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Chandler-Bostock R, Bingham RJ, Clark S, Scott AJP, Wroblewski E, Barker A, White SJ, Dykeman EC, Mata CP, Bohon J, Farquhar E, Twarock R, Stockley PG. Genome-regulated Assembly of a ssRNA Virus May Also Prepare It for Infection. J Mol Biol 2022; 434:167797. [PMID: 35998704 DOI: 10.1016/j.jmb.2022.167797] [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: 05/20/2022] [Revised: 08/09/2022] [Accepted: 08/15/2022] [Indexed: 11/17/2022]
Abstract
Many single-stranded, positive-sense RNA viruses regulate assembly of their infectious virions by forming multiple, cognate coat protein (CP)-genome contacts at sites termed Packaging Signals (PSs). We have determined the secondary structures of the bacteriophage MS2 ssRNA genome (gRNA) frozen in defined states using constraints from X-ray synchrotron footprinting (XRF). Comparison of the footprints from phage and transcript confirms the presence of multiple PSs in contact with CP dimers in the former. This is also true for a virus-like particle (VLP) assembled around the gRNA in vitro in the absence of the single-copy Maturation Protein (MP) found in phage. Since PS folds are present at many sites across gRNA transcripts, it appears that this genome has evolved to facilitate this mechanism of assembly regulation. There are striking differences between the gRNA-CP contacts seen in phage and the VLP, suggesting that the latter are inappropriate surrogates for aspects of phage structure/function. Roughly 50% of potential PS sites in the gRNA are not in contact with the protein shell of phage. However, many of these sit adjacent to, albeit not in contact with, PS-binding sites on CP dimers. We hypothesize that these act as PSs transiently during assembly but subsequently dissociate. Combining the XRF data with PS locations from an asymmetric cryo-EM reconstruction suggests that the genome positions of such dissociations are non-random and may facilitate infection. The loss of many PS-CP interactions towards the 3' end of the gRNA would allow this part of the genome to transit more easily through the narrow basal body of the pilus extruding machinery. This is the known first step in phage infection. In addition, each PS-CP dissociation event leaves the protein partner trapped in a non-lowest free-energy conformation. This destabilizes the protein shell which must disassemble during infection, further facilitating this stage of the life-cycle.
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Affiliation(s)
| | - Richard J Bingham
- Departments of Mathematics and Biology & York Cross-Disciplinary Centre for Systems Analysis, University of York, York, UK
| | - Sam Clark
- Departments of Mathematics and Biology & York Cross-Disciplinary Centre for Systems Analysis, University of York, York, UK
| | - Andrew J P Scott
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Emma Wroblewski
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Amy Barker
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Simon J White
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Eric C Dykeman
- Departments of Mathematics and Biology & York Cross-Disciplinary Centre for Systems Analysis, University of York, York, UK
| | - Carlos P Mata
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Jen Bohon
- CWRU Center for Synchrotron Biosciences, NSLS-II, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Erik Farquhar
- CWRU Center for Synchrotron Biosciences, NSLS-II, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Reidun Twarock
- Departments of Mathematics and Biology & York Cross-Disciplinary Centre for Systems Analysis, University of York, York, UK.
| | - Peter G Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
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2
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Measurements of the self-assembly kinetics of individual viral capsids around their RNA genome. Proc Natl Acad Sci U S A 2019; 116:22485-22490. [PMID: 31570619 PMCID: PMC6842639 DOI: 10.1073/pnas.1909223116] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Self-assembly is a process in which functional nanoscale structures build themselves, driven by Brownian motion and interactions between components. The term was originally coined to describe the formation of a viral capsid, the protein shell that protects the genome of a virus. Despite decades of study, how capsids self-assemble has remained a mystery, because there were no methods to measure the assembly kinetics of individual capsids. We surmount this obstacle using a sensitive microscopy technique based on laser interferometry. The measurements show that a small nucleus of proteins must form on the viral RNA before the capsid assembles. These results might help researchers design strategies to stop the assembly of pathogenic viruses or to build synthetic nanostructures. Self-assembly is widely used by biological systems to build functional nanostructures, such as the protein capsids of RNA viruses. But because assembly is a collective phenomenon involving many weakly interacting subunits and a broad range of timescales, measurements of the assembly pathways have been elusive. We use interferometric scattering microscopy to measure the assembly kinetics of individual MS2 bacteriophage capsids around MS2 RNA. By recording how many coat proteins bind to each of many individual RNA strands, we find that assembly proceeds by nucleation followed by monotonic growth. Our measurements reveal the assembly pathways in quantitative detail and also show their failure modes. We use these results to critically examine models of the assembly process.
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3
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Twarock R, Stockley PG. RNA-Mediated Virus Assembly: Mechanisms and Consequences for Viral Evolution and Therapy. Annu Rev Biophys 2019; 48:495-514. [PMID: 30951648 PMCID: PMC7612295 DOI: 10.1146/annurev-biophys-052118-115611] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Viruses, entities composed of nucleic acids, proteins, and in some cases lipids lack the ability to replicate outside their target cells. Their components self-assemble at the nanoscale with exquisite precision-a key to their biological success in infection. Recent advances in structure determination and the development of biophysical tools such as single-molecule spectroscopy and noncovalent mass spectrometry allow unprecedented access to the detailed assembly mechanisms of simple virions. Coupling these techniques with mathematical modeling and bioinformatics has uncovered a previously unsuspected role for genomic RNA in regulating formation of viral capsids, revealing multiple, dispersed RNA sequence/structure motifs [packaging signals (PSs)] that bind cognate coat proteins cooperatively. The PS ensemble controls assembly efficiency and accounts for the packaging specificity seen in vivo. The precise modes of action of the PSs vary between viral families, but this common principle applies across many viral families, including major human pathogens. These insights open up the opportunity to block or repurpose PS function in assembly for both novel antiviral therapy and gene/drug/vaccine applications.
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Affiliation(s)
- Reidun Twarock
- Departments of Mathematics and Biology, and York Cross-disciplinary Centre for Systems Analysis, University of York, York YO10 5GE, United Kingdom;
| | - Peter G Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom;
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4
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Gemmill D, D'souza S, Meier-Stephenson V, Patel TR. Current approaches for RNA-labelling to identify RNA-binding proteins. Biochem Cell Biol 2019; 98:31-41. [PMID: 30931575 DOI: 10.1139/bcb-2019-0041] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
RNA is involved in all domains of life, playing critical roles in a host of gene expression processes, host-defense mechanisms, cell proliferation, and diseases. A critical component in many of these events is the ability for RNA to interact with proteins. Over the past few decades, our understanding of such RNA-protein interactions and their importance has driven the search and development of new techniques for the identification of RNA-binding proteins. In determining which proteins bind to the RNA of interest, it is often useful to use the approach where the RNA molecule is the "bait" and allow it to capture proteins from a lysate or other relevant solution. Here, we review a collection of methods for modifying RNA to capture RNA-binding proteins. These include small-molecule modification, the addition of aptamers, DNA-anchoring, and nucleotide substitution. With each, we provide examples of their application, as well as highlight their advantages and potential challenges.
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Affiliation(s)
- Darren Gemmill
- Alberta RNA Research and Training Institute & Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada
| | - Simmone D'souza
- Alberta RNA Research and Training Institute & Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada
| | - Vanessa Meier-Stephenson
- Alberta RNA Research and Training Institute & Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada.,Department of Microbiology, Immunology and Infectious Disease, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Trushar R Patel
- Alberta RNA Research and Training Institute & Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, AB T1K 3M4, Canada.,Department of Microbiology, Immunology and Infectious Disease, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada.,Li Ka Shing Institute of Virology and Discovery Lab, University of Alberta, Edmonton, AB T6G 2E1, Canada
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5
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Samatanga B, Cléry A, Barraud P, Allain FHT, Jelesarov I. Comparative analyses of the thermodynamic RNA binding signatures of different types of RNA recognition motifs. Nucleic Acids Res 2017; 45:6037-6050. [PMID: 28334819 PMCID: PMC5449602 DOI: 10.1093/nar/gkx136] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 02/16/2017] [Indexed: 01/05/2023] Open
Abstract
RNA recognition motifs (RRMs) are structurally versatile domains important in regulation of alternative splicing. Structural mechanisms of sequence-specific recognition of single-stranded RNAs (ssRNAs) by RRMs are well understood. The thermodynamic strategies are however unclear. Therefore, we utilized microcalorimetry and semi-empirical analyses to comparatively analyze the cognate ssRNA binding thermodynamics of four different RRM domains, each with a different RNA binding mode. The different binding modes are: canonical binding to the β-sheet surface; canonical binding with involvement of N- and C-termini; binding to conserved loops; and binding to an α-helix. Our results identify enthalpy as the sole and general force driving association at physiological temperatures. Also, networks of weak interactions are a general feature regulating stability of the different RRM–ssRNA complexes. In agreement, non-polyelectrolyte effects contributed between ∼75 and 90% of the overall free energy of binding in the considered complexes. The various RNA binding modes also displayed enormous heat capacity differences, that upon dissection revealed large differential changes in hydration, conformations and dynamics upon binding RNA. Altogether, different modes employed by RRMs to bind cognate ssRNAs utilize various thermodynamics strategies during the association process.
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Affiliation(s)
- Brighton Samatanga
- Institute of Molecular Biology and Biophysics, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland.,Department of Biochemistry, University of Zürich, Wintherthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Antoine Cléry
- Institute of Molecular Biology and Biophysics, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland
| | - Pierre Barraud
- Institute of Molecular Biology and Biophysics, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland
| | - Frédéric H-T Allain
- Institute of Molecular Biology and Biophysics, Swiss Federal Institute of Technology, CH-8093 Zurich, Switzerland
| | - Ilian Jelesarov
- Department of Biochemistry, University of Zürich, Wintherthurerstrasse 190, CH-8057 Zurich, Switzerland
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6
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Shakeel S, Dykeman EC, White SJ, Ora A, Cockburn JJB, Butcher SJ, Stockley PG, Twarock R. Genomic RNA folding mediates assembly of human parechovirus. Nat Commun 2017; 8:5. [PMID: 28232749 PMCID: PMC5431903 DOI: 10.1038/s41467-016-0011-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 11/16/2016] [Indexed: 01/04/2023] Open
Abstract
Assembly of the major viral pathogens of the Picornaviridae family is poorly understood. Human parechovirus 1 is an example of such viruses that contains 60 short regions of ordered RNA density making identical contacts with the protein shell. We show here via a combination of RNA-based systematic evolution of ligands by exponential enrichment, bioinformatics analysis and reverse genetics that these RNA segments are bound to the coat proteins in a sequence-specific manner. Disruption of either the RNA coat protein recognition motif or its contact amino acid residues is deleterious for viral assembly. The data are consistent with RNA packaging signals playing essential roles in virion assembly. Their binding sites on the coat proteins are evolutionarily conserved across the Parechovirus genus, suggesting that they represent potential broad-spectrum anti-viral targets.The mechanism underlying packaging of genomic RNA into viral particles is not well understood for human parechoviruses. Here the authors identify short RNA motifs in the parechovirus genome that bind capsid proteins, providing approximately 60 specific interactions for virion assembly.
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Affiliation(s)
- Shabih Shakeel
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, Helsinki, 00790, Finland
| | - Eric C Dykeman
- Departments of Mathematics and Biology and York Centre for Complex Systems Analysis, University of York, York, YO10 5DD, UK
| | - Simon J White
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Ari Ora
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, Helsinki, 00790, Finland
- Department of Applied Physics and Department of Biotechnology and Chemical Technology, Aalto University, Espoo, 02150, Finland
| | - Joseph J B Cockburn
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Sarah J Butcher
- Institute of Biotechnology and Department of Biosciences, University of Helsinki, Helsinki, 00790, Finland.
| | - Peter G Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
| | - Reidun Twarock
- Departments of Mathematics and Biology and York Centre for Complex Systems Analysis, University of York, York, YO10 5DD, UK.
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7
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Tethered Function Assays as Tools to Elucidate the Molecular Roles of RNA-Binding Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 907:61-88. [PMID: 27256382 DOI: 10.1007/978-3-319-29073-7_3] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Dynamic regulation of RNA molecules is critical to the survival and development of cells. Messenger RNAs are transcribed in the nucleus as intron-containing pre-mRNAs and bound by RNA-binding proteins, which control their fate by regulating RNA stability, splicing, polyadenylation, translation, and cellular localization. Most RBPs have distinct mRNA-binding and functional domains; thus, the function of an RBP can be studied independently of RNA-binding by artificially recruiting the RBP to a reporter RNA and then measuring the effect of RBP recruitment on reporter splicing, stability, translational efficiency, or intracellular trafficking. These tethered function assays therefore do not require prior knowledge of the RBP's endogenous RNA targets or its binding sites within these RNAs. Here, we provide an overview of the experimental strategy and the strengths and limitations of common tethering systems. We illustrate specific examples of the application of the assay in elucidating the function of various classes of RBPs. We also discuss how classic tethering assay approaches and insights gained from them have been empowered by more recent technological advances, including efficient genome editing and high-throughput RNA-sequencing.
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8
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Faoro C, Ataide SF. Ribonomic approaches to study the RNA-binding proteome. FEBS Lett 2014; 588:3649-64. [PMID: 25150170 DOI: 10.1016/j.febslet.2014.07.039] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 07/04/2014] [Accepted: 07/04/2014] [Indexed: 01/23/2023]
Abstract
Gene expression is controlled through a complex interplay among mRNAs, non-coding RNAs and RNA-binding proteins (RBPs), which all assemble along with other RNA-associated factors in dynamic and functional ribonucleoprotein complexes (RNPs). To date, our understanding of RBPs is largely limited to proteins with known or predicted RNA-binding domains. However, various methods have been recently developed to capture an RNA of interest and comprehensively identify its associated RBPs. In this review, we discuss the RNA-affinity purification methods followed by mass spectrometry analysis (AP-MS); RBP screening within protein libraries and computational methods that can be used to study the RNA-binding proteome (RBPome).
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Affiliation(s)
- Camilla Faoro
- School of Molecular Biosciences, University of Sydney, NSW, Australia
| | - Sandro F Ataide
- School of Molecular Biosciences, University of Sydney, NSW, Australia.
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9
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Supraspliceosomes at defined functional states portray the pre-assembled nature of the pre-mRNA processing machine in the cell nucleus. Int J Mol Sci 2014; 15:11637-64. [PMID: 24983480 PMCID: PMC4139805 DOI: 10.3390/ijms150711637] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Revised: 06/05/2014] [Accepted: 06/18/2014] [Indexed: 02/02/2023] Open
Abstract
When isolated from mammalian cell nuclei, all nuclear pre-mRNAs are packaged in multi-subunit large ribonucleoprotein complexes-supraspliceosomes-composed of four native spliceosomes interconnected by the pre-mRNA. Supraspliceosomes contain all five spliceosomal U snRNPs, together with other splicing factors, and are functional in splicing. Supraspliceosomes studied thus far represent the steady-state population of nuclear pre-mRNAs that were isolated at different stages of the splicing reaction. To analyze specific splicing complexes, here, we affinity purified Pseudomonas aeruginosa phage 7 (PP7)-tagged splicing complexes assembled in vivo on Adenovirus Major Late (AdML) transcripts at specific functional stages, and characterized them using molecular techniques including mass spectrometry. First, we show that these affinity purified splicing complexes assembled on PP7-tagged AdML mRNA or on PP7-tagged AdML pre-mRNA are assembled in supraspliceosomes. Second, similar to the general population of supraspliceosomes, these defined supraspliceosomes populations are assembled with all five U snRNPs at all splicing stages. This study shows that dynamic changes in base-pairing interactions of U snRNA:U snRNA and U snRNA:pre-mRNA that occur in vivo during the splicing reaction do not require changes in U snRNP composition of the supraspliceosome. Furthermore, there is no need to reassemble a native spliceosome for the splicing of each intron, and rearrangements of the interactions will suffice.
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10
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Solving a Levinthal's paradox for virus assembly identifies a unique antiviral strategy. Proc Natl Acad Sci U S A 2014; 111:5361-6. [PMID: 24706827 DOI: 10.1073/pnas.1319479111] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
One of the important puzzles in virology is how viruses assemble the protein containers that package their genomes rapidly and efficiently in vivo while avoiding triggering their hosts' antiviral defenses. Viral assembly appears directed toward a relatively small subset of the vast number of all possible assembly intermediates and pathways, akin to Levinthal's paradox for the folding of polypeptide chains. Using an in silico assembly model, we demonstrate that this reduction in complexity can be understood if aspects of in vivo assembly, which have mostly been neglected in in vitro experimental and theoretical modeling assembly studies, are included in the analysis. In particular, we show that the increasing viral coat protein concentration that occurs in infected cells plays unexpected and vital roles in avoiding potential kinetic assembly traps, significantly reducing the number of assembly pathways and assembly initiation sites, and resulting in enhanced assembly efficiency and genome packaging specificity. Because capsid assembly is a vital determinant of the overall fitness of a virus in the infection process, these insights have important consequences for our understanding of how selection impacts on the evolution of viral quasispecies. These results moreover suggest strategies for optimizing the production of protein nanocontainers for drug delivery and of virus-like particles for vaccination. We demonstrate here in silico that drugs targeting the specific RNA-capsid protein contacts can delay assembly, reduce viral load, and lead to an increase of misencapsidation of cellular RNAs, hence opening up unique avenues for antiviral therapy.
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11
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Cao J, Arha M, Sudrik C, Bugaj LJ, Schaffer DV, Kane RS. Light-inducible activation of target mRNA translation in mammalian cells. Chem Commun (Camb) 2014; 49:8338-40. [PMID: 23925486 DOI: 10.1039/c3cc44866e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A genetically encoded optogenetic system was constructed that activates mRNA translation in mammalian cells in response to light. Blue light induces the reconstitution of an RNA binding domain and a translation initiation domain, thereby activating target mRNA translation downstream of the binding sites.
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Affiliation(s)
- Jicong Cao
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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12
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Dykeman EC, Stockley PG, Twarock R. Packaging signals in two single-stranded RNA viruses imply a conserved assembly mechanism and geometry of the packaged genome. J Mol Biol 2013; 425:3235-49. [PMID: 23763992 DOI: 10.1016/j.jmb.2013.06.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/22/2013] [Accepted: 06/03/2013] [Indexed: 11/29/2022]
Abstract
The current paradigm for assembly of single-stranded RNA viruses is based on a mechanism involving non-sequence-specific packaging of genomic RNA driven by electrostatic interactions. Recent experiments, however, provide compelling evidence for sequence specificity in this process both in vitro and in vivo. The existence of multiple RNA packaging signals (PSs) within viral genomes has been proposed, which facilitates assembly by binding coat proteins in such a way that they promote the protein-protein contacts needed to build the capsid. The binding energy from these interactions enables the confinement or compaction of the genomic RNAs. Identifying the nature of such PSs is crucial for a full understanding of assembly, which is an as yet untapped potential drug target for this important class of pathogens. Here, for two related bacterial viruses, we determine the sequences and locations of their PSs using Hamiltonian paths, a concept from graph theory, in combination with bioinformatics and structural studies. Their PSs have a common secondary structure motif but distinct consensus sequences and positions within the respective genomes. Despite these differences, the distributions of PSs in both viruses imply defined conformations for the packaged RNA genomes in contact with the protein shell in the capsid, consistent with a recent asymmetric structure determination of the MS2 virion. The PS distributions identified moreover imply a preferred, evolutionarily conserved assembly pathway with respect to the RNA sequence with potentially profound implications for other single-stranded RNA viruses known to have RNA PSs, including many animal and human pathogens.
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Affiliation(s)
- Eric C Dykeman
- Departments of Mathematics and Biology and York Centre for Complex Systems Analysis, University of York, York YO10 5DD, UK
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13
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Stockley PG, Ranson NA, Twarock R. A new paradigm for the roles of the genome in ssRNA viruses. Future Virol 2013. [DOI: 10.2217/fvl.12.84] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Recent work with RNA phages and an ssRNA plant satellite virus challenges the widely held view that the sequences and structures of genomic RNAs are unimportant for virion assembly. In the T=3 phages, RNA–coat protein interactions occur throughout the genome, defining the quasiconformers of their protein shells. In the plant virus, there are multiple packaging signals dispersed throughout the genome that overcome electrostatic barriers to protein self-assembly. Both viral coat proteins cause the solution structures of their cognate genomes to collapse into a form that is readily encapsidated in a two-stage assembly process. Such similar behavior in two structurally unrelated viral protein folds implies that this might be a conserved feature of many viral assembly reactions. These results suggest a highly defined structure for the RNA in the virions, consistent with recent structural studies. They also have implications both for subsequent genome release during infection and for the evolution of viral sequences.
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Affiliation(s)
- Peter G Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
| | - Neil A Ranson
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Reidun Twarock
- Departments of Biology & Mathematics, York Centre for Complex Systems Analysis, University of York, York, YO10 5DD, UK
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14
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Mateu MG. Assembly, stability and dynamics of virus capsids. Arch Biochem Biophys 2012; 531:65-79. [PMID: 23142681 DOI: 10.1016/j.abb.2012.10.015] [Citation(s) in RCA: 155] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 10/18/2012] [Accepted: 10/28/2012] [Indexed: 12/13/2022]
Abstract
Most viruses use a hollow protein shell, the capsid, to enclose the viral genome. Virus capsids are large, symmetric oligomers made of many copies of one or a few types of protein subunits. Self-assembly of a viral capsid is a complex oligomerization process that proceeds along a pathway regulated by ordered interactions between the participating protein subunits, and that involves a series of (usually transient) assembly intermediates. Assembly of many virus capsids requires the assistance of scaffolding proteins or the viral nucleic acid, which interact with the capsid subunits to promote and direct the process. Once assembled, many capsids undergo a maturation reaction that involves covalent modification and/or conformational rearrangements, which may increase the stability of the particle. The final, mature capsid is a relatively robust protein complex able to protect the viral genome from physicochemical aggressions; however, it is also a metastable, dynamic structure poised to undergo controlled conformational transitions required to perform biologically critical functions during virus entry into cells, intracellular trafficking, and viral genome uncoating. This article provides an updated general overview on structural, biophysical and biochemical aspects of the assembly, stability and dynamics of virus capsids.
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Affiliation(s)
- Mauricio G Mateu
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma de Madrid, 28049 Madrid, Spain.
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15
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Oeffinger M. Two steps forward--one step back: advances in affinity purification mass spectrometry of macromolecular complexes. Proteomics 2012; 12:1591-608. [PMID: 22592981 DOI: 10.1002/pmic.201100509] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Cellular functions are defined by the dynamic interactions of proteins within macromolecular networks. Deciphering these complex interplays is the key to getting a comprehensive picture of cellular behavior and to understanding biological systems, from a simple bacterial cell to highly regulated neuronal cells or cancerous tissue. In the last decade, affinity purification (AP) coupled to mass spectrometry has emerged as a powerful tool to comprehensively study interaction networks and their macromolecular assemblies. This review discusses recent advances in AP approaches, from cell lysis to the importance of sample preparation and the choice of AP matrix as well as the development of different epitope tags and strategies to study dynamic interactions, with an emphasis on RNA-protein interaction networks.
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Affiliation(s)
- Marlene Oeffinger
- Institut de Recherches Cliniques de Montréal, Montréal, Québec, Canada.
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16
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Bunka DHJ, Lane SW, Lane CL, Dykeman EC, Ford RJ, Barker AM, Twarock R, Phillips SEV, Stockley PG. Degenerate RNA packaging signals in the genome of Satellite Tobacco Necrosis Virus: implications for the assembly of a T=1 capsid. J Mol Biol 2011; 413:51-65. [PMID: 21839093 DOI: 10.1016/j.jmb.2011.07.063] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 07/20/2011] [Accepted: 07/26/2011] [Indexed: 11/26/2022]
Abstract
Using a recombinant, T=1 Satellite Tobacco Necrosis Virus (STNV)-like particle expressed in Escherichia coli, we have established conditions for in vitro disassembly and reassembly of the viral capsid. In vivo assembly is dependent on the presence of the coat protein (CP) N-terminal region, and in vitro assembly requires RNA. Using immobilised CP monomers under reassembly conditions with "free" CP subunits, we have prepared a range of partially assembled CP species for RNA aptamer selection. SELEX directed against the RNA-binding face of the STNV CP resulted in the isolation of several clones, one of which (B3) matches the STNV-1 genome in 16 out of 25 nucleotide positions, including across a statistically significant 10/10 stretch. This 10-base region folds into a stem-loop displaying the motif ACAA and has been shown to bind to STNV CP. Analysis of the other aptamer sequences reveals that the majority can be folded into stem-loops displaying versions of this motif. Using a sequence and secondary structure search motif to analyse the genomic sequence of STNV-1, we identified 30 stem-loops displaying the sequence motif AxxA. The implication is that there are many stem-loops in the genome carrying essential recognition features for binding STNV CP. Secondary structure predictions of the genomic RNA using Mfold showed that only 8 out of 30 of these stem-loops would be formed in the lowest-energy structure. These results are consistent with an assembly mechanism based on kinetically driven folding of the RNA.
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Affiliation(s)
- David H J Bunka
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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17
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Dykeman EC, Grayson NE, Toropova K, Ranson NA, Stockley PG, Twarock R. Simple rules for efficient assembly predict the layout of a packaged viral RNA. J Mol Biol 2011; 408:399-407. [PMID: 21354423 DOI: 10.1016/j.jmb.2011.02.039] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/15/2011] [Accepted: 02/17/2011] [Indexed: 11/17/2022]
Abstract
Single-stranded RNA (ssRNA) viruses, which include major human pathogens, package their genomes as they assemble their capsids. We show here that the organization of the viral genomes within the capsids provides intriguing insights into the highly cooperative nature of the assembly process. A recent cryo-electron microscopy structure of bacteriophage MS2, determined with only 5-fold symmetry averaging, has revealed the asymmetric distribution of its encapsidated genome. Here we show that this RNA distribution is consistent with an assembly mechanism that follows two simple rules derived from experiment: (1) the binding of the MS2 maturation protein to the RNA constrains its conformation into a loop, and (2) the capsid must be built in an energetically favorable way. These results provide a new level of insight into the factors that drive efficient assembly of ssRNA viruses in vivo.
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Affiliation(s)
- E C Dykeman
- York Centre for Complex Systems Analysis, University of York, York YO10 5DD, UK
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18
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Rolfsson Ó, Toropova K, Ranson NA, Stockley PG. Mutually-induced conformational switching of RNA and coat protein underpins efficient assembly of a viral capsid. J Mol Biol 2010; 401:309-322. [PMID: 20684044 PMCID: PMC4793595 DOI: 10.1016/j.jmb.2010.05.058] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Single-stranded RNA viruses package their genomes into capsids enclosing fixed volumes. We assayed the ability of bacteriophage MS2 coat protein to package large, defined fragments of its genomic, single-stranded RNA. We show that the efficiency of packaging into a T=3 capsid in vitro is inversely proportional to RNA length, implying that there is a free-energy barrier to be overcome during assembly. All the RNAs examined have greater solution persistence lengths than the internal diameter of the capsid into which they become packaged, suggesting that protein-mediated RNA compaction must occur during assembly. Binding ethidium bromide to one of these RNA fragments, which would be expected to reduce its flexibility, severely inhibited packaging, consistent with this idea. Cryo-EM structures of the capsids assembled in these experiments with the sub-genomic RNAs show a layer of RNA density beneath the coat protein shell but lack density for the inner RNA shell seen in the wild-type virion. The inner layer is restored when full-length virion RNA is used in the assembly reaction, implying that it becomes ordered only when the capsid is filled, presumably because of the effects of steric and/or electrostatic repulsions. The cryo-EM results explain the length dependence of packaging. In addition, they show that for the sub-genomic fragments the strongest ordered RNA density occurs below the coat protein dimers forming the icosahedral 5-fold axes of the capsid. There is little such density beneath the proteins at the 2-fold axes, consistent with our model in which coat protein dimers binding to RNA stem-loops located at sites throughout the genome leads to switching of their preferred conformations, thus regulating the placement of the quasi-conformers needed to build the T=3 capsid. The data are consistent with mutual chaperoning of both RNA and coat protein conformations, partially explaining the ability of such viruses to assemble so rapidly and accurately.
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Affiliation(s)
- Óttar Rolfsson
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Katerina Toropova
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Neil A. Ranson
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Peter G. Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
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19
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Basnak G, Morton VL, Rolfsson Ó, Stonehouse NJ, Ashcroft AE, Stockley PG. Viral genomic single-stranded RNA directs the pathway toward a T=3 capsid. J Mol Biol 2010; 395:924-36. [PMID: 19913556 PMCID: PMC4785722 DOI: 10.1016/j.jmb.2009.11.018] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 11/02/2009] [Accepted: 11/05/2009] [Indexed: 11/20/2022]
Abstract
The molecular mechanisms controlling genome packaging by single-stranded RNA viruses are still largely unknown. It is necessary in most cases for the protein to adopt different conformations at different positions on the capsid lattice in order to form a viral capsid from multiple copies of a single protein. We showed previously that such quasi-equivalent conformers of RNA bacteriophage MS2 coat protein dimers (CP(2)) can be switched by sequence-specific interaction with a short RNA stem-loop (TR) that occurs only once in the wild-type phage genome. In principle, multiple switching events are required to generate the phage T=3 capsid. We have therefore investigated the sequence dependency of this event using two RNA aptamer sequences selected to bind the phage coat protein and an analogous packaging signal from phage Qbeta known to be discriminated against by MS2 coat protein both in vivo and in vitro. All three non-cognate stem-loops support T=3 shell formation, but none shows the kinetic-trapping effect seen when TR is mixed with equimolar CP(2). We show that this reflects the fact that they are poor ligands compared with TR, failing to saturate the coat protein under the assay conditions, ensuring that sufficient amounts of both types of dimer required for efficient assembly are present in these reactions. Increasing the non-cognate RNA concentration restores the kinetic trap, confirming this interpretation. We have also assessed the effects of extending the TR stem-loop at the 5' or 3' end with short genomic sequences. These longer RNAs all show evidence of the kinetic trap, reflecting the fact that they all contain the TR sequence and are more efficient at promoting capsid formation than TR. Mass spectrometry has shown that at least two pathways toward the T=3 shell occur in TR-induced assembly reactions: one via formation of a 3-fold axis and another that creates an extended 5-fold complex. The longer genomic RNAs suppress the 5-fold pathway, presumably as a consequence of steric clashes between multiply bound RNAs. Reversing the orientation of the extension sequences with respect to the TR stem-loop produces RNAs that are poor assembly initiators. The data support the idea that RNA-induced protein conformer switching occurs throughout assembly of the T=3 shell and show that both positional and sequence-specific effects outside the TR stem-loop can have significant impacts on the precise assembly pathway followed.
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Affiliation(s)
- Gabriella Basnak
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Victoria L. Morton
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Óttar Rolfsson
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Nicola J. Stonehouse
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Alison E. Ashcroft
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - Peter G. Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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20
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Sharma G, First EA. Thermodynamic analysis reveals a temperature-dependent change in the catalytic mechanism of bacillus stearothermophilus tyrosyl-tRNA synthetase. J Biol Chem 2008; 284:4179-90. [PMID: 19098308 DOI: 10.1074/jbc.m808500200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Catalysis of tRNA(Tyr) aminoacylation by tyrosyl-tRNA synthetase can be divided into two steps. In the first step, tyrosine is activated by ATP to form the tyrosyl-adenylate intermediate. In the second step, the tyrosyl moiety is transferred to the 3' end of tRNA. To investigate the roles that enthalpic and entropic contributions play in catalysis by Bacillus stearothermophilus tyrosyl-tRNA synthetase (TyrRS), the temperature dependence for the activation of tyrosine and subsequent transfer to tRNA(Tyr) has been determined using single turnover kinetic methods. A van't Hoff plot for binding of ATP to the TyrRS.Tyr complex reveals three distinct regions. Particularly striking is the change occurring at 25 degrees C, where the values of DeltaH(0) and DeltaS(0) go from -144 kJ/mol and -438 J/mol K below 25 degrees C to +137.9 kJ/mol and +507 J/mol K above 25 degrees C. Nonlinear Eyring and van't Hoff plots are also observed for formation of the TyrRS.[Tyr-ATP](double dagger) and TyrRS.Tyr-AMP complexes. Comparing the van't Hoff plots for the binding of ATP to tyrosyl-tRNA synthetase in the absence and presence of saturating tyrosine concentrations indicates that the temperature-dependent changes in DeltaH(0) and DeltaS(0) for the binding of ATP only occur when tyrosine is bound to the enzyme. Previous investigations revealed a similar synergistic interaction between the tyrosine and ATP substrates when the "KMSKS" signature sequence is deleted or replaced by a nonfunctional sequence. We propose that the temperature-dependent changes in DeltaH(0) and DeltaS(0) are because of the KMSKS signature sequence being conformationally constrained and unable to disrupt this synergistic interaction below 25 degrees C.
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Affiliation(s)
- Gyanesh Sharma
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130, USA
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21
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Cho HD, Sood VD, Baker D, Weiner AM. On the role of a conserved, potentially helix-breaking residue in the tRNA-binding alpha-helix of archaeal CCA-adding enzymes. RNA (NEW YORK, N.Y.) 2008; 14:1284-1289. [PMID: 18495940 PMCID: PMC2441987 DOI: 10.1261/rna.1060308] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 04/18/2008] [Indexed: 05/26/2023]
Abstract
Archaeal class I CCA-adding enzymes use a ribonucleoprotein template to build and repair the universally conserved 3'-terminal CCA sequence of the acceptor stem of all tRNAs. A wealth of structural and biochemical data indicate that the Archaeoglobus fulgidus CCA-adding enzyme binds primarily to the tRNA acceptor stem through a long, highly conserved alpha-helix that lies nearly parallel to the acceptor stem and makes many contacts with its sugar-phosphate backbone. Although the geometry of this alpha-helix is nearly ideal in all available cocrystal structures, the helix contains a highly conserved, potentially helix-breaking proline or glycine near the N terminus. We performed a mutational analysis to dissect the role of this residue in CCA-addition activity. We found that the phylogenetically permissible P295G mutant and the phylogenetically absent P295T had little effect on CCA addition, whereas P295A and P295S progressively interfered with CCA addition (C74>C75>A76 addition). We also examined the effects of these mutations on tRNA binding and the kinetics of CCA addition, and performed a computational analysis using Rosetta Design to better understand the role of P295 in nucleotide transfer. Our data indicate that CCA-adding activity does not correlate with the stability of the pre-addition cocrystal structures visualized by X-ray crystallography. Rather, the data are consistent with a transient conformational change involving P295 of the tRNA-binding alpha-helix during or between one or more steps in CCA addition.
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Affiliation(s)
- Hyundae D Cho
- Department of Biochemistry, School of Medicine, University of Washington, Seattle, Washington 98195-7350, USA
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22
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Gomila RC, Gehrke L. Biochemical approaches for characterizing RNA-protein complexes in preparation for high resolution structure analysis. Methods Mol Biol 2008; 451:279-291. [PMID: 18370263 DOI: 10.1007/978-1-59745-102-4_20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
RNA-protein interactions control viral RNA replication, transcription, translation, and particle assembly. Progress toward understanding the functional significance of RNA-protein complexes in the viral life cycle is hindered by the lack of high resolution structural information. Challenges to acquiring structural data include RNA's inherent instability and conformational plasticity, coupled with the comparatively high cost of generating large quantities of RNA for biophysical experiments. The potential for successful structure determination is increased by conducting biochemical experiments that outline interacting domains and identify key residues. These approaches are aimed at defining and characterizing RNA and protein substrates that are suitable for high resolution structural analysis.
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Affiliation(s)
- Raúl C Gomila
- HST Division, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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23
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Hogg JR, Collins K. RNA-based affinity purification reveals 7SK RNPs with distinct composition and regulation. RNA (NEW YORK, N.Y.) 2007; 13:868-80. [PMID: 17456562 PMCID: PMC1869041 DOI: 10.1261/rna.565207] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Recent studies have uncovered an unanticipated diversity of noncoding RNAs (ncRNAs), although these studies provide limited insight into their biological significance. Numerous general methods for identification and characterization of protein interactions have been developed, but similar approaches for characterizing cellular ncRNA interactions are lacking. Here we describe RNA Affinity in Tandem (RAT), an original, entirely RNA tag-based method for affinity purification of endogenously assembled RNP complexes. We demonstrate the general utility of RAT by isolating RNPs assembled in vivo on ncRNAs transcribed by RNA polymerase II or III. Using RAT in conjunction with protein identification by mass spectrometry and protein-RNA interaction assays, we define and characterize previously unanticipated protein subunits of endogenously assembled human 7SK RNPs. We show that 7SK RNA resides in a mixed population of RNPs with different protein compositions and responses to cellular stress. Depletion of a newly identified 7SK RNP component, hnRNP K, alters the partitioning of 7SK RNA among distinct RNPs. Our results establish the utility of a generalizable RNA-based RNP affinity purification method and provide insight into 7SK RNP dynamics.
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Affiliation(s)
- J Robert Hogg
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720-3200, USA
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24
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Stockley PG, Rolfsson O, Thompson GS, Basnak G, Francese S, Stonehouse NJ, Homans SW, Ashcroft AE. A simple, RNA-mediated allosteric switch controls the pathway to formation of a T=3 viral capsid. J Mol Biol 2007; 369:541-52. [PMID: 17434527 PMCID: PMC7612263 DOI: 10.1016/j.jmb.2007.03.020] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2007] [Revised: 03/04/2007] [Accepted: 03/05/2007] [Indexed: 10/23/2022]
Abstract
Using mass spectrometry we have detected both assembly intermediates and the final product, the T=3 viral capsid, during reassembly of the RNA bacteriophage MS2. Assembly is only efficient when both types of quasiequivalent coat protein dimer seen in the final capsid are present in solution. NMR experiments confirm that interconversion of these conformers is allosterically regulated by sequence-specific binding of a short RNA stem-loop. Isotope pulse-chase experiments confirm that all intermediates observed are competent for further coat protein addition, i.e., they are all on the pathway to capsid formation, and that the unit of capsid growth is a coat protein dimer. The major intermediate species are dominated by stoichiometries derived from formation of the particle threefold axis, implying that there is a defined pathway toward the T=3 shell. These results provide the first experimental evidence for a detailed mechanistic explanation of the regulation of quasiequivalent capsid assembly. They suggest a direct role for the encapsidated RNA in assembly in vivo, which is consistent with the structure of the genomic RNA within wild-type phage.
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Affiliation(s)
- Peter G Stockley
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
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25
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Coller J, Wickens M. Tethered Function Assays: An Adaptable Approach to Study RNA Regulatory Proteins. Methods Enzymol 2007; 429:299-321. [PMID: 17913629 DOI: 10.1016/s0076-6879(07)29014-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Proteins and protein complexes that regulate mRNA metabolism must possess two activities. They bind the mRNA, and then elicit some function, that is, regulate mRNA splicing, transport, localization, translation, or stability. These two activities can often reside in different proteins in a complex, or in different regions of a single polypeptide. Much can be learned about the function of the protein or complex once it is stripped of the constraints imposed by RNA binding. With this in mind, we developed a "tethered function" assay, in which the mRNA regulatory protein is brought to the 3' UTR of an mRNA reporter through a heterologous RNA-protein interaction. In this manner, the functional activity of the protein can be studied independent of its intrinsic ability to recognize and bind to RNA. This simple assay has proven useful in dissecting numerous proteins involved in posttranscriptional regulation. We discuss the basic assay, consider technical issues, and present case studies that exemplify the strengths and limitations of the approach.
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Affiliation(s)
- Jeff Coller
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, Ohio, USA
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26
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Hobson D, Uhlenbeck OC. Alanine scanning of MS2 coat protein reveals protein-phosphate contacts involved in thermodynamic hot spots. J Mol Biol 2005; 356:613-24. [PMID: 16380130 DOI: 10.1016/j.jmb.2005.11.046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Revised: 11/10/2005] [Accepted: 11/14/2005] [Indexed: 10/25/2022]
Abstract
The co-crystal structure of the MS2 coat protein dimer with its RNA operator reveals eight amino acid side-chains contacting seven of the RNA phosphates. These eight amino acids and five nearby control positions were individually changed to an alanine residue and the binding affinities of the mutant proteins to the RNA were determined. In general, the data agreed well with the crystal structure and previous RNA modification data. Interestingly, amino acid residues that are energetically most important for complex formation cluster in the middle of the RNA binding interface, forming thermodynamic hot spots, and are surrounded by energetically less relevant amino acids. In order to evaluate whether or not a given alanine mutation causes a global change in the RNA-protein interface, the affinities of the mutant proteins to RNAs containing one of 14 backbone modifications spanning the entire interface were determined. In three of six protein mutations tested, thermodynamic coupling between the site of the mutation and RNA groups that can be even more than 16 A away was detected. This suggests that, in some cases, the mutation may subtly alter the entire protein-RNA interface.
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Affiliation(s)
- Dagmar Hobson
- Department of Biochemistry, Molecular Biology, Cell Biology, Northwestern University 2205 Tech Drive, Hogan 2-100, Evanston, IL 60208, USA
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27
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Kumarevel T, Mizuno H, Kumar PKR. Characterization of the metal ion binding site in the anti-terminator protein, HutP, of Bacillus subtilis. Nucleic Acids Res 2005; 33:5494-502. [PMID: 16192572 PMCID: PMC1236978 DOI: 10.1093/nar/gki868] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
HutP is an RNA-binding protein that regulates the expression of the histidine utilization (hut) operon in Bacillus subtilis, by binding to cis-acting regulatory sequences on hut mRNA. It requires L-histidine and an Mg2+ ion for binding to the specific sequence within the hut mRNA. In the present study, we show that several divalent cations can mediate the HutP–RNA interactions. The best divalent cations were Mn2+, Zn2+ and Cd2+, followed by Mg2+, Co2+ and Ni2+, while Cu2+, Yb2+ and Hg2+ were ineffective. In the HutP–RNA interactions, divalent cations cannot be replaced by monovalent cations, suggesting that a divalent metal ion is required for mediating the protein–RNA interactions. To clarify their importance, we have crystallized HutP in the presence of three different metal ions (Mg2+, Mn2+ and Ba2+), which revealed the importance of the metal ion binding site. Furthermore, these analyses clearly demonstrated how the metal ions cause the structural rearrangements that are required for the hut mRNA recognition.
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Affiliation(s)
| | - Hiroshi Mizuno
- NEC Soft Ltd1-18-6, Shinkiba, Koto-ku, Tokyo 106-8608, Japan
| | - Penmetcha K. R. Kumar
- To whom correspondence should be addressed. Tel: +81 298 61 6085; Fax: +81 298 61 6095;
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28
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Russo G, Cuccurese M, Monti G, Russo A, Amoresano A, Pucci P, Pietropaolo C. Ribosomal protein L7a binds RNA through two distinct RNA-binding domains. Biochem J 2005; 385:289-99. [PMID: 15361074 PMCID: PMC1134697 DOI: 10.1042/bj20040371] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The human ribosomal protein L7a is a component of the major ribosomal subunit. We previously identified three nuclear-localization-competent domains within L7a, and demonstrated that the domain defined by aa (amino acids) 52-100 is necessary, although not sufficient, to target the L7a protein to the nucleoli. We now demonstrate that L7a interacts in vitro with a presumably G-rich RNA structure, which has yet to be defined. We also demonstrate that the L7a protein contains two RNA-binding domains: one encompassing aa 52-100 (RNAB1) and the other encompassing aa 101-161 (RNAB2). RNAB1 does not contain any known nucleic-acid-binding motif, and may thus represent a new class of such motifs. On the other hand, a specific region of RNAB2 is highly conserved in several other protein components of the ribonucleoprotein complex. We have investigated the topology of the L7a-RNA complex using a recombinant form of the protein domain that encompasses residues 101-161 and a 30mer poly(G) oligonucleotide. Limited proteolysis and cross-linking experiments, and mass spectral analyses of the recombinant protein domain and its complex with poly(G) revealed the RNA-binding region.
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Affiliation(s)
- Giulia Russo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Monica Cuccurese
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Gianluca Monti
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
| | - Annapina Russo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
| | - Angela Amoresano
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
| | - Pietro Pucci
- †Dipartimento di Chimica Organica e Biologica, Università Federico II, Complesso Universitario Monte S. Angelo, Via Cinthia 4, I-80126 Italy
- ‡CEINGE Biotecnologie Avanzate S.C.a.r.l., Via Comunale Margherita 482 Napoli, I-80145 Italy
| | - Concetta Pietropaolo
- *Dipartimento di Biochimica e Biotecnologie Mediche, Università Federico II, Via Sergio Pansini 5 Napoli, I-80131 Italy
- To whom correspondence should be addressed (email )
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29
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Petrillo JE, Rocheleau G, Kelley-Clarke B, Gehrke L. Evaluation of the conformational switch model for alfalfa mosaic virus RNA replication. J Virol 2005; 79:5743-51. [PMID: 15827189 PMCID: PMC1082754 DOI: 10.1128/jvi.79.9.5743-5751.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Key elements of the conformational switch model describing regulation of alfalfa mosaic virus (AMV) replication (R. C. Olsthoorn, S. Mertens, F. T. Brederode, and J. F. Bol, EMBO J. 18:4856-4864, 1999) have been tested using biochemical assays and functional studies in nontransgenic protoplasts. Although comparative sequence analysis suggests that the 3' untranslated regions of AMV and ilarvirus RNAs have the potential to fold into pseudoknots, we were unable to confirm that a proposed pseudoknot forms or has a functional role in regulating coat protein-RNA binding or viral RNA replication. Published work has suggested that the pseudoknot is part of a tRNA-like structure (TLS); however, we argue that the canonical sequence and functional features that define the TLS are absent. We suggest here that the absence of the TLS correlates directly with the distinctive requirement for coat protein to activate replication in these viruses. Experimental data are evidence that elevated magnesium concentrations proposed to stabilize the pseudoknot structure do not block coat protein binding. Additionally, covarying nucleotide changes proposed to reestablish pseudoknot pairings do not rescue replication. Furthermore, as described in the accompanying paper (L. M. Guogas, S. M. Laforest, and L. Gehrke, J. Virol. 79:5752-5761, 2005), coat protein is not, by definition, inhibitory to minus-strand RNA synthesis. Rather, the activation of viral RNA replication by coat protein is shown to be concentration dependent. We describe the 3' organization model as an alternate model of AMV replication that offers an improved fit to the available data.
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Affiliation(s)
- Jessica E Petrillo
- HST Division, MIT E25-545, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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30
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Day-Storms JJ, Niranjanakumari S, Fierke CA. Ionic interactions between PRNA and P protein in Bacillus subtilis RNase P characterized using a magnetocapture-based assay. RNA (NEW YORK, N.Y.) 2004; 10:1595-608. [PMID: 15337847 PMCID: PMC1370646 DOI: 10.1261/rna.7550104] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Ribonuclease P (RNase P) is a ribonucleoprotein complex that catalyzes the cleavage of the 5' end of precursor tRNA. To characterize the interface between the Bacillus subtilis RNA (PRNA) and protein (P protein) components, the intraholoenzyme KD is determined as a function of ionic strength using a magnetocapture-based assay. Three distinct phases are evident. At low ionic strength, the affinity of PRNA for P protein is enhanced as the ionic strength increases mainly due to stabilization of the PRNA structure by cations. Lithium substitution in lieu of potassium enhances the affinity at low ionic strength, whereas the addition of ATP, known to stabilize the structure of P protein, does not affect the affinity. At high ionic strength, the observed affinity decreases as the ionic strength increases, consistent with disruption of ionic interactions. These data indicate that three to four ions are released on formation of holoenzyme, reflecting the number of ion pairs that occur between the P protein and PRNA. At moderate ionic strength, the two effects balance so that the apparent KD is not dependent on the ionic strength. The KD between the catalytic domain (C domain) and P protein has a similar triphasic dependence on ionic strength. Furthermore, the intraholoenzyme KD is identical to or tighter than that of full-length PRNA, demonstrating that the P protein binds solely to the C domain. Finally, pre-tRNAasp (but not tRNAasp) stabilizes the PRNA*P protein complex, as predicted by the direct interaction between the P protein and pre-tRNA leader.
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Affiliation(s)
- Jeremy J Day-Storms
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109, USA
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31
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Blount KF, Tor Y. Using pyrene-labeled HIV-1 TAR to measure RNA-small molecule binding. Nucleic Acids Res 2003; 31:5490-500. [PMID: 14500811 PMCID: PMC206455 DOI: 10.1093/nar/gkg755] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Revised: 08/05/2003] [Accepted: 08/05/2003] [Indexed: 11/14/2022] Open
Abstract
To quantitatively understand the binding affinity and target selectivity of small-molecule RNA interactions, it is useful to have a rapid, highly reproducible binding assay that can be readily generalized to different RNA targets. To that end, an assay has been developed and validated for measuring the binding of low-molecular weight ligands to RNA by monitoring the fluorescence of a covalently incorporated fluorophore. As a test system, the fluorescence of a pyrene-derivatized HIV-1 TAR (transactivating response element) RNA was measured upon titration with aminoglycoside antibiotics. The binding isotherms thus obtained fit well with a model for a 1:1 interaction and yield an accurate measure of the equilibrium dissociation constant. Among a series of natural aminoglycosides, the binding affinity correlates with the number of amines, supporting an electrostatic compensation model for binding. Furthermore, the ionic strength dependence confirms that much of the binding energy is electrostatic. Finally, by measuring the binding affinity in the presence of nucleic acid competitors, we confirm that although aminoglycosides show high RNA to DNA selectivity, their selectivity among different RNA targets is sub- optimal. We conclude that this newly developed assay can be generalized to measure the binding affinities and selectivities of a variety of small molecules to a specific RNA target.
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Affiliation(s)
- Kenneth F Blount
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358, USA
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32
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Sengupta S, Jang BC, Wu MT, Paik JH, Furneaux H, Hla T. The RNA-binding protein HuR regulates the expression of cyclooxygenase-2. J Biol Chem 2003; 278:25227-33. [PMID: 12704185 DOI: 10.1074/jbc.m301813200] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The cyclooxygenase-2 (COX-2) gene encodes the inducible prostaglandin synthase enzyme implicated in inflammation, cell growth, and tumorigenesis. Regulation of the COX-2 gene expression at the post-transcriptional level is poorly understood. For example, protein factors that regulate the post-transcriptional mRNA metabolism of COX-2 have not been fully characterized. In this study, we demonstrate that the RNA-binding protein HuR binds to COX-2 mRNA and regulates its expression. We show that there are three binding sites for HuR in the 3'-untranslated region of human COX-2. These sites are located at the following positions in the COX-2 3'-untranslated region: 39-84 nucleotides (nt), 1155-1187 nt, and 1244-1256 nt (hereinafter referred to as Sites I, II and III, respectively). Although all three sites are present in the 4.6-kb COX-2 mRNA, only site I is present in the shorter 2.8-kb isoform. HuR in MDA-MB-231 cell extracts associated with COX-2 mRNA at the identified sites. Further, HuR location in the cytoplasm was induced by serum withdrawal, a stimulus known to induce COX-2 mRNA. Down-regulation of HuR by two independent methods, namely RNA interference as well as antisense RNA expression, significantly attenuated serum withdrawal-induced increase in COX-2 mRNA (both the 4.6- and 2.8-kb isoforms) and protein levels. These data suggest that HuR binding to COX-2 is critical for its post-transcriptional mRNA stabilization.
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Affiliation(s)
- Sibani Sengupta
- Center for Vascular Biology, Department of Physiology, University of Connecticut Health Center, 263 Farmington Avenue, 06030-3501, USA
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33
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Müller UF, Göringer HU. Mechanism of the gBP21-mediated RNA/RNA annealing reaction: matchmaking and charge reduction. Nucleic Acids Res 2002; 30:447-55. [PMID: 11788706 PMCID: PMC99830 DOI: 10.1093/nar/30.2.447] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2001] [Revised: 11/16/2001] [Accepted: 11/16/2001] [Indexed: 01/17/2023] Open
Abstract
The guide RNA-binding protein gBP21 has been characterized as a mitochondrial RNA/RNA annealing factor. The protein co-immunoprecipitates with RNA editing ribonucleoprotein complexes, which suggests that gBP21 contributes its annealing activity to the RNA editing machinery. In support of this view, gBP21 was found to accelerate the hybridization of cognate guide (g)RNA/pre-edited mRNA pairs. Here we analyze the mechanism of the gBP21-mediated RNA annealing reaction. Three possible modes of action are considered: chaperone function, matchmaker function and product stabilization. We conclude that gBP21 works as a matchmaker by binding to gRNAs as one of the two RNA annealing reactants. Three lines of evidence substantiate this model. First, gBP21 and gRNAs form a thermodynamically and kinetically stable complex in a 1 + 1 stoichiometry. Secondly, gRNA-bound gBP21 stabilizes single-stranded RNA, which can be considered the transition state in the annealing reaction. Thirdly, gBP21 has a low affinity for double-stranded RNAs, suggesting the release of the annealed reaction product after the hybridization step. In the process, up to six ionic bonds are formed between gBP21 and a gRNA, which decreases the net negative charge of the RNA. As a consequence, the electrostatic repulsion between the two annealing reactants is reduced favoring the hybridization reaction.
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Affiliation(s)
- Ulrich F Müller
- Department of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
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34
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Brusca EM, True HL, Celander DW. Novel RNA-binding properties of Pop3p support a role for eukaryotic RNase P protein subunits in substrate recognition. J Biol Chem 2001; 276:42543-8. [PMID: 11527978 DOI: 10.1074/jbc.m107293200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribonuclease P (RNase P) catalyzes the 5'-end maturation of transfer RNA molecules. Recent evidence suggests that the eukaryotic protein subunits may provide substrate-binding functions (True, H. L., and Celander, D. W. (1998) J. Biol. Chem. 273, 7193-7196). We now report that Pop3p, an essential protein subunit of the holoenzyme in Saccharomyces cerevisiae, displays novel RNA-binding properties. A recombinant form of Pop3p (H6Pop3p) displays a 3-fold greater affinity for binding pre-tRNA substrates relative to tRNA products. The recognition sequence for the H6Pop3p-substrate interaction in vitro was mapped to a 39-nucleotide long sequence that extends from position -21 to +18 surrounding the natural processing site in pre-tRNA substrates. H6Pop3p binds a variety of RNA molecules with high affinity (K(d) = 16-25 nm) and displays a preference for single-stranded RNAs. Removal or modification of basic C-terminal residues attenuates the RNA-binding properties displayed by the protein specifically for a pre-tRNA substrate. These studies support the model that eukaryotic RNase P proteins bind simultaneously to the RNA subunit and RNA substrate.
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Affiliation(s)
- E M Brusca
- Department of Chemistry, Loyola University Chicago, Chicago, Illinois 60626, USA
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35
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Lim F, Downey TP, Peabody DS. Translational repression and specific RNA binding by the coat protein of the Pseudomonas phage PP7. J Biol Chem 2001; 276:22507-13. [PMID: 11306589 DOI: 10.1074/jbc.m102411200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PP7 is a single-strand RNA bacteriophage of Pseudomonas aeroginosa and a distant relative to coliphages like MS2 and Qbeta. Here we show that PP7 coat protein is a specific RNA-binding protein, capable of repressing the translation of sequences fused to the translation initiation region of PP7 replicase. Its RNA binding activity is specific since it represses the translational operator of PP7, but does not repress the operators of the MS2 or Qbeta phages. Conditions for the purification of coat protein and for the reconstitution of its RNA binding activity from disaggregated virus-like particles were established. Its dissociation constant for PP7 operator RNA in vitro was determined to be about 1 nm. Using a genetic system in which coat protein represses translation of a replicase-beta-galactosidase fusion protein, amino acid residues important for binding of PP7 RNA were identified.
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Affiliation(s)
- F Lim
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131, USA
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36
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Caprara MG, Myers CA, Lambowitz AM. Interaction of the Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (CYT-18 protein) with the group I intron P4-P6 domain. Thermodynamic analysis and the role of metal ions. J Mol Biol 2001; 308:165-90. [PMID: 11327760 DOI: 10.1006/jmbi.2001.4581] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (CYT-18 protein) functions in splicing group I introns by promoting the formation of the catalytically active structure of the intron's catalytic core. Previous studies suggested a model in which the protein binds first to the intron's P4-P6 domain, and then makes additional contacts with the P3-P9 domain to stabilize the two domains in the correct relative orientation to form the intron's active site. Here, we analyzed the interaction of CYT-18 with a small RNA (P4-P6 RNA) corresponding to the isolated P4-P6 domain of the N. crassa mitochondrial large subunit ribosomal RNA intron. RNA footprinting and modification-interference experiments showed that CYT-18 binds to this small RNA around the junction of the P4-P6 stacked helices on the side opposite the active-site cleft, as it does to the P4-P6 domain in the intact intron. The binding is inhibited by chemical modifications that disrupt base-pairing in P4, P6, and P6a, indicating that a partially folded structure of the P4-P6 domain is required. The temperature-dependence of binding indicates that the interaction is driven by a favorable enthalpy change, but is accompanied by an unfavorable entropy change. The latter may reflect entropically unfavorable conformational changes or decreased conformational flexibility in the complex. CYT-18 binding is inhibited at > or =125 mM KCl, indicating a strong dependence on phosphodiester-backbone interactions. On the other hand, Mg(2+) is absolutely required for CYT-18 binding, with titration experiments showing approximately 1.5 magnesium ions bound per complex. Metal ion-cleavage experiments identified a divalent cation-binding site near the boundary of P6 and J6/6a, and chemical modification showed that Mg(2+) binding induces RNA conformational changes in this region, as well as elsewhere, particularly in J4/5. Together, these findings suggest a model in which the binding of Mg(2+) near J6/6a and possibly at one additional location in the P4-P6 RNA induces formation of a specific phosphodiester-backbone geometry that is required for CYT-18 binding. The binding of CYT-18 may then establish the correct structure at the junction of the P4/P6 stacked helices for assembly of the P3-P9 domain. The interaction of CYT-18 with the P4-P6 domain appears similar to the TyrRS interaction with the D-/anticodon arm stacked helices of tRNA(Tyr).
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Affiliation(s)
- M G Caprara
- Institute for Cellular and Molecular Biology, Department of Chemistry and Biochemistry, Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas at Austin, Austin, TX 78712, USA
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37
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Lago H, Parrott AM, Moss T, Stonehouse NJ, Stockley PG. Probing the kinetics of formation of the bacteriophage MS2 translational operator complex: identification of a protein conformer unable to bind RNA. J Mol Biol 2001; 305:1131-44. [PMID: 11162119 DOI: 10.1006/jmbi.2000.4355] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have investigated the kinetics of complex formation between bacteriophage MS2 coat protein subunits and synthetic RNA fragments encompassing the natural translational operator site, or the consensus sequences of three distinct RNA aptamer families, which are known to bind to the same site on the protein. Reactions were assayed using stopped-flow fluorescence spectroscopy and either the intrinsic tryptophan fluorescence of the protein or the signals from RNA fragments site-specifically substituted with the fluorescent adenosine analogue 2'-deoxy, 2-aminopurine. The kinetics observed were independent of the fluorophore being monitored or its position within the complex, indicating that the data report global events occurring during complex formation. Competition assays show that the complex being formed consists of a single coat protein dimer and one RNA molecule. The binding reaction is at least biphasic. The faster phase, constituting 80-85 % of the amplitude, is a largely diffusion driven RNA-protein interaction (k1 approximately 2x10(9) M(-1) s(-1)). The salt dependence of the forward reaction and the similarities of the on-rates of lower-affinity RNA fragments are consistent with a diffusion-controlled step dominated by electrostatic steering. The slower phase is independent of reactant concentration, and appears to correspond to isomerisation of the coat protein subunit(s) prior to RNA binding (k(iso) approximately 0.23 s(-1)). Measurements with a coat protein mutant (Pro78Asn) show that this phase is not due to cis-trans isomerisation at this residue. The conformational changes in the protein ligand during formation of an RNA-protein complex might play a role in the triggering of capsid self-assembly and a model for this is discussed.
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Affiliation(s)
- H Lago
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
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38
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Workman CJ, Voss EW. Interaction of dual-specific autoantibodies with dsDNA and a synthetic dimer peptide simulating the hinge region of IgG2a molecules. Mol Immunol 2000; 37:931-9. [PMID: 11282396 DOI: 10.1016/s0161-5890(00)00108-5] [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: 10/18/2022]
Abstract
Anti-dsDNA autoantibodies and immune complex formation are major factors in SLE pathogenesis. Understanding stable immune complex formation is critical in deciphering mechanisms of autoimmune pathogenesis. Previous studies identified a subpopulation of murine lupus monoclonal autoantibodies that exhibited dual specificity (anti-DNA and anti-IgG2a hinge) and formed stable immune complexes [J. Mol. Rec. 10(1997)225]. Two monoclonal autoantibodies, BV 17-45 and BV 16-13, were extensively studied because of their dual specificity. To quantitatively assess the role of each specificity in the formation of stable immune complexes, studies were performed to determine binding affinities for various sized dsDNA fragments (21, 43, 84, and 114 bp) and the covalent dimer of a nine amino acid hinge peptide. Results characterizing BV 17-45 showed that the affinity for dsDNA directly correlated with increased dsDNA size. Results with BV 16-13 revealed a generally lower affinity for the various dsDNA fragments. Binding inhibition studies, using a covalently linked dimer of a nine amino acid synthetic hinge peptide as an inhibitor of the antibody-43 bp dsDNA interaction, yielded relative affinities for the anti-hinge activity. Binding affinities for the synthetic hinge specificity were lower than affinities measured for the anti-dsDNA activity. Collectively, the binding and inhibition studies provided insight into the correlation between dual specificity and avid immune complex formation. A model was proposed based on the concept that large dsDNA fragments caused localization of the dual-specific antibodies through the anti-dsDNA activity, thereby facilitating subsequent binding and cross-linkage via the anti-hinge specificity. These synergistic interactions resulted in the formation of avid immune complexes.
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Affiliation(s)
- C J Workman
- Department of Microbiology, University of Illinois, B103 Chem. Life Sciences Lab, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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39
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Abstract
We have incorporated 5-fluorouridine into several sites within a 19-mer RNA modelled on the translational operator of the MS2 bacteriophage. The 19F NMR spectra demonstrate the different chemical shifts of helical and loop fluorouridines of the hairpin secondary structure. Addition of salt gives rise to a species in which the loop fluorouridine gains the chemical shift of its helical counterparts, due to the formation of the alternative bi-molecular duplex form. This is supported by UV thermal melting behaviour which becomes highly dependent on the RNA concentration. Distinct 19F NMR signals for duplex and hairpin forms allow the duplex-hairpin equilibrium constant to be determined under a range of conditions, enabling thermodynamic characterisation and its salt dependence to be determined. Mg2+ also promotes duplex formation, but more strongly than Na+, such that at 25 degrees C, 10 mM MgCl2 has a comparable duplex-promoting effect to 300 mM NaCl. A similar effect is observed with Sr2+, but not Ca2+ or Ba2+. Additional hairpin species are observed in the presence of Na+ as well as Mg2+, Ca2+, Sr2+ and Ba2+ ions. The overall, ensemble average, hairpin conformation is therefore salt-dependent. Electrostatic considerations are thus involved in the balance between different hairpin conformers as well as the duplex-hairpin equilibrium. The data presented here demonstrate that 19F NMR is a powerful tool for the study of conformational heterogeneity in RNA, which is particularly important for probing the effects of metal ions on RNA structure. The thermodynamic characterisation of duplex-hairpin equilibria will also be valuable in the development of theoretical models of nucleic acid structure.
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Affiliation(s)
- J R Arnold
- School of Biology, University of Leeds, UK.
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40
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GuhaThakurta D, Draper DE. Contributions of basic residues to ribosomal protein L11 recognition of RNA. J Mol Biol 2000; 295:569-80. [PMID: 10623547 DOI: 10.1006/jmbi.1999.3372] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The C-terminal domain of ribosomal protein L11, L11-C76, binds in the distorted minor groove of a helix within a 58 nucleotide domain of 23 S rRNA. To study the electrostatic component of RNA recognition in this protein, arginine and lysine residues have been individually mutated to alanine or methionine residues at the nine sequence positions that are conserved as basic residues among bacterial L11 homologs. In measurements of the salt dependence of RNA-binding, five of these mutants have a reduced value of - partial differentiallog(K(obs))/ partial differentiallog[KCl] as compared to the parent L11-C76 sequence, indicating that these residues interact with the RNA electrostatic field. These five residues are located at the perimeter of the RNA-binding surface of the protein; all five of them form salt bridges with phosphates in the crystal structure of the complex. A sixth residue, Lys47, was found to make an electrostatic contribution to binding when measurements were made at pH 6.0, but not at pH 7.0; its pK in the free protein must be <6.5. The unusual behavior of Lys47 is explained by its burial in the hydrophobic core of the free protein, and unburial in the RNA-bound protein, where it forms a salt bridge with a phosphate. The contributions of these six residues to the electrostatic component of binding are not additive; thus the magnitude of the salt dependence cannot be used to count the number of ionic interactions in this complex. By interacting with irregular features of the RNA backbone, including an S-turn, these basic residues contribute to the specificity of L11 for its target site.
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Affiliation(s)
- D GuhaThakurta
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
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41
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Severson W, Partin L, Schmaljohn CS, Jonsson CB. Characterization of the Hantaan nucleocapsid protein-ribonucleic acid interaction. J Biol Chem 1999; 274:33732-9. [PMID: 10559265 DOI: 10.1074/jbc.274.47.33732] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nucleocapsid (N) protein functions in hantavirus replication through its interactions with the viral genomic and antigenomic RNAs. To address the biological functions of the N protein, it was critical to first define this binding interaction. The dissociation constant, K(d), for the interaction of the Hantaan virus (HTNV) N protein and its genomic S segment (vRNA) was measured under several solution conditions. Overall, increasing the NaCl and Mg(2+) in these binding reactions had little impact on the K(d). However, the HTNV N protein showed an enhanced specificity for HTNV vRNA as compared with the S segment open reading frame RNA or a nonviral RNA with increasing ionic strength and the presence of Mg(2+). In contrast, the assembly of Sin Nombre virus N protein-HTNV vRNA complexes was inhibited by the presence of Mg(2+) or an increase in the ionic strength. The K(d) values for HTNV and Sin Nombre virus N proteins were nearly identical for the S segment open reading frame RNA, showing weak affinity over several binding reaction conditions. Our data suggest a model in which specific recognition of the HTNV vRNA by the HTNV N protein resides in the noncoding regions of the HTNV vRNA.
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Affiliation(s)
- W Severson
- Graduate Program in Molecular Biology, New Mexico State University, Las Cruces, New Mexico 88003, USA
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42
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Besançon W, Wagner R. Characterization of transient RNA-RNA interactions important for the facilitated structure formation of bacterial ribosomal 16S RNA. Nucleic Acids Res 1999; 27:4353-62. [PMID: 10536142 PMCID: PMC148716 DOI: 10.1093/nar/27.22.4353] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The co-transcribed leader sequences of bacterial rRNA are known to affect the structure and function of the small ribosomal subunits. Base changes in the leader nut -like sequence elements have been shown to cause misfolded but correctly processed 16S rRNA structures at low growth temperature. Transient interactions of leader sequences with the nascent 16S rRNA are considered to guide rRNA folding and to facilitate correct structure formation. In order to understand this chaperone-like activity of the leader RNA we have analyzed the thermodynamic stabilities of wild-type and mutant leader transcripts. We show here that base changes cause subtle differences in the melting profiles of the corresponding leader transcripts. Furthermore, we show that direct interaction between leader transcripts and the 16S rRNA is limited to the 5'-domain of the 16S rRNA for both wild-type and mutant leaders. Binding studies of mutant and wild-type leader transcripts to 16S rRNA revealed small changes in the affinities and the thermal stabilities as a consequence of the base changes. Different complex stabilities as a function of the Mg(2+) ion concentration indicated that mutant and wild-type leader transcripts interact differently with the 16S rRNA, consistent with a less stable and tightly folded structure of the mutant leader. Employing time-resolved oligonucleotide hybridization assays we could show different folding kinetics for 16S rRNA molecules when linked to wild-type leader, mutant leader or in the absence of leader RNA. The studies help to understand how bacterial rRNA leader transcripts may affect the folding of the small subunit rRNA.
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Affiliation(s)
- W Besançon
- Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany
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43
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Abstract
Atomic resolution structures are now available for more than 20 complexes of proteins with specific RNAs. This review examines two main themes that appear in this set of structures. A "groove binder" class of proteins places a protein structure (alpha-helix, 310-helix, beta-ribbon, or irregular loop) in the groove of an RNA helix, recognizing both the specific sequence of bases and the shape or dimensions of the groove, which are sometimes distorted from the normal A-form. A second class of proteins uses beta-sheet surfaces to create pockets that examine single-stranded RNA bases. Some of these proteins recognize completely unstructured RNA, and in others RNA secondary structure indirectly promotes binding by constraining bases in an appropriate orientation. Thermodynamic studies have shown that binding specificity is generally a function of several factors, including base-specific hydrogen bonds, non-polar contacts, and mutual accommodation of the protein and RNA-binding surfaces. The recognition strategies and structural frameworks used by RNA binding proteins are not exotically different from those employed by DNA-binding proteins, suggesting that the two kinds of nucleic acid-binding proteins have not evolved independently.
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Affiliation(s)
- D E Draper
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA.
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44
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Johansson HE, Dertinger D, LeCuyer KA, Behlen LS, Greef CH, Uhlenbeck OC. A thermodynamic analysis of the sequence-specific binding of RNA by bacteriophage MS2 coat protein. Proc Natl Acad Sci U S A 1998; 95:9244-9. [PMID: 9689065 PMCID: PMC21323 DOI: 10.1073/pnas.95.16.9244] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Most mutations in the sequence of the RNA hairpin that specifically binds MS2 coat protein either reduce the binding affinity or have no effect. However, one RNA mutation, a uracil to cytosine change in the loop, has the unusual property of increasing the binding affinity to the protein by nearly 100-fold. Guided by the structure of the protein-RNA complex, we used a series of protein mutations and RNA modifications to evaluate the thermodynamic basis for the improved affinity: The tight binding of the cytosine mutation is due to (i) the amino group of the cytosine residue making an intra-RNA hydrogen bond that increases the propensity of the free RNA to adopt the structure seen in the complex and (ii) the increased affinity of hydrogen bonds between the protein and a phosphate two bases away from the cytosine residue. The data are in good agreement with a recent comparison of the cocrystal structures of the two complexes, where small differences in the two structures are seen at the thermodynamically important sites.
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Affiliation(s)
- H E Johansson
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, USA
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45
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Ansel-McKinney P, Gehrke L. RNA determinants of a specific RNA-coat protein peptide interaction in alfalfa mosaic virus: conservation of homologous features in ilarvirus RNAs. J Mol Biol 1998; 278:767-85. [PMID: 9614941 DOI: 10.1006/jmbi.1998.1656] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Alfalfa mosaic virus (AMV) coat protein and tobacco streak virus (TSV) coat protein bind specifically to the 3' untranslated regions of the viral RNAs and are required with the genomic RNAs to initiate virus replication. A combination of nucleotide substitutions, hydroxyl radical footprinting, and ethylation and chemical modification interference analysis has been used to define the RNA determinants important for the specific binding of the 3'-terminal 39 nucleotides of AMV RNA 3/4 (AMV843-881) to an amino-terminal coat protein peptide (CP26). The results demonstrate that potential phosphate and base-specific contacts as well as ribose moieties protected upon peptide binding cluster in lower hairpin stems and flanking AUGC sequences of the viral RNA, without direct involvement of loop nucleotides. Nucleotides identified in the modification-interference analyses as important for RNA-protein interactions are highly conserved among AMV and the ilarvirus RNAs. This RNA sequence homology, coupled with the recent identification of an RNA binding consensus sequence for AMV and ilarvirus coat proteins, provides a framework for understanding the functional equivalence of AMV and TSV coat proteins in binding RNA and activating virus replication and may explain why heterologous AMV and ilarvirus coat protein-RNA mixtures are infectious.
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Affiliation(s)
- P Ansel-McKinney
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA
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Bridonneau P, Chang YF, O'Connell D, Gill SC, Snyder DW, Johnson L, Goodson T, Herron DK, Parma DH. High-affinity aptamers selectively inhibit human nonpancreatic secretory phospholipase A2 (hnps-PLA2). J Med Chem 1998; 41:778-86. [PMID: 9526554 DOI: 10.1021/jm970579k] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A family of sequence-related 2'-aminopyrimidine, 2'-hydroxylpurine aptamers, developed by oligonucleotide-based combinatorial chemistry, SELEX (systematic evolution of ligand by exponential enrichment) technology, binds human nonpancreatic secretory phospholipase A2 (hnps-PLA2) with nanomolar affinities and inhibits enzymatic activity. Aptamer 15, derived from the family, binds hnps-PLA2 with a Kd equal to 1.7 +/- 0.2 nM and, in a standard chromogenic assay of enzymatic activity, inhibits hnps-PLA2 with an IC50 of 4 nM, at a mole fraction of substrate concentration of 4 x 10(-6) and a calculated Ki of 0.14 nM. Aptamer 15 is selective for hnps-PLA2, having a 25- and 2500-fold lower affinity, respectively, for the unrelated proteins human neutrophil elastase and human IgG. Contractions of guinea pig lung pleural strips induced by hnps-PLA2 are abolished by 0.3 microM aptamer 15, whereas contractions induced by arachidonic acid are not altered. The structure that is essential for binding and inhibition appears to be a 40-base hairpin/loop motif with an asymmetrical internal loop. The affinity and activity of the aptamers demonstrate the ability of the SELEX process to isolate antagonists of nonnucleic-acid-binding proteins from vast oligonucleotide combinatorial libraries.
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Affiliation(s)
- P Bridonneau
- NeXstar Pharmaceuticals, Inc., Boulder, Colorado 80301, USA
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Fouts DE, True HL, Celander DW. Functional recognition of fragmented operator sites by R17/MS2 coat protein, a translational repressor. Nucleic Acids Res 1997; 25:4464-73. [PMID: 9358153 PMCID: PMC147100 DOI: 10.1093/nar/25.22.4464] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The R17/MS2 coat protein serves as a translational repressor of replicase by binding to a 19 nt RNA hairpin containing the Shine-Dalgarno sequence and the initiation codon of the replicase gene. We have explored the structural features of the RNA operator site that are necessary for efficient translational repression by the R17/MS2 coat protein in vivo . The R17/MS2 coat protein efficiently directs lysogen formation for P22 R17 , a bacteriophage P22 derivative that carries the R17/MS2 RNA operator site within the P22 phage ant mRNA. Phages were constructed that contain fragmented operator sites such that the Shine-Dalgarno sequence and the initiation codon of the affected gene are not located within the RNA hairpin. The wild-type coat protein directs efficient lysogen formation for P22 phages that carry several fragmented RNA operator sites, including one in which the Shine-Dalgarno sequence is positioned 4 nt outside the coat protein binding site. Neither the wild-type R17/MS2 coat protein nor super-repressor mutants induce lysogen formation for a P22 phage encoding an RNA hairpin at a distance of 9 nt from the Shine-Dalgarno sequence, implying that a discrete region of biological repression is defined by the coat protein-RNA hairpin interaction. The assembly of RNA species into capsid structures is not an efficient means whereby the coat protein achieves translational repression of target mRNA transcripts. The R17/MS2 coat protein exerts translational regulation that extends considerably beyond the natural biological RNA operator site structure; however, the coat protein still mediates repression in these constructs by preventing ribosome access to linear sequence determinants of the translational initiation region by the formation of a stable RNA secondary structure. An efficient translational regulatory mechanism in bacteria appears to reside in the ability of proteins to regulate RNA folding states for host cell and phage mRNAs.
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Affiliation(s)
- D E Fouts
- Department of Microbiology and College of Medicine, University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA
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Serganov A, Rak A, Garber M, Reinbolt J, Ehresmann B, Ehresmann C, Grunberg-Manago M, Portier C. Ribosomal protein S15 from Thermus thermophilus--cloning, sequencing, overexpression of the gene and RNA-binding properties of the protein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 246:291-300. [PMID: 9208917 DOI: 10.1111/j.1432-1033.1997.00291.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A 6-kb DNA fragment from an extreme thermophile, Thermus thermophilus, carrying the genes for cytochrome oxidase ba3 subunit I (cbaA) and the ribosomal protein S15 (rpsO) was cloned into Escherichia coli. The gene rpsO was sequenced. The deduced amino acid sequence exhibits 59% identity to the corresponding protein from E. coli. Expression of rpsO in E. coli requires the use of a fully repressed inducible promoter because S15 from T. thermophilus is toxic for E. coli cells. When purified without denaturation from either overproducing E. coli strain or from T. thermophilus ribosomes, the S15 protein is stable and binds a cloned T. thermophilus 16S rRNA fragment (nucleotides 559-753), with low identical dissociation constants (2.5 nM), thus demonstrating that the thermophilic protein folds correctly in a mesophilic bacterium. The rRNA fragment bound corresponds in position and structure to the 16S rRNA fragment of E. coli. A similar high affinity was also found for the binding of S15 from T. thermophilus or E. coli to the corresponding E. coli 16S rRNA fragment, whereas a slightly lower affinity was observed in binding experiments between E. coli S15 and T. thermophilus 16S rRNA fragment. These results suggest that S15 from T. thermophilus recognizes similar determinants in both rRNA fragments. Competition experiments support this conclusion.
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Affiliation(s)
- A Serganov
- Institute of Protein Research, Pushchino, Russia
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Bovia F, Wolff N, Ryser S, Strub K. The SRP9/14 subunit of the human signal recognition particle binds to a variety of Alu-like RNAs and with higher affinity than its mouse homolog. Nucleic Acids Res 1997; 25:318-26. [PMID: 9016560 PMCID: PMC146433 DOI: 10.1093/nar/25.2.318] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The heterodimeric subunit, SRP9/14, of the signal recognition particle (SRP) has previously been found to bind to scAlu and scB1 RNAs in vitro and to exist in large excess over SRP in anthropoid cells. Here we show that human and mouse SRP9/14 bind with high affinities to other Alu-like RNAs of different evolutionary ages including the neuron-specific BC200 RNA. The relative dissociation constants of the different RNA-protein complexes are inversely proportional to the evolutionary distance between the Alu RNA species and 7SL RNA. In addition, the human SRP9/14 binds with higher affinity than mouse SRP9/14 to all RNAs analyzed and this difference is not explained by the additional C-terminal domain present in the anthropoid SRP14. The conservation of high affinity interactions between SRP9/14 and Alu-like RNAs strongly indicates that these Alu-like RNPs exist in vivo and that they have cellular functions. The observation that human SRP9/14 binds better than its mouse counterpart to distantly related Alu RNAs, such as recently transposed elements, suggests that the anthropoid-specific excess of SRP9/14 may have a role in controlling Alu amplification rather than in compensating a defect in SRP assembly and functions.
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Affiliation(s)
- F Bovia
- Département de Biologie Cellulaire, Université de Genève, Sciences III, CH-1211 Geneva 4, Switzerland
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