microscopy high-resolution single particle reconstructions of the φ6 complete unexpanded procapsid, the protein P2-minus procapsid (P2 is the RNA directed RNA-polymerase), and the P7-minus procapsid, show that prior to RNA packaging the P7 protein is located near the three-fold axis of symmetry. Difference maps highlight the precise position of P7 and demonstrate that in P7-minus particles the P2 proteins are less localized with reduced densities at the three-fold axes. We propose that P7 performs the mechanical function of stabilizing P2 on the inner protein P1 shell which ensures that entering viral single-stranded RNA is replicated.
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25
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Packaging accessory protein P7 and polymerase P2 have mutually occluding binding sites inside the bacteriophage 6 procapsid. J Virol 2012; 86:11616-24. [PMID: 22896624 DOI: 10.1128/jvi.01347-12] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Bacteriophage 6 is a double-stranded RNA (dsRNA) virus whose genome is packaged sequentially as three single-stranded RNA (ssRNA) segments into an icosahedral procapsid which serves as a compartment for genome replication and transcription. The procapsid shell consists of 60 copies each of P1(A) and P1(B), two nonequivalent conformers of the P1 protein. Hexamers of the packaging ATPase P4 are mounted over the 5-fold vertices, and monomers of the RNA-dependent RNA polymerase (P2) attach to the inner surface, near the 3-fold axes. A fourth protein, P7, is needed for packaging and also promotes assembly. We used cryo-electron microscopy to localize P7 by difference mapping of procapsids with different protein compositions. We found that P7 resides on the interior surface of the P1 shell and appears to be monomeric. Its binding sites are arranged around the 3-fold axes, straddling the interface between two P1(A) subunits. Thus, P7 may promote assembly by stabilizing an initiation complex. Only about 20% of the 60 P7 binding sites were occupied in our preparations. P7 density overlaps P2 density similarly mapped, implying mutual occlusion. The known structure of the 12 homolog fits snugly into the P7 density. Both termini-which have been implicated in RNA binding-are oriented toward the adjacent 5-fold vertex, the entry pathway of ssRNA segments. Thus, P7 may promote packaging either by interacting directly with incoming RNA or by modulating the structure of the translocation pore.
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26
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Bacteriophage ϕ6 nucleocapsid surface protein 8 interacts with virus-specific membrane vesicles containing major envelope protein 9. J Virol 2012; 86:5376-9. [PMID: 22379079 DOI: 10.1128/jvi.00172-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enveloped double-stranded RNA (dsRNA) bacterial virus Pseudomonas phage ϕ6 has been developed into an advanced assembly system where purified virion proteins and genome segments self-assemble into infectious viral particles, inferring the assembly pathway. The most intriguing step is the membrane assembly occurring inside the bacterial cell. Here, we demonstrate that the middle virion shell, made of protein 8, associates with the expanded viral core particle and the virus-specific membrane vesicle.
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