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Naniima P, Naimo E, Koch S, Curth U, Alkharsah KR, Ströh LJ, Binz A, Beneke JM, Vollmer B, Böning H, Borst EM, Desai P, Bohne J, Messerle M, Bauerfeind R, Legrand P, Sodeik B, Schulz TF, Krey T. Assembly of infectious Kaposi's sarcoma-associated herpesvirus progeny requires formation of a pORF19 pentamer. PLoS Biol 2021; 19:e3001423. [PMID: 34735435 PMCID: PMC8568140 DOI: 10.1371/journal.pbio.3001423] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 09/22/2021] [Indexed: 12/25/2022] Open
Abstract
Herpesviruses cause severe diseases particularly in immunocompromised patients. Both genome packaging and release from the capsid require a unique portal channel occupying one of the 12 capsid vertices. Here, we report the 2.6 Å crystal structure of the pentameric pORF19 of the γ-herpesvirus Kaposi’s sarcoma-associated herpesvirus (KSHV) resembling the portal cap that seals this portal channel. We also present the structure of its β-herpesviral ortholog, revealing a striking structural similarity to its α- and γ-herpesviral counterparts despite apparent differences in capsid association. We demonstrate pORF19 pentamer formation in solution and provide insights into how pentamerization is triggered in infected cells. Mutagenesis in its lateral interfaces blocked pORF19 pentamerization and severely affected KSHV capsid assembly and production of infectious progeny. Our results pave the way to better understand the role of pORF19 in capsid assembly and identify a potential novel drug target for the treatment of herpesvirus-induced diseases. In herpesviruses, genome packaging and release from the capsid require a unique portal channel. Here, the authors have resolved the crystal structure of a pentameric KSHV pORF19 assembly and find that it resembles the herpesviral portal cap and provides insights how the viral genome is retained within the capsid.
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Affiliation(s)
- Peter Naniima
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
| | - Eleonora Naimo
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
| | - Sandra Koch
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
| | - Ute Curth
- Institute for Biophysical Chemistry, Hannover Medical School, Hannover, Germany
| | - Khaled R. Alkharsah
- Department of Microbiology, College of Medicine, Imam Abdulrahman Bin Faisal University (IAU), Dammam, Saudi Arabia
| | - Luisa J. Ströh
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Anne Binz
- Institute of Virology, Hannover Medical School, Hannover, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, Hannover, Germany
| | - Jan-Marc Beneke
- Center of Structural and Cell Biology in Medicine, Institute of Biochemistry, University of Luebeck, Luebeck, Germany
| | - Benjamin Vollmer
- Centre for Structural Systems Biology, Leibniz-Institut für Experimentelle Virologie (HPI), Hamburg, Germany
| | - Heike Böning
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Eva Maria Borst
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Prashant Desai
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jens Bohne
- Institute of Virology, Hannover Medical School, Hannover, Germany
| | - Martin Messerle
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, Hannover, Germany
| | - Rudolf Bauerfeind
- Research Core Unit Laser Microscopy, Hannover Medical School, Hannover, Germany
| | - Pierre Legrand
- Synchrotron SOLEIL, L’Orme des Merisiers, Gif-sur-Yvette, France
| | - Beate Sodeik
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, Hannover, Germany
| | - Thomas F. Schulz
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, Hannover, Germany
| | - Thomas Krey
- Institute of Virology, Hannover Medical School, Hannover, Germany
- German Center for Infection Research (DZIF), partner sites Hannover-Braunschweig and Hamburg-Lübeck-Borstel-Riems, Braunschweig, Germany
- Excellence Cluster 2155 RESIST, Hannover Medical School, Hannover, Germany
- Center of Structural and Cell Biology in Medicine, Institute of Biochemistry, University of Luebeck, Luebeck, Germany
- Centre for Structural Systems Biology (CSSB), Hamburg, Germany
- * E-mail:
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Grzesik P, MacMath D, Henson B, Prasad S, Joshi P, Desai PJ. Incorporation of the Kaposi's sarcoma-associated herpesvirus capsid vertex-specific component (CVSC) into self-assembled capsids. Virus Res 2017; 236:9-13. [PMID: 28456575 DOI: 10.1016/j.virusres.2017.04.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 03/30/2017] [Accepted: 04/21/2017] [Indexed: 11/18/2022]
Abstract
Self-assembly of herpesvirus capsids can be accomplished in heterologous expression systems provided all six capsid proteins are present. We have demonstrated the assembly of icosahedral Kaposi's sarcoma-associated herpesvirus (KSHV) capsids in insect cells using the baculovirus expression system. Using this self-assembly system we investigated whether we could add additional capsid associated proteins and determine their incorporation into the assembled capsid. We chose the capsid vertex-specific component (CVSC) proteins encoded by open reading frames (ORFs) 19 and 32 to test this. This complex sits on the capsid vertex and is important for capsid maturation in herpesvirus-infected cells. Co-immunoprecipitation assays were used to initially confirm a bi-molecular interaction between ORF19 and ORF32. Both proteins also precipitated the triplex proteins of the capsid shell (ORF26 and ORF62) as well as the major capsid protein (ORF25). Capsid immunoprecipitation assays revealed the incorporation of ORF19 as well as ORF32 into assembled capsids. Similar experiments also showed that the incorporation of each protein occurred independent of the other. These studies reveal biochemically how the KSHV CVSC interacts with the capsid shell.
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Affiliation(s)
- Peter Grzesik
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Derek MacMath
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Brandon Henson
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Sanjana Prasad
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Poorval Joshi
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA
| | - Prashant J Desai
- Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins University, Baltimore, MD, USA.
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Abstract
The Epstein-Barr virus (EBV) capsid contains a major capsid protein, VCA; two minor capsid proteins, BDLF1 and BORF1; and a small capsid protein, BFRF3. During the lytic cycle, these capsid proteins are synthesized and imported into the host nucleus for capsid assembly. This study finds that EBV capsid proteins colocalize with promyelocytic leukemia (PML) nuclear bodies (NBs) in P3HR1 cells during the viral lytic cycle, appearing as nuclear speckles under a confocal laser scanning microscope. In a glutathione S-transferase pulldown study, we show that BORF1 interacts with PML-NBs in vitro. BORF1 also colocalizes with PML-NBs in EBV-negative Akata cells after transfection and is responsible for bringing VCA and the VCA-BFRF3 complex from the cytoplasm to PML-NBs in the nucleus. Furthermore, BDLF1 is dispersed throughout the cell when expressed alone but colocalizes with PML-NBs when BORF1 is also present in the cell. In addition, this study finds that knockdown of PML expression by short hairpin RNA does not influence the intracellular levels of capsid proteins but reduces the number of viral particles produced by P3HR1 cells. Together, these results demonstrate that BORF1 plays a critical role in bringing capsid proteins to PML-NBs, which may likely be the assembly sites of EBV capsids. The mechanisms elucidated in this study are critical to understanding the process of EBV capsid assembly. IMPORTANCE Capsid assembly is an important event during the Epstein-Barr virus (EBV) lytic cycle, as this process is required for the production of virions. In this study, confocal microscopy revealed that the EBV capsid protein BORF1 interacts with promyelocytic leukemia (PML) nuclear bodies (NBs) in the host nucleus and is responsible for transporting the other EBV capsid proteins, including VCA, BDLF1, and BFRF3, to these subnuclear locations prior to initiation of capsid assembly. This study also found that knockdown of PML expression by short hairpin RNA significantly reduces EBV capsid assembly capabilities. This enhanced understanding of capsid assembly offers potential for the development of novel antiviral strategies and therapies that can prevent the propagation and spread of EBV.
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CryoEM and mutagenesis reveal that the smallest capsid protein cements and stabilizes Kaposi's sarcoma-associated herpesvirus capsid. Proc Natl Acad Sci U S A 2015; 112:E649-56. [PMID: 25646489 DOI: 10.1073/pnas.1420317112] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With just one eighth the size of the major capsid protein (MCP), the smallest capsid protein (SCP) of human tumor herpesviruses--Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV)--is vital to capsid assembly, yet its mechanism of action is unknown. Here, by cryoEM of KSHV at 6-Å resolution, we show that SCP forms a crown on each hexon and uses a kinked helix to cross-link neighboring MCP subunits. SCP-null mutation decreased viral titer by 1,000 times and impaired but did not fully abolish capsid assembly, indicating an important but nonessential role of SCP. By truncating the C-terminal half of SCP and performing cryoEM reconstruction, we demonstrate that SCP's N-terminal half is responsible for the observed structure and function whereas the C-terminal half is flexible and dispensable. Serial truncations further highlight the critical importance of the N-terminal 10 aa, and cryoEM reconstruction of the one with six residues truncated localizes the N terminus of SCP in the cryoEM density map and enables us to construct a pseudoatomic model of SCP. Fitting of this SCP model and a homology model for the MCP upper domain into the cryoEM map reveals that SCP binds MCP largely via hydrophobic interactions and the kinked helix of SCP bridges over neighboring MCPs to form noncovalent cross-links. These data support a mechanistic model that tumor herpesvirus SCP reinforces the capsid for genome packaging, thus acting as a cementing protein similar to those found in many bacteriophages.
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