1
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Michel HM, Lemkul JA. Base pair dynamics, electrostatics, and thermodynamics at the LTR-III quadruplex:duplex junction. Biophys J 2024; 123:1129-1138. [PMID: 38576161 PMCID: PMC11079942 DOI: 10.1016/j.bpj.2024.03.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/10/2024] [Accepted: 03/29/2024] [Indexed: 04/06/2024] Open
Abstract
G-quadruplexes (GQs) play key regulatory roles within the human genome and have also been identified to play similar roles in other eukaryotes, bacteria, archaea, and viruses. Human immunodeficiency virus 1, the etiological agent of acquired immunodeficiency syndrome, can form two GQs in its long terminal repeat (LTR) promoter region, each of which act to regulate viral gene expression in opposing manners. The major LTR GQ, called LTR-III, is a distinct hybrid GQ containing a 12-nucleotide duplex loop attached to the quadruplex motif. The resulting quadruplex:duplex junction (QDJ) has been hypothesized to serve as a selective drug targeting site. To better understand the dynamics of this QDJ, we performed conventional and enhanced-sampling molecular dynamics simulations using the Drude-2017 force field. We observed unbiased and reversible formation of additional base pairs in the QDJ, between Ade4:Thy14 and Gua3:Thy14. Both base pairs were electrostatically favored, but geometric constraints within the junction may drive the formation of, and preference for, the Ade4:Thy14 base pair. Finally, we demonstrated that the base pairs are separated only by small energy barriers that may enable transitions between both base-paired states. Together, these simulations provide new insights into the dynamics, electrostatics, and thermodynamics of the LTR-III QDJ.
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Affiliation(s)
- Haley M Michel
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia
| | - Justin A Lemkul
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia; Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia.
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2
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Olson WK, Li Y, Fenley MO. Insights into DNA solvation found in protein-DNA structures. Biophys J 2022; 121:4749-4758. [PMID: 36380591 PMCID: PMC9808563 DOI: 10.1016/j.bpj.2022.11.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/31/2022] [Accepted: 11/10/2022] [Indexed: 11/16/2022] Open
Abstract
The proteins that bind double-helical DNA present various microenvironments that sense and/or induce signals in the genetic material. The high-resolution structures of protein-DNA complexes reveal the nature of both the microenvironments and the conformational responses in DNA and protein. Complex networks of interactions within the structures somehow tie the protein and DNA together and induce the observed spatial forms. Here we show how the cumulative buildup of amino acid atoms around the sugars, phosphates, and bases in different protein-DNA complexes produces a binding cloud around the double helix and how different types of atoms fill that cloud. Rather than focusing on the principles of molecular binding and recognition suggested by the arrangements of amino acids and nucleotides in the macromolecular complexes, we consider the proteins in contact with DNA as organized solvents. We describe differences in the mix of atoms that come in closest contact with DNA, subtle sequence-dependent features in the microenvironment of the sugar-phosphate backbone, a direct link between the localized buildup of ionic species and the electrostatic potential surfaces of the DNA bases, and sites of atomic buildup above and below the basepair planes that transmit the unique features of the base environments along the chain backbone. The inferences about solvation that can be drawn from the survey provide new stimuli for improvement of nucleic acid force fields and fresh ideas for exploration of the properties of DNA in solution.
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Affiliation(s)
- Wilma K Olson
- Department of Chemistry and Chemical Biology and Center for Quantitative Biology, Rutgers, the State University of New Jersey, Piscataway, New Jersey.
| | - Yun Li
- Department of Chemistry and Chemical Biology and Center for Quantitative Biology, Rutgers, the State University of New Jersey, Piscataway, New Jersey
| | - Marcia O Fenley
- Department of Chemistry and Chemical Biology and Center for Quantitative Biology, Rutgers, the State University of New Jersey, Piscataway, New Jersey; Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida
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3
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Pramanik S, Mahato P, Pramanik U, Nandy A, Khamari L, Shrivastava S, Rai S, Mukherjee S. DNA-Templated Modulation in the Photophysical Properties of a Fluorescent Molecular Rotor Auramine O by Varying the DNA Composition. J Phys Chem B 2022; 126:2658-2668. [PMID: 35357836 DOI: 10.1021/acs.jpcb.2c00172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This work delineates an integrative approach combining spectroscopic and computational studies to decipher the association-induced fluorescence properties of a fluorescent molecular rotor, viz., auramine O (AuO), after interacting with 20-mer duplex DNA having diverse well-matched base pairs. While exploring the scarcely explored sequence-dependent interaction mechanism of AuO and DNA, we observed that DNA could act as a conducive scaffold to the formation of AuO dimer through noncovalent interactions at lower molecular density. The photophysical properties of AuO depend on the nucleotide compositions as described from sequence-dependent shifting in the emission and absorption maxima. Furthermore, we explored such DNA base pair-dependent fluorescence spectral characteristics of AuO toward discriminating the thermodynamically most stable single nucleotide mismatch in a 20-mer sequence. Our results are interesting and could be useful in developing analogues with further enhanced emission properties toward mismatched DNA sequences.
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Affiliation(s)
- Srikrishna Pramanik
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Paritosh Mahato
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Ushasi Pramanik
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Atanu Nandy
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Laxmikanta Khamari
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Shivam Shrivastava
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Saurabh Rai
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Saptarshi Mukherjee
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
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4
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Valdiviezo J, Zhang P, Beratan DN. Electron ratcheting in self-assembled soft matter. J Chem Phys 2021; 155:055102. [PMID: 34364335 DOI: 10.1063/5.0044420] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Ratcheted multi-step hopping electron transfer systems can plausibly produce directional charge transport over very large distances without requiring a source-drain voltage bias. We examine molecular strategies to realize ratcheted charge transport based on multi-step charge hopping, and we illustrate two ratcheting mechanisms with examples based on DNA structures. The charge transport times and currents that may be generated in these assemblies are also estimated using kinetic simulations. The first ratcheting mechanism described for nanoscale systems requires local electric fields on the 109 V/m scale to realize nearly 100% population transport. The second ratcheting mechanism for even larger systems, based on electrochemical gating, is estimated to generate currents as large as 0.1 pA for DNA structures that are a few μm in length with a gate voltage of about 5 V, a magnitude comparable to currents measured in DNA wires at the nanoscale when a source-drain voltage bias of similar magnitude is applied, suggesting an approach to considerably extend the distance range over which DNA charge transport devices may operate.
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Affiliation(s)
- Jesús Valdiviezo
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
| | - Peng Zhang
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
| | - David N Beratan
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
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5
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Cavanna F, Alvarado J. Quantification of the mesh structure of bundled actin filaments. SOFT MATTER 2021; 17:5034-5043. [PMID: 33912871 DOI: 10.1039/d1sm00428j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Biopolymer networks are essential for a wide variety of cellular functions. The biopolymer actin is known to self-assemble into a variety of spatial structures in response to physiological and physical mechanisms. So far, the mechanics of networks of single actin filaments and bundles has previously been described. However, the spatial structure of actin bundles remains poorly understood. Here, we investigate this question by bundling actin filaments with systematically varied concentrations of known physical bundling agents (MgCl2 and PEG) and physiological bundling agents (α-actinin and fascin). We image bundled actin networks with confocal microscopy and perform analysis to describe their mesh size and the nearest-distance distribution, which we call "mesh structure". We find that the mesh size ξ scales universally with actin concentration as ξ ∼ [actin]-1/2. However, the dependence of ξ on the concentration of the bundling agent depends on the agent used. Finally, we find that nearest-distance distributions are best fit by Weibull and Gamma distributions. A complete understanding of the mesh structure of biopolymer networks leads to a more mechanistic understanding of the structure of the cytoskeleton, and can be exploited to design filters with variable porosity for microfluidic devices.
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Affiliation(s)
- Francis Cavanna
- UT Austin Department of Physics, 2515 Speedway, Austin, Texas, USA.
| | - José Alvarado
- UT Austin Department of Physics, 2515 Speedway, Austin, Texas, USA.
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6
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Pramanik S, Nandy A, Chakraborty S, Pramanik U, Nandi S, Mukherjee S. Preferential Binding of Thioflavin T to AT-Rich DNA: White Light Emission through Intramolecular Förster Resonance Energy Transfer. J Phys Chem Lett 2020; 11:2436-2442. [PMID: 32141760 DOI: 10.1021/acs.jpclett.0c00237] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Herein we report the effect of different nucleobase pair compositions on the association-induced fluorescence enhancement property of Thioflavin T (ThT), upon binding with 20 base pair long double-stranded DNA (dsDNA). Analysis of binding and decay constants along with the association (Kass) and dissociation (Kdiss) rate constants obtained from the fluctuation in the fluorescence intensity of ThT after binding with different DNA revealed selective affinity of ThT toward AT-rich dsDNA. Molecular docking also substantiates the experimental results. We also observed that addition of orange-emitting ethidium bromide (EtBr) to cyan-emitting ThT-DNA complexes leads to bright white light emission (WLE) through Förster resonance energy transfer. Additionally, the emission of white light is far greater in the case of intra-DNA strands. Besides endorsing the binding insights of ThT to AT-rich dsDNA, the present investigations open a new perspective for realizing promising WLE from two biomarkers without labeling the DNA.
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Affiliation(s)
- Srikrishna Pramanik
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
| | - Atanu Nandy
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
| | - Subhajit Chakraborty
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
| | - Ushasi Pramanik
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
| | - Somen Nandi
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
| | - Saptarshi Mukherjee
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, Madhya Pradesh, India
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7
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Theoretical analyses and experimental validation of the effects caused by the fluorinated substituent modification of DNA. Sci Rep 2020; 10:1138. [PMID: 31980685 PMCID: PMC6981298 DOI: 10.1038/s41598-020-57899-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 01/03/2020] [Indexed: 11/20/2022] Open
Abstract
Halogen-modified nucleic acid molecules, such as trifluorothymidine (FTD) and 5-fluorouracil, are widely used in medical science and clinical site. These compounds have a very similar nucleobase structure. It is reported that both of these compounds could be incorporated into DNA. The incorporation of FTD produces highly anti-tumor effect. However, it is not known whether to occur a significant effect by the incorporation of 5-fluorouracil. Nobody knows why such a difference will occur. To understand the reason why there is large differences between trifluorothymidine and 5-fluorouracil, we have performed the molecular dynamics simulations and molecular orbital calculations. Although the active interaction energy between Halogen-modified nucleic acids or and complementary adenine was increased, in only FTD incorporated DNA, more strongly dispersion force interactions with an adjacent base were detected in many thermodynamic DNA conformations. As the results, the conformational changes occur even if it is in internal body temperature. Then the break of hydrogen bonding between FTD and complementary adenine base occur more frequently. The double helix structural destabilization of DNA with FTD is resulted from autoagglutination caused by the bonding via halogen orbitals such as halogen bonding and the general van der Waals interactions such as CH–\documentclass[12pt]{minimal}
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\begin{document}$${\rm{\pi }}$$\end{document}π interactions. Therefore, it is strongly speculated that such structural changes caused by trifluoromethyl group is important for the anti-tumor effect of FTD alone.
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8
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SERS assessment of the cancer-specific methylation pattern of genomic DNA: towards the detection of acute myeloid leukemia in patients undergoing hematopoietic stem cell transplantation. Anal Bioanal Chem 2019; 411:7907-7913. [PMID: 31745615 DOI: 10.1007/s00216-019-02213-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 09/04/2019] [Accepted: 10/14/2019] [Indexed: 10/25/2022]
Abstract
In this label-free surface-enhanced Raman scattering (SERS) study of genomic DNA, we demonstrate that the cancer-specific DNA methylation pattern translates into specific spectral differences. Thus, DNA extracted from an acute myeloid leukemia (AML) cell line presented a decreased intensity of the 1005 cm-1 band of 5-methylcytosine compared to normal DNA, in line with the well-described hypomethylation of cancer DNA. The unique methylation pattern of cancer DNA also influences the DNA adsorption geometry, resulting in higher adenine SERS intensities for cancer DNA. The possibility of detecting cancer DNA based on its SERS spectrum was validated on peripheral blood genomic DNA samples from n = 17 AML patients and n = 17 control samples, yielding an overall classification of 82% based on the 1005 cm-1 band of 5-methylcytosine. By demonstrating the potential of SERS in assessing the methylation status in the case of real-life DNA samples, the study paves the way for novel methods of diagnosing cancer. Graphical abstract.
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9
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Stellwagen NC, Stellwagen E. DNA Thermal Stability Depends on Solvent Viscosity. J Phys Chem B 2019; 123:3649-3657. [DOI: 10.1021/acs.jpcb.9b01217] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Nancy C. Stellwagen
- Department of Biochemistry, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
| | - Earle Stellwagen
- Department of Biochemistry, University of Iowa, 51 Newton Road, Iowa City, Iowa 52242, United States
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10
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Nakagawa O, Fujii A, Kishimoto Y, Nakatsuji Y, Nozaki N, Obika S. 2'-O,4'-C-Methylene-Bridged Nucleic Acids Stabilize Metal-Mediated Base Pairing in a DNA Duplex. Chembiochem 2018; 19:2372-2379. [PMID: 30168891 DOI: 10.1002/cbic.201800448] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Indexed: 11/08/2022]
Abstract
The 2'-O,4'-C-methylene-bridged or locked nucleic acid (2',4'-BNA/LNA), with an N-type sugar conformation, effectively improves duplex-forming ability. 2',4'-BNA/LNA is widely used to improve gene knockdown in nucleic acid based therapies and is used in gene diagnosis. Metal-mediated base pairs (MMBPs), such as thymine (T)-HgII -T and cytosine (C)-AgI -C have been developed and used as attractive tools in DNA nanotechnology studies. This study aimed to investigate the application of 2',4'-BNA/LNA in the field of MMBPs. 2',4'-BNA/LNA with 5-methylcytosine stabilized the MMBP of C with AgI ions. Moreover, the 2',4'-BNA/LNA sugar significantly improved the duplex-forming ability of the DNA/DNA complex, relative to that by the unmodified sugar. These results suggest that the sugar conformation is important for improving the stability of duplex-containing MMBPs. The results indicate that 2',4'-BNA/LNA can be applied not only to nucleic acid based therapies, but also to MMBP technologies.
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Affiliation(s)
- Osamu Nakagawa
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
| | - Akane Fujii
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
| | - Yuki Kishimoto
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
| | - Yusuke Nakatsuji
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
| | - Natsumi Nozaki
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
| | - Satoshi Obika
- Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka Suita, Osaka, 565-0871, Japan
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11
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Non-canonical DNA structures: Comparative quantum mechanical study. Biophys Chem 2018; 235:19-28. [DOI: 10.1016/j.bpc.2018.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 02/06/2018] [Accepted: 02/06/2018] [Indexed: 11/21/2022]
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12
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Zhitnikova M, Shestopalova A. DNA minor groove electrostatic potential: influence of sequence-specific transitions of the torsion angle gamma and deoxyribose conformations. J Biomol Struct Dyn 2017; 35:3384-3397. [DOI: 10.1080/07391102.2016.1255259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- M.Y. Zhitnikova
- O. Ya. Usikov Institute for Radiophysics and Electronics, National Academy of Sciences of Ukraine, Acad. Proskury Street, 12 Kharkiv 61085, Ukraine
| | - A.V. Shestopalova
- O. Ya. Usikov Institute for Radiophysics and Electronics, National Academy of Sciences of Ukraine, Acad. Proskury Street, 12 Kharkiv 61085, Ukraine
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13
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Todolli S, Perez PJ, Clauvelin N, Olson WK. Contributions of Sequence to the Higher-Order Structures of DNA. Biophys J 2016; 112:416-426. [PMID: 27955889 DOI: 10.1016/j.bpj.2016.11.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Revised: 11/11/2016] [Accepted: 11/15/2016] [Indexed: 11/17/2022] Open
Abstract
One of the critical unanswered questions in genome biophysics is how the primary sequence of DNA bases influences the global properties of very-long-chain molecules. The local sequence-dependent features of DNA found in high-resolution structures introduce irregularities in the disposition of adjacent residues that facilitate the specific binding of proteins and modulate the global folding and interactions of double helices with hundreds of basepairs. These features also determine the positions of nucleosomes on DNA and the lengths of the interspersed DNA linkers. Like the patterns of basepair association within DNA, the arrangements of nucleosomes in chromatin modulate the properties of longer polymers. The intrachromosomal loops detected in genomic studies contain hundreds of nucleosomes, and given that the simulated configurations of chromatin depend on the lengths of linker DNA, the formation of these loops may reflect sequence-dependent information encoded within the positioning of the nucleosomes. With knowledge of the positions of nucleosomes on a given genome, methods are now at hand to estimate the looping propensities of chromatin in terms of the spacing of nucleosomes and to make a direct connection between the DNA base sequence and larger-scale chromatin folding.
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Affiliation(s)
- Stefjord Todolli
- Center for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Pamela J Perez
- Center for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Nicolas Clauvelin
- Center for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey
| | - Wilma K Olson
- Department of Chemistry and Chemical Biology, The State University of New Jersey, Piscataway, New Jersey; Center for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey.
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14
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Samchenko AA, Kiselev SS, Kabanov AV, Kondratjev MS, Komarov VM. On the nature of the domination of oligomeric (dA:dT) n tracts in the structure of eukaryotic genomes. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916060233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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15
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Wang J, Moore PB. On the interpretation of electron microscopic maps of biological macromolecules. Protein Sci 2016; 26:122-129. [PMID: 27706888 DOI: 10.1002/pro.3060] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/03/2016] [Accepted: 10/03/2016] [Indexed: 01/03/2023]
Abstract
The images of flash-frozen biological macromolecules produced by cryo-electron microscopy (EM) can be used to generate accurate, three-dimensional, electric potential maps for these molecules that resemble X-ray-derived electron density maps. However, unlike electron density maps, electric potential maps can include negative features that might for example represent the negatively charged, backbone phosphate groups of nucleic acids or protein carboxylate side chains, which can complicate their interpretation. This study examines the images of groups that include charged atoms that appear in recently-published, high-resolution EM potential maps of the ribosome and β-galactosidase. Comparisons of simulated maps of these same groups with their experimental counterparts highlight the impact that charge has on the appearance of electric potential maps.
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Affiliation(s)
- Jimin Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520
| | - Peter B Moore
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, 06520.,Department of Chemistry, Yale University, New Haven, Connecticut, 06520
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16
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Biophysical Reviews publications on DNA structure and function that complement this Special Issue on DNA supercoiling. Biophys Rev 2016; 8:157-158. [PMID: 28510214 DOI: 10.1007/s12551-016-0213-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 06/20/2016] [Indexed: 10/21/2022] Open
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17
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Coarse-grained modeling of RNA 3D structure. Methods 2016; 103:138-56. [PMID: 27125734 DOI: 10.1016/j.ymeth.2016.04.026] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Revised: 04/21/2016] [Accepted: 04/22/2016] [Indexed: 12/21/2022] Open
Abstract
Functional RNA molecules depend on three-dimensional (3D) structures to carry out their tasks within the cell. Understanding how these molecules interact to carry out their biological roles requires a detailed knowledge of RNA 3D structure and dynamics as well as thermodynamics, which strongly governs the folding of RNA and RNA-RNA interactions as well as a host of other interactions within the cellular environment. Experimental determination of these properties is difficult, and various computational methods have been developed to model the folding of RNA 3D structures and their interactions with other molecules. However, computational methods also have their limitations, especially when the biological effects demand computation of the dynamics beyond a few hundred nanoseconds. For the researcher confronted with such challenges, a more amenable approach is to resort to coarse-grained modeling to reduce the number of data points and computational demand to a more tractable size, while sacrificing as little critical information as possible. This review presents an introduction to the topic of coarse-grained modeling of RNA 3D structures and dynamics, covering both high- and low-resolution strategies. We discuss how physics-based approaches compare with knowledge based methods that rely on databases of information. In the course of this review, we discuss important aspects in the reasoning process behind building different models and the goals and pitfalls that can result.
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18
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Mazur AK. Homologous Pairing between Long DNA Double Helices. PHYSICAL REVIEW LETTERS 2016; 116:158101. [PMID: 27127987 DOI: 10.1103/physrevlett.116.158101] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Indexed: 06/05/2023]
Abstract
Molecular recognition between two double stranded (ds) DNA with homologous sequences may not seem compatible with the B-DNA structure because the sequence information is hidden when it is used for joining the two strands. Nevertheless, it has to be invoked to account for various biological data. Using quantum chemistry, molecular mechanics, and hints from recent genetics experiments, I show here that direct recognition between homologous dsDNA is possible through the formation of short quadruplexes due to direct complementary hydrogen bonding of major-groove surfaces in parallel alignment. The constraints imposed by the predicted structures of the recognition units determine the mechanism of complexation between long dsDNA. This mechanism and concomitant predictions agree with the available experimental data and shed light upon the sequence effects and the possible involvement of topoisomerase II in the recognition.
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Affiliation(s)
- Alexey K Mazur
- UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, Paris 75005, France
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Effects of monohydration on an adenine–thymine base pair. Theor Chem Acc 2015. [DOI: 10.1007/s00214-015-1686-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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20
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Esguerra M, Nilsson L, Villa A. Triple helical DNA in a duplex context and base pair opening. Nucleic Acids Res 2014; 42:11329-38. [PMID: 25228466 PMCID: PMC4191418 DOI: 10.1093/nar/gku848] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
It is fundamental to explore in atomic detail the behavior of DNA triple helices as a means to understand the role they might play in vivo and to better engineer their use in genetic technologies, such as antigene therapy. To this aim we have performed atomistic simulations of a purine-rich antiparallel triple helix stretch of 10 base triplets flanked by canonical Watson–Crick double helices. At the same time we have explored the thermodynamic behavior of a flipping Watson–Crick base pair in the context of the triple and double helix. The third strand can be accommodated in a B-like duplex conformation. Upon binding, the double helix changes shape, and becomes more rigid. The triple-helical region increases its major groove width mainly by oversliding in the negative direction. The resulting conformations are somewhere between the A and B conformations with base pairs remaining almost perpendicular to the helical axis. The neighboring duplex regions maintain a B DNA conformation. Base pair opening in the duplex regions is more probable than in the triplex and binding of the Hoogsteen strand does not influence base pair breathing in the neighboring duplex region.
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Affiliation(s)
- Mauricio Esguerra
- Department of Biosciences and Nutrition, Karolinska Institutet, Hälsovägen 7, SE-141 83 Huddinge, Sweden
| | - Lennart Nilsson
- Department of Biosciences and Nutrition, Karolinska Institutet, Hälsovägen 7, SE-141 83 Huddinge, Sweden
| | - Alessandra Villa
- Department of Biosciences and Nutrition, Karolinska Institutet, Hälsovägen 7, SE-141 83 Huddinge, Sweden
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21
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Zubatiuk TA, Shishkin OV, Gorb L, Hovorun DM, Leszczynski J. B-DNA characteristics are preserved in double stranded d(A)3·d(T)3 and d(G)3·d(C)3 mini-helixes: conclusions from DFT/M06-2X study. Phys Chem Chem Phys 2014; 15:18155-66. [PMID: 24065071 DOI: 10.1039/c3cp51584b] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We report the results of the first comprehensive DFT study on the d(A)3·d(T)3 and d(G)3·d(C)3 nucleic acid duplexes. The ability of mini-helixes to preserve the conformation of B-DNA in the gas phase and under the influence of such factors as: solvent, uncompensated charge, and counter-ions was evaluated using M06-2X functional with 6-31G(d,p) basis set. The accuracy of the models was ascertained based on their ability to reproduce key structural features of natural B-DNA. Analysis of the helicity suggests that the helical conformations adopt geometrical parameters which are close to those of the B-DNA form. The torsion angles fall somewhere between the values observed for BI/BII conformational classes. The comparative analysis of parameters of isolated Watson-Crick base pairs versus B-DNA-like conformations indicates the same tendency of base-pair polarization and hydration. Specifically, effects of polarization of nucleobases in continuum type dielectric medium mimicking water are stronger than those caused by the presence of backbone. Polar environment as well as the presence of counterions stabilizes duplexes, facilitating helix formation. Substantial conformational changes of nucleotides upon duplex formation decrease the binding energy. In spite of structural and energetic changes, the placement of a mini-helix into the gas phase does not lead to significant disruption of the structure. On the contrary, the duplex preserves its helicity and the strands remain bound.
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Affiliation(s)
- Tetiana A Zubatiuk
- Division of Functional Materials Chemistry, SSI "Institute for Single Crystals" National Academy of Science of Ukraine, 60 Lenina Ave., Kharkiv, 61001, Ukraine
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22
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Caporale LH, Doyle J. In Darwinian evolution, feedback from natural selection leads to biased mutations. Ann N Y Acad Sci 2013; 1305:18-28. [PMID: 24033385 DOI: 10.1111/nyas.12235] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Natural selection provides feedback through which information about the environment and its recurring challenges is captured, inherited, and accumulated within genomes in the form of variations that contribute to survival. The variation upon which natural selection acts is generally described as "random." Yet evidence has been mounting for decades, from such phenomena as mutation hotspots, horizontal gene transfer, and highly mutable repetitive sequences, that variation is far from the simplifying idealization of random processes as white (uniform in space and time and independent of the environment or context). This paper focuses on what is known about the generation and control of mutational variation, emphasizing that it is not uniform across the genome or in time, not unstructured with respect to survival, and is neither memoryless nor independent of the (also far from white) environment. We suggest that, as opposed to frequentist methods, Bayesian analysis could capture the evolution of nonuniform probabilities of distinct classes of mutation, and argue not only that the locations, styles, and timing of real mutations are not correctly modeled as generated by a white noise random process, but that such a process would be inconsistent with evolutionary theory.
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Affiliation(s)
- Lynn Helena Caporale
- Control and Dynamical Systems California Institute of Technology, Pasadena, California 91125
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23
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Daido M, Kawashima Y, Tachikawa M. Nuclear quantum effect and temperature dependency on the hydrogen-bonded structure of base pairs. J Comput Chem 2013; 34:2403-11. [DOI: 10.1002/jcc.23399] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 06/28/2013] [Accepted: 07/05/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Masashi Daido
- Quantum Chemistry Division; Graduate School of Science; Yokohama City University; Seto 22-2, Kanazawa-ku; Yokohama; 236-0027; Japan
| | - Yukio Kawashima
- Quantum Chemistry Division; Graduate School of Science; Yokohama City University; Seto 22-2, Kanazawa-ku; Yokohama; 236-0027; Japan
| | - Masanori Tachikawa
- Quantum Chemistry Division; Graduate School of Science; Yokohama City University; Seto 22-2, Kanazawa-ku; Yokohama; 236-0027; Japan
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24
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DNA self-assembly: from chirality to evolution. Int J Mol Sci 2013; 14:8252-70. [PMID: 23591841 PMCID: PMC3645741 DOI: 10.3390/ijms14048252] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 03/03/2013] [Accepted: 03/21/2013] [Indexed: 01/12/2023] Open
Abstract
Transient or long-term DNA self-assembly participates in essential genetic functions. The present review focuses on tight DNA-DNA interactions that have recently been found to play important roles in both controlling DNA higher-order structures and their topology. Due to their chirality, double helices are tightly packed into stable right-handed crossovers. Simple packing rules that are imposed by DNA geometry and sequence dictate the overall architecture of higher order DNA structures. Close DNA-DNA interactions also provide the missing link between local interactions and DNA topology, thus explaining how type II DNA topoisomerases may sense locally the global topology. Finally this paper proposes that through its influence on DNA self-assembled structures, DNA chirality played a critical role during the early steps of evolution.
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25
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Gonzalez O, Petkevičiūtė D, Maddocks JH. A sequence-dependent rigid-base model of DNA. J Chem Phys 2013; 138:055102. [DOI: 10.1063/1.4789411] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
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26
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Guéroult M, Boittin O, Mauffret O, Etchebest C, Hartmann B. Mg2+ in the major groove modulates B-DNA structure and dynamics. PLoS One 2012; 7:e41704. [PMID: 22844516 PMCID: PMC3402463 DOI: 10.1371/journal.pone.0041704] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 06/25/2012] [Indexed: 12/12/2022] Open
Abstract
This study investigates the effect of Mg(2+) bound to the DNA major groove on DNA structure and dynamics. The analysis of a comprehensive dataset of B-DNA crystallographic structures shows that divalent cations are preferentially located in the DNA major groove where they interact with successive bases of (A/G)pG and the phosphate group of 5'-CpA or TpG. Based on this knowledge, molecular dynamics simulations were carried out on a DNA oligomer without or with Mg(2+) close to an ApG step. These simulations showed that the hydrated Mg(2+) forms a stable intra-strand cross-link between the two purines in solution. ApG generates an electrostatic potential in the major groove that is particularly attractive for cations; its intrinsic conformation is well-adapted to the formation of water-mediated hydrogen bonds with Mg(2+). The binding of Mg(2+) modulates the behavior of the 5'-neighboring step by increasing the BII (ε-ζ>0°) population of its phosphate group. Additional electrostatic interactions between the 5'-phosphate group and Mg(2+) strengthen both the DNA-cation binding and the BII character of the 5'-step. Cation binding in the major groove may therefore locally influence the DNA conformational landscape, suggesting a possible avenue for better understanding how strong DNA distortions can be stabilized in protein-DNA complexes.
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Affiliation(s)
- Marc Guéroult
- Dynamique des Structures et Interactions des Macromolécules Biologiques, UMR 665 INSERM-Université Paris Diderot, Sorbonne Paris Cité, Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, Institut de Biologie Physico-Chimique, Paris, France
| | - Olivier Boittin
- Dynamique des Structures et Interactions des Macromolécules Biologiques, UMR 665 INSERM-Université Paris Diderot, Sorbonne Paris Cité, Institut National de la Transfusion Sanguine, Paris, France
| | - Oliver Mauffret
- Laboratoire de Biologie et Pharmacologie Appliquée, UMR 8113 CNRS-ENS de Cachan, Cachan, France
| | - Catherine Etchebest
- Dynamique des Structures et Interactions des Macromolécules Biologiques, UMR 665 INSERM-Université Paris Diderot, Sorbonne Paris Cité, Institut National de la Transfusion Sanguine, Paris, France
| | - Brigitte Hartmann
- Dynamique des Structures et Interactions des Macromolécules Biologiques, UMR 665 INSERM-Université Paris Diderot, Sorbonne Paris Cité, Institut National de la Transfusion Sanguine, Paris, France
- Laboratoire de Biologie et Pharmacologie Appliquée, UMR 8113 CNRS-ENS de Cachan, Cachan, France
- * E-mail:
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27
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Christofferson A, Zhao L, Sun H, Huang Z, Huang N. Theoretical studies of the base pair fidelity of selenium-modified DNA. J Phys Chem B 2011; 115:10041-8. [PMID: 21770426 DOI: 10.1021/jp204204x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The introduction of selenium into DNA in the place of oxygen provides a unique opportunity for studying the fidelity of DNA replication, as well as providing advantages in the growth of DNA crystals and the greater resolution of their structures. However, the atomic mechanisms of the relative stability and base pair recognition of the selenium-modified DNA are poorly understood. In the present study, quantum mechanics calculations were performed on base pairings, base stacking, and base-water interactions for both unmodified thymine and thymine with the 2-exo-oxygen replaced with selenium, and the results were used to develop and validate CHARMM force field parameters for the 2-Se-thymine. Subsequently, molecular dynamics simulations and free-energy perturbation calculations were performed on 11-base DNA sequences containing native thymine and the 2-Se-thymine. The calculated relative free-energy values are in good agreement with experimentally determined relative stability, where the 2-Se-thymine offers similar stability to T-A in cognate DNA, while it dramatically destabilizes the DNA containing the T-G mismatch base pair when 2-Se-thymine is incorporated. Thus, 2-Se-thymine largely increases the native T-A base pair fidelity by discouraging the T-G wobble pair. Insights into the high pairing specificity and the relative stability of selenium-modified DNA were obtained based on detailed structural and energetic analysis of molecular dynamics trajectories. Our studies move one step further toward an understanding of the high base pair fidelity and thermodynamic properties of Se-DNA in solution and in protein-DNA complexes.
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Affiliation(s)
- Andrew Christofferson
- National Institute of Biological Sciences, Beijing, No. 7 Science Park Road, Zhongguancun Life Science Park, Changping District, Beijing 102206, People's Republic of China
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28
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Peckham HE, Olson WK. Nucleic-acid structural deformability deduced from anisotropic displacement parameters. Biopolymers 2010; 95:254-69. [PMID: 21280021 DOI: 10.1002/bip.21570] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2010] [Revised: 10/11/2010] [Accepted: 11/10/2010] [Indexed: 11/09/2022]
Abstract
The growing numbers of very well resolved nucleic-acid crystal structures with anisotropic displacement parameters provide an unprecedented opportunity to learn about the natural motions of DNA and RNA. Here we report a new Monte-Carlo approach that takes direct account of this information to extract the distortions of covalent structure, base pairing, and dinucleotide geometry intrinsic to regularly organized double-helical molecules. We present new methods to test the validity of the anisotropic parameters and examine the apparent deformability of a variety of structures, including several A, B, and Z DNA duplexes, an AB helical intermediate, an RNA, a ligand-DNA complex, and an enzyme-bound DNA. The rigid-body parameters characterizing the positions of the bases in the structures mirror the mean parameters found when atomic motion is taken into account. The base-pair fluctuations intrinsic to a single structure, however, differ from those extracted from collections of nucleic-acid structures, although selected base-pair steps undergo conformational excursions along routes suggested by the ensembles. The computations reveal surprising new molecular insights, such as the stiffening of DNA and concomitant separation of motions of contacted nucleotides on opposite strands by the binding of Escherichia coli endonuclease VIII, which suggest how the protein may direct enzymatic action.
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Affiliation(s)
- Heather E Peckham
- Wright-Riemann Laboratories, Department of Chemistry and Chemical Biology, BioMaPS Institute for Quantitative Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
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29
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Fenley MO, Harris RC, Jayaram B, Boschitsch AH. Revisiting the association of cationic groove-binding drugs to DNA using a Poisson-Boltzmann approach. Biophys J 2010; 99:879-86. [PMID: 20682266 DOI: 10.1016/j.bpj.2010.04.066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 04/15/2010] [Accepted: 04/27/2010] [Indexed: 11/26/2022] Open
Abstract
Proper modeling of nonspecific salt-mediated electrostatic interactions is essential to understanding the binding of charged ligands to nucleic acids. Because the linear Poisson-Boltzmann equation (PBE) and the more approximate generalized Born approach are applied routinely to nucleic acids and their interactions with charged ligands, the reliability of these methods is examined vis-à-vis an efficient nonlinear PBE method. For moderate salt concentrations, the negative derivative, SK(pred), of the electrostatic binding free energy, DeltaG(el), with respect to the logarithm of the 1:1 salt concentration, [M(+)], for 33 cationic minor groove drugs binding to AT-rich DNA sequences is shown to be consistently negative and virtually constant over the salt range considered (0.1-0.4 M NaCl). The magnitude of SK(pred) is approximately equal to the charge on the drug, as predicted by counterion condensation theory (CCT) and observed in thermodynamic binding studies. The linear PBE is shown to overestimate the magnitude of SK(pred), whereas the nonlinear PBE closely matches the experimental results. The PBE predictions of SK(pred) were not correlated with DeltaG(el) in the presence of a dielectric discontinuity, as would be expected from the CCT. Because this correlation does not hold, parameterizing the PBE predictions of DeltaG(el) against the reported experimental data is not possible. Moreover, the common practice of extracting the electrostatic and nonelectrostatic contributions to the binding of charged ligands to biopolyelectrolytes based on the simple relation between experimental SK values and the electrostatic binding free energy that is based on CCT is called into question by the results presented here. Although the rigid-docking nonlinear PB calculations provide reliable predictions of SK(pred), at least for the charged ligand-nucleic acid complexes studied here, accurate estimates of DeltaG(el) will require further development in theoretical and experimental approaches.
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Affiliation(s)
- Marcia O Fenley
- Department of Physics and Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, USA.
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30
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Sharma P, Chawla M, Sharma S, Mitra A. On the role of Hoogsteen:Hoogsteen interactions in RNA: ab initio investigations of structures and energies. RNA (NEW YORK, N.Y.) 2010; 16:942-957. [PMID: 20354152 PMCID: PMC2856888 DOI: 10.1261/rna.1919010] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Accepted: 01/27/2010] [Indexed: 05/28/2023]
Abstract
We use a combination of database analysis and quantum chemical studies to investigate the role of cis and trans Hoogsteen:Hoogsteen (H:H) base pairs and associated higher-order structures in RNA. We add three new examples to the list of previously identified base-pair combinations belonging to these families and, in addition to contextual classification and characterization of their structural and energetic features, we compare their interbase interaction energies and propensities toward participation in triplets and quartets. We find that some base pairs, which are nonplanar in their isolated minimum energy geometries, attain planarity and stability upon triplet formation. A:A H:H trans is the most frequent H:H combination in RNA structures. This base pair occurs at many distinct positions in known rRNA structures, where it helps in the interaction of ribosomal domains in the 50S subunit. It is also present as a part of tertiary interaction in tRNA structures. Although quantum chemical studies suggest an intrinsically nonplanar geometry for this base pair in isolated form, it has the tendency to attain planar geometry in RNA crystal structures by forming higher-order tertiary interactions or in the presence of additional base-phosphate interactions. The tendency of this base pair to form such additional interactions may be helpful in bringing together different segments of RNA, thus making it suitable for the role of facilitator for RNA folding. This also explains the high occurrence frequency of this base pair among all H:H interactions.
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Affiliation(s)
- Purshotam Sharma
- Center for Computational Natural Sciences and Bioinformatics (CCNSB), International Institute of Information Technology (IIIT-H), Gachibowli, Hyderabad 500032, India
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31
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Pallan PS, Egli M. Pairing geometry of the hydrophobic thymine analogue 2,4-difluorotoluene in duplex DNA as analyzed by X-ray crystallography. J Am Chem Soc 2009; 131:12548-9. [PMID: 19685868 DOI: 10.1021/ja905739j] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Certain DNA polymerases (pols) were found to efficiently insert A opposite the hydrophobic T isostere 2,4-difluorotoluene (F) and vice versa, resulting in the widely held belief that some pols rely on shape rather than H-bonding for accurate replication. Using X-ray crystallography we have analyzed the geometry of F:A pairs in duplex DNA and observed a distance between fluorine and the exocyclic amino group of A that is consistent with a H-bond, thus challenging the assumption that the F analogue is unable to engage in H-bonding as well as the steric hypothesis of DNA replication. Therefore, shape and H-bonding are inherently related, and steric constraints at a pol active site, or conferred by stacking or the DNA backbone conformation, may enable H-bonding by F.
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Affiliation(s)
- Pradeep S Pallan
- Department of Biochemistry, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA
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