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Corda PO, Bollen M, Ribeiro D, Fardilha M. Emerging roles of the Protein Phosphatase 1 (PP1) in the context of viral infections. Cell Commun Signal 2024; 22:65. [PMID: 38267954 PMCID: PMC10807198 DOI: 10.1186/s12964-023-01468-8] [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: 10/16/2023] [Accepted: 12/30/2023] [Indexed: 01/26/2024] Open
Abstract
Protein Phosphatase 1 (PP1) is a major serine/threonine phosphatase in eukaryotes, participating in several cellular processes and metabolic pathways. Due to their low substrate specificity, PP1's catalytic subunits do not exist as free entities but instead bind to Regulatory Interactors of Protein Phosphatase One (RIPPO), which regulate PP1's substrate specificity and subcellular localization. Most RIPPOs bind to PP1 through combinations of short linear motifs (4-12 residues), forming highly specific PP1 holoenzymes. These PP1-binding motifs may, hence, represent attractive targets for the development of specific drugs that interfere with a subset of PP1 holoenzymes. Several viruses exploit the host cell protein (de)phosphorylation machinery to ensure efficient virus particle formation and propagation. While the role of many host cell kinases in viral life cycles has been extensively studied, the targeting of phosphatases by viral proteins has been studied in less detail. Here, we compile and review what is known concerning the role of PP1 in the context of viral infections and discuss how it may constitute a putative host-based target for the development of novel antiviral strategies.
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Affiliation(s)
- Pedro O Corda
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal
| | - Mathieu Bollen
- Department of Cellular and Molecular Medicine, Laboratory of Biosignaling & Therapeutics, Katholieke Universiteit Leuven, Louvain, Belgium
| | - Daniela Ribeiro
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.
| | - Margarida Fardilha
- Institute of Biomedicine (iBiMED), Department of Medical Sciences, University of Aveiro, Aveiro, Portugal.
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2
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Edwards MR, Vogel OA, Mori H, Davey RA, Basler CF. Marburg Virus VP30 Is Required for Transcription Initiation at the Glycoprotein Gene. mBio 2022; 13:e0224322. [PMID: 35997284 PMCID: PMC9601197 DOI: 10.1128/mbio.02243-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 08/08/2022] [Indexed: 12/04/2022] Open
Abstract
Marburg virus (MARV) is an enveloped, negative-sense RNA virus from the filovirus family that causes outbreaks of severe, frequently fatal illness in humans. Of the seven MARV proteins, the VP30 protein stands out because it is essential for viral growth but lacks a definitive function. Here, we used model MARV genome RNAs for one or two reporter genes and the MARV VP40, glycoprotein (GP), and VP24 genes to demonstrate that VP30 is dispensable for the transcription of some genes but critical for transcription reinitiation at the GP gene. This results in the loss of the expression of GP and downstream genes and the impaired production of infectious particles when VP30 is absent. Bicistronic minigenome assays demonstrate that the VP40 gene end/GP gene start junction specifically confers VP30 dependence. A region at the GP gene start site predicted to form a stem-loop contributes to VP30 dependence because the replacement of the GP stem-loop with corresponding sequences from the MARV VP35 gene relieves VP30 dependence. Finally, a Cys3-His zinc binding motif characteristic of filovirus VP30 proteins was demonstrated to be critical for reinitiation at GP. These findings address a long-standing gap in our understanding of MARV biology by defining a critical role for VP30 in MARV transcription. IMPORTANCE Marburg virus and Ebola virus encode VP30 proteins. While the role of VP30 in Ebola virus transcription has been well studied, the role of VP30 in the Marburg virus life cycle is not well understood. The work here demonstrates that different gene start sites within the Marburg viral genome have variable levels of dependence on Marburg virus VP30, with its expression being critical for transcription reinitiation at the GP gene start site. These findings address a long-standing question regarding Marburg virus VP30 function and further our understanding of how Marburg virus gene expression is regulated.
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Affiliation(s)
- Megan R. Edwards
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA
| | - Olivia A. Vogel
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Hiroyuki Mori
- Department of Microbiology, National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA
| | - Robert A. Davey
- Department of Microbiology, National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, USA
| | - Christopher F. Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, Georgia, USA
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, New York, USA
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3
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Abstract
Ebola virus (EBOV) VP30 regulates viral genome transcription and replication by switching its phosphorylation status. However, the importance of VP30 phosphorylation and dephosphorylation in other viral replication processes such as nucleocapsid and virion assembly is unclear. Interestingly, VP30 is predominantly dephosphorylated by cellular phosphatases in viral inclusions, while it is phosphorylated in the released virions. Thus, uncertainties regarding how VP30 phosphorylation in nucleocapsids is achieved and whether VP30 phosphorylation provides any advantages in later steps in viral replication have arisen. In the present study, to characterize the roles of VP30 phosphorylation in nucleocapsid formation, we used electron microscopic analyses and live cell imaging systems. We identified VP30 localized to the surface of protrusions surrounding nucleoprotein (NP)-forming helical structures in the nucleocapsid, suggesting the involvement in assembly and transport of nucleocapsids. Interestingly, VP30 phosphorylation facilitated its association with nucleocapsid-like structures (NCLSs). On the contrary, VP30 phosphorylation does not influence the transport characteristics and NCLS number leaving from and coming back into viral inclusions, indicating that the phosphorylation status of VP30 is not a prerequisite for NCLS departure. Moreover, the phosphorylation status of VP30 did not cause major differences in nucleocapsid transport in authentic EBOV-infected cells. In the following budding step, the association of VP30 and its phosphorylation status did not influence the budding efficiency of virus-like particles. Taken together, it is plausible that EBOV may utilize the phosphorylation of VP30 for its selective association with nucleocapsids, without affecting nucleocapsid transport and virion budding processes. IMPORTANCE Ebola virus (EBOV) causes severe fevers with unusually high case fatality rates. The nucleocapsid provides the template for viral genome transcription and replication. Thus, understanding the regulatory mechanism behind its formation is important for the development of novel therapeutic approaches. Previously, we established a live-cell imaging system based on the ectopic expression of viral fluorescent fusion proteins, allowing the visualization and characterization of intracytoplasmic transport of nucleocapsid-like structures. EBOV VP30 is an essential transcriptional factor for viral genome synthesis, and, although its role in viral genome transcription and replication is well understood, the functional importance of VP30 phosphorylation in assembly of nucleocapsids is still unclear. Our work determines the localization of VP30 at the surface of ruffled nucleocapsids, which differs from the localization of polymerase in EBOV-infected cells. This study sheds light on the novel role of VP30 phosphorylation in nucleocapsid assembly, which is an important prerequisite for virion formation.
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4
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Sun W, Luan F, Wang J, Ma L, Li X, Yang G, Hao C, Qin X, Dong S. Structural insights into the interactions between lloviu virus VP30 and nucleoprotein. Biochem Biophys Res Commun 2022; 616:82-88. [PMID: 35649303 DOI: 10.1016/j.bbrc.2022.05.059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 05/17/2022] [Indexed: 11/19/2022]
Abstract
The family Filoviridae comprises many notorious viruses, such as Ebola virus (EBOV) and Marburg virus (MARV), that can infect humans and nonhuman primates. Lloviu virus (LLOV), a less well studied filovirus, is considered a potential pathogen for humans. The VP30 C-terminal domain (CTD) of these filoviruses exhibits nucleoprotein (NP) binding and plays an essential role in viral transcription, replication and assembly. In this study, we confirmed the interactions between LLOV VP30 CTD and its NP fragment, and also determined the crystal structure of the chimeric dimeric LLOV NP-VP30 CTD at 2.50 Å resolution. The structure is highly conserved across the family Filoviridae. While in the dimer structure, only one VP30 CTD binds the NP fragment, which indicates that the interaction between LLOV VP30 CTD and NP is not strong. Our work provides a preliminary model to investigate the interactions between LLOV VP30 and NP and suggests a potential target for anti-filovirus drug development.
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Affiliation(s)
- Weiyan Sun
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Fuchen Luan
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Jiajia Wang
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Lin Ma
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Xiuxiu Li
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, China
| | - Gongxian Yang
- School of Chemistry and Chemical Engineering, University of Jinan, Jinan, China
| | - Chenyang Hao
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Xiaochun Qin
- School of Biological Science and Technology, University of Jinan, Jinan, China; School of Chemistry and Chemical Engineering, University of Jinan, Jinan, China.
| | - Shishang Dong
- School of Biological Science and Technology, University of Jinan, Jinan, China.
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5
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Galão RP, Wilson H, Schierhorn KL, Debeljak F, Bodmer BS, Goldhill D, Hoenen T, Wilson SJ, Swanson CM, Neil SJD. TRIM25 and ZAP target the Ebola virus ribonucleoprotein complex to mediate interferon-induced restriction. PLoS Pathog 2022; 18:e1010530. [PMID: 35533151 PMCID: PMC9119685 DOI: 10.1371/journal.ppat.1010530] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 05/19/2022] [Accepted: 04/18/2022] [Indexed: 12/14/2022] Open
Abstract
Ebola virus (EBOV) causes highly pathogenic disease in primates. Through screening a library of human interferon-stimulated genes (ISGs), we identified TRIM25 as a potent inhibitor of EBOV transcription-and-replication-competent virus-like particle (trVLP) propagation. TRIM25 overexpression inhibited the accumulation of viral genomic and messenger RNAs independently of the RNA sensor RIG-I or secondary proinflammatory gene expression. Deletion of TRIM25 strongly attenuated the sensitivity of trVLPs to inhibition by type-I interferon. The antiviral activity of TRIM25 required ZAP and the effect of type-I interferon was modulated by the CpG dinucleotide content of the viral genome. We find that TRIM25 interacts with the EBOV vRNP, resulting in its autoubiquitination and ubiquitination of the viral nucleoprotein (NP). TRIM25 is recruited to incoming vRNPs shortly after cell entry and leads to dissociation of NP from the vRNA. We propose that TRIM25 targets the EBOV vRNP, exposing CpG-rich viral RNA species to restriction by ZAP.
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Affiliation(s)
- Rui Pedro Galão
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
| | - Harry Wilson
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
| | - Kristina L. Schierhorn
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
| | - Franka Debeljak
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
| | - Bianca S. Bodmer
- Institute for Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald, Germany
| | - Daniel Goldhill
- Section of Virology, Department of Medicine, Imperial College London, London, United Kingdom
| | - Thomas Hoenen
- Institute for Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald, Germany
| | - Sam J. Wilson
- MRC Centre for Virus Research, University of Glasgow, United Kingdom
| | - Chad M. Swanson
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
| | - Stuart J. D. Neil
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, United Kingdom
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6
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van Tol S, Kalveram B, Ilinykh PA, Ronk A, Huang K, Aguilera-Aguirre L, Bharaj P, Hage A, Atkins C, Giraldo MI, Wakamiya M, Gonzalez-Orozco M, Warren AN, Bukreyev A, Freiberg AN, Rajsbaum R. Ubiquitination of Ebola virus VP35 at lysine 309 regulates viral transcription and assembly. PLoS Pathog 2022; 18:e1010532. [PMID: 35533195 PMCID: PMC9119628 DOI: 10.1371/journal.ppat.1010532] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 05/19/2022] [Accepted: 04/18/2022] [Indexed: 11/18/2022] Open
Abstract
Ebola virus (EBOV) VP35 is a polyfunctional protein involved in viral genome packaging, viral polymerase function, and host immune antagonism. The mechanisms regulating VP35's engagement in different functions are not well-understood. We previously showed that the host E3 ubiquitin ligase TRIM6 ubiquitinates VP35 at lysine 309 (K309) to facilitate virus replication. However, how K309 ubiquitination regulates the function of VP35 as the viral polymerase co-factor and the precise stage(s) of the EBOV replication cycle that require VP35 ubiquitination are not known. Here, we generated recombinant EBOVs encoding glycine (G) or arginine (R) mutations at VP35/K309 (rEBOV-VP35/K309G/-R) and show that both mutations prohibit VP35/K309 ubiquitination. The K309R mutant retains dsRNA binding and efficient type-I Interferon (IFN-I) antagonism due to the basic residue conservation. The rEBOV-VP35/K309G mutant loses the ability to efficiently antagonize the IFN-I response, while the rEBOV-VP35/K309R mutant's suppression is enhanced. The replication of both mutants was significantly attenuated in both IFN-competent and -deficient cells due to impaired interactions with the viral polymerase. The lack of ubiquitination on VP35/K309 or TRIM6 deficiency disrupts viral transcription with increasing severity along the transcriptional gradient. This disruption of the transcriptional gradient results in unbalanced viral protein production, including reduced synthesis of the viral transcription factor VP30. In addition, lack of ubiquitination on K309 results in enhanced interactions with the viral nucleoprotein and premature nucleocapsid packaging, leading to dysregulation of virus assembly. Overall, we identified a novel role of VP35 ubiquitination in coordinating viral transcription and assembly.
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Affiliation(s)
- Sarah van Tol
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Birte Kalveram
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Philipp A. Ilinykh
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Adam Ronk
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Kai Huang
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Leopoldo Aguilera-Aguirre
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Preeti Bharaj
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Adam Hage
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Colm Atkins
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Maria I. Giraldo
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Maki Wakamiya
- Transgenic Mouse Core Facility, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Maria Gonzalez-Orozco
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Abbey N. Warren
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Alexander Bukreyev
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Alexander N. Freiberg
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Galveston National Laboratory, University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Ricardo Rajsbaum
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
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7
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Fang J, Pietzsch C, Tsaprailis G, Crynen G, Cho KF, Ting AY, Bukreyev A, de la Torre JC, Saphire EO. Functional interactomes of the Ebola virus polymerase identified by proximity proteomics in the context of viral replication. Cell Rep 2022; 38:110544. [PMID: 35320713 PMCID: PMC10496643 DOI: 10.1016/j.celrep.2022.110544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 12/26/2021] [Accepted: 03/01/2022] [Indexed: 11/21/2022] Open
Abstract
Ebola virus (EBOV) critically depends on the viral polymerase to replicate and transcribe the viral RNA genome in the cytoplasm of host cells, where cellular factors can antagonize or facilitate the virus life cycle. Here we leverage proximity proteomics and conduct a small interfering RNA (siRNA) screen to define the functional interactome of EBOV polymerase. As a proof of principle, we validate two cellular mRNA decay factors from 35 identified host factors: eukaryotic peptide chain release factor subunit 3a (eRF3a/GSPT1) and up-frameshift protein 1 (UPF1). Our data suggest that EBOV can subvert restrictions of cellular mRNA decay and repurpose GSPT1 and UPF1 to promote viral replication. Treating EBOV-infected human hepatocytes with a drug candidate that targets GSPT1 for degradation significantly reduces viral RNA load and particle production. Our work demonstrates the utility of proximity proteomics to capture the functional host interactome of the EBOV polymerase and to illuminate host-dependent regulation of viral RNA synthesis.
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Affiliation(s)
- Jingru Fang
- La Jolla Institute for Immunology, La Jolla, CA 92037, USA; Department of Immunology and Microbiology, Scripps Research, La Jolla, CA 92037, USA
| | - Colette Pietzsch
- Department of Pathology and Galveston National Laboratory, University of Texas Medical Branch, Galveston, TX 77555, USA
| | | | - Gogce Crynen
- Bioinformatics and Statistics Core, Scripps Research, Jupiter, FL 33458, USA
| | - Kelvin Frank Cho
- Cancer Biology Program, Stanford University, Stanford, CA 94305, USA
| | - Alice Y Ting
- Department of Genetics, Department of Biology, and Department of Chemistry, Stanford University, Stanford, CA 94305, USA; Chan Zuckerberg Biohub, San Francisco, CA 94158, USA
| | - Alexander Bukreyev
- Department of Pathology and Galveston National Laboratory, University of Texas Medical Branch, Galveston, TX 77555, USA; Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77550, USA.
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8
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Bach S, Demper JC, Klemm P, Schlereth J, Lechner M, Schoen A, Kämper L, Weber F, Becker S, Biedenkopf N, Hartmann RK. Identification and characterization of short leader and trailer RNAs synthesized by the Ebola virus RNA polymerase. PLoS Pathog 2021; 17:e1010002. [PMID: 34699554 PMCID: PMC8547711 DOI: 10.1371/journal.ppat.1010002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022] Open
Abstract
Transcription of non-segmented negative sense (NNS) RNA viruses follows a stop-start mechanism and is thought to be initiated at the genome’s very 3’-end. The synthesis of short abortive leader transcripts (leaderRNAs) has been linked to transcription initiation for some NNS viruses. Here, we identified the synthesis of abortive leaderRNAs (as well as trailer RNAs) that are specifically initiated opposite to (anti)genome nt 2; leaderRNAs are predominantly terminated in the region of nt ~ 60–80. LeaderRNA synthesis requires hexamer phasing in the 3’-leader promoter. We determined a steady-state NP mRNA:leaderRNA ratio of ~10 to 30-fold at 48 h after Ebola virus (EBOV) infection, and this ratio was higher (70 to 190-fold) for minigenome-transfected cells. LeaderRNA initiation at nt 2 and the range of termination sites were not affected by structure and length variation between promoter elements 1 and 2, nor the presence or absence of VP30. Synthesis of leaderRNA is suppressed in the presence of VP30 and termination of leaderRNA is not mediated by cryptic gene end (GE) signals in the 3’-leader promoter. We further found different genomic 3’-end nucleotide requirements for transcription versus replication, suggesting that promoter recognition is different in the replication and transcription mode of the EBOV polymerase. We further provide evidence arguing against a potential role of EBOV leaderRNAs as effector molecules in innate immunity. Taken together, our findings are consistent with a model according to which leaderRNAs are abortive replicative RNAs whose synthesis is not linked to transcription initiation. Rather, replication and transcription complexes are proposed to independently initiate RNA synthesis at separate sites in the 3’-leader promoter, i.e., at the second nucleotide of the genome 3’-end and at the more internally positioned transcription start site preceding the first gene, respectively, as reported for Vesicular stomatitis virus. The RNA polymerase (RdRp) of Ebola virus (EBOV) initiates RNA synthesis at the 3’-leader promoter of its encapsidated, non-segmented negative sense (NNS) RNA genome, either at the penultimate 3’-end position of the genome in the replicative mode or more internally (position 56) at the transcription start site (TSS) in its transcription mode. Here we identified the synthesis of abortive replicative RNAs that are specifically initiated opposite to genome nt 2 (termed leaderRNAs) and predominantly terminated in the region of nt ~ 60–80 near the TSS. The functional role of abortive leaderRNA synthesis is still enigmatic; a role in interferon induction could be excluded. Our findings indirectly link leaderRNA termination to nucleoprotein (NP) availability for encapsidation of nascent replicative RNA or to NP removal from the template RNA. Our findings further argue against the model that leaderRNA synthesis is a prerequisite for each transcription initiation event at the TSS. Rather, our findings are in line with the existence of distinct replicase and transcriptase complexes of RdRp that interact differently with the 3’-leader promoter and intiate RNA synthesis independently at different sites (position 2 or 56 of the genome), mechanistically similar to another NNS virus, Vesicular stomatitis virus.
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Affiliation(s)
- Simone Bach
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Jana-Christin Demper
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Paul Klemm
- Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
| | - Julia Schlereth
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Marcus Lechner
- Zentrum für Synthetische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
| | - Andreas Schoen
- Institut für Virologie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Lennart Kämper
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Friedemann Weber
- Institut für Virologie, Justus-Liebig-Universität Gießen, Gießen, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Nadine Biedenkopf
- Institut für Virologie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail: (NB); (RKH)
| | - Roland K. Hartmann
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
- * E-mail: (NB); (RKH)
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9
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Banerjee G, Shokeen K, Chakraborty N, Agarwal S, Mitra A, Kumar S, Banerjee P. Modulation of immune response in Ebola virus disease. Curr Opin Pharmacol 2021; 60:158-167. [PMID: 34425392 DOI: 10.1016/j.coph.2021.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2021] [Revised: 06/29/2021] [Accepted: 07/13/2021] [Indexed: 10/20/2022]
Abstract
Ebola virus disease targets and destroys immune cells, including macrophages and dendritic cells, leading to impairment of host response. After infection, a combination of strategies including alteration and evasion of immune response culminating in a strong inflammatory response can lead to multi-organ failure and death in most infected patients. This review discusses immune response dynamics, mainly focusing on how Ebola manipulates innate and adaptive immune responses and strategizes to thwart host immune responses. We also discuss the challenges and prospects of developing therapeutics and vaccines against Ebola.
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Affiliation(s)
- Goutam Banerjee
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Kamal Shokeen
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Nilanjan Chakraborty
- Department of Microbiology, Adamas University, Kolkata, West Bengal, 700126, India
| | - Saumya Agarwal
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Arindam Mitra
- Department of Microbiology, Adamas University, Kolkata, West Bengal, 700126, India.
| | - Sachin Kumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India.
| | - Pratik Banerjee
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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10
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Batra J, Mori H, Small GI, Anantpadma M, Shtanko O, Mishra N, Zhang M, Liu D, Williams CG, Biedenkopf N, Becker S, Gross ML, Leung DW, Davey RA, Amarasinghe GK, Krogan NJ, Basler CF. Non-canonical proline-tyrosine interactions with multiple host proteins regulate Ebola virus infection. EMBO J 2021; 40:e105658. [PMID: 34260076 DOI: 10.15252/embj.2020105658] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/23/2021] [Accepted: 07/09/2021] [Indexed: 01/08/2023] Open
Abstract
The Ebola virus VP30 protein interacts with the viral nucleoprotein and with host protein RBBP6 via PPxPxY motifs that adopt non-canonical orientations, as compared to other proline-rich motifs. An affinity tag-purification mass spectrometry approach identified additional PPxPxY-containing host proteins hnRNP L, hnRNPUL1, and PEG10, as VP30 interactors. hnRNP L and PEG10, like RBBP6, inhibit viral RNA synthesis and EBOV infection, whereas hnRNPUL1 enhances. RBBP6 and hnRNP L modulate VP30 phosphorylation, increase viral transcription, and exert additive effects on viral RNA synthesis. PEG10 has more modest inhibitory effects on EBOV replication. hnRNPUL1 positively affects viral RNA synthesis but in a VP30-independent manner. Binding studies demonstrate variable capacity of the PPxPxY motifs from these proteins to bind VP30, define PxPPPPxY as an optimal binding motif, and identify the fifth proline and the tyrosine as most critical for interaction. Competition binding and hydrogen-deuterium exchange mass spectrometry studies demonstrate that each protein binds a similar interface on VP30. VP30 therefore presents a novel proline recognition domain that is targeted by multiple host proteins to modulate viral transcription.
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Affiliation(s)
- Jyoti Batra
- J. David Gladstone Institutes, San Francisco, CA, USA.,Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA.,Quantitative Biosciences Institute, University of California, San Francisco, CA, USA
| | - Hiroyuki Mori
- Department of Microbiology, NEIDL, Boston University School of Medicine, Boston, MA, USA
| | - Gabriel I Small
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.,John T. Milliken Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Manu Anantpadma
- Department of Microbiology, NEIDL, Boston University School of Medicine, Boston, MA, USA
| | - Olena Shtanko
- Host-Pathogen Interactions, Texas Biomedical Research Institute, San Antonio, TX, USA
| | - Nawneet Mishra
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Mengru Zhang
- Department of Chemistry, Washington University School of Medicine, St. Louis, MO, USA
| | - Dandan Liu
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Caroline G Williams
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, USA
| | - Nadine Biedenkopf
- Institute of Virology, Philipps University of Marburg, Marburg, Germany
| | - Stephan Becker
- Institute of Virology, Philipps University of Marburg, Marburg, Germany
| | - Michael L Gross
- Department of Chemistry, Washington University School of Medicine, St. Louis, MO, USA
| | - Daisy W Leung
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.,John T. Milliken Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, MO, USA
| | - Robert A Davey
- Department of Microbiology, NEIDL, Boston University School of Medicine, Boston, MA, USA
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Nevan J Krogan
- J. David Gladstone Institutes, San Francisco, CA, USA.,Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA, USA.,Quantitative Biosciences Institute, University of California, San Francisco, CA, USA
| | - Christopher F Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, USA
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11
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Bach S, Demper JC, Grünweller A, Becker S, Biedenkopf N, Hartmann RK. Regulation of VP30-Dependent Transcription by RNA Sequence and Structure in the Genomic Ebola Virus Promoter. J Virol 2021; 95:JVI.02215-20. [PMID: 33268520 PMCID: PMC8092829 DOI: 10.1128/jvi.02215-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 11/22/2020] [Indexed: 01/16/2023] Open
Abstract
Viral transcription and replication of Ebola virus (EBOV) is balanced by transcription factor VP30, an RNA binding protein. An RNA hairpin at the transcription start site (TSS) of the first gene (NP hairpin) in the 3'-leader promoter is thought to mediate the VP30 dependency of transcription. Here, we investigated the constraints of VP30 dependency using a series of monocistronic minigenomes with sequence, structure and length deviations from the native NP hairpin. Hairpin stabilizations decreased while destabilizations increased transcription in the absence of VP30, but in all cases, transcription activity was higher in the presence versus absence of VP30. This also pertains to a mutant that is unable to form any RNA secondary structure at the TSS, demonstrating that the activity of VP30 is not simply determined by the capacity to form a hairpin structure at the TSS. Introduction of continuous 3'-UN5 hexamer phasing between promoter elements PE1 and PE2 by a single point mutation in the NP hairpin boosted VP30-independent transcription. Moreover, this point mutation, but also hairpin stabilizations, impaired the relative increase of replication in the absence of VP30. Our results suggest that the native NP hairpin is optimized for tight regulation by VP30 while avoiding an extent of hairpin stability that impairs viral transcription, as well as for enabling the switch from transcription to replication when VP30 is not part of the polymerase complex.IMPORTANCE A detailed understanding is lacking how the Ebola virus (EBOV) protein VP30 regulates activity of the viral polymerase complex. Here, we studied how RNA sequence, length and structure at the transcription start site (TSS) in the 3'-leader promoter influence the impact of VP30 on viral polymerase activity. We found that hairpin stabilizations tighten the VP30 dependency of transcription but reduce transcription efficiency and attenuate the switch to replication in the absence of VP30. Upon hairpin destabilization, VP30-independent transcription - already weakly detectable at the native promoter - increases, but never reaches the same extent as in the presence of VP30. We conclude that the native hairpin structure involving the TSS (i) establishes an optimal balance between efficient transcription and tight regulation by VP30, (ii) is linked to hexamer phasing in the promoter, and (iii) favors the switch to replication when VP30 is absent.
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Affiliation(s)
- Simone Bach
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037 Marburg, Germany
| | - Jana-Christin Demper
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037 Marburg, Germany
| | - Arnold Grünweller
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037 Marburg, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Str. 2, 35043 Marburg
| | - Nadine Biedenkopf
- Institut für Virologie, Philipps-Universität Marburg, Hans-Meerwein-Str. 2, 35043 Marburg
| | - Roland K Hartmann
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35037 Marburg, Germany
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12
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Yoon YS, Jang Y, Hoenen T, Shin H, Lee Y, Kim M. Antiviral activity of sertindole, raloxifene and ibutamoren against transcription and replication-competent Ebola virus-like particles. BMB Rep 2020. [PMID: 31964466 PMCID: PMC7118351 DOI: 10.5483/bmbrep.2020.53.3.175] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A chemical library comprising 2,354 drug-like compounds was screened using a transcription and replication-competent virus-like particle (trVLP) system implementing the whole Ebola virus (EBOV) life cycle. Dose-dependent inhibition of Ebola trVLP replication was induced by 15 hit compounds, which primarily target different types of G protein-coupled receptors (GPCRs). Based on the chemical structure, the compounds were divided into three groups, diphenylmethane derivatives, promazine derivatives and chemicals with no conserved skeletons. The third group included sertindole, raloxifene, and ibutamoren showing prominent antiviral effects in cells. They downregulated the expression of viral proteins, including the VP40 matrix protein and the envelope glycoprotein. They also reduced the amount of EBOV-derived tetracistronic minigenome RNA incorporated into progeny trVLPs in the culture supernatant. Particularly, ibutamoren, which is a known agonist of growth hormone secretagogue receptor (GHSR), showed the most promising antiviral activity with a 50% effective concentration of 0.2 μM, a 50% cytotoxic concentration of 42.4 μM, and a selectivity index of 222.8. Here, we suggest a strategy for development of anti-EBOV therapeutics by adopting GHSR agonists as hit compounds.
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Affiliation(s)
- Yi-Seul Yoon
- Virus Research Group, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
| | - Yejin Jang
- Virus Research Group, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
| | - Thomas Hoenen
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald-Insel Riems 17493, Germany
| | - Heegwon Shin
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Younghoon Lee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Meehyein Kim
- Virus Research Group, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea
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13
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Bach S, Demper JC, Biedenkopf N, Becker S, Hartmann RK. RNA secondary structure at the transcription start site influences EBOV transcription initiation and replication in a length- and stability-dependent manner. RNA Biol 2020; 18:523-536. [PMID: 32882148 DOI: 10.1080/15476286.2020.1818459] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Ebola virus (EBOV) RNA has the potential to form hairpin structures at the transcription start sequence (TSS) and reinitiation sites of internal genes, both on the genomic and antigenomic/mRNA level. Hairpin formation involving the TSS and the spacer sequence between promotor elements (PE) 1 and 2 was suggested to regulate viral transcription. Here, we provide evidence that such RNA structures form during RNA synthesis by the viral polymerase and affect its activity. This was analysed using monocistronic minigenomes carrying hairpin structure variants in the TSS-spacer region that differ in length and stability. Transcription and replication were measured via reporter activity and by qRT-PCR quantification of the distinct viral RNA species. We demonstrate that viral RNA synthesis is remarkably tolerant to spacer extensions of up to ~54 nt, but declines beyond this length limit (~25% residual activity for a 66-nt extension). Minor incremental stabilizations of hairpin structures in the TSS-spacer region and on the mRNA/antigenomic level were found to rapidly abolish viral polymerase activity, which may be exploited for antisense strategies to inhibit viral RNA synthesis. Finally, balanced viral transcription and replication can still occur when any RNA structure formation potential at the TSS is eliminated, provided that hexamer phasing in the promoter region is maintained. Altogether, the findings deepen and refine our insight into structure and length constraints within the EBOV transcription and replication promoter and suggest a remarkable flexibility of the viral polymerase in recognition of PE1 and PE2.
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Affiliation(s)
- Simone Bach
- Institut fuür Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Jana-Christin Demper
- Institut fuür Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
| | - Nadine Biedenkopf
- Institut fuü;r Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Stephan Becker
- Institut fuü;r Virologie, Philipps-Universität Marburg, Marburg, Germany
| | - Roland K Hartmann
- Institut fuür Pharmazeutische Chemie, Philipps-Universität Marburg, Marburg, Germany
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14
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Dong S, Wen K, Chu H, Li H, Yu Q, Wang C, Qin X. Crystal structure of the Měnglà virus VP30 C-terminal domain. Biochem Biophys Res Commun 2020; 525:392-397. [PMID: 32093889 DOI: 10.1016/j.bbrc.2020.02.089] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 02/12/2020] [Indexed: 11/26/2022]
Abstract
The family Filoviridae contains many important human viruses, including Marburg virus (MARV) and Ebola virus (EBOV). Měnglà virus (MLAV), a newly discovered filovirus, is considered a potential human pathogen. The VP30 C-terminal domain (CTD) of these filoviruses plays an essential role in virion assembly. In common with other filoviruses, MLAV VP30 CTD mainly exists as a dimer in solution. In this work, we determined the crystal structure of recombinant MLAV VP30 CTD monomer, verifying that C-terminal helix-7 (H7) is critical for the dimerization process. This study provides a preliminary model for investigation of MLAV VP30 CTD as an anti-filovirus drug development target.
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Affiliation(s)
- Shishang Dong
- School of Biological Science and Technology, University of Jinan, Jinan, China.
| | - Kangning Wen
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Hongguan Chu
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Hui Li
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Qianqian Yu
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Changhui Wang
- School of Biological Science and Technology, University of Jinan, Jinan, China
| | - Xiaochun Qin
- School of Biological Science and Technology, University of Jinan, Jinan, China.
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15
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Bach S, Biedenkopf N, Grünweller A, Becker S, Hartmann RK. Hexamer phasing governs transcription initiation in the 3'-leader of Ebola virus. RNA (NEW YORK, N.Y.) 2020; 26:439-453. [PMID: 31924730 PMCID: PMC7075260 DOI: 10.1261/rna.073718.119] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 01/08/2020] [Indexed: 05/05/2023]
Abstract
The genomic, bipartite replication promoter of Ebola virus (EBOV) consists of elements 1 (PE1) and 2 (PE2). PE1 (55 nt at the 3'-terminus) is separated from PE2 (harboring eight 3'-UN5 hexamers) by the transcription start sequence (TSS) of the first nucleoprotein (NP) gene plus a spacer sequence. Insertions or deletions in the spacer were reported to support genome replication if comprising 6 or 12, but not 1/2/3/5/9 nt. This gave rise to the formulation of the "rule of 6" for the EBOV replication promoter. Here, we studied the impact of such hexamer phasing on viral transcription using a series of replication-competent and -deficient monocistronic minigenomes, in which the spacer of the NP gene was mutated or replaced with that of internal EBOV genes and mutated variants thereof. Beyond reporter gene assays, we conducted qRT-PCR to determine the levels of mRNA, genomic and antigenomic RNA. We demonstrate that hexamer phasing is also essential for viral transcription, that UN5 hexamer periodicity extends into PE1 and that the spacer region can be expanded by 48 nt without losses of transcriptional activity. Making the UN5 hexamer phasing continuous between PE1 and PE2 enhanced the efficiency of transcription and replication. We show that the 2 nt preceding the TSS are essential for transcription. We further propose a role for UN5 hexamer phasing in positioning NP during initiation of RNA synthesis, or in dissociation/reassociation of NP from the template RNA strand while threading the RNA through the active site of the elongating polymerase during replication and transcription.
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Affiliation(s)
- Simone Bach
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Nadine Biedenkopf
- Institut für Virologie, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Arnold Grünweller
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, 35037 Marburg, Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Roland K Hartmann
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, 35037 Marburg, Germany
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16
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Protein Kinase C subtype δ interacts with Venezuelan equine encephalitis virus capsid protein and regulates viral RNA binding through modulation of capsid phosphorylation. PLoS Pathog 2020; 16:e1008282. [PMID: 32150585 PMCID: PMC7082041 DOI: 10.1371/journal.ppat.1008282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 03/19/2020] [Accepted: 12/13/2019] [Indexed: 12/31/2022] Open
Abstract
Protein phosphorylation plays an important role during the life cycle of many viruses. Venezuelan equine encephalitis virus (VEEV) capsid protein has recently been shown to be phosphorylated at four residues. Here those studies are extended to determine the kinase responsible for phosphorylation and the importance of capsid phosphorylation during the viral life cycle. Phosphorylation site prediction software suggests that Protein Kinase C (PKC) is responsible for phosphorylation of VEEV capsid. VEEV capsid co-immunoprecipitated with PKCδ, but not other PKC isoforms and siRNA knockdown of PKCδ caused a decrease in viral replication. Furthermore, knockdown of PKCδ by siRNA decreased capsid phosphorylation. A virus with capsid phosphorylation sites mutated to alanine (VEEV CPD) displayed a lower genomic copy to pfu ratio than the parental virus; suggesting more efficient viral assembly and more infectious particles being released. RNA:capsid binding was significantly increased in the mutant virus, confirming these results. Finally, VEEV CPD is attenuated in a mouse model of infection, with mice showing increased survival and decreased clinical signs as compared to mice infected with the parental virus. Collectively our data support a model in which PKCδ mediated capsid phosphorylation regulates viral RNA binding and assembly, significantly impacting viral pathogenesis.
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17
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Abstract
The largest Ebola virus (EBOV) epidemic in West Africa ever caused more than 28,000 cases and 11,000 deaths, and the current EBOV epidemic in the Democratic Republic of the Congo continues, with more than 3,000 cases to date. Therefore, it is essential to develop antivirals against EBOV. Recently, an inhibitor of the cellular phosphatase PP2A-mediated dephosphorylation of the EBOV transcription factor VP30 has been shown to suppress the spread of Ebola virus. Here, we identified the protein kinase SRPK1 as a VP30-specific kinase that phosphorylates serine 29, the same residue that is dephosphorylated by PP2A. SRPK1-mediated phosphorylation of serine 29 enabled primary viral transcription. Mutation of the SRPK1 recognition motif in VP30 resulted in significant growth inhibition of EBOV. Similarly, elevation of the phosphorylation status of serine 29 by overexpression of SRPK1 inhibited EBOV growth, highlighting the importance of reversible phosphorylation of VP30 as a potential therapeutic target. Ebola virus (EBOV) causes a severe and often fatal disease for which no approved vaccines or antivirals are currently available. EBOV VP30 has been described as a viral phosphoprotein, and nonphosphorylated VP30 is essential and sufficient to support secondary transcription in an EBOV-specific minigenome system; however, phosphorylatable serine residues near the N terminus of VP30 are required to support primary viral transcription as well as the reinitiation of VP30-mediated transcription at internal EBOV genes. While the dephosphorylation of VP30 by the cellular phosphatase PP2A was found to be mediated by nucleoprotein, the VP30-specific kinases and the role of phosphorylation remain unknown. Here, we report that serine-arginine protein kinase 1 (SRPK1) and SRPK2 phosphorylate serine 29 of VP30, which is located in an N-terminal R26xxS29 motif. Interaction with VP30 via the R26xxS29 motif recruits SRPK1 into EBOV-induced inclusion bodies, the sites of viral RNA synthesis, and an inhibitor of SRPK1/SRPK2 downregulates primary viral transcription. When the SRPK1 recognition motif of VP30 was mutated in a recombinant EBOV, virus replication was severely impaired. It is presumed that the interplay between SRPK1 and PP2A in the EBOV inclusions provides a comprehensive regulatory circuit to ensure the activity of VP30 in EBOV transcription. Thus, the identification of SRPK1 is an important mosaic stone that completes our picture of the players involved in Ebola virus transcription regulation.
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18
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Rohde C, Becker S, Krähling V. Marburg virus regulates the IRE1/XBP1-dependent unfolded protein response to ensure efficient viral replication. Emerg Microbes Infect 2020; 8:1300-1313. [PMID: 31495285 PMCID: PMC6746283 DOI: 10.1080/22221751.2019.1659552] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Viruses regulate cellular signalling pathways to ensure optimal viral replication. During Marburg virus (MARV) infection, large quantities of the viral glycoprotein GP are produced in the ER; this may result in the activation of the unfolded protein response (UPR). The most conserved pathway to trigger UPR is initiated by IRE1. Activation of IRE1 results in auto-phosphorylation, splicing of the XBP1 mRNA and translation of the XBP1s protein. XBP1s binds cis-acting UPR elements (UPRE) which leads to the enhanced expression of genes which should restore ER homeostasis. XBP1u protein is translated, if IRE1 is not activated. Here we show that ectopic expression of MARV GP activated the IRE1-XBP1 axis of UPR as monitored by UPRE luciferase assays. However, while at 24 h of infection with MARV IRE1 was phosphorylated, expression of XBP1s was only slightly enhanced and UPRE activity was not detected. The IRE1-XBP1 axis was not active at 48 h p.i. Co-expression studies of MARV proteins demonstrated that the MARV protein VP30 suppressed UPRE activation. Co-immunoprecipitation analyses revealed an RNA-dependent interaction of VP30 with XBP1u. Knock-out of IRE1 supported MARV infection at late time points. Taken together, these results suggest that efficient MARV propagation requires specific regulation of IRE1 activity.
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Affiliation(s)
- Cornelius Rohde
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
| | - Stephan Becker
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
| | - Verena Krähling
- Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany.,Deutsches Zentrum für Infektionsforschung (DZIF), Gießen - Marburg - Langen , Marburg , Germany
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19
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Chen J, He Z, Yuan Y, Huang F, Luo B, Zhang J, Pan T, Zhang H, Zhang J. Host factor SMYD3 is recruited by Ebola virus nucleoprotein to facilitate viral mRNA transcription. Emerg Microbes Infect 2020; 8:1347-1360. [PMID: 31516086 PMCID: PMC6758638 DOI: 10.1080/22221751.2019.1662736] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The polymerase complex of Ebola virus (EBOV) is the functional unit for transcription and replication of viral genome. Nucleoprotein (NP) is a multifunctional protein with high RNA binding affinity and recruits other viral proteins to form functional polymerase complex. In our study, we investigated host proteins associated with EBOV polymerase complex using NP as bait in a transcription and replication competent minigenome system by mass spectrometry analysis and identified SET and MYND domain-containing protein 3 (SMYD3) as a novel host protein which was required for the replication of EBOV. SMYD3 specifically interacted with NP and was recruited to EBOV inclusion bodies through NP. The depletion of SMYD3 dramatically suppressed EBOV mRNA production. A mimic of non-phosphorylated VP30, which is a transcription activator, could partially rescue the viral mRNA production downregulated by the depletion of SMYD3. In addition, SMYD3 promoted NP-VP30 interaction in a dose-dependent manner. These results revealed that SMYD3 was a novel host factor recruited by NP to supporting EBOV mRNA transcription through increasing the binding of VP30 to NP. Thus, our study provided a new understanding of mechanism underlying the transcription of EBOV genome, and a novel anti-EBOV drug design strategy by targeting SMYD3.
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Affiliation(s)
- Jingliang Chen
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Zhangping He
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Yaochang Yuan
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Feng Huang
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China.,Department of Respiration, Affiliated Guangzhou Women and Children's Hospital, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Baohong Luo
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Jianhua Zhang
- CAS Key Laboratory for Pathogenic Microbiology, Institute of Microbiology, Chinese Academy of Sciences , Beijing , People's Republic of China
| | - Ting Pan
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Hui Zhang
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
| | - Junsong Zhang
- Institute of Human Virology, Key Laboratory of Tropical Disease Control of Ministry of Education, Guangdong Engineering Research Center for Antimicrobial Agent and Immunotechnology, Zhongshan School of Medicine, Sun Yat-Sen University , Guangzhou , People's Republic of China
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20
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Hume AJ, Mühlberger E. Distinct Genome Replication and Transcription Strategies within the Growing Filovirus Family. J Mol Biol 2019; 431:4290-4320. [PMID: 31260690 PMCID: PMC6879820 DOI: 10.1016/j.jmb.2019.06.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 05/31/2019] [Accepted: 06/24/2019] [Indexed: 11/18/2022]
Abstract
Research on filoviruses has historically focused on the highly pathogenic ebola- and marburgviruses. Indeed, until recently, these were the only two genera in the filovirus family. Recent advances in sequencing technologies have facilitated the discovery of not only a new ebolavirus, but also three new filovirus genera and a sixth proposed genus. While two of these new genera are similar to the ebola- and marburgviruses, the other two, discovered in saltwater fishes, are considerably more diverse. Nonetheless, these viruses retain a number of key features of the other filoviruses. Here, we review the key characteristics of filovirus replication and transcription, highlighting similarities and differences between the viruses. In particular, we focus on key regulatory elements in the genomes, replication and transcription strategies, and the conservation of protein domains and functions among the viruses. In addition, using computational analyses, we were able to identify potential homology and functions for some of the genes of the novel filoviruses with previously unknown functions. Although none of the newly discovered filoviruses have yet been isolated, initial studies of some of these viruses using minigenome systems have yielded insights into their mechanisms of replication and transcription. In general, the Cuevavirus and proposed Dianlovirus genera appear to follow the transcription and replication strategies employed by the ebola- and marburgviruses, respectively. While our knowledge of the fish filoviruses is currently limited to sequence analysis, the lack of certain conserved motifs and even entire genes necessitates that they have evolved distinct mechanisms of replication and transcription.
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Affiliation(s)
- Adam J Hume
- Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, USA; National Emerging Infectious Diseases Laboratories, Boston University, Boston, MA 02118, USA
| | - Elke Mühlberger
- Department of Microbiology, Boston University School of Medicine, Boston, MA 02118, USA; National Emerging Infectious Diseases Laboratories, Boston University, Boston, MA 02118, USA.
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21
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Batra J, Hultquist JF, Liu D, Shtanko O, Von Dollen J, Satkamp L, Jang GM, Luthra P, Schwarz TM, Small GI, Arnett E, Anantpadma M, Reyes A, Leung DW, Kaake R, Haas P, Schmidt CB, Schlesinger LS, LaCount DJ, Davey RA, Amarasinghe GK, Basler CF, Krogan NJ. Protein Interaction Mapping Identifies RBBP6 as a Negative Regulator of Ebola Virus Replication. Cell 2018; 175:1917-1930.e13. [PMID: 30550789 PMCID: PMC6366944 DOI: 10.1016/j.cell.2018.08.044] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 05/17/2018] [Accepted: 08/17/2018] [Indexed: 01/21/2023]
Abstract
Ebola virus (EBOV) infection often results in fatal illness in humans, yet little is known about how EBOV usurps host pathways during infection. To address this, we used affinity tag-purification mass spectrometry (AP-MS) to generate an EBOV-host protein-protein interaction (PPI) map. We uncovered 194 high-confidence EBOV-human PPIs, including one between the viral transcription regulator VP30 and the host ubiquitin ligase RBBP6. Domain mapping identified a 23 amino acid region within RBBP6 that binds to VP30. A crystal structure of the VP30-RBBP6 peptide complex revealed that RBBP6 mimics the viral nucleoprotein (NP) binding to the same interface of VP30. Knockdown of endogenous RBBP6 stimulated viral transcription and increased EBOV replication, whereas overexpression of either RBBP6 or the peptide strongly inhibited both. These results demonstrate the therapeutic potential of biologics that target this interface and identify additional PPIs that may be leveraged for novel therapeutic strategies.
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Affiliation(s)
- Jyoti Batra
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Judd F Hultquist
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA; Division of Infectious Diseases, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Dandan Liu
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63105, USA
| | - Olena Shtanko
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX 78245, USA
| | - John Von Dollen
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Laura Satkamp
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Gwendolyn M Jang
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Priya Luthra
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA
| | - Toni M Schwarz
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Gabriel I Small
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63105, USA
| | - Eusondia Arnett
- Texas Biomedical Research Institute, San Antonio, TX 78245, USA
| | - Manu Anantpadma
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX 78245, USA
| | - Ann Reyes
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX 78245, USA
| | - Daisy W Leung
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63105, USA
| | - Robyn Kaake
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Paige Haas
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | - Carson B Schmidt
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA
| | | | - Douglas J LaCount
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
| | - Robert A Davey
- Department of Virology and Immunology, Texas Biomedical Research Institute, San Antonio, TX 78245, USA
| | - Gaya K Amarasinghe
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63105, USA
| | - Christopher F Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA.
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA; Quantitative Biosciences Institute, University of California, San Francisco, San Francisco, CA 94158, USA; J. David Gladstone Institutes, San Francisco, CA 94158, USA.
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22
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Phosphorylated VP30 of Marburg Virus Is a Repressor of Transcription. J Virol 2018; 92:JVI.00426-18. [PMID: 30135121 DOI: 10.1128/jvi.00426-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 08/06/2018] [Indexed: 12/29/2022] Open
Abstract
The filoviruses Marburg virus (MARV) and Ebola virus (EBOV) cause hemorrhagic fever in humans and nonhuman primates, with high case fatality rates. MARV VP30 is known to be phosphorylated and to interact with nucleoprotein (NP), but its role in regulation of viral transcription is disputed. Here, we analyzed phosphorylation of VP30 by mass spectrometry, which resulted in identification of multiple phosphorylated amino acids. Modeling the full-length three-dimensional structure of VP30 and mapping the identified phosphorylation sites showed that all sites lie in disordered regions, mostly in the N-terminal domain of the protein. Minigenome analysis of the identified phosphorylation sites demonstrated that phosphorylation of a cluster of amino acids at positions 46 through 53 inhibits transcription. To test the effect of VP30 phosphorylation on its interaction with other MARV proteins, coimmunoprecipitation analyses were performed. They demonstrated the involvement of VP30 phosphorylation in interaction with two other proteins of the MARV ribonucleoprotein complex, NP and VP35. To identify the role of protein phosphatase 1 (PP1) in the identified effects, a small molecule, 1E7-03, targeting a noncatalytic site of the enzyme that previously was shown to increase EBOV VP30 phosphorylation was used. Treatment of cells with 1E7-03 increased phosphorylation of VP30 at a cluster of phosphorylated amino acids from Ser-46 to Thr-53, reduced transcription of MARV minigenome, enhanced binding to NP and VP35, and dramatically reduced replication of infectious MARV particles. Thus, MARV VP30 phosphorylation can be targeted for development of future antivirals such as PP1-targeting compounds. IMPORTANCE The largest outbreak of MARV occurred in Angola in 2004 to 2005 and had a 90% case fatality rate. There are no approved treatments available for MARV. Development of antivirals as therapeutics requires a fundamental understanding of the viral life cycle. Because of the close similarity of MARV to another member of Filoviridae family, EBOV, it was assumed that the two viruses have similar mechanisms of regulation of transcription and replication. Here, characterization of the role of VP30 and its phosphorylation sites in transcription of the MARV genome demonstrated differences from those of EBOV. The identified phosphorylation sites appeared to inhibit transcription and appeared to be involved in interaction with both NP and VP35 ribonucleoproteins. A small molecule targeting PP1 inhibited transcription of the MARV genome, effectively suppressing replication of the viral particles. These data demonstrate the possibility developing antivirals based on compounds targeting PP1.
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Protein Phosphatase 1α Interacts with Venezuelan Equine Encephalitis Virus Capsid Protein and Regulates Viral Replication through Modulation of Capsid Phosphorylation. J Virol 2018; 92:JVI.02068-17. [PMID: 29769351 DOI: 10.1128/jvi.02068-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 05/01/2018] [Indexed: 12/11/2022] Open
Abstract
Protein phosphatase 1 (PP1) is a serine/threonine phosphatase which has been implicated in the regulation of a number of viruses, including HIV-1, Ebolavirus, and Rift Valley fever virus. Catalytic subunits of PP1 (PP1α, PP1β, and PP1γ) interact with a host of regulatory subunits and target a wide variety of cellular substrates through a combination of short binding motifs, including an RVxF motif present in the majority of PP1 regulatory subunits. Targeting the RVxF-interacting site on PP1 with the small molecule 1E7-03 inhibits HIV-1, Ebolavirus, and Rift Valley fever virus replication. In this study, we determined the effect of PP1 on Venezuelan equine encephalitis virus (VEEV) replication. Treatment of VEEV-infected cells with 1E7-03 decreased viral replication by more than 2 logs (50% effective concentration [EC50] = 0.6 μM). 1E7-03 treatment reduced viral titers starting at 8 h postinfection. Viral replication was also decreased after treatment with PP1α-targeting small interfering RNA (siRNA). Confocal microscopy demonstrated that PP1α shuttles toward the cytosol during infection with VEEV and that PP1α colocalizes with VEEV capsid. Coimmunoprecipitation experiments confirmed VEEV capsid interaction with PP1α. Furthermore, immunoprecipitation and mass spectrometry data showed that VEEV capsid is phosphorylated and that phosphorylation is moderated by PP1α. Finally, less viral RNA is associated with capsid after treatment with 1E7-03. Coupled with data showing that 1E7-03 inhibits several alphaviruses, this study indicates that inhibition of the PP1α RVxF binding pocket is a promising therapeutic target and provides novel evidence that PP1α modulation of VEEV capsid phosphorylation influences viral replication.IMPORTANCE Venezuelan equine encephalitis virus (VEEV) causes moderate flu-like symptoms and can lead to severe encephalitic disease and potentially death. There are currently no FDA-approved therapeutics or vaccines for human use, and understanding the molecular underpinning of host-virus interactions can aid in the rational design of intervention strategies. The significance of our research is in identifying the interaction between protein phosphatase 1 (PP1) and the viral capsid protein. This interaction is important for viral replication, as inhibition of PP1 results in decrease viral replication. Inhibition of PP1 also inhibited multiple biomedically important alphaviruses, indicating that PP1 may be a potential therapeutic target for alphavirus-induced disease.
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Abstract
In 2014, the world witnessed the largest Ebolavirus outbreak in recorded history. The subsequent humanitarian effort spurred extensive research, significantly enhancing our understanding of ebolavirus replication and pathogenicity. The main functions of each ebolavirus protein have been studied extensively since the discovery of the virus in 1976; however, the recent expansion of ebolavirus research has led to the discovery of new protein functions. These newly discovered roles are revealing new mechanisms of virus replication and pathogenicity, whilst enhancing our understanding of the broad functions of each ebolavirus viral protein (VP). Many of these new functions appear to be unrelated to the protein's primary function during virus replication. Such new functions range from bystander T-lymphocyte death caused by VP40-secreted exosomes to new roles for VP24 in viral particle formation. This review highlights the newly discovered roles of ebolavirus proteins in order to provide a more encompassing view of ebolavirus replication and pathogenicity.
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Affiliation(s)
- Diego Cantoni
- School of Biosciences, University of Kent, Canterbury, United Kingdom
| | - Jeremy S. Rossman
- School of Biosciences, University of Kent, Canterbury, United Kingdom
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25
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Molina IG, Esperante SA, Marino-Buslje C, Chemes LB, de Prat-Gay G. Cooperative RNA Recognition by a Viral Transcription Antiterminator. J Mol Biol 2018; 430:777-792. [PMID: 29414675 DOI: 10.1016/j.jmb.2018.01.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 01/18/2023]
Abstract
RNA transcription of mononegavirales decreases gradually from the 3' leader promoter toward the 5' end of the genome, due to a decay in polymerase processivity. In the respiratory syncytial virus and metapneumovirus, the M2-1 protein ensures transcription anti-termination. Despite being a homotetramer, respiratory syncytial virus M2-1 binds two molecules of RNA of 13mer or longer per tetramer, and temperature-sensitive secondary structure in the RNA ligand is unfolded by stoichiometric interaction with M2-1. Fine quantitative analysis shows positive cooperativity, indicative of conformational asymmetry in the tetramer. RNA binds to M2-1 through a fast bimolecular association followed by slow rearrangements corresponding to an induced-fit mechanism, providing a sequential description of the time events of cooperativity. The first binding event of half of the RNA molecule to one of the sites increases the affinity of the second binding event on the adjacent contacting protomer by 15-fold, product of increased effective concentration caused by the entropic link. This mechanism allows for high-affinity binding with an otherwise relaxed sequence specificity, and instead suggests a yet undefined structural recognition signature in the RNA for modulating gene transcription. This work provides a basis for an essential event for understanding transcription antitermination in pneumoviruses and its counterpart Ebola virus VP30.
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Affiliation(s)
- Ivana G Molina
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Sebastian A Esperante
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Cristina Marino-Buslje
- Structural Bioinformatics Unit, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Lucía B Chemes
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
| | - Gonzalo de Prat-Gay
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
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26
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Abstract
The Filoviridae are a family of negative-strand RNA viruses that include several important human pathogens. Ebola virus (EBOV) and Marburg virus are well-known filoviruses which cause life-threatening viral hemorrhagic fever in human and nonhuman primates. In addition to severe pathogenesis, filoviruses also exhibit a propensity for human-to-human transmission by close contact, posing challenges to containment and crisis management. Past outbreaks, in particular the recent West African EBOV epidemic, have been responsible for thousands of deaths and vaulted the filoviruses into public consciousness. Both national and international health agencies continue to regard potential filovirus outbreaks as critical threats to global public health. To develop effective countermeasures, a basic understanding of filovirus biology is needed. This review encompasses the epidemiology, ecology, molecular biology, and evolution of the filoviruses.
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Affiliation(s)
- Jackson Emanuel
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States
| | - Andrea Marzi
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States
| | - Heinz Feldmann
- Laboratory of Virology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, United States.
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27
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Takamatsu Y, Kolesnikova L, Becker S. Ebola virus proteins NP, VP35, and VP24 are essential and sufficient to mediate nucleocapsid transport. Proc Natl Acad Sci U S A 2018; 115:1075-1080. [PMID: 29339477 PMCID: PMC5798334 DOI: 10.1073/pnas.1712263115] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The intracytoplasmic movement of nucleocapsids is a crucial step in the life cycle of enveloped viruses. Determination of the viral components necessary for viral nucleocapsid transport competency is complicated by the dynamic and complex nature of nucleocapsid assembly and the lack of appropriate model systems. Here, we established a live-cell imaging system based on the ectopic expression of fluorescent Ebola virus (EBOV) fusion proteins, allowing the visualization and analysis of the movement of EBOV nucleocapsid-like structures with different protein compositions. Only three of the five EBOV nucleocapsid proteins-nucleoprotein, VP35, and VP24-were necessary and sufficient to form transport-competent nucleocapsid-like structures. The transport of these structures was found to be dependent on actin polymerization and to have dynamics that were undistinguishable from those of nucleocapsids in EBOV-infected cells. The intracytoplasmic movement of nucleocapsid-like structures was completely independent of the viral matrix protein VP40 and the viral surface glycoprotein GP. However, VP40 greatly enhanced the efficiency of nucleocapsid recruitment into filopodia, the sites of EBOV budding.
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Affiliation(s)
- Yuki Takamatsu
- Institute of Virology, Faculty of Medicine, Philipps University Marburg, 35037 Marburg, Germany
| | - Larissa Kolesnikova
- Institute of Virology, Faculty of Medicine, Philipps University Marburg, 35037 Marburg, Germany
| | - Stephan Becker
- Institute of Virology, Faculty of Medicine, Philipps University Marburg, 35037 Marburg, Germany;
- Thematic Translational Unit Emerging Infections, German Center of Infection Research (DZIF), 35037 Marburg, Germany
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28
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Muniyandi S, Pangratiou G, Edwards TA, Barr JN. Structure and Function of the Human Respiratory Syncytial Virus M2-1 Protein. Subcell Biochem 2018; 88:245-260. [PMID: 29900500 DOI: 10.1007/978-981-10-8456-0_11] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Human respiratory syncytial virus (HRSV) is a non-segmented negative stranded RNA virus and is recognized as the most important viral agent of lower respiratory tract infection worldwide, responsible for up to 199,000 deaths each year. The only FDA-approved regime to prevent HRSV-mediated disease is pre-exposure administration of a humanized HRSV-specific monoclonal antibody, which although being effective, is not in widespread usage due to its cost. No HRSV vaccine exists and so there remains a strong need for alternative and complementary anti-HRSV therapies. The HRSV M2-1 protein is a transcription factor and represents an attractive target for the development of antiviral compounds, based on its essential role in the viral replication cycle. To this end, a detailed analysis of M2-1 structure and functions will aid in identifying rational targets for structure-based antiviral drug design that can be developed in future translational research. Here we present an overview of the current understanding of the structure and function of HRSV M2-1, drawing on additional information derived from its structural homologues from other related viruses.
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Affiliation(s)
- Selvaraj Muniyandi
- School of Molecular and Cellular Biology, and The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - Georgia Pangratiou
- School of Molecular and Cellular Biology, and The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - Thomas A Edwards
- School of Molecular and Cellular Biology, and The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
| | - John N Barr
- School of Molecular and Cellular Biology, and The Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK.
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29
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Kruse T, Biedenkopf N, Hertz EPT, Dietzel E, Stalmann G, López-Méndez B, Davey NE, Nilsson J, Becker S. The Ebola Virus Nucleoprotein Recruits the Host PP2A-B56 Phosphatase to Activate Transcriptional Support Activity of VP30. Mol Cell 2017; 69:136-145.e6. [PMID: 29290611 DOI: 10.1016/j.molcel.2017.11.034] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 11/01/2017] [Accepted: 11/27/2017] [Indexed: 10/18/2022]
Abstract
Transcription of the Ebola virus genome depends on the viral transcription factor VP30 in its unphosphorylated form, but the underlying molecular mechanism of VP30 dephosphorylation is unknown. Here we show that the Ebola virus nucleoprotein (NP) recruits the host PP2A-B56 protein phosphatase through a B56-binding LxxIxE motif and that this motif is essential for VP30 dephosphorylation and viral transcription. The LxxIxE motif and the binding site of VP30 in NP are in close proximity, and both binding sites are required for the dephosphorylation of VP30. We generate a specific inhibitor of PP2A-B56 and show that it suppresses Ebola virus transcription and infection. This work dissects the molecular mechanism of VP30 dephosphorylation by PP2A-B56, and it pinpoints this phosphatase as a potential target for therapeutic intervention.
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Affiliation(s)
- Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Nadine Biedenkopf
- Institute of Virology, Philipps Universität Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Giessen-Marburg-Langen, Marburg, Germany
| | - Emil Peter Thrane Hertz
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Erik Dietzel
- Institute of Virology, Philipps Universität Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Giessen-Marburg-Langen, Marburg, Germany
| | - Gertrud Stalmann
- Institute of Virology, Philipps Universität Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Giessen-Marburg-Langen, Marburg, Germany
| | - Blanca López-Méndez
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark
| | - Norman E Davey
- Conway Institute of Biomolecular and Biomedical Sciences, University College Dublin, Dublin 4, Ireland
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen, Denmark.
| | - Stephan Becker
- Institute of Virology, Philipps Universität Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Giessen-Marburg-Langen, Marburg, Germany.
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30
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Lier C, Becker S, Biedenkopf N. Dynamic phosphorylation of Ebola virus VP30 in NP-induced inclusion bodies. Virology 2017; 512:39-47. [PMID: 28915404 DOI: 10.1016/j.virol.2017.09.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 08/18/2017] [Accepted: 09/07/2017] [Indexed: 12/22/2022]
Abstract
Zaire Ebolavirus (EBOV) causes a severe feverish disease with high case fatality rates. Transcription of EBOV is dependent on the activity of the nucleocapsid protein VP30 which represents an essential viral transcription factor. Activity of VP30 is regulated via phosphorylation at six N-terminal serine residues. Recent data demonstrated that dynamic phosphorylation and dephosphorylation of serine residue 29 is essential for transcriptional support activity of VP30. To analyze the spatio/temporal dynamics of VP30 phosphorylation, we generated a peptide antibody recognizing specifically VP30 phosphorylated at serine 29. Using this antibody we could demonstrate that (i) the majority of VP30 molecules in EBOV-infected cells is dephosphorylated at the crucial position serine 29, (ii) both, VP30 phosphorylation and dephosphorylation take place in viral inclusion bodies that are induced by the nucleoprotein NP and (iii) NP influences the phosphorylation state of VP30.
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Affiliation(s)
- Clemens Lier
- Institute of Virology, Philipps-University Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, Marburg, Germany
| | - Stephan Becker
- Institute of Virology, Philipps-University Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, Marburg, Germany.
| | - Nadine Biedenkopf
- Institute of Virology, Philipps-University Marburg, Marburg, Germany; German Center of Infection Research (DZIF), Partner Site Giessen-Marburg-Langen, Marburg, Germany.
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31
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He F, Melén K, Maljanen S, Lundberg R, Jiang M, Österlund P, Kakkola L, Julkunen I. Ebolavirus protein VP24 interferes with innate immune responses by inhibiting interferon-λ1 gene expression. Virology 2017; 509:23-34. [PMID: 28595092 DOI: 10.1016/j.virol.2017.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 05/25/2017] [Accepted: 06/01/2017] [Indexed: 10/19/2022]
Abstract
Ebolaviruses (EBOV) cause severe disease with a recent outbreak in West Africa in 2014-2015 leading to more than 28 000 cases and 11 300 fatalities. This emphasizes the urgent need for better knowledge on these highly pathogenic RNA viruses. Host innate immune responses play a key role in restricting the spread of a viral disease. In this study we systematically analyzed the effects of cloned EBOV genes on the main host immune response to RNA viruses: the activation of RIG-I pathway and type I and III interferon (IFN) gene expression. EBOV VP24, in addition of inhibiting IFN-induced antiviral responses, was found to efficiently inhibit type III IFN-λ1 gene expression. This inhibition was found to occur downstream of IRF3 activation and to be dependent on VP24 importin binding residues. These results emphasize the importance of VP24 in EBOV infection cycle, making VP24 as an excellent target for drug development.
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Affiliation(s)
- Felix He
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
| | - Krister Melén
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland; Expert Microbiology Unit, National Institute for Health and Welfare, Mannerheimintie 166, 00300 Helsinki, Finland.
| | - Sari Maljanen
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
| | - Rickard Lundberg
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
| | - Miao Jiang
- Expert Microbiology Unit, National Institute for Health and Welfare, Mannerheimintie 166, 00300 Helsinki, Finland.
| | - Pamela Österlund
- Expert Microbiology Unit, National Institute for Health and Welfare, Mannerheimintie 166, 00300 Helsinki, Finland.
| | - Laura Kakkola
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
| | - Ilkka Julkunen
- Institute of Biomedicine/Virology, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
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32
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The Host E3-Ubiquitin Ligase TRIM6 Ubiquitinates the Ebola Virus VP35 Protein and Promotes Virus Replication. J Virol 2017; 91:JVI.00833-17. [PMID: 28679761 DOI: 10.1128/jvi.00833-17] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 06/27/2017] [Indexed: 01/25/2023] Open
Abstract
Ebola virus (EBOV), a member of the Filoviridae family, is a highly pathogenic virus that causes severe hemorrhagic fever in humans and is responsible for epidemics throughout sub-Saharan, central, and West Africa. The EBOV genome encodes VP35, an important viral protein involved in virus replication by acting as an essential cofactor of the viral polymerase as well as a potent antagonist of the host antiviral type I interferon (IFN-I) system. By using mass spectrometry analysis and coimmunoprecipitation assays, we show here that VP35 is ubiquitinated on lysine 309 (K309), a residue located on its IFN antagonist domain. We also found that VP35 interacts with TRIM6, a member of the E3-ubiquitin ligase tripartite motif (TRIM) family. We recently reported that TRIM6 promotes the synthesis of unanchored K48-linked polyubiquitin chains, which are not covalently attached to any protein, to induce efficient antiviral IFN-I-mediated responses. Consistent with this notion, VP35 also associated noncovalently with polyubiquitin chains and inhibited TRIM6-mediated IFN-I induction. Intriguingly, we also found that TRIM6 enhances EBOV polymerase activity in a minigenome assay and TRIM6 knockout cells have reduced replication of infectious EBOV, suggesting that VP35 hijacks TRIM6 to promote EBOV replication through ubiquitination. Our work provides evidence that TRIM6 is an important host cellular factor that promotes EBOV replication, and future studies will focus on whether TRIM6 could be targeted for therapeutic intervention against EBOV infection.IMPORTANCE EBOV belongs to a family of highly pathogenic viruses that cause severe hemorrhagic fever in humans and other mammals with high mortality rates (40 to 90%). Because of its high pathogenicity and lack of licensed antivirals and vaccines, EBOV is listed as a tier 1 select-agent risk group 4 pathogen. An important mechanism for the severity of EBOV infection is its suppression of innate immune responses. The EBOV VP35 protein contributes to pathogenesis, because it serves as an essential cofactor of the viral polymerase as well as a potent antagonist of innate immunity. However, how VP35 function is regulated by host cellular factors is poorly understood. Here, we report that the host E3-ubiquitin ligase TRIM6 promotes VP35 ubiquitination and is important for efficient virus replication. Therefore, our study identifies a new host factor, TRIM6, as a potential target in the development of antiviral drugs against EBOV.
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Filovirus proteins for antiviral drug discovery: Structure/function bases of the replication cycle. Antiviral Res 2017; 141:48-61. [PMID: 28192094 DOI: 10.1016/j.antiviral.2017.02.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 01/12/2017] [Accepted: 02/07/2017] [Indexed: 12/26/2022]
Abstract
Filoviruses are important pathogens that cause severe and often fatal hemorrhagic fever in humans, for which no approved vaccines and antiviral treatments are yet available. In an earlier article (Martin et al., Antiviral Research, 2016), we reviewed the role of the filovirus surface glycoprotein in replication and as a target for drugs and vaccines. In this review, we focus on recent findings on the filovirus replication machinery and how they could be used for the identification of new therapeutic targets and the development of new antiviral compounds. First, we summarize the recent structural and functional advances on the molecules involved in filovirus replication/transcription cycle, particularly the NP, VP30, VP35 proteins, and the "large" protein L, which harbors the RNA-dependent RNA polymerase (RdRp) and mRNA capping activities. These proteins are essential for viral mRNA synthesis and genome replication, and consequently they constitute attractive targets for drug design. We then describe how these insights into filovirus replication mechanisms and the structure/function characterization of the involved proteins have led to the development of new and innovative antiviral strategies that may help reduce the filovirus disease case fatality rate through post-exposure or prophylactic treatments.
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Sztuba-Solinska J, Diaz L, Kumar MR, Kolb G, Wiley MR, Jozwick L, Kuhn JH, Palacios G, Radoshitzky SR, J Le Grice SF, Johnson RF. A small stem-loop structure of the Ebola virus trailer is essential for replication and interacts with heat-shock protein A8. Nucleic Acids Res 2016; 44:9831-9846. [PMID: 27651462 PMCID: PMC5175359 DOI: 10.1093/nar/gkw825] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/07/2016] [Accepted: 09/08/2016] [Indexed: 01/03/2023] Open
Abstract
Ebola virus (EBOV) is a single-stranded negative-sense RNA virus belonging to the Filoviridae family. The leader and trailer non-coding regions of the EBOV genome likely regulate its transcription, replication, and progeny genome packaging. We investigated the cis-acting RNA signals involved in RNA–RNA and RNA–protein interactions that regulate replication of eGFP-encoding EBOV minigenomic RNA and identified heat shock cognate protein family A (HSC70) member 8 (HSPA8) as an EBOV trailer-interacting host protein. Mutational analysis of the trailer HSPA8 binding motif revealed that this interaction is essential for EBOV minigenome replication. Selective 2′-hydroxyl acylation analyzed by primer extension analysis of the secondary structure of the EBOV minigenomic RNA indicates formation of a small stem-loop composed of the HSPA8 motif, a 3′ stem-loop (nucleotides 1868–1890) that is similar to a previously identified structure in the replicative intermediate (RI) RNA and a panhandle domain involving a trailer-to-leader interaction. Results of minigenome assays and an EBOV reverse genetic system rescue support a role for both the panhandle domain and HSPA8 motif 1 in virus replication.
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Affiliation(s)
- Joanna Sztuba-Solinska
- RT Biochemistry Section, Basic Research Laboratory, National Cancer Institute-Frederick, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Larissa Diaz
- Emerging Viral Pathogens Section, National Institute of Allergy and Infectious Disease, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Mia R Kumar
- Emerging Viral Pathogens Section, National Institute of Allergy and Infectious Disease, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Gaëlle Kolb
- Emerging Viral Pathogens Section, National Institute of Allergy and Infectious Disease, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Michael R Wiley
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702, USA
| | - Lucas Jozwick
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702, USA
| | - Jens H Kuhn
- Integrated Research Facility at Fort Detrick, National Institute of Allergy and Infectious Disease, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Gustavo Palacios
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702, USA
| | - Sheli R Radoshitzky
- United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702, USA
| | - Stuart F J Le Grice
- RT Biochemistry Section, Basic Research Laboratory, National Cancer Institute-Frederick, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
| | - Reed F Johnson
- Emerging Viral Pathogens Section, National Institute of Allergy and Infectious Disease, National Institutes of Health, Fort Detrick, Frederick, MD 21702, USA
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Schlereth J, Grünweller A, Biedenkopf N, Becker S, Hartmann RK. RNA binding specificity of Ebola virus transcription factor VP30. RNA Biol 2016; 13:783-98. [PMID: 27315567 DOI: 10.1080/15476286.2016.1194160] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The transcription factor VP30 of the non-segmented RNA negative strand Ebola virus balances viral transcription and replication. Here, we comprehensively studied RNA binding by VP30. Using a novel VP30:RNA electrophoretic mobility shift assay, we tested truncated variants of 2 potential natural RNA substrates of VP30 - the genomic Ebola viral 3'-leader region and its complementary antigenomic counterpart (each ∼155 nt in length) - and a series of other non-viral RNAs. Based on oligonucleotide interference, the major VP30 binding region on the genomic 3'-leader substrate was assigned to the internal expanded single-stranded region (∼ nt 125-80). Best binding to VP30 was obtained with ssRNAs of optimally ∼ 40 nt and mixed base composition; underrepresentation of purines or pyrimidines was tolerated, but homopolymeric sequences impaired binding. A stem-loop structure, particularly at the 3'-end or positioned internally, supports stable binding to VP30. In contrast, dsRNA or RNAs exposing large internal loops flanked by entirely helical arms on both sides are not bound. Introduction of a 5´-Cap(0) structure impaired VP30 binding. Also, ssDNAs bind substantially weaker than isosequential ssRNAs and heparin competes with RNA for binding to VP30, indicating that ribose 2'-hydroxyls and electrostatic contacts of the phosphate groups contribute to the formation of VP30:RNA complexes. Our results indicate a rather relaxed RNA binding specificity of filoviral VP30, which largely differs from that of the functionally related transcription factor of the Paramyxoviridae which binds to ssRNAs as short as 13 nt with a preference for oligo(A) sequences.
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Affiliation(s)
- Julia Schlereth
- a Institut für Pharmazeutische Chemie, Philipps-Universität Marburg , Marburg , Germany
| | - Arnold Grünweller
- a Institut für Pharmazeutische Chemie, Philipps-Universität Marburg , Marburg , Germany
| | - Nadine Biedenkopf
- b Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany
| | - Stephan Becker
- b Institut für Virologie, Philipps-Universität Marburg , Marburg , Germany
| | - Roland K Hartmann
- a Institut für Pharmazeutische Chemie, Philipps-Universität Marburg , Marburg , Germany
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