1
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Ciaco S, Aronne R, Fiabane M, Mori M. The Rise of Bacterial G-Quadruplexes in Current Antimicrobial Discovery. ACS OMEGA 2024; 9:24163-24180. [PMID: 38882119 PMCID: PMC11170735 DOI: 10.1021/acsomega.4c01731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 05/10/2024] [Accepted: 05/17/2024] [Indexed: 06/18/2024]
Abstract
Antimicrobial resistance (AMR) is a silent critical issue that poses several challenges to health systems. While the discovery of novel antibiotics is currently stalled and prevalently focused on chemical variations of the scaffolds of available drugs, novel targets and innovative strategies are urgently needed to face this global threat. In this context, bacterial G-quadruplexes (G4s) are emerging as timely and profitable targets for the design and development of antimicrobial agents. Indeed, they are expressed in regulatory regions of bacterial genomes, and their modulation has been observed to provide antimicrobial effects with translational perspectives in the context of AMR. In this work, we review the current knowledge of bacterial G4s as well as their modulation by small molecules, including tools and techniques suitable for these investigations. Finally, we critically analyze the needs and future directions in the field, with a focus on the development of small molecules as bacterial G4s modulators endowed with remarkable drug-likeness.
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Affiliation(s)
- Stefano Ciaco
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Rossella Aronne
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Martina Fiabane
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Mattia Mori
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
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2
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Pandey A, Roy S, Srivatsan SG. Probing the Competition between Duplex, G-Quadruplex and i-Motif Structures of the Oncogenic c-Myc DNA Promoter Region. Chem Asian J 2023; 18:e202300510. [PMID: 37541298 DOI: 10.1002/asia.202300510] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/09/2023] [Indexed: 08/06/2023]
Abstract
Development of probe systems that provide unique spectral signatures for duplex, G-quadruplex (GQ) and i-motif (iM) structures is very important to understand the relative propensity of a G-rich-C-rich promoter region to form these structures. Here, we devise a platform using a combination of two environment-sensitive nucleoside analogs namely, 5-fluorobenzofuran-modified 2'-deoxyuridine (FBF-dU) and 5-fluoro-2'-deoxyuridine (F-dU) to study the structures adopted by a promoter region of the c-Myc oncogene. FBF-dU serves as a dual-purpose probe containing a fluorescent and 19 F NMR label. When incorporated into the C-rich sequence, it reports the formation of different iMs via changes in its fluorescence properties and 19 F signal. F-dU incorporated into the G-rich ON reports the formation of a GQ structure whose 19 F signal is clearly different from the signals obtained for iMs. Rewardingly, the labeled ONs when mixed with respective complementary strands allows us to determine the relative population of different structures formed by the c-Myc promoter by the virtue of the probe's ability to produce distinct and resolved 19 F signatures for different structures. Our results indicate that at physiological pH and temperature the c-Myc promoter forms duplex, random coil and GQ structures, and does not form an iM. Whereas at acidic pH, the mixture largely forms iM and GQ structures. Taken together, our system will complement existing tools and provide unprecedented insights on the population equilibrium and dynamics of nucleic acid structures under different conditions.
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Affiliation(s)
- Akanksha Pandey
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune, 411008, India
| | - Sarupa Roy
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune, 411008, India
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune, 411008, India
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3
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Oblak D, Hadži S, Podlipnik Č, Lah J. Binding-Induced Diversity of a Human Telomeric G-Quadruplex Stability Phase Space. Pharmaceuticals (Basel) 2022; 15:ph15091150. [PMID: 36145371 PMCID: PMC9501445 DOI: 10.3390/ph15091150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/06/2022] [Accepted: 09/11/2022] [Indexed: 11/25/2022] Open
Abstract
The structural polymorphism of G-quadruplex nucleic acids is an important factor in their recognition by proteins and small-molecule ligands. However, it is not clear why the binding of several ligands alters G-quadruplex topology. We addressed this question by following the (un)folding and binding of the human telomeric fragment 5′-(GGGTTA)3GGGT-3′ (22GT) by calorimetry (DSC, ITC) and spectroscopy (CD). A thermodynamic analysis of the obtained data led to a detailed description of the topological phase space of stability (phase diagram) of 22GT and shows how it changes in the presence of a specific bisquinolinium ligand (360A). Various 1:1 and 2:1 ligand–quadruplex complexes were observed. With increasing temperature, the 1:1 complexes transformed into 2:1 complexes, which is attributed to the preferential binding of the ligand to the folding intermediates. Overall, the dissection of the thermodynamic parameters in combination with molecular modelling clarified the driving forces of the topological quadruplex transformations in a wide range of ligand concentrations and temperatures.
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4
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Amato J, Iaccarino N, D'Aria F, D'Amico F, Randazzo A, Giancola C, Cesàro A, Di Fonzo S, Pagano B. Conformational plasticity of DNA secondary structures: probing the conversion between i-motif and hairpin species by circular dichroism and ultraviolet resonance Raman spectroscopies. Phys Chem Chem Phys 2022; 24:7028-7044. [PMID: 35258065 DOI: 10.1039/d2cp00058j] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The promoter regions of important oncogenes such as BCL2 and KRAS contain GC-rich sequences that can form distinctive noncanonical DNA structures involved in the regulation of transcription: G-quadruplexes on the G-rich strand and i-motifs on the C-rich strand. Interestingly, BCL2 and KRAS promoter i-motifs are highly dynamic in nature and exist in a pH-dependent equilibrium with hairpin and even with hybrid i-motif/hairpin species. Herein, the effects of pH and presence of cell-mimicking molecular crowding conditions on conformational equilibria of the BCL2 and KRAS i-motif-forming sequences were investigated by ultraviolet resonance Raman (UVRR) and circular dichroism (CD) spectroscopies. Multivariate analysis of CD data was essential to model the presence and identity of the species involved. Analysis of UVRR spectra measured as a function of pH, performed also by the two-dimensional correlation spectroscopy (2D-COS) technique, showed the role of several functional groups in the DNA conformational transitions, and provided structural and dynamic information. Thus, the UVRR investigation of intramolecular interactions and of local and environmental dynamics in promoting the different species induced by the solution conditions provided valuable insights into i-motif conformational transitions. The combined use of the two spectroscopic tools is emphasized by the relevant possibility of working in the same DNA concentration range and by the heterospectral UVRR/CD 2D-COS analysis. The results of this study shed light on the factors that can influence at the molecular level the equilibrium between the different conformational species putatively involved in the oncogene expression.
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Affiliation(s)
- Jussara Amato
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Nunzia Iaccarino
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Federica D'Aria
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Francesco D'Amico
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Antonio Randazzo
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Concetta Giancola
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
| | - Attilio Cesàro
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Silvia Di Fonzo
- Elettra-Sincrotrone Trieste S. C. p. A., Science Park, Trieste, I-34149, Italy.
| | - Bruno Pagano
- Department of Pharmacy, University of Naples Federico II, Naples, I-80131, Italy.
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5
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Liu YC, Yang DY, Sheu SY. Insights into the free energy landscape and salt-controlled mechanism of the conformational conversions between human telomeric G-quadruplex structures. Int J Biol Macromol 2021; 191:230-242. [PMID: 34536474 DOI: 10.1016/j.ijbiomac.2021.09.057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/23/2021] [Accepted: 09/10/2021] [Indexed: 12/16/2022]
Abstract
G-quadruplexes have become attractive drug targets in cancer therapy. However, due to the polymorphism of G-quadruplex structures, it is difficult to experimentally verify the relevant structures of multiple intermediates and transition states in dynamic equilibrium. Hence, understanding the mechanism by which structural conversions of G-quadruplexes occur is still challenging. We conducted targeted molecular dynamics simulation with umbrella sampling to investigate how salt affects the conformational conversion of human telomeric G-quadruplex. Our results explore a unique view into the structures and energy barrier of the intermediates and transition states in the interconversion process. The pathway of G-quadruplex conformational interconversion was mapped out by a free energy landscape, consisting of branched parallel pathways with multiple energy basins. We propose a salt-controlled mechanism that as the salt concentration increases, the conformational conversion mechanism switches from multi-pathway folding to sequential folding pathways. The hybrid-I and hybrid-II structures are intermediates in the basket-propeller transformation. In high-salt solutions, the conformational conversion upon K+ binding is more feasible than upon Na+ binding. The free energy barrier for conformational conversions ranges from 1.6 to 4.6 kcal/mol. Our work will be beneficial in developing anticancer agents.
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Affiliation(s)
- Yu-Cheng Liu
- Institute of Biomedical Informatics, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Dah-Yen Yang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan.
| | - Sheh-Yi Sheu
- Institute of Biomedical Informatics, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan.
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6
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Ribaudo G, Ongaro A, Oselladore E, Memo M, Gianoncelli A. Combining Electrospray Mass Spectrometry (ESI-MS) and Computational Techniques in the Assessment of G-Quadruplex Ligands: A Hybrid Approach to Optimize Hit Discovery. J Med Chem 2021; 64:13174-13190. [PMID: 34510895 PMCID: PMC8474113 DOI: 10.1021/acs.jmedchem.1c00962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
![]()
Guanine-rich sequences
forming G-quadruplexes (GQs) are present
in several genomes, ranging from viral to human. Given their peculiar
localization, the induction of GQ formation or GQ stabilization with
small molecules represents a strategy for interfering with crucial
biological functions. Investigating the recognition event at the molecular
level, with the aim of fully understanding the triggered pharmacological
effects, is challenging. Native electrospray ionization mass spectrometry
(ESI-MS) is being optimized to study these noncovalent assemblies.
Quantitative parameters retrieved from ESI-MS studies, such as binding
affinity, the equilibrium binding constant, and sequence selectivity,
will be overviewed. Computational experiments supporting the ESI-MS
investigation and boosting its efficiency in the search for GQ ligands
will also be discussed with practical examples. The combination of
ESI-MS and in silico techniques in a hybrid high-throughput-screening
workflow represents a valuable tool for the medicinal chemist, providing
data on the quantitative and structural aspects of ligand–GQ
interactions.
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Affiliation(s)
- Giovanni Ribaudo
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Alberto Ongaro
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Erika Oselladore
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Maurizio Memo
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Alessandra Gianoncelli
- Department of Molecular and Translational Medicine, University of Brescia, Viale Europa 11, 25123 Brescia, Italy
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7
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Laouer K, Schmid M, Wien F, Changenet P, Hache F. Folding Dynamics of DNA G-Quadruplexes Probed by Millisecond Temperature Jump Circular Dichroism. J Phys Chem B 2021; 125:8088-8098. [PMID: 34279936 DOI: 10.1021/acs.jpcb.1c01993] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
G-quadruplexes play important roles in cellular regulatory functions, but despite significant experimental and theoretical efforts, their folding mechanisms remain poorly understood. In this context, we developed a T-jump experiment to access the thermal denaturation and renaturation dynamics of short intramolecular G-quadruplexes in vitro, on the time scale of a few hundred milliseconds. With this new setup, we compared the thermal denaturation and renaturation kinetics of three antiparallel topologies made of the human telomeric sequences d[(5'-GGG(TTAGGG)3-3']/Na+ and d[5'-AGGG(TTAGGG)3-3']/Na+ and the thrombin-binding aptamer sequence d[5'-GGTTGGTGTGGTTGG-3']/K+, with those of the parallel topology made of the human CEB25 minisatellite d[5'-AAGGGTGGGTGTAAGTGTGGGTGGGT-3']/Na+. In all cases, exponential kinetics of the order of several hundred milliseconds were observed. Measurements performed for different initial temperatures revealed distinct denaturation and renaturation dynamics, ruling out a simple two-state mechanism. The parallel topology, in which all guanines adopt an anti conformation, displays much slower dynamics than antiparallel topologies associated with very low activation barriers. This behavior can be explained by the constrained conformational space due to the presence of the single-base propeller loops that likely hinders the movement of the coiled DNA strand and reduces the contribution of the entropy during the renaturation process at high temperatures.
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Affiliation(s)
- K Laouer
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS -INSERM, Institut Polytechnique de Paris, 91128 Cedex Palaiseau, France
| | - M Schmid
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS -INSERM, Institut Polytechnique de Paris, 91128 Cedex Palaiseau, France
| | - F Wien
- L'orme des merisiers, Synchrotron SOLEIL, 91192 Gif sur Yvette, France
| | - P Changenet
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS -INSERM, Institut Polytechnique de Paris, 91128 Cedex Palaiseau, France
| | - F Hache
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, CNRS -INSERM, Institut Polytechnique de Paris, 91128 Cedex Palaiseau, France
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8
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Cadoni E, Magalhães PR, Emídio RM, Mendes E, Vítor J, Carvalho J, Cruz C, Victor BL, Paulo A. New (Iso)quinolinyl-pyridine-2,6-dicarboxamide G-Quadruplex Stabilizers. A Structure-Activity Relationship Study. Pharmaceuticals (Basel) 2021; 14:ph14070669. [PMID: 34358095 PMCID: PMC8308870 DOI: 10.3390/ph14070669] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 07/06/2021] [Accepted: 07/09/2021] [Indexed: 12/15/2022] Open
Abstract
G-quadruplex (G4)-interactive small molecules have a wide range of potential applications, not only as drugs, but also as sensors of quadruplex structures. The purpose of this work is the synthesis of analogues of the bis-methylquinolinium-pyridine-2,6-dicarboxamide G4 ligand 360A, to identify relevant structure-activity relationships to apply to the design of other G4-interactive small molecules bearing bis-quinoline or bis-isoquinoline moieties. Thermal denaturation experiments revealed that non-methylated derivatives with a relative 1,4 position between the amide linker and the nitrogen of the quinoline ring are moderate G4 stabilizers, with a preference for the hybrid h-Telo G4, a 21-nt sequence present in human telomeres. Insertion of a positive charge upon methylation of quinoline/isoquinoline nitrogen increases compounds' ability to selectively stabilize G4s compared to duplex DNA, with a preference for parallel structures. Among these, compounds having a relative 1,3-position between the charged methylquinolinium/isoquinolinium nitrogen and the amide linker are the best G4 stabilizers. More interestingly, these ligands showed different capacities to selectively block DNA polymerization in a PCR-stop assay and to induce G4 conformation switches of hybrid h-Telo G4. Molecular dynamic simulations with the parallel G4 formed by a 21-nt sequence present in k-RAS gene promoter, showed that the relative spatial orientation of the two methylated quinoline/isoquinoline rings determines the ligands mode and strength of binding to G4s.
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Affiliation(s)
- Enrico Cadoni
- Faculty of Pharmacy, Research Institute for Medicines (iMed.ULisboa), Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal; (E.C.); (E.M.)
| | - Pedro R. Magalhães
- Faculty of Sciences, BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Campo Grande, C8 bdg, 1749-016 Lisboa, Portugal; (P.R.M.); (R.M.E.); (B.L.V.)
| | - Rita M. Emídio
- Faculty of Sciences, BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Campo Grande, C8 bdg, 1749-016 Lisboa, Portugal; (P.R.M.); (R.M.E.); (B.L.V.)
| | - Eduarda Mendes
- Faculty of Pharmacy, Research Institute for Medicines (iMed.ULisboa), Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal; (E.C.); (E.M.)
- Department of Pharmaceutical Sciences and Medicines, Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Jorge Vítor
- Department of Pharmacy, Pharmacology and Health Technologies, Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal;
| | - Josué Carvalho
- CICS-UBI-Centro de Investigação em Ciências da Saúde, Universidade da Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal; (J.C.); (C.C.)
| | - Carla Cruz
- CICS-UBI-Centro de Investigação em Ciências da Saúde, Universidade da Beira Interior, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal; (J.C.); (C.C.)
| | - Bruno L. Victor
- Faculty of Sciences, BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Campo Grande, C8 bdg, 1749-016 Lisboa, Portugal; (P.R.M.); (R.M.E.); (B.L.V.)
| | - Alexandra Paulo
- Faculty of Pharmacy, Research Institute for Medicines (iMed.ULisboa), Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal; (E.C.); (E.M.)
- Department of Pharmaceutical Sciences and Medicines, Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
- Correspondence:
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9
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Dziuba D, Didier P, Ciaco S, Barth A, Seidel CAM, Mély Y. Fundamental photophysics of isomorphic and expanded fluorescent nucleoside analogues. Chem Soc Rev 2021; 50:7062-7107. [PMID: 33956014 DOI: 10.1039/d1cs00194a] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fluorescent nucleoside analogues (FNAs) are structurally diverse mimics of the natural essentially non-fluorescent nucleosides which have found numerous applications in probing the structure and dynamics of nucleic acids as well as their interactions with various biomolecules. In order to minimize disturbance in the labelled nucleic acid sequences, the FNA chromophoric groups should resemble the natural nucleobases in size and hydrogen-bonding patterns. Isomorphic and expanded FNAs are the two groups that best meet the criteria of non-perturbing fluorescent labels for DNA and RNA. Significant progress has been made over the past decades in understanding the fundamental photophysics that governs the spectroscopic and environmentally sensitive properties of these FNAs. Herein, we review recent advances in the spectroscopic and computational studies of selected isomorphic and expanded FNAs. We also show how this information can be used as a rational basis to design new FNAs, select appropriate sequences for optimal spectroscopic response and interpret fluorescence data in FNA applications.
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Affiliation(s)
- Dmytro Dziuba
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Pascal Didier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
| | - Stefano Ciaco
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France. and Department of Biotechnology, Chemistry and Pharmacy, University of Siena, via Aldo Moro 2, 53100 Siena, Italy
| | - Anders Barth
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Claus A M Seidel
- Institut für Physikalische Chemie, Lehrstuhl für Molekulare Physikalische Chemie, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Yves Mély
- Laboratoire de Bioimagerie et Pathologies, UMR 7021, Université de Strasbourg, 74 route du Rhin, 67401 Illkirch, France.
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10
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Chaires JB, Gray RD, Dean WL, Monsen R, DeLeeuw LW, Stribinskis V, Trent JO. Human POT1 unfolds G-quadruplexes by conformational selection. Nucleic Acids Res 2020; 48:4976-4991. [PMID: 32232414 PMCID: PMC7229828 DOI: 10.1093/nar/gkaa202] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 03/13/2020] [Accepted: 03/18/2020] [Indexed: 12/14/2022] Open
Abstract
The reaction mechanism by which the shelterin protein POT1 (Protection of Telomeres 1) unfolds human telomeric G-quadruplex structures is not fully understood. We report here kinetic, thermodynamic, hydrodynamic and computational studies that show that a conformational selection mechanism, in which POT1 binding is coupled to an obligatory unfolding reaction, is the most plausible mechanism. Stopped-flow kinetic and spectroscopic titration studies, along with isothermal calorimetry, were used to show that binding of the single-strand oligonucleotide d[TTAGGGTTAG] to POT1 is both fast (80 ms) and strong (-10.1 ± 0.3 kcal mol-1). In sharp contrast, kinetic studies showed the binding of POT1 to an initially folded 24 nt G-quadruplex structure is four orders of magnitude slower. Fluorescence, circular dichroism and analytical ultracentrifugation studies showed that POT1 binding is coupled to quadruplex unfolding, with a final complex with a stoichiometry of 2 POT1 per 24 nt DNA. The binding isotherm for the POT1-quadruplex interaction was sigmoidal, indicative of a complex reaction. A conformational selection model that includes equilibrium constants for both G-quadruplex unfolding and POT1 binding to the resultant single-strand provided an excellent quantitative fit to the experimental binding data. POT1 unfolded and bound to any conformational form of human telomeric G-quadruplex (antiparallel, hybrid, parallel monomers or a 48 nt sequence with two contiguous quadruplexes), but did not avidly interact with duplex DNA or with other G-quadruplex structures. Finally, molecular dynamics simulations provided a detailed structural model of a 2:1 POT1:DNA complex that is fully consistent with experimental biophysical results.
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Affiliation(s)
- Jonathan B Chaires
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Robert D Gray
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - William L Dean
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Robert Monsen
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Lynn W DeLeeuw
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - Vilius Stribinskis
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
| | - John O Trent
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock St., Louisville, KY 40202, USA
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11
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Nguyen TQN, Lim KW, Phan AT. Folding Kinetics of G-Quadruplexes: Duplex Stem Loops Drive and Accelerate G-Quadruplex Folding. J Phys Chem B 2020; 124:5122-5130. [DOI: 10.1021/acs.jpcb.0c02548] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Thi Quynh Ngoc Nguyen
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Kah Wai Lim
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Anh Tuân Phan
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- NTU Institute of Structural Biology, Nanyang Technological University, Singapore 636921, Singapore
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12
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Schnarr L, Jana J, Preckwinkel P, Weisz K. Impact of a Snap-Back Loop on Stability and Ligand Binding to a Parallel G-Quadruplex. J Phys Chem B 2020; 124:2778-2787. [DOI: 10.1021/acs.jpcb.0c00700] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Lena Schnarr
- Institute of Biochemistry, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17487 Greifswald, Germany
| | - Jagannath Jana
- Institute of Biochemistry, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17487 Greifswald, Germany
| | - Pit Preckwinkel
- Institute of Biochemistry, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17487 Greifswald, Germany
| | - Klaus Weisz
- Institute of Biochemistry, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17487 Greifswald, Germany
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13
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Nuthanakanti A, Ahmed I, Khatik SY, Saikrishnan K, Srivatsan SG. Probing G-quadruplex topologies and recognition concurrently in real time and 3D using a dual-app nucleoside probe. Nucleic Acids Res 2020; 47:6059-6072. [PMID: 31106340 PMCID: PMC6614846 DOI: 10.1093/nar/gkz419] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 04/30/2019] [Accepted: 05/06/2019] [Indexed: 12/30/2022] Open
Abstract
Comprehensive understanding of structure and recognition properties of regulatory nucleic acid elements in real time and atomic level is highly important to devise efficient therapeutic strategies. Here, we report the establishment of an innovative biophysical platform using a dual-app nucleoside analog, which serves as a common probe to detect and correlate different GQ structures and ligand binding under equilibrium conditions and in 3D by fluorescence and X-ray crystallography techniques. The probe (SedU) is composed of a microenvironment-sensitive fluorophore and an excellent anomalous X-ray scatterer (Se), which is assembled by attaching a selenophene ring at 5-position of 2'-deoxyuridine. SedU incorporated into the loop region of human telomeric DNA repeat fluorescently distinguished subtle differences in GQ topologies and enabled quantify ligand binding to different topologies. Importantly, anomalous X-ray dispersion signal from Se could be used to determine the structure of GQs. As the probe is minimally perturbing, a direct comparison of fluorescence data and crystal structures provided structural insights on how the probe senses different GQ conformations without affecting the native fold. Taken together, our dual-app probe represents a new class of tool that opens up new experimental strategies to concurrently investigate nucleic acid structure and recognition in real time and 3D.
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Affiliation(s)
- Ashok Nuthanakanti
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Ishtiyaq Ahmed
- Department of Biology, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Saddam Y Khatik
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Kayarat Saikrishnan
- Department of Biology, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India
- Correspondence may also be addressed to Kayarat Saikrishnan.
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India
- To whom correspondence should be addressed. Tel: +91 2025908086;
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14
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He Y, Chen D, Huang PJJ, Zhou Y, Ma L, Xu K, Yang R, Liu J. Misfolding of a DNAzyme for ultrahigh sodium selectivity over potassium. Nucleic Acids Res 2019; 46:10262-10271. [PMID: 30215808 PMCID: PMC6212836 DOI: 10.1093/nar/gky807] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Accepted: 09/08/2018] [Indexed: 02/07/2023] Open
Abstract
Herein, the excellent Na+ selectivity of a few RNA-cleaving DNAzymes was exploited, where Na+ can be around 3000-fold more effective than K+ for promoting catalysis. By using a double mutant based on the Ce13d DNAzyme, and by lowering the temperature, increased 2-aminopurine (2AP) fluorescence was observed with addition of both Na+ and K+. The fluorescence increase was similar for these two metals at below 10 mM, after which K+ took a different pathway. Since 2AP probes its local base stacking environment, K+ can be considered to induce misfolding. Binding of both Na+ and K+ was specific, since single base mutations could fully inhibit 2AP fluorescence for both metals. The binding thermodynamics was measured by temperature-dependent experiments revealing enthalpy-driven binding for both metals and less coordination sites compared to G-quadruplex DNA. Cleavage activity assays indicated a moderate cleavage activity with 10 mM K+, while further increase of K+ inhibited the activity, also supporting its misfolding of the DNAzyme. For comparison, a G-quadruplex DNA was also studied using the same system, where Na+ and K+ led to the same final state with only around 8-fold difference in Kd. This study provides interesting insights into strategies for discriminating Na+ and K+.
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Affiliation(s)
- Yanping He
- State Key Laboratory of Precision Measurement Technology and Instruments, University of Tianjin, Tianjin 300072, China.,Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Da Chen
- State Key Laboratory of Precision Measurement Technology and Instruments, University of Tianjin, Tianjin 300072, China
| | - Po-Jung Jimmy Huang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Yibo Zhou
- School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Changsha 410114, P. R. China
| | - Lingzi Ma
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Kexin Xu
- State Key Laboratory of Precision Measurement Technology and Instruments, University of Tianjin, Tianjin 300072, China
| | - Ronghua Yang
- School of Chemistry and Biological Engineering, Changsha University of Science and Technology, Changsha 410114, P. R. China
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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15
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Ma G, Yu Z, Zhou W, Li Y, Fan L, Li X. Investigation of Na+ and K+ Competitively Binding with a G-Quadruplex and Discovery of a Stable K+–Na+-Quadruplex. J Phys Chem B 2019; 123:5405-5411. [DOI: 10.1021/acs.jpcb.9b02823] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ge Ma
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Ze Yu
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Wei Zhou
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Yunchao Li
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Louzhen Fan
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Xiaohong Li
- Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China
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16
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Sabale PM, Tanpure AA, Srivatsan SG. Probing the competition between duplex and G-quadruplex/i-motif structures using a conformation-sensitive fluorescent nucleoside probe. Org Biomol Chem 2019; 16:4141-4150. [PMID: 29781489 PMCID: PMC6086326 DOI: 10.1039/c8ob00646f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Double-stranded segments of a genome that can potentially form G-quadruplex (GQ) and/or i-motif (iM) structures are considered to be important regulatory elements. Hence, the development of a common probe that can detect GQ and iM structures and also distinguish them from a duplex structure will be highly useful in understanding the propensity of such segments to adopt duplex or non-canonical four-stranded structures. Here, we describe the utility of a conformation-sensitive fluorescent nucleoside analog, which was originally developed as a GQ sensor, in detecting the iM structures of C-rich DNA oligonucleotides (ONs). The analog is based on a 5-(benzofuran-2-yl)uracil scaffold, which when incorporated into C-rich ONs (e.g., telomeric repeats) fluorescently distinguishes an iM from random coil and duplex structures. Steady-state and time-resolved fluorescence techniques enabled the determination of transition pH for the transformation of a random coil to an iM structure. Furthermore, a qualitative understanding on the relative population of duplex and GQ/iM forms under physiological conditions could be gained by correlating the fluorescence, CD and thermal melting data. Taken together, this sensor could provide a general platform to profile double-stranded promoter regions in terms of their ability to adopt four-stranded structures, and also could support approaches to discover functional GQ and iM binders.
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Affiliation(s)
- Pramod M Sabale
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune, Dr. Homi Bhabha Road, Pune 411008, India.
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17
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Prislan I, Sajko S, Ulrih NP, Fürst L. Proof of concept web application for understanding the energetic basis of oligonucleotide unfolding. RSC Adv 2019; 9:41453-41461. [PMID: 35541576 PMCID: PMC9076490 DOI: 10.1039/c9ra09800c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/27/2019] [Indexed: 11/21/2022] Open
Abstract
Measuring and quantifying thermodynamic parameters that determine both the stability of and interactions between biological macromolecules are an essential and necessary complement to structural studies. Although basic thermodynamic parameters for an observed process can be readily obtained, the data interpretation is often slow and analysis quality can be extremely variable. We have started to develop a web application that will help users to perform thermodynamic characterizations of oligonucleotide unfolding. The application can perform global fitting of calorimetric and spectroscopic data, and uses a three-state equilibrium model to obtain thermodynamic parameters for each transition step – namely, the Gibbs energy, the enthalpy, and the heat capacity. In addition, the application can define the number of K+ ions and the number of water molecules being released or taken up during unfolding. To test our application, we used UV spectroscopy, circular dichroism, and differential scanning calorimetry to monitor folding and unfolding of a model 22-nucleotide-long sequence of a human 3′-telomeric overhang, known as Tel22. The obtained data were uploaded to the web application and the global fit revealed that unfolding of Tel22 involves at least one intermediate state, and that K+ ions are released during the unfolding, whereas water molecules are taken up. A novel web application: performing global fitting of oligonucleotide unfolding experimental data in style.![]()
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Affiliation(s)
- Iztok Prislan
- Biotechnical Faculty
- University of Ljubljana
- Ljubljana
- Slovenia
| | - Sara Sajko
- Max Perutz Labs Vienna
- Medical University of Vienna
- 1030 Vienna
- Austria
| | | | - Luka Fürst
- Faculty of Computer and Information Science
- University of Ljubljana
- Ljubljana
- Slovenia
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18
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Pagano B, Iaccarino N, Di Porzio A, Randazzo A, Amato J. Screening of DNA G-quadruplex stabilizing ligands by nano differential scanning fluorimetry. Analyst 2019; 144:6512-6516. [DOI: 10.1039/c9an01463b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A proof of principle study on the use of nanoDSF as a screening tool for G-quadruplex targeting compounds.
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Affiliation(s)
- Bruno Pagano
- Department of Pharmacy
- University of Naples Federico II
- 80131 Naples
- Italy
| | - Nunzia Iaccarino
- Department of Pharmacy
- University of Naples Federico II
- 80131 Naples
- Italy
| | - Anna Di Porzio
- Department of Pharmacy
- University of Naples Federico II
- 80131 Naples
- Italy
| | - Antonio Randazzo
- Department of Pharmacy
- University of Naples Federico II
- 80131 Naples
- Italy
| | - Jussara Amato
- Department of Pharmacy
- University of Naples Federico II
- 80131 Naples
- Italy
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19
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Manna S, Srivatsan SG. Fluorescence-based tools to probe G-quadruplexes in cell-free and cellular environments. RSC Adv 2018; 8:25673-25694. [PMID: 30210793 PMCID: PMC6130854 DOI: 10.1039/c8ra03708f] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 07/08/2018] [Indexed: 12/26/2022] Open
Abstract
Biophysical and biochemical investigations provide compelling evidence connecting the four-stranded G-quadruplex (GQ) structure with its role in regulating multiple cellular processes. Hence, modulating the function of GQs by using small molecule binders is being actively pursued as a strategy to develop new chemotherapeutic agents. However, sequence diversity and structural polymorphism of GQs have posed immense challenges in terms of understanding what conformation a G-rich sequence adopts inside the cell and how to specifically target a GQ motif amidst several other GQ-forming sequences. In this context, here we review recent developments in the applications of biophysical tools that use fluorescence readout to probe the GQ structure and recognition in cell-free and cellular environments. First, we provide a detailed discussion on the utility of covalently labeled environment-sensitive fluorescent nucleoside analogs in assessing the subtle difference in GQ structures and their ligand binding abilities. Furthermore, a detailed discussion on structure-specific antibodies and small molecule probes used to visualize and confirm the existence of DNA and RNA GQs in cells is provided. We also highlight the open challenges in the study of tetraplexes (GQ and i-motif structures) and how addressing these challenges by developing new tools and techniques will have a profound impact on tetraplex-directed therapeutic strategies.
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Affiliation(s)
- Sudeshna Manna
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), PuneDr. Homi Bhabha RoadPune 411008India
| | - Seergazhi G. Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research (IISER), PuneDr. Homi Bhabha RoadPune 411008India
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20
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Rigo R, Dean WL, Gray RD, Chaires JB, Sissi C. Conformational profiling of a G-rich sequence within the c-KIT promoter. Nucleic Acids Res 2018; 45:13056-13067. [PMID: 29069417 PMCID: PMC5727440 DOI: 10.1093/nar/gkx983] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 10/11/2017] [Indexed: 12/03/2022] Open
Abstract
G-quadruplexes (G4) within oncogene promoters are considered to be promising anticancer targets. However, often they undergo complex structural rearrangements that preclude a precise description of the optimal target. Moreover, even when solved structures are available, they refer to the thermodynamically stable forms but little or no information is supplied about their complex multistep folding pathway. To shed light on this issue, we systematically followed the kinetic behavior of a G-rich sequence located within the c-KIT proximal promoter (kit2) in the presence of monovalent cations K+ and Na+. A very short-lived intermediate was observed to start the G4 folding process in both salt conditions. Subsequently, the two pathways diverge to produce distinct thermodynamically stable species (parallel and antiparallel G-quadruplex in K+ and Na+, respectively). Remarkably, in K+-containing solution a branched pathway is required to drive the wild type sequence to distribute between a monomeric and dimeric G-quadruplex. Our approach has allowed us to identify transient forms whose relative abundance is regulated by the environment; some of them were characterized by a half-life within the timescale of physiological DNA processing events and thus may represent possible unexpected targets for ligands recognition.
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Affiliation(s)
- Riccardo Rigo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy
| | - William L Dean
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Robert D Gray
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Jonathan B Chaires
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Claudia Sissi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy
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21
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Peng P, Du Y, Sun Y, Liu S, Mi L, Li T. Probing the propeller-like loops of DNA G-quadruplexes with looped-out 2-aminopurine for label-free switchable molecular sensing. Analyst 2018; 143:3814-3820. [DOI: 10.1039/c8an00914g] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We report a novel ligand-free signal readout mechanism for probing the propeller-like loops of DNA G-quadruplexes with looped-out 2-aminopurine.
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Affiliation(s)
- Pai Peng
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
| | - Yi Du
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
| | - Yudie Sun
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
| | - Shuangna Liu
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
| | - Lan Mi
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
| | - Tao Li
- Department of Chemistry
- University of Science and Technology of China
- Hefei
- P.R. China
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22
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Ihmels H, Löhl K, Paululat T, Uebach S. NMR-spectroscopic investigation of the complex between tetraazoniapentapheno[6,7-h]pentaphene and quadruplex DNA Tel26. NEW J CHEM 2018. [DOI: 10.1039/c8nj01931b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The tetraazoniapentapheno[6,7-h]pentaphene binds to the hybrid-1 quadruplex structure of the oligonucleotide Tel26 by terminal π stacking, likely on top of the A3–A9–A21 triplet.
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Affiliation(s)
- Heiko Ihmels
- Department of Chemistry and Biology
- University of Siegen
- Siegen 57068
- Germany
| | - Katharina Löhl
- Department of Chemistry and Biology
- University of Siegen
- Siegen 57068
- Germany
| | - Thomas Paululat
- Department of Chemistry and Biology
- University of Siegen
- Siegen 57068
- Germany
| | - Sandra Uebach
- Department of Chemistry and Biology
- University of Siegen
- Siegen 57068
- Germany
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23
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Sagi J. In What Ways Do Synthetic Nucleotides and Natural Base Lesions Alter the Structural Stability of G-Quadruplex Nucleic Acids? J Nucleic Acids 2017; 2017:1641845. [PMID: 29181193 PMCID: PMC5664352 DOI: 10.1155/2017/1641845] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Accepted: 08/15/2017] [Indexed: 01/03/2023] Open
Abstract
Synthetic analogs of natural nucleotides have long been utilized for structural studies of canonical and noncanonical nucleic acids, including the extensively investigated polymorphic G-quadruplexes (GQs). Dependence on the sequence and nucleotide modifications of the folding landscape of GQs has been reviewed by several recent studies. Here, an overview is compiled on the thermodynamic stability of the modified GQ folds and on how the stereochemical preferences of more than 70 synthetic and natural derivatives of nucleotides substituting for natural ones determine the stability as well as the conformation. Groups of nucleotide analogs only stabilize or only destabilize the GQ, while the majority of analogs alter the GQ stability in both ways. This depends on the preferred syn or anti N-glycosidic linkage of the modified building blocks, the position of substitution, and the folding architecture of the native GQ. Natural base lesions and epigenetic modifications of GQs explored so far also stabilize or destabilize the GQ assemblies. Learning the effect of synthetic nucleotide analogs on the stability of GQs can assist in engineering a required stable GQ topology, and exploring the in vitro action of the single and clustered natural base damage on GQ architectures may provide indications for the cellular events.
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Affiliation(s)
- Janos Sagi
- Rimstone Laboratory, RLI, Carlsbad, CA 92010, USA
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24
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Manna S, Panse CH, Sontakke VA, Sangamesh S, Srivatsan SG. Probing Human Telomeric DNA and RNA Topology and Ligand Binding in a Cellular Model by Using Responsive Fluorescent Nucleoside Probes. Chembiochem 2017; 18:1604-1615. [PMID: 28569423 PMCID: PMC5724660 DOI: 10.1002/cbic.201700283] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Indexed: 01/03/2023]
Abstract
The development of biophysical systems that enable an understanding of the structure and ligand-binding properties of G-quadruplex (GQ)-forming nucleic acid sequences in cells or models that mimic the cellular environment would be highly beneficial in advancing GQ-directed therapeutic strategies. Herein, the establishment of a biophysical platform to investigate the structure and recognition properties of human telomeric (H-Telo) DNA and RNA repeats in a cell-like confined environment by using conformation-sensitive fluorescent nucleoside probes and a widely used cellular model, bis(2-ethylhexyl) sodium sulfosuccinate reverse micelles (RMs), is described. The 2'-deoxy and ribonucleoside probes, composed of a 5-benzofuran uracil base analogue, faithfully report the aqueous micellar core through changes in their fluorescence properties. The nucleoside probes incorporated into different loops of H-Telo DNA and RNA oligonucleotide repeats are minimally perturbing and photophysically signal the formation of respective GQ structures in both aqueous buffer and RMs. Furthermore, these sensors enable a direct comparison of the binding affinity of a ligand to H-Telo DNA and RNA GQ structures in the bulk and confined environment of RMs. These results demonstrate that this combination of a GQ nucleoside probe and easy-to-handle RMs could provide new opportunities to study and devise screening-compatible assays in a cell-like environment to discover GQ binders of clinical potential.
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Affiliation(s)
- Sudeshna Manna
- Department of ChemistryIndian Institute of Science Education and Research (IISER)Dr. Homi Bhabha RoadPune411008India
| | - Cornelia H. Panse
- Department of ChemistryIndian Institute of Science Education and Research (IISER)Dr. Homi Bhabha RoadPune411008India
| | - Vyankat A. Sontakke
- Department of ChemistryIndian Institute of Science Education and Research (IISER)Dr. Homi Bhabha RoadPune411008India
| | - Sarangamath Sangamesh
- Department of ChemistryIndian Institute of Science Education and Research (IISER)Dr. Homi Bhabha RoadPune411008India
| | - Seergazhi G. Srivatsan
- Department of ChemistryIndian Institute of Science Education and Research (IISER)Dr. Homi Bhabha RoadPune411008India
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25
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Folding of the silver aptamer in a DNAzyme probed by 2-aminopurine fluorescence. Biochimie 2017; 145:145-150. [PMID: 28711684 DOI: 10.1016/j.biochi.2017.07.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2017] [Accepted: 07/04/2017] [Indexed: 12/28/2022]
Abstract
The RNA-cleaving Ag10c DNAzyme was recently isolated via in vitro selection and it can bind two Ag+ ions for activity. The Ag10c contains a well-defined Ag+ binding aptamer as indicated by DMS footprinting. Since aptamer binding is often accompanied with conformational changes, we herein used 2-aminopurine (2AP) to probe its folding in the presence of Ag+. The Ag10c was respectively labeled with 2AP at three different positions, both in the substrate strand and in the enzyme strand, one at a time. Ag+-induced folding was observed at the substrate cleavage junction and the A9 position of the enzyme strand, consistent with aptamer binding. The measured Kd at the A9 position was 18 μM Ag+ with a Hill coefficient of 2.17, similar to those obtained from the previous cleavage activity based assays. However, labeling a 2AP at the A2 position inhibited the activity and folding. Compared to other metal ions, Ag+ has a unique sigmoidal folding profile indicative of multiple silver binding cooperatively. This suggests that Ag+ can induce a local folding in the enzyme loop and this folding is important for activity. This study provides important biophysical insights into this new DNAzyme, suggesting the possibility of designing folding-based biosensors for Ag+.
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26
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Brown RV, Wang T, Chappeta VR, Wu G, Onel B, Chawla R, Quijada H, Camp SM, Chiang ET, Lassiter QR, Lee C, Phanse S, Turnidge MA, Zhao P, Garcia JGN, Gokhale V, Yang D, Hurley LH. The Consequences of Overlapping G-Quadruplexes and i-Motifs in the Platelet-Derived Growth Factor Receptor β Core Promoter Nuclease Hypersensitive Element Can Explain the Unexpected Effects of Mutations and Provide Opportunities for Selective Targeting of Both Structures by Small Molecules To Downregulate Gene Expression. J Am Chem Soc 2017; 139:7456-7475. [PMID: 28471683 PMCID: PMC5977998 DOI: 10.1021/jacs.6b10028] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The platelet-derived growth factor receptor β (PDGFR-β) signaling pathway is a validated and important target for the treatment of certain malignant and nonmalignant pathologies. We previously identified a G-quadruplex-forming nuclease hypersensitive element (NHE) in the human PDGFR-β promoter that putatively forms four overlapping G-quadruplexes. Therefore, we further investigated the structures and biological roles of the G-quadruplexes and i-motifs in the PDGFR-β NHE with the ultimate goal of demonstrating an alternate and effective strategy for molecularly targeting the PDGFR-β pathway. Significantly, we show that the primary G-quadruplex receptor for repression of PDGFR-β is the 3'-end G-quadruplex, which has a GGA sequence at the 3'-end. Mutation studies using luciferase reporter plasmids highlight a novel set of G-quadruplex point mutations, some of which seem to provide conflicting results on effects on gene expression, prompting further investigation into the effect of these mutations on the i-motif-forming strand. Herein we characterize the formation of an equilibrium between at least two different i-motifs from the cytosine-rich (C-rich) sequence of the PDGFR-β NHE. The apparently conflicting mutation results can be rationalized if we take into account the single base point mutation made in a critical cytosine run in the PDGFR-β NHE that dramatically affects the equilibrium of i-motifs formed from this sequence. We identified a group of ellipticines that targets the G-quadruplexes in the PDGFR-β promoter, and from this series of compounds, we selected the ellipticine analog GSA1129, which selectively targets the 3'-end G-quadruplex, to shift the dynamic equilibrium in the full-length sequence to favor this structure. We also identified a benzothiophene-2-carboxamide (NSC309874) as a PDGFR-β i-motif-interactive compound. In vitro, GSA1129 and NSC309874 downregulate PDGFR-β promoter activity and transcript in the neuroblastoma cell line SK-N-SH at subcytotoxic cell concentrations. GSA1129 also inhibits PDGFR-β-driven cell proliferation and migration. With an established preclinical murine model of acute lung injury, we demonstrate that GSA1129 attenuates endotoxin-mediated acute lung inflammation. Our studies underscore the importance of considering the effects of point mutations on structure formation from the G- and C-rich sequences and provide further evidence for the involvement of both strands and associated structures in the control of gene expression.
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Affiliation(s)
- Robert V. Brown
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
| | - Ting Wang
- College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States
| | | | - Guanhui Wu
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
| | - Buket Onel
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
| | - Reena Chawla
- BIO5 Institute, 1657 East Helen Street, Tucson, Arizona 85721, United States
| | - Hector Quijada
- College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States
| | - Sara M. Camp
- College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States
| | - Eddie T. Chiang
- College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States
| | - Quinea R. Lassiter
- College of Agriculture & Life Sciences, University of Arizona, 1117 East Lowell Street, Tucson, Arizona 85721, United States
| | - Carmen Lee
- College of Agriculture & Life Sciences, University of Arizona, 1117 East Lowell Street, Tucson, Arizona 85721, United States
- College of Science, University of Arizona, 1040 East Fourth Street, Tucson, Arizona 85721, United States
| | - Shivani Phanse
- College of Science, University of Arizona, 1040 East Fourth Street, Tucson, Arizona 85721, United States
| | - Megan A. Turnidge
- College of Science, University of Arizona, 1040 East Fourth Street, Tucson, Arizona 85721, United States
| | - Ping Zhao
- School of Chemistry and Chemical Engineering, Guangdong Pharmaceutical University, No. 280 Waihuandong Road, Education Mega Centre, Guanzhou 510006, Peoples Republic of China
| | - Joe G. N. Garcia
- College of Medicine, University of Arizona, 1501 North Campbell Avenue, Tucson, Arizona 85724, United States
| | - Vijay Gokhale
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
- BIO5 Institute, 1657 East Helen Street, Tucson, Arizona 85721, United States
| | - Danzhou Yang
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
- BIO5 Institute, 1657 East Helen Street, Tucson, Arizona 85721, United States
- University of Arizona Cancer Center, 1515 North Campbell Avenue, Tucson, Arizona 85724, United States
| | - Laurence H. Hurley
- College of Pharmacy, University of Arizona, 1703 East Mabel Street, Tucson, Arizona 85721, United States
- BIO5 Institute, 1657 East Helen Street, Tucson, Arizona 85721, United States
- University of Arizona Cancer Center, 1515 North Campbell Avenue, Tucson, Arizona 85724, United States
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Wu T, Ye M, Mao T, Lin F, Hu Y, Gan N, Shao Y. Human telomeric hybrid-2-over-hybrid-1 G-quadruplex targeting and a selective hypersaline-tolerant sensor using abasic site-engineered monomorphism. Anal Chim Acta 2017; 964:161-169. [DOI: 10.1016/j.aca.2017.01.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Revised: 01/13/2017] [Accepted: 01/21/2017] [Indexed: 02/02/2023]
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Lecours MJ, Marchand A, Anwar A, Guetta C, Hopkins WS, Gabelica V. What stoichiometries determined by mass spectrometry reveal about the ligand binding mode to G-quadruplex nucleic acids. Biochim Biophys Acta Gen Subj 2017; 1861:1353-1361. [PMID: 28087374 DOI: 10.1016/j.bbagen.2017.01.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 11/27/2022]
Abstract
G-quadruplexes (G4s) have become important drug targets to regulate gene expression and telomere maintenance. Many studies on G4 ligand binding focus on determining the ligand binding affinities and selectivities. Ligands, however, can also affect the G4 conformation. Here we explain how to use electrospray ionization mass spectrometry (ESI-MS) to monitor simultaneously ligand binding and cation binding stoichiometries. The changes in potassium binding stoichiometry upon ligand binding hint at ligand-induced conformational changes involving a modification of the number of G-quartets. We investigated the interaction of three quadruplex ligands (PhenDC3, 360A and Pyridostatin) with a variety of G4s. Electrospray mass spectrometry makes it easy to detect K+ displacement (interpreted as quartet disruption) upon ligand binding, and to determine how many ligand molecules must be bound for the quartet opening to occur. The reasons for ligand-induced conversion to antiparallel structures with fewer quartets are discussed. Conversely, K+ intake (hence quartet formation) was detected upon ligand binding to G-rich sequences that did not form quadruplexes in 1mM K+ alone. This demonstrates the value of mass spectrometry for assessing not only ligand binding, but also ligand-induced rearrangements in the target sequence. This article is part of a Special Issue entitled "G-quadruplex" Guest Editor: Dr. Concetta Giancola and Dr. Daniela Montesarchio.
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Affiliation(s)
- Michael J Lecours
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Adrien Marchand
- INSERM, CNRS, Université de Bordeaux, Laboratoire Acides Nucléiques: Régulations Naturelle et Artificielle (ARNA, U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France
| | - Ahdia Anwar
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Corinne Guetta
- Institut Curie, CNRS, INSERM, Univ. Paris Sud, Laboratoire de Chimie, modélisation et imagerie pour la biologie (CMIB, U1196, UMR9187), Orsay, France
| | - W Scott Hopkins
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Valérie Gabelica
- INSERM, CNRS, Université de Bordeaux, Laboratoire Acides Nucléiques: Régulations Naturelle et Artificielle (ARNA, U1212, UMR5320), IECB, 2 rue Robert Escarpit, 33607 Pessac, France.
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29
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Marchand A, Gabelica V. Folding and misfolding pathways of G-quadruplex DNA. Nucleic Acids Res 2016; 44:10999-11012. [PMID: 27924036 PMCID: PMC5159560 DOI: 10.1093/nar/gkw970] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 10/07/2016] [Accepted: 10/15/2016] [Indexed: 12/13/2022] Open
Abstract
G-quadruplexes adopt various folding topologies, but information on their folding pathways remains scarce. Here, we used electrospray mass spectrometry to detect and quantify the specifically bound potassium ions, and circular dichroism to characterize the stacking topology of each ensemble. For human telomeric (hTel) sequences containing the d((GGGTTA)3GGG) core, K+ binding affinity and cooperativity strongly depends on the chosen construct. The shortest sequences bind only one K+ at low KCl concentration, and this 2-quartet G-quadruplex is antiparallel. Flanking bases increase the K+ binding cooperativity. To decipher the folding pathways, we investigated the kinetics of K+ binding to telomeric (hybrid) and c-myc (parallel) G-quadruplexes. G-quadruplexes fold via branched pathways with multiple parallel reactions. Up to six states (one ensemble without K+, two ensembles with 1-K+ and three ensembles with 2-K+) are separated based on their formation rates and ion mobility spectrometry. All G-quadruplexes first form long-lived misfolded structures (off-pathway compared to the most stable structures) containing one K+ and two quartets in an antiparallel stacking arrangement. The results highlight the particular ruggedness of G-quadruplex nucleic acid folding landscapes. Misfolded structures can play important roles for designing artificial G-quadruplex based structures, and for conformational selection by ligands or proteins in a biological context.
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Affiliation(s)
- Adrien Marchand
- INSERM, CNRS, Univ. Bordeaux, U1212 / UMR5320 - Acides Nucléiques: Régulations Naturelle et Artificielle, IECB, 2 rue Robert Escarpit, 33607 Pessac, France
| | - Valérie Gabelica
- INSERM, CNRS, Univ. Bordeaux, U1212 / UMR5320 - Acides Nucléiques: Régulations Naturelle et Artificielle, IECB, 2 rue Robert Escarpit, 33607 Pessac, France
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30
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Zhou W, Ding J, Liu J. A highly specific sodium aptamer probed by 2-aminopurine for robust Na+ sensing. Nucleic Acids Res 2016; 44:10377-10385. [PMID: 27655630 PMCID: PMC5137442 DOI: 10.1093/nar/gkw845] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 09/10/2016] [Accepted: 09/13/2016] [Indexed: 12/12/2022] Open
Abstract
Sodium is one of the most abundant metals in the environment and in biology, playing critical ecological and physiological roles. Na+ is also the most common buffer salt for nucleic acids research, while its specific interaction with DNA has yet to be fully studied. Herein, we probe a highly selective and robust Na+ aptamer using 2-aminopurine (2AP), a fluorescent adenine analog. This aptamer has two DNA strands derived from the Ce13d DNAzyme. By introducing a 2AP at the cleavage site of the substrate strand, Na+ induces ∼40% fluorescence increase. The signaling is improved by a series of rational mutations, reaching >600% with the C10A20 double mutant. This fluorescence enhancement suggests relaxed base stacking near the 2AP label upon Na+ binding. By replacing a non-conserved adenine in the enzyme strand by 2AP, Na+-dependent fluorescence quenching is observed, suggesting that the enzyme loop folds into a more compact structure upon Na+ binding. The fluorescence changes allow for Na+ detection. With an optimized sequence, a detection limit of 0.4 mM Na+ is achieved, reaching saturated signal in less than 10 s. The sensor response is insensitive to ionic strength, which is critical for Na+ detection.
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Affiliation(s)
- Wenhu Zhou
- School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China.,Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Jinsong Ding
- School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China
| | - Juewen Liu
- School of Pharmaceutical Sciences, Central South University, Changsha, Hunan 410013, China .,Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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31
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Bouilly D, Hon J, Daly NS, Trocchia S, Vernick S, Yu J, Warren S, Wu Y, Gonzalez RL, Shepard KL, Nuckolls C. Single-Molecule Reaction Chemistry in Patterned Nanowells. NANO LETTERS 2016; 16:4679-85. [PMID: 27270004 PMCID: PMC5176326 DOI: 10.1021/acs.nanolett.6b02149] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A new approach to synthetic chemistry is performed in ultraminiaturized, nanofabricated reaction chambers. Using lithographically defined nanowells, we achieve single-point covalent chemistry on hundreds of individual carbon nanotube transistors, providing robust statistics and unprecedented spatial resolution in adduct position. Each device acts as a sensor to detect, in real-time and through quantized changes in conductance, single-point functionalization of the nanotube as well as consecutive chemical reactions, molecular interactions, and molecular conformational changes occurring on the resulting single-molecule probe. In particular, we use a set of sequential bioconjugation reactions to tether a single-strand of DNA to the device and record its repeated, reversible folding into a G-quadruplex structure. The stable covalent tether allows us to measure the same molecule in different solutions, revealing the characteristic increased stability of the G-quadruplex structure in the presence of potassium ions (K(+)) versus sodium ions (Na(+)). Nanowell-confined reaction chemistry on carbon nanotube devices offers a versatile method to isolate and monitor individual molecules during successive chemical reactions over an extended period of time.
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Affiliation(s)
- Delphine Bouilly
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
| | - Jason Hon
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
| | - Nathan S. Daly
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
| | - Scott Trocchia
- Department of Electrical Engineering, Columbia University, 500 W. 120th Street, New York, New York 10027 United
States
| | - Sefi Vernick
- Department of Electrical Engineering, Columbia University, 500 W. 120th Street, New York, New York 10027 United
States
| | - Jaeeun Yu
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
| | - Steven Warren
- Department of Electrical Engineering, Columbia University, 500 W. 120th Street, New York, New York 10027 United
States
| | - Ying Wu
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
| | - Ruben L. Gonzalez
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
- E-mail:
| | - Kenneth L. Shepard
- Department of Electrical Engineering, Columbia University, 500 W. 120th Street, New York, New York 10027 United
States
- E-mail:
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027 United
States
- E-mail:
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32
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Sabale PM, Srivatsan SG. Responsive Fluorescent PNA Analogue as a Tool for Detecting G-quadruplex Motifs of Oncogenes and Activity of Toxic Ribosome-Inactivating Proteins. Chembiochem 2016; 17:1665-73. [PMID: 27271025 DOI: 10.1002/cbic.201600192] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Indexed: 12/13/2022]
Abstract
Fluorescent oligomers that are resistant to enzymatic degradation and report their binding to target oligonucleotides (ONs) by changes in fluorescence properties are highly useful in developing nucleic-acid-based diagnostic tools and therapeutic strategies. Here, we describe the synthesis and photophysical characterization of fluorescent peptide nucleic acid (PNA) building blocks made of microenvironment-sensitive 5-(benzofuran-2-yl)- and 5-(benzothiophen-2-yl)-uracil cores. The emissive monomers, when incorporated into PNA oligomers and hybridized to complementary ONs, are minimally perturbing and are highly sensitive to their neighboring base environment. In particular, benzothiophene-modified PNA reports the hybridization process with significant enhancement in fluorescence intensity, even when placed in the vicinity of guanine residues, which often quench fluorescence. This feature was used in the turn-on detection of G-quadruplex-forming promoter DNA sequences of human proto-oncogenes (c-myc and c-kit). Furthermore, the ability of benzothiophene-modified PNA oligomer to report the presence of an abasic site in RNA enabled us to develop a simple fluorescence hybridization assay to detect and estimate the depurination activity of ribosome-inactivating protein toxins. Our results demonstrate that this approach with responsive PNA probes will provide new opportunities to develop robust tools to study nucleic acids.
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Affiliation(s)
- Pramod M Sabale
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, 411008, India.
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33
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Kejnovská I, Vorlíčková M, Brázdová M, Sagi J. Stability of human telomere quadruplexes at high DNA concentrations. Biopolymers 2016; 101:428-38. [PMID: 24037480 DOI: 10.1002/bip.22400] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Revised: 08/13/2013] [Accepted: 08/20/2013] [Indexed: 01/22/2023]
Abstract
For mimicking macromolecular crowding of DNA quadruplexes, various crowding agents have been used, typically PEG, with quadruplexes of micromolar strand concentrations. Thermal and thermodynamic stabilities of these quadruplexes increased with the concentration of the agents, the rise depended on the crowder used. A different phenomenon was observed, and is presented in this article, when the crowder was the quadruplex itself. With DNA strand concentrations ranging from 3 µM to 9 mM, the thermostability did not change up to ∼2 mM, above which it increased, indicating that the unfolding quadruplex units were not monomolecular above ∼2 mM. The results are explained by self-association of the G-quadruplexes above this concentration. The ΔG(°) 37 values, evaluated only below 2 mM, did not become more negative, as with the non-DNA crowders, instead, slightly increased. Folding topology changed from antiparallel to hybrid above 2 mM, and then to parallel quadruplexes at high, 6-9 mM strand concentrations. In this range, the concentration of the DNA phosphate anions approached the concentration of the K(+) counterions used. Volume exclusion is assumed to promote the topological changes of quadruplexes toward the parallel, and the decreased screening of anions could affect their stability.
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Affiliation(s)
- Iva Kejnovská
- Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i., Kralovopolska 135,, CZ-612 65, Brno, Czech Republic
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Virgilio A, Esposito V, Mayol L, Giancola C, Petraccone L, Galeone A. The oxidative damage to the human telomere: effects of 5-hydroxymethyl-2'-deoxyuridine on telomeric G-quadruplex structures. Org Biomol Chem 2016; 13:7421-9. [PMID: 25997822 DOI: 10.1039/c5ob00748h] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
As part of the genome, human telomeric regions can be damaged by the chemically reactive molecules responsible for oxidative DNA damage. Considering that G-quadruplex structures have been proven to occur in human telomere regions, several studies have been devoted to investigating the effect of oxidation products on the properties of these structures. However only investigations concerning the presence in G-quadruplexes of the main oxidation products of deoxyguanosine and deoxyadenosine have appeared in the literature. Here, we investigated the effects of 5-hydroxymethyl-2'-deoxyuridine (5-hmdU), one of the main oxidation products of T, on the physical-chemical properties of the G-quadruplex structures formed by two human telomeric sequences. Collected calorimetric, circular dichroism and electrophoretic data suggest that, in contrast to most of the results on other damage, the replacement of a T with a 5-hmdU results in only negligible effects on structural stability. Reported results and other data from literature suggest a possible protecting effect of the loop residues on the other parts of the G-quadruplexes.
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Affiliation(s)
- Antonella Virgilio
- Dipartimento di Farmacia, Università degli Studi di Napoli "Federico II", Via D. Montesano 49, I-80131 Napoli, Italy.
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35
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Bončina M, Hamon F, Islam B, Teulade-Fichou MP, Vesnaver G, Haider S, Lah J. Dominant Driving Forces in Human Telomere Quadruplex Binding-Induced Structural Alterations. Biophys J 2016; 108:2903-11. [PMID: 26083930 DOI: 10.1016/j.bpj.2015.05.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 04/07/2015] [Accepted: 05/03/2015] [Indexed: 01/23/2023] Open
Abstract
Recently various pathways of human telomere (ht) DNA folding into G-quadruplexes and of ligand binding to these structures have been proposed. However, the key issue as to the nature of forces driving the folding and recognition processes remains unanswered. In this study, structural changes of 22-mer ht-DNA fragment (Tel22), induced by binding of ions (K(+), Na(+)) and specific bisquinolinium ligands, were monitored by calorimetric and spectroscopic methods and by gel electrophoresis. Using the global model analysis of a wide variety of experimental data, we were able to characterize the thermodynamic forces that govern the formation of stable Tel22 G-quadruplexes, folding intermediates, and ligand-quadruplex complexes, and then predict Tel22 behavior in aqueous solutions as a function of temperature, salt concentration, and ligand concentration. On the basis of the above, we believe that our work sets the framework for better understanding the heterogeneity of ht-DNA folding and binding pathways, and its structural polymorphism.
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Affiliation(s)
- Matjaž Bončina
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Florian Hamon
- Institut Curie, Centre National de la Recherche Scientifique UMR-176, Centre Universitaire d'Orsay, Orsay, France
| | - Barira Islam
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK
| | - Marie-Paule Teulade-Fichou
- Institut Curie, Centre National de la Recherche Scientifique UMR-176, Centre Universitaire d'Orsay, Orsay, France
| | - Gorazd Vesnaver
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
| | - Shozeb Haider
- Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Belfast, UK; University College London School of Pharmacy, Bloomsbury, London, UK
| | - Jurij Lah
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia.
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36
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Wang ZF, Li MH, Chen WW, Hsu STD, Chang TC. A novel transition pathway of ligand-induced topological conversion from hybrid forms to parallel forms of human telomeric G-quadruplexes. Nucleic Acids Res 2016; 44:3958-68. [PMID: 26975658 PMCID: PMC4856992 DOI: 10.1093/nar/gkw145] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/01/2016] [Indexed: 11/17/2022] Open
Abstract
The folding topology of DNA G-quadruplexes (G4s) depends not only on their nucleotide sequences but also on environmental factors and/or ligand binding. Here, a G4 ligand, 3,6-bis(1-methyl-4-vinylpyridium iodide)-9-(1-(1-methyl-piperidinium iodide)-3,6,9-trioxaundecane) carbazole (BMVC-8C3O), can induce topological conversion of non-parallel to parallel forms in human telomeric DNA G4s. Nuclear magnetic resonance (NMR) spectroscopy with hydrogen-deuterium exchange (HDX) reveals the presence of persistent imino proton signals corresponding to the central G-quartet during topological conversion of Tel23 and Tel25 G4s from hybrid to parallel forms, implying that the transition pathway mainly involves local rearrangements. In contrast, rapid HDX was observed during the transition of 22-CTA G4 from an anti-parallel form to a parallel form, resulting in complete disappearance of all the imino proton signals, suggesting the involvement of substantial unfolding events associated with the topological transition. Site-specific imino proton NMR assignments of Tel23 G4 enable determination of the interconversion rates of individual guanine bases and detection of the presence of intermediate states. Since the rate of ligand binding is much higher than the rate of ligand-induced topological conversion, a three-state kinetic model was evoked to establish the associated energy diagram for the topological conversion of Tel23 G4 induced by BMVC-8C3O.
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Affiliation(s)
- Zi-Fu Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan, Republic of China
| | - Ming-Hao Li
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan, Republic of China
| | - Wei-Wen Chen
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan, Republic of China Molecular Science and Technology Program, Taiwan International Graduate Program, Academia Sinica, Taipei 106, Taiwan, Republic of China Department of Chemistry, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China
| | - Shang-Te Danny Hsu
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan, Republic of China Institute of Biochemical Sciences, National Taiwan University, Taipei 10617, Taiwan, Republic of China
| | - Ta-Chau Chang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan, Republic of China
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37
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Kogut M, Kleist C, Czub J. Molecular dynamics simulations reveal the balance of forces governing the formation of a guanine tetrad-a common structural unit of G-quadruplex DNA. Nucleic Acids Res 2016; 44:3020-30. [PMID: 26980278 PMCID: PMC4838382 DOI: 10.1093/nar/gkw160] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 03/01/2016] [Indexed: 12/13/2022] Open
Abstract
G-quadruplexes (G4) are nucleic acid conformations of guanine-rich sequences, in which guanines are arranged in the square-planar G-tetrads, stacked on one another. G4 motifs form in vivo and are implicated in regulation of such processes as gene expression and chromosome maintenance. The structure and stability of various G4 topologies were determined experimentally; however, the driving forces for their formation are not fully understood at the molecular level. Here, we used all-atom molecular dynamics to probe the microscopic origin of the G4 motif stability. By computing the free energy profiles governing the dissociation of the 3′-terminal G-tetrad in the telomeric parallel-stranded G4, we examined the thermodynamic and kinetic stability of a single G-tetrad, as a common structural unit of G4 DNA. Our results indicate that the energetics of guanine association alone does not explain the overall stability of the G-tetrad and that interactions involving sugar–phosphate backbone, in particular, the constrained minimization of the phosphate–phosphate repulsion energy, are crucial in providing the observed enthalpic stabilization. This enthalpic gain is largely compensated by the unfavorable entropy change due to guanine association and optimization of the backbone topology.
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Affiliation(s)
- Mateusz Kogut
- Department of Physical Chemistry, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland
| | - Cyprian Kleist
- Department of Physical Chemistry, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland
| | - Jacek Czub
- Department of Physical Chemistry, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland
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Abstract
Metal ions are essential cofactors for the structure and functions of nucleic acids. Yet, the early discovery in the 70s of the crucial role of Mg(2+) in stabilizing tRNA structures has occulted for a long time the importance of monovalent cations. Renewed interest in these ions was brought in the late 90s by the discovery of specific potassium metal ions in the core of a group I intron. Their importance in nucleic acid folding and catalytic activity is now well established. However, detection of K(+) and Na(+) ions is notoriously problematic and the question about their specificity is recurrent. Here we review the different methods that can be used to detect K(+) and Na(+) ions in nucleic acid structures such as X-ray crystallography, nuclear magnetic resonance or molecular dynamics simulations. We also discuss specific versus non-specific binding to different structures through various examples.
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Affiliation(s)
- Pascal Auffinger
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC, CNRS, 15 rue René Descartes, F-67084, Strasbourg, France.
| | - Luigi D'Ascenzo
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC, CNRS, 15 rue René Descartes, F-67084, Strasbourg, France.
| | - Eric Ennifar
- Architecture et Réactivité de l'ARN, Université de Strasbourg, IBMC, CNRS, 15 rue René Descartes, F-67084, Strasbourg, France.
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39
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Largy E, Mergny JL, Gabelica V. Role of Alkali Metal Ions in G-Quadruplex Nucleic Acid Structure and Stability. Met Ions Life Sci 2016; 16:203-58. [PMID: 26860303 DOI: 10.1007/978-3-319-21756-7_7] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
G-quadruplexes are guanine-rich nucleic acids that fold by forming successive quartets of guanines (the G-tetrads), stabilized by intra-quartet hydrogen bonds, inter-quartet stacking, and cation coordination. This specific although highly polymorphic type of secondary structure deviates significantly from the classical B-DNA duplex. G-quadruplexes are detectable in human cells and are strongly suspected to be involved in a number of biological processes at the DNA and RNA levels. The vast structural polymorphism exhibited by G-quadruplexes, together with their putative biological relevance, makes them attractive therapeutic targets compared to canonical duplex DNA. This chapter focuses on the essential and specific coordination of alkali metal cations by G-quadruplex nucleic acids, and most notably on studies highlighting cation-dependent dissimilarities in their stability, structure, formation, and interconversion. Section 1 surveys G-quadruplex structures and their interactions with alkali metal ions while Section 2 presents analytical methods used to study G-quadruplexes. The influence of alkali cations on the stability, structure, and kinetics of formation of G-quadruplex structures of quadruplexes will be discussed in Sections 3 and 4. Section 5 focuses on the cation-induced interconversion of G-quadruplex structures. In Sections 3 to 5, we will particularly emphasize the comparisons between cations, most often K(+) and Na(+) because of their prevalence in the literature and in cells.
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Affiliation(s)
- Eric Largy
- ARNA Laboratory, Université Bordeaux, IECB, 2, rue Robert Escarpit, F-33600, Pessac, France.,ARNA Laboratory, INSERM, U869, F-33000, Bordeaux, France
| | - Jean-Louis Mergny
- ARNA Laboratory, Université Bordeaux, IECB, 2, rue Robert Escarpit, F-33600, Pessac, France. .,ARNA Laboratory, INSERM, U869, F-33000, Bordeaux, France.
| | - Valérie Gabelica
- ARNA Laboratory, Université Bordeaux, IECB, 2, rue Robert Escarpit, F-33600, Pessac, France. .,ARNA Laboratory, INSERM, U869, F-33000, Bordeaux, France.
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40
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Bončina M, Podlipnik Č, Piantanida I, Eilmes J, Teulade-Fichou MP, Vesnaver G, Lah J. Thermodynamic fingerprints of ligand binding to human telomeric G-quadruplexes. Nucleic Acids Res 2015; 43:10376-86. [PMID: 26546516 PMCID: PMC4666371 DOI: 10.1093/nar/gkv1167] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 10/21/2015] [Indexed: 01/13/2023] Open
Abstract
Thermodynamic studies of ligand binding to human telomere (ht) DNA quadruplexes, as a rule, neglect the involvement of various ht-DNA conformations in the binding process. Therefore, the thermodynamic driving forces and the mechanisms of ht-DNA G-quadruplex-ligand recognition remain poorly understood. In this work we characterize thermodynamically and structurally binding of netropsin (Net), dibenzotetraaza[14]annulene derivatives (DP77, DP78), cationic porphyrin (TMPyP4) and two bisquinolinium ligands (Phen-DC3, 360A-Br) to the ht-DNA fragment (Tel22) AGGG(TTAGGG)3 using isothermal titration calorimetry, CD and fluorescence spectroscopy, gel electrophoresis and molecular modeling. By global thermodynamic analysis of experimental data we show that the driving forces characterized by contributions of specific interactions, changes in solvation and conformation differ significantly for binding of ligands with low quadruplex selectivity over duplexes (Net, DP77, DP78, TMPyP4; KTel22 ≈ <KdsDNA) and for highly selective quadruplex-specific ligands (Phen-DC3, 360A-Br; KTel22 > KdsDNA). These contributions are in accordance with the observed structural features (changes) and suggest that upon binding Net, DP77, DP78 and TMPyP4 select hybrid-1 and/or hybrid-2 conformation while Phen-DC3 and 360A-Br induce the transition of hybrid-1 and hybrid-2 to the structure with characteristics of antiparallel or hybrid-3 type conformation.
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Affiliation(s)
- Matjaž Bončina
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Črtomir Podlipnik
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Ivo Piantanida
- Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, PO Box 180, HR-10002 Zagreb, Croatia
| | - Julita Eilmes
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland
| | | | - Gorazd Vesnaver
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
| | - Jurij Lah
- Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia
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41
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Islam B, Stadlbauer P, Krepl M, Koca J, Neidle S, Haider S, Sponer J. Extended molecular dynamics of a c-kit promoter quadruplex. Nucleic Acids Res 2015; 43:8673-93. [PMID: 26245347 PMCID: PMC4605300 DOI: 10.1093/nar/gkv785] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 07/21/2015] [Indexed: 01/29/2023] Open
Abstract
The 22-mer c-kit promoter sequence folds into a parallel-stranded quadruplex with a unique structure, which has been elucidated by crystallographic and NMR methods and shows a high degree of structural conservation. We have carried out a series of extended (up to 10 μs long, ∼50 μs in total) molecular dynamics simulations to explore conformational stability and loop dynamics of this quadruplex. Unfolding no-salt simulations are consistent with a multi-pathway model of quadruplex folding and identify the single-nucleotide propeller loops as the most fragile part of the quadruplex. Thus, formation of propeller loops represents a peculiar atomistic aspect of quadruplex folding. Unbiased simulations reveal μs-scale transitions in the loops, which emphasizes the need for extended simulations in studies of quadruplex loops. We identify ion binding in the loops which may contribute to quadruplex stability. The long lateral-propeller loop is internally very stable but extensively fluctuates as a rigid entity. It creates a size-adaptable cleft between the loop and the stem, which can facilitate ligand binding. The stability gain by forming the internal network of GA base pairs and stacks of this loop may be dictating which of the many possible quadruplex topologies is observed in the ground state by this promoter quadruplex.
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Affiliation(s)
- Barira Islam
- Central European Institute of Technology (CEITEC), Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic
| | - Petr Stadlbauer
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
| | - Miroslav Krepl
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
| | - Jaroslav Koca
- Central European Institute of Technology (CEITEC), Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic National Center for Biomolecular Research, Faculty of Science, Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic
| | - Stephen Neidle
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Shozeb Haider
- UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Jiri Sponer
- Central European Institute of Technology (CEITEC), Masaryk University, Campus Bohunice, Kamenice 5, 625 00 Brno, Czech Republic Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 612 65 Brno, Czech Republic
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42
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Tanpure AA, Srivatsan SG. Conformation-sensitive nucleoside analogues as topology-specific fluorescence turn-on probes for DNA and RNA G-quadruplexes. Nucleic Acids Res 2015. [PMID: 26202965 PMCID: PMC4678839 DOI: 10.1093/nar/gkv743] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Development of probes that can discriminate G-quadruplex (GQ) structures and indentify efficient GQ binders on the basis of topology and nucleic acid type is highly desired to advance GQ-directed therapeutic strategies. In this context, we describe the development of minimally perturbing and environment-sensitive pyrimidine nucleoside analogues, based on a 5-(benzofuran-2-yl)uracil core, as topology-specific fluorescence turn-on probes for human telomeric DNA and RNA GQs. The pyrimidine residues of one of the loop regions (TTA) of telomeric DNA and RNA GQ oligonucleotide (ON) sequences were replaced with 5-benzofuran-modified 2′-deoxyuridine and uridine analogues. Depending on the position of modification the fluorescent nucleoside analogues distinguish antiparallel, mixed parallel-antiparallel and parallel stranded DNA and RNA GQ topologies from corresponding duplexes with significant enhancement in fluorescence intensity and quantum yield. Further, these GQ sensors enabled the development of a simple fluorescence binding assay to quantify topology- and nucleic acid-specific binding of small molecule ligands to GQ structures. Together, our results demonstrate that these nucleoside analogues are useful GQ probes, which are anticipated to provide new opportunities to study and discover efficient G-quadruplex binders of therapeutic potential.
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Affiliation(s)
- Arun A Tanpure
- Department of Chemistry, Indian Institute of Science Education and Research, Pune, Dr Homi Bhabha Road, Pashan, Pune 411008, India
| | - Seergazhi G Srivatsan
- Department of Chemistry, Indian Institute of Science Education and Research, Pune, Dr Homi Bhabha Road, Pashan, Pune 411008, India
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43
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Miller MC, Ohrenberg CJ, Kuttan A, Trent JO. Separation of Quadruplex Polymorphism in DNA Sequences by Reversed-Phase Chromatography. CURRENT PROTOCOLS IN NUCLEIC ACID CHEMISTRY 2015; 61:17.7.1-17.7.18. [PMID: 26344226 PMCID: PMC4561857 DOI: 10.1002/0471142700.nc1707s61] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
This unit describes a method for the separation of a mixture of quadruplex conformations formed from the same parent sequence via reversed-phase chromatography (RPC). Polymorphism is inherent to quadruplex formation and even relatively simple quadruplex-forming sequences can fold into a cornucopia of possible conformations and topologies. Isolation of a specific conformation for study can be problematic. This is especially true for conformations of the human telomere sequence d(GGG(TTAGGG)3). High performance liquid chromatography (HPLC), especially reversed-phase chromatography, has been a mainstay of nucleic acid research and purification for many decades. We have successfully applied this method to the problem of separating individual quadruplex species in the ensemble from the same parent sequence.
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Affiliation(s)
- M. Clarke Miller
- Department of Chemistry and Biochemistry, University of North Georgia, 3820 Mundy Mill Road, Oakwood, Georgia 30566
- James Graham Brown Cancer Center, Clinical Translational Research Building, University of Louisville, 505 South Hancock Street, Louisville, KY 40202
| | - Carl J. Ohrenberg
- Department of Chemistry and Biochemistry, University of North Georgia, 3820 Mundy Mill Road, Oakwood, Georgia 30566
| | - Ashani Kuttan
- James Graham Brown Cancer Center, Clinical Translational Research Building, University of Louisville, 505 South Hancock Street, Louisville, KY 40202
| | - John O. Trent
- James Graham Brown Cancer Center, Clinical Translational Research Building, University of Louisville, 505 South Hancock Street, Louisville, KY 40202
- Department of Medicine, University of Louisville, Clinical Translational Research Building, University of Louisville, 505 South Hancock Street, Louisville, KY 40202
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44
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Triplex intermediates in folding of human telomeric quadruplexes probed by microsecond-scale molecular dynamics simulations. Biochimie 2014; 105:22-35. [DOI: 10.1016/j.biochi.2014.07.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 07/01/2014] [Indexed: 11/23/2022]
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Largy E, Mergny JL. Shape matters: size-exclusion HPLC for the study of nucleic acid structural polymorphism. Nucleic Acids Res 2014; 42:e149. [PMID: 25143531 PMCID: PMC4231728 DOI: 10.1093/nar/gku751] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, an increasing number of reports have been focused on the structure and biological role of non-canonical nucleic acid secondary structures. Many of these studies involve the use of oligonucleotides that can often adopt a variety of structures depending on the experimental conditions, and hence change the outcome of an assay. The knowledge of the structure(s) formed by oligonucleotides is thus critical to correctly interpret the results, and gain insight into the biological role of these particular sequences. Herein we demonstrate that size-exclusion HPLC (SE-HPLC) is a simple yet surprisingly powerful tool to quickly and effortlessly assess the secondary structure(s) formed by oligonucleotides. For the first time, an extensive calibration and validation of the use of SE-HPLC to confidently detect the presence of different species displaying various structure and/or molecularity, involving >110 oligonucleotides forming a variety of secondary structures (antiparallel, parallel, A-tract bent and mismatched duplexes, triplexes, G-quadruplexes and i-motifs, RNA stem loops), is performed. Moreover, we introduce simple metrics that allow the use of SE-HPLC without the need for a tedious calibration work. We show that the remarkable versatility of the method allows to quickly establish the influence of a number of experimental parameters on nucleic acid structuration and to operate on a wide range of oligonucleotide concentrations. Case studies are provided to clearly illustrate the all-terrain capabilities of SE-HPLC for oligonucleotide secondary structure analysis. Finally, this manuscript features a number of important observations contributing to a better understanding of nucleic acid structural polymorphism.
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Affiliation(s)
- Eric Largy
- ARNA Laboratory, University of Bordeaux, Bordeaux 33000, France INSERM, U869, IECB, Pessac 33600, France
| | - Jean-Louis Mergny
- ARNA Laboratory, University of Bordeaux, Bordeaux 33000, France INSERM, U869, IECB, Pessac 33600, France
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46
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Le HT, Dean WL, Buscaglia R, Chaires JB, Trent JO. An investigation of G-quadruplex structural polymorphism in the human telomere using a combined approach of hydrodynamic bead modeling and molecular dynamics simulation. J Phys Chem B 2014; 118:5390-405. [PMID: 24779348 PMCID: PMC4032189 DOI: 10.1021/jp502213y] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/21/2014] [Indexed: 01/12/2023]
Abstract
Guanine-rich oligonucleotides can adopt noncanonical tertiary structures known as G-quadruplexes, which can exist in different forms depending on experimental conditions. High-resolution structural methods, such as X-ray crystallography and NMR spectroscopy, have been of limited usefulness in resolving the inherent structural polymorphism associated with G-quadruplex formation. The lack of, or the ambiguous nature of, currently available high-resolution structural data, in turn, has severely hindered investigations into the nature of these structures and their interactions with small-molecule inhibitors. We have used molecular dynamics in conjunction with hydrodynamic bead modeling to study the structures of the human telomeric G-quadruplex-forming sequences at the atomic level. We demonstrated that molecular dynamics can reproduce experimental hydrodynamic measurements and thus can be a powerful tool in the structural study of existing G-quadruplex sequences or in the prediction of new G-quadruplex structures.
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Affiliation(s)
- Huy T. Le
- Department
of Biochemistry and Molecular Biology, School of Medicine, University of Louisville, HSC-A Building, Room 616, Louisville, Kentucky 40202, United States
| | - William L. Dean
- Department
of Biochemistry and Molecular Biology, School of Medicine, University of Louisville, HSC-A Building, Room 616, Louisville, Kentucky 40202, United States
- James
Graham Brown Cancer Center, University of
Louisville, 529 South
Jackson Street, Louisville, Kentucky 40202, United
States
| | - Robert Buscaglia
- Department
of Biochemistry and Molecular Biology, School of Medicine, University of Louisville, HSC-A Building, Room 616, Louisville, Kentucky 40202, United States
| | - Jonathan B. Chaires
- Department
of Biochemistry and Molecular Biology, School of Medicine, University of Louisville, HSC-A Building, Room 616, Louisville, Kentucky 40202, United States
- James
Graham Brown Cancer Center, University of
Louisville, 529 South
Jackson Street, Louisville, Kentucky 40202, United
States
- Department
of Medicine, School of Medicine, University
of Louisville, 550 South
Jackson Street, Louisville, Kentucky 40202, United
States
| | - John O. Trent
- Department
of Biochemistry and Molecular Biology, School of Medicine, University of Louisville, HSC-A Building, Room 616, Louisville, Kentucky 40202, United States
- James
Graham Brown Cancer Center, University of
Louisville, 529 South
Jackson Street, Louisville, Kentucky 40202, United
States
- Department
of Medicine, School of Medicine, University
of Louisville, 550 South
Jackson Street, Louisville, Kentucky 40202, United
States
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47
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Gray RD, Trent JO, Chaires JB. Folding and unfolding pathways of the human telomeric G-quadruplex. J Mol Biol 2014; 426:1629-50. [PMID: 24487181 DOI: 10.1016/j.jmb.2014.01.009] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 11/30/2022]
Abstract
Sequence analogs of human telomeric DNA such as d[AGGG(TTAGGG)3] (Tel22) fold into monomeric quadruplex structures in the presence of a suitable cation. To investigate the pathway for unimolecular quadruplex formation, we monitored the kinetics of K(+)-induced folding of Tel22 by circular dichroism (CD), intrinsic 2-aminopurine fluorescence, and fluorescence resonance energy transfer (FRET). The results are consistent with a four-step pathway U ↔ I1 ↔ I2 ↔ I3 ↔ F where U and F represent unfolded and folded conformational ensembles and I1, I2, and I3 are intermediates. Previous kinetic studies have shown that I1 is formed in a rapid pre-equilibrium and may consist of an ensemble of "prefolded" hairpin structures brought about by cation-induced electrostatic collapse of the DNA. The current study shows that I1 converts to I2 with a relaxation time τ1=0.1s at 25 °C in 25 mM KCl. The CD spectrum of I2 is characteristic of an antiparallel quadruplex that could form as a result of intramolecular fold-over of the I1 hairpins. I3 is relatively slowly formed (τ2≈3700s) and has CD and FRET properties consistent with those expected of a triplex structure as previously observed in equilibrium melting studies. I3 converts to F with τ3≈750s. Identical pathways with different kinetic constants involving a rapidly formed antiparallel intermediate were observed with oligonucleotides forming mixed parallel/antiparallel hybrid-1 and hybrid-2 topologies {e.g. d[TTGGG(TTAGGG)3A] and d[TAGGG(TTAGGG)3TT]}. Aspects of the kinetics of unfolding were also monitored by the spectroscopic methods listed above and by time-resolved fluorescence lifetime measurements using a complementary strand trap assay. These experiments reveal a slow, rate-limiting step along the unfolding pathway.
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Affiliation(s)
- Robert D Gray
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - John O Trent
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA
| | - Jonathan B Chaires
- James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA.
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48
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Liu L, Shao Y, Peng J, Huang C, Liu H, Zhang L. Molecular Rotor-Based Fluorescent Probe for Selective Recognition of Hybrid G-Quadruplex and as a K+ Sensor. Anal Chem 2014; 86:1622-31. [DOI: 10.1021/ac403326m] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Lingling Liu
- Institute of Physical
Chemistry, Zhejiang Normal University, Jinhua 321004, Zhejiang, People’s Republic of China
| | - Yong Shao
- Institute of Physical
Chemistry, Zhejiang Normal University, Jinhua 321004, Zhejiang, People’s Republic of China
| | - Jian Peng
- Institute of Physical
Chemistry, Zhejiang Normal University, Jinhua 321004, Zhejiang, People’s Republic of China
| | - Chaobiao Huang
- Department
of Chemistry, College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, People’s Republic of China
| | - Hua Liu
- Institute of Physical
Chemistry, Zhejiang Normal University, Jinhua 321004, Zhejiang, People’s Republic of China
| | - Lihua Zhang
- Institute of Physical
Chemistry, Zhejiang Normal University, Jinhua 321004, Zhejiang, People’s Republic of China
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49
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Sattin G, Artese A, Nadai M, Costa G, Parrotta L, Alcaro S, Palumbo M, Richter SN. Conformation and stability of intramolecular telomeric G-quadruplexes: sequence effects in the loops. PLoS One 2013; 8:e84113. [PMID: 24367632 PMCID: PMC3867476 DOI: 10.1371/journal.pone.0084113] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 11/12/2013] [Indexed: 01/15/2023] Open
Abstract
Telomeres are guanine-rich sequences that protect the ends of chromosomes. These regions can fold into G-quadruplex structures and their stabilization by G-quadruplex ligands has been employed as an anticancer strategy. Genetic analysis in human telomeres revealed extensive allelic variation restricted to loop bases, indicating that the variant telomeric sequences maintain the ability to fold into G-quadruplex. To assess the effect of mutations in loop bases on G-quadruplex folding and stability, we performed a comprehensive analysis of mutant telomeric sequences by spectroscopic techniques, molecular dynamics simulations and gel electrophoresis. We found that when the first position in the loop was mutated from T to C or A the resulting structure adopted a less stable antiparallel topology; when the second position was mutated to C or A, lower thermal stability and no evident conformational change were observed; in contrast, substitution of the third position from A to C induced a more stable and original hybrid conformation, while mutation to T did not significantly affect G-quadruplex topology and stability. Our results indicate that allelic variations generate G-quadruplex telomeric structures with variable conformation and stability. This aspect needs to be taken into account when designing new potential anticancer molecules.
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Affiliation(s)
- Giovanna Sattin
- Department of Molecular Medicine, University of Padua, Padua, Italy
| | - Anna Artese
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Matteo Nadai
- Department of Molecular Medicine, University of Padua, Padua, Italy
| | - Giosuè Costa
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Lucia Parrotta
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Stefano Alcaro
- Dipartimento di Scienze della Salute, Università "Magna Græcia" di Catanzaro, Catanzaro, Italy
| | - Manlio Palumbo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Padua, Italy
| | - Sara N. Richter
- Department of Molecular Medicine, University of Padua, Padua, Italy
- * E-mail:
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50
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Buscaglia R, Gray RD, Chaires JB. Thermodynamic characterization of human telomere quadruplex unfolding. Biopolymers 2013; 99:1006-18. [PMID: 23536479 PMCID: PMC4274053 DOI: 10.1002/bip.22247] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/14/2013] [Accepted: 03/25/2013] [Indexed: 01/02/2023]
Abstract
The 3'-terminal extensions of eukaryotic chromosomes are unique examples of functional single-stranded DNA. Human telomeres are constructed of the repeated DNA sequence 5'-d(TTAGGG). Four-repeats of human telomeric DNA have been characterized by high-resolution techniques to be capable of forming at least five distinct monomeric conformations. The predominant solution topology is influenced by solution conditions and the presence of 3'- or 5'-flanking residues. This study describes the unfolding mechanisms for human telomeric quadruplexes formed by eight sequence variants that form three unique antiparallel topologies in K(+) solution. Thermal unfolding monitored by circular dichroism is analyzed by singular value decomposition to enumerate the number of significant spectral species required to model the unfolding process. Thermal denaturation of all quadruplexes studied is found to be best modeled by a four-state sequential mechanism with two populated intermediates. The thermal unfolding was also investigated in 50% (v/v) acetonitrile in which a parallel topology is favored. Under these dehydrating conditions, quadruplex thermal denaturation is best modeled by a three-state sequential unfolding mechanism with one populated intermediate. Dehydrated parallel quadruplexes demonstrate increased thermal stability. The spectral properties of the unfolding intermediate suggest that it is most likely a triple-helical structure.
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Affiliation(s)
- R Buscaglia
- James Graham Brown Cancer Center, University of Louisville, 505 S. Hancock, Louisville, KY 40202
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