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Abdelhady AM, Hirano Y, Onizuka K, Okamura H, Komatsu Y, Nagatsugi F. Synthesis of Crosslinked 2'-OMe RNA Duplexes Using 2-Amino-6-Vinylpurine and Their Application for Effective Inhibition of miRNA Function. Curr Protoc 2022; 2:e386. [PMID: 35316581 DOI: 10.1002/cpz1.386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Crosslinking reactions to nucleic acids are an effective way to prepare stable complexes formed by covalent bonding. We demonstrated that fully 2'-O-methylated (2'-OMe) RNAs having a 2-amino-6-vinylpurine (AVP) exhibited an efficient crosslinking to uracil in the target RNA. Recently, we reported the preparation of crosslinked 2'-OMe RNA duplexes using AVP and the anti-miRNA oligonucleotides (AMOs) containing crosslinked duplexes at the terminal positions. These AMOs exhibited efficient microRNA (miRNA) inhibition at very low concentrations. In this article, we describe the chemical synthesis of 2'-OMe oligonucleotides containing AVP and preparation of the AMOs bearing crosslinked 2'-OMe RNA duplexes using AVP. In addition, we describe in detail the miRNA inhibition assay using these AMOs. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of phosphoramidite of 2-amino-6-vinylguanosine derivative Basic Protocol 2: Synthesis of AVP-2'-OMe RNA Basic Protocol 3: Evaluation of the crosslink reactivity of CFO containing AVP to the 2'-OMe RNA and preparation of AMOs containing crosslinked duplex Basic Protocol 4: miRNA inhibition assays.
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Affiliation(s)
- Ahmed Mostafa Abdelhady
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
- Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egypt
| | - Yu Hirano
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Toyohira-ku, Sapporo, Hokkaido, Japan
| | - Kazumitsu Onizuka
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
- Division for the Establishment of Frontier Sciences of Organization for Advanced Studies, Tohoku University, Sendai, Miyagi, Japan
| | - Hidenori Okamura
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
| | - Yasuo Komatsu
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Toyohira-ku, Sapporo, Hokkaido, Japan
| | - Fumi Nagatsugi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Miyagi, Japan
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
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2
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O'Flaherty DK, Wilds CJ. AGT Activity Towards Intrastrand Crosslinked DNA is Modulated by the Alkylene Linker. Chembiochem 2017; 18:2351-2357. [PMID: 28980757 DOI: 10.1002/cbic.201700450] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Indexed: 11/12/2022]
Abstract
DNA oligomers containing dimethylene and trimethylene intrastrand crosslinks (IaCLs) between the O4 and O6 atoms of neighboring thymidine (T) and 2'-deoxyguanosine (dG) residues were prepared by solid-phase synthesis. UV thermal denaturation (Tm ) experiments revealed that these IaCLs had a destabilizing effect on the DNA duplex relative to the control. Circular dichroism spectroscopy suggested these IaCLs induced minimal structural distortions. Susceptibility to dealkylation by reaction with various O6 -alkylguanine DNA alkyltransferases (AGTs) from human and Escherichia coli was evaluated. It was revealed that only human AGT displayed activity towards the IaCL DNA, with reduced efficiency as the IaCL shortened (from four to two methylene linkages). Changing the site of attachment of the ethylene linkage at the 5'-end of the IaCL to the N3 atom of T had minimal influence on duplex stability and structure, and was refractory to AGT activity.
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Affiliation(s)
- Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University Montreal, 7141 Sherbrooke Street W., Montreal, Quebec, H4B 1R6, Canada.,Present address: Howard Hughes Medical Institute, Department of Molecular Biology and, Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University Montreal, 7141 Sherbrooke Street W., Montreal, Quebec, H4B 1R6, Canada
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3
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Carter AR, Seaberg MH, Fan HF, Sun G, Wilds CJ, Li HW, Perkins TT. Sequence-dependent nanometer-scale conformational dynamics of individual RecBCD-DNA complexes. Nucleic Acids Res 2016; 44:5849-60. [PMID: 27220465 PMCID: PMC4937329 DOI: 10.1093/nar/gkw445] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 05/09/2016] [Indexed: 01/02/2023] Open
Abstract
RecBCD is a multifunctional enzyme that possesses both helicase and nuclease activities. To gain insight into the mechanism of its helicase function, RecBCD unwinding at low adenosine triphosphate (ATP) (2-4 μM) was measured using an optical-trapping assay featuring 1 base-pair (bp) precision. Instead of uniformly sized steps, we observed forward motion convolved with rapid, large-scale (∼4 bp) variations in DNA length. We interpret this motion as conformational dynamics of the RecBCD-DNA complex in an unwinding-competent state, arising, in part, by an enzyme-induced, back-and-forth motion relative to the dsDNA that opens and closes the duplex. Five observations support this interpretation. First, these dynamics were present in the absence of ATP. Second, the onset of the dynamics was coupled to RecBCD entering into an unwinding-competent state that required a sufficiently long 5' strand to engage the RecD helicase. Third, the dynamics were modulated by the GC-content of the dsDNA. Fourth, the dynamics were suppressed by an engineered interstrand cross-link in the dsDNA that prevented unwinding. Finally, these dynamics were suppressed by binding of a specific non-hydrolyzable ATP analog. Collectively, these observations show that during unwinding, RecBCD binds to DNA in a dynamic mode that is modulated by the nucleotide state of the ATP-binding pocket.
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Affiliation(s)
- Ashley R Carter
- Department of Physics, Amherst College, Amherst, MA 01002, USA
| | - Maasa H Seaberg
- Department of Physics, University of Colorado, Boulder, CO 80309, USA JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO 80309, USA
| | - Hsiu-Fang Fan
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B1R6, Canada
| | - Gang Sun
- Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
| | | | - Hung-Wen Li
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec H4B1R6, Canada
| | - Thomas T Perkins
- JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO 80309, USA Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
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4
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Kusano S, Ishiyama S, Lam SL, Mashima T, Katahira M, Miyamoto K, Aida M, Nagatsugi F. Crosslinking reactions of 4-amino-6-oxo-2-vinylpyrimidine with guanine derivatives and structural analysis of the adducts. Nucleic Acids Res 2015; 43:7717-30. [PMID: 26245348 PMCID: PMC4652779 DOI: 10.1093/nar/gkv797] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/28/2015] [Indexed: 12/28/2022] Open
Abstract
DNA interstrand crosslinks (ICLs) are the primary mechanism for the cytotoxic activity of many clinical anticancer drugs, and numerous strategies for forming ICLs have been developed. One such method is using crosslink-forming oligonucleotides (CFOs). In this study, we designed a 4-amino-6-oxo-2-vinylpyrimidine (AOVP) derivative with an acyclic spacer to react selectively with guanine. The AOVP CFO exhibited selective crosslinking reactivity with guanine and thymine in DNA, and with guanine in RNA. These crosslinking reactions with guanine were accelerated in the presence of CoCl2, NiCl2, ZnCl2 and MnCl2. In addition, we demonstrated that the AOVP CFO was reactive toward 8-oxoguanine opposite AOVP in the duplex DNA. The structural analysis of each guanine and 8-oxoguanine adduct in the duplex DNA was investigated by high-resolution NMR. The results suggested that AOVP reacts at the N2 amine in guanine and at the N1 or N2 amines in 8-oxoguanine in the duplex DNA. This study demonstrated the first direct determination of the adduct structure in duplex DNA without enzyme digestion.
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Affiliation(s)
- Shuhei Kusano
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi, Miyagi 980-8577, Japan
| | - Shogo Ishiyama
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi, Miyagi 980-8577, Japan
| | - Sik Lok Lam
- Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Tsukasa Mashima
- Institute of Advanced Energy, Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Masato Katahira
- Institute of Advanced Energy, Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Kengo Miyamoto
- Department of Chemistry, Graduate School of Science, Hiroshima University,1-3-1, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Misako Aida
- Department of Chemistry, Graduate School of Science, Hiroshima University,1-3-1, Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
| | - Fumi Nagatsugi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi, Miyagi 980-8577, Japan
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Ciuk AK, Lindhorst TK. Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency. Beilstein J Org Chem 2015; 11:668-74. [PMID: 26124869 PMCID: PMC4464435 DOI: 10.3762/bjoc.11.75] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/24/2015] [Indexed: 11/23/2022] Open
Abstract
Multivalency effects are essential in carbohydrate recognition processes as occurring on the cell surface. Thus many synthetic multivalent glycoconjugates have been developed as important tools for glycobiological research. We are expanding this collection of molecules by the introduction of carbohydrate-scaffolded divalent glycothymine derivatives that can be intramolecularily dimerized by [2 + 2] photocycloaddition. Thus, thymine functions as a control element that allows to restrict the conformational flexibility of the scaffolded sugar ligands and thus to "organize" multivalency. With this work we add a parameter to multivalency studies additional to valency.
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Affiliation(s)
- Anna K Ciuk
- Christiana Albertina University of Kiel, Otto Diels Institute of Organic Chemistry, Otto-Hahn-Platz 3/4, D-24118 Kiel, Germany, Fax: +49 431 8807410
| | - Thisbe K Lindhorst
- Christiana Albertina University of Kiel, Otto Diels Institute of Organic Chemistry, Otto-Hahn-Platz 3/4, D-24118 Kiel, Germany, Fax: +49 431 8807410
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6
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O'Flaherty DK, McManus FP, Noronha AM, Wilds CJ. Synthesis of building blocks and oligonucleotides containing {T}O4-alkylene-O4{T} interstrand cross-links. ACTA ACUST UNITED AC 2014; 55:5.13.1-19. [PMID: 25631535 DOI: 10.1002/0471142700.nc0513s55] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This protocol describes the preparation of O(4)-thymidine-alkylene-O(4)-thymidine dimer bis-phosphoramidites and precursors for incorporation into DNA sequences to produce site-specific DNA interstrand cross-links. Linkers are introduced at the 4-position of thymidine by reacting the sodium salt of a diol with a pyrimidinyl-convertible nucleoside to produce mono-adducts, which then undergo reaction with a stoichiometric equivalent of a pyrimidinyl-convertible nucleoside under basic conditions to form O(4)-thymidine-alkylene-O(4)-thymidine dimers. Bis-phosphoramidites are incorporated into oligonucleotides by solid-phase synthesis, and mild conditions for deprotection and cleavage from the solid support are employed to prevent degradation of the thymidine modifications. Purification of these cross-linked oligonucleotides is performed by denaturing polyacrylamide gel electrophoresis. This approach allows for the preparation of cross-linked DNA substrates in quantities and purity sufficient for a wide range of biophysical experiments and biochemical studies as substrates to investigate DNA repair pathways.
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Affiliation(s)
- Derek K O'Flaherty
- Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, Canada
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7
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Beuck C, Weinhold E. Reversibly locked thionucleobase pairs in DNA to study base flipping enzymes. Beilstein J Org Chem 2014; 10:2293-306. [PMID: 25298797 PMCID: PMC4187101 DOI: 10.3762/bjoc.10.239] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 08/28/2014] [Indexed: 12/16/2022] Open
Abstract
Covalently interstrand cross-linked DNA is an interesting tool to study DNA binding proteins that locally open up the DNA duplex by flipping single bases out of the DNA helix or melting whole stretches of base pairs to perform their function. The ideal DNA cross-link to study protein–DNA interactions should be specific and easy to synthesize, be stable during protein binding experiments, have a short covalent linker to avoid steric hindrance of protein binding, and should be available as a mimic for both A/T and G/C base pairs to cover all possible binding specificities. Several covalent interstrand cross-links have been described in the literature, but most of them fall short of at least one of the above criteria. We developed an efficient method to site-specifically and reversibly cross-link thionucleoside base pairs in synthetic duplex oligodeoxynucleotides by bisalkylation with 1,2-diiodoethane resulting in an ethylene-bridged base pair. Both linked A/T and G/C base pair analogs can conveniently be prepared which allows studying any base pair-opening enzyme regardless of its sequence specificity. The cross-link is stable in the absence of reducing agents but the linker can be quickly and tracelessly removed by the addition of thiol reagents like dithiothreitol. This property makes the cross-linking reaction fully reversible and allows for a switching of the linked base pair from locked to unlocked during biochemical experiments. Using the DNA methyltransferase from Thermus aquaticus (M.TaqI) as example, we demonstrate that the presented cross-linked DNA with an ethylene-linked A/T base pair analog at the target position is a useful tool to determine the base-flipping equilibrium constant of a base-flipping enzyme which lies mostly on the extrahelical side for M.TaqI.
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Affiliation(s)
- Christine Beuck
- Department of Structural & Medicinal Biochemistry, University of Duisburg-Essen, Universitätsstr. 2-5, D-45141 Essen, Germany
| | - Elmar Weinhold
- Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, D-52056 Aachen, Germany
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8
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Mukherjee S, Guainazzi A, Schärer OD. Synthesis of structurally diverse major groove DNA interstrand crosslinks using three different aldehyde precursors. Nucleic Acids Res 2014; 42:7429-35. [PMID: 24782532 PMCID: PMC4066762 DOI: 10.1093/nar/gku328] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
DNA interstrand crosslinks (ICLs) are extremely cytotoxic lesions that block essential cellular processes, such as replication and transcription. Crosslinking agents are widely used in cancer chemotherapy and form an array of structurally diverse ICLs. Despite the clinical success of these agents, resistance of tumors to crosslinking agents, for example, through repair of these lesions by the cellular machinery remains a problem. We have previously reported the synthesis of site-specific ICLs mimicking those formed by nitrogen mustards to facilitate the studies of cellular responses to ICL formation. Here we extend these efforts and report the synthesis of structurally diverse major groove ICLs that induce severe, little or no distortion in the DNA. Our approach employs the incorporation of aldehyde precursors of different lengths into complementary strands and ICL formation using a double reductive amination with a variety of amines. Our studies provide insight into the structure and reactivity parameters of ICL formation by double reductive amination and yield a set of diverse ICLs that will be invaluable for exploring structure–activity relationships in ICL repair.
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Affiliation(s)
- Shivam Mukherjee
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA
| | - Angelo Guainazzi
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651, USA
| | - Orlando D Schärer
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794-8651, USA
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9
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Sun G, Noronha AM, Miller PS, Wilds CJ. Synthesis of building blocks and oligonucleotides with {T}N3-alkylene-N3{T} cross-links. ACTA ACUST UNITED AC 2013; Chapter 5:Unit5.11. [PMID: 23255204 DOI: 10.1002/0471142700.nc0511s51] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
This unit describes two methods to directly prepare oligonucleotide duplexes containing an N3thymidine-alkylene-N3thymidine inter-strand cross-link. The inter-strand cross-link can be engineered into the duplex with a number of possible orientations. Both methods require the preparation of a protected thymidine dimer where the N3 atoms of the two nucleosides are covalently attached by an alkyl linker. This linker is prepared starting from a protected diol using two successive alkylation reactions under basic conditions to accomplish the alkylation selectively at the N3 atom of the nucleoside. The chain length of the cross-link can be varied based on the selection of the diol used in the dimer synthesis. The solid-phase mono-phosphoramidite approach involves oligonucleotide synthesis with 3'-O-phosphoramidites, on-column removal of a 3'-O-tert-butyldimethylsilyl protecting group, and continued oligonucleotide synthesis with 5'-O-phosphoramidites. The bis-phosphoramidite approach does not require synthesis with 5'-O-phosphoramidites. At the end of synthesis using either method, the N3thymidine-alkylene-N3thymidine inter-strand cross-linked oligonucleotides can be removed from the solid-support and purified using standard techniques (ion-exchange HPLC) in yields sufficient for various structural studies and repair assays.
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Affiliation(s)
- Gang Sun
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada
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10
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Ingale SA, Seela F. Stepwise Click Functionalization of DNA through a Bifunctional Azide with a Chelating and a Nonchelating Azido Group. J Org Chem 2013; 78:3394-9. [DOI: 10.1021/jo400059b] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Sachin A. Ingale
- Laboratory of Bioorganic Chemistry
and Chemical Biology, Center for Nanotechnology, Heisenbergstraße 11,
48149 Münster, Germany
- Laboratorium für
Organische und Bioorganische
Chemie, Institut für Chemie, Universität Osnabrück, Barbarastraße 7, 49069 Osnabrück,
Germany
| | - Frank Seela
- Laboratory of Bioorganic Chemistry
and Chemical Biology, Center for Nanotechnology, Heisenbergstraße 11,
48149 Münster, Germany
- Laboratorium für
Organische und Bioorganische
Chemie, Institut für Chemie, Universität Osnabrück, Barbarastraße 7, 49069 Osnabrück,
Germany
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11
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Terrazas M, Alagia A, Faustino I, Orozco M, Eritja R. Functionalization of the 3'-ends of DNA and RNA strands with N-ethyl-N-coupled nucleosides: a promising approach to avoid 3'-exonuclease-catalyzed hydrolysis of therapeutic oligonucleotides. Chembiochem 2013; 14:510-20. [PMID: 23362010 DOI: 10.1002/cbic.201200611] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 01/29/2023]
Abstract
The development of nucleic acid derivatives to generate novel medical treatments has become increasingly popular, but the high vulnerability of oligonucleotides to nucleases limits their practical use. We explored the possibility of increasing the stability against 3'-exonucleases by replacing the two 3'-terminal nucleotides by N-ethyl-N-coupled nucleosides. Molecular dynamics simulations of 3'-N-ethyl-N-modified DNA:Klenow fragment complexes suggested that this kind of alteration has negative effects on the correct positioning of the adjacent scissile phosphodiester bond at the active site of the enzyme, and accordingly was expected to protect the oligonucleotide from degradation. We verified that these modifications conferred complete resistance to 3'-exonucleases. Furthermore, cellular RNAi experiments with 3'-N-ethyl-N-modified siRNAs showed that these modifications were compatible with the RNAi machinery. Overall, our experimental and theoretical studies strongly suggest that these modified oligonucleotides could be valuable for therapeutic applications.
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Affiliation(s)
- Montserrat Terrazas
- Institute for Research in Biomedicine (IRB Barcelona) and Institute for Advanced Chemistry of Catalonia (IQAC), Spanish Research Council (CSIC), Cluster Building, Baldiri i Reixac 10, 08028 Barcelona, Spain.
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12
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McManus FP, Khaira A, Noronha AM, Wilds CJ. Preparation of covalently linked complexes between DNA and O(6)-alkylguanine-DNA alkyltransferase using interstrand cross-linked DNA. Bioconjug Chem 2013; 24:224-33. [PMID: 23347328 DOI: 10.1021/bc300553u] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
O(6)-alkylguanine-DNA alkyltransferases (AGT) are responsible for the removal of alkylation at both the O(6) atom of guanine and O(4) atom of thymine. AGT homologues show vast substrate differences with respect to the size of the adduct and which alkylated atoms they can restore. The human AGT (hAGT) has poor capabilities for removal of methylation at the O(4) atom of thymidine, which is not the case in most homologues. No structural data are available to explain this poor hAGT repair. We prepared and characterized O(6)G-butylene-O(4)T (XLGT4) and O(6)G-heptylene-O(4)T (XLGT7) interstrand cross-linked (ICL) DNA as probes for hAGT and the Escherichia coli homologues, OGT and Ada-C, for the formation of DNA-AGT covalent complexes. XLGT7 reacted only with hAGT and did so with a cross-linking efficiency of 25%, while XLGT4 was inert to all AGT tested. The hAGT mediated repair of XLGT7 occurred slowly, on the order of hours as opposed to the repair of O(6)-methyl-2'-deoxyguanosine which requires seconds. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the repair reaction revealed the formation of a covalent complex with an observed migration in accordance with a DNA-AGT complex. The identity of this covalent complex, as determined by mass spectrometry, was composed of a heptamethylene bridge between the O(4) atom of thymidine (in an 11-mer DNA strand) to residue Cys145 of hAGT. This procedure can be applied to produce well-defined covalent complexes between AGT with DNA.
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Affiliation(s)
- Francis P McManus
- Department of Chemistry and Biochemistry, Concordia University, 7141 Sherbrooke St. West, Montréal, QC, Canada H4B 1R6
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13
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Sun G, Noronha A, Wilds C. Preparation of N3-thymidine–butylene–N3-thymidine interstrand cross-linked DNA via an orthogonal deprotection strategy. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.07.043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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14
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Xiong H, Seela F. Cross-linked DNA: site-selective "click" ligation in duplexes with bis-azides and stability changes caused by internal cross-links. Bioconjug Chem 2012; 23:1230-43. [PMID: 22554072 DOI: 10.1021/bc300074k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Heterodimeric interstrand cross-linked DNA was constructed by the "bis-click" reaction carried out on preformed oligonucleotide duplexes with the bis-azide 1. For this, alkynylated 8-aza-7-deazapurine or corresponding 5-substituted pyrimidine nucleosides were synthesized. Cross-linking resulted in chemoselective formation of heterodimeric duplexes while homodimers were suppressed. For product identification, heterodimeric DNA was prepared by the "stepwise click" reaction, while noncomplementary homodimers were accessible by "bis-click" chemistry, unequivocally. Studies on duplex melting of complementary cross-linked duplexes (heterodimers) revealed significantly increased Tm values compared to the non-cross-linked congeners. The stability of this cross-linked DNA depends on the linker length and the site of modification. Cross-linked homodimers hybridized with single-stranded complementary oligonucleotides show much lower stability.
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Affiliation(s)
- Hai Xiong
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology , Heisenbergstraße 11, 48149 Münster, Germany
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15
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Aralov AV, Klykov VN, Chakhmakhcheva OG, Efimov VA. [Monomers containing 2'-o-alkoxymethyl groups as synthons for the synthesis of oligoribonucleotides by the phosphotriester method]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2012; 37:654-61. [PMID: 22332361 DOI: 10.1134/s1068162011050025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A general scheme for the synthesis of ribonucleotide monomers containing alkoxymethyl group in 2'-O-position for the solid-phase phosphotriester oligonucleotide synthesis using O-nucleophilic intramolecular catalysis has been developed. In particular, the monomers containing 2'-O-modifying 2-azidoethoxymethyl, propargyloxymethyl, or 3,4-cyclocarbonatebutoxymethyl groups has been prepared.
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16
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Hentschel S, Alzeer J, Angelov T, Schärer OD, Luedtke NW. Synthese von DNA-Interstrang-Crosslinks unter Verwendung einer photoaktivierbaren Nucleobase. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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17
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Hentschel S, Alzeer J, Angelov T, Schärer OD, Luedtke NW. Synthesis of DNA Interstrand Cross-Links Using a Photocaged Nucleobase. Angew Chem Int Ed Engl 2012; 51:3466-9. [DOI: 10.1002/anie.201108018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Indexed: 12/16/2022]
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18
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McManus FP, O'Flaherty DK, Noronha AM, Wilds CJ. O4-Alkyl-2′-deoxythymidine cross-linked DNA to probe recognition and repair by O6-alkylguanine DNA alkyltransferases. Org Biomol Chem 2012; 10:7078-90. [DOI: 10.1039/c2ob25705j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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19
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Wilds CJ, Booth JDM, Noronha AM. Synthesis of building blocks and oligonucleotides with {G}O⁶-alkyl-O⁶{G} cross-links. CURRENT PROTOCOLS IN NUCLEIC ACID CHEMISTRY 2011; Chapter 5:Unit5.9. [PMID: 21400706 DOI: 10.1002/0471142700.nc0509s44] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This unit describes two methods for preparing oligonucleotides containing an O(6)-2'-deoxyguanosine-alkyl-O(6)-2'-deoxyguanosine interstrand cross-link by a solid-phase synthesis approach. Depending on the desired orientation of the cross-link in the DNA duplex, either a bis- or a mono-phosphoramidite synthesis strategy can be employed. Both procedures require the preparation of a protected 2'-deoxyguanosine-containing dimer where the two nucleosides are attached at the O(6)-atoms by an alkyl linker. This linker is introduced as a protected diol using two successive Mitsunobu reactions to produce a cross-linked amidite that is incorporated into an oligonucleotide via solid-phase synthesis. The use of a protected diol lends versatility to this method, as cross-links of variable chain length may be prepared. The bis-phosphoramidite approach is a direct method to preparing the cross-linked duplex, whereas the mono-phosphoramidite strategy requires additional manipulation of the solid support to prepare cross-linked oligonucleotides. Once all synthetic steps are completed, these oligonucleotides can then be removed from the solid support and deprotected, and then purified via ion-exchange HPLC to produce sufficient quantities of substrates that can be used in DNA repair studies.
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20
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Xiong H, Seela F. Stepwise "click" chemistry for the template independent construction of a broad variety of cross-linked oligonucleotides: influence of linker length, position, and linking number on DNA duplex stability. J Org Chem 2011; 76:5584-97. [PMID: 21591729 DOI: 10.1021/jo2004988] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cross-linked DNA was constructed by a "stepwise click" reaction using a bis-azide. The reaction is performed in the absence of a template, and a monofunctionalized oligonucleotide bearing an azido-function is formed as intermediate. For this, an excess of the bis-azide has to be used compared to the alkynylated oligonucleotide. The cross-linking can be carried out with any alkynylated DNA having a terminal triple bond at any position of the oligonucleotide, independent of chain length or sequence with identical or nonidentical chains. Short and long linkers with terminal triple bonds were introduced in the 7-position of 8-aza-7-deaza-2'-deoxyguanosine (1 or 2), and the outcome of the "stepwise" click and the "bis-click" reaction was compared. The cross-linked DNAs form cross-linked duplexes when hybridized with single-stranded complementary oligonucleotides. The stability of these cross-linked duplexes is as high as respective individual duplexes when they were ligated at terminal positions with linkers of sufficient length. The stability decreases when the linkers are incorporated at central positions. The highest duplex stability was reached when two complementary cross-linked oligonucleotides were hybridized.
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Affiliation(s)
- Hai Xiong
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Münster, Germany
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21
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Rojsitthisak P, Jongaroonngamsang N, Romero RM, Haworth IS. HPLC-UV, MALDI-TOF-MS and ESI-MS/MS analysis of the mechlorethamine DNA crosslink at a cytosine-cytosine mismatch pair. PLoS One 2011; 6:e20745. [PMID: 21673963 PMCID: PMC3108972 DOI: 10.1371/journal.pone.0020745] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 05/12/2011] [Indexed: 01/19/2023] Open
Abstract
Background Mechlorethamine [ClCH2CH2N(CH3)CH2CH2Cl], a nitrogen mustard alkylating agent, has been proven to form a DNA interstrand crosslink at a cytosine-cytosine (C-C) mismatch pair using gel electrophoresis. However, the atomic connectivity of this unusual crosslink is unknown. Methodology/Principal Findings HPLC-UV, MALDI-TOF-MS, and ESI-MS/MS were used to determine the atomic connectivity of the DNA C-C crosslink formed by mechlorethamine, MALDI-TOF-MS of the HPLC-purified reaction product of mechlorethamine with the DNA duplex d[CTCACACCGTGGTTC]•d[GAACCACCGTGTGAG] (underlined bases are a C-C mismatch pair) indicated formation of an interstrand crosslink at m/z 9222.088 [M−2H+Na]+. Following enzymatic digestion of the crosslinked duplex by snake venom phosphodiesterase and calf intestinal phosphatase, ESI-MS/MS indicated the presence of dC-mech-dC [mech = CH2CH2N(CH3)CH2CH2] at m/z 269.2 [M]2+ (expected m/z 269.6, exact mass 539.27) and its hydrolytic product dC-mech-OH at m/z 329.6 [M]+ (expected m/z 329.2). Fragmentation of dC-mech-dC gave product ions at m/z 294.3 and 236.9 [M]+, which are both due to loss of the 4-amino group of cytosine (as ammonia), in addition to dC and dC+HN(CH3)CH = CH2, respectively. The presence of m/z 269.2 [M]2+ and loss of ammonia exclude crosslink formation at cytosine N4 or O2 and indicate crosslinking through cytosine N3 with formation of two quaternary ammonium ions. Conclusions Our results provide an important addition to the literature, as the first example of the use of HPLC and MS for analysis of a DNA adduct at the N3 position of cytosine.
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Affiliation(s)
- Pornchai Rojsitthisak
- Department of Food and Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok, Thailand.
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22
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Stevens K, Claeys DD, Catak S, Figaroli S, Hocek M, Tromp JM, Schürch S, Van Speybroeck V, Madder A. Furan-oxidation-triggered inducible DNA cross-linking: acyclic versus cyclic furan-containing building blocks--on the benefit of restoring the cyclic sugar backbone. Chemistry 2011; 17:6940-53. [PMID: 21598324 DOI: 10.1002/chem.201100067] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Indexed: 01/06/2023]
Abstract
Oligodeoxynucleotides incorporating a reactive functionality can cause irreversible cross-linking to the target sequence and have been widely studied for their potential in inhibition of gene expression or development of diagnostic probes for gene analysis. Reactive oligonucleotides further show potential in a supramolecular context for the construction of nanometer-sized DNA-based objects. Inspired by the cytochrome P450 catalyzed transformation of furan into a reactive enal species, we recently introduced a furan-oxidation-based methodology for cross-linking of nucleic acids. Previous experiments using a simple acyclic building block equipped with a furan moiety for incorporation into oligodeoxynucleotides have shown that cross-linking occurs in a very fast and efficient way and that substantial amounts of stable, site-selectively cross-linked species can be isolated. Given the destabilization of duplexes observed upon introduction of the initially designed furan-modified building block into DNA duplexes, we explore here the potential benefits of two new building blocks featuring an extended aromatic system and a restored cyclic backbone. Thorough experimental analysis of cross-linking reactions in a series of contexts, combined with theoretical calculations, permit structural characterization of the formed species and allow assessment of the origin of the enhanced cross-link selectivity. Our experiments clearly show that the modular nature of the furan-modified building blocks used in the current cross-linking strategy allow for fine tuning of both yield and selectivity of the interstrand cross-linking reaction.
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Affiliation(s)
- Kristof Stevens
- Laboratory for Organic and Biomimetic Chemistry, Department of Organic Chemistry, Ghent University, Krijgslaan 281, S4, 9000 Gent, Belgium
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23
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Guainazzi A, Campbell AJ, Angelov T, Simmerling C, Schärer OD. Synthesis and molecular modeling of a nitrogen mustard DNA interstrand crosslink. Chemistry 2011; 16:12100-3. [PMID: 20842675 DOI: 10.1002/chem.201002041] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Angelo Guainazzi
- Department of Pharmacological Sciences and Chemistry, Stony Brook University, Stony Brook, NY 11794-3400, USA
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24
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Jawalekar AM, Op de Beeck M, van Delft FL, Madder A. Synthesis and incorporation of a furan-modified adenosine building block for DNA interstrand crosslinking. Chem Commun (Camb) 2011; 47:2796-8. [DOI: 10.1039/c0cc04667a] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Ono T, Yoshida K, Saotome Y, Sakabe R, Okamoto I, Ono A. Synthesis of covalently linked parallel and antiparallel DNA duplexes containing the metal-mediated base pairs T–Hg(ii)–T and C–Ag(i)–C. Chem Commun (Camb) 2011; 47:1542-4. [DOI: 10.1039/c0cc02028a] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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26
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Op de Beeck M, Madder A. Unprecedented C-selective interstrand cross-linking through in situ oxidation of furan-modified oligodeoxynucleotides. J Am Chem Soc 2010; 133:796-807. [PMID: 21162525 DOI: 10.1021/ja1048169] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Chemical reagents that form interstrand cross-links have been used for a long time in cancer therapy. They covalently link two strands of DNA, thereby blocking transcription. Cross-link repair enzymes, however, can restore the transcription processes, causing resistance to certain anti-cancer drugs. The mechanism of these cross-link repair processes has not yet been fully revealed. One of the obstacles in this study is the lack of sufficient amounts of well-defined, stable, cross-linked duplexes to study the pathways of cross-link repair enzymes. Our group has developed a cross-link strategy where a furan moiety is incorporated into oligodeoxynucleotides (ODNs). These furan-modified nucleic acids can form interstrand cross-links upon selective furan oxidation with N-bromosuccinimide. We here report on the incorporation of the furan moiety at the 2'-position of a uridine through an amido or ureido linker. The resulting modified ODNs display an unprecedented selectivity for cross-linking toward a cytidine opposite the modified residue, forming one specific cross-linked duplex, which could be isolated in good yield. Furthermore, the structure of the formed cross-linked duplexes could be unambiguously characterized.
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Affiliation(s)
- Marieke Op de Beeck
- Laboratory for Organic and Biomimetic Chemistry, University of Ghent, Krijgslaan 281 S4, B-9000 Ghent, Belgium
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27
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Pujari SS, Xiong H, Seela F. Cross-linked DNA generated by "bis-click" reactions with bis-functional azides: site independent ligation of oligonucleotides via nucleobase alkynyl chains. J Org Chem 2010; 75:8693-6. [PMID: 21070038 DOI: 10.1021/jo101809w] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Template-free cross-linking of single-stranded DNA bearing octadiynyl side chains at the 7-position of 8-aza-7-deazapurine moieties with bisfunctional azides is reported employing a Cu(I)-catalyzed azide-alkyne "bis-click" reaction. Bis-adducts were formed when the bis-azide:oligonucleotide ratio was 1:1; monofunctionalization occurred when the ratio was 15:1. Four-stranded DNA consisting of two cross-linked duplexes was obtained after hydridization. Cross-linked duplexes are as stable as individual duplexes when ligation was introduced at terminal positions; ligation at a central position led to a slight duplex destabilization.
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Affiliation(s)
- Suresh S Pujari
- Laboratory of Bioorganic Chemistry and Chemical Biology, Center for Nanotechnology, Heisenbergstrasse 11, 48149 Münster, Germany
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28
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Guainazzi A, Schärer OD. Using synthetic DNA interstrand crosslinks to elucidate repair pathways and identify new therapeutic targets for cancer chemotherapy. Cell Mol Life Sci 2010; 67:3683-97. [PMID: 20730555 PMCID: PMC3732395 DOI: 10.1007/s00018-010-0492-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 07/28/2010] [Indexed: 01/16/2023]
Abstract
Many cancer chemotherapeutic agents form DNA interstrand crosslinks (ICLs), extremely cytotoxic lesions that form covalent bonds between two opposing DNA strands, blocking DNA replication and transcription. However, cellular responses triggered by ICLs can cause resistance in tumor cells, limiting the efficacy of such treatment. Here we discuss recent advances in our understanding of the mechanisms of ICL repair that cause this resistance. The recent development of strategies for the synthesis of site-specific ICLs greatly contributed to these insights. Key features of repair are similar for all ICLs, but there is increasing evidence that the specifics of lesion recognition and synthesis past ICLs by DNA polymerases are dependent upon the structure of ICLs. These new insights provide a basis for the improvement of antitumor therapy by targeting DNA repair pathways that lead to resistance to treatment with crosslinking agents.
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Affiliation(s)
- Angelo Guainazzi
- Departments of Pharmacological Sciences, Chemistry 619, Stony Brook University, Stony Brook, NY 11794-3400 USA
| | - Orlando D. Schärer
- Departments of Pharmacological Sciences and Chemistry, Chemistry 619, Stony Brook University, Stony Brook, NY 11794-3400 USA
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29
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Hlavin EM, Smeaton MB, Noronha AM, Wilds CJ, Miller PS. Cross-link structure affects replication-independent DNA interstrand cross-link repair in mammalian cells. Biochemistry 2010; 49:3977-88. [PMID: 20373772 DOI: 10.1021/bi902169q] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
DNA interstrand cross-links (ICLs) are cytotoxic products of common anticancer drugs and cellular metabolic processes, whose mechanism(s) of repair remains poorly understood. In this study, we show that cross-link structure affects ICL repair in nonreplicating reporter plasmids that contain a mispaired N(4)C-ethyl-N(4)C (C-C), N3T-ethyl-N3T (T-T), or N1I-ethyl-N3T (I-T) ICL. The T-T and I-T cross-links obstruct the hydrogen bond face of the base and mimic the N1G-ethyl-N3C ICL created by bis-chloroethylnitrosourea, whereas the C-C cross-link does not interfere with base pair formation. Host-cell reactivation (HCR) assays in human and hamster cells showed that repair of these ICLs primarily involves the transcription-coupled nucleotide excision repair (TC-NER) pathway. Repair of the C-C ICL was 5-fold more efficient than repair of the T-T or I-T ICLs, suggesting the latter cross-links hinder lesion bypass following initial ICL unhooking. The level of luciferase expression from plasmids containing a C-C cross-link remnant on either the transcribed or nontranscribed strand increased in NER-deficient cells, indicating NER involvement occurs at a step prior to remnant removal, whereas expression from similar T-T remnant plasmids was inhibited in NER-deficient cells, demonstrating NER is required for remnant removal. Sequence analysis of repaired plasmids showed a high proportion of C residues inserted at the site of the T-T and I-T cross-links, and HCR assays showed that Rev1 was likely responsible for these insertions. In contrast, both C and G residues were inserted at the C-C cross-link site, and Rev1 was not required for repair, suggesting replicative or other translesion polymerases can bypass the C-C remnant.
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Affiliation(s)
- Erica M Hlavin
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205, USA
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30
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Gates KS. An overview of chemical processes that damage cellular DNA: spontaneous hydrolysis, alkylation, and reactions with radicals. Chem Res Toxicol 2010; 22:1747-60. [PMID: 19757819 DOI: 10.1021/tx900242k] [Citation(s) in RCA: 348] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The sequence of heterocyclic bases on the interior of the DNA double helix constitutes the genetic code that drives the operation of all living organisms. With this said, it is not surprising that chemical modification of cellular DNA can have profound biological consequences. Therefore, the organic chemistry of DNA damage is fundamentally important to diverse fields including medicinal chemistry, toxicology, and biotechnology. This review is designed to provide a brief overview of the common types of chemical reactions that lead to DNA damage under physiological conditions.
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Affiliation(s)
- Kent S Gates
- Departments of Chemistry and Biochemistry, University of Missouri-Columbia, 125 Chemistry Building, Columbia, Missouri 65211.
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31
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Hou X, Wang G, Gaffney BL, Jones RA. Synthesis of guanosine and deoxyguanosine phosphoramidites with cross-linkable thioalkyl tethers for direct incorporation into RNA and DNA. NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS 2009; 28:1076-94. [PMID: 20183575 PMCID: PMC2829721 DOI: 10.1080/15257770903368385] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
We describe the synthesis of protected phosphoramidites of deoxyriboguanosine and guanosine derivatives containing a thiopropyl tether at the guanine N2 (7a,b) for site-specific crosslinking from the minor groove of either DNA or RNA to a thiol of a protein or another nucleic acid. The thiol is initially protected as a tert-butyl disulfide that is stable during oligonucleotide synthesis. While the completed oligonucleotide is still attached to the support, or after purification, the tert-butyl thiol can readily be removed or replaced by thioethylamine or 5-thio-2-nitrobenzoic acid, which have more favorable crosslinking rates.
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Affiliation(s)
- Xiaorong Hou
- Department of Chemistry and Chemical Biology, 610 Taylor Road, Rutgers, The State University of New Jersey, Piscataway New Jersey 08854
| | - Gang Wang
- Department of Chemistry and Chemical Biology, 610 Taylor Road, Rutgers, The State University of New Jersey, Piscataway New Jersey 08854
| | - Barbara L. Gaffney
- Department of Chemistry and Chemical Biology, 610 Taylor Road, Rutgers, The State University of New Jersey, Piscataway New Jersey 08854
| | - Roger A. Jones
- Department of Chemistry and Chemical Biology, 610 Taylor Road, Rutgers, The State University of New Jersey, Piscataway New Jersey 08854
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32
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Smeaton MB, Hlavin EM, Noronha AM, Murphy SP, Wilds CJ, Miller PS. Effect of cross-link structure on DNA interstrand cross-link repair synthesis. Chem Res Toxicol 2009; 22:1285-97. [PMID: 19580249 DOI: 10.1021/tx9000896] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
DNA interstrand cross-links (ICLs) are products of chemotherapeutic agents and cellular metabolic processes that block both replication and transcription. If left unrepaired, ICLs are extremely toxic to cells, and ICL repair mechanisms contribute to the survival of certain chemotherapeutic resistance tumors. A critical step in ICL repair involves unhooking the cross-link. In the absence of a homologous donor sequence, the resulting gap can be filled in by a repair synthesis step involving bypass of the cross-link remnant. Here, we examine the effect of cross-link structure on the ability of unhooked DNA substrates to undergo repair synthesis in mammalian whole cell extracts. Using 32P incorporation assays, we found that repair synthesis occurs efficiently past the site of damage when a DNA substrate containing a single N4C-ethyl-N4C cross-link is incubated in HeLa or Chinese hamster ovary cell extracts. This lesion, which can base pair with deoxyguanosine, is readily bypassed by both Escherichia coli DNA polymerase I and T7 DNA polymerase in a primer extension assay. In contrast, bypass was not observed in the primer extension assay or in mammalian cell extracts when DNA substrates containing a N3T-ethyl-N3T or N1I-ethyl-N3T cross-link, whose linkers obstruct the hydrogen bond face of the bases, were used. A modified phosphorothioate sequencing method was used to analyze the ICL repair patches created in the mammalian cell extracts. In the case of the N4C-ethyl-N4C substrate, the repair patch spanned the site of the cross-link, and the lesion was bypassed in an error-free manner. However, although the N3T-ethyl-N3T and N1I-ethyl-N3T substrates were unhooked in the extracts, bypass was not detected. These and our previous results suggest that although the chemical structure of an ICL may not affect initial cross-link unhooking, it can play a significant role in subsequent processing of the cross-link. Understanding how the physical and chemical differences of ICLs affect repair may provide a better understanding of the cytotoxic and mutagenic potential of specific ICLs.
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Affiliation(s)
- Michael B Smeaton
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205, USA
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33
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Angelov T, Guainazzi A, Schärer OD. Generation of DNA interstrand cross-links by post-synthetic reductive amination. Org Lett 2009; 11:661-4. [PMID: 19132933 DOI: 10.1021/ol802719a] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
DNA interstrand cross-links (ICLs) are the clinically most relevant adducts formed by many antitumor agents. To facilitate the study of biological responses triggered by ICLs, we developed a new approach toward the synthesis of mimics of nitrogen mustard ICLs. 7-Deazaguanine residues bearing acetaldehyde groups were incorporated into complementary strands of DNA and cross-link formation induced by double reductive amination. Our strategy enables the synthesis of major groove cross-links in high yields and purity.
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Affiliation(s)
- Todor Angelov
- Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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34
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Kumar R, Ujjinamatada RK, Hosmane RS. The first synthesis of a novel 5:7:5-fused diimidazodiazepine ring system and some of its chemical properties. Org Lett 2008; 10:4681-4. [PMID: 18816128 DOI: 10.1021/ol8020176] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The first synthesis of a novel 5:7:5-fused heterocyclic ring system, a diimidazodiazepine, is reported. The propensity of the ring system to undergo facile, acid-catalyzed nucleophilic addition reactions by neutral carbon and nitrogen nucleophiles has been explored. The ring system has potential future applications in mechanistic studies of formation and repair of DNA interstrand cross-links.
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Affiliation(s)
- Raj Kumar
- Laboratory For Drug Design and Synthesis, Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, USA
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35
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Kocalka P, El-Sagheer AH, Brown T. Rapid and efficient DNA strand cross-linking by click chemistry. Chembiochem 2008; 9:1280-5. [PMID: 18418819 DOI: 10.1002/cbic.200800006] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Click chemistry has been used to covalently cross-link complementary DNA strands between bases to form very stable duplexes. Several alkyne- and azide-modified uracil monomers were used to evaluate the effect of the linkers on the efficiency of the click reaction. All cross-linked duplexes had much higher thermal stabilities than non-cross-linked ones, with increases in melting temperature of up to 30 degrees C. In some cases, the conversion was near-quantitative, and the reaction was complete in 5 min.
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Affiliation(s)
- Petr Kocalka
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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36
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Smeaton MB, Hlavin EM, McGregor Mason T, Noronha AM, Wilds CJ, Miller PS. Distortion-dependent unhooking of interstrand cross-links in mammalian cell extracts. Biochemistry 2008; 47:9920-30. [PMID: 18702509 DOI: 10.1021/bi800925e] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Interstrand cross-links (ICLs) are formed by many chemotherapeutic agents and may also arise endogenously. The mechanisms used to repair these lesions remain unclear in mammalian cells. Repair in Escherichia coli and Saccharomyces cerevisiae requires an initial unhooking step to release the tethered DNA strands. We used a panel of linear substrates containing different site-specific ICLs to characterize how structure affects ICL processing in mammalian cell extracts. We demonstrate that ICL-induced distortions affect NER-dependent and -independent processing events. The NER-dependent pathway produces dual incisions 5' to the site of the ICL as described previously [Bessho, T., et al. (1997) Mol. Cell. Biol. 17 (12), 6822-6830] but does not release the cross-link. Surprisingly, we also found that the interstrand cross-linked duplexes were unhooked in mammalian cell extracts in a manner independent of the NER pathway. Unhooking occurred identically in extracts prepared from human and rodent cells and is dependent on ATP hydrolysis and metal ions. The structure of the unhooked product was characterized and was found to contain the remnant of the cross-link. Both the NER-mediated dual 5' incisions and unhooking reactions were greatly stimulated by ICL-induced distortions, including increased local flexibility and disruption of base pairs surrounding the site of the ICL. These results suggest that in DNA not undergoing transcription or replication, distortions induced by the presence of an ICL could contribute significantly to initial cross-link recognition and processing.
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Affiliation(s)
- Michael B Smeaton
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205, USA
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37
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Yoshimura Y, Fujimoto K. Ultrafast reversible photo-cross-linking reaction: toward in situ DNA manipulation. Org Lett 2008; 10:3227-30. [PMID: 18582065 DOI: 10.1021/ol801112j] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We describe a novel ultrafast reversible DNA interstrand photo-cross-linking reaction via 3-cyanovinylcarbazole nucleoside ( (CNV)K). Oligodeoxynucleotide (ODN) containing (CNV)K can be photo-cross-linked by irradiation at 366 nm for 1 s, and the photo-cross-linked ODN can be split by irradiation at 312 nm for 60 s.
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Affiliation(s)
- Yoshinaga Yoshimura
- School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan
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38
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Wilds CJ, Xu F, Noronha AM. Synthesis and characterization of DNA containing an N1-2'-deoxyinosine-ethyl-N3-thymidine interstrand cross-link: a structural mimic of the cross-link formed by 1,3-bis-(2-chloroethyl)-1-nitrosourea. Chem Res Toxicol 2008; 21:686-95. [PMID: 18257558 DOI: 10.1021/tx700422h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Interstrand cross-links, which are generated by chemotherapeutic treatment with bis-alkylating agents, exert their therapeutic effect by connecting the nucleobases of adjacent DNA strands together and represent some of the most threatening forms of damage suffered by genomic DNA. However, one of the reasons for treatment failure using these agents is due to enhanced repair of this DNA damage. The pursuit of understanding the repair of interstrand cross-links by repair systems has necessitated the synthesis of sufficient quantities of such damaged DNA. We report the synthesis of a site-specific interstrand cross-linked duplex containing an ethylene-bridged N (1)-2'-deoxyinosine- N (3)-thymidine base pair prepared by solution and solid-phase synthesis as a mimic for the lesion formed by the therapeutic agent 1,3-bis-(2-chloroethyl)-1-nitrosourea using both a phosphoramidite and a bis-phosphoramidite approach. UV thermal denaturation experiments revealed that this cross-linked duplex was stabilized by 52 degrees C relative to the noncross-linked control, and circular dichroism studies indicated little deviation from a B-form structure compared to a duplex that contained a G-C base pair at the same position. Molecular models of the cross-linked duplex that were geometry optimized using the AMBER forcefield also suggest that this lesion induces minimal distortion in B-form DNA. This modified oligonucleotide will be useful for studies related to the investigation of interstrand cross-linked DNA repair.
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Affiliation(s)
- Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia UniVersity, Montreal, Quebec, Canada.
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Wilds CJ, Palus E, Noronha AM. An approach for the synthesis of duplexes containing N3T-butyl-N3T interstrand cross-links via a bisphosphoramidite strategy. CAN J CHEM 2007. [DOI: 10.1139/v07-015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
DNA duplexes containing an interstrand cross-link have been synthesized utilizing a bis-3′-O-phosphoramidite deoxythymidine dimer where the N3 atoms are bridged by a butyl linker. With this approach sufficient quantities of high purity cross-linked duplexes are obtained that will enable various biochemical and structural studies to aid in research directed towards understanding the mechanism of interstrand cross-linked DNA repair. This methodology has advantages over a previously reported method to synthesize cross-linked DNA duplexes involving a monophosphoramidite of the same cross-linked thymidine dimer including circumventing the use of costly 5′-O-deoxyphosphoramidites in the assembly of the cross-linked duplex by solid-phase synthesis. This strategy can be employed to produce cross-linked duplexes in which the lesions are engineered to have a directly opposed (1–1) or staggered (1–2 or 2–1) orientations. Biophysical studies of duplexes containing this N3T-butyl-N3T cross-link in staggered 1–2 and 2–1 orientations reveal that both duplexes have a higher Tm than a non-cross-linked duplex suggesting that these linkages do not result in the destabilization of duplex DNA. Circular dichroism spectra of the 1–2 and 2–1 cross-linked duplexes exhibit minor differences from B-form structure, which correlates with molecular modeling studies.Key words: chemically modified oligonucleotides, interstrand cross-link, DNA adduct, DNA repair.
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Alzeer J, Schärer OD. A modified thymine for the synthesis of site-specific thymine-guanine DNA interstrand crosslinks. Nucleic Acids Res 2006; 34:4458-66. [PMID: 16945959 PMCID: PMC1636361 DOI: 10.1093/nar/gkl587] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 07/26/2006] [Accepted: 07/28/2006] [Indexed: 01/14/2023] Open
Abstract
DNA interstrand crosslinks (ICLs) are highly cytotoxic lesions formed by a variety of important anti-tumor agents. Despite the clinical importance of ICLs, the mechanisms by which these lesions are repaired in mammalian cells have so far remained elusive. One of the obstacles in the study of ICL repair has been the limited availability of suitable methods for the synthesis of defined site-specific ICLs. We report here the synthesis of a site-specific ICL containing an ethylene-bridged G-T base pair based on the incorporation of a crosslink precursor containing a selectively reactive group on one strand using solid-phase synthesis. 3-(2-chloroethyl)thymidine was incorporated into oligonucleotides and underwent ICL formation upon annealing to a complementary strand by reacting with the base opposite to the modified T residue. A strong preference for ICL formation with a G residue opposite the reactive T was observed. Detailed characterization of the reaction product revealed that the alkylation reaction occurred with the O-6 group of G and a mechanism accounting for this preference is proposed. These G-T crosslinks introduced here will be useful for studies of ICL repair.
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Affiliation(s)
- Jawad Alzeer
- Institute of Molecular Cancer Research, University of ZurichWinterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Orlando D. Schärer
- Institute of Molecular Cancer Research, University of ZurichWinterthurerstrasse 190, 8057 Zurich, Switzerland
- Department of Pharmacological Sciences, Chemistry Graduate Building 619, Stony Brook UniversityStony Brook, NY11794-3400
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Affiliation(s)
- Mark Lukin
- Department of Pharmacological Sciences, State University of New York at Stony Brook, School of Medicine, 11794-8651, USA
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Affiliation(s)
| | - Tracey McGregor Mason
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205
| | - Paul S. Miller
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205
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Wilds CJ, Noronha AM, Robidoux S, Miller PS. Synthesis and characterization of DNA duplexes containing an N3T-ethyl-N3T interstrand crosslink in opposite orientations. NUCLEOSIDES NUCLEOTIDES & NUCLEIC ACIDS 2005; 24:965-9. [PMID: 16248073 DOI: 10.1081/ncn-200059329] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
DNA duplexes containing an ethyl interstrand crosslink that bridges the N3 atoms of thymidines on the opposite strands have been synthesized using an approach that combines conventional solid phase oligonucleotide synthesis and the selective removal of protecting groups of a crosslinked thymidine dimer. This approach allows for the assembly of a crosslinked duplex directly on the solid support. Duplexes that contain a N3T-ethyl-N3T interstrand crosslink in a staggered orientation at either a -TA- or -AT-step in a duplex have been prepared. When placed in an -AT- step of a duplex the effect was stabilizing relative to the non-crosslinked control duplex (deltaTm= +24 degrees C) and this crosslinked duplex was found to efficiently form multimers in the presence of T4 ligase. In the case of the -TA- crosslinked duplex the stabilizing effect was less pronounced (deltaT.= +6 degrees C) and likewise did not undergo self ligation under identical conditions. Molecular modeling studies suggested that the -AT- containing lesion had little deviation in structure relative to the non-crosslinked duplex DNA control, whereas the -TA- crosslinked duplex exhibited significant buckling of the base pairs flanking the lesion.
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Affiliation(s)
- Christopher J Wilds
- Department of Chemistry and Biochemistry, Concordia University, Montreal, Quebec, Canada
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da Silva MW, Bierbryer RG, Wilds CJ, Noronha AM, Colvin OM, Miller PS, Gamcsik MP. Intrastrand base-stacking buttresses widening of major groove in interstrand cross-linked B-DNA. Bioorg Med Chem 2005; 13:4580-7. [PMID: 15953553 DOI: 10.1016/j.bmc.2005.03.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2005] [Accepted: 03/16/2005] [Indexed: 11/27/2022]
Abstract
The introduction of a covalent interstrand cross-link induces changes in the intrinsic structure and deformability of the DNA helix that are recognized by elements of the DNA repair apparatus. In this context, the solution structure of the undecamer d(CGAAAT*TTTCG)2, where T* represents a N3T-butyl-N3T interstrand cross-link, was determined using molecular dynamics calculations restrained by NOE and dihedral angle data obtained from NMR spectroscopy. The structure of this cross-linked undecamer shows dramatic widening of the major groove of the B-DNA stem without disruption of Watson-Crick base pairing. This change in tertiary structure illustrates the cumulative effect of cooperativity in intrastrand base stacking of an A-tract of three adenines. Further, it is the direct result from the imposition of geometric angular constraints by the cross-link chain on an ApT* and T*pT steps in the segment AAAT*T. The widening of the major groove is due to the dominant contribution of base stacking to the stability of the ApT compared to the TpT step suggesting that the latter is more deformable within a DNA stem. Compared to earlier structures of ethyl cross-linked oligonucleotides, this unique perturbation induced by the butyl moiety offers a new probe for systematic studies of DNA repair mechanisms.
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Affiliation(s)
- Mateus Webba da Silva
- Department of Medicine, Duke University Medical Center, DUMC Box 2638, Durham, NC 27710, USA
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Park S, Anderson C, Loeber R, Seetharaman M, Jones R, Tretyakova N. Interstrand and Intrastrand DNA−DNA Cross-Linking by 1,2,3,4-Diepoxybutane: Role of Stereochemistry. J Am Chem Soc 2005; 127:14355-65. [PMID: 16218630 DOI: 10.1021/ja051979x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
1,2,3,4-Diepoxybutane (DEB) is a bifunctional electrophile capable of forming DNA-DNA and DNA-protein cross-links. DNA alkylation by DEB produces N7-(2'-hydroxy-3',4'-epoxybut-1'-yl)-guanine monoadducts, which can then form 1,4-bis-(guan-7-yl)-2,3-butanediol (bis-N7G-BD) lesions. All three optical isomers of DEB are produced metabolically from 1,3-butadiene, but S,S-DEB is the most cytotoxic and genotoxic. In the present work, interstrand and intrastrand DNA-DNA cross-linking by individual DEB stereoisomers was investigated by PAGE, mass spectrometry, and stable isotope labeling. S,S-, R,R-, and meso-diepoxides were synthesized from l-dimethyl-2,3-O-isopropylidene-tartrate, d-dimethyl-2,3-O-isopropylidene-tartrate, and meso-erythritol, respectively. Total numbers of bis-N7G-BD lesions (intrastrand and interstrand) in calf thymus DNA treated separately with S,S-, R,R-, or meso-DEB (0.01-0.5 mM) were similar as determined by capillary HPLC-ESI(+)-MS/MS of DNA hydrolysates. However, denaturing PAGE has revealed that S,S-DEB produced the highest number of interchain cross-links in 5'-GGC-3'/3'-CCG-5' sequences. Intrastrand adduct formation by DEB was investigated by a novel methodology based on stable isotope labeling HPLC-ESI(+)-MS/MS. Meso DEB treatment of DNA duplexes containing 5'-[1,7, NH(2)-(15)N(3),2-(13)C-G]GC-3'/3'-CCG-5' and 5'-GGC-3'/3'-CC[(15)N(3),2-(13)C-G]-5' trinucleotides gave rise to comparable numbers of 1,2-intrastrand and 1,3-interstrand bis-N7G-BD cross-links, while S,S DEB produced few intrastrand lesions. R,R-DEB treated DNA contained mostly 1,3-interstrand bis-N7G-BD, along with smaller amounts of 1,2-interstrand and 1,2-intrastrand adducts. The effects of DEB stereochemistry on its ability to form DNA-DNA cross-links may be rationalized by the spatial relationships between the epoxy alcohol side chains in stereoisomeric N7-(2'-hydroxy-3',4'-epoxybut-1'-yl)-guanine adducts and their DNA environment. Different cross-linking specificities of DEB stereoisomers provide a likely structural basis for their distinct biological activities.
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Affiliation(s)
- Soobong Park
- Cancer Center and the Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
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Schärer OD. DNA interstrand crosslinks: natural and drug-induced DNA adducts that induce unique cellular responses. Chembiochem 2005; 6:27-32. [PMID: 15637664 DOI: 10.1002/cbic.200400287] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Orlando D Schärer
- Institute of Molecular Cancer Research, University of Zürich, August Forel Strasse 7, 8008 Zürich, Switzerland.
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da Silva MW, Wilds CJ, Noronha AM, Colvin OM, Miller PS, Gamcsik MP. Accommodation of mispair aligned N3T-ethyl-N3T DNA interstrand cross link. Biochemistry 2004; 43:12549-54. [PMID: 15449944 DOI: 10.1021/bi0486435] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The solution structure of the undecamer d(CGAAATTTTCG)(2), where T represents a N(3)T-ethyl-N(3)T interstrand cross link, was elucidated using molecular dynamics calculations restrained by NOE and dihedral data obtained from NMR spectroscopy. The ethyl moiety is particularly well-accommodated between the minor and major grooves. This is an exceptional example of the plasticity along the axis defined by the stem and a unique finding of an interstrand cross link occupying the area associating minor and major grooves. The mismatch-aligned tethered bases preserve good intrastrand stacking with flanking bases. Base-pair steps adjacent to the lesion site are overwound. Accommodation of the lesion also results in an increase in mispair staggering alignment modulated by flexibility because of the tetrahedral geometry of the exocyclic ethyl carbon atoms. This is mechanically coupled with a small measure of concomitant propeller twisting without an increase in intrastrand base-step distance. Both x displacement and sugar puckering are indicative of canonical B DNA throughout the stem. We have thus established that the lesion defined by mismatch-aligned minor groove N(3)T-ethyl-N(3)T cross-linked thymine bases produces very localized distortions in a DNA stem that may be difficult to recognize by repair mechanisms that are not transcription- or replication-coupled. Thus, this synthetic DNA is a valuable structural probe to study mechanisms of repair.
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Affiliation(s)
- Mateus Webba da Silva
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA
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