1
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Shepherd JW, Guilbaud S, Zhou Z, Howard JAL, Burman M, Schaefer C, Kerrigan A, Steele-King C, Noy A, Leake MC. Correlating fluorescence microscopy, optical and magnetic tweezers to study single chiral biopolymers such as DNA. Nat Commun 2024; 15:2748. [PMID: 38553446 PMCID: PMC10980717 DOI: 10.1038/s41467-024-47126-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 03/21/2024] [Indexed: 04/02/2024] Open
Abstract
Biopolymer topology is critical for determining interactions inside cell environments, exemplified by DNA where its response to mechanical perturbation is as important as biochemical properties to its cellular roles. The dynamic structures of chiral biopolymers exhibit complex dependence with extension and torsion, however the physical mechanisms underpinning the emergence of structural motifs upon physiological twisting and stretching are poorly understood due to technological limitations in correlating force, torque and spatial localization information. We present COMBI-Tweez (Combined Optical and Magnetic BIomolecule TWEEZers), a transformative tool that overcomes these challenges by integrating optical trapping, time-resolved electromagnetic tweezers, and fluorescence microscopy, demonstrated on single DNA molecules, that can controllably form and visualise higher order structural motifs including plectonemes. This technology combined with cutting-edge MD simulations provides quantitative insight into complex dynamic structures relevant to DNA cellular processes and can be adapted to study a range of filamentous biopolymers.
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Affiliation(s)
- Jack W Shepherd
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
- Department of Biology, University of York, York, YO10 5DD, England
| | - Sebastien Guilbaud
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
| | - Zhaokun Zhou
- Guangdong Provincial Key Lab of Robotics and Intelligent System, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China
| | - Jamieson A L Howard
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
| | - Matthew Burman
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
| | - Charley Schaefer
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
| | - Adam Kerrigan
- The York-JEOL Nanocentre, University of York, York, YO10 5BR, England
| | - Clare Steele-King
- Bioscience Technology Facility, University of York, York, YO10 5DD, England
| | - Agnes Noy
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England
| | - Mark C Leake
- School of Physics, Engineering and Technology, University of York, York, YO10 5DD, England.
- Department of Biology, University of York, York, YO10 5DD, England.
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2
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Mondal S, Mukherjee S, Bagchi B. Melting and Bubble Formation in a Double-Stranded DNA: Microscopic Aspects of Early Base-Pair Opening Events and the Role of Water. J Phys Chem B 2024; 128:2076-2086. [PMID: 38389118 DOI: 10.1021/acs.jpcb.3c06519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Despite its rigid structure, DNA is a remarkably flexible molecule. Flexibility is essential for biological functions (such as transcription and gene repair), which require large-amplitude structural changes such as bubble formation. The bubbles thus formed are required to have a certain stability of their own and survive long on the time scale of molecular motions. A molecular understanding of fluctuations leading to quasi-stable structures is not available. Through extensive atomistic molecular dynamics simulations, we identify a sequence of microscopic events that culminate in local bubble formation, which is initiated by base-pair (BP) opening, resulting from the cleavage of native BP hydrogen bonds (HBs). This is followed by the formation of mismatched BPs with non-native contacts. These metastable structures can either revert to their original forms or undergo a flipping transition to form a local bubble that can span across 3-4 BPs. A substantial distortion of the DNA backbone and a disruption of BP stacking are observed because of the structural changes induced by these local perturbations. We also explored how water helps in the entire process. A small number of water molecules undergo rearrangement to stabilize the intermediate states by forming HBs with DNA bases. Water thus acts as a lubricant that counteracts the enthalpic penalty suffered from the loss of native BP contacts. Although the process of bubble formation is reversible, the sequence of steps involved poses an entropic barrier, preventing it from easily retracing the path to the native state.
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Affiliation(s)
- Sayantan Mondal
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Saumyak Mukherjee
- Center for Theoretical Chemistry, Ruhr University Bochum, Universitätsstraße 150, Bochum D-44780, Germany
| | - Biman Bagchi
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, Karnataka 560012, India
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3
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Junier I, Ghobadpour E, Espeli O, Everaers R. DNA supercoiling in bacteria: state of play and challenges from a viewpoint of physics based modeling. Front Microbiol 2023; 14:1192831. [PMID: 37965550 PMCID: PMC10642903 DOI: 10.3389/fmicb.2023.1192831] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 09/25/2023] [Indexed: 11/16/2023] Open
Abstract
DNA supercoiling is central to many fundamental processes of living organisms. Its average level along the chromosome and over time reflects the dynamic equilibrium of opposite activities of topoisomerases, which are required to relax mechanical stresses that are inevitably produced during DNA replication and gene transcription. Supercoiling affects all scales of the spatio-temporal organization of bacterial DNA, from the base pair to the large scale chromosome conformation. Highlighted in vitro and in vivo in the 1960s and 1970s, respectively, the first physical models were proposed concomitantly in order to predict the deformation properties of the double helix. About fifteen years later, polymer physics models demonstrated on larger scales the plectonemic nature and the tree-like organization of supercoiled DNA. Since then, many works have tried to establish a better understanding of the multiple structuring and physiological properties of bacterial DNA in thermodynamic equilibrium and far from equilibrium. The purpose of this essay is to address upcoming challenges by thoroughly exploring the relevance, predictive capacity, and limitations of current physical models, with a specific focus on structural properties beyond the scale of the double helix. We discuss more particularly the problem of DNA conformations, the interplay between DNA supercoiling with gene transcription and DNA replication, its role on nucleoid formation and, finally, the problem of scaling up models. Our primary objective is to foster increased collaboration between physicists and biologists. To achieve this, we have reduced the respective jargon to a minimum and we provide some explanatory background material for the two communities.
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Affiliation(s)
- Ivan Junier
- CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, Université Grenoble Alpes, Grenoble, France
| | - Elham Ghobadpour
- CNRS, UMR 5525, VetAgro Sup, Grenoble INP, TIMC, Université Grenoble Alpes, Grenoble, France
- École Normale Supérieure (ENS) de Lyon, CNRS, Laboratoire de Physique and Centre Blaise Pascal de l'ENS de Lyon, Lyon, France
| | - Olivier Espeli
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
| | - Ralf Everaers
- École Normale Supérieure (ENS) de Lyon, CNRS, Laboratoire de Physique and Centre Blaise Pascal de l'ENS de Lyon, Lyon, France
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4
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Curuksu JD. Spectral analysis of DNA superhelical dynamics from molecular minicircle simulations. J Chem Phys 2023; 159:105101. [PMID: 37694753 DOI: 10.1063/5.0164440] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 08/22/2023] [Indexed: 09/12/2023] Open
Abstract
Torsional and bending deformations of DNA molecules often occur in vivo and are important for biological functions. DNA "under stress" is a conformational state, which is by far the most frequent state during DNA-protein and gene regulation. In DNA minicircles of length <100 base pairs (bp), the combined effect of torsional and bending stresses can cause local unusual conformations, with certain base pair steps often absorbing most of the stress, leaving other steps close to their relaxed conformation. To better understand the superhelical dynamics of DNA under stress, molecular simulations of 94 bp minicircles with different torsional linking numbers were interpreted using Fourier analyses and principal component analyses. Sharp localized bends of nearly 90° in the helical axis were observed, which in turn decreased fluctuations of the rotational register and helped redistribute the torsional stress into writhe, i.e., superhelical turn up to 360°. In these kinked minicircles, only two-thirds of the DNA molecule bends and writhes and the remaining segment stays close to straight and preserves a conformational flexibility typical of canonical B-DNA (bending of 39° ± 17° distributed parsimoniously across 36 bp), which was confirmed and visualized by principal component analysis. These results confirm that stressed DNA molecules are highly heterogeneous along their sequence, with segments designed to locally store and release stress so that nearby segments can stay relaxed.
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Affiliation(s)
- Jeremy D Curuksu
- Amazon.com, Inc., New York, New York 10001, USA and Center for Data Science, New York University, New York, New York 10011, USA
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5
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Lapierre J, Hub JS. DNA opening during transcription initiation by RNA polymerase II in atomic detail. Biophys J 2022; 121:4299-4310. [PMID: 36230000 PMCID: PMC9703100 DOI: 10.1016/j.bpj.2022.10.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 09/01/2022] [Accepted: 10/07/2022] [Indexed: 12/14/2022] Open
Abstract
RNA polymerase II (RNAP II) synthesizes RNA by reading the DNA code. During transcription initiation, RNAP II opens the double-stranded DNA to expose the DNA template to the active site. The molecular interactions driving and controlling DNA opening are not well understood. We used all-atom steered molecular dynamics simulations to derive a continuous pathway of DNA opening in human RNAP II, involving a 55 Å DNA strand displacement and a nearly 360° DNA helix rotation. To drive such large-scale transitions, we used a combination of RMSD-based collective variables, a newly designed rotational coordinate, and a path collective variable. The simulations reveal extensive interactions of the DNA with three conserved protein loops near the active site, namely with the rudder, fork loop 1, and fork loop 2. According to the simulations, DNA-protein interactions support DNA opening by a twofold mechanism; they catalyze DNA opening by attacking Watson-Crick hydrogen bonds, and they stabilize the open DNA bubble by the formation of a wide set of DNA-protein salt bridges.
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Affiliation(s)
- Jeremy Lapierre
- Theoretical Physics and Center for Biophysics, Saarland University, Saarbrücken, Germany
| | - Jochen S Hub
- Theoretical Physics and Center for Biophysics, Saarland University, Saarbrücken, Germany.
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6
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Lim W, Randisi F, Doye JPK, Louis AA. The interplay of supercoiling and thymine dimers in DNA. Nucleic Acids Res 2022; 50:2480-2492. [PMID: 35188542 PMCID: PMC8934635 DOI: 10.1093/nar/gkac082] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 01/21/2022] [Accepted: 02/04/2022] [Indexed: 11/16/2022] Open
Abstract
Thymine dimers are a major mutagenic photoproduct induced by UV radiation. While they have been the subject of extensive theoretical and experimental investigations, questions of how DNA supercoiling affects local defect properties, or, conversely, how the presence of such defects changes global supercoiled structure, are largely unexplored. Here, we introduce a model of thymine dimers in the oxDNA forcefield, parametrized by comparison to melting experiments and structural measurements of the thymine dimer induced bend angle. We performed extensive molecular dynamics simulations of double-stranded DNA as a function of external twist and force. Compared to undamaged DNA, the presence of a thymine dimer lowers the supercoiling densities at which plectonemes and bubbles occur. For biologically relevant supercoiling densities and forces, thymine dimers can preferentially segregate to the tips of the plectonemes, where they enhance the probability of a localized tip-bubble. This mechanism increases the probability of highly bent and denatured states at the thymine dimer site, which may facilitate repair enzyme binding. Thymine dimer-induced tip-bubbles also pin plectonemes, which may help repair enzymes to locate damage. We hypothesize that the interplay of supercoiling and local defects plays an important role for a wider set of DNA damage repair systems.
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Affiliation(s)
- Wilber Lim
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Ferdinando Randisi
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- FabricNano Limited, 192 Drummond St, London NW1 3HP, UK
| | - Jonathan P K Doye
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
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7
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Wong CK, Tang C, Schreck JS, Doye JPK. Characterizing the free-energy landscapes of DNA origamis. NANOSCALE 2022; 14:2638-2648. [PMID: 35129570 DOI: 10.1039/d1nr05716b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We show how coarse-grained modelling combined with umbrella sampling using distance-based order parameters can be applied to compute the free-energy landscapes associated with mechanical deformations of large DNA nanostructures. We illustrate this approach for the strong bending of DNA nanotubes and the potentially bistable landscape of twisted DNA origami sheets. The homogeneous bending of the DNA nanotubes is well described by the worm-like chain model; for more extreme bending the nanotubes reversibly buckle with the bending deformations localized at one or two "kinks". For a twisted one-layer DNA origami, the twist is coupled to the bending of the sheet giving rise to a free-energy landscape that has two nearly-degenerate minima that have opposite curvatures. By contrast, for a two-layer origami, the increased stiffness with respect to bending leads to a landscape with a single free-energy minimum that has a saddle-like geometry. The ability to compute such landscapes is likely to be particularly useful for DNA mechanotechnology and for understanding stress accumulation during the self-assembly of origamis into higher-order structures.
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Affiliation(s)
- Chak Kui Wong
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
| | - Chuyan Tang
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
| | - John S Schreck
- National Center for Atmospheric Research, Computational and Information Systems Laboratory, 850 Table Mesa Drive, Boulder, CO 80305, USA
| | - Jonathan P K Doye
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK.
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8
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Wan B, Yu J. Two-phase dynamics of DNA supercoiling based on DNA polymer physics. Biophys J 2022; 121:658-669. [PMID: 35016860 PMCID: PMC8873955 DOI: 10.1016/j.bpj.2022.01.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 10/11/2021] [Accepted: 01/05/2022] [Indexed: 11/28/2022] Open
Abstract
DNA supercoils are generated in genome regulation processes such as transcription and replication and provide mechanical feedback to such processes. Under tension, a DNA supercoil can present a coexistence state of plectonemic and stretched phases. Experiments have revealed the dynamic behaviors of plectonemes, e.g., diffusion, nucleation, and hopping. To represent these dynamics with conformational changes, we demonstrated first the fast dynamics on the DNA to reach torque equilibrium within the plectonemic and stretched phases, and then identified the two-phase boundaries as collective slow variables to describe the essential dynamics. According to the timescale separation demonstrated here, we developed a two-phase model on the dynamics of DNA supercoiling, which can capture physiologically relevant events across timescales of several orders of magnitudes. In this model, we systematically characterized the slow dynamics between the two phases and compared the numerical results with those from the DNA polymer physics-based worm-like chain model. The supercoiling dynamics, including the nucleation, diffusion, and hopping of plectonemes, have been well represented and reproduced, using the two-phase dynamic model, at trivial computational costs. Our current developments, therefore, can be implemented to explore multiscale physical mechanisms of the DNA supercoiling-dependent physiological processes.
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Affiliation(s)
- Biao Wan
- Complex Systems Division, Beijing Computational Science Research Center, Beijing, China.
| | - Jin Yu
- Department of Physics and Astronomy, Department of Chemistry, NSF-Simons Center for Multiscale Cell Fate Research, University of California, Irvine, California.
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9
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Kim M, Hong CC, Lee S, Kim JS. Dynamics of a
DNA
minicircle: Poloidal rotation and in‐plane circular vibration. B KOREAN CHEM SOC 2022. [DOI: 10.1002/bkcs.12492] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Minjung Kim
- Department of Chemistry and Nanoscience Ewha Womans University Seoul South Korea
| | - Chi Cheng Hong
- Department of Chemistry and Nanoscience Ewha Womans University Seoul South Korea
- School of Chemistry University of Edinburgh Edinburgh UK
| | - Saeyeon Lee
- Department of Chemistry and Nanoscience Ewha Womans University Seoul South Korea
| | - Jun Soo Kim
- Department of Chemistry and Nanoscience Ewha Womans University Seoul South Korea
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10
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Henriksen RA, Jenjaroenpun P, Sjøstrøm IB, Jensen KR, Prada-Luengo I, Wongsurawat T, Nookaew I, Regenberg B. Circular DNA in the human germline and its association with recombination. Mol Cell 2022; 82:209-217.e7. [PMID: 34951964 PMCID: PMC10707452 DOI: 10.1016/j.molcel.2021.11.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 08/24/2021] [Accepted: 11/23/2021] [Indexed: 12/24/2022]
Abstract
Extrachromosomal circular DNA (eccDNA) is common in somatic tissue, but its existence and effects in the human germline are unexplored. We used microscopy, long-read DNA sequencing, and new analytic methods to document thousands of eccDNAs from human sperm. EccDNAs derived from all genomic regions and mostly contained a single DNA fragment, although some consisted of multiple fragments. The generation of eccDNA inversely correlates with the meiotic recombination rate, and chromosomes with high coding-gene density and Alu element abundance form the least eccDNA. Analysis of insertions in human genomes further indicates that eccDNA can persist in the human germline when the circular molecules reinsert themselves into the chromosomes. Our results suggest that eccDNA has transient and permanent effects on the germline. They explain how differences in the physical and genetic map might arise and offer an explanation of how Alu elements coevolved with genes to protect genome integrity against deleterious mutations producing eccDNA.
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Affiliation(s)
- Rasmus Amund Henriksen
- Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Piroon Jenjaroenpun
- Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Ida Borup Sjøstrøm
- Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | | - Iñigo Prada-Luengo
- Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Thidathip Wongsurawat
- Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Intawat Nookaew
- Department of Biomedical Informatics, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Birgitte Regenberg
- Ecology and Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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11
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Watson GD, Chan EW, Leake MC, Noy A. Structural interplay between DNA-shape protein recognition and supercoiling: The case of IHF. Comput Struct Biotechnol J 2022; 20:5264-5274. [PMID: 36212531 PMCID: PMC9519438 DOI: 10.1016/j.csbj.2022.09.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 11/03/2022] Open
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12
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Kim M, Bae S, Oh I, Yoo J, Kim JS. Sequence-dependent twist-bend coupling in DNA minicircles. NANOSCALE 2021; 13:20186-20196. [PMID: 34847218 DOI: 10.1039/d1nr04672a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Looping of double-stranded DNA molecules with 100-200 base pairs into minicircles, catenanes, and rotaxanes has been suggested as a potential tool for DNA nanotechnologies. However, sharp DNA bending into a minicircle with a diameter of several to ten nanometers occurs with alterations in the DNA helical structure and may lead to defective kink formation that hampers the use of DNA minicircles, catenanes, and rotaxanes in nanoscale DNA applications. Here, we investigated local variations of a helical twist in sharply bent DNA using microsecond-long all-atom molecular dynamics simulations of six different DNA minicircles, focusing on the sequence dependence of the coupling between DNA bending and its helical twist. Twist angles between consecutive base pairs were analyzed at different locations relative to the direction of DNA bending and, among 10 unique dinucleotide steps, we identified four dinucleotide steps with strong twist-bend coupling, the pyrimidine-purine dinucleotide steps of TA/TA, CG/CG, and CA/TG and the purine-purine dinucleotide step of GA/TC. This work suggests the sequence-dependent structural responses of DNA to strong mechanical deformation, providing new molecular-level insights into the structure and stability of sharply bent DNA minicircles for nanoscale applications.
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Affiliation(s)
- Minjung Kim
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea.
| | - Sehui Bae
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea.
| | - Inrok Oh
- LG Chem Ltd, LG Science Park, Seoul 07796, Republic of Korea
| | - Jejoong Yoo
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Jun Soo Kim
- Department of Chemistry and Nanoscience, Ewha Womans University, Seoul 03760, Republic of Korea.
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13
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Yoo J, Park S, Maffeo C, Ha T, Aksimentiev A. DNA sequence and methylation prescribe the inside-out conformational dynamics and bending energetics of DNA minicircles. Nucleic Acids Res 2021; 49:11459-11475. [PMID: 34718725 PMCID: PMC8599915 DOI: 10.1093/nar/gkab967] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 09/27/2021] [Accepted: 10/11/2021] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic genome and methylome encode DNA fragments' propensity to form nucleosome particles. Although the mechanical properties of DNA possibly orchestrate such encoding, the definite link between 'omics' and DNA energetics has remained elusive. Here, we bridge the divide by examining the sequence-dependent energetics of highly bent DNA. Molecular dynamics simulations of 42 intact DNA minicircles reveal that each DNA minicircle undergoes inside-out conformational transitions with the most likely configuration uniquely prescribed by the nucleotide sequence and methylation of DNA. The minicircles' local geometry consists of straight segments connected by sharp bends compressing the DNA's inward-facing major groove. Such an uneven distribution of the bending stress favors minimum free energy configurations that avoid stiff base pair sequences at inward-facing major grooves. Analysis of the minicircles' inside-out free energy landscapes yields a discrete worm-like chain model of bent DNA energetics that accurately account for its nucleotide sequence and methylation. Experimentally measuring the dependence of the DNA looping time on the DNA sequence validates the model. When applied to a nucleosome-like DNA configuration, the model quantitatively reproduces yeast and human genomes' nucleosome occupancy. Further analyses of the genome-wide chromatin structure data suggest that DNA bending energetics is a fundamental determinant of genome architecture.
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Affiliation(s)
- Jejoong Yoo
- Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
| | - Sangwoo Park
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Christopher Maffeo
- Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Taekjip Ha
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA
- Howard Hughes Medical Institute, Baltimore, MD 21218, USA
| | - Aleksei Aksimentiev
- Department of Physics and the Center for the Physics of Living Cells, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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14
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Fogg JM, Judge AK, Stricker E, Chan HL, Zechiedrich L. Supercoiling and looping promote DNA base accessibility and coordination among distant sites. Nat Commun 2021; 12:5683. [PMID: 34584096 PMCID: PMC8478907 DOI: 10.1038/s41467-021-25936-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 08/30/2021] [Indexed: 11/29/2022] Open
Abstract
DNA in cells is supercoiled and constrained into loops and this supercoiling and looping influence every aspect of DNA activity. We show here that negative supercoiling transmits mechanical stress along the DNA backbone to disrupt base pairing at specific distant sites. Cooperativity among distant sites localizes certain sequences to superhelical apices. Base pair disruption allows sharp bending at superhelical apices, which facilitates DNA writhing to relieve torsional strain. The coupling of these processes may help prevent extensive denaturation associated with genomic instability. Our results provide a model for how DNA can form short loops, which are required for many essential processes, and how cells may use DNA loops to position nicks to facilitate repair. Furthermore, our results reveal a complex interplay between site-specific disruptions to base pairing and the 3-D conformation of DNA, which influences how genomes are stored, replicated, transcribed, repaired, and many other aspects of DNA activity.
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Affiliation(s)
- Jonathan M Fogg
- Department of Molecular Virology and Microbiology, Houston, TX, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA
- Department of Pharmacology and Chemical Biology, Houston, TX, USA
| | - Allison K Judge
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA
| | - Erik Stricker
- Department of Molecular Virology and Microbiology, Houston, TX, USA
| | - Hilda L Chan
- Graduate Program in Immunology and Microbiology, Houston, TX, USA
- Medical Scientist Training Program, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - Lynn Zechiedrich
- Department of Molecular Virology and Microbiology, Houston, TX, USA.
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Houston, TX, USA.
- Department of Pharmacology and Chemical Biology, Houston, TX, USA.
- Graduate Program in Immunology and Microbiology, Houston, TX, USA.
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15
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Mills A, Gago F. Structural Landscape of the Transition from an ssDNA Dumbbell Plus Its Complementary Hairpin to a dsDNA Microcircle Via a Kissing Loop Intermediate. Molecules 2021; 26:molecules26103017. [PMID: 34069399 PMCID: PMC8158708 DOI: 10.3390/molecules26103017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 11/17/2022] Open
Abstract
The experimental construction of a double-stranded DNA microcircle of only 42 base pairs entailed a great deal of ingenuity and hard work. However, figuring out the three-dimensional structures of intermediates and the final product can be particularly baffling. Using a combination of model building and unrestrained molecular dynamics simulations in explicit solvent we have characterized the different DNA structures involved along the process. Our 3D models of the single-stranded DNA molecules provide atomic insight into the recognition event that must take place for the DNA bases in the cohesive tail of the hairpin to pair with their complementary bases in the single-stranded loops of the dumbbell. We propose that a kissing loop involving six base pairs makes up the core of the nascent dsDNA microcircle. We also suggest a feasible pathway for the hybridization of the remaining complementary bases and characterize the final covalently closed dsDNA microcircle as possessing two well-defined U-turns. Additional models of the pre-ligation complex of T4 DNA ligase with the DNA dumbbell and the post-ligation pre-release complex involving the same enzyme and the covalently closed DNA microcircle are shown to be compatible with enzyme recognition and gap ligation.
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16
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Schlick T, Portillo-Ledesma S, Myers CG, Beljak L, Chen J, Dakhel S, Darling D, Ghosh S, Hall J, Jan M, Liang E, Saju S, Vohr M, Wu C, Xu Y, Xue E. Biomolecular Modeling and Simulation: A Prospering Multidisciplinary Field. Annu Rev Biophys 2021; 50:267-301. [PMID: 33606945 PMCID: PMC8105287 DOI: 10.1146/annurev-biophys-091720-102019] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We reassess progress in the field of biomolecular modeling and simulation, following up on our perspective published in 2011. By reviewing metrics for the field's productivity and providing examples of success, we underscore the productive phase of the field, whose short-term expectations were overestimated and long-term effects underestimated. Such successes include prediction of structures and mechanisms; generation of new insights into biomolecular activity; and thriving collaborations between modeling and experimentation, including experiments driven by modeling. We also discuss the impact of field exercises and web games on the field's progress. Overall, we note tremendous success by the biomolecular modeling community in utilization of computer power; improvement in force fields; and development and application of new algorithms, notably machine learning and artificial intelligence. The combined advances are enhancing the accuracy andscope of modeling and simulation, establishing an exemplary discipline where experiment and theory or simulations are full partners.
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Affiliation(s)
- Tamar Schlick
- Department of Chemistry, New York University, New York, New York 10003, USA;
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10012, USA
- New York University-East China Normal University Center for Computational Chemistry, New York University Shanghai, Shanghai 200122, China
| | | | - Christopher G Myers
- Department of Chemistry, New York University, New York, New York 10003, USA;
| | - Lauren Beljak
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Justin Chen
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sami Dakhel
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Daniel Darling
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sayak Ghosh
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Joseph Hall
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Mikaeel Jan
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Emily Liang
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Sera Saju
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Mackenzie Vohr
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Chris Wu
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Yifan Xu
- College of Arts and Science, New York University, New York, New York 10003, USA
| | - Eva Xue
- College of Arts and Science, New York University, New York, New York 10003, USA
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17
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Pyne ALB, Noy A, Main KHS, Velasco-Berrelleza V, Piperakis MM, Mitchenall LA, Cugliandolo FM, Beton JG, Stevenson CEM, Hoogenboom BW, Bates AD, Maxwell A, Harris SA. Base-pair resolution analysis of the effect of supercoiling on DNA flexibility and major groove recognition by triplex-forming oligonucleotides. Nat Commun 2021; 12:1053. [PMID: 33594049 PMCID: PMC7887228 DOI: 10.1038/s41467-021-21243-y] [Citation(s) in RCA: 64] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 01/16/2021] [Indexed: 12/16/2022] Open
Abstract
In the cell, DNA is arranged into highly-organised and topologically-constrained (supercoiled) structures. It remains unclear how this supercoiling affects the detailed double-helical structure of DNA, largely because of limitations in spatial resolution of the available biophysical tools. Here, we overcome these limitations, by a combination of atomic force microscopy (AFM) and atomistic molecular dynamics (MD) simulations, to resolve structures of negatively-supercoiled DNA minicircles at base-pair resolution. We observe that negative superhelical stress induces local variation in the canonical B-form DNA structure by introducing kinks and defects that affect global minicircle structure and flexibility. We probe how these local and global conformational changes affect DNA interactions through the binding of triplex-forming oligonucleotides to DNA minicircles. We show that the energetics of triplex formation is governed by a delicate balance between electrostatics and bonding interactions. Our results provide mechanistic insight into how DNA supercoiling can affect molecular recognition, that may have broader implications for DNA interactions with other molecular species.
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Affiliation(s)
- Alice L B Pyne
- Department of Materials Science and Engineering, University of Sheffield, Sheffield, UK.
- London Centre for Nanotechnology, University College London, London, UK.
| | - Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, UK.
| | - Kavit H S Main
- London Centre for Nanotechnology, University College London, London, UK
- UCL Cancer Institute, University College London, London, UK
| | | | - Michael M Piperakis
- Department of Biological Chemistry, John Innes Centre, Norwich, UK
- Department of Chemistry, University of Reading, Whiteknights, Reading, UK
| | | | - Fiorella M Cugliandolo
- Department of Biological Chemistry, John Innes Centre, Norwich, UK
- Department of Pathology, Division of Immunology, University of Cambridge, Cambridge, UK
| | - Joseph G Beton
- London Centre for Nanotechnology, University College London, London, UK
- Department of Crystallography, Institute of Structural and Molecular Biology, Birkbeck, University of London, London, UK
| | | | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London, UK
- Department of Physics and Astronomy, University College London, London, UK
| | - Andrew D Bates
- Institute of Integrative Biology, University of Liverpool, Liverpool, UK
| | - Anthony Maxwell
- Department of Biological Chemistry, John Innes Centre, Norwich, UK
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, Leeds, UK.
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK.
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18
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Park G, Cho MK, Jung Y. Sequence-Dependent Kink Formation in Short DNA Loops: Theory and Molecular Dynamics Simulations. J Chem Theory Comput 2021; 17:1308-1317. [PMID: 33570937 DOI: 10.1021/acs.jctc.0c01116] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Kink formation is essential in highly bent DNA complexed with gene regulatory proteins such as histones to release the bending stress stored within the DNA duplex. Local opening of the double-stranded DNA creates a sharp turn along the specific sequence, which leads to the global bending of the DNA strand. Despite the critical role of kink formation, it is still challenging to predict the position of kink formation for a given DNA sequence. In this study, we propose a theoretical model and perform molecular dynamics simulations to quantify the sequence-dependent kink probability of a strongly bent DNA. By incorporating the elastic bending energy and the sequence-specific thermodynamic parameters, we investigate the importance of the DNA sequence on kink formation. We find that the sequence with TA dinucleotide repeats flanked by GC steps increases the kink propensity by more than an order of magnitude under the same bending stress. The number of base pairs involved in the local opening is found to be coupled with the sequence-specific bubble formation free energy. Our study elucidates the molecular origin of the sequence heterogeneity on kink formation, which is fundamental to understanding protein-DNA recognition.
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Affiliation(s)
- Gyehyun Park
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - Myung Keun Cho
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
| | - YounJoon Jung
- Department of Chemistry, Seoul National University, Seoul 08826, Korea
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19
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Desai PR, Brahmachari S, Marko JF, Das S, Neuman KC. Coarse-grained modelling of DNA plectoneme pinning in the presence of base-pair mismatches. Nucleic Acids Res 2020; 48:10713-10725. [PMID: 33045724 DOI: 10.1093/nar/gkaa836] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 09/14/2020] [Accepted: 09/18/2020] [Indexed: 12/27/2022] Open
Abstract
Damaged or mismatched DNA bases result in the formation of physical defects in double-stranded DNA. In vivo, defects in DNA must be rapidly and efficiently repaired to maintain cellular function and integrity. Defects can also alter the mechanical response of DNA to bending and twisting constraints, both of which are important in defining the mechanics of DNA supercoiling. Here, we use coarse-grained molecular dynamics (MD) simulation and supporting statistical-mechanical theory to study the effect of mismatched base pairs on DNA supercoiling. Our simulations show that plectoneme pinning at the mismatch site is deterministic under conditions of relatively high force (>2 pN) and high salt concentration (>0.5 M NaCl). Under physiologically relevant conditions of lower force (0.3 pN) and lower salt concentration (0.2 M NaCl), we find that plectoneme pinning becomes probabilistic and the pinning probability increases with the mismatch size. These findings are in line with experimental observations. The simulation framework, validated with experimental results and supported by the theoretical predictions, provides a way to study the effect of defects on DNA supercoiling and the dynamics of supercoiling in molecular detail.
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Affiliation(s)
- Parth Rakesh Desai
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.,Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - John F Marko
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.,Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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20
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Alexiou TS, Alatas PV, Tsalikis DG, Mavrantzas VG. Conformational and Dynamic Properties of Short DNA Minicircles in Aqueous Solution from Atomistic Molecular Dynamics Simulations. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00821] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Terpsichori S. Alexiou
- Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504, Greece
| | - Panagiotis V. Alatas
- Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504, Greece
| | - Dimitrios G. Tsalikis
- Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504, Greece
| | - Vlasis G. Mavrantzas
- Department of Chemical Engineering, University of Patras & FORTH-ICE/HT, Patras, GR 26504, Greece
- Department of Mechanical and Process Engineering, Particle Technology Laboratory, ETH Zürich, CH-8092 Zürich, Switzerland
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21
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Jayaraman A. 100th Anniversary of Macromolecular Science Viewpoint: Modeling and Simulation of Macromolecules with Hydrogen Bonds: Challenges, Successes, and Opportunities. ACS Macro Lett 2020; 9:656-665. [PMID: 35648569 DOI: 10.1021/acsmacrolett.0c00134] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Macromolecular materials with directional interactions such as hydrogen bonds exhibit numerous attractive features in terms of structure, thermodynamics, and dynamics. Besides enabling precise tuning of desirable geometries in the assembled state (e.g., programmable coordination numbers depending on the valency of the directional interaction), mixing in a blend/composite through stabilization via hydrogen bonds between the various components, hydrogen bonds can also impart responsiveness to external stimuli (e.g., temperature, pH). In biomacromolecules (e.g., proteins, DNA, polysaccharides), hydrogen bonds play a key role in stabilizing secondary and tertiary structures, which in turn define the function of these macromolecules. In this Viewpoint, I present the challenges, successes, and opportunities for molecular modeling and simulations to conduct fundamental and application-focused research on macromolecular materials with hydrogen bonding interactions. The past successes and limitations of atomistic simulations are discussed first, followed by highlights from recent developments in coarse-grained modeling and their use in studies of (synthetic and biologically relevant) macromolecular materials. Model development focused on polynucleotides (e.g., DNA, RNA, etc.), polypeptides, polysaccharides, and synthetic polymers at experimentally relevant conditions are highlighted. This viewpoint ends with potential future directions for macromolecular modeling and simulations with other types of directional interactions beyond hydrogen bonding.
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Affiliation(s)
- Arthi Jayaraman
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
- Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716, United States
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22
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Liebl K, Zacharias M. How global DNA unwinding causes non-uniform stress distribution and melting of DNA. PLoS One 2020; 15:e0232976. [PMID: 32413048 PMCID: PMC7228070 DOI: 10.1371/journal.pone.0232976] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 04/24/2020] [Indexed: 12/31/2022] Open
Abstract
DNA unwinding is an important process that controls binding of proteins, gene expression and melting of double-stranded DNA. In a series of all-atom MD simulations on two DNA molecules containing a transcription start TATA-box sequence we demonstrate that application of a global restraint on the DNA twisting dramatically changes the coupling between helical parameters and the distribution of deformation energy along the sequence. Whereas only short range nearest-neighbor coupling is observed in the relaxed case, long-range coupling is induced in the globally restrained case. With increased overall unwinding the elastic deformation energy is strongly non-uniformly distributed resulting ultimately in a local melting transition of only the TATA box segment during the simulations. The deformation energy tends to be stored more in cytidine/guanine rich regions associated with a change in conformational substate distribution. Upon TATA box melting the deformation energy is largely absorbed by the melting bubble with the rest of the sequences relaxing back to near B-form. The simulations allow us to characterize the structural changes and the propagation of the elastic energy but also to calculate the associated free energy change upon DNA unwinding up to DNA melting. Finally, we design an Ising model for predicting the local melting transition based on empirical parameters. The direct comparison with the atomistic MD simulations indicates a remarkably good agreement for the predicted necessary torsional stress to induce a melting transition, for the position and length of the melted region and for the calculated associated free energy change between both approaches.
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Affiliation(s)
- Korbinian Liebl
- Physics Department T38, Technical University of Munich, Garching, Germany
| | - Martin Zacharias
- Physics Department T38, Technical University of Munich, Garching, Germany
- * E-mail:
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23
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Atomistic insight into sequence-directed DNA bending and minicircle formation propensity in the absence and presence of phased A-tracts. J Comput Aided Mol Des 2020; 34:253-265. [PMID: 31950463 DOI: 10.1007/s10822-020-00288-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Accepted: 01/09/2020] [Indexed: 12/21/2022]
Abstract
Bending of double-stranded (ds) DNA plays a crucial role in many important biological processes and is relevant for nanotechnological applications. Among all the elements that have been studied in relation to dsDNA bending, A-tracts stand out as one of the most controversial. The "ApA wedge" theory was disproved when a series of linear polynucleotides containing phased 5'-A4T4-3' or 5'-T4A4-3' runs were shown to be bent or straight, respectively, and crystallographic evidence revealed that A-tracts are unbent. Furthermore, some of the smallest dsDNA minicircles described to date (~ 100 bp in size) lack A-tracts and are subjected to varying levels of torsional stress. Representative DNA sequences from this experimental background were modeled in atomic detail and their dynamic behavior was simulated over hundreds of nanoseconds using the AMBER force field ParmBSC1. Subsequent analysis of the resulting trajectories allowed us to (i) unambiguously establish the location of the bends in all cases; (ii) identify the structural elements that are directly responsible for the macroscopically detected curvature; and (iii) reveal the importance not only of coherently summing the effects of the bending elements when they are in synchrony with the natural repeat of the helix (i.e. separated by an integral number of helical turns) but also when alternated with a half-integral separation of opposite effects. We conclude that the major determinant of the macroscopically observed bending is the proper grouping and phasing of the positive roll imposed by pyrimidine-purine (YR) steps and the negative or null roll characteristic of RY steps and A-tracts, respectively. This conclusion is in very good agreement with the structural parameters experimentally derived for much smaller DNA molecules either alone or as found in DNA-protein complexes. We expect that this work will pave the way for future studies on drug-induced DNA bending, DNA shape readout by transcription factors, structure of circular extrachromosomal DNA, and custom design of curved DNA origami scaffolds.
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24
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Dahlke K, Sing CE. Influence of Nucleoid-Associated Proteins on DNA Supercoiling. J Phys Chem B 2019; 123:10152-10162. [PMID: 31710235 DOI: 10.1021/acs.jpcb.9b07436] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
DNA supercoiling, where the DNA strand forms a writhe to relieve torsional stress, plays a vital role in packaging the genetic material in cells. Experiment, simulation, and theory have all demonstrated how supercoiling emerges due to the over- or underwinding of the DNA strand. Nucleoid-associated proteins (NAPs) help structure DNA in prokaryotes, yet the role that they play in the supercoiling process has not been as thoroughly investigated. We develop a coarse-grained simulation to model DNA supercoiling in the presence of proteins, providing a rigorous physical understanding of how NAPs affect supercoiling behavior. Specifically, we demonstrate how the force and torque necessary to form supercoils are affected by the presence of NAPs. NAPs that bend DNA stabilize the supercoil, thus shifting the transition between extended and supercoiled DNAs. We develop a theory to explain how NAP binding affects DNA supercoiling. This provides insight into how NAPs modulate DNA compaction via a combination of supercoiling and local protein-dependent deformations.
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Affiliation(s)
- Katelyn Dahlke
- Department of Chemical and Biomolecular Engineering , University of Illinois Urbana-Champaign , Urbana , Illinois 61801 , United States
| | - Charles E Sing
- Department of Chemical and Biomolecular Engineering , University of Illinois Urbana-Champaign , Urbana , Illinois 61801 , United States
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25
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Drozdetski AV, Mukhopadhyay A, Onufriev AV. Strongly Bent Double-Stranded DNA: Reconciling Theory and Experiment. FRONTIERS IN PHYSICS 2019; 7:195. [PMID: 32601596 PMCID: PMC7323118 DOI: 10.3389/fphy.2019.00195] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The strong bending of polymers is poorly understood. We propose a general quantitative framework of polymer bending that includes both the weak and strong bending regimes on the same footing, based on a single general physical principle. As the bending deformation increases beyond a certain (polymer-specific) point, the change in the convexity properties of the effective bending energy of the polymer makes the harmonic deformation energetically unfavorable: in this strong bending regime the energy of the polymer varies linearly with the average bending angle as the system follows the convex hull of the deformation energy function. For double-stranded DNA, the effective bending deformation energy becomes non-convex for bends greater than ~ 2° per base-pair, equivalent to the curvature of a closed circular loop of ~ 160 base pairs. A simple equation is derived for the polymer loop energy that covers both the weak and strong bending regimes. The theory shows quantitative agreement with recent DNA cyclization experiments on short DNA fragments, while maintaining the expected agreement with experiment in the weak bending regime. Counter-intuitively, cyclization probability (j-factor) of very short DNA loops is predicted to increase with decreasing loop length; the j-factor reaches its minimum for loops of ≃ 45 base pairs. Atomistic simulations reveal that the attractive component of the short-range Lennard-Jones interaction between the backbone atoms can explain the underlying non-convexity of the DNA effective bending energy, leading to the linear bending regime. Applicability of the theory to protein-DNA complexes, including the nucleosome, is discussed.
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Affiliation(s)
| | | | - Alexey V. Onufriev
- Department of Physics, Virginia Tech, Blacksburg, VA, United States
- Department of Computer Science, Virginia Tech, Blacksburg, VA, United States
- Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, United States
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26
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Zechiedrich L, Fogg JM. BIOPHYSICS MEETS GENE THERAPY: HOW EXPLORING SUPERCOILING-DEPENDENT STRUCTURAL CHANGES IN DNA LED TO THE DEVELOPMENT OF MINIVECTOR DNA. TECHNOLOGY AND INNOVATION 2019; 20:427-439. [PMID: 33815681 DOI: 10.21300/20.4.2019.427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Supercoiling affects every aspect of DNA function (replication, transcription, repair, recombination, etc.), yet the vast majority of studies on DNA and crystal structures of the molecule utilize short linear duplex DNA, which cannot be supercoiled. To study how supercoiling drives DNA biology, we developed and patented methods to make milligram quantities of tiny supercoiled circles of DNA called minicircles. We used a collaborative and multidisciplinary approach, including computational simulations (both atomistic and coarse-grained), biochemical experimentation, and biophysical methods to study these minicircles. By determining the three-dimensional conformations of individual supercoiled DNA minicircles, we revealed the structural diversity of supercoiled DNA and its highly dynamic nature. We uncovered profound structural changes, including sequence-specific base-flipping (where the DNA base flips out into the solvent), bending, and denaturing in negatively supercoiled minicircles. Counterintuitively, exposed DNA bases emerged in the positively supercoiled minicircles, which may result from inside-out DNA (Pauling-like, or "P-DNA"). These structural changes strongly influence how enzymes interact with or act on DNA. We hypothesized that, because of their small size and lack of bacterial sequences, these small supercoiled DNA circles may be efficient at delivering DNA into cells for gene therapy applications. "Minivectors," as we named them for this application, have proven to have therapeutic potential. We discovered that minivectors efficiently transfect a wide range of cell types, including many clinically important cell lines that are refractory to transfection with conventional plasmid vectors. Minivectors can be aerosolized for delivery to lungs and transfect human cells in culture to express RNA or genes. Importantly, minivectors demonstrate no obvious vector-associated toxicity. Minivectors can be repeatedly delivered and are long-lasting without integrating into the genome. Requests from colleagues around the world for minicircle and minivector DNA revealed a demand for our invention. We successfully obtained start-up funding for Twister Biotech, Inc. to help fulfill this demand, providing DNA for those who needed it, with a long-term goal of developing human therapeutics. In summary, what started as a tool for studying DNA structure has taken us in new and unanticipated directions.
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Affiliation(s)
- Lynn Zechiedrich
- Department of Molecular Virology and Microbiology, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, and Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX, USA
| | - Jonathan M Fogg
- Department of Molecular Virology and Microbiology, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, and Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, TX, USA
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27
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Harrison RM, Romano F, Ouldridge TE, Louis AA, Doye JPK. Identifying Physical Causes of Apparent Enhanced Cyclization of Short DNA Molecules with a Coarse-Grained Model. J Chem Theory Comput 2019; 15:4660-4672. [PMID: 31282669 PMCID: PMC6694408 DOI: 10.1021/acs.jctc.9b00112] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
![]()
DNA
cyclization is a powerful technique to gain insight into the nature
of DNA bending. While the wormlike chain model provides a good description
of small to moderate bending fluctuations, it is expected to break
down for large bending. Recent cyclization experiments on strongly
bent shorter molecules indeed suggest enhanced flexibility over and
above that expected from the wormlike chain. Here, we use a coarse-grained
model of DNA to investigate the subtle thermodynamics of DNA cyclization
for molecules ranging from 30 to 210 base pairs. As the molecules
get shorter, we find increasing deviations between our computed equilibrium j-factor and the classic wormlike chain predictions of Shimada
and Yamakawa for a torsionally aligned looped molecule. These deviations
are due to sharp kinking, first at nicks, and only subsequently in
the body of the duplex. At the shortest lengths, substantial fraying
at the ends of duplex domains is the dominant method of relaxation.
We also estimate the dynamic j-factor measured in
recent FRET experiments. We find that the dynamic j-factor is systematically larger than its equilibrium counterpart—with
the deviation larger for shorter molecules—because not all
the stress present in the fully cyclized state is present in the transition
state. These observations are important for the interpretation of
recent cyclization experiments, suggesting that measured anomalously
high j-factors may not necessarily indicate non-WLC
behavior in the body of duplexes.
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Affiliation(s)
- Ryan M Harrison
- Physical & Theoretical Chemistry Laboratory, Department of Chemistry , University of Oxford , South Parks Road , Oxford OX1 3QZ , United Kingdom
| | - Flavio Romano
- Dipartimento di Scienze Molecolari e Nanosistemi , Universitá Ca' Foscari Venezia , I-30123 Venezia , Italy
| | - Thomas E Ouldridge
- Imperial College Centre for Synthetic Biology and Department of Bioengineering , Imperial College London , 180 Queen's Road , London SW7 2AZ , United Kingdom
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, Department of Physics , University of Oxford , 1 Keble Road , Oxford OX1 3NP , United Kingdom
| | - Jonathan P K Doye
- Physical & Theoretical Chemistry Laboratory, Department of Chemistry , University of Oxford , South Parks Road , Oxford OX1 3QZ , United Kingdom
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28
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Suma A, Poppleton E, Matthies M, Šulc P, Romano F, Louis AA, Doye JPK, Micheletti C, Rovigatti L. TacoxDNA: A user-friendly web server for simulations of complex DNA structures, from single strands to origami. J Comput Chem 2019; 40:2586-2595. [PMID: 31301183 DOI: 10.1002/jcc.26029] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/20/2019] [Accepted: 06/22/2019] [Indexed: 12/11/2022]
Abstract
Simulations of nucleic acids at different levels of structural details are increasingly used to complement and interpret experiments in different fields, from biophysics to medicine and materials science. However, the various structural models currently available for DNA and RNA and their accompanying suites of computational tools can be very rarely used in a synergistic fashion. The tacoxDNA webserver and standalone software package presented here are a step toward a long-sought interoperability of nucleic acids models. The webserver offers a simple interface for converting various common input formats of DNA structures and setting up molecular dynamics (MD) simulations. Users can, for instance, design DNA rings with different topologies, such as knots, with and without supercoiling, by simply providing an XYZ coordinate file of the DNA centre-line. More complex DNA geometries, as designable in the cadnano, CanDo and Tiamat tools, can also be converted to all-atom or oxDNA representations, which can then be used to run MD simulations. Though the latter are currently geared toward the native and LAMMPS oxDNA representations, the open-source package is designed to be further expandable. TacoxDNA is available at http://tacoxdna.sissa.it. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Antonio Suma
- Institute for Computational Molecular Science, Temple University, Philadelphia, Pennsylvania, 19122.,SISSA-Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea, 265, 34136, Trieste, Italy
| | - Erik Poppleton
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, 1001, South McAllister Avenue, Tempe, Arizona 85281
| | - Michael Matthies
- Center for Advancing Electronics Dresden (cfaed), Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, 01062, Dresden, Germany
| | - Petr Šulc
- Center for Molecular Design and Biomimetics, The Biodesign Institute, Arizona State University, 1001, South McAllister Avenue, Tempe, Arizona 85281
| | - Flavio Romano
- Dipartimento di Scienze Molecolari e Nanosistemi, Universitá Ca Foscari di Venezia, Via Torino, 155, 30172, Venezia Mestre, Italy
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, UK
| | - Jonathan P K Doye
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QZ, UK
| | - Cristian Micheletti
- SISSA-Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea, 265, 34136, Trieste, Italy
| | - Lorenzo Rovigatti
- Dipartimento di Fisica, Sapienza Universitá di Roma, Piazzale A. Moro, 2, 00185, Rome, Italy.,CNR-ISC, Uos Sapienza, Piazzale A. Moro, 2, 00185, Rome, Italy
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29
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Simonov KA. Strong deformations of DNA: Effect on the persistence length. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:114. [PMID: 30259229 DOI: 10.1140/epje/i2018-11722-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 08/30/2018] [Indexed: 06/08/2023]
Abstract
Extreme deformations of the DNA double helix attracted a lot of attention during the past decades. Particularly, the determination of the persistence length of DNA with extreme local disruptions, or kinks, has become a crucial problem in the studies of many important biological processes. In this paper we review an approach to calculate the persistence length of the double helix by taking into account the formation of kinks of arbitrary configuration. The reviewed approach improves the Kratky-Porod model to determine the type and nature of kinks that occur in the double helix, by measuring a reduction of the persistence length of the kinkable DNA.
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Affiliation(s)
- Kyryło A Simonov
- Fakultät für Mathematik, Universität Wien, Oskar-Morgenstern-Platz 1, 1090, Vienna, Austria.
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30
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Coronel L, Suma A, Micheletti C. Dynamics of supercoiled DNA with complex knots: large-scale rearrangements and persistent multi-strand interlocking. Nucleic Acids Res 2018; 46:7533-7541. [PMID: 29931074 PMCID: PMC6125635 DOI: 10.1093/nar/gky523] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 05/22/2018] [Accepted: 05/24/2018] [Indexed: 02/04/2023] Open
Abstract
Knots and supercoiling are both introduced in bacterial plasmids by catalytic processes involving DNA strand passages. While the effects on plasmid organization has been extensively studied for knotting and supercoiling taken separately, much less is known about their concurrent action. Here, we use molecular dynamics simulations and oxDNA, an accurate mesoscopic DNA model, to study the kinetic and metric changes introduced by complex (five-crossing) knots and supercoiling in 2 kbp-long DNA rings. We find several unexpected results. First, the conformational ensemble is dominated by two distinct states, differing in branchedness and knot size. Secondly, fluctuations between these states are as fast as the metric relaxation of unknotted rings. In spite of this, certain boundaries of knotted and plectonemically-wound regions can persist over much longer timescales. These pinned regions involve multiple strands that are interlocked by the cooperative action of topological and supercoiling constraints. Their long-lived character may be relevant for the simplifying action of topoisomerases.
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Affiliation(s)
- Lucia Coronel
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, 34136 Trieste, Italy
| | - Antonio Suma
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, 34136 Trieste, Italy
- Institute for Computational Molecular Science, College of Science and Technology, Temple University, Philadelphia, PA 19122, USA
| | - Cristian Micheletti
- SISSA - Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265, 34136 Trieste, Italy
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31
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Reymer A, Zakrzewska K, Lavery R. Sequence-dependent response of DNA to torsional stress: a potential biological regulation mechanism. Nucleic Acids Res 2018; 46:1684-1694. [PMID: 29267977 PMCID: PMC5829783 DOI: 10.1093/nar/gkx1270] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 12/07/2017] [Accepted: 12/09/2017] [Indexed: 01/31/2023] Open
Abstract
Torsional restraints on DNA change in time and space during the life of the cell and are an integral part of processes such as gene expression, DNA repair and packaging. The mechanical behavior of DNA under torsional stress has been studied on a mesoscopic scale, but little is known concerning its response at the level of individual base pairs and the effects of base pair composition. To answer this question, we have developed a geometrical restraint that can accurately control the total twist of a DNA segment during all-atom molecular dynamics simulations. By applying this restraint to four different DNA oligomers, we are able to show that DNA responds to both under- and overtwisting in a very heterogeneous manner. Certain base pair steps, in specific sequence environments, are able to absorb most of the torsional stress, leaving other steps close to their relaxed conformation. This heterogeneity also affects the local torsional modulus of DNA. These findings suggest that modifying torsional stress on DNA could act as a modulator for protein binding via the heterogeneous changes in local DNA structure.
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Affiliation(s)
- Anna Reymer
- Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg 40530, Sweden
- Institut de Biologie et Chimie des Protéines, Université de Lyon I/CNRS UMR 5086, Lyon 69367, France
| | - Krystyna Zakrzewska
- Institut de Biologie et Chimie des Protéines, Université de Lyon I/CNRS UMR 5086, Lyon 69367, France
| | - Richard Lavery
- Institut de Biologie et Chimie des Protéines, Université de Lyon I/CNRS UMR 5086, Lyon 69367, France
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32
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Sutthibutpong T, Noy A, Harris S. Atomistic Molecular Dynamics Simulations of DNA Minicircle Topoisomers: A Practical Guide to Setup, Performance, and Analysis. Methods Mol Biol 2017; 1431:195-219. [PMID: 27283311 DOI: 10.1007/978-1-4939-3631-1_15] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
While DNA supercoiling is ubiquitous in vivo, the structure of supercoiled DNA is more challenging to study experimentally than simple linear sequences because the DNA must have a closed topology in order to sustain superhelical stress. DNA minicircles, which are closed circular double-stranded DNA sequences typically containing between 60 and 500 base pairs, have proven to be useful biochemical tools for the study of supercoiled DNA mechanics. We present detailed protocols for constructing models of DNA minicircles in silico, for performing atomistic molecular dynamics (MD) simulations of supercoiled minicircle DNA, and for analyzing the results of the calculations. These simulations are computationally challenging due to the large system sizes. However, improvements in parallel computing software and hardware promise access to improve conformational sampling and simulation timescales. Given the concurrent improvements in the resolution of experimental techniques such as atomic force microscopy (AFM) and cryo-electron microscopy, the study of DNA minicircles will provide a more complete understanding of both the structure and the mechanics of supercoiled DNA.
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Affiliation(s)
- Thana Sutthibutpong
- Theoretical and Computational Science Center (TaCS), Science Laboratory Building, Faculty of Science, King Mongkut University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mod, Thung Khru, Bangkok, 10140, Thailand.
| | - Agnes Noy
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
| | - Sarah Harris
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
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33
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Pasi M, Zakrzewska K, Maddocks JH, Lavery R. Analyzing DNA curvature and its impact on the ionic environment: application to molecular dynamics simulations of minicircles. Nucleic Acids Res 2017; 45:4269-4277. [PMID: 28180333 PMCID: PMC5397150 DOI: 10.1093/nar/gkx092] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 02/07/2017] [Indexed: 01/16/2023] Open
Abstract
We propose a method for analyzing the magnitude and direction of curvature within nucleic acids, based on the curvilinear helical axis calculated by Curves+. The method is applied to analyzing curvature within minicircles constructed with varying degrees of over- or under-twisting. Using the molecular dynamics trajectories of three different minicircles, we are able to quantify how curvature varies locally both in space and in time. We also analyze how curvature influences the local environment of the minicircles, notably via increased heterogeneity in the ionic distributions surrounding the double helix. The approach we propose has been integrated into Curves+ and the utilities Canal (time trajectory analysis) and Canion (environmental analysis) and can be used to study a wide variety of static and dynamic structural data on nucleic acids.
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Affiliation(s)
- Marco Pasi
- MMSB, University of Lyon I/CNRS UMR 5086, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, 69367 Lyon, France
| | - Krystyna Zakrzewska
- MMSB, University of Lyon I/CNRS UMR 5086, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, 69367 Lyon, France
| | - John H Maddocks
- Section de Mathématiques, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland
| | - Richard Lavery
- MMSB, University of Lyon I/CNRS UMR 5086, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, 69367 Lyon, France
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34
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Wang Q, Irobalieva RN, Chiu W, Schmid MF, Fogg JM, Zechiedrich L, Pettitt BM. Influence of DNA sequence on the structure of minicircles under torsional stress. Nucleic Acids Res 2017; 45:7633-7642. [PMID: 28609782 PMCID: PMC5737869 DOI: 10.1093/nar/gkx516] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Revised: 05/26/2017] [Accepted: 06/01/2017] [Indexed: 01/09/2023] Open
Abstract
The sequence dependence of the conformational distribution of DNA under various levels of torsional stress is an important unsolved problem. Combining theory and coarse-grained simulations shows that the DNA sequence and a structural correlation due to topology constraints of a circle are the main factors that dictate the 3D structure of a 336 bp DNA minicircle under torsional stress. We found that DNA minicircle topoisomers can have multiple bend locations under high torsional stress and that the positions of these sharp bends are determined by the sequence, and by a positive mechanical correlation along the sequence. We showed that simulations and theory are able to provide sequence-specific information about individual DNA minicircles observed by cryo-electron tomography (cryo-ET). We provided a sequence-specific cryo-ET tomogram fitting of DNA minicircles, registering the sequence within the geometric features. Our results indicate that the conformational distribution of minicircles under torsional stress can be designed, which has important implications for using minicircle DNA for gene therapy.
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Affiliation(s)
- Qian Wang
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Rossitza N. Irobalieva
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Wah Chiu
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Michael F. Schmid
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jonathan M. Fogg
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston TX, 77030, USA
| | - Lynn Zechiedrich
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston TX, 77030, USA
| | - B. Montgomery Pettitt
- Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
- Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
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35
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Zoli M. Twist-stretch profiles of DNA chains. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:225101. [PMID: 28394255 DOI: 10.1088/1361-648x/aa6c50] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Helical molecules change their twist number under the effect of a mechanical load. We study the twist-stretch relation for a set of short DNA molecules modeled by a mesoscopic Hamiltonian. Finite temperature path integral techniques are applied to generate a large ensemble of possible configurations for the base pairs of the sequence. The model also accounts for the bending and twisting fluctuations between adjacent base pairs along the molecules stack. Simulating a broad range of twisting conformation, we compute the helix structural parameters by averaging over the ensemble of base pairs configurations. The method selects, for any applied force, the average twist angle which minimizes the molecule's free energy. It is found that the chains generally over-twist under an applied stretching and the over-twisting is physically associated to the contraction of the average helix diameter, i.e. to the damping of the base pair fluctuations. Instead, assuming that the maximum amplitude of the bending fluctuations may decrease against the external load, the DNA molecule first over-twists for weak applied forces and then untwists above a characteristic force value. Our results are discussed in relation to available experimental information albeit for kilo-base long molecules.
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Affiliation(s)
- Marco Zoli
- School of Science and Technology, University of Camerino, I-62032 Camerino, Italy
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36
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Simulation of DNA Supercoil Relaxation. Biophys J 2017; 110:2176-84. [PMID: 27224483 DOI: 10.1016/j.bpj.2016.03.041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 03/24/2016] [Accepted: 03/28/2016] [Indexed: 01/17/2023] Open
Abstract
Several recent single-molecule experiments observe the response of supercoiled DNA to nicking endonucleases and topoisomerases. Typically in these experiments, indirect measurements of supercoil relaxation are obtained by observing the motion of a large micron-sized bead. The bead, which also serves to manipulate DNA, experiences significant drag and thereby obscures supercoil dynamics. Here we employ our discrete wormlike chain model to bypass experimental limitations and simulate the dynamic response of supercoiled DNA to a single strand nick. From our simulations, we make three major observations. First, extension is a poor dynamic measure of supercoil relaxation; in fact, the linking number relaxes so fast that it cannot have much impact on extension. Second, the rate of linking number relaxation depends upon its initial partitioning into twist and writhe as determined by tension. Third, the extensional response strongly depends upon the initial position of plectonemes.
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37
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Noy A, Maxwell A, Harris SA. Interference between Triplex and Protein Binding to Distal Sites on Supercoiled DNA. Biophys J 2017; 112:523-531. [PMID: 28108011 PMCID: PMC5300792 DOI: 10.1016/j.bpj.2016.12.034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 09/09/2016] [Accepted: 12/16/2016] [Indexed: 11/29/2022] Open
Abstract
We have explored the interdependence of the binding of a DNA triplex and a repressor protein to distal recognition sites on supercoiled DNA minicircles using MD simulations. We observe that the interaction between the two ligands through their influence on their DNA template is determined by a subtle interplay of DNA mechanics and electrostatics, that the changes in flexibility induced by ligand binding play an important role and that supercoiling can instigate additional ligand-DNA contacts that would not be possible in simple linear DNA sequences.
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Affiliation(s)
- Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, United Kingdom
| | - Anthony Maxwell
- Department of Biological Chemistry, John Innes Centre Norwich Research Park, Norwich, United Kingdom
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, Leeds, United Kingdom; Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, United Kingdom.
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38
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Medalion S, Rabin Y. Effect of sequence-dependent rigidity on plectoneme localization in dsDNA. J Chem Phys 2016; 144:135101. [PMID: 27059589 DOI: 10.1063/1.4945010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We use Monte-Carlo simulations to study the effect of variable rigidity on plectoneme formation and localization in supercoiled double-stranded DNA. We show that the presence of soft sequences increases the number of plectoneme branches and that the edges of the branches tend to be localized at these sequences. We propose an experimental approach to test our results in vitro, and discuss the possible role played by plectoneme localization in the search process of transcription factors for their targets (promoter regions) on the bacterial genome.
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Affiliation(s)
- Shlomi Medalion
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Yitzhak Rabin
- Department of Physics and Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
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39
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Noy A, Sutthibutpong T, A Harris S. Protein/DNA interactions in complex DNA topologies: expect the unexpected. Biophys Rev 2016; 8:145-155. [PMID: 28035245 PMCID: PMC5153831 DOI: 10.1007/s12551-016-0241-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/13/2016] [Indexed: 01/09/2023] Open
Abstract
DNA supercoiling results in compacted DNA structures that can bring distal sites into close proximity. It also changes the local structure of the DNA, which can in turn influence the way it is recognised by drugs, other nucleic acids and proteins. Here, we discuss how DNA supercoiling and the formation of complex DNA topologies can affect the thermodynamics of DNA recognition. We then speculate on the implications for transcriptional control and the three-dimensional organisation of the genetic material, using examples from our own simulations and from the literature. We introduce and discuss the concept of coupling between the multiple length-scales associated with hierarchical nuclear structural organisation through DNA supercoiling and topology.
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Affiliation(s)
- Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, YO10 5DD UK
| | - Thana Sutthibutpong
- Theoretical and Computational Physics Group, Department of Physics, King Mongkut University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mod, Thung Khru, Bangkok, Thailand 10140
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT ; Astbury Centre for Structural and Molecular Biology, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT
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40
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Krueger E, Shim J, Fathizadeh A, Chang AN, Subei B, Yocham KM, Davis PH, Graugnard E, Khalili-Araghi F, Bashir R, Estrada D, Fologea D. Modeling and Analysis of Intercalant Effects on Circular DNA Conformation. ACS NANO 2016; 10:8910-7. [PMID: 27559753 PMCID: PMC5111899 DOI: 10.1021/acsnano.6b04876] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The large-scale conformation of DNA molecules plays a critical role in many basic elements of cellular functionality and viability. By targeting the structural properties of DNA, many cancer drugs, such as anthracyclines, effectively inhibit tumor growth but can also produce dangerous side effects. To enhance the development of innovative medications, rapid screening of structural changes to DNA can provide important insight into their mechanism of interaction. In this study, we report changes to circular DNA conformation from intercalation with ethidium bromide using all-atom molecular dynamics simulations and characterized experimentally by translocation through a silicon nitride solid-state nanopore. Our measurements reveal three distinct current blockade levels and a 6-fold increase in translocation times for ethidium bromide-treated circular DNA as compared to untreated circular DNA. We attribute these increases to changes in the supercoiled configuration hypothesized to be branched or looped structures formed in the circular DNA molecule. Further evidence of the conformational changes is demonstrated by qualitative atomic force microscopy analysis. These results expand the current methodology for predicting and characterizing DNA tertiary structure and advance nanopore technology as a platform for deciphering structural changes of other important biomolecules.
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Affiliation(s)
- Eric Krueger
- Department of Physics, Boise State University, Boise, ID, United States
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | - Jiwook Shim
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Arman Fathizadeh
- Department of Physics, University of Illinois at Chicago, Chicago, IL, United States
| | - A. Nicole Chang
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | - Basheer Subei
- Department of Physics, University of Illinois at Chicago, Chicago, IL, United States
| | - Katie M. Yocham
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | - Paul H. Davis
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | - Elton Graugnard
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | | | - Rashid Bashir
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - David Estrada
- Department of Materials Science and Engineering, Boise State University, Boise, ID, United States
| | - Daniel Fologea
- Department of Physics, Boise State University, Boise, ID, United States
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41
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Sutthibutpong T, Matek C, Benham C, Slade GG, Noy A, Laughton C, K Doye JP, Louis AA, Harris SA. Long-range correlations in the mechanics of small DNA circles under topological stress revealed by multi-scale simulation. Nucleic Acids Res 2016; 44:9121-9130. [PMID: 27664220 PMCID: PMC5100592 DOI: 10.1093/nar/gkw815] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 09/03/2016] [Indexed: 12/14/2022] Open
Abstract
It is well established that gene regulation can be achieved through activator and repressor proteins that bind to DNA and switch particular genes on or off, and that complex metabolic networks determine the levels of transcription of a given gene at a given time. Using three complementary computational techniques to study the sequence-dependence of DNA denaturation within DNA minicircles, we have observed that whenever the ends of the DNA are constrained, information can be transferred over long distances directly by the transmission of mechanical stress through the DNA itself, without any requirement for external signalling factors. Our models combine atomistic molecular dynamics (MD) with coarse-grained simulations and statistical mechanical calculations to span three distinct spatial resolutions and timescale regimes. While they give a consensus view of the non-locality of sequence-dependent denaturation in highly bent and supercoiled DNA loops, each also reveals a unique aspect of long-range informational transfer that occurs as a result of restraining the DNA within the closed loop of the minicircles.
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Affiliation(s)
- Thana Sutthibutpong
- School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.,Theoretical and Computational Science Center (TaCS), Science Laboratory Building, Faculty of Science, King Mongkut's University of Technology Thonburi (KMUTT), 126 Pracha-Uthit Road, Bang Mod, Thrung Khru, Bangkok 10140, Thailand
| | - Christian Matek
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Craig Benham
- UC Davis Genome Centre, Health Sciences Drive, Davis, CA 95616, USA
| | - Gabriel G Slade
- Department of Physics, São Paulo State University, Rua Cristovão, São José do Rio Preto, SP 15054-000, Brazil
| | - Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, YO10 5DD, UK
| | - Charles Laughton
- School of Pharmacy and Centre for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Jonathan P K Doye
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Ard A Louis
- Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK .,Astbury Centre for Structural and Molecular Biology, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
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42
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Noy A, Sutthibutpong T, A Harris S. Protein/DNA interactions in complex DNA topologies: expect the unexpected. Biophys Rev 2016; 8:233-243. [PMID: 27738452 PMCID: PMC5039213 DOI: 10.1007/s12551-016-0208-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/13/2016] [Indexed: 12/31/2022] Open
Abstract
DNA supercoiling results in compacted DNA structures that can bring distal sites into close proximity. It also changes the local structure of the DNA, which can in turn influence the way it is recognised by drugs, other nucleic acids and proteins. Here, we discuss how DNA supercoiling and the formation of complex DNA topologies can affect the thermodynamics of DNA recognition. We then speculate on the implications for transcriptional control and the three-dimensional organisation of the genetic material, using examples from our own simulations and from the literature. We introduce and discuss the concept of coupling between the multiple length-scales associated with hierarchical nuclear structural organisation through DNA supercoiling and topology.
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Affiliation(s)
- Agnes Noy
- Department of Physics, Biological Physical Sciences Institute, University of York, York, YO10 5DD UK
| | - Thana Sutthibutpong
- Theoretical and Computational Physics Group, Department of Physics, King Mongkut University of Technology Thonburi, 126 Pracha Uthit Road, Bang Mod, Thung Khru, Bangkok, Thailand 10140
| | - Sarah A Harris
- School of Physics and Astronomy, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT ; Astbury Centre for Structural and Molecular Biology, University of Leeds, 192 Woodhouse Lane, Leeds, UK LS2 9JT
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43
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Jeong J, Le TT, Kim HD. Single-molecule fluorescence studies on DNA looping. Methods 2016; 105:34-43. [PMID: 27064000 PMCID: PMC4967024 DOI: 10.1016/j.ymeth.2016.04.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 04/01/2016] [Accepted: 04/05/2016] [Indexed: 11/17/2022] Open
Abstract
Structure and dynamics of DNA impact how the genetic code is processed and maintained. In addition to its biological importance, DNA has been utilized as building blocks of various nanomachines and nanostructures. Thus, understanding the physical properties of DNA is of fundamental importance to basic sciences and engineering applications. DNA can undergo various physical changes. Among them, DNA looping is unique in that it can bring two distal sites together, and thus can be used to mediate interactions over long distances. In this paper, we introduce a FRET-based experimental tool to study DNA looping at the single molecule level. We explain the connection between experimental measurables and a theoretical concept known as the J factor with the intent of raising awareness of subtle theoretical details that should be considered when drawing conclusions. We also explore DNA looping-assisted protein diffusion mechanism called intersegmental transfer using protein induced fluorescence enhancement (PIFE). We present some preliminary results and future outlooks.
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Affiliation(s)
- Jiyoun Jeong
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
| | - Tung T Le
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
| | - Harold D Kim
- School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta 30332, USA.
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44
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Pasi M, Mornico D, Volant S, Juchet A, Batisse J, Bouchier C, Parissi V, Ruff M, Lavery R, Lavigne M. DNA minicircles clarify the specific role of DNA structure on retroviral integration. Nucleic Acids Res 2016; 44:7830-47. [PMID: 27439712 PMCID: PMC5027509 DOI: 10.1093/nar/gkw651] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 07/11/2016] [Indexed: 01/26/2023] Open
Abstract
Chromatin regulates the selectivity of retroviral integration into the genome of infected cells. At the nucleosome level, both histones and DNA structure are involved in this regulation. We propose a strategy that allows to specifically study a single factor: the DNA distortion induced by the nucleosome. This strategy relies on mimicking this distortion using DNA minicircles (MCs) having a fixed rotational orientation of DNA curvature, coupled with atomic-resolution modeling. Contrasting MCs with linear DNA fragments having identical sequences enabled us to analyze the impact of DNA distortion on the efficiency and selectivity of integration. We observed a global enhancement of HIV-1 integration in MCs and an enrichment of integration sites in the outward-facing DNA major grooves. Both of these changes are favored by LEDGF/p75, revealing a new, histone-independent role of this integration cofactor. PFV integration is also enhanced in MCs, but is not associated with a periodic redistribution of integration sites, thus highlighting its distinct catalytic properties. MCs help to separate the roles of target DNA structure, histone modifications and integrase (IN) cofactors during retroviral integration and to reveal IN-specific regulation mechanisms.
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Affiliation(s)
- Marco Pasi
- MMSB UMR5086 University of Lyon I/CNRS, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, Lyon 69367, France
| | - Damien Mornico
- Institut Pasteur-Bioinformatics and Biostatistics Hub-C3BI, USR 3756 IP-CNRS, Paris 75015, France
| | - Stevenn Volant
- Institut Pasteur-Bioinformatics and Biostatistics Hub-C3BI, USR 3756 IP-CNRS, Paris 75015, France
| | - Anna Juchet
- Institut Pasteur, Unité de Virologie Moléculaire et Vaccinologie, UMR 3569 IP-CNRS, Paris 75015, France
| | - Julien Batisse
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Dpt de Biologie Structurale Intégrative, UDS, U596 INSERM, UMR7104 CNRS, Illkirch 67400, France
| | - Christiane Bouchier
- Institut Pasteur, PF1, Plate-forme Génomique-Pôle Biomics, Citech, Paris 75015, France
| | - Vincent Parissi
- Laboratoire de Microbiologie Fondamentale et Pathogénicité, UMR 5234 CNRS-Université de Bordeaux, Bordeaux 33000, France
| | - Marc Ruff
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Dpt de Biologie Structurale Intégrative, UDS, U596 INSERM, UMR7104 CNRS, Illkirch 67400, France
| | - Richard Lavery
- MMSB UMR5086 University of Lyon I/CNRS, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, Lyon 69367, France
| | - Marc Lavigne
- Institut Pasteur, Unité de Virologie Moléculaire et Vaccinologie, UMR 3569 IP-CNRS, Paris 75015, France
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45
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Tavakoli S, Panaretos VM. Detecting and Localizing Differences in Functional Time Series Dynamics: A Case Study in Molecular Biophysics. J Am Stat Assoc 2016. [DOI: 10.1080/01621459.2016.1147355] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Shahin Tavakoli
- Statistical Laboratory, University of Cambridge, Cambridge, UK
| | - Victor M. Panaretos
- Institut de Mathématiques, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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46
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Pasi M, Lavery R. Structure and dynamics of DNA loops on nucleosomes studied with atomistic, microsecond-scale molecular dynamics. Nucleic Acids Res 2016; 44:5450-6. [PMID: 27098037 PMCID: PMC4914111 DOI: 10.1093/nar/gkw293] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 04/08/2016] [Accepted: 04/08/2016] [Indexed: 01/25/2023] Open
Abstract
DNA loop formation on nucleosomes is strongly implicated in chromatin remodeling and occurs spontaneously in nucleosomes subjected to superhelical stress. The nature of such loops depends crucially on the balance between DNA deformation and DNA interaction with the nucleosome core. Currently, no high-resolution structural data on these loops exist. Although uniform rod models have been used to study loop size and shape, these models make assumptions concerning DNA mechanics and DNA-core binding. We present here atomic-scale molecular dynamics simulations for two different loop sizes. The results point to the key role of localized DNA kinking within the loops. Kinks enable the relaxation of DNA bending strain to be coupled with improved DNA-core interactions. Kinks lead to small, irregularly shaped loops that are asymmetrically positioned with respect to the nucleosome core. We also find that loop position can influence the dynamics of the DNA segments at the extremities of the nucleosome.
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Affiliation(s)
- Marco Pasi
- MMSB, University Lyon I/CNRS UMR 5086, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, 69367 Lyon, France
| | - Richard Lavery
- MMSB, University Lyon I/CNRS UMR 5086, Institut de Biologie et Chimie des Protéines, 7 passage du Vercors, 69367 Lyon, France
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47
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Iacovelli F, Alves C, Falconi M, Oteri F, de Oliveira CLP, Desideri A. Influence of the single-strand linker composition on the structural/dynamical properties of a truncated octahedral DNA nano-cage family. Biopolymers 2016; 101:992-9. [PMID: 26819976 DOI: 10.1002/bip.22475] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The structural/dynamical properties of three truncated octahedral DNA nano-cages composed by identical double helices but single strand linkers with different composition, namely 7 thymidines, 7 adenines, and 7 alternated thymidines and adenines, have been investigated through classical molecular dynamics simulations. Trajectories have been analyzed to investigate the role of the linkers in defining nano-cages stability and flexibility, including possible influence on the internal cages motions. The data indicate that the cages behavior is almost identical and that the structural/dynamical parameters measured along the trajectories are not particularly affected by the presence of different bases. These results demonstrate that the constraints imposed by the nano-structure geometry are the main factor in modulating these properties
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48
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Abstract
Understanding how the sequence of a DNA molecule affects its dynamic properties is a central problem affecting biochemistry and biotechnology. The process of cyclizing short DNA, as a critical step in molecular cloning, lacks a comprehensive picture of the kinetic process containing sequence information. We have elucidated this process by using coarse-grained simulations, enhanced sampling methods, and recent theoretical advances. We are able to identify the types and positions of structural defects during the looping process at a base-pair level. Correlations along a DNA molecule dictate critical sequence positions that can affect the looping rate. Structural defects change the bending elasticity of the DNA molecule from a harmonic to subharmonic potential with respect to bending angles. We explore the subelastic chain as a possible model in loop formation kinetics. A sequence-dependent model is developed to qualitatively predict the relative loop formation time as a function of DNA sequence.
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49
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Iacovelli F, Falconi M, Knudsen BR, Desideri A. Comparative simulative analysis of single and double stranded truncated octahedral DNA nanocages. RSC Adv 2016. [DOI: 10.1039/c5ra27591a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Spacefill view of double (DSL) and single (SSL) stranded linkers DNA cages. The blue atoms represent the shared cages scaffold, while the yellow atoms show the single stranded DNA oligonucleotides shaping the double stranded linkers of the DSL cage.
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Affiliation(s)
| | - Mattia Falconi
- Department of Biology
- University of Rome “Tor Vergata”
- 00133 Rome
- Italy
| | - Birgitta R. Knudsen
- Interdisciplinary Nanoscience Center (iNANO) and Department of Molecular Biology and Genetics
- Åarhus University
- Åarhus
- Denmark
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50
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Abstract
By regulating access to the genetic code, DNA supercoiling strongly affects DNA metabolism. Despite its importance, however, much about supercoiled DNA (positively supercoiled DNA, in particular) remains unknown. Here we use electron cryo-tomography together with biochemical analyses to investigate structures of individual purified DNA minicircle topoisomers with defined degrees of supercoiling. Our results reveal that each topoisomer, negative or positive, adopts a unique and surprisingly wide distribution of three-dimensional conformations. Moreover, we uncover striking differences in how the topoisomers handle torsional stress. As negative supercoiling increases, bases are increasingly exposed. Beyond a sharp supercoiling threshold, we also detect exposed bases in positively supercoiled DNA. Molecular dynamics simulations independently confirm the conformational heterogeneity and provide atomistic insight into the flexibility of supercoiled DNA. Our integrated approach reveals the three-dimensional structures of DNA that are essential for its function. DNA supercoiling strongly affects its metabolism. By electron cryo-tomography, biochemical assays and molecular dynamics simulations, here the authors show that supercoiled DNA minicircles adopt unique and wide distributions of three-dimensional conformations, many with disrupted base pairs.
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