1
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Fernandez R, Berro J. CRISPR-Cas9 editing efficiency in fission yeast is not limited by homology search and is improved by combining gap-repair with fluoride selection. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001191. [PMID: 38778900 PMCID: PMC11109758 DOI: 10.17912/micropub.biology.001191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 01/01/1970] [Accepted: 05/03/2024] [Indexed: 05/25/2024]
Abstract
Protocols for CRISPR-Cas9 editing have been implemented in most model organisms, including fission yeast, for which some improvements have also been later described. Here, we report an improvement to the CRISPR-Cas9 protocol in fission yeast, as we combine a cloning free gap-repair method with our previously described fluoride selection marker, which speeds up genome editing. We also report a wide variability of editing efficiencies at different loci along the genome, and we demonstrate that this variability cannot be explained by the location of the edited sequences in the genome. Lastly, our attempt at improving editing efficiency by targeting the donor DNA to the cut site using a HaloTag strategy to link the donor DNA to two proteins of the homologous recombination repair machinery ( Rad51 or Rad52 ) fell short, which shows that editing efficiency in fission yeast is likely not limited by homology search.
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Affiliation(s)
- Ronan Fernandez
- Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States
| | - Julien Berro
- Molecular Biophysics & Biochemistry, Yale University, New Haven, Connecticut, United States
- Cell Biology, Yale University School of Medicine
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2
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Dulin D. An Introduction to Magnetic Tweezers. Methods Mol Biol 2024; 2694:375-401. [PMID: 37824014 DOI: 10.1007/978-1-0716-3377-9_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Magnetic tweezers are a single-molecule force and torque spectroscopy technique that enable the mechanical interrogation in vitro of biomolecules, such as nucleic acids and proteins. They use a magnetic field originating from either permanent magnets or electromagnets to attract a magnetic particle, thus stretching the tethering biomolecule. They nicely complement other force spectroscopy techniques such as optical tweezers and atomic force microscopy (AFM) as they operate as a very stable force clamp, enabling long-duration experiments over a very broad range of forces spanning from 10 fN to 1 nN, with 1-10 milliseconds time and sub-nanometer spatial resolution. Their simplicity, robustness, and versatility have made magnetic tweezers a key technique within the field of single-molecule biophysics, being broadly applied to study the mechanical properties of, e.g., nucleic acids, genome processing molecular motors, protein folding, and nucleoprotein filaments. Furthermore, magnetic tweezers allow for high-throughput single-molecule measurements by tracking hundreds of biomolecules simultaneously both in real-time and at high spatiotemporal resolution. Magnetic tweezers naturally combine with surface-based fluorescence spectroscopy techniques, such as total internal reflection fluorescence microscopy, enabling correlative fluorescence and force/torque spectroscopy on biomolecules. This chapter presents an introduction to magnetic tweezers including a description of the hardware, the theory behind force calibration, its spatiotemporal resolution, combining it with other techniques, and a (non-exhaustive) overview of biological applications.
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Affiliation(s)
- David Dulin
- LaserLaB Amsterdam and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
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3
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Maman N, Kumar P, Yadav A, Feingold M. Single Molecule Study of the Polymerization of RecA on dsDNA: The Dynamics of Individual Domains. Front Mol Biosci 2021; 8:609076. [PMID: 33842536 PMCID: PMC8025788 DOI: 10.3389/fmolb.2021.609076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 02/02/2021] [Indexed: 11/13/2022] Open
Abstract
In the Escherichia coli, RecA plays a central role in the recombination and repair of the DNA. For homologous recombination, RecA binds to ssDNA forming a nucleoprotein filament. The RecA-ssDNA filament searches for a homologous sequence on a dsDNA and, subsequently, RecA mediates strand exchange between the ssDNA and the dsDNA. In vitro, RecA binds to both ssDNA and dsDNA. Despite a wide range of studies of the polymerization of RecA on dsDNA, both at the single molecule level and by means of biochemical methods, important aspects of this process are still awaiting a better understanding. Specifically, a detailed, quantitative description of the nucleation and growth dynamics of the RecA-dsDNA filaments is still lacking. Here, we use Optical Tweezers together with a single molecule analysis approach to measure the dynamics of the individual RecA domains on dsDNA and the corresponding growth rates for each of their fronts. We focus on the regime where the nucleation and growth rate constants, kn and kg, are comparable, leading to a coverage of the dsDNA molecule that consists of a small number of RecA domains. For the case of essentially irreversible binding (using ATPγS instead of ATP), we find that domain growth is highly asymmetric with a ratio of about 10:1 between the fast and slow fronts growth rates.
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Affiliation(s)
- Nitzan Maman
- Department of Physics, Ben Gurion University of the Negev, Beer Sheva, Israel.,The Ilse Katz Center for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva, Israel
| | - Pramod Kumar
- Department of Physics, Ben Gurion University of the Negev, Beer Sheva, Israel
| | - Amarjeet Yadav
- Department of Physics, Ben Gurion University of the Negev, Beer Sheva, Israel.,Department of Applied Physics, Babasaheb Bhimrao Ambedkar University, Lucknow, India
| | - Mario Feingold
- Department of Physics, Ben Gurion University of the Negev, Beer Sheva, Israel.,The Ilse Katz Center for Nanotechnology, Ben Gurion University of the Negev, Beer Sheva, Israel
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4
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Zhao XC, Fu H, Song L, Yang YJ, Zhou EC, Liu GX, Chen XF, Li Z, Wu WQ, Zhang XH. S-DNA and RecA/RAD51-Mediated Strand Exchange in Vitro. Biochemistry 2019; 58:2009-2016. [PMID: 30900876 DOI: 10.1021/acs.biochem.8b01125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
S-DNA (stretched DNA) is an elongated base-paired DNA conformation under high tension. Because the RecA/Rad51 family DNA recombinases form helical filaments on DNA and mediate the formation of the DNA triplex (D-loop), in which the DNA is stretched, and because the extension of these nucleoprotein filaments is similar to the extension of S-DNA, S-DNA has long been hypothesized as a possible state of DNA that participants in RecA/Rad51-mediated DNA strand exchange in homologous recombination. Such a hypothesis, however, is still lacking direct experimental studies. In this work, we have studied the polymerization and strand exchange on S-DNA mediated by Escherichia coli RecA, human Rad51, and Saccharomyces cerevisiae Rad51 by single-molecule magnetic tweezers. We report that RecA/Rad51 polymerizes faster on S-DNA than on B-DNA with the same buffer conditions. Furthermore, the RecA/Rad51-mediated DNA triplex forms faster from S-DNA than from B-DNA together with the homologous single-stranded DNA. These results provide evidence that S-DNA can interact with RecA and Rad51 and shed light on the possible functions of S-DNA.
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Affiliation(s)
- Xiao-Cong Zhao
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Hang Fu
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Lun Song
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Ya-Jun Yang
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Er-Chi Zhou
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Guang-Xue Liu
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Xue-Feng Chen
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
| | - Zhuo Li
- Third Institute of Oceanography , State Oceanic Administration , Xiamen 361005 , China
| | - Wen-Qiang Wu
- Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology , Henan University , Kaifeng 475001 , China
| | - Xing-Hua Zhang
- College of Life Sciences, The Institute for Advanced Studies, State Key Laboratory of Virology, Hubei Key Laboratory of Cell Homeostasis , Wuhan University , Wuhan 430072 , China
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5
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Yu M, Le S, Efremov AK, Zeng X, Bershadsky A, Yan J. Effects of Mechanical Stimuli on Profilin- and Formin-Mediated Actin Polymerization. NANO LETTERS 2018; 18:5239-5247. [PMID: 29976069 DOI: 10.1021/acs.nanolett.8b02211] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Self-assembling actin filaments not only form the basis of the cytoskeleton network in cells but also are utilized as nanosized building blocks to make novel active matter in which the dynamic polymerization and depolymerization of actin filaments play a key role. Formins belong to a main family of actin nucleation factors that bind to the barbed end of actin filaments and regulate actin polymerization through an interaction with profilin. Due to actomyosin contractility and relative rotation between formin and actin filaments, formin-dependent actin polymerization is subject to force and rotation constraints. However, it remains unclear how force and rotation constraints affect formin-dependent actin polymerization in the presence of profilin. Here, we show that for rotation-unconstrained actin filaments, elongation is accelerated by both force and profilin. The combined effect leads to surprisingly fast actin elongation that can approach the diffusion-limited rate at forces of a few piconewtons. The elongation of rotation-constrained filaments is also accelerated by profilin but is insensitive to applied force. We show that FH2, the main actin binding domain, plays the primary mechanosensing role. Together, the findings not only significantly advance our understanding of the mechanochemical regulation of formin-mediated actin polymerization in cells but also can potentially be utilized to make novel actin-based active matter.
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Affiliation(s)
- Miao Yu
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
| | - Shimin Le
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
| | - Artem K Efremov
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Centre for Bioimaging Sciences , National University of Singapore , Singapore 117546
| | - Xiangjun Zeng
- Department of Physics , National University of Singapore , Singapore 117542
| | - Alexander Bershadsky
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Molecular Cell Biology , Weizmann Institute of Science , Rehovot 76100 , Israel
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore , Singapore 117411
- Department of Physics , National University of Singapore , Singapore 117542
- Centre for Bioimaging Sciences , National University of Singapore , Singapore 117546
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6
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Chen J, Tang Q, Guo S, Lu C, Le S, Yan J. Parallel triplex structure formed between stretched single-stranded DNA and homologous duplex DNA. Nucleic Acids Res 2017; 45:10032-10041. [PMID: 28973442 PMCID: PMC5622322 DOI: 10.1093/nar/gkx628] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/11/2017] [Indexed: 02/01/2023] Open
Abstract
The interaction between the single-stranded DNA and the homologous duplex DNA is essential for DNA homologous repair. Here, we report that parallel triplex structure can form spontaneously between a mechanically extended ssDNA and a homologous dsDNA in protein-free condition. The triplex has a contour length close to that of a B-form DNA duplex and remains stable after force is released. The binding energy between the ssDNA and the homologous dsDNA in the triplex is estimated to be comparable to the basepairing energy in a B-form dsDNA. As ssDNA is in a similar extended conformation within recombinase-coated nucleoprotein filaments, we propose that the parallel triplex may form and serve as an intermediate during recombinase-catalyzed homologous joint formation.
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Affiliation(s)
- Jin Chen
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Qingnan Tang
- Department of Physics, National University of Singapore, 117542, Singapore
| | - Shiwen Guo
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Chen Lu
- Mechanobiology Institute, National University of Singapore, 117411, Singapore.,Centre for Bioimaging Sciences, National University of Singapore, 117546, Singapore
| | - Shimin Le
- Mechanobiology Institute, National University of Singapore, 117411, Singapore.,Department of Physics, National University of Singapore, 117542, Singapore
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, 117411, Singapore.,Department of Physics, National University of Singapore, 117542, Singapore.,Centre for Bioimaging Sciences, National University of Singapore, 117546, Singapore
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7
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From bead to rod: Comparison of theories by measuring translational drag coefficients of micron-sized magnetic bead-chains in Stokes flow. PLoS One 2017; 12:e0188015. [PMID: 29145447 PMCID: PMC5690466 DOI: 10.1371/journal.pone.0188015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Accepted: 10/29/2017] [Indexed: 11/19/2022] Open
Abstract
Frictional drag force on an object in Stokes flow follows a linear relationship with the velocity of translation and a translational drag coefficient. This drag coefficient is related to the size, shape, and orientation of the object. For rod-like objects, analytical solutions of the drag coefficients have been proposed based on three rough approximations of the rod geometry, namely the bead model, ellipsoid model, and cylinder model. These theories all agree that translational drag coefficients of rod-like objects are functions of the rod length and aspect ratio, but differ among one another on the correction factor terms in the equations. By tracking the displacement of the particles through stationary fluids of calibrated viscosity in magnetic tweezers setup, we experimentally measured the drag coefficients of micron-sized beads and their bead-chain formations with chain length of 2 to 27. We verified our methodology with analytical solutions of dimers of two touching beads, and compared our measured drag coefficient values of rod-like objects with theoretical calculations. Our comparison reveals several analytical solutions that used more appropriate approximation and derived formulae that agree with our measurement better.
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8
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Yakimov A, Pobegalov G, Bakhlanova I, Khodorkovskii M, Petukhov M, Baitin D. Blocking the RecA activity and SOS-response in bacteria with a short α-helical peptide. Nucleic Acids Res 2017; 45:9788-9796. [PMID: 28934502 PMCID: PMC5766188 DOI: 10.1093/nar/gkx687] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 07/24/2017] [Indexed: 01/19/2023] Open
Abstract
The RecX protein, a very active natural RecA protein inhibitor, can completely disassemble RecA filaments at nanomolar concentrations that are two to three orders of magnitude lower than that of RecA protein. Based on the structure of RecX protein complex with the presynaptic RecA filament, we designed a short first in class α-helical peptide that both inhibits RecA protein activities in vitro and blocks the bacterial SOS-response in vivo. The peptide was designed using SEQOPT, a novel method for global sequence optimization of protein α-helices. SEQOPT produces artificial peptide sequences containing only 20 natural amino acids with the maximum possible conformational stability at a given pH, ionic strength, temperature, peptide solubility. It also accounts for restrictions due to known amino acid residues involved in stabilization of protein complexes under consideration. The results indicate that a few key intermolecular interactions inside the RecA protein presynaptic complex are enough to reproduce the main features of the RecX protein mechanism of action. Since the SOS-response provides a major mechanism of bacterial adaptation to antibiotics, these results open new ways for the development of antibiotic co-therapy that would not cause bacterial resistance.
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Affiliation(s)
- Alexander Yakimov
- Department of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute (B.P.Konstantinov of National Research Centre 'Kurchatov Institute'), Gatchina 188300, Russia.,Peter the Great St Petersburg Polytechnic University, St Petersburg 195251, Russia
| | - Georgii Pobegalov
- Peter the Great St Petersburg Polytechnic University, St Petersburg 195251, Russia
| | - Irina Bakhlanova
- Department of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute (B.P.Konstantinov of National Research Centre 'Kurchatov Institute'), Gatchina 188300, Russia.,Peter the Great St Petersburg Polytechnic University, St Petersburg 195251, Russia
| | | | - Michael Petukhov
- Department of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute (B.P.Konstantinov of National Research Centre 'Kurchatov Institute'), Gatchina 188300, Russia.,Peter the Great St Petersburg Polytechnic University, St Petersburg 195251, Russia
| | - Dmitry Baitin
- Department of Molecular and Radiation Biophysics, Petersburg Nuclear Physics Institute (B.P.Konstantinov of National Research Centre 'Kurchatov Institute'), Gatchina 188300, Russia.,Peter the Great St Petersburg Polytechnic University, St Petersburg 195251, Russia
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9
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Kochugaeva MP, Shvets AA, Kolomeisky AB. On the Mechanism of Homology Search by RecA Protein Filaments. Biophys J 2017; 112:859-867. [PMID: 28297645 DOI: 10.1016/j.bpj.2017.01.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 01/20/2017] [Accepted: 01/24/2017] [Indexed: 10/20/2022] Open
Abstract
Genetic stability is a key factor in maintaining, survival, and reproduction of biological cells. It relies on many processes, but one of the most important is a homologous recombination, in which the repair of breaks in double-stranded DNA molecules is taking place with a help of several specific proteins. In bacteria, this task is accomplished by RecA proteins that are active as nucleoprotein filaments formed on single-stranded segments of DNA. A critical step in the homologous recombination is a search for a corresponding homologous region on DNA, which is called a homology search. Recent single-molecule experiments clarified some aspects of this process, but its molecular mechanisms remain not well understood. We developed a quantitative theoretical approach to analyze the homology search. It is based on a discrete-state stochastic model that takes into account the most relevant physical-chemical processes in the system. Using a method of first-passage processes, a full dynamic description of the homology search is presented. It is found that the search dynamics depends on the degree of extension of DNA molecules and on the size of RecA nucleoprotein filaments, in agreement with experimental single-molecule measurements of DNA pairing by RecA proteins. Our theoretical calculations, supported by extensive Monte Carlo computer simulations, provide a molecular description of the mechanisms of the homology search.
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Affiliation(s)
- Maria P Kochugaeva
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas
| | - Alexey A Shvets
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas
| | - Anatoly B Kolomeisky
- Department of Chemistry, Rice University, Houston, Texas; Center for Theoretical Biological Physics, Rice University, Houston, Texas.
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10
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Theoretical Methods for Studying DNA Structural Transitions under Applied Mechanical Constraints. Polymers (Basel) 2017; 9:polym9020074. [PMID: 30970752 PMCID: PMC6432069 DOI: 10.3390/polym9020074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 02/14/2017] [Indexed: 11/24/2022] Open
Abstract
Recent progress in single-molecule manipulation technologies has made it possible to exert force and torque on individual DNA biopolymers to probe their mechanical stability and interaction with various DNA-binding proteins. It was revealed in these experiments that the DNA structure and formation of nucleoprotein complexes by DNA-architectural proteins can be strongly modulated by an intricate interplay between the entropic elasticity of DNA and its global topology, which is closely related to the mechanical constraints applied to the DNA. Detailed understanding of the physical processes underlying the DNA behavior observed in single-molecule experiments requires the development of a general theoretical framework, which turned out to be a rather challenging task. Here, we review recent advances in theoretical methods that can be used to interpret single-molecule manipulation experiments on DNA.
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11
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Pobegalov G, Cherevatenko G, Alekseev A, Sabantsev A, Kovaleva O, Vedyaykin A, Morozova N, Baitin D, Khodorkovskii M. Deinococcus radiodurans RecA nucleoprotein filaments characterized at the single-molecule level with optical tweezers. Biochem Biophys Res Commun 2015; 466:426-30. [DOI: 10.1016/j.bbrc.2015.09.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 09/08/2015] [Indexed: 01/08/2023]
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12
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Le S, Yao M, Chen J, Efremov AK, Azimi S, Yan J. Disturbance-free rapid solution exchange for magnetic tweezers single-molecule studies. Nucleic Acids Res 2015; 43:e113. [PMID: 26007651 PMCID: PMC4787821 DOI: 10.1093/nar/gkv554] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 05/15/2015] [Indexed: 11/16/2022] Open
Abstract
Single-molecule manipulation technologies have been extensively applied to studies of the structures and interactions of DNA and proteins. An important aspect of such studies is to obtain the dynamics of interactions; however the initial binding is often difficult to obtain due to large mechanical perturbation during solution introduction. Here, we report a simple disturbance-free rapid solution exchange method for magnetic tweezers single-molecule manipulation experiments, which is achieved by tethering the molecules inside microwells (typical dimensions–diameter (D): 40–50 μm, height (H): 100 μm; H:D∼2:1). Our simulations and experiments show that the flow speed can be reduced by several orders of magnitude near the bottom of the microwells from that in the flow chamber, effectively eliminating the flow disturbance to molecules tethered in the microwells. We demonstrate a wide scope of applications of this method by measuring the force dependent DNA structural transitions in response to solution condition change, and polymerization dynamics of RecA on ssDNA/SSB-coated ssDNA/dsDNA of various tether lengths under constant forces, as well as the dynamics of vinculin binding to α-catenin at a constant force (< 5 pN) applied to the α-catenin protein.
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Affiliation(s)
- Shimin Le
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Mingxi Yao
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Jin Chen
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Artem K Efremov
- Mechanobiology Institute, National University of Singapore, 117411, Singapore
| | - Sara Azimi
- Department of Physics, National University of Singapore, 117542, Singapore
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, 117411, Singapore Department of Physics, National University of Singapore, 117542, Singapore Centre for Bioimaging Sciences, National University of Singapore, 117557, Singapore
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13
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Kim SH, Park J, Joo C, Kim D, Ha T. Dynamic growth and shrinkage govern the pH dependence of RecA filament stability. PLoS One 2015; 10:e0115611. [PMID: 25608006 PMCID: PMC4301630 DOI: 10.1371/journal.pone.0115611] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 11/30/2014] [Indexed: 11/19/2022] Open
Abstract
RecA proteins form a long stable filament on a single-stranded DNA and catalyze strand exchange reaction. The stability of RecA filament changes dramatically with pH, yet its detailed mechanism is not known. Here, using a single molecule assay, we determined the binding and dissociation rates of RecA monomers at the filament ends at various pH. The pH-induced rate changes were moderate but occurred in opposite directions for binding and dissociation, resulting in a substantial increase in filament stability in lower pH. The highly charged residues in C-terminal domain do not contribute to the pH dependent stability. The stability enhancement of RecA filament in low pH may help the cell to cope with acidic stress by fine-tuning of the binding and dissociation rates without losing the highly dynamic nature of the filament required for strand exchange.
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Affiliation(s)
- Sung Hyun Kim
- Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul, Korea
| | - Jeehae Park
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Chirlmin Joo
- Kavli Institute of NanoScience, Department of BioNanoScience, Delft University of Technology, Delft, The Netherlands
| | - Doseok Kim
- Department of Physics and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul, Korea
- * E-mail: (TH); (DK)
| | - Taekjip Ha
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Howard Hughes Medical Institute, Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail: (TH); (DK)
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14
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15
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Le S, Chen H, Zhang X, Chen J, Patil KN, Muniyappa K, Yan J. Mechanical force antagonizes the inhibitory effects of RecX on RecA filament formation in Mycobacterium tuberculosis. Nucleic Acids Res 2014; 42:11992-9. [PMID: 25294832 PMCID: PMC4231760 DOI: 10.1093/nar/gku899] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 09/08/2014] [Accepted: 09/17/2014] [Indexed: 11/13/2022] Open
Abstract
Efficient bacterial recombinational DNA repair involves rapid cycles of RecA filament assembly and disassembly. The RecX protein plays a crucial inhibitory role in RecA filament formation and stability. As the broken ends of DNA are tethered during homologous search, RecA filaments assembled at the ends are likely subject to force. In this work, we investigated the interplay between RecX and force on RecA filament formation and stability. Using magnetic tweezers, at single molecular level, we found that Mycobacterium tuberculosis (Mt) RecX could catalyze stepwise de-polymerization of preformed MtRecA filament in the presence of ATP hydrolysis at low forces (<7 pN). However, applying larger forces antagonized the inhibitory effects of MtRecX, and a partially de-polymerized MtRecA filament could re-polymerize in the presence of MtRecX, which cannot be explained by previous models. Theoretical analysis of force-dependent conformational free energies of naked ssDNA and RecA nucleoprotein filament suggests that mechanical force stabilizes RecA filament, which provides a possible mechanism for the observation. As the antagonizing effect of force on the inhibitory function of RecX takes place in a physiological range; these findings broadly suggest a potential mechanosensitive regulation during homologous recombination.
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Affiliation(s)
- Shimin Le
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Hu Chen
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, Xiamen University, Xiamen 361005, China
| | - Xinghua Zhang
- BioSystems and Micromechanics (BioSyM) IRG, Singapore-MIT Alliance for Research and Technology, National University of Singapore, Singapore 138602, Singapore
| | - Jin Chen
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | | | - Kalappa Muniyappa
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore Centre for Bioimaging Sciences, National University of Singapore, Singapore 117557, Singapore
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Loh IY, Cheng J, Tee SR, Efremov A, Wang Z. From bistate molecular switches to self-directed track-walking nanomotors. ACS NANO 2014; 8:10293-10304. [PMID: 25268955 DOI: 10.1021/nn5034983] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Track-walking nanomotors and larger systems integrating these motors are important for wide real-world applications of nanotechnology. However, inventing these nanomotors remains difficult, a sharp contrast to the widespread success of simpler switch-like nanodevices, even though the latter already encompasses basic elements of the former such as engine-like bistate contraction/extension or leg-like controllable binding. This conspicuous gap reflects an impeding bottleneck for the nanomotor development, namely, lack of a modularized construction by which spatially and functionally separable "engines" and "legs" are flexibly assembled into a self-directed motor. Indeed, all track-walking nanomotors reported to date combine the engine and leg functions in the same molecular part, which largely underpins the device-motor gap. Here we propose a general design principle allowing the modularized nanomotor construction from disentangled engine-like and leg-like motifs, and provide an experimental proof of concept by implementing a bipedal DNA nanomotor up to a best working regime of this versatile design principle. The motor uses a light-powered contraction-extension switch to drive a coordinated hand-over-hand directional walking on a DNA track. Systematic fluorescence experiments confirm the motor's directional motion and suggest that the motor possesses two directional biases, one for rear leg dissociation and one for forward leg binding. This study opens a viable route to develop track-walking nanomotors from numerous molecular switches and binding motifs available from nanodevice research and biology.
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Affiliation(s)
- Iong Ying Loh
- Department of Physics, ‡NUS Graduate School for Integrative Sciences and Engineering, §Center for Computational Science and Engineering, National University of Singapore , Singapore 117542
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Mechanosensing of DNA bending in a single specific protein-DNA complex. Sci Rep 2013; 3:3508. [PMID: 24336435 PMCID: PMC3863814 DOI: 10.1038/srep03508] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 11/29/2013] [Indexed: 01/10/2023] Open
Abstract
Many crucial biological processes are regulated by mechanical stimuli. Here, we report new findings that pico-Newton forces can drastically affect the stability of the site-specific DNA binding of a single transcription factor, the E. coli integration host factor (IHF), by stretching a short ~150 nm DNA containing a single IHF binding site. Dynamic binding and unbinding of single IHF were recorded and analyzed for the force-dependent stability of the IHF-DNA complex. Our results demonstrate that the IHF-DNA interaction is fine tuned by force in different salt concentration and temperature over physiological ranges, indicating that, besides other physiological factors, force may play equally important role in transcription regulation. These findings have broad implications with regard to general mechanosensitivity of site-specific DNA bending proteins.
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