title: NMR characterization of clustered bistrand abasic site lesions: effect of orientation on their solution structure.
abstract: A unique characteristic of ionizing radiation and radiomimetic anticancer drugs is the induction of clustered damage: two or more DNA lesions (oxidized bases, abasic sites, or strand breaks) occurring in the same or different strands of the DNA molecule within a single turn of the helix. In spite of arising at a lower frequency than single lesions, clustered DNA damage represents an exotic challenge to the repair systems present in the cells and, in some cases, these lesions may escape detection and/or processing. To understand the structural properties of clustered DNA lesions we have prepared two oligodeoxynucleotide duplexes containing adjacent tetrahydrofuran residues (abasic site analogues), positioned one in each strand of the duplex in a 5' or 3' orientation, and determined their solution structure by NMR spectroscopy and molecular dynamics simulations. The NMR data indicate that both duplex structures are right-handed helices of high similarity outside the clustered damage site. The thermal stability of the duplexes is severely reduced by the presence of the abasic residues, especially in a 5' orientation where the melting temperature is 5 degrees C lower. The structures show remarkable differences at the lesion site where the extrahelical location of the tetrahydrofuran residues in the (AP)(2)-5'-staggered duplex contrasts with their smooth alignment along the sugar-phosphate backbone in the (AP)(2)-3'-staggered duplex.
authors.affiliation: Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794-8651, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: de los Santos
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D004249:DNA Damage / Q000235:genetics* / Q000528:radiation effects; D005663:Furans / Q000378:metabolism; D006860:Hydrogen Bonding; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation / Q000528:radiation effects; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011522:Protons; D011839:Radiation, Ionizing; D012996:Solutions; D013696:Temperature
chemical_list: D005663:Furans; D009838:Oligodeoxyribonucleotides; D011522:Protons; D012996:Solutions; C018674:tetrahydrofuran; D004247:DNA