Energetics,conformation, and recognition of DNA duplexes containing a major adduct of an anticancer azolato-bridged dinuclear Pt complex |
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Authors: | Jarmila Mlcouskova Jaroslav Malina Vojtech Novohradsky Jana Kasparkova Seiji Komeda Viktor Brabec |
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Institution: | 1. Department of Biophysics, Faculty of Science, Palacky University, 17. listopadu 12, CZ-77146 Olomouc, Czech Republic;2. Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, 61265 Brno, Czech Republic;3. Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka 513‐8670, Japan |
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Abstract: | BackgroundThe design of anticancer metallodrugs is currently focused on platinum complexes which form on DNA major adducts that cannot readily be removed by DNA repair systems. Hence, antitumor azolato-bridged dinuclear PtII complexes, such as {cis-Pt(NH3)2}2(μ‐OH)(μ-pyrazolate)]2+ (AMPZ), have been designed and synthesized. These complexes exhibit markedly higher toxic effects in tumor cell lines than mononuclear conventional cisplatin.MethodsBiophysical and biochemical aspects of the alterations induced in short DNA duplexes uniquely and site-specifically modified by the major DNA adduct of AMPZ, namely 1,2-GG intrastrand cross-links, were examined. Attention was also paid to conformational distortions induced in DNA by the adducts of AMPZ and cisplatin, associated alterations in the thermodynamic stability of the duplexes, and recognition of these adducts by high-mobility-group (HMG) domain proteins.ResultsChemical probing of DNA conformation, DNA bending studies and translesion synthesis by DNA polymerase across the platinum adduct revealed that the distortion induced in DNA by the major adduct of AMPZ was significantly less pronounced than that induced by similar cross-links from cisplatin. Concomitantly, the cross-link from AMPZ reduced the thermodynamic stability of the modified duplex considerably less. In addition, HMGB1 protein recognizes major DNA adducts of AMPZ markedly less than those of cisplatin.General significanceThe experimental evidence demonstrates why the major DNA adducts of the new anticancer azolato-bridged dinuclear PtII complexes are poor substrates for DNA repair observed in a previously published report. The relative resistance to DNA repair explains why these platinum complexes show major pharmacological advantages over cisplatin in tumor cells. |
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Keywords: | AMPZ [{cis-{Pt(NH3)2}2(μ-OH)(μ-pyrazolate)]2+ cisplatin [cis-diamminedichloridoplatinum(II)] bp base pair CL cross-link CT calf thymus DSC differential scanning calorimetry EMSA electrophoretic mobility shift assay FAAS flameless atomic absorption spectrometry DMS dimethyl sulfate dNTP deoxyribonucleotide triphosphate HPLC high-pressure liquid chromatography HMG high mobility group HMGB1a domain A of full length HMGB1 protein HMGB1b domain B of full length HMGB1 protein LD linear dichroism Tm melting temperature NER nucleotide excision repair PAA polyacrylamide Polη DNA polymerase η rb the number of molecules of the platinum complex bound per nucleotide residue SDS sodium dodecyl sulfate XPA xeroderma pigmentosum group A |
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