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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: 9] [Impact Index Per Article: 3.0] [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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Ahmadian Dehaghani Z, Chubak I, Likos CN, Ejtehadi MR. Effects of topological constraints on linked ring polymers in solvents of varying quality. SOFT MATTER 2020; 16:3029-3038. [PMID: 32129365 DOI: 10.1039/c9sm02374g] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We investigate the effects of topological constraints in catenanes composed of interlinked ring polymers on their size in a good solvent as well as on the location of their θ-point when the solvent quality is worsened. We mainly focus on poly[n]catenanes consisting of n ring polymers each of length m interlocked in a linear fashion. Using molecular dynamics simulations, we study the scaling of the poly[n]catenane's radius of gyration in a good solvent, assuming in general that Rg∼mμnν and we find that μ = 0.65 ± 0.02 and ν = 0.60 ± 0.01 for the range of n and m considered. These findings are further rationalized with the help of a mean-field Flory-like theory yielding the values of μ = 16/25 and ν = 3/5, consistent with the numerical results. We show that individual rings within catenanes feature a surplus swelling due to the presence of NL topological links. Furthermore, we consider poly[n]catenanes in solvents of varying quality and we demonstrate that the presence of topological links leads to an increase of its θ-temperature in comparison to isolated linear and ring chains with the following ordering: T > T > T. Finally, we show that the presence of links similarly raises the θ-temperature of a single linked ring in comparison to an unlinked one, bringing its θ-temperature close to the one of a poly[n]catenane.
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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: 9] [Impact Index Per Article: 1.8] [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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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: 19] [Impact Index Per Article: 3.8] [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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Teng X, Hwang W. Effect of Methylation on Local Mechanics and Hydration Structure of DNA. Biophys J 2019; 114:1791-1803. [PMID: 29694859 DOI: 10.1016/j.bpj.2018.03.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 03/03/2018] [Accepted: 03/14/2018] [Indexed: 12/31/2022] Open
Abstract
Cytosine methylation affects mechanical properties of DNA and potentially alters the hydration fingerprint for recognition by proteins. The atomistic origin for these effects is not well understood, and we address this via all-atom molecular dynamics simulations. We find that the stiffness of the methylated dinucleotide step changes marginally, whereas the neighboring steps become stiffer. Stiffening is further enhanced for consecutively methylated steps, providing a mechanistic origin for the effect of hypermethylation. Steric interactions between the added methyl groups and the nonpolar groups of the neighboring nucleotides are responsible for the stiffening in most cases. By constructing hydration maps, we found that methylation also alters the surface hydration structure in distinct ways. Its resistance to deformation may contribute to the stiffening of DNA for deformational modes lacking steric interactions. These results highlight the sequence- and deformational-mode-dependent effects of cytosine methylation.
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Affiliation(s)
- Xiaojing Teng
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas
| | - Wonmuk Hwang
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas; Department of Materials Science & Engineering, Texas A&M University, College Station, Texas; School of Computational Sciences, Korea Institute for Advanced Study, Seoul, Korea.
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Abstract
For short DNA molecules in crowded environments, we evaluate macroscopic parameters such as the average end-to-end distance and the twist conformation by tuning the strength of the site specific confinement driven by the crowders.
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Affiliation(s)
- Marco Zoli
- School of Science and Technology
- University of Camerino
- I-62032 Camerino
- Italy
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Skoruppa E, Laleman M, Nomidis SK, Carlon E. DNA elasticity from coarse-grained simulations: The effect of groove asymmetry. J Chem Phys 2018; 146:214902. [PMID: 28595422 DOI: 10.1063/1.4984039] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
It is well established that many physical properties of DNA at sufficiently long length scales can be understood by means of simple polymer models. One of the most widely used elasticity models for DNA is the twistable worm-like chain (TWLC), which describes the double helix as a continuous elastic rod with bending and torsional stiffness. An extension of the TWLC, which has recently received some attention, is the model by Marko and Siggia, who introduced an additional twist-bend coupling, expected to arise from the groove asymmetry. By performing computer simulations of two available versions of oxDNA, a coarse-grained model of nucleic acids, we investigate the microscopic origin of twist-bend coupling. We show that this interaction is negligible in the oxDNA version with symmetric grooves, while it appears in the oxDNA version with asymmetric grooves. Our analysis is based on the calculation of the covariance matrix of equilibrium deformations, from which the stiffness parameters are obtained. The estimated twist-bend coupling coefficient from oxDNA simulations is G=30±1 nm. The groove asymmetry induces a novel twist length scale and an associated renormalized twist stiffness κt≈80 nm, which is different from the intrinsic torsional stiffness C≈110 nm. This naturally explains the large variations on experimental estimates of the intrinsic stiffness performed in the past.
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Affiliation(s)
- Enrico Skoruppa
- Institute for Theoretical Physics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Michiel Laleman
- Institute for Theoretical Physics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Stefanos K Nomidis
- Institute for Theoretical Physics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
| | - Enrico Carlon
- Institute for Theoretical Physics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
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Zoli M. End-to-end distance and contour length distribution functions of DNA helices. J Chem Phys 2018; 148:214902. [DOI: 10.1063/1.5021639] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Marco Zoli
- School of Science and Technology, University of Camerino, I-62032 Camerino, Italy
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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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Salari H, Eslami-Mossallam B, Ranjbar HF, Ejtehadi MR. Stiffer double-stranded DNA in two-dimensional confinement due to bending anisotropy. Phys Rev E 2017; 94:062407. [PMID: 28085439 DOI: 10.1103/physreve.94.062407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Indexed: 11/07/2022]
Abstract
Using analytical approach and Monte Carlo (MC) simulations, we study the elastic behavior of the intrinsically twisted elastic ribbons with bending anisotropy, such as double-stranded DNA (dsDNA), in two-dimensional (2D) confinement. We show that, due to the bending anisotropy, the persistence length of dsDNA in 2D conformations is always greater than three-dimensional (3D) conformations. This result is in consistence with the measured values for DNA persistence length in 2D and 3D in equal biological conditions. We also show that in two dimensions, an anisotropic, intrinsically twisted polymer exhibits an implicit twist-bend coupling, which leads to the transient curvature increasing with a half helical turn periodicity along the bent polymer.
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Affiliation(s)
- H Salari
- Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran
| | - B Eslami-Mossallam
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, the Netherlands
| | - H F Ranjbar
- Institute of Complex Systems (ICS-2), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425 Jülich, Germany
| | - M R Ejtehadi
- Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran, Iran and School of Nano Science, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran
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Abstract
DNA bending is critical for DNA packaging, recognition, and repair, and occurs toward either the major or the minor groove. The anisotropy of B-DNA groove bending was quantified for eight DNA sequences by free energy simulations employing a novel reaction coordinate. The simulations show that bending toward the major groove is preferred for non-A-tracts while the A-tract has a high tendency of bending toward the minor groove. Persistence lengths were generally larger for bending toward the minor groove, which is thought to originate from differences in groove hydration. While this difference in stiffness is one of the factors determining the overall preference of bending direction, the dominant contribution is shown to be a free energy offset between major and minor groove bending. The data suggests that, for the A-tract, this offset is largely determined by inherent structural properties, while differences in groove hydration play a large role for non-A-tracts. By quantifying the energetics of DNA groove bending and rationalizing the origins of the anisotropy, the calculations provide important new insights into a key biological process.
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Affiliation(s)
- Ning Ma
- Department of Chemistry, University of South Florida , 4202 East Fowler Avenue, CHE 205, Tampa, Florida 33620, United States
| | - Arjan van der Vaart
- Department of Chemistry, University of South Florida , 4202 East Fowler Avenue, CHE 205, Tampa, Florida 33620, United States
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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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