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Goldstein SA, Feeley TM, Babler KM, Hilbert ZA, Downhour DM, Moshiri N, Elde NC. Hidden evolutionary constraints dictate the retention of coronavirus accessory genes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.10.12.561935. [PMID: 37873270 PMCID: PMC10592793 DOI: 10.1101/2023.10.12.561935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Coronaviruses exhibit many mechanisms of genetic innovation (1-5), including the acquisition of accessory genes that originate by capture of cellular genes or through duplication of existing viral genes (6,7). Accessory genes influence viral host range and cellular tropism, but little is known about how selection acts on these variable regions of virus genomes. We used experimental evolution of mouse hepatitis virus (MHV) encoding a cellular AKAP7 phosphodiesterase and an inactive native phosphodiesterase, NS2 (ref 8) to simulate the capture of a host gene and analyze its evolution. After courses of serial infection, the gene encoding inactive NS2, ORF2, unexpectedly remained intact, suggesting it is under cryptic constraint uncoupled from the function of NS2. In contrast, AKAP7 was retained under strong selection but rapidly lost under relaxed selection. Guided by the retention of ORF2 and similar patterns in related betacoronaviruses, we analyzed ORF8 of SARS-CoV-2, which arose via gene duplication6 and contains premature stop codons in several globally successful lineages. As with MHV ORF2, the coding-defective SARS-CoV-2 ORF8 gene remains largely intact, mirroring patterns observed during MHV experimental evolution, challenging assumptions on the dynamics of gene loss in virus genomes and extending these findings to viruses currently adapting to humans.
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2
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Goldstein SA, Elde NC. Recurrent viral capture of cellular phosphodiesterases that antagonize OAS-RNase L. Proc Natl Acad Sci U S A 2024; 121:e2312691121. [PMID: 38277437 PMCID: PMC10835031 DOI: 10.1073/pnas.2312691121] [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: 07/25/2023] [Accepted: 11/20/2023] [Indexed: 01/28/2024] Open
Abstract
Phosphodiesterases (PDEs) encoded by viruses are putatively acquired by horizontal transfer of cellular PDE ancestor genes. Viral PDEs inhibit the OAS-RNase L antiviral pathway, a key effector component of the innate immune response. Although the function of these proteins is well-characterized, the origins of these gene acquisitions are less clear. Phylogenetic analysis revealed at least five independent PDE acquisition events by ancestral viruses. We found evidence that PDE-encoding genes were horizontally transferred between coronaviruses belonging to different genera. Three clades of viruses within Nidovirales: merbecoviruses (MERS-CoV), embecoviruses (HCoV-OC43), and toroviruses encode independently acquired PDEs, and a clade of rodent alphacoronaviruses acquired an embecovirus PDE via recent horizontal transfer. Among rotaviruses, the PDE of rotavirus A was acquired independently from rotavirus B and G PDEs, which share a common ancestor. Conserved motif analysis suggests a link between all viral PDEs and a similar ancestor among the mammalian AKAP7 proteins despite low levels of sequence conservation. Additionally, we used ancestral sequence reconstruction and structural modeling to reveal that sequence and structural divergence are not well-correlated among these proteins. Specifically, merbecovirus PDEs are as structurally divergent from the ancestral protein and the solved structure of human AKAP7 PDE as they are from each other. In contrast, comparisons of rotavirus B and G PDEs reveal virtually unchanged structures despite evidence for loss of function in one, suggesting impactful changes that lie outside conserved catalytic sites. These findings highlight the complex and volatile evolutionary history of viral PDEs and provide a framework to facilitate future studies.
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Affiliation(s)
- Stephen A. Goldstein
- Department of Human Genetics, University of Utah, School of Medicine, Salt Lake City, UT84112
- HHMI, Chevy Chase, MD20815
| | - Nels C. Elde
- Department of Human Genetics, University of Utah, School of Medicine, Salt Lake City, UT84112
- HHMI, Chevy Chase, MD20815
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3
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Goldstein SA, Elde NC. Recurrent Viral Capture of Cellular Phosphodiesterases that Antagonize OAS-RNase L. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.12.540623. [PMID: 37745432 PMCID: PMC10515750 DOI: 10.1101/2023.05.12.540623] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
Phosphodiesterases (PDEs) encoded by viruses are putatively acquired by horizontal transfer of cellular PDE ancestor genes. Viral PDEs inhibit the OAS-RNase L antiviral pathway, a key effector component of the innate immune response. Although the function of these proteins is well-characterized, the origins of these gene acquisitions is less clear. Phylogenetic analysis revealed at least five independent PDE acquisition events by ancestral viruses. We found evidence that PDE-encoding genes were horizontally transferred between coronavirus genera. Three clades of viruses within Nidovirales: merbecoviruses (MERS-CoV), embecoviruses (OC43), and toroviruses encode independently acquired PDEs, and a clade of rodent alphacoronaviruses acquired an embecovirus PDE via recent horizontal transfer. Among rotaviruses, the PDE of Rotavirus A was acquired independently from Rotavirus B and G PDEs, which share a common ancestor. Conserved motif analysis suggests a link between all viral PDEs and a similar ancestor among the mammalian AKAP7 proteins despite low levels of sequence conservation. Additionally, we used ancestral sequence reconstruction and structural modeling to reveal that sequence and structural divergence are not well-correlated among these proteins. Specifically, merbecovirus PDEs are as structurally divergent from the ancestral protein and the solved structure of human AKAP7 PDE as they are from each other. In contrast, comparisons of Rotavirus B and G PDEs reveal virtually unchanged structures despite evidence for loss of function in one, suggesting impactful changes that lie outside conserved catalytic sites. These findings highlight the complex and volatile evolutionary history of viral PDEs and provide a framework to facilitate future studies.
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Affiliation(s)
- Stephen A Goldstein
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT, USA Howard Hughes Medical Institute, 4000 Jones Bridge Rd, Chevy Chase, MD 20815, USA
| | - Nels C Elde
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT, USA Howard Hughes Medical Institute, 4000 Jones Bridge Rd, Chevy Chase, MD 20815, USA
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4
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Thursz M, Sadiq F, Tree JA, Karayiannis P, Beasley DWC, Dejnirattisai W, Mongkolsapaya J, Screaton G, Wand M, Elmore MJ, Carroll MW, Matthews I, Thomas H. Inhibition of phosphodiesterase 12 results in antiviral activity against several RNA viruses including SARS-CoV-2. J Gen Virol 2023; 104. [PMID: 37432877 DOI: 10.1099/jgv.0.001865] [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] [Indexed: 07/13/2023] Open
Abstract
The 2',5'- oligoadenylate synthetase (OAS) - ribonuclease L (RNAseL) - phosphodiesterase 12 (PDE12) pathway is an essential interferon-induced effector mechanism against RNA virus infection. Inhibition of PDE12 leads to selective amplification of RNAseL activity in infected cells. We aimed to investigate PDE12 as a potential pan-RNA virus antiviral drug target and develop PDE12 inhibitors that elicit antiviral activity against a range of viruses. A library of 18 000 small molecules was screened for PDE12 inhibitor activity using a fluorescent probe specific for PDE12. The lead compounds (CO-17 or CO-63) were tested in cell-based antiviral assays using encephalomyocarditis virus (EMCV), hepatitis C virus (HCV), dengue virus (DENV), West Nile virus (WNV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in vitro. Cross reactivity of PDE12 inhibitors with other PDEs and in vivo toxicity were measured. In EMCV assays, CO-17 potentiated the effect of IFNα by 3 log10. The compounds were selective for PDE12 when tested against a panel of other PDEs and non-toxic at up to 42 mg kg-1 in rats in vivo. Thus, we have identified PDE12 inhibitors (CO-17 and CO-63), and established the principle that inhibitors of PDE12 have antiviral properties. Early studies suggest these PDE12 inhibitors are well tolerated at the therapeutic range, and reduce viral load in studies of DENV, HCV, WNV and SARS-CoV-2 in human cells and WNV in a mouse model.
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Affiliation(s)
- Mark Thursz
- Department of Metabolism, Digestion and Reproduction, Imperial College, London W2 1NY, UK
| | - Fouzia Sadiq
- Department of Metabolism, Digestion and Reproduction, Imperial College, London W2 1NY, UK
- Present address: Directorate of Research, Shifa Tameer-e-Millat University, Islamabad, Pakistan
| | - Julia A Tree
- UK Health Security Agency, Porton Down, Salisbury, SP4 0JG, UK
| | - Peter Karayiannis
- University of Nicosia Medical School, Nicosia, Cyprus
- RioTech Pharmaceuticals, 49 Arrivato Plaza, St Helens, WA10 1GH, UK
| | - David W C Beasley
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
- Centre for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
- Sealy Institute for Vaccine Sciences, University of Texas Medical Branch, Galveston, TX 77555-1019, USA
| | | | | | - Gavin Screaton
- Medical Science Division, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Matthew Wand
- UK Health Security Agency, Porton Down, Salisbury, SP4 0JG, UK
| | | | - Miles W Carroll
- UK Health Security Agency, Porton Down, Salisbury, SP4 0JG, UK
| | - Ian Matthews
- RioTech Pharmaceuticals, 49 Arrivato Plaza, St Helens, WA10 1GH, UK
| | - Howard Thomas
- Department of Metabolism, Digestion and Reproduction, Imperial College, London W2 1NY, UK
- RioTech Pharmaceuticals, 49 Arrivato Plaza, St Helens, WA10 1GH, UK
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5
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Comar CE, Otter CJ, Pfannenstiel J, Doerger E, Renner DM, Tan LH, Perlman S, Cohen NA, Fehr AR, Weiss SR. MERS-CoV endoribonuclease and accessory proteins jointly evade host innate immunity during infection of lung and nasal epithelial cells. Proc Natl Acad Sci U S A 2022; 119:e2123208119. [PMID: 35594398 PMCID: PMC9173776 DOI: 10.1073/pnas.2123208119] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 04/13/2022] [Indexed: 12/25/2022] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) emerged into humans in 2012, causing highly lethal respiratory disease. The severity of disease may be, in part, because MERS-CoV is adept at antagonizing early innate immune pathways—interferon (IFN) production and signaling, protein kinase R (PKR), and oligoadenylate synthetase/ribonuclease L (OAS/RNase L)—activated in response to viral double-stranded RNA (dsRNA) generated during genome replication. This is in contrast to severe acute respiratory syndrome CoV-2 (SARS-CoV-2), which we recently reported to activate PKR and RNase L and, to some extent, IFN signaling. We previously found that MERS-CoV accessory proteins NS4a (dsRNA binding protein) and NS4b (phosphodiesterase) could weakly suppress these pathways, but ablation of each had minimal effect on virus replication. Here we investigated the antagonist effects of the conserved coronavirus endoribonuclease (EndoU), in combination with NS4a or NS4b. Inactivation of EndoU catalytic activity alone in a recombinant MERS-CoV caused little if any effect on activation of the innate immune pathways during infection. However, infection with recombinant viruses containing combined mutations with inactivation of EndoU and deletion of NS4a or inactivation of the NS4b phosphodiesterase promoted robust activation of dsRNA-induced innate immune pathways. This resulted in at least tenfold attenuation of replication in human lung–derived A549 and primary nasal cells. Furthermore, replication of these recombinant viruses could be rescued to the level of wild-type MERS-CoV by knockout of host immune mediators MAVS, PKR, or RNase L. Thus, EndoU and accessory proteins NS4a and NS4b together suppress dsRNA-induced innate immunity during MERS-CoV infection in order to optimize viral replication.
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Affiliation(s)
- Courtney E. Comar
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
- Penn Center for Research on Coronaviruses and Other Emerging Pathogens, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Clayton J. Otter
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
- Penn Center for Research on Coronaviruses and Other Emerging Pathogens, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | | | - Ethan Doerger
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045
| | - David M. Renner
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
- Penn Center for Research on Coronaviruses and Other Emerging Pathogens, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Li Hui Tan
- Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA 19104
| | - Stanley Perlman
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA 52242
| | - Noam A. Cohen
- Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA 19104
- Department of Surgery, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, PA 19104
| | - Anthony R. Fehr
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA 52242
| | - Susan R. Weiss
- Department of Microbiology, University of Pennsylvania, Philadelphia, PA 19104
- Penn Center for Research on Coronaviruses and Other Emerging Pathogens, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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6
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MERS-CoV ORF4b employs an unusual binding mechanism to target IMPα and block innate immunity. Nat Commun 2022; 13:1604. [PMID: 35338144 PMCID: PMC8956657 DOI: 10.1038/s41467-022-28851-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 02/11/2022] [Indexed: 11/25/2022] Open
Abstract
The MERS coronavirus (MERS-CoV) is a highly pathogenic, emerging virus that produces accessory proteins to antagonize the host innate immune response. The MERS-CoV ORF4b protein has been shown to bind preferentially to the nuclear import adapter IMPα3 in infected cells, thereby inhibiting NF-κB-dependent innate immune responses. Here, we report high-resolution structures of ORF4b bound to two distinct IMPα family members. Each exhibit highly similar binding mechanisms that, in both cases, lack a prototypical Lys bound at their P2 site. Mutations within the NLS region dramatically alter the mechanism of binding, which reverts to the canonical P2 Lys binding mechanism. Mutational studies confirm that the novel binding mechanism is important for its nuclear import, IMPα interaction, and inhibition of innate immune signaling pathways. In parallel, we determined structures of the nuclear binding domain of NF-κB component p50 bound to both IMPα2 and α3, demonstrating that p50 overlaps with the ORF4b binding sites, suggesting a basis for inhibition. Our results provide a detailed structural basis that explains how a virus can target the IMPα nuclear import adapter to impair immunity, and illustrate how small mutations in ORF4b, like those found in closely related coronaviruses such as HKU5, change the IMPα binding mechanism. MERS-CoV ORF4b antagonizes host innate immune response, partially via blocking nuclear import adapter IMPα activity and preventing nuclear translocation of NF-κB. Here, Munasinghe and Edwards et al. biochemically and structurally define the interaction between ORF4b and IMPα-family members and find a non-canonical interaction between ORF4b NLS and IMPα2 and IMPα3.
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7
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Comar CE, Otter CJ, Pfannenstiel J, Doerger E, Renner DM, Tan LH, Perlman S, Cohen NA, Fehr AR, Weiss SR. MERS-CoV endoribonuclease and accessory proteins jointly evade host innate immunity during infection of lung and nasal epithelial cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2021. [PMID: 34981054 DOI: 10.1101/2021.12.20.473564] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) emerged into humans in 2012, causing highly lethal respiratory disease. The severity of disease may be in part because MERS-CoV is adept at antagonizing early innate immune pathways - interferon (IFN) production and signaling, protein kinase R (PKR), and oligoadenylate synthetase ribonuclease L (OAS/RNase L) - generated in response to viral double-stranded (ds)RNA generated during genome replication. This is in contrast to SARS-CoV-2, which we recently reported activates PKR and RNase L and to some extent, IFN signaling. We previously found that MERS-CoV accessory proteins NS4a (dsRNA binding protein) and NS4b (phosphodiesterase) could weakly suppress these pathways, but ablation of each had minimal effect on virus replication. Here we investigated the antagonist effects of the conserved coronavirus endoribonuclease (EndoU), in combination with NS4a or NS4b. Inactivation of EndoU catalytic activity alone in a recombinant MERS-CoV caused little if any effect on activation of the innate immune pathways during infection. However, infection with recombinant viruses containing combined mutations with inactivation of EndoU and deletion of NS4a or inactivation of the NS4b phosphodiesterase promoted robust activation of the dsRNA-induced innate immune pathways. This resulted in ten-fold attenuation of replication in human lung derived A549 and primary nasal cells. Furthermore, replication of these recombinant viruses could be rescued to the level of WT MERS-CoV by knockout of host immune mediators MAVS, PKR, or RNase L. Thus, EndoU and accessory proteins NS4a and NS4b together suppress dsRNA-induced innate immunity during MERS-CoV infection in order to optimize viral replication. IMPORTANCE Middle East Respiratory Syndrome Coronavirus (MERS-CoV) causes highly lethal respiratory disease. MERS-CoV encodes several innate immune antagonists, accessory proteins NS4a and NS4b unique to the merbeco lineage and the nsp15 protein endoribonuclease (EndoU), conserved among all coronaviruses. While mutation of each antagonist protein alone has little effect on innate immunity, infections with recombinant MERS-CoVs with mutations of EndoU in combination with either NS4a or NS4b, activate innate signaling pathways and are attenuated for replication. Our data indicate that EndoU and accessory proteins NS4a and NS4b together suppress innate immunity during MERS-CoV infection, to optimize viral replication. This is in contrast to SARS-CoV-2 which activates these pathways and consistent with greater mortality observed during MERS-CoV infection compared to SARS-CoV-2.
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8
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Wickenhagen A, Sugrue E, Lytras S, Kuchi S, Noerenberg M, Turnbull ML, Loney C, Herder V, Allan J, Jarmson I, Cameron-Ruiz N, Varjak M, Pinto RM, Lee JY, Iselin L, Palmalux N, Stewart DG, Swingler S, Greenwood EJD, Crozier TWM, Gu Q, Davies EL, Clohisey S, Wang B, Trindade Maranhão Costa F, Freire Santana M, de Lima Ferreira LC, Murphy L, Fawkes A, Meynert A, Grimes G, Da Silva Filho JL, Marti M, Hughes J, Stanton RJ, Wang ECY, Ho A, Davis I, Jarrett RF, Castello A, Robertson DL, Semple MG, Openshaw PJM, Palmarini M, Lehner PJ, Baillie JK, Rihn SJ, Wilson SJ. A prenylated dsRNA sensor protects against severe COVID-19. Science 2021; 374:eabj3624. [PMID: 34581622 PMCID: PMC7612834 DOI: 10.1126/science.abj3624] [Citation(s) in RCA: 122] [Impact Index Per Article: 40.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 09/23/2021] [Indexed: 12/11/2022]
Abstract
Inherited genetic factors can influence the severity of COVID-19, but the molecular explanation underpinning a genetic association is often unclear. Intracellular antiviral defenses can inhibit the replication of viruses and reduce disease severity. To better understand the antiviral defenses relevant to COVID-19, we used interferon-stimulated gene (ISG) expression screening to reveal that 2′-5′-oligoadenylate synthetase 1 (OAS1), through ribonuclease L, potently inhibits severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We show that a common splice-acceptor single-nucleotide polymorphism (Rs10774671) governs whether patients express prenylated OAS1 isoforms that are membrane-associated and sense-specific regions of SARS-CoV-2 RNAs or if they only express cytosolic, nonprenylated OAS1 that does not efficiently detect SARS-CoV-2. In hospitalized patients, expression of prenylated OAS1 was associated with protection from severe COVID-19, suggesting that this antiviral defense is a major component of a protective antiviral response.
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Affiliation(s)
- Arthur Wickenhagen
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Elena Sugrue
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Spyros Lytras
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Srikeerthana Kuchi
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Marko Noerenberg
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Matthew L. Turnbull
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Colin Loney
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Vanessa Herder
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Jay Allan
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Innes Jarmson
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Natalia Cameron-Ruiz
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Margus Varjak
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Rute M. Pinto
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Jeffrey Y. Lee
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Louisa Iselin
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Natasha Palmalux
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Douglas G. Stewart
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Simon Swingler
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Edward J. D. Greenwood
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, Cambridge, UK
| | - Thomas W. M. Crozier
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, Cambridge, UK
| | - Quan Gu
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Emma L. Davies
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Sara Clohisey
- Roslin Institute, University of Edinburgh, Edinburgh, UK
| | - Bo Wang
- Roslin Institute, University of Edinburgh, Edinburgh, UK
| | - Fabio Trindade Maranhão Costa
- Laboratory of Tropical Diseases, Department of Genetics, Evolution, Microbiology and Immunology, Institute of Biology, University of Campinas, Campinas, Sao Paolo, Brazil
| | - Monique Freire Santana
- Department of Education and Research, Oncology Control Centre of Amazonas State (FCECON), Manaus, Amazonas, Brazil
| | - Luiz Carlos de Lima Ferreira
- Postgraduate Program in Tropical Medicine, Tropical Medicine Foundation Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil
| | - Lee Murphy
- Edinburgh Clinical Research Facility, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - Angie Fawkes
- Edinburgh Clinical Research Facility, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - Alison Meynert
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - Graeme Grimes
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, UK
| | - ISARIC4C Investigators
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, Cambridge, UK
- Roslin Institute, University of Edinburgh, Edinburgh, UK
- Laboratory of Tropical Diseases, Department of Genetics, Evolution, Microbiology and Immunology, Institute of Biology, University of Campinas, Campinas, Sao Paolo, Brazil
- Department of Education and Research, Oncology Control Centre of Amazonas State (FCECON), Manaus, Amazonas, Brazil
- Postgraduate Program in Tropical Medicine, Tropical Medicine Foundation Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil
- Edinburgh Clinical Research Facility, University of Edinburgh, Western General Hospital, Edinburgh, UK
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, UK
- Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
- Division of Infection & Immunity, Cardiff University, Cardiff, UK
- NIHR Health Protection Research Unit for Emerging and Zoonotic Infections, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
- Respiratory Medicine, Alder Hey Children’s Hospital, Liverpool, UK
- National Heart and Lung Institute, Imperial College London, London, UK
- Imperial College Healthcare, National Health Service Trust London, London, UK
- Intensive Care Unit, Royal Infirmary of Edinburgh, Edinburgh, UK
| | - Joao Luiz Da Silva Filho
- Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - Matthias Marti
- Wellcome Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - Joseph Hughes
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | | | - Eddie C. Y. Wang
- Division of Infection & Immunity, Cardiff University, Cardiff, UK
| | - Antonia Ho
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Ilan Davis
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Ruth F. Jarrett
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Alfredo Castello
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - David L. Robertson
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Malcolm G. Semple
- NIHR Health Protection Research Unit for Emerging and Zoonotic Infections, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK
- Respiratory Medicine, Alder Hey Children’s Hospital, Liverpool, UK
| | - Peter J. M. Openshaw
- National Heart and Lung Institute, Imperial College London, London, UK
- Imperial College Healthcare, National Health Service Trust London, London, UK
| | - Massimo Palmarini
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Paul J. Lehner
- Cambridge Institute of Therapeutic Immunology and Infectious Disease, University of Cambridge, Cambridge, UK
| | - J. Kenneth Baillie
- Roslin Institute, University of Edinburgh, Edinburgh, UK
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, UK
- Intensive Care Unit, Royal Infirmary of Edinburgh, Edinburgh, UK
| | - Suzannah J. Rihn
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
| | - Sam J. Wilson
- Medical Research Council–University of Glasgow Centre for Virus Research (CVR), Institute of Infection, Inflammation and Immunity, University of Glasgow, Glasgow, UK
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9
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Specificity and Mechanism of Coronavirus, Rotavirus, and Mammalian Two-Histidine Phosphoesterases That Antagonize Antiviral Innate Immunity. mBio 2021; 12:e0178121. [PMID: 34372695 PMCID: PMC8406329 DOI: 10.1128/mbio.01781-21] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The 2′,5′-oligoadenylate (2-5A)-dependent endoribonuclease, RNase L, is a principal mediator of the interferon (IFN) antiviral response. Therefore, the regulation of cellular levels of 2-5A is a key point of control in antiviral innate immunity. Cellular 2-5A levels are determined by IFN-inducible 2′,5′-oligoadenylate synthetases (OASs) and by enzymes that degrade 2-5A. Importantly, many coronaviruses (CoVs) and rotaviruses encode 2-5A-degrading enzymes, thereby antagonizing RNase L and its antiviral effects. A-kinase-anchoring protein 7 (AKAP7), a mammalian counterpart, could possibly limit tissue damage from excessive or prolonged RNase L activation during viral infections or from self-double-stranded RNAs that activate OAS. We show that these enzymes, members of the two-histidine phosphoesterase (2H-PE) superfamily, constitute a subfamily referred here as 2′,5′-PEs. 2′,5′-PEs from the mouse CoV mouse hepatitis virus (MHV) (NS2), Middle East respiratory syndrome coronavirus (MERS-CoV) (NS4b), group A rotavirus (VP3), and mouse (AKAP7) were investigated for their evolutionary relationships and activities. While there was no activity against 3′,5′-oligoribonucleotides, they all cleaved 2′,5′-oligoadenylates efficiently but with variable activity against other 2′,5′-oligonucleotides. The 2′,5′-PEs are shown to be metal ion-independent enzymes that cleave trimer 2-5A (2′,5′-p3A3) producing mono- or diadenylates with 2′,3′-cyclic phosphate termini. Our results suggest that the elimination of 2-5A might be the sole function of viral 2′,5′-PEs, thereby promoting viral escape from innate immunity by preventing or limiting the activation of RNase L.
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10
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Ramnani B, Manivannan P, Jaggernauth S, Malathi K. ABCE1 Regulates RNase L-Induced Autophagy during Viral Infections. Viruses 2021; 13:v13020315. [PMID: 33670646 PMCID: PMC7922175 DOI: 10.3390/v13020315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/14/2021] [Accepted: 02/16/2021] [Indexed: 12/15/2022] Open
Abstract
Host response to a viral infection includes the production of type I interferon (IFN) and the induction of interferon-stimulated genes that have broad antiviral effects. One of the key antiviral effectors is the IFN-inducible oligoadenylate synthetase/ribonuclease L (OAS/RNase L) pathway, which is activated by double-stranded RNA to synthesize unique oligoadenylates, 2-5A, to activate RNase L. RNase L exerts an antiviral effect by cleaving diverse RNA substrates, limiting viral replication; many viruses have evolved mechanisms to counteract the OAS/RNase L pathway. Here, we show that the ATP-binding cassette E1 (ABCE1) transporter, identified as an inhibitor of RNase L, regulates RNase L activity and RNase L-induced autophagy during viral infections. ABCE1 knockdown cells show increased RNase L activity when activated by 2-5A. Compared to parental cells, the autophagy-inducing activity of RNase L in ABCE1-depleted cells is enhanced with early onset. RNase L activation in ABCE1-depleted cells inhibits cellular proliferation and sensitizes cells to apoptosis. Increased activity of caspase-3 causes premature cleavage of autophagy protein, Beclin-1, promoting a switch from autophagy to apoptosis. ABCE1 regulates autophagy during EMCV infection, and enhanced autophagy in ABCE1 knockdown cells promotes EMCV replication. We identify ABCE1 as a host protein that inhibits the OAS/RNase L pathway by regulating RNase L activity, potentially affecting antiviral effects.
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11
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Kondratova AA, Cheon H, Dong B, Holvey-Bates EG, Hasipek M, Taran I, Gaughan C, Jha BK, Silverman RH, Stark GR. Suppressing PARylation by 2',5'-oligoadenylate synthetase 1 inhibits DNA damage-induced cell death. EMBO J 2020; 39:e101573. [PMID: 32323871 DOI: 10.15252/embj.2019101573] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 03/05/2020] [Accepted: 03/12/2020] [Indexed: 12/14/2022] Open
Abstract
High expression of 2',5'-oligoadenylate synthetase 1 (OAS1), which adds AMP residues in 2',5' linkage to a variety of substrates, is observed in many cancers as a part of the interferon-related DNA damage resistance signature (IRDS). Poly(ADP-ribose) (PAR) is rapidly synthesized from NAD+ at sites of DNA damage to facilitate repair, but excessive PAR synthesis due to extensive DNA damage results in cell death by energy depletion and/or activation of PAR-dependent programmed cell death pathways. We find that OAS1 adds AMP residues in 2',5' linkage to PAR, inhibiting its synthesis in vitro and reducing its accumulation in cells. Increased OAS1 expression substantially improves cell viability following DNA-damaging treatments that stimulate PAR synthesis during DNA repair. We conclude that high expression of OAS1 in cancer cells promotes their ability to survive DNA damage by attenuating PAR synthesis and thus preventing cell death.
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Affiliation(s)
- Anna A Kondratova
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.,Department of Psychiatry, Case Western Reserve University, Cleveland, OH, USA
| | - HyeonJoo Cheon
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Beihua Dong
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Elise G Holvey-Bates
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Metis Hasipek
- Taussig Cancer Center, Cleveland Clinic, Cleveland, OH, USA
| | - Irina Taran
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Christina Gaughan
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - Babal K Jha
- Taussig Cancer Center, Cleveland Clinic, Cleveland, OH, USA
| | - Robert H Silverman
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - George R Stark
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
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12
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Kranzusch PJ. cGAS and CD-NTase enzymes: structure, mechanism, and evolution. Curr Opin Struct Biol 2019; 59:178-187. [PMID: 31593902 PMCID: PMC7127440 DOI: 10.1016/j.sbi.2019.08.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 07/25/2019] [Accepted: 08/25/2019] [Indexed: 01/22/2023]
Abstract
Cyclic GMP-AMP synthase (cGAS) is a signaling enzyme in human cells that controls immune-sensing of cytosolic DNA. The recent discoveries of diverse structural homologs of cGAS in animals and bacteria reveal that cGAS-like signaling is surprisingly ancient and widespread in biology. Together with the Vibrio cholerae protein dinucleotide cyclase in Vibrio (DncV), cGAS and DncV homologs comprise a family of cGAS/DncV-like nucleotidyltransferase (CD-NTase) enzymes that synthesize noncanonical RNA signals including cyclic dinucleotides, cyclic trinucleotides, and linear oligonucleotides. Structural and biochemical breakthroughs provide a framework to understand how CD-NTase signaling allows cells to respond to changing environmental conditions. The CD-NTase family also includes uncharacterized human genes like MB21D2 and Mab21L1, highlighting emerging functions of cGAS-like signaling beyond innate immunity.
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Affiliation(s)
- Philip J Kranzusch
- Department of Microbiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02115, USA; Parker Institute for Cancer Immunotherapy at Dana-Farber Cancer Institute, Boston, MA 02115, USA.
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13
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Rath S, Prangley E, Donovan J, Demarest K, Wingreen NS, Meir Y, Korennykh A. Concerted 2-5A-Mediated mRNA Decay and Transcription Reprogram Protein Synthesis in the dsRNA Response. Mol Cell 2019; 75:1218-1228.e6. [PMID: 31494033 DOI: 10.1016/j.molcel.2019.07.027] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/13/2019] [Accepted: 07/16/2019] [Indexed: 01/09/2023]
Abstract
Viral and endogenous double-stranded RNA (dsRNA) is a potent trigger for programmed RNA degradation by the 2-5A/RNase L complex in cells of all mammals. This 2-5A-mediated decay (2-5AMD) is a conserved stress response switching global protein synthesis from homeostasis to production of interferons (IFNs). To understand this mechanism, we examined 2-5AMD in human cells and found that it triggers polysome collapse characteristic of inhibited translation initiation. We determined that translation initiation complexes and ribosomes purified from translation-arrested cells remain functional. However, spike-in RNA sequencing (RNA-seq) revealed cell-wide decay of basal mRNAs accompanied by rapid accumulation of mRNAs encoding innate immune proteins. Our data attribute this 2-5AMD evasion to better stability of defense mRNAs and positive feedback in the IFN response amplified by RNase L-resistant molecules. We conclude that 2-5AMD and transcription act in concert to refill mammalian cells with defense mRNAs, thereby "prioritizing" the synthesis of innate immune proteins.
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Affiliation(s)
- Sneha Rath
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Eliza Prangley
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Jesse Donovan
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Kaitlin Demarest
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ned S Wingreen
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Yigal Meir
- Department of Physics, Ben Gurion University, Beer-Sheva 84105, Israel
| | - Alexei Korennykh
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
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14
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Identification of 2H phosphoesterase superfamily proteins with 2'-CPDase activity. Biochimie 2019; 165:235-244. [PMID: 31422053 DOI: 10.1016/j.biochi.2019.08.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 08/13/2019] [Indexed: 12/22/2022]
Abstract
The 2H phosphoesterase superfamily (2H family) proteins are widely conserved among organisms. The 2H family is classified into several subgroups, including YjcG-like proteins whose enzymatic activity has not been reported. In the present study, we found that two YjcG-like proteins (Staphylococcus aureus SA0873 and Bacillus subtilis YjcG) have 2'-CPDase activity that hydrolyzes a 2',3'-cyclic nucleotide, thereby producing a nucleotide with a 3'-phosphate. The SA0873 protein selectively hydrolyzes a 2',3'-cyclic nucleotide with a purine base. Four SA0873 mutant proteins (H34A, T36A, H115A, and T117A), in which alanine was substituted for amino acid residues in the HxT/Sx motifs that are conserved in the 2H family, abolished the 2'-CPDase activity. Comparison of three-dimensional structures between the YjcG-like proteins with 2'-CPDase activity and another 2H family subgroup, LigT/2'-5' RNA ligase-like proteins with 3'-CPDase activity, revealed that the orientation of the substrate binding pocket is reversed between the two groups. Our findings revealed that YjcG-like proteins not only have a substrate-binding pocket different from that of LigT/2'-5' RNA ligase-like proteins, but they also have 2'-CPDase activity.
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15
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Antagonism of dsRNA-Induced Innate Immune Pathways by NS4a and NS4b Accessory Proteins during MERS Coronavirus Infection. mBio 2019; 10:mBio.00319-19. [PMID: 30914508 PMCID: PMC6437052 DOI: 10.1128/mbio.00319-19] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) is the second novel zoonotic
coronavirus to emerge in the 21st century and cause outbreaks of severe respiratory
disease. More than 2,200 cases and 800 deaths have been reported to date, yet there are no
licensed vaccines or treatments. Coronaviruses encode unique accessory proteins that are
not required for replication but most likely play roles in immune antagonism and/or
pathogenesis. Our study describes the functions of MERS-CoV accessory proteins NS4a and
NS4b during infection of a human airway-derived cell line. Loss of these accessory
proteins during MERS-CoV infection leads to host antiviral activation and modestly
attenuates replication. In the case of both NS4a and NS4b, we have identified roles during
infection not previously described, yet the lack of robust activation suggests much
remains to be learned about the interactions between MERS-CoV and the infected host. Middle East respiratory syndrome coronavirus (MERS-CoV) was first identified in 2012 as a
novel etiological agent of severe respiratory disease in humans. As during infection by
other viruses, host sensing of viral double-stranded RNA (dsRNA) induces several antiviral
pathways. These include interferon (IFN), oligoadenylate synthetase (OAS)-RNase L, and
protein kinase R (PKR). Coronaviruses, including MERS-CoV, potently suppress the
activation of these pathways, inducing only modest host responses. Our study describes the
functions of two accessory proteins unique to MERS-CoV and related viruses, NS4a and NS4b,
during infection in human airway epithelium-derived A549 cells. NS4a has been previously
characterized as a dsRNA binding protein, while NS4b is a
2′,5′-phosphodiesterase with structural and enzymatic similarity to NS2
encoded by mouse hepatitis virus (MHV). We found that deletion of NS4a results in
increased interferon lambda (IFNL1) expression, as does mutation of
either the catalytic site or nuclear localization sequence of NS4b. All of the mutant
viruses we tested exhibited slight decreases in replication. We previously reported that,
like MHV NS2, NS4b antagonizes OAS-RNase L, but suppression of IFN is a previously
unidentified function for viral phosphodiesterases. Unexpectedly, deletion of NS4a does
not result in robust activation of the PKR or OAS-RNase L pathways. Therefore, MERS-CoV
likely encodes other proteins that contribute to suppression or evasion of these antiviral
innate immune pathways that should be an important focus of future work. This study
provides additional insight into the complex interactions between MERS-CoV and the host
immune response.
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16
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OAS-RNase L innate immune pathway mediates the cytotoxicity of a DNA-demethylating drug. Proc Natl Acad Sci U S A 2019; 116:5071-5076. [PMID: 30814222 PMCID: PMC6421468 DOI: 10.1073/pnas.1815071116] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Drugs that cause epigenetic modification of DNA, such as 5-azacytidine (AZA), are used clinically to treat myelodysplastic syndromes and acute myeloid leukemia. In addition, AZA is being investigated for use against a range of different types of solid tumors, including lung and colorectal cancers. Treatment with AZA causes demethylation of DNA, thus increasing RNA synthesis, including the synthesis of double-stranded RNA, which is otherwise produced in virus-infected cells. We determined that cell death in response to AZA requires the antiviral enzyme RNase L. The results identify a drug target for enhancing the anticancer activity and reducing the toxicity of AZA and related drugs. Drugs that reverse epigenetic silencing, such as the DNA methyltransferase inhibitor (DNMTi) 5-azacytidine (AZA), have profound effects on transcription and tumor cell survival. AZA is an approved drug for myelodysplastic syndromes and acute myeloid leukemia, and is under investigation for different solid malignant tumors. AZA treatment generates self, double-stranded RNA (dsRNA), transcribed from hypomethylated repetitive elements. Self dsRNA accumulation in DNMTi-treated cells leads to type I IFN production and IFN-stimulated gene expression. Here we report that cell death in response to AZA treatment occurs through the 2′,5′-oligoadenylate synthetase (OAS)-RNase L pathway. OASs are IFN-induced enzymes that synthesize the RNase L activator 2-5A in response to dsRNA. Cells deficient in RNase L or OAS1 to 3 are highly resistant to AZA, as are wild-type cells treated with a small-molecule inhibitor of RNase L. A small-molecule inhibitor of c-Jun NH2-terminal kinases (JNKs) also antagonizes RNase L-dependent cell death in response to AZA, consistent with a role for JNK in RNase L-induced apoptosis. In contrast, the rates of AZA-induced and RNase L-dependent cell death were increased by transfection of 2-5A, by deficiencies in ADAR1 (which edits and destabilizes dsRNA), PDE12 or AKAP7 (which degrade 2-5A), or by ionizing radiation (which induces IFN-dependent signaling). Finally, OAS1 expression correlates with AZA sensitivity in the NCI-60 set of tumor cell lines, suggesting that the level of OAS1 can be a biomarker for predicting AZA sensitivity of tumor cells. These studies may eventually lead to pharmacologic strategies for regulating the antitumor activity and toxicity of AZA and related drugs.
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17
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Real-time 2-5A kinetics suggest that interferons β and λ evade global arrest of translation by RNase L. Proc Natl Acad Sci U S A 2019; 116:2103-2111. [PMID: 30655338 DOI: 10.1073/pnas.1818363116] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Cells of all mammals recognize double-stranded RNA (dsRNA) as a foreign material. In response, they release interferons (IFNs) and activate a ubiquitously expressed pseudokinase/endoribonuclease RNase L. RNase L executes regulated RNA decay and halts global translation. Here, we developed a biosensor for 2',5'-oligoadenylate (2-5A), the natural activator of RNase L. Using this biosensor, we found that 2-5A was acutely synthesized by cells in response to dsRNA sensing, which immediately triggered cellular RNA cleavage by RNase L and arrested host protein synthesis. However, translation-arrested cells still transcribed IFN-stimulated genes and secreted IFNs of types I and III (IFN-β and IFN-λ). Our data suggest that IFNs escape from the action of RNase L on translation. We propose that the 2-5A/RNase L pathway serves to rapidly and accurately suppress basal protein synthesis, preserving privileged production of defense proteins of the innate immune system.
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18
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Nomura Y, Roston D, Montemayor EJ, Cui Q, Butcher SE. Structural and mechanistic basis for preferential deadenylation of U6 snRNA by Usb1. Nucleic Acids Res 2018; 46:11488-11501. [PMID: 30215753 PMCID: PMC6265477 DOI: 10.1093/nar/gky812] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/27/2018] [Accepted: 08/29/2018] [Indexed: 01/08/2023] Open
Abstract
Post-transcriptional modification of snRNA is central to spliceosome function. Usb1 is an exoribonuclease that shortens the oligo-uridine tail of U6 snRNA, resulting in a terminal 2',3' cyclic phosphate group in most eukaryotes, including humans. Loss of function mutations in human Usb1 cause the rare disorder poikiloderma with neutropenia (PN), and result in U6 snRNAs with elongated 3' ends that are aberrantly adenylated. Here, we show that human Usb1 removes 3' adenosines with 20-fold greater efficiency than uridines, which explains the presence of adenylated U6 snRNAs in cells lacking Usb1. We determined three high-resolution co-crystal structures of Usb1: wild-type Usb1 bound to the substrate analog adenosine 5'-monophosphate, and an inactive mutant bound to RNAs with a 3' terminal adenosine and uridine. These structures, along with QM/MM MD simulations of the catalytic mechanism, illuminate the molecular basis for preferential deadenylation of U6 snRNA. The extent of Usb1 processing is influenced by the secondary structure of U6 snRNA.
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Affiliation(s)
- Yuichiro Nomura
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Daniel Roston
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
- Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Eric J Montemayor
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Qiang Cui
- Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA
| | - Samuel E Butcher
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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19
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Lopp A, Reintamm T, Kuusksalu A, Olspert A, Kelve M. Identification of a novel member of 2H phosphoesterases, 2',5'-oligoadenylate degrading ribonuclease from the oyster Crassostrea gigas. Biochimie 2018; 156:181-195. [PMID: 30195052 DOI: 10.1016/j.biochi.2018.09.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 09/03/2018] [Indexed: 11/16/2022]
Abstract
Several genes of IFN-mediated pathways in vertebrates, among them the genes that participate in the 2',5'-oligoadenylate synthetase (OAS)/RNase L pathway, have been identified in C. gigas. In the present study, we identified genes, which encode proteins having 2',5'-oligoadenylate degrading activity in C. gigas. These proteins belong to the 2H phosphoesterase superfamily and have sequence similarity to the mammalian A kinase anchoring protein 7 (AKAP7) central domain, which is responsible for the 2',5'-phosphodiesterase (2',5'-PDE) activity. Comparison of the genomic structures of C. gigas proteins with that of AKAP7 suggests that these enzymes originate from a direct common ancestor. However, the identified nucleases are not typical 2',5'-PDEs. The found enzymes catalyse the degradation of 2',5'-linked oligoadenylates in a metal-ion-independent way, yielding products with 2',3' -cyclic phosphate and 5'-OH termini similarly to the 3'-5' bond cleavage in RNA, catalyzed by metal-independent ribonucleases. 3',5'-linked oligoadenylates are not substrates for them. The preferred substrates for the C. gigas enzymes are 5'-triphosphorylated 2',5'-oligoadenylates, whose major cleavage reaction results in the removal of the 5'-triphosphorylated 2',3'-cyclic phosphate derivative, leaving behind the respective unphosphorylated 2',5'-oligoadenylate. Such a cleavage reaction results in the direct inactivation of the biologically active 2-5A molecule. The 2',5'-ribonucleases (2',5'-RNases) from C. gigas could be members of the ancient group of ribonucleases, specific to 2'-5' phosphodiester bond, together with the enzyme that was characterized previously from the marine sponge Tethya aurantium. The novel 2',5'-RNases may play a role in the control of cellular 2-5A levels, thereby limiting damage to host cells after viral infection.
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Affiliation(s)
- Annika Lopp
- Department of Chemistry and Biotechnology, Division of Gene Technology, Tallinn University of Technology, Akadeemia Tee 15, Tallinn, 12618, Estonia.
| | - Tõnu Reintamm
- Department of Chemistry and Biotechnology, Division of Gene Technology, Tallinn University of Technology, Akadeemia Tee 15, Tallinn, 12618, Estonia
| | - Anne Kuusksalu
- Department of Chemistry and Biotechnology, Division of Gene Technology, Tallinn University of Technology, Akadeemia Tee 15, Tallinn, 12618, Estonia
| | - Allan Olspert
- Department of Chemistry and Biotechnology, Division of Gene Technology, Tallinn University of Technology, Akadeemia Tee 15, Tallinn, 12618, Estonia
| | - Merike Kelve
- Department of Chemistry and Biotechnology, Division of Gene Technology, Tallinn University of Technology, Akadeemia Tee 15, Tallinn, 12618, Estonia
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20
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O'Connell GC, Treadway MB, Petrone AB, Tennant CS, Lucke-Wold N, Chantler PD, Barr TL. Peripheral blood AKAP7 expression as an early marker for lymphocyte-mediated post-stroke blood brain barrier disruption. Sci Rep 2017; 7:1172. [PMID: 28446746 PMCID: PMC5430856 DOI: 10.1038/s41598-017-01178-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/24/2017] [Indexed: 01/26/2023] Open
Abstract
Our group recently identified 16 genes whose peripheral blood expression levels are differentially regulated in acute ischemic stroke. The purpose of this study was to determine whether the early expression levels of any of these 16 genes are predictive for post-stroke blood brain barrier (BBB) disruption. Transcriptional expression levels of candidate genes were measured in peripheral blood sampled from ischemic stroke patients at emergency department admission, and BBB permeability was assessed at 24 hour follow up via perfusion-weighted imaging. Early heightened expression levels of AKAP7, a gene encoding a protein kinase A-binding scaffolding molecule, were significantly associated with BBB disruption 24 hours post-hospital admission. We then determined that AKAP7 is predominantly expressed by lymphocytes in peripheral blood, and strongly co-expressed with ITGA3, a gene encoding the adhesion molecule integrin alpha 3. Subsequent in vitro experiments revealed that heightened expression of AKAP7 and ITGA3 in primary human lymphocytes is associated with a highly adherent phenotype. Collectively, our results suggest that AKAP7 expression levels may have clinical utility as a prognostic biomarker for post-stroke BBB complications, and are likely elevated early in patients who later develop post-stroke BBB disruption due to the presence of an invasive lymphocyte population in the peripheral blood.
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Affiliation(s)
- Grant C O'Connell
- Center for Basic and Translational Stroke Research, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia, USA. .,Department of Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia, USA.
| | - Madison B Treadway
- Department of Biology, Eberly College of Arts and Sciences, West Virginia University, Morgantown, West Virginia, USA
| | - Ashley B Petrone
- Center for Basic and Translational Stroke Research, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia, USA
| | - Connie S Tennant
- Center for Basic and Translational Stroke Research, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia, USA
| | - Noelle Lucke-Wold
- Center for Basic and Translational Stroke Research, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia, USA
| | - Paul D Chantler
- Center for Cardiovascular and Respiratory Sciences, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, West Virginia, USA.,Division of Exercise Physiology, School of Medicine, West Virginia University, Morgantown, West Virginia, USA
| | - Taura L Barr
- Valtari Bio Incorporated, Morgantown, West Virginia, USA
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21
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Li Y, Banerjee S, Goldstein SA, Dong B, Gaughan C, Rath S, Donovan J, Korennykh A, Silverman RH, Weiss SR. Ribonuclease L mediates the cell-lethal phenotype of double-stranded RNA editing enzyme ADAR1 deficiency in a human cell line. eLife 2017; 6. [PMID: 28362255 PMCID: PMC5404912 DOI: 10.7554/elife.25687] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 03/30/2017] [Indexed: 12/13/2022] Open
Abstract
ADAR1 isoforms are adenosine deaminases that edit and destabilize double-stranded RNA reducing its immunostimulatory activities. Mutation of ADAR1 leads to a severe neurodevelopmental and inflammatory disease of children, Aicardi-Goutiéres syndrome. In mice, Adar1 mutations are embryonic lethal but are rescued by mutation of the Mda5 or Mavs genes, which function in IFN induction. However, the specific IFN regulated proteins responsible for the pathogenic effects of ADAR1 mutation are unknown. We show that the cell-lethal phenotype of ADAR1 deletion in human lung adenocarcinoma A549 cells is rescued by CRISPR/Cas9 mutagenesis of the RNASEL gene or by expression of the RNase L antagonist, murine coronavirus NS2 accessory protein. Our result demonstrate that ablation of RNase L activity promotes survival of ADAR1 deficient cells even in the presence of MDA5 and MAVS, suggesting that the RNase L system is the primary sensor pathway for endogenous dsRNA that leads to cell death. DOI:http://dx.doi.org/10.7554/eLife.25687.001
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Affiliation(s)
- Yize Li
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Shuvojit Banerjee
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, United States
| | - Stephen A Goldstein
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
| | - Beihua Dong
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, United States
| | - Christina Gaughan
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, United States
| | - Sneha Rath
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Jesse Donovan
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Alexei Korennykh
- Department of Molecular Biology, Princeton University, Princeton, United States
| | - Robert H Silverman
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, United States
| | - Susan R Weiss
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, United States
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Lineage A Betacoronavirus NS2 Proteins and the Homologous Torovirus Berne pp1a Carboxy-Terminal Domain Are Phosphodiesterases That Antagonize Activation of RNase L. J Virol 2017; 91:JVI.02201-16. [PMID: 28003490 DOI: 10.1128/jvi.02201-16] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 12/13/2016] [Indexed: 01/22/2023] Open
Abstract
Viruses in the family Coronaviridae, within the order Nidovirales, are etiologic agents of a range of human and animal diseases, including both mild and severe respiratory diseases in humans. These viruses encode conserved replicase and structural proteins as well as more diverse accessory proteins, encoded in the 3' ends of their genomes, that often act as host cell antagonists. We previously showed that 2',5'-phosphodiesterases (2',5'-PDEs) encoded by the prototypical Betacoronavirus, mouse hepatitis virus (MHV), and by Middle East respiratory syndrome-associated coronavirus antagonize the oligoadenylate-RNase L (OAS-RNase L) pathway. Here we report that additional coronavirus superfamily members, including lineage A betacoronaviruses and toroviruses infecting both humans and animals, encode 2',5'-PDEs capable of antagonizing RNase L. We used a chimeric MHV system (MHVMut) in which exogenous PDEs were expressed from an MHV backbone lacking the gene for a functional NS2 protein, the endogenous RNase L antagonist. With this system, we found that 2',5'-PDEs encoded by the human coronavirus HCoV-OC43 (OC43; an agent of the common cold), human enteric coronavirus (HECoV), equine coronavirus (ECoV), and equine torovirus Berne (BEV) are enzymatically active, rescue replication of MHVMut in bone marrow-derived macrophages, and inhibit RNase L-mediated rRNA degradation in these cells. Additionally, PDEs encoded by OC43 and BEV rescue MHVMut replication and restore pathogenesis in wild-type (WT) B6 mice. This finding expands the range of viruses known to encode antagonists of the potent OAS-RNase L antiviral pathway, highlighting its importance in a range of species as well as the selective pressures exerted on viruses to antagonize it.IMPORTANCE Viruses in the family Coronaviridae include important human and animal pathogens, including the recently emerged viruses severe acute respiratory syndrome-associated coronavirus (SARS-CoV) and Middle East respiratory syndrome-associated coronavirus (MERS-CoV). We showed previously that two viruses within the genus Betacoronavirus, mouse hepatitis virus (MHV) and MERS-CoV, encode 2',5'-phosphodiesterases (2',5'-PDEs) that antagonize the OAS-RNase L pathway, and we report here that these proteins are furthermore conserved among additional coronavirus superfamily members, including lineage A betacoronaviruses and toroviruses, suggesting that they may play critical roles in pathogenesis. As there are no licensed vaccines or effective antivirals against human coronaviruses and few against those infecting animals, identifying viral proteins contributing to virulence can inform therapeutic development. Thus, this work demonstrates that a potent antagonist of host antiviral defenses is encoded by multiple and diverse viruses within the family Coronaviridae, presenting a possible broad-spectrum therapeutic target.
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Myllykoski M, Kursula P. Structural aspects of nucleotide ligand binding by a bacterial 2H phosphoesterase. PLoS One 2017; 12:e0170355. [PMID: 28141848 PMCID: PMC5283653 DOI: 10.1371/journal.pone.0170355] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 01/03/2017] [Indexed: 01/19/2023] Open
Abstract
The 2H phosphoesterase family contains enzymes with two His-X-Ser/Thr motifs in the active site. 2H enzymes are found in all kingdoms of life, sharing little sequence identity despite the conserved overall fold and active site. For many 2H enzymes, the physiological function is unknown. Here, we studied the structure of the 2H family member LigT from Escherichia coli both in the apo form and complexed with different active-site ligands, including ATP, 2′-AMP, 3′-AMP, phosphate, and NADP+. Comparisons to the well-characterized vertebrate myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) highlight specific features of the catalytic cycle and substrate recognition in both enzymes. The role played by the helix α7, unique to CNPases within the 2H family, is apparently taken over by Arg130 in the bacterial enzyme. Other residues and loops lining the active site groove are likely to be important for RNA substrate binding. We visualized conformational changes related to ligand binding, as well as the position of the nucleophilic water molecule. We also present a low-resolution model of E. coli LigT bound to tRNA in solution, and provide a model for RNA binding by LigT, involving flexible loops lining the active site cavity. Taken together, our results both aid in understanding the common features of 2H family enzymes and help highlight the distinct features in the 2H family members, which must result in different reaction mechanisms. Unique aspects in different 2H family members can be observed in ligand recognition and binding, and in the coordination of the nucleophilic water molecule and the reactive phosphate moiety.
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Affiliation(s)
- Matti Myllykoski
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Oulu, Finland
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Oulu, Finland
- Department of Biomedicine, University of Bergen, Bergen, Norway
- * E-mail:
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24
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Forni D, Cagliani R, Clerici M, Sironi M. Molecular Evolution of Human Coronavirus Genomes. Trends Microbiol 2016; 25:35-48. [PMID: 27743750 PMCID: PMC7111218 DOI: 10.1016/j.tim.2016.09.001] [Citation(s) in RCA: 472] [Impact Index Per Article: 59.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 08/22/2016] [Accepted: 09/07/2016] [Indexed: 12/25/2022]
Abstract
Human coronaviruses (HCoVs), including SARS-CoV and MERS-CoV, are zoonotic pathogens that originated in wild animals. HCoVs have large genomes that encode a fixed array of structural and nonstructural components, as well as a variety of accessory proteins that differ in number and sequence even among closely related CoVs. Thus, in addition to recombination and mutation, HCoV genomes evolve through gene gains and losses. In this review we summarize recent findings on the molecular evolution of HCoV genomes, with special attention to recombination and adaptive events that generated new viral species and contributed to host shifts and to HCoV emergence. VIDEO ABSTRACT.
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Affiliation(s)
- Diego Forni
- Scientific Institute IRCCS E. MEDEA, Bioinformatics, Bosisio Parini, Italy
| | - Rachele Cagliani
- Scientific Institute IRCCS E. MEDEA, Bioinformatics, Bosisio Parini, Italy
| | - Mario Clerici
- Department of Physiopathology and Transplantation, University of Milan, Milan, Italy; Don C. Gnocchi Foundation ONLUS, IRCCS, Milan, Italy
| | - Manuela Sironi
- Scientific Institute IRCCS E. MEDEA, Bioinformatics, Bosisio Parini, Italy.
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25
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Gusho E, Baskar D, Banerjee S. New advances in our understanding of the "unique" RNase L in host pathogen interaction and immune signaling. Cytokine 2016; 133:153847. [PMID: 27595182 PMCID: PMC7128181 DOI: 10.1016/j.cyto.2016.08.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 08/08/2016] [Accepted: 08/08/2016] [Indexed: 12/22/2022]
Abstract
Ever since the discovery of the existence of an interferon (IFN)-regulated ribonuclease, significant advances have been made in understanding the mechanism and associated regulatory effects of its action. What had been studied initially as a "unique" endoribonuclease is currently known as ribonuclease L (RNase L where "L" stands for latent). Some of the key developments include discovery of the RNase L signaling pathway, its structural characterization, and its molecular cloning. RNase L has been implicated in antiviral and antibacterial defense, as well as in hereditary prostate cancer. RNase L is activated by 2'-5' linked oligoadenylates (2-5A), which are synthesized by the oligoadenylate synthetases (OASs), a family of IFN-regulated pathogen recognition receptors that sense double-stranded RNAs. Activated RNase L cleaves single stranded RNAs, including viral RNAs and cellular RNAs. The catalytic activity of RNase L has been found to lead into the activation of several cellular signaling pathways, including those involved in autophagy, apoptosis, IFN-β production, NLRP3 inflammasome activation leading to IL-1β secretion, inhibition of cell migration, and cell adhesion. In this review, we will highlight the newest advances in our understanding of the catalytic role of RNase L in the context of different cellular pathways and extend the scope of these findings to discussion of potential therapeutic targets for antimicrobial drug development.
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Affiliation(s)
- Elona Gusho
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue Cleveland, OH 44195, USA
| | - Danika Baskar
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue Cleveland, OH 44195, USA; Pediatrics Division Office, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA(1)
| | - Shuvojit Banerjee
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue Cleveland, OH 44195, USA.
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26
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Abstract
Middle East respiratory syndrome coronavirus (MERS-CoV) is the first highly pathogenic human coronavirus to emerge since severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002. Like many coronaviruses, MERS-CoV carries genes that encode multiple accessory proteins that are not required for replication of the genome but are likely involved in pathogenesis. Evasion of host innate immunity through interferon (IFN) antagonism is a critical component of viral pathogenesis. The IFN-inducible oligoadenylate synthetase (OAS)-RNase L pathway activates upon sensing of viral double-stranded RNA (dsRNA). Activated RNase L cleaves viral and host single-stranded RNA (ssRNA), which leads to translational arrest and subsequent cell death, preventing viral replication and spread. Here we report that MERS-CoV, a lineage C Betacoronavirus, and related bat CoV NS4b accessory proteins have phosphodiesterase (PDE) activity and antagonize OAS-RNase L by enzymatically degrading 2′,5′-oligoadenylate (2-5A), activators of RNase L. This is a novel function for NS4b, which has previously been reported to antagonize IFN signaling. NS4b proteins are distinct from lineage A Betacoronavirus PDEs and rotavirus gene-encoded PDEs, in having an amino-terminal nuclear localization signal (NLS) and are localized mostly to the nucleus. However, the expression level of cytoplasmic MERS-CoV NS4b protein is sufficient to prevent activation of RNase L. Finally, this is the first report of an RNase L antagonist expressed by a human or bat coronavirus and provides a specific mechanism by which this occurs. Our findings provide a potential mechanism for evasion of innate immunity by MERS-CoV while also identifying a potential target for therapeutic intervention. Middle East respiratory syndrome coronavirus (MERS-CoV) is the first highly pathogenic human coronavirus to emerge since severe acute respiratory syndrome coronavirus (SARS-CoV). MERS-CoV, like other coronaviruses, carries genes that encode accessory proteins that antagonize the host antiviral response, often the type I interferon response, and contribute to virulence. We found that MERS-CoV NS4b and homologs from related lineage C bat betacoronaviruses BtCoV-SC2013 (SC2013) and BtCoV-HKU5 (HKU5) are members of the 2H-phosphoesterase (2H-PE) enzyme family with phosphodiesterase (PDE) activity. Like murine coronavirus NS2, a previously characterized PDE, MERS NS4b, can antagonize activation of the OAS-RNase L pathway, an interferon-induced potent antiviral activity. Furthermore, MERS-CoV mutants with deletion of genes encoding accessory proteins NS3 to NS5 or NS4b alone or inactivation of the PDE can activate RNase L during infection of Calu-3 cells. Our report may offer a potential target for therapeutic intervention if NS4b proves to be critical to pathogenesis in in vivo models of MERS-CoV infection.
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Wong LYR, Lui PY, Jin DY. A molecular arms race between host innate antiviral response and emerging human coronaviruses. Virol Sin 2016; 31:12-23. [PMID: 26786772 PMCID: PMC7090626 DOI: 10.1007/s12250-015-3683-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Accepted: 01/07/2016] [Indexed: 02/07/2023] Open
Abstract
Coronaviruses have been closely related with mankind for thousands of years. Communityacquired human coronaviruses have long been recognized to cause common cold. However, zoonotic coronaviruses are now becoming more a global concern with the discovery of highly pathogenic severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses causing severe respiratory diseases. Infections by these emerging human coronaviruses are characterized by less robust interferon production. Treatment of patients with recombinant interferon regimen promises beneficial outcomes, suggesting that compromised interferon expression might contribute at least partially to the severity of disease. The mechanisms by which coronaviruses evade host innate antiviral response are under intense investigations. This review focuses on the fierce arms race between host innate antiviral immunity and emerging human coronaviruses. Particularly, the host pathogen recognition receptors and the signal transduction pathways to mount an effective antiviral response against SARS and MERS coronavirus infection are discussed. On the other hand, the counter-measures evolved by SARS and MERS coronaviruses to circumvent host defense are also dissected. With a better understanding of the dynamic interaction between host and coronaviruses, it is hoped that insights on the pathogenesis of newly-identified highly pathogenic human coronaviruses and new strategies in antiviral development can be derived.![]()
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Affiliation(s)
- Lok-Yin Roy Wong
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Pak-Yin Lui
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Dong-Yan Jin
- School of Biomedical Sciences, The University of Hong Kong, Hong Kong SAR, China.
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28
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Sui B, Huang J, Jha BK, Yin P, Zhou M, Fu ZF, Silverman RH, Weiss SR, Peng G, Zhao L. Crystal structure of the mouse hepatitis virus ns2 phosphodiesterase domain that antagonizes RNase L activation. J Gen Virol 2016; 97:880-886. [PMID: 26757803 DOI: 10.1099/jgv.0.000395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Prior studies have demonstrated that the mouse hepatitis virus (MHV) A59 strain ns2 protein is a member of the 2H phosphoesterase family and exhibits 2',5'-phosphodiesterase (PDE) activity. During the IFN antiviral response, ns2 cleaves 2',5'-oligoadenylate (2-5A), a key mediator of RNase L activation, thereby subverting the activation of RNase L and evading host innate immunity. However, the mechanism of 2-5A cleavage by ns2 remains unclear. Here, we present the crystal structure of the MHV ns2 PDE domain and demonstrate a PDE fold similar to that of the cellular protein, a kinase anchoring protein 7 central domain (AKAP7(CD)) and rotavirus VP3 carboxy-terminal domain. The structure displays a pair of strictly conserved HxT/Sx motifs and forms a deep, positively charged catalytic groove with β-sheets and an arginine-containing loop. These findings provide insight into the structural basis for 2-5A binding of MHV ns2.
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Affiliation(s)
- Baokun Sui
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PRChina
| | - Junhua Huang
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PRChina
| | - Babal K Jha
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Ping Yin
- National Key Laboratory of Crop Improvement, Huazhong Agricultural University, Wuhan 430070, PRChina
| | - Ming Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PRChina
| | - Zhen F Fu
- Department of Pathology, University of Georgia, Athens, GA 30602, USA
| | - Robert H Silverman
- Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA
| | - Susan R Weiss
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Guiqing Peng
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PRChina
| | - Ling Zhao
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, PRChina
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29
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Human RNase L tunes gene expression by selectively destabilizing the microRNA-regulated transcriptome. Proc Natl Acad Sci U S A 2015; 112:15916-21. [PMID: 26668391 DOI: 10.1073/pnas.1513034112] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Double-stranded RNA (dsRNA) activates the innate immune system of mammalian cells and triggers intracellular RNA decay by the pseudokinase and endoribonuclease RNase L. RNase L protects from pathogens and regulates cell growth and differentiation by destabilizing largely unknown mammalian RNA targets. We developed an approach for transcriptome-wide profiling of RNase L activity in human cells and identified hundreds of direct RNA targets and nontargets. We show that this RNase L-dependent decay selectively affects transcripts regulated by microRNA (miR)-17/miR-29/miR-200 and other miRs that function as suppressors of mammalian cell adhesion and proliferation. RNase L mimics the effects of these miRs and acts as a suppressor of proliferation and adhesion in mammalian cells. Our data suggest that RNase L-dependent decay serves to establish an antiproliferative state via destabilization of the miR-regulated transcriptome.
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30
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Myllykoski M, Seidel L, Muruganandam G, Raasakka A, Torda AE, Kursula P. Structural and functional evolution of 2',3'-cyclic nucleotide 3'-phosphodiesterase. Brain Res 2015; 1641:64-78. [PMID: 26367445 DOI: 10.1016/j.brainres.2015.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 09/02/2015] [Accepted: 09/03/2015] [Indexed: 02/06/2023]
Abstract
2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) is an abundant membrane-associated enzyme within the vertebrate myelin sheath. While the physiological function of CNPase still remains to be characterized in detail, it is known - in addition to its in vitro enzymatic activity - to interact with other proteins, small molecules, and membrane surfaces. From an evolutionary point of view, it can be deduced that CNPase is not restricted to myelin-forming cells or vertebrate tissues. Its evolution has involved gene fusion, addition of other small segments with distinct functions, such as membrane attachment, and possibly loss of function at the polynucleotide kinase-like domain. Currently, it is unclear whether the enzymatic function of the conserved phosphodiesterase domain in vertebrate myelin has a physiological role, or if CNPase could actually function - like many other classical myelin proteins - in a more structural role. This article is part of a Special Issue entitled SI: Myelin Evolution.
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Affiliation(s)
- Matti Myllykoski
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Aapistie 7, 90220 Oulu, Finland
| | - Leonie Seidel
- Centre for Bioinformatics, University of Hamburg, Bundesstraße 43, 20146 Hamburg, Germany
| | | | - Arne Raasakka
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Aapistie 7, 90220 Oulu, Finland; Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway
| | - Andrew E Torda
- Centre for Bioinformatics, University of Hamburg, Bundesstraße 43, 20146 Hamburg, Germany
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine & Biocenter Oulu, University of Oulu, Aapistie 7, 90220 Oulu, Finland; German Electron Synchrotron, Notkestraße 85, 22607 Hamburg, Germany; Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway.
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31
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Structural basis for 2'-5'-oligoadenylate binding and enzyme activity of a viral RNase L antagonist. J Virol 2015; 89:6633-45. [PMID: 25878106 DOI: 10.1128/jvi.00701-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
UNLABELLED Synthesis of 2'-5'-oligoadenylates (2-5A) by oligoadenylate synthetase (OAS) is an important innate cellular response that limits viral replication by activating the latent cellular RNase, RNase L, to degrade single-stranded RNA. Some rotaviruses and coronaviruses antagonize the OAS/RNase L pathway through the activity of an encoded 2H phosphoesterase domain that cleaves 2-5A. These viral 2H phosphoesterases are phylogenetically related to the cellular A kinase anchoring protein 7 (AKAP7) and share a core structure and an active site that contains two well-defined HΦ(S/T)Φ (where Φ is a hydrophobic residue) motifs, but their mechanism of substrate binding is unknown. Here, we report the structures of a viral 2H phosphoesterase, the C-terminal domain (CTD) of the group A rotavirus (RVA) VP3 protein, both alone and in complex with 2-5A. The domain forms a compact fold, with a concave β-sheet that contains the catalytic cleft, but it lacks two α-helical regions and two β-strands observed in AKAP7 and other 2H phosphoesterases. The cocrystal structure shows significant conformational changes in the R loop upon ligand binding. Bioinformatics and biochemical analyses reveal that conserved residues and residues required for catalytic activity and substrate binding comprise the catalytic motifs and a region on one side of the binding cleft. We demonstrate that the VP3 CTD of group B rotavirus, but not that of group G, cleaves 2-5A. These findings suggest that the VP3 CTD is a streamlined version of a 2H phosphoesterase with a ligand-binding mechanism that is shared among 2H phosphodiesterases that cleave 2-5A. IMPORTANCE The C-terminal domain (CTD) of rotavirus VP3 is a 2H phosphoesterase that cleaves 2'-5'-oligoadenylates (2-5A), potent activators of an important innate cellular antiviral pathway. 2H phosphoesterase superfamily proteins contain two conserved catalytic motifs and a proposed core structure. Here, we present structures of a viral 2H phosphoesterase, the rotavirus VP3 CTD, alone and in complex with its substrate, 2-5A. The domain lacks two α-helical regions and β-strands present in other 2H phosphoesterases. A loop of the protein undergoes significant structural changes upon substrate binding. Together with our bioinformatics and biochemical findings, the crystal structures suggest that the RVA VP3 CTD domain is a streamlined version of a cellular enzyme that shares a ligand-binding mechanism with other 2H phosphodiesterases that cleave 2-5A but differs from those of 2H phosphodiesterases that cleave other substrates. These findings may aid in the future design of antivirals targeting viral phosphodiesterases with cleavage specificity for 2-5A.
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Wood ER, Bledsoe R, Chai J, Daka P, Deng H, Ding Y, Harris-Gurley S, Kryn LH, Nartey E, Nichols J, Nolte RT, Prabhu N, Rise C, Sheahan T, Shotwell JB, Smith D, Tai V, Taylor JD, Tomberlin G, Wang L, Wisely B, You S, Xia B, Dickson H. The Role of Phosphodiesterase 12 (PDE12) as a Negative Regulator of the Innate Immune Response and the Discovery of Antiviral Inhibitors. J Biol Chem 2015; 290:19681-96. [PMID: 26055709 PMCID: PMC4528132 DOI: 10.1074/jbc.m115.653113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/20/2015] [Indexed: 11/06/2022] Open
Abstract
2',5'-Oligoadenylate synthetase (OAS) enzymes and RNase-L constitute a major effector arm of interferon (IFN)-mediated antiviral defense. OAS produces a unique oligonucleotide second messenger, 2',5'-oligoadenylate (2-5A), that binds and activates RNase-L. This pathway is down-regulated by virus- and host-encoded enzymes that degrade 2-5A. Phosphodiesterase 12 (PDE12) was the first cellular 2-5A- degrading enzyme to be purified and described at a molecular level. Inhibition of PDE12 may up-regulate the OAS/RNase-L pathway in response to viral infection resulting in increased resistance to a variety of viral pathogens. We generated a PDE12-null cell line, HeLaΔPDE12, using transcription activator-like effector nuclease-mediated gene inactivation. This cell line has increased 2-5A levels in response to IFN and poly(I-C), a double-stranded RNA mimic compared with the parental cell line. Moreover, HeLaΔPDE12 cells were resistant to viral pathogens, including encephalomyocarditis virus, human rhinovirus, and respiratory syncytial virus. Based on these results, we used DNA-encoded chemical library screening to identify starting points for inhibitor lead optimization. Compounds derived from this effort raise 2-5A levels and exhibit antiviral activity comparable with the effects observed with PDE12 gene inactivation. The crystal structure of PDE12 complexed with an inhibitor was solved providing insights into the structure-activity relationships of inhibitor potency and selectivity.
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Affiliation(s)
| | | | - Jing Chai
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Philias Daka
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Hongfeng Deng
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Yun Ding
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | | | | | | | | | | | - Ninad Prabhu
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Cecil Rise
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Timothy Sheahan
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - J Brad Shotwell
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | - Vince Tai
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | | | | | | | - Shihyun You
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Bing Xia
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Hamilton Dickson
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
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33
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Poulsen JB, Kjær KH, Justesen J, Martensen PM. Enzyme assays for synthesis and degradation of 2-5As and other 2'-5' oligonucleotides. BMC BIOCHEMISTRY 2015; 16:15. [PMID: 26113370 PMCID: PMC4481073 DOI: 10.1186/s12858-015-0043-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 05/15/2015] [Indexed: 01/12/2023]
Abstract
Background The 5′-triphosphorylated, 2′-5′-linked oligoadenylate polyribonucleotides (2-5As) are central to the interferon-induced antiviral 2-5A system. The 2-5As bind and activate the RNase L, an endoRNase degrading viral and cellular RNA leading to inhibition of viral replication. The 2-5A system is tightly controlled by synthesis and degradation of 2-5As. Whereas synthesis is mediated by the 2′-5′ oligoadenylate synthetase family of enzymes, degradation seems to be orchestrated by multiple enzyme nucleases including phosphodiesterase 12, the ectonucleotide pyrophosphatase/phosphodiesterase 1 and the A-kinase anchoring protein 7. Results Here we present assay tools for identification and characterization of the enzymes regulating cellular 2-5A levels. A procedure is described for the production of 2′-5′ oligoadenylates, which are then used as substrates for development and demonstration of enzyme assays measuring synthetase and nuclease activities, respectively. The synthetase assays produce only a single reaction product allowing for very precise kinetic assessment of the enzymes. We present an assay using dATP and the A(pA)3 tetramer core as substrates, which requires prior isolation of A(pA)3. A synthetase assay using either of the dNTPs individually together with NAD+ as substrates is also presented. The nuclease reactions make use of the isolated 2′-5′ oligoadenylates in producing a mixture of shorter reaction products, which are resolved by ion-exchange chromatography to determine the enzyme activities. A purified human 2′-5′ oligoadenylate synthetase and a purified human phosphodiesterase 12 along with crude extracts expressing those proteins, are used to demonstrate the assays. Conclusions This paper comprises an assay toolbox for identification and characterization of the synthetases and nucleases regulating cellular 2-5A levels. Assays are presented for both enzyme families. The assays can also be used to address a broader cellular role of the OAS enzymes, based on the multiple substrate specificity intrinsic to these proteins. Electronic supplementary material The online version of this article (doi:10.1186/s12858-015-0043-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jesper Buchhave Poulsen
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, DK-8000, Aarhus C, Denmark.
| | - Karina Hansen Kjær
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, DK-8000, Aarhus C, Denmark.
| | - Just Justesen
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, DK-8000, Aarhus C, Denmark.
| | - Pia Møller Martensen
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, DK-8000, Aarhus C, Denmark.
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Brandmann T, Jinek M. Crystal structure of the C-terminal 2',5'-phosphodiesterase domain of group A rotavirus protein VP3. Proteins 2015; 83:997-1002. [PMID: 25758703 PMCID: PMC5068548 DOI: 10.1002/prot.24794] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 02/24/2015] [Indexed: 11/20/2022]
Abstract
In response to viral infections, the mammalian innate immune system induces the production of the second messenger 2′–5′ oligoadenylate (2–5A) to activate latent ribonuclease L (RNase L) that restricts viral replication and promotes apoptosis. A subset of rotaviruses and coronaviruses encode 2′,5′‐phosphodiesterase enzymes that hydrolyze 2–5A, thereby inhibiting RNase L activation. We report the crystal structure of the 2′,5′‐phosphodiesterase domain of group A rotavirus protein VP3 at 1.39 Å resolution. The structure exhibits a 2H phosphoesterase fold and reveals conserved active site residues, providing insights into the mechanism of 2–5A degradation in viral evasion of host innate immunity. Proteins 2015; 83:997–1002. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Tobias Brandmann
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
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35
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Morelli M, Ogden KM, Patton JT. Silencing the alarms: Innate immune antagonism by rotavirus NSP1 and VP3. Virology 2015; 479-480:75-84. [PMID: 25724417 PMCID: PMC4940189 DOI: 10.1016/j.virol.2015.01.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 12/23/2014] [Accepted: 01/05/2015] [Indexed: 12/22/2022]
Abstract
The innate immune response involves a broad array of pathogen sensors that stimulate the production of interferons (IFNs) to induce an antiviral state. Rotavirus, a significant cause of childhood gastroenteritis and a member of the Reoviridae family of segmented, double-stranded RNA viruses, encodes at least two direct antagonists of host innate immunity: NSP1 and VP3. NSP1, a putative E3 ubiquitin ligase, mediates the degradation of cellular factors involved in both IFN induction and downstream signaling. VP3, the viral capping enzyme, utilizes a 2H-phosphodiesterase domain to prevent activation of the cellular oligoadenylate synthase (OAS)/RNase L pathway. Computational, molecular, and biochemical studies have provided key insights into the structural and mechanistic basis of innate immune antagonism by NSP1 and VP3 of group A rotaviruses (RVA). Future studies with non-RVA isolates will be essential to understand how other rotavirus species evade host innate immune responses. Rotavirus NSP1 and VP3 directly antagonize host innate immune pathways. NSP1, a putative E3 ubiquitin ligase, mediates turnover of multiple immune factors. VP3, the viral capping enzyme, has phosphodiesterase activity to block OAS/RNase L.
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Affiliation(s)
- Marco Morelli
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Kristen M Ogden
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - John T Patton
- Rotavirus Molecular Biology Section, Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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