title: Covalent binding of antitumor benzoacronycines to double-stranded DNA induces helix opening and the formation of single-stranded DNA: unique consequences of a novel DNA-bonding mechanism.
abstract: The majority of DNA-binding small molecules known thus far stabilize duplex DNA against heat denaturation. A high, drug-induced increase in the melting temperature (Tm) of DNA is generally viewed as a good criterion to select DNA ligands and is a common feature of several anticancer drugs such as intercalators (e.g., anthracyclines) and alkylators (e.g., ecteinascidin 743). The reverse situation (destabilization of DNA to facilitate its denaturation) may be an attractive option for the identification of therapeutic agents acting on the DNA structure. We have identified the tumor-active benzoacronycine derivative S23906-1 [(+/-)-cis-1,2-diacetoxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2]acridin-7-one] as a potent DNA alkylating agent endowed with a helicase-like activity. Using complementary molecular approaches, we show that covalent binding to DNA of the diacetate compound S23906-1 and its monoacetate analogue S28687-1 induces a marked destabilization of the double helix with the formation of alkylated ssDNA. The DNA-bonding properties and effects on DNA structure of a series of benzoacronycine derivatives, including the dicarbamate analogue S29385-1, were studied using complementary biochemical (electromobility shift assay, nuclease S1 mapping) and spectroscopic (fluorescence and Tm measurements) approaches. Alkylation of guanines in DNA by S28687-1 leads to a local denaturation of DNA, which becomes susceptible to cleavage by nuclease S1 and significantly decreases the Tm of DNA. The drug also directly alkylates single-strand DNA, but mass spectrometry experiments indicate that guanines in duplexes are largely preferred over single-stranded structures. This molecular study expands the repertoire of DNA-binding mechanisms and provides a new dimension for DNA recognition by small molecules.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, Institut de Recherches sur le Cancer de Lille, Place de Verdun, Lille 59045, France. david@lille.inserm.fr
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: David-Cordonnier
authors.forename: William
authors.initials: W
authors.lastname: Laine
authors.forename: Amélie
authors.initials: A
authors.lastname: Lansiaux
authors.forename: Frédéric
authors.initials: F
authors.lastname: Rosu
authors.forename: Pierre
authors.initials: P
authors.lastname: Colson
authors.forename: Edwin
authors.initials: E
authors.lastname: de Pauw
authors.forename: Sylvie
authors.initials: S
authors.lastname: Michel
authors.forename: Francois
authors.initials: F
authors.lastname: Tillequin
authors.forename: Michel
authors.initials: M
authors.lastname: Koch
authors.forename: John A
authors.initials: JA
authors.lastname: Hickman
authors.forename: Alain
authors.initials: A
authors.lastname: Pierré
authors.forename: Christian
authors.initials: C
authors.lastname: Bailly
mesh_terms: D000175:Acronine / Q000031:analogs & derivatives* / Q000633:toxicity*; D000477:Alkylating Agents / Q000633:toxicity; D018943:Anthracyclines / Q000633:toxicity; D000970:Antineoplastic Agents / Q000633:toxicity*; D004247:DNA / Q000737:chemistry* / Q000187:drug effects*; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000187:drug effects*; D007364:Intercalating Agents / Q000633:toxicity; D007700:Kinetics; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry
chemical_list: D000477:Alkylating Agents; D018943:Anthracyclines; D000970:Antineoplastic Agents; D004277:DNA, Single-Stranded; D007364:Intercalating Agents; D009838:Oligodeoxyribonucleotides; D004247:DNA; D000175:Acronine