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Braun MR, Noton SL, Blanchard EL, Shareef A, Santangelo PJ, Johnson WE, Fearns R. Respiratory syncytial virus M2-1 protein associates non-specifically with viral messenger RNA and with specific cellular messenger RNA transcripts. PLoS Pathog 2021; 17:e1009589. [PMID: 34003848 PMCID: PMC8162694 DOI: 10.1371/journal.ppat.1009589] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 05/28/2021] [Accepted: 04/26/2021] [Indexed: 11/18/2022] Open
Abstract
Respiratory syncytial virus (RSV) is a major cause of respiratory disease in infants and the elderly. RSV is a non-segmented negative strand RNA virus. The viral M2-1 protein plays a key role in viral transcription, serving as an elongation factor to enable synthesis of full-length mRNAs. M2-1 contains an unusual CCCH zinc-finger motif that is conserved in the related human metapneumovirus M2-1 protein and filovirus VP30 proteins. Previous biochemical studies have suggested that RSV M2-1 might bind to specific virus RNA sequences, such as the transcription gene end signals or poly A tails, but there was no clear consensus on what RSV sequences it binds. To determine if M2-1 binds to specific RSV RNA sequences during infection, we mapped points of M2-1:RNA interactions in RSV-infected cells at 8 and 18 hours post infection using crosslinking immunoprecipitation with RNA sequencing (CLIP-Seq). This analysis revealed that M2-1 interacts specifically with positive sense RSV RNA, but not negative sense genome RNA. It also showed that M2-1 makes contacts along the length of each viral mRNA, indicating that M2-1 functions as a component of the transcriptase complex, transiently associating with nascent mRNA being extruded from the polymerase. In addition, we found that M2-1 binds specific cellular mRNAs. In contrast to the situation with RSV mRNA, M2-1 binds discrete sites within cellular mRNAs, with a preference for A/U rich sequences. These results suggest that in addition to its previously described role in transcription elongation, M2-1 might have an additional role involving cellular RNA interactions.
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Affiliation(s)
- Molly R. Braun
- Department of Microbiology, Boston University School of Medicine; National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, United States of America
| | - Sarah L. Noton
- Department of Microbiology, Boston University School of Medicine; National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, United States of America
| | - Emmeline L. Blanchard
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States of America
| | - Afzaal Shareef
- Department of Microbiology, Boston University School of Medicine; National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, United States of America
| | - Philip J. Santangelo
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States of America
| | - W. Evan Johnson
- Division of Computational Biomedicine and Bioinformatics Program and Department of Biostatistics, Boston University, Boston, Massachusetts, United States of America
| | - Rachel Fearns
- Department of Microbiology, Boston University School of Medicine; National Emerging Infectious Diseases Laboratories, Boston University, Boston, Massachusetts, United States of America
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2
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Insights into Interactions of Flavanones with Target Human Respiratory Syncytial Virus M 2-1 Protein from STD-NMR, Fluorescence Spectroscopy, and Computational Simulations. Int J Mol Sci 2020; 21:ijms21062241. [PMID: 32213871 PMCID: PMC7139479 DOI: 10.3390/ijms21062241] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/17/2020] [Accepted: 03/19/2020] [Indexed: 02/06/2023] Open
Abstract
The human Respiratory Syncytial Virus (hRSV) is the most frequent agent of respiratory infections in infants and children with no currently approved vaccine. The M2-1 protein is an important transcriptional antitermination factor and a potential target for viral replication inhibitor development. Hesperetin (HST) and hesperidin (HSD) are flavonoids from the flavanone group, naturally found in citrus and have, as one of their properties, antiviral activity. The present study reports on the interactions between hRSV M2-1 and these flavanones using experimental techniques in association with computational tools. STD-NMR results showed that HST and HSD bind to M2-1 by positioning their aromatic rings into the target protein binding site. Fluorescence quenching measurements revealed that HST had an interaction affinity greater than HSD towards M2-1. The thermodynamic analysis suggested that hydrogen bonds and van der Waals interactions are important for the molecular stabilization of the complexes. Computational simulations corroborated with the experimental results and indicated that the possible interaction region for the flavonoids is the AMP-binding site in M2-1. Therefore, these results point that HST and HSD bind stably to a critical region in M2-1, which is vital for its biological function, and thus might play a possible role antiviral against hRSV.
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3
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Esperante SA, Alvarez-Paggi D, Salgueiro M, Prat Gay GD. Mechanism of Tetramer Dissociation, Unfolding, and Oligomer Assembly of Pneumovirus M2-1 Transcription Antiterminators. ACS OMEGA 2018; 3:14732-14745. [PMID: 30555987 PMCID: PMC6289497 DOI: 10.1021/acsomega.8b01600] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/17/2018] [Indexed: 06/09/2023]
Abstract
Among Mononegavirales, the Pneumovirus family stands out by its RNA polymerase processivity that relies on a transcription antiterminator, the M2-1 protein, which also plays a key role in viral particle assembly. Biophysical and structural evidence shows that this RNA-binding tetramer is strongly modulated by a CCCH Zn2+ binding motif. We show that while the global dissociation/unfolding free energy is 10 kcal mol-1, more stable for the respiratory syncytial virus M2-1, the human metapneumovirus (HMPV) counterpart shows a 7 kcal mol-1 higher intersubunit affinity. Removal of Zn2+ from both homologues leads to an apo-monomer of identical secondary structure that further undergoes a slow irreversible oligomerization. Mutation of the histidine residue of the Zn2+ motif to cysteine or alanine leads directly to large oligomers, strongly suggesting that metal coordination has an exquisite precision for modulating the quaternary arrangement. Zn2+ removal is very slow and requires subdenaturing concentrations of guanidine chloride, suggesting a likely local folding energy barrier. Exploring a broad combination of denaturant and ethylenediaminetetraacetic acid conditions, we showed that the metapneumovirus protein has to overcome a higher energy barrier to trigger Zn2+ removal-driven dissociation, in concordance with a slower dissociation kinetics. In silico modeling of open and close conformations for both M2-1 tetramers together with interaction energy calculations reveals that the gradual opening of protomers decreases the number of intersubunit contacts. Half of the interaction energy holding each protomer in the tetramer comes from the CCCH motif, while HMPV-M2-1 harbors additional contacts between the CCCH motif of one subunit and the core domain of a protomer located in trans, allowing the rationalization of the experimental data obtained. Overall, the evidence points at a key role of the CCCH motif in switching between structural and consequently functional alternatives of the M2-1 protein.
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4
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Molina IG, Esperante SA, Marino-Buslje C, Chemes LB, de Prat-Gay G. Cooperative RNA Recognition by a Viral Transcription Antiterminator. J Mol Biol 2018; 430:777-792. [PMID: 29414675 DOI: 10.1016/j.jmb.2018.01.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 01/18/2023]
Abstract
RNA transcription of mononegavirales decreases gradually from the 3' leader promoter toward the 5' end of the genome, due to a decay in polymerase processivity. In the respiratory syncytial virus and metapneumovirus, the M2-1 protein ensures transcription anti-termination. Despite being a homotetramer, respiratory syncytial virus M2-1 binds two molecules of RNA of 13mer or longer per tetramer, and temperature-sensitive secondary structure in the RNA ligand is unfolded by stoichiometric interaction with M2-1. Fine quantitative analysis shows positive cooperativity, indicative of conformational asymmetry in the tetramer. RNA binds to M2-1 through a fast bimolecular association followed by slow rearrangements corresponding to an induced-fit mechanism, providing a sequential description of the time events of cooperativity. The first binding event of half of the RNA molecule to one of the sites increases the affinity of the second binding event on the adjacent contacting protomer by 15-fold, product of increased effective concentration caused by the entropic link. This mechanism allows for high-affinity binding with an otherwise relaxed sequence specificity, and instead suggests a yet undefined structural recognition signature in the RNA for modulating gene transcription. This work provides a basis for an essential event for understanding transcription antitermination in pneumoviruses and its counterpart Ebola virus VP30.
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Affiliation(s)
- Ivana G Molina
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Sebastian A Esperante
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Cristina Marino-Buslje
- Structural Bioinformatics Unit, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina
| | - Lucía B Chemes
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
| | - Gonzalo de Prat-Gay
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Av. Patricias Argentinas 435, 1405 Buenos Aires, Argentina.
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5
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Molina IG, Josts I, Almeida Hernandez Y, Esperante S, Salgueiro M, Garcia Alai MM, de Prat-Gay G, Tidow H. Structure and stability of the Human respiratory syncytial virus M 2-1 RNA-binding core domain reveals a compact and cooperative folding unit. Acta Crystallogr F Struct Biol Commun 2018; 74:23-30. [PMID: 29372904 PMCID: PMC5947689 DOI: 10.1107/s2053230x17017381] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 12/04/2017] [Indexed: 11/10/2022] Open
Abstract
Human syncytial respiratory virus is a nonsegmented negative-strand RNA virus with serious implications for respiratory disease in infants, and has recently been reclassified into a new family, Pneumoviridae. One of the main reasons for this classification is the unique presence of a transcriptional antiterminator, called M2-1. The puzzling mechanism of action of M2-1, which is a rarity among antiterminators in viruses and is part of the RNA polymerase complex, relies on dissecting the structure and function of this multidomain tetramer. The RNA-binding activity is located in a monomeric globular `core' domain, a high-resolution crystal structure of which is now presented. The structure reveals a compact domain which is superimposable on the full-length M2-1 tetramer, with additional electron density for the C-terminal tail that was not observed in the previous models. Moreover, its folding stability was determined through chemical denaturation, which shows that the secondary and tertiary structure unfold concomitantly, which is indicative of a two-state equilibrium. These results constitute a further step in the understanding of this unique RNA-binding domain, for which there is no sequence or structural counterpart outside this virus family, in addition to its implications in transcription regulation and its likeliness as an antiviral target.
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Affiliation(s)
- Ivana G. Molina
- Protein Structure–Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA–CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Inokentijs Josts
- The Hamburg Centre for Ultrafast Imaging and Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Yasser Almeida Hernandez
- The Hamburg Centre for Ultrafast Imaging and Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Sebastian Esperante
- Protein Structure–Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA–CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Mariano Salgueiro
- Protein Structure–Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA–CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Maria M. Garcia Alai
- European Molecular Biology Laboratory (EMBL), Hamburg Unit, Notkestrasse 85, 22607 Hamburg, Germany
| | - Gonzalo de Prat-Gay
- Protein Structure–Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA–CONICET, Avenida Patricias Argentinas 435, C1405BWE Buenos Aires, Argentina
| | - Henning Tidow
- The Hamburg Centre for Ultrafast Imaging and Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
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6
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Zhang X, Patel A, Celma CC, Yu X, Roy P, Zhou ZH. Atomic model of a nonenveloped virus reveals pH sensors for a coordinated process of cell entry. Nat Struct Mol Biol 2015; 23:74-80. [PMID: 26641711 PMCID: PMC5669276 DOI: 10.1038/nsmb.3134] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 11/04/2015] [Indexed: 12/28/2022]
Abstract
Viruses sense environmental cues (such as pH) to engage in membrane interactions for cell entry during infection but how non-enveloped viruses sense pH is largely undefined. Here, we report the structures — at high and low pH conditions — of bluetongue virus (BTV), which enters cells via a two-stage endosomal process. The receptor-binding protein VP2 possesses a zinc-finger and a conserved His866, which may function to maintain VP2 in a metastable state and to sense early-endosomal pH, respectively. The membrane penetration protein VP5 has three domains: dagger, unfurling, and anchoring. Notably, the β-meander motif of the anchoring domain contains a histidine cluster that could sense the late-endosomal pH and four putative membrane-interaction elements. Exposing BTV to low pH detaches VP2 and dramatically refolds the dagger and unfurling domains of VP5. Our biochemical and structure-guided mutagenesis studies support these coordinated pH-sensing mechanisms.
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Affiliation(s)
- Xing Zhang
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, California, USA
| | - Avnish Patel
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Cristina C Celma
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Xuekui Yu
- Department of Microbiology, Immunology &Molecular Genetics, UCLA, Los Angeles, California, USA
| | - Polly Roy
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles (UCLA), Los Angeles, California, USA.,Department of Microbiology, Immunology &Molecular Genetics, UCLA, Los Angeles, California, USA
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7
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Leyrat C, Renner M, Harlos K, Huiskonen JT, Grimes JM. Drastic changes in conformational dynamics of the antiterminator M2-1 regulate transcription efficiency in Pneumovirinae. eLife 2014; 3:e02674. [PMID: 24842877 PMCID: PMC4051120 DOI: 10.7554/elife.02674] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/15/2014] [Indexed: 12/24/2022] Open
Abstract
The M2-1 protein of human metapneumovirus (HMPV) is a zinc-binding transcription antiterminator which is highly conserved among pneumoviruses. We report the structure of tetrameric HMPV M2-1. Each protomer features a N-terminal zinc finger domain and an α-helical tetramerization motif forming a rigid unit, followed by a flexible linker and an α-helical core domain. The tetramer is asymmetric, three of the protomers exhibiting a closed conformation, and one an open conformation. Molecular dynamics simulations and SAXS demonstrate a dynamic equilibrium between open and closed conformations in solution. Structures of adenosine monophosphate- and DNA- bound M2-1 establish the role of the zinc finger domain in base-specific recognition of RNA. Binding to 'gene end' RNA sequences stabilized the closed conformation of M2-1 leading to a drastic shift in the conformational landscape of M2-1. We propose a model for recognition of gene end signals and discuss the implications of these findings for transcriptional regulation in pneumoviruses.DOI: http://dx.doi.org/10.7554/eLife.02674.001.
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Affiliation(s)
- Cedric Leyrat
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Max Renner
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Karl Harlos
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Juha T Huiskonen
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Jonathan M Grimes
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom Diamond Light Source Ltd, Didcot, United Kingdom
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8
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Esperante SA, Noval MG, Altieri TA, de Oliveira GAP, Silva JL, de Prat-Gay G. Fine modulation of the respiratory syncytial virus M2-1 protein quaternary structure by reversible zinc removal from its Cys(3)-His(1) motif. Biochemistry 2013; 52:6779-89. [PMID: 23984912 DOI: 10.1021/bi401029q] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human respiratory syncytial virus (hRSV) is a worldwide distributed pathogen that causes respiratory disease mostly in infants and the elderly. The M2-1 protein of hRSV functions as a transcription antiterminator and partakes in virus particle budding. It is present only in Pneumovirinae, namely, Pneumovirus (RSV) and Metapneumovirus, making it an interesting target for specific antivirals. hRSV M2-1 is a tight tetramer bearing a Cys3-His1 zinc-binding motif, present in Ebola VP30 protein and some eukaryotic proteins, whose integrity was shown to be essential for protein function but without a biochemical mechanistic basis. We showed that removal of the zinc atom causes dissociation to a monomeric apo-M2-1 species. Surprisingly, the secondary structure and stability of the apo-monomer is indistinguishable from that of the M2-1 tetramer. Dissociation reported by a highly sensitive tryptophan residue is much increased at pH 5.0 compared to pH 7.0, suggesting a histidine protonation cooperating in zinc removal. The monomeric apo form binds RNA at least as well as the tetramer, and this interaction is outcompeted by the phosphoprotein P, the RNA polymerase cofactor. The role of zinc goes beyond stabilization of local structure, finely tuning dissociation to a fully folded and binding competent monomer. Removal of zinc is equivalent to the disruption of the motif by mutation, only that the former is potentially reversible in the cellular context. Thus, this process could be triggered by a natural chelator such as glutathione or thioneins, where reversibility strongly suggests a modulatory role in the participation of M2-1 in the assembly of the polymerase complex or in virion budding.
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Affiliation(s)
- Sebastián A Esperante
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBA-Conicet , Patricias Argentinas 435, (1405) Buenos Aires, Argentina
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9
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Esperante SA, Paris G, de Prat-Gay G. Modular unfolding and dissociation of the human respiratory syncytial virus phosphoprotein p and its interaction with the m(2-1) antiterminator: a singular tetramer-tetramer interface arrangement. Biochemistry 2012; 51:8100-10. [PMID: 22978633 DOI: 10.1021/bi300765c] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Paramyxoviruses share the essential RNA polymerase complex components, namely, the polymerase (L), phosphoprotein (P), and nucleoprotein (N). Human respiratory syncytial virus (RSV) P is the smallest polypeptide among the family, sharing a coiled coil tetramerization domain, which disruption renders the virus inactive. We show that unfolding of P displays a first transition with low cooperativity but substantial loss of α-helix content and accessibility to hydrophobic sites, indicative of loose chain packing and fluctuating tertiary structure, typical of molten globules. The lack of unfolding baseline indicates a native state in conformational exchange and metastable at 20 °C. The second transition starts from a true intermediate state, with only the tetramerization domain remaining folded. The tetramerization domain undergoes a two-state dissociation/unfolding reaction (37.3 kcal mol(-1)). The M(2-1) transcription antiterminator, unique to RSV and Metapneumovirus, forms a nonglobular P:M(2-1) complex with a 1:1 stoichiometry and a K(D) of 8.1 nM determined by fluorescence anisotropy, far from the strikingly coincident dissociation range of P and M(2-1) tetramers (10(-28) M(3)). The M(2-1) binding region has been previously mapped to the N-terminal module of P, strongly suggesting the latter as the metastable molten globule domain. Folding, oligomerization, and assembly events between proteins and with RNA are coupled in the RNA polymerase complex. Quantitative assessment of the hierarchy of these interactions and their mechanisms contribute to the general understanding of RNA replication and transcription in Paramyxoviruses. In particular, the unique P-M(2-1) interface present in RSV provides a valuable antiviral target for this worldwide spread human pathogen.
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Affiliation(s)
- Sebastián A Esperante
- Protein Structure-Function and Engineering Laboratory, Fundación Instituto Leloir and IIBBA-CONICET, Patricias Argentinas 435, (1405) Buenos Aires, Argentina
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10
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Blondot ML, Dubosclard V, Fix J, Lassoued S, Aumont-Nicaise M, Bontems F, Eléouët JF, Sizun C. Structure and functional analysis of the RNA- and viral phosphoprotein-binding domain of respiratory syncytial virus M2-1 protein. PLoS Pathog 2012; 8:e1002734. [PMID: 22675274 PMCID: PMC3364950 DOI: 10.1371/journal.ppat.1002734] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 04/20/2012] [Indexed: 02/07/2023] Open
Abstract
Respiratory syncytial virus (RSV) protein M2-1 functions as an essential transcriptional cofactor of the viral RNA-dependent RNA polymerase (RdRp) complex by increasing polymerase processivity. M2-1 is a modular RNA binding protein that also interacts with the viral phosphoprotein P, another component of the RdRp complex. These binding properties are related to the core region of M2-1 encompassing residues S58 to K177. Here we report the NMR structure of the RSV M2-1(58-177) core domain, which is structurally homologous to the C-terminal domain of Ebola virus VP30, a transcription co-factor sharing functional similarity with M2-1. The partial overlap of RNA and P interaction surfaces on M2-1(58-177), as determined by NMR, rationalizes the previously observed competitive behavior of RNA versus P. Using site-directed mutagenesis, we identified eight residues located on these surfaces that are critical for an efficient transcription activity of the RdRp complex. Single mutations of these residues disrupted specifically either P or RNA binding to M2-1 in vitro. M2-1 recruitment to cytoplasmic inclusion bodies, which are regarded as sites of viral RNA synthesis, was impaired by mutations affecting only binding to P, but not to RNA, suggesting that M2-1 is associated to the holonucleocapsid by interacting with P. These results reveal that RNA and P binding to M2-1 can be uncoupled and that both are critical for the transcriptional antitermination function of M2-1.
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Affiliation(s)
- Marie-Lise Blondot
- Unité de Virologie et Immunologie Moléculaires (UR892), INRA, Jouy-en-Josas, France
| | - Virginie Dubosclard
- Unité de Virologie et Immunologie Moléculaires (UR892), INRA, Jouy-en-Josas, France
| | - Jenna Fix
- Unité de Virologie et Immunologie Moléculaires (UR892), INRA, Jouy-en-Josas, France
| | - Safa Lassoued
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Gif-sur-Yvette, France
| | | | - François Bontems
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Gif-sur-Yvette, France
| | - Jean-François Eléouët
- Unité de Virologie et Immunologie Moléculaires (UR892), INRA, Jouy-en-Josas, France
- * E-mail:
| | - Christina Sizun
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Gif-sur-Yvette, France
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