1
|
Qian J, Cartee A, Xu W, Yan Y, Wang B, Artsimovitch I, Dunlap D, Finzi L. Reciprocating RNA Polymerase batters through roadblocks. Nat Commun 2024; 15:3193. [PMID: 38609371 PMCID: PMC11014978 DOI: 10.1038/s41467-024-47531-x] [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] [Received: 06/20/2023] [Accepted: 04/04/2024] [Indexed: 04/14/2024] Open
Abstract
RNA polymerases must transit through protein roadblocks to produce full-length transcripts. Here we report real-time measurements of Escherichia coli RNA polymerase passing through different barriers. As intuitively expected, assisting forces facilitated, and opposing forces hindered, RNA polymerase passage through lac repressor protein bound to natural binding sites. Force-dependent differences were significant at magnitudes as low as 0.2 pN and were abolished in the presence of the transcript cleavage factor GreA, which rescues backtracked RNA polymerase. In stark contrast, opposing forces promoted passage when the rate of RNA polymerase backtracking was comparable to, or faster than the rate of dissociation of the roadblock, particularly in the presence of GreA. Our experiments and simulations indicate that RNA polymerase may transit after roadblocks dissociate, or undergo cycles of backtracking, recovery, and ramming into roadblocks to pass through. We propose that such reciprocating motion also enables RNA polymerase to break protein-DNA contacts that hold RNA polymerase back during promoter escape and RNA chain elongation. This may facilitate productive transcription in vivo.
Collapse
Affiliation(s)
- Jin Qian
- Physics Department, Emory University, Atlanta, GA, USA
| | | | - Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA, USA
| | - Yan Yan
- Physics Department, Emory University, Atlanta, GA, USA
| | - Bing Wang
- The Center for RNA Biology and Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - Irina Artsimovitch
- The Center for RNA Biology and Department of Microbiology, The Ohio State University, Columbus, OH, USA
| | - David Dunlap
- Physics Department, Emory University, Atlanta, GA, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA, USA.
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
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]
|
4
|
Soukarié D, Rousseau P, Salhi M, de Caro A, Escudier JM, Tardin C, Ecochard V, Salomé L. Single-Molecule Sandwich Aptasensing on Nanoarrays by Tethered Particle Motion Analysis. Anal Chem 2022; 94:4319-4327. [PMID: 35226451 DOI: 10.1021/acs.analchem.1c04995] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
High-throughput single-molecule techniques are expected to challenge the demand for rapid, simple, and sensitive detection methods in health and environmental fields. Based on a single-DNA-molecule biochip for the parallelization of tethered particle motion analyses by videomicroscopy coupled to image analysis and its smart combination with aptamers, we successfully developed an aptasensor enabling the detection of single target molecules by a sandwich assay. One aptamer is grafted to the nanoparticles tethered to the surface by a long DNA molecule bearing the second aptamer in its middle. The detection and quantification of the target are direct. The recognition of the target by a pair of aptamers leads to a looped configuration of the DNA-particle complex associated with a restricted motion of the particles, which is monitored in real time. An analytical range extending over 3 orders of magnitude of target concentration with a limit of detection in the picomolar range was obtained for thrombin.
Collapse
Affiliation(s)
- Diana Soukarié
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, 31077 Toulouse, France
| | - Philippe Rousseau
- Centre de Biologie Intégrative de Toulouse, Laboratoire de Microbiologie et Génétique Moléculaires, Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Maya Salhi
- Centre de Biologie Intégrative de Toulouse, Laboratoire de Microbiologie et Génétique Moléculaires, Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Alexia de Caro
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, 31077 Toulouse, France
| | - Jean-Marc Escudier
- Laboratoire de Synthèse et Physico-Chimie de Molécules d'Intérêt Biologique, Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Catherine Tardin
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, 31077 Toulouse, France
| | - Vincent Ecochard
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, 31077 Toulouse, France
| | - Laurence Salomé
- Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, CNRS, UPS, 31077 Toulouse, France
| |
Collapse
|
5
|
Xu W, Yan Y, Artsimovitch I, Dunlap D, Finzi L. Positive supercoiling favors transcription elongation through lac repressor-mediated DNA loops. Nucleic Acids Res 2022; 50:2826-2835. [PMID: 35188572 PMCID: PMC8934669 DOI: 10.1093/nar/gkac093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 12/22/2021] [Accepted: 02/20/2022] [Indexed: 11/30/2022] Open
Abstract
Some proteins, like the lac repressor (LacI), mediate long-range loops that alter DNA topology and create torsional barriers. During transcription, RNA polymerase generates supercoiling that may facilitate passage through such barriers. We monitored E. coli RNA polymerase progress along templates in conditions that prevented, or favored, 400 bp LacI-mediated DNA looping. Tethered particle motion measurements revealed that RNA polymerase paused longer at unlooped LacI obstacles or those barring entry to a loop than those barring exit from the loop. Enhanced dissociation of a LacI roadblock by the positive supercoiling generated ahead of a transcribing RNA polymerase within a torsion-constrained DNA loop may be responsible for this reduction in pause time. In support of this idea, RNA polymerase transcribed 6-fold more slowly through looped DNA and paused at LacI obstacles for 66% less time on positively supercoiled compared to relaxed templates, especially under increased tension (torque). Positive supercoiling propagating ahead of polymerase facilitated elongation along topologically complex, protein-coated templates.
Collapse
Affiliation(s)
- Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA, USA
| | - Yan Yan
- Physics Department, Emory University, Atlanta, GA, USA
| | | | - David Dunlap
- Physics Department, Emory University, Atlanta, GA, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA, USA
| |
Collapse
|
6
|
van Dongen JE, Spoelstra LR, Berendsen JTW, Loessberg-Zahl JT, Eijkel JCT, Segerink LI. A Multiplexable Plasmonic Hairpin-DNA Sensor Based On Target-specific Tether Dynamics. ACS Sens 2021; 6:4297-4303. [PMID: 34851614 PMCID: PMC8715532 DOI: 10.1021/acssensors.1c02097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
The need for measurements
of multiple biomarkers simultaneously
at subnanomolar concentrations asks for the development of new sensors
with high sensitivity, specificity, precision, and accuracy. Currently,
multiplexed sensing in single molecule sensors increases the complexity
of the system in terms of reagents and sample read-out. In this letter,
we propose a novel approach to multiplex hairpin-based single-DNA
molecule sensors, which overcomes the limitations of the present approaches
for multiplexing. By target-dependent ssDNA hairpin design, we can
create DNA tethers that have distinct tether dynamics upon target
binding. Our numerical model shows that by changing the stem length
of the ssDNA hairpin, significantly different dynamic tether behavior
will be observed. By exploiting the distance-dependent coupling of
AuNPs to gold films, we can probe this dynamic behavior along the z-axis using a simple laser equipped microscope.
Collapse
Affiliation(s)
- Jeanne Elisabeth van Dongen
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Laurens Rudi Spoelstra
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Johanna Theodora Wilhelmina Berendsen
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Joshua Taylor Loessberg-Zahl
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Jan Cornelis Titus Eijkel
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| | - Loes Irene Segerink
- BIOS Lab on a Chip Group, MESA+ & TechMed Institutes, Max Planck Center for Complex Fluid Dynamics, University of Twente, P.O. Box 217 7500 AE Enschede, The Netherlands
| |
Collapse
|
7
|
Yan Y, Xu W, Kumar S, Zhang A, Leng F, Dunlap D, Finzi L. Negative DNA supercoiling makes protein-mediated looping deterministic and ergodic within the bacterial doubling time. Nucleic Acids Res 2021; 49:11550-11559. [PMID: 34723343 PMCID: PMC8599721 DOI: 10.1093/nar/gkab946] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 09/28/2021] [Accepted: 10/04/2021] [Indexed: 11/14/2022] Open
Abstract
Protein-mediated DNA looping is fundamental to gene regulation and such loops occur stochastically in purified systems. Additional proteins increase the probability of looping, but these probabilities maintain a broad distribution. For example, the probability of lac repressor-mediated looping in individual molecules ranged 0–100%, and individual molecules exhibited representative behavior only in observations lasting an hour or more. Titrating with HU protein progressively compacted the DNA without narrowing the 0–100% distribution. Increased negative supercoiling produced an ensemble of molecules in which all individual molecules more closely resembled the average. Furthermore, in only 12 min of observation, well within the doubling time of the bacterium, most molecules exhibited the looping probability of the ensemble. DNA supercoiling, an inherent feature of all genomes, appears to impose time-constrained, emergent behavior on otherwise random molecular activity.
Collapse
Affiliation(s)
- Yan Yan
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Wenxuan Xu
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Sandip Kumar
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Alexander Zhang
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Fenfei Leng
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - David Dunlap
- Physics Department, Emory University, Atlanta, GA 30322, USA
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA 30322, USA
| |
Collapse
|
8
|
Hirokawa S, Chure G, Belliveau NM, Lovely GA, Anaya M, Schatz DG, Baltimore D, Phillips R. Sequence-dependent dynamics of synthetic and endogenous RSSs in V(D)J recombination. Nucleic Acids Res 2020; 48:6726-6739. [PMID: 32449932 PMCID: PMC7337519 DOI: 10.1093/nar/gkaa418] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/20/2020] [Accepted: 05/07/2020] [Indexed: 12/25/2022] Open
Abstract
Developing lymphocytes of jawed vertebrates cleave and combine distinct gene segments to assemble antigen-receptor genes. This process called V(D)J recombination that involves the RAG recombinase binding and cutting recombination signal sequences (RSSs) composed of conserved heptamer and nonamer sequences flanking less well-conserved 12- or 23-bp spacers. Little quantitative information is known about the contributions of individual RSS positions over the course of the RAG-RSS interaction. We employ a single-molecule method known as tethered particle motion to track the formation, lifetime and cleavage of individual RAG-12RSS-23RSS paired complexes (PCs) for numerous synthetic and endogenous 12RSSs. We reveal that single-bp changes, including in the 12RSS spacer, can significantly and selectively alter PC formation or the probability of RAG-mediated cleavage in the PC. We find that some rarely used endogenous gene segments can be mapped directly to poor RAG binding on their adjacent 12RSSs. Finally, we find that while abrogating RSS nicking with Ca2+ leads to substantially shorter PC lifetimes, analysis of the complete lifetime distributions of any 12RSS even on this reduced system reveals that the process of exiting the PC involves unidentified molecular details whose involvement in RAG-RSS dynamics are crucial to quantitatively capture kinetics in V(D)J recombination.
Collapse
Affiliation(s)
- Soichi Hirokawa
- Department of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA
| | - Griffin Chure
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Nathan M Belliveau
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Geoffrey A Lovely
- National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Michael Anaya
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - David G Schatz
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - David Baltimore
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Rob Phillips
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA
| |
Collapse
|
9
|
Ma G, Wan Z, Zhu H, Tao N. Roles of entropic and solvent damping forces in the dynamics of polymer tethered nanoparticles and implications for single molecule sensing. Chem Sci 2019; 11:1283-1289. [PMID: 33376589 PMCID: PMC7747464 DOI: 10.1039/c9sc05434k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 12/10/2019] [Indexed: 01/19/2023] Open
Abstract
Tethering a particle to a surface with a single molecule allows detection of the molecule and analysis of molecular conformations and interactions.
Tethering a particle to a surface with a single molecule allows detection of the molecule and analysis of molecular conformations and interactions. Understanding the dynamics of the system is critical to all applications. Here we present a plasmonic imaging study of two important forces that govern the dynamics. One is entropic force arising from the conformational change of the molecular tether, and the other is solvent damping on the particle and the molecule. We measure the response of the particle by driving it into oscillation with an alternating electric field. By varying the field frequency, we study the dynamics on different time scales. We also vary the type of the tether molecule (DNA and polyethylene glycol), size of the particle, and viscosity of the solvent, and describe the observations with a model. The study allows us to derive a single parameter to predict the relative importance of the entropic and damping forces. The findings provide insights into single molecule studies using not only tethered particles, but also other approaches, including force spectroscopy using atomic force microscopy and nanopores.
Collapse
Affiliation(s)
- Guangzhong Ma
- Biodesign Center for Biosensors and Bioelectronics , Arizona State University , Tempe , Arizona 85287 , USA .
| | - Zijian Wan
- Biodesign Center for Biosensors and Bioelectronics , Arizona State University , Tempe , Arizona 85287 , USA . .,School of Electrical, Computer and Energy Engineering , Arizona State University , Tempe , Arizona 85287 , USA
| | - Hao Zhu
- State Key Laboratory of Analytical Chemistry for Life Science , School of Chemistry and Chemical Engineering , Nanjing University , Nanjing 210023 , P. R. China
| | - Nongjian Tao
- Biodesign Center for Biosensors and Bioelectronics , Arizona State University , Tempe , Arizona 85287 , USA . .,School of Electrical, Computer and Energy Engineering , Arizona State University , Tempe , Arizona 85287 , USA
| |
Collapse
|
10
|
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.
Collapse
|
11
|
Yan Y, Ding Y, Leng F, Dunlap D, Finzi L. Protein-mediated loops in supercoiled DNA create large topological domains. Nucleic Acids Res 2019. [PMID: 29538766 PMCID: PMC5961096 DOI: 10.1093/nar/gky153] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Supercoiling can alter the form and base pairing of the double helix and directly impact protein binding. More indirectly, changes in protein binding and the stress of supercoiling also influence the thermodynamic stability of regulatory, protein-mediated loops and shift the equilibria of fundamental DNA/chromatin transactions. For example, supercoiling affects the hierarchical organization and function of chromatin in topologically associating domains (TADs) in both eukaryotes and bacteria. On the other hand, a protein-mediated loop in DNA can constrain supercoiling within a plectonemic structure. To characterize the extent of constrained supercoiling, 400 bp, lac repressor-secured loops were formed in extensively over- or under-wound DNA under gentle tension in a magnetic tweezer. The protein-mediated loops constrained variable amounts of supercoiling that often exceeded the maximum writhe expected for a 400 bp plectoneme. Loops with such high levels of supercoiling appear to be entangled with flanking domains. Thus, loop-mediating proteins operating on supercoiled substrates can establish topological domains that may coordinate gene regulation and other DNA transactions across spans in the genome that are larger than the separation between the binding sites.
Collapse
Affiliation(s)
- Yan Yan
- Department of Physics, Emory University, 400 Dowman Dr., Atlanta, GA 30322, USA
| | - Yue Ding
- Department of Physics, Emory University, 400 Dowman Dr., Atlanta, GA 30322, USA
| | - Fenfei Leng
- Department of Chemistry and Biochemistry, Biomolecular Sciences Institute, Florida International University, 11200 SW 8th St., Miami, FL 33199, USA
| | - David Dunlap
- 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
| |
Collapse
|
12
|
Yan Y, Leng F, Finzi L, Dunlap D. Protein-mediated looping of DNA under tension requires supercoiling. Nucleic Acids Res 2019; 46:2370-2379. [PMID: 29365152 PMCID: PMC5861448 DOI: 10.1093/nar/gky021] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 01/12/2018] [Indexed: 02/06/2023] Open
Abstract
Protein-mediated DNA looping is ubiquitous in chromatin organization and gene regulation, but to what extent supercoiling or nucleoid associated proteins promote looping is poorly understood. Using the lac repressor (LacI), a paradigmatic loop-mediating protein, we measured LacI-induced looping as a function of either supercoiling or the concentration of the HU protein, an abundant nucleoid protein in Escherichia coli. Negative supercoiling to physiological levels with magnetic tweezers easily drove the looping probability from 0 to 100% in single DNA molecules under slight tension that likely exists in vivo. In contrast, even saturating (micromolar) concentrations of HU could not raise the looping probability above 30% in similarly stretched DNA or 80% in DNA without tension. Negative supercoiling is required to induce significant looping of DNA under any appreciable tension.
Collapse
Affiliation(s)
- Yan Yan
- Department of Physics, Emory University, 400 Dowman Dr., Atlanta, GA 30322, USA
| | - Fenfei Leng
- Department of Chemistry and Biochemistry, Biomolecular Sciences Institute, Florida International University, 11200 SW 8th St., Miami, FL 33199, 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
| |
Collapse
|
13
|
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.
Collapse
|
14
|
Limouse C, Bell JC, Fuller CJ, Straight AF, Mabuchi H. Measurement of Mesoscale Conformational Dynamics of Freely Diffusing Molecules with Tracking FCS. Biophys J 2018; 114:1539-1550. [PMID: 29642025 PMCID: PMC5954409 DOI: 10.1016/j.bpj.2018.01.044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Revised: 11/27/2017] [Accepted: 01/02/2018] [Indexed: 11/19/2022] Open
Abstract
Few techniques are suited to probe the structure and dynamics of molecular complexes at the mesoscale level (∼100-1000 nm). We have developed a single-molecule technique that uses tracking fluorescence correlation spectroscopy (tFCS) to probe the conformation and dynamics of mesoscale molecular assemblies. tFCS measures the distance fluctuations between two fluorescently labeled sites within an untethered, freely diffusing biomolecule. To achieve subdiffraction spatial resolution, we developed a feedback scheme that allows us to maintain the molecule at an optimal position within the laser intensity gradient for fluorescence correlation spectroscopy. We characterized tFCS spatial sensitivity by measuring the Brownian end-to-end dynamics of DNA molecules as short as 1000 bp. We demonstrate that tFCS detects changes in the compaction of reconstituted nucleosome arrays and can assay transient protein-mediated interactions between distant sites in an individual DNA molecule. Our measurements highlight the applicability of tFCS to a wide variety of biochemical processes involving mesoscale conformational dynamics.
Collapse
Affiliation(s)
| | - Jason C Bell
- Department of Biochemistry, Stanford University, Stanford, California
| | - Colin J Fuller
- Department of Biochemistry, Stanford University, Stanford, California
| | - Aaron F Straight
- Department of Biochemistry, Stanford University, Stanford, California.
| | | |
Collapse
|
15
|
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.
Collapse
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.
| |
Collapse
|
16
|
Merkus KE, Prins MWJ, Storm C. Single-Bond Association Kinetics Determined by Tethered Particle Motion: Concept and Simulations. Biophys J 2017; 111:1612-1620. [PMID: 27760349 DOI: 10.1016/j.bpj.2016.08.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Revised: 07/20/2016] [Accepted: 08/01/2016] [Indexed: 11/30/2022] Open
Abstract
Tethered particle motion (TPM), the motion of a micro- or nanoparticle tethered to a substrate by a macromolecule, is a system that has proven to be extremely useful for its ability to reveal physical features of the tether, because the thermal motion of the bound particle reports sensitively on parameters like the length, the rigidity, or the folding state of its tether. In this article, we survey the applicability of TPM to probe the kinetics of single secondary bonds, bonds that form and break between the tethered particle and a substrate due, for instance, to receptor/ligand pairs on particle and substrate. Much like the tether itself affects the motion pattern, so do the presence and absence of such secondary connections. Keeping the tether properties constant, we demonstrate how raw positional TPM data may be parsed to generate detailed insights into the association and dissociation kinetics of single secondary bonds. We do this using coarse-grained molecular dynamics simulations specifically developed to treat the motion of particles close to interfaces.
Collapse
Affiliation(s)
- Koen E Merkus
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands
| | - Menno W J Prins
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands; Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, the Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands.
| | - Cornelis Storm
- Department of Applied Physics, Eindhoven University of Technology, Eindhoven, the Netherlands; Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, the Netherlands
| |
Collapse
|
17
|
Vörös Z, Yan Y, Kovari DT, Finzi L, Dunlap D. Proteins mediating DNA loops effectively block transcription. Protein Sci 2017; 26:1427-1438. [PMID: 28295806 PMCID: PMC5477534 DOI: 10.1002/pro.3156] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 03/07/2017] [Accepted: 03/08/2017] [Indexed: 12/17/2022]
Abstract
Loops are ubiquitous topological elements formed when proteins simultaneously bind to two noncontiguous DNA sites. While a loop‐mediating protein may regulate initiation at a promoter, the presence of the protein at the other site may be an obstacle for RNA polymerases (RNAP) transcribing a different gene. To test whether a DNA loop alters the extent to which a protein blocks transcription, the lac repressor (LacI) was used. The outcome of in vitro transcription along templates containing two LacI operators separated by 400 bp in the presence of LacI concentrations that produced both looped and unlooped molecules was visualized with scanning force microscopy (SFM). An analysis of transcription elongation complexes, moving for 60 s at an average of 10 nt/s on unlooped DNA templates, revealed that they more often surpassed LacI bound to the lower affinity O2 operator than to the highest affinity Os operator. However, this difference was abrogated in looped DNA molecules where LacI became a strong roadblock independently of the affinity of the operator. Recordings of transcription elongation complexes, using magnetic tweezers, confirmed that they halted for several minutes upon encountering a LacI bound to a single operator. The average pause lifetime is compatible with RNAP waiting for LacI dissociation, however, the LacI open conformation visualized in the SFM images also suggests that LacI could straddle RNAP to let it pass. Independently of the mechanism by which RNAP bypasses the LacI roadblock, the data indicate that an obstacle with looped topology more effectively interferes with transcription.
Collapse
Affiliation(s)
- Zsuzsanna Vörös
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Yan Yan
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Daniel T Kovari
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - Laura Finzi
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, Georgia, 30322
| |
Collapse
|
18
|
Ucuncuoglu S, Schneider DA, Weeks ER, Dunlap D, Finzi L. Multiplexed, Tethered Particle Microscopy for Studies of DNA-Enzyme Dynamics. Methods Enzymol 2016; 582:415-435. [PMID: 28062044 DOI: 10.1016/bs.mie.2016.08.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
DNA is the carrier of genetic information and, as such, is at the center of most essential cellular processes. To regulate its physiological function, specific proteins and motor enzymes constantly change conformational states with well-controlled dynamics. Twenty-five years ago, Schafer, Gelles, Sheetz, and Landick employed the tethered particle motion (TPM) technique for the first time to study transcription by RNA polymerase at the single-molecule level. TPM has since then remained one of the simplest, most affordable, and yet incisive single-molecule techniques available. It is an in vitro technique which allows investigation of DNA-protein interactions that change the effective length of a DNA tether. In this chapter, we will describe a recent strategy to multiplex TPM which substantially increases the throughput of TPM experiments, as well as a simulation to estimate the time resolution of experiments, such as transcriptional elongation assays, in which lengthy time averaging of the signal is impossible due to continual change of the DNA tether length. These improvements allow efficient study of several DNA-protein systems, including transcriptionally active DNA-RNA polymerase I complexes and DNA-gyrase complexes.
Collapse
Affiliation(s)
| | - D A Schneider
- University of Alabama at Birmingham, Birmingham, AL, United States
| | - E R Weeks
- Emory University, Atlanta, GA, United States
| | - D Dunlap
- Emory University, Atlanta, GA, United States
| | - L Finzi
- Emory University, Atlanta, GA, United States.
| |
Collapse
|
19
|
Ucuncuoglu S, Engel KL, Purohit PK, Dunlap DD, Schneider DA, Finzi L. Direct Characterization of Transcription Elongation by RNA Polymerase I. PLoS One 2016; 11:e0159527. [PMID: 27455049 PMCID: PMC4959687 DOI: 10.1371/journal.pone.0159527] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 07/04/2016] [Indexed: 11/18/2022] Open
Abstract
RNA polymerase I (Pol I) transcribes ribosomal DNA and is responsible for more than 60% of transcription in a growing cell. Despite this fundamental role that directly impacts cell growth and proliferation, the kinetics of transcription by Pol I are poorly understood. This study provides direct characterization of S. Cerevisiae Pol I transcription elongation using tethered particle microscopy (TPM). Pol I was shown to elongate at an average rate of approximately 20 nt/s. However, the maximum speed observed was, in average, about 60 nt/s, comparable to the rate calculated based on the in vivo number of active genes, the cell division rate and the number of engaged polymerases observed in EM images. Addition of RNA endonucleases to the TPM elongation assays enhanced processivity. Together, these data suggest that additional transcription factors contribute to efficient and processive transcription elongation by RNA polymerase I in vivo.
Collapse
Affiliation(s)
- Suleyman Ucuncuoglu
- Physics Department, Emory University, Atlanta, GA, 30322, United States of America
| | - Krysta L. Engel
- Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35294, United States of America
| | - Prashant K. Purohit
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA, 19104, United States of America
| | - David D. Dunlap
- Physics Department, Emory University, Atlanta, GA, 30322, United States of America
| | - David A. Schneider
- Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35294, United States of America
- * E-mail: (LF); (DAS)
| | - Laura Finzi
- Physics Department, Emory University, Atlanta, GA, 30322, United States of America
- * E-mail: (LF); (DAS)
| |
Collapse
|
20
|
Mustin B, Stoeber B. Single Layer Deposition of Polystyrene Particles onto Planar Polydimethylsiloxane Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:88-101. [PMID: 26646665 DOI: 10.1021/acs.langmuir.5b02914] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This work investigates the deposition of polystyrene particles onto cross-linked polydimethylsiloxane (PDMS) substrates by using an impinging jet flow cell for different concentrations of sodium chloride in solution. Particle tracking reveals that particles near the substrate can be immobilized to different degrees. An attempt is made to classify the mobility of the particles close to the surface by distinguishing between weakly immobilized and strongly immobilized particles where only the latter ones are considered as deposited. Subsequently, the measured initial deposition rates for different concentrations of sodium chloride in solution are compared to the commonly applied theory based on the convective diffusion equation in which different surface interaction potentials were considered. With currently available data on the surface properties of PDMS, the extended Derjaguin-Landau-Verwey-Overbeek (extended DLVO) theory gave a better description of the observed deposition rates as compared to the DLVO theory; however, in either case, the presence of significant surface charge heterogeneity had to be assumed in order to capture the observed trend of the deposition rates with respect to the electrolyte concentration. Careful analysis of the more weakly immobilized particles through particle displacement step analysis reveals that there is a buildup of a particle accumulation layer near the substrate in which particle motion parallel to the substrate is hindered by nonhydrodynamic effects. Possible reasons for the reduced particle motion in the accumulation layer are discussed. As a result, the presence of lateral surface interaction forces resulting from charge heterogeneity and surface roughness of the PDMS substrate is found to be the most plausible explanation for the hindered particle motion in the accumulation layer. This suggests that particles associated with the secondary minimum of the surface interaction potential may not always be freely mobile in any direction parallel to the substrate.
Collapse
Affiliation(s)
- B Mustin
- The University of British Columbia , 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada
| | - B Stoeber
- The University of British Columbia , 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4, Canada
| |
Collapse
|
21
|
Kuroda M, Murayama Y. Simple method to measure and analyze the fluctuations of a small particle in biopolymer solutions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:125105. [PMID: 26724071 DOI: 10.1063/1.4936879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
We developed a simple method to investigate the motion of a small particle in biopolymer solutions. Using optical tweezers with low stiffness, a trapped probe particle fluctuates widely for a long time along the light axis, which reflects the rheological properties of the surrounding environment. We present a convenient technique for three-dimensional position tracking and the analysis focused on the distribution of particle positions and its variance in a given time interval. It allows us to obtain useful information about the dynamics of a small particle in a wide range from a free diffusive motion to a constrained motion with statistical significance. We applied this method to investigate the dynamics in collagen and DNA solutions; it was found that a collagen solution behaves as a simple viscous liquid and a DNA solution has apparent elasticity due to the slow relaxation of the configuration of molecules.
Collapse
Affiliation(s)
- Masafumi Kuroda
- Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Yoshihiro Murayama
- Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| |
Collapse
|
22
|
Brunet A, Tardin C, Salomé L, Rousseau P, Destainville N, Manghi M. Dependence of DNA Persistence Length on Ionic Strength of Solutions with Monovalent and Divalent Salts: A Joint Theory–Experiment Study. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b00735] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Annaël Brunet
- CNRS, Institut de Pharmacologie et de Biologie Structurale (IPBS) 205 route de Narbonne, BP 64182, F-31077 Toulouse, France
- UPS,
IPBS, Université de Toulouse F-31077 Toulouse, France
- UPS, Laboratoire
de Physique Théorique (IRSAMC), Université de Toulouse, F-31062 Toulouse, France
- CNRS, Laboratoire de Physique Théorique (IRSAMC), F-31062 Toulouse, France
| | - Catherine Tardin
- CNRS, Institut de Pharmacologie et de Biologie Structurale (IPBS) 205 route de Narbonne, BP 64182, F-31077 Toulouse, France
- UPS,
IPBS, Université de Toulouse F-31077 Toulouse, France
| | - Laurence Salomé
- CNRS, Institut de Pharmacologie et de Biologie Structurale (IPBS) 205 route de Narbonne, BP 64182, F-31077 Toulouse, France
- UPS,
IPBS, Université de Toulouse F-31077 Toulouse, France
| | - Philippe Rousseau
- UPS,
Laboratoire de Microbiologie et Génétique Moléculaires
(LMGM), Université de Toulouse, F-31062 Toulouse, France
- CNRS, LMGM, UMR CNRS-UPS 5100, F-31062 Toulouse, France
| | - Nicolas Destainville
- UPS, Laboratoire
de Physique Théorique (IRSAMC), Université de Toulouse, F-31062 Toulouse, France
- CNRS, Laboratoire de Physique Théorique (IRSAMC), F-31062 Toulouse, France
| | - Manoel Manghi
- UPS, Laboratoire
de Physique Théorique (IRSAMC), Université de Toulouse, F-31062 Toulouse, France
- CNRS, Laboratoire de Physique Théorique (IRSAMC), F-31062 Toulouse, France
| |
Collapse
|
23
|
Quantitation of interactions between two DNA loops demonstrates loop domain insulation in E. coli cells. Proc Natl Acad Sci U S A 2014; 111:E4449-57. [PMID: 25288735 DOI: 10.1073/pnas.1410764111] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Eukaryotic gene regulation involves complex patterns of long-range DNA-looping interactions between enhancers and promoters, but how these specific interactions are achieved is poorly understood. Models that posit other DNA loops--that aid or inhibit enhancer-promoter contact--are difficult to test or quantitate rigorously in eukaryotic cells. Here, we use the well-characterized DNA-looping proteins Lac repressor and phage λ CI to measure interactions between pairs of long DNA loops in E. coli cells in the three possible topological arrangements. We find that side-by-side loops do not affect each other. Nested loops assist each other's formation consistent with their distance-shortening effect. In contrast, alternating loops, where one looping element is placed within the other DNA loop, inhibit each other's formation, thus providing clear support for the loop domain model for insulation. Modeling shows that combining loop assistance and loop interference can provide strong specificity in long-range interactions.
Collapse
|