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1.
Molecules ; 27(7)2022 Mar 31.
Article in English | MEDLINE | ID: covidwho-1792596

ABSTRACT

As a continuation of our earlier work against SARS-CoV-2, seven FDA-approved drugs were designated as the best SARS-CoV-2 nsp16-nsp10 2'-o-methyltransferase (2'OMTase) inhibitors through 3009 compounds. The in silico inhibitory potential of the examined compounds against SARS-CoV-2 nsp16-nsp10 2'-o-methyltransferase (PDB ID: (6W4H) was conducted through a multi-step screening approach. At the beginning, molecular fingerprints experiment with SAM (S-Adenosylmethionine), the co-crystallized ligand of the targeted enzyme, unveiled the resemblance of 147 drugs. Then, a structural similarity experiment recommended 26 compounds. Therefore, the 26 compounds were docked against 2'OMTase to reveal the potential inhibitory effect of seven promising compounds (Protirelin, (1187), Calcium folinate (1913), Raltegravir (1995), Regadenoson (2176), Ertapenem (2396), Methylergometrine (2532), and Thiamine pyrophosphate hydrochloride (2612)). Out of the docked ligands, Ertapenem (2396) showed an ideal binding mode like that of the co-crystallized ligand (SAM). It occupied all sub-pockets of the active site and bound the crucial amino acids. Accordingly, some MD simulation experiments (RMSD, RMSF, Rg, SASA, and H-bonding) have been conducted for the 2'OMTase-Ertapenem complex over 100 ns. The performed MD experiments verified the correct binding mode of Ertapenem against 2'OMTase exhibiting low energy and optimal dynamics. Finally, MM-PBSA studies indicated that Ertapenem bonded advantageously to the targeted protein with a free energy value of -43 KJ/mol. Furthermore, the binding free energy analysis revealed the essential amino acids of 2'OMTase that served positively to the binding. The achieved results bring hope to find a treatment for COVID-19 via in vitro and in vivo studies for the pointed compounds.


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/drug therapy , Ertapenem , Humans , Ligands , Methyltransferases/metabolism , Molecular Docking Simulation , Molecular Dynamics Simulation , S-Adenosylmethionine/chemistry
2.
Elife ; 112022 01 21.
Article in English | MEDLINE | ID: covidwho-1716085

ABSTRACT

Methyltransferase like-3 (METTL3) and METTL14 complex transfers a methyl group from S-adenosyl-L-methionine to N6 amino group of adenosine bases in RNA (m6A) and DNA (m6dA). Emerging evidence highlights a role of METTL3-METTL14 in the chromatin context, especially in processes where DNA and RNA are held in close proximity. However, a mechanistic framework about specificity for substrate RNA/DNA and their interrelationship remain unclear. By systematically studying methylation activity and binding affinity to a number of DNA and RNA oligos with different propensities to form inter- or intra-molecular duplexes or single-stranded molecules in vitro, we uncover an inverse relationship for substrate binding and methylation and show that METTL3-METTL14 preferentially catalyzes the formation of m6dA in single-stranded DNA (ssDNA), despite weaker binding affinity to DNA. In contrast, it binds structured RNAs with high affinity, but methylates the target adenosine in RNA (m6A) much less efficiently than it does in ssDNA. We also show that METTL3-METTL14-mediated methylation of DNA is largely restricted by structured RNA elements prevalent in long noncoding and other cellular RNAs.


Subject(s)
DNA Methylation/physiology , Methyltransferases/metabolism , DNA, Single-Stranded/metabolism , Deoxyadenosines/metabolism , Humans , RNA/chemistry , RNA/metabolism
3.
Cell Rep ; 38(10): 110503, 2022 03 08.
Article in English | MEDLINE | ID: covidwho-1705992

ABSTRACT

Natural killer (NK) cells are innate immune cells that contribute to host defense against virus infections. NK cells respond to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro and are activated in patients with acute coronavirus disease 2019 (COVID-19). However, by which mechanisms NK cells detect SARS-CoV-2-infected cells remains largely unknown. Here, we show that the Non-structural protein 13 of SARS-CoV-2 encodes for a peptide that is presented by human leukocyte antigen E (HLA-E). In contrast with self-peptides, the viral peptide prevents binding of HLA-E to the inhibitory receptor NKG2A, thereby rendering target cells susceptible to NK cell attack. In line with these observations, NKG2A-expressing NK cells are particularly activated in patients with COVID-19 and proficiently limit SARS-CoV-2 replication in infected lung epithelial cells in vitro. Thus, these data suggest that a viral peptide presented by HLA-E abrogates inhibition of NKG2A+ NK cells, resulting in missing self-recognition.


Subject(s)
COVID-19 , Histocompatibility Antigens Class I , Killer Cells, Natural , Methyltransferases , NK Cell Lectin-Like Receptor Subfamily C , RNA Helicases , SARS-CoV-2 , Viral Nonstructural Proteins , COVID-19/immunology , Histocompatibility Antigens Class I/immunology , Humans , Killer Cells, Natural/immunology , Methyltransferases/immunology , NK Cell Lectin-Like Receptor Subfamily C/immunology , NK Cell Lectin-Like Receptor Subfamily C/metabolism , Peptides/metabolism , RNA Helicases/immunology , Viral Nonstructural Proteins/immunology
4.
Biochem Biophys Res Commun ; 601: 129-136, 2022 04 23.
Article in English | MEDLINE | ID: covidwho-1699331

ABSTRACT

COVID-19, caused by SARS-CoV-2, has been spreading worldwide for more than two years and has led to immense challenges to human health. Despite the great efforts that have been made, our understanding of SARS-CoV-2 is still limited. The viral helicase, NSP13 is an important enzyme involved in SARS-CoV-2 replication and transcription. Here we highlight the important role of the stalk domain in the enzymatic activity of NSP13. Without the stalk domain, NSP13 loses its dsRNA unwinding ability due to the lack of ATPase activity. The stalk domain of NSP13 also provides a rigid connection between the ZBD and helicase domain. We found that the tight connection between the stalk and helicase is necessary for NSP13-mediated dsRNA unwinding. When a short flexible linker was inserted between the stalk and helicase domains, the helicase activity of NSP13 was impaired, although its ATPase activity remained intact. Further study demonstrated that linker insertion between the stalk and helicase domains attenuated the RNA binding ability and affected the thermal stability of NSP13. In summary, our results suggest the crucial role of the stalk domain in NSP13 enzymatic activity and provide mechanistic insight into dsRNA unwinding by SARS-CoV-2 NSP13.


Subject(s)
COVID-19/prevention & control , Methyltransferases/metabolism , RNA Helicases/metabolism , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/metabolism , Adenosine Triphosphatases/genetics , Adenosine Triphosphatases/metabolism , Binding Sites/genetics , COVID-19/virology , Enzyme Stability , Humans , Methyltransferases/chemistry , Methyltransferases/genetics , Models, Molecular , Mutation , Protein Conformation , RNA/chemistry , RNA/genetics , RNA/metabolism , RNA Helicases/chemistry , RNA Helicases/genetics , Recombinant Proteins/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/physiology , Temperature , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/genetics
5.
Nature ; 602(7896): 343-348, 2022 02.
Article in English | MEDLINE | ID: covidwho-1671588

ABSTRACT

Carbapenems are antibiotics of last resort in the clinic. Owing to their potency and broad-spectrum activity, they are an important part of the antibiotic arsenal. The vital role of carbapenems is exemplified by the approval acquired by Merck from the US Food and Drug Administration (FDA) for the use of an imipenem combination therapy to treat the increased levels of hospital-acquired and ventilator-associated bacterial pneumonia that have occurred during the COVID-19 pandemic1. The C6 hydroxyethyl side chain distinguishes the clinically used carbapenems from the other classes of ß-lactam antibiotics and is responsible for their low susceptibility to inactivation by occluding water from the ß-lactamase active site2. The construction of the C6 hydroxyethyl side chain is mediated by cobalamin- or B12-dependent radical S-adenosylmethionine (SAM) enzymes3. These radical SAM methylases (RSMTs) assemble the alkyl backbone by sequential methylation reactions, and thereby underlie the therapeutic usefulness of clinically used carbapenems. Here we present X-ray crystal structures of TokK, a B12-dependent RSMT that catalyses three-sequential methylations during the biosynthesis of asparenomycin A. These structures, which contain the two metallocofactors of the enzyme and were determined in the presence and absence of a carbapenam substrate, provide a visualization of a B12-dependent RSMT that uses the radical mechanism that is shared by most of these enzymes. The structures provide insight into the stereochemistry of initial C6 methylation and suggest that substrate positioning governs the rate of each methylation event.


Subject(s)
Carbapenems/biosynthesis , Methyltransferases/chemistry , Methyltransferases/metabolism , S-Adenosylmethionine/metabolism , Streptomyces/enzymology , Thienamycins/biosynthesis , Vitamin B 12/metabolism , Binding Sites , Biocatalysis , Coenzymes/metabolism , Crystallography, X-Ray , Kinetics , Methylation , Models, Molecular , Protein Binding , Protein Domains , Streptomyces/metabolism , beta-Lactamase Inhibitors/metabolism , beta-Lactamases/chemistry , beta-Lactamases/metabolism
6.
Nucleic Acids Res ; 50(2): 635-650, 2022 01 25.
Article in English | MEDLINE | ID: covidwho-1621653

ABSTRACT

Coronaviral methyltransferases (MTases), nsp10/16 and nsp14, catalyze the last two steps of viral RNA-cap creation that takes place in cytoplasm. This cap is essential for the stability of viral RNA and, most importantly, for the evasion of innate immune system. Non-capped RNA is recognized by innate immunity which leads to its degradation and the activation of antiviral immunity. As a result, both coronaviral MTases are in the center of scientific scrutiny. Recently, X-ray and cryo-EM structures of both enzymes were solved even in complex with other parts of the viral replication complex. High-throughput screening as well as structure-guided inhibitor design have led to the discovery of their potent inhibitors. Here, we critically summarize the tremendous advancement of the coronaviral MTase field since the beginning of COVID pandemic.


Subject(s)
Antiviral Agents/chemistry , Antiviral Agents/pharmacology , Coronavirus/drug effects , Coronavirus/enzymology , Methyltransferases/antagonists & inhibitors , Methyltransferases/chemistry , Methyltransferases/metabolism , Amino Acid Sequence , Amino Acids/chemistry , Binding Sites , Coronavirus/genetics , Drug Discovery , Humans , Methylation , Models, Molecular , Molecular Conformation , Molecular Structure , Protein Binding , RNA, Viral/chemistry , RNA, Viral/genetics , RNA, Viral/metabolism , Structure-Activity Relationship
7.
J Immunol ; 208(3): 753-761, 2022 02 01.
Article in English | MEDLINE | ID: covidwho-1614089

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has seriously threatened global public health. Severe COVID-19 has been reported to be associated with an impaired IFN response. However, the mechanisms of how SARS-CoV-2 antagonizes the host IFN response are poorly understood. In this study, we report that SARS-CoV-2 helicase NSP13 inhibits type I IFN production by directly targeting TANK-binding kinase 1 (TBK1) for degradation. Interestingly, inhibition of autophagy by genetic knockout of Beclin1 or pharmacological inhibition can rescue NSP13-mediated TBK1 degradation in HEK-293T cells. Subsequent studies revealed that NSP13 recruits TBK1 to p62, and the absence of p62 can also inhibit TBK1 degradation in HEK-293T and HeLa cells. Finally, TBK1 and p62 degradation and p62 aggregation were observed during SARS-CoV-2 infection in HeLa-ACE2 and Calu3 cells. Overall, our study shows that NSP13 inhibits type I IFN production by recruiting TBK1 to p62 for autophagic degradation, enabling it to evade the host innate immune response, which provides new insights into the transmission and pathogenesis of SARS-CoV-2 infection.


Subject(s)
Autophagy , COVID-19/immunology , Interferon Type I/biosynthesis , Methyltransferases/physiology , RNA Helicases/physiology , SARS-CoV-2/physiology , Sequestosome-1 Protein/metabolism , Viral Nonstructural Proteins/physiology , Beclin-1/antagonists & inhibitors , Cell Line , Down-Regulation , Humans , Immune Evasion , Immunity, Innate , Immunoprecipitation , Interferon Type I/genetics , Multiprotein Complexes , Protein Aggregates , Protein Interaction Mapping
8.
Antiviral Res ; 197: 105232, 2022 01.
Article in English | MEDLINE | ID: covidwho-1588314

ABSTRACT

We report the in vitro antiviral activity of DZNep (3-Deazaneplanocin A; an inhibitor of S-adenosylmethionine-dependent methyltransferase) against SARS-CoV-2, besides demonstrating its protective efficacy against lethal infection of infectious bronchitis virus (IBV, a member of the Coronaviridae family). DZNep treatment resulted in reduced synthesis of SARS-CoV-2 RNA and proteins without affecting other steps of viral life cycle. We demonstrated that deposition of N6-methyl adenosine (m6A) in SARS-CoV-2 RNA in the infected cells recruits heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), an RNA binding protein which serves as a m6A reader. DZNep inhibited the recruitment of hnRNPA1 at m6A-modified SARS-CoV-2 RNA which eventually suppressed the synthesis of the viral genome. In addition, m6A-marked RNA and hnRNPA1 interaction was also shown to regulate early translation to replication switch of SARS-CoV-2 genome. Furthermore, abrogation of methylation by DZNep also resulted in defective synthesis of the 5' cap of viral RNA, thereby resulting in its failure to interact with eIF4E (a cap-binding protein), eventually leading to a decreased synthesis of viral proteins. Most importantly, DZNep-resistant mutants could not be observed upon long-term sequential passage of SARS-CoV-2 in cell culture. In summary, we report the novel role of methylation in the life cycle of SARS-CoV-2 and propose that targeting the methylome using DZNep could be of significant therapeutic value against SARS-CoV-2 infection.


Subject(s)
Adenosine/analogs & derivatives , Genome, Viral/drug effects , Methyltransferases/antagonists & inhibitors , SARS-CoV-2/drug effects , Adenosine/pharmacology , Animals , Chick Embryo , Chlorocebus aethiops , Chromatin Immunoprecipitation Sequencing , DNA Methylation/drug effects , DNA Methylation/physiology , Drug Resistance, Viral/drug effects , Genome, Viral/genetics , Heterogeneous Nuclear Ribonucleoprotein A1/metabolism , Humans , Lethal Dose 50 , Mice , Protein Biosynthesis/drug effects , RNA, Viral/drug effects , RNA, Viral/metabolism , Rabbits , SARS-CoV-2/genetics , Specific Pathogen-Free Organisms , Transcription, Genetic/drug effects , Vero Cells
9.
Int J Mol Sci ; 23(1)2021 Dec 28.
Article in English | MEDLINE | ID: covidwho-1580696

ABSTRACT

The inhibition of key enzymes that may contain the viral replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have assumed central importance in drug discovery projects. Nonstructural proteins (nsps) are essential for RNA capping and coronavirus replication since it protects the virus from host innate immune restriction. In particular, nonstructural protein 16 (nsp16) in complex with nsp10 is a Cap-0 binding enzyme. The heterodimer formed by nsp16-nsp10 methylates the 5'-end of virally encoded mRNAs to mimic cellular mRNAs and thus it is one of the enzymes that is a potential target for antiviral therapy. In this study, we have evaluated the mechanism of the 2'-O methylation of the viral mRNA cap using hybrid quantum mechanics/molecular mechanics (QM/MM) approach. It was found that the calculated free energy barriers obtained at M062X/6-31+G(d,p) is in agreement with experimental observations. Overall, we provide a detailed molecular analysis of the catalytic mechanism involving the 2'-O methylation of the viral mRNA cap and, as expected, the results demonstrate that the TS stabilization is critical for the catalysis.


Subject(s)
Methyltransferases/metabolism , RNA Caps/chemistry , RNA Caps/metabolism , SARS-CoV-2/enzymology , SARS-CoV-2/genetics , Viral Nonstructural Proteins/metabolism , Viral Regulatory and Accessory Proteins/metabolism , Biocatalysis , Biomechanical Phenomena , Methylation , Methyltransferases/chemistry , Molecular Dynamics Simulation , Quantum Theory , RNA Processing, Post-Transcriptional , Viral Nonstructural Proteins/chemistry , Viral Regulatory and Accessory Proteins/chemistry
10.
J Virol ; 95(15): e0046321, 2021 07 12.
Article in English | MEDLINE | ID: covidwho-1486505

ABSTRACT

The OC43 coronavirus is a human pathogen that usually causes only the common cold. One of its key enzymes, similar to other coronaviruses, is the 2'-O-RNA methyltransferase (MTase), which is essential for viral RNA stability and expression. Here, we report the crystal structure of the 2'-O-RNA MTase in a complex with the pan-methyltransferase inhibitor sinefungin solved at 2.2-Å resolution. The structure reveals an overall fold consistent with the fold observed in other coronaviral MTases. The major differences are in the conformation of the C terminus of the nsp16 subunit and an additional helix in the N terminus of the nsp10 subunits. The structural analysis also revealed very high conservation of the S-adenosyl methionine (SAM) binding pocket, suggesting that the SAM pocket is a suitable spot for the design of antivirals effective against all human coronaviruses. IMPORTANCE Some coronaviruses are dangerous pathogens, while some cause only common colds. The reasons are not understood, although the spike proteins probably play an important role. However, to understand the coronaviral biology in sufficient detail, we need to compare the key enzymes from different coronaviruses. We solved the crystal structure of 2'-O-RNA methyltransferase of the OC43 coronavirus, a virus that usually causes mild colds. The structure revealed some differences in the overall fold but also revealed that the SAM binding site is conserved, suggesting that development of antivirals against multiple coronaviruses is feasible.


Subject(s)
Betacoronavirus/enzymology , Methyltransferases/chemistry , Viral Proteins/chemistry , Betacoronavirus/genetics , Binding Sites , Crystallography, X-Ray , Methyltransferases/genetics , Protein Conformation, alpha-Helical , Viral Proteins/genetics
11.
Sci Rep ; 11(1): 19752, 2021 10 05.
Article in English | MEDLINE | ID: covidwho-1454813

ABSTRACT

Although metabolic syndrome (MetS) is linked to an elevated risk of cardiovascular disease (CVD), the cardiac-specific risk mechanism is unknown. Obesity, hypertension, and diabetes (all MetS components) are the most common form of CVD and represent risk factors for worse COVID-19 outcomes compared to their non MetS peers. Here, we use obese Yorkshire pigs as a highly relevant animal model of human MetS, where pigs develop the hallmarks of human MetS and reproducibly mimics the myocardial pathophysiology in patients. Myocardium-specific mass spectroscopy-derived metabolomics, proteomics, and transcriptomics enabled the identity and quality of proteins and metabolites to be investigated in the myocardium to greater depth. Myocardium-specific deregulation of pro-inflammatory markers, propensity for arterial thrombosis, and platelet aggregation was revealed by computational analysis of differentially enriched pathways between MetS and control animals. While key components of the complement pathway and the immune response to viruses are under expressed, key N6-methyladenosin RNA methylation enzymes are largely overexpressed in MetS. Blood tests do not capture the entirety of metabolic changes that the myocardium undergoes, making this analysis of greater value than blood component analysis alone. Our findings create data associations to further characterize the MetS myocardium and disease vulnerability, emphasize the need for a multimodal therapeutic approach, and suggests a mechanism for observed worse outcomes in MetS patients with COVID-19 comorbidity.


Subject(s)
COVID-19/pathology , Disease Susceptibility , Metabolic Syndrome/pathology , Animals , Blood Coagulation Factors/genetics , Blood Coagulation Factors/metabolism , COVID-19/complications , COVID-19/virology , Cyclooxygenase 2/genetics , Cyclooxygenase 2/metabolism , Diet, High-Fat/veterinary , Disease Models, Animal , Humans , Immunity, Innate/genetics , Metabolic Syndrome/complications , Metabolic Syndrome/metabolism , Methyltransferases/genetics , Methyltransferases/metabolism , Myocardium/metabolism , Oxidative Stress/genetics , Platelet Aggregation , Receptors, Purinergic P2Y1/genetics , Receptors, Purinergic P2Y1/metabolism , Renin-Angiotensin System , Risk Factors , SARS-CoV-2/isolation & purification , Swine , Urokinase-Type Plasminogen Activator/genetics , Urokinase-Type Plasminogen Activator/metabolism
12.
Microbiol Spectr ; 9(2): e0131221, 2021 10 31.
Article in English | MEDLINE | ID: covidwho-1443363

ABSTRACT

The large (L) polymerase proteins of most nonsegmented, negative-stranded (NNS) RNA viruses have conserved methyltransferase motifs, (G)-G-G-D and K-D-K-E, which are important for the stabilization and translation of mRNA. However, the function of the (G)-G-G-D and K-D-K-E motifs in the NNS RNA virus Newcastle disease virus (NDV) remains unclear. We observed G-G-D and K-D-K-E motifs in all NDV genotypes. By using the infection cloning system of NDV rSG10 strain, recombinant NDVs with a single amino acid mutated to alanine in one motif (G-G-D or K-D-K-E) were rescued. The intracerebral pathogenicity index and mean death time assay results revealed that the G-G-D motif and K-D-K-E motif attenuate the virulence of NDV to various degrees. The replication, transcription, and translation levels of the K-D-K-E motif-mutant strains were significantly higher than those of wild-type virus owing to their altered regulation of the affinity between nucleocapsid protein and eukaryotic translation initiation factor 4E. When the infection dose was changed from a multiplicity of infection (MOI) of 10 to an MOI of 0.01, the cell-to-cell spread abilities of G-G-D- and K-D-K-E-mutant strains were reduced, according to plaque assay and dynamic indirect immunofluorescence assay results. Finally, we found that NDV strains with G-G-D or K-D-K-E motif mutations had less pathogenicity in 3-week-old specific-pathogen-free chickens than wild-type NDV. Therefore, these methyltransferase motifs can affect virulence by regulating the translation and cell-to-cell spread abilities of NDV. This work provides a feasible approach for generating vaccine candidates for viruses with methyltransferase motifs. IMPORTANCE Newcastle disease virus (NDV) is an important pathogen that is widespread globally. Research on its pathogenic mechanism is an important means of improving prevention and control efforts. Our study found that a deficiency in its methyltransferase motifs (G-G-D and K-D-K-E motifs) can attenuate NDV and revealed the molecular mechanism by which these motifs affect pathogenicity, which provides a new direction for the development of NDV vaccines. In addition to the (G)-G-G-D and K-D-K-E motifs of many nonsegmented, negative-stranded RNA viruses, similar motifs have been found in dengue virus, Zika virus, Japanese encephalitis virus (JEV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This suggests that such motifs may be present in more viruses. Our finding also provides a molecular basis for the discovery and functional study of (G)-G-G-D and K-D-K-E motifs of other viruses.


Subject(s)
Amino Acid Motifs/genetics , Methyltransferases/genetics , Newcastle Disease/transmission , Newcastle disease virus/growth & development , Newcastle disease virus/genetics , Viral Proteins/genetics , Animals , Cell Line , Chickens , Chlorocebus aethiops , Cricetinae , Genome, Viral/genetics , Newcastle disease virus/pathogenicity , Poultry Diseases/transmission , Poultry Diseases/virology , RNA, Viral/biosynthesis , RNA, Viral/genetics , Vero Cells , Virulence/genetics , Virus Replication/genetics
13.
J Virol ; 95(20): e0059221, 2021 09 27.
Article in English | MEDLINE | ID: covidwho-1440799

ABSTRACT

The current pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to dramatic economic and health burdens. Although the worldwide SARS-CoV-2 vaccination campaign has begun, exploration of other vaccine candidates is needed due to uncertainties with the current approved vaccines, such as durability of protection, cross-protection against variant strains, and costs of long-term production and storage. In this study, we developed a methyltransferase-defective recombinant vesicular stomatitis virus (mtdVSV)-based SARS-CoV-2 vaccine candidate. We generated mtdVSVs expressing SARS-CoV-2 full-length spike (S) protein, S1, or its receptor-binding domain (RBD). All of these recombinant viruses grew to high titers in mammalian cells despite high attenuation in cell culture. The SARS-CoV-2 S protein and its truncations were highly expressed by the mtdVSV vector. These mtdVSV-based vaccine candidates were completely attenuated in both immunocompetent and immunocompromised mice. Among these constructs, mtdVSV-S induced high levels of SARS-CoV-2-specific neutralizing antibodies (NAbs) and Th1-biased T-cell immune responses in mice. In Syrian golden hamsters, the serum levels of SARS-CoV-2-specific NAbs triggered by mtdVSV-S were higher than the levels of NAbs in convalescent plasma from recovered COVID-19 patients. In addition, hamsters immunized with mtdVSV-S were completely protected against SARS-CoV-2 replication in lung and nasal turbinate tissues, cytokine storm, and lung pathology. Collectively, our data demonstrate that mtdVSV expressing SARS-CoV-2 S protein is a safe and highly efficacious vaccine candidate against SARS-CoV-2 infection. IMPORTANCE Viral mRNA cap methyltransferase (MTase) is essential for mRNA stability, protein translation, and innate immune evasion. Thus, viral mRNA cap MTase activity is an excellent target for development of live attenuated or live vectored vaccine candidates. Here, we developed a panel of MTase-defective recombinant vesicular stomatitis virus (mtdVSV)-based SARS-CoV-2 vaccine candidates expressing full-length S, S1, or several versions of the RBD. These mtdVSV-based vaccine candidates grew to high titers in cell culture and were completely attenuated in both immunocompetent and immunocompromised mice. Among these vaccine candidates, mtdVSV-S induces high levels of SARS-CoV-2-specific neutralizing antibodies (Nabs) and Th1-biased immune responses in mice. Syrian golden hamsters immunized with mtdVSV-S triggered SARS-CoV-2-specific NAbs at higher levels than those in convalescent plasma from recovered COVID-19 patients. Furthermore, hamsters immunized with mtdVSV-S were completely protected against SARS-CoV-2 challenge. Thus, mtdVSV is a safe and highly effective vector to deliver SARS-CoV-2 vaccine.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , SARS-CoV-2/immunology , Vesicular stomatitis Indiana virus/genetics , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Brain/virology , COVID-19/immunology , Cell Line , Cytokine Release Syndrome/prevention & control , DNA-Directed RNA Polymerases/genetics , DNA-Directed RNA Polymerases/metabolism , Humans , Immunogenicity, Vaccine , Lung/immunology , Lung/pathology , Lung/virology , Mesocricetus , Methyltransferases/genetics , Methyltransferases/metabolism , Mice , Protein Domains , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology , Th1 Cells/immunology , Vaccines, Synthetic/immunology , Vesicular stomatitis Indiana virus/enzymology , Vesicular stomatitis Indiana virus/physiology , Viral Proteins/genetics , Viral Proteins/metabolism , Virus Replication
14.
Sci Signal ; 14(689)2021 06 29.
Article in English | MEDLINE | ID: covidwho-1406596

ABSTRACT

Capping of viral messenger RNAs is essential for efficient translation, for virus replication, and for preventing detection by the host cell innate response system. The SARS-CoV-2 genome encodes the 2'-O-methyltransferase nsp16, which, when bound to the coactivator nsp10, uses S-adenosylmethionine (SAM) as a donor to transfer a methyl group to the first ribonucleotide of the mRNA in the final step of viral mRNA capping. Here, we provide biochemical and structural evidence that this reaction requires divalent cations, preferably Mn2+, and a coronavirus-specific four-residue insert. We determined the x-ray structures of the SARS-CoV-2 2'-O-methyltransferase (the nsp16-nsp10 heterodimer) in complex with its reaction substrates, products, and divalent metal cations. These structural snapshots revealed that metal ions and the insert stabilize interactions between the capped RNA and nsp16, resulting in the precise alignment of the ribonucleotides in the active site. Comparison of available structures of 2'-O-methyltransferases with capped RNAs from different organisms revealed that the four-residue insert unique to coronavirus nsp16 alters the backbone conformation of the capped RNA in the binding groove, thereby promoting catalysis. This insert is highly conserved across coronaviruses, and its absence in mammalian methyltransferases makes this region a promising site for structure-guided drug design of selective coronavirus inhibitors.


Subject(s)
COVID-19/virology , RNA Caps/metabolism , RNA, Viral/metabolism , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/metabolism , Amino Acid Sequence , Catalytic Domain , Crystallography, X-Ray , Humans , Manganese/metabolism , Methylation , Methyltransferases/chemistry , Methyltransferases/genetics , Methyltransferases/metabolism , Models, Molecular , Nucleic Acid Conformation , RNA Caps/chemistry , RNA Caps/genetics , RNA Stability , RNA, Messenger/chemistry , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Viral/chemistry , RNA, Viral/genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , S-Adenosylmethionine/chemistry , S-Adenosylmethionine/metabolism , SARS-CoV-2/genetics , Signal Transduction , Substrate Specificity , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/genetics
15.
Viruses ; 13(9)2021 08 30.
Article in English | MEDLINE | ID: covidwho-1390783

ABSTRACT

The ongoing COVID-19 pandemic exemplifies the general need to better understand viral infections. The positive single-strand RNA genome of its causative agent, the SARS coronavirus 2 (SARS-CoV-2), encodes all viral enzymes. In this work, we focused on one particular methyltransferase (MTase), nsp16, which, in complex with nsp10, is capable of methylating the first nucleotide of a capped RNA strand at the 2'-O position. This process is part of a viral capping system and is crucial for viral evasion of the innate immune reaction. In light of recently discovered non-canonical RNA caps, we tested various dinucleoside polyphosphate-capped RNAs as substrates for nsp10-nsp16 MTase. We developed an LC-MS-based method and discovered four types of capped RNA (m7Gp3A(G)- and Gp3A(G)-RNA) that are substrates of the nsp10-nsp16 MTase. Our technique is an alternative to the classical isotope labelling approach for the measurement of 2'-O-MTase activity. Further, we determined the IC50 value of sinefungin to illustrate the use of our approach for inhibitor screening. In the future, this approach may be an alternative technique to the radioactive labelling method for screening inhibitors of any type of 2'-O-MTase.


Subject(s)
COVID-19/virology , Methyltransferases/metabolism , SARS-CoV-2/enzymology , Viral Nonstructural Proteins/metabolism , Viral Regulatory and Accessory Proteins/metabolism , Chromatography, Liquid , Gene Expression Regulation, Viral , Humans , Mass Spectrometry , Methylation , Methyltransferases/genetics , RNA Caps , RNA, Viral/genetics , SARS-CoV-2/genetics , Substrate Specificity , Viral Nonstructural Proteins/genetics , Viral Regulatory and Accessory Proteins/genetics
16.
Cell ; 184(1): 184-193.e10, 2021 01 07.
Article in English | MEDLINE | ID: covidwho-1385213

ABSTRACT

Transcription of SARS-CoV-2 mRNA requires sequential reactions facilitated by the replication and transcription complex (RTC). Here, we present a structural snapshot of SARS-CoV-2 RTC as it transitions toward cap structure synthesis. We determine the atomic cryo-EM structure of an extended RTC assembled by nsp7-nsp82-nsp12-nsp132-RNA and a single RNA-binding protein, nsp9. Nsp9 binds tightly to nsp12 (RdRp) NiRAN, allowing nsp9 N terminus inserting into the catalytic center of nsp12 NiRAN, which then inhibits activity. We also show that nsp12 NiRAN possesses guanylyltransferase activity, catalyzing the formation of cap core structure (GpppA). The orientation of nsp13 that anchors the 5' extension of template RNA shows a remarkable conformational shift, resulting in zinc finger 3 of its ZBD inserting into a minor groove of paired template-primer RNA. These results reason an intermediate state of RTC toward mRNA synthesis, pave a way to understand the RTC architecture, and provide a target for antiviral development.


Subject(s)
Coronavirus RNA-Dependent RNA Polymerase/chemistry , Cryoelectron Microscopy , RNA, Messenger/chemistry , RNA, Viral/chemistry , SARS-CoV-2/chemistry , Viral Replicase Complex Proteins/chemistry , Amino Acid Sequence , Coronavirus/chemistry , Coronavirus/classification , Coronavirus/enzymology , Coronavirus RNA-Dependent RNA Polymerase/metabolism , Methyltransferases/metabolism , Models, Molecular , RNA Helicases/metabolism , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/metabolism , SARS-CoV-2/enzymology , Sequence Alignment , Transcription, Genetic , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Virus Replication
17.
Angew Chem Int Ed Engl ; 60(24): 13280-13286, 2021 06 07.
Article in English | MEDLINE | ID: covidwho-1384109

ABSTRACT

Eukaryotic mRNAs are emerging modalities for protein replacement therapy and vaccination. Their 5' cap is important for mRNA translation and immune response and can be naturally methylated at different positions by S-adenosyl-l-methionine (AdoMet)-dependent methyltransferases (MTases). We report on the cosubstrate scope of the MTase CAPAM responsible for methylation at the N6 -position of adenosine start nucleotides using synthetic AdoMet analogs. The chemo-enzymatic propargylation enabled production of site-specifically modified reporter-mRNAs. These cap-propargylated mRNAs were efficiently translated and showed ≈3-fold increased immune response in human cells. The same effects were observed when the receptor binding domain (RBD) of SARS-CoV-2-a currently tested epitope for mRNA vaccination-was used. Site-specific chemo-enzymatic modification of eukaryotic mRNA may thus be a suitable strategy to modulate translation and immune response of mRNAs for future therapeutic applications.


Subject(s)
RNA Caps/immunology , RNA, Messenger/immunology , COVID-19/pathology , COVID-19/virology , Chromatography, High Pressure Liquid , Genes, Reporter , HEK293 Cells , Humans , Mass Spectrometry , Methylation , Methyltransferases/metabolism , Protein Biosynthesis , Protein Domains/genetics , Protein Domains/immunology , RNA Caps/analysis , RNA Caps/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , S-Adenosylmethionine/chemistry , S-Adenosylmethionine/immunology , S-Adenosylmethionine/metabolism , SARS-CoV-2/genetics , SARS-CoV-2/isolation & purification , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology
18.
Nucleic Acids Res ; 49(9): 5382-5392, 2021 05 21.
Article in English | MEDLINE | ID: covidwho-1387965

ABSTRACT

The emergence of SARS-CoV-2 infection has posed unprecedented threat to global public health. The virus-encoded non-structural protein 14 (nsp14) is a bi-functional enzyme consisting of an exoribonuclease (ExoN) domain and a methyltransferase (MTase) domain and plays a pivotal role in viral replication. Here, we report the structure of SARS-CoV-2 nsp14-ExoN domain bound to its co-factor nsp10 and show that, compared to the SARS-CoV nsp10/nsp14-full-length complex, SARS-CoV-2 nsp14-ExoN retains an integral exoribonuclease fold and preserves an active configuration in the catalytic center. Analysis of the nsp10/nsp14-ExoN interface reveals a footprint in nsp10 extensively overlapping with that observed in the nsp10/nsp16 structure. A marked difference in the co-factor when engaging nsp14 and nsp16 lies in helix-α1', which is further experimentally ascertained to be involved in nsp14-binding but not in nsp16-engagement. Finally, we also show that nsp10/nsp14-ExoN is enzymatically active despite the absence of nsp14-MTase domain. These data demonstrate that SARS-CoV-2 nsp10/nsp14-ExoN functions as an exoribonuclease with both structural and functional integrity.


Subject(s)
Biocatalysis , Exoribonucleases/chemistry , Exoribonucleases/metabolism , SARS-CoV-2/chemistry , SARS-CoV-2/enzymology , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/metabolism , Viral Regulatory and Accessory Proteins/chemistry , Viral Regulatory and Accessory Proteins/metabolism , Binding Sites , Crystallography, X-Ray , Exoribonucleases/genetics , Guanine , Methyltransferases/chemistry , Methyltransferases/deficiency , Methyltransferases/genetics , Methyltransferases/metabolism , Models, Molecular , Protein Domains/genetics , SARS-CoV-2/genetics , Viral Nonstructural Proteins/genetics , Viral Regulatory and Accessory Proteins/genetics
19.
Nat Commun ; 11(1): 5874, 2020 11 18.
Article in English | MEDLINE | ID: covidwho-1387320

ABSTRACT

Non-structural proteins (nsp) constitute the SARS-CoV-2 replication and transcription complex (RTC) to play a pivotal role in the virus life cycle. Here we determine the atomic structure of a SARS-CoV-2 mini RTC, assembled by viral RNA-dependent RNA polymerase (RdRp, nsp12) with a template-primer RNA, nsp7 and nsp8, and two helicase molecules (nsp13-1 and nsp13-2), by cryo-electron microscopy. Two groups of mini RTCs with different conformations of nsp13-1 are identified. In both of them, nsp13-1 stabilizes overall architecture of the mini RTC by contacting with nsp13-2, which anchors the 5'-extension of RNA template, as well as interacting with nsp7-nsp8-nsp12-RNA. Orientation shifts of nsp13-1 results in its variable interactions with other components in two forms of mini RTC. The mutations on nsp13-1:nsp12 and nsp13-1:nsp13-2 interfaces prohibit the enhancement of helicase activity achieved by mini RTCs. These results provide an insight into how helicase couples with polymerase to facilitate its function in virus replication and transcription.


Subject(s)
Betacoronavirus/chemistry , Betacoronavirus/physiology , Virus Replication , Betacoronavirus/genetics , Betacoronavirus/metabolism , Binding Sites , Cryoelectron Microscopy , Humans , Methyltransferases/chemistry , Methyltransferases/genetics , Methyltransferases/metabolism , Models, Molecular , Mutation , Protein Binding , Protein Conformation , RNA Helicases/chemistry , RNA Helicases/genetics , RNA Helicases/metabolism , RNA, Viral/metabolism , SARS-CoV-2 , Structure-Activity Relationship , Transcription, Genetic , Viral Nonstructural Proteins/chemistry , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolism
20.
Nat Commun ; 12(1): 4848, 2021 08 11.
Article in English | MEDLINE | ID: covidwho-1354102

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.


Subject(s)
Methyltransferases/chemistry , RNA Helicases/chemistry , SARS-CoV-2/chemistry , Viral Nonstructural Proteins/chemistry , Adenosine Triphosphate/chemistry , Adenosine Triphosphate/metabolism , Amino Acid Sequence , Apoenzymes/chemistry , Apoenzymes/metabolism , Binding Sites , Crystallography, X-Ray , Drug Design , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/metabolism , Methyltransferases/antagonists & inhibitors , Methyltransferases/metabolism , Models, Molecular , Phosphates/chemistry , Phosphates/metabolism , Protein Conformation , RNA Helicases/antagonists & inhibitors , RNA Helicases/metabolism , RNA, Viral/chemistry , RNA, Viral/metabolism , SARS-CoV-2/enzymology , Structure-Activity Relationship , Viral Nonstructural Proteins/antagonists & inhibitors , Viral Nonstructural Proteins/metabolism
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