1
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Kersten C, Archambault P, Köhler LP. Assessment of Nucleobase Protomeric and Tautomeric States in Nucleic Acid Structures for Interaction Analysis and Structure-Based Ligand Design. J Chem Inf Model 2024; 64:4485-4499. [PMID: 38766733 DOI: 10.1021/acs.jcim.4c00520] [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: 05/22/2024]
Abstract
With increasing interest in RNA as a therapeutic and a potential target, the role of RNA structures has become more important. Even slight changes in nucleobases, such as modifications or protomeric and tautomeric states, can have a large impact on RNA structure and function, while local environments in turn affect protonation and tautomerization. In this work, the application of empirical tools for pKa and tautomer prediction for RNA modifications was elucidated and compared with ab initio quantum mechanics (QM) methods and expanded toward macromolecular RNA structures, where QM is no longer feasible. In this regard, the Protonate3D functionality within the molecular operating environment (MOE) was expanded for nucleobase protomer and tautomer predictions and applied to reported examples of altered protonation states depending on the local environment. Overall, observations of nonstandard protomers and tautomers were well reproduced, including structural C+G:C(A) and A+GG motifs, several mismatches, and protonation of adenosine or cytidine as the general acid in nucleolytic ribozymes. Special cases, such as cobalt hexamine-soaked complexes or the deprotonation of guanosine as the general base in nucleolytic ribozymes, proved to be challenging. The collected set of examples shall serve as a starting point for the development of further RNA protonation prediction tools, while the presented Protonate3D implementation already delivers reasonable protonation predictions for RNA and DNA macromolecules. For cases where higher accuracy is needed, like following catalytic pathways of ribozymes, incorporation of QM-based methods can build upon the Protonate3D-generated starting structures. Likewise, this protonation prediction can be used for structure-based RNA-ligand design approaches.
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Affiliation(s)
- Christian Kersten
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University, Staudingerweg 5, 55128 Mainz, Germany
- Institute for Quantitative and Computational Biosciences, Johannes Gutenberg-University, BioZentrum I, Hanns-Dieter-Hüsch.Weg 15, 55128 Mainz, Germany
| | - Philippe Archambault
- Chemical Computing Group, 910-1010 Sherbrooke W., Montreal, Quebec, Canada H3A 2R7
| | - Luca P Köhler
- Institute of Pharmaceutical and Biomedical Sciences, Johannes Gutenberg-University, Staudingerweg 5, 55128 Mainz, Germany
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2
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Bessi I, Stiller C, Schroeder T, Schäd B, Grüne M, Dietzsch J, Höbartner C. The Tautomeric State of N4-Hydroxycytidine within Base-Paired RNA. ACS CENTRAL SCIENCE 2024; 10:1084-1093. [PMID: 38799674 PMCID: PMC11117714 DOI: 10.1021/acscentsci.4c00146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/12/2024] [Accepted: 04/12/2024] [Indexed: 05/29/2024]
Abstract
Antiviral nucleoside analogues (e.g., Molnupiravir, Remdesivir) played key roles in the treatment of COVID-19 by targeting SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). The nucleoside of Molnupiravir, N4-hydroxycytidine (NHC), exists in two tautomeric forms that pair either with G or A within the RdRp active site, causing an accumulation of viral RNA mutations during replication. Detailed insights into the tautomeric states within base pairs and the structural influence of NHC in RNA are still missing. In this study, we investigate the properties of NHC:G and NHC:A base pairs in a self-complementary RNA duplex by UV thermal melting and NMR spectroscopy using atom-specifically 15N-labeled versions of NHC that were incorporated into oligonucleotides by solid-phase synthesis. NMR analysis revealed that NHC forms a Watson-Crick base pair with G via its amino form, whereas two equally populated conformations were detected for the NHC:A base pair: a weakly hydrogen-bonded Watson-Crick base pair with NHC in the imino form and another conformation with A shifted toward the minor groove. Moreover, we found a variable influence of NHC:G and NHC:A base pairs on the neighboring duplex environment. This study provides conclusive experimental evidence for the existence of two tautomeric forms of NHC within RNA base pairs.
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Affiliation(s)
- Irene Bessi
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Carina Stiller
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Till Schroeder
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Benedikt Schäd
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Matthias Grüne
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Julia Dietzsch
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
| | - Claudia Höbartner
- Institute
of Organic Chemistry, Julius-Maximilians-University
Würzburg, Am Hubland, 97074 Würzburg, Bavaria, Germany
- Center
for Nanosystems Chemistry, Julius-Maximilians-University
Würzburg, 97074 Würzburg, Bavaria, Germany
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3
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Błaszczyk L, Ryczek M, Das B, Mateja-Pluta M, Bejger M, Śliwiak J, Nakatani K, Kiliszek A. Antisense RNA C9orf72 hexanucleotide repeat associated with amyotrophic lateral sclerosis and frontotemporal dementia forms a triplex-like structure and binds small synthetic ligand. Nucleic Acids Res 2024:gkae376. [PMID: 38738637 DOI: 10.1093/nar/gkae376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 04/05/2024] [Accepted: 04/26/2024] [Indexed: 05/14/2024] Open
Abstract
The abnormal expansion of GGGGCC/GGCCCC hexanucleotide repeats (HR) in C9orf72 is associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Structural polymorphisms of HR result in the multifactorial pathomechanism of ALS/FTD. Consequently, many ongoing studies are focused at developing therapies targeting pathogenic HR RNA. One of them involves small molecules blocking sequestration of important proteins, preventing formation of toxic nuclear foci. However, rational design of potential therapeutics is hindered by limited number of structural studies of RNA-ligand complexes. We determined the crystal structure of antisense HR RNA in complex with ANP77 ligand (1.1 Å resolution) and in the free form (0.92 and 1.5 Å resolution). HR RNA folds into a triplex structure composed of four RNA chains. ANP77 interacted with two neighboring single-stranded cytosines to form pseudo-canonical base pairs by adopting sandwich-like conformation and adjusting the position of its naphthyridine units to the helical twist of the RNA. In the unliganded structure, the cytosines formed a peculiar triplex i-motif, assembled by trans C•C+ pair and a third cytosine located at the Hoogsteen edge of the C•C+ pair. These results extend our knowledge of the structural polymorphisms of HR and can be used for rational design of small molecules targeting disease-related RNAs.
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Affiliation(s)
- Leszek Błaszczyk
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
| | - Marcin Ryczek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
| | - Bimolendu Das
- Department of Regulatory Bioorganic Chemistry, SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Japan
| | - Martyna Mateja-Pluta
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
| | - Magdalena Bejger
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
| | - Joanna Śliwiak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
| | - Kazuhiko Nakatani
- Department of Regulatory Bioorganic Chemistry, SANKEN (The Institute of Scientific and Industrial Research), Osaka University, 8-1 Mihogaoka, Ibaraki 567-0047, Japan
| | - Agnieszka Kiliszek
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Z. Noskowskiego 12/14, 61-704, Poland
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Complete genome sequence of a novel polerovirus infecting chickpea (Cicer arietinum L.). Arch Virol 2022; 167:2783-2788. [PMID: 36269414 DOI: 10.1007/s00705-022-05581-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/20/2022] [Indexed: 12/14/2022]
Abstract
The complete genome sequence of a novel polerovirus identified in chickpea (C. arietinum L.) is presented. Its sequence was assembled using small RNA sequencing and assembly (sRSA) and confirmed by RT-PCR, 5' and 3' RACE, and Sanger sequencing. According to the current ICTV sequence demarcation criterion of greater than 10% amino acid (aa) sequence divergence in all gene products when compared to other poleroviruses, the newly identified polerovirus should be classified as a member of a new species, and we propose the name "chickpea leafroll virus" (CpLRV) for this virus. The genome of CpLRV is 5,770 nucleotides (nt) long and is organized into seven open reading frames (ORFs), designated as ORF0, ORF1, ORF2, ORF3a, ORF3, ORF4, and ORF5, which code for putative P0, P1, P1-P2, P3a, P3, P4, and P3-P5 proteins, respectively. The 5' untranslated region (UTR) consists of 27 nt, starting with the conserved sequence 5'-ACAAAA-3', which is typical of poleroviruses, while the 3' UTR consists of 229 nt. Phylogenetic analysis based on the aa sequences of P0, P1, P1-P2, P3, P4, and P3-P5 showed that CpLRV clustered with members of the genus Polerovirus and is closely related to chickpea chlorotic stunt virus (CpCSV) and faba bean polerovirus 1 (FBPV1). Recombination analysis suggested that CpLRV is a recombinant of two unknown viruses that share the highest nucleotide sequence similarity with FBPV1 (76.9% identity) and suakwa aphid-borne yellows virus (SAbYV) (64.8% identity). The putative recombination event was identified in the 5' region of the CpLRV genome, the region that encodes proteins P0, P1, and P1-P2. This is the first report of a polerovirus infecting chickpea in Mexico.
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Zhang J, Fakharzadeh A, Roland C, Sagui C. RNA as a Major-Groove Ligand: RNA-RNA and RNA-DNA Triplexes Formed by GAA and UUC or TTC Sequences. ACS OMEGA 2022; 7:38728-38743. [PMID: 36340174 PMCID: PMC9631886 DOI: 10.1021/acsomega.2c04358] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
Friedreich's ataxia is associated with noncanonical nucleic acid structures that emerge when GAA:TTC repeats in the first intron of the FXN gene expand beyond a critical number of repeats. Specifically, the noncanonical repeats are associated with both triplexes and R-loops. Here, we present an in silico investigation of all possible triplexes that form by attaching a third RNA strand to an RNA:RNA or DNA:DNA duplex, complementing previous DNA-based triplex studies. For both new triplexes results are similar. For a pyridimine UUC+ third strand, the parallel orientation is stable while its antiparallel counterpart is unstable. For a neutral GAA third strand, the parallel conformation is stable. A protonated GA+A third strand is stable in both parallel and antiparallel orientations. We have also investigated Na+ and Mg2+ ion distributions around the triplexes. The presence of Mg2+ ions helps stabilize neutral, antiparallel GAA triplexes. These results (along with previous DNA-based studies) allow for the emergence of a complete picture of the stability and structural characteristics of triplexes based on the GAA and TTC/UUC sequences, thereby contributing to the field of trinucleotide repeats and the associated unusual structures that trigger expansion.
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6
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RNA-As-Graphs Motif Atlas—Dual Graph Library of RNA Modules and Viral Frameshifting-Element Applications. Int J Mol Sci 2022; 23:ijms23169249. [PMID: 36012512 PMCID: PMC9408923 DOI: 10.3390/ijms23169249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/13/2022] [Accepted: 08/14/2022] [Indexed: 11/25/2022] Open
Abstract
RNA motif classification is important for understanding structure/function connections and building phylogenetic relationships. Using our coarse-grained RNA-As-Graphs (RAG) representations, we identify recurrent dual graph motifs in experimentally solved RNA structures based on an improved search algorithm that finds and ranks independent RNA substructures. Our expanded list of 183 existing dual graph motifs reveals five common motifs found in transfer RNA, riboswitch, and ribosomal 5S RNA components. Moreover, we identify three motifs for available viral frameshifting RNA elements, suggesting a correlation between viral structural complexity and frameshifting efficiency. We further partition the RNA substructures into 1844 distinct submotifs, with pseudoknots and junctions retained intact. Common modules are internal loops and three-way junctions, and three submotifs are associated with riboswitches that bind nucleotides, ions, and signaling molecules. Together, our library of existing RNA motifs and submotifs adds to the growing universe of RNA modules, and provides a resource of structures and substructures for novel RNA design.
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Umar M, Tegg RS, Farooq T, Thangavel T, Wilson CR. Abundance of Poleroviruses within Tasmanian Pea Crops and Surrounding Weeds, and the Genetic Diversity of TuYV Isolates Found. Viruses 2022; 14:1690. [PMID: 36016314 PMCID: PMC9416036 DOI: 10.3390/v14081690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/28/2022] [Accepted: 07/28/2022] [Indexed: 01/08/2023] Open
Abstract
The genus Polerovirus contains positive-sense, single-stranded RNA plant viruses that cause significant disease in many agricultural crops, including vegetable legumes. This study aimed to identify and determine the abundance of Polerovirus species present within Tasmanian pea crops and surrounding weeds that may act as virus reservoirs. We further sought to examine the genetic diversity of TuYV, the most commonly occurring polerovirus identified. Pea and weed samples were collected during 2019-2020 between October and January from thirty-four sites across three different regions (far northwest, north, and midlands) of Tasmania and tested by RT-PCR assay, with selected samples subject to next-generation sequencing. Results revealed that the presence of polerovirus infection and the prevalence of TuYV in both weeds and pea crops varied across the three Tasmanian cropping regions, with TuYV infection levels in pea crops ranging between 0 and 27.5% of tested plants. Overall, two species members from each genus, Polerovirus and Potyvirus, one member from each of Luteovirus, Potexvirus, and Carlavirus, and an unclassified virus from the family Partitiviridae were also found as a result of NGS data analysis. Analysis of gene sequences of the P0 and P3 genes of Tasmanian TuYV isolates revealed substantial genetic diversity within the collection, with a few isolates appearing more closely aligned with BrYV isolates. Questions remain around the differentiation of TuYV and BrYV species. Phylogenetic inconsistency in the P0 and P3 ORFs supports the concept that recombination may have played a role in TuYV evolution in Tasmania. Results of the evolutionary analysis showed that the selection pressure was higher in the P0 gene than in the P3 gene, and the majority of the codons for each gene are evolving under purifying selection. Future full genome-based analyses of the genetic variations will expand our understanding of the evolutionary patterns existing among TuYV populations in Tasmania.
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Affiliation(s)
- Muhammad Umar
- New Town Research Laboratories, Tasmanian Institute of Agriculture, University of Tasmania, 13 St. Johns Avenue, New Town, Hobart, TAS 7008, Australia; (M.U.); (R.S.T.); (T.T.)
| | - Robert S. Tegg
- New Town Research Laboratories, Tasmanian Institute of Agriculture, University of Tasmania, 13 St. Johns Avenue, New Town, Hobart, TAS 7008, Australia; (M.U.); (R.S.T.); (T.T.)
| | - Tahir Farooq
- Guangdong Provincial Key Laboratory of High Technology for Plant Protection, Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China;
| | - Tamilarasan Thangavel
- New Town Research Laboratories, Tasmanian Institute of Agriculture, University of Tasmania, 13 St. Johns Avenue, New Town, Hobart, TAS 7008, Australia; (M.U.); (R.S.T.); (T.T.)
- Department of Agriculture and Fisheries (Queensland), Bundaberg Research Facility, 49 Ashfield Road, Bundaberg, QLD 4670, Australia
| | - Calum R. Wilson
- New Town Research Laboratories, Tasmanian Institute of Agriculture, University of Tasmania, 13 St. Johns Avenue, New Town, Hobart, TAS 7008, Australia; (M.U.); (R.S.T.); (T.T.)
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8
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Andrikos C, Makris E, Kolaitis A, Rassias G, Pavlatos C, Tsanakas P. Knotify: An Efficient Parallel Platform for RNA Pseudoknot Prediction Using Syntactic Pattern Recognition. Methods Protoc 2022; 5:mps5010014. [PMID: 35200530 PMCID: PMC8876629 DOI: 10.3390/mps5010014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/27/2022] [Accepted: 01/30/2022] [Indexed: 11/16/2022] Open
Abstract
Obtaining valuable clues for noncoding RNA (ribonucleic acid) subsequences remains a significant challenge, acknowledging that most of the human genome transcribes into noncoding RNA parts related to unknown biological operations. Capturing these clues relies on accurate “base pairing” prediction, also known as “RNA secondary structure prediction”. As COVID-19 is considered a severe global threat, the single-stranded SARS-CoV-2 virus reveals the importance of establishing an efficient RNA analysis toolkit. This work aimed to contribute to that by introducing a novel system committed to predicting RNA secondary structure patterns (i.e., RNA’s pseudoknots) that leverage syntactic pattern-recognition strategies. Having focused on the pseudoknot predictions, we formalized the secondary structure prediction of the RNA to be primarily a parsing and, secondly, an optimization problem. The proposed methodology addresses the problem of predicting pseudoknots of the first order (H-type). We introduce a context-free grammar (CFG) that affords enough expression power to recognize potential pseudoknot pattern. In addition, an alternative methodology of detecting possible pseudoknots is also implemented as well, using a brute-force algorithm. Any input sequence may highlight multiple potential folding patterns requiring a strict methodology to determine the single biologically realistic one. We conscripted a novel heuristic over the widely accepted notion of free-energy minimization to tackle such ambiguity in a performant way by utilizing each pattern’s context to unveil the most prominent pseudoknot pattern. The overall process features polynomial-time complexity, while its parallel implementation enhances the end performance, as proportional to the deployed hardware. The proposed methodology does succeed in predicting the core stems of any RNA pseudoknot of the test dataset by performing a 76.4% recall ratio. The methodology achieved a F1-score equal to 0.774 and MCC equal 0.543 in discovering all the stems of an RNA sequence, outperforming the particular task. Measurements were taken using a dataset of 262 RNA sequences establishing a performance speed of 1.31, 3.45, and 7.76 compared to three well-known platforms. The implementation source code is publicly available under knotify github repo.
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Affiliation(s)
- Christos Andrikos
- School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., 15780 Athens, Greece; (C.A.); (E.M.); (A.K.); (G.R.); (P.T.)
| | - Evangelos Makris
- School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., 15780 Athens, Greece; (C.A.); (E.M.); (A.K.); (G.R.); (P.T.)
| | - Angelos Kolaitis
- School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., 15780 Athens, Greece; (C.A.); (E.M.); (A.K.); (G.R.); (P.T.)
| | - Georgios Rassias
- School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., 15780 Athens, Greece; (C.A.); (E.M.); (A.K.); (G.R.); (P.T.)
| | - Christos Pavlatos
- Hellenic Air Force Academy, Dekelia Air Base, Acharnes, 13671 Athens, Greece
- Correspondence: ; Tel.: +30-210-7722541
| | - Panayiotis Tsanakas
- School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytechniou St., 15780 Athens, Greece; (C.A.); (E.M.); (A.K.); (G.R.); (P.T.)
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Identifying Inhibitors of −1 Programmed Ribosomal Frameshifting in a Broad Spectrum of Coronaviruses. Viruses 2022; 14:v14020177. [PMID: 35215770 PMCID: PMC8876150 DOI: 10.3390/v14020177] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/30/2021] [Accepted: 01/10/2022] [Indexed: 02/06/2023] Open
Abstract
Recurrent outbreaks of novel zoonotic coronavirus (CoV) diseases in recent years have highlighted the importance of developing therapeutics with broad-spectrum activity against CoVs. Because all CoVs use −1 programmed ribosomal frameshifting (−1 PRF) to control expression of key viral proteins, the frameshift signal in viral mRNA that stimulates −1 PRF provides a promising potential target for such therapeutics. To test the viability of this strategy, we explored whether small-molecule inhibitors of −1 PRF in SARS-CoV-2 also inhibited −1 PRF in a range of bat CoVs—the most likely source of future zoonoses. Six inhibitors identified in new and previous screens against SARS-CoV-2 were evaluated against the frameshift signals from a panel of representative bat CoVs as well as MERS-CoV. Some drugs had strong activity against subsets of these CoV-derived frameshift signals, while having limited to no effect on −1 PRF caused by frameshift signals from other viruses used as negative controls. Notably, the serine protease inhibitor nafamostat suppressed −1 PRF significantly for multiple CoV-derived frameshift signals. These results suggest it is possible to find small-molecule ligands that inhibit −1 PRF specifically in a broad spectrum of CoVs, establishing frameshift signals as a viable target for developing pan-coronaviral therapeutics.
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10
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LaTourrette K, Holste NM, Garcia-Ruiz H. Polerovirus genomic variation. Virus Evol 2021; 7:veab102. [PMID: 35299789 PMCID: PMC8923251 DOI: 10.1093/ve/veab102] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 11/21/2021] [Accepted: 12/03/2021] [Indexed: 01/01/2023] Open
Abstract
Abstract
The polerovirus (family Solemoviridae, genus Polerovirus) genome consists of single-, positive-strand RNA organized in overlapping open reading frames (ORFs) that, in addition to others, code for protein 0 (P0, a gene silencing suppressor), a coat protein (CP, ORF3), and a read-through domain (ORF5) that is fused to the CP to form a CP-read-through (RT) protein. The genus Polerovirus contains twenty-six virus species that infect a wide variety of plants from cereals to cucurbits, to peppers. Poleroviruses are transmitted by a wide range of aphid species in the genera Rhopalosiphum, Stiobion, Aphis, and Myzus. Aphid transmission is mediated both by the CP and by the CP-RT. In viruses, mutational robustness and structural flexibility are necessary for maintaining functionality in genetically diverse sets of host plants and vectors. Under this scenario, within a virus genome, mutations preferentially accumulate in areas that are determinants of host adaptation or vector transmission. In this study, we profiled genomic variation in poleroviruses. Consistent with their multifunctional nature, single-nucleotide variation and selection analyses showed that ORFs coding for P0 and the read-through domain within the CP-RT are the most variable and contain the highest frequency of sites under positive selection. An order/disorder analysis showed that protein P0 is not disordered. In contrast, proteins CP-RT and virus protein genome-linked (VPg) contain areas of disorder. Disorder is a property of multifunctional proteins with multiple interaction partners. The results described here suggest that using contrasting mechanisms, P0, VPg, and CP-RT mediate adaptation to host plants and to vectors and are contributors to the broad host and vector range of poleroviruses. Profiling genetic variation across the polerovirus genome has practical applications in diagnostics, breeding for resistance, and identification of susceptibility genes and contributes to our understanding of virus interactions with their host, vectors, and environment.
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Affiliation(s)
- Katherine LaTourrette
- Nebraska Center for Virology, University of Nebraska-Lincoln, 4240 Fair Street, Lincoln, NE 68583, USA
- Department of Plant Pathology, University of Nebraska-Lincoln, 406 Plant Science Hall, Lincoln, NE 68583, USA
- Complex Biosystems Interdisciplinary Life Sciences Program, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, 2200 Vine Street, Lincoln, NE 68583, USA
| | - Natalie M Holste
- Nebraska Center for Virology, University of Nebraska-Lincoln, 4240 Fair Street, Lincoln, NE 68583, USA
- Department of Plant Pathology, University of Nebraska-Lincoln, 406 Plant Science Hall, Lincoln, NE 68583, USA
| | - Hernan Garcia-Ruiz
- Nebraska Center for Virology, University of Nebraska-Lincoln, 4240 Fair Street, Lincoln, NE 68583, USA
- Department of Plant Pathology, University of Nebraska-Lincoln, 406 Plant Science Hall, Lincoln, NE 68583, USA
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11
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Halma MTJ, Ritchie DB, Woodside MT. Conformational Shannon Entropy of mRNA Structures from Force Spectroscopy Measurements Predicts the Efficiency of -1 Programmed Ribosomal Frameshift Stimulation. PHYSICAL REVIEW LETTERS 2021; 126:038102. [PMID: 33543960 DOI: 10.1103/physrevlett.126.038102] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Accepted: 12/15/2020] [Indexed: 06/12/2023]
Abstract
-1 programmed ribosomal frameshifting (-1 PRF) is stimulated by structures in messenger RNA (mRNA), but the factors determining -1 PRF efficiency are unclear. We show that -1 PRF efficiency varies directly with the conformational heterogeneity of the stimulatory structure, quantified as the Shannon entropy of the state occupancy, for a panel of stimulatory structures with efficiencies from 2% to 80%. The correlation is force dependent and vanishes at forces above those applied by the ribosome. These results support the hypothesis that heterogeneous conformational dynamics are a key factor in stimulating -1 PRF.
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Affiliation(s)
- Matthew T J Halma
- Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Dustin B Ritchie
- Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Michael T Woodside
- Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
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12
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Yang L, Toh DFK, Krishna MS, Zhong Z, Liu Y, Wang S, Gong Y, Chen G. Tertiary Base Triple Formation in the SRV-1 Frameshifting Pseudoknot Stabilizes Secondary Structure Components. Biochemistry 2020; 59:4429-4438. [PMID: 33166472 DOI: 10.1021/acs.biochem.0c00611] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Minor-groove base triples formed between stem 1 and loop 2 of the simian retrovirus type 1 (SRV-1) mRNA frameshifting pseudoknot are essential in stimulating -1 ribosomal frameshifting. How tertiary base triple formation affects the local stabilities of secondary structures (stem 1 and stem 2) and thus ribosomal frameshifting efficiency is not well understood. We made a short peptide nucleic acid (PNA) that is expected to invade stem 1 of the SRV-1 pseudoknot by PNA-RNA duplex formation to mimic the stem 1 unwinding process by a translating ribosome. In addition, we used a PNA for invading stem 2 in the SRV-1 pseudoknot. Our nondenaturing polyacrylamide gel electrophoresis data for the binding of PNA to the SRV-1 pseudoknot and mutants reveal that mutations in loop 2 disrupting base triple formation between loop 2 and stem 1 in the SRV-1 pseudoknot result in enhanced invasion by both PNAs. Our data suggest that tertiary stem 1-loop 2 base triple interactions in the SRV-1 pseudoknot can stabilize both of the secondary structural components, stem 1 and stem 2. Stem 2 stability is thus coupled to the structural stability of stem 1-loop 2 base triples, mediated through a long-range effect. The apparent dissociation constants of both PNAs are positively correlated with the pseudoknot mechanical stabilities and frameshifting efficiencies. The relatively simple PNA local invasion experiment may be used to characterize the energetic contribution of tertiary interactions and ligand binding in many other RNA and DNA structures.
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Affiliation(s)
- Lixia Yang
- School of Life Science and Technology, University of Electronic Science and Technology of China, No. 4, Section 2, North Jianshe Road, Chengdu, Sichuan 610054, P. R. China.,School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen (CUHK-Shenzhen), No. 2001 Longxiang Boulevard, Longgang District, Shenzhen, Guangdong 518172, P. R. China.,Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Desiree-Faye Kaixin Toh
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Manchugondanahalli S Krishna
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
| | - Zhensheng Zhong
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, P. R. China
| | - Yiyao Liu
- School of Life Science and Technology, University of Electronic Science and Technology of China, No. 4, Section 2, North Jianshe Road, Chengdu, Sichuan 610054, P. R. China
| | - Shaomeng Wang
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, No. 4, Section 2, North Jianshe Road, Chengdu, Sichuan 610054, P. R. China
| | - Yubin Gong
- School of Electronic Science and Engineering, University of Electronic Science and Technology of China, No. 4, Section 2, North Jianshe Road, Chengdu, Sichuan 610054, P. R. China
| | - Gang Chen
- School of Life and Health Sciences, The Chinese University of Hong Kong, Shenzhen (CUHK-Shenzhen), No. 2001 Longxiang Boulevard, Longgang District, Shenzhen, Guangdong 518172, P. R. China.,Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
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13
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Schroeder GM, Dutta D, Cavender CE, Jenkins J, Pritchett EM, Baker CD, Ashton JM, Mathews DH, Wedekind JE. Analysis of a preQ1-I riboswitch in effector-free and bound states reveals a metabolite-programmed nucleobase-stacking spine that controls gene regulation. Nucleic Acids Res 2020; 48:8146-8164. [PMID: 32597951 PMCID: PMC7641330 DOI: 10.1093/nar/gkaa546] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/13/2020] [Accepted: 06/16/2020] [Indexed: 01/20/2023] Open
Abstract
Riboswitches are structured RNA motifs that recognize metabolites to alter the conformations of downstream sequences, leading to gene regulation. To investigate this molecular framework, we determined crystal structures of a preQ1-I riboswitch in effector-free and bound states at 2.00 Å and 2.65 Å-resolution. Both pseudoknots exhibited the elusive L2 loop, which displayed distinct conformations. Conversely, the Shine-Dalgarno sequence (SDS) in the S2 helix of each structure remained unbroken. The expectation that the effector-free state should expose the SDS prompted us to conduct solution experiments to delineate environmental changes to specific nucleobases in response to preQ1. We then used nudged elastic band computational methods to derive conformational-change pathways linking the crystallographically-determined effector-free and bound-state structures. Pathways featured: (i) unstacking and unpairing of L2 and S2 nucleobases without preQ1-exposing the SDS for translation and (ii) stacking and pairing L2 and S2 nucleobases with preQ1-sequestering the SDS. Our results reveal how preQ1 binding reorganizes L2 into a nucleobase-stacking spine that sequesters the SDS, linking effector recognition to biological function. The generality of stacking spines as conduits for effector-dependent, interdomain communication is discussed in light of their existence in adenine riboswitches, as well as the turnip yellow mosaic virus ribosome sensor.
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Affiliation(s)
- Griffin M Schroeder
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Debapratim Dutta
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Chapin E Cavender
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Jermaine L Jenkins
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Elizabeth M Pritchett
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Cameron D Baker
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - John M Ashton
- Genomics Research Center, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - David H Mathews
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
| | - Joseph E Wedekind
- Department of Biochemistry & Biophysics, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
- Center for RNA Biology, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642, USA
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14
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Rangadurai A, Kremser J, Shi H, Kreutz C, Al-Hashimi HM. Direct evidence for (G)O6···H 2-N4(C) + hydrogen bonding in transient G(syn)-C + and G(syn)-m 5C + Hoogsteen base pairs in duplex DNA from cytosine amino nitrogen off-resonance R 1ρ relaxation dispersion measurements. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 308:106589. [PMID: 31539864 PMCID: PMC6933314 DOI: 10.1016/j.jmr.2019.106589] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/30/2019] [Accepted: 09/02/2019] [Indexed: 06/10/2023]
Abstract
NMR relaxation dispersion studies have shown that Watson-Crick G-C and A-T base pairs in duplex DNA exist in dynamic equilibrium with their Hoogsteen counterparts. Hoogsteen base pairs form through concurrent rotation of the purine base about the glycosidic bond from an anti to a syn conformation and constriction of the C1'-C1' distance across the base pair by ∼2 Å to allow Hoogsteen type hydrogen bonding. Owing to their unique structure, Hoogsteen base pairs can play important roles in DNA recognition, the accommodation, recognition, and repair of DNA damage, and in DNA replication. NMR relaxation dispersion experiments targeting imino nitrogen and protonated base and sugar carbons have provided insights into many structural features of transient Hoogsteen base pairs, including one of two predicted hydrogen bonds involving (G)N7···H-N3(C)+ and (A)N7···H-N3(T). Here, through measurement of cytosine amino (N4) R1ρ relaxation dispersion, we provide direct evidence for the second (G)O6···H2-N4(C)+ hydrogen bond in G(syn)-C+ transient Hoogsteen base pairs. The utility of cytosine N4 R1ρ relaxation dispersion as a new sensitive probe of transient Hoogsteen base pairs, and cytosine dynamics in general, is further demonstrated by measuring G(syn)-C+ Hoogsteen exchange near neutral pH and in the context of the naturally occurring DNA modification 5-methyl cytosine (m5C), in DNA samples prepared using chemical synthesis and a 15N labeled m5C phosphoramidite.
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Affiliation(s)
- Atul Rangadurai
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Johannes Kremser
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Honglue Shi
- Department of Chemistry, Duke University, Durham, NC 27710, USA
| | - Christoph Kreutz
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria.
| | - Hashim M Al-Hashimi
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA; Department of Chemistry, Duke University, Durham, NC 27710, USA.
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15
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Wu B, Zhang H, Sun R, Peng S, Cooperman BS, Goldman YE, Chen C. Translocation kinetics and structural dynamics of ribosomes are modulated by the conformational plasticity of downstream pseudoknots. Nucleic Acids Res 2019; 46:9736-9748. [PMID: 30011005 PMCID: PMC6182138 DOI: 10.1093/nar/gky636] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 07/03/2018] [Indexed: 11/21/2022] Open
Abstract
Downstream stable mRNA secondary structures can stall elongating ribosomes by impeding the concerted movements of tRNAs and mRNA on the ribosome during translocation. The addition of a downstream mRNA structure, such as a stem-loop or a pseudoknot, is essential to induce -1 programmed ribosomal frameshifting (-1 PRF). Interestingly, previous studies revealed that -1 PRF efficiencies correlate with conformational plasticity of pseudoknots, defined as their propensity to form incompletely folded structures, rather than with the mechanical properties of pseudoknots. To elucidate the detailed molecular mechanisms of translocation and -1 PRF, we applied several smFRET assays to systematically examine how translocation rates and conformational dynamics of ribosomes were affected by different pseudoknots. Our results show that initial pseudoknot-unwinding significantly inhibits late-stage translocation and modulates conformational dynamics of ribosomal post-translocation complexes. The effects of pseudoknots on the structural dynamics of ribosomes strongly correlate with their abilities to induce -1 PRF. Our results lead us to propose a kinetic scheme for translocation which includes an initial power-stroke step and a following thermal-ratcheting step. This scheme provides mechanistic insights on how selective modulation of late-stage translocation by pseudoknots affects -1 PRF. Overall our findings advance current understanding of translocation and ribosome-induced mRNA structure unwinding.
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Affiliation(s)
- Bo Wu
- School of Life Sciences; Tsinghua-Peking Joint Center for Life Sciences; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, China
| | - Haibo Zhang
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA.,Spark Therapeutics, 3737 Market Street, Philadelphia, PA, 19104, USA
| | - Ruirui Sun
- School of Life Sciences; Tsinghua-Peking Joint Center for Life Sciences; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, China
| | - Sijia Peng
- School of Life Sciences; Tsinghua-Peking Joint Center for Life Sciences; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, China
| | - Barry S Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yale E Goldman
- Pennsylvania Muscle Institute, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Chunlai Chen
- School of Life Sciences; Tsinghua-Peking Joint Center for Life Sciences; Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing 100084, China
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16
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Rangadurai A, Szymaski ES, Kimsey IJ, Shi H, Al-Hashimi HM. Characterizing micro-to-millisecond chemical exchange in nucleic acids using off-resonance R 1ρ relaxation dispersion. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 112-113:55-102. [PMID: 31481159 PMCID: PMC6727989 DOI: 10.1016/j.pnmrs.2019.05.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 05/10/2023]
Abstract
This review describes off-resonance R1ρ relaxation dispersion NMR methods for characterizing microsecond-to-millisecond chemical exchange in uniformly 13C/15N labeled nucleic acids in solution. The review opens with a historical account of key developments that formed the basis for modern R1ρ techniques used to study chemical exchange in biomolecules. A vector model is then used to describe the R1ρ relaxation dispersion experiment, and how the exchange contribution to relaxation varies with the amplitude and frequency offset of an applied spin-locking field, as well as the population, exchange rate, and differences in chemical shifts of two exchanging species. Mathematical treatment of chemical exchange based on the Bloch-McConnell equations is then presented and used to examine relaxation dispersion profiles for more complex exchange scenarios including three-state exchange. Pulse sequences that employ selective Hartmann-Hahn cross-polarization transfers to excite individual 13C or 15N spins are then described for measuring off-resonance R1ρ(13C) and R1ρ(15N) in uniformly 13C/15N labeled DNA and RNA samples prepared using commercially available 13C/15N labeled nucleotide triphosphates. Approaches for analyzing R1ρ data measured at a single static magnetic field to extract a full set of exchange parameters are then presented that rely on numerical integration of the Bloch-McConnell equations or the use of algebraic expressions. Methods for determining structures of nucleic acid excited states are then reviewed that rely on mutations and chemical modifications to bias conformational equilibria, as well as structure-based approaches to calculate chemical shifts. Applications of the methodology to the study of DNA and RNA conformational dynamics are reviewed and the biological significance of the exchange processes is briefly discussed.
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Affiliation(s)
- Atul Rangadurai
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Eric S Szymaski
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA
| | - Isaac J Kimsey
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA; Nymirum, 4324 S. Alston Avenue, Durham, NC 27713, USA(1)
| | - Honglue Shi
- Department of Chemistry, Duke University, Durham, NC 27710, USA
| | - Hashim M Al-Hashimi
- Department of Biochemistry, Duke University School of Medicine, Durham, NC 27710, USA; Department of Chemistry, Duke University, Durham, NC 27710, USA.
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17
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Keller H, Weickhmann AK, Bock T, Wöhnert J. Adenine protonation enables cyclic-di-GMP binding to cyclic-GAMP sensing riboswitches. RNA (NEW YORK, N.Y.) 2018; 24:1390-1402. [PMID: 30006500 PMCID: PMC6140456 DOI: 10.1261/rna.067470.118] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Accepted: 07/09/2018] [Indexed: 05/22/2023]
Abstract
In certain structural or functional contexts, RNA structures can contain protonated nucleotides. However, a direct role for stably protonated nucleotides in ligand binding and ligand recognition has not yet been demonstrated unambiguously. Previous X-ray structures of c-GAMP binding riboswitch aptamer domains in complex with their near-cognate ligand c-di-GMP suggest that an adenine of the riboswitch either forms two hydrogen bonds to a G nucleotide of the ligand in the unusual enol tautomeric form or that the adenine in its N1 protonated form binds the G nucleotide of the ligand in its canonical keto tautomeric state. By using NMR spectroscopy we demonstrate that the c-GAMP riboswitches bind c-di-GMP using a stably protonated adenine in the ligand binding pocket. Thereby, we provide novel insights into the putative biological functions of protonated nucleotides in RNA, which in this case influence the ligand selectivity in a riboswitch.
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Affiliation(s)
- Heiko Keller
- Institute for Molecular Biosciences and Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - A Katharina Weickhmann
- Institute for Molecular Biosciences and Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Thomas Bock
- Institute for Molecular Biosciences and Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
| | - Jens Wöhnert
- Institute for Molecular Biosciences and Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt, 60438 Frankfurt am Main, Germany
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18
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Zhang P, Liu Y, Liu W, Cao M, Massart S, Wang X. Identification, Characterization and Full-Length Sequence Analysis of a Novel Polerovirus Associated with Wheat Leaf Yellowing Disease. Front Microbiol 2017; 8:1689. [PMID: 28932215 PMCID: PMC5592212 DOI: 10.3389/fmicb.2017.01689] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/21/2017] [Indexed: 11/13/2022] Open
Abstract
To identify the pathogens responsible for leaf yellowing symptoms on wheat samples collected from Jinan, China, we tested for the presence of three known barley/wheat yellow dwarf viruses (BYDV-GAV, -PAV, WYDV-GPV) (most likely pathogens) using RT-PCR. A sample that tested negative for the three viruses was selected for small RNA sequencing. Twenty-five million sequences were generated, among which 5% were of viral origin. A novel polerovirus was discovered and temporarily named wheat leaf yellowing-associated virus (WLYaV). The full genome of WLYaV corresponds to 5,772 nucleotides (nt), with six AUG-initiated open reading frames, one non-AUG-initiated open reading frame, and three untranslated regions, showing typical features of the family Luteoviridae. Sequence comparison and phylogenetic analyses suggested that WLYaV had the closest relationship with sugarcane yellow leaf virus (ScYLV), but the identities of full genomic nucleotides and deduced amino acid sequence of coat protein (CP) were 64.9 and 86.2%, respectively, below the species demarcation thresholds (90%) in the family Luteoviridae. Furthermore, agroinoculation of Nicotiana benthamiana leaves with a cDNA clone of WLYaV caused yellowing symptoms on the plant. Our study adds a new polerovirus that is associated with wheat leaf yellowing disease, which would help to identify and control pathogens of wheat.
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Affiliation(s)
- Peipei Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing, China
- Laboratory of Phytopathology, University of Liège, Gembloux Agro-Bio TechGembloux, Belgium
| | - Yan Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing, China
| | - Wenwen Liu
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing, China
| | - Mengji Cao
- National Citrus Engineering Research Center, Citrus Research Institute, Southwest UniversityChongqing, China
| | - Sebastien Massart
- Laboratory of Phytopathology, University of Liège, Gembloux Agro-Bio TechGembloux, Belgium
| | - Xifeng Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural SciencesBeijing, China
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19
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Atkins JF, Loughran G, Bhatt PR, Firth AE, Baranov PV. Ribosomal frameshifting and transcriptional slippage: From genetic steganography and cryptography to adventitious use. Nucleic Acids Res 2016; 44:7007-78. [PMID: 27436286 PMCID: PMC5009743 DOI: 10.1093/nar/gkw530] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 05/26/2016] [Indexed: 12/15/2022] Open
Abstract
Genetic decoding is not ‘frozen’ as was earlier thought, but dynamic. One facet of this is frameshifting that often results in synthesis of a C-terminal region encoded by a new frame. Ribosomal frameshifting is utilized for the synthesis of additional products, for regulatory purposes and for translational ‘correction’ of problem or ‘savior’ indels. Utilization for synthesis of additional products occurs prominently in the decoding of mobile chromosomal element and viral genomes. One class of regulatory frameshifting of stable chromosomal genes governs cellular polyamine levels from yeasts to humans. In many cases of productively utilized frameshifting, the proportion of ribosomes that frameshift at a shift-prone site is enhanced by specific nascent peptide or mRNA context features. Such mRNA signals, which can be 5′ or 3′ of the shift site or both, can act by pairing with ribosomal RNA or as stem loops or pseudoknots even with one component being 4 kb 3′ from the shift site. Transcriptional realignment at slippage-prone sequences also generates productively utilized products encoded trans-frame with respect to the genomic sequence. This too can be enhanced by nucleic acid structure. Together with dynamic codon redefinition, frameshifting is one of the forms of recoding that enriches gene expression.
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Affiliation(s)
- John F Atkins
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland School of Microbiology, University College Cork, Cork, Ireland Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pramod R Bhatt
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Andrew E Firth
- Division of Virology, Department of Pathology, University of Cambridge, Hills Road, Cambridge CB2 0QQ, UK
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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20
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Chen JL, Bellaousov S, Tubbs JD, Kennedy SD, Lopez MJ, Mathews DH, Turner DH. Nuclear Magnetic Resonance-Assisted Prediction of Secondary Structure for RNA: Incorporation of Direction-Dependent Chemical Shift Constraints. Biochemistry 2015; 54:6769-82. [PMID: 26451676 PMCID: PMC4666457 DOI: 10.1021/acs.biochem.5b00833] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Knowledge
of RNA
structure is necessary to determine structure–function relationships
and to facilitate design of potential therapeutics.
RNA secondary structure prediction can be improved by applying constraints
from nuclear magnetic resonance (NMR) experiments to a dynamic programming
algorithm. Imino proton walks from NOESY spectra reveal double-stranded
regions. Chemical shifts of protons in GH1, UH3, and UH5 of GU pairs,
UH3, UH5, and AH2 of AU pairs, and GH1 of GC pairs were analyzed to
identify constraints for the 5′ to 3′ directionality
of base pairs in helices. The 5′ to 3′ directionality
constraints were incorporated into an NMR-assisted prediction of secondary
structure (NAPSS-CS) program. When it was tested on 18 structures,
including nine pseudoknots, the sensitivity and positive predictive
value were improved relative to those of three unrestrained programs.
The prediction accuracy for the pseudoknots improved the most. The
program also facilitates assignment of chemical shifts to individual
nucleotides, a necessary step for determining three-dimensional structure.
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Affiliation(s)
- Jonathan L Chen
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Stanislav Bellaousov
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry , Rochester, New York 14642, United States
| | - Jason D Tubbs
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - Scott D Kennedy
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry , Rochester, New York 14642, United States
| | - Michael J Lopez
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States
| | - David H Mathews
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry , Rochester, New York 14642, United States.,Center for RNA Biology, University of Rochester , Rochester, New York 14642, United States
| | - Douglas H Turner
- Department of Chemistry, University of Rochester , Rochester, New York 14627, United States.,Center for RNA Biology, University of Rochester , Rochester, New York 14642, United States
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21
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Song Y, Hua L, Shapiro BA, Wang JTL. Effective alignment of RNA pseudoknot structures using partition function posterior log-odds scores. BMC Bioinformatics 2015; 16:39. [PMID: 25727492 PMCID: PMC4339682 DOI: 10.1186/s12859-015-0464-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 01/13/2015] [Indexed: 11/18/2022] Open
Abstract
Background RNA pseudoknots play important roles in many biological processes. Previous methods for comparative pseudoknot analysis mainly focus on simultaneous folding and alignment of RNA sequences. Little work has been done to align two known RNA secondary structures with pseudoknots taking into account both sequence and structure information of the two RNAs. Results In this article we present a novel method for aligning two known RNA secondary structures with pseudoknots. We adopt the partition function methodology to calculate the posterior log-odds scores of the alignments between bases or base pairs of the two RNAs with a dynamic programming algorithm. The posterior log-odds scores are then used to calculate the expected accuracy of an alignment between the RNAs. The goal is to find an optimal alignment with the maximum expected accuracy. We present a heuristic to achieve this goal. The performance of our method is investigated and compared with existing tools for RNA structure alignment. An extension of the method to multiple alignment of pseudoknot structures is also discussed. Conclusions The method described here has been implemented in a tool named RKalign, which is freely accessible on the Internet. As more and more pseudoknots are revealed, collected and stored in public databases, we anticipate a tool like RKalign will play a significant role in data comparison, annotation, analysis, and retrieval in these databases. Electronic supplementary material The online version of this article (doi:10.1186/s12859-015-0464-9) contains supplementary material, which is available to authorized users.
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22
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Cantara WA, Olson ED, Musier-Forsyth K. Progress and outlook in structural biology of large viral RNAs. Virus Res 2014; 193:24-38. [PMID: 24956407 PMCID: PMC4252365 DOI: 10.1016/j.virusres.2014.06.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 02/05/2023]
Abstract
The field of viral molecular biology has reached a precipice for which pioneering studies on the structure of viral RNAs are beginning to bridge the gap. It has become clear that viral genomic RNAs are not simply carriers of hereditary information, but rather are active players in many critical stages during replication. Indeed, functions such as cap-independent translation initiation mechanisms are, in some cases, primarily driven by RNA structural determinants. Other stages including reverse transcription initiation in retroviruses, nuclear export and viral packaging are specifically dependent on the proper 3-dimensional folding of multiple RNA domains to recruit necessary viral and host factors required for activity. Furthermore, a large-scale conformational change within the 5'-untranslated region of HIV-1 has been proposed to regulate the temporal switch between viral protein synthesis and packaging. These RNA-dependent functions are necessary for replication of many human disease-causing viruses such as severe acute respiratory syndrome (SARS)-associated coronavirus, West Nile virus, and HIV-1. The potential for antiviral development is currently hindered by a poor understanding of RNA-driven molecular mechanisms, resulting from a lack of structural information on large RNAs and ribonucleoprotein complexes. Herein, we describe the recent progress that has been made on characterizing these large RNAs and provide brief descriptions of the techniques that will be at the forefront of future advances. Ongoing and future work will contribute to a more complete understanding of the lifecycles of retroviruses and RNA viruses and potentially lead to novel antiviral strategies.
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Affiliation(s)
| | | | - Karin Musier-Forsyth
- Department of Chemistry and Biochemistry, Center for Retrovirus Research, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, United States
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23
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Devi G, Zhou Y, Zhong Z, Toh DFK, Chen G. RNA triplexes: from structural principles to biological and biotech applications. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 6:111-28. [DOI: 10.1002/wrna.1261] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 06/30/2014] [Accepted: 07/14/2014] [Indexed: 12/29/2022]
Affiliation(s)
- Gitali Devi
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore Singapore
| | - Yuan Zhou
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore Singapore
| | - Zhensheng Zhong
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore Singapore
| | - Desiree-Faye Kaixin Toh
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore Singapore
| | - Gang Chen
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences; Nanyang Technological University; Singapore Singapore
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24
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Gottstein-Schmidtke SR, Duchardt-Ferner E, Groher F, Weigand JE, Gottstein D, Suess B, Wöhnert J. Building a stable RNA U-turn with a protonated cytidine. RNA (NEW YORK, N.Y.) 2014; 20:1163-72. [PMID: 24951555 PMCID: PMC4105743 DOI: 10.1261/rna.043083.113] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 05/16/2014] [Indexed: 05/28/2023]
Abstract
The U-turn is a classical three-dimensional RNA folding motif first identified in the anticodon and T-loops of tRNAs. It also occurs frequently as a building block in other functional RNA structures in many different sequence and structural contexts. U-turns induce sharp changes in the direction of the RNA backbone and often conform to the 3-nt consensus sequence 5'-UNR-3' (N = any nucleotide, R = purine). The canonical U-turn motif is stabilized by a hydrogen bond between the N3 imino group of the U residue and the 3' phosphate group of the R residue as well as a hydrogen bond between the 2'-hydroxyl group of the uridine and the N7 nitrogen of the R residue. Here, we demonstrate that a protonated cytidine can functionally and structurally replace the uridine at the first position of the canonical U-turn motif in the apical loop of the neomycin riboswitch. Using NMR spectroscopy, we directly show that the N3 imino group of the protonated cytidine forms a hydrogen bond with the backbone phosphate 3' from the third nucleotide of the U-turn analogously to the imino group of the uridine in the canonical motif. In addition, we compare the stability of the hydrogen bonds in the mutant U-turn motif to the wild type and describe the NMR signature of the C+-phosphate interaction. Our results have implications for the prediction of RNA structural motifs and suggest simple approaches for the experimental identification of hydrogen bonds between protonated C-imino groups and the phosphate backbone.
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Affiliation(s)
- Sina R Gottstein-Schmidtke
- Institute of Molecular Biosciences, Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany Center for Biomolecular Magnetic Resonance (BMRZ), Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany
| | - Elke Duchardt-Ferner
- Institute of Molecular Biosciences, Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany Center for Biomolecular Magnetic Resonance (BMRZ), Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany
| | - Florian Groher
- Department of Biology, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - Julia E Weigand
- Department of Biology, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - Daniel Gottstein
- Institute for Biophysical Chemistry, Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany
| | - Beatrix Suess
- Department of Biology, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - Jens Wöhnert
- Institute of Molecular Biosciences, Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany Center for Biomolecular Magnetic Resonance (BMRZ), Johann-Wolfgang-Goethe-University Frankfurt/M., 60438 Frankfurt, Germany
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25
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Weigand JE, Gottstein-Schmidtke SR, Demolli S, Groher F, Duchardt-Ferner E, Wöhnert J, Suess B. Sequence elements distal to the ligand binding pocket modulate the efficiency of a synthetic riboswitch. Chembiochem 2014; 15:1627-37. [PMID: 24954073 DOI: 10.1002/cbic.201402067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Indexed: 01/16/2023]
Abstract
Synthetic riboswitches can serve as sophisticated genetic control devices in synthetic biology, regulating gene expression through direct RNA-ligand interactions. We analyzed a synthetic neomycin riboswitch, which folds into a stem loop structure with an internal loop important for ligand binding and regulation. It is closed by a terminal hexaloop containing a U-turn and a looped-out adenine. We investigated the relationship between sequence, structure, and biological activity in the terminal loop by saturating mutagenesis, ITC, and NMR. Mutants corresponding to the canonical U-turn fold retained biological activity. An improvement of stacking interactions in the U-turn led to an RNA element with slightly enhanced regulatory activity. For the first position of the U-turn motif and the looped out base, sequence-activity relationships that could not initially be explained on the basis of the structure of the aptamer-ligand complex were observed. However, NMR studies of these mutants revealed subtle relationships between structure and dynamics of the aptamer in its free or bound state and biological activity.
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Affiliation(s)
- Julia E Weigand
- Department of Biology, Technical University Darmstadt, Schnittspahnstrasse 10, 64287 Darmstadt (Germany)
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26
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A genome-wide analysis of RNA pseudoknots that stimulate efficient -1 ribosomal frameshifting or readthrough in animal viruses. BIOMED RESEARCH INTERNATIONAL 2013; 2013:984028. [PMID: 24298557 PMCID: PMC3835772 DOI: 10.1155/2013/984028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/21/2013] [Indexed: 02/01/2023]
Abstract
Programmed −1 ribosomal frameshifting (PRF) and stop codon readthrough are two translational recoding mechanisms utilized by some RNA viruses to express their structural and enzymatic proteins at a defined ratio. Efficient recoding usually requires an RNA pseudoknot located several nucleotides downstream from the recoding site. To assess the strategic importance of the recoding pseudoknots, we have carried out a large scale genome-wide analysis in which we used an in-house developed program to detect all possible H-type pseudoknots within the genomic mRNAs of 81 animal viruses. Pseudoknots are detected downstream from ~85% of the recoding sites, including many previously unknown pseudoknots. ~78% of the recoding pseudoknots are the most stable pseudoknot within the viral genomes. However, they are not as strong as some designed pseudoknots that exhibit roadblocking effect on the translating ribosome. Strong roadblocking pseudoknots are not detected within the viral genomes. These results indicate that the decoding pseudoknots have evolved to possess optimal stability for efficient recoding. We also found that the sequence at the gag-pol frameshift junction of HIV1 harbors potential elaborated pseudoknots encompassing the frameshift site. A novel mechanism is proposed for possible involvement of the elaborated pseudoknots in the HIV1 PRF event.
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27
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Wilcox JL, Bevilacqua PC. A Simple Fluorescence Method for pKa Determination in RNA and DNA Reveals Highly Shifted pKa’s. J Am Chem Soc 2013; 135:7390-3. [DOI: 10.1021/ja3125299] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jennifer L. Wilcox
- Department of Chemistry
and Center for RNA Molecular
Biology, Pennsylvania State University,
University Park, Pennsylvania 16802, United States
| | - Philip C. Bevilacqua
- Department of Chemistry
and Center for RNA Molecular
Biology, Pennsylvania State University,
University Park, Pennsylvania 16802, United States
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28
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Banáš P, Sklenovský P, Wedekind JE, Šponer J, Otyepka M. Molecular mechanism of preQ1 riboswitch action: a molecular dynamics study. J Phys Chem B 2012; 116:12721-34. [PMID: 22998634 PMCID: PMC3505677 DOI: 10.1021/jp309230v] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Riboswitches often occur in the 5'-untranslated regions of bacterial mRNA where they regulate gene expression. The preQ(1) riboswitch controls the biosynthesis of a hypermodified nucleoside queuosine in response to binding the queuosine metabolic intermediate. Structures of the ligand-bound and ligand-free states of the preQ(1) riboswitch from Thermoanaerobacter tengcongensis were determined recently by X-ray crystallography. We used multiple, microsecond-long molecular dynamics simulations (29 μs in total) to characterize the structural dynamics of preQ(1) riboswitches in both states. We observed different stabilities of the stem in the bound and free states, resulting in different accessibilities of the ribosome-binding site. These differences are related to different stacking interactions between nucleotides of the stem and the associated loop, which itself adopts different conformations in the bound and free states. We suggest that the loop not only serves to bind preQ(1) but also transmits information about ligand binding from the ligand-binding pocket to the stem, which has implications for mRNA accessibility to the ribosome. We explain functional results obscured by a high salt crystallization medium and help to refine regions of disordered electron density, which demonstrates the predictive power of our approach. Besides investigating the functional dynamics of the riboswitch, we have also utilized this unique small folded RNA system for analysis of performance of the RNA force field on the μs time scale. The latest AMBER parmbsc0χ(OL3) RNA force field is capable of providing stable trajectories of the folded molecule on the μs time scale. On the other hand, force fields that are not properly balanced lead to significant structural perturbations on the sub-μs time scale, which could easily lead to inappropriate interpretation of the simulation data.
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Affiliation(s)
- Pavel Banáš
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
| | - Petr Sklenovský
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic
| | - Joseph E. Wedekind
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Box 712, Rochester, NY 14620, USA
| | - Jiří Šponer
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
- CEITEC – Central European Institute of Technology, Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, tr. 17. listopadu 12, 771 46 Olomouc, Czech Republic
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29
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Programmed -1 frameshifting efficiency correlates with RNA pseudoknot conformational plasticity, not resistance to mechanical unfolding. Proc Natl Acad Sci U S A 2012; 109:16167-72. [PMID: 22988073 DOI: 10.1073/pnas.1204114109] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Programmed -1 frameshifting, whereby the reading frame of a ribosome on messenger RNA is shifted in order to generate an alternate gene product, is often triggered by a pseudoknot structure in the mRNA in combination with an upstream slippery sequence. The efficiency of frameshifting varies widely for different sites, but the factors that determine frameshifting efficiency are not yet fully understood. Previous work has suggested that frameshifting efficiency is related to the resistance of the pseudoknot against mechanical unfolding. We tested this hypothesis by studying the mechanical properties of a panel of pseudoknots with frameshifting efficiencies ranging from 2% to 30%: four pseudoknots from retroviruses, two from luteoviruses, one from a coronavirus, and a nonframeshifting bacteriophage pseudoknot. Using optical tweezers to apply tension across the RNA, we measured the distribution of forces required to unfold each pseudoknot. We found that neither the average unfolding force, nor the unfolding kinetics, nor the parameters describing the energy landscape for mechanical unfolding of the pseudoknot (energy barrier height and distance to the transition state) could be correlated to frameshifting efficiency. These results indicate that the resistance of pseudoknots to mechanical unfolding is not a primary determinant of frameshifting efficiency. However, increased frameshifting efficiency was correlated with an increased tendency to form alternate, incompletely folded structures, suggesting a more complex picture of the role of the pseudoknot involving the conformational dynamics.
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30
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Cao S, Chen SJ. Statistical mechanical modeling of RNA folding: from free energy landscape to tertiary structural prediction. NUCLEIC ACIDS AND MOLECULAR BIOLOGY 2012; 27:185-212. [PMID: 27293312 DOI: 10.1007/978-3-642-25740-7_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In spite of the success of computational methods for predicting RNA secondary structure, the problem of predicting RNA tertiary structure folding remains. Low-resolution structural models show promise as they allow for rigorous statistical mechanical computation for the conformational entropies, free energies, and the coarse-grained structures of tertiary folds. Molecular dynamics refinement of coarse-grained structures leads to all-atom 3D structures. Modeling based on statistical mechanics principles also has the unique advantage of predicting the full free energy landscape, including local minima and the global free energy minimum. The energy landscapes combined with the 3D structures form the basis for quantitative predictions of RNA functions. In this chapter, we present an overview of statistical mechanical models for RNA folding and then focus on a recently developed RNA statistical mechanical model -- the Vfold model. The main emphasis is placed on the physics underpinning the models, the computational strategies, and the connections to RNA biology.
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Affiliation(s)
- Song Cao
- Department of Physics and Department of Biochemistry, University of Missouri, Columbia, MO 65211
| | - Shi-Jie Chen
- Department of Physics and Department of Biochemistry, University of Missouri, Columbia, MO 65211
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31
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Yu CH, Noteborn MH, Pleij CWA, Olsthoorn RCL. Stem-loop structures can effectively substitute for an RNA pseudoknot in -1 ribosomal frameshifting. Nucleic Acids Res 2011; 39:8952-9. [PMID: 21803791 PMCID: PMC3203594 DOI: 10.1093/nar/gkr579] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
-1 Programmed ribosomal frameshifting (PRF) in synthesizing the gag-pro precursor polyprotein of Simian retrovirus type-1 (SRV-1) is stimulated by a classical H-type pseudoknot which forms an extended triple helix involving base-base and base-sugar interactions between loop and stem nucleotides. Recently, we showed that mutation of bases involved in triple helix formation affected frameshifting, again emphasizing the role of the triple helix in -1 PRF. Here, we investigated the efficiency of hairpins of similar base pair composition as the SRV-1 gag-pro pseudoknot. Although not capable of triple helix formation they proved worthy stimulators of frameshifting. Subsequent investigation of ∼30 different hairpin constructs revealed that next to thermodynamic stability, loop size and composition and stem irregularities can influence frameshifting. Interestingly, hairpins carrying the stable GAAA tetraloop were significantly less shifty than other hairpins, including those with a UUCG motif. The data are discussed in relation to natural shifty hairpins.
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Affiliation(s)
- Chien-Hung Yu
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
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32
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Park SJ, Kim YG, Park HJ. Identification of RNA pseudoknot-binding ligand that inhibits the -1 ribosomal frameshifting of SARS-coronavirus by structure-based virtual screening. J Am Chem Soc 2011; 133:10094-100. [PMID: 21591761 DOI: 10.1021/ja1098325] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Programmed -1 ribosomal frameshifting (-1 RF) is an essential regulating mechanism of translation used by SARS-CoV (severe acute respiratory syndrome coronavirus) to synthesize the key replicative proteins encoded by two overlapping open reading frames. The integrity of RNA pseudoknot stability and structure in the -1 RF site is important for efficient -1 RF. Thus, small molecules interacting with high affinity and selectivity with the RNA pseudoknot in the -1 RF site of SARS-CoV (SARS-pseudoknot) would disrupt -1 RF and be fatal to viral infectivity and production. To discover ligands for the SARS-pseudoknot by virtual screening, we constructed a 3D structural model of the SARS-pseudoknot and conducted a computational screening of the chemical database. After virtual screening of about 80,000 compounds against the SARS-pseudoknot structure, high-ranked compounds were selected and their activities were examined by in vitro and cell-based -1 RF assay. We successfully identified a novel ligand 43 that dramatically inhibits the -1 RF of SARS-CoV. This antiframeshift agent is an interesting lead for the design of novel antiviral agents against SARS-CoV.
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Affiliation(s)
- So-Jung Park
- School of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea
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33
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Chawla M, Sharma P, Halder S, Bhattacharyya D, Mitra A. Protonation of base pairs in RNA: context analysis and quantum chemical investigations of their geometries and stabilities. J Phys Chem B 2011; 115:1469-84. [PMID: 21254753 DOI: 10.1021/jp106848h] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Base pairs involving protonated nucleobases play important roles in mediating global macromolecular conformational changes and in facilitation of catalysis in a variety of functional RNA molecules. Here we present our attempts at understanding the role of such base pairs by detecting possible protonated base pairs in the available RNA crystal structures using BPFind software, in their specific structural contexts, and by the characterization of their geometries, interaction energies, and stabilities using advanced quantum chemical computations. We report occurrences of 18 distinct protonated base pair combinations from a representative data set of RNA crystal structures and propose a theoretical model for one putative base pair combination. Optimization of base pair geometries was carried out at the B3LYP/cc-pVTZ level, and the BSSE corrected interaction energies were calculated at the MP2/aug-cc-pVDZ level of theory. The geometries for each of the base pairs were characterized in terms of H-bonding patterns observed, rmsd values observed on optimization, and base pair geometrical parameters. In addition, the intermolecular interaction in these complexes was also analyzed using Morokuma energy decomposition. The gas phase interaction energies of the base pairs range from -24 to -49 kcal/mol and reveal the dominance of Hartree-Fock component of interaction energy constituting 73% to 98% of the total interaction energy values. On the basis of our combined bioinformatics and quantum chemical analysis of different protonated base pairs, we suggest resolution of structural ambiguities and correlate their geometric and energetic features with their structural and functional roles. In addition, we also examine the suitability of specific base pairs as key elements in molecular switches and as nucleators for higher order structures such as base triplets and quartets.
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Affiliation(s)
- Mohit Chawla
- Center for Computational Natural Sciences and Bioinformatics (CCNSB), International Institute of Information Technology (IIIT-H) Gachibowli, Hyderabad 500032, India
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34
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Durney MA, D'Souza VM. Preformed protein-binding motifs in 7SK snRNA: structural and thermodynamic comparisons with retroviral TAR. J Mol Biol 2010; 404:555-67. [PMID: 20816986 DOI: 10.1016/j.jmb.2010.08.042] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 08/20/2010] [Accepted: 08/20/2010] [Indexed: 11/30/2022]
Abstract
The 7SK small nuclear RNA is a highly conserved non-coding RNA that regulates transcriptional elongation. 7SK utilizes the HEXIM proteins to sequester the transcription factor P-TEFb by a mechanism similar to that used by retroviral TAR RNA to engage Tat and P-TEFb. Tat has also recently been shown to bind 7SK directly and recruit P-TEFb to TAR. We report here the solution structures of the free and arginine-bound forms of stem loop 4 of 7SK (7SK-SL4). Comparison of the 7SK-SL4 and TAR structures demonstrates the presence of a common arginine sandwich motif. However, arginine binding to 7SK-SL4 is mechanistically distinct and occurs via docking into a pre-organized pocket resulting in a 1000-fold increased affinity. Furthermore, whereas formation of the binding pocket in TAR requires a critical base-triple, hydrogen-bond formation between the equivalent bases in 7SK-SL4 is not essential and the pocket is stabilized solely by a pseudo base-triple platform. In addition, this theme of preformed protein binding motifs also extends into the pentaloop. The configuration of the loop suggests that 7SK-SL4 is poised to make ternary contacts with P-TEFb and HEXIM or Tat. These key differences between 7SK-SL4 and TAR present an opportunity to understand RNA structural adaptation and have implications for understanding differential interactions with Tat.
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Affiliation(s)
- Michael A Durney
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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35
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Veeraraghavan N, Bevilacqua PC, Hammes-Schiffer S. Long-distance communication in the HDV ribozyme: insights from molecular dynamics and experiments. J Mol Biol 2010; 402:278-91. [PMID: 20643139 DOI: 10.1016/j.jmb.2010.07.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 07/12/2010] [Accepted: 07/13/2010] [Indexed: 11/18/2022]
Abstract
The hepatitis delta virus ribozyme is a small, self-cleaving RNA with a compact tertiary structure and buried active site that is important in the life cycle of the virus. The ribozyme's function in nature is to cleave an internal phosphodiester bond and linearize concatemers during rolling circle replication. Crystal structures of the ribozyme have been solved in both pre-cleaved and post-cleaved (product) forms and reveal an intricate network of interactions that conspire to catalyze bond cleavage. In addition, extensive biochemical studies have been performed to work out a mechanism for bond cleavage in which C75 and a magnesium ion catalyze the reaction by general acid-base chemistry. One issue that has remained unclear in this ribozyme and in other ribozymes is the nature of long-distance communication between peripheral regions of the RNA and the buried active site. We performed molecular dynamics simulations on the hepatitis delta virus ribozyme in the product form and assessed communication between a distal structural portion of the ribozyme-the protonated C41 base triple-and the active site containing the critical C75. We varied the ionization state of C41 in both the wild type and a C41 double mutant variant and determined the impact on the active site. In all four cases, effects at the active site observed in the simulations agree with experimental studies on ribozyme activity. Overall, these studies indicate that small functional RNAs have the potential to communicate interactions over long distances and that wild-type RNAs may have evolved ways to prevent such interactions from interfering with catalysis.
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Affiliation(s)
- Narayanan Veeraraghavan
- Huck Institutes of Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
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36
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Olsthoorn RCL, Reumerman R, Hilbers CW, Pleij CWA, Heus HA. Functional analysis of the SRV-1 RNA frameshifting pseudoknot. Nucleic Acids Res 2010; 38:7665-72. [PMID: 20639537 PMCID: PMC2995055 DOI: 10.1093/nar/gkq629] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Simian retrovirus type-1 uses programmed ribosomal frameshifting to control expression of the Gag-Pol polyprotein from overlapping gag and pol open-reading frames. The frameshifting signal consists of a heptanucleotide slippery sequence and a downstream-located 12-base pair pseudoknot. The solution structure of this pseudoknot, previously solved by NMR [Michiels,P.J., Versleijen,A.A., Verlaan,P.W., Pleij,C.W., Hilbers,C.W. and Heus,H.A. (2001) Solution structure of the pseudoknot of SRV-1 RNA, involved in ribosomal frameshifting. J. Mol. Biol., 310, 1109-1123] has a classical H-type fold and forms an extended triple helix by interactions between loop 2 and the minor groove of stem 1 involving base-base and base-sugar contacts. A mutational analysis was performed to test the functional importance of the triple helix for -1 frameshifting in vitro. Changing bases in L2 or base pairs in S1 involved in a base triple resulted in a 2- to 5-fold decrease in frameshifting efficiency. Alterations in the length of L2 had adverse effects on frameshifting. The in vitro effects were well reproduced in vivo, although the effect of enlarging L2 was more dramatic in vivo. The putative role of refolding kinetics of frameshifter pseudoknots is discussed. Overall, the data emphasize the role of the triple helix in -1 frameshifting.
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Affiliation(s)
- René C L Olsthoorn
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
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37
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Cao S, Giedroc DP, Chen SJ. Predicting loop-helix tertiary structural contacts in RNA pseudoknots. RNA (NEW YORK, N.Y.) 2010; 16:538-52. [PMID: 20100813 PMCID: PMC2822919 DOI: 10.1261/rna.1800210] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 11/24/2009] [Indexed: 05/28/2023]
Abstract
Tertiary interactions between loops and helical stems play critical roles in the biological function of many RNA pseudoknots. However, quantitative predictions for RNA tertiary interactions remain elusive. Here we report a statistical mechanical model for the prediction of noncanonical loop-stem base-pairing interactions in RNA pseudoknots. Central to the model is the evaluation of the conformational entropy for the pseudoknotted folds with defined loop-stem tertiary structural contacts. We develop an RNA virtual bond-based conformational model (Vfold model), which permits a rigorous computation of the conformational entropy for a given fold that contains loop-stem tertiary contacts. With the entropy parameters predicted from the Vfold model and the energy parameters for the tertiary contacts as inserted parameters, we can then predict the RNA folding thermodynamics, from which we can extract the tertiary contact thermodynamic parameters from theory-experimental comparisons. These comparisons reveal a contact enthalpy (DeltaH) of -14 kcal/mol and a contact entropy (DeltaS) of -38 cal/mol/K for a protonated C(+)*(G-C) base triple at pH 7.0, and (DeltaH = -7 kcal/mol, DeltaS = -19 cal/mol/K) for an unprotonated base triple. Tests of the model for a series of pseudoknots show good theory-experiment agreement. Based on the extracted energy parameters for the tertiary structural contacts, the model enables predictions for the structure, stability, and folding pathways for RNA pseudoknots with known or postulated loop-stem tertiary contacts from the nucleotide sequence alone.
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Affiliation(s)
- Song Cao
- Department of Physics, University of Missouri, Columbia, Missouri 65211, USA
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38
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Chou MY, Chang KY. An intermolecular RNA triplex provides insight into structural determinants for the pseudoknot stimulator of -1 ribosomal frameshifting. Nucleic Acids Res 2010; 38:1676-85. [PMID: 20007152 PMCID: PMC2836554 DOI: 10.1093/nar/gkp1107] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 11/08/2009] [Accepted: 11/10/2009] [Indexed: 01/03/2023] Open
Abstract
An efficient -1 programmed ribosomal frameshifting (PRF) signal requires an RNA slippery sequence and a downstream RNA stimulator, and the hairpin-type pseudoknot is the most common stimulator. However, a pseudoknot is not sufficient to promote -1 PRF. hTPK-DU177, a pseudoknot derived from human telomerase RNA, shares structural similarities with several -1 PRF pseudoknots and is used to dissect the roles of distinct structural features in the stimulator of -1 PRF. Structure-based mutagenesis on hTPK-DU177 reveals that the -1 PRF efficiency of this stimulator can be modulated by sequential removal of base-triple interactions surrounding the helical junction. Further analysis of the junction-flanking base triples indicates that specific stem-loop interactions and their relative positions to the helical junction play crucial roles for the -1 PRF activity of this pseudoknot. Intriguingly, a bimolecular pseudoknot approach based on hTPK-DU177 reveals that continuing triplex structure spanning the helical junction, lacking one of the loop-closure features embedded in pseudoknot topology, can stimulate -1 PRF. Therefore, the triplex structure is an essential determinant for the DU177 pseudoknot to stimulate -1 PRF. Furthermore, it suggests that -1 PRF, induced by an in-trans RNA via specific base-triple interactions with messenger RNAs, can be a plausible regulatory function for non-coding RNAs.
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Affiliation(s)
| | - Kung-Yao Chang
- Graduate Institute of Biochemistry, National Chung-Hsing University, 250 Kuo-Kung Road, Taichung 402, Taiwan
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39
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Abstract
RNA pseudoknots are important for function. Three-dimensional structural information is available, insights into factors affecting pseudoknot stability are being reported, and computer programs are available for predicting pseudoknots.
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Affiliation(s)
- Biao Liu
- Department of Chemistry120 Trustee RoadUniversity of RochesterRochester, NY 14627USA
| | - David H Mathews
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry601 Elmwood AveUniversity of RochesterRochester, NY 14642USA
- Center for RNA Biology, School of Medicine and Dentistry, University of RochesterRochester, NY 14642USA
| | - Douglas H Turner
- Department of Chemistry120 Trustee RoadUniversity of RochesterRochester, NY 14627USA
- Center for RNA Biology, School of Medicine and Dentistry, University of RochesterRochester, NY 14642USA
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40
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Zhang L, Bao P, Leibowitz MJ, Zhang Y. Slow formation of a pseudoknot structure is rate limiting in the productive co-transcriptional folding of the self-splicing Candida intron. RNA (NEW YORK, N.Y.) 2009; 15:1986-1992. [PMID: 19710184 PMCID: PMC2764484 DOI: 10.1261/rna.1638609] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Accepted: 07/30/2009] [Indexed: 05/28/2023]
Abstract
Pseudoknots play critical roles in packing the active structure of various functional RNAs. The importance of the P3-P7 pseudoknot in refolding of group I intron ribozymes has been recently appreciated, while little is known about the pseudoknot function in co-transcriptional folding. Here we used the Candida group I intron as a model to address the question. We show that co-transcriptional folding of the active self-splicing intron is twice as fast as refolding. The P3-P7 pseudoknot folds slowly during co-transcriptional folding at a rate constant similar to the folding of the active ribozyme, and folding of both P3-P7 and P1-P10 pseudoknots are inhibited by antisense oligonucleotides. We conclude that when RNA folding is coupled with transcription, formation of pseudoknot structures dominates the productive folding pathway and serves as a rate-limiting step in producing the self-splicing competent Candida intron.
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Affiliation(s)
- Libin Zhang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, People's Republic of China
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41
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Grossoehme NE, Li L, Keane SC, Liu P, Dann CE, Leibowitz JL, Giedroc DP. Coronavirus N protein N-terminal domain (NTD) specifically binds the transcriptional regulatory sequence (TRS) and melts TRS-cTRS RNA duplexes. J Mol Biol 2009; 394:544-57. [PMID: 19782089 PMCID: PMC2783395 DOI: 10.1016/j.jmb.2009.09.040] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2009] [Revised: 09/11/2009] [Accepted: 09/16/2009] [Indexed: 11/03/2022]
Abstract
All coronaviruses (CoVs), including the causative agent of severe acute respiratory syndrome (SARS), encode a nucleocapsid (N) protein that harbors two independent RNA binding domains of known structure, but poorly characterized RNA binding properties. We show here that the N-terminal domain (NTD) of N protein from mouse hepatitis virus (MHV), a virus most closely related to SARS-CoV, employs aromatic amino acid-nucleobase stacking interactions with a triple adenosine motif to mediate high-affinity binding to single-stranded RNAs containing the transcriptional regulatory sequence (TRS) or its complement (cTRS). Stoichiometric NTD fully unwinds a TRS-cTRS duplex that mimics a transiently formed transcription intermediate in viral subgenomic RNA synthesis. Mutation of the solvent-exposed Y127, positioned on the beta-platform surface of our 1.75 A structure, binds the TRS far less tightly and is severely crippled in its RNA unwinding activity. In contrast, the C-terminal domain (CTD) exhibits no RNA unwinding activity. Viruses harboring Y127A N mutation are strongly selected against and Y127A N does not support an accessory function in MHV replication. We propose that the helix melting activity of the coronavirus N protein NTD plays a critical accessory role in subgenomic RNA synthesis and other processes requiring RNA remodeling.
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Mouse hepatitis virus stem-loop 2 adopts a uYNMG(U)a-like tetraloop structure that is highly functionally tolerant of base substitutions. J Virol 2009; 83:12084-93. [PMID: 19759148 DOI: 10.1128/jvi.00915-09] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Stem-loop 2 (SL2) of the 5'-untranslated region of the mouse hepatitis virus (MHV) contains a highly conserved pentaloop (C47-U48-U49-G50-U51) stacked on a 5-bp stem. Solution nuclear magnetic resonance experiments are consistent with a 5'-uYNMG(U)a or uCUYG(U)a tetraloop conformation characterized by an anti-C47-syn-G50 base-pairing interaction, with U51 flipped out into solution and G50 stacked on A52. Previous studies showed that U48C and U48A substitutions in MHV SL2 were lethal, while a U48G substitution was viable. Here, we characterize viruses harboring all remaining single-nucleotide substitutions in the pentaloop of MHV SL2 and also investigate the degree to which the sequence context of key pentaloop point mutations influences the MHV replication phenotype. U49 or U51 substitution mutants all are viable; C47 substitution mutants also are viable but produce slightly smaller plaques than wild-type virus. In contrast, G50A and G50C viruses are severely crippled and form much smaller plaques. Virus could not be recovered from G50U-containing mutants; rather, only true wild-type revertants or a virus, G50U/C47A, containing a second site mutation were recovered. These functional data suggest that the Watson-Crick edges of C47 and G50 (or A47 and U50 in the G50U/C47A mutant) are in close enough proximity to a hydrogen bond with U51 flipped out of the hairpin. Remarkably, increasing the helical stem stability rescues the previously lethal mutants U48C and G50U. These studies suggest that SL2 functions as an important, but rather plastic, structural element in stimulating subgenomic RNA synthesis in coronaviruses.
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Mazauric MH, Leroy JL, Visscher K, Yoshizawa S, Fourmy D. Footprinting analysis of BWYV pseudoknot-ribosome complexes. RNA (NEW YORK, N.Y.) 2009; 15:1775-1786. [PMID: 19625386 PMCID: PMC2743054 DOI: 10.1261/rna.1385409] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Accepted: 05/26/2009] [Indexed: 05/28/2023]
Abstract
Many viruses regulate translation of polycistronic mRNA using a -1 ribosomal frameshift induced by an RNA pseudoknot. When the ribosome encounters the pseudoknot barrier that resists unraveling, transient mRNA-tRNA dissociation at the decoding site, results in a shift of the reading frame. The eukaryotic frameshifting pseudoknot from the beet western yellow virus (BWYV) has been well characterized, both structurally and functionally. Here, we show that in order to obtain eukaryotic levels of frameshifting efficiencies using prokaryotic Escherichia coli ribosomes, which depend upon the structural integrity of the BWYV pseudoknot, it is necessary to shorten the mRNA spacer between the slippery sequence and the pseudoknot by 1 or 2 nucleotides (nt). Shortening of the spacer is likely to re-establish tension and/or ribosomal contacts that were otherwise lost with the smaller E. coli ribosomes. Chemical probing experiments for frameshifting and nonframeshifting BWYV constructs were performed to investigate the structural integrity of the pseudoknot confined locally at the mRNA entry site. These data, obtained in the pretranslocation state, show a compact overall pseudoknot structure, with changes in the conformation of nucleotides (i.e., increase in reactivity to chemical probes) that are first "hit" by the ribosomal helicase center. Interestingly, with the 1-nt shortened spacer, this increase of reactivity extends to a downstream nucleotide in the first base pair (bp) of stem 1, consistent with melting of this base pair. Thus, the 3 bp that will unfold upon translocation are different in both constructs with likely consequences on unfolding kinetics.
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Affiliation(s)
- Marie-Hélène Mazauric
- Laboratoire de Chimie et Biologie Structurales, FRC3115, ICSN-CNRS, Gif-sur-Yvette 91190, France
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Triplex structures in an RNA pseudoknot enhance mechanical stability and increase efficiency of -1 ribosomal frameshifting. Proc Natl Acad Sci U S A 2009; 106:12706-11. [PMID: 19628688 DOI: 10.1073/pnas.0905046106] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Many viruses use programmed -1 ribosomal frameshifting to express defined ratios of structural and enzymatic proteins. Pseudoknot structures in messenger RNAs stimulate frameshifting in upstream slippery sequences. The detailed molecular determinants of pseudoknot mechanical stability and frameshifting efficiency are not well understood. Here we use single-molecule unfolding studies by optical tweezers, and frameshifting assays to elucidate how mechanical stability of a pseudoknot and its frameshifting efficiency are regulated by tertiary stem-loop interactions. Mechanical unfolding of a model pseudoknot and mutants designed to dissect specific interactions reveals that mechanical stability depends strongly on triplex structures formed by stem-loop interactions. Combining single-molecule and mutational studies facilitates the identification of pseudoknot folding intermediates. Average unfolding forces of the pseudoknot and mutants ranging from 50 to 22 picoNewtons correlated with frameshifting efficiencies ranging from 53% to 0%. Formation of major-groove and minor-groove triplex structures enhances pseudoknot stem stability and torsional resistance, and may thereby stimulate frameshifting. Better understanding of the molecular determinants of frameshifting efficiency may facilitate the development of anti-virus therapeutics targeting frameshifting.
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45
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Atkins JF, Gesteland RF. Ribosomal Frameshifting in Decoding Plant Viral RNAs. RECODING: EXPANSION OF DECODING RULES ENRICHES GENE EXPRESSION 2009; 24. [PMCID: PMC7122378 DOI: 10.1007/978-0-387-89382-2_9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Frameshifting provides an elegant mechanism by which viral RNA both encodes overlapping genes and controls expression levels of those genes. As in animal viruses, the −1 ribosomal frameshift site in the viral mRNA consists of a canonical shifty heptanucleotide followed by a highly structured frameshift stimulatory element, and the gene translated as a result of frameshifting usually encodes the RNA-dependent RNA polymerase. In plant viruses, the −1 frameshift stimulatory element consists of either (i) a small pseudoknot stabilized by many triple-stranded regions and a triple base pair containing a protonated cytidine at the helical junction, (ii) an unusual apical loop–internal loop interaction in which a stem-loop in the 3′ untranslated region 4 kb downstream base pairs to a bulged stem-loop at the frameshift site, or (iii) a potential simple stem-loop. Other less well-characterized changes in reading frame occur on plant viral RNAs, including a possible +1 frameshift, and net −1 reading frame changes that do not utilize canonical frameshift signals. All these studies reveal the remarkable ways in which plant viral RNAs interact with ribosomes to precisely control protein expression at the ratios needed to sustain virus replication.
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Affiliation(s)
- John F. Atkins
- grid.223827.e0000000121930096Molecular Biology Program, University of Utah, N. 2030 E. 15, Salt Late City, 84112-5330 U.S.A.
| | - Raymond F. Gesteland
- grid.223827.e0000000121930096Dept. Bioengineering, University of Utah, Salt Lake City, 84112 U.S.A.
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46
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Atkins JF, Gesteland RF, Pennell S. Pseudoknot-Dependent Programmed —1 Ribosomal Frameshifting: Structures, Mechanisms and Models. RECODING: EXPANSION OF DECODING RULES ENRICHES GENE EXPRESSION 2009; 24. [PMCID: PMC7119991 DOI: 10.1007/978-0-387-89382-2_7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Programmed —1 ribosomal frameshifting is a translational recoding strategy that takes place during the elongation phase of protein biosynthesis. Frameshifting occurs in response to specific signals in the mRNA; a slippery sequence, where the ribosome changes frame, and a stimulatory RNA secondary structure, usually a pseudoknot, located immediately downstream. During the frameshift the ribosome slips backwards by a single nucleotide (in the 5′-wards/—1 direction) and continues translation in the new, overlapping reading frame, generating a fusion protein composed of the products of both the original and the —1 frame coding regions. In eukaryotes, frameshifting is largely a phenomenon of virus gene expression and associated predominantly with the expression of viral replicases. Research on frameshifting impacts upon diverse topics, including the ribosomal elongation cycle, RNA structure and function, tRNA modification, virus replication, antiviral intervention, evolution and bioinformatics. This chapter focuses on the structure and function of frameshift-stimulatory RNA pseudoknots and mechanistic aspects of ribosomal frameshifting. A variety of models of the frameshifting process are discussed in the light of recent advances in our understanding of ribosome structure and the elongation cycle.
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Affiliation(s)
- John F. Atkins
- grid.223827.e0000000121930096Molecular Biology Program, University of Utah, N. 2030 E. 15, Salt Late City, 84112-5330 U.S.A.
| | - Raymond F. Gesteland
- grid.223827.e0000000121930096Dept. Bioengineering, University of Utah, Salt Lake City, 84112 U.S.A.
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Structural Elements Contributing to Efficient -1 Ribosomal Frameshifting in BWYV Pseudoknot. B KOREAN CHEM SOC 2009. [DOI: 10.5012/bkcs.2009.30.2.509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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48
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Hart JM, Kennedy SD, Mathews DH, Turner DH. NMR-assisted prediction of RNA secondary structure: identification of a probable pseudoknot in the coding region of an R2 retrotransposon. J Am Chem Soc 2008; 130:10233-9. [PMID: 18613678 PMCID: PMC2646634 DOI: 10.1021/ja8026696] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Indexed: 12/30/2022]
Abstract
As the rate of functional RNA sequence discovery escalates, high-throughput techniques for reliable structural determination are becoming crucial for revealing the essential features of these RNAs in a timely fashion. Computational predictions of RNA secondary structure quickly generate reasonable models but suffer from several approximations, including overly simplified models and incomplete knowledge of significant interactions. Similar problems limit the accuracy of predictions for other self-folding polymers, including DNA and peptide nucleic acid (PNA). The work presented here demonstrates that incorporating unassigned data from simple nuclear magnetic resonance (NMR) experiments into a dynamic folding algorithm greatly reduces the potential folding space of a given RNA and therefore increases the confidence and accuracy of modeling. This procedure has been packaged into an NMR-assisted prediction of secondary structure (NAPSS) algorithm that can produce pseudoknotted as well as non-pseudoknotted secondary structures. The method reveals a probable pseudoknot in the part of the coding region of the R2 retrotransposon from Bombyx mori that orchestrates second-strand DNA cleavage during insertion into the genome.
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Affiliation(s)
- James M Hart
- Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627, USA
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Abstract
Programmed ribosomal frameshifting (PRF) is one of the multiple translational recoding processes that fundamentally alters triplet decoding of the messenger RNA by the elongating ribosome. The ability of the ribosome to change translational reading frames in the −1 direction (−1 PRF) is employed by many positive strand RNA viruses, including economically important plant viruses and many human pathogens, such as retroviruses, e.g., HIV-1, and coronaviruses, e.g., the causative agent of severe acute respiratory syndrome (SARS), in order to properly express their genomes. −1 PRF is programmed by a bipartite signal embedded in the mRNA and includes a heptanucleotide “slip site” over which the paused ribosome “backs up” by one nucleotide, and a downstream stimulatory element, either an RNA pseudoknot or a very stable RNA stem–loop. These two elements are separated by six to eight nucleotides, a distance that places the 5′ edge of the downstream stimulatory element in direct contact with the mRNA entry channel of the 30S ribosomal subunit. The precise mechanism by which the downstream RNA stimulates −1 PRF by the translocating ribosome remains unclear. This review summarizes the recent structural and biophysical studies of RNA pseudoknots and places this work in the context of our evolving mechanistic understanding of translation elongation. Support for the hypothesis that the downstream stimulatory element provides a kinetic barrier to the ribosome-mediated unfolding is discussed.
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50
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Pennell S, Manktelow E, Flatt A, Kelly G, Smerdon SJ, Brierley I. The stimulatory RNA of the Visna-Maedi retrovirus ribosomal frameshifting signal is an unusual pseudoknot with an interstem element. RNA (NEW YORK, N.Y.) 2008; 14:1366-77. [PMID: 18495941 PMCID: PMC2441976 DOI: 10.1261/rna.1042108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The stimulatory RNA of the Visna-Maedi virus (VMV) -1 ribosomal frameshifting signal has not previously been characterized but can be modeled either as a two-stem helix, reminiscent of the HIV-1 frameshift-stimulatory RNA, or as an RNA pseudoknot. The pseudoknot is unusual in that it would include a 7 nucleotide loop (termed here an interstem element [ISE]) between the two stems. In almost all frameshift-promoting pseudoknots, ISEs are absent or comprise a single adenosine residue. Using a combination of RNA structure probing, site directed mutagenesis, NMR, and phylogenetic sequence comparisons, we show here that the VMV stimulatory RNA is indeed a pseudoknot, conforming closely to the modeled structure, and that the ISE is essential for frameshifting. Pseudoknot function was predictably sensitive to changes in the length of the ISE, yet altering its sequence to alternate pyrimidine/purine bases was also detrimental to frameshifting, perhaps through modulation of local tertiary interactions. How the ISE is placed in the context of an appropriate helical junction conformation is not known, but its presence impacts on other elements of the pseudoknot, for example, the necessity for a longer than expected loop 1. This may be required to accommodate an increased flexibility of the pseudoknot brought about by the ISE. In support of this, (1)H NMR analysis at increasing temperatures revealed that stem 2 of the VMV pseudoknot is more labile than stem 1, perhaps as a consequence of its connection to stem 1 solely via flexible single-stranded loops.
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Affiliation(s)
- Simon Pennell
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
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