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Merici G, Amidani D, Dieci G, Rivetti C. A New Strategy to Investigate RNA:DNA Triplex Using Atomic Force Microscopy. Int J Mol Sci 2024; 25:3035. [PMID: 38474280 DOI: 10.3390/ijms25053035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 02/26/2024] [Accepted: 03/04/2024] [Indexed: 03/14/2024] Open
Abstract
Over the past decade, long non-coding RNAs (lncRNAs) have been recognized as key players in gene regulation, influencing genome organization and expression. The locus-specific binding of these non-coding RNAs (ncRNAs) to DNA involves either a non-covalent interaction with DNA-bound proteins or a direct sequence-specific interaction through the formation of RNA:DNA triplexes. In an effort to develop a novel strategy for characterizing a triple-helix formation, we employed atomic force microscopy (AFM) to visualize and study a regulatory RNA:DNA triplex formed between the Khps1 lncRNA and the enhancer of the proto-oncogene SPHK1. The analysis demonstrates the successful formation of RNA:DNA triplexes under various conditions of pH and temperature, indicating the effectiveness of the AFM strategy. Despite challenges in discriminating between the triple-helix and R-loop configurations, this approach opens new perspectives for investigating the role of lncRNAs in gene regulation at the single-molecule level.
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Affiliation(s)
- Giovanni Merici
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | - Davide Amidani
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | - Giorgio Dieci
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
| | - Claudio Rivetti
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, 43124 Parma, Italy
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2
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Rahman M, Islam KR, Islam MR, Islam MJ, Kaysir MR, Akter M, Rahman MA, Alam SMM. A Critical Review on the Sensing, Control, and Manipulation of Single Molecules on Optofluidic Devices. MICROMACHINES 2022; 13:968. [PMID: 35744582 PMCID: PMC9229244 DOI: 10.3390/mi13060968] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 05/19/2022] [Accepted: 05/23/2022] [Indexed: 02/06/2023]
Abstract
Single-molecule techniques have shifted the paradigm of biological measurements from ensemble measurements to probing individual molecules and propelled a rapid revolution in related fields. Compared to ensemble measurements of biomolecules, single-molecule techniques provide a breadth of information with a high spatial and temporal resolution at the molecular level. Usually, optical and electrical methods are two commonly employed methods for probing single molecules, and some platforms even offer the integration of these two methods such as optofluidics. The recent spark in technological advancement and the tremendous leap in fabrication techniques, microfluidics, and integrated optofluidics are paving the way toward low cost, chip-scale, portable, and point-of-care diagnostic and single-molecule analysis tools. This review provides the fundamentals and overview of commonly employed single-molecule methods including optical methods, electrical methods, force-based methods, combinatorial integrated methods, etc. In most single-molecule experiments, the ability to manipulate and exercise precise control over individual molecules plays a vital role, which sometimes defines the capabilities and limits of the operation. This review discusses different manipulation techniques including sorting and trapping individual particles. An insight into the control of single molecules is provided that mainly discusses the recent development of electrical control over single molecules. Overall, this review is designed to provide the fundamentals and recent advancements in different single-molecule techniques and their applications, with a special focus on the detection, manipulation, and control of single molecules on chip-scale devices.
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Affiliation(s)
- Mahmudur Rahman
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Kazi Rafiqul Islam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Rashedul Islam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Jahirul Islam
- Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology, Khulna 9203, Bangladesh;
| | - Md. Rejvi Kaysir
- Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada;
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Ave. W, Waterloo, ON N2L 3G1, Canada
| | - Masuma Akter
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - Md. Arifur Rahman
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
| | - S. M. Mahfuz Alam
- Department of Electrical and Electronic Engineering, Dhaka University of Engineering & Technology, Gazipur 1707, Bangladesh; (M.R.); (K.R.I.); (M.R.I.); (M.A.); (M.A.R.)
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Main KHS, Provan JI, Haynes PJ, Wells G, Hartley JA, Pyne ALB. Atomic force microscopy-A tool for structural and translational DNA research. APL Bioeng 2021; 5:031504. [PMID: 34286171 PMCID: PMC8272649 DOI: 10.1063/5.0054294] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/07/2021] [Indexed: 12/26/2022] Open
Abstract
Atomic force microscopy (AFM) is a powerful imaging technique that allows for structural characterization of single biomolecules with nanoscale resolution. AFM has a unique capability to image biological molecules in their native states under physiological conditions without the need for labeling or averaging. DNA has been extensively imaged with AFM from early single-molecule studies of conformational diversity in plasmids, to recent examinations of intramolecular variation between groove depths within an individual DNA molecule. The ability to image dynamic biological interactions in situ has also allowed for the interaction of various proteins and therapeutic ligands with DNA to be evaluated-providing insights into structural assembly, flexibility, and movement. This review provides an overview of how innovation and optimization in AFM imaging have advanced our understanding of DNA structure, mechanics, and interactions. These include studies of the secondary and tertiary structure of DNA, including how these are affected by its interactions with proteins. The broader role of AFM as a tool in translational cancer research is also explored through its use in imaging DNA with key chemotherapeutic ligands, including those currently employed in clinical practice.
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Affiliation(s)
| | - James I. Provan
- Institute of Molecular, Cell, and Systems Biology, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | | | - Geoffrey Wells
- UCL School of Pharmacy, University College London, London WC1N 1AX, United Kingdom
| | - John A. Hartley
- UCL Cancer Institute, University College London, London WC1E 6DD, United Kingdom
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4
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Li N, Wang J, Ma K, Liang L, Mi L, Huang W, Ma X, Wang Z, Zheng W, Xu L, Chen JH, Yu Z. The dynamics of forming a triplex in an artificial telomere inferred by DNA mechanics. Nucleic Acids Res 2019; 47:e86. [PMID: 31114915 PMCID: PMC6735771 DOI: 10.1093/nar/gkz464] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 05/06/2019] [Accepted: 05/15/2019] [Indexed: 11/21/2022] Open
Abstract
A telomere carrying repetitive sequences ends with a single-stranded overhang. The G-rich overhang could fold back and bind in the major groove of its upstream duplex, forming an antiparallel triplex structure. The telomeric triplex has been proposed to function in protecting chromosome ends. However, we lack strategies to mechanically probe the dynamics of a telomeric triplex. Here, we show that the topological dynamics of a telomeric triplex involves 3' overhang binding at the ds/ssDNA junction inferred by DNA mechanics. Assisted by click chemistry and branched polymerase chain reaction, we developed a rescue-rope-strategy for mechanically manipulating an artificial telomeric DNA with a free end. Using single-molecule magnetic tweezers, we identified a rarely forming (5%) telomeric triplex which pauses at an intermediate state upon unzipping the Watson-Crick paired duplex. Our findings revealed that a mechanically stable triplex formed in a telomeric DNA can resist a force of 20 pN for a few seconds in a physiological buffer. We also demonstrated that the rescue-rope-strategy assisted mechanical manipulation can directly rupture the interactions between the third strand and its targeting duplex in a DNA triplex. Our single-molecule rescue-rope-strategy will serve as a general tool to investigate telomere dynamics and further develop triplex-based biotechnologies.
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Affiliation(s)
- Ning Li
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Junli Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Kangkang Ma
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Lin Liang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Lipei Mi
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Wei Huang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Xiaofeng Ma
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Zeyu Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Wei Zheng
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
| | - Linyan Xu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China
| | - Jun-Hu Chen
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Center for Tropical Diseases, National Center for International Research on Tropical Diseases, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai 200025, China
| | - Zhongbo Yu
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, China
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5
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Traeger JC, Schwartz DK. Surface-Mediated DNA Hybridization: Effects of DNA Conformation, Surface Chemistry, and Electrostatics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12651-12659. [PMID: 29023127 DOI: 10.1021/acs.langmuir.7b02675] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Single-molecule Förster Resonance Energy Transfer (FRET) was used to study the dynamic association of mobile donor-labeled ssDNA oligonucleotides ("target") with covalently immobilized complementary acceptor-labeled ssDNA oligonucleotides ("probe"). While probe-target association events were resolved for all experiments, such FRET events were far more likely to occur in systems with complementarity and on hydrophobic, as compared to hydrophilic, surfaces. The distribution of donor-acceptor association-time intervals did not exhibit simple first-order kinetics, and when decomposed into a superposition of first-order processes, only a small fraction of events corresponded to a long-lived state that was presumed to represent true DNA hybridization, while the majority of association events were transient, representing nonspecific associations or partial hybridization. The structure of the DNA target and probe affected both the stability of the hybridized state, as well as the likelihood that an association between the two led to hybridization. In particular, the likelihood of hybridization decreased for longer target strands and for targets with stem-loop secondary structure. The presence of oligonucleotide secondary structure reduced the stability of hybridization, while greater complementarity increased stability of the hybridized state. Interestingly, increased ionic strength (i.e., greater electrostatic screening) increased the probability of hybridization but did not influence the lifetime of the hybridized state. Combined, these observations provide a nuanced view of surface-mediated DNA hybridization, where various factors independently influence the probability and stability of hybridization.
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Affiliation(s)
- Jeremiah C Traeger
- Department of Chemical and Biological Engineering University of Colorado Boulder , Boulder, Colorado 80309, United States
| | - Daniel K Schwartz
- Department of Chemical and Biological Engineering University of Colorado Boulder , Boulder, Colorado 80309, United States
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6
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Artificial Nucleic Acid Probes and Their Applications in Clinical Microbiology. METHODS IN MICROBIOLOGY 2015. [DOI: 10.1016/bs.mim.2015.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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8
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Govedarica B, Sovány T, Pintye-Hódi K, Škarabot M, Baumgartner S, Muševič I, Srčič S. Addressing potent single molecule AFM study in prediction of swelling and dissolution rate in polymer matrix tablets. Eur J Pharm Biopharm 2012; 80:217-25. [DOI: 10.1016/j.ejpb.2011.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2011] [Accepted: 09/12/2011] [Indexed: 10/17/2022]
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9
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Prado-Gotor R, Grueso E. A kinetic study of the interaction of DNA with gold nanoparticles: mechanistic aspects of the interaction. Phys Chem Chem Phys 2010; 13:1479-89. [PMID: 21132199 DOI: 10.1039/c0cp00901f] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A kinetic study of the interaction of gold nanoparticles capped with N-(2-mercaptopropionyl)glycine with double stranded DNA was carried out in water and in salt (NaCl) solutions. The kinetic curves are biexponential and reveal the presence of three kinetic steps. The dependence of the reciprocal fast and slow relaxation time, on the DNA concentration, is a curve and tends to a plateau at high DNA concentrations. The simplest mechanism consistent with the kinetic results involves a simple three-step series mechanism reaction scheme. The first step corresponds to a very fast step that is related to a diffusion controlled formation of an external precursor complex (DNA, AuNPs); the second step involves the formation of a (DNA/AuNPs)(I) complex, as a result of the binding affinity between hydrophilic groups of the tiopronin and the DNA grooves. Finally, the third step has been interpreted as a consequence of a conformational change of the (DNA/AuNPs)(I) complex formed in the second step, to a more compacted form (DNA/AuNPs)(II). The values of the rate constants of each step decrease as NaCl concentration increases. The results have been discussed in terms of solvation of the species and changes in the viscosity of the solution.
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Affiliation(s)
- Rafael Prado-Gotor
- Department of Physical Chemistry, Faculty of Chemistry, University of Sevilla, C/Profesor García González s/n, 41012 Sevilla, Spain
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10
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Lyubchenko YL. Preparation of DNA and nucleoprotein samples for AFM imaging. Micron 2010; 42:196-206. [PMID: 20864349 DOI: 10.1016/j.micron.2010.08.011] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 08/24/2010] [Accepted: 08/24/2010] [Indexed: 02/06/2023]
Abstract
Sample preparation techniques allowing reliable and reproducible imaging of DNA with various structures, topologies and complexes with proteins are reviewed. The major emphasis is given to methods utilizing chemical functionalization of mica, enabling preparation of the surfaces with required characteristics. The methods are illustrated by examples of imaging of different DNA structures. Special attention is given to the possibility of AFM to image the dynamics of DNA at the nanoscale. The capabilities of time-lapse AFM in aqueous solutions are illustrated by imaging of dynamic processes as transitions of local alternative structures (transition of DNA between H and B forms). The application of AFM to studies of protein-DNA complexes is illustrated by a few examples of imaging site-specific complexes, as well as such systems as chromatin. The time-lapse AFM studies of protein-DNA complexes including very recent advances with the use of high-speed AFM are reviewed.
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Affiliation(s)
- Yuri L Lyubchenko
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE 68198-6025, United States.
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11
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Singer A, Wanunu M, Morrison W, Kuhn H, Frank-Kamenetskii M, Meller A. Nanopore based sequence specific detection of duplex DNA for genomic profiling. NANO LETTERS 2010; 10:738-42. [PMID: 20088590 PMCID: PMC2834191 DOI: 10.1021/nl100058y] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We demonstrate a purely electrical method for the single-molecule detection of specific DNA sequences, achieved by hybridizing double-stranded DNA (dsDNA) with peptide nucleic acid (PNA) probes and electrophoretically threading the DNA through sub-5 nm silicon nitride pores. Bis-PNAs were used as the tagging probes in order to achieve high affinity and sequence specificity. Sequence detection is performed by reading the ion current traces of individual translocating DNA molecules, which display a characteristic secondary blockade level, absent in untagged molecules. The potential for barcoding DNA is demonstrated through nanopore analysis of once-tagged and twice-tagged DNA at different locations on the same genomic fragment. Our high-throughput, long-read length method can be used to identify key sequences embedded in individual DNA molecules, without the need for amplification or fluorescent/radio labeling. This opens up a wide range of possibilities in human genomics as well as in pathogen detection for fighting infectious diseases.
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Affiliation(s)
- Alon Singer
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
| | - Meni Wanunu
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
| | - Will Morrison
- Department of Physics, Boston University, Boston, MA 02215
| | - Heiko Kuhn
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
| | | | - Amit Meller
- Department of Biomedical Engineering, Boston University, Boston, MA 02215
- Department of Physics, Boston University, Boston, MA 02215
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Duca M, Vekhoff P, Oussedik K, Halby L, Arimondo PB. The triple helix: 50 years later, the outcome. Nucleic Acids Res 2008; 36:5123-38. [PMID: 18676453 PMCID: PMC2532714 DOI: 10.1093/nar/gkn493] [Citation(s) in RCA: 265] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Triplex-forming oligonucleotides constitute an interesting DNA sequence-specific tool that can be used to target cleaving or cross-linking agents, transcription factors or nucleases to a chosen site on the DNA. They are not only used as biotechnological tools but also to induce modifications on DNA with the aim to control gene expression, such as by site-directed mutagenesis or DNA recombination. Here, we report the state of art of the triplex-based anti-gene strategy 50 years after the discovery of such a structure, and we show the importance of the actual applications and the main challenges that we still have ahead of us.
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Affiliation(s)
- Maria Duca
- LCMBA CNRS UMR6001, University of Nice-Sophia Antipolis, Parc Valrose, 06108 NICE Cedex 2, France
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Piergentili R, Mencarelli C. Drosophila melanogaster kl-3 and kl-5 Y-loops harbor triple-stranded nucleic acids. J Cell Sci 2008; 121:1605-12. [PMID: 18430782 DOI: 10.1242/jcs.025320] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Primary spermatocyte nuclei of Drosophila melanogaster contain three prominent lampbrush-like loops. The development of these structures has been associated with the transcription of three fertility factors located on the Y chromosome, named kl-5, kl-3 and ks-1. These loci have huge physical dimensions and contain extremely long introns. In addition, kl-3 and kl-5 were shown to encode two putative dynein subunits required for the correct assembly of the sperm axoneme. Here, we show that both the kl-5 and kl-3 loops are intensely decorated by monoclonal antibodies recognizing triple-stranded nucleic acids, and that each loop presents a peculiar molecular organization of triplex structures. Moreover, immunostaining of Drosophila hydei primary spermatocytes revealed that also in this species - which diverged from D. melanogaster 58 million years ago - Y-loops are decorated by anti-triplex antibodies, strongly suggesting a conserved role of loop-associated triplexes. Finally, we showed that in D. melanogaster wild-type lines that are raised at the non-permissive temperature of 31+/-0.5 degrees C (which is known to induce male sterility in flies) both the triplex immunostaining and the axonemal dynein heavy chains encoded by kl-3 and kl-5 are no longer detectable, which suggests a functional correlation between loop-associated triplexes, the presence of axonemal proteins and male fertility in fly.
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Affiliation(s)
- Roberto Piergentili
- Department of Genetics and Molecular Biology - Sapienza Università di Roma, 00185 Rome, Italy.
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Uno T, Tabata H, Kawai T. Peptide-nucleic acid-modified ion-sensitive field-effect transistor-based biosensor for direct detection of DNA hybridization. Anal Chem 2007; 79:52-9. [PMID: 17194121 DOI: 10.1021/ac060273y] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here, we report the development of a peptide-nucleic acid (PNA)-modified ion-sensitive field-effect transistor (IS-FET)-based biosensor that takes advantage of the change in the surface potential upon hybridization of a negatively charged DNA. PNA was immobilized on a silicon nitride gate insulator by an addition reaction between a maleimide group introduced on the gate surface, the succinimide group of N-(6-maleimidocaproyloxy) succinimide, and the thiol group of the terminal cysteine in PNA. The surface was characterized after each step of the reaction by X-ray photoelectron spectroscopy analysis, and the kinetic analysis of the hybridization events was assessed by surface plasmon resonance. In addition, we measured the -potential before and after PNA-DNA hybridization in the presence of counterions to investigate the change in surface charge density at the surface-solution interface within the order of the Debye length. On the basis of the zeta-potential, the surface charge density, DeltaQ, calculated using the Grahame equation was approximately 4.0 x 10(-3) C/m2 and the estimated number of hybridized molecules was at least 1.7 x 10(11)/cm2. The I-V characteristics revealed that the PNA-DNA duplexes induce a positive shift in the threshold voltage, VT, and a decrease in the saturated drain current, ID. These results demonstrate that direct detection of DNA hybridization should be possible using a PNA-modified IS-FET-based biosensor. PNA is particularly advantageous for this system because it enables highly specific and selective binding at low ionic strength.
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Affiliation(s)
- Takeshi Uno
- The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
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15
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Escudé C, Roulon T, Lyonnais S, Le Cam E. Multiple topological labeling for imaging single plasmids. Anal Biochem 2007; 362:55-62. [PMID: 17250797 DOI: 10.1016/j.ab.2006.12.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 12/06/2006] [Accepted: 12/13/2006] [Indexed: 11/18/2022]
Abstract
Sequence-specific labeling methods for double-stranded DNA are required for mapping protein binding sites or specific DNA structures on circular DNA molecules by high-resolution imaging techniques such as electron and atomic force microscopies. Site-specific labeling can be achieved by ligating a DNA fragment to a stem-loop-triplex-forming oligonucleotide, thereby forming a topologically linked complex. The superhelicity of the plasmid is not altered and the process can be applied to two different target sites simultaneously, using DNA fragments of different sizes. Observation of the labeled plasmids by electron microscopy revealed that, under conditions where the triple helices were stable, the two labels were located at 339+/-34 bp from one another, in agreement with the distance between the two target sequences for triple helix formation (350 bp). Under conditions where the triple helices were not stable, the short DNA fragments could slide away from their target site. The concomitant attachment of two different stable labels makes it possible, for the first time to our knowledge, to label a circular DNA molecule and obtain information on its direction. In addition to its potential applications as a tool for structural investigations of single DNA molecules and their interactions with proteins, this DNA labeling method may also prove useful in biotechnology and gene therapy.
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Affiliation(s)
- Christophe Escudé
- Département Régulations, Développement et Diversité Moléculaire, USM 0503 Muséum National d'Histoire Naturelle, INSERM U565, CNRS UMR5153, Case postale 26, 43 Rue Cuvier, 75231 Paris Cedex 05, France.
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16
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Du Q, Vologodskaia M, Kuhn H, Frank-Kamenetskii M, Vologodskii A. Gapped DNA and cyclization of short DNA fragments. Biophys J 2005; 88:4137-45. [PMID: 15778443 PMCID: PMC1305644 DOI: 10.1529/biophysj.104.055657] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We use the cyclization of small DNA molecules, approximately 200 bp in length, to study conformational properties of DNA fragments with single-stranded gaps. The approach is extremely sensitive to DNA conformational properties and, being complemented by computations, allows a very accurate determination of the fragment's conformational parameters. Sequence-specific nicking endonucleases are used to create the 4-nt-long gap. We determined the bending rigidity of the single-stranded region in the gapped DNA. We found that the gap of 4 nt in length makes all torsional orientations of DNA ends equally probable. Our results also show that the gap has isotropic bending rigidity. This makes it very attractive to use gapped DNA in the cyclization experiments to determine DNA conformational properties, since the gap eliminates oscillations of the cyclization efficiency with the DNA length. As a result, the number of measurements is greatly reduced in the approach, and the analysis of the data is greatly simplified. We have verified our approach on DNA fragments containing well-characterized intrinsic bends caused by A-tracts. The obtained experimental results and theoretical analysis demonstrate that gapped-DNA cyclization is an exceedingly sensitive and accurate approach for the determination of DNA bending.
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Affiliation(s)
- Quan Du
- Department of Chemistry, New York University, New York, 10003, USA
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17
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Zelphati O, Felgner J, Wang Y, Liang X, Felgner P. Medicinal chemistry of plasmid DNA with peptide nucleic acids: A new strategy for gene therapy. Int J Pept Res Ther 2005. [DOI: 10.1007/s10989-005-4907-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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Biebricher A, Paul A, Tinnefeld P, Gölzhäuser A, Sauer M. Controlled three-dimensional immobilization of biomolecules on chemically patterned surfaces. J Biotechnol 2004; 112:97-107. [PMID: 15288945 DOI: 10.1016/j.jbiotec.2004.03.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2003] [Revised: 03/15/2004] [Accepted: 03/19/2004] [Indexed: 11/23/2022]
Abstract
We used electron-beam lithography to fabricate chemical nanostructures, i.e. amino groups in aromatic self-assembled monolayers (SAMs) on gold surfaces. The amino groups are utilized as reactive species for mild covalent attachment of fluorescently labeled proteins. Since non-radiative energy transfer results in strong quenching of fluorescent dyes in the vicinity of the metal surfaces, different labeling strategies were investigated. Spacers of varying length were introduced between the gold surface and the fluorescently labeled proteins. First, streptavidin was directly coupled to the amino groups of the SAMs via a glutaraldehyde linker and fluorescently labeled biotin (X-Biotin) was added, resulting in a distance of approximately 2 nm between the dyes and the surface. Scanning confocal fluorescence images show that efficient energy transfer from the dye to the surface occurs, which is reflected in poor signal-to-background (S/B) ratios of approximately 1. Coupling of a second streptavidin layer increases the S/B-ratio only slightly to approximately 2. The S/B-ratio of the fluorescence signals could be further increased to approximately 4 by coupling of an additional fluorescently labeled antibody layer. Finally, we introduced tetraethylenepentamine as functional spacer molecule to diminish fluorescence quenching by the surface. We demonstrate that the use of this spacer in combination with multiple antibody layers enables the controlled fabrication of highly fluorescent three-dimensional nanostructures with S/B-ratios of >20. The presented technique might be used advantageously for the controlled three-dimensional immobilization of single protein or DNA molecules and the well-defined assembly of protein complexes.
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Affiliation(s)
- A Biebricher
- Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany
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19
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Kuhn H, Cherny DI, Demidov VV, Frank-Kamenetskii MD. Inducing and modulating anisotropic DNA bends by pseudocomplementary peptide nucleic acids. Proc Natl Acad Sci U S A 2004; 101:7548-53. [PMID: 15136738 PMCID: PMC419643 DOI: 10.1073/pnas.0308756101] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA bending is significant for various DNA functions in the cell. Here, we demonstrate that pseudocomplementary peptide nucleic acids (pcPNAs) represent a class of versatile, sequence-specific DNA-bending agents. The occurrence of anisotropic DNA bends induced by pcPNAs is shown by gel electrophoretic phasing analysis. The magnitude of DNA bending is determined by circular permutation assay and by electron microscopy, with good agreement of calculated mean values between both methods. Binding of a pair of 10-meric pcPNAs to its target DNA sequence results in moderate DNA bending with a mean value of 40-45 degrees, while binding of one self-pc 8-mer PNA to target DNA yields a somewhat larger average value of the induced DNA bend. Both bends are found to be in phase when the pcPNA target sites are separated by distances of half-integer numbers of helical turns of regular duplex DNA, resulting in an enhanced DNA bend with an average value in the range of 80-90 degrees. The occurrence of such a sharp bend within the DNA double helix is confirmed and exploited through efficient formation of 170-bp-long DNA minicircles by means of dimerization of two bent DNA fragments. The pcPNAs offer two main advantages over previously designed classes of nonnatural DNA-bending agents: they have very mild sequence limitations while targeting duplex DNA and they can easily be designed for a chosen target sequence, because their binding obeys the principle of complementarity. We conclude that pcPNAs are promising tools for inducing bends in DNA at virtually any chosen site.
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Affiliation(s)
- Heiko Kuhn
- Center for Advanced Biotechnology and Department of Biomedical Engineering, Boston University, 36 Cummington Street, Boston, MA 02215, USA
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20
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Nakao H, Gad M, Sugiyama S, Otobe K, Ohtani T. Transfer-printing of highly aligned DNA nanowires. J Am Chem Soc 2003; 125:7162-3. [PMID: 12797774 DOI: 10.1021/ja034185w] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We developed a simple method of reproducibly creating highly aligned DNA nanowires without any surface modifications or special equipment. Stretched DNA molecules initially present on the PDMS sheet were transferred onto another surface using transfer-printing (TP). Fluorescent microscopic and atomic force microscopic images revealed that many DNA molecules were highly aligned on surfaces after TP. Furthermore, it was also possible to realize the two-dimensional assembly of DNA nanowires by repeating TP.
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Affiliation(s)
- Hidenobu Nakao
- National Agricultural Research Organization, 3-1-1 Kannondai, Tsukuba, Ibaraki 305-8518, Japan
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21
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Medicinal chemistry of plasmid DNA with peptide nucleic acids: A new strategy for gene therapy. Int J Pept Res Ther 2003. [DOI: 10.1007/s10989-004-4906-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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22
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Medicinal chemistry of plasmid DNA with peptide nucleic acids: A new strategy for gene therapy. Int J Pept Res Ther 2003. [DOI: 10.1007/bf02484566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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23
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Zuccheri G, Samorì B. Scanning force microscopy studies on the structure and dynamics of single DNA molecules. Methods Cell Biol 2003; 68:357-95. [PMID: 12053739 DOI: 10.1016/s0091-679x(02)68018-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023]
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24
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Seong GH, Yanagida Y, Aizawa M, Kobatake E. Atomic force microscopy identification of transcription factor NFkappaB bound to streptavidin-pin-holding DNA probe. Anal Biochem 2002; 309:241-7. [PMID: 12413457 DOI: 10.1016/s0003-2697(02)00303-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A novel method for identifying DNA-binding proteins from image analysis using AFM was developed. Here, transcription factor NFkappaB, which a well-studied example of transcription activator proteins, was used as a target protein. 5'-biotinlynated double-stranded DNA probe was labeled site specifically through high affinity with streptavidin. When the biotinylated DNA fragments were incubated with the streptavidin at a 1:2 molar ratio of DNA:streptavidin, the overall efficiency of labeling was over 90%. The double-stranded DNA probes were immobilized on a mica surface by the adsorption of streptavidin that attached to the 5'-end of DNA and applied for selection of the target protein NFkappaB in solution and then AFM was used to image the DNA probe-NFkappaB complexes. The length of the distance between 5'-labeled streptavidin and NFkappaB bound on DNA probes from AFM images is 0.64, the normalized position of the NFkappaB binding site, and this result is in close agreement with the expected 299 and 167bp values.
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Affiliation(s)
- Gi Hun Seong
- Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
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25
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Kato M, McAllister CJ, Hokabe S, Shimizu N, Lyubchenko YL. Structural heterogeneity of pyrimidine/purine-biased DNA sequence analyzed by atomic force microscopy. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:3632-6. [PMID: 12153559 DOI: 10.1046/j.1432-1033.2002.03063.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report here the direct evidence for the formation of alternative DNA structures in a plasmid DNA, termed pTIR10, containing a 0.23-kb pyrimidine/purine-biased (Pyr/Pur) stretch isolated from the rat genome. Long Pyr/Pur sequences are abundant in eukaryotic genomes, and they may modulate the biological activity of genes and genomes via formation of various types of triplex-related structures. The plasmid DNA in sodium acetate buffer (pH 4.35) was deposited on APS-modified mica, and after drying it was imaged with an atomic force microscope in air. Various types of thick protrusions have been observed on pTIR10 DNA. Structural parameters (width and height) of DNA molecules suggest that the alternative structures observed here are variations on the theme of an intramolecular triplex. The biological relevance of the structural features within Pyr/Pur stretches is discussed.
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Affiliation(s)
- Mikio Kato
- Department of Life Science, Osaka Prefecture University College of Integrated Arts and Sciences, Sakai, Japan.
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26
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Roulon T, Coulaud D, Delain E, Le Cam E, Hélène C, Escudé C. Padlock oligonucleotides as a tool for labeling superhelical DNA. Nucleic Acids Res 2002; 30:E12. [PMID: 11809900 PMCID: PMC100311 DOI: 10.1093/nar/30.3.e12] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2001] [Revised: 12/03/2001] [Accepted: 12/03/2001] [Indexed: 11/14/2022] Open
Abstract
Labeling of a covalently closed circular double-stranded DNA was achieved using a so-called 'padlock oligonucleotide'. The oligonucleotide was targeted to a sequence which is present in the replication origin of phage f1 and thus in numerous commonly used plasmids. After winding around the double-stranded target DNA sequence by ligand-induced triple helix formation, a biotinylated oligonucleotide was circularized using T4 DNA ligase and in this way became catenated to the plasmid. A gel shift assay was developed to measure the extent of plasmid modification by the padlock oligonucleotide. A similar assay showed that a modified supercoiled plasmid was capable of binding one streptavidin molecule thanks to the biotinylated oligonucleotide and that this binding was quantitative. The catenated complex was visualized by electron and atomic force microscopies using streptavidin conjugates or single strand-binding proteins as protein tags for the padlock oligonucleotide. This method provides a versatile tool for plasmid functionalization which offers new perspectives in the physical study of supercoiled DNA and in the development of improved vectors for gene therapy.
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Affiliation(s)
- Thibaut Roulon
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U201, CNRS UMR8646, 43 Rue Cuvier, F-75231 Paris Cedex 05, France
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27
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Nagami F, Zuccheri G, Samorì B, Kuroda R. Time-lapse imaging of conformational changes in supercoiled DNA by scanning force microscopy. Anal Biochem 2002; 300:170-6. [PMID: 11779108 DOI: 10.1006/abio.2001.5435] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Most of the scanning force microscopy (SFM) images of supercoiled DNA on untreated mica thus far reported have not shown tight plectonemic structure seen by electron microscopy, but instead less coiled molecules and sometimes a partly "condensed" state with intimate chain-chain interactions. By observing time-lapse images of conformational changes of DNA induced by decreasing ionic strength of imaging buffer in solution SFM, we could show that the process of water rinsing, an indispensable step for preparation of dried samples, may be responsible for some of the conformational anomalies in the images previously reported. We have studied several protocols to observe supercoiled DNA molecules by SFM and discuss the merits and the demerits. Images obtained following uranyl acetate treatment may be ideal for the detection of DNA damage, as the supercoiled and nicked forms are easily distinguishable.
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Affiliation(s)
- Fuji Nagami
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
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28
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Kim JM, Ohtani T, Sugiyama S, Hirose T, Muramatsu H. Simultaneous topographic and fluorescence imaging of single DNA molecules for DNA analysis with a scanning near-field optical/atomic force microscope. Anal Chem 2001; 73:5984-91. [PMID: 11791570 DOI: 10.1021/ac010536i] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-resolution fluorescence imaging of lambda-phage DNA molecules, intercalated with the dye YOYO-1, has been performed by a SNOM/AFM based on a bent-type optical fiber probe. A modified design of the optical probe has been made, and successful near-field optical resolution has been obtained for the strongly stretched lambda-phage DNA molecules. The best optical resolution was estimated at 45 nm for the dye-intercalated single lambda-DNA molecules by a mean width evaluation. In our comparison between the far-field fluorescence and high-resolution near-field fluorescence images for the DNA, it has been found that the near-field images much better defined the intercalation state of the dye. Finally, the relation between the DNA shapes and the dye distribution states, and the discrimination between the double-stranded and single-stranded DNA molecules, are discussed by comparing the topography and fluorescence images of the SNOM/AFM.
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Affiliation(s)
- J M Kim
- Department of Food Engineering, National Food Research Institute, Tsukuba, Ibaraki, Japan
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29
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Abstract
SFM is a viable effective method for determining the mode of binding, the extent of binding, and the site of binding of intercalators to nucleic acids. Establishing the presence of a groove-bound ligand can be achieved either by competitive binding experiments with a well-defined intercalator (minor groove) or by changes in apparent contrast (major groove). In our opinion, SFM has an important role in resolving the structural polymorphisms for small molecule-DNA complexes. Application of these assays in the study of polyintercalator molecules is currently underway in our laboratory. SFM is an important, new tool in the study of protein-DNA complexes. New insights into the structure and function of these complexes are enabled by real-time visualization. Currently the temporal resolution of the SFM limits the degree to which definitive rate data can be determined. Several binding and unbinding events could take place in the time it takes to acquire one image. New developments in SFM technology will allow faster scanning and will improve the temporal resolution of so-called SFM movies. To this end, the Hansma group is developing small cantilevers and improved optical deflection systems to enable intermittent imaging at scanning rates of 1.7 sec per image. These improvements will enable SFM visualization of complex biological processes as they occur, one molecule at a time.
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Affiliation(s)
- P T Lillehei
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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30
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Abstract
The atomic force microscope operates on surfaces. Since surfaces occupy much of the space in living organisms, surface biology is a valid and valuable form of biology that has been difficult to investigate in the past owing to a lack of good technology. Atomic force microscopy (AFM) of DNA has been used to investigate DNA condensation for gene therapy, DNA mapping and sizing, and a few applications to cancer research and to nanotechnology. Some of the most exciting new applications for atomic force microscopy of DNA involve pulling on single DNA molecules to obtain measurements of single-molecule mechanics and thermodynamics.
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Affiliation(s)
- H G Hansma
- Department of Physics, University of California, Santa Barbara, California 93106, USA.
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31
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Seong GH, Niimi T, Yanagida Y, Kobatake E, Aizawa M. Single-molecular AFM probing of specific DNA sequencing using RecA-promoted homologous pairing and strand exchange. Anal Chem 2000; 72:1288-93. [PMID: 10740872 DOI: 10.1021/ac990893h] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The specific sequence in a linearlized double-stranded DNA target has been identified at a single-molecular level by atomic force microscopy (AFM). This was accomplished using RecA-coated, single-stranded DNA probes which were paired with a specific complementary DNA sequence in a linear double-stranded DNA target by strand-exchange reaction at a homologous sequence site with target DNA. The sites of interaction between the nucleoprotein filaments and the double-stranded DNA targets were directly visualized by AFM in solution containing 4 mM magnesium acetate. Measurements of the position of RecA-coated probes paired to individual target DNA showed that DNA probes specifically paired at their corresponding homologous target sequences. Strand exchange promoted by RecA and the visualization by AFM provided a rapid and efficient way to identify homologous sequence on a single-molecule target DNA.
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Affiliation(s)
- G H Seong
- Department of Biological Information, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan
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32
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Cherny DI, Striker G, Subramaniam V, Jett SD, Palecek E, Jovin TM. DNA bending due to specific p53 and p53 core domain-DNA interactions visualized by electron microscopy. J Mol Biol 1999; 294:1015-26. [PMID: 10588903 DOI: 10.1006/jmbi.1999.3299] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have used transmission electron microscopy to analyze the specificity and the extent of DNA bending upon binding of full-length wild-type human tumor suppressor protein p53 (p53) and the p53 core domain (p53CD) encoding amino acid residues 94-312, to linear double-stranded DNA bearing the consensus sequence 5'-AGACATGCCTAGACATGCCT-3' (p53CON). Both proteins interacted with high specificity and efficiency with the recognition sequence in the presence of 50 mM KCl at low temperature ( approximately 4 degrees C) while the p53CD also exhibits a strong and specific interaction at physiological temperature. Specific complex formation did not result in an apparent reduction of the DNA contour length. The interaction of p53 and the p53CD with p53CON induced a noticeable salt-dependent bending of the DNA axis. According to quantitative analysis with folded Gaussian distributions, the bending induced by p53 varied from approximately 40 degrees to 48 degrees upon decreasing of the KCl concentration from 50 mM to approximately 1 mM in the mounting buffer used for adsorption of the complexes to the carbon film surface. The p53CD bent DNA by 35-37 degrees for all salt concentrations used in the mounting buffer. The bending angle of the p53/DNA complex under low salt conditions showed a somewhat broader distribution (sigma approximately 39 degrees ) than at high salt concentration (sigma approximately 31 degrees ) or for p53CD (sigma approximately 24-27 degrees ). Together, these results demonstrate that the p53CD has a dominant role in complex formation and that the complexes formed both by p53 and p53CD under moderate salt conditions are similar. However, the dependence of the bending parameters on ambient conditions suggest that the segments flanking the p53CD contribute to complex formation as well. The problems associated with the analysis of bending angles in electron microscopy experiments are discussed.
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Affiliation(s)
- D I Cherny
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, D-37077, Germany.
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33
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McMaster TJ, Berry M, Corfield AP, Miles MJ. Atomic force microscopy of the submolecular architecture of hydrated ocular mucins. Biophys J 1999; 77:533-41. [PMID: 10388778 PMCID: PMC1300350 DOI: 10.1016/s0006-3495(99)76910-9] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
High-resolution atomic force microscopy has been applied to the imaging of intact human ocular mucins in a near-physiological buffer. The mucins displayed a range of lengths from several hundred nanometers to several microns. By varying the ionic composition of the imaging environment, it was possible to image molecules rigidly fixed to the substrate and the motion of single molecules across the substrate. From static molecular images, high-resolution line profiles show a variation of up to +/-0.75 nm in thickness along the molecule. This variation is localized in regions of several tens of nanometers. It is interpreted in terms of the varying glycosylation along the mucin and is consistent with the known size of oligosaccharides in ocular mucins. The dynamic images indicate the possibility of following mucin interactions in situ.
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Affiliation(s)
- T J McMaster
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, England.
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34
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Margeat E, Le Grimellec C, Royer CA. Visualization of trp repressor and its complexes with DNA by atomic force microscopy. Biophys J 1998; 75:2712-20. [PMID: 9826594 PMCID: PMC1299945 DOI: 10.1016/s0006-3495(98)77715-x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
We used tapping mode atomic force microscopy to visualize the protein/protein and the protein/DNA complexes involved in transcriptional regulation by the trp repressor (TR). Plasmid fragments bearing the natural operators trp EDCBA and trp R, as well as nonspecific fragments, were deposited onto mica in the presence of varying concentrations of TR and imaged. In the presence of L-tryptophan, both specific and nonspecific complexes of TR with DNA are apparent, as well as free TR assemblies directly deposited onto the mica surface. We observed the expected decrease in specificity of TR for its operators with increasing protein concentration (1-5 nM). This loss of DNA-binding specificity is accompanied by the formation of large protein assemblies of varying sizes on the mica surface, consistent with the known tendency of the repressor to oligomerize in solution. When the co-repressor is omitted, no repressor molecules are seen, either on the plasmid fragments or free on the mica surface, probably because of the formation of larger aggregates that are removed from the surface upon washing. All these findings support a role for protein/protein interactions as an additional mechanism of transcriptional regulation by the trp repressor.
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Affiliation(s)
- E Margeat
- Centre de Biochimie Structurale, INSERM U 414-CNRS UMR 9955-Université Montpellier I, Montpellier, France
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35
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Klinov DV, Lagutina IV, Prokhorov VV, Neretina T, Khil PP, Lebedev YB, Cherny DI, Demin VV, Sverdlov ED. High resolution mapping DNAs by R-loop atomic force microscopy. Nucleic Acids Res 1998; 26:4603-10. [PMID: 9753727 PMCID: PMC147898 DOI: 10.1093/nar/26.20.4603] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
R-loops formed by short RNA transcripts have been imaged by atomic force microscopy (AFM) at a constant force in the height mode. The technique was applied to mapping the human endogenous retrovirus K10 family (HERV-K10) long terminal repeats (LTR) within individual plasmids and cosmids. RNA probes specific for the U3 (384 nt) and U5 (375 nt) LTR regions separated by a span of 200 bp were used for R-loop formation with LTRs located within plasmid (3.8 kb) or cosmid ( approximately 40 kb) DNAs. R-loops stabilized by glyoxal treatment and adsorbed onto the mica surface in the presence of magnesium ions looked like looped out segments of RNA:DNA hybrids. The total yield of R-loops was usually approximately 95%. The RNA:DNA hybrids were found to be 12-15% shorter than the corresponding DNA:DNA duplex. The two regions of the LTR could be easily discerned in the AFM images as clearly separated loops. R-loop positions determined on cosmids by AFM were accurate to approximately 0.5% of the cosmid length. This technique might be easily adapted for mapping various sequences such as gene exons or regulatory regions and for detecting insertions, deletions and rearrangements that cause human genetic diseases.
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Affiliation(s)
- D V Klinov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry and Institute of Molecular Genetics,Russian Academy of Sciences, Miklukho-Maklaya 16/10, Moscow 117871, Russia
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36
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Révet B, Fourcade A. Short unligated sticky ends enable the observation of circularised DNA by atomic force and electron microscopies. Nucleic Acids Res 1998; 26:2092-7. [PMID: 9547265 PMCID: PMC147521 DOI: 10.1093/nar/26.9.2092] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A comparative study of the stabilisation of DNA sticky ends by divalent cations was carried out by atomic force microscopy (AFM), electron microscopy and agarose gel electrophoresis. At room temperature, molecules bearing such extremities are immediately oligomerised or circularised by addition of Mg2+or Ca2+. This phenomenon, more clearly detected by AFM, requires the presence of uranyl salt, which stabilises the structures induced by Mg2+or Ca2+. DNA fragments were obtained by restriction enzymes producing sticky ends of 2 or 4 nucleotides (nt) in length with different guanine plus cytosine (GC) contents. The stability of the pairing is high when ends of 4 nt display a 100% GC-content. In that case, 95% of DNA fragments are maintained circular by the divalent cations, although 2 nt GC-sticky ends are sufficient for a stable pairing. DNA fragments with one blunt end and the other sticky appear as dimers in the presence of Mg2+. Dimerisation was analysed by varying the lengths and concentrations of DNA fragments, the base composition of the sticky ends, and also the temperature. Our observation provides a new powerful tool for construction of inverted dimers, and circularisation, ligation analysis or short bases sequence interaction studies.
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Affiliation(s)
- B Révet
- Laboratoire de Microscopie Cellulaire et Moléculaire, CNRS URA 147, Institut Gustave-Roussy, F-94805 Villejuif Cedex, France.
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