1
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Lee J, Wu M, Inman JT, Singh G, Park SH, Lee JH, Fulbright RM, Hong Y, Jeong J, Berger JM, Wang MD. Chromatinization Modulates Topoisomerase II Processivity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.03.560726. [PMID: 37873421 PMCID: PMC10592930 DOI: 10.1101/2023.10.03.560726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Type IIA topoisomerases are essential DNA processing enzymes that must robustly and reliably relax DNA torsional stress in vivo. While cellular processes constantly create different degrees of torsional stress, how this stress feeds back to control type IIA topoisomerase function remains obscure. Using a suite of single-molecule approaches, we examined the torsional impact on supercoiling relaxation of both naked DNA and chromatin by eukaryotic topoisomerase II (topo II). We observed that topo II was at least ~ 50-fold more processive on plectonemic DNA than previously estimated, capable of relaxing > 6000 turns. We further discovered that topo II could relax supercoiled DNA prior to plectoneme formation, but with a ~100-fold reduction in processivity; strikingly, the relaxation rate in this regime decreased with diminishing torsion in a manner consistent with the capture of transient DNA loops by topo II. Chromatinization preserved the high processivity of the enzyme under high torsional stress. Interestingly, topo II was still highly processive (~ 1000 turns) even under low torsional stress, consistent with the predisposition of chromatin to readily form DNA crossings. This work establishes that chromatin is a major stimulant of topo II function, capable of enhancing function even under low torsional stress.
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Affiliation(s)
- Jaeyoon Lee
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
| | - Meiling Wu
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
| | - James T. Inman
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
| | - Gundeep Singh
- Biophysics Program, Cornell University, Ithaca, NY 14853, USA
| | - Seong ha Park
- Biophysics Program, Cornell University, Ithaca, NY 14853, USA
| | - Joyce H. Lee
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | - Yifeng Hong
- Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Joshua Jeong
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James M. Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Michelle D. Wang
- Physics Department & LASSP, Cornell University, Ithaca, NY 14853, USA
- Howard Hughes Medical Institute, Cornell University, Ithaca, NY 14853, USA
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2
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Bartas M, Slychko K, Červeň J, Pečinka P, Arndt-Jovin DJ, Jovin TM. Extensive Bioinformatics Analyses Reveal a Phylogenetically Conserved Winged Helix (WH) Domain (Zτ) of Topoisomerase IIα, Elucidating Its Very High Affinity for Left-Handed Z-DNA and Suggesting Novel Putative Functions. Int J Mol Sci 2023; 24:10740. [PMID: 37445918 DOI: 10.3390/ijms241310740] [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: 04/19/2023] [Revised: 06/13/2023] [Accepted: 06/22/2023] [Indexed: 07/15/2023] Open
Abstract
The dynamic processes operating on genomic DNA, such as gene expression and cellular division, lead inexorably to topological challenges in the form of entanglements, catenanes, knots, "bubbles", R-loops, and other outcomes of supercoiling and helical disruption. The resolution of toxic topological stress is the function attributed to DNA topoisomerases. A prominent example is the negative supercoiling (nsc) trailing processive enzymes such as DNA and RNA polymerases. The multiple equilibrium states that nscDNA can adopt by redistribution of helical twist and writhe include the left-handed double-helical conformation known as Z-DNA. Thirty years ago, one of our labs isolated a protein from Drosophila cells and embryos with a 100-fold greater affinity for Z-DNA than for B-DNA, and identified it as topoisomerase II (gene Top2, orthologous to the human UniProt proteins TOP2A and TOP2B). GTP increased the affinity and selectivity for Z-DNA even further and also led to inhibition of the isomerase enzymatic activity. An allosteric mechanism was proposed, in which topoII acts as a Z-DNA-binding protein (ZBP) to stabilize given states of topological (sub)domains and associated multiprotein complexes. We have now explored this possibility by comprehensive bioinformatic analyses of the available protein sequences of topoII representing organisms covering the whole tree of life. Multiple alignment of these sequences revealed an extremely high level of evolutionary conservation, including a winged-helix protein segment, here denoted as Zτ, constituting the putative structural homolog of Zα, the canonical Z-DNA/Z-RNA binding domain previously identified in the interferon-inducible RNA Adenosine-to-Inosine-editing deaminase, ADAR1p150. In contrast to Zα, which is separate from the protein segment responsible for catalysis, Zτ encompasses the active site tyrosine of topoII; a GTP-binding site and a GxxG sequence motif are in close proximity. Quantitative Zτ-Zα similarity comparisons and molecular docking with interaction scoring further supported the "B-Z-topoII hypothesis" and has led to an expanded mechanism for topoII function incorporating the recognition of Z-DNA segments ("Z-flipons") as an inherent and essential element. We further propose that the two Zτ domains of the topoII homodimer exhibit a single-turnover "conformase" activity on given G(ate) B-DNA segments ("Z-flipins"), inducing their transition to the left-handed Z-conformation. Inasmuch as the topoII-Z-DNA complexes are isomerase inactive, we infer that they fulfill important structural roles in key processes such as mitosis. Topoisomerases are preeminent targets of anti-cancer drug discovery, and we anticipate that detailed elucidation of their structural-functional interactions with Z-DNA and GTP will facilitate the design of novel, more potent and selective anti-cancer chemotherapeutic agents.
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Affiliation(s)
- Martin Bartas
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Kristyna Slychko
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Jiří Červeň
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Petr Pečinka
- Department of Biology and Ecology, University of Ostrava, 710 00 Ostrava, Czech Republic
| | - Donna J Arndt-Jovin
- Emeritus Laboratory of Cellular Dynamics, Max Planck Institute for Multidisciplinary Sciences, 37077 Göttingen, Germany
| | - Thomas M Jovin
- Emeritus Laboratory of Cellular Dynamics, Max Planck Institute for Multidisciplinary Sciences, 37077 Göttingen, Germany
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3
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Galvin CJ, Hobson M, Meng JX, Ierokomos A, Ivanov IE, Berger JM, Bryant Z. Single-molecule dynamics of DNA gyrase in evolutionarily distant bacteria Mycobacterium tuberculosis and Escherichia coli. J Biol Chem 2023; 299:103003. [PMID: 36775125 PMCID: PMC10130225 DOI: 10.1016/j.jbc.2023.103003] [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: 05/18/2022] [Revised: 02/06/2023] [Accepted: 02/07/2023] [Indexed: 02/12/2023] Open
Abstract
DNA gyrase is an essential nucleoprotein motor present in all bacteria and is a major target for antibiotic treatment of Mycobacterium tuberculosis (MTB) infection. Gyrase hydrolyzes ATP to add negative supercoils to DNA using a strand passage mechanism that has been investigated using biophysical and biochemical approaches. To analyze the dynamics of substeps leading to strand passage, single-molecule rotor bead tracking (RBT) has been used previously to follow real-time supercoiling and conformational transitions in Escherichia coli (EC) gyrase. However, RBT has not yet been applied to gyrase from other pathogenically relevant bacteria, and it is not known whether substeps are conserved across evolutionarily distant species. Here, we compare gyrase supercoiling dynamics between two evolutionarily distant bacterial species, MTB and EC. We used RBT to measure supercoiling rates, processivities, and the geometries and transition kinetics of conformational states of purified gyrase proteins in complex with DNA. Our results show that E. coli and MTB gyrases are both processive, with the MTB enzyme displaying velocities ∼5.5× slower than the EC enzyme. Compared with EC gyrase, MTB gyrase also more readily populates an intermediate state with DNA chirally wrapped around the enzyme, in both the presence and absence of ATP. Our substep measurements reveal common features in conformational states of EC and MTB gyrases interacting with DNA but also suggest differences in populations and transition rates that may reflect distinct cellular needs between these two species.
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Affiliation(s)
- Cooper J Galvin
- Program in Biophysics, Stanford University, Stanford, California, USA; Department of Bioengineering, Stanford University, Stanford, California, USA
| | - Matthew Hobson
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | | | - Athena Ierokomos
- Program in Biophysics, Stanford University, Stanford, California, USA; Department of Bioengineering, Stanford University, Stanford, California, USA
| | - Ivan E Ivanov
- Department of Bioengineering, Stanford University, Stanford, California, USA; Department of Chemical Engineering, Stanford University, Stanford, California, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Zev Bryant
- Program in Biophysics, Stanford University, Stanford, California, USA; Department of Bioengineering, Stanford University, Stanford, California, USA; Department of Structural Biology, Stanford University Medical Center, Stanford, California, USA.
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4
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Michieletto D, Fosado YAG, Melas E, Baiesi M, Tubiana L, Orlandini E. Dynamic and facilitated binding of topoisomerase accelerates topological relaxation. Nucleic Acids Res 2022; 50:4659-4668. [PMID: 35474478 PMCID: PMC9071436 DOI: 10.1093/nar/gkac260] [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: 10/18/2021] [Revised: 03/28/2022] [Accepted: 04/21/2022] [Indexed: 12/24/2022] Open
Abstract
How type 2 Topoisomerase (TopoII) proteins relax and simplify the topology of DNA molecules is one of the most intriguing open questions in genome and DNA biophysics. Most of the existing models neglect the dynamics of TopoII which is expected of proteins searching their targets via facilitated diffusion. Here, we show that dynamic binding of TopoII speeds up the topological relaxation of knotted substrates by enhancing the search of the knotted arc. Intriguingly, this in turn implies that the timescale of topological relaxation is virtually independent of the substrate length. We then discover that considering binding biases due to facilitated diffusion on looped substrates steers the sampling of the topological space closer to the boundaries between different topoisomers yielding an optimally fast topological relaxation. We discuss our findings in the context of topological simplification in vitro and in vivo.
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Affiliation(s)
| | | | - Elias Melas
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - Marco Baiesi
- Department of Physics and Astronomy, University of Padova, Via Marzolo 8, I-35131 Padova, Italy,INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padova, Italy
| | - Luca Tubiana
- Physics Department, University of Trento, via Sommarive 14, I-38123 Trento, Italy,INFN-TIFPA, Trento Institute for Fundamental Physics and Applications, I-38123 Trento, Italy,Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
| | - Enzo Orlandini
- Department of Physics and Astronomy, University of Padova, Via Marzolo 8, I-35131 Padova, Italy,INFN, Sezione di Padova, Via Marzolo 8, I-35131 Padova, Italy
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5
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McKie SJ, Desai P, Seol Y, Allen AM, Maxwell A, Neuman KC. Topoisomerase VI is a chirally-selective, preferential DNA decatenase. eLife 2022; 11:67021. [PMID: 35076393 PMCID: PMC8837201 DOI: 10.7554/elife.67021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 01/24/2022] [Indexed: 11/28/2022] Open
Abstract
DNA topoisomerase VI (topo VI) is a type IIB DNA topoisomerase found predominantly in archaea and some bacteria, but also in plants and algae. Since its discovery, topo VI has been proposed to be a DNA decatenase; however, robust evidence and a mechanism for its preferential decatenation activity was lacking. Using single-molecule magnetic tweezers measurements and supporting ensemble biochemistry, we demonstrate that Methanosarcina mazei topo VI preferentially unlinks, or decatenates DNA crossings, in comparison to relaxing supercoils, through a preference for certain DNA crossing geometries. In addition, topo VI demonstrates a significant increase in ATPase activity, DNA binding and rate of strand passage, with increasing DNA writhe, providing further evidence that topo VI is a DNA crossing sensor. Our study strongly suggests that topo VI has evolved an intrinsic preference for the unknotting and decatenation of interlinked chromosomes by sensing and preferentially unlinking DNA crossings with geometries close to 90°.
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Affiliation(s)
- Shannon J McKie
- Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Parth Desai
- Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Yeonee Seol
- Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Adam Mb Allen
- Department of Biochemistry and Metabolism, John Innes Centre, Norwich, United Kingdom
| | - Anthony Maxwell
- Department of Biochemistry and Metabolism, John Innes Centre, Norwich, United Kingdom
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, United States
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6
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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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7
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DNA-Topology Simplification by Topoisomerases. Molecules 2021; 26:molecules26113375. [PMID: 34204901 PMCID: PMC8199745 DOI: 10.3390/molecules26113375] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/20/2021] [Accepted: 05/26/2021] [Indexed: 11/17/2022] Open
Abstract
The topological properties of DNA molecules, supercoiling, knotting, and catenation, are intimately connected with essential biological processes, such as gene expression, replication, recombination, and chromosome segregation. Non-trivial DNA topologies present challenges to the molecular machines that process and maintain genomic information, for example, by creating unwanted DNA entanglements. At the same time, topological distortion can facilitate DNA-sequence recognition through localized duplex unwinding and longer-range loop-mediated interactions between the DNA sequences. Topoisomerases are a special class of essential enzymes that homeostatically manage DNA topology through the passage of DNA strands. The activities of these enzymes are generally investigated using circular DNA as a model system, in which case it is possible to directly assay the formation and relaxation of DNA supercoils and the formation/resolution of knots and catenanes. Some topoisomerases use ATP as an energy cofactor, whereas others act in an ATP-independent manner. The free energy of ATP hydrolysis can be used to drive negative and positive supercoiling or to specifically relax DNA topologies to levels below those that are expected at thermodynamic equilibrium. The latter activity, which is known as topology simplification, is thus far exclusively associated with type-II topoisomerases and it can be understood through insight into the detailed non-equilibrium behavior of type-II enzymes. We use a non-equilibrium topological-network approach, which stands in contrast to the equilibrium models that are conventionally used in the DNA-topology field, to gain insights into the rates that govern individual transitions between topological states. We anticipate that our quantitative approach will stimulate experimental work and the theoretical/computational modeling of topoisomerases and similar enzyme systems.
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8
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Ziraldo R, Hanke A, Levene SD. Kinetic pathways of topology simplification by Type-II topoisomerases in knotted supercoiled DNA. Nucleic Acids Res 2019; 47:69-84. [PMID: 30476194 PMCID: PMC6326819 DOI: 10.1093/nar/gky1174] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/02/2018] [Indexed: 11/13/2022] Open
Abstract
The topological state of covalently closed, double-stranded DNA is defined by the knot type $K$ and the linking-number difference $\Delta Lk$ relative to unknotted relaxed DNA. DNA topoisomerases are essential enzymes that control the topology of DNA in all cells. In particular, type-II topoisomerases change both $K$ and $\Delta Lk$ by a duplex-strand-passage mechanism and have been shown to simplify the topology of DNA to levels below thermal equilibrium at the expense of ATP hydrolysis. It remains a key question how small enzymes are able to preferentially select strand passages that result in topology simplification in much larger DNA molecules. Using numerical simulations, we consider the non-equilibrium dynamics of transitions between topological states $(K,\Delta Lk)$ in DNA induced by type-II topoisomerases. For a biological process that delivers DNA molecules in a given topological state $(K,\Delta Lk)$ at a constant rate we fully characterize the pathways of topology simplification by type-II topoisomerases in terms of stationary probability distributions and probability currents on the network of topological states $(K,\Delta Lk)$. In particular, we observe that type-II topoisomerase activity is significantly enhanced in DNA molecules that maintain a supercoiled state with constant torsional tension. This is relevant for bacterial cells in which torsional tension is maintained by enzyme-dependent homeostatic mechanisms such as DNA-gyrase activity.
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Affiliation(s)
- Riccardo Ziraldo
- Department of Bioengineering, University of Texas at Dallas, TX 75080, USA
| | - Andreas Hanke
- Department of Physics and Astronomy, University of Texas Rio Grande Valley, Brownsville, TX 78520, USA
| | - Stephen D Levene
- Department of Bioengineering, University of Texas at Dallas, TX 75080, USA.,Department of Biological Sciences, University of Texas at Dallas, Richardson, TX 75080, USA.,Department of Physics, University of Texas at Dallas, Richardson, TX 75080, USA
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9
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Jang Y, Son H, Lee SW, Hwang W, Jung SR, Byl JAW, Osheroff N, Lee S. Selection of DNA Cleavage Sites by Topoisomerase II Results from Enzyme-Induced Flexibility of DNA. Cell Chem Biol 2019; 26:502-511.e3. [PMID: 30713098 DOI: 10.1016/j.chembiol.2018.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 10/04/2018] [Accepted: 12/04/2018] [Indexed: 12/26/2022]
Abstract
Topoisomerase II cleaves DNA at preferred sequences with different efficiencies; however, the mechanism of cleavage site selection is not known. Here we used single-molecule fluorescence assays that monitor several critical steps of DNA-topoisomerase II interactions, including binding/dissociation, bending/straightening, and cleavage/religation, and reveal that the cleavage site is selected mainly during the bending step. Furthermore, despite the sensitivity of the bending rate to the DNA sequence, it is not an intrinsic property of the DNA itself. Rather, it is determined by protein-DNA interactions.
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Affiliation(s)
- Yunsu Jang
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea
| | - Heyjin Son
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea
| | - Sang-Wook Lee
- Department of Physics and Astronomy, National Center for Creative Research Initiatives, Seoul National University, Seoul 08826, South Korea
| | - Wonseok Hwang
- Department of Physics and Astronomy, National Center for Creative Research Initiatives, Seoul National University, Seoul 08826, South Korea
| | - Seung-Ryoung Jung
- Department of Physics and Astronomy, National Center for Creative Research Initiatives, Seoul National University, Seoul 08826, South Korea
| | - Jo Ann W Byl
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Neil Osheroff
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA; Department of Medicine (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA; VA Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
| | - Sanghwa Lee
- Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 61005, South Korea.
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10
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Basu A, Hobson M, Lebel P, Fernandes LE, Tretter EM, Berger JM, Bryant Z. Dynamic coupling between conformations and nucleotide states in DNA gyrase. Nat Chem Biol 2018; 14:565-574. [PMID: 29662209 PMCID: PMC10121156 DOI: 10.1038/s41589-018-0037-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 02/21/2018] [Indexed: 11/09/2022]
Abstract
Gyrase is an essential bacterial molecular motor that supercoils DNA using a conformational cycle in which chiral wrapping of > 100 base pairs confers directionality on topoisomerization. To understand the mechanism of this nucleoprotein machine, global structural transitions must be mapped onto the nucleotide cycle of ATP binding, hydrolysis and product release. Here we investigate coupling mechanisms using single-molecule tracking of DNA rotation and contraction during Escherichia coli gyrase activity under varying nucleotide conditions. We find that ADP must be exchanged for ATP to drive the rate-limiting remodeling transition that generates the chiral wrap. ATP hydrolysis accelerates subsequent duplex strand passage and is required for resetting the enzyme and recapturing transiently released DNA. Our measurements suggest how gyrase coordinates DNA rearrangements with the dynamics of its ATP-driven protein gate, how the motor minimizes futile cycles of ATP hydrolysis and how gyrase may respond to changing cellular energy levels to link gene expression with metabolism.
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Affiliation(s)
- Aakash Basu
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,Department of Bioengineering, Stanford University, Stanford, CA, USA.,Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Matthew Hobson
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD, USA
| | - Paul Lebel
- Department of Applied Physics, Stanford University, Stanford, CA, USA.,Department of Bioengineering, Stanford University, Stanford, CA, USA.,Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Louis E Fernandes
- Department of Bioengineering, Stanford University, Stanford, CA, USA.,Program in Biophysics, Stanford University, Stanford, CA, USA.,Tempus, Inc., Chicago, IL, USA
| | - Elsa M Tretter
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.,Nurix Inc., San Francisco, CA, USA
| | - James M Berger
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Zev Bryant
- Department of Bioengineering, Stanford University, Stanford, CA, USA. .,Department of Structural Biology, Stanford University Medical Center, Stanford, CA, USA.
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11
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Dataset on the effects of spermidine on linking number differences between histone H1-free and histone H1-bound circular polynucleosomes. Data Brief 2018; 17:709-715. [PMID: 29511714 PMCID: PMC5832644 DOI: 10.1016/j.dib.2018.01.091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 11/02/2017] [Accepted: 01/30/2018] [Indexed: 11/27/2022] Open
Abstract
The data presented in this article are related to the research article entitled "Quantitative determination of linking number differences between circular polynucleosomes and histone H1-bound circular polynucleosomes" Zhang et al. (in press) [1]. DNA linking number differences between histone H1-free and histone H1-bound circular polynucleosomes at various spermidine concentrations was quantitatively determined by chloroquine-based gel electrophoretic analysis in this work, which provides information on the topological effects of histone H1 and spermidine on the linker DNA between nucleosomes.
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12
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Hede MS, Fjelstrup S, Lötsch F, Zoleko RM, Klicpera A, Groger M, Mischlinger J, Endame L, Veletzky L, Neher R, Simonsen AKW, Petersen E, Mombo-Ngoma G, Stougaard M, Ho YP, Labouriau R, Ramharter M, Knudsen BR. Detection of the Malaria causing Plasmodium Parasite in Saliva from Infected Patients using Topoisomerase I Activity as a Biomarker. Sci Rep 2018. [PMID: 29515150 PMCID: PMC5841400 DOI: 10.1038/s41598-018-22378-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Malaria is among the major threats to global health with the main burden of disease being in rural areas of developing countries where accurate diagnosis based on non-invasive samples is in high demand. We here present a novel molecular assay for detection of malaria parasites based on technology that may be adapted for low-resource settings. Moreover, we demonstrate the exploitation of this assay for detection of malaria in saliva. The setup relies on pump-free microfluidics enabled extraction combined with a DNA sensor substrate that is converted to a single-stranded DNA circle specifically by topoisomerase I expressed by the malaria causing Plasmodium parasite. Subsequent rolling circle amplification of the generated DNA circle in the presence of biotin conjugated deoxynucleotides resulted in long tandem repeat products that was visualized colorimetrically upon binding of horse radish peroxidase (HRP) and addition of 3,3′,5,5′-Tetramethylbenzidine that was converted to a blue colored product by HRP. The assay was directly quantitative, specific for Plasmodium parasites, and allowed detection of Plasmodium infection in a single drop of saliva from 35 out of 35 infected individuals tested. The results could be determined directly by the naked eye and documented by quantifying the color intensity using a standard paper scanner.
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Affiliation(s)
| | - Søren Fjelstrup
- Department of Molecular Biology and Genetics, University of Aarhus, Aarhus, Denmark
| | - Felix Lötsch
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.,Department of Medicine, I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria
| | | | - Anna Klicpera
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Mirjam Groger
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Johannes Mischlinger
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.,Department of Medicine, I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria.,Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany
| | - Lilian Endame
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Luzia Veletzky
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon
| | - Ronja Neher
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.,Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany
| | | | - Eskild Petersen
- Department of Infectious Diseases, Aarhus University Hospital, Aarhus, Denmark.,Department of Infectious Diseases, The Royal Hospital, Muscat, Oman
| | - Ghyslain Mombo-Ngoma
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.,Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany
| | - Magnus Stougaard
- Department of Clinical Medicine, University of Aarhus, Aarhus, Denmark
| | - Yi-Ping Ho
- Division of Biomedical Engineering, Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China
| | | | - Michael Ramharter
- Centre de Recherches Médicales de Lambaréné, Lambaréné, Gabon.,Department of Medicine, I, Division of Infectious Diseases and Tropical Medicine, Medical University of Vienna, Vienna, Austria.,Institut für Tropenmedizin, Universität Tübingen, Tübingen, Germany
| | - Birgitta Ruth Knudsen
- Department of Molecular Biology and Genetics, University of Aarhus, Aarhus, Denmark.
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13
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Quantitative determination of linking number differences between circular polynucleosomes and histone H1-bound circular polynucleosomes. Bioorg Med Chem Lett 2018; 28:537-540. [DOI: 10.1016/j.bmcl.2017.10.072] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 10/26/2017] [Accepted: 10/28/2017] [Indexed: 11/21/2022]
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14
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Ashley RE, Dittmore A, McPherson SA, Turnbough CL, Neuman KC, Osheroff N. Activities of gyrase and topoisomerase IV on positively supercoiled DNA. Nucleic Acids Res 2017; 45:9611-9624. [PMID: 28934496 PMCID: PMC5766186 DOI: 10.1093/nar/gkx649] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 07/14/2017] [Indexed: 11/12/2022] Open
Abstract
Although bacterial gyrase and topoisomerase IV have critical interactions with positively supercoiled DNA, little is known about the actions of these enzymes on overwound substrates. Therefore, the abilities of Bacillus anthracis and Escherichia coli gyrase and topoisomerase IV to relax and cleave positively supercoiled DNA were analyzed. Gyrase removed positive supercoils ∼10-fold more rapidly and more processively than it introduced negative supercoils into relaxed DNA. In time-resolved single-molecule measurements, gyrase relaxed overwound DNA with burst rates of ∼100 supercoils per second (average burst size was 6.2 supercoils). Efficient positive supercoil removal required the GyrA-box, which is necessary for DNA wrapping. Topoisomerase IV also was able to distinguish DNA geometry during strand passage and relaxed positively supercoiled substrates ∼3-fold faster than negatively supercoiled molecules. Gyrase maintained lower levels of cleavage complexes with positively supercoiled (compared with negatively supercoiled) DNA, whereas topoisomerase IV generated similar levels with both substrates. Results indicate that gyrase is better suited than topoisomerase IV to safely remove positive supercoils that accumulate ahead of replication forks. They also suggest that the wrapping mechanism of gyrase may have evolved to promote rapid removal of positive supercoils, rather than induction of negative supercoils.
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Affiliation(s)
- Rachel E Ashley
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA
| | - Andrew Dittmore
- Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20982, USA
| | - Sylvia A McPherson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Charles L Turnbough
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20982, USA
| | - Neil Osheroff
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.,VA Tennessee Valley Healthcare System, Nashville, TN 37212, USA.,Department of Medicine (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, TN 37232-6307, USA
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15
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Kristoffersen EL, Givskov A, Jørgensen LA, Jensen PW, W Byl JA, Osheroff N, Andersen AH, Stougaard M, Ho YP, Knudsen BR. Interlinked DNA nano-circles for measuring topoisomerase II activity at the level of single decatenation events. Nucleic Acids Res 2017; 45:7855-7869. [PMID: 28541438 PMCID: PMC5570003 DOI: 10.1093/nar/gkx480] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 05/22/2017] [Indexed: 12/23/2022] Open
Abstract
DNA nano-structures present appealing new means for monitoring different molecules. Here, we demonstrate the assembly and utilization of a surface-attached double-stranded DNA catenane composed of two intact interlinked DNA nano-circles for specific and sensitive measurements of the life essential topoisomerase II (Topo II) enzyme activity. Topo II activity was detected via the numeric release of DNA nano-circles, which were visualized at the single-molecule level in a fluorescence microscope upon isothermal amplification and fluorescence labeling. The transition of each enzymatic reaction to a micrometer sized labeled product enabled quantitative detection of Topo II activity at the single decatenation event level rendering activity measurements in extracts from as few as five cells possible. Topo II activity is a suggested predictive marker in cancer therapy and, consequently, the described highly sensitive monitoring of Topo II activity may add considerably to the toolbox of individualized medicine where decisions are based on very sparse samples.
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Affiliation(s)
- Emil L Kristoffersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark.,Interdisciplinary Nanoscience Center - iNANO, Aarhus University, 8000 Aarhus C, Denmark
| | - Asger Givskov
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Line A Jørgensen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Pia W Jensen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Jo Ann W Byl
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Neil Osheroff
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.,VA Tennessee Valley Healthcare System, Nashville, TN 37212, USA
| | - Anni H Andersen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark
| | - Magnus Stougaard
- Department of Pathology, Aarhus University Hospital, 8000 Aarhus C, Denmark
| | - Yi-Ping Ho
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark.,Interdisciplinary Nanoscience Center - iNANO, Aarhus University, 8000 Aarhus C, Denmark.,Division of Biomedical Engineering, Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China
| | - Birgitta R Knudsen
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus C, Denmark.,Interdisciplinary Nanoscience Center - iNANO, Aarhus University, 8000 Aarhus C, Denmark
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16
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Beckwitt EC, Kong M, Van Houten B. Studying protein-DNA interactions using atomic force microscopy. Semin Cell Dev Biol 2017; 73:220-230. [PMID: 28673677 DOI: 10.1016/j.semcdb.2017.06.028] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 06/27/2017] [Accepted: 06/29/2017] [Indexed: 12/12/2022]
Abstract
Atomic force microscopy (AFM) has made significant contributions to the study of protein-DNA interactions by making it possible to topographically image biological samples. A single protein-DNA binding reaction imaged by AFM can reveal protein binding specificity and affinity, protein-induced DNA bending, and protein binding stoichiometry. Changes in DNA structure, complex conformation, and cooperativity, can also be analyzed. In this review we highlight some important examples in the literature and discuss the advantages and limitations of these measurements. We also discuss important advances in technology that will facilitate the progress of AFM in the future.
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Affiliation(s)
- Emily C Beckwitt
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA
| | - Muwen Kong
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA
| | - Bennett Van Houten
- Program in Molecular Biophysics and Structural Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA; The University of Pittsburgh Cancer Institute, Hillman Cancer Center, Pittsburgh, PA 15213, USA; Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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17
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Huang WC, Lee CY, Hsieh TS. Single-molecule Förster resonance energy transfer (FRET) analysis discloses the dynamics of the DNA-topoisomerase II (Top2) interaction in the presence of TOP2-targeting agents. J Biol Chem 2017. [PMID: 28630044 DOI: 10.1074/jbc.m117.792861] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Topoisomerases play crucial roles in DNA replication, transcription, and recombination. For instance, topoisomerase II (Top2) is critically important for resolving DNA tangles during cell division, and as such, it is a broad anticancer drug target. Top2 regulates DNA topology by transiently breaking one double-stranded DNA molecule (cleavage), allowing a second double strand to pass through the opened DNA gate (opening), and then closing the gate by rejoining the broken ends. Drugs that modulate Top2 catalysis may therefore affect enzymatic activity at several different steps. Previous studies have focused on examining DNA cleavage and ligation; however, the dynamic opening and closing of the DNA gate has been less explored. Here, we used the single-molecule Förster resonance energy transfer (smFRET) method to observe the open and closed state of the DNA gate and to measure dwell times in each state. Our results show that Top2 binds and bends DNA to increase the energy transfer efficiency (EFRET), and ATP treatment further induces the fluctuation of EFRET, representing the gate opening and closing. Additionally, our results demonstrate that both types of Top2-targeting anticancer drugs, the catalytic inhibitor dexrazoxane (ICRF187) and mechanistic poison teniposide (VM26), can interfere with DNA gate dynamics and shorten the dwell time in the closed state. Moreover, Top2 bound to the nonhydrolyzable ATP analog 5'-adenylyl-β,γ-imidodiphosphate exhibits altered DNA gate dynamics, but the DNA gate appears to open and close even after N-gate closure. In summary, we have utilized single-molecule detection to unravel Top2 DNA gate dynamics and reveal previously unknown effects of Top2 drugs on these dynamics.
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Affiliation(s)
- Wan-Chen Huang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan.
| | - Chun-Ying Lee
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan; Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
| | - Tao-Shih Hsieh
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei 115, Taiwan; Department of Chemistry, National Taiwan University, Taipei 106, Taiwan; Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
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18
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Optimized Detection of Plasmodium falciparum Topoisomerase I Enzyme Activity in a Complex Biological Sample by the Use of Molecular Beacons. SENSORS 2016; 16:s16111916. [PMID: 27854277 PMCID: PMC5134575 DOI: 10.3390/s16111916] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 10/31/2016] [Accepted: 11/04/2016] [Indexed: 12/16/2022]
Abstract
The so-called Rolling Circle Amplification allows for amplification of circular DNA structures in a manner that can be detected in real-time using nucleotide-based molecular beacons that unfold upon recognition of the DNA product, which is being produced during the amplification process. The unfolding of the molecular beacons results in a fluorescence increase as the Rolling Circle Amplification proceeds. This can be measured in a fluorometer. In the current study, we have investigated the possibility of using two different molecular beacons to detect two distinct Rolling Circle Amplification reactions proceeding simultaneously and in the same reaction tube by measurement of fluorescence over time. We demonstrate the application of this fluorometric readout method, for automated and specific detection of the activity of the type IB topoisomerase from the malaria parasite Plasmodium falciparum in the presence of human cell extract containing the related topoisomerase I from humans. The obtained results point towards a future use of the presented assay setup for malaria diagnostics or drug screening purposes. In longer terms the method may be applied more broadly for real-time sensing of various Rolling Circle Amplification reactions.
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19
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Seol Y, Neuman KC. The dynamic interplay between DNA topoisomerases and DNA topology. Biophys Rev 2016; 8:101-111. [PMID: 28510219 DOI: 10.1007/s12551-016-0240-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 06/07/2016] [Indexed: 01/03/2023] Open
Abstract
Topological properties of DNA influence its structure and biochemical interactions. Within the cell, DNA topology is constantly in flux. Transcription and other essential processes, including DNA replication and repair, not only alter the topology of the genome but also introduce additional complications associated with DNA knotting and catenation. These topological perturbations are counteracted by the action of topoisomerases, a specialized class of highly conserved and essential enzymes that actively regulate the topological state of the genome. This dynamic interplay among DNA topology, DNA processing enzymes, and DNA topoisomerases is a pervasive factor that influences DNA metabolism in vivo. Building on the extensive structural and biochemical characterization over the past four decades that has established the fundamental mechanistic basis of topoisomerase activity, scientists have begun to explore the unique roles played by DNA topology in modulating and influencing the activity of topoisomerases. In this review we survey established and emerging DNA topology-dependent protein-DNA interactions with a focus on in vitro measurements of the dynamic interplay between DNA topology and topoisomerase activity.
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Affiliation(s)
- Yeonee Seol
- Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health, 50 South Dr., Room 3517, Bethesda, MD, 20892, USA
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health, 50 South Dr., Room 3517, Bethesda, MD, 20892, USA.
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20
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Roca J. In silico, in vitro and in vivo imageries of type II topoisomerases. Phys Life Rev 2016; 18:147-149. [DOI: 10.1016/j.plrev.2016.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 07/04/2016] [Indexed: 11/29/2022]
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21
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Abstract
Topological properties of DNA influence its structure and biochemical interactions. Within the cell DNA topology is constantly in flux. Transcription and other essential processes including DNA replication and repair, alter the topology of the genome, while introducing additional complications associated with DNA knotting and catenation. These topological perturbations are counteracted by the action of topoisomerases, a specialized class of highly conserved and essential enzymes that actively regulate the topological state of the genome. This dynamic interplay among DNA topology, DNA processing enzymes, and DNA topoisomerases, is a pervasive factor that influences DNA metabolism in vivo. Building on the extensive structural and biochemical characterization over the past four decades that established the fundamental mechanistic basis of topoisomerase activity, the unique roles played by DNA topology in modulating and influencing the activity of topoisomerases have begun to be explored. In this review we survey established and emerging DNA topology dependent protein-DNA interactions with a focus on in vitro measurements of the dynamic interplay between DNA topology and topoisomerase activity.
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Affiliation(s)
- Yeonee Seol
- Laboratory of Single Molecule Biophysics, NHLBI, National Institutes of Health, Bethesda, MD, 20892, U.S.A
| | - Keir C Neuman
- Laboratory of Single Molecule Biophysics, NHLBI, National Institutes of Health, Bethesda, MD, 20892, U.S.A
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22
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Vologodskii A. Disentangling DNA molecules. Phys Life Rev 2016; 18:118-134. [PMID: 27173054 DOI: 10.1016/j.plrev.2016.05.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 01/12/2023]
Abstract
The widespread circular form of DNA molecules inside cells creates very serious topological problems during replication. Due to the helical structure of the double helix the parental strands of circular DNA form a link of very high order, and yet they have to be unlinked before the cell division. DNA topoisomerases, the enzymes that catalyze passing of one DNA segment through another, solve this problem in principle. However, it is very difficult to remove all entanglements between the replicated DNA molecules due to huge length of DNA comparing to the cell size. One strategy that nature uses to overcome this problem is to create the topoisomerases that can dramatically reduce the fraction of linked circular DNA molecules relative to the corresponding fraction at thermodynamic equilibrium. This striking property of the enzymes means that the enzymes that interact with DNA only locally can access their topology, a global property of circular DNA molecules. This review considers the experimental studies of the phenomenon and analyzes the theoretical models that have been suggested in attempts to explain it. We describe here how various models of enzyme action can be investigated computationally. There is no doubt at the moment that we understand basic principles governing enzyme action. Still, there are essential quantitative discrepancies between the experimental data and the theoretical predictions. We consider how these discrepancies can be overcome.
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23
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Herbert KM, Sarkar SK, Mills M, Delgado De la Herran HC, Neuman KC, Steitz JA. A heterotrimer model of the complete Microprocessor complex revealed by single-molecule subunit counting. RNA (NEW YORK, N.Y.) 2016; 22:175-183. [PMID: 26683315 PMCID: PMC4712668 DOI: 10.1261/rna.054684.115] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 11/17/2015] [Indexed: 05/30/2023]
Abstract
During microRNA (miRNA) biogenesis, the Microprocessor complex (MC), composed minimally of Drosha, an RNaseIII enzyme, and DGCR8, a double-stranded RNA-binding protein, cleaves the primary-miRNA (pri-miRNA) to release the pre-miRNA stem-loop structure. Size-exclusion chromatography of the MC, isolated from mammalian cells, suggested multiple copies of one or both proteins in the complex. However, the exact stoichiometry was unknown. Initial experiments suggested that DGCR8 bound pri-miRNA substrates specifically, and given that Drosha could not be bound or cross-linked to RNA, a sequential model for binding was established in which DGCR8 bound first and recruited Drosha. Therefore, many laboratories have studied DGCR8 binding to RNA in the absence of Drosha and have shown that deletion constructs of DGCR8 can multimerize in the presence of RNA. More recently, it was demonstrated that Drosha can bind pri-miRNA substrates in the absence of DGCR8, casting doubt on the sequential model of binding. In the same study, using a single-molecule photobleaching assay, fluorescent protein-tagged deletion constructs of DGCR8 and Drosha assembled into a heterotrimeric complex on RNA, comprising two DGCR8 molecules and one Drosha molecule. To determine the stoichiometry of Drosha and DGCR8 within the MC in the absence of added RNA, we also used a single-molecule photobleaching assay and confirmed the heterotrimeric model of the human MC. We demonstrate that a heterotrimeric complex is likely preformed in the absence of RNA and exists even when full-length proteins are expressed and purified from human cells, and when hAGT-derived tags are used rather than fluorescent proteins.
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Affiliation(s)
- Kristina M Herbert
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Ensenada, Baja California 22860, Mexico
| | - Susanta K Sarkar
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Maria Mills
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Hilda C Delgado De la Herran
- Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Ensenada, Baja California 22860, Mexico
| | - Keir C Neuman
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Joan A Steitz
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06536, USA
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24
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Liu Z, Chan HS. Consistent rationalization of type-2 topoisomerases' unknotting, decatenating, supercoil-relaxing actions and their scaling relation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:354103. [PMID: 26291958 DOI: 10.1088/0953-8984/27/35/354103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
How type-2 topoisomerases discern global topology from local properties of DNA is not known precisely but the hypothesis that the enzymes selectively pass double-helix strands at hook-like juxtapositions is promising. Building upon an investigation of unknotting and decatenating using an improved wormlike DNA model, here we focus primarily on the enzymes' action in narrowing the distribution of linking number (Lk) in supercoiled DNA. Consistent with experiments, with selective passage at a hooked juxtaposition, the simulated narrowing factor RLk diminishes with decreasing DNA circle size but approaches an asymptotic RLk ≈ 1.7-1.8 for circle size ≳3.5 kb. For the larger DNA circles, we found that (RLk - 1) ≈ 0.42log10RK ≈ 0.68log10RL and thus RK ≈ (RL)(1.6) holds for the computed RLk and knot and catenane reduction factors RK and RL attained by selective passage at different juxtaposition geometries. Remarkably, this general scaling relation is essentially identical to that observed experimentally for several type-2 topoisomerases from a variety of organisms, indicating that the different disentangling powers of the topoisomerases likely arise from variations in the hooked geometries they select. Taken together, our results suggest strongly that type-2 topoisomerases recognize not only the curvature of the G-segment but also that of the T-segment.
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Affiliation(s)
- Zhirong Liu
- College of Chemistry and Molecular Engineering, Center for Quantitative Biology, and Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, People's Republic of China
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25
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Kristoffersen EL, Jørgensen LA, Franch O, Etzerodt M, Frøhlich R, Bjergbæk L, Stougaard M, Ho YP, Knudsen BR. Real-time investigation of human topoisomerase I reaction kinetics using an optical sensor: a fast method for drug screening and determination of active enzyme concentrations. NANOSCALE 2015; 7:9825-9834. [PMID: 25963854 DOI: 10.1039/c5nr01474c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Human DNA topoisomerase I (hTopI) is a nuclear enzyme that catalyzes relaxation of super helical tension that arises in the genome during essential DNA metabolic processes. This is accomplished through a common reaction mechanism shared among the type IB topoisomerase enzymes, including eukaryotic and poxvirus topoisomerase I. The mechanism of hTopI is specifically targeted in cancer treatment using camptothecin derivatives. These drugs convert the hTopI activity into a cellular poison, and hence the cytotoxic effects of camptothecin derivatives correlate with the hTopI activity. Therefore, fast and reliable techniques for high throughput measurements of hTopI activity are of high clinical interest. Here we demonstrate potential applications of a fluorophore-quencher based DNA sensor designed for measurement of hTopI cleavage-ligation activities, which are the catalytic steps affected by camptothecin. The kinetic analysis of the hTopI reaction with the DNA sensor exhibits a characteristic burst profile. This is the result of a two-step ping-pong reaction mechanism, where a fast first reaction, the one creating the signal, is followed by a slower second reaction necessary for completion of the catalytic cycle. Hence, the burst profile holds information about two reactions in the enzymatic mechanism. Moreover, it allows the amount of active enzyme in the reaction to be determined. The presented results pave the way for future high throughput drug screening and the potential of measuring active hTopI concentrations in clinical samples for individualized treatment.
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26
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E. coli Gyrase Fails to Negatively Supercoil Diaminopurine-Substituted DNA. J Mol Biol 2015; 427:2305-18. [PMID: 25902201 DOI: 10.1016/j.jmb.2015.04.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 03/06/2015] [Accepted: 04/10/2015] [Indexed: 12/18/2022]
Abstract
Type II topoisomerases modify DNA supercoiling, and crystal structures suggest that they sharply bend DNA in the process. Bacterial gyrases are a class of type II topoisomerases that can introduce negative supercoiling by creating a wrap of DNA before strand passage. Isoforms of these essential enzymes were compared to reveal whether they can bend or wrap artificially stiffened DNA. Escherichia coli gyrase and human topoisomerase IIα were challenged with normal DNA or stiffer DNA produced by polymerase chain reaction reactions in which diaminopurine (DAP) replaced adenine deoxyribonucleotide triphosphates. On single DNA molecules twisted with magnetic tweezers to create plectonemes, the rates or pauses during relaxation of positive supercoils in DAP-substituted versus normal DNA were distinct for both enzymes. Gyrase struggled to bend or perhaps open a gap in DAP-substituted DNA, and segments of wider DAP DNA may have fit poorly into the N-gate of the human topoisomerase IIα. Pauses during processive activity on both types of DNA exhibited ATP dependence consistent with two pathways leading to the strand-passage-competent state with a bent gate segment and a transfer segment trapped by an ATP-loaded and latched N-gate. However, E. coli DNA gyrase essentially failed to negatively supercoil 35% stiffer DAP DNA.
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27
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Colomb W, Sarkar SK. Extracting physics of life at the molecular level: A review of single-molecule data analyses. Phys Life Rev 2015; 13:107-37. [PMID: 25660417 DOI: 10.1016/j.plrev.2015.01.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 01/09/2015] [Indexed: 12/31/2022]
Abstract
Studying individual biomolecules at the single-molecule level has proved very insightful recently. Single-molecule experiments allow us to probe both the equilibrium and nonequilibrium properties as well as make quantitative connections with ensemble experiments and equilibrium thermodynamics. However, it is important to be careful about the analysis of single-molecule data because of the noise present and the lack of theoretical framework for processes far away from equilibrium. Biomolecular motion, whether it is free in solution, on a substrate, or under force, involves thermal fluctuations in varying degrees, which makes the motion noisy. In addition, the noise from the experimental setup makes it even more complex. The details of biologically relevant interactions, conformational dynamics, and activities are hidden in the noisy single-molecule data. As such, extracting biological insights from noisy data is still an active area of research. In this review, we will focus on analyzing both fluorescence-based and force-based single-molecule experiments and gaining biological insights at the single-molecule level. Inherently nonequilibrium nature of biological processes will be highlighted. Simulated trajectories of biomolecular diffusion will be used to compare and validate various analysis techniques.
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Affiliation(s)
- Warren Colomb
- Department of Physics, Colorado School of Mines, Golden, CO 80401, United States
| | - Susanta K Sarkar
- Department of Physics, Colorado School of Mines, Golden, CO 80401, United States.
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28
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Litwin TR, Solà M, Holt IJ, Neuman KC. A robust assay to measure DNA topology-dependent protein binding affinity. Nucleic Acids Res 2014; 43:e43. [PMID: 25552413 PMCID: PMC4402506 DOI: 10.1093/nar/gku1381] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Accepted: 12/18/2014] [Indexed: 02/04/2023] Open
Abstract
DNA structure and topology pervasively influence aspects of DNA metabolism including replication, transcription and segregation. However, the effects of DNA topology on DNA-protein interactions have not been systematically explored due to limitations of standard affinity assays. We developed a method to measure protein binding affinity dependence on the topology (topological linking number) of supercoiled DNA. A defined range of DNA topoisomers at equilibrium with a DNA binding protein is separated into free and protein-bound DNA populations using standard nitrocellulose filter binding techniques. Electrophoretic separation and quantification of bound and free topoisomers combined with a simple normalization procedure provide the relative affinity of the protein for the DNA as a function of linking number. Employing this assay we measured topology-dependent DNA binding of a helicase, a type IB topoisomerase, a type IIA topoisomerase, a non-specific mitochondrial DNA binding protein and a type II restriction endonuclease. Most of the proteins preferentially bind negatively supercoiled DNA but the details of the topology-dependent affinity differ among proteins in ways that expose differences in their interactions with DNA. The topology-dependent binding assay provides a robust and easily implemented method to probe topological influences on DNA-protein interactions for a wide range of DNA binding proteins.
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Affiliation(s)
- Tamara R Litwin
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA Mitochondrial Biology Unit, Medical Research Council, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Maria Solà
- Department of Structural Biology, Molecular Biology Institute of Barcelona (CSIC), 08028 Barcelona, Spain
| | - Ian J Holt
- National Institute for Medical Research, Medical Research Council, The Ridgeway, Mill Hill, London, NW7 1AA, UK
| | - Keir C Neuman
- National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20814, USA
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29
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Mazur AK, Maaloum M. Atomic force microscopy study of DNA flexibility on short length scales: smooth bending versus kinking. Nucleic Acids Res 2014; 42:14006-12. [PMID: 25414337 PMCID: PMC4267637 DOI: 10.1093/nar/gku1192] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The apparently anomalous flexibility of DNA on short length scales has attracted a lot of attention in recent years. We use atomic force microscopy (AFM) in solution to directly study the DNA bending statistics for small lengths down to one helical turn. The accuracy of experimental estimates could be improved due to a large data volume and a refined algorithm for image processing and measuring bend angles. It is found that, at length scales beyond two helical turns (7 nm), DNA is well described by the harmonic worm-like chain (WLC) model with the bending persistence length of 56 nm. Below this threshold, the AFM data are also described by the WLC model assuming that the accuracy of measured bend angles is limited by the physical width of the double helix. We conclude that the double helical DNA behaves as a uniform elastic rod even at very short length scales. Strong bends due to kinks, melting bubbles and other deviations from the WLC model are statistically negligible.
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Affiliation(s)
- Alexey K Mazur
- UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 13, rue Pierre et Marie Curie, Paris 75005, France
| | - Mounir Maaloum
- Institut Charles Sadron, CNRS-University of Strasbourg, 23 rue du Loess, BP 84087, 67034 Strasbourg Cedex 2, France
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Aldred KJ, Breland EJ, Vlčková V, Strub MP, Neuman KC, Kerns RJ, Osheroff N. Role of the water-metal ion bridge in mediating interactions between quinolones and Escherichia coli topoisomerase IV. Biochemistry 2014; 53:5558-67. [PMID: 25115926 PMCID: PMC4151693 DOI: 10.1021/bi500682e] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
Although
quinolones have been in clinical use for decades, the
mechanism underlying drug activity and resistance has remained elusive.
However, recent studies indicate that clinically relevant quinolones
interact with Bacillus anthracis (Gram-positive)
topoisomerase IV through a critical water–metal ion bridge
and that the most common quinolone resistance mutations decrease drug
activity by disrupting this bridge. As a first step toward determining
whether the water–metal ion bridge is a general mechanism of
quinolone–topoisomerase interaction, we characterized drug
interactions with wild-type Escherichia coli (Gram-negative)
topoisomerase IV and a series of ParC enzymes with mutations (S80L,
S80I, S80F, and E84K) in the predicted bridge-anchoring residues.
Results strongly suggest that the water–metal ion bridge is
essential for quinolone activity against E. coli topoisomerase
IV. Although the bridge represents a common and critical mechanism
that underlies broad-spectrum quinolone function, it appears to play
different roles in B. anthracis and E. coli topoisomerase IV. The water–metal ion bridge is the most
important binding contact of clinically relevant quinolones with the
Gram-positive enzyme. However, it primarily acts to properly align
clinically relevant quinolones with E. coli topoisomerase
IV. Finally, even though ciprofloxacin is unable to increase levels
of DNA cleavage mediated by several of the Ser80 and Glu84 mutant E. coli enzymes, the drug still retains the ability to inhibit
the overall catalytic activity of these topoisomerase IV proteins.
Inhibition parallels drug binding, suggesting that the presence of
the drug in the active site is sufficient to diminish DNA relaxation
rates.
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Affiliation(s)
- Katie J Aldred
- Department of Biochemistry and ‡Department of Medicine (Hematology/Oncology), Vanderbilt University School of Medicine , Nashville, Tennessee 37232-0146, United States
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31
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Thomson NH, Santos S, Mitchenall LA, Stuchinskaya T, Taylor JA, Maxwell A. DNA G-segment bending is not the sole determinant of topology simplification by type II DNA topoisomerases. Sci Rep 2014; 4:6158. [PMID: 25142513 PMCID: PMC4139952 DOI: 10.1038/srep06158] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/04/2014] [Indexed: 11/28/2022] Open
Abstract
DNA topoisomerases control the topology of DNA. Type II topoisomerases exhibit topology simplification, whereby products of their reactions are simplified beyond that expected based on thermodynamic equilibrium. The molecular basis for this process is unknown, although DNA bending has been implicated. To investigate the role of bending in topology simplification, the DNA bend angles of four enzymes of different types (IIA and IIB) were measured using atomic force microscopy (AFM). The enzymes tested were Escherichia coli topo IV and yeast topo II (type IIA enzymes that exhibit topology simplification), and Methanosarcina mazei topo VI and Sulfolobus shibatae topo VI (type IIB enzymes, which do not). Bend angles were measured using the manual tangent method from topographical AFM images taken with a novel amplitude-modulated imaging mode: small amplitude small set-point (SASS), which optimises resolution for a given AFM tip size and minimises tip convolution with the sample. This gave improved accuracy and reliability and revealed that all 4 topoisomerases bend DNA by a similar amount: ~120° between the DNA entering and exiting the enzyme complex. These data indicate that DNA bending alone is insufficient to explain topology simplification and that the ‘exit gate' may be an important determinant of this process.
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Affiliation(s)
- Neil H Thomson
- Department of Oral Biology, School of Dentistry and Molecular and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - Sergio Santos
- 1] Department of Oral Biology, School of Dentistry and Molecular and Nanoscale Physics Group, School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom [2]
| | - Lesley A Mitchenall
- Department of Biological Chemistry, John Innes Centre Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Tanya Stuchinskaya
- 1] Department of Biological Chemistry, John Innes Centre Norwich Research Park, Norwich NR4 7UH, United Kingdom [2]
| | - James A Taylor
- 1] Department of Biological Chemistry, John Innes Centre Norwich Research Park, Norwich NR4 7UH, United Kingdom [2]
| | - Anthony Maxwell
- Department of Biological Chemistry, John Innes Centre Norwich Research Park, Norwich NR4 7UH, United Kingdom
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32
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Donczew R, Zakrzewska-Czerwińska J, Zawilak-Pawlik A. Beyond DnaA: the role of DNA topology and DNA methylation in bacterial replication initiation. J Mol Biol 2014; 426:2269-82. [PMID: 24747048 DOI: 10.1016/j.jmb.2014.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/10/2014] [Accepted: 04/11/2014] [Indexed: 12/31/2022]
Abstract
The replication of chromosomal DNA is a fundamental event in the life cycle of every cell. The first step of replication, initiation, is controlled by multiple factors to ensure only one round of replication per cell cycle. The process of initiation has been described most thoroughly for bacteria, especially Escherichia coli, and involves many regulatory proteins that vary considerably between different species. These proteins control the activity of the two key players of initiation in bacteria: the initiator protein DnaA and the origin of chromosome replication (oriC). Factors involved in the control of the availability, activity, or oligomerization of DnaA during initiation are generally regarded as the most important and thus have been thoroughly characterized. Other aspects of the initiation process, such as origin accessibility and susceptibility to unwinding, have been less explored. However, recent findings indicate that these factors have a significant role. This review focuses on DNA topology, conformation, and methylation as important factors that regulate the initiation process in bacteria. We present a comprehensive summary of the factors involved in the modulation of DNA topology, both locally at oriC and more globally at the level of the entire chromosome. We show clearly that the conformation of oriC dynamically changes, and control of this conformation constitutes another, important factor in the regulation of bacterial replication initiation. Furthermore, the process of initiation appears to be associated with the dynamics of the entire chromosome and this association is an important but largely unexplored phenomenon.
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Affiliation(s)
- Rafał Donczew
- Institute of Immunology and Experimental Therapy, Department of Microbiology, Polish Academy of Sciences, Weigla 12, 53-114 Wrocław, Poland.
| | - Jolanta Zakrzewska-Czerwińska
- Institute of Immunology and Experimental Therapy, Department of Microbiology, Polish Academy of Sciences, Weigla 12, 53-114 Wrocław, Poland; Faculty of Biotechnology, University of Wrocław, Joliot-Curie 14a, 50-138 Wrocław, Poland.
| | - Anna Zawilak-Pawlik
- Institute of Immunology and Experimental Therapy, Department of Microbiology, Polish Academy of Sciences, Weigla 12, 53-114 Wrocław, Poland.
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33
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Ketron AC, Osheroff N. Phytochemicals as Anticancer and Chemopreventive Topoisomerase II Poisons. PHYTOCHEMISTRY REVIEWS : PROCEEDINGS OF THE PHYTOCHEMICAL SOCIETY OF EUROPE 2014; 13:19-35. [PMID: 24678287 PMCID: PMC3963363 DOI: 10.1007/s11101-013-9291-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Phytochemicals are a rich source of anticancer drugs and chemopreventive agents. Several of these chemicals appear to exert at least some of their effects through interactions with topoisomerase II, an essential enzyme that regulates DNA supercoiling and removes knots and tangles from the genome. Topoisomerase II-active phytochemicals function by stabilizing covalent protein-cleaved DNA complexes that are intermediates in the catalytic cycle of the enzyme. As a result, these compounds convert topoisomerase II to a cellular toxin that fragments the genome. Because of their mode of action, they are referred to as topoisomerase II poisons as opposed to catalytic inhibitors. The first sections of this article discuss DNA topology, the catalytic cycle of topoisomerase II, and the two mechanisms (interfacial vs. covalent) by which different classes of topoisomerase II poisons alter enzyme activity. Subsequent sections discuss the effects of several phytochemicals on the type II enzyme, including demethyl-epipodophyllotoxins (semisynthetic anticancer drugs) as well as flavones, flavonols, isoflavones, catechins, isothiocyanates, and curcumin (dietary chemopreventive agents). Finally, the leukemogenic potential of topoisomerase II-targeted phytochemicals is described.
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Affiliation(s)
- Adam C. Ketron
- Department of Biochemistry and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
| | - Neil Osheroff
- Departments of Biochemistry and Medicine (Hematology/Oncology) and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232 USA
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34
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Fluorescent methods to study transcription initiation and transition into elongation. EXPERIENTIA SUPPLEMENTUM (2012) 2014; 105:105-30. [PMID: 25095993 PMCID: PMC4430081 DOI: 10.1007/978-3-0348-0856-9_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The DNA-dependent RNA polymerases induce specific conformational changes in the promoter DNA during transcription initiation. Fluorescence spectroscopy sensitively monitors these DNA conformational changes in real time and at equilibrium providing powerful ways to estimate interactions in transcriptional complexes and to assess how transcription is regulated by the promoter DNA sequence, transcription factors, and small ligands. Ensemble fluorescence methods described here probe the individual steps of promoter binding, bending, opening, and transition into the elongation using T7 phage and mitochondrial transcriptional systems as examples.
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35
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Martínez-García B, Fernández X, Díaz-Ingelmo O, Rodríguez-Campos A, Manichanh C, Roca J. Topoisomerase II minimizes DNA entanglements by proofreading DNA topology after DNA strand passage. Nucleic Acids Res 2013; 42:1821-30. [PMID: 24185700 PMCID: PMC3919613 DOI: 10.1093/nar/gkt1037] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
By transporting one DNA double helix (T-segment) through a double-strand break in another (G-segment), topoisomerase II reduces fractions of DNA catenanes, knots and supercoils to below equilibrium values. How DNA segments are selected to simplify the equilibrium DNA topology is enigmatic, and the biological relevance of this activity is unclear. Here we examined the transit of the T-segment across the three gates of topoisomerase II (entry N-gate, DNA-gate and exit C-gate). Our experimental results uncovered that DNA transport probability is determined not only during the capture of a T-segment at the N-gate. When a captured T-segment has crossed the DNA-gate, it can backtrack to the N-gate instead of exiting by the C-gate. When such backtracking is precluded by locking the N-gate or by removing the C-gate, topoisomerase II no longer simplifies equilibrium DNA topology. Therefore, we conclude that the C-gate enables a post-DNA passage proofreading mechanism, which challenges the release of passed T-segments to either complete or cancel DNA transport. This proofreading activity not only clarifies how type-IIA topoisomerases simplify the equilibrium topology of DNA in free solution, but it may explain also why these enzymes are able to solve the topological constraints of intracellular DNA without randomly entangling adjacent chromosomal regions.
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Affiliation(s)
- Belén Martínez-García
- Instituto de Biología Molecular de Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona 08028, Spain
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36
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The tail that wags the dog: topoisomerase IV ParC C-terminal domain controls strand passage activity through multipartite topology-dependent interactions with DNA. J Mol Biol 2013; 425:3025-8. [PMID: 23851170 DOI: 10.1016/j.jmb.2013.07.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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37
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Vos SM, Lee I, Berger JM. Distinct regions of the Escherichia coli ParC C-terminal domain are required for substrate discrimination by topoisomerase IV. J Mol Biol 2013; 425:3029-45. [PMID: 23867279 DOI: 10.1016/j.jmb.2013.04.033] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 04/14/2013] [Accepted: 04/16/2013] [Indexed: 11/16/2022]
Abstract
Type IIA DNA topoisomerases are essential enzymes that use ATP to maintain chromosome supercoiling and remove links between sister chromosomes. In Escherichia coli, the type IIA topoisomerase topo IV rapidly removes positive supercoils and catenanes from DNA but is significantly slower when confronted with negatively supercoiled substrates. The ability of topo IV to discriminate between positively and negatively supercoiled DNA requires the C-terminal domain (CTD) of one of its two subunits, ParC. To determine how the ParC CTD might assist with substrate discrimination, we identified potential DNA interacting residues on the surface of the CTD, mutated these residues, and tested their effect on both topo IV enzymatic activity and DNA binding by the isolated domain. Surprisingly, different regions of the ParC CTD do not bind DNA equivalently, nor contribute equally to the action of topo IV on different types of DNA substrates. Moreover, we find that the CTD contains an autorepressive element that inhibits activity on negatively supercoiled and catenated substrates, as well as a distinct region that aids in bending the DNA duplex that tracks through the enzyme's nucleolytic center. Our data demonstrate that the CTD is essential for proper engagement of both gate and transfer segment DNAs, reconciling different models to explain how topo IV discriminates between distinct DNAs topologies.
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Affiliation(s)
- Seychelle M Vos
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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38
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Papillon J, Ménétret JF, Batisse C, Hélye R, Schultz P, Potier N, Lamour V. Structural insight into negative DNA supercoiling by DNA gyrase, a bacterial type 2A DNA topoisomerase. Nucleic Acids Res 2013; 41:7815-27. [PMID: 23804759 PMCID: PMC3763546 DOI: 10.1093/nar/gkt560] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Type 2A DNA topoisomerases (Topo2A) remodel DNA topology during replication, transcription and chromosome segregation. These multisubunit enzymes catalyze the transport of a double-stranded DNA through a transient break formed in another duplex. The bacterial DNA gyrase, a target for broad-spectrum antibiotics, is the sole Topo2A enzyme able to introduce negative supercoils. We reveal here for the first time the architecture of the full-length Thermus thermophilus DNA gyrase alone and in a cleavage complex with a 155 bp DNA duplex in the presence of the antibiotic ciprofloxacin, using cryo-electron microscopy. The structural organization of the subunits of the full-length DNA gyrase points to a central role of the ATPase domain acting like a 'crossover trap' that may help to sequester the DNA positive crossover before strand passage. Our structural data unveil how DNA is asymmetrically wrapped around the gyrase-specific C-terminal β-pinwheel domains and guided to introduce negative supercoils through cooperativity between the ATPase and β-pinwheel domains. The overall conformation of the drug-induced DNA binding-cleavage complex also suggests that ciprofloxacin traps a DNA pre-transport conformation.
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Affiliation(s)
- Julie Papillon
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Jean-François Ménétret
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Claire Batisse
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Reynald Hélye
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Patrick Schultz
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Noëlle Potier
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Valérie Lamour
- IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
- *To whom correspondence should be addressed. Tel: +33 3 88 65 32 36; Fax: +33 3 88 65 32 01;
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Lee I, Dong KC, Berger JM. The role of DNA bending in type IIA topoisomerase function. Nucleic Acids Res 2013; 41:5444-56. [PMID: 23580548 PMCID: PMC3664819 DOI: 10.1093/nar/gkt238] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Type IIA topoisomerases control DNA supercoiling and separate newly replicated chromosomes using a complex DNA strand cleavage and passage mechanism. Structural and biochemical studies have shown that these enzymes sharply bend DNA by as much as 150°; an invariant isoleucine, which has been seen structurally to intercalate between two base pairs outside of the DNA cleavage site, has been suggested to promote deformation. To test this assumption, we examined the role of isoleucine on DNA binding, bending and catalytic activity for a bacterial type IIA topoisomerase, Escherichia coli topoisomerase IV (topo IV), using a combination of site-directed mutagenesis and biochemical assays. Our data show that alteration of the isoleucine (Ile172) did not affect the basal ATPase activity of topo IV or its affinity for DNA. However, the amino acid was important for DNA bending, DNA cleavage and supercoil relaxation. Moreover, an ability to bend DNA correlated with efficacy with which nucleic acid substrates stimulate ATP hydrolysis. These data show that DNA binding and bending by topo IV can be uncoupled, and indicate that the stabilization of a highly curved DNA geometry is critical to the type IIA topoisomerase catalytic cycle.
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Affiliation(s)
- Imsang Lee
- Department of Molecular and Cell Biology, MC 3220 University of California, Berkeley, CA 94720-3220, USA
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40
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Seol Y, Hardin AH, Strub MP, Charvin G, Neuman KC. Comparison of DNA decatenation by Escherichia coli topoisomerase IV and topoisomerase III: implications for non-equilibrium topology simplification. Nucleic Acids Res 2013; 41:4640-9. [PMID: 23460205 PMCID: PMC3632123 DOI: 10.1093/nar/gkt136] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Type II topoisomerases are essential enzymes that regulate DNA topology through a strand-passage mechanism. Some type II topoisomerases relax supercoils, unknot and decatenate DNA to below thermodynamic equilibrium. Several models of this non-equilibrium topology simplification phenomenon have been proposed. The kinetic proofreading (KPR) model postulates that strand passage requires a DNA-bound topoisomerase to collide twice in rapid succession with a second DNA segment, implying a quadratic relationship between DNA collision frequency and relaxation rate. To test this model, we used a single-molecule assay to measure the unlinking rate as a function of DNA collision frequency for Escherichia coli topoisomerase IV (topo IV) that displays efficient non-equilibrium topology simplification activity, and for E. coli topoisomerase III (topo III), a type IA topoisomerase that unlinks and unknots DNA to equilibrium levels. Contrary to the predictions of the KPR model, topo IV and topo III unlinking rates were linearly related to the DNA collision frequency. Furthermore, topo III exhibited decatenation activity comparable with that of topo IV, supporting proposed roles for topo III in DNA segregation. This study enables us to rule out the KPR model for non-equilibrium topology simplification. More generally, we establish an experimental approach to systematically control DNA collision frequency.
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Affiliation(s)
- Yeonee Seol
- Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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41
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New insights into DNA-binding by type IIA topoisomerases. Curr Opin Struct Biol 2013; 23:125-33. [DOI: 10.1016/j.sbi.2012.11.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/28/2012] [Accepted: 11/29/2012] [Indexed: 11/18/2022]
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42
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The structure of DNA-bound human topoisomerase II alpha: conformational mechanisms for coordinating inter-subunit interactions with DNA cleavage. J Mol Biol 2012; 424:109-24. [PMID: 22841979 PMCID: PMC3584591 DOI: 10.1016/j.jmb.2012.07.014] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 07/18/2012] [Indexed: 01/07/2023]
Abstract
Type II topoisomerases are required for the management of DNA superhelicity and chromosome segregation, and serve as frontline targets for a variety of small-molecule therapeutics. To better understand how these enzymes act in both contexts, we determined the 2.9-Å-resolution structure of the DNA cleavage core of human topoisomerase IIα (TOP2A) bound to a doubly nicked, 30-bp duplex oligonucleotide. In accord with prior biochemical and structural studies, TOP2A significantly bends its DNA substrate using a bipartite, nucleolytic center formed at an N-terminal dimerization interface of the cleavage core. However, the protein also adopts a global conformation in which the second of its two inter-protomer contact points, one at the C-terminus, has separated. This finding, together with comparative structural analyses, reveals that the principal site of DNA engagement undergoes highly quantized conformational transitions between distinct binding, cleavage, and drug-inhibited states that correlate with the control of subunit-subunit interactions. Additional consideration of our TOP2A model in light of an etoposide-inhibited complex of human topoisomerase IIβ (TOP2B) suggests possible modification points for developing paralog-specific inhibitors to overcome the tendency of topoisomerase II-targeting chemotherapeutics to generate secondary malignancies.
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43
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Abstract
The predominant protein-centric perspective in protein-DNA-binding studies assumes that the protein drives the interaction. Research focuses on protein structural motifs, electrostatic surfaces and contact potentials, while DNA is often ignored as a passive polymer to be manipulated. Recent studies of DNA topology, the supercoiling, knotting, and linking of the helices, have shown that DNA has the capability to be an active participant in its transactions. DNA topology-induced structural and geometric changes can drive, or at least strongly influence, the interactions between protein and DNA. Deformations of the B-form structure arise from both the considerable elastic energy arising from supercoiling and from the electrostatic energy. Here, we discuss how these energies are harnessed for topology-driven, sequence-specific deformations that can allow DNA to direct its own metabolism.
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44
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Abstract
It is well known that remnants of partial or whole copies of mitochondrial DNA, known as Nuclear MiTochondrial sequences (NUMTs), are found in nuclear genomes. Since whole genome sequences have become available, many bioinformatics studies have identified putative NUMTs and from those attempted to infer the factors involved in NUMT creation. These studies conclude that NUMTs represent randomly chosen regions of the mitochondrial genome. There is less consensus regarding the nuclear insertion sites of NUMTs - previous studies have discussed the possible role of retrotransposons, but some recent ones have reported no correlation or even anti-correlation between NUMT sites and retrotransposons. These studies have generally defined NUMT sites using BLAST with default parameters. We analyze a redefined set of human NUMTs, computed with a carefully considered protocol. We discover that the inferred insertion points of NUMTs have a strong tendency to have high-predicted DNA curvature, occur in experimentally defined open chromatin regions and often occur immediately adjacent to A + T oligomers. We also show clear evidence that their flanking regions are indeed rich in retrotransposons. Finally we show that parts of the mitochondrial genome D-loop are under-represented as a source of NUMTs in primate evolution.
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Affiliation(s)
- Junko Tsuji
- Department of Computational Biology, Graduate School of Frontier Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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Sarkar SK, Marmer B, Goldberg G, Neuman KC. Single-molecule tracking of collagenase on native type I collagen fibrils reveals degradation mechanism. Curr Biol 2012; 22:1047-56. [PMID: 22578418 DOI: 10.1016/j.cub.2012.04.012] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 03/09/2012] [Accepted: 04/02/2012] [Indexed: 12/31/2022]
Abstract
BACKGROUND Collagen, the most abundant human protein, is the principal component of the extracellular matrix and plays important roles in maintaining tissue and organ integrity. Highly resistant to proteolysis, fibrillar collagen is degraded by specific matrix metalloproteases (MMPs). Degradation of fibrillar collagen underlies processes including tissue remodeling, wound healing, and cancer metastasis. However, the mechanism of native collagen fibril degradation remains poorly understood. RESULTS Here we present the results of high-resolution tracking of individual MMPs degrading type I collagen fibrils. MMP1 exhibits cleavage-dependent biased and hindered diffusion but spends 90% ± 3% of the time in one of at least two distinct pause states. One class of exponentially distributed pauses (class I pauses) occurs randomly along the fibril, whereas a second class of pauses (class II pauses) exhibits multistep escape kinetics and occurs periodically at intervals of 1.3 ± 0.2 μm and 1.5 ± 0.2 μm along the fibril. After these class II pauses, MMP1 moved faster and farther in one direction along the fibril, indicative of biased motion associated with cleavage. Simulations indicate that 5% ± 2% of the class II pauses result in the initiation of processive collagen degradation, which continues for bursts of 15 ± 4 consecutive cleavage events. CONCLUSIONS These findings provide a mechanistic paradigm for type I collagen degradation by MMP1 and establish a general approach to investigate MMP-fibrillar collagen interactions. More generally, this work demonstrates the fundamental role of enzyme-substrate interactions including binding and motion in determining the activity of an enzyme on an extended substrate.
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Affiliation(s)
- Susanta K Sarkar
- Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Affiliation(s)
- Alexander Vologodskii
- Department
of Chemistry, New York University, New
York, New York 10003, United States
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DNA cleavage and opening reactions of human topoisomerase IIα are regulated via Mg2+-mediated dynamic bending of gate-DNA. Proc Natl Acad Sci U S A 2012; 109:2925-30. [PMID: 22323612 DOI: 10.1073/pnas.1115704109] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Topoisomerase II resolves intrinsic topological problems of double-stranded DNA. As part of its essential cellular functions, the enzyme generates DNA breaks, but the regulation of this potentially dangerous process is not well understood. Here we report single-molecule fluorescence experiments that reveal a previously uncharacterized sequence of events during DNA cleavage by topoisomerase II: nonspecific DNA binding, sequence-specific DNA bending, and stochastic cleavage of DNA. We have identified unexpected structural roles of Mg(2+) ions coordinated in the TOPRIM (topoisomerase-primase) domain in inducing cleavage-competent DNA bending. A break at one scissile bond dramatically stabilized DNA bending, explaining how two scission events in opposing strands can be coordinated to achieve a high probability of double-stranded cleavage. Clamping of the protein N-gate greatly enhanced the rate and degree of DNA bending, resulting in a significant stimulation of the DNA cleavage and opening reactions. Our data strongly suggest that the accurate cleavage of DNA by topoisomerase II is regulated through a tight coordination with DNA bending.
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Vařecha M, Potěšilová M, Matula P, Kozubek M. Endonuclease G interacts with histone H2B and DNA topoisomerase II alpha during apoptosis. Mol Cell Biochem 2011; 363:301-7. [PMID: 22160858 DOI: 10.1007/s11010-011-1182-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 11/24/2011] [Indexed: 11/25/2022]
Abstract
Apoptosis is a natural form of cell death involved in many physiological changes in the cell. Defects in the process of apoptosis can lead to serious diseases. During some apoptotic pathways, proteins apoptosis-inducing factor (AIF) and endonuclease G (EndoG) are released from the mitochondria and they translocate into the cell nuclei, where they probably participate in chromatin degradation together with other nuclear proteins. Exact mechanism of EndoG activity in cell nucleus is still unknown. Some interacting partners like flap endonuclease 1, DNase I, and exonuclease III were already suggested, but also other interacting partners were proposed. We conducted a living-cell confocal fluorescence microscopy followed by an image analysis of fluorescence resonance energy transfer to analyze the possibility of protein interactions of EndoG with histone H2B and human DNA topoisomerase II alpha (TOPO2a). Our results show that EndoG interacts with both these proteins during apoptotic cell death. Therefore, we can conclude that EndoG and TOPO2a may actively participate in apoptotic chromatin degradation. The possible existence of a degradation complex consisting of EndoG and TOPO2a and possibly other proteins like AIF and cyclophilin A have yet to be investigated.
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Affiliation(s)
- Miroslav Vařecha
- Centre for Biomedical Image Analysis, Faculty of Informatics, Masaryk University, Botanická 68a, 602 00 Brno, Czech Republic.
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Vologodskii A. Unlinking of supercoiled DNA catenanes by type IIA topoisomerases. Biophys J 2011; 101:1403-11. [PMID: 21943421 DOI: 10.1016/j.bpj.2011.08.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 07/21/2011] [Accepted: 08/11/2011] [Indexed: 11/29/2022] Open
Abstract
It was found recently that DNA catenanes, formed during replication of circular plasmids, become positively (+) supercoiled, and the unlinking of such catenanes by type IIA topoisomerases proceeds much more efficiently than the unlinking of negatively (-) supercoiled catenanes. In an attempt to explain this striking finding we studied, by computer simulation, conformational properties of supercoiled DNA catenanes. Although the simulation showed that conformational properties of (+) and (-) supercoiled replication catenanes are very different, these properties per se do not give any advantage to (+) supercoiled over (-) supercoiled DNA catenanes for unlinking. An advantage became evident, however, when we took into account the established features of the enzymatic reaction catalyzed by the topoisomerases. The enzymes create a sharp DNA bend in the first bound DNA segment and allow for the transport of the second segment only from inside the bend to its outside. We showed that in (-) supercoiled DNA catenanes this protein-bound bent segment becomes nearly inaccessible for segments of the other linked DNA molecule, inhibiting the unlinking.
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