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Geel TM, Ruiters MHJ, Cool RH, Halby L, Voshart DC, Andrade Ruiz L, Niezen-Koning KE, Arimondo PB, Rots MG. The past and presence of gene targeting: from chemicals and DNA via proteins to RNA. Philos Trans R Soc Lond B Biol Sci 2018; 373:20170077. [PMID: 29685979 PMCID: PMC5915719 DOI: 10.1098/rstb.2017.0077] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2017] [Indexed: 12/19/2022] Open
Abstract
The ability to target DNA specifically at any given position within the genome allows many intriguing possibilities and has inspired scientists for decades. Early gene-targeting efforts exploited chemicals or DNA oligonucleotides to interfere with the DNA at a given location in order to inactivate a gene or to correct mutations. We here describe an example towards correcting a genetic mutation underlying Pompe's disease using a nucleotide-fused nuclease (TFO-MunI). In addition to the promise of gene correction, scientists soon realized that genes could be inactivated or even re-activated without inducing potentially harmful DNA damage by targeting transcriptional modulators to a particular gene. However, it proved difficult to fuse protein effector domains to the first generation of programmable DNA-binding agents. The engineering of gene-targeting proteins (zinc finger proteins (ZFPs), transcription activator-like effectors (TALEs)) circumvented this problem. The disadvantage of protein-based gene targeting is that a fusion protein needs to be engineered for every locus. The recent introduction of CRISPR/Cas offers a flexible approach to target a (fusion) protein to the locus of interest using cheap designer RNA molecules. Many research groups now exploit this platform and the first human clinical trials have been initiated: CRISPR/Cas has kicked off a new era of gene targeting and is revolutionizing biomedical sciences.This article is part of a discussion meeting issue 'Frontiers in epigenetic chemical biology'.
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Affiliation(s)
- T M Geel
- Epigenetic Editing, Dept Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - M H J Ruiters
- Epigenetic Editing, Dept Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - R H Cool
- Chemical and Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - L Halby
- CNRS FRE3600 ETaC, bât IBCG, 31062 Toulouse, France
| | - D C Voshart
- Epigenetic Editing, Dept Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - L Andrade Ruiz
- Epigenetic Editing, Dept Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - K E Niezen-Koning
- Laboratory of Metabolic Diseases, Dept Laboratory Medicine, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
| | - P B Arimondo
- CNRS FRE3600 ETaC, bât IBCG, 31062 Toulouse, France
| | - M G Rots
- Epigenetic Editing, Dept Pathology and Medical Biology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
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Arimondo PB, Bailly C, Boutorine AS, Ryabinin VA, Syniakov AN, Sun JS, Garestier T, Hélène C. Directing topoisomerase I mediated DNA cleavage to specific sites by camptothecin tethered to minor- and major-groove ligands. Angew Chem Int Ed Engl 2002; 40:3045-8. [PMID: 12203644 DOI: 10.1002/1521-3773(20010817)40:16<3045::aid-anie3045>3.0.co;2-a] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2001] [Indexed: 12/25/2022]
Abstract
The covalent linkage of a hairpin polyamide, which binds in the minor groove, to camptothecin provides an efficient system to direct topoisomerase I mediated DNA cleavage to specific sites. These conjugates are equally as potent at targeting the enzyme to a single site in a DNA fragment as camptothecin conjugates of ligands that bind in the major groove (triplex-forming oligonucleotides).
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, INSERM U201, UMR 8646 CNRS Muséum National d'Histoire Naturelle 43 rue Cuvier, 75231 Paris cedex 05, France, Fax: (+33) 1-40793705
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3
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Arimondo PB, Hélène C. Design of new anti-cancer agents based on topoisomerase poisons targeted to specific DNA sequences. Curr Med Chem Anticancer Agents 2001; 1:219-35. [PMID: 12678755 DOI: 10.2174/1568011013354642] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is considerable interest in the development of sequence-selective DNA drugs. Chemical agents able to interfere with DNA topoisomerases - essential nuclear enzymes- are widespread in nature, and some of them have outstanding therapeutic efficacy in human cancer and infectious diseases. Several classes of antineoplastic drugs, such as amsacrine, daunorubicin, etoposide (acting on type II topoisomerases), camptothecin and indolocarbazole derivatives of the antibiotic rebeccamycin (acting on type IB topoisomerases), have been shown to stimulate DNA cleavage by topoisomerases leading to cell death. However, these molecules exhibit little sequence preference. A convenient strategy to confer sequence specificity consists in the attachment of these topoisomerase poisons to sequence-specific DNA binding elements. Among sequence-specific DNA ligands, oligonucleotides can bind with high specificity of recognition to the major groove of double-helical DNA, resulting in triple helix formation. In this context, derivatives of camptothecin, indolocarbazole, anthracycline and acridine poisons have been covalently tethered to triple helix-forming oligonucleotides. The use of triple-helical DNA structures offers an efficient system to target topoisomerase I and II-mediated DNA cleavage to specific sequences and to increase the drug efficacy at these sites. Chemical optimization of the conjugates is essential to the efficacy of drug targeting. Consequently, the rational design of this new class of anti-cancer agents, conceived from topoisomerase poisons and triplex-forming oligonucleotides, may be exploited to improve the efficacy and selectivity of the DNA damage induced by topoisomerases.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, UMR8646 CNRS, INSERM U201, 43 rue Cuvier 75005 Paris France.
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Arimondo PB, Baldeyrou B, Laine W, Bal C, Alphonse FA, Routier S, Coudert G, Mérour JY, Colson P, Houssier C, Bailly C. DNA interaction and cytotoxicity of a new series of indolo[2,3-b]quinoxaline and pyridopyrazino[2,3-b]indole derivatives. Chem Biol Interact 2001; 138:59-75. [PMID: 11640915 DOI: 10.1016/s0009-2797(01)00260-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Absorption, melting temperature and linear dichroism measurements were performed to investigate the interaction with DNA of a series of 16 tricyclic and tetracyclic compounds related to the antiviral agent B-220. The relative DNA affinity of the test compounds containing an indolo[2,3-b]quinoxaline, pyridopyrazino[2,3-b]indoles or pyrazino[2,3-b]indole planar chromophore varies significantly depending on the nature of the side chain grafted onto the indole nitrogen. Compounds with a dimethylaminoethyl chain strongly bind to DNA and exhibit a preference for GC-rich DNA sequences, as revealed by DNase I footprinting. Weaker DNA interactions were detected with those bearing a morpholinoethyl side chain. The incorporation of a 2,3-dihydroxypropyl side chain does not reinforce the DNA interaction compared with the unsubstituted analogues. Both the DNA relaxation assay and cytotoxicity study using two human leukemia cell lines sensitive (HL-60) or resistant (HL-60/MX2) to the antitumor drug mitoxantrone, indicate that topoisomerase II is not a privileged target for the test compounds which only weakly interfere with the catalytic activity of the DNA cleaving enzyme. Cytometry studies showed that the most cytotoxic compounds induce a massive accumulation of cells in the G2/M phase of the cell cycle. Collectively, the data show a relationship between DNA binding and cytotoxicity in the indolo[2,3-b]quinoxaline series.
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Affiliation(s)
- P B Arimondo
- INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place de Verdun, 59045 Cedex, Lille, France
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5
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Arimondo PB, Bailly C, Boutorine AS, Moreau P, Prudhomme M, Sun JS, Garestier T, Hélène C. Triple helix-forming oligonucleotides conjugated to indolocarbazole poisons direct topoisomerase I-mediated DNA cleavage to a specific site. Bioconjug Chem 2001; 12:501-9. [PMID: 11459453 DOI: 10.1021/bc000162k] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Topoisomerase I is an ubiquitous DNA-cleaving enzyme and an important therapeutic target in cancer chemotherapy for camptothecins as well as for indolocarbazole antibiotics such as rebeccamycin. To achieve a sequence-specific cleavage of DNA by topoisomerase I, a triple helix-forming oligonucleotide was covalently linked to indolocarbazole-type topoisomerase I poisons. The three indolocarbazole-oligonucleotide conjugates investigated were able to direct topoisomerase I cleavage at a specific site based upon sequence recognition by triplex formation. The efficacy of topoisomerase I-mediated DNA cleavage depends markedly on the intrinsic potency of the drug. We show that DNA cleavage depends also upon the length of the linker arm between the triplex-forming oligonucleotide and the drug. Based on a known structure of the DNA-topoisomerase I complex, a molecular model of the oligonucleotide conjugates bound to the DNA-topoisomerase I complex was elaborated to facilitate the design of a potent topoisomerase I inhibitor-oligonucleotide conjugate with an optimized linker between the two moieties. The resulting oligonucleotide-indolocarbazole conjugate at 10 nM induced cleavage at the triple helix site 2-fold more efficiently than 5 microM of free indolocarbazole, while the other drug-sensitive sites were not cleaved. The rational design of drug-oligonucleotide conjugates carrying a DNA topoisomerase poison may be exploited to improve the efficacy and selectivity of chemotherapeutic cancer treatments by targeting specific genes and reducing drug toxicity.
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Affiliation(s)
- P B Arimondo
- INSERM U524 and Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place Verdun, 59045 Lille, France
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Mergny JL, Lacroix L, Teulade-Fichou MP, Hounsou C, Guittat L, Hoarau M, Arimondo PB, Vigneron JP, Lehn JM, Riou JF, Garestier T, Hélène C. Telomerase inhibitors based on quadruplex ligands selected by a fluorescence assay. Proc Natl Acad Sci U S A 2001; 98:3062-7. [PMID: 11248032 PMCID: PMC30607 DOI: 10.1073/pnas.051620698] [Citation(s) in RCA: 251] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/27/2000] [Indexed: 11/18/2022] Open
Abstract
The reactivation of telomerase activity in most cancer cells supports the concept that telomerase is a relevant target in oncology, and telomerase inhibitors have been proposed as new potential anticancer agents. The telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to inhibit telomerase activity. We used a fluorescence assay to identify molecules that stabilize G-quadruplexes. Intramolecular folding of an oligonucleotide with four repeats of the human telomeric sequence into a G-quadruplex structure led to fluorescence excitation energy transfer between a donor (fluorescein) and an acceptor (tetramethylrhodamine) covalently attached to the 5' and 3' ends of the oligonucleotide, respectively. The melting of the G-quadruplex was monitored in the presence of putative G-quadruplex-binding molecules by measuring the fluorescence emission of the donor. A series of compounds (pentacyclic crescent-shaped dibenzophenanthroline derivatives) was shown to increase the melting temperature of the G-quadruplex by 2-20 degrees C at 1 microM dye concentration. This increase in T(m) value was well correlated with an increase in the efficiency of telomerase inhibition in vitro. The best telomerase inhibitor showed an IC(50) value of 28 nM in a standard telomerase repeat amplification protocol assay. Fluorescence energy transfer can thus be used to reveal the formation of four-stranded DNA structures, and its stabilization by quadruplex-binding agents, in an effort to discover new potent telomerase inhibitors.
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Affiliation(s)
- J L Mergny
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, Institut National de la Santé et de la Recherche Médicale Unité 201, Centre National de la Recherche Scientifique Unité Mixte 8646, 43 Rue Cuvier, 75005 Paris, France.
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7
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Koeppel F, Riou JF, Laoui A, Mailliet P, Arimondo PB, Labit D, Petitgenet O, Hélène C, Mergny JL. Ethidium derivatives bind to G-quartets, inhibit telomerase and act as fluorescent probes for quadruplexes. Nucleic Acids Res 2001; 29:1087-96. [PMID: 11222758 PMCID: PMC29720 DOI: 10.1093/nar/29.5.1087] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2000] [Revised: 01/09/2001] [Accepted: 01/09/2001] [Indexed: 11/12/2022] Open
Abstract
The telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to directly inhibit telomerase activity. The reactivation of this enzyme in immortalized and most cancer cells suggests that telomerase is a relevant target in oncology, and telomerase inhibitors have been proposed as new potential anticancer agents. In this paper, we describe ethidium derivatives that stabilize G-quadruplexes. These molecules were shown to increase the melting temperature of an intramolecular quadruplex structure, as shown by fluorescence and absorbance measurements, and to facilitate the formation of intermolecular quadruplex structures. In addition, these molecules may be used to reveal the formation of multi-stranded DNA structures by standard fluorescence imaging, and therefore become fluorescent probes of quadruplex structures. This recognition was associated with telomerase inhibition in vitro: these derivatives showed a potent anti-telomerase activity, with IC(50) values of 18-100 nM in a standard TRAP assay.
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Affiliation(s)
- F Koeppel
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U201, CNRS UMR 8646, 43 rue Cuvier, 75005 Paris, France
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Arimondo PB, Garestier T, Hélène C, Sun JS. Detection of competing DNA structures by thermal gradient gel electrophoresis: from self-association to triple helix formation by (G,A)-containing oligonucleotides. Nucleic Acids Res 2001; 29:E15. [PMID: 11160935 PMCID: PMC29622 DOI: 10.1093/nar/29.4.e15] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Sequence-specific recognition of DNA can be achieved by triple helix-forming oligonucleotides that bind to the major groove of double-helical DNA. These oligonucleotides have been used as sequence-specific DNA ligands for various purposes, including sequence-specific gene regulation in the so-called 'antigene strategy'. In particular, (G,A)-containing oligonucleotides can form stable triple helices under physiological conditions. However, triplex formation may be in competition with self-association of these oligonucleotides. For biological applications it would be interesting to identify the conditions under which one structure is favoured as compared to the other(s). Here we have directly studied competition between formation of a parallel (G,A) homoduplex and that of a triple helix by a 13 nt (G,A)-containing oligonucleotide. Temperature gradient gel electrophoresis allows simultaneous detection of competition between the two structures, because of their different temperature dependencies and gel electrophoretic mobilities, and characterisation of this competition.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique UMR 8646 CNRS-Muséum National d'Histoire Naturelle, INSERM U201, 43 rue Cuvier, 75231 Paris Cedex 05, France
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Arimondo PB, Riou JF, Mergny JL, Tazi J, Sun JS, Garestier T, Hélène C. Interaction of human DNA topoisomerase I with G-quartet structures. Nucleic Acids Res 2000; 28:4832-8. [PMID: 11121473 PMCID: PMC115246 DOI: 10.1093/nar/28.24.4832] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Because of their role in the control of the topological state of DNA, topoisomerases are ubiquitous and vital enzymes, which participate in nearly all events related to DNA metabolism including replication and transcription. We show here that human topoisomerase I (Topo I) plays an unexpected role of 'molecular matchmaker' for G-quartet formation. G-quadruplexes are multi-stranded structures held together by square planes of four guanines ('G-quartets') interacting by forming Hoogsteen hydrogen bonds. Topo I is able to promote the formation of four-stranded intermolecular DNA structures when added to single-stranded DNA containing a stretch of at least five guanines. We provide evidence that these complexes are parallel G-quartet structures, mediated by tetrads of hydrogen-bonded guanine. In addition, Topo I binds specifically to pre-formed parallel and anti-parallel G4-DNA.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle CNRS UMR 8646, INSERM U201, 43 rue Cuvier, 75231 Paris cedex 05, France
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10
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Abstract
The high mobility group protein HMG-D is known to bind preferentially to DNA of irregular structures with little or no sequence specificity. Upon binding to DNA, this HMG-box protein widens the minor groove of the double helix and induces a significant bending of the helix. We show here that HMG-D can strongly bind to double-stranded RNA. Electrophoretic mobility shift assays show that HMG-D100 interacts with the transactivation response region (TAR) RNA from HIV-1. Strong interaction with a high affinity Rev protein binding element (RBE) RNA was also characterized. Gel shift experiments performed with several TAR RNA constructs lacking the lateral pyrimidine bulge or with modified apical loop regions indicate that the protein does not recognize the single-strand domains of the RNA but apparently interacts directly with the double-stranded stem regions. No protein-RNA complexes could be detected when using single-stranded oligoribonucleotides. HMG-D protein could bind to the wide minor groove of the A-form TAR RNA. The comparison of the amino acid sequence of HMG-D with that of known RNA binding proteins suggests that the interaction of the protein with a double-stranded RNA implicates the basic region of HMG-D as well as its HMG-box domain. From the in vitro data reported here, we propose a novel functional role for proteins of the HMG-1 family. The results suggest that architectural HMG proteins can be recruited by double-stranded RNA for the development of HIV-1 in the host cell.
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Affiliation(s)
- P B Arimondo
- Institut National de la Santé et la Recherche Médicale, Lille, France
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Lacroix L, Arimondo PB, Takasugi M, Hélène C, Mergny JL. Pyrimidine morpholino oligonucleotides form a stable triple helix in the absence of magnesium ions. Biochem Biophys Res Commun 2000; 270:363-9. [PMID: 10753631 DOI: 10.1006/bbrc.2000.2438] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oligonucleotides can be used as sequence-specific DNA ligands by forming a local triple helix. In order to form more stable triple-helical structures or prevent their degradation in cells, oligonucleotide analogues that are modified at either the backbone or base level are routinely used. Morpholino oligonucleotides appeared recently as a promising modification for antisense applications. We report here a study that indicates the possibility of a triple helix formation with a morpholino pyrimidine TFO and its comparison with a phosphodiester and a phosphoramidate oligonucleotide. At a neutral pH and in the presence of a high magnesium ion concentration (10 mM), the phosphoramidate oligomer forms the most stable triple helix, whereas in the absence of magnesium ion but at a physiological monovalent cation concentration (0.14 M) only morpholino oligonucleotides form a stable triplex. To our knowledge, this is the first report of a stable triple helix in the pyrimidine motif formed by a noncharged oligonucleotide third strand (the morpholino oligonucleotide) and a DNA duplex. We show here that the structure formed with the morpholino oligomer is a bona fide triple helix and it is destabilized by high concentrations of potassium ions or divalent cations (Mg(2+)).
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Affiliation(s)
- L Lacroix
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle INSERM U201, CNRS UMR8646, 43, rue Cuvier, Paris, 75005, France
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Arimondo PB, Moreau P, Boutorine A, Bailly C, Prudhomme M, Sun JS, Garestier T, Hélène C. Recognition and cleavage of DNA by rebeccamycin- or benzopyridoquinoxaline conjugated of triple helix-forming oligonucleotides. Bioorg Med Chem 2000; 8:777-84. [PMID: 10819166 DOI: 10.1016/s0968-0896(00)00012-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Indolocarbazole and benzopyridoquinoxaline derivatives have been shown to have anti-tumor activity and to stimulate DNA topoisomerase I-mediated cleavage. Two indolocarbazole compounds (R-6 and R-95) and one benzopyridoquinoxaline derivative (BPQ(1256)) were covalently attached to the 3'-end of a 16mer triple helix-forming oligonucleotide (TFO). These conjugates bind to DNA with a higher affinity than the unsubstituted oligonucleotides. Furthermore, they induce topoisomerase I-mediated and triplex-directed DNA cleavage in a sequence-specific manner.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, UMR 8646 CNRS-Muséum National d'Histoire Naturelle, INSERM U201, Paris, France
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Mills M, Arimondo PB, Lacroix L, Garestier T, Hélène C, Klump H, Mergny JL. Energetics of strand-displacement reactions in triple helices: a spectroscopic study. J Mol Biol 1999; 291:1035-54. [PMID: 10518941 DOI: 10.1006/jmbi.1999.3014] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
DNA triple helices offer exciting new perspectives toward oligonucleotide-directed inhibition of gene expression. Purine and GT triplexes appear to be the most promising motifs for stable binding under physiological conditions compared to the pyrimidine motif, which forms at relatively low pH. There are, however, very little data available for comparison of the relative stabilities of the different classes of triplexes under identical conditions. We, therefore, designed a model system which allowed us to set up a competition between the oligonucleotides of the purine and pyrimidine motifs targeting the same Watson-Crick duplex. Several conclusions may be drawn: (i) a weak hypochromism at 260 nm is associated with purine triplex formation; (ii) delta H degree of GA, GT and TC triplex formation (at pH 7.0) was calculated as -0.1, -2.5 and -6.1 kcal/mol per base triplet, respectively. This unexpectedly low delta H degree for the purine triple helix formation implies that its delta G degree is nearly temperature-independent and it explains why these triplexes may still be observed at high temperatures. In contrast, the pyrimidine triplex is strongly favoured at lower temperatures; (iii) as a consequence, in a system where two third-strands compete for triplex formation, displacement of the GA or GT strand by a pyrimidine strand may be observed at neutral pH upon lowering the temperature. This original purine-to-pyrimidine triplex conversion shows a significant hypochromism at 260 nm and a hyperchromism at 295 nm which is similar to the duplex-to-triplex conversion in the pyrimidine motif. Further evidence for this triplex-to-triplex conversion is provided by mung bean-nuclease foot-printing assay.
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Affiliation(s)
- M Mills
- Department of Biochemistry, University of Cape Town, Republic of South Africa
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Arimondo PB, Bailly C, Boutorine A, Sun JS, Garestier T, Hélène C. Targeting topoisomerase I cleavage to specific sequences of DNA by triple helix-forming oligonucleotide conjugates. A comparison between a rebeccamycin derivative and camptothecin. C R Acad Sci III 1999; 322:785-90. [PMID: 10547719 DOI: 10.1016/s0764-4469(00)80037-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Topoisomerase I is an ubiquitous DNA cleaving enzyme and an important therapeutic target in cancer chemotherapy for the camptothecins as well as for indolocarbazole antibiotics such as rebeccamycin and its synthetic derivatives, which stabilize the cleaved DNA-topoisomerase I complex. The covalent linkage of a triple helixforming oligonucleotide to camptothecin or to the indolocarbazole derivative R-6 directs DNA cleavage by topoisomerase I to specific sequences. Sequence-specific recognition of DNA is achieved by the triple helix-forming oligonucleotide, which binds to the major groove of double-helical DNA and positions the drug at a specific site. The efficacy of topoisomerase I-induced DNA cleavage mediated by the rebeccamycin-conjugate and the camptothecin-conjugate was compared and related to the intrinsic potency of the isolated drugs.
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Affiliation(s)
- P B Arimondo
- Laboratoire de biophysique, UMR 8646 CNRS-Muséum national d'histoire naturelle, Inserm U201, Paris, France
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Arimondo PB, Barcelo F, Sun JS, Maurizot JC, Garestier T, Hélène C. Triple helix formation by (G,A)-containing oligonucleotides: asymmetric sequence effect. Biochemistry 1998; 37:16627-35. [PMID: 9843430 DOI: 10.1021/bi9805588] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sequence effects on the stability of purine-motif (also called (G, A)-motif) triple helix have been investigated through two symmetry-related systems: one of them had a 5'(GGA)43' core sequence of triplex-forming oligonucleotides (TFOs), whereas the other one had a reversed 5'(AGG)43' core sequence. These (G,A)-containing TFOs were prone to self-associate into intermolecular complexes at room temperature. The competition of TFOs' self-association with triple helix formation was assessed, and minimized. By varying the lengths and the terminal base sequences of TFOs, the following were found that (1) The stability of two triple helices with identical length and base composition but reverse strand orientation may be significantly different (up to a factor of 6). (2) When the 5'(GGA)43' core sequence was extended at the 3'-end by a G, the 13-nt TFO exhibited 3- and 5-fold higher affinity toward the target double-stranded DNA (dsDNA) than the longer 14-nt and 15-nt TFOs in which one and two A(s) were added at the 3'-end of the 13-nt TFO, respectively. In contrast, when the similar extensions occurred at the 5'-end of the 5'(AGG)43' core sequence, the length increase provided a higher binding affinity of TFOs toward the target duplex. (3) The nature of the base triplets involved at the ends of triple helices may have great influence on triplex stability. The observed asymmetric sequence effect of the (G,A)-motif triple helix formation is discussed in terms of the binding strength of the first base triplet(s) at the 3' end which seems to be deeply involved in the nucleation step of triple helix formation and therefore to be a determining factor for triplex stability.
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Affiliation(s)
- P B Arimondo
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U201, CNRS URA 481, Paris, France
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