1
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Baral P, Sengul MY, MacKerell AD. Grand canonical Monte Carlo and deep learning assisted enhanced sampling to characterize the distribution of Mg2+ and influence of the Drude polarizable force field on the stability of folded states of the twister ribozyme. J Chem Phys 2024; 161:225102. [PMID: 39665326 PMCID: PMC11646137 DOI: 10.1063/5.0241246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2024] [Accepted: 11/21/2024] [Indexed: 12/13/2024] Open
Abstract
Molecular dynamics simulations are crucial for understanding the structural and dynamical behavior of biomolecular systems, including the impact of their environment. However, there is a gap between the time scale of these simulations and that of real-world experiments. To address this problem, various enhanced simulation methods have been developed. In addition, there has been a significant advancement of the force fields used for simulations associated with the explicit treatment of electronic polarizability. In this study, we apply oscillating chemical potential grand canonical Monte Carlo and machine learning methods to determine reaction coordinates combined with metadynamics simulations to explore the role of Mg2+ distribution and electronic polarizability in the context of the classical Drude oscillator polarizable force field on the stability of the twister ribozyme. The introduction of electronic polarizability along with the details of the distribution of Mg2+ significantly stabilizes the simulations with respect to sampling the crystallographic conformation. The introduction of electronic polarizability leads to increased stability over that obtained with the additive CHARMM36 FF reported in a previous study, allowing for a distribution of a wider range of ions to stabilize twister. Specific interactions contributing to stabilization are identified, including both those observed in the crystal structures and additional experimentally unobserved interactions. Interactions of Mg2+ with the bases are indicated to make important contributions to stabilization. Notably, the presence of specific interactions between the Mg2+ ions and bases or the non-bridging phosphate oxygens (NBPOs) leads to enhanced dipole moments of all three moieties. Mg2+-NBPO interactions led to enhanced dipoles of the phosphates but, interestingly, not in all the participating ions. The present results further indicate the importance of electronic polarizability in stabilizing RNA in molecular simulations and the complicated nature of the relationship of Mg2+-RNA interactions with the polarization response of the bases and phosphates.
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Affiliation(s)
- Prabin Baral
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, USA
| | - Mert Y. Sengul
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, USA
| | - Alexander D. MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, Baltimore, Maryland 21201, USA
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2
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Anders AG, Tidwell ED, Gadkari VV, Koutmos M, Ruotolo BT. Collision-Induced Unfolding Reveals Disease-Associated Stability Shifts in Mitochondrial Transfer Ribonucleic Acids. J Am Chem Soc 2024; 146:4412-4420. [PMID: 38329282 DOI: 10.1021/jacs.3c09230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Ribonucleic acids (RNAs) remain challenging targets for structural biology, creating barriers to understanding their vast functions in cellular biology and fully realizing their applications in biotechnology. The inherent dynamism of RNAs creates numerous obstacles in capturing their biologically relevant higher-order structures (HOSs), and as a result, many RNA functions remain unknown. In this study, we describe the development of native ion mobility-mass spectrometry and collision-induced unfolding (CIU) for the structural characterization of a variety of RNAs. We evaluate the ability of these techniques to preserve native structural features in the gas phase across a wide range of functional RNAs. Finally, we apply these tools to study the elusive mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes-associated A3243G mutation. Our data demonstrate that our experimentally determined conditions preserve some solution-state memory of RNAs via the correlated complexity of CIU fingerprints and RNA HOS, the observation of predicted stability shifts in the control RNA samples, and the retention of predicted magnesium binding events in gas-phase RNA ions. Significant differences in collision cross section and stability are observed as a function of the A3243G mutation across a subset of the mitochondrial tRNA maturation pathway. We conclude by discussing the potential application of CIU for the development of RNA-based biotherapeutics and, more broadly, transcriptomic characterization.
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Affiliation(s)
- Anna G Anders
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Elizabeth D Tidwell
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Varun V Gadkari
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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3
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Arteaga S, Dolenz BJ, Znosko BM. Competitive Influence of Alkali Metals in the Ion Atmosphere on Nucleic Acid Duplex Stability. ACS OMEGA 2024; 9:1287-1297. [PMID: 38222622 PMCID: PMC10785066 DOI: 10.1021/acsomega.3c07563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 12/04/2023] [Accepted: 12/11/2023] [Indexed: 01/16/2024]
Abstract
The nonspecific atmosphere around nucleic acids, often termed the ion atmosphere, encompasses a collection of weak ion-nucleic acid interactions. Although nonspecific, the ion atmosphere has been shown to influence nucleic acid folding and structural stability. Studies investigating the composition of the ion atmosphere have shown competitive occupancy of the atmosphere between metal ions in the same solution. Many studies have investigated single ion effects on nucleic acid secondary structure stability; however, no comprehensive studies have investigated how the competitive occupancy of mixed ions in the ion atmosphere influences nucleic acid secondary structure stability. Here, six oligonucleotides were optically melted in buffers containing molar quantities, or mixtures, of either XCl (X = Li, K, Rb, or Cs) or NaCl. A correction factor was developed to better predict RNA duplex stability in solutions containing mixed XCl/NaCl. For solutions containing a 1:1 mixture of XCl/NaCl, one alkali metal chloride contributed more to duplex stability than the other. Overall, there was a 54% improvement in predictive capabilities with the correction factor compared with the standard 1.0 M NaCl nearest-neighbor models. This correction factor can be used in models to better predict RNA secondary structure in solutions containing mixed XCl/NaCl.
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Affiliation(s)
- Sebastian
J. Arteaga
- Department of Chemistry, Saint Louis University, Saint
Louis, Missouri 63103, United States
| | - Bruce J. Dolenz
- Department of Chemistry, Saint Louis University, Saint
Louis, Missouri 63103, United States
| | - Brent M. Znosko
- Department of Chemistry, Saint Louis University, Saint
Louis, Missouri 63103, United States
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4
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Hori N, Thirumalai D. Watching ion-driven kinetics of ribozyme folding and misfolding caused by energetic and topological frustration one molecule at a time. Nucleic Acids Res 2023; 51:10737-10751. [PMID: 37758176 PMCID: PMC10602927 DOI: 10.1093/nar/gkad755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/23/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023] Open
Abstract
Folding of ribozymes into well-defined tertiary structures usually requires divalent cations. How Mg2+ ions direct the folding kinetics has been a long-standing unsolved problem because experiments cannot detect the positions and dynamics of ions. To address this problem, we used molecular simulations to dissect the folding kinetics of the Azoarcus ribozyme by monitoring the path each molecule takes to reach the folded state. We quantitatively establish that Mg2+ binding to specific sites, coupled with counter-ion release of monovalent cations, stimulate the formation of secondary and tertiary structures, leading to diverse pathways that include direct rapid folding and trapping in misfolded structures. In some molecules, key tertiary structural elements form when Mg2+ ions bind to specific RNA sites at the earliest stages of the folding, leading to specific collapse and rapid folding. In others, the formation of non-native base pairs, whose rearrangement is needed to reach the folded state, is the rate-limiting step. Escape from energetic traps, driven by thermal fluctuations, occurs readily. In contrast, the transition to the native state from long-lived topologically trapped native-like metastable states is extremely slow. Specific collapse and formation of energetically or topologically frustrated states occur early in the assembly process.
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Affiliation(s)
- Naoto Hori
- Department of Chemistry, University of Texas, Austin, TX 78712, USA
- School of Pharmacy, University of Nottingham, Nottingham, UK
| | - D Thirumalai
- Department of Chemistry, University of Texas, Austin, TX 78712, USA
- Department of Physics, University of Texas, Austin, TX 78712, USA
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5
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Rico-Pasto M, Ritort F. Temperature-dependent elastic properties of DNA. BIOPHYSICAL REPORTS 2022; 2:100067. [PMID: 36425333 PMCID: PMC9680767 DOI: 10.1016/j.bpr.2022.100067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 07/20/2022] [Indexed: 06/02/2023]
Abstract
Knowledge of the elastic properties, e.g., the persistence length or interphosphate distance, of single-stranded (ss) and double-stranded (ds) DNA under different experimental conditions is critical to characterizing molecular reactions studied with single-molecule techniques. While previous experiments have addressed the dependence of the elastic parameters upon varying ionic strength and contour length, temperature-dependent effects are less studied. Here, we examine the temperature-dependent elasticity of ssDNA and dsDNA in the range 5°C-50°C using a temperature-jump optical trap. We find a temperature softening for dsDNA and a temperature stiffening for ssDNA. Our results highlight the need for a general theory explaining the phenomenology observed.
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Affiliation(s)
- Marc Rico-Pasto
- Small Biosystems Lab, Condensed Matter Physics Department, University of Barcelona, Barcelona, Spain
| | - Felix Ritort
- Small Biosystems Lab, Condensed Matter Physics Department, University of Barcelona, Barcelona, Spain
- Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, Barcelona, Spain
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6
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Sun LZ, Qian JL, Cai P, Xu X. Mutual effects between single-stranded DNA conformation and Na +-Mg 2+ ion competition in mixed salt solutions. Phys Chem Chem Phys 2022; 24:20867-20881. [PMID: 36043348 DOI: 10.1039/d2cp02737b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ion-dependence of single-stranded DNA (ssDNA) conformational changes has attracted growing attention because of its biological and technological importance. Although single-species ion effects have been extensively explored, it is challenging to study the ssDNA conformational properties under mixed monovalent/divalent ion conditions due to the complications of ssDNA flexibility and ion-ion competition. In this study, we apply Langevin dynamics simulations to investigate mixed Na+/Mg2+ ion-dependent ssDNA conformations. The ssDNA structure is described using a coarse-grained model, in which the phosphate, base, and sugar of each nucleotide are represented by three different beads. A novel improvement in our simulation model is that mixed-salt-related electrostatic interactions are computed via combining Manning counterion condensation (MCC) theory with the Monte Carlo tightly bound ion (MCTBI) model. Based on this MCC-MCTBI combination, we report new empirical functions to describe the ion-concentration-dependent and ssDNA conformation/structure-dependent electrostatic effects. The calculation results relating to the ion binding properties and the simulation results relating to the ssDNA conformational properties are validated against experimental results. In addition, our simulation results suggest a quantitative relationship between the ssDNA conformation and Na+-Mg2+ competition; this in turn reveals their mutual impact in the ion atmosphere.
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Affiliation(s)
- Li-Zhen Sun
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Jun-Lin Qian
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Pinggen Cai
- Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China.
| | - Xiaojun Xu
- Institute of Bioinformatics and Medical Engineering, Jiangsu University of Technology, Changzhou, 213001, China
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7
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Martinez-Monge A, Pastor I, Bustamante C, Manosas M, Ritort F. Measurement of the specific and non-specific binding energies of Mg 2+ to RNA. Biophys J 2022; 121:3010-3022. [PMID: 35864738 PMCID: PMC9463699 DOI: 10.1016/j.bpj.2022.07.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Determining the non-specific and specific electrostatic contributions of magnesium binding to RNA is a challenging problem. We introduce a single-molecule method based on measuring the folding energy of a native RNA in magnesium and at its equivalent sodium concentration. The latter is defined so that the folding energy in sodium equals the non-specific electrostatic contribution in magnesium. The sodium equivalent can be estimated according to the empirical 100/1 rule (1 M NaCl is equivalent to 10 mM MgCl2), which is a good approximation for most RNAs. The method is applied to an RNA three-way junction (3WJ) that contains specific Mg2+ binding sites and misfolds into a double hairpin structure without binding sites. We mechanically pull the RNA with optical tweezers and use fluctuation theorems to determine the folding energies of the native and misfolded structures in magnesium (10 mM MgCl2) and at the equivalent sodium condition (1 M NaCl). While the free energies of the misfolded structure are equal in magnesium and sodium, they are not for the native structure, the difference being due to the specific binding energy of magnesium to the 3WJ, which equals ΔG≃ 10 kcal/mol. Besides stabilizing the 3WJ, Mg2+ also kinetically rescues it from the misfolded structure over timescales of tens of seconds in a force-dependent manner. The method should generally be applicable to determine the specific binding energies of divalent cations to other tertiary RNAs.
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Affiliation(s)
- A Martinez-Monge
- Small Biosystems Lab, Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Carrer de Martí i Franquès, 1, 08028 Barcelona, Spain
| | - Isabel Pastor
- Small Biosystems Lab, Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Carrer de Martí i Franquès, 1, 08028 Barcelona, Spain; Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Carlos Bustamante
- Departments of Chemistry, Physics and Molecular and Cell Biology, University of California Berkeley, Berkeley, California; Howard Hughes Medical Institute University of California Berkeley, Berkeley, California; Kavli Energy Nanosciences Institute, University of California Berkeley, Berkeley, California
| | - Maria Manosas
- Small Biosystems Lab, Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Carrer de Martí i Franquès, 1, 08028 Barcelona, Spain; Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
| | - Felix Ritort
- Small Biosystems Lab, Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Carrer de Martí i Franquès, 1, 08028 Barcelona, Spain; Institut de Nanociència i Nanotecnologia (IN2UB), Universitat de Barcelona, 08028 Barcelona, Spain.
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8
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Henning-Knechtel A, Thirumalai D, Kirmizialtin S. Differences in ion-RNA binding modes due to charge density variations explain the stability of RNA in monovalent salts. SCIENCE ADVANCES 2022; 8:eabo1190. [PMID: 35857829 PMCID: PMC9299541 DOI: 10.1126/sciadv.abo1190] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The stability of RNA increases as the charge density of the alkali metal cations increases. The molecular mechanism for this phenomenon remains elusive. To fill this gap, we performed all-atom molecular dynamics pulling simulations of HIV-1 trans-activation response RNA. We first established that the free energy landscape obtained in the simulations is in excellent agreement with the single-molecule optical tweezer experiments. The origin of the stronger stability in sodium compared to potassium is found to be due to the differences in the charge density-related binding modes. The smaller hydrated sodium ion preferentially binds to the highly charged phosphates that have high surface area. In contrast, the larger potassium ions interact with the major grooves. As a result, more cations condense around phosphate groups in the case of sodium ions, leading to the reduction of electrostatic repulsion. Because the proposed mechanism is generic, we predict that the same conclusions are valid for divalent alkaline earth metal cations.
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Affiliation(s)
| | - D. Thirumalai
- Department of Chemistry, University of Texas, Austin, TX 78712, USA
- Corresponding author. (D.T.); (S.K.)
| | - Serdal Kirmizialtin
- Chemistry Program, Math and Sciences, New York University Abu Dhabi, Abu Dhabi, UAE
- Corresponding author. (D.T.); (S.K.)
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9
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Kumar S, Reddy G. TPP Riboswitch Populates Holo-Form-like Structure Even in the Absence of Cognate Ligand at High Mg 2+ Concentration. J Phys Chem B 2022; 126:2369-2381. [PMID: 35298161 DOI: 10.1021/acs.jpcb.1c10794] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Riboswitches are noncoding RNA that regulate gene expression by folding into specific three-dimensional structures (holo-form) upon binding by their cognate ligand in the presence of Mg2+. Riboswitch functioning is also hypothesized to be under kinetic control requiring large cognate ligand concentrations. We ask the question under thermodynamic conditions, can the riboswitches populate structures similar to the holo-form only in the presence of Mg2+ and absence of cognate ligand binding. We addressed this question using thiamine pyrophosphate (TPP) riboswitch as a model system and computer simulations using a coarse-grained model for RNA. The folding free energy surface (FES) shows that with the initial increase in Mg2+ concentration ([Mg2+]), the aptamer domain (AD) of TPP riboswitch undergoes a barrierless collapse in its dimensions. On further increase in [Mg2+], intermediates separated by barriers appear on the FES, and one of the intermediates has a TPP ligand-binding competent structure. We show that site-specific binding of the Mg2+ aids in the formation of tertiary contacts. For [Mg2+] greater than physiological concentration, AD folds into a structure similar to the crystal structure of the TPP holo-form even in the absence of the TPP ligand. The folding kinetics shows that TPP AD populates an intermediate due to the misalignment of two arms present in the structure, which acts as a kinetic trap, leading to larger folding timescales. The predictions of the intermediate structures from the simulations are amenable for experimental verification.
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Affiliation(s)
- Sunil Kumar
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka 560012, India
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka 560012, India
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10
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Jambrec D, Gebala M. DNA Electrostatics: From Theory to Application. ChemElectroChem 2022. [DOI: 10.1002/celc.202101415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Daliborka Jambrec
- Analytische Chemie – Elektroanalytik & Sensorik Ruhr-Universität Bochum Universitätsstr. 150 D-44780 Bochum Germany
| | - Magdalena Gebala
- Department of Biochemistry Stanford University Stanford 94305, CA USA
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11
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Yamagami R, Sieg JP, Bevilacqua PC. Functional Roles of Chelated Magnesium Ions in RNA Folding and Function. Biochemistry 2021; 60:2374-2386. [PMID: 34319696 DOI: 10.1021/acs.biochem.1c00012] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA regulates myriad cellular events such as transcription, translation, and splicing. To perform these essential functions, RNA often folds into complex tertiary structures in which its negatively charged ribose-phosphate backbone interacts with metal ions. Magnesium, the most abundant divalent metal ion in cells, neutralizes the backbone, thereby playing essential roles in RNA folding and function. This has been known for more than 50 years, and there are now thousands of in vitro studies, most of which have used ≥10 mM free Mg2+ ions to achieve optimal RNA folding and function. In the cell, however, concentrations of free Mg2+ ions are much lower, with most Mg2+ ions chelated by metabolites. In this Perspective, we curate data from a number of sources to provide extensive summaries of cellular concentrations of metabolites that bind Mg2+ and to estimate cellular concentrations of metabolite-chelated Mg2+ species, in the representative prokaryotic and eukaryotic systems Escherichia coli, Saccharomyces cerevisiae, and iBMK cells. Recent research from our lab and others has uncovered the fact that such weakly chelated Mg2+ ions can enhance RNA function, including its thermodynamic stability, chemical stability, and catalysis. We also discuss how metabolite-chelated Mg2+ complexes may have played roles in the origins of life. It is clear from this analysis that bound Mg2+ should not be simply considered non-RNA-interacting and that future RNA research, as well as protein research, could benefit from considering chelated magnesium.
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Affiliation(s)
- Ryota Yamagami
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Jacob P Sieg
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Philip C Bevilacqua
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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12
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Kognole AA, MacKerell AD. Contributions and competition of Mg 2+ and K + in folding and stabilization of the Twister ribozyme. RNA (NEW YORK, N.Y.) 2020; 26:1704-1715. [PMID: 32769092 PMCID: PMC7566569 DOI: 10.1261/rna.076851.120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 08/02/2020] [Indexed: 06/11/2023]
Abstract
Native folded and compact intermediate states of RNA typically involve tertiary structures in the presence of divalent ions such as Mg2+ in a background of monovalent ions. In a recent study, we have shown how the presence of Mg2+ impacts the transition from partially unfolded to folded states through a "push-pull" mechanism where the ion both favors and disfavors the sampling of specific phosphate-phosphate interactions. To further understand the ion atmosphere of RNA in folded and partially folded states results from atomistic umbrella sampling and oscillating chemical potential grand canonical Monte Carlo/molecular dynamics (GCMC/MD) simulations are used to obtain atomic-level details of the distributions of Mg2+ and K+ ions around Twister RNA. Results show the presence of 100 mM Mg2+ to lead to increased charge neutralization over that predicted by counterion condensation theory. Upon going from partially unfolded to folded states, overall charge neutralization increases at all studied ion concentrations that, while associated with an increase in the number of direct ion-phosphate interactions, is fully accounted for by the monovalent K+ ions. Furthermore, K+ preferentially interacts with purine N7 atoms of helical regions in partially unfolded states, thereby potentially stabilizing the helical regions. Thus, both secondary helical structures and formation of tertiary structures leads to increased counterion condensation, thereby stabilizing those structural features of Twister. Notably, it is shown that K+ can act as a surrogate for Mg2+ by participating in specific interactions with nonsequential phosphate pairs that occur in the folded state, explaining the ability of Twister to self-cleave at submillimolar Mg2+ concentrations.
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Affiliation(s)
- Abhishek A Kognole
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, USA
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201, USA
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13
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Halder A, Kumar S, Valsson O, Reddy G. Mg 2+ Sensing by an RNA Fragment: Role of Mg 2+-Coordinated Water Molecules. J Chem Theory Comput 2020; 16:6702-6715. [PMID: 32941038 DOI: 10.1021/acs.jctc.0c00589] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RNA molecules selectively bind to specific metal ions to populate their functional active states, making it important to understand their source of ion selectivity. In large RNA systems, metal ions interact with the RNA at multiple locations, making it difficult to decipher the precise role of ions in folding. To overcome this complexity, we studied the role of different metal ions (Mg2+, Ca2+, and K+) in the folding of a small RNA hairpin motif (5'-ucCAAAga-3') using unbiased all-atom molecular dynamics simulations. The advantage of studying this system is that it requires specific binding of a single metal ion to fold to its native state. We find that even for this small RNA, the folding free energy surface (FES) is multidimensional as different metal ions present in the solution can simultaneously facilitate folding. The FES shows that specific binding of a metal ion is indispensable for its folding. We further show that in addition to the negatively charged phosphate groups, the spatial organization of electronegative nucleobase atoms drives the site-specific binding of the metal ions. Even though the binding site cannot discriminate between different metal ions, RNA folds efficiently only in a Mg2+ solution. We show that the rigid network of Mg2+-coordinated water molecules facilitates the formation of important interactions in the transition state. The other metal ions such as K+ and Ca2+ cannot facilitate the formation of such interactions. These results allow us to hypothesize possible metal-sensing mechanisms in large metalloriboswitches and also provide useful insights into the design of appropriate collective variables for studying large RNA molecules using enhanced sampling methods.
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Affiliation(s)
- Antarip Halder
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
| | - Sunil Kumar
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
| | - Omar Valsson
- Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru 560012, Karnataka, India
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14
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Zhao C, Zhang D, Jiang Y, Chen SJ. Modeling Loop Composition and Ion Concentration Effects in RNA Hairpin Folding Stability. Biophys J 2020; 119:1439-1455. [PMID: 32949490 PMCID: PMC7568001 DOI: 10.1016/j.bpj.2020.07.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 06/12/2020] [Accepted: 07/08/2020] [Indexed: 12/21/2022] Open
Abstract
The ability to accurately predict RNA hairpin structure and stability for different loop sequences and salt conditions is important for understanding, modeling, and designing larger RNA folds. However, traditional RNA secondary structure models cannot treat loop-sequence and ionic effects on RNA hairpin folding. Here, we describe a general, three-dimensional (3D) conformation-based computational method for modeling salt concentration-dependent conformational distributions and the detailed 3D structures for a set of three RNA hairpins that contain a variable, 15-nucleotide loop sequence. For a given RNA sequence, the new, to our knowledge, method integrates a Vfold2D two-dimensional structure folding model with IsRNA coarse-grained molecular dynamics 3D folding simulations and Monte Carlo tightly bound ion estimations of ion-mediated electrostatic interactions. The model predicts free-energy landscapes for the different RNA hairpin-forming sequences with variable salt conditions. The theoretically predicted results agree with the experimental fluorescence measurements, validating the strategy. Furthermore, the theoretical model goes beyond the experimental results by enabling in-depth 3D structural analysis, revealing energetic mechanisms for the sequence- and salt-dependent folding stability. Although the computational framework presented here is developed for RNA hairpin systems, the general method may be applied to investigate other RNA systems, such as multiway junctions or pseudoknots in mixed metal ion solutions.
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Affiliation(s)
- Chenhan Zhao
- Department of Physics, Department of Biochemistry, and Institute for Data Science and Informatics, University of Missouri, Columbia, Missouri
| | - Dong Zhang
- Department of Physics, Department of Biochemistry, and Institute for Data Science and Informatics, University of Missouri, Columbia, Missouri
| | - Yangwei Jiang
- Department of Physics, Department of Biochemistry, and Institute for Data Science and Informatics, University of Missouri, Columbia, Missouri
| | - Shi-Jie Chen
- Department of Physics, Department of Biochemistry, and Institute for Data Science and Informatics, University of Missouri, Columbia, Missouri.
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15
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Nguyen HT, Thirumalai D. Charge Density of Cation Determines Inner versus Outer Shell Coordination to Phosphate in RNA. J Phys Chem B 2020; 124:4114-4122. [PMID: 32342689 DOI: 10.1021/acs.jpcb.0c02371] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Divalent cations are often required to fold RNA, which is a highly charged polyanion. Condensation of ions, such as Mg2+ or Ca2+, in the vicinity of RNA renormalizes the effective charges on the phosphate groups, thus minimizing the intra RNA electrostatic repulsion. The prevailing view is that divalent ions bind diffusively in a nonspecific manner. In sharp contrast, we arrive at the exact opposite conclusion using a theory for the interaction of ions with the phosphate groups using RISM theory in conjunction with simulations based on an accurate three-interaction-site RNA model. The divalent ions bind in a nucleotide-specific manner using either the inner (partially dehydrated) or outer (fully hydrated) shell coordination. The high charge density Mg2+ ion has a preference to bind to the outer shell, whereas the opposite is the case for Ca2+. Surprisingly, we find that bridging interactions, involving ions that are coordinated to two or more phosphate groups, play a crucial role in maintaining the integrity of the folded state. Their importance could become increasingly prominent as the size of the RNA increases. Because the modes of interaction of divalent ions with DNA are likely to be similar, we propose that specific inner and outer shell coordination could play a role in DNA condensation, and perhaps genome organization as well.
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Affiliation(s)
- Hung T Nguyen
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - D Thirumalai
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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16
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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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17
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Tack DC, Su Z, Yu Y, Bevilacqua PC, Assmann SM. Tissue-specific changes in the RNA structurome mediate salinity response in Arabidopsis. RNA (NEW YORK, N.Y.) 2020; 26:492-511. [PMID: 31937672 PMCID: PMC7075263 DOI: 10.1261/rna.072850.119] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 01/13/2020] [Indexed: 05/22/2023]
Abstract
Little is known concerning the effects of abiotic factors on in vivo RNA structures. We applied Structure-seq to assess the in vivo mRNA structuromes of Arabidopsis thaliana under salinity stress, which negatively impacts agriculture. Structure-seq utilizes dimethyl sulfate reactivity to identify As and Cs that lack base-pairing or protection. Salt stress refolded transcripts differentially in root versus shoot, evincing tissue specificity of the structurome. Both tissues exhibited an inverse correlation between salt stress-induced changes in transcript reactivity and changes in abundance, with stress-related mRNAs showing particular structural dynamism. This inverse correlation is more pronounced in mRNAs wherein the mean reactivity of the 5'UTR, CDS, and 3'UTR concertedly change under salinity stress, suggesting increased susceptibility to abundance control mechanisms in transcripts exhibiting this phenomenon, which we name "concordancy." Concordant salinity-induced increases in reactivity were notably observed in photosynthesis genes, thereby implicating mRNA structural loss in the well-known depression of photosynthesis by salt stress. Overall, changes in secondary structure appear to impact mRNA abundance, molding the functional specificity of the transcriptome under stress.
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Affiliation(s)
- David C Tack
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Spectrum Health Office of Research, Grand Rapids, Michigan 49503, USA
| | - Zhao Su
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Yunqing Yu
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Philip C Bevilacqua
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Sarah M Assmann
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- Center for RNA Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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18
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Kognole AA, MacKerell AD. Mg 2+ Impacts the Twister Ribozyme through Push-Pull Stabilization of Nonsequential Phosphate Pairs. Biophys J 2020; 118:1424-1437. [PMID: 32053774 PMCID: PMC7091459 DOI: 10.1016/j.bpj.2020.01.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 12/23/2019] [Accepted: 01/21/2020] [Indexed: 11/15/2022] Open
Abstract
RNA molecules perform a variety of biological functions for which the correct three-dimensional structure is essential, including as ribozymes where they catalyze chemical reactions. Metal ions, especially Mg2+, neutralize these negatively charged nucleic acids and specifically stabilize RNA tertiary structures as well as impact the folding landscape of RNAs as they assume their tertiary structures. Specific binding sites of Mg2+ in folded conformations of RNA have been studied extensively; however, the full range of interactions of the ion with compact intermediates and unfolded states of RNA is challenging to investigate, and the atomic details of the mechanism by which the ion facilitates tertiary structure formation is not fully known. Here, umbrella sampling combined with oscillating chemical potential Grand Canonical Monte Carlo/molecular dynamics simulations are used to capture the energetics and atomic-level details of Mg2+-RNA interactions that occur along an unfolding pathway of the Twister ribozyme. The free energy profiles reveal stabilization of partially unfolded states by Mg2+, as observed in unfolding experiments, with this stabilization being due to increased sampling of simultaneous interactions of Mg2+ with two or more nonsequential phosphate groups. Notably, these results indicate a push-pull mechanism in which the Mg2+-RNA interactions actually lead to destabilization of specific nonsequential phosphate-phosphate interactions (i.e., pushed apart), whereas other interactions are stabilized (i.e., pulled together), a balance that stabilizes unfolded states and facilitates the folding of Twister, including the formation of hydrogen bonds associated with the tertiary structure. This study establishes a better understanding of how Mg2+-ion interactions contribute to RNA structural properties and stability.
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Affiliation(s)
- Abhishek A Kognole
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland
| | - Alexander D MacKerell
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland.
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19
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Sung HL, Nesbitt DJ. Correction: High pressure single-molecule FRET studies of the lysine riboswitch: cationic and osmolytic effects on pressure induced denaturation. Phys Chem Chem Phys 2020; 22:17008-17009. [DOI: 10.1039/d0cp90155e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Correction for ‘High pressure single-molecule FRET studies of the lysine riboswitch: cationic and osmolytic effects on pressure induced denaturation’ by Hsuan-Lei Sung et al., Phys. Chem. Chem. Phys., 2020, DOI: 10.1039/d0cp01921f.
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Affiliation(s)
- Hsuan-Lei Sung
- JILA
- National Institute of Standards and Technology and University of Colorado
- Boulder
- USA
- Department of Chemistry and Biochemistry
| | - David J. Nesbitt
- JILA
- National Institute of Standards and Technology and University of Colorado
- Boulder
- USA
- Department of Chemistry and Biochemistry
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20
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Theory and simulations for RNA folding in mixtures of monovalent and divalent cations. Proc Natl Acad Sci U S A 2019; 116:21022-21030. [PMID: 31570624 DOI: 10.1073/pnas.1911632116] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
RNA molecules cannot fold in the absence of counterions. Experiments are typically performed in the presence of monovalent and divalent cations. How to treat the impact of a solution containing a mixture of both ion types on RNA folding has remained a challenging problem for decades. By exploiting the large concentration difference between divalent and monovalent ions used in experiments, we develop a theory based on the reference interaction site model (RISM), which allows us to treat divalent cations explicitly while keeping the implicit screening effect due to monovalent ions. Our theory captures both the inner shell and outer shell coordination of divalent cations to phosphate groups, which we demonstrate is crucial for an accurate calculation of RNA folding thermodynamics. The RISM theory for ion-phosphate interactions when combined with simulations based on a transferable coarse-grained model allows us to predict accurately the folding of several RNA molecules in a mixture containing monovalent and divalent ions. The calculated folding free energies and ion-preferential coefficients for RNA molecules (pseudoknots, a fragment of the rRNA, and the aptamer domain of the adenine riboswitch) are in excellent agreement with experiments over a wide range of monovalent and divalent ion concentrations. Because the theory is general, it can be readily used to investigate ion and sequence effects on DNA properties.
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21
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Sun LZ, Zhou Y, Chen SJ. Predicting Monovalent Ion Correlation Effects in Nucleic Acids. ACS OMEGA 2019; 4:13435-13446. [PMID: 31460472 PMCID: PMC6705202 DOI: 10.1021/acsomega.9b01689] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2019] [Accepted: 07/18/2019] [Indexed: 05/14/2023]
Abstract
Ion correlation and fluctuation can play a potentially significant role in metal ion-nucleic acid interactions. Previous studies have focused on the effects for multivalent cations. However, the correlation and fluctuation effects can be important also for monovalent cations around the nucleic acid surface. Here, we report a model, gMCTBI, that can explicitly treat discrete distributions of both monovalent and multivalent cations and can account for the correlation and fluctuation effects for the cations in the solution. The gMCTBI model enables investigation of the global ion binding properties as well as the detailed discrete distributions of the bound ions. Accounting for the ion correlation effect for monovalent ions can lead to more accurate predictions, especially in a mixed monovalent and multivalent salt solution, for the number and location of the bound ions. Furthermore, although the monovalent ion-mediated correlation does not show a significant effect on the number of bound ions, the correlation may enhance the accumulation of monovalent ions near the nucleic acid surface and hence affect the ion distribution. The study further reveals novel ion correlation-induced effects in the competition between the different cations around nucleic acids.
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Affiliation(s)
- Li-Zhen Sun
- Department
of Applied Physics, Zhejiang University
of Technology, Hangzhou 310023, China
- Department
of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri, Columbia, Missouri 65211, United States
| | - Yuanzhe Zhou
- Department
of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri, Columbia, Missouri 65211, United States
| | - Shi-Jie Chen
- Department
of Physics, Department of Biochemistry, and Informatics Institute, University of Missouri, Columbia, Missouri 65211, United States
- E-mail:
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22
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Hori N, Denesyuk NA, Thirumalai D. Ion Condensation onto Ribozyme Is Site Specific and Fold Dependent. Biophys J 2019; 116:2400-2410. [PMID: 31130233 DOI: 10.1016/j.bpj.2019.04.037] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 04/12/2019] [Accepted: 04/23/2019] [Indexed: 01/20/2023] Open
Abstract
The highly charged RNA molecules, with each phosphate carrying a single negative charge, cannot fold into well-defined architectures with tertiary interactions in the absence of ions. For ribozymes, divalent cations are known to be more efficient than monovalent ions in driving them to a compact state, although Mg2+ ions are needed for catalytic activities. Therefore, how ions interact with RNA is relevant in understanding RNA folding. It is often thought that most of the ions are territorially and nonspecifically bound to the RNA, as predicted by the counterion condensation theory. Here, we show using simulations of Azoarcus ribozyme, based on an accurate coarse-grained three-site interaction model with explicit divalent and monovalent cations, that ion condensation is highly specific and depends on the nucleotide position. The regions with high coordination between the phosphate groups and the divalent cations are discernible even at very low Mg2+ concentrations when the ribozyme does not form tertiary interactions. Surprisingly, these regions also contain the secondary structural elements that nucleate subsequently in the self-assembly of RNA, implying that ion condensation is determined by the architecture of the folded state. These results are in sharp contrast to interactions of ions (monovalent and divalent) with rigid charged rods, in which ion condensation is uniform and position independent. The differences are explained in terms of the dramatic nonmonotonic shape fluctuations in the ribozyme as it folds with increasing Mg2+ or Ca2+ concentration.
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Affiliation(s)
- Naoto Hori
- Department of Chemistry, University of Texas, Austin, Texas
| | - Natalia A Denesyuk
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland
| | - D Thirumalai
- Department of Chemistry, University of Texas, Austin, Texas.
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23
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Mandic A, Hayes RL, Lammert H, Cheng RR, Onuchic JN. Structure-Based Model of RNA Pseudoknot Captures Magnesium-Dependent Folding Thermodynamics. J Phys Chem B 2019; 123:1505-1511. [PMID: 30676755 DOI: 10.1021/acs.jpcb.8b10791] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We develop a simple, coarse-grained approach for simulating the folding of the Beet Western Yellow Virus (BWYV) pseudoknot toward the goal of creating a transferable model that can be used to study other small RNA molecules. This approach combines a structure-based model (SBM) of RNA with an electrostatic scheme that has previously been shown to correctly reproduce ionic condensation in the native basin. Mg2+ ions are represented explicitly, directly incorporating ion-ion correlations into the system, and K+ is represented implicitly, through the mean-field generalized Manning counterion condensation theory. Combining the electrostatic scheme with a SBM enables the electrostatic scheme to be tested beyond the native basin. We calibrate the SBM to reproduce experimental BWYV unfolding data by eliminating overstabilizing backbone interactions from the molecular contact map and by strengthening base pairing and stacking contacts relative to other native contacts, consistent with the experimental observation that relative helical stabilities are central determinants of the RNA unfolding sequence. We find that this approach quantitatively captures the Mg2+ dependence of the folding temperature and generates intermediate states that better approximate those revealed by experiment. Finally, we examine how our model captures Mg2+ condensation about the BWYV pseudoknot and a U-tail variant, for which the nine 3' end nucleotides are replaced with uracils, and find our results to be consistent with experimental condensation measurements. This approach can be easily transferred to other RNA molecules by eliminating and strengthening the same classes of contacts in the SBM and including generalized Manning counterion condensation.
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Affiliation(s)
- Ana Mandic
- Center for Theoretical Biological Physics , Rice University , Houston , Texas 77005 , United States
| | - Ryan L Hayes
- Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Heiko Lammert
- Center for Theoretical Biological Physics , Rice University , Houston , Texas 77005 , United States
| | - Ryan R Cheng
- Center for Theoretical Biological Physics , Rice University , Houston , Texas 77005 , United States
| | - José N Onuchic
- Center for Theoretical Biological Physics , Rice University , Houston , Texas 77005 , United States
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24
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Denesyuk NA, Hori N, Thirumalai D. Molecular Simulations of Ion Effects on the Thermodynamics of RNA Folding. J Phys Chem B 2018; 122:11860-11867. [PMID: 30468380 DOI: 10.1021/acs.jpcb.8b08142] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
How ions affect RNA folding thermodynamics and kinetics is an important but a vexing problem that remains unsolved. Experiments have shown that the free-energy change, Δ G( c), of RNA upon folding varies with the salt concentration ( c) as, Δ G( c) = k c ln c + const, where the coefficient k c is proportional to the difference in the ion preferential coefficient, ΔΓ. We performed simulations of a coarse-grained model, by modeling electrostatic interactions implicitly and with explicit representation of ions, to elucidate the molecular underpinnings of the relationship between Δ G and ΔΓ. The simulations quantitatively reproduce the heat capacity for a pseudoknot, thus validating the model. We show that Δ G( c), calculated directly from ΔΓ, varies linearly with ln c ( c < 0.2 M), for a hairpin and the pseudoknot, demonstrating a molecular link between the two quantities. Explicit ion simulations also show the linear dependence of Δ G( c) on ln c at all c with k c = 2 kB T, except that Δ G( c) values are shifted by ∼2 kcal/mol higher than experiments. The discrepancy is due to an underestimation of Γ for both the folded and unfolded states while giving accurate values for ΔΓ. The predictions for the salt dependence of ΔΓ are amenable to test using single-molecule pulling experiments. The framework provided here can be used to obtain accurate thermodynamics for other RNA molecules as well.
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Affiliation(s)
- Natalia A Denesyuk
- Department of Chemistry and Biochemistry and Biophysics Program, Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States
| | - Naoto Hori
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
| | - D Thirumalai
- Department of Chemistry , University of Texas at Austin , Austin , Texas 78712 , United States
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25
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Roh JH, Kilburn D, Behrouzi R, Sung W, Briber RM, Woodson SA. Effects of Preferential Counterion Interactions on the Specificity of RNA Folding. J Phys Chem Lett 2018; 9:5726-5732. [PMID: 30211556 PMCID: PMC6351067 DOI: 10.1021/acs.jpclett.8b02086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The real-time search for native RNA structure is essential for the operation of regulatory RNAs. We previously reported that a fraction of the Azoarcus ribozyme achieves a compact structure in less than a millisecond. To scrutinize the forces that drive initial folding steps, we used time-resolved SAXS to compare the folding dynamics of this ribozyme in thermodynamically isostable concentrations of different counterions. The results show that the size of the fast-folding population increases with the number of available counterions and correlates with the flexibility of initial RNA structures. Within 1 ms of folding, Mg2+ exhibits a smaller preferential interaction coefficient per charge, ΔΓ+/ Z, than Na+ or [Co(NH3)6]3+. The lower ΔΓ+/ Z corresponds to a smaller yield of folded RNA, although Mg2+ stabilizes native RNA more efficiently than other ions at equilibrium. These results suggest that strong Mg2+-RNA interactions impede the search for globally native structure during early folding stages.
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Affiliation(s)
- Joon Ho Roh
- Department of Materials Science and Engineering , University of Maryland , College Park , Maryland 20742 , United States
- T. C. Jenkins Department of Biophysics , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Duncan Kilburn
- T. C. Jenkins Department of Biophysics , Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Reza Behrouzi
- Cell Biology , Harvard Medical School , Boston , Massachusetts 02115 , United States
| | - Wokyung Sung
- Department of Physics , Pohang University of Science and Technology , Pohang 37673 , Republic of Korea
| | - R M Briber
- Department of Materials Science and Engineering , University of Maryland , College Park , Maryland 20742 , United States
| | - Sarah A Woodson
- T. C. Jenkins Department of Biophysics , Johns Hopkins University , Baltimore , Maryland 21218 , United States
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26
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Elucidating Solvation Structures for Rational Design of Multivalent Electrolytes-A Review. Top Curr Chem (Cham) 2018; 376:19. [PMID: 29700688 PMCID: PMC5920006 DOI: 10.1007/s41061-018-0195-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 03/23/2018] [Indexed: 11/25/2022]
Abstract
Fundamental molecular-level understanding of functional properties of liquid solutions provides an important basis for designing optimized electrolytes for numerous applications. In particular, exhaustive knowledge of solvation structure, stability, and transport properties is critical for developing stable electrolytes for fast-charging and high-energy-density next-generation energy storage systems. Accordingly, there is growing interest in the rational design of electrolytes for beyond lithium-ion systems by tuning the molecular-level interactions of solvate species present in the electrolytes. Here we present a review of the solvation structure of multivalent electrolytes and its impact on the electrochemical performance of these batteries. A direct correlation between solvate species present in the solution and macroscopic properties of electrolytes is sparse for multivalent electrolytes and contradictory results have been reported in the literature. This review aims to illustrate the current understanding, compare results, and highlight future needs and directions to enable the deep understanding needed for the rational design of improved multivalent electrolytes.
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27
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Šponer J, Bussi G, Krepl M, Banáš P, Bottaro S, Cunha RA, Gil-Ley A, Pinamonti G, Poblete S, Jurečka P, Walter NG, Otyepka M. RNA Structural Dynamics As Captured by Molecular Simulations: A Comprehensive Overview. Chem Rev 2018; 118:4177-4338. [PMID: 29297679 PMCID: PMC5920944 DOI: 10.1021/acs.chemrev.7b00427] [Citation(s) in RCA: 357] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Indexed: 12/14/2022]
Abstract
With both catalytic and genetic functions, ribonucleic acid (RNA) is perhaps the most pluripotent chemical species in molecular biology, and its functions are intimately linked to its structure and dynamics. Computer simulations, and in particular atomistic molecular dynamics (MD), allow structural dynamics of biomolecular systems to be investigated with unprecedented temporal and spatial resolution. We here provide a comprehensive overview of the fast-developing field of MD simulations of RNA molecules. We begin with an in-depth, evaluatory coverage of the most fundamental methodological challenges that set the basis for the future development of the field, in particular, the current developments and inherent physical limitations of the atomistic force fields and the recent advances in a broad spectrum of enhanced sampling methods. We also survey the closely related field of coarse-grained modeling of RNA systems. After dealing with the methodological aspects, we provide an exhaustive overview of the available RNA simulation literature, ranging from studies of the smallest RNA oligonucleotides to investigations of the entire ribosome. Our review encompasses tetranucleotides, tetraloops, a number of small RNA motifs, A-helix RNA, kissing-loop complexes, the TAR RNA element, the decoding center and other important regions of the ribosome, as well as assorted others systems. Extended sections are devoted to RNA-ion interactions, ribozymes, riboswitches, and protein/RNA complexes. Our overview is written for as broad of an audience as possible, aiming to provide a much-needed interdisciplinary bridge between computation and experiment, together with a perspective on the future of the field.
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Affiliation(s)
- Jiří Šponer
- Institute of Biophysics of the Czech Academy of Sciences , Kralovopolska 135 , Brno 612 65 , Czech Republic
| | - Giovanni Bussi
- Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , Trieste 34136 , Italy
| | - Miroslav Krepl
- Institute of Biophysics of the Czech Academy of Sciences , Kralovopolska 135 , Brno 612 65 , Czech Republic
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science , Palacky University Olomouc , 17. listopadu 12 , Olomouc 771 46 , Czech Republic
| | - Pavel Banáš
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science , Palacky University Olomouc , 17. listopadu 12 , Olomouc 771 46 , Czech Republic
| | - Sandro Bottaro
- Structural Biology and NMR Laboratory, Department of Biology , University of Copenhagen , Copenhagen 2200 , Denmark
| | - Richard A Cunha
- Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , Trieste 34136 , Italy
| | - Alejandro Gil-Ley
- Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , Trieste 34136 , Italy
| | - Giovanni Pinamonti
- Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , Trieste 34136 , Italy
| | - Simón Poblete
- Scuola Internazionale Superiore di Studi Avanzati , Via Bonomea 265 , Trieste 34136 , Italy
| | - Petr Jurečka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science , Palacky University Olomouc , 17. listopadu 12 , Olomouc 771 46 , Czech Republic
| | - Nils G Walter
- Single Molecule Analysis Group and Center for RNA Biomedicine, Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science , Palacky University Olomouc , 17. listopadu 12 , Olomouc 771 46 , Czech Republic
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28
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The 2D Structure of the T. brucei Preedited RPS12 mRNA Is Not Affected by Macromolecular Crowding. J Nucleic Acids 2017; 2017:6067345. [PMID: 28698807 PMCID: PMC5494072 DOI: 10.1155/2017/6067345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 04/04/2017] [Indexed: 11/17/2022] Open
Abstract
Mitochondrial transcript maturation in African trypanosomes requires RNA editing to convert sequence-deficient pre-mRNAs into translatable mRNAs. The different pre-mRNAs have been shown to adopt highly stable 2D folds; however, it is not known whether these structures resemble the in vivo folds given the extreme "crowding" conditions within the mitochondrion. Here, we analyze the effects of macromolecular crowding on the structure of the mitochondrial RPS12 pre-mRNA. We use high molecular mass polyethylene glycol as a macromolecular cosolute and monitor the structure of the RNA globally and with nucleotide resolution. We demonstrate that crowding has no impact on the 2D fold and we conclude that the MFE structure in dilute solvent conditions represents a good proxy for the folding of the pre-mRNA in its mitochondrial solvent context.
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29
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Lemkul J, Lakkaraju SK, MacKerell AD. Characterization of Mg 2+ Distributions around RNA in Solution. ACS OMEGA 2016; 1:680-688. [PMID: 27819065 PMCID: PMC5088455 DOI: 10.1021/acsomega.6b00241] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Accepted: 10/17/2016] [Indexed: 05/20/2023]
Abstract
Binding of metal ions is an important factor governing the folding and dynamics of RNA. Shielding of charges in the polyanionic backbone allows RNA to adopt a diverse range of folded structures that give rise to their many functions within the cell. Some RNA sequences fold only in the presence of Mg2+, which may be bound via direct interactions or occupy the more diffuse "ion atmosphere" around the RNA. To understand the driving forces for RNA folding, it is important to be able to fully characterize the distribution of metal ions around the RNA. In this work, a combined Grand Canonical Monte Carlo-Molecular Dynamics (GCMC-MD) method is applied to characterize Mg2+ distributions around folded RNA structures. The GCMC-MD approach identifies known inner- and outer-shell Mg2+ coordination, while also predicting new regions occupied by Mg2+ that are not observed in crystal structures but that may be relevant in solution, including the case of the Mg2+ riboswitch, for which alternate Mg2+ binding sites may have implications for its function. This work represents a significant step forward in establishing a structural and thermodynamic description of RNA-Mg2+ interactions and their role in RNA structure and function.
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30
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Kilburn D, Behrouzi R, Lee HT, Sarkar K, Briber RM, Woodson SA. Entropic stabilization of folded RNA in crowded solutions measured by SAXS. Nucleic Acids Res 2016; 44:9452-9461. [PMID: 27378777 PMCID: PMC5100557 DOI: 10.1093/nar/gkw597] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 06/21/2016] [Indexed: 01/29/2023] Open
Abstract
Non-coding RNAs must fold into specific structures that are stabilized by metal ions and other co-solutes in the cell's interior. Large crowder molecules such as PEG stabilize a bacterial group I ribozyme so that the RNA folds in low Mg2+ concentrations typical of the cell's interior. To understand the thermodynamic origins of stabilization by crowder molecules, small angle X-ray scattering was used to measure the folding and helix assembly of a bacterial group I ribozyme at different temperatures and in different MgCl2 and polyethylene glycol (PEG) concentrations. The resulting phase diagrams show that perturbations to folding by each variable do not overlap. A favorable enthalpy change drives the formation of compact, native-like structures, but requires Mg2+ ions at all temperatures studied (5–55°C). PEG reduces the entropic cost of helix assembly and increases correlations between RNA segments at all temperatures. The phase diagrams also revealed a semi-compact intermediate between the unfolded and folded ensemble that is locally more flexible than the unfolded state, as judged by SHAPE modification. These results suggest that environmental variables such as temperature and solute density will favor different types of RNA structures.
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Affiliation(s)
- Duncan Kilburn
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Reza Behrouzi
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Hui-Ting Lee
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Krishnarjun Sarkar
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Robert M Briber
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Sarah A Woodson
- T. C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA
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31
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Hori N, Denesyuk NA, Thirumalai D. Salt Effects on the Thermodynamics of a Frameshifting RNA Pseudoknot under Tension. J Mol Biol 2016; 428:2847-59. [PMID: 27315694 DOI: 10.1016/j.jmb.2016.06.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/06/2016] [Accepted: 06/07/2016] [Indexed: 12/24/2022]
Abstract
Because of the potential link between -1 programmed ribosomal frameshifting and response of a pseudoknot (PK) RNA to force, a number of single-molecule pulling experiments have been performed on PKs to decipher the mechanism of programmed ribosomal frameshifting. Motivated in part by these experiments, we performed simulations using a coarse-grained model of RNA to describe the response of a PK over a range of mechanical forces (fs) and monovalent salt concentrations (Cs). The coarse-grained simulations quantitatively reproduce the multistep thermal melting observed in experiments, thus validating our model. The free energy changes obtained in simulations are in excellent agreement with experiments. By varying f and C, we calculated the phase diagram that shows a sequence of structural transitions, populating distinct intermediate states. As f and C are changed, the stem-loop tertiary interactions rupture first, followed by unfolding of the 3'-end hairpin (I⇌F). Finally, the 5'-end hairpin unravels, producing an extended state (E⇌I). A theoretical analysis of the phase boundaries shows that the critical force for rupture scales as (logCm)(α) with α=1(0.5) for E⇌I (I⇌F) transition. This relation is used to obtain the preferential ion-RNA interaction coefficient, which can be quantitatively measured in single-molecule experiments, as done previously for DNA hairpins. A by-product of our work is the suggestion that the frameshift efficiency is likely determined by the stability of the 5'-end hairpin that the ribosome first encounters during translation.
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Affiliation(s)
- Naoto Hori
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
| | - Natalia A Denesyuk
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA
| | - D Thirumalai
- Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, MD 20742, USA.
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32
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How do metal ions direct ribozyme folding? Nat Chem 2015; 7:793-801. [PMID: 26391078 DOI: 10.1038/nchem.2330] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 07/20/2015] [Indexed: 02/07/2023]
Abstract
Ribozymes, which carry out phosphoryl-transfer reactions, often require Mg(2+) ions for catalytic activity. The correct folding of the active site and ribozyme tertiary structure is also regulated by metal ions in a manner that is not fully understood. Here we employ coarse-grained molecular simulations to show that individual structural elements of the group I ribozyme from the bacterium Azoarcus form spontaneously in the unfolded ribozyme even at very low Mg(2+) concentrations, and are transiently stabilized by the coordination of Mg(2+) ions to specific nucleotides. However, competition for scarce Mg(2+) and topological constraints that arise from chain connectivity prevent the complete folding of the ribozyme. A much higher Mg(2+) concentration is required for complete folding of the ribozyme and stabilization of the active site. When Mg(2+) is replaced by Ca(2+) the ribozyme folds, but the active site remains unstable. Our results suggest that group I ribozymes utilize the same interactions with specific metal ligands for both structural stability and chemical activity.
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33
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Hayes RL, Noel JK, Mandic A, Whitford PC, Sanbonmatsu KY, Mohanty U, Onuchic JN. Generalized Manning Condensation Model Captures the RNA Ion Atmosphere. PHYSICAL REVIEW LETTERS 2015; 114:258105. [PMID: 26197147 PMCID: PMC4833092 DOI: 10.1103/physrevlett.114.258105] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Indexed: 05/27/2023]
Abstract
RNA is highly sensitive to the ionic environment and typically requires Mg(2+) to form compact structures. There is a need for models capable of describing the ion atmosphere surrounding RNA with quantitative accuracy. We present a model of RNA electrostatics and apply it within coarse-grained molecular dynamics simulation. The model treats Mg(2+) ions explicitly to account for ion-ion correlations neglected by mean-field theories. Since mean-field theories capture KCl well, it is treated implicitly by a generalized Manning counterion condensation model. The model extends Manning condensation to deal with arbitrary RNA conformations, nonlimiting KCl concentrations, and the ion inaccessible volume of RNA. The model is tested against experimental measurements of the excess Mg(2+) associated with the RNA, Γ(2+), because Γ(2+) is directly related to the Mg(2+)-RNA interaction free energy. The excellent agreement with experiment demonstrates that the model captures the ionic dependence of the RNA free energy landscape.
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Affiliation(s)
- Ryan L Hayes
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas 77030, USA
| | - Jeffrey K Noel
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas 77030, USA
| | - Ana Mandic
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77004, USA
| | - Paul C Whitford
- Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA
| | - Karissa Y Sanbonmatsu
- Theoretic Biology and Biophysics, Theoretic Division, Los Alamos National Labs, Los Alamos, New Mexico 87545, USA
| | - Udayan Mohanty
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02467, USA
| | - José N Onuchic
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas 77030, USA
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34
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Sun X, Zhu X, Zhang N, Guo J, Guo S, Huang X. Controlling and self assembling of monodisperse platinum nanocubes as efficient methanol oxidation electrocatalysts. Chem Commun (Camb) 2015; 51:3529-32. [DOI: 10.1039/c5cc00155b] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An efficient approach that enables the direct controlling and assembling of Pt nanocubes was developed for the first time.
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Affiliation(s)
- Xiuhui Sun
- College of Chemistry
- Chemical Engineering and Materials Science
- Soochow University
- Jiangsu 215123
- China
| | - Xing Zhu
- Testing & Analysis Center
- Soochow University
- Jiangsu
- China
| | - Nan Zhang
- College of Chemistry
- Chemical Engineering and Materials Science
- Soochow University
- Jiangsu 215123
- China
| | - Jun Guo
- Testing & Analysis Center
- Soochow University
- Jiangsu
- China
| | - Shaojun Guo
- Physical Chemistry and Applied Spectroscopy
- Los Alamos National Laboratory
- Los Alamos
- 87545
- USA
| | - Xiaoqing Huang
- College of Chemistry
- Chemical Engineering and Materials Science
- Soochow University
- Jiangsu 215123
- China
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35
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RNA folding: structure prediction, folding kinetics and ion electrostatics. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 827:143-83. [PMID: 25387965 DOI: 10.1007/978-94-017-9245-5_11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Beyond the "traditional" functions such as gene storage, transport and protein synthesis, recent discoveries reveal that RNAs have important "new" biological functions including the RNA silence and gene regulation of riboswitch. Such functions of noncoding RNAs are strongly coupled to the RNA structures and proper structure change, which naturally leads to the RNA folding problem including structure prediction and folding kinetics. Due to the polyanionic nature of RNAs, RNA folding structure, stability and kinetics are strongly coupled to the ion condition of solution. The main focus of this chapter is to review the recent progress in the three major aspects in RNA folding problem: structure prediction, folding kinetics and ion electrostatics. This chapter will introduce both the recent experimental and theoretical progress, while emphasize the theoretical modelling on the three aspects in RNA folding.
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36
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Hu C, Lin K, Wang X, Liu S, Yi J, Tian Y, Wu B, Chen G, Yang H, Dai Y, Li H, Zheng N. Electrostatic Self-Assembling Formation of Pd Superlattice Nanowires from Surfactant-Free Ultrathin Pd Nanosheets. J Am Chem Soc 2014; 136:12856-9. [DOI: 10.1021/ja507409p] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Chengyi Hu
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Kaiqiang Lin
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Xingli Wang
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Shengjie Liu
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Jun Yi
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yu Tian
- State
Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China
| | - Binghui Wu
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Guangxu Chen
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Huayan Yang
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Yan Dai
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Huan Li
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Nanfeng Zheng
- State
Key Laboratory for Physical Chemistry of Solid Surfaces, Collaborative
Innovation Center of Chemistry for Energy Materials, and Department
of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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37
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Gopal A, Egecioglu DE, Yoffe AM, Ben-Shaul A, Rao ALN, Knobler CM, Gelbart WM. Viral RNAs are unusually compact. PLoS One 2014; 9:e105875. [PMID: 25188030 PMCID: PMC4154850 DOI: 10.1371/journal.pone.0105875] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 07/21/2014] [Indexed: 01/28/2023] Open
Abstract
A majority of viruses are composed of long single-stranded genomic RNA molecules encapsulated by protein shells with diameters of just a few tens of nanometers. We examine the extent to which these viral RNAs have evolved to be physically compact molecules to facilitate encapsulation. Measurements of equal-length viral, non-viral, coding and non-coding RNAs show viral RNAs to have among the smallest sizes in solution, i.e., the highest gel-electrophoretic mobilities and the smallest hydrodynamic radii. Using graph-theoretical analyses we demonstrate that their sizes correlate with the compactness of branching patterns in predicted secondary structure ensembles. The density of branching is determined by the number and relative positions of 3-helix junctions, and is highly sensitive to the presence of rare higher-order junctions with 4 or more helices. Compact branching arises from a preponderance of base pairing between nucleotides close to each other in the primary sequence. The density of branching represents a degree of freedom optimized by viral RNA genomes in response to the evolutionary pressure to be packaged reliably. Several families of viruses are analyzed to delineate the effects of capsid geometry, size and charge stabilization on the selective pressure for RNA compactness. Compact branching has important implications for RNA folding and viral assembly.
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Affiliation(s)
- Ajaykumar Gopal
- Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Defne E. Egecioglu
- Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Aron M. Yoffe
- Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - Avinoam Ben-Shaul
- Institute of Chemistry & The Fritz Haber Research Center, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, Israel
| | - Ayala L. N. Rao
- Department of Plant Pathology, University of California Riverside, Riverside, California, United States of America
| | - Charles M. Knobler
- Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
| | - William M. Gelbart
- Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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38
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Hyeon C, Denesyuk NA, Thirumalai D. Development and Applications of Coarse-Grained Models for RNA. Isr J Chem 2014. [DOI: 10.1002/ijch.201400029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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39
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Dong H, Klein ML, Fiorin G. Counterion-Assisted Cation Transport in a Biological Calcium Channel. J Phys Chem B 2014; 118:9668-76. [DOI: 10.1021/jp5059897] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Hao Dong
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Michael L. Klein
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Giacomo Fiorin
- Institute for Computational
Molecular Science, Temple University, Philadelphia, Pennsylvania 19122, United States
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40
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Hayes RL, Noel JK, Whitford PC, Mohanty U, Sanbonmatsu KY, Onuchic JN. Reduced model captures Mg(2+)-RNA interaction free energy of riboswitches. Biophys J 2014; 106:1508-19. [PMID: 24703312 PMCID: PMC3976530 DOI: 10.1016/j.bpj.2014.01.042] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 01/22/2014] [Accepted: 01/29/2014] [Indexed: 12/17/2022] Open
Abstract
The stability of RNA tertiary structures depends heavily on Mg(2+). The Mg(2+)-RNA interaction free energy that stabilizes an RNA structure can be computed experimentally through fluorescence-based assays that measure Γ2+, the number of excess Mg(2+) associated with an RNA molecule. Previous explicit-solvent simulations predict that the majority of excess Mg(2+) ions interact closely and strongly with the RNA, unlike monovalent ions such as K(+), suggesting that an explicit treatment of Mg(2+) is important for capturing RNA dynamics. Here we present a reduced model that accurately reproduces the thermodynamics of Mg(2+)-RNA interactions. This model is able to characterize long-timescale RNA dynamics coupled to Mg(2+) through the explicit representation of Mg(2+) ions. KCl is described by Debye-Hückel screening and a Manning condensation parameter, which represents condensed K(+) and models its competition with condensed Mg(2+). The model contains one fitted parameter, the number of condensed K(+) ions in the absence of Mg(2+). Values of Γ2+ computed from molecular dynamics simulations using the model show excellent agreement with both experimental data on the adenine riboswitch and previous explicit-solvent simulations of the SAM-I riboswitch. This agreement confirms the thermodynamic accuracy of the model via the direct relation of Γ2+ to the Mg(2+)-RNA interaction free energy, and provides further support for the predictions from explicit-solvent calculations. This reduced model will be useful for future studies of the interplay between Mg(2+) and RNA dynamics.
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Affiliation(s)
- Ryan L Hayes
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas
| | - Jeffrey K Noel
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas
| | - Paul C Whitford
- Department of Physics, Northeastern University, Boston, Massachusetts
| | - Udayan Mohanty
- Department of Chemistry, Boston College, Chestnut Hill, Massachusetts
| | - Karissa Y Sanbonmatsu
- Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Labs, Los Alamos, New Mexico.
| | - José N Onuchic
- Center for Theoretical Biological Physics and Department of Physics and Astronomy, Rice University, Houston, Texas; Department of Chemistry and Department of Biochemistry and Cell Biology, Rice University, Houston, Texas.
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41
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Abstract
Ions surround nucleic acids in what is referred to as an ion atmosphere. As a result, the folding and dynamics of RNA and DNA and their complexes with proteins and with each other cannot be understood without a reasonably sophisticated appreciation of these ions' electrostatic interactions. However, the underlying behavior of the ion atmosphere follows physical rules that are distinct from the rules of site binding that biochemists are most familiar and comfortable with. The main goal of this review is to familiarize nucleic acid experimentalists with the physical concepts that underlie nucleic acid-ion interactions. Throughout, we provide practical strategies for interpreting and analyzing nucleic acid experiments that avoid pitfalls from oversimplified or incorrect models. We briefly review the status of theories that predict or simulate nucleic acid-ion interactions and experiments that test these theories. Finally, we describe opportunities for going beyond phenomenological fits to a next-generation, truly predictive understanding of nucleic acid-ion interactions.
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Affiliation(s)
- Jan Lipfert
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ Delft, Netherlands;
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42
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Bosco A, Camunas-Soler J, Ritort F. Elastic properties and secondary structure formation of single-stranded DNA at monovalent and divalent salt conditions. Nucleic Acids Res 2014; 42:2064-74. [PMID: 24225314 PMCID: PMC3919573 DOI: 10.1093/nar/gkt1089] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 10/16/2013] [Accepted: 10/17/2013] [Indexed: 11/16/2022] Open
Abstract
Single-stranded DNA (ssDNA) plays a major role in several biological processes. It is therefore of fundamental interest to understand how the elastic response and the formation of secondary structures are modulated by the interplay between base pairing and electrostatic interactions. Here we measure force-extension curves (FECs) of ssDNA molecules in optical tweezers set up over two orders of magnitude of monovalent and divalent salt conditions, and obtain its elastic parameters by fitting the FECs to semiflexible models of polymers. For both monovalent and divalent salts, we find that the electrostatic contribution to the persistence length is proportional to the Debye screening length, varying as the inverse of the square root of cation concentration. The intrinsic persistence length is equal to 0.7 nm for both types of salts, and the effectivity of divalent cations in screening electrostatic interactions appears to be 100-fold as compared with monovalent salt, in line with what has been recently reported for single-stranded RNA. Finally, we propose an analysis of the FECs using a model that accounts for the effective thickness of the filament at low salt condition and a simple phenomenological description that quantifies the formation of non-specific secondary structure at low forces.
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Affiliation(s)
- Alessandro Bosco
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy, Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14 - km 163,5 in AREA Science Park, 34149 Basovizza Trieste, Italy, Departament de Física Fonamental, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain and CIBER de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid, Spain
| | - Joan Camunas-Soler
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy, Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14 - km 163,5 in AREA Science Park, 34149 Basovizza Trieste, Italy, Departament de Física Fonamental, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain and CIBER de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid, Spain
| | - Felix Ritort
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy, Elettra-Sincrotrone Trieste S.C.p.A., Strada Statale 14 - km 163,5 in AREA Science Park, 34149 Basovizza Trieste, Italy, Departament de Física Fonamental, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain and CIBER de Bioingeniería, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid, Spain
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43
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Denning EJ, Thirumalai D, MacKerell AD. Protonation of trimethylamine N-oxide (TMAO) is required for stabilization of RNA tertiary structure. Biophys Chem 2013; 184:8-16. [PMID: 24012912 DOI: 10.1016/j.bpc.2013.08.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 08/08/2013] [Accepted: 08/08/2013] [Indexed: 01/10/2023]
Abstract
The osmolyte trimethylamine N-oxide (TMAO) stabilizes the tertiary but not the secondary structures of RNA. However, molecular dynamics simulations performed on the PreQ1 riboswitch showed that TMAO destabilizes the tertiary riboswitch structure, leading us to hypothesize that the presence of RNA could result in enhanced population of the protonated form, TMAOP. Constant pH replica exchange simulations showed that a percentage of TMAO is indeed protonated, thus contributing to the stability of the tertiary but not the secondary structure of PreQ1. TMAOP results in an unfavorable dehydration of phosphodiester backbone, which is compensated by electrostatic attraction between TMAOP and the phosphate groups. In addition, TMAOP interacts with specific sites in the tertiary RNA structure, mimicking the behavior of positively charged ions and of the PreQ1 ligand in stabilizing RNA. Finally, we predict that TMAO-induced stabilization of RNA tertiary structures should be strongly pH dependent.
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Affiliation(s)
- Elizabeth J Denning
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA
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44
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Supramolecular assembly of two two-folded helical structures based on 2-substituted 8-hydroxyquinoline complexes. INORG CHEM COMMUN 2013. [DOI: 10.1016/j.inoche.2013.03.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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45
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Denesyuk NA, Thirumalai D. Coarse-grained model for predicting RNA folding thermodynamics. J Phys Chem B 2013; 117:4901-11. [PMID: 23527587 DOI: 10.1021/jp401087x] [Citation(s) in RCA: 106] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We present a thermodynamically robust coarse-grained model to simulate folding of RNA in monovalent salt solutions. The model includes stacking, hydrogen bond, and electrostatic interactions as fundamental components in describing the stability of RNA structures. The stacking interactions are parametrized using a set of nucleotide-specific parameters, which were calibrated against the thermodynamic measurements for single-base stacks and base-pair stacks. All hydrogen bonds are assumed to have the same strength, regardless of their context in the RNA structure. The ionic buffer is modeled implicitly, using the concept of counterion condensation and the Debye-Hückel theory. The three adjustable parameters in the model were determined by fitting the experimental data for two RNA hairpins and a pseudoknot. A single set of parameters provides good agreement with thermodynamic data for the three RNA molecules over a wide range of temperatures and salt concentrations. In the process of calibrating the model, we establish the extent of counterion condensation onto the single-stranded RNA backbone. The reduced backbone charge is independent of the ionic strength and is 60% of the RNA bare charge at 37 °C. Our model can be used to predict the folding thermodynamics for any RNA molecule in the presence of monovalent ions.
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Affiliation(s)
- Natalia A Denesyuk
- Department of Chemistry and Biochemistry and Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, United States
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Chen C, Mitra S, Jonikas M, Martin J, Brenowitz M, Laederach A. Understanding the role of three-dimensional topology in determining the folding intermediates of group I introns. Biophys J 2013; 104:1326-37. [PMID: 23528092 DOI: 10.1016/j.bpj.2013.02.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 01/28/2013] [Accepted: 02/07/2013] [Indexed: 11/30/2022] Open
Abstract
Many RNA molecules exert their biological function only after folding to unique three-dimensional structures. For long, noncoding RNA molecules, the complexity of finding the native topology can be a major impediment to correct folding to the biologically active structure. An RNA molecule may fold to a near-native structure but not be able to continue to the correct structure due to a topological barrier such as crossed strands or incorrectly stacked helices. Achieving the native conformation thus requires unfolding and refolding, resulting in a long-lived intermediate. We investigate the role of topology in the folding of two phylogenetically related catalytic group I introns, the Twort and Azoarcus group I ribozymes. The kinetic models describing the Mg(2+)-mediated folding of these ribozymes were previously determined by time-resolved hydroxyl (∙OH) radical footprinting. Two intermediates formed by parallel intermediates were resolved for each RNA. These data and analytical ultracentrifugation compaction analyses are used herein to constrain coarse-grained models of these folding intermediates as we investigate the role of nonnative topology in dictating the lifetime of the intermediates. Starting from an ensemble of unfolded conformations, we folded the RNA molecules by progressively adding native constraints to subdomains of the RNA defined by the ∙OH time-progress curves to simulate folding through the different kinetic pathways. We find that nonnative topologies (arrangement of helices) occur frequently in the folding simulations despite using only native constraints to drive the reaction, and that the initial conformation, rather than the folding pathway, is the major determinant of whether the RNA adopts nonnative topology during folding. From these analyses we conclude that biases in the initial conformation likely determine the relative flux through parallel RNA folding pathways.
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Affiliation(s)
- Chunxia Chen
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
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Yin P, Zhang J, Li T, Zuo X, Hao J, Warner AM, Chattopadhyay S, Shibata T, Wei Y, Liu T. Self-Recognition of Structurally Identical, Rod-Shaped Macroions with Different Central Metal Atoms during Their Assembly Process. J Am Chem Soc 2013; 135:4529-36. [DOI: 10.1021/ja400656j] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Panchao Yin
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Jin Zhang
- Department of Chemistry, Tsinghua University, Beijing 100084, P.R. China
| | - Tao Li
- X-ray Science Division, Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Xiaobing Zuo
- X-ray Science Division, Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jian Hao
- Department of Chemistry, Tsinghua University, Beijing 100084, P.R. China
| | - Anna Marie Warner
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
| | - Soma Chattopadhyay
- CSRRI-IIT, MRCAT, Sector 10,
Building 433B, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616, United
States
| | - Tomohiro Shibata
- CSRRI-IIT, MRCAT, Sector 10,
Building 433B, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616, United
States
| | - Yongge Wei
- Department of Chemistry, Tsinghua University, Beijing 100084, P.R. China
| | - Tianbo Liu
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States
- Department of Polymer
Science, The University of Akron, Akron,
Ohio 44325, United
States
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48
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Kraft JJ, Treder K, Peterson MS, Miller WA. Cation-dependent folding of 3' cap-independent translation elements facilitates interaction of a 17-nucleotide conserved sequence with eIF4G. Nucleic Acids Res 2013; 41:3398-413. [PMID: 23361463 PMCID: PMC3597692 DOI: 10.1093/nar/gkt026] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The 3′-untranslated regions of many plant viral RNAs contain cap-independent translation elements (CITEs) that drive translation initiation at the 5′-end of the mRNA. The barley yellow dwarf virus-like CITE (BTE) stimulates translation by binding the eIF4G subunit of translation initiation factor eIF4F with high affinity. To understand this interaction, we characterized the dynamic structural properties of the BTE, mapped the eIF4G-binding sites on the BTE and identified a region of eIF4G that is crucial for BTE binding. BTE folding involves cooperative uptake of magnesium ions and is driven primarily by charge neutralization. Footprinting experiments revealed that functional eIF4G fragments protect the highly conserved stem–loop I and a downstream bulge. The BTE forms a functional structure in the absence of protein, and the loop that base pairs the 5′-untranslated region (5′-UTR) remains solvent-accessible at high eIF4G concentrations. The region in eIF4G between the eIF4E-binding site and the MIF4G region is required for BTE binding and translation. The data support the model in which the eIF4F complex binds directly to the BTE which base pairs simultaneously to the 5′-UTR, allowing eIF4F to recruit the 40S ribosomal subunit to the 5′-end.
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Affiliation(s)
- Jelena J Kraft
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA 50011, USA
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49
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Tan ZJ, Chen SJ. Ion-mediated RNA structural collapse: effect of spatial confinement. Biophys J 2013; 103:827-36. [PMID: 22947944 DOI: 10.1016/j.bpj.2012.06.048] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 06/25/2012] [Accepted: 06/27/2012] [Indexed: 12/28/2022] Open
Abstract
RNAs are negatively charged molecules that reside in cellular environments with macromolecular crowding. Macromolecular confinement can influence the ion effects in RNA folding. In this work, using the recently developed tightly bound ion model for ion fluctuation and correlation, we investigate the effect of confinement on ion-mediated RNA structural collapse for a simple model system. We find that for both Na(+) and Mg(2+), the ion efficiencies in mediating structural collapse/folding are significantly enhanced by the structural confinement. This enhancement of ion efficiency is attributed to the decreased electrostatic free-energy difference between the compact conformation ensemble and the (restricted) extended conformation ensemble due to the spatial restriction.
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Affiliation(s)
- 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, People's Republic of China.
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Hennelly SP, Novikova IV, Sanbonmatsu KY. The expression platform and the aptamer: cooperativity between Mg2+ and ligand in the SAM-I riboswitch. Nucleic Acids Res 2012; 41:1922-35. [PMID: 23258703 PMCID: PMC3562059 DOI: 10.1093/nar/gks978] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Riboswitch operation involves the complex interplay between the aptamer domain and the expression platform. During transcription, these two domains compete against each other for shared sequence. In this study, we explore the cooperative effects of ligand binding and Magnesium interactions in the SAM-I riboswitch in the context of aptamer collapse and anti-terminator formation. Overall, our studies show the apo-aptamer acts as (i) a pre-organized aptamer competent to bind ligand and undergo structural collapse and (ii) a conformation that is more accessible to anti-terminator formation. We show that both Mg(2+) ions and SAM are required for a collapse transition to occur. We then use competition between the aptamer and expression platform for shared sequence to characterize the stability of the collapsed aptamer. We find that SAM and Mg(2+) interactions in the aptamer are highly cooperative in maintaining switch polarity (i.e. aptamer 'off-state' versus anti-terminator 'on-state'). We further show that the aptamer off-state is preferentially stabilized by Mg(2+) and similar divalent ions. Furthermore, the functional switching assay was used to select for phosphorothioate interference, and identifies potential magnesium chelation sites while characterizing their coordinated role with SAM in aptamer stabilization. In addition, we find that Mg(2+) interactions with the apo-aptamer are required for the full formation of the anti-terminator structure, and that higher concentrations of Mg(2+) (>4 mM) shift the equilibrium toward the anti-terminator on-state even in the presence of SAM.
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Affiliation(s)
- Scott P Hennelly
- Theoretical Biology and Biophysics Group, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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