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Wang Y, Liu T, Yu T, Tan ZJ, Zhang W. Salt effect on thermodynamics and kinetics of a single RNA base pair. RNA (NEW YORK, N.Y.) 2020; 26:470-480. [PMID: 31988191 PMCID: PMC7075264 DOI: 10.1261/rna.073882.119] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/11/2020] [Indexed: 05/09/2023]
Abstract
Due to the polyanionic nature of RNAs, the structural folding of RNAs are sensitive to solution salt conditions, while there is still lack of a deep understanding of the salt effect on the thermodynamics and kinetics of RNAs at a single base-pair level. In this work, the thermodynamic and the kinetic parameters for the base-pair AU closing/opening at different salt concentrations were calculated by 3-µsec all-atom molecular dynamics (MD) simulations at different temperatures. It was found that for the base-pair formation, the enthalpy change [Formula: see text] is nearly independent of salt concentration, while the entropy change [Formula: see text] exhibits a linear dependence on the logarithm of salt concentration, verifying the empirical assumption based on thermodynamic experiments. Our analyses revealed that such salt concentration dependence of the entropy change mainly results from the dependence of ion translational entropy change for the base pair closing/opening on salt concentration. Furthermore, the closing rate increases with the increasing of salt concentration, while the opening rate is nearly independent of salt concentration. Additionally, our analyses revealed that the free energy surface for describing the base-pair opening and closing dynamics becomes more rugged with the decrease of salt concentration.
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Affiliation(s)
- Yujie Wang
- Department of Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, Hubei, 430072, P.R. China
- Department of Physics and Telecommunication Engineering, Zhoukou Normal University, Zhoukou, Henan, 466001, P.R. China
| | - Taigang Liu
- Department of Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, Hubei, 430072, P.R. China
- School of Medical Engineering, Xinxiang Medical University, Xinxiang, Henan, 453003, P.R. China
| | - Ting Yu
- Department of Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, Hubei, 430072, P.R. China
| | - Zhi-Jie Tan
- Department of Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, Hubei, 430072, P.R. China
| | - Wenbing Zhang
- Department of Physics and Key Laboratory of Artificial Micro and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, Hubei, 430072, P.R. China
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2
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Bayegan AH, Clote P. RNAmountAlign: Efficient software for local, global, semiglobal pairwise and multiple RNA sequence/structure alignment. PLoS One 2020; 15:e0227177. [PMID: 31978147 PMCID: PMC6980424 DOI: 10.1371/journal.pone.0227177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/13/2019] [Indexed: 11/19/2022] Open
Abstract
Alignment of structural RNAs is an important problem with a wide range of applications. Since function is often determined by molecular structure, RNA alignment programs should take into account both sequence and base-pairing information for structural homology identification. This paper describes C++ software, RNAmountAlign, for RNA sequence/structure alignment that runs in O(n3) time and O(n2) space for two sequences of length n; moreover, our software returns a p-value (transformable to expect value E) based on Karlin-Altschul statistics for local alignment, as well as parameter fitting for local and global alignment. Using incremental mountain height, a representation of structural information computable in cubic time, RNAmountAlign implements quadratic time pairwise local, global and global/semiglobal (query search) alignment using a weighted combination of sequence and structural similarity. RNAmountAlign is capable of performing progressive multiple alignment as well. Benchmarking of RNAmountAlign against LocARNA, LARA, FOLDALIGN, DYNALIGN, STRAL, MXSCARNA, and MUSCLE shows that RNAmountAlign has reasonably good accuracy and faster run time supporting all alignment types. Additionally, our extension of RNAmountAlign, called RNAmountAlignScan, which scans a target genome sequence to find hits having high sequence and structural similarity to a given query sequence, outperforms RSEARCH and sequence-only query scans and runs faster than FOLDALIGN query scan.
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Affiliation(s)
- Amir H. Bayegan
- Biology Department, Boston College, Chestnut Hill, MA, United States of America
| | - Peter Clote
- Biology Department, Boston College, Chestnut Hill, MA, United States of America
- * E-mail:
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3
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Boyapati VK, Huang W, Spedale J, Aboul-ela F. Basis for ligand discrimination between ON and OFF state riboswitch conformations: the case of the SAM-I riboswitch. RNA (NEW YORK, N.Y.) 2012; 18:1230-1243. [PMID: 22543867 PMCID: PMC3358645 DOI: 10.1261/rna.032177.111] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 03/17/2012] [Indexed: 05/31/2023]
Abstract
Riboswitches are RNA elements that bind to effector ligands and control gene expression. Most consist of two domains. S-Adenosyl Methionine (SAM) binds the aptamer domain of the SAM-I riboswitch and induces conformational changes in the expression domain to form an intrinsic terminator (transcription OFF state). Without SAM the riboswitch forms the transcription ON state, allowing read-through transcription. The mechanistic link between the SAM/aptamer recognition event and subsequent secondary structure rearrangement by the riboswitch is unclear. We probed for those structural features of the Bacillus subtilis yitJ SAM-I riboswitch responsible for discrimination between the ON and OFF states by SAM. We designed SAM-I riboswitch RNA segments forming "hybrid" structures of the ON and OFF states. The choice of segment constrains the formation of a partial P1 helix, characteristic of the OFF state, together with a partial antiterminator (AT) helix, characteristic of the ON state. For most choices of P1 vs. AT helix lengths, SAM binds with micromolar affinity according to equilibrium dialysis. Mutational analysis and in-line probing confirm that the mode of SAM binding by hybrid structures is similar to that of the aptamer. Altogether, binding measurements and in-line probing are consistent with the hypothesis that when SAM is present, stacking interactions with the AT helix stabilize a partially formed P1 helix in the hybrids. Molecular modeling indicates that continuous stacking between the P1 and the AT helices is plausible with SAM bound. Our findings raise the possibility that conformational intermediates may play a role in ligand-induced aptamer folding.
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Affiliation(s)
- Vamsi Krishna Boyapati
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70802, USA
| | - Wei Huang
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70802, USA
| | - Jessica Spedale
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70802, USA
| | - Fareed Aboul-ela
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70802, USA
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4
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Huang W, Kim J, Jha S, Aboul-Ela F. Conformational heterogeneity of the SAM-I riboswitch transcriptional ON state: a chaperone-like role for S-adenosyl methionine. J Mol Biol 2012; 418:331-49. [PMID: 22425639 DOI: 10.1016/j.jmb.2012.02.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 02/09/2012] [Accepted: 02/15/2012] [Indexed: 10/28/2022]
Abstract
Riboswitches are promising targets for the design of novel antibiotics and engineering of portable genetic regulatory elements. There is evidence that variability in riboswitch properties allows tuning of expression for genes involved in different stages of biosynthetic pathways by mechanisms that are not currently understood. Here, we explore the mechanism for tuning of S-adenosyl methionine (SAM)-I riboswitch folding. Most SAM-I riboswitches function at the transcriptional level by sensing the cognate ligand SAM. SAM-I riboswitches orchestrate the biosynthetic pathways of cysteine, methionine, SAM, and so forth. We use base-pair probability predictions to examine the secondary-structure folding landscape of several SAM-I riboswitch sequences. We predict different folding behaviors for different SAM-I riboswitch sequences. We identify several "decoy" base-pairing interactions involving 5' riboswitch residues that can compete with the formation of a P1 helix, a component of the ligand-bound "transcription OFF" state, in the absence of SAM. We hypothesize that blockage of these interactions through SAM contacts contributes to stabilization of the OFF state in the presence of ligand. We also probe folding patterns for a SAM-I riboswitch RNA using constructs with different 3' truncation points experimentally. Folding was monitored through fluorescence, susceptibility to base-catalyzed cleavage, nuclear magnetic resonance, and indirectly through SAM binding. We identify key decision windows at which SAM can affect the folding pathway towards the OFF state. The presence of decoy conformations and differential sensitivities to SAM at different transcript lengths is crucial for SAM-I riboswitches to modulate gene expression in the context of global cellular metabolism.
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Affiliation(s)
- Wei Huang
- Department of Biological Science, Louisiana State University, Baton Rouge, LA 70803, USA
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5
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de Meaux J, Hu JY, Tartler U, Goebel U. Structurally different alleles of the ath-MIR824 microRNA precursor are maintained at high frequency in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2008; 105:8994-9. [PMID: 18579782 PMCID: PMC2440359 DOI: 10.1073/pnas.0803218105] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Indexed: 12/21/2022] Open
Abstract
In plants and animals, gene expression can be down-regulated at the posttranscriptional level by microRNAs (miRNAs), a class of small endogenous RNA. Comparative analysis of miRNA content across species indicates continuous birth and death of these loci in the course of evolution. However, little is known about the microevolutionary dynamics of these genetic elements, especially in plants. In this article we examine polymorphism at two miRNA-encoding loci in Arabidopsis thaliana, miR856 and miR824, which are not found in rice or poplar. We compare their diversity to other miRNA-encoding loci conserved across distant taxa. We find that levels of variation vary significantly across loci and that the two recently derived loci harbor patterns of diversity deviating from neutrality. miRNA miR856 shows a weak signature of a selective sweep whereas miR824 displays signs of balancing selection. A detailed examination of structural variation among alleles found at the miR824-encoding locus suggests nonrandom evolution of a thermoresistant substructure in the precursor. Expression analysis of pre-miR824 and its target, AGL16, indicates that these structural differences likely impact the processing of mature miR824. Our work highlights the relevance of RNA structure in precursor sequence evolution, suggesting that the evolutionary dynamics of miRNA-encoding loci is more complex than suggested by the constraints exerted on the interaction between mature miRNA fragments and their target exon.
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Affiliation(s)
- Juliette de Meaux
- Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany
| | - Jin-Yong Hu
- Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany
| | - Ute Tartler
- Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany
| | - Ulrike Goebel
- Max Planck Institute for Plant Breeding Research, Carl-von-Linné Weg 10, 50829 Cologne, Germany
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6
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Gruber AR, Bernhart SH, Hofacker IL, Washietl S. Strategies for measuring evolutionary conservation of RNA secondary structures. BMC Bioinformatics 2008; 9:122. [PMID: 18302738 PMCID: PMC2335298 DOI: 10.1186/1471-2105-9-122] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 02/26/2008] [Indexed: 02/01/2023] Open
Abstract
Background Evolutionary conservation of RNA secondary structure is a typical feature of many functional non-coding RNAs. Since almost all of the available methods used for prediction and annotation of non-coding RNA genes rely on this evolutionary signature, accurate measures for structural conservation are essential. Results We systematically assessed the ability of various measures to detect conserved RNA structures in multiple sequence alignments. We tested three existing and eight novel strategies that are based on metrics of folding energies, metrics of single optimal structure predictions, and metrics of structure ensembles. We find that the folding energy based SCI score used in the RNAz program and a simple base-pair distance metric are by far the most accurate. The use of more complex metrics like for example tree editing does not improve performance. A variant of the SCI performed particularly well on highly conserved alignments and is thus a viable alternative when only little evolutionary information is available. Surprisingly, ensemble based methods that, in principle, could benefit from the additional information contained in sub-optimal structures, perform particularly poorly. As a general trend, we observed that methods that include a consensus structure prediction outperformed equivalent methods that only consider pairwise comparisons. Conclusion Structural conservation can be measured accurately with relatively simple and intuitive metrics. They have the potential to form the basis of future RNA gene finders, that face new challenges like finding lineage specific structures or detecting mis-aligned sequences.
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Affiliation(s)
- Andreas R Gruber
- Institute for Theoretical Chemistry, University of Vienna, Währingerstrasse 17, 1090 Wien, Austria.
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7
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Structural constraints and neutrality in RNA. Bioinformatics 2005. [DOI: 10.1007/bfb0033214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] Open
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8
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Peleg O, Trifonov EN, Bolshoy A. Hidden messages in the nef gene of human immunodeficiency virus type 1 suggest a novel RNA secondary structure. Nucleic Acids Res 2003; 31:4192-200. [PMID: 12853637 PMCID: PMC165969 DOI: 10.1093/nar/gkg454] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The coexistence of multiple codes in the genome of human immunodeficiency virus type 1 (HIV-1) was analyzed. We explored factors constraining the variability of the virus genome primarily in relation to conserved RNA secondary structures overlapping coding sequences, and used a simple combination of algorithms for RNA secondary structure prediction based on the nearest-neighbor thermodynamic rules and a statistical approach. In our previous study, we applied this combination to a non- redundant data set of env nucleotide sequences, confirmed the conservative secondary structure of the rev-responsive element (RRE) and found a new RNA structure in the first conserved (C1) region of the env gene. In this study, we analyzed the variability of putative RNA secondary structures inside the nef gene of HIV-1 by applying these algorithms to a non-redundant data set of 104 nef sequences retrieved from the Los Alamos HIV database, and predicted the existence of a novel functional RNA secondary structure in the beta3/beta4 regions of nef. The predicted RNA fold in the beta3/beta4 region of nef appears in two forms with different loop sizes. The loop of the first fold consists of seven nucleotides (positions 494-500), with consensus UCAAGCU appearing in 79% of sequences. The other has a five-base loop (positions 495-499) with consensus CAAGC. The difference in size between these two loops may reflect the difference between respective counterparts in the hairpin recognition. This may also have an adaptive biological significance.
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Affiliation(s)
- Ofer Peleg
- Genome Diversity Center, Institute of Evolution, Haifa University, Mt Carmel, Haifa 31905, Israel
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9
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Abbink TEM, Berkhout B. A novel long distance base-pairing interaction in human immunodeficiency virus type 1 RNA occludes the Gag start codon. J Biol Chem 2003; 278:11601-11. [PMID: 12458192 DOI: 10.1074/jbc.m210291200] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 5'-untranslated region (5'-UTR) is the most conserved part of the HIV-1 RNA genome, and it contains regulatory motifs that mediate various steps in the viral life cycle. Previous work showed that the 5'-terminal 290 nucleotides of HIV-1 RNA adopt two mutually exclusive secondary structures, long distance interaction (LDI) and branched multiple hairpin (BMH). BMH has multiple hairpins, including the dimer initiation signal (DIS) hairpin that mediates RNA dimerization. LDI contains a long distance base-pairing interaction that occludes the DIS region. Consequently, the two conformations differ in their ability to form RNA dimers. In this study, we have presented evidence that the full-length 5'-UTR also adopts the LDI and BMH conformations. The downstream 290-352 region, including the Gag start codon, folds differently in the context of the LDI and BMH structures. These nucleotides form an extended hairpin structure in the LDI conformation, but the same sequences create a novel long distance interaction with upstream U5 sequences in the BMH conformation. The presence of this U5-AUG duplex was confirmed by computer-assisted RNA structure prediction, biochemical analyses, and a phylogenetic survey of different virus isolates. The U5-AUG duplex may influence translation of the Gag protein because it occludes the start codon of the Gag open reading frame.
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Affiliation(s)
- Truus E M Abbink
- Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, 1100 DE Amsterdam, The Netherlands
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10
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Peleg O, Brunak S, Trifonov EN, Nevo E, Bolshoy A. RNA secondary structure and squence conservation in C1 region of human immunodeficiency virus type 1 env gene. AIDS Res Hum Retroviruses 2002; 18:867-78. [PMID: 12201910 DOI: 10.1089/08892220260190353] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
We have analyzed amino acid, nucleotide sequence, and RNA secondary structure variability in the env gene of human immunodeficiency virus type (HIV-1). In applying algorithms for computing optimal RNA-folding patterns to a nonredundant data set of 178 env nucleotide sequences, we found a conserved RNA stem-loop structure in the first conserved (C1) region of the env gene. This detailed examination also revealed the known secondary structure conservation of the Rev-responsive element (RRE). This finding is also supported by a higher third position conservation of the translatable reading frame along these subregions. The typical folding of the C1 region consists of two isolated stem-loop structures. These highly conserved structures are likely to have a biological function. This assumption is supported by the conservation of the third position along the coding region of these structures. The third position retains a conservation level above what would be statistically expected.
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Affiliation(s)
- Ofer Peleg
- Genome Diversity Center, Institute of Evolution, Haifa University, Mt. Carmel, Haifa 31905, Israel
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11
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Abstract
Global properties of the genotype-phenotype map induced by RNA secondary structures can be described by random graph theory. The success of this approach depends on details of the respective secondary structure. A small selection of these dependencies, such as stem length, free energy and well-definedness, are analyzed in this paper. In addition, we present an algorithm, which, given a network that complies to a random graph model, provides estimates whether the network is connected or not. The algorithm is linear in time and in the sequence length, local connectivity provided, which is a graph property of the random graph model.
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12
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Cardozo AK, De Meirleir L, Liebaers I, Lissens W. Analysis of exonic mutations leading to exon skipping in patients with pyruvate dehydrogenase E1 alpha deficiency. Pediatr Res 2000; 48:748-53. [PMID: 11102541 DOI: 10.1203/00006450-200012000-00008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The pyruvate dehydrogenase (PDH) complex is situated at a key position in energy metabolism and is responsible for the conversion of pyruvate to acetyl CoA. In the literature, two unrelated patients with a PDH complex deficiency and splicing out of exon 6 of the PDH E1 alpha gene have been described, although intronic/exonic boundaries on either side of exon 6 were completely normal. Analysis of exon 6 in genomic DNA of these patients revealed two exonic mutations, a silent and a missense mutation. Although not experimentally demonstrated, the authors in both publications suggested that the exonic mutations were responsible for the exon skipping. In this work, we were able to demonstrate, by performing splicing experiments, that the two exonic mutations described in the PDH E1 alpha gene lead to aberrant splicing. We observed a disruption of the predicted wild-type pre-mRNA secondary structure of exon 6 by the mutated sequences described. However, when we constructed mutations that either reverted or disrupted the wild-type predicted pre-mRNA secondary structure of exon 6, we were unable to establish a correlation between the aberrant splicing and disruption of the predicted structure. The mutagenic experiments described here and the silent mutation found in one of the patients suggest the presence of an exonic splicing enhancer in the middle region of exon 6 of the PDH E1alpha gene.
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Affiliation(s)
- A K Cardozo
- Center for Medical Genetics, University Hospital, Vrije Universiteit Brussel, 1090 Brussels, Belgium
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13
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Abstract
New results for calculating nucleic acid secondary structure by free energy minimization and phylogenetic comparisons have recently been reported. A complete set of DNA energy parameters is now available and the RNA parameters have been improved. Although databases of RNA secondary structures are still derived and expanded using computer-assisted, ad hoc comparative analysis, a number of new computer algorithms combine covariation analysis with energy methods.
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Affiliation(s)
- M Zuker
- Department of Biochemistry and Molecular Biophysics, Washington University, St Louis, 63110, USA.
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14
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Fekete M, Hofacker IL, Stadler PF. Prediction of RNA base pairing probabilities on massively parallel computers. J Comput Biol 2000; 7:171-82. [PMID: 10890394 DOI: 10.1089/10665270050081441] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
We present an implementation of McCaskill's algorithm for computing the base pair probabilities of an RNA molecule for massively parallel message passing architectures. The program can be used to routinely fold RNA sequences of more than 10,000 nucleotides. Applications to complete viral genomes are discussed.
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Affiliation(s)
- M Fekete
- Institut für Theoretische Chemie, Universität Wien, Austria
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15
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Hofacker IL, Stadler PF. Automatic detection of conserved base pairing patterns in RNA virus genomes. COMPUTERS & CHEMISTRY 1999; 23:401-14. [PMID: 10404627 DOI: 10.1016/s0097-8485(99)00013-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Almost all RNA molecules--and consequently also almost all subsequences of a large RNA molecule-form secondary structures. The presence of secondary structure in itself therefore does not indicate any functional significance. In fact, we cannot expect a conserved secondary structure for all parts of a viral genome or a mRNA, even if there is a significant level of sequence conservation. We present a novel method for detecting conserved RNA secondary structures in a family of related RNA sequences. The method is based on combining the prediction of base pair probability matrices and comparative sequence analysis. It can be applied to small sets of long sequences and does not require a prior knowledge of conserved sequence or structure motifs. As such it can be used to scan large amounts of sequence data for regions that warrant further experimental investigation. Applications to complete genomic RNAs of some viruses show that in all cases the known secondary structure features are identified. In addition, we predict a substantial number of conserved structural elements which have not been described so far.
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Affiliation(s)
- I L Hofacker
- Institut für Theoretische Chemie, Universität Wien, Austria
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16
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Abstract
An algorithm is presented for generating rigorously all suboptimal secondary structures between the minimum free energy and an arbitrary upper limit. The algorithm is particularly fast in the vicinity of the minimum free energy. This enables the efficient approximation of statistical quantities, such as the partition function or measures for structural diversity. The density of states at low energies and its associated structures are crucial in assessing from a thermodynamic point of view how well-defined the ground state is. We demonstrate this by exploring the role of base modification in tRNA secondary structures, both at the level of individual sequences from Escherichia coli and by comparing artificially generated ensembles of modified and unmodified sequences with the same tRNA structure. The two major conclusions are that (1) base modification considerably sharpens the definition of the ground state structure by constraining energetically adjacent structures to be similar to the ground state, and (2) sequences whose ground state structure is thermodynamically well defined show a significant tendency to buffer single point mutations. This can have evolutionary implications, since selection pressure to improve the definition of ground states with biological function may result in increased neutrality.
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Affiliation(s)
- S Wuchty
- Institut für Theoretische Chemie, Universität Wien, Austria
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17
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18
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Bork P, Dandekar T, Diaz-Lazcoz Y, Eisenhaber F, Huynen M, Yuan Y. Predicting function: from genes to genomes and back. J Mol Biol 1998; 283:707-25. [PMID: 9790834 DOI: 10.1006/jmbi.1998.2144] [Citation(s) in RCA: 262] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Predicting function from sequence using computational tools is a highly complicated procedure that is generally done for each gene individually. This review focuses on the added value that is provided by completely sequenced genomes in function prediction. Various levels of sequence annotation and function prediction are discussed, ranging from genomic sequence to that of complex cellular processes. Protein function is currently best described in the context of molecular interactions. In the near future it will be possible to predict protein function in the context of higher order processes such as the regulation of gene expression, metabolic pathways and signalling cascades. The analysis of such higher levels of function description uses, besides the information from completely sequenced genomes, also the additional information from proteomics and expression data. The final goal will be to elucidate the mapping between genotype and phenotype.
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Affiliation(s)
- P Bork
- European Molecular Biology Laboratory, Meyerhofstr. 1, Heidelberg, PF 10.2209, Germany.
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19
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Hofacker IL, Fekete M, Flamm C, Huynen MA, Rauscher S, Stolorz PE, Stadler PF. Automatic detection of conserved RNA structure elements in complete RNA virus genomes. Nucleic Acids Res 1998; 26:3825-36. [PMID: 9685502 PMCID: PMC147758 DOI: 10.1093/nar/26.16.3825] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We propose a new method for detecting conserved RNA secondary structures in a family of related RNA sequences. Our method is based on a combination of thermodynamic structure prediction and phylogenetic comparison. In contrast to purely phylogenetic methods, our algorithm can be used for small data sets of approximately 10 sequences, efficiently exploiting the information contained in the sequence variability. The procedure constructs a prediction only for those parts of sequences that are consistent with a single conserved structure. Our implementation produces reasonable consensus structures without user interference. As an example we have analysed the complete HIV-1 and hepatitis C virus (HCV) genomes as well as the small segment of hantavirus. Our method confirms the known structures in HIV-1 and predicts previously unknown conserved RNA secondary structures in HCV.
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Affiliation(s)
- I L Hofacker
- Institut für Theoretische Chemie, Universität Wien, Wien, Austria, EMBL, Heidelberg, Germany, Max Delbrück Center, Berlin, Germany
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20
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Huynen M, Gutell R, Konings D. Assessing the reliability of RNA folding using statistical mechanics. J Mol Biol 1997; 267:1104-12. [PMID: 9150399 DOI: 10.1006/jmbi.1997.0889] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have analyzed the base-pairing probability distributions of 16 S and 16 S-like, and 23 S and 23 S-like ribosomal RNAs of Archaea, Bacteria, chloroplasts, mitochondria and Eukarya, as predicted by the partition function approach for RNA folding introduced by McCaskill. A quantitative analysis of the reliability of RNA folding is done by comparing the base-pairing probability distributions with the structures predicted by comparative sequence analysis (comparative structures). We distinguish two factors that show a relationship to the reliability of RNA minimum free energy structure. The first factor is the dominance of one particular base-pair or the absence of base-pairing for a given base within the base-pairing probability distribution (BPPD). We characterize the BPPD per base, including the probability of not base-pairing, by its Shannon entropy (S). The S value indicates the uncertainty about the base-pairing of a base: low S values result from BPPDs that are strongly dominated by a single base-pair or by the absence of base-pairing. We show that bases with low S values have a relatively high probability that their minimum free energy (MFE) structure corresponds to the comparative structure. The BPPDs of prokaryotes that live at high temperatures (thermophilic Archaea and Bacteria) have, calculated at 37 degrees C, lower S values than the BPPDs of prokaryotes that live at lower temperatures (mesophilic and psychrophilic Archaea and Bacteria). This reflects an adaptation of the ribosomal RNAs to the environmental temperature. A second factor that is important to consider with regard to the reliability of MFE structure folding is a variable degree of applicability of the thermodynamic model of RNA folding for different groups of RNAs. Here we show that among the bases that show low S values, the Archaea and Bacteria have similar, high probabilities (0.96 and 0.94 in 16 S and 0.93 and 0.91 in 23 S, respectively) that the MFE structure corresponds to the comparative structure. These probabilities are lower in the chloroplasts (16 S 0.91, 23 S 0.79), mitochondria (16 S-like 0.89, 23 S-like 0.69) and Eukarya (18 S 0.81, 28 S 0.86).
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Affiliation(s)
- M Huynen
- Center for Nonlinear Studies, Los Alamos National Laboratory, NM 87545, USA
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Schuster P, Stadler PF, Renner A. RNA structures and folding: from conventional to new issues in structure predictions. Curr Opin Struct Biol 1997; 7:229-35. [PMID: 9094330 DOI: 10.1016/s0959-440x(97)80030-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Prediction and modeling of RNA structures has become an indispensable tool of biological research disciplines. Currently, reliable predictions require massive input of experimental data. Structure-forming elements are conventional base pairs, as well as a rapidly increasing repertoire of novel structural motifs. New developments extend structural analysis beyond the one-sequence/one-structure paradigm and allow questions that are relevant to molecular evolution to be answered.
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Affiliation(s)
- P Schuster
- Institut für Theoretische Chemie und Strahlenchemie, Universität Wien, Währingerstrabetae 17, A-1090, Wien, Austria.
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Abstract
RNA secondary-structure folding algorithms predict the existence of connected networks of RNA sequences with identical secondary structures. Fitness landscapes that are based on the mapping between RNA sequence and RNA secondary structure hence have many neutral paths. A neutral walk on these fitness landscapes gives access to a virtually unlimited number of secondary structures that are a single point mutation from the neutral path. This shows that neutral evolution explores phenotype space and can play a role in adaptation.
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Affiliation(s)
- M A Huynen
- Theoretical Biology and Biophysics, Los Alamos National Laboratory, MS-K710, Los Alamos, NM 87545, USA
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