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Pagano B, Mattia CA, Giancola C. Applications of isothermal titration calorimetry in biophysical studies of G-quadruplexes. Int J Mol Sci 2009; 10:2935-2957. [PMID: 19742177 PMCID: PMC2738904 DOI: 10.3390/ijms10072935] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 06/29/2009] [Accepted: 06/29/2009] [Indexed: 01/07/2023] Open
Abstract
G-quadruplexes are higher-order nucleic acids structures formed by G-rich sequences that are stabilized by tetrads of hydrogen-bonded guanine bases. Recently, there has been growing interest in the study of G-quadruplexes because of their possible involvement in many biological processes. Isothermal titration calorimetry (ITC) has been proven to be a useful tool to study the energetic aspects of G-quadruplex interactions. Particularly, ITC has been applied many times to determine the thermodynamic properties of drug-quadruplex interactions to screening among various drugs and to address drug design. In the present review, we will focus on the ITC studies of G-quadruplex structures and their interaction with proteins and drugs and the most significant results will be discussed.
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Affiliation(s)
- Bruno Pagano
- Dipartimento di Scienze Farmaceutiche, Università di Salerno, Via Ponte Don Melillo, 84084, Fisciano (SA), Italy; E-Mail:
(C.M.)
- Authors to whom correspondence should be addressed; E-Mail:
(B.P.); Tel. +39-089-969759; Fax: +39-089-969602; E-Mail:
(C.G.); Tel. +39-081-674266; Fax: +39-081-674257
| | - Carlo Andrea Mattia
- Dipartimento di Scienze Farmaceutiche, Università di Salerno, Via Ponte Don Melillo, 84084, Fisciano (SA), Italy; E-Mail:
(C.M.)
| | - Concetta Giancola
- Dipartimento di Chimica, Università di Napoli Federico II, via Cintia, 80126, Napoli, Italy
- Authors to whom correspondence should be addressed; E-Mail:
(B.P.); Tel. +39-089-969759; Fax: +39-089-969602; E-Mail:
(C.G.); Tel. +39-081-674266; Fax: +39-081-674257
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52
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Snásel J, Rosenberg I, Paces O, Pichová I. The strand transfer oligonucleotide inhibitors of HIV-integrase. J Enzyme Inhib Med Chem 2009; 24:241-6. [PMID: 18608742 DOI: 10.1080/14756360802051578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Retroviral integrase participates in two catalytic reactions, which require interactions with the two ends of the viral DNA in the 3'processing reaction, and with a targeted host DNA in the strand transfer reaction. The 3'-hydroxyl group of 2'-deoxyadenosine resulting from the specific removing of GT dinucleotide from the viral DNA in the processing reaction provides the attachment site for the host DNA in a transesterification reaction. We synthesized oligonucleotides (ONs) of various lengths that mimic the processed HIV-1 U5 terminus of the proviral long terminal repeat (LTR) and are ended by 2'-deoxyadenosine containing a 3'-O-phosphonomethyl group. The duplex stability of phosphonomethyl ONs was increased by covalent linkage of the modified strand with its complementary strand by a triethylene glycol loop (TEG). Modified ONs containing up to 10 bases inhibited in vitro the strand transfer reaction catalyzed by HIV-1 integrase at nanomolar concentrations.
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Affiliation(s)
- Jan Snásel
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic
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53
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Shim JW, Tan Q, Gu LQ. Single-molecule detection of folding and unfolding of the G-quadruplex aptamer in a nanopore nanocavity. Nucleic Acids Res 2009; 37:972-82. [PMID: 19112078 PMCID: PMC2647319 DOI: 10.1093/nar/gkn968] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 11/12/2008] [Accepted: 11/16/2008] [Indexed: 11/12/2022] Open
Abstract
Guanine-rich nucleic acids can form G-quadruplexes that are important in gene regulation, biosensor design and nano-structure construction. In this article, we report on the development of a nanopore encapsulating single-molecule method for exploring how cations regulate the folding and unfolding of the G-quadruplex formed by the thrombin-binding aptamer (TBA, GGTTGGTGTGGTTGG). The signature blocks in the nanopore revealed that the G-quadruplex formation is cation-selective. The selectivity sequence is K(+) > NH(4)(+) approximately Ba(2+) > Cs(+) approximately Na(+) > Li(+), and G-quadruplex was not detected in Mg(2+) and Ca(2+). Ba(2+) can form a long-lived G-quadruplex with TBA. However, the capability is affected by the cation-DNA interaction. The cation-selective formation of the G-quadruplex is correlated with the G-quadruplex volume, which varies with cation species. The high formation capability of the K(+)-induced G-quadruplex is contributed largely by the slow unfolding reaction. Although the Na(+)- and Li(+)-quadruplexes feature similar equilibrium properties, they undergo radically different pathways. The Na(+)-quadruplex folds and unfolds most rapidly, while the Li(+)-quadruplex performs both reactions at the slowest rates. Understanding these ion-regulated properties of oligonucleotides is beneficial for constructing fine-tuned biosensors and nano-structures. The methodology in this work can be used for studying other quadruplexes and protein-aptamer interactions.
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Affiliation(s)
| | | | - Li-Qun Gu
- Department of Biological Engineering, Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
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Li T, Shi L, Wang E, Dong S. Multifunctional G-quadruplex aptamers and their application to protein detection. Chemistry 2009; 15:1036-42. [PMID: 19053089 DOI: 10.1002/chem.200801282] [Citation(s) in RCA: 131] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Two significant G-quadruplex aptamers named AGRO100 and T30695 are identified as multifunctional aptamers that can bind the protein ligands nucleolin or HIV-1 integrase and hemin. Besides their strong binding to target proteins, both AGRO100 and T30695 exhibit high hemin-binding affinities comparable to that of the known aptamer (termed PS2M) selected by the in vitro evolution process. Most importantly, their corresponding hemin-DNA complexes reveal excellent peroxidase-like activities, higher than that of the reported hemin-PS2M DNAzyme. This enables these multifunctional aptamers to be applied to the sensitive detection of proteins, which is demonstrated by applying AGRO100 to the chemiluminescence detection of nucleolin expressed at the surface of HeLa cells. Based on the specific AGRO100-nucleolin interaction, the surface-expressed nucleolin of HeLa cells is labeled in situ with the hemin-AGRO100 DNAzyme, and then determined in the luminol-H(2)O(2) system. Through this approach, the sensitive detection of total nucleolin expressed at the surface of about 6000 HeLa cells is accomplished. Our results suggest that exploiting new functions of existing aptamers will help to extend their potential applications in the biochemical field.
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Affiliation(s)
- Tao Li
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, China
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55
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Li H, Yuan G. Collision-induced dissociation of dimeric G-quadruplexes of HIV-1 integrase inhibitors and their complexes by tandem-in-time mass spectrometry. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2009; 15:731-737. [PMID: 19940339 DOI: 10.1255/ejms.1033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The collision-dissociation behavior of two novel dimeric G-quadruplexes of HIV-1 integrase inhibitors and their noncovalent complex ions with a perylene derivative (Tel03), polyamides (ImImImbetaDp and PyPyPybetaDp) was investigated by tandem-in-time electrospray ionization mass spectrometry (ESI-MS). It was found that the dimeric ion loses five ammonium ions one by one at activation energy of 10%, so the loss of NH(4)(+) is the predominant fragmentation pathway at lower collision energy. When the activation amplitude is increased to 16%, the loss of guanine nucleobases from backbones of the oligonucleotide is the predominant fragmentation pathway. And the stability of the complex ion of the dimeric G-quadruplex and Tel03 is higher than that of ImImImbetaDp and PyPyPybetaDp. The results of the MS/MS spectra of the complex ion indicated that Tel03 binding molecule favor the stabilization of the novel G-quadruplex structure.
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Affiliation(s)
- Huihui Li
- Jiangsu Key Laboratory of Biofunctional Materials, School of Chemistry and Environmental Science, Nanjing Normal University, Nanjing, 210097, China
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56
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Michalowski D, Chitima-Matsiga R, Held DM, Burke DH. Novel bimodular DNA aptamers with guanosine quadruplexes inhibit phylogenetically diverse HIV-1 reverse transcriptases. Nucleic Acids Res 2008; 36:7124-35. [PMID: 18996899 PMCID: PMC2602765 DOI: 10.1093/nar/gkn891] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
DNA aptamers RT5, RT6 and RT47 form a group of related sequences that inhibit HIV-1 reverse transcriptase (RT). The essential inhibitory structure is identified here as bimodular, with a 5' stem-loop module physically connected to a 3'-guanosine quadruplex module. The stem-loop tolerates considerable sequence plasticity. Connections between the guanosine triplets in the quadruplex could be simplified to a single nucleotide or a nonnucleic acid linker, such as hexaethylene glycol. All 12 quadruplex guanosines are required in an aptamer retaining most of the original loop sequence from RT6; only 11 are required for aptamer R1T (single T residue in intra-quadruplex loops). Circular dichroism (CD) spectroscopy gave ellipticity minima and maxima at 240 nm and 264 nm, indicating a parallel arrangement of the quadruplex strands. The simplified aptamers displayed increased overall stability. An aptamer carrying the original intra-quadruplex loops from RT6 inhibited RT in K(+) buffers but not in Na(+) buffers and displayed significant CD spectral broadening in Na(+) buffers, while R1T inhibited RT in both buffers and displayed less broadening in Na(+) buffers. The bimodular ssDNA aptamers inhibited RT from diverse primate lentiviruses with low nM IC(50) values. These data provide insight into the requirements for broad-spectrum RT inhibition by nucleic acid aptamers.
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Affiliation(s)
- Daniel Michalowski
- Department of Molecular Microbiology & Immunology, University of Missouri School of Medicine, Columbia, MO 65211, USA
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57
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Weerasinghe P, Li Y, Guan Y, Zhang R, Tweardy DJ, Jing N. T40214/PEI complex: a potent therapeutics for prostate cancer that targets STAT3 signaling. Prostate 2008; 68:1430-42. [PMID: 18615483 PMCID: PMC2574665 DOI: 10.1002/pros.20807] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Prostate cancer (PC) is the most common cancer among men in American and the second leading cause of cancer death. The treatment options employed for patients with advanced and metastatic PC are limited. As a critical mediator of oncogenic signaling, STAT3 is active in 82% of patients with PC. STAT3 has become a very important molecular target for PC therapy since it upregulates the oncogenes encoding apoptosis inhibitors, cell cycle regulators, and inducers of angiogenesis. However, no anti-tumor drug whose primary mode of action is to target STAT3 has yet reached the clinic. To this end, we have laid the initial groundwork to develop the STAT3-inhibiting G-quartet oligodeoxynucleotide (GQ-ODN), T40214, for treatment of PCs. METHODS We employed in vitro and in vivo assays, including Western blots, EMSA, cell cycle analysis, TUNEL and xenograft models, to determine the drug efficacy and mechanism of T40214/PEI complex. RESULTS The results demonstrated that (i) T40214 significantly inhibited STAT3 activation and induced apoptosis in both androgen-dependent and androgen-independent PC cells; (ii) T40214 delivered by ployethylenimine (PEI) significantly suppressed prostate tumor growth in tumor-bearing nude mice due to that T40214 inhibited STAT3 activation and then greatly promoted apoptosis, reduced angiogenesis and cell proliferation in prostate tumors. CONCLUSION Our studies suggested that STAT3 is a critical oncogenic signal, which strongly influences the progression of PCs and that T40214/PEI complex is a promising candidate for treatment of patients with prostate tumors and represents a novel strategy for PC therapy.
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Affiliation(s)
- Priya Weerasinghe
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
| | - Yifei Li
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
| | - Yongli Guan
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
| | - Ruiwen Zhang
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, AL
| | - David J. Tweardy
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
- Dan Duncan Cancer Center, Baylor College of Medicine, Houston, TX 77030
| | - Naijie Jing
- Department of Medicine, Baylor College of Medicine, Houston, TX 77030
- Dan Duncan Cancer Center, Baylor College of Medicine, Houston, TX 77030
- Corresponding Author: Naijie Jing, Ph.D.*, Department of Medicine and Cancer, Center Baylor College of Medicine, One Baylor Plaza - N520, Houston, Texas 77030 USA, Tel: 713-798-3685, Fax 713-798-8948,
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58
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Li HH, Yuan G. Investigation of formation of dimeric G-quadruplex of HIV-1 integrase inhibitor by nuclear magnetic resonance. CHINESE CHEM LETT 2008. [DOI: 10.1016/j.cclet.2008.06.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Mastrolorenzo A, Maresca A, Rusconi S, Supuran CT. Update on the development of HIV entry inhibitors. ACTA ACUST UNITED AC 2008. [DOI: 10.2217/17469600.2.5.479] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
HIV fusion and entry are two steps in the viral lifecycle that can be targeted by several classes of antiviral drugs. The discovery of chemokines focused the attention on cellular co-receptors used by the virus for entering cells, and on the various steps of such processes that are subject to interactions with small molecules. Intense research has led to a wide range of effective compounds that are able to inhibit these initial steps of viral replication. All steps in the process of HIV entry into the cell may be targeted by specific compounds, grouped into three main classes (attachment inhibitors, co-receptor binding inhibitors and fusion inhibitors), which may be developed as novel antiretrovirals. Thus, several inhibitors of the gp120–CD4 interaction have been discovered (e.g., zintevir and BMS-378806). Small molecule chemokine receptor antagonists acting as HIV entry inhibitors have also been described recently, including those which interact with both the CXCR4 co-receptor (e.g., AMD3100, AMD3465, ALX40-4C, T22, T134 and T140) and CCR5 co-receptor antagonists (TAK-779, TAK-220, E913, AK-602 and NSC 651016 in clinical trials). Recently, a third family of antivirals started to be used clinically (in addition to reverse transcriptase and protease inhibitors), with the advent of enfuvirtide (T20), the first fusion inhibitor to be approved as an anti-HIV agent. Some of these compounds demonstrated in vitro synergism with other classes of antivirals, thus offering the rationale for their combination in therapies for HIV-infected individuals. Many HIV entry and fusion inhibitors are currently being investigated in controlled clinical trials, and a number of them are bioavailable as oral formulations. In 2007, the US FDA approved maraviroc as an anti-HIV agent. Maraviroc is the product of a medicinal chemistry effort initiated following identification of an imidazopyridine CCR5 ligand from a high-throughput screen of the Pfizer compound file. Maraviroc demonstrated potent antiviral activity against all CCR5-tropic HIV-1 viruses tested, including 43 primary isolates from various clades and diverse geographic origin. Maraviroc was active against 200 clinically derived HIV-1 envelope-recombinant pseudoviruses, 100 of which were derived from viruses resistant to existing drug classes. Furthermore, in October 2007, the FDA announced the approval of raltegravir for the treatment of HIV-1 infection as part of combination antiretroviral therapy in treatment-experienced patients with evidence of HIV-1 replication despite optimized background antiretroviral therapy. At present, raltegravir is the only drug in the integrase inhibitor class approved for clinical use. With the approval of raltegravir, oral agents targeting all three constitutive viral enzymes, reverse transcriptase, protease and integrase, are now represented in FDA-approved therapies.
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Affiliation(s)
- Antonio Mastrolorenzo
- Università degli Studi di Firenze, Dipartimento di Scienze Dermatologiche, Centro MTS, Via degli Alfani 37, I-50121 Florence, Italy
| | - Alfonso Maresca
- Università degli Studi di Firenze, Dipartimento di Chimica, Laboratorio di Chimica Bioinorganica, Via della Lastruccia, 3, Rm. 188, I-50019 Sesto Fiorentino (Florence), Italy
| | - Stefano Rusconi
- Dipartimento di Scienze Cliniche “Luigi Sacco”, Cattedra di Malattie Infettive e Tropicali, Università degli Studi, Ospedale Luigi Sacco, Via GB Grassi 74, 20157 Milano, Italy
| | - Claudiu T Supuran
- Università degli Studi di Firenze, Dipartimento di Chimica, Laboratorio di Chimica Bioinorganica, Via della Lastruccia, 3, Rm. 188, I-50019 Sesto Fiorentino (Florence), Italy
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60
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Schwartz TR, Vasta CA, Bauer TL, Parekh-Olmedo H, Kmiec EB. G-rich oligonucleotides alter cell cycle progression and induce apoptosis specifically in OE19 esophageal tumor cells. Oligonucleotides 2008; 18:51-63. [PMID: 18321162 DOI: 10.1089/oli.2007.0109] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Short synthetic oligonucleotides (ODNs) can be used to block cellular processes involved in cell growth and proliferation. Often acting as aptamers, these molecules interact with critical proteins that regulate the induction of apoptosis or necrosis. We have used a specialized class of ODNs that contain a monomeric sequence of guanosine to induce apoptosis specifically in the malignant esophageal cell line, OE19, in cell culture, and in a NODscid mouse model. OE19 cells were grown in culture and treated with a stable G-rich oligonucleotide (GRO). Cells were processed and apoptosis was measured by FACS analyses, caspase activity, and Hoescht staining. Circular dichroism (CD) was used to define the structure and stability of various GROs. The GRO works by first inducing retardation in the progression of the cell cycle and then by creating a sub-G1 population of apoptotic cells. The reaction is dose dependent, and appears to rely on the capacity of the G-rich ODN to adopt a G-quartet conformation. Apoptosis was measured by determining caspase 3/7 levels and by staining for nuclear fragmentation using the Hoechst dye. Importantly, nonmalignant esophageal cells or normal human lung fibroblasts are not impeded in their cell cycle progression when incubated with the G-rich ODNs. These results suggest that a selective killing of esophageal tumor cells is directed by G-rich ODNs. Selective killing was demonstrated in the unique activity of the GRO compared to other ODNs of different sequences as well as the response of oncogenic cells compared to nononcogenic cells.
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Affiliation(s)
- Timothy R Schwartz
- Department of Biological Sciences, University of Delaware, Newark, DE 19711, USA
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61
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Li H, Yuan G, Du D. Investigation of formation, recognition, stabilization, and conversion of dimeric G-quadruplexes of HIV-1 integrase inhibitors by electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:550-559. [PMID: 18313939 DOI: 10.1016/j.jasms.2008.01.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 01/27/2008] [Accepted: 01/28/2008] [Indexed: 05/26/2023]
Abstract
The dimeric G-quadruplex structures of d(GGGTGGGTGGGTGGGT) (S1) and d(GTGGTGGGTGGGTGGGT) (S2), the potent nanomolar HIV-1 integrase inhibitors, were detected by electrospray ionization mass spectrometry (ESI-MS) for the first time. The formation and conversion of the dimers were induced by NH(4)(+), DNA concentration, pH, and the binding molecules. We directly observed the specific binding of a perylene derivative (Tel03) and ImImImbetaDp in one system consisting of the intramolecular and the dimeric G-quadruplexes of the HIV-1 integrase inhibitor, which suggested that Tel03 could shift the equilibrium to the dimeric G-quadruplex formation, while ImImImbetaDp induces preferentially a structural change from the dimer to the intramolecular G-quadruplex. The results of this study indicated that Tel03 and ImImImbetaDp favor the stabilization of the dimeric G-quadruplex structures.
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Affiliation(s)
- Huihui Li
- Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
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62
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Marincola FC, Virno A, Randazzo A, Lai A. Effect of rubidium and cesium ions on the dimeric quaduplex formed by the Oxytricha nova telomeric repeat oligonucleotide d(GGGGTTTTGGGG). NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2008; 26:1129-32. [PMID: 18058551 DOI: 10.1080/15257770701521821] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The DNA sequence d(GGGGTTTTGGGG) consists of 1.5 units of the repeat in telomeres of Oxytricha nova. It has been shown by NMR and x-ray crystallographic analysis that it is capable to form a dimeric quadruplex structure and that a variety of cations, namely K(+), Na(+), and NH(4)(+), are able to interact with this complex with different affinity, leading to complexes characterized by different local conformations. Thus, in order to improve the knowledge of this kind of molecule, and in particular to provide further insight into the role of monovalent cations in the G-quadruplex folding and conformation, we have investigated by (1)H-NMR the effect of the addition of Rb(+) and Cs(+) to the quadruplex formed by the oligonucleotide d(GGGGTTTTGGGG).
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Affiliation(s)
- Flaminia Cesare Marincola
- Dipartimento di Scienze Chimiche, Università di Cagliari-Cittadella Universitaria di Monserrato, Monserrato, CA, Italy.
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63
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Qin Y, Hurley LH. Structures, folding patterns, and functions of intramolecular DNA G-quadruplexes found in eukaryotic promoter regions. Biochimie 2008; 90:1149-71. [PMID: 18355457 DOI: 10.1016/j.biochi.2008.02.020] [Citation(s) in RCA: 373] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Accepted: 02/22/2008] [Indexed: 12/16/2022]
Abstract
In its simplest form, a DNA G-quadruplex is a four-stranded DNA structure that is composed of stacked guanine tetrads. G-quadruplex-forming sequences have been identified in eukaryotic telomeres, as well as in non-telomeric genomic regions, such as gene promoters, recombination sites, and DNA tandem repeats. Of particular interest are the G-quadruplex structures that form in gene promoter regions, which have emerged as potential targets for anticancer drug development. Evidence for the formation of G-quadruplex structures in living cells continues to grow. In this review, we examine recent studies on intramolecular G-quadruplex structures that form in the promoter regions of some human genes in living cells and discuss the biological implications of these structures. The identification of G-quadruplex structures in promoter regions provides us with new insights into the fundamental aspects of G-quadruplex topology and DNA sequence-structure relationships. Progress in G-quadruplex structural studies and the validation of the biological role of these structures in cells will further encourage the development of small molecules that target these structures to specifically modulate gene transcription.
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Affiliation(s)
- Yong Qin
- College of Pharmacy, 1703 E. Mabel, University of Arizona, Tucson, AZ 85721, USA
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64
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Zhu Q, Jing N. Computational study on mechanism of G-quartet oligonucleotide T40214 selectively targeting Stat3. J Comput Aided Mol Des 2007; 21:641-8. [PMID: 18034310 DOI: 10.1007/s10822-007-9147-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Accepted: 11/01/2007] [Indexed: 12/22/2022]
Abstract
The mounting evidences have shown that signal transducer and activator of transcription 3 (Stat3) is a critical target for cancer therapy. Recently, we developed a G-quartet oligonucleotide T40214 as a novel and potent Stat3 inhibitor. T40214 specifically inhibited DNA-binding activity of Stat3 and significantly suppressed the growth of many tumor xenografts in nude mice. To determine the mechanism of GQ-ODNs selectively targeting Stat3, we established a 3D model of complex T40214/p-Stat3 dimer based on experimental evidences. The binding site of T40214 within Stat3 dimer was determined by statistical docking analysis. The results indicated that T40214 strongly interacted within the region from residue E638 through E652 of Stat3 dimer. The binding model refined by Hex docking disclosed that T40214 binds to SH2 domain of Stat3 and forms H-bonds with residues Q643, Q644, N646, and N647, which are critical for the binding interaction. The 3D models also suggested that T40214 inhibits Stat3 activity through disrupting the binding interaction between Stat3 dimer and DNA duplex for transcription. Our computational studies provided a platform for future structure-based drug design of novel Stat3 inhibitors.
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Affiliation(s)
- Qiqing Zhu
- Department of Medicine, Baylor College of Medicine, One Baylor Plaza, N1317.05, Houston, TX 77030, USA
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65
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Tang CF, Shafer RH. Engineering the quadruplex fold: nucleoside conformation determines both folding topology and molecularity in guanine quadruplexes. J Am Chem Soc 2007; 128:5966-73. [PMID: 16637665 PMCID: PMC2597528 DOI: 10.1021/ja0603958] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nucleic acid quadruplexes, based on the guanine quartet, can arise from one or several strands, depending on the sequence. Those consisting of a single strand are usually folded in one of two principal topologies: antiparallel, in which all or half of the guanine stretches are antiparallel to each other, or parallel, in which all guanine stretches are parallel to each other. In the latter, all guanine nucleosides possess the anti conformation about the glycosidic bond, while in the former, half possess the anti conformation, and half possess the syn conformation. While antiparallel is the more common fold, examples of biologically important, parallel quadruplexes are becoming increasingly common. Thus, it is of interest to understand the forces that determine the quadruplex fold. Here, we examine the influence of individual nucleoside conformation on the overall folding topology by selective substitution of rG for dG. We can reverse the antiparallel fold of the thrombin binding aptamer (TBA) by this approach. Additionally, this substitution converts a unimolecular quadruplex into a bimolecular one. Similar reverse substitutions in the all-RNA analogue of TBA result in a parallel to antiparallel change in topology and alter the strand configuration from bimolecular to unimolecular. On the basis of the specific substitutions made, we conclude that the strong preference of guanine ribonucleosides for the anti conformation is the driving force for the change in topology. These results demonstrate how conformational properties of guanine nucleosides govern not only the quadruplex folding topology but also impact quadruplex molecularity and provide a means to control these properties.
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Affiliation(s)
- Chung-Fei Tang
- Department of Pharmaceutical Chemistry, School of Pharmacy and Graduate Group in Chemistry and Chemical Biology, University of California, San Francisco, California 94143-0446, USA
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66
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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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67
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Métifiot M, Faure A, Guyonnet-Duperat V, Bellecave P, Litvak S, Ventura M, Andréola ML. Cellular uptake of ODNs in HIV-1 human-infected cells: a role for viral particles in DNA delivery? Oligonucleotides 2007; 17:151-65. [PMID: 17638520 DOI: 10.1089/oli.2006.0061] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
We have previously described how a 16 nucleotides ODN (termed 93del) is capable of inhibiting the activity of recombinant integrase in a cell-free system as well as HIV-1 replication in human-infected cells with IC(50) in the low nanomolar range. Intracellular HIV-1 replication was inhibited when the ODN was added at the onset of infection. These results raise several questions. Is a naked ODN able to enter the cell? Does the virus play a role in ODN entry? The uptake of several ODNs (93del, 60del(sc), TBA, T30923) was evaluated and then tracked by labeling the ODN with a fluorescent dye and assessing its intracellular localization by confocal microscopy. A significant level of cellular uptake of free ODN was observed in several cell lines: HeLa epithelial cells, Huh7 hepatic cells, and H9 lymphocytes, and was detected for all ODNs tested except for TBA. Striking differences were observed when naked ODNs were added to cell in the presence or absence of the virus. When HIV-1 virions were present a sharp increase in cellular fluorescence was observed. These results strongly suggest a role for HIV-1 virions in the uptake of certain ODNs.
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Affiliation(s)
- Mathieu Métifiot
- UMR 5097 CNRS, Université Victor Segalen Bordeaux 2, 33076 Bordeaux cedex, France
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68
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Wochner A, Menger M, Rimmele M. Characterisation of aptamers for therapeutic studies. Expert Opin Drug Discov 2007; 2:1205-24. [DOI: 10.1517/17460441.2.9.1205] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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69
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Famulok M, Hartig JS, Mayer G. Functional aptamers and aptazymes in biotechnology, diagnostics, and therapy. Chem Rev 2007; 107:3715-43. [PMID: 17715981 DOI: 10.1021/cr0306743] [Citation(s) in RCA: 666] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Michael Famulok
- LIMES Institute, Program Unit Chemical Biology and Medicinal Chemistry, c/o Kekulé-Institut für Organische Chemie und Biochemie, Gerhard Domagk-Strasse 1, 53121 Bonn, Germany.
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70
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Peng CG, Damha MJ. G-quadruplex induced stabilization by 2'-deoxy-2'-fluoro-D-arabinonucleic acids (2'F-ANA). Nucleic Acids Res 2007; 35:4977-88. [PMID: 17636049 PMCID: PMC1976452 DOI: 10.1093/nar/gkm520] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Revised: 06/13/2007] [Accepted: 06/21/2007] [Indexed: 02/07/2023] Open
Abstract
The impact of 2'-deoxy-2'-fluoroarabinonucleotide residues (2'F-araN) on different G-quadruplexes derived from a thrombin-binding DNA aptamer d(G2T2G2TGTG2T2G2), an anti-HIV phosphorothioate aptamer PS-d(T2G4T2) and a DNA telomeric sequence d(G4T4G4) via UV thermal melting (T(m)) and circular dichroism (CD) experiments has been investigated. Generally, replacement of deoxyguanosines that adopt the anti conformation (anti-guanines) with 2'F-araG can stabilize G-quartets and maintain the quadruplex conformation, while replacement of syn-guanines with 2'F-araG is not favored and results in a dramatic switch to an alternative quadruplex conformation. It was found that incorporation of 2'F-araG or T residues into a thrombin-binding DNA G-quadruplex stabilizes the complex (DeltaT(m) up to approximately +3 degrees C/2'F-araN modification); 2'F-araN units also increased the half-life in 10% fetal bovine serum (FBS) up to 48-fold. Two modified thrombin-binding aptamers (PG13 and PG14) show an approximately 4-fold increase in binding affinity to thrombin, as assessed via a nitrocellulose filter binding assay, both with increased thermal stability (approximately 1 degrees C/2'F-ANA modification increase in T(m)) and nuclease resistance (4-7-fold) as well. Therefore, the 2'-deoxy-2'-fluoro-d-arabinonucleic acid (2'F-ANA) modification is well suited to tune (and improve) the physicochemical and biological properties of naturally occurring DNA G-quartets.
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Affiliation(s)
| | - Masad J. Damha
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC, Canada H3A 2K6
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71
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Qi J, Shafer RH. Human telomere quadruplex: refolding and selection of individual conformers via RNA/DNA chimeric editing. Biochemistry 2007; 46:7599-606. [PMID: 17539606 DOI: 10.1021/bi602392u] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformation of the guanine quadruplex formed by the human telomere (HT) repeat in solutions containing physiological concentrations of K+ ions has been a topic of intensive investigation during the past several years. Of particular interest are the directionality of the overall folding pattern, i.e., parallel, antiparallel, or a combination of these two modes, and the alternation, if any, of the glycosidic bond conformation between syn and anti. An additional issue involves resolving mixtures of conformations when more than one species is present. We approach these questions using selective substitution of riboguanosine, rG, for deoxyriboguanosine, dG. Using a combination of circular dichroism, gel electrophoresis, equilibrium ultracentrifugation, and imino proton NMR, we are able to show that these modifications can yield sequences which fold into parallel or antiparallel conformations consisting of one or two strands. We also demonstrate that chimeric editing of the HT sequence permits isolating one of two conformational isomers existing in solution in the presence of KCl. The ability to engineer and control quadruplex folding motifs illustrated here with HT may prove useful more generally for a variety of quadruplex-forming sequences.
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Affiliation(s)
- Jianying Qi
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, San Francisco, California 94143-0446, USA
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72
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Chen F, Zhou J, Luo F, Mohammed AB, Zhang XL. Aptamer from whole-bacterium SELEX as new therapeutic reagent against virulent Mycobacterium tuberculosis. Biochem Biophys Res Commun 2007; 357:743-8. [PMID: 17442275 DOI: 10.1016/j.bbrc.2007.04.007] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2007] [Accepted: 04/03/2007] [Indexed: 10/23/2022]
Abstract
Worldwide, tuberculosis (TB) remains the most frequent and important infectious disease causing morbidity and death. One-third of the world's population is infected with Mycobacterium tuberculosis (MTB), the etiologic agent of TB. Because of the global health problems of TB, the development of potent new anti-TB drugs without cross-resistance with known antimycobacterial agents is urgently needed. In this study, we have applied a Systematic Evolution of Ligands by Exponential Enrichment (SELEX) process to identify a single aptamer (NK2) that binds to virulent strain M. tuberculosis (H37Rv) with high affinity and specificity. We have found that this aptamer improves CD4(+)T cells to produce IFN-gamma after binding to H37Rv. The different component between H37Rv and BCG was identified as some membrane protein. Moreover, the survival rates of mice challenged with i.v. H37Rv have been prolonged after treatment with single injection of aptamer NK2. The bacterial numbers were significantly lower in the spleen of mice treated with aptamer NK2. The histopathological examination of lung biopsy specimens showed lesser pulmonary alveolar fusion and swelling in the presence of the aptamer. These results suggest that aptamer NK2 has inhibitory effects on M. tuberculosis and can be used as antimycobacterial agent.
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Affiliation(s)
- Fan Chen
- Department of Immunology, Hubei Province Key Laboratory of Allergy and Immunology, State Key Laboratory of Virology, Wuhan University School of Medicine, Donghu Road 165#, Wuhan 430071, Hubei Province, China
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Abstract
Aptamers are artificial nucleic acid ligands that can be generated in vitro against a wide range of molecules, including the gene products of viruses. Aptamers are isolated from complex libraries of synthetic nucleic acids by an iterative, cell-free process that involves repetitively reducing the complexity of the library by partitioning on the basis of selective binding to the target molecule, followed by reamplification. For virologists, aptamers have potential uses as tools to help to analyse the molecular biology of virus replication, as a complement to the more familiar monoclonal antibodies. They also have potential applications as diagnostic biosensors and in the development of antiviral agents. In recent years, these two promising avenues have been explored increasingly by virologists; here, the progress that has been made is reviewed.
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Affiliation(s)
- William James
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX2 3RE, UK
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74
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Szilagyi A, Bonn GK, Guttman A. Capillary gel electrophoresis analysis of G-quartet forming oligonucleotides used in DNA-protein interaction studies. J Chromatogr A 2007; 1161:15-21. [PMID: 17391683 DOI: 10.1016/j.chroma.2007.03.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2006] [Revised: 02/28/2007] [Accepted: 03/05/2007] [Indexed: 10/23/2022]
Abstract
DNA-protein binding is among the most frequently studied biomolecular interactions with high importance in modern systems biology research. One interesting aspect of this rapidly developing field is the affinity capture of proteins by G-quartet forming oligonucleotides also referred to as aptamers. G-quartets are structural motifs formed by guanine-rich sequences commonly occurring in the human genome. In this paper, we describe a capillary gel electrophoresis based method to validate G-quartet formation of in-house designed oligonucleotides and discuss the effect of monovalent cation concentration on the development of this structure. The relevant aptamer was then bound to magnetic beads to form an affinity capture surface for target proteins, which were then analyzed by matrix-assisted laser desorption/ionization mass spectrometry.
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Affiliation(s)
- Agnes Szilagyi
- Horváth Laboratory of Bioseparation Sciences, Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, Innrain 66, A-6020 Innsbruck, Austria
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75
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Rachwal PA, Brown T, Fox KR. Effect of G-tract length on the topology and stability of intramolecular DNA quadruplexes. Biochemistry 2007; 46:3036-44. [PMID: 17311417 DOI: 10.1021/bi062118j] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G-Rich sequences are known to form four-stranded structures that are based on stacks of G-quartets, and sequences with the potential to adopt these structures are common in eukaryotic genomes. However, there are few rules for predicting the relative stability of folded complexes that are adopted by sequences with different-length G-tracts or variable-length linkers between them. We have used thermal melting, circular dichroism, and gel electrophoresis to examine the topology and stability of intramolecular G-quadruplexes that are formed by sequences of the type d(GnT)4 and d(GnT2)4 (n = 3-7) in the presence of varying concentrations of sodium and potassium. In the presence of potassium or sodium, d(GnT)4 sequences form intramolecular parallel complexes with the following order of stability: n = 3 > n = 7 > n = 6 > n = 5 > n = 4. d(G3T)4 is anomalously stable. In contrast, the stability of d(GnT2)4 increases with the length of the G-tract (n = 7 > n = 6 > n = 5 > n = 4 > n = 3). The CD spectra for d(GnT)4 in the presence of potassium exhibit positive peaks around 260 nm, consistent with the formation of parallel topologies. These peaks are retained in sodium-containing buffers, but when n = 4, 5, or 6, CD maxima are observed around 290 nm, suggesting that these sequences [especially d(G5T)4] have some antiparallel characteristics. d(G3T2)4 adopts a parallel conformation in the presence of both sodium and potassium, while all the other d(GnT2)4 complexes exhibit predominantly antiparallel features. The properties of these complexes are also affected by the rate of annealing, and faster rates favor parallel complexes.
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Affiliation(s)
- Phillip A Rachwal
- School of Biological Sciences, University of Southampton, Bassett Crescent East, UK
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76
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Abstract
Protein recognition by synthetic molecules is a challenging endeavour, since these materials must bind to a large relatively flat surface domain and recognize a unique distribution of amino acid residues of varying charge, size and shape. The most promising routes involve specific metal coordination, epitope-docking on miniature proteins, aptamer selection, nonnatural peptide isosteres, functionalized platforms, secondary structure mimetics, molecular imprinting and receptors embedded in lipid layers.
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Affiliation(s)
- Thomas Schrader
- University Duisburg-Essen, Department of Chemistry, Universitätsstr. 5, 45117, Essen, Germany
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77
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Abstract
HIV-1 integrase is a protein of Mr 32 000 encoded at the 3'-end of the pol gene. Integration of HIV DNA into the host cell chromosomal DNA apparently occurs by a carefully defined sequence of DNA tailoring (3'-processing (3'P)) and coupling (integration) reactions. Integration of HIV DNA into human DNA represents the biochemical completion of the invasion of the human cell (e.g., T-cell) by HIV. Unlike major successes seen in the development of clinically approved anti-HIV agents against HIV reverse transcriptase and HIV protease, there are no FDA-approved anti-HIV drugs in clinical use where the mechanism of action is inhibition of HIV integrase. This review summarises some key advances in the area of integrase inhibitors with the major focus being on new generation inhibitors. Special emphasis is placed on diketo acids with aromatic and heteroaromatic moieties, diketo acids with nucleobase scaffolds, bis-diketo acids, functionalised naphthyridines and other isosteres of diketo acids. Data pertaining to integrase inhibition and in vitro anti-HIV activity are discussed. Mention is made of drugs in clinical trials, both past (S-1360, L-870,810 and L-870,812 and present (GS-9137 and MK-0518). Other promising drugs, including those from the authors' laboratory, are referred. Resistant mutants arising from key integrase inhibitors and cross-resistance are indicated.
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Affiliation(s)
- Vasu Nair
- Department of Pharmaceutical and Biomedical Sciences, The Center for Drug Discovery, University of Georgia, Athens, GA 30602, USA.
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78
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Yang D, Hurley LH. Structure of the biologically relevant G-quadruplex in the c-MYC promoter. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2006; 25:951-68. [PMID: 16901825 DOI: 10.1080/15257770600809913] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The nuclease hypersensitivity element III1 (NHE III1) in the c-MYC promoter controls up to 80-90% of the transcriptional activity of this gene. We have demonstrated that the guanine-rich strand of the NHE III1 forms a G-quadruplex consisting of a mixture of four biologically relevant loop isomers that function as a silencer element. NMR studies have shown that these G-quadruplexes are propeller-type parallel structures consisting of three stacked G-tetrads and three double-chain reversal loops. An NMR-derived solution structure for this quadruplex provides insight into the unusual stability of the structure. This structure is a target for small molecule inhibitors of c-MYC gene expression.
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Affiliation(s)
- Danzhou Yang
- University of Arizona, College of Pharmacy, Tucson, AZ 85721, USA
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79
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Yin H, Hamilton AD. Strategies for targeting protein-protein interactions with synthetic agents. Angew Chem Int Ed Engl 2006; 44:4130-63. [PMID: 15954154 DOI: 10.1002/anie.200461786] [Citation(s) in RCA: 375] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The development of small-molecule modulators of protein-protein interactions is a formidable goal, albeit one that possesses significant potential for the discovery of novel therapeutics. Despite the daunting challenges, a variety of examples exists for the inhibition of two large protein partners with low-molecular-weight ligands. This review discusses the strategies for targeting protein-protein interactions and the state of the art in the rational design of molecules that mimic the structures and functions of their natural targets.
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Affiliation(s)
- Hang Yin
- Yale University, New Haven, CT, USA
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80
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Jain ML, Bruice TC. Solid-phase synthesis of positively charged deoxynucleic guanidine (DNG) oligonucleotide incorporating 7-deazaguanine bases. Bioorg Med Chem 2006; 14:7333-46. [PMID: 16945544 DOI: 10.1016/j.bmc.2006.05.074] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2006] [Revised: 05/31/2006] [Accepted: 05/31/2006] [Indexed: 10/24/2022]
Abstract
DNG nucleotides represent a positively charged DNA analog in which the negatively charged phosphodiester linkages of DNA are replaced by positively charged guanidinium linkages. We report herein the synthesis of 3'-end, middle, and 5'-end monomers required for the synthesis of a DNG sequence in which the natural guanine base is replaced by 7-deazaguanine (c(7)G). 7-Deazaguanine nucleobase was chosen because of their unique glycoside bond stability and their ability to prevent G-quartet formation. A facile and high yield two-step synthesis of xylo-7-deazaguanine 7, a key intermediate for introducing 3'-amino functionality, is carried out under Mitsunobu conditions. Subsequently, the 3'-Fmoc-protected thiourea monomers 13 and 19 were prepared from 7 via their corresponding 3'-amino-7-deazaguanines 11 and 18, respectively. The smooth coupling of these thiourea monomers with monomethoxytrityl (MMTr)-protected 3'-end monomer 25, prepared from 5, occurred on solid phase in 3'-->5' direction. The resultant trimeric HO-c(7)Ggc(7)Ggc(7)G-OH (1) has been designed to be included into DNA using standard DNA synthesis technology. The combination of C-c(7)G base pairing and electrostatic association of phosphodiester and guanidinium backbone allows the small synthesized DNG trimer 1 to form 1:1 complex with DNA-C pentamer.
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Affiliation(s)
- Moti L Jain
- Department of Chemistry and Biochemistry, University Of California, Santa Barbara, 93106, USA
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81
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Baldrich E, Restrepo A, O'Sullivan CK. Aptasensor development: elucidation of critical parameters for optimal aptamer performance. Anal Chem 2006; 76:7053-63. [PMID: 15571359 DOI: 10.1021/ac049258o] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aptamers are synthetic oligonucleotides specifically selected to bind a certain target. Thanks to their high affinity and sensitivity, aptamers appear as alternative candidates to antibodies for analytical devices and several assays have been reported. However, and contrary to what happens with DNA probes, the aptamers' ability to bind their targets depends on folding and 3-D structure, which may be affected by the incubation conditions and buffer composition. In this report, a systematic evaluation of the parameters with potential effect on the ELAA (Enzyme Linked Aptamer Assay) performance has been carried out. Additionally, diverse ELAA and mixed ELISA/ELAA formats exploiting the thrombin-binding aptamer have been optimized and their efficiencies compared. ELAA results have been confirmed using nuclear magnetic resonance, electrophoresis, and surface plasmon resonance. Our results indicate that parameters such as immobilization strategy, incubation time/temperature, and buffer composition should be optimized for each aptamer as they affect folding and, thus, binding efficiency. Among the studied assays, the mixed ELISA/ELAA sandwich formats showed the lowest limit of detection observed (<1 nM thrombin), while a competition ELAA appeared as the best assay in terms of high sensitivity (1.8 nM) and short assay time (1 h, 30 min). The elucidation of optimal parameters for assay performance reported here clearly indicates that aptamers are unique structures. Formation of the 3-D structures required for target binding is influenced by variable parameters, and unlike DNA/antibody based assays, there are no general recommendations, with each assay requiring individual optimization of parameters.
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Affiliation(s)
- Eva Baldrich
- Nanobiotechnology and Bioanalysis Group, Department of Chemical Engineering, Universitat Rovira i Virgili, Avinguda Països Catalans 26, 43007 Tarragona, Spain
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82
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Jing N, Zhu Q, Yuan P, Li Y, Mao L, Tweardy DJ. Targeting signal transducer and activator of transcription 3 with G-quartet oligonucleotides: a potential novel therapy for head and neck cancer. Mol Cancer Ther 2006; 5:279-86. [PMID: 16505101 DOI: 10.1158/1535-7163.mct-05-0302] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Signal transducer and activator of transcription 3 (Stat3) is a critical mediator of oncogenic signaling activated frequently in many types of human cancer where it contributes to tumor cell growth and resistance to apoptosis. Stat3 has been proposed as a promising target for anticancer drug discovery. Recently, we developed a series of G-quartet oligodeoxynucleotides (GQ-ODN) as novel and potent Stat3 inhibitors, which significantly suppressed the growth of prostate and breast tumors in nude mice. In the present study, we showed that GQ-ODN specifically inhibited DNA-binding activity of Stat3 as opposed to Stat1. Computer-based docking analysis revealed that GQ-ODN predominantly interacts with the SH2 domains of Stat3 homodimers to destabilize dimer formation and disrupt DNA-binding activity. We employed five regimens in the treatment of nude mice with tumors of head and neck squamous cell carcinoma (HNSCC): placebo, paclitaxel, GQ-ODN T40214, GQ-ODN T40231, and T40214 plus paclitaxel. The mean size of HNSCC tumors over 21 days only increased by 1.7-fold in T40214-treated mice and actually decreased by 35% in T40214 plus paclitaxel-treated mice whereas the mean size of HNSCC tumors increased 9.4-fold in placebo-treated mice in the same period. These findings show that GQ-ODN has potent activity against HNSCC tumor xenografts alone and in combination with paclitaxel.
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Affiliation(s)
- Naijie Jing
- Department of Medicine and Cancer Center, Baylor College of Medicine, One Baylor Plaza, N520, Houston, TX 77030, USA.
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83
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Petraccone L, Pagano B, Esposito V, Randazzo A, Piccialli G, Barone G, Mattia CA, Giancola C. Thermodynamics and kinetics of PNA-DNA quadruplex-forming chimeras. J Am Chem Soc 2006; 127:16215-23. [PMID: 16287312 DOI: 10.1021/ja0545923] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PNA-DNA chimeras present the interesting properties of PNA, such as the high binding affinity to complementary single-strand (DNA or RNA), and the resistance to nuclease and protease degradation. At the same time, the limitations of an oligomer containing all PNA residues, such as low water solubility, self-aggregation, and low cellular uptake, are effectively overcome. Further, PNA-DNA chimeras possess interesting biological properties as antisense agents. We have explored the ability of PNA-DNA chimeric strands to assemble in quadruplex structures. The rate constant for association of the quadruplexes and their thermodynamic properties have been determined by CD spectroscopy and differential scanning calorimetry (DSC). Thermal denaturation experiments indicated higher thermal and thermodynamic stabilities for chimeric quadruplexes in comparison with the corresponding unmodified DNA quadruplex. Singular value decomposition analysis (SVD) suggests the presence of kinetically stable intermediate species in the quadruplex formation process. The experimental results have been discussed on the basis of molecular dynamic simulations. The ability of PNA-DNA chimeras to form stable quadruplex structures expands their potential utility as therapeutic agents.
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Affiliation(s)
- Luigi Petraccone
- Dipartimento di Scienze Farmaceutiche, Via Ponte Don Melillo, 84084, Fisciano (SA), Italy
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84
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Lee DS, Jung KE, Yoon CH, Lim H, Bae YS. Newly designed six-membered azasugar nucleotide-containing phosphorothioate oligonucleotides as potent human immunodeficiency virus type 1 inhibitors. Antimicrob Agents Chemother 2006; 49:4110-20. [PMID: 16189087 PMCID: PMC1251495 DOI: 10.1128/aac.49.10.4110-4120.2005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A series of modified oligonucleotides (ONs), characterized by a phosphorothioate (P S) backbone and a six-membered azasugar (6-AZS) as a sugar substitute in a nucleotide, were newly synthesized and assessed for their ability to inhibit human immunodeficiency virus type 1 (HIV-1) via simple treatment of HIV-1-infected cultures, without any transfection process. While unmodified P S ONs exhibited only minor anti-HIV-1 activity, the six-membered azasugar nucleotide (6-AZN)-containing P S oligonucleotides (AZPSONs) exhibited remarkable antiviral activity against HIV-1/simian-human immunodeficiency virus (SHIV) replication and syncytium formation (50% effective concentration = 0.02 to 0.2 microM). The AZPSONs exhibited little cytotoxicity at concentrations of up to 100 microM. DBM 2198, one of the most effective AZPSONs, exhibited antiviral activity against a broad spectrum of HIV-1, including T-cell-tropic, monotropic, and even drug-resistant HIV-1 variants. The anti-HIV-1 activities of DBM 2198 were similarly maintained in HIV-1-infected cultures of peripheral blood mononuclear cells. When we treated severely infected cultures with DBM 2198, syncytia disappeared completely within 2 days. Taken together, our results indicate that DBM 2198 and other AZPSONs may prove useful in the further development of safe and effective AIDS-therapeutic drugs against a broad spectrum of HIV-1 variants.
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Affiliation(s)
- Dong-Seong Lee
- Department of Biological Science, Sungkyunkwan University, Jangan-gu, Suwon, Gyounggi-do, South Korea
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85
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Kankia BI, Barany G, Musier-Forsyth K. Unfolding of DNA quadruplexes induced by HIV-1 nucleocapsid protein. Nucleic Acids Res 2005; 33:4395-403. [PMID: 16077025 PMCID: PMC1182697 DOI: 10.1093/nar/gki741] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The human immunodeficiency virus type 1 nucleocapsid protein (NC) is a nucleic acid chaperone that catalyzes the rearrangement of nucleic acids into their thermodynamically most stable structures. In the present study, a combination of optical and thermodynamic techniques were used to characterize the influence of NC on the secondary structure, thermal stability and energetics of monomolecular DNA quadruplexes formed by the sequence d(GGTTGGTGTGGTTGG) in the presence of K+ or Sr2+. Circular dichroism studies demonstrate that NC effectively unfolds the quadruplexes. Studies carried out with NC variants suggest that destabilization is mediated by the zinc fingers of NC. Calorimetric studies reveal that NC destabilization is enthalpic in origin, probably owing to unstacking of the G-quartets upon protein binding. In contrast, parallel studies performed on a related DNA duplex reveal that under conditions where NC readily destabilizes and unfolds the quadruplexes, its effect on the DNA duplex is much less pronounced. The differences in NC's ability to destabilize quadruplex versus duplex is in accordance with the higher ΔG of melting for the latter, and with the inverse correlation between nucleic acid stability and the destabilizing activity of NC.
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Affiliation(s)
- Besik I Kankia
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
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86
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Abstract
Guanine (G)-rich DNA sequences can adopt stable G-quadruplex structures by G-tetrad hydrogen-bonding and hydrophobic stacking. Recently, it has been shown that a DNA sequence forms an aptamer (termed 93del) and adopts a novel dimeric quadruplex folding topology in K+ solution. This aptamer exhibits anti-HIV1 integrase activity in the nanomolar range in vitro. A docking-based model of the 93del-integrase complex positions the DNA aptamer within a channel of the tetrameric integrase. This mutual fitting blocks several catalytic amino acid residues that are essential for integrase function, and accounts for the anti-HIV1 activity of the 93del aptamer.
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Affiliation(s)
- Shan-Ho Chou
- Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China.
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87
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Ikebukuro K, Okumura Y, Sumikura K, Karube I. A novel method of screening thrombin-inhibiting DNA aptamers using an evolution-mimicking algorithm. Nucleic Acids Res 2005; 33:e108. [PMID: 16002787 PMCID: PMC1174901 DOI: 10.1093/nar/gni108] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Thrombin-inhibiting DNA aptamers have already been obtained through the systematic evolution of ligands by exponential enrichment (SELEX). However, SELEX is a method that screens DNA aptamers that bind to their target molecules, and it sometimes fails to screen good inhibitors. Therefore, it is necessary to develop a method of screening DNA aptamers based on their inhibitory effects on the target molecules. We developed a novel method of detecting aptamers using an evolution-mimicking algorithm, and we applied it to the search of new aptamers which inhibit thrombin. First, we randomly designed and synthesized ten 15mer oligonucleotides presumed to form G-quartet structures, and then measured their thrombin-inhibiting activities. The aptamers showing high inhibitory activity were selected, and we shuffled and mutated those sequences in silico to generate 10 new sequences of next-generation aptamers. After repeating the cycle five times, we successfully obtained the same aptamers reported previously, and they showed high inhibitory activity. In addition, we added 8mer oligonucleotides to both the 5' and the 3' end of the selected 15mer aptamers, and then repeated the evolution in silico. After two cycles, we were able to obtain aptamers with higher inhibitory activity than that of the 15mer aptamers.
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Affiliation(s)
- Kazunori Ikebukuro
- Department of Biotechnology and Life Science, Tokyo University of Agriculture & Technology 2-24-16 Naka-machi, Koganei, Tokyo 184-8588, Japan.
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88
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Yin H, Hamilton AD. Strategien zur Modulation von Protein-Protein-Wechselwirkungen mit synthetischen Substanzen. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200461786] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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89
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Miyoshi D, Karimata H, Sugimoto N. Drastic Effect of a Single Base Difference between Human andTetrahymena Telomere Sequences on Their Structures under Molecular Crowding Conditions. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462667] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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90
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Horváth A, Tokés S, Hartman T, Watson K, Turpin JA, Buckheit RW, Sebestyén Z, Szöllosi J, Benko I, Bardos TJ, Dunn JA, Fésüs L, Tóth FD, Aradi J. Potent inhibition of HIV-1 entry by (s4dU)35. Virology 2005; 334:214-23. [PMID: 15780871 DOI: 10.1016/j.virol.2005.01.033] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 01/04/2005] [Accepted: 01/26/2005] [Indexed: 11/24/2022]
Abstract
We have previously reported the potent in vitro HIV-1 anti-reverse transcriptase activity of a 35-mer of 4-thio-deoxyuridylate [(s(4)dU)(35)]. In efforts to define its activity in a more physiological system, studies were carried out to determine the stage of viral infection that this compound mediates its anti-viral effect. Results of the studies reported herein show that (s(4)dU)(35) is nontoxic and is capable of inhibiting both single and multi-drug resistant HIV strains (IC(50): 0.8-25.4 microg/ml) in vitro. Besides its previously reported anti-RT activity, (s(4)dU)(35) mediated its antiviral action by preventing virus attachment (IC(50): 0.002-0.003 microg/ml), and was stable in vitro and slowly degraded by DNAses. Competition studies and fluorescence resonance energy transfer (FRET) experiments indicated that (s(4)dU)(35) preferentially binds to CD4 receptors, but not to CD48. Confocal laser scanning microscopy (CLSM) studies showed that (s(4)dU)(35) did not penetrate into the cells and colocalized with cell surface thioredoxin. Our studies identify (s(4)dU)(35) as a potential novel HIV entry inhibitor that may have utility as either a systemic antiretroviral or as a preventing agent for HIV transmission.
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Affiliation(s)
- András Horváth
- Department of Biochemistry and Molecular Biology, University of Debrecen, H-4012 Debrecen, Nagyerdei krt. 98, Hungary
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91
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Miyoshi D, Karimata H, Sugimoto N. Drastic Effect of a Single Base Difference between Human andTetrahymena Telomere Sequences on Their Structures under Molecular Crowding Conditions. Angew Chem Int Ed Engl 2005; 44:3740-4. [PMID: 15861380 DOI: 10.1002/anie.200462667] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Daisuke Miyoshi
- Frontier Institute for Biomolecular Engineering Research, Konan University, Kobe, Japan
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92
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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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93
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Phan AT, Kuryavyi V, Ma JB, Faure A, Andréola ML, Patel DJ. An interlocked dimeric parallel-stranded DNA quadruplex: a potent inhibitor of HIV-1 integrase. Proc Natl Acad Sci U S A 2005; 102:634-9. [PMID: 15637158 PMCID: PMC545538 DOI: 10.1073/pnas.0406278102] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report on the NMR-based solution structure of the 93del d(GGGGTGGGAGGAGGGT) aptamer, a potent nanomolar inhibitor of HIV-1 integrase. This guanine-rich DNA sequence adopts an unusually stable dimeric quadruplex architecture in K+ solution. Within each 16-nt monomer subunit, which contains one A.(G.G.G.G) pentad sandwiched between two G.G.G.G tetrads, all G-stretches are parallel, and all guanines are anti with the exception of G1, which is syn. Dimer formation is achieved through mutual pairing of G1 of one monomer, with G2, G6, and G13 of the other monomer, to complete G.G.G.G tetrad formation. There are three single-nucleotide double-chain-reversal loops within each monomer fold, such that the first (T5) and third (A12) loops bridge three G-tetrad layers, whereas the second (A9) loop bridges two G-tetrad layers and participates in A.(G.G.G.G) pentad formation. Results of NMR and of integrase inhibition assays on loop-modified sequences allowed us to propose a strategy toward the potential design of improved HIV-1 integrase inhibitors. Finally, we propose a model, based on molecular docking approaches, for positioning the 93del dimeric DNA quadruplex within a basic channel/canyon formed between subunits of a dimer of dimers of HIV-1 integrase.
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Affiliation(s)
- Anh Tuân Phan
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
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94
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Jing N, Li Y, Xiong W, Sha W, Jing L, Tweardy DJ. G-quartet oligonucleotides: a new class of signal transducer and activator of transcription 3 inhibitors that suppresses growth of prostate and breast tumors through induction of apoptosis. Cancer Res 2004; 64:6603-9. [PMID: 15374974 DOI: 10.1158/0008-5472.can-03-4041] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Stat3 is a signaling molecular and oncogene activated frequently in many human malignancies including the majority of prostate, breast, and head and neck cancers; yet, no current chemotherapeutic approach has been implemented clinically that specifically targets Stat3. We recently developed G-rich oligodeoxynucleotides, which form intramolecular G-quartet structures (GQ-ODN), as a new class of Stat3 inhibitor. GQ-ODN targeted Stat3 protein directly inhibiting its ability to bind DNA. When delivered into cells using polyethyleneimine as vehicle, GQ-ODN blocked ligand-induced Stat3 activation and Stat3-mediated transcription of antiapoptotic genes. To establish the effectiveness of GQ-ODN as a potential new chemotherapeutic agent, we systemically administered GQ-ODN (T40214 or T40231) plus polyethyleneimine or polyethyleneimine alone (placebo) by tail-vein injection into nude mice with prostate and breast tumor xenografts. Whereas the mean volume of breast tumor xenografts in placebo-treated mice increased >7-fold over 18 days, xenografts in the GQ-ODN-treated mice remained unchanged. Similarly, whereas the mean volume of prostate tumor xenografts in placebo-treated mice increased 9-fold over 10 days, xenografts in GQ-ODN-treated mice increased by only 2-fold. Biochemical examination of tumors from GQ-ODN-treated mice demonstrated a significant reduction in Stat3 activation, levels of the antiapoptotic proteins Bcl-2 and Bcl-xL, and an 8-fold increase in the number of apoptotic cells compared with the tumors of placebo-treated mice. Thus, GQ-ODN targeting Stat3 induces tumor cell apoptosis when delivered into tumor xenografts and represents a novel class of chemotherapeutic agents that holds promise for the systemic treatment of many forms of metastatic cancer.
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Affiliation(s)
- Naijie Jing
- Department of Medicine, Section of Infectious Diseases, Baylor College of Medicine, Houston, TX, USA.
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95
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Esposito V, Randazzo A, Galeone A, Varra M, Mayol L. Structural study of four-stranded quadruplex structures containing 2'-deoxy-8-(propyn-1-yl)adenosine. Bioorg Med Chem 2004; 12:1191-7. [PMID: 14980630 DOI: 10.1016/j.bmc.2003.11.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2003] [Accepted: 11/18/2003] [Indexed: 11/21/2022]
Abstract
In this paper, we report the NMR structural study of two quadruplex structures formed by truncations of the human telomeric sequence and containing a modified base, namely d(AprGGGT) and d(TAprGGGT), where Apr indicates 2'-deoxy-8-(propyn-1-yl)adenosines. Both oligonucleotides have been found to form 4-fold symmetric G-quadruplex structures with all strands parallel and equivalent to each other and characterized by higher thermal stabilities than the natural counterparts. The presence of the propynyl groups affects the conformations of the 5' edge of both quadruplexes in such a way to prevent the formation of one of the two possible H-bond patterns observed for a canonical A-tetrad. The increased thermal stabilities of the modified quadruplexes seem to be mostly due to a prevalent syn glycosidic conformation assumed by the Apr residues.
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Affiliation(s)
- Veronica Esposito
- Dipartimento di Chimica delle Sostanze Naturali, Università degli Studi di Napoli 'Federico II' via D. Montesano 49, I-80131 Naples, Italy
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96
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Kanaori K, Sakamoto S, Yoshida H, Guga P, Stec W, Tajima K, Makino K. Effect of phosphorothioate chirality on i-motif structure and stability. Biochemistry 2004; 43:5672-9. [PMID: 15134441 DOI: 10.1021/bi035419r] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The P-chiral stereo-defined phosphorothioate groups have been introduced into all of the four internucleotide positions of d(T(PS1)C(PS2)C(PS3)C(PS4)C) (PSn = phosphorothioate group), and among the 16 possible diastereomers of PS-d(TC(4)), 10 stereomers have been synthesized to investigate the effects of the sense of the P-chirality upon the structure and stability of the i-motif structure. The temperature dependence of circular dichroism spectra showed that the melting temperature (T(m)) of the [all R(p)]-PS-d(TC(4)) i-motifs was 31 degrees C, identical to that of the parent oligomer, PO-d(TC(4)), while that of the [all S(p)]-PS-d(TC(4)) i-motif was largely decreased by 11 degrees C. Single substitution of R(p) with S(p) caused a decrease of T(m) by 3-4 degrees C at positions of PS1, PS2, and PS3 and by 1 degrees C at that of PS4, showing the additive property of the T(m) suppression. The comparison of the NOESY spectra between [all R(p)]-PS-, [all S(p)]-PS-, and PO-d(TC(4)) showed that intraresidual H6-H3' and H2' '-H4' NOE cross-peaks of the all S(p) isomer are weaker than those of the all R(p) isomer and PO-d(TC(4)), indicating the change in the C3'-endo conformation and glycosidic bond angle. The structural alternation for the i-motif formed by [all S(p)]-PS-d(TC(4)) is also suggested by the chemical shift differences of C2/C3/C4 H2''and H4' protons from those of [all R(p)]-PS-d(TC(4)) and PO-d(TC(4)). These results suggest that the S(p) configuration at phosphorus of the phosphorothioate linkage changes the sugar-phosphorothioate conformation and intermolecular interaction in the narrow groove, leading to the destabilization of the i-motif structure.
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Affiliation(s)
- Kenji Kanaori
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
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97
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Cogoi S, Quadrifoglio F, Xodo LE. G-rich oligonucleotide inhibits the binding of a nuclear protein to the Ki-ras promoter and strongly reduces cell growth in human carcinoma pancreatic cells. Biochemistry 2004; 43:2512-23. [PMID: 14992588 DOI: 10.1021/bi035754f] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oligonucleotides are able to recognize both nucleic acids and proteins with a high degree of specificity and are therefore investigated as a new and innovative class of therapeutic anticancer drugs. In the present study, we have constructed from Panc-1 cells a stable transfectant (AG transfectant) generating constitutively a short transcript (T-22AG), which is potentially capable of forming a triplex with a critical polypurine/polypyrimidine (pur/pyr) motif located in the Ki-ras promoter. Because of the presence of a G-rich element in its sequence, transcript T-22AG was also capable, under physiological conditions, of adopting a tetraplex conformation. We found that the levels of Ki-ras mRNA and p21(RAS) protein in the AG transfectant were, respectively, 52 +/- 8 and 40 +/- 4% of those observed in the control cell lines: untransfected Panc-1 cells and stably transfected Panc-1 cells producing a control transcript (T-22SCR). The downregulation of Ki-ras resulted in a strong reduction of colony formation (42 +/- 7% of the control) and cell proliferation (34 +/- 5% of the control) capacity. As in vitro experiments showed that the G-rich element of T-22AG (22AG) formed with the Ki-ras pur/pyr motif a triplex of low thermodynamic stability, it is unlikely that the strong bioactivity exhibited by transcript T-22AG is mediated by a triplex-based mechanism, although we cannot totally exclude that in vivo polyamine levels may increase the triplex stability. We found that 22AG adopted a tetraplex conformation and competitively inhibited the binding of a nuclear factor to the Ki-ras pur/pyr sequence. This effect was specific and virtually entirely abrogated when 22AG was denatured by heating. Our data showed that transcript T-22AG acted as a molecular aptamer, binding specifically to a nuclear factor essential for Ki-ras expression. The biological implications of this study are discussed.
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Affiliation(s)
- Susanna Cogoi
- Department of Biomedical Science and Technology, School of Medicine, University of Udine, Piazzale Kolbe, 4, 33100 Udine, Italy
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98
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Risitano A, Fox KR. Influence of loop size on the stability of intramolecular DNA quadruplexes. Nucleic Acids Res 2004; 32:2598-606. [PMID: 15141030 PMCID: PMC419475 DOI: 10.1093/nar/gkh598] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We have determined the stability of intramolecular DNA quadruplexes in which the four G(3)-tracts are connected by non-nucleosidic linkers containing propanediol, octanediol or hexaethylene glycol, replacing the TTA loops in the human telomeric repeat sequence. We find that these sequences all fold to form intramolecular complexes, which are stabilized by lithium < sodium < potassium. Quadruplex stability increases in the order propanediol < hexaethylene glycol < octanediol. The shallower shape of the melting profile with propanediol linkers and its lower dependency on potassium concentration suggests that this complex contains fewer stacks of G-quartets. The sequence with octanediol linkers displays a biphasic melting profile, suggesting that it can adopt more than one stable structure. All these complexes display melting temperatures above 310 K in the presence of 10 mM lithium, without added potassium, in contrast to the telomeric repeat sequence. These complexes also fold much faster than the telomeric repeat and there is little or no hysteresis between their melting and annealing profiles. In contrast, the human telomeric repeat sequence and a complex containing two hexaethylene glycol groups in each loop, are less stable and fold more slowly. The melting and annealing profiles for the latter sequence show significant differences, even when heated at 0.2 degrees C min(-1). CD spectra for the oligonucleotides containing non-nucleosidic linkers show positive maxima at 264 nm, with negative minima approximately 244 nm, which are characteristic of parallel quadruplex structures. These results show that the structure and stability of intramolecular quadruplexes is profoundly influenced by the length and composition of the loops.
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Affiliation(s)
- Antonina Risitano
- School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK
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99
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Phan AT, Modi YS, Patel DJ. Two-repeat Tetrahymena telomeric d(TGGGGTTGGGGT) Sequence interconverts between asymmetric dimeric G-quadruplexes in solution. J Mol Biol 2004; 338:93-102. [PMID: 15050825 PMCID: PMC4690524 DOI: 10.1016/j.jmb.2004.02.042] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2003] [Revised: 02/17/2004] [Accepted: 02/18/2004] [Indexed: 10/26/2022]
Abstract
Recently, the two-repeat human telomeric d(TAGGGTTAGGGT) sequence has been shown to form interconverting parallel and antiparallel G-quadruplex structures in solution. Here, we examine the structures formed by the two-repeat Tetrahymena telomeric d(TGGGGTTGGGGT) sequence, which differs from the human sequence only by one G-for-A replacement in each repeat. We show by NMR that this sequence forms two novel G-quadruplex structures in Na+-containing solution. Both structures are asymmetric, dimeric G-quadruplexes involving a core of four stacked G-tetrads and two edgewise loops. The adjacent strands of the G-tetrad core are alternately parallel and antiparallel. All G-tetrads adopt syn.syn.anti.anti alignments, which occur with 5'-syn-anti-syn-anti-3' alternations along G-tracks. In the first structure (head-to-head), two loops are at one end of the G-tetrad core; in the second structure (head-to-tail), two loops are located on opposite ends of the G-tetrad core. In contrast to the human telomere counterpart, the proportions of the two forms here are similar for a wide range of temperatures; their unfolding rates are also similar, with an activation enthalpy of 153 kJ/mol.
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Affiliation(s)
- Anh Tuân Phan
- Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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100
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Jing N, Li Y, Xu X, Sha W, Li P, Feng L, Tweardy DJ. Targeting Stat3 with G-quartet oligodeoxynucleotides in human cancer cells. DNA Cell Biol 2004; 22:685-96. [PMID: 14659041 DOI: 10.1089/104454903770946665] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Stat3 is an oncogene that is activated in many human cancer cells. Genetic approaches that disrupt Stat3 activity result in inhibition of cancer cell growth and enhanced cell apoptosis supporting the development of novel drugs targeting Stat3 for cancer therapy. G-quartet oligodeoxynucleotides (ODNs) were demonstrated to be potent inhibitors of Stat3 DNA binding activity in vitro with the G-quartet ODN, T40214, having an IC(50) of 7 microM. Computer-simulated docking studies indicated that G-quartet ODNs mainly interacted with the SH2 domain of Stat3 and were capable of inserting between the SH2 domains of Stat3 dimers bound to DNA. We demonstrated that the G-rich ODN T40214, which forms a G-quartet structure at intracellular but not extracellular K+ ion concentrations, is delivered efficiently into the cytoplasm and nucleus of cancer cells where it inhibited IL-6-stimulated Stat3 activation and suppressed Stat3-mediated upregulation of bcl-x and mcl-1 gene expression. Thus, G-quartet represents a new class of drug for targeting of Stat3 within cancer cells.
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Affiliation(s)
- Naijie Jing
- Section of Infectious Diseases, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA.
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