101
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Geiger F, Acker J, Papa G, Wang X, Arter WE, Saar KL, Erkamp NA, Qi R, Bravo JPK, Strauss S, Krainer G, Burrone OR, Jungmann R, Knowles TPJ, Engelke H, Borodavka A. Liquid-liquid phase separation underpins the formation of replication factories in rotaviruses. EMBO J 2021; 40:e107711. [PMID: 34524703 PMCID: PMC8561643 DOI: 10.15252/embj.2021107711] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 08/23/2021] [Accepted: 08/27/2021] [Indexed: 12/29/2022] Open
Abstract
RNA viruses induce the formation of subcellular organelles that provide microenvironments conducive to their replication. Here we show that replication factories of rotaviruses represent protein-RNA condensates that are formed via liquid-liquid phase separation of the viroplasm-forming proteins NSP5 and rotavirus RNA chaperone NSP2. Upon mixing, these proteins readily form condensates at physiologically relevant low micromolar concentrations achieved in the cytoplasm of virus-infected cells. Early infection stage condensates could be reversibly dissolved by 1,6-hexanediol, as well as propylene glycol that released rotavirus transcripts from these condensates. During the early stages of infection, propylene glycol treatments reduced viral replication and phosphorylation of the condensate-forming protein NSP5. During late infection, these condensates exhibited altered material properties and became resistant to propylene glycol, coinciding with hyperphosphorylation of NSP5. Some aspects of the assembly of cytoplasmic rotavirus replication factories mirror the formation of other ribonucleoprotein granules. Such viral RNA-rich condensates that support replication of multi-segmented genomes represent an attractive target for developing novel therapeutic approaches.
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102
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Conners R, McLaren M, Łapińska U, Sanders K, Stone MRL, Blaskovich MAT, Pagliara S, Daum B, Rakonjac J, Gold VAM. CryoEM structure of the outer membrane secretin channel pIV from the f1 filamentous bacteriophage. Nat Commun 2021; 12:6316. [PMID: 34728631 PMCID: PMC8563730 DOI: 10.1038/s41467-021-26610-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/13/2021] [Indexed: 11/09/2022] Open
Abstract
The Ff family of filamentous bacteriophages infect gram-negative bacteria, but do not cause lysis of their host cell. Instead, new virions are extruded via the phage-encoded pIV protein, which has homology with bacterial secretins. Here, we determine the structure of pIV from the f1 filamentous bacteriophage at 2.7 Å resolution by cryo-electron microscopy, the first near-atomic structure of a phage secretin. Fifteen f1 pIV subunits assemble to form a gated channel in the bacterial outer membrane, with associated soluble domains projecting into the periplasm. We model channel opening and propose a mechanism for phage egress. By single-cell microfluidics experiments, we demonstrate the potential for secretins such as pIV to be used as adjuvants to increase the uptake and efficacy of antibiotics in bacteria. Finally, we compare the f1 pIV structure to its homologues to reveal similarities and differences between phage and bacterial secretins.
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103
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F Dudás E, Puglisi R, Korn SM, Alfano C, Bellone ML, Piaz FD, Kelly G, Monaca E, Schlundt A, Schwalbe H, Pastore A. Backbone chemical shift spectral assignments of SARS coronavirus-2 non-structural protein nsp9. BIOMOLECULAR NMR ASSIGNMENTS 2021; 15:235-241. [PMID: 33755914 PMCID: PMC7985572 DOI: 10.1007/s12104-021-10011-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 02/24/2021] [Indexed: 06/12/2023]
Abstract
As part of an International consortium aiming at the characterization by NMR of the proteins of the SARS-CoV-2 virus, we have obtained the virtually complete assignment of the backbone atoms of the non-structural protein nsp9. This small (12 kDa) protein is encoded by ORF1a, binds to RNA and seems to be essential for viral RNA synthesis. The crystal structures of the SARS-CoV-2 protein and other homologues suggest that the protein is dimeric as also confirmed by analytical ultracentrifugation and dynamic light scattering. Our data constitute the prerequisite for further NMR-based characterization, and provide the starting point for the identification of small molecule lead compounds that could interfere with RNA binding and prevent viral replication.
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104
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Wang Y, Kirkpatrick J, Zur Lage S, Korn SM, Neißner K, Schwalbe H, Schlundt A, Carlomagno T. 1H, 13C, and 15N backbone chemical-shift assignments of SARS-CoV-2 non-structural protein 1 (leader protein). BIOMOLECULAR NMR ASSIGNMENTS 2021; 15:287-295. [PMID: 33770349 PMCID: PMC7996116 DOI: 10.1007/s12104-021-10019-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 03/13/2021] [Indexed: 05/30/2023]
Abstract
The current COVID-19 pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has become a worldwide health crisis, necessitating coordinated scientific research and urgent identification of new drug targets for treatment of COVID-19 lung disease. The covid19-nmr consortium seeks to support drug development by providing publicly accessible NMR data on the viral RNA elements and proteins. The SARS-CoV-2 genome comprises a single RNA of about 30 kb in length, in which 14 open reading frames (ORFs) have been annotated, and encodes approximately 30 proteins. The first two-thirds of the SARS-CoV-2 genome is made up of two large overlapping open-reading-frames (ORF1a and ORF1b) encoding a replicase polyprotein, which is subsequently cleaved to yield 16 so-called non-structural proteins. The non-structural protein 1 (Nsp1), which is considered to be a major virulence factor, suppresses host immune functions by associating with host ribosomal complexes at the very end of its C-terminus. Furthermore, Nsp1 facilitates initiation of viral RNA translation via an interaction of its N-terminal domain with the 5' untranslated region (UTR) of the viral RNA. Here, we report the near-complete backbone chemical-shift assignments of full-length SARS-CoV-2 Nsp1 (19.8 kDa), which reveal the domain organization, secondary structure and backbone dynamics of Nsp1, and which will be of value to further NMR-based investigations of both the biochemical and physiological functions of Nsp1.
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105
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Perry JK, Appleby TC, Bilello JP, Feng JY, Schmitz U, Campbell EA. An atomistic model of the coronavirus replication-transcription complex as a hexamer assembled around nsp15. J Biol Chem 2021; 297:101218. [PMID: 34562452 PMCID: PMC8494237 DOI: 10.1016/j.jbc.2021.101218] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 09/15/2021] [Accepted: 09/16/2021] [Indexed: 12/23/2022] Open
Abstract
The SARS-CoV-2 replication-transcription complex is an assembly of nonstructural viral proteins that collectively act to reproduce the viral genome and generate mRNA transcripts. While the structures of the individual proteins involved are known, how they assemble into a functioning superstructure is not. Applying molecular modeling tools, including protein-protein docking, to the available structures of nsp7-nsp16 and the nucleocapsid, we have constructed an atomistic model of how these proteins associate. Our principal finding is that the complex is hexameric, centered on nsp15. The nsp15 hexamer is capped on two faces by trimers of nsp14/nsp16/(nsp10)2, which then recruit six nsp12/nsp7/(nsp8)2 polymerase subunits to the complex. To this, six subunits of nsp13 are arranged around the superstructure, but not evenly distributed. Polymerase subunits that coordinate dimers of nsp13 are capable of binding the nucleocapsid, which positions the 5'-UTR TRS-L RNA over the polymerase active site, a state distinguishing transcription from replication. Analysis of the viral RNA path through the complex indicates the dsRNA that exits the polymerase passes over the nsp14 exonuclease and nsp15 endonuclease sites before being unwound by a convergence of zinc fingers from nsp10 and nsp14. The template strand is then directed away from the complex, while the nascent strand is directed to the sites responsible for mRNA capping. The model presents a cohesive picture of the multiple functions of the coronavirus replication-transcription complex and addresses fundamental questions related to proofreading, template switching, mRNA capping, and the role of the endonuclease.
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106
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Tseng YY, Kuan CY, Mibayashi M, Chen CJ, Palese P, Albrecht RA, Hsu WL. Interaction between NS1 and Cellular MAVS Contributes to NS1 Mitochondria Targeting. Viruses 2021; 13:1909. [PMID: 34696339 PMCID: PMC8537625 DOI: 10.3390/v13101909] [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: 08/26/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 11/16/2022] Open
Abstract
Influenza A virus nonstructural protein 1 (NS1) plays an important role in evading host innate immunity. NS1 inhibits interferon (IFN) responses via multiple mechanisms, including sequestering dsRNA and suppressing retinoic acid-inducible gene I (RIG-I) signaling by interacting with RIG-I and tripartite motif-containing protein 25 (TRIM25). In the current study, we demonstrated the mitochondrial localization of NS1 at the early stage of influenza virus infection. Since NS1 does not contain mitochondria-targeting signals, we suspected that there is an association between the NS1 and mitochondrial proteins. This hypothesis was tested by demonstrating the interaction of NS1 with mitochondrial antiviral-signaling protein (MAVS) in a RIG-I-independent manner. Importantly, the association with MAVS facilitated the mitochondrial localization of NS1 and thereby significantly impeded MAVS-mediated Type I IFN production.
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107
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Chaudhary JK, Yadav R, Chaudhary PK, Maurya A, Roshan R, Azam F, Mehta J, Handu S, Prasad R, Jain N, Pandey AK, Dhamija P. Host Cell and SARS-CoV-2-Associated Molecular Structures and Factors as Potential Therapeutic Targets. Cells 2021; 10:cells10092427. [PMID: 34572076 PMCID: PMC8467010 DOI: 10.3390/cells10092427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 08/28/2021] [Accepted: 08/31/2021] [Indexed: 02/07/2023] Open
Abstract
Coronavirus disease 19 (COVID-19) is caused by an enveloped, positive-sense, single-stranded RNA virus, referred to as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which belongs to the realm Riboviria, order Nidovirales, family Coronaviridae, genus Betacoronavirus and the species Severe acute respiratory syndrome-related coronavirus. This viral disease is characterized by a myriad of varying symptoms, such as pyrexia, cough, hemoptysis, dyspnoea, diarrhea, muscle soreness, dysosmia, lymphopenia and dysgeusia amongst others. The virus mainly infects humans, various other mammals, avian species and some other companion livestock. SARS-CoV-2 cellular entry is primarily accomplished by molecular interaction between the virus’s spike (S) protein and the host cell surface receptor, angiotensin-converting enzyme 2 (ACE2), although other host cell-associated receptors/factors, such as neuropilin 1 (NRP-1) and neuropilin 2 (NRP-2), C-type lectin receptors (CLRs), as well as proteases such as TMPRSS2 (transmembrane serine protease 2) and furin, might also play a crucial role in infection, tropism, pathogenesis and clinical outcome. Furthermore, several structural and non-structural proteins of the virus themselves are very critical in determining the clinical outcome following infection. Considering such critical role(s) of the abovementioned host cell receptors, associated proteases/factors and virus structural/non-structural proteins (NSPs), it may be quite prudent to therapeutically target them through a multipronged clinical regimen to combat the disease.
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108
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Uday RVS, Misra R, Harika A, Dolui S, Saha A, Pal U, Ravichandiran V, Maiti NC. Dabrafenib, idelalisib and nintedanib act as significant allosteric modulator for dengue NS3 protease. PLoS One 2021; 16:e0257206. [PMID: 34506566 PMCID: PMC8432871 DOI: 10.1371/journal.pone.0257206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 08/25/2021] [Indexed: 11/18/2022] Open
Abstract
Dengue virus (DENV) encodes a unique protease (NS3/NS2B) essential for its maturation and infectivity and, it has become a key target for anti-viral drug design to treat dengue and other flavivirus related infections. Present investigation established that some of the drug molecules currently used mainly in cancer treatment are susceptible to bind non-active site (allosteric site/ cavity) of the NS3 protease enzyme of dengue virus. Computational screening and molecular docking analysis found that dabrafenib, idelalisib and nintedanib can bind at the allosteric site of the enzyme. The binding of the molecules to the allosteric site found to be stabilized via pi-cation and hydrophobic interactions, hydrogen-bond formation and π-stacking interaction with the molecules. Several interacting residues of the enzyme were common in all the five serotypes. However, the interaction/stabilizing forces were not uniformly distributed; the π-stacking was dominated with DENV3 proteases, whereas, a charged/ionic interaction was the major force behind interaction with DENV2 type proteases. In the allosteric cavity of protease from DENV1, the residues Lys73, Lys74, Thr118, Glu120, Val123, Asn152 and Ala164 were involved in active interaction with the three molecules (dabrafenib, idelalisib and nintedanib). Molecular dynamics (MD) analysis further revealed that the molecules on binding to NS3 protease caused significant changes in structural fluctuation and gained enhanced stability. Most importantly, the binding of the molecules effectively perturbed the protein conformation. These changes in the protein conformation and dynamics could generate allosteric modulation and thus may attenuate/alter the NS3 protease functionality and mobility at the active site. Experimental studies may strengthen the notion whether the binding reduce/enhance the catalytic activity of the enzyme, however, it is beyond the scope of this study.
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109
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Wang B, Svetlov D, Artsimovitch I. NMPylation and de-NMPylation of SARS-CoV-2 nsp9 by the NiRAN domain. Nucleic Acids Res 2021; 49:8822-8835. [PMID: 34352100 PMCID: PMC8385902 DOI: 10.1093/nar/gkab677] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/15/2021] [Accepted: 07/26/2021] [Indexed: 12/11/2022] Open
Abstract
The catalytic subunit of SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) contains two active sites that catalyze nucleotidyl-monophosphate transfer (NMPylation). Mechanistic studies and drug discovery have focused on RNA synthesis by the highly conserved RdRp. The second active site, which resides in a Nidovirus RdRp-Associated Nucleotidyl transferase (NiRAN) domain, is poorly characterized, but both catalytic reactions are essential for viral replication. One study showed that NiRAN transfers NMP to the first residue of RNA-binding protein nsp9; another reported a structure of nsp9 containing two additional N-terminal residues bound to the NiRAN active site but observed NMP transfer to RNA instead. We show that SARS-CoV-2 RdRp NMPylates the native but not the extended nsp9. Substitutions of the invariant NiRAN residues abolish NMPylation, whereas substitution of a catalytic RdRp Asp residue does not. NMPylation can utilize diverse nucleotide triphosphates, including remdesivir triphosphate, is reversible in the presence of pyrophosphate, and is inhibited by nucleotide analogs and bisphosphonates, suggesting a path for rational design of NiRAN inhibitors. We reconcile these and existing findings using a new model in which nsp9 remodels both active sites to alternately support initiation of RNA synthesis by RdRp or subsequent capping of the product RNA by the NiRAN domain.
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110
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Beddingfield BJ, Hartnett JN, Wilson RB, Kulakosky PC, Andersen KG, Robles-Sikisaka R, Grubaugh ND, Aybar A, Nunez MZ, Fermin CD, Garry RF. Zika Virus Non-Structural Protein 1 Antigen-Capture Immunoassay. Viruses 2021; 13:v13091771. [PMID: 34578352 PMCID: PMC8473068 DOI: 10.3390/v13091771] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 08/24/2021] [Accepted: 09/03/2021] [Indexed: 01/01/2023] Open
Abstract
Infection with Zika virus (ZIKV), a member of the Flavivirus genus of the Flaviviridae family, typically results in mild self-limited illness, but severe neurological disease occurs in a limited subset of patients. In contrast, serious outcomes commonly occur in pregnancy that affect the developing fetus, including microcephaly and other major birth defects. The genetic similarity of ZIKV to other widespread flaviviruses, such as dengue virus (DENV), presents a challenge to the development of specific ZIKV diagnostic assays. Nonstructural protein 1 (NS1) is established for use in immunodiagnostic assays for flaviviruses. To address the cross-reactivity of ZIKV NS1 with proteins from other flaviviruses we used site-directed mutagenesis to modify putative epitopes. Goat polyclonal antibodies to variant ZIKV NS1 were affinity-purified to remove antibodies binding to the closely related NS1 protein of DENV. An antigen-capture ELISA configured with the affinity-purified polyclonal antibody showed a linear dynamic range between approximately 500 and 30 ng/mL, with a limit of detection of between 1.95 and 7.8 ng/mL. NS1 proteins from DENV, yellow fever virus, St. Louis encephalitis virus and West Nile virus showed significantly reduced reactivity in the ZIKV antigen-capture ELISA. Refinement of approaches similar to those employed here could lead to development of ZIKV-specific immunoassays suitable for use in areas where infections with related flaviviruses are common.
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111
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Zhao K, Ke Z, Hu H, Liu Y, Li A, Hua R, Guo F, Xiao J, Zhang Y, Duan L, Yan XF, Gao YG, Liu B, Xia Y, Li Y. Structural Basis and Function of the N Terminus of SARS-CoV-2 Nonstructural Protein 1. Microbiol Spectr 2021; 9:e0016921. [PMID: 34132580 PMCID: PMC8552758 DOI: 10.1128/spectrum.00169-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 05/12/2021] [Indexed: 11/20/2022] Open
Abstract
Nonstructural protein 1 (Nsp1) of severe acute respiratory syndrome coronaviruses (SARS-CoVs) is an important pathogenic factor that inhibits host protein translation by means of its C terminus. However, its N-terminal function remains elusive. Here, we determined the crystal structure of the N terminus (amino acids [aa] 11 to 125) of SARS-CoV-2 Nsp1 at a 1.25-Å resolution. Further functional assays showed that the N terminus of SARS-CoVs Nsp1 alone loses the ability to colocalize with ribosomes and inhibit protein translation. The C terminus of Nsp1 can colocalize with ribosomes, but its protein translation inhibition ability is significantly weakened. Interestingly, fusing the C terminus of Nsp1 with enhanced green fluorescent protein (EGFP) or other proteins in place of its N terminus restored the protein translation inhibitory ability to a level equivalent to that of full-length Nsp1. Thus, our results suggest that the N terminus of Nsp1 is able to stabilize the binding of the Nsp1 C terminus to ribosomes and act as a nonspecific barrier to block the mRNA channel, thus abrogating host mRNA translation.
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112
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Dultz G, Srikakulam SK, Konetschnik M, Shimakami T, Doncheva NT, Dietz J, Sarrazin C, Biondi RM, Zeuzem S, Tampé R, Kalinina OV, Welsch C. Epistatic interactions promote persistence of NS3-Q80K in HCV infection by compensating for protein folding instability. J Biol Chem 2021; 297:101031. [PMID: 34339738 PMCID: PMC8405986 DOI: 10.1016/j.jbc.2021.101031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 07/27/2021] [Accepted: 07/29/2021] [Indexed: 11/28/2022] Open
Abstract
The Q80K polymorphism in the NS3-4A protease of the hepatitis C virus is associated with treatment failure of direct-acting antiviral agents. This polymorphism is highly prevalent in genotype 1a infections and stably transmitted between hosts. Here, we investigated the underlying molecular mechanisms of evolutionarily conserved coevolving amino acids in NS3-Q80K and revealed potential implications of epistatic interactions in immune escape and variants persistence. Using purified protein, we characterized the impact of epistatic amino acid substitutions on the physicochemical properties and peptide cleavage kinetics of the NS3-Q80K protease. We found that Q80K destabilized the protease protein fold (p < 0.0001). Although NS3-Q80K showed reduced peptide substrate turnover (p < 0.0002), replicative fitness in an H77S.3 cell culture model of infection was not significantly inferior to the WT virus. Epistatic substitutions at residues 91 and 174 in NS3-Q80K stabilized the protein fold (p < 0.0001) and leveraged the WT protease stability. However, changes in protease stability inversely correlated with enzymatic activity. In infectious cell culture, these secondary substitutions were not associated with a gain of replicative fitness in NS3-Q80K variants. Using molecular dynamics, we observed that the total number of residue contacts in NS3-Q80K mutants correlated with protein folding stability. Changes in the number of contacts reflected the compensatory effect on protein folding instability by epistatic substitutions. In summary, epistatic substitutions in NS3-Q80K contribute to viral fitness by mechanisms not directly related to RNA replication. By compensating for protein-folding instability, epistatic interactions likely protect NS3-Q80K variants from immune cell recognition.
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113
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Newman JA, Douangamath A, Yadzani S, Yosaatmadja Y, Aimon A, Brandão-Neto J, Dunnett L, Gorrie-Stone T, Skyner R, Fearon D, Schapira M, von Delft F, Gileadi O. Structure, mechanism and crystallographic fragment screening of the SARS-CoV-2 NSP13 helicase. Nat Commun 2021; 12:4848. [PMID: 34381037 DOI: 10.1101/2021.03.15.435326] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 07/28/2021] [Indexed: 05/25/2023] Open
Abstract
There is currently a lack of effective drugs to treat people infected with SARS-CoV-2, the cause of the global COVID-19 pandemic. The SARS-CoV-2 Non-structural protein 13 (NSP13) has been identified as a target for anti-virals due to its high sequence conservation and essential role in viral replication. Structural analysis reveals two "druggable" pockets on NSP13 that are among the most conserved sites in the entire SARS-CoV-2 proteome. Here we present crystal structures of SARS-CoV-2 NSP13 solved in the APO form and in the presence of both phosphate and a non-hydrolysable ATP analog. Comparisons of these structures reveal details of conformational changes that provide insights into the helicase mechanism and possible modes of inhibition. To identify starting points for drug development we have performed a crystallographic fragment screen against NSP13. The screen reveals 65 fragment hits across 52 datasets opening the way to structure guided development of novel antiviral agents.
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114
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Newman JA, Douangamath A, Yadzani S, Yosaatmadja Y, Aimon A, Brandão-Neto J, Dunnett L, Gorrie-Stone T, Skyner R, Fearon D, Schapira M, von Delft F, Gileadi O. Structure, mechanism and crystallographic fragment screening of the SARS-CoV-2 NSP13 helicase. Nat Commun 2021; 12:4848. [PMID: 34381037 PMCID: PMC8358061 DOI: 10.1038/s41467-021-25166-6] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 07/28/2021] [Indexed: 12/24/2022] Open
Abstract
There is currently a lack of effective drugs to treat people infected with SARS-CoV-2, the cause of the global COVID-19 pandemic. The SARS-CoV-2 Non-structural protein 13 (NSP13) has been identified as a target for anti-virals due to its high sequence conservation and essential role in viral replication. Structural analysis reveals two "druggable" pockets on NSP13 that are among the most conserved sites in the entire SARS-CoV-2 proteome. Here we present crystal structures of SARS-CoV-2 NSP13 solved in the APO form and in the presence of both phosphate and a non-hydrolysable ATP analog. Comparisons of these structures reveal details of conformational changes that provide insights into the helicase mechanism and possible modes of inhibition. To identify starting points for drug development we have performed a crystallographic fragment screen against NSP13. The screen reveals 65 fragment hits across 52 datasets opening the way to structure guided development of novel antiviral agents.
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115
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Courouble VV, Dey SK, Yadav R, Timm J, Harrison JJEK, Ruiz FX, Arnold E, Griffin PR. Revealing the Structural Plasticity of SARS-CoV-2 nsp7 and nsp8 Using Structural Proteomics. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1618-1630. [PMID: 34121407 PMCID: PMC8231661 DOI: 10.1021/jasms.1c00086] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 05/24/2021] [Accepted: 05/28/2021] [Indexed: 06/12/2023]
Abstract
Coronavirus (CoV) nonstructural proteins (nsps) assemble to form the replication-transcription complex (RTC) responsible for viral RNA synthesis. nsp7 and nsp8 are important cofactors of the RTC, as they interact and regulate the activity of RNA-dependent RNA polymerase and other nsps. To date, no structure of the full-length SARS-CoV-2 nsp7:nsp8 complex has been published. The current understanding of this complex is based on structures from truncated constructs, with missing electron densities, or from related CoV species where SARS-CoV-2 nsp7 and nsp8 share upward of 90% sequence identity. Despite available structures solved using crystallography and cryo-EM representing detailed static snapshots of the nsp7:nsp8 complex, it is evident that the complex has a high degree of structural plasticity. However, relatively little is known about the conformational dynamics of the individual proteins and how they complex to interact with other nsps. Here, the solution-based structural proteomic techniques, hydrogen-deuterium exchange mass spectrometry (HDX-MS) and cross-linking mass spectrometry (XL-MS), illuminate the dynamics of SARS-CoV-2 full-length nsp7 and nsp8 proteins and the nsp7:nsp8 protein complex. Results presented from the two techniques are complementary and validate the interaction surfaces identified from the published three-dimensional heterotetrameric crystal structure of the SARS-CoV-2 truncated nsp7:nsp8 complex. Furthermore, mapping of XL-MS data onto higher-order complexes suggests that SARS-CoV-2 nsp7 and nsp8 do not assemble into a hexadecameric structure as implied by the SARS-CoV full-length nsp7:nsp8 crystal structure. Instead, our results suggest that the nsp7:nsp8 heterotetramer can dissociate into a stable dimeric unit that might bind to nsp12 in the RTC without significantly altering nsp7-nsp8 interactions.
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116
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Wilamowski M, Sherrell DA, Minasov G, Kim Y, Shuvalova L, Lavens A, Chard R, Maltseva N, Jedrzejczak R, Rosas-Lemus M, Saint N, Foster IT, Michalska K, Satchell KJF, Joachimiak A. 2'-O methylation of RNA cap in SARS-CoV-2 captured by serial crystallography. Proc Natl Acad Sci U S A 2021; 118:e2100170118. [PMID: 33972410 PMCID: PMC8166198 DOI: 10.1073/pnas.2100170118] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The genome of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) coronavirus has a capping modification at the 5'-untranslated region (UTR) to prevent its degradation by host nucleases. These modifications are performed by the Nsp10/14 and Nsp10/16 heterodimers using S-adenosylmethionine as the methyl donor. Nsp10/16 heterodimer is responsible for the methylation at the ribose 2'-O position of the first nucleotide. To investigate the conformational changes of the complex during 2'-O methyltransferase activity, we used a fixed-target serial synchrotron crystallography method at room temperature. We determined crystal structures of Nsp10/16 with substrates and products that revealed the states before and after methylation, occurring within the crystals during the experiments. Here we report the crystal structure of Nsp10/16 in complex with Cap-1 analog (m7GpppAm2'-O). Inhibition of Nsp16 activity may reduce viral proliferation, making this protein an attractive drug target.
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Sun X, Sun M, Zhang L, Yu Z, Li J, Xie W, Su J. Amino Acid Substitutions in NS5 Contribute Differentially to Tembusu Virus Attenuation in Ducklings and Cell Cultures. Viruses 2021; 13:v13050921. [PMID: 34065634 PMCID: PMC8156267 DOI: 10.3390/v13050921] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Revised: 05/07/2021] [Accepted: 05/11/2021] [Indexed: 01/04/2023] Open
Abstract
Tembusu virus (TMUV), a highly infectious pathogenic flavivirus, causes severe egg-drop and encephalitis in domestic waterfowl, while the determinants responsible for viral pathogenicity are largely unknown. In our previous studies, virulent strain JXSP2-4 had been completely attenuated by successive passages in BHK-21 cells and the avirulent strain was designated as JXSP-310. Based on the backbone of JXSP2-4, a series of chimeric viruses were generated according to the amino acid substitutions in NS5 and their infectivities were also analyzed in cell cultures and ducklings. The results showed that the viral titers of RNA-dependent RNA polymerase (RdRp) domain-swapped cheimeric mutant (JXSP-310RdRp) in cells and ducklings were both markedly decreased compared with JXSP2-4, indicating that mutations in the RdRp domain affected viral replication. There are R543K and V711A two amino acid substitutions in the RdRp domain. Further site-directed mutagenesis showed that single-point R543K mutant (JXSP-R543K) exhibited similar replication efficacy compared with JXSP2-4 in cells, but the viral loads in JXSP-R543K-infected ducklings were significantly lower than that of JXSP2-4 and higher than JXSP-310RdRp. Surprisingly, the single-point V711A mutation we introduced rapidly reverted. In addition, qRT-PCR and Western blot confirmed that the mutations in the RdRp domain significantly affected the replication of the virus. Taken together, these results show that R543K substitution in the RdRp domain impairs the in vivo growth of TMUV, but sustaining its attenuated infectivity requires the concurrent presence of the V711A mutation.
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Rocha REO, Chaves EJF, Fischer PHC, Costa LSC, Grillo IB, da Cruz LEG, Guedes FC, da Silveira CH, Scotti MT, Camargo AD, Machado KS, Werhli AV, Ferreira RS, Rocha GB, de Lima LHF. A higher flexibility at the SARS-CoV-2 main protease active site compared to SARS-CoV and its potentialities for new inhibitor virtual screening targeting multi-conformers. J Biomol Struct Dyn 2021; 40:9214-9234. [PMID: 33970798 PMCID: PMC8127201 DOI: 10.1080/07391102.2021.1924271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 04/26/2021] [Indexed: 12/14/2022]
Abstract
The main-protease (Mpro) catalyzes a crucial step for the SARS-CoV-2 life cycle. The recent SARS-CoV-2 presents the main protease (MCoV2pro) with 12 mutations compared to SARS-CoV (MCoV1pro). Recent studies point out that these subtle differences lead to mobility variances at the active site loops with functional implications. We use metadynamics simulations and a sort of computational analysis to probe the dynamic, pharmacophoric and catalytic environment differences between the monomers of both enzymes. So, we verify how much intrinsic distinctions are preserved in the functional dimer of MCoV2pro, as well as its implications for ligand accessibility and optimized drug screening. We find a significantly higher accessibility to open binding conformers in the MCoV2pro monomer compared to MCoV1pro. A higher hydration propensity for the MCoV2pro S2 loop with the A46S substitution seems to exercise a key role. Quantum calculations suggest that the wider conformations for MCoV2pro are less catalytically active in the monomer. However, the statistics for contacts involving the N-finger suggest higher maintenance of this activity at the dimer. Docking analyses suggest that the ability to vary the active site width can be important to improve the access of the ligand to the active site in different ways. So, we carry out a multiconformational virtual screening with different ligand bases. The results point to the importance of taking into account the protein conformational multiplicity for new promissors anti MCoV2pro ligands. We hope these results will be useful in prospecting, repurposing and/or designing new anti SARS-CoV-2 drugs.Communicated by Ramaswamy H. Sarma.
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Alkhatib M, Di Maio VC, De Murtas V, Polilli E, Milana M, Teti E, Fiorentino G, Calvaruso V, Barbaliscia S, Bertoli A, Scutari R, Carioti L, Cento V, Santoro MM, Orro A, Maida I, Lenci I, Sarmati L, Craxì A, Pasquazzi C, Parruti G, Babudieri S, Milanesi L, Andreoni M, Angelico M, Perno CF, Ceccherini-Silberstein F, Svicher V, Salpini R. Genetic Determinants in a Critical Domain of NS5A Correlate with Hepatocellular Carcinoma in Cirrhotic Patients Infected with HCV Genotype 1b. Viruses 2021; 13:v13050743. [PMID: 33922732 PMCID: PMC8146897 DOI: 10.3390/v13050743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 04/14/2021] [Accepted: 04/22/2021] [Indexed: 12/05/2022] Open
Abstract
HCV is an important cause of hepatocellular carcinoma (HCC). HCV NS5A domain-1 interacts with cellular proteins inducing pro-oncogenic pathways. Thus, we explore genetic variations in NS5A domain-1 and their association with HCC, by analyzing 188 NS5A sequences from HCV genotype-1b infected DAA-naïve cirrhotic patients: 34 with HCC and 154 without HCC. Specific NS5A mutations significantly correlate with HCC: S3T (8.8% vs. 1.3%, p = 0.01), T122M (8.8% vs. 0.0%, p < 0.001), M133I (20.6% vs. 3.9%, p < 0.001), and Q181E (11.8% vs. 0.6%, p < 0.001). By multivariable analysis, the presence of ≥1 of them independently correlates with HCC (OR (95%CI): 21.8 (5.7–82.3); p < 0.001). Focusing on HCC-group, the presence of these mutations correlates with higher viremia (median (IQR): 5.7 (5.4–6.2) log IU/mL vs. 5.3 (4.4–5.6) log IU/mL, p = 0.02) and lower ALT (35 (30–71) vs. 83 (48–108) U/L, p = 0.004), suggesting a role in enhancing viral fitness without affecting necroinflammation. Notably, these mutations reside in NS5A regions known to interact with cellular proteins crucial for cell-cycle regulation (p53, p85-PIK3, and β-catenin), and introduce additional phosphorylation sites, a phenomenon known to ameliorate NS5A interaction with cellular proteins. Overall, these results provide a focus for further investigations on molecular bases of HCV-mediated oncogenesis. The role of these NS5A domain-1 mutations in triggering pro-oncogenic stimuli that can persist also despite achievement of sustained virological response deserves further investigation.
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Sui M, Xiong M, Li Y, Zhou Q, Shen X, Jia D, Gou M, Sun Q. Cancer Therapy with Nanoparticle-Medicated Intracellular Expression of Peptide CRM1-Inhibitor. Int J Nanomedicine 2021; 16:2833-2847. [PMID: 33883894 PMCID: PMC8054660 DOI: 10.2147/ijn.s266398] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 09/29/2020] [Indexed: 02/05/2023] Open
Abstract
INTRODUCTION Peptides can be rationally designed as non-covalent inhibitors for molecularly targeted therapy. However, it remains challenging to efficiently deliver the peptides into the targeted cells, which often severely affects their therapeutic efficiency. METHODS Herein, we created a novel non-covalent peptide inhibitor against nuclear export factor CRM1 by a structure-guided drug design method and targetedly delivered the peptide into cancer cells by a nanoparticle-mediated gene expression system for use as a cancer therapy. RESULTS The nuclear export signal (NES)-optimized CRM1 peptide inhibitor colocalized with CRM1 to the nuclear envelope and inhibited nuclear export in cancer cell lines in vitro. The crystal structures of the inhibitors complexed with CRM1 were solved. In contrast to the covalent inhibitors, the peptides were similarly effective against cells harboring the CRM1 C528S mutation. Moreover, a plasmid encoding the peptides was delivered by a iRGD-modified nanoparticle to efficiently target and transfect the cancer cells in vivo after intravenous administration. The peptides could be selectively expressed in the tumor, resulting in the efficient inhibition of subcutaneous melanoma xenografts without obvious systemic toxicity. DISCUSSION This work provides an effective strategy to design peptide-based molecularly targeted therapeutics, which could lead to the development of future targeted therapy.
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Yadav R, Chaudhary JK, Jain N, Chaudhary PK, Khanra S, Dhamija P, Sharma A, Kumar A, Handu S. Role of Structural and Non-Structural Proteins and Therapeutic Targets of SARS-CoV-2 for COVID-19. Cells 2021; 10:cells10040821. [PMID: 33917481 PMCID: PMC8067447 DOI: 10.3390/cells10040821] [Citation(s) in RCA: 219] [Impact Index Per Article: 73.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 03/31/2021] [Accepted: 04/01/2021] [Indexed: 02/07/2023] Open
Abstract
Coronavirus belongs to the family of Coronaviridae, comprising single-stranded, positive-sense RNA genome (+ ssRNA) of around 26 to 32 kilobases, and has been known to cause infection to a myriad of mammalian hosts, such as humans, cats, bats, civets, dogs, and camels with varied consequences in terms of death and debilitation. Strikingly, novel coronavirus (2019-nCoV), later renamed as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), and found to be the causative agent of coronavirus disease-19 (COVID-19), shows 88% of sequence identity with bat-SL-CoVZC45 and bat-SL-CoVZXC21, 79% with SARS-CoV and 50% with MERS-CoV, respectively. Despite key amino acid residual variability, there is an incredible structural similarity between the receptor binding domain (RBD) of spike protein (S) of SARS-CoV-2 and SARS-CoV. During infection, spike protein of SARS-CoV-2 compared to SARS-CoV displays 10-20 times greater affinity for its cognate host cell receptor, angiotensin-converting enzyme 2 (ACE2), leading proteolytic cleavage of S protein by transmembrane protease serine 2 (TMPRSS2). Following cellular entry, the ORF-1a and ORF-1ab, located downstream to 5' end of + ssRNA genome, undergo translation, thereby forming two large polyproteins, pp1a and pp1ab. These polyproteins, following protease-induced cleavage and molecular assembly, form functional viral RNA polymerase, also referred to as replicase. Thereafter, uninterrupted orchestrated replication-transcription molecular events lead to the synthesis of multiple nested sets of subgenomic mRNAs (sgRNAs), which are finally translated to several structural and accessory proteins participating in structure formation and various molecular functions of virus, respectively. These multiple structural proteins assemble and encapsulate genomic RNA (gRNA), resulting in numerous viral progenies, which eventually exit the host cell, and spread infection to rest of the body. In this review, we primarily focus on genomic organization, structural and non-structural protein components, and potential prospective molecular targets for development of therapeutic drugs, convalescent plasm therapy, and a myriad of potential vaccines to tackle SARS-CoV-2 infection.
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Kubatova N, Qureshi NS, Altincekic N, Abele R, Bains JK, Ceylan B, Ferner J, Fuks C, Hargittay B, Hutchison MT, de Jesus V, Kutz F, Wirtz Martin MA, Meiser N, Linhard V, Pyper DJ, Trucks S, Fürtig B, Hengesbach M, Löhr F, Richter C, Saxena K, Schlundt A, Schwalbe H, Sreeramulu S, Wacker A, Weigand JE, Wirmer-Bartoschek J, Wöhnert J. 1H, 13C, and 15N backbone chemical shift assignments of coronavirus-2 non-structural protein Nsp10. BIOMOLECULAR NMR ASSIGNMENTS 2021; 15:65-71. [PMID: 33159807 PMCID: PMC7648550 DOI: 10.1007/s12104-020-09984-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/03/2020] [Indexed: 06/11/2023]
Abstract
The international Covid19-NMR consortium aims at the comprehensive spectroscopic characterization of SARS-CoV-2 RNA elements and proteins and will provide NMR chemical shift assignments of the molecular components of this virus. The SARS-CoV-2 genome encodes approximately 30 different proteins. Four of these proteins are involved in forming the viral envelope or in the packaging of the RNA genome and are therefore called structural proteins. The other proteins fulfill a variety of functions during the viral life cycle and comprise the so-called non-structural proteins (nsps). Here, we report the near-complete NMR resonance assignment for the backbone chemical shifts of the non-structural protein 10 (nsp10). Nsp10 is part of the viral replication-transcription complex (RTC). It aids in synthesizing and modifying the genomic and subgenomic RNAs. Via its interaction with nsp14, it ensures transcriptional fidelity of the RNA-dependent RNA polymerase, and through its stimulation of the methyltransferase activity of nsp16, it aids in synthesizing the RNA cap structures which protect the viral RNAs from being recognized by the innate immune system. Both of these functions can be potentially targeted by drugs. Our data will aid in performing additional NMR-based characterizations, and provide a basis for the identification of possible small molecule ligands interfering with nsp10 exerting its essential role in viral replication.
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Lin MH, Huang YP, Chang CF, Hsu CH. NMR assignments of the macro domain from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). BIOMOLECULAR NMR ASSIGNMENTS 2021; 15:137-142. [PMID: 33486617 PMCID: PMC7826497 DOI: 10.1007/s12104-020-09996-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 12/11/2020] [Indexed: 05/05/2023]
Abstract
SARS-CoV-2 is a novel pathogen causing pneumonia named COVID-19 and leading to a severe pandemic since the end of 2019. The genome of SARS-CoV-2 contains a macro domain that may play an important role in regulating ADP-ribosylation in host cells and initiating viral replication. Here, we report the 1H, 13C, and 15N resonance assignments of the SARS-CoV-2 macro domain. This work provides the ground for further structural deciphering and biophysical investigation in protein function and antiviral agent design.
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Buchko GW, Zhou M, Craig JK, Van Voorhis WC, Myler PJ. Backbone chemical shift assignments for the SARS-CoV-2 non-structural protein Nsp9: intermediate (ms - μs) dynamics in the C-terminal helix at the dimer interface. BIOMOLECULAR NMR ASSIGNMENTS 2021; 15:107-116. [PMID: 33392924 PMCID: PMC7779335 DOI: 10.1007/s12104-020-09992-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 11/24/2020] [Indexed: 05/28/2023]
Abstract
The Betacoronavirus SARS-CoV-2 non-structural protein Nsp9 is a 113-residue protein that is essential for viral replication, and consequently, a potential target for the development of therapeutics against COVID19 infections. To capture insights into the dynamics of the protein's backbone in solution and accelerate the identification and mapping of ligand-binding surfaces through chemical shift perturbation studies, the backbone 1H, 13C, and 15N NMR chemical shifts for Nsp9 have been extensively assigned. These assignments were assisted by the preparation of an ~ 70% deuterated sample and residue-specific, 15N-labelled samples (V, L, M, F, and K). A major feature of the assignments was the "missing" amide resonances for N96-L106 in the 1H-15N HSQC spectrum, a region that comprises almost the complete C-terminal α-helix that forms a major part of the homodimer interface in the crystal structure of SARS-CoV-2 Nsp9, suggesting this region either undergoes intermediate motion in the ms to μs timescale and/or is heterogenous. These "missing" amide resonances do not unambiguously appear in the 1H-15N HSQC spectrum of SARS-CoV-2 Nsp9 collected at a concentration of 0.0007 mM. At this concentration, at the detection limit, native mass spectrometry indicates the protein is exclusively in the monomeric state, suggesting the intermediate motion in the C-terminal of Nsp9 may be due to intramolecular dynamics. Perhaps this intermediate ms to μs timescale dynamics is the physical basis for a previously suggested "fluidity" of the C-terminal helix that may be responsible for homophilic (Nsp9-Nsp9) and postulated heterophilic (Nsp9-Unknown) protein-protein interactions.
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Fang P, Hong Y, Xia S, Zhang J, Ren J, Zhou Y, Fang L, Xiao S. Porcine deltacoronavirus nsp10 antagonizes interferon-β production independently of its zinc finger domains. Virology 2021; 559:46-56. [PMID: 33813212 DOI: 10.1016/j.virol.2021.03.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 11/18/2022]
Abstract
Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus that causes serious vomiting and diarrhea in piglets. Previous work demonstrated that PDCoV infection inhibits type I interferon (IFN) production. Here, we found that ectopic expression of PDCoV nsp10 significantly inhibited Sendai virus (SeV)-induced IFN-β production by impairing the phosphorylation and nuclear translocation of two transcription factors, IRF3 and NF-κB p65 subunit. Interestingly, experiments with truncated mutants and site-directed mutagenesis revealed that PDCoV nsp10 mutants with missing or destroyed zinc fingers (ZFs) domains also impeded SeV-induced IFN-β production, suggesting that nsp10 does not require its ZF domains to antagonize IFN-β production. Further work found that co-expression of nsp10 with nsp14 or nsp16, two replicative enzymes, significantly enhanced the inhibitory effects of nsp10 on IFN-β. Taken together, our results demonstrate that PDCoV nsp10 antagonizes IFN via a ZF-independent mechanism and has a synergistic effect with nsp14 and nsp16 on inhibiting IFN-β production.
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