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Zhang Z, Mlýnský V, Krepl M, Šponer J, Stadlbauer P. Mechanical Stability and Unfolding Pathways of Parallel Tetrameric G-Quadruplexes Probed by Pulling Simulations. J Chem Inf Model 2024; 64:3896-3911. [PMID: 38630447 PMCID: PMC11094737 DOI: 10.1021/acs.jcim.4c00227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 04/02/2024] [Accepted: 04/02/2024] [Indexed: 05/14/2024]
Abstract
Guanine quadruplex (GQ) is a noncanonical nucleic acid structure formed by guanine-rich DNA and RNA sequences. Folding of GQs is a complex process, where several aspects remain elusive, despite being important for understanding structure formation and biological functions of GQs. Pulling experiments are a common tool for acquiring insights into the folding landscape of GQs. Herein, we applied a computational pulling strategy─steered molecular dynamics (SMD) simulations─in combination with standard molecular dynamics (MD) simulations to explore the unfolding landscapes of tetrameric parallel GQs. We identified anisotropic properties of elastic conformational changes, unfolding transitions, and GQ mechanical stabilities. Using a special set of structural parameters, we found that the vertical component of pulling force (perpendicular to the average G-quartet plane) plays a significant role in disrupting GQ structures and weakening their mechanical stabilities. We demonstrated that the magnitude of the vertical force component depends on the pulling anchor positions and the number of G-quartets. Typical unfolding transitions for tetrameric parallel GQs involve base unzipping, opening of the G-stem, strand slippage, and rotation to cross-like structures. The unzipping was detected as the first and dominant unfolding event, and it usually started at the 3'-end. Furthermore, results from both SMD and standard MD simulations indicate that partial spiral conformations serve as a transient ensemble during the (un)folding of GQs.
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Affiliation(s)
- Zhengyue Zhang
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
- CEITEC−Central
European Institute of Technology, Masaryk
University, Kamenice
5, Brno 625 00, Czech Republic
- National
Center for Biomolecular Research,
Faculty of Science, Masaryk University, Kamenice 5, Brno 625 00, Czech Republic
| | - Vojtěch Mlýnský
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Miroslav Krepl
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Jiří Šponer
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
| | - Petr Stadlbauer
- Institute
of Biophysics of the Czech Academy of Sciences, Královopolská 135, Brno 61200, Czech Republic
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2
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Riccardi C, Pérez de Carvasal K, Platella C, Meyer A, Smietana M, Morvan F, Montesarchio D. Probing naphthalene diimide and 3-hydroxypropylphosphate as end-conjugating moieties for improved thrombin binding aptamers: Structural and biological effects. Bioorg Chem 2023; 141:106917. [PMID: 37865055 DOI: 10.1016/j.bioorg.2023.106917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 09/27/2023] [Accepted: 10/09/2023] [Indexed: 10/23/2023]
Abstract
The limitations associated with the in vivo use of the thrombin binding aptamer (TBA or TBA15) have dramatically stimulated the search of suitable chemically modified analogues in order to discover effective and reversible inhibitors of thrombin activity. In this context, we previously proposed cyclic and pseudo-cyclic TBA analogues with improved stability that proved to be more active than the parent aptamer. Herein, we have investigated a novel library of TBA derivatives carrying naphthalene diimide (NDI) moieties at the 3'- or 5'-end. In a subset of the investigated oligonucleotides, additional 3-hydroxypropylphosphate (HPP) groups were introduced at one or both ends of the TBA sequence. Evaluation of the G-quadruplex thermal stability, serum nuclease resistance and in vitro anticoagulant activity of the new TBA analogues allowed rationalizing the effect of these appendages on the activity of the aptamer on the basis of their relative position. Notably, most of the different TBA analogues tested were more potent thrombin inhibitors than unmodified TBA. Particularly, the analogue carrying an NDI group at the 5'-end and an HPP group at the 3'-end, named N-TBA-p, exhibited enhanced G-quadruplex thermal stability (ΔTm + 14° C) and ca. 10-fold improved nuclease resistance in serum compared to the native aptamer. N-TBA-p also induced prolonged and dose-dependent clotting times, showing a ca. 11-fold higher anticoagulant activity compared to unmodified TBA, as determined by spectroscopic methods. Overall, N-TBA-p proved to be in vitro a more efficient thrombin inhibitor than all the best ones previously investigated in our group. Its interesting features, associated with its easy preparation, make it a very promising candidate for future in vivo studies.
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Affiliation(s)
- Claudia Riccardi
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Kévan Pérez de Carvasal
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, 34095 Montpellier, France
| | - Chiara Platella
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy
| | - Albert Meyer
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, 34095 Montpellier, France
| | - Michael Smietana
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, 34095 Montpellier, France
| | - François Morvan
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, 34095 Montpellier, France.
| | - Daniela Montesarchio
- Department of Chemical Sciences, University of Naples Federico II, 80126 Naples, Italy.
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3
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Pérez de Carvasal K, Riccardi C, Russo Krauss I, Cavasso D, Vasseur JJ, Smietana M, Morvan F, Montesarchio D. Charge-Transfer Interactions Stabilize G-Quadruplex-Forming Thrombin Binding Aptamers and Can Improve Their Anticoagulant Activity. Int J Mol Sci 2021; 22:9510. [PMID: 34502432 PMCID: PMC8430690 DOI: 10.3390/ijms22179510] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/24/2021] [Accepted: 08/27/2021] [Indexed: 02/07/2023] Open
Abstract
In the search for optimized thrombin binding aptamers (TBAs), we herein describe the synthesis of a library of TBA analogues obtained by end-functionalization with the electron-rich 1,5-dialkoxy naphthalene (DAN) and the electron-deficient 1,8,4,5-naphthalenetetra-carboxylic diimide (NDI) moieties. Indeed, when these G-rich oligonucleotides were folded into the peculiar TBA G-quadruplex (G4) structure, effective donor-acceptor charge transfer interactions between the DAN and NDI residues attached to the extremities of the sequence were induced, providing pseudo-cyclic structures. Alternatively, insertion of NDI groups at both extremities produced TBA analogues stabilized by π-π stacking interactions. All the doubly-modified TBAs were characterized by different biophysical techniques and compared with the analogues carrying only the DAN or NDI residue and unmodified TBA. These modified TBAs exhibited higher nuclease resistance, and their G4 structures were markedly stabilized, as evidenced by increased Tm values compared to TBA. These favorable properties were also associated with improved anticoagulant activity for one DAN/NDI-modified TBA, and for one NDI/NDI-modified TBA. Our results indicated that TBA pseudo-cyclic structuring by ad hoc designed end-functionalization represents an efficient approach to improve the aptamer features, while pre-organizing and stabilizing the G4 structure but allowing sufficient flexibility to the aptamer folding, which is necessary for optimal thrombin recognition.
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Affiliation(s)
- Kévan Pérez de Carvasal
- Institut des Biomolécules Max Mousseron, University Montpellier, CNRS, ENSCM, 34095 Montpellier, France; (K.P.d.C.); (J.-J.V.); (M.S.)
| | - Claudia Riccardi
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Naples, Italy; (C.R.); (I.R.K.); (D.C.)
| | - Irene Russo Krauss
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Naples, Italy; (C.R.); (I.R.K.); (D.C.)
- CSGI—Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Italy
| | - Domenico Cavasso
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Naples, Italy; (C.R.); (I.R.K.); (D.C.)
- CSGI—Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, Via della Lastruccia 3, I-50019 Sesto Fiorentino, Italy
| | - Jean-Jacques Vasseur
- Institut des Biomolécules Max Mousseron, University Montpellier, CNRS, ENSCM, 34095 Montpellier, France; (K.P.d.C.); (J.-J.V.); (M.S.)
| | - Michael Smietana
- Institut des Biomolécules Max Mousseron, University Montpellier, CNRS, ENSCM, 34095 Montpellier, France; (K.P.d.C.); (J.-J.V.); (M.S.)
| | - François Morvan
- Institut des Biomolécules Max Mousseron, University Montpellier, CNRS, ENSCM, 34095 Montpellier, France; (K.P.d.C.); (J.-J.V.); (M.S.)
| | - Daniela Montesarchio
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Naples, Italy; (C.R.); (I.R.K.); (D.C.)
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4
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Design, Synthesis and Characterization of Cyclic NU172 Analogues: A Biophysical and Biological Insight. Int J Mol Sci 2020; 21:ijms21113860. [PMID: 32485818 PMCID: PMC7312020 DOI: 10.3390/ijms21113860] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 05/20/2020] [Accepted: 05/28/2020] [Indexed: 11/16/2022] Open
Abstract
NU172—a 26-mer oligonucleotide able to bind exosite I of human thrombin and inhibit its activity—was the first aptamer to reach Phase II clinical studies as an anticoagulant in heart disease treatments. With the aim of favoring its functional duplex-quadruplex conformation and thus improving its enzymatic stability, as well as its thrombin inhibitory activity, herein a focused set of cyclic NU172 analogues—obtained by connecting its 5′- and 3′-extremities with flexible linkers—was synthesized. Two different chemical approaches were exploited in the cyclization procedure, one based on the oxime ligation method and the other on Cu(I)-assisted azide-alkyne cycloaddition (CuAAC), affording NU172 analogues including circularizing linkers with different length and chemical nature. The resulting cyclic NU172 derivatives were characterized using several biophysical techniques (ultraviolet (UV) and circular dichroism (CD) spectroscopies, gel electrophoresis) and then investigated for their serum resistance and anticoagulant activity in vitro. All the cyclic NU172 analogues showed higher thermal stability and nuclease resistance compared to unmodified NU172. These favorable properties were, however, associated with reduced—even though still significant—anticoagulant activity, suggesting that the conformational constraints introduced upon cyclization were somehow detrimental for protein recognition. These results provide useful information for the design of improved analogues of NU172 and related duplex-quadruplex structures.
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5
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Riccardi C, Meyer A, Vasseur JJ, Russo Krauss I, Paduano L, Morvan F, Montesarchio D. Fine-tuning the properties of the thrombin binding aptamer through cyclization: Effect of the 5'-3' connecting linker on the aptamer stability and anticoagulant activity. Bioorg Chem 2019; 94:103379. [PMID: 31699393 DOI: 10.1016/j.bioorg.2019.103379] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 09/21/2019] [Accepted: 10/21/2019] [Indexed: 12/14/2022]
Abstract
A small library of cyclic TBA analogues (named cycTBA I-IV), obtained by covalently connecting its 5'- and 3'-ends with flexible linkers, has been synthesized with the aim of improving its chemical and enzymatic stability, as well as its anticoagulant properties. Two chemical procedures have been exploited to achieve the desired cyclization, based on the oxime ligation method (providing cycTBA I and II) or on Cu(I)-assisted azide-alkyne cycloaddition (CuAAC) protocols (for cycTBA III and IV), leading to analogues containing circularizing linkers with different chemical nature and length, overall spanning from 22 to 48 atoms. The resulting cyclic TBAs have been characterized using a variety of biophysical methods (UV, CD, gel electrophoresis, SE-HPLC analyses) and then tested for their serum resistance and anticoagulant activity under in vitro experiments. A fine-tuning of the length and flexibility of the linker allowed identifying a cyclic analogue, cycTBA II, with improved anticoagulant activity, associated with a dramatically stabilized G-quadruplex structure (ΔTm = +17 °C) and a 6.6-fold higher enzymatic resistance in serum compared to unmodified TBA.
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Affiliation(s)
- Claudia Riccardi
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Napoli, Italy
| | - Albert Meyer
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Jean-Jacques Vasseur
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Irene Russo Krauss
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Napoli, Italy; CSGI - Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Fi), Italy
| | - Luigi Paduano
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Napoli, Italy; CSGI - Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Fi), Italy
| | - François Morvan
- Institut des Biomolécules Max Mousseron, Université de Montpellier, CNRS, ENSCM, Montpellier, France.
| | - Daniela Montesarchio
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, I-80126 Napoli, Italy.
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6
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Tucker BA, Hudson JS, Ding L, Lewis E, Sheardy RD, Kharlampieva E, Graves D. Stability of the Na + Form of the Human Telomeric G-Quadruplex: Role of Adenines in Stabilizing G-Quadruplex Structure. ACS OMEGA 2018; 3:844-855. [PMID: 30023791 PMCID: PMC6045420 DOI: 10.1021/acsomega.7b01649] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 01/09/2018] [Indexed: 06/08/2023]
Abstract
G-quadruplexes are higher order DNA structures that play significant roles in gene transcription and telomeric maintenance. The formation and stability of the G-quadruplex structures are under thermodynamic control and may be of biological significance for regulatory function of cellular processes. Here, we report the structural influence and energetic contributions of the adenine bases in the loop sequences that flank G-repeats in human telomeric DNA sequence. Spectroscopic and calorimetric techniques are used to measure the thermal stability and thermodynamic contributions to the stability of human telomeric G-quadruplexes that have been designed with systematic changes of A to T throughout the telomeric sequence. These studies demonstrate that the thermal stability of the G-quadruplex structure is directly related to the number and position of the adenines that are present in the telomeric sequence. The melting temperature (Tm) was reduced from 59 °C for the wild-type sequence to 47 °C for the sequence where all four adenines were replaced with thymines (0123TTT). Furthermore, the enthalpy required for transitioning from the folded to unfolded G-quadruplex structure was reduced by 15 kcal/mol when the adenines were replaced with thymines (37 kcal/mol for the wild-type telomeric sequence reduced to 22 kcal/mol for the sequence where all four adenines were replaced with thymines (0123TTT)). The circular dichroism melting studies for G-quadruplex sequences having a single A to T change showed significantly sloping pretransition baselines and their differential scanning calorimetry (DSC) thermograms revealed biphasic melting profiles. In contrast, the deoxyoligonucleotides having sequences with two or more A to T changes did not exhibit sloping baselines or biphasic DSC thermograms. We attribute the biphasic unfolding profile and reduction in the enthalpy of unfolding to the energetic contributions of adenine hydrogen bonding within the loops as well as the adenine stacking to the G-tetrads of the G-quadruplex structure.
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Affiliation(s)
- Brenna A. Tucker
- Department
of Chemistry, Department of Biochemistry and Molecular Genetics, and Comprehensive
Cancer Center, University of Alabama at
Birmingham, Birmingham, Alabama 35294, United States
| | - Jason S. Hudson
- Department
of Chemistry, Department of Biochemistry and Molecular Genetics, and Comprehensive
Cancer Center, University of Alabama at
Birmingham, Birmingham, Alabama 35294, United States
| | - Lei Ding
- Department
of Chemistry, Department of Biochemistry and Molecular Genetics, and Comprehensive
Cancer Center, University of Alabama at
Birmingham, Birmingham, Alabama 35294, United States
| | - Edwin Lewis
- Department
of Chemistry, Mississippi State University, Mississippi, Mississippi
State 39762, United
States
| | - Richard D. Sheardy
- Department
of Chemistry & Biochemistry, Texas Women’s
University, Denton, Texas 782042, United States
| | - Eugenia Kharlampieva
- Department
of Chemistry, Department of Biochemistry and Molecular Genetics, and Comprehensive
Cancer Center, University of Alabama at
Birmingham, Birmingham, Alabama 35294, United States
| | - David Graves
- Department
of Chemistry, Department of Biochemistry and Molecular Genetics, and Comprehensive
Cancer Center, University of Alabama at
Birmingham, Birmingham, Alabama 35294, United States
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7
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Li MH, Wang ZF, Kuo MHJ, Hsu STD, Chang TC. Unfolding kinetics of human telomeric G-quadruplexes studied by NMR spectroscopy. J Phys Chem B 2014; 118:931-6. [PMID: 24404940 DOI: 10.1021/jp410034d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Characterization of the unfolding kinetics of G-quadruplexes (G4s) is the key to a better understanding of the biological function of G4s and is important for biomedical research and material design. Of interest is that slight variations of human telomeric sequences can form different types of G4 structures. In general, there is a correlation between unfolding kinetics and thermal stability. Here we examined this correlation by first systematic analysis of the unfolding kinetics of a variety of telomeric G4 structures using the real-time imino proton NMR spectra of DNA hybridization and hydrogen-deuterium exchange (HDX). We then measured the melting temperature (Tm) and determined the Gibbs free energy (ΔG) of these G4 structures using differential scanning calorimetry (DSC). Our results showed that both Tm and ΔG are slightly structure-dependent, except the Tm of the parallel G4 structure is ∼10 °C higher than that of nonparallel G4 structures. The hybridization results showed that the decay times of different imino proton signals for each telomeric G4 structure are quite similar, which are also consistent with the time constant of the central G-tetrad obtained from HDX measurements. It is suggested that global unfolding is the rate-determining step for HDX, and each real-time imino proton NMR measurement can provide the intrinsic unfolding rate constant. The key finding is that the unfolding times of these various G4 structures are quite different and show no correlation between thermal stability and unfolding kinetics. Our results raised an issue that the folding and unfolding kinetics is more relevant for better understanding of biological function of G4 structures.
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Affiliation(s)
- Ming-Hao Li
- Institute of Atomic and Molecular Sciences, Academia Sinica , Taipei 106, Taiwan, R.O.C
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8
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Xue Y, Liu JQ, Zheng KW, Kan ZY, Hao YH, Tan Z. Kinetic and Thermodynamic Control of G-Quadruplex Folding. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201101759] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Xue Y, Liu JQ, Zheng KW, Kan ZY, Hao YH, Tan Z. Kinetic and Thermodynamic Control of G-Quadruplex Folding. Angew Chem Int Ed Engl 2011; 50:8046-50. [DOI: 10.1002/anie.201101759] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/30/2011] [Indexed: 12/18/2022]
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10
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Petraccone L, Erra E, Randazzo A, Giancola C. Energetic aspects of locked nucleic acids quadruplex association and dissociation. Biopolymers 2007; 83:584-94. [PMID: 16944520 DOI: 10.1002/bip.20591] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The design of modified nucleic acid aptamers is improved by considering thermodynamics and kinetics of their association/dissociation processes. Locked Nucleic Acids (LNA) is a promising class of nucleic acid analogs. In this work the thermodynamic and kinetic properties of a LNA quadruplex formed by the TGGGT sequence, containing only conformationally restricted LNA residues, are reported and compared to those of 2'-OMe-RNA (O-RNA) and DNA quadruplexes. The thermodynamic analysis indicates that the sugar-modified quadruplexes (LNA and O-RNA) are stabilized by entropic effects. The kinetic analysis shows that LNA and O-RNA quadruplexes are characterized by a slower dissociation and a faster association with respect to DNA quadruplex. Interestingly, the LNA quadruplex formation process shows a second-order kinetics with respect to single strand concentration and has a negative activation energy. To explain these data, a mechanism for tetramer formation with two intermediate states was proposed.
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Affiliation(s)
- Luigi Petraccone
- Dipartimento di Scienze Farmaceutiche, Via Ponte Don Melillo, 84084 Fisciano (SA), Italy
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11
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Xue Y, Kan ZY, Wang Q, Yao Y, Liu J, Hao YH, Tan Z. Human Telomeric DNA Forms Parallel-Stranded Intramolecular G-Quadruplex in K+Solution under Molecular Crowding Condition. J Am Chem Soc 2007; 129:11185-91. [PMID: 17705383 DOI: 10.1021/ja0730462] [Citation(s) in RCA: 243] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The G-rich strand of human telomeric DNA can fold into a four-stranded structure called G-quadruplex and inhibit telomerase activity that is expressed in 85-90% tumor cells. For this reason, telomere quadruplex is emerging as a potential therapeutic target for cancer. Information on the structure of the quadruplex in the physiological environment is important for structure-based drug design targeting the quadruplex. Recent studies have raised significant controversy regarding the exact structure of the quadruplex formed by human telomeric DNA in a physiological relevant environment. Studies on the crystal prepared in K+ solution revealed a distinct propeller-shaped parallel-stranded conformation. However, many later works failed to confirm such structure in physiological K+ solution but rather led to the identification of a different hybrid-type mixed parallel/antiparallel quadruplex. Here we demonstrate that human telomere DNA adopts a parallel-stranded conformation in physiological K+ solution under molecular crowding conditions created by PEG. At the concentration of 40% (w/v), PEG induced complete structural conversion to a parallel-stranded G-quadruplex. We also show that the quadruplex formed under such a condition has unusual stability and significant negative impact on telomerase processivity. Since the environment inside cells is molecularly crowded, our results obtained under the cell mimicking condition suggest that the parallel-stranded quadruplex may be the more favored structure under physiological conditions, and drug design targeting the human telomeric quadruplex should take this into consideration.
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Affiliation(s)
- Yong Xue
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, Wuhan University, Wuhan 430072, P. R. China
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12
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Kan ZY, Lin Y, Wang F, Zhuang XY, Zhao Y, Pang DW, Hao YH, Tan Z. G-quadruplex formation in human telomeric (TTAGGG)4 sequence with complementary strand in close vicinity under molecularly crowded condition. Nucleic Acids Res 2007; 35:3646-53. [PMID: 17488850 PMCID: PMC1920240 DOI: 10.1093/nar/gkm203] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Chromosomes in vertebrates are protected at both ends by telomere DNA composed of tandem (TTAGGG)n repeats. DNA replication produces a blunt-ended leading strand telomere and a lagging strand telomere carrying a single-stranded G-rich overhang at its end. The G-rich strand can form G-quadruplex structure in the presence of K+ or Na+. At present, it is not clear whether quadruplex can form in the double-stranded telomere region where the two complementary strands are constrained in close vicinity and quadruplex formation, if possible, has to compete with the formation of the conventional Watson-Crick duplex. In this work, we studied quadruplex formation in oligonucleotides and double-stranded DNA containing both the G- and C-rich sequences to better mimic the in vivo situation. Under such competitive condition only duplex was observed in dilute solution containing physiological concentration of K+. However, quadruplex could preferentially form and dominate over duplex structure under molecular crowding condition created by PEG as a result of significant quadruplex stabilization and duplex destabilization. This observation suggests quadruplex may potentially form or be induced at the blunt end of a telomere, which may present a possible alternative form of structures at telomere ends.
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Affiliation(s)
- Zhong-yuan Kan
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Yi Lin
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Feng Wang
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Xin-ying Zhuang
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Yong Zhao
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Dai-wen Pang
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Yu-hua Hao
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
| | - Zheng Tan
- Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
- *To whom correspondence should be addressed. +86 27 6875 4351+86 27 6875 6661, The authors wish it to be known that, in their opinion, the first three authors should be regarded as joint First Authors
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Martino L, Virno A, Randazzo A, Virgilio A, Esposito V, Giancola C, Bucci M, Cirino G, Mayol L. A new modified thrombin binding aptamer containing a 5'-5' inversion of polarity site. Nucleic Acids Res 2006; 34:6653-62. [PMID: 17145716 PMCID: PMC1751544 DOI: 10.1093/nar/gkl915] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The solution structure of a new modified thrombin binding aptamer (TBA) containing a 5'-5' inversion of polarity site, namely d(3'GGT5'-5'TGGTGTGGTTGG3'), is reported. NMR and CD spectroscopy, as well as molecular dynamic and mechanic calculations, have been used to characterize the 3D structure. The modified oligonucleotide is characterized by a chair-like structure consisting of two G-tetrads connected by three edge-wise TT, TGT and TT loops. d(3'GGT5'-5'TGGTGTGGTTGG3') is characterized by an unusual folding, being three strands parallel to each other and only one strand oriented in opposite manner. This led to an anti-anti-anti-syn and syn-syn-syn-anti arrangement of the Gs in the two tetrads. The thermal stability of the modified oligonucleotide is 4 degrees C higher than the corresponding unmodified TBA. d(3'GGT5'-5'TGGTGTGGTTGG3') continues to display an anticoagulant activity, even if decreased with respect to the TBA.
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Affiliation(s)
| | - Ada Virno
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | - Antonio Randazzo
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | - Antonella Virgilio
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | - Veronica Esposito
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | | | - Mariarosaria Bucci
- Dipartimento di Farmacologia Sperimentale, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | - Giuseppe Cirino
- Dipartimento di Farmacologia Sperimentale, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
| | - Luciano Mayol
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli ‘Federico II’via D. Montesano 49, I-80131 Napoli, Italy
- To whom correspondence should be addressed. Tel: +39 081 678508; Fax: +39 081 678552;
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Petraccone L, Erra E, Esposito V, Randazzo A, Galeone A, Barone G, Giancola C. Biophysical properties of quadruple helices of modified human telomeric DNA. Biopolymers 2005; 77:75-85. [PMID: 15614794 DOI: 10.1002/bip.20189] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Telomeric DNA of a variety of vertebrates including humans contains the tandem repeat d(TTAGGG)n. The guanine rich strand can fold into four-stranded G-quadruplex structures, which have recently become attractive for biomedical research. Indeed, the aptamers based on the quadruplex motif may prove useful as tools aimed at binding and inhibiting particular proteins, catalyzing various biochemical reactions, or even serving as pharmaceutically active agents. The incorporation of modified bases into oligonucleotides can have profound effects on their folding and may produce useful changes in physical and biological properties of the resulting DNA fragments. In this work, the adenines of the human telomeric repeat oligonucleotide d(TAGGGT) and d(AGGGT) were substituted by 2'-deoxy-8-(propyn-1-yl)adenosine (A-->APr) or by 8-bromodeoxyadenosine (A-->ABr). The biophysical properties of the resulting quadruplex structures were compared with the unmodified quadruplexes. NMR and CD spectra of the studied sequences were characteristic of parallel-stranded, tetramolecular quadruplexes. The analysis of the equilibrium melting curves reveals that the modifications stabilize the quadruplex structure. The results are useful when considering the design of novel aptameric nucleic acids with diverse molecular recognition capabilities that would not be present using native RNA/DNA sequences.
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Affiliation(s)
- Luigi Petraccone
- Dipartimento di Scienze Farmaceutiche, Via Ponte Don Melillo, 84084, Fisciano (SA), Italy
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Abstract
Fluorescently labeled oligodeoxyribonucleotides containing a single tract of four successive guanines have been used to study the thermodynamic and kinetic properties of short intermolecular DNA quadruplexes. When these assemble to form intermolecular quadruplexes the fluorophores are in close proximity and the fluorescence is quenched. On raising the temperature these complexes dissociate and there is a large increase in fluorescence. These complexes are exceptionally stable in potassium-containing buffers, and possess Tm values that are too high to measure. Tm values were determined in sodium-containing buffers for which the rate of reannealing is extremely slow; the melting profiles are effectively irreversible, and the apparent melting temperatures are dependent on the rates of heating. The dissociation kinetics of these complexes was estimated by rapidly increasing the temperature and following the time-dependent changes in fluorescence. From these data we have estimated the half-lives of these quadruplexes at 37 degrees C. Addition of a T to the unlabeled end of the oligonucleotide increases quadruplex stability. In contrast, addition of a T between the fluorophore and the oligonucleotide leads to a decrease in stability.
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Affiliation(s)
- Elena E Merkina
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, United Kingdom
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