22 results on '"Mickaël, Bouvet"'
Search Results
2. First Days in the Life of Naive Human B Lymphocytes Infected with Epstein-Barr Virus
- Author
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Dagmar Pich, Paulina Mrozek-Gorska, Mickaël Bouvet, Atsuko Sugimoto, Ezgi Akidil, Adam Grundhoff, Stephan Hamperl, Paul D. Ling, and Wolfgang Hammerschmidt
- Subjects
B lymphocytes ,human herpesviruses ,reprogramming ,transformation ,Microbiology ,QR1-502 - Abstract
ABSTRACT Epstein-Barr virus (EBV) infects and activates resting human B lymphocytes, reprograms them, induces their proliferation, and establishes a latent infection in them. In established EBV-infected cell lines, many viral latent genes are expressed. Their roles in supporting the continuous proliferation of EBV-infected B cells in vitro are known, but their functions in the early, prelatent phase of infection have not been investigated systematically. In studies during the first 8 days of infection using derivatives of EBV with mutations in single genes of EBVs, we found only Epstein-Barr nuclear antigen 2 (EBNA2) to be essential for activating naive human B lymphocytes, inducing their growth in cell volume, driving them into rapid cell divisions, and preventing cell death in a subset of infected cells. EBNA-LP, latent membrane protein 2A (LMP2A), and the viral microRNAs have supportive, auxiliary functions, but mutants of LMP1, EBNA3A, EBNA3C, and the noncoding Epstein-Barr virus with small RNA (EBERs) had no discernible phenotype compared with wild-type EBV. B cells infected with a double mutant of EBNA3A and 3C had an unexpected proliferative advantage and did not regulate the DNA damage response (DDR) of the infected host cell in the prelatent phase. Even EBNA1, which has very critical long-term functions in maintaining and replicating the viral genomic DNA in established cell lines, was dispensable for the early activation of infected cells. Our findings document that the virus dose is a decisive parameter and indicate that EBNA2 governs the infected cells initially and implements a strictly controlled temporal program independent of other viral latent genes. It thus appears that EBNA2 is sufficient to control all requirements for clonal cellular expansion and to reprogram human B lymphocytes from energetically quiescent to activated cells. IMPORTANCE The preferred target of Epstein-Barr virus (EBV) is human resting B lymphocytes. We found that their infection induces a well-coordinated, time-driven program that starts with a substantial increase in cell volume, followed by cellular DNA synthesis after 3 days and subsequent rapid rounds of cell divisions on the next day accompanied by some DNA replication stress (DRS). Two to 3 days later, the cells decelerate and turn into stably proliferating lymphoblast cell lines. With the aid of 16 different recombinant EBV strains, we investigated the individual contributions of EBV’s multiple latent genes during early B-cell infection and found that many do not exert a detectable phenotype or contribute little to EBV’s prelatent phase. The exception is EBNA2 that is essential in governing all aspects of B-cell reprogramming. EBV relies on EBNA2 to turn the infected B lymphocytes into proliferating lymphoblasts preparing the infected host cell for the ensuing stable, latent phase of viral infection. In the early steps of B-cell reprogramming, viral latent genes other than EBNA2 are dispensable, but some, EBNA-LP, for example, support the viral program and presumably stabilize the infected cells once viral latency is established.
- Published
- 2019
- Full Text
- View/download PDF
3. Multiple viral micrornas regulate interferon release and signaling early during infection with epstein-barr virus
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Yan Chen, Yen-Fu Adam Chen, Rebecca L. Skalsky, Mickaël Bouvet, Christine Göbel, Dagmar Pich, Takanobu Tagawa, Wolfgang Hammerschmidt, Manuel Albanese, Stefanie Voigt, and Devin N. Fachko
- Subjects
Epstein-Barr Virus Infections ,Herpesvirus 4, Human ,medicine.disease_cause ,0302 clinical medicine ,Interferon ,hemic and lymphatic diseases ,0303 health sciences ,B-Lymphocytes ,microRNA ,interferon ,B Cells ,Epstein-barr Virus ,Immune Evasion ,Interferons ,Microrna ,Plasmacytoid Dendritic Cells ,QR1-502 ,interferons ,plasmacytoid dendritic cells ,Host-Pathogen Interactions ,RNA, Viral ,Signal Transduction ,medicine.drug ,Research Article ,Gene Expression Regulation, Viral ,Biology ,Antiviral Agents ,Microbiology ,Virus ,03 medical and health sciences ,Immune system ,EBV ,Virology ,medicine ,Humans ,Epstein-Barr virus ,Secretion ,Transcription factor ,Gene ,030304 developmental biology ,miRNA ,immune evasion ,B cells ,Interferon-alpha ,pDCs ,TLR9 ,Interferon-beta ,ncRNA ,Epstein–Barr virus ,MicroRNAs ,Toll-Like Receptor 7 ,Commentary ,030215 immunology - Abstract
Acute antiviral functions of all nucleated cells rely on type I interferon (IFN-I) pathways triggered upon viral infection. Host responses encompass the sensing of incoming viruses, the activation of specific transcription factors that induce the transcription of IFN-I genes, the secretion of different IFN-I types and their recognition by the heterodimeric IFN-α/β receptor, the subsequent activation of JAK/STAT signaling pathways, and, finally, the transcription of many IFN-stimulated genes (ISGs)., Epstein-Barr virus (EBV), a human herpesvirus, encodes 44 microRNAs (miRNAs), which regulate many genes with various functions in EBV-infected cells. Multiple target genes of the EBV miRNAs have been identified, some of which play important roles in adaptive antiviral immune responses. Using EBV mutant derivatives, we identified additional roles of viral miRNAs in governing versatile type I interferon (IFN) responses upon infection of human primary mature B cells. We also found that Epstein-Barr virus-encoded small RNAs (EBERs) and LF2, viral genes with previously reported functions in inducing or regulating IFN-I pathways, had negligible or even contrary effects on secreted IFN-α in our model. Data mining and Ago PAR-CLIP experiments uncovered more than a dozen previously uncharacterized, direct cellular targets of EBV miRNA associated with type I IFN pathways. We also identified indirect targets of EBV miRNAs in B cells, such as TRL7 and TLR9, in the prelatent phase of infection. The presence of epigenetically naive, non-CpG methylated viral DNA was essential to induce IFN-α secretion during EBV infection in a TLR9-dependent manner. In a newly established fusion assay, we verified that EBV virions enter a subset of plasmacytoid dendritic cells (pDCs) and determined that these infected pDCs are the primary producers of IFN-α in EBV-infected peripheral blood mononuclear cells. Our findings document that many EBV-encoded miRNAs regulate type I IFN response in newly EBV infected primary human B cells in the prelatent phase of infection and dampen the acute release of IFN-α in pDCs upon their encounter with EBV.
- Published
- 2021
4. Les enzymes de la réplication/transcription chez les coronavirus
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Lorenzo, Subissi, Étienne, Decroly, Mickaël, Bouvet, Laure, Gluais, Bruno, Canard, and Isabelle, Imbert
- Abstract
The discovery of a new coronavirus (CoV) as the causative agent of the severe acute respiratory syndrome (SARS) pandemic outbreak in 2003 has stimulated a number of studies on the molecular biology of SARS-CoV and related viruses. This research has provided significant new insight into functions and activities of the CoV replication-transcription complex, a multi-protein complex that directs coordinated processes of both continuous and discontinuous RNA synthesis to replicate and transcribe the large CoV genome, a single-stranded, positive-sense RNA of ∼30 kilobases. In this review, we summarize current understanding of the expression and functions of key replicative enzymes, such as RNA polymerases, ribonucleases, methyltransferases and other replicase gene encoded proteins involved in genome expression, virus-host interactions and other processes. Collectively, these recent studies reveal fascinating details of a huge enzymatic machinery unique in the RNA virus world.
- Published
- 2020
5. Structures and exoribonuclease activity fonctions in arenavirus and coronavirus
- Author
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Mickaël, Bouvet, Isabelle, Imbert, François, Ferron, Bruno, Canard, and Etienne, Decroly
- Abstract
RNA viruses encode dedicated protein machinery required through the viral life cycle. Some enzymatic activities are generally associated with RNA viruses such as RNA- or DNA-dependent RNA polymerases, RNA helicases or proteases. Some viral enzyme activities are however unique to some viral families. This is the case of two 3'-5' exoribonuclease activities identified in arenavirus and coronavirus proteomes. Arenaviruses have a segmented ambisense single stranded RNA genome of negative polarity while coronaviruses have a positive single-stranded genomic RNA. Although both enzymes belong to the same exo(ribo)nuclease superfamily, available data indicate that they are involved in very different pathways. Indeed, the exoribonuclease activity carried by the arenavirus nucleoprotein seems to counteract the innate immunity antiviral response while the exoribonuclease activity carried by the coronavirus nsp14 protein is likely involved in a unique RNA repair mechanism. In this review, we present our current knowledge about these two viral enzymes and their functions in the viral life cycle.
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- 2020
6. Correction: Reconstitution of SARS-Coronavirus mRNA Cap Methylation.
- Author
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Mickaël Bouvet, Claire Debarnot, Isabelle Imbert, Barbara Selisko, Eric J. Snijder, Bruno Canard, and Etienne Decroly
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Immunologic diseases. Allergy ,RC581-607 ,Biology (General) ,QH301-705.5 - Published
- 2010
- Full Text
- View/download PDF
7. In vitro reconstitution of SARS-coronavirus mRNA cap methylation.
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Mickaël Bouvet, Claire Debarnot, Isabelle Imbert, Barbara Selisko, Eric J Snijder, Bruno Canard, and Etienne Decroly
- Subjects
Immunologic diseases. Allergy ,RC581-607 ,Biology (General) ,QH301-705.5 - Abstract
SARS-coronavirus (SARS-CoV) genome expression depends on the synthesis of a set of mRNAs, which presumably are capped at their 5' end and direct the synthesis of all viral proteins in the infected cell. Sixteen viral non-structural proteins (nsp1 to nsp16) constitute an unusually large replicase complex, which includes two methyltransferases putatively involved in viral mRNA cap formation. The S-adenosyl-L-methionine (AdoMet)-dependent (guanine-N7)-methyltransferase (N7-MTase) activity was recently attributed to nsp14, whereas nsp16 has been predicted to be the AdoMet-dependent (nucleoside-2'O)-methyltransferase. Here, we have reconstituted complete SARS-CoV mRNA cap methylation in vitro. We show that mRNA cap methylation requires a third viral protein, nsp10, which acts as an essential trigger to complete RNA cap-1 formation. The obligate sequence of methylation events is initiated by nsp14, which first methylates capped RNA transcripts to generate cap-0 (7Me)GpppA-RNAs. The latter are then selectively 2'O-methylated by the 2'O-MTase nsp16 in complex with its activator nsp10 to give rise to cap-1 (7Me)GpppA(2'OMe)-RNAs. Furthermore, sensitive in vitro inhibition assays of both activities show that aurintricarboxylic acid, active in SARS-CoV infected cells, targets both MTases with IC(50) values in the micromolar range, providing a validated basis for anti-coronavirus drug design.
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- 2010
- Full Text
- View/download PDF
8. First Days in the Life of Naive Human B Lymphocytes Infected with Epstein-Barr Virus
- Author
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Mickaël Bouvet, Dagmar Pich, Atsuko Sugimoto, Paul D. Ling, Paulina Mrozek-Gorska, Wolfgang Hammerschmidt, Ezgi Akidil, Stephan Hamperl, and Adam Grundhoff
- Subjects
Gene Expression Regulation, Viral ,Herpesvirus 4, Human ,viruses ,Cell ,Biology ,medicine.disease_cause ,Microbiology ,Virus ,Host-Microbe Biology ,03 medical and health sciences ,human herpesviruses ,Viral Proteins ,Antigen ,Virology ,hemic and lymphatic diseases ,medicine ,Humans ,Gene ,Cells, Cultured ,030304 developmental biology ,Cell Proliferation ,0303 health sciences ,B-Lymphocytes ,030306 microbiology ,Lymphoblast ,transformation ,reprogramming ,Cell Transformation, Viral ,Epstein–Barr virus ,QR1-502 ,3. Good health ,Virus Latency ,MicroRNAs ,medicine.anatomical_structure ,Epstein-Barr Virus Nuclear Antigens ,Cell culture ,Reprogramming ,Research Article ,B lymphocytes - Abstract
The preferred target of Epstein-Barr virus (EBV) is human resting B lymphocytes. We found that their infection induces a well-coordinated, time-driven program that starts with a substantial increase in cell volume, followed by cellular DNA synthesis after 3 days and subsequent rapid rounds of cell divisions on the next day accompanied by some DNA replication stress (DRS). Two to 3 days later, the cells decelerate and turn into stably proliferating lymphoblast cell lines. With the aid of 16 different recombinant EBV strains, we investigated the individual contributions of EBV’s multiple latent genes during early B-cell infection and found that many do not exert a detectable phenotype or contribute little to EBV’s prelatent phase. The exception is EBNA2 that is essential in governing all aspects of B-cell reprogramming. EBV relies on EBNA2 to turn the infected B lymphocytes into proliferating lymphoblasts preparing the infected host cell for the ensuing stable, latent phase of viral infection. In the early steps of B-cell reprogramming, viral latent genes other than EBNA2 are dispensable, but some, EBNA-LP, for example, support the viral program and presumably stabilize the infected cells once viral latency is established., Epstein-Barr virus (EBV) infects and activates resting human B lymphocytes, reprograms them, induces their proliferation, and establishes a latent infection in them. In established EBV-infected cell lines, many viral latent genes are expressed. Their roles in supporting the continuous proliferation of EBV-infected B cells in vitro are known, but their functions in the early, prelatent phase of infection have not been investigated systematically. In studies during the first 8 days of infection using derivatives of EBV with mutations in single genes of EBVs, we found only Epstein-Barr nuclear antigen 2 (EBNA2) to be essential for activating naive human B lymphocytes, inducing their growth in cell volume, driving them into rapid cell divisions, and preventing cell death in a subset of infected cells. EBNA-LP, latent membrane protein 2A (LMP2A), and the viral microRNAs have supportive, auxiliary functions, but mutants of LMP1, EBNA3A, EBNA3C, and the noncoding Epstein-Barr virus with small RNA (EBERs) had no discernible phenotype compared with wild-type EBV. B cells infected with a double mutant of EBNA3A and 3C had an unexpected proliferative advantage and did not regulate the DNA damage response (DDR) of the infected host cell in the prelatent phase. Even EBNA1, which has very critical long-term functions in maintaining and replicating the viral genomic DNA in established cell lines, was dispensable for the early activation of infected cells. Our findings document that the virus dose is a decisive parameter and indicate that EBNA2 governs the infected cells initially and implements a strictly controlled temporal program independent of other viral latent genes. It thus appears that EBNA2 is sufficient to control all requirements for clonal cellular expansion and to reprogram human B lymphocytes from energetically quiescent to activated cells.
- Published
- 2019
9. The first days in the life of naïve human B-lymphocytes infected with Epstein-Barr virus
- Author
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Atsuko Sugimoto, Dagmar Pich, Adam Grundhoff, Ezgi Akidil, Stephan Hamperl, Paulina Mrozek-Gorska, Paul D. Ling, Mickaël Bouvet, and Wolfgang Hammerschmidt
- Subjects
Programmed cell death ,viruses ,Lymphoblast ,Cell ,Biology ,medicine.disease_cause ,Virology ,Epstein–Barr virus ,Virus ,medicine.anatomical_structure ,Cell culture ,hemic and lymphatic diseases ,medicine ,Gene ,Reprogramming - Abstract
Epstein-Barr virus (EBV) infects and activates resting human B-lymphocytes, reprograms them, induces their proliferation, and establishes a latent infection in them. In established EBV-infected cell lines many viral latent genes are expressed. Their roles in supporting the continuous proliferation of EBV-infected B cellsin vitroare known, but their functions in the early, pre-latent phase of infection have not been investigated systematically. In studies during the first eight days of infection using derivatives of EBV with mutations in single genes of EBVs we found only EBNA2 to be essential for activating naïve human B-lymphocytes, inducing their growth in cell volume, driving them into rapid cell divisions, and preventing cell death in a subset of infected cells. EBNA-LP, LMP2A and the viral microRNAs have supportive, auxiliary functions, but mutants of LMP1, EBNA3A, EBNA3C, and the noncoding EBER RNAs had no discernable phenotype compared with wild-type EBV. B cells infected with a double mutant of EBNA3A and 3C had an unexpected proliferative advantage and did not regulate the DNA damage response (DDR) of the infected host cell in the pre-latent phase. Even EBNA1 which has very critical long-term functions in maintaining and replicating the viral genomic DNA in established cell lines, was dispensable for the early activation of infected cells. Our findings document that the virus dose is a critical parameter and indicate that EBNA2 governs the infected cells initially and implements a strictly controlled temporal program independent of other viral latent genes. It thus appears that EBNA2 is sufficient to control all requirements for clonal cellular expansion and to reprogram human B-lymphocytes from energetically quiescent to activated cells.Author summaryThe preferred target of Epstein-Barr virus (EBV) are human resting B-lymphocytes. We found that their infection induces a well-coordinated, time-driven program that starts with a substantial increase in cell volume followed by cellular DNA synthesis after three days and subsequent rapid rounds of cell divisions on the next day accompanied by some DNA replication stress (DRS). Two to three days later the cells decelerate and turn into stably proliferating lymphoblast cell lines. With the aid of 16 different recombinant EBV strains we investigated the individual contributions of EBV’s multiple latent genes during early B-cell infection and found that many do not exert a detectable phenotype or contribute little to EBV’s pre-latent phase. The exception is EBNA2 that is essential in governing all aspects of B-cell reprogramming. EBV relies on EBNA2 to turn the infected B-lymphocytes into proliferating lymphoblasts preparing the infected host cell for the ensuing stable, latent phase of viral infection. In the early steps of B-cell reprogramming viral latent genes other than EBNA2 are dispensable but some, EBNA-LP for example, support the viral program and presumably stabilize the infected cells once viral latency is established.
- Published
- 2019
10. Epstein-Barr viral miRNAs inhibit antiviral CD4+ T cell responses targeting IL-12 and peptide processing
- Author
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Maximilian Hastreiter, Wolfgang Hammerschmidt, Jonathan Hoser, Bill Sugden, Mickaël Bouvet, Dominik Lutter, Vigo Heissmeyer, Manuel Albanese, Josef Mautner, Mitch Hayes, Andreas Moosmann, Christina E. Zielinski, and Takanobu Tagawa
- Subjects
CD4-Positive T-Lymphocytes ,0301 basic medicine ,Herpesvirus 4, Human ,Immunology ,Receptors, Cell Surface ,Biology ,Article ,Virus ,Proinflammatory cytokine ,03 medical and health sciences ,0302 clinical medicine ,Immune system ,Species Specificity ,hemic and lymphatic diseases ,Tumor Virus ,Humans ,Immunology and Allergy ,Cytotoxic T cell ,Research Articles ,Antigen Presentation ,B-Lymphocytes ,Cell Death ,Effector ,Immunogenicity ,Cell Membrane ,Immunity ,Cell Differentiation ,Th1 Cells ,Interleukin-12 ,Virology ,3. Good health ,MicroRNAs ,HEK293 Cells ,030104 developmental biology ,030220 oncology & carcinogenesis ,Interleukin 12 ,Cytokines ,Inflammation Mediators ,Lysosomes ,Peptides - Abstract
EBV reduces the activation of cytotoxic CD4+ effector T cells by inducing a state of reduced immunogenicity in infected B cells. EBV-derived miRNAs suppress release of proinflammatory cytokines, interfere with peptide processing and presentation on HLA class II, repress differentiation of naive CD4+ T cells to Th1 cells, and ultimately avoid killing of infected B cells., Epstein-Barr virus (EBV) is a tumor virus that establishes lifelong infection in most of humanity, despite eliciting strong and stable virus-specific immune responses. EBV encodes at least 44 miRNAs, most of them with unknown function. Here, we show that multiple EBV miRNAs modulate immune recognition of recently infected primary B cells, EBV's natural target cells. EBV miRNAs collectively and specifically suppress release of proinflammatory cytokines such as IL-12, repress differentiation of naive CD4+ T cells to Th1 cells, interfere with peptide processing and presentation on HLA class II, and thus reduce activation of cytotoxic EBV-specific CD4+ effector T cells and killing of infected B cells. Our findings identify a previously unknown viral strategy of immune evasion. By rapidly expressing multiple miRNAs, which are themselves nonimmunogenic, EBV counteracts recognition by CD4+ T cells and establishes a program of reduced immunogenicity in recently infected B cells, allowing the virus to express viral proteins required for establishment of life-long infection.
- Published
- 2016
11. Epstein-Barr virus microRNAs reduce immune surveillance by virus-specific CD8+ T cells
- Author
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Takanobu Tagawa, Liridona Maliqi, Jonathan Hoser, Larissa K. Martin, Maximilian Hastreiter, Manuel Albanese, Mickaël Bouvet, Mitch Hayes, Andreas Moosmann, Dominik Lutter, Wolfgang Hammerschmidt, and Bill Sugden
- Subjects
0301 basic medicine ,Cytotoxicity, Immunologic ,Gene Expression Regulation, Viral ,Epstein-Barr Virus Infections ,Herpesvirus 4, Human ,Cd8 T Cells ,Adaptive Immunity ,Herpesvirus ,Immune Evasion ,Microrna ,Cell Survival ,medicine.medical_treatment ,Epitopes, T-Lymphocyte ,CD8-Positive T-Lymphocytes ,medicine.disease_cause ,Virus ,Cell Line ,03 medical and health sciences ,0302 clinical medicine ,hemic and lymphatic diseases ,MHC class I ,medicine ,Cytotoxic T cell ,Humans ,Receptors, Cytokine ,Immunologic Surveillance ,MHC class II ,Antigen Presentation ,B-Lymphocytes ,Multidisciplinary ,biology ,Histocompatibility Antigens Class I ,Acquired immune system ,Epstein–Barr virus ,Virology ,MicroRNAs ,030104 developmental biology ,Cytokine ,PNAS Plus ,biology.protein ,Cytokines ,RNA, Viral ,CD8 ,030215 immunology - Abstract
Infection with Epstein-Barr virus (EBV) affects most humans worldwide and persists life-long in the presence of robust virus-specific T-cell responses. In both immunocompromised and some immunocompetent people, EBV causes several cancers and lymphoproliferative diseases. EBV transforms B cells in vitro and encodes at least 44 microRNAs (miRNAs), most of which are expressed in EBV-transformed B cells, but their functions are largely unknown. Recently, we showed that EBV miRNAs inhibit CD4(+) T-cell responses to infected B cells by targeting IL-12, MHC class II, and lysosomal proteases. Here we investigated whether EBV miRNAs also counteract surveillance by CD8(+) T cells. We have found that EBV miRNAs strongly inhibit recognition and killing of infected B cells by EBV-specific CD8(+) T cells through multiple mechanisms. EBV miRNAs directly target the peptide transporter subunit TAP2 and reduce levels of the TAP1 subunit, MHC class I molecules, and EBNA1, a protein expressed in most forms of EBV latency and a target of EBV-specific CD8(+) T cells. Moreover, miRNA-mediated down-regulation of the cytokine IL-12 decreases the recognition of infected cells by EBV-specific CD8(+) T cells. Thus, EBV miRNAs use multiple, distinct pathways, allowing the virus to evade surveillance not only by CD4(+) but also by antiviral CD8(+) T cells.
- Published
- 2016
12. Stratégies de formation de la structure coiffe chez les virus à ARN
- Author
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Barbara Selisko, Mickaël Bouvet, Bruno Coutard, Laure Gluais, François Ferron, Etienne Decroly, Bruno Canard, and Isabelle Imbert
- Subjects
chemistry.chemical_classification ,Messenger RNA ,Innate immune system ,medicine.drug_class ,viruses ,RNA ,Translation (biology) ,General Medicine ,Biology ,General Biochemistry, Genetics and Molecular Biology ,Cell biology ,Cap snatching ,Enzyme ,Protein structure ,chemistry ,medicine ,Antiviral drug - Abstract
Most viruses use the mRNA-cap dependent cellular translation machinery to translate their mRNAs into proteins. The addition of a cap structure at the 5' end of mRNA is therefore an essential step for the replication of many virus families. Additionally, the cap protects the viral RNA from degradation by cellular nucleases and prevents viral RNA recognition by innate immunity mechanisms. Viral RNAs acquire their cap structure either by using cellular capping enzymes, by stealing the cap of cellular mRNA in a process named "cap snatching", or using virus-encoded capping enzymes. Many viral enzymes involved in this process have recently been structurally and functionally characterized. These studies have revealed original cap synthesis mechanisms and pave the way towards the development of specific inhibitors bearing antiviral drug potential.
- Published
- 2012
13. RNA 3'-end mismatch excision by the severe acute respiratory syndrome coronavirus nonstructural protein nsp10/nsp14 exoribonuclease complex
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Bruno Canard, Laure Gluais, Etienne Decroly, Mickaël Bouvet, Lorenzo Subissi, and Isabelle Imbert
- Subjects
0303 health sciences ,Multidisciplinary ,Base Pair Mismatch ,030302 biochemistry & molecular biology ,RNA-dependent RNA polymerase ,RNA ,Biology ,Biological Sciences ,Viral Nonstructural Proteins ,Molecular biology ,3. Good health ,03 medical and health sciences ,Exon ,RNA silencing ,Open Reading Frames ,Severe acute respiratory syndrome-related coronavirus ,Exoribonuclease ,Transcription preinitiation complex ,Exoribonucleases ,Exoribonuclease complex ,RNA, Viral ,DNA mismatch repair ,RNA Processing, Post-Transcriptional ,030304 developmental biology - Abstract
The replication/transcription complex of severe acute respiratory syndrome coronavirus is composed of at least 16 nonstructural proteins (nsp1–16) encoded by the ORF-1a/1b. This complex includes replication enzymes commonly found in positive-strand RNA viruses, but also a set of RNA-processing activities unique to some nidoviruses. The nsp14 protein carries both exoribonuclease (ExoN) and (guanine-N7)-methyltransferase (N7-MTase) activities. The nsp14 ExoN activity ensures a yet-uncharacterized function in the virus life cycle and must be regulated to avoid nonspecific RNA degradation. In this work, we show that the association of nsp10 with nsp14 stimulates >35-fold the ExoN activity of the latter while playing no effect on N7-MTase activity. Nsp10 mutants unable to interact with nsp14 are not proficient for ExoN activation. The nsp10/nsp14 complex hydrolyzes double-stranded RNA in a 3′ to 5′ direction as well as a single mismatched nucleotide at the 3′-end mimicking an erroneous replication product. In contrast, di-, tri-, and longer unpaired ribonucleotide stretches, as well as 3′-modified RNAs, resist nsp10/nsp14-mediated excision. In addition to the activation of nsp16-mediated 2′-O-MTase activity, nsp10 also activates nsp14 in an RNA processing function potentially connected to a replicative mismatch repair mechanism.
- Published
- 2012
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14. Molecular Mapping of the RNA Cap 2′-O-Methyltransferase Activation Interface between Severe Acute Respiratory Syndrome Coronavirus nsp10 and nsp16
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Etienne Decroly, Stephane Betzi, Bruno Canard, Xavier Morelli, Aurélie Hermant, Jean-Claude Guillemot, Emmanuel Bonnaud, Jean-Paul Borg, Adrien Lugari, Claire Debarnot, Patrick Lécine, and Mickaël Bouvet
- Subjects
Methyltransferase ,Mutation, Missense ,Viral Nonstructural Proteins ,Biology ,medicine.disease_cause ,Microbiology ,Biochemistry ,Cell Line ,Protein–protein interaction ,Enzyme activator ,medicine ,Humans ,Molecular Biology ,chemistry.chemical_classification ,Mutation ,Mutagenesis ,RNA ,Methyltransferases ,Cell Biology ,Molecular biology ,Amino acid ,Enzyme Activation ,Severe acute respiratory syndrome-related coronavirus ,chemistry ,Proteome - Abstract
Several protein-protein interactions within the SARS-CoV proteome have been identified, one of them being between non-structural proteins nsp10 and nsp16. In this work, we have mapped key residues on the nsp10 surface involved in this interaction. Alanine-scanning mutagenesis, bioinformatics, and molecular modeling were used to identify several "hot spots," such as Val(42), Met(44), Ala(71), Lys(93), Gly(94), and Tyr(96), forming a continuous protein-protein surface of about 830 Å(2), bearing very conserved amino acids among coronaviruses. Because nsp16 carries RNA cap 2'-O-methyltransferase (2'O-MTase) activity only in the presence of its interacting partner nsp10 (Bouvet, M., Debarnot, C., Imbert, I., Selisko, B., Snijder, E. J., Canard, B., and Decroly, E. (2010) PLoS Pathog. 6, e1000863), functional consequences of mutations on this surface were evaluated biochemically. Most changes that disrupted the nsp10-nsp16 interaction without structural perturbations were shown to abrogate stimulation of nsp16 RNA cap 2'O-MTase activity. More strikingly, the Y96A mutation abrogates stimulation of nsp16 2'O-MTase activity, whereas Y96F overstimulates it. Thus, the nsp10-nsp16 interface may represent an attractive target for antivirals against human and animal pathogenic coronaviruses.
- Published
- 2010
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15. Coronavirus Nsp10, a critical co-factor for activation of multiple replicative enzymes
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Jessika C. Zevenhoven, Stéphanie Bernard, Bruno Canard, Xavier Morelli, Mickaël Bouvet, Patrick Lécine, Jean-Claude Guillemot, Susanne Pfefferle, Christian Drosten, Eric J. Snijder, Isabelle Imbert, Adrien Lugari, Stephane Betzi, Etienne Decroly, Clara C. Posthuma, Architecture et fonction des macromolécules biologiques (AFMB), Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche en Cancérologie de Marseille (CRCM), Aix Marseille Université (AMU)-Institut Paoli-Calmettes, Fédération nationale des Centres de lutte contre le Cancer (FNCLCC)-Fédération nationale des Centres de lutte contre le Cancer (FNCLCC)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Leiden University Medical Center (LUMC), Biologie cellulaire des infections virales – Cell biology of viral infection, Centre International de Recherche en Infectiologie - UMR (CIRI), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Centre International de Recherche en Infectiologie (CIRI), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut Paoli-Calmettes, and Fédération nationale des Centres de lutte contre le Cancer (FNCLCC)-Fédération nationale des Centres de lutte contre le Cancer (FNCLCC)-Aix Marseille Université (AMU)
- Subjects
viruses ,Mutant ,Viral Nonstructural Proteins ,medicine.disease_cause ,Crystallography, X-Ray ,Virus Replication ,Biochemistry ,Medical and Health Sciences ,Exoribonuclease ,Protein Interaction Maps ,skin and connective tissue diseases ,Coronavirus ,Genetics ,0303 health sciences ,Crystallography ,030302 biochemistry & molecular biology ,Biological Sciences ,SARS Virus ,3. Good health ,Cell biology ,Severe acute respiratory syndrome-related coronavirus ,[SDV.MP.VIR]Life Sciences [q-bio]/Microbiology and Parasitology/Virology ,[SDV.IMM]Life Sciences [q-bio]/Immunology ,Coronavirus Infections ,Exoribonuclease activity ,Biochemistry & Molecular Biology ,RNA Methyltransferase ,Protein subunit ,Archaeal Proteins ,Mutagenesis (molecular biology technique) ,Biology ,Microbiology ,Viral Transcription ,03 medical and health sciences ,medicine ,Humans ,Molecular Biology ,030304 developmental biology ,RNA Virus ,fungi ,Cell Biology ,Methyltransferases ,[SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology ,Viral Replication ,Protein-Protein Interaction ,respiratory tract diseases ,body regions ,Viral replication ,Mutagenesis ,Viral replication complex ,Chemical Sciences ,Exoribonucleases ,X-Ray - Abstract
International audience; The RNA-synthesizing machinery of the severe acute respiratory syndrome Coronavirus (SARS-CoV) is composed of 16 non-structural proteins (nsp1-16) encoded by ORF1a/1b. The 148-amino acid nsp10 subunit contains two zinc fingers and is known to interact with both nsp14 and nsp16, stimulating their respective 3'-5' exoribonuclease and 2'-O-methyltransferase activities. Using alanine-scanning mutagenesis, in cellulo bioluminescence resonance energy transfer experiments, and in vitro pulldown assays, we have now identified the key residues on the nsp10 surface that interact with nsp14. The functional consequences of mutations introduced at these positions were first evaluated biochemically by monitoring nsp14 exoribonuclease activity. Disruption of the nsp10-nsp14 interaction abrogated the nsp10-driven activation of the nsp14 exoribonuclease. We further showed that the nsp10 surface interacting with nsp14 overlaps with the surface involved in the nsp10-mediated activation of nsp16 2'-O-methyltransferase activity, suggesting that nsp10 is a major regulator of SARS-CoV replicase function. In line with this notion, reverse genetics experiments supported an essential role of the nsp10 surface that interacts with nsp14 in SARS-CoV replication, as several mutations that abolished the interaction in vitro yielded a replication-negative viral phenotype. In contrast, mutants in which the nsp10-nsp16 interaction was disturbed proved to be crippled but viable. These experiments imply that the nsp10 surface that interacts with nsp14 and nsp16 and possibly other subunits of the viral replication complex may be a target for the development of antiviral compounds against pathogenic coronaviruses.
- Published
- 2014
16. [Capping strategies in RNA viruses]
- Author
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Mickaël, Bouvet, François, Ferron, Isabelle, Imbert, Laure, Gluais, Barbara, Selisko, Bruno, Coutard, Bruno, Canard, and Etienne, Decroly
- Subjects
Models, Molecular ,RNA Caps ,Eukaryotic Cells ,Animals ,Humans ,Nucleic Acid Conformation ,RNA Viruses ,RNA, Viral ,RNA Processing, Post-Transcriptional ,Protein Structure, Quaternary ,Models, Biological ,Protein Structure, Secondary ,Acid Anhydride Hydrolases - Abstract
Most viruses use the mRNA-cap dependent cellular translation machinery to translate their mRNAs into proteins. The addition of a cap structure at the 5' end of mRNA is therefore an essential step for the replication of many virus families. Additionally, the cap protects the viral RNA from degradation by cellular nucleases and prevents viral RNA recognition by innate immunity mechanisms. Viral RNAs acquire their cap structure either by using cellular capping enzymes, by stealing the cap of cellular mRNA in a process named "cap snatching", or using virus-encoded capping enzymes. Many viral enzymes involved in this process have recently been structurally and functionally characterized. These studies have revealed original cap synthesis mechanisms and pave the way towards the development of specific inhibitors bearing antiviral drug potential.
- Published
- 2012
17. Crystallization and diffraction analysis of the SARS coronavirus nsp10-nsp16 complex
- Author
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Claire Debarnot, Bruno Canard, Isabelle Varlet, François Ferron, Laure Gluais, Mickaël Bouvet, Etienne Decroly, Julien Lescar, Nicolas Papageorgiou, Isabelle Imbert, Centre de recherche en neurobiologie - neurophysiologie de Marseille (CRN2M), Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Architecture et fonction des macromolécules biologiques (AFMB), Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), Division Eau et Environnement (LCPC/EAU), Laboratoire Central des Ponts et Chaussées (LCPC)-PRES Université Nantes Angers Le Mans (UNAM), and Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Methyltransferase ,viruses ,Molecular Sequence Data ,Biophysics ,MESH: SARS Virus ,RNA-dependent RNA polymerase ,Biology ,Viral Nonstructural Proteins ,Crystallography, X-Ray ,Biochemistry ,law.invention ,03 medical and health sciences ,Structural Biology ,law ,MESH: Methyltransferases ,Genetics ,Viral structural protein ,Humans ,Cap formation ,MESH: Cloning, Molecular ,Crystallization ,Cloning, Molecular ,[SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM] ,skin and connective tissue diseases ,Gene ,030304 developmental biology ,MESH: Crystallization ,0303 health sciences ,Messenger RNA ,MESH: Humans ,MESH: Molecular Sequence Data ,030302 biochemistry & molecular biology ,fungi ,RNA virus ,Methyltransferases ,Condensed Matter Physics ,biology.organism_classification ,RNA-Dependent RNA Polymerase ,MESH: Crystallography, X-Ray ,Virology ,3. Good health ,[SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biomolecules [q-bio.BM] ,body regions ,Severe acute respiratory syndrome-related coronavirus ,Crystallization Communications ,MESH: Viral Nonstructural Proteins ,MESH: RNA Replicase - Abstract
International audience; To date, the SARS coronavirus is the only known highly pathogenic human coronavirus. In 2003, it was responsible for a large outbreak associated with a 10% fatality rate. This positive RNA virus encodes a large replicase polyprotein made up of 16 gene products (nsp1-16), amongst which two methyltransferases, nsp14 and nsp16, are involved in viral mRNA cap formation. The crystal structure of nsp16 is unknown. Nsp16 is an RNA-cap AdoMet-dependent (nucleoside-2'-O-)-methyltransferase that is only active in the presence of nsp10. In this paper, the expression, purification and crystallization of nsp10 in complex with nsp16 are reported. The crystals diffracted to a resolution of 1.9 Å resolution and crystal structure determination is in progress.
- Published
- 2011
18. Correction: In Vitro Reconstitution of SARS-Coronavirus mRNA Cap Methylation
- Author
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Etienne Decroly, Bruno Canard, Barbara Selisko, Isabelle Imbert, Eric J. Snijder, Claire Debarnot, and Mickaël Bouvet
- Subjects
Messenger RNA ,Virology ,Immunology ,Genetics ,Correction ,Parasitology ,Severe acute respiratory syndrome coronavirus ,Methylation ,Biology ,Molecular Biology ,Microbiology ,In vitro - Abstract
An error was introduced in the preparation of this article for publication. The incorrect figure file was provided for Figure 4. Please view the correct Figure 4 here
- Published
- 2010
19. Flaviviral methyltransferase/RNA interaction: structural basis for enzyme inhibition
- Author
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Mario Milani, Martino Bolognesi, Barbara Selisko, Bruno Canard, Michela Bollati, Mickaël Bouvet, Eloise Mastrangelo, and Etienne Decroly
- Subjects
Models, Molecular ,RNA Caps ,RNA capping ,Methyltransferase ,Context (language use) ,Dengue virus ,Viral Nonstructural Proteins ,ATA, aurintricarboxylic acid ,medicine.disease_cause ,Crystallography, X-Ray ,Article ,AdoHcy, S-adenosyl-l-homocysteine ,RdRp, RNA dependent RNA polymerase ,GMP, guanosine monophosphate ,GTP, guanosine triphosphate ,Virology ,N7 MTase, guanine N7 methyltransferase ,Protein biosynthesis ,medicine ,LBS, putative low affinity RNA binding site ,WNv, West Nile virus ,Pharmacology ,HBS, high affinity RNA binding site ,Virtual docking ,Messenger RNA ,biology ,Wv, Wesselsbron virus ,Flavivirus ,RNA ,PMSF, phenylmethylsulphonyl fluoride ,Viral RNA capping ,Methyltransferases ,TLC, thin-layer chromatography ,biology.organism_classification ,2′O MTase, nucleoside-2′O methyltransferase ,PPNDS, pyridoxal-5′-phosphate-6-(2′-naphthylazo-6′-nitro-4′,8′-disulfonate) tetrasodium salt ,Biochemistry ,NS, non-structural protein ,Dv, Dengue virus ,Viral methyltransferase ,RNA, Viral ,AdoMet, S-adenosyl-l-methionine ,Methyltransferase inhibition ,Protein Binding - Abstract
Flaviviruses are the causative agents of severe diseases such as Dengue or Yellow fever. The replicative machinery used by the virus is based on few enzymes including a methyltransferase, located in the N-terminal domain of the NS5 protein. Flaviviral methyltransferases are involved in the last two steps of the mRNA capping process, transferring a methyl group from S-adenosyl-l-methionine onto the N7 position of the cap guanine (guanine-N7 methyltransferase) and the ribose 2?O position of the first nucleotide following the cap guanine (nucleoside-2?O methyltransferase). The RNA capping process is crucial for mRNA stability, protein synthesis and virus replication. Such an essential function makes methyltransferases attractive targets for the design of antiviral drugs. In this context, starting from the crystal structure of Wesselsbron flavivirus methyltransferase, we elaborated a mechanistic model describing protein/RNA interaction during N7 methyl transfer. Next we used an in silico docking procedure to identify commercially available compounds that would display high affinity for the methyltransferase active site. The best candidates selected were tested in vitro to assay their effective inhibition on 2?O and N7 methyltransferase activities on Wesselsbron and Dengue virus (Dv) methyltransferases. The results of such combined computational and experimental screening approach led to the identification of a high-potency inhibitor.
- Published
- 2008
20. Road soil retention of Pb leached from MSWI bottom ash
- Author
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D. François, Christophe Schwartz, Mickaël Bouvet, Laboratoire Central des Ponts et Chaussées, Laboratoire Sols et Environnement (LSE), and Institut National de la Recherche Agronomique (INRA)-Université de Lorraine (UL)
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Conservation of Natural Resources ,0211 other engineering and technologies ,02 engineering and technology ,Incineration ,010501 environmental sciences ,01 natural sciences ,Soil ,plomb ,Desorption ,021105 building & construction ,Soil Pollutants ,Leachate ,métal lourd ,Solubility ,MACHEFER ,Waste Management and Disposal ,0105 earth and related environmental sciences ,soil pollution ,sorption ,Road construction ,Construction Materials ,Environmental engineering ,Sorption ,Heavy metals ,CONSTRUCTION DE ROUTE ,INCINERATEUR DE DECHETS ,pollution du sol ,[SDE.ES]Environmental Sciences/Environmental and Society ,6. Clean water ,Lead ,Bottom ash ,Soil water ,Environmental science ,SOL DE ROUTE ,Water Pollutants, Chemical ,Environmental Monitoring - Abstract
Municipal solid waste incinerator (MSWI) bottom ash may be used as a road construction material; it potentially contains however a sizable quantity of heavy metals, which under the effect of rainfall infiltration through the road structure can be leached out from the material and infiltrate into the underlying soil. An eco-compatibility assessment of MSWI bottom ash reuse in road construction applications necessitates examining the solubility and retention of heavy metals in road soils. This study is dedicated to Pb transfer, sorption and desorption (NEN 7341 standard test) within various soils. These experiments yield results relative to the interaction between road soils and an MSWI bottom ash leachate representative of a “fresh” product, with a high leaching potential. For the soils investigated, the sorption of lead varies between 90% and 99%. For an extraction at pH 7, Pb release is very low (
- Published
- 2005
21. Crystal Structure and Functional Analysis of the SARS-Coronavirus RNA Cap 2′-O-Methyltransferase nsp10/nsp16 Complex
- Author
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François Ferron, Claire Debarnot, Bruno Canard, Andrew J. Sharff, Etienne Decroly, Julien Lescar, Gérard Bricogne, Bruno Coutard, Nicolas Papageorgiou, Isabelle Imbert, Miguel Ortiz-Lombardía, Laure Gluais, and Mickaël Bouvet
- Subjects
RNA Caps ,Protein Structure ,S-Adenosylmethionine ,Five-prime cap ,Adenosine ,RNA capping ,QH301-705.5 ,Immunology ,Viral Nonstructural Proteins ,Biochemistry ,Microbiology ,Chromatin remodeling ,Emerging Viral Diseases ,Virology ,Genetics ,Magnesium ,Biology (General) ,Biomacromolecule-Ligand Interactions ,Nucleic acid structure ,Biology ,Molecular Biology ,Messenger RNA ,biology ,Ribozyme ,Proteins ,RNA ,Methyltransferases ,RC581-607 ,Antivirals ,Enzymes ,Severe acute respiratory syndrome-related coronavirus ,Viral Enzymes ,Mutation ,biology.protein ,Nucleic acid ,RNA, Viral ,Parasitology ,Immunologic diseases. Allergy ,Crystallization ,Research Article ,Plasmids ,Protein Binding - Abstract
Cellular and viral S-adenosylmethionine-dependent methyltransferases are involved in many regulated processes such as metabolism, detoxification, signal transduction, chromatin remodeling, nucleic acid processing, and mRNA capping. The Severe Acute Respiratory Syndrome coronavirus nsp16 protein is a S-adenosylmethionine-dependent (nucleoside-2′-O)-methyltransferase only active in the presence of its activating partner nsp10. We report the nsp10/nsp16 complex structure at 2.0 Å resolution, which shows nsp10 bound to nsp16 through a ∼930 Å2 surface area in nsp10. Functional assays identify key residues involved in nsp10/nsp16 association, and in RNA binding or catalysis, the latter likely through a SN2-like mechanism. We present two other crystal structures, the inhibitor Sinefungin bound in the S-adenosylmethionine binding pocket and the tighter complex nsp10(Y96F)/nsp16, providing the first structural insight into the regulation of RNA capping enzymes in (+)RNA viruses., Author Summary A novel coronavirus emerged in 2003 and was identified as the etiological agent of the deadly disease called Severe Acute Respiratory Syndrome. This coronavirus replicates and transcribes its giant genome using sixteen non-structural proteins (nsp1-16). Viral RNAs are capped to ensure stability, efficient translation, and evading the innate immunity system of the host cell. The nsp16 protein is a RNA cap modifying enzyme only active in the presence of its activating partner nsp10. We have crystallized the nsp10/16 complex and report its crystal structure at atomic resolution. Nsp10 binds to nsp16 through a ∼930 Å2 activation surface area in nsp10, and the resulting complex exhibits RNA cap (nucleoside-2′-O)-methyltransferase activity. We have performed mutational and functional assays to identify key residues involved in catalysis and/or in RNA binding, and in the association of nsp10 to nsp16. We present two additional crystal structures, that of the known inhibitor Sinefungin bound in the SAM binding pocket, and that of a tighter complex made of the mutant nsp10(Y96F) bound to nsp16. Our study provides a basis for antiviral drug design as well as the first structural insight into the regulation of RNA capping enzymes in (+)RNA viruses.
- Published
- 2011
22. In Vitro Reconstitution of SARS-Coronavirus mRNA Cap Methylation
- Author
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Barbara Selisko, Isabelle Imbert, Etienne Decroly, Bruno Canard, Mickaël Bouvet, Claire Debarnot, and Eric J. Snijder
- Subjects
Gene Expression Regulation, Viral ,RNA Caps ,Five-prime cap ,RNA capping ,Methyltransferase ,QH301-705.5 ,acute respiratory syndrome vaccinia virus hepatitis-virus (nucleoside-2o)-methyltransferase activity methyltransferase activity stimulatory activities structural insights murine coronavirus crystal-structure protein nsp10 ,Viral protein ,viruses ,Immunology ,In Vitro Techniques ,Viral Nonstructural Proteins ,Biology ,medicine.disease_cause ,Methylation ,Microbiology ,Virology/Emerging Viral Diseases ,Virology ,Genetics ,medicine ,RNA, Messenger ,Biology (General) ,Molecular Biology ,Virology/Antivirals, including Modes of Action and Resistance ,tRNA Methyltransferases ,Messenger RNA ,RNA ,RC581-607 ,Molecular biology ,TRNA Methyltransferases ,Severe acute respiratory syndrome-related coronavirus ,Virology/Viral Replication and Gene Regulation ,Exoribonucleases ,Parasitology ,Immunologic diseases. Allergy ,Research Article - Abstract
SARS-coronavirus (SARS-CoV) genome expression depends on the synthesis of a set of mRNAs, which presumably are capped at their 5′ end and direct the synthesis of all viral proteins in the infected cell. Sixteen viral non-structural proteins (nsp1 to nsp16) constitute an unusually large replicase complex, which includes two methyltransferases putatively involved in viral mRNA cap formation. The S-adenosyl-L-methionine (AdoMet)-dependent (guanine-N7)-methyltransferase (N7-MTase) activity was recently attributed to nsp14, whereas nsp16 has been predicted to be the AdoMet-dependent (nucleoside-2′O)-methyltransferase. Here, we have reconstituted complete SARS-CoV mRNA cap methylation in vitro. We show that mRNA cap methylation requires a third viral protein, nsp10, which acts as an essential trigger to complete RNA cap-1 formation. The obligate sequence of methylation events is initiated by nsp14, which first methylates capped RNA transcripts to generate cap-0 7MeGpppA-RNAs. The latter are then selectively 2′O-methylated by the 2′O-MTase nsp16 in complex with its activator nsp10 to give rise to cap-1 7MeGpppA2′OMe-RNAs. Furthermore, sensitive in vitro inhibition assays of both activities show that aurintricarboxylic acid, active in SARS-CoV infected cells, targets both MTases with IC50 values in the micromolar range, providing a validated basis for anti-coronavirus drug design., Author Summary In 2003, an emerging coronavirus (CoV) was identified as the etiological agent of severe acute respiratory syndrome (SARS). SARS-CoV replicates and transcribes its large RNA genome using a membrane-bound enzyme complex containing a variety of viral nonstructural proteins. A critical step during RNA synthesis is the addition of a cap structure to the newly produced viral mRNAs, ensuring their efficient translation by host cell ribosomes. Viruses generally acquire their cap structure either from cellular mRNAs (e.g., “cap snatching” of influenza virus) or employ their own capping machinery, as is supposed to be the case for coronaviruses. mRNA caps synthesized by viruses are structurally and functionally undistinguishable from cellular mRNAs caps. In coronaviruses, methylation of mRNA caps seems to be essential, since mutations in viral methyltransferases nsp14 or nsp16 render non-viable virus. We have discovered an unexpected key role for SARS-CoV nsp10, a protein of previously unknown function, within mRNA cap methylation. Nsp10 induces selective 2′O-methylation of guanine-N7 methylated capped RNAs through direct activation of the otherwise inactive nsp16. This finding allows the full reconstitution of the SARS-CoV mRNA cap methylation sequence in vitro and opens the way to exploit the mRNA cap methyltransferases as targets for anti-coronavirus drug design.
- Published
- 2010
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