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Murray MT, Wetmore SD. Unlocking precision in aptamer engineering: a case study of the thrombin binding aptamer illustrates why modification size, quantity, and position matter. Nucleic Acids Res 2024:gkae729. [PMID: 39217472 DOI: 10.1093/nar/gkae729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Revised: 08/02/2024] [Accepted: 08/23/2024] [Indexed: 09/04/2024] Open
Abstract
The thrombin binding aptamer (TBA) is a prototypical platform used to understand the impact of chemically-modified nucleotides on aptamer stability and target affinity. To provide structural insight into the experimentally-observed effects of modification size, location, and number on aptamer performance, long time-scale molecular dynamics (MD) simulations were performed on multiple binding orientations of TBA-thrombin complexes that contain a large, flexible tryptophan thymine derivative (T-W) or a truncated analogue (T-K). Depending on modification position, T-W alters aptamer-target binding orientations, fine-tunes aptamer-target interactions, strengthens networks of nucleic acid-protein contacts, and/or induces target conformational changes to enhance binding. The proximity and 5'-to-3' directionality of nucleic acid structural motifs also play integral roles in the behavior of the modifications. Modification size can differentially influence target binding by promoting more than one aptamer-target binding pose. Multiple modifications can synergistically strengthen aptamer-target binding by generating novel nucleic acid-protein structural motifs that are unobtainable for single modifications. By studying a diverse set of modified aptamers, our work uncovers design principles that must be considered in the future development of aptamers containing chemically-modified nucleotides for applications in medicine and biotechnology, highlighting the value of computational studies in nucleic acids research.
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Affiliation(s)
- Makay T Murray
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
| | - Stacey D Wetmore
- Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive West, Lethbridge, Alberta T1K 3M4, Canada
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2
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A Comprehensive Analysis of the Thrombin Binding Aptamer Containing Functionalized Pyrrolo-2'-deoxycytidines. Pharmaceuticals (Basel) 2021; 14:ph14121326. [PMID: 34959726 PMCID: PMC8709445 DOI: 10.3390/ph14121326] [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: 11/24/2021] [Revised: 12/15/2021] [Accepted: 12/16/2021] [Indexed: 01/07/2023] Open
Abstract
Aptamers constitute an answer for the growing need for targeted therapy development. One of the most well-known representatives of this group of compounds is thrombin binding aptamers (TBA) targeted towards thrombin. The TBA inhibitory activity is determined by its spatial arrangement, which consists of two G-tetrads linked by two shorter TT loops and one longer TGT loop and folds into a unimolecular, antiparallel G-quadruplex structure. Interesting properties of the aptamer can be further improved via the introduction of a number of chemical modifications. Herein, a comprehensive analysis of the influence of pyrrolo-2’-deoxycytidine (Py-dC) and its derivatives on TBA physicochemical and biological properties has been presented. The studies have shown that the presence of modified residues at the T7 position of the TGT loop has only minor effects on TBA thermodynamic stability without affecting its folding topology. All analyzed oligomers exhibit anticoagulant properties, but only aptamer modified with a decyl derivative of Py-dC was able to inhibit thrombin activity more efficiently than unmodified, parental compounds. Importantly, the same compound also possessed the potential to effectively restrain HeLa cell line growth.
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3
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Yum JH, Ishizuka T, Fukumoto K, Hori D, Bao HL, Xu Y, Sugiyama H, Park S. Systematic Approach to DNA Aptamer Design Using Amino Acid-Nucleic Acid Hybrids (ANHs) Targeting Thrombin. ACS Biomater Sci Eng 2021; 7:1338-1343. [PMID: 33756075 DOI: 10.1021/acsbiomaterials.1c00060] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chemical modifications of innate DNA/RNA aptamers facilitate the improvement of their function. Herein, we report our modular strategy to manipulate a thrombin-binding DNA aptamer (TBA) to improve its anticoagulation activity and binding affinity. A set of amino acid conjugates, termed amino acid-nucleic acid hybrids or ANHs, was synthesized and incorporated into a TBA loop sequences. We found that substitutions with hydrophobic amino acids in the loop region possessed significantly enhanced antithrombin activity, up to 3-fold higher than the native TBA. We investigated the correlations between thrombin-binding affinity and the features of our amino-acid conjugates using experimental techniques including circular dichroism spectroscopy, surface plasmon resonance assay, and molecular modeling. The present study demonstrates a systematic approach to aptamer design based on amino-acid characteristics, allowing the development of advanced aptamers.
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Affiliation(s)
- Ji Hye Yum
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Takumi Ishizuka
- Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Koyuki Fukumoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Daisuke Hori
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Hong-Liang Bao
- Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Yan Xu
- Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.,Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Yoshida-ushinomiyacho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Soyoung Park
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
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4
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Bao HL, Ishizuka T, Yamashita A, Furukoji E, Asada Y, Xu Y. Improving Thermodynamic Stability and Anticoagulant Activity of a Thrombin Binding Aptamer by Incorporation of 8-trifluoromethyl-2'-deoxyguanosine. J Med Chem 2020; 64:711-718. [PMID: 33289557 DOI: 10.1021/acs.jmedchem.0c01711] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In this study, we incorporated 8-trifluoromethyl-2'-deoxyguanosine (FG) into a thrombin binding aptamer (TBA). Circular dichroism, nuclear magnetic resonance (NMR), electrophoresis, and prothrombin time (PT) assay were performed to investigate the structure, thermodynamic stability, biological stability, and anticoagulant activity of the FG-modified TBA sequences. We found that the replacement of FG into TBA sequences led to a remarkable improvement in the melting temperature up to 30 °C compared with the native sequence. The trifluoromethyl group allowed us to investigate the TBA G-quadruplex structure by 19F NMR spectroscopy. Furthermore, PT assays showed that the modified sequences can significantly improve the anticoagulant activity in comparison with the native TBA. Finally, we demonstrated that the trifluoromethyl-modified TBA sequence could function as an anticoagulant reagent in live rats. Our results strongly suggested that FG is a powerful nucleoside derivative to increase the thermodynamic stability and anticoagulant activity of TBA.
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Affiliation(s)
- Hong-Liang Bao
- Division of Chemistry, Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Takumi Ishizuka
- Division of Chemistry, Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Atsushi Yamashita
- Department of Pathology, Division of Pathophysiology, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Eiji Furukoji
- Department of Radiology, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Yujiro Asada
- Department of Pathology, Division of Pathophysiology, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
| | - Yan Xu
- Division of Chemistry, Department of Medical Sciences, Faculty of Medicine, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan
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5
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Riccardi C, Napolitano E, Platella C, Musumeci D, Montesarchio D. G-quadruplex-based aptamers targeting human thrombin: Discovery, chemical modifications and antithrombotic effects. Pharmacol Ther 2020; 217:107649. [PMID: 32777331 DOI: 10.1016/j.pharmthera.2020.107649] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 07/29/2020] [Indexed: 02/07/2023]
Abstract
First studies on thrombin-inhibiting DNA aptamers were reported in 1992, and since then a large number of anticoagulant aptamers has been discovered. TBA - also named HD1, a 15-mer G-quadruplex (G4)-forming oligonucleotide - is the best characterized thrombin binding aptamer, able to specifically recognize the protein exosite I, thus inhibiting the conversion of soluble fibrinogen into insoluble fibrin strands. Unmodified nucleic acid-based aptamers, in general, and TBA in particular, exhibit limited pharmacokinetic properties and are rapidly degraded in vivo by nucleases. In order to improve the biological performance of aptamers, a widely investigated strategy is the introduction of chemical modifications in their backbone at the level of the nucleobases, sugar moieties or phosphodiester linkages. Besides TBA, also other thrombin binding aptamers, able to adopt a well-defined G4 structure, e.g. mixed duplex/quadruplex sequences, as well as homo- and hetero-bivalent constructs, have been identified and optimized. Considering the growing need of new efficient anticoagulant agents associated with the strong therapeutic potential of these thrombin inhibitors, the research on thrombin binding aptamers is still a very hot and intriguing field. Herein, we comprehensively described the state-of-the-art knowledge on the DNA-based aptamers targeting thrombin, especially focusing on the optimized analogues obtained by chemically modifying the oligonucleotide backbone, and their biological performances in therapeutic applications.
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Affiliation(s)
- Claudia Riccardi
- Department of Chemical Sciences, University of Naples Federico II, via Cintia 21, I-80126 Naples, Italy; Department of Advanced Medical and Surgical Sciences, 2(nd) Division of Neurology, Center for Rare Diseases and InterUniversity Center for Research in Neurosciences, University of Campania Luigi Vanvitelli, via Sergio Pansini, 5, I-80131 Naples, Italy.
| | - Ettore Napolitano
- Department of Chemical Sciences, University of Naples Federico II, via Cintia 21, I-80126 Naples, Italy.
| | - Chiara Platella
- Department of Chemical Sciences, University of Naples Federico II, via Cintia 21, I-80126 Naples, Italy.
| | - Domenica Musumeci
- Department of Chemical Sciences, University of Naples Federico II, via Cintia 21, I-80126 Naples, Italy; Institute of Biostructures and Bioimages, CNR, via Mezzocannone 16, I-80134 Naples, Italy.
| | - Daniela Montesarchio
- Department of Chemical Sciences, University of Naples Federico II, via Cintia 21, I-80126 Naples, Italy.
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Roxo C, Kotkowiak W, Pasternak A. G-Quadruplex-Forming Aptamers-Characteristics, Applications, and Perspectives. Molecules 2019; 24:E3781. [PMID: 31640176 PMCID: PMC6832456 DOI: 10.3390/molecules24203781] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 10/16/2019] [Accepted: 10/18/2019] [Indexed: 12/31/2022] Open
Abstract
G-quadruplexes constitute a unique class of nucleic acid structures formed by G-rich oligonucleotides of DNA- or RNA-type. Depending on their chemical nature, loops length, and localization in the sequence or structure molecularity, G-quadruplexes are highly polymorphic structures showing various folding topologies. They may be formed in the human genome where they are believed to play a pivotal role in the regulation of multiple biological processes such as replication, transcription, and translation. Thus, natural G-quadruplex structures became prospective targets for disease treatment. The fast development of systematic evolution of ligands by exponential enrichment (SELEX) technologies provided a number of G-rich aptamers revealing the potential of G-quadruplex structures as a promising molecular tool targeted toward various biologically important ligands. Because of their high stability, increased cellular uptake, ease of chemical modification, minor production costs, and convenient storage, G-rich aptamers became interesting therapeutic and diagnostic alternatives to antibodies. In this review, we describe the recent advances in the development of G-quadruplex based aptamers by focusing on the therapeutic and diagnostic potential of this exceptional class of nucleic acid structures.
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Affiliation(s)
- Carolina Roxo
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
| | - Weronika Kotkowiak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
| | - Anna Pasternak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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7
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Sun L, Xie X, Weng W, Jin H. Structural and mechanistic insights into modified G-quadruplex thrombin-binding DNA aptamers. Biochem Biophys Res Commun 2019; 513:753-759. [PMID: 30992128 DOI: 10.1016/j.bbrc.2019.04.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 04/03/2019] [Indexed: 11/26/2022]
Abstract
Thrombin-binding aptamer (TBA) can fold into a G-quadruplex structure necessary for interacting with thrombin. When one thymidine residue of the TGT loop at position 7 is replaced with unlocked uracil (UNA), d-isothymidine (D-isoT) or l-isothymidine (L-isoT), these modified sequences display different activities. To date, the mechanisms of how D/L-isoT and UNA influence the biological properties of TBA have not been illustrated in the literature. In this paper, we fill this gap by probing the structure variations and binding modes of these modified TBAs via molecular dynamics (MD) simulation and free energy calculation. Comparative structural analyses demonstrated that both D-IsoT and UNA changed the local conformation of TGT loop and formed stronger interactions with the target protein. Particularly, D-IsoT and UNA adopted similar conformation which can well explain their similar biological activities. In addition, the flexibility of the two TT loops were described clearly. In contrast, L-IsoT at position 7 led to an obvious tendency to unfold. Free energy calculation and the analysis of key residues energy contributions eventually provide a clear picture of interactions for further understanding of the structure-activity relationships. Collectively, our findings open the way for a rational design of modified aptamers.
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Affiliation(s)
- Lidan Sun
- College of Chemical Engineering and Material Science, Quanzhou Normal University, Quanzhou, China.
| | - Xiaolan Xie
- College of Chemical Engineering and Material Science, Quanzhou Normal University, Quanzhou, China
| | - Wenting Weng
- College of Chemical Engineering and Material Science, Quanzhou Normal University, Quanzhou, China
| | - Hongwei Jin
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing, 100191, China
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8
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Li L, Yang X, Li K, Zhang G, Ma Y, Cai B, Li S, Ding H, Deng J, Nan X, Sun J, Wu Y, Shao N, Zhang L, Yang Z. d-/l-Isothymidine incorporation in the core sequence of aptamer BC15 enhanced its binding affinity to the hnRNP A1 protein. Org Biomol Chem 2019; 16:7488-7497. [PMID: 30272759 DOI: 10.1039/c8ob01454j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) was reported to participate in the development of a variety of tumors. BC15 is a DNA aptamer targeting hnRNP A1. Firstly, through sequence truncation, we identified 31-mer sequence BC15-31 as the core sequence of BC15 with a strong binding affinity and high selectivity to the hnRNP A1 protein. Isothymidine (isoT) modification was then applied for the structural optimization of BC15-31, systematic modification and biological evaluation were carried out. Incorporation of isoT in the 1,3 sites at the 5'-end of BC15-31 can significantly enhance the protein affinity. Chemical modifications close to the 3'-end can greatly improve the stability of the aptamer. Furthermore, BC15-31 modified with isoT at both the 5'-end and 3'-end displayed an additive effect with enhanced bioactivity and stability at the same time. Our study strategy on BC15 provides a useful guideline for chemical modification and optimization of the aptamer for further clinical application.
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Affiliation(s)
- Liyu Li
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing 100191, China.
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Wilson SJ, Connolly TM, Peters G, Ghosh A, Johnson M, Newby DE. Exosite 1 thrombin inhibition with JNJ-64179375 inhibits thrombus formation in a human translational model of thrombosis. Cardiovasc Res 2019; 115:669-677. [PMID: 30184110 PMCID: PMC6383059 DOI: 10.1093/cvr/cvy227] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2018] [Revised: 08/15/2018] [Accepted: 09/02/2018] [Indexed: 01/06/2023] Open
Abstract
AIMS JNJ-64179375 (hereafter JNJ-9375) is a first-in-class, highly specific, large molecule, exosite 1 thrombin inhibitor. In preclinical studies, JNJ-9375 demonstrated robust antithrombotic protection with a wider therapeutic index when compared to apixaban. The purpose of the present study was to examine for the first time the antiplatelet, anticoagulant and antithrombotic effects of JNJ-9375 in a translational model of ex vivo human thrombosis. METHODS AND RESULTS Fifteen healthy volunteers participated in a double-blind randomized crossover study of JNJ-9375 (2.5, 25, and 250 μg/mL), bivalirudin (6 μg/mL; positive control), and matched placebo. Coagulation, platelet activation, and thrombus formation were determined using coagulation assays, flow cytometry, and an ex vivo perfusion chamber, respectively.JNJ-9375 caused concentration-dependent prolongation of all measures of blood coagulation (prothrombin time, activated partial thromboplastin time, and thrombin time; P < 0.001 for all) and agonist selective inhibition of thrombin (0.1 U/mL) stimulated platelet p-selectin expression (P < 0.001) and platelet-monocyte aggregates (P = 0.002). Compared to placebo, JNJ-9375 (250 μg/mL) reduced mean total thrombus area by 41.1% (95% confidence intervals 22.3 to 55.3%; P < 0.001) at low shear and 32.3% (4.9 to 51.8%; P = 0.025) at high shear. Under both shear conditions, there was a dose-dependent decrease in fibrin-rich thrombus (P < 0.001 for both) but not platelet-rich thrombus (P = ns for both). CONCLUSION Exosite 1 inhibition with JNJ-9375 caused prolongation of blood coagulation, selective inhibition of thrombin-mediated platelet activation, and reductions in ex vivo thrombosis driven by a decrease in fibrin-rich thrombus formation. JNJ-9375 represents a novel class of anticoagulant with potential therapeutic applications.
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Affiliation(s)
- Simon J Wilson
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Room SU305, Chancellor’s Building, 49 Little France Crescent, Edinburgh EH16 4SA, UK
| | | | - Gary Peters
- Janssen Research & Development, LLC, Spring House, PA, USA
| | | | | | - David E Newby
- British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Room SU305, Chancellor’s Building, 49 Little France Crescent, Edinburgh EH16 4SA, UK
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Kotkowiak W, Wengel J, Scotton CJ, Pasternak A. Improved RE31 Analogues Containing Modified Nucleic Acid Monomers: Thermodynamic, Structural, and Biological Effects. J Med Chem 2019; 62:2499-2507. [PMID: 30735377 DOI: 10.1021/acs.jmedchem.8b01806] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
RE31 is a 31-nt DNA aptamer, consisting of the G-quadruplex and a duplex domain, which is able to effectively prolong thrombin time. This article reports on the influence of certain modified nucleotide residues on thermodynamic and biological properties as well as the folding topology of RE31. Particularly, the effect of the presence of nucleosides in unlocked nucleic acid (UNA), locked nucleic acid (LNA), or β-l-RNA series was evaluated. The studies presented herein show that all modified residues can influence thermal and biological stabilities of G-quadruplex in a position-dependent manner. The aptamers modified simultaneously with UNA at the T15 position and LNAs in the duplex part possess the highest value of melting temperature and a 2-fold higher anticoagulant effect. Importantly, RE31 variants modified with nucleosides in UNA, LNA, or β-l-RNA series exhibit unchanged G-quadruplex folding topology. Crucially, introduction of any of the modified residues into RE31 causes prolongation of aptamer stability in human serum.
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Affiliation(s)
- Weronika Kotkowiak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry , Polish Academy of Sciences , Noskowskiego 12/14 , 61-704 Poznan , Poland
| | - Jesper Wengel
- Department of Physics, Chemistry, and Pharmacy, Biomolecular Nanoscale Engineering Center , University of Southern Denmark , Campusvej 55 , Odense M 5230 , Denmark
| | - Chris J Scotton
- Institute of Biomedical and Clinical Science, College of Medicine & Health , University of Exeter, St Luke's Campus , Exeter EX1 2LU , U.K
| | - Anna Pasternak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry , Polish Academy of Sciences , Noskowskiego 12/14 , 61-704 Poznan , Poland
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11
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Mo M, Kong D, Ji H, Lin D, Tang X, Yang Z, He Y, Wu L. Reversible Photocontrol of Thrombin Activity by Replacing Loops of Thrombin Binding Aptamer using Azobenzene Derivatives. Bioconjug Chem 2019; 30:231-241. [PMID: 30582682 DOI: 10.1021/acs.bioconjchem.8b00848] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The photoisomerization of azobenzenes provides a general means for the photocontrol of many important biomolecular structures and organismal functions. For temporal and spatial control activity of thrombin binding aptamer (TBA) by light, azobenzene derivatives were carefully selected as light-triggered molecular switches to replace TT loops and the TGT loop of TBA to reversibly control enzyme activity. These molecules interconverted between the trans and cis states under alternate UV and visible light irradiation, which consequently triggered reversible formation of G-quadruplex morphology. In addition, we investigated the impact of three azobenzene derivatives on stability, thrombin binding ability, and anticoagulant properties. The result showed that 4,4'-bis(hydroxymethyl)azobenzene at the TGT loop position significantly photoregulated affinity to thrombin and blood clotting in human plasma, which provided a successful strategy to control blood clotting in human plasma and a further evidence for design of TBA analogues with pivotal positions of modifications.
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Affiliation(s)
- Mengwu Mo
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Dejia Kong
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Heming Ji
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Dao Lin
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Xinjing Tang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences , Peking University , Beijing 100191 , China
| | - Zhenjun Yang
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences , Peking University , Beijing 100191 , China
| | - Yujian He
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Li Wu
- School of Chemical Sciences , University of Chinese Academy of Sciences , Beijing 100049 , China.,State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences , Peking University , Beijing 100191 , China
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12
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Kotkowiak W, Czapik T, Pasternak A. Novel isoguanine derivative of unlocked nucleic acid-Investigations of thermodynamics and biological potential of modified thrombin binding aptamer. PLoS One 2018; 13:e0197835. [PMID: 29795635 PMCID: PMC5967839 DOI: 10.1371/journal.pone.0197835] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Accepted: 05/09/2018] [Indexed: 11/18/2022] Open
Abstract
Thrombin binding aptamer (TBA), is a short DNA 15-mer that forms G-quadruplex structure and possesses anticoagulant properties. Some chemical modifications, including unlocked nucleic acids (UNA), 2'-deoxy-isoguanosine and 2'-deoxy-4-thiouridine were previously found to enhance the biological activity of TBA. In this paper, we present thermodynamic and biological characteristics of TBA variants that have been modified with novel isoguanine derivative of UNA as well as isoguanosine. Additionally, UNA-4-thiouracil and 4-thiouridine were also introduced simultaneously with isoguanine derivatives. Thermodynamic analysis indicates that the presence of isoguanosine in UNA or RNA series significantly decreases the stability of G-quadruplex structure. The highest destabilization is observed for substitution at one of the G-tetrad position. Addition of 4-thiouridine in UNA or RNA series usually decreases the unfavorable energetic cost of the presence of UNA or RNA isoguanine. Circular dichroism and thermal denaturation spectra in connection with thrombin time assay indicate that the introduction of UNA-isoguanine or isoguanosine into TBA negatively affects G-quadruplex folding and TBA anticoagulant properties. These findings demonstrate that the highly-ordered structure of TBA is essential for inhibition of thrombin activity.
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Affiliation(s)
- Weronika Kotkowiak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego, Poznan, Poland
| | - Tomasz Czapik
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego, Poznan, Poland
| | - Anna Pasternak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego, Poznan, Poland
- * E-mail:
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13
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Kotkowiak W, Lisowiec-Wachnicka J, Grynda J, Kierzek R, Wengel J, Pasternak A. Thermodynamic, Anticoagulant, and Antiproliferative Properties of Thrombin Binding Aptamer Containing Novel UNA Derivative. MOLECULAR THERAPY. NUCLEIC ACIDS 2018; 10:304-316. [PMID: 29499943 PMCID: PMC5862132 DOI: 10.1016/j.omtn.2017.12.013] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 12/21/2017] [Accepted: 12/21/2017] [Indexed: 12/25/2022]
Abstract
Thrombin is a serine protease that plays a crucial role in hemostasis, fibrinolysis, cell proliferation, and migration. Thrombin binding aptamer (TBA) is able to inhibit the activity of thrombin molecule via binding to its exosite I. This 15-nt DNA oligonucleotide forms an intramolecular, antiparallel G-quadruplex structure with a chair-like conformation. In this paper, we report on our investigations on the influence of certain modified nucleotide residues on thermodynamic stability, folding topology, and biological properties of TBA variants. In particular, the effect of single incorporation of a novel 4-thiouracil derivative of unlocked nucleic acid (UNA), as well as single incorporation of 4-thiouridine and all four canonical UNAs, was evaluated. The studies presented herein have shown that 4-thiouridine in RNA and UNA series, as well as all four canonical UNAs, can efficiently modulate G-quadruplex thermodynamic and biological stability, and that the effect is strongly position dependent. Interestingly, TBA variants containing the modified nucleotide residues are characterized by unchanged folding topology. Thrombin time assay revealed that incorporation of certain UNA residues may improve G-quadruplex anticoagulant properties. Noteworthy, some TBA variants, characterized by decreased ability to inhibit thrombin activity, possess significant antiproliferative properties reducing the viability of the HeLa cell line even by 95% at 10 μM concentration.
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Affiliation(s)
- Weronika Kotkowiak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
| | - Jolanta Lisowiec-Wachnicka
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Jakub Grynda
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Gabriela Narutowicza 11/12, 80-233 Gdansk, Poland
| | - Ryszard Kierzek
- Department of Structural Chemistry and Biology of Nucleic Acids, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Jesper Wengel
- Department of Physics, Chemistry and Pharmacy, Biomolecular Nanoscale Engineering Center, University of Southern Denmark, Campusvej 55, Odense M 5230, Denmark
| | - Anna Pasternak
- Department of Nucleic Acids Bioengineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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14
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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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15
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Platella C, Riccardi C, Montesarchio D, Roviello GN, Musumeci D. G-quadruplex-based aptamers against protein targets in therapy and diagnostics. Biochim Biophys Acta Gen Subj 2017; 1861:1429-1447. [PMID: 27865995 PMCID: PMC7117017 DOI: 10.1016/j.bbagen.2016.11.027] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 12/17/2022]
Abstract
Nucleic acid aptamers are single-stranded DNA or RNA molecules identified to recognize with high affinity specific targets including proteins, small molecules, ions, whole cells and even entire organisms, such as viruses or bacteria. They can be identified from combinatorial libraries of DNA or RNA oligonucleotides by SELEX technology, an in vitro iterative selection procedure consisting of binding (capture), partitioning and amplification steps. Remarkably, many of the aptamers selected against biologically relevant protein targets are G-rich sequences that can fold into stable G-quadruplex (G4) structures. Aiming at disseminating novel inspiring ideas within the scientific community in the field of G4-structures, the emphasis of this review is placed on: 1) recent advancements in SELEX technology for the efficient and rapid identification of new candidate aptamers (introduction of microfluidic systems and next generation sequencing); 2) recurrence of G4 structures in aptamers selected by SELEX against biologically relevant protein targets; 3) discovery of several G4-forming motifs in important regulatory regions of the human or viral genome bound by endogenous proteins, which per se can result into potential aptamers; 4) an updated overview of G4-based aptamers with therapeutic potential and 5) a discussion on the most attractive G4-based aptamers for diagnostic applications. 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)
- Chiara Platella
- Department of Chemical Sciences, University of Napoli Federico II, Napoli, Italy
| | - Claudia Riccardi
- Department of Chemical Sciences, University of Napoli Federico II, Napoli, Italy
| | - Daniela Montesarchio
- Department of Chemical Sciences, University of Napoli Federico II, Napoli, Italy
| | | | - Domenica Musumeci
- Department of Chemical Sciences, University of Napoli Federico II, Napoli, Italy; Institute of Biostructures and Bioimages, CNR, Napoli, Italy.
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16
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Reshetnikov R, Golovin A, Spiridonova V, Kopylov A, Šponer J. Structural Dynamics of Thrombin-Binding DNA Aptamer d(GGTTGGTGTGGTTGG) Quadruplex DNA Studied by Large-Scale Explicit Solvent Simulations. J Chem Theory Comput 2015; 6:3003-14. [PMID: 26616765 DOI: 10.1021/ct100253m] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The thrombin-binding aptamer (15-TBA) is a 15-mer DNA oligonucleotide with sequence d(GGTTGGTGTGGTTGG). 15-TBA folds into a quadruplex DNA (G-DNA) structure with two planar G-quartets connected by three single-stranded loops. The arrangement of the 15-TBA-thrombin complex is unclear, particularly with respect to the precise 15-TBA residues that interact with the thrombin structure. Our present understanding suggests either the 15-TBA single stranded loops containing sequential thymidines (TT) or alternatively a single-stranded loop, containing a guanine flanked by 2 thymidines (TGT), physically associates with thrombin protein. In the present study, the explicit solvent molecular dynamics (MD) simulation method was utilized to further analyze the 15-TBA-thrombin three-dimensional structure. Functional annotation of the loop residues was made with long simulations in the parmbsc0 force field. In total, the elapsed time of simulations carried out in this study exceeds 12 microseconds, substantially surpassing previous G-DNA simulation reports. Our simulations suggest that the TGT-loop function is to stabilize the structure of the aptamer, while the TT-loops participate in direct binding to thrombin. The findings of the present report advance our understanding of the molecular structure of the 15-TBA-thrombin structure further enabling the construction of biosensors for aptamer bases and the development of anticoagulant agents.
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Affiliation(s)
- Roman Reshetnikov
- Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,A.N.Belozersky Institute of Physical Chemical Biology, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Chemistry Department, Lomonosov Moscow State University, Gsp-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic
| | - Andrey Golovin
- Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,A.N.Belozersky Institute of Physical Chemical Biology, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Chemistry Department, Lomonosov Moscow State University, Gsp-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic
| | - Vera Spiridonova
- Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,A.N.Belozersky Institute of Physical Chemical Biology, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Chemistry Department, Lomonosov Moscow State University, Gsp-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic
| | - Alexei Kopylov
- Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,A.N.Belozersky Institute of Physical Chemical Biology, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Chemistry Department, Lomonosov Moscow State University, Gsp-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic
| | - Jiří Šponer
- Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Department of Boiengineering and Bioinformatics, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,A.N.Belozersky Institute of Physical Chemical Biology, Lomonosov Moscow State University, GSP-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Chemistry Department, Lomonosov Moscow State University, Gsp-1, Leninskie Gory, Moscow, 119991, Russian Federation.,Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, 61265 Brno, Czech Republic
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17
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Abstract
In this study we describe new modified analogs of the thrombin binding aptamer (TBA) containing 5-nitroindole residues. It has been shown that all modified TBAs form an anti-parallel G-quadruplex structure and retain the ability to inhibit thrombin. The most advanced TBA variant (TBA-N8) has a substantially increased clotting time and two-fold lower IC50 value compared to the unmodified prototype. Molecular modelling studies suggest that the improved anticoagulant properties of TBA-N8 result from changes in the binding mode of the analog. A modified central loop in TBA-N8 is presumed to participate in the binding of the target protein. Studies of FAM labelled TBA and TBA-N8 showed an improved binding affinity of the modified aptamer and provided evidence of a direct interaction between the modified central loop and thrombin. Our findings have implications for the design of new aptamers with improved binding affinities.
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18
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Abstract
Coagulation and anticoagulation system is kept in balance by the orchestrated action of a variety of biological factors, and the disruption of this balance leads to the risk of hemorrhage or thrombosis. Oligonucleotide aptamers are single-stranded DNA (ssDNA) or RNA ligands that are synthesized in vitro and bind to target molecules through dimensional structure with high specificity and affinity, and thus represent attractive candidates for the development of agents to maintain the balance of coagulation and anticoagulation. In this review, we summarize recent progress in aptamer-based application in the modulation of coagulation. The aptamers with specific chemical and biological characteristics have great potential to be explored as agents for the treatment of blood coagulation abnormalities.
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19
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Scuotto M, Rivieccio E, Varone A, Corda D, Bucci M, Vellecco V, Cirino G, Virgilio A, Esposito V, Galeone A, Borbone N, Varra M, Mayol L. Site specific replacements of a single loop nucleoside with a dibenzyl linker may switch the activity of TBA from anticoagulant to antiproliferative. Nucleic Acids Res 2015; 43:7702-16. [PMID: 26250112 PMCID: PMC4652776 DOI: 10.1093/nar/gkv789] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/23/2015] [Indexed: 12/20/2022] Open
Abstract
Many antiproliferative G-quadruplexes (G4s) arise from the folding of GT-rich strands. Among these, the Thrombin Binding Aptamer (TBA), as a rare example, adopts a monomolecular well-defined G4 structure. Nevertheless, the potential anticancer properties of TBA are severely hampered by its anticoagulant action and, consequently, no related studies have appeared so far in the literature. We wish to report here that suitable chemical modifications in the TBA sequence can preserve its antiproliferative over anticoagulant activity. Particularly, we replaced one residue of the TT or TGT loops with a dibenzyl linker to develop seven new quadruplex-forming TBA based sequences (TBA-bs), which were studied for their structural (CD, CD melting, 1D NMR) and biological (fibrinogen, PT and MTT assays) properties. The three-dimensional structures of the TBA-bs modified at T13 (TBA-bs13) or T12 (TBA-bs12), the former endowed with selective antiproliferative activity, and the latter acting as potently as TBA in both coagulation and MTT assays, were further studied by 2D NMR restrained molecular mechanics. The comparative structural analyses indicated that neither the stability, nor the topology of the G4s, but the different localization of the two benzene rings of the linker was responsible for the loss of the antithrombin activity for TBA-bs13.
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Affiliation(s)
- Maria Scuotto
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Elisa Rivieccio
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Alessia Varone
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Daniela Corda
- Institute of Protein Biochemistry, National Research Council, Via Pietro Castellino 111, 80131 Naples, Italy
| | - Mariarosaria Bucci
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Valentina Vellecco
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Giuseppe Cirino
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Antonella Virgilio
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Veronica Esposito
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Aldo Galeone
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Nicola Borbone
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Michela Varra
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
| | - Luciano Mayol
- Department of Pharmacy, University of Naples Federico II, Via Domenico Montesano 49, Naples, Italy
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20
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Cai B, Yang X, Sun L, Fan X, Li L, Jin H, Wu Y, Guan Z, Zhang L, Zhang L, Yang Z. Stability and bioactivity of thrombin binding aptamers modified with D-/L-isothymidine in the loop regions. Org Biomol Chem 2015; 12:8866-76. [PMID: 25264858 DOI: 10.1039/c4ob01525h] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thrombin binding aptamer (TBA) is a 15-mer single-strand DNA that was identified by SELEX screening technology. It adopts a chair-type antiparallel G-quadruplex and can specifically interact with thrombin, thus inhibiting blood coagulation. Isonucleoside (isoNA) is a type of nucleoside isomer in which the base is shifted to 2′-positions of the glycosyl group, endowed with the ability to modulate local conformation of nucleotides, and L-isoNA could alter the conformation more due to the inversion of glycosyl configuration. Incorporation of L-isothymidine (L-isoT) at T3, T9, T12 positions and D-isoT at the T7 position in TBA's loop regions promoted the formation of G-quadruplex, resulting in enhanced affinity with thrombin and an increased anticoagulant effect. Computer simulation indicated that TBA-12L showed the strongest binding with thrombin, which was consistent with experimental results. The bioactivity of double isoNA incorporated TBA with D-IsoT at T7 and L-IsoT at T12 was comparable to that of TBA-12L, suggesting that the T12 of TBA was very important in interaction with thrombin. Our study also suggested that TBA might interact with two thrombin molecules through the TT loops (T3T4, T12T13) and TGT loop, but the second bonding did not show additional biological effects.
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Affiliation(s)
- Baobin Cai
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191, PR China.
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21
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Kolganova NA, Varizhuk AM, Novikov RA, Florentiev VL, Pozmogova GE, Borisova OF, Shchyolkina AK, Smirnov IP, Kaluzhny DN, Timofeev EN. Anomeric DNA quadruplexes. ARTIFICIAL DNA, PNA & XNA 2015; 5:e28422. [PMID: 25483931 DOI: 10.4161/adna.28422] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thrombin-binding aptamer (TBA) is a 15-nt DNA oligomer that efficiently inhibits thrombin. It has been shown that TBA folds into an anti-parallel unimolecular G-quadruplex. Its three-dimensional chair-like structure consists of two G-tetrads connected by TT and TGT loops. TBA undergoes fast degradation by nucleases in vivo. To improve the nuclease resistance of TBA, a number of modified analogs have been proposed. Here, we describe anomeric modifications of TBA. Non-natural α anomers were used to replace selected nucleotides in the loops and core. Significant stabilization of the quadruplex was observed for the anomeric modification of TT loops at T4 and T13. Replacement of the core guanines either prevents quadruplex assembly or induces rearrangement in G-tetrads. It was found that the anticoagulant properties of chimeric aptamers could be retained only with intact TT loops. On the contrary, modification of the TGT loop was shown to substantially increase nuclease resistance of the chimeric aptamer without a notable disturbance of its anticoagulant activity.
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Affiliation(s)
- Natalia A Kolganova
- a Engelhardt Institute of Molecular Biology; Russian Academy of Sciences; Moscow, Russia
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22
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Virgilio A, Petraccone L, Scuotto M, Vellecco V, Bucci M, Mayol L, Varra M, Esposito V, Galeone A. 5-Hydroxymethyl-2'-deoxyuridine residues in the thrombin binding aptamer: investigating anticoagulant activity by making a tiny chemical modification. Chembiochem 2014; 15:2427-34. [PMID: 25214456 DOI: 10.1002/cbic.201402355] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Indexed: 11/07/2022]
Abstract
We report an investigation into analogues of the thrombin binding aptamer (TBA). Individual thymidines were replaced by the unusual residue 5-hydroxymethyl-2'-deoxyuridine (hmU). This differs from the canonical thymidine by a hydroxyl group on the 5-methyl group. NMR and CD data clearly indicate that all TBA derivatives retain the ability to fold into the "chair-like" quadruplex structure. The presence of the hmU residue does not significantly affect the thermal stability of the modified aptamers compared to the parent, except for analogue H9, which showed a marked increase in melting temperature. Although all TBA analogues showed decreased affinities to thrombin, H3, H7, and H9 proved to have improved anticoagulant activities. Our data open up the possibility to enhance TBA biological properties, simply by introducing small chemical modifications.
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Affiliation(s)
- Antonella Virgilio
- Dipartimento di Farmacia, Università degli Studi di Napoli "Federico II", Via D. Montesano 49, 80131 Napoli (Italy)
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23
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Sun L, Jin H, Zhao X, Liu Z, Guan Y, Yang Z, Zhang L, Zhang L. Unfolding and conformational variations of thrombin-binding DNA aptamers: synthesis, circular dichroism and molecular dynamics simulations. ChemMedChem 2014; 9:993-1001. [PMID: 24715713 DOI: 10.1002/cmdc.201300564] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Revised: 03/14/2014] [Indexed: 01/08/2023]
Abstract
Thrombin-binding DNA aptamer (TBA), with a consensus 15-base sequence: d(GGTTGGTGTGGTTGG), can fold into an antiparallel unimolecular G-quadruplex structure that is necessary for its interaction with thrombin. For the first time, using steered molecular dynamics (SMD) simulations, we have successfully simulated the unfolding process of native TBA G-quadruplex. The unfolding pathway proposed is in agreement with previously reported experimental NMR data. Moreover, the critical intermediate structure in the unfolding pathway, predicted by the NMR results, was identified. The structural characteristics of several TBA oligonucleotides modified with locked nucleoside (LNA) or 2'-O-methyl-nucleoside (MNA) at different positions and number were also investigated by CD spectroscopy. An oligonucleotide substituted with either LNA or MNA at position 2 folds into a native-like G-quadruplex, while doubly substituted derivatives of TBA where LNA or MNA is incorporated at positions 11 and 14 are no longer able to form a G-quadruplex. Starting from the same initial intermediate structure, we successfully overcame sampling limitations, and simulated the large conformational variations in structures of native TBA and modified TBAs by classic MD. Analysis of the models showed that inversion of the glycosyl orientation at position 14 contributes significantly to the disruption of G-quadruplex formation in both of the di-substituted modified TBA systems. Our calculations provide a simple and reliable theoretical model that can be used to investigate and predict the effects of the modifications of an oligonucleotide on the resultant G-quadruplex structure. In addition, the computational protocol described can also be applied for other G-quadruplex systems.
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Affiliation(s)
- Lidan Sun
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing 100191 (P. R. China)
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24
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Li Z, Lech CJ, Phan AT. Sugar-modified G-quadruplexes: effects of LNA-, 2'F-RNA- and 2'F-ANA-guanosine chemistries on G-quadruplex structure and stability. Nucleic Acids Res 2013; 42:4068-79. [PMID: 24371274 PMCID: PMC3973314 DOI: 10.1093/nar/gkt1312] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G-quadruplex-forming oligonucleotides containing modified nucleotide chemistries have demonstrated promising pharmaceutical potential. In this work, we systematically investigate the effects of sugar-modified guanosines on the structure and stability of a (4+0) parallel and a (3+1) hybrid G-quadruplex using over 60 modified sequences containing a single-position substitution of 2′-O-4′-C-methylene-guanosine (LNAG), 2′-deoxy-2′-fluoro-riboguanosine (FG) or 2′-deoxy-2′-fluoro-arabinoguanosine (FANAG). Our results are summarized in two parts: (I) Generally, LNAG substitutions into ‘anti’ position guanines within a guanine-tetrad lead to a more stable G-quadruplex, while substitutions into ‘syn’ positions disrupt the native G-quadruplex conformation. However, some interesting exceptions to this trend are observed. We discover that a LNAG modification upstream of a short propeller loop hinders G-quadruplex formation. (II) A single substitution of either FG or FANAG into a ‘syn’ position is powerful enough to perturb the (3+1) G-quadruplex. Substitution of either FG or FANAG into any ‘anti’ position is well tolerated in the two G-quadruplex scaffolds. FANAG substitutions to ‘anti’ positions are better tolerated than their FG counterparts. In both scaffolds, FANAG substitutions to the central tetrad layer are observed to be the most stabilizing. The observations reported herein on the effects of LNAG, FG and FANAG modifications on G-quadruplex structure and stability will enable the future design of pharmaceutically relevant oligonucleotides.
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Affiliation(s)
- Zhe Li
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
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25
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De Tito S, Morvan F, Meyer A, Vasseur JJ, Cummaro A, Petraccone L, Pagano B, Novellino E, Randazzo A, Giancola C, Montesarchio D. Fluorescence enhancement upon G-quadruplex folding: synthesis, structure, and biophysical characterization of a dansyl/cyclodextrin-tagged thrombin binding aptamer. Bioconjug Chem 2013; 24:1917-27. [PMID: 24094251 DOI: 10.1021/bc400352s] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A novel fluorescent thrombin binding aptamer (TBA), conjugated with the environmentally sensitive dansyl probe at the 3'-end and a β-cyclodextrin residue at the 5'-end, has been efficiently synthesized exploiting Cu(I)-catalyzed azide-alkyne cycloaddition procedures. Its conformation and stability in solution have been studied by an integrated approach, combining in-depth NMR, CD, fluorescence, and DSC studies. ITC measurements have allowed us to analyze in detail its interaction with human thrombin. All the collected data show that this bis-conjugated aptamer fully retains its G-quadruplex formation ability and thrombin recognition properties, with the terminal appendages only marginally interfering with the conformational behavior of TBA. Folding of this modified aptamer into the chairlike, antiparallel G-quadruplex structure, promoted by K(+) and/or thrombin binding, typical of TBA, is associated with a net fluorescence enhancement, due to encapsulation of dansyl, attached at the 3'-end, into the apolar cavity of the β-cyclodextrin at the 5'-end. Overall, the structural characterization of this novel, bis-conjugated TBA fully demonstrates its potential as a diagnostic tool for thrombin recognition, also providing a useful basis for the design of suitable aptamer-based devices for theranostic applications, allowing simultaneously both detection and inhibition or modulation of the thrombin activity.
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Affiliation(s)
- Stefano De Tito
- Department of Pharmacy, University of Naples Federico II , via D. Montesano 49, I-80131 Naples, Italy
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Shiang YC, Ou CM, Chen SJ, Ou TY, Lin HJ, Huang CC, Chang HT. Highly efficient inhibition of human immunodeficiency virus type 1 reverse transcriptase by aptamers functionalized gold nanoparticles. NANOSCALE 2013; 5:2756-2764. [PMID: 23429884 DOI: 10.1039/c3nr33403a] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We have developed aptamer (Apt)-conjugated gold nanoparticles (Apt-Au NPs, 13 nm in diameter) as highly effective inhibitors for human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT). Two Apts, RT1t49 (Aptpol) and ODN 93 (AptRH), which recognize the polymerase and RNase H regions of HIV-1 RT, are used to conjugate Au NPs to prepare Aptpol-Au NPs and AptRH-Au NPs, respectively. In addition to DNA sequence, the surface density of the aptamers on Au NPs (nApt-Au NPs; n is the number of aptamer molecules on each Au NP) and the linker length number (Tm; m is the base number of the deoxythymidine linker) between the aptamer and Au NPs play important roles in determining their inhibition activity. A HIV-lentiviral vector-based antiviral assay has been applied to determine the inhibitory effect of aptamers or Apt-Au NPs on the early stages of their replication cycle. The nuclease-stable G-quadruplex structure of 40AptRH-T45-Au NPs shows inhibitory efficiency in the retroviral replication cycle with a decreasing infectivity (40.2%).
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Affiliation(s)
- Yen-Chun Shiang
- Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
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Doluca O, Withers JM, Filichev VV. Molecular engineering of guanine-rich sequences: Z-DNA, DNA triplexes, and G-quadruplexes. Chem Rev 2013; 113:3044-83. [PMID: 23391174 DOI: 10.1021/cr300225q] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Osman Doluca
- Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
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Polyvalent nucleic acid aptamers and modulation of their activity: a focus on the thrombin binding aptamer. Pharmacol Ther 2012; 136:202-15. [PMID: 22850531 DOI: 10.1016/j.pharmthera.2012.07.011] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 07/16/2012] [Indexed: 01/29/2023]
Abstract
Nucleic acid-based aptamers can be selected from combinatorial libraries of synthetic oligonucleotides to bind, with affinity and specificity similar to antibodies, a wide range of biomedically relevant targets. Compared to protein therapeutics, aptamers exhibit significant advantages in terms of size, non-immunogenicity and wide synthetic accessibility. Various chemical modifications have been introduced in the natural oligonucleotide backbone of aptamers in order to increase their half-life, as well as their pharmacological properties. Very effective alternative approaches, devised in order to improve both the aptamer activity and stability, were based on the design of polyvalent aptamers, able to establish multivalent interactions with the target: thus, multiple copies of an aptamer can be assembled on the same molecular- or nanomaterial-based scaffold. In the present review, the thrombin binding aptamers (TBAs) are analyzed as a model system to study multiple-aptamer constructs aimed at improving their anticoagulation activity in terms of binding to the target and stability to enzymatic degradation. Indeed - even if the large number of chemically modified TBAs investigated in the last 20 years has led to encouraging results - a significant progress has been obtained only recently with bivalent or engineered dendritic TBA aptamers, or assemblies of TBAs on nanoparticles and DNA nanostructures. Furthermore, the modulation of the aptamers activity by means of tailored drug-active reversal agents, especially in the field of anticoagulant aptamers, as well as the reversibility of the TBA activity through the use of antidotes, such as porphyrins, complementary oligonucleotides or of external stimuli, are discussed.
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Wang P, Yang Y, Hong H, Zhang Y, Cai W, Fang D. Aptamers as therapeutics in cardiovascular diseases. Curr Med Chem 2012; 18:4169-74. [PMID: 21848510 DOI: 10.2174/092986711797189673] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2011] [Revised: 05/26/2011] [Accepted: 05/28/2011] [Indexed: 12/18/2022]
Abstract
With many advantages over other therapeutic agents such as monoclonal antibodies, aptamers have recently emerged as a novel and powerful class of ligands with excellent potential for diagnostic and therapeutic applications. Typically generated through Systematic Evolution of Ligands by EXponential enrichment (SELEX), aptamers have been selected against a wide range of targets such as proteins, phospholipids, sugars, nucleic acids, as well as whole cells. DNA/RNA aptamers are single-stranded DNA/RNA oligonucleotides (with a molecular weight of 5-40 kDa) that can fold into well-defined 3D structures and bind to their target molecules with high affinity and specificity. A number of strategies have been adopted to synthesize aptamers with enhanced in vitro/in vivo stability, aiming at potential therapeutic/diagnostic applications in the clinic. In cardiovascular diseases, aptamers can be developed into therapeutic agents as anti-thrombotics, anti-coagulants, among others. This review focuses on aptamers that were selected against various molecular targets involved in cardiovascular diseases: von Willebrand factor (vWF), thrombin, factor IX, phospholamban, P-selectin, platelet-derived growth factor, integrin α(v)β(3), CXCL10, vasopressin, among others. With continued effort in the development of aptamer-based therapeutics, aptamers will find their niches in cardiovascular diseases and significantly impact clinical patient management.
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Affiliation(s)
- P Wang
- Department of Gastroenterology, Southwest Hospital, The Third Military Medical University, Chongqing, China
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30
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Musumeci D, Oliviero G, Roviello GN, Bucci EM, Piccialli G. G-quadruplex-forming oligonucleotide conjugated to magnetic nanoparticles: synthesis, characterization, and enzymatic stability assays. Bioconjug Chem 2012; 23:382-91. [PMID: 22239558 DOI: 10.1021/bc200305t] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the present work, we report the conjugation of superparamagnetic nanoparticles to a fluorescently labeled oligodeoxyribonucleotide (ODN) able to fold into stable unimolecular guanine quadruple helix under proper ion conditions by means of its thrombin-binding aptamer (TBA) sequence. The novel modified ODN, which contained a fluorescent dU(Py) unit at 3'-end and a 12-amino-dodecyl spacer (C(12)-NH(2)) at 5' terminus, was characterized by ESI-MS and optical spectroscopy (UV, CD, fluorescence), and analyzed by RP-HPLC chromatography and electrophoresis. From CD and fluorescence experiments, we verified that dU(Py) and C(12)-NH(2) incorporation does not interfere with the conformational stability of the G-quadruplex. Subsequently, the conjugation of the pyrene-labeled ODN with the magnetite particles was performed, and the ODN-conjugated nanoparticles were studied through optical spectroscopy (UV, CD, fluorescence) and by enzymatic and chemical assays. We found that the nanoparticles enhanced the stability of the TBA ODN to enzymatic degradation. Finally, we evaluated the amount of the TBA-conjugated nanoparticles immobilized on a magnetic separator in view of the potential use of the nanosystem for the magnetic capture of thrombin from complex mixtures.
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Affiliation(s)
- Domenica Musumeci
- Dipartimento di Chimica delle Sostanze Naturali, Università di Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy.
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Hsu CL, Wei SC, Jian JW, Chang HT, Chen WH, Huang CC. Highly flexible and stable aptamer-caged nanoparticles for control of thrombin activity. RSC Adv 2012. [DOI: 10.1039/c1ra00344e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Zavyalova EG, Protopopova AD, Yaminsky IV, Kopylov AM. Kinetic characterization of inhibition of human thrombin with DNA aptamers by turbidimetric assay. Anal Biochem 2011; 421:234-9. [PMID: 22056408 DOI: 10.1016/j.ab.2011.10.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 10/06/2011] [Accepted: 10/07/2011] [Indexed: 10/16/2022]
Abstract
A sensitive turbidimetric method for detecting fibrin association was used to study the kinetics of fibrinogen hydrolysis with thrombin. The data were complemented by high-performance liquid chromatography (HPLC) measurements of the peptide products, fibrinopeptides released during hydrolysis. Atomic force microscopy (AFM) data showed that the fibril diameter is the main geometric parameter influencing the turbidity. The turbidimetric assay was validated using thrombin with the standard activity. To study thrombin inhibitors, a kinetic model that allows estimating the inhibition constants and the type of inhibition was proposed. The kinetic model was used to study the inhibitory activity of the two DNA aptamers 15-TBA (thrombin-binding aptamer) and 31-TBA, which bind to thrombin exosites. For the first time, 31-TBA was shown to possess the competitive inhibition type, whereas the shortened aptamer 15-TBA has the noncompetitive inhibition type.
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Affiliation(s)
- Elena G Zavyalova
- Department of Chemistry, M V Lomonosov Moscow State University, Moscow 119991, Russian Federation.
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Collie GW, Parkinson GN. The application of DNA and RNA G-quadruplexes to therapeutic medicines. Chem Soc Rev 2011; 40:5867-92. [PMID: 21789296 DOI: 10.1039/c1cs15067g] [Citation(s) in RCA: 461] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The intriguing structural diversity in folded topologies available to guanine-rich nucleic acid repeat sequences have made four-stranded G-quadruplex structures the focus of both basic and applied research, from cancer biology and novel therapeutics through to nanoelectronics. Distributed widely in the human genome as targets for regulating gene expression and chromosomal maintenance, they offer unique avenues for future cancer drug development. In particular, the recent advances in chemical and structural biology have enabled the construction of bespoke selective DNA based aptamers to be used as novel therapeutic agents and access to detailed structural models for structure based drug discovery. In this critical review, we will explore the important underlying characteristics of G-quadruplexes that make them functional, stable, and predictable nanoscaffolds. We will review the current structural database of folding topologies, molecular interfaces and novel interaction surfaces, with a consideration to their future exploitation in drug discovery, molecular biology, supermolecular assembly and aptamer design. In recent years the number of potential applications for G-quadruplex motifs has rapidly grown, so in this review we aim to explore the many future challenges and highlight where possible successes may lie. We will highlight the similarities and differences between DNA and RNA folded G-quadruplexes in terms of stability, distribution, and exploitability as small molecule targets. Finally, we will provide a detailed review of basic G-quadruplex geometry, experimental tools used, and a critical evaluation of the application of high-resolution structural biology and its ability to provide meaningful and valid models for future applications (255 references).
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Affiliation(s)
- Gavin W Collie
- CRUK Biomolecular Structure Group, The School of Pharmacy, University of London, London, UK WC1N 1AX
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Reshetnikov RV, Golovin AV, Kopylov AM. Comparison of models of thrombin-binding 15-mer DNA aptamer by molecular dynamics simulation. BIOCHEMISTRY (MOSCOW) 2011; 75:1017-24. [PMID: 21073423 DOI: 10.1134/s0006297910080109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Two models of 15-mer thrombin-binding DNA aptamer (15TGT) were comparatively analyzed by molecular dynamics simulation using the GROMACS software package. The two original models of 15TGT were obtained by NMR and X-ray analyses. The models significantly differ in the topology of loops and the direction of oligodeoxyribonucleotide chain. The evolution of the two structures in parm99 force fields and parmbsc0 optimized for nucleic acids was analyzed in our adaptation of GROMACS architecture. It is shown that the best system for description of the 15TGT structure is the model obtained by X-ray analysis in the parmbsc0 force field.
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Affiliation(s)
- R V Reshetnikov
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119991, Russia.
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Pasternak A, Hernandez FJ, Rasmussen LM, Vester B, Wengel J. Improved thrombin binding aptamer by incorporation of a single unlocked nucleic acid monomer. Nucleic Acids Res 2010; 39:1155-64. [PMID: 20870750 PMCID: PMC3035450 DOI: 10.1093/nar/gkq823] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A 15-mer DNA aptamer (named TBA) adopts a G-quadruplex structure that strongly inhibits fibrin-clot formation by binding to thrombin. We have performed thermodynamic analysis, binding affinity and biological activity studies of TBA variants modified by unlocked nucleic acid (UNA) monomers. UNA-U placed in position U3, U7 or U12 increases the thermodynamic stability of TBA by 0.15–0.50 kcal/mol. In contrast, modification of any position within the two G-quartet structural elements is unfavorable for quadruplex formation. The intramolecular folding of the quadruplexes is confirmed by Tm versus ln c analysis. Moreover, circular dichroism and thermal difference spectra of the modified TBAs displaying high thermodynamic stability show bands that are characteristic for antiparallel quadruplex formation. Surface plasmon resonance studies of the binding of the UNA-modified TBAs to thrombin show that a UNA monomer is allowed in many positions of the aptamer without significantly changing the thrombin-binding properties. The biological effect of a selection of the modified aptamers was tested by a thrombin time assay and showed that most of the UNA-modified TBAs possess anticoagulant properties, and that the construct with a UNA-U monomer in position 7 is a highly potent inhibitor of fibrin-clot formation.
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Affiliation(s)
- Anna Pasternak
- Nucleic Acid Center, Department of Physics and Chemistry, University of Southern Denmark, 5230 Odense M, Denmark.
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