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Mainan A, Kundu R, Singh RK, Roy S. Magnesium Regulates RNA Ring Dynamics and Folding in Subgenomic Flaviviral RNA. J Phys Chem B 2024; 128:9680-9691. [PMID: 39344128 DOI: 10.1021/acs.jpcb.4c03981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Mosquito-borne flaviviruses including dengue, Zika, yellow fever, and regional encephalitis produce a large amount of short subgenomic flaviviral RNAs during infection. A segment of these RNAs named as xrRNA1 features a multi-pseudoknot (PK)-associated structure, which resists the host cell enzyme (XRN1) from degrading the viral RNA. We investigate how this long-range RNA PK folds in the presence of counterions, specifically in a mix of monovalent (K+) and divalent (Mg2+) salts at physiological concentrations. In this study, we use extensive explicit solvent molecular dynamics (MD) simulations to characterize the RNA ion environment of the folded RNA conformation, as determined by the crystal structure. This allowed us to identify the precise locations of various coordinated RNA-Mg2+ interactions, including inner-sphere/chelated and outer-sphere coordinated Mg2+. Given that RNA folding involves large-scale conformational changes, making it challenging to explore through classical MD simulations, we investigate the folding mechanism of xrRNA1 using an all-atom structure-based RNA model with a hybrid implicit-explicit treatment of the ion environment via the dynamic counterion condensation model, both with and without physiological Mg2+ concentration. The study reveals potential folding pathways for this xrRNA1, which is consistent with the results obtained from optical tweezer experiments. The equilibrium and free energy simulations both capture a dynamic equilibrium between the ring-open and ring-close states of the RNA, driven by a long-range PK interaction. Free energy calculations reveal that with the addition of Mg2+ ions, the equilibrium shifts more toward the ring-close state. A detailed analysis of the free energy pathways and ion-mediated contact probability map highlights the critical role of Mg2+ in bridging G50 and A33. This Mg2+-mediated connection helps form the long-range PK which in turn controls the transition between the ring-open and ring-close states. The study underscores the critical role of Mg2+ in the RNA folding transition, highlighting specific locations of Mg2+ contributing to the stabilization of long-range PK connections likely to enhance the robustness of Xrn1 resistance of flaviviral xrRNAs.
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Affiliation(s)
- Avijit Mainan
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Rimi Kundu
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Rishabh K Singh
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Susmita Roy
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
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Terrell JR, Le TT, Paul A, Brinton MA, Wilson WD, Poon GMK, Germann MW, Siemer JL. Structure of an RNA G-quadruplex from the West Nile virus genome. Nat Commun 2024; 15:5428. [PMID: 38926367 PMCID: PMC11208454 DOI: 10.1038/s41467-024-49761-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
Potential G-quadruplex sites have been identified in the genomes of DNA and RNA viruses and proposed as regulatory elements. The genus Orthoflavivirus contains arthropod-transmitted, positive-sense, single-stranded RNA viruses that cause significant human disease globally. Computational studies have identified multiple potential G-quadruplex sites that are conserved across members of this genus. Subsequent biophysical studies established that some G-quadruplexes predicted in Zika and tickborne encephalitis virus genomes can form and known quadruplex binders reduced viral yields from cells infected with these viruses. The susceptibility of RNA to degradation and the variability of loop regions have made structure determination challenging. Despite these difficulties, we report a high-resolution structure of the NS5-B quadruplex from the West Nile virus genome. Analysis reveals two stacked tetrads that are further stabilized by a stacked triad and transient noncanonical base pairing. This structure expands the landscape of solved RNA quadruplex structures and demonstrates the diversity and complexity of biological quadruplexes. We anticipate that the availability of this structure will assist in solving further viral RNA quadruplexes and provides a model for a conserved antiviral target in Orthoflavivirus genomes.
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Affiliation(s)
- J Ross Terrell
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Thao T Le
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Ananya Paul
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Margo A Brinton
- Department of Biology, Georgia State University, Atlanta, GA, 30303, USA
| | - W David Wilson
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Gregory M K Poon
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA
| | - Markus W Germann
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA.
- Department of Biology, Georgia State University, Atlanta, GA, 30303, USA.
| | - Jessica L Siemer
- Department of Chemistry, Georgia State University, Atlanta, GA, 30303, USA.
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Dilweg IW, Peer J, Olsthoorn RCL. Xrn1-resistant RNA motifs are disseminated throughout the RNA virome and are able to block scanning ribosomes. Sci Rep 2023; 13:15987. [PMID: 37749116 PMCID: PMC10520033 DOI: 10.1038/s41598-023-43001-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 09/18/2023] [Indexed: 09/27/2023] Open
Abstract
RNAs that are able to prevent degradation by the 5'-3' exoribonuclease Xrn1 have emerged as crucial structures during infection by an increasing number of RNA viruses. Several plant viruses employ the so-called coremin motif, an Xrn1-resistant RNA that is usually located in 3' untranslated regions. Investigation of its structural and sequence requirements has led to its identification in plant virus families beyond those in which the coremin motif was initially discovered. In this study, we identified coremin-like motifs that deviate from the original in the number of nucleotides present in the loop region of the 5' proximal hairpin. They are present in a number of viral families that previously did not have an Xrn1-resistant RNA identified yet, including the double-stranded RNA virus families Hypoviridae and Chrysoviridae. Through systematic mutational analysis, we demonstrated that a coremin motif carrying a 6-nucleotide loop in the 5' proximal hairpin generally requires a YGNNAD consensus for stalling Xrn1, similar to the previously determined YGAD consensus required for Xrn1 resistance of the original coremin motif. Furthermore, we determined the minimal requirements for the 3' proximal hairpin. Since some putative coremin motifs were found in intergenic regions or coding sequences, we demonstrated their capacity for inhibiting translation through an in vitro ribosomal scanning inhibition assay. Consequently, this study provides a further expansion on the number of viral families with known Xrn1-resistant elements, while adding a novel, potentially regulatory function for this structure.
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Affiliation(s)
- Ivar W Dilweg
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - Jasper Peer
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands
| | - René C L Olsthoorn
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC, Leiden, The Netherlands.
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Vicens Q, Kieft JS. Shared properties and singularities of exoribonuclease-resistant RNAs in viruses. Comput Struct Biotechnol J 2021; 19:4373-4380. [PMID: 34471487 PMCID: PMC8374639 DOI: 10.1016/j.csbj.2021.07.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 11/29/2022] Open
Abstract
What viral RNA genomes lack in size, they make up for in intricacy. Elaborate RNA structures embedded in viral genomes can hijack essential cellular mechanisms aiding virus propagation. Exoribonuclease-resistant RNAs (xrRNAs) are an emerging class of viral elements, which resist degradation by host cellular exoribonucleases to produce viral RNAs with diverse roles during infection. Detailed three-dimensional structural studies of xrRNAs from flaviviruses and a subset of plant viruses led to a mechanistic model in which xrRNAs block enzymatic digestion using a ring-like structure that encircles the 5' end of the resistant structure. In this mini-review, we describe the state of our understanding of the phylogenetic distribution of xrRNAs, their structures, and their conformational dynamics. Because xrRNAs have now been found in several major superfamilies of RNA viruses, they may represent a more widely used strategy than currently appreciated. Could xrRNAs represent a 'molecular clock' that would help us understand virus evolution and pathogenicity? The more we study xrRNAs in viruses, the closer we get to finding xrRNAs within cellular RNAs.
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Affiliation(s)
- Quentin Vicens
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
- RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
| | - Jeffrey S. Kieft
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
- RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA
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Dilweg IW, Savina A, Köthe S, Gultyaev AP, Bredenbeek PJ, Olsthoorn RCL. All genera of Flaviviridae host a conserved Xrn1-resistant RNA motif. RNA Biol 2021; 18:2321-2329. [PMID: 33858294 PMCID: PMC8632102 DOI: 10.1080/15476286.2021.1907044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
After infection by flaviviruses like Zika and West Nile virus, eukaryotic hosts employ the well-conserved endoribonuclease Xrn1 to degrade the viral genomic RNA. Within the 3' untranslated regions, this enzyme encounters intricate Xrn1-resistant structures. This results in the accumulation of subgenomic flaviviral RNAs, an event that improves viral growth and aggravates viral pathogenicity. Xrn1-resistant RNAs have been established throughout the flaviviral genus, but not yet throughout the entire Flaviviridae family. In this work, we use previously determined characteristics of these structures to identify homologous sequences in many members of the genera pegivirus, hepacivirus and pestivirus. We used structural alignment and mutational analyses to establish that these sequences indeed represent Xrn1-resistant RNA and that they employ the general features of the flaviviral xrRNAs, consisting of a double pseudoknot formed by five base-paired regions stitched together by a crucial triple base interaction. Furthermore, we demonstrate that the pestivirus Bungowannah virus produces subgenomic RNA in vivo. Altogether, these results indicate that viruses make use of a universal Xrn1-resistant RNA throughout the Flaviviridae family.
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Affiliation(s)
- Ivar W Dilweg
- Leiden Institute of Chemistry, Leiden University, RA, Leiden, The Netherlands
| | - Anya Savina
- Leiden Institute of Chemistry, Leiden University, RA, Leiden, The Netherlands
| | - Susanne Köthe
- Friedrich-Loeffler-Institut, Institute of Diagnostic Virology, Greifswald, Germany
| | - Alexander P Gultyaev
- Leiden Institute of Advanced Computer Science, Leiden University, RA, Leiden, The Netherlands.,Department of Viroscience, Erasmus Medical Center, CA, Rotterdam, The Netherlands
| | - Peter J Bredenbeek
- Department of Medical Microbiology, Leiden University Medical Center, RC, Leiden, The Netherlands
| | - René C L Olsthoorn
- Leiden Institute of Chemistry, Leiden University, RA, Leiden, The Netherlands
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Ramos-Lorente S, Romero-López C, Berzal-Herranz A. Information Encoded by the Flavivirus Genomes beyond the Nucleotide Sequence. Int J Mol Sci 2021; 22:3738. [PMID: 33916729 PMCID: PMC8038387 DOI: 10.3390/ijms22073738] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 03/30/2021] [Accepted: 03/31/2021] [Indexed: 02/05/2023] Open
Abstract
The genus Flavivirus comprises numerous, small, single positive-stranded RNA viruses, many of which are important human pathogens. To store all the information required for their successful propagation, flaviviruses use discrete structural genomic RNA elements to code for functional information by the establishment of dynamic networks of long-range RNA-RNA interactions that promote specific folding. These structural elements behave as true cis-acting, non-coding RNAs (ncRNAs) and have essential regulatory roles in the viral cycle. These include the control of the formation of subgenomic RNAs, known as sfRNAs, via the prevention of the complete degradation of the RNA genome. These sfRNAs are important in ensuring viral fitness. This work summarizes our current knowledge of the functions performed by the genome conformations and the role of RNA-RNA interactions in these functions. It also reviews the role of RNA structure in the production of sfRNAs across the genus Flavivirus, and their existence in related viruses.
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Affiliation(s)
| | - Cristina Romero-López
- Instituto de Parasitología y Biomedicina López-Neyra (IPBLN-CSIC), Av. Conocimiento 17, Armilla, 18016 Granada, Spain;
| | - Alfredo Berzal-Herranz
- Instituto de Parasitología y Biomedicina López-Neyra (IPBLN-CSIC), Av. Conocimiento 17, Armilla, 18016 Granada, Spain;
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