1
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Joyeux M. Tethered Particle Motion Technique in Crowded Media: Compaction of DNA by Globular Macromolecules. J Phys Chem B 2024; 128:7227-7236. [PMID: 38986040 DOI: 10.1021/acs.jpcb.4c03033] [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: 07/12/2024]
Abstract
Tethered Particle Motion (TPM) is a single molecule technique, which consists in tracking the motion of a nanoparticle (NP) immersed in a fluid and tethered to a glass surface by a DNA molecule. The present work addresses the question of the applicability of TPM to fluids which contain crowders at volume fractions ranging from that of the nucleoid of living bacteria (around 30%) up to the jamming threshold (around 66%). In particular, we were interested in determining whether TPM can be used to characterize the compaction of DNA by globular crowders. To this end, extensive Brownian Dynamics simulations were performed with a specifically built coarse-grained model. Analysis of the simulations reveals several effects not observed in dilute media, which impose constraints on the TPM setup. In particular, the Tethered Fluorophore Motion (TFM) technique, which consists in replacing the NP by a much smaller fluorophore, is probably better suited than standard TPM. Moreover, a sample preparation technique which does not involve hydrophilic patches may be required. Finally, the use of a DNA brush may be needed to achieve DNA concentrations close to in vivo ones.
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Affiliation(s)
- Marc Joyeux
- Laboratoire Interdisciplinaire de Physique, CNRS and Université Grenoble Alpes, 38400 St Martin d'Hères, France
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2
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Qian J, Collette D, Finzi L, Dunlap D. Detecting DNA Loops Using Tethered Particle Motion. Methods Mol Biol 2024; 2694:451-466. [PMID: 37824017 PMCID: PMC10906717 DOI: 10.1007/978-1-0716-3377-9_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
The range of motion of a micron-sized bead tethered by a single polymer provides a dynamic readout of the effective length of the polymer. The excursions of the bead may reflect the intrinsic flexibility and/or topology of the polymer as well as changes due to the action activity of ligands that bind the polymer. This is a simple yet powerful experimental approach to investigate such interactions between DNA and proteins as demonstrated by experiments with the lac repressor. This protein forms a stable, tetrameric oligomer with two binding sites and can produce a loop of DNA between recognition sites separated along the length of a DNA molecule.
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Affiliation(s)
- Jin Qian
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Dylan Collette
- Department of Physics, Emory University, Atlanta, GA, USA
| | - Laura Finzi
- Department of Physics, Emory University, Atlanta, GA, USA
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, GA, USA.
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3
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van der Valk RA, Zarguit I, Laurens N, Dame RT. Tethered Particle Motion Analysis of DNA-Binding Properties of Architectural Proteins. Methods Mol Biol 2024; 2819:477-496. [PMID: 39028520 DOI: 10.1007/978-1-0716-3930-6_22] [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: 07/20/2024]
Abstract
Architectural DNA-binding proteins are key to the organization and compaction of genomic DNA inside cells. Tethered particle motion (TPM) permits analysis of DNA conformation and detection of changes in conformation induced by such proteins at the single molecule level in vitro. As many individual protein-DNA complexes can be investigated in parallel, these experiments have high throughput. TPM is therefore well suited for characterization of the effects of protein-DNA stoichiometry and changes in physicochemical conditions (pH, osmolarity, and temperature). Here, we describe in detail how to perform tethered particle motion experiments on complexes between DNA and architectural proteins to determine their structural and biochemical characteristics.
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Affiliation(s)
| | - Ilias Zarguit
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
| | - Niels Laurens
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
- Faculty Governance and Global Affairs, Leiden University, Leiden, The Netherlands
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
- Centre for Interdisciplinary Genome Research, Leiden University, Leiden, The Netherlands.
- Centre for Microbial Cell Biology, Leiden University, Leiden, The Netherlands.
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4
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Fan H. Single‐molecule tethered particle motion to study
protein‐DNA
interaction. J CHIN CHEM SOC-TAIP 2023. [DOI: 10.1002/jccs.202300051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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5
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Mohapatra S, Lin CT, Feng XA, Basu A, Ha T. Single-Molecule Analysis and Engineering of DNA Motors. Chem Rev 2019; 120:36-78. [DOI: 10.1021/acs.chemrev.9b00361] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | | | - Taekjip Ha
- Howard Hughes Medical Institute, Baltimore, Maryland 21205, United States
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6
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Statistical physics and mesoscopic modeling to interpret tethered particle motion experiments. Methods 2019; 169:57-68. [PMID: 31302177 DOI: 10.1016/j.ymeth.2019.07.006] [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] [Received: 03/01/2019] [Revised: 06/11/2019] [Accepted: 07/07/2019] [Indexed: 11/22/2022] Open
Abstract
Tethered particle motion experiments are versatile single-molecule techniques enabling one to address in vitro the molecular properties of DNA and its interactions with various partners involved in genetic regulations. These techniques provide raw data such as the tracked particle amplitude of movement, from which relevant information about DNA conformations or states must be recovered. Solving this inverse problem appeals to specific theoretical tools that have been designed in the two last decades, together with the data pre-processing procedures that ought to be implemented to avoid biases inherent to these experimental techniques. These statistical tools and models are reviewed in this paper.
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7
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Parallelized DNA tethered bead measurements to scrutinize DNA mechanical structure. Methods 2019; 169:46-56. [PMID: 31351926 DOI: 10.1016/j.ymeth.2019.07.020] [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] [Received: 02/07/2019] [Revised: 07/01/2019] [Accepted: 07/22/2019] [Indexed: 01/05/2023] Open
Abstract
Tethering beads to DNA offers a panel of single molecule techniques for the refined analysis of the conformational dynamics of DNA and the elucidation of the mechanisms of enzyme activity. Recent developments include the massive parallelization of these techniques achieved by the fabrication of dedicated nanoarrays by soft nanolithography. We focus here on two of these techniques: the Tethered Particle motion and Magnetic Tweezers allowing analysis of the behavior of individual DNA molecules in the absence of force and under the application of a force and/or a torque, respectively. We introduce the experimental protocols for the parallelization and discuss the benefits already gained, and to come, for these single molecule investigations.
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8
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Tethered multifluorophore motion reveals equilibrium transition kinetics of single DNA double helices. Proc Natl Acad Sci U S A 2018; 115:E7512-E7521. [PMID: 30037988 PMCID: PMC6094131 DOI: 10.1073/pnas.1800585115] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Understanding cellular functions and dysfunctions often begins with quantifying the interactions between the binding partners involved in the processes. Learning about the kinetics of the interactions is of particular importance to understand the dynamics of cellular processes. We created a tethered multifluorophore motion assay using DNA origami that enables over 1-hour-long recordings of the statistical binding and unbinding of single pairs of biomolecules directly in equilibrium. The experimental concept is simple and the data interpretation is very direct, which makes the system easy to use for a wide variety of researchers. Due to the modularity and addressability of the DNA origami-based assay, our system may be readily adapted to study various other molecular interactions. We describe a tethered multifluorophore motion assay based on DNA origami for revealing bimolecular reaction kinetics on the single-molecule level. Molecular binding partners may be placed at user-defined positions and in user-defined stoichiometry; and binding states are read out by tracking the motion of quickly diffusing fluorescent reporter units. Multiple dyes per reporter unit enable singe-particle observation for more than 1 hour. We applied the system to study in equilibrium reversible hybridization and dissociation of complementary DNA single strands as a function of tether length, cation concentration, and sequence. We observed up to hundreds of hybridization and dissociation events per single reactant pair and could produce cumulative statistics with tens of thousands of binding and unbinding events. Because the binding partners per particle do not exchange, we could also detect subtle heterogeneity from molecule to molecule, which enabled separating data reflecting the actual target strand pair binding kinetics from falsifying influences stemming from chemically truncated oligonucleotides. Our data reflected that mainly DNA strand hybridization, but not strand dissociation, is affected by cation concentration, in agreement with previous results from different assays. We studied 8-bp-long DNA duplexes with virtually identical thermodynamic stability, but different sequences, and observed strongly differing hybridization kinetics. Complementary full-atom molecular-dynamics simulations indicated two opposing sequence-dependent phenomena: helical templating in purine-rich single strands and secondary structures. These two effects can increase or decrease, respectively, the fraction of strand collisions leading to successful nucleation events for duplex formation.
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9
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Fan HF, Ma CH, Jayaram M. Single-Molecule Tethered Particle Motion: Stepwise Analyses of Site-Specific DNA Recombination. MICROMACHINES 2018; 9:E216. [PMID: 30424148 PMCID: PMC6187709 DOI: 10.3390/mi9050216] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/25/2018] [Accepted: 04/28/2018] [Indexed: 12/17/2022]
Abstract
Tethered particle motion/microscopy (TPM) is a biophysical tool used to analyze changes in the effective length of a polymer, tethered at one end, under changing conditions. The tether length is measured indirectly by recording the Brownian motion amplitude of a bead attached to the other end. In the biological realm, DNA, whose interactions with proteins are often accompanied by apparent or real changes in length, has almost exclusively been the subject of TPM studies. TPM has been employed to study DNA bending, looping and wrapping, DNA compaction, high-order DNA⁻protein assembly, and protein translocation along DNA. Our TPM analyses have focused on tyrosine and serine site-specific recombinases. Their pre-chemical interactions with DNA cause reversible changes in DNA length, detectable by TPM. The chemical steps of recombination, depending on the substrate and the type of recombinase, may result in a permanent length change. Single molecule TPM time traces provide thermodynamic and kinetic information on each step of the recombination pathway. They reveal how mechanistically related recombinases may differ in their early commitment to recombination, reversibility of individual steps, and in the rate-limiting step of the reaction. They shed light on the pre-chemical roles of catalytic residues, and on the mechanisms by which accessory proteins regulate recombination directionality.
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Affiliation(s)
- Hsiu-Fang Fan
- Biophotonics and Molecular Imaging Center, Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan.
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan.
| | - Chien-Hui Ma
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
| | - Makkuni Jayaram
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA.
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10
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Kovari DT, Yan Y, Finzi L, Dunlap D. Tethered Particle Motion: An Easy Technique for Probing DNA Topology and Interactions with Transcription Factors. Methods Mol Biol 2018; 1665:317-340. [PMID: 28940077 DOI: 10.1007/978-1-4939-7271-5_17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Tethered Particle Motion (TPM) is a versatile in vitro technique for monitoring the conformations a linear macromolecule, such as DNA, can exhibit. The technique involves monitoring the diffusive motion of a particle anchored to a fixed point via the macromolecule of interest, which acts as a tether. In this chapter, we provide an overview of TPM, review the fundamental principles that determine the accuracy with which effective tether lengths can be used to distinguish different tether conformations, present software tools that assist in capturing and analyzing TPM data, and provide a protocol which uses TPM to characterize lac repressor-induced DNA looping. Critical to any TPM assay is the understanding of the timescale over which the diffusive motion of the particle must be observed to accurately distinguish tether conformations. Approximating the tether as a Hookean spring, we show how to estimate the diffusion timescale and discuss how it relates to the confidence with which tether conformations can be distinguished. Applying those estimates to a lac repressor titration assay, we describe how to perform a TPM experiment. We also provide graphically driven software which can be used to speed up data collection and analysis. Lastly, we detail how TPM data from the titration assay can be used to calculate relevant molecular descriptors such as the J factor for DNA looping and lac repressor-operator dissociation constants. While the included protocol is geared toward studying DNA looping, the technique, fundamental principles, and analytical methods are more general and can be adapted to a wide variety of molecular systems.
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Affiliation(s)
- Daniel T Kovari
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - Yan Yan
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - Laura Finzi
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA
| | - David Dunlap
- Department of Physics, Emory University, 400 Dowman Dr, Atlanta, GA, 30322, USA.
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11
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Tutkus M, Sasnauskas G, Rutkauskas D. Probing the dynamics of restriction endonuclease NgoMIV-DNA interaction by single-molecule FRET. Biopolymers 2017; 107. [DOI: 10.1002/bip.23075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 09/22/2017] [Accepted: 10/04/2017] [Indexed: 11/09/2022]
Affiliation(s)
- Marijonas Tutkus
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu 231; Vilnius 02300 Lithuania
| | - Giedrius Sasnauskas
- Institute of Biotechnology, Vilnius University, Sauletekio av. 7; Vilnius 10257 Lithuania
| | - Danielis Rutkauskas
- Institute of Physics, Center for Physical Sciences and Technology, Savanoriu 231; Vilnius 02300 Lithuania
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12
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Kamagata K, Murata A, Itoh Y, Takahashi S. Characterization of facilitated diffusion of tumor suppressor p53 along DNA using single-molecule fluorescence imaging. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY C-PHOTOCHEMISTRY REVIEWS 2017. [DOI: 10.1016/j.jphotochemrev.2017.01.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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13
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Tethered Particle Motion Analysis of the DNA Binding Properties of Architectural Proteins. Methods Mol Biol 2017; 1624:127-143. [PMID: 28842881 DOI: 10.1007/978-1-4939-7098-8_11] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Architectural DNA binding proteins are key to the organization and compaction of genomic DNA inside cells. Tethered Particle Motion (TPM) permits analysis of DNA conformation and detection of changes in conformation induced by such proteins at the single molecule level in vitro. As many individual protein-DNA complexes can be investigated in parallel, these experiments have high throughput. TPM is therefore well suited for characterization of the effects of protein-DNA stoichiometry and changes in physicochemical conditions (pH, osmolarity, and temperature). Here, we describe in detail how to perform Tethered Particle Motion experiments on complexes between DNA and architectural proteins to determine their structural and biochemical characteristics.
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14
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Sitters G, Laurens N, de Rijk EJ, Kress H, Peterman EJG, Wuite GJL. Optical Pushing: A Tool for Parallelized Biomolecule Manipulation. Biophys J 2016; 110:44-50. [PMID: 26745408 DOI: 10.1016/j.bpj.2015.11.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 10/25/2015] [Accepted: 11/17/2015] [Indexed: 01/05/2023] Open
Abstract
The ability to measure and manipulate single molecules has greatly advanced the field of biophysics. Yet, the addition of more single-molecule tools that enable one to measure in a parallel fashion is important to diversify the questions that can be addressed. Here we present optical pushing (OP), a single-molecule technique that is used to exert forces on many individual biomolecules tethered to microspheres using a single collimated laser beam. Forces ranging from a few femtoNewtons to several picoNewtons can be applied with a submillisecond response time. To determine forces exerted on the tethered particles by the laser, we analyzed their measured Brownian motion using, to our knowledge, a newly derived analytical model and numerical simulations. In the model, Brownian rotation of the microspheres is taken into account, which proved to be a critical component to correctly determine the applied forces. We used our OP technique to map the energy landscape of the protein-induced looping dynamics of DNA. OP can be used to apply loading rates in the range of 10(-4)-10(6) pN/s to many molecules at the same time, which makes it a tool suitable for dynamic force spectroscopy.
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Affiliation(s)
- Gerrit Sitters
- Department of Physics and Astronomy and LaserLaB, VU University Amsterdam, Amsterdam, The Netherlands
| | - Niels Laurens
- Department of Physics and Astronomy and LaserLaB, VU University Amsterdam, Amsterdam, The Netherlands
| | - Emilie J de Rijk
- Department of Physics and Astronomy and LaserLaB, VU University Amsterdam, Amsterdam, The Netherlands
| | - Holger Kress
- Experimental Physics I, University of Bayreuth, Bayreuth, Germany; Department of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands
| | - Erwin J G Peterman
- Department of Physics and Astronomy and LaserLaB, VU University Amsterdam, Amsterdam, The Netherlands
| | - Gijs J L Wuite
- Department of Physics and Astronomy and LaserLaB, VU University Amsterdam, Amsterdam, The Netherlands.
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15
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Driessen RPC, Lin SN, Waterreus WJ, van der Meulen ALH, van der Valk RA, Laurens N, Moolenaar GF, Pannu NS, Wuite GJL, Goosen N, Dame RT. Diverse architectural properties of Sso10a proteins: Evidence for a role in chromatin compaction and organization. Sci Rep 2016; 6:29422. [PMID: 27403582 PMCID: PMC4941522 DOI: 10.1038/srep29422] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 06/17/2016] [Indexed: 11/19/2022] Open
Abstract
Sso10a proteins are small DNA-binding proteins expressed by the crenarchaeal model organism Sulfolobus solfataricus. Based on the structure of Sso10a1, which contains a winged helix-turn-helix motif, it is believed that Sso10a proteins function as sequence-specific transcription factors. Here we show that Sso10a1 and Sso10a2 exhibit different distinct DNA-binding modes. While the ability to bend DNA is shared between the two proteins, DNA bridging is observed only for Sso10a1 and only Sso10a2 exhibits filament formation along DNA. The architectural properties of Sso10a proteins suggest that these proteins fulfil generic roles in chromatin organization and compaction. As these proteins exhibit different binding behaviour depending on their DNA binding stoichiometry, altered levels of expression in the cell can be exploited to drive changes in local genome folding, which may operate to modulate transcription.
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Affiliation(s)
- Rosalie P C Driessen
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Szu-Ning Lin
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.,Department of Physics and Astronomy, VU University, Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Willem-Jan Waterreus
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Alson L H van der Meulen
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Ramon A van der Valk
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Niels Laurens
- Department of Physics and Astronomy, VU University, Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Geri F Moolenaar
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Navraj S Pannu
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Gijs J L Wuite
- Department of Physics and Astronomy, VU University, Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
| | - Nora Goosen
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
| | - Remus T Dame
- Leiden Institute of Chemistry, Cell Observatory and Centre for Microbial Cell Biology, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
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16
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Chintakayala K, Sellars LE, Singh SS, Shahapure R, Westerlaken I, Meyer AS, Dame RT, Grainger DC. DNA recognition by Escherichia coli CbpA protein requires a conserved arginine-minor-groove interaction. Nucleic Acids Res 2015; 43:2282-92. [PMID: 25670677 PMCID: PMC4344490 DOI: 10.1093/nar/gkv012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Curved DNA binding protein A (CbpA) is a co-chaperone and nucleoid associated DNA binding protein conserved in most γ-proteobacteria. Best studied in Escherichia coli, CbpA accumulates to >2500 copies per cell during periods of starvation and forms aggregates with DNA. However, the molecular basis for DNA binding is unknown; CbpA lacks motifs found in other bacterial DNA binding proteins. Here, we have used a combination of genetics and biochemistry to elucidate the mechanism of DNA recognition by CbpA. We show that CbpA interacts with the DNA minor groove. This interaction requires a highly conserved arginine side chain. Substitution of this residue, R116, with alanine, specifically disrupts DNA binding by CbpA, and its homologues from other bacteria, whilst not affecting other CbpA activities. The intracellular distribution of CbpA alters dramatically when DNA binding is negated. Hence, we provide a direct link between DNA binding and the behaviour of CbpA in cells.
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Affiliation(s)
- Kiran Chintakayala
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Laura E Sellars
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Shivani S Singh
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Rajesh Shahapure
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Leiden, The Netherlands
| | - Ilja Westerlaken
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Anne S Meyer
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | - Remus T Dame
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Leiden, The Netherlands
| | - David C Grainger
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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17
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18
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Driessen RPC, Sitters G, Laurens N, Moolenaar GF, Wuite GJL, Goosen N, Dame RT. Effect of temperature on the intrinsic flexibility of DNA and its interaction with architectural proteins. Biochemistry 2014; 53:6430-8. [PMID: 25291500 PMCID: PMC5451147 DOI: 10.1021/bi500344j] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
![]()
The
helical structure of double-stranded DNA is destabilized by
increasing temperature. Above a critical temperature (the melting
temperature), the two strands in duplex DNA become fully separated.
Below this temperature, the structural effects are localized. Using
tethered particle motion in a temperature-controlled sample chamber,
we systematically investigated the effect of increasing temperature
on DNA structure and the interplay between this effect and protein
binding. Our measurements revealed that (1) increasing temperature
enhances DNA flexibility, effectively leading to more compact folding
of the double-stranded DNA chain, and (2) temperature differentially
affects different types of DNA-bending chromatin proteins from mesophilic
and thermophilic organisms. Thus, our findings aid in understanding
genome organization in organisms thriving at moderate as well as extreme
temperatures. Moreover, our results underscore the importance of carefully
controlling and measuring temperature in single-molecule DNA (micromanipulation)
experiments.
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Affiliation(s)
- Rosalie P C Driessen
- Molecular Genetics, Leiden Institute of Chemistry and Cell Observatory, Leiden University , 2333 CC Leiden, The Netherlands
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19
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Kumar S, Manzo C, Zurla C, Ucuncuoglu S, Finzi L, Dunlap D. Enhanced tethered-particle motion analysis reveals viscous effects. Biophys J 2014; 106:399-409. [PMID: 24461015 DOI: 10.1016/j.bpj.2013.11.4501] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 09/16/2013] [Accepted: 11/25/2013] [Indexed: 12/29/2022] Open
Abstract
Tethered-particle motion experiments do not require expensive or technically complex hardware, and increasing numbers of researchers are adopting this methodology to investigate the topological effects of agents that act on the tethering polymer or the characteristics of the polymer itself. These investigations depend on accurate measurement and interpretation of changes in the effective length of the tethering polymer (often DNA). However, the bead size, tether length, and buffer affect the confined diffusion of the bead in this experimental system. To evaluate the effects of these factors, improved measurements to calibrate the two-dimensional range of motion (excursion) versus DNA length were carried out. Microspheres of 160 or 240 nm in radius were tethered by DNA molecules ranging from 225 to 3477 basepairs in length in aqueous buffers containing 100 mM potassium glutamate and 8 mM MgCl2 or 10 mM Tris-HCl and 200 mM KCl, with or without 0.5% Tween added to the buffer, and the motion was recorded. Different buffers altered the excursion of beads on identical DNA tethers. Buffer with only 10 mM NaCl and >5 mM magnesium greatly reduced excursion. Glycerol added to increase viscosity slowed confined diffusion of the tethered beads but did not change excursion. The confined-diffusion coefficients for all tethered beads were smaller than those expected for freely diffusing beads and decreased for shorter tethers. Tethered-particle motion is a sensitive framework for diffusion experiments in which small beads on long leashes most closely resemble freely diffusing, untethered beads.
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Affiliation(s)
- Sandip Kumar
- Department of Cell Biology, Emory University, Atlanta, Georgia
| | - Carlo Manzo
- Department of Physics, Emory University, Atlanta, Georgia
| | - Chiara Zurla
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia
| | | | - Laura Finzi
- Department of Physics, Emory University, Atlanta, Georgia
| | - David Dunlap
- Department of Cell Biology, Emory University, Atlanta, Georgia.
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20
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Johnson S, van de Meent JW, Phillips R, Wiggins CH, Lindén M. Multiple LacI-mediated loops revealed by Bayesian statistics and tethered particle motion. Nucleic Acids Res 2014; 42:10265-77. [PMID: 25120267 PMCID: PMC4176382 DOI: 10.1093/nar/gku563] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The bacterial transcription factor LacI loops DNA by binding to two separate locations on the DNA simultaneously. Despite being one of the best-studied model systems for transcriptional regulation, the number and conformations of loop structures accessible to LacI remain unclear, though the importance of multiple coexisting loops has been implicated in interactions between LacI and other cellular regulators of gene expression. To probe this issue, we have developed a new analysis method for tethered particle motion, a versatile and commonly used in vitro single-molecule technique. Our method, vbTPM, performs variational Bayesian inference in hidden Markov models. It learns the number of distinct states (i.e. DNA–protein conformations) directly from tethered particle motion data with better resolution than existing methods, while easily correcting for common experimental artifacts. Studying short (roughly 100 bp) LacI-mediated loops, we provide evidence for three distinct loop structures, more than previously reported in single-molecule studies. Moreover, our results confirm that changes in LacI conformation and DNA-binding topology both contribute to the repertoire of LacI-mediated loops formed in vitro, and provide qualitatively new input for models of looping and transcriptional regulation. We expect vbTPM to be broadly useful for probing complex protein–nucleic acid interactions.
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Affiliation(s)
- Stephanie Johnson
- Department of Biochemistry and Molecular Biophysics, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125
| | - Jan-Willem van de Meent
- Department of Statistics, Columbia University, 1255 Amsterdam Avenue MC 4690, New York, New York 10027
| | - Rob Phillips
- Departments of Applied Physics and Biology, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125
| | - Chris H Wiggins
- Department of Applied Physics and Applied Mathematics, Columbia University, 200 S.W. Mudd, 500 W. 120th St. MC 4701, New York, New York 10027
| | - Martin Lindén
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden Department of Cell and Molecular Biology, Uppsala University, Box 256, SE-751 05 Uppsala, Sweden
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21
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Rutkauskas D, Petkelyte M, Naujalis P, Sasnauskas G, Tamulaitis G, Zaremba M, Siksnys V. Restriction Enzyme Ecl18kI-Induced DNA Looping Dynamics by Single-Molecule FRET. J Phys Chem B 2014; 118:8575-82. [DOI: 10.1021/jp504546v] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Danielis Rutkauskas
- Institute
of Physics, Center for Physical Sciences and Technology, Savanoriu
231, LT-02300, Vilnius, Lithuania
| | - Milda Petkelyte
- Institute
of Physics, Center for Physical Sciences and Technology, Savanoriu
231, LT-02300, Vilnius, Lithuania
| | - Paulius Naujalis
- Institute
of Physics, Center for Physical Sciences and Technology, Savanoriu
231, LT-02300, Vilnius, Lithuania
| | - Giedrius Sasnauskas
- Institute of Biotechnology, Vilnius University, Graiciuno 8, LT-02241, Vilnius, Lithuania
| | - Gintautas Tamulaitis
- Institute of Biotechnology, Vilnius University, Graiciuno 8, LT-02241, Vilnius, Lithuania
| | - Mindaugas Zaremba
- Institute of Biotechnology, Vilnius University, Graiciuno 8, LT-02241, Vilnius, Lithuania
| | - Virginijus Siksnys
- Institute of Biotechnology, Vilnius University, Graiciuno 8, LT-02241, Vilnius, Lithuania
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22
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Diagne CT, Salhi M, Crozat E, Salomé L, Cornet F, Rousseau P, Tardin C. TPM analyses reveal that FtsK contributes both to the assembly and the activation of the XerCD-dif recombination synapse. Nucleic Acids Res 2013; 42:1721-32. [PMID: 24214995 PMCID: PMC3919580 DOI: 10.1093/nar/gkt1024] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Circular chromosomes can form dimers during replication and failure to resolve those into monomers prevents chromosome segregation, which leads to cell death. Dimer resolution is catalysed by a highly conserved site-specific recombination system, called XerCD-dif in Escherichia coli. Recombination is activated by the DNA translocase FtsK, which is associated with the division septum, and is thought to contribute to the assembly of the XerCD-dif synapse. In our study, direct observation of the assembly of the XerCD-dif synapse, which had previously eluded other methods, was made possible by the use of Tethered Particle Motion, a single molecule approach. We show that XerC, XerD and two dif sites suffice for the assembly of XerCD-dif synapses in absence of FtsK, but lead to inactive XerCD-dif synapses. We also show that the presence of the γ domain of FtsK increases the rate of synapse formation and convert them into active synapses where recombination occurs. Our results represent the first direct observation of the formation of the XerCD-dif recombination synapse and its activation by FtsK.
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Affiliation(s)
- Cheikh Tidiane Diagne
- CNRS; IPBS (Institut de Pharmacologie et de Biologie Structurale); 205 route de Narbonne BP 64182, F-31077 Toulouse, France, Université de Toulouse; UPS; IPBS; F-31077 Toulouse, France, Université de Toulouse; UPS; LMGM (Laboratoire de Microbiologie et Génétique Moléculaires); F-31062 Toulouse, France and CNRS; LMGM; F-31062 Toulouse, France
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23
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Protein sliding and DNA denaturation are essential for DNA organization by human mitochondrial transcription factor A. Nat Commun 2013; 3:1013. [PMID: 22910359 DOI: 10.1038/ncomms2001] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 07/10/2012] [Indexed: 11/08/2022] Open
Abstract
Mitochondria organize their genome in protein-DNA complexes called nucleoids. The mitochondrial transcription factor A (TFAM), a protein that regulates mitochondrial transcription, is abundant in these nucleoids. TFAM is believed to be essential for mitochondrial DNA compaction, yet the exact mechanism has not been resolved. Here we use a combination of single-molecule manipulation and fluorescence microscopy to show the nonspecific DNA-binding dynamics and compaction by TFAM. We observe that single TFAM proteins diffuse extensively over DNA (sliding) and, by collisions, form patches on DNA in a cooperative manner. Moreover, we demonstrate that TFAM induces compaction by changing the flexibility of the DNA, which can be explained by local denaturation of the DNA (melting). Both sliding of TFAM and DNA melting are also necessary characteristics for effective, specific transcription regulation by TFAM. This apparent connection between transcription and DNA organization clarifies how TFAM can accomplish two complementary roles in the mitochondrial nucleoid at the same time.
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24
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Laurens N, Rusling DA, Pernstich C, Brouwer I, Halford SE, Wuite GJL. DNA looping by FokI: the impact of twisting and bending rigidity on protein-induced looping dynamics. Nucleic Acids Res 2012; 40:4988-97. [PMID: 22373924 PMCID: PMC3367208 DOI: 10.1093/nar/gks184] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Protein-induced DNA looping is crucial for many genetic processes such as transcription, gene regulation and DNA replication. Here, we use tethered-particle motion to examine the impact of DNA bending and twisting rigidity on loop capture and release, using the restriction endonuclease FokI as a test system. To cleave DNA efficiently, FokI bridges two copies of an asymmetric sequence, invariably aligning the sites in parallel. On account of the fixed alignment, the topology of the DNA loop is set by the orientation of the sites along the DNA. We show that both the separation of the FokI sites and their orientation, altering, respectively, the twisting and the bending of the DNA needed to juxtapose the sites, have profound effects on the dynamics of the looping interaction. Surprisingly, the presence of a nick within the loop does not affect the observed rigidity of the DNA. In contrast, the introduction of a 4-nt gap fully relaxes all of the torque present in the system but does not necessarily enhance loop stability. FokI therefore employs torque to stabilise its DNA-looping interaction by acting as a ‘torsional’ catch bond.
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Affiliation(s)
- Niels Laurens
- Department of Physics and Astronomy, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
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25
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Rusling DA, Laurens N, Pernstich C, Wuite GJL, Halford SE. DNA looping by FokI: the impact of synapse geometry on loop topology at varied site orientations. Nucleic Acids Res 2012; 40:4977-87. [PMID: 22362745 PMCID: PMC3367207 DOI: 10.1093/nar/gks183] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Most restriction endonucleases, including FokI, interact with two copies of their recognition sequence before cutting DNA. On DNA with two sites they act in cis looping out the intervening DNA. While many restriction enzymes operate symmetrically at palindromic sites, FokI acts asymmetrically at a non-palindromic site. The directionality of its sequence means that two FokI sites can be bridged in either parallel or anti-parallel alignments. Here we show by biochemical and single-molecule biophysical methods that FokI aligns two recognition sites on separate DNA molecules in parallel and that the parallel arrangement holds for sites in the same DNA regardless of whether they are in inverted or repeated orientations. The parallel arrangement dictates the topology of the loop trapped between sites in cis: the loop from inverted sites has a simple 180° bend, while that with repeated sites has a convoluted 360° turn. The ability of FokI to act at asymmetric sites thus enabled us to identify the synapse geometry for sites in trans and in cis, which in turn revealed the relationship between synapse geometry and loop topology.
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Affiliation(s)
- David A Rusling
- The DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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26
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Kelly D, Dillingham M, Hudson A, Wiesner K. A new method for inferring hidden markov models from noisy time sequences. PLoS One 2012; 7:e29703. [PMID: 22247783 PMCID: PMC3256161 DOI: 10.1371/journal.pone.0029703] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 12/02/2011] [Indexed: 02/05/2023] Open
Abstract
We present a new method for inferring hidden Markov models from noisy time sequences without the necessity of assuming a model architecture, thus allowing for the detection of degenerate states. This is based on the statistical prediction techniques developed by Crutchfield et al. and generates so called causal state models, equivalent in structure to hidden Markov models. The new method is applicable to any continuous data which clusters around discrete values and exhibits multiple transitions between these values such as tethered particle motion data or Fluorescence Resonance Energy Transfer (FRET) spectra. The algorithms developed have been shown to perform well on simulated data, demonstrating the ability to recover the model used to generate the data under high noise, sparse data conditions and the ability to infer the existence of degenerate states. They have also been applied to new experimental FRET data of Holliday Junction dynamics, extracting the expected two state model and providing values for the transition rates in good agreement with previous results and with results obtained using existing maximum likelihood based methods. The method differs markedly from previous Markov-model reconstructions in being able to uncover truly hidden states.
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Affiliation(s)
- David Kelly
- School of Mathematics, University of Bristol, Bristol, United Kingdom.
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27
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Suzuki Y, Gilmore JL, Yoshimura SH, Henderson RM, Lyubchenko YL, Takeyasu K. Visual analysis of concerted cleavage by type IIF restriction enzyme SfiI in subsecond time region. Biophys J 2011; 101:2992-8. [PMID: 22208198 DOI: 10.1016/j.bpj.2011.09.064] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 09/14/2011] [Accepted: 09/30/2011] [Indexed: 10/14/2022] Open
Abstract
Many DNA regulatory factors require communication between distantly separated DNA sites for their activity. The type IIF restriction enzyme SfiI is often used as a model system of site communication. Here, we used fast-scanning atomic force microscopy to monitor the DNA cleavage process with SfiI and the changes in the single SfiI-DNA complex in the presence of either Mg²⁺ or Ca²⁺ at a scan rate of 1-2 fps. The increased time resolution allowed us to visualize the concerted cleavage of the protein at two cognate sites. The four termini generated by the cleavage were released in a multistep manner. The high temporal resolution enabled us to visualize the translocation of a DNA strand on a looped complex and intersegmental transfer of the SfiI protein in which swapping of the site is performed without protein dissociation. On the basis of our results, we propose that the SfiI tetramer can remain bound to one of the sites even after cleavage, allowing the other site on the DNA molecule to fill the empty DNA-binding cleft by combining a one-dimensional diffusion-mediated sliding and a segment transfer mechanism.
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Affiliation(s)
- Yuki Suzuki
- Laboratory of Plasma Membrane and Nuclear Signaling, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
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28
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Bond LM, Peters JP, Becker NA, Kahn JD, Maher LJ. Gene repression by minimal lac loops in vivo. Nucleic Acids Res 2010; 38:8072-82. [PMID: 21149272 PMCID: PMC3001091 DOI: 10.1093/nar/gkq755] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 08/09/2010] [Accepted: 08/09/2010] [Indexed: 01/25/2023] Open
Abstract
The inflexibility of double-stranded DNA with respect to bending and twisting is well established in vitro. Understanding apparent DNA physical properties in vivo is a greater challenge. Here, we exploit repression looping with components of the Escherichia coli lac operon to monitor DNA flexibility in living cells. We create a minimal system for testing the shortest possible DNA repression loops that contain an E. coli promoter, and compare the results to prior experiments. Our data reveal that loop-independent repression occurs for certain tight operator/promoter spacings. When only loop-dependent repression is considered, fits to a thermodynamic model show that DNA twisting limits looping in vivo, although the apparent DNA twist flexibility is 2- to 4-fold higher than in vitro. In contrast, length-dependent resistance to DNA bending is not observed in these experiments, even for the shortest loops constraining <0.4 persistence lengths of DNA. As observed previously for other looping configurations, loss of the nucleoid protein heat unstable (HU) markedly disables DNA looping in vivo. Length-independent DNA bending energy may reflect the activities of architectural proteins and the structure of the DNA topological domain. We suggest that the shortest loops are formed in apical loops rather than along the DNA plectonemic superhelix.
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Affiliation(s)
- Laura M. Bond
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Justin P. Peters
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Nicole A. Becker
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - Jason D. Kahn
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
| | - L. James Maher
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
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29
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Manghi M, Tardin C, Baglio J, Rousseau P, Salomé L, Destainville N. Probing DNA conformational changes with high temporal resolution by tethered particle motion. Phys Biol 2010; 7:046003. [PMID: 20952812 DOI: 10.1088/1478-3975/7/4/046003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The tethered particle motion (TPM) technique informs about conformational changes of DNA molecules, e.g. upon looping or interaction with proteins, by tracking the Brownian motion of a particle probe tethered to a surface by a single DNA molecule and detecting changes of its amplitude of movement. We discuss in this context the time resolution of TPM, which strongly depends on the particle-DNA complex relaxation time, i.e. the characteristic time it takes to explore its configuration space by diffusion. By comparing theory, simulations and experiments, we propose a calibration of TPM at the dynamical level: we analyze how the relaxation time grows with both DNA contour length (from 401 to 2080 base pairs) and particle radius (from 20 to 150 nm). Notably we demonstrate that, for a particle of radius 20 nm or less, the hydrodynamic friction induced by the particle and the surface does not significantly slow down the DNA. This enables us to determine the optimal time resolution of TPM in distinct experimental contexts which can be as short as 20 ms.
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Affiliation(s)
- Manoel Manghi
- Université de Toulouse, UPS, Laboratoire de Physique Théorique (IRSAMC), F-31062 Toulouse, France. CNRS, F-31062 Toulouse, France
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30
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Zaremba M, Owsicka A, Tamulaitis G, Sasnauskas G, Shlyakhtenko LS, Lushnikov AY, Lyubchenko YL, Laurens N, van den Broek B, Wuite GJL, Siksnys V. DNA synapsis through transient tetramerization triggers cleavage by Ecl18kI restriction enzyme. Nucleic Acids Res 2010; 38:7142-54. [PMID: 20571089 PMCID: PMC2978343 DOI: 10.1093/nar/gkq560] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
To cut DNA at their target sites, restriction enzymes assemble into different oligomeric structures. The Ecl18kI endonuclease in the crystal is arranged as a tetramer made of two dimers each bound to a DNA copy. However, free in solution Ecl18kI is a dimer. To find out whether the Ecl18kI dimer or tetramer represents the functionally important assembly, we generated mutants aimed at disrupting the putative dimer–dimer interface and analysed the functional properties of Ecl18kI and mutant variants. We show by atomic force microscopy that on two-site DNA, Ecl18kI loops out an intervening DNA fragment and forms a tetramer. Using the tethered particle motion technique, we demonstrate that in solution DNA looping is highly dynamic and involves a transient interaction between the two DNA-bound dimers. Furthermore, we show that Ecl18kI cleaves DNA in the synaptic complex much faster than when acting on a single recognition site. Contrary to Ecl18kI, the tetramerization interface mutant R174A binds DNA as a dimer, shows no DNA looping and is virtually inactive. We conclude that Ecl18kI follows the association model for the synaptic complex assembly in which it binds to the target site as a dimer and then associates into a transient tetrameric form to accomplish the cleavage reaction.
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Affiliation(s)
- Mindaugas Zaremba
- Institute of Biotechnology, Graiciuno 8, LT-02241, Vilnius, Lithuania
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31
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Efcavitch JW, Thompson JF. Single-molecule DNA analysis. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2010; 3:109-128. [PMID: 20636036 DOI: 10.1146/annurev.anchem.111808.073558] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The ability to detect single molecules of DNA or RNA has led to an extremely rich area of exploration of the single most important biomolecule in nature. In cases in which the nucleic acid molecules are tethered to a solid support, confined to a channel, or simply allowed to diffuse into a detection volume, novel techniques have been developed to manipulate the DNA and to examine properties such as structural dynamics and protein-DNA interactions. Beyond the analysis of the properties of nucleic acids themselves, single-molecule detection has enabled dramatic improvements in the throughput of DNA sequencing and holds promise for continuing progress. Both optical and nonoptical detection methods that use surfaces, nanopores, and zero-mode waveguides have been attempted, and one optically based instrument is already commercially available. The breadth of literature related to single-molecule DNA analysis is vast; this review focuses on a survey of efforts in molecular dynamics and nucleic acid sequencing.
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32
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Bellamy SRW, Kovacheva YS, Zulkipli IH, Halford SE. Differences between Ca2+ and Mg2+ in DNA binding and release by the SfiI restriction endonuclease: implications for DNA looping. Nucleic Acids Res 2009; 37:5443-53. [PMID: 19596810 PMCID: PMC2760798 DOI: 10.1093/nar/gkp569] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many enzymes acting on DNA require Mg(2+) ions not only for catalysis but also to bind DNA. Binding studies often employ Ca(2+) as a substitute for Mg(2+), to promote DNA binding whilst disallowing catalysis. The SfiI endonuclease requires divalent metal ions to bind DNA but, in contrast to many systems where Ca(2+) mimics Mg(2+), Ca(2+) causes SfiI to bind DNA almost irreversibly. Equilibrium binding by wild-type SfiI cannot be conducted with Mg(2+) present as the DNA is cleaved so, to study the effect of Mg(2+) on DNA binding, two catalytically-inactive mutants were constructed. The mutants bound DNA in the presence of either Ca(2+) or Mg(2+) but, unlike wild-type SfiI with Ca(2+), the binding was reversible. With both mutants, dissociation was slow with Ca(2+) but was in one case much faster with Mg(2+). Hence, Ca(2+) can affect DNA binding differently from Mg(2+). Moreover, SfiI is an archetypal system for DNA looping; on DNA with two recognition sites, it binds to both sites and loops out the intervening DNA. While the dynamics of looping cannot be measured with wild-type SfiI and Ca(2+), it becomes accessible with the mutant and Mg(2+).
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Affiliation(s)
- Stuart R W Bellamy
- The DNA-Protein Interactions Unit, Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, UK
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