title: The G.C base-pair preference of 2-N-methyl 9-hydroxyellipticinium.
abstract: Among the DNA-intercalating drugs in the ellipticinium series, 9-hydroxy derivatives elicit the highest antitumoral properties. In water these drugs display a very low fluorescence quantum yield. Replacement of H2O by D2O partially restores the fluorescence of the ellipticinium chromophore. The possibility that such a proton-exchange mechanism could be involved in a base-recognizing process at the DNA level (and therefore be responsible for some base preference) was examined by direct fluorescence titration in deuterated buffer and DNA/drug fluorescence energy transfer. These experimental approaches provide mutually consistent results showing that the 9-hydroxylated drug recognizes specific DNA sites that are not recognized by the non-hydroxylated drug. When compared to 2-N-methyl ellipticinium, the 2-N-methyl 9-hydroxyellipticinium presents: (1) higher binding constants for each DNA studied; (2) a base dependence of the fluorescence properties of the bound form (fluorescence increment upon DNA binding varying over 5-11); (3) a base dependence of its DNA affinity constants (1.1-3.3 x 10(6) M-1) and of its site size (exclusion parameters varying over 3.0-4.4); (4) a base dependence of its energy transfer from DNA bases. Analysis of the binding data suggests that the 9-hydroxyl group of 2-N-methyl ellipticinium is responsible for a G.C base-pair preference, the preferred binding site being a doublet sequence of two adjacent G.C which could be flanked either by a additional G.C base pair or by an A.T base pair.
authors.affiliation: Unité de Biochimie-Enzymologie, UA 147 CNRS, U 140 INSERM, Villejuif, France.
authors.forename: M A
authors.initials: MA
authors.lastname: Schwaller
authors.forename: J
authors.initials: J
authors.lastname: Aubard
authors.forename: C
authors.initials: C
authors.lastname: Auclair
authors.forename: C
authors.initials: C
authors.lastname: Paoletti
authors.forename: G
authors.initials: G
authors.lastname: Dodin
mesh_terms: D000470:Alkaloids / Q000494:pharmacology; D001482:Base Composition; D003596:Cytosine; D004247:DNA / Q000187:drug effects; D004611:Ellipticines / Q000494:pharmacology; D004735:Energy Transfer; D006147:Guanine; D007364:Intercalating Agents; D007700:Kinetics; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation; D011067:Poly dA-dT; D011089:Polydeoxyribonucleotides; D013050:Spectrometry, Fluorescence
chemical_list: D000470:Alkaloids; D004611:Ellipticines; D007364:Intercalating Agents; D011089:Polydeoxyribonucleotides; C027767:elliptinium; C016681:poly(dG).poly(dC); D011067:Poly dA-dT; D006147:Guanine; D003596:Cytosine; D004247:DNA