title: Conformations of stereoisomeric base adducts to 4-hydroxyequilenin.
abstract: Exposure to estrogen through estrogen replacement therapy increases the risk of women developing cancer in hormone sensitive tissues. Premarin (Wyeth), which has been the most frequent choice for estrogen replacement therapy in the United States, contains the equine estrogens equilin and equilenin as major components. 4-Hydroxyequilenin (4-OHEN) is a phase I metabolite of both of these substances. This catechol estrogen autoxidizes to potent cytotoxic quinoids that can react with dG, dA, and dC to form unusual stereoisomeric cyclic adducts (Bolton, J. L., et al. (1998) Chem. Res. Toxicol. 11, 1113-1127). Like other bulky DNA adducts, these lesions may exhibit different susceptibilities to DNA repair and mutagenic potential, if not repaired in a structure-dependent manner. To ultimately gain insights into structure-function relationships, we computed conformations of stereoisomeric guanine, adenine, and cytosine base adducts using density functional theory. We find near mirror image conformations in stereoisomer adduct pairs for each modified base, suggesting opposite orientations with respect to the 5' --> 3' direction of the modified strand when the stereoisomer pairs are incorporated into duplex DNA. Such opposite orientations could cause stereoisomer pairs of lesions to respond differently to DNA replication and repair enzymes.
authors.affiliation: Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003, USA.
authors.forename: Shuang
authors.initials: S
authors.lastname: Ding
authors.forename: Robert
authors.initials: R
authors.lastname: Shapiro
authors.forename: Nicholas E
authors.initials: NE
authors.lastname: Geacintov
authors.forename: Suse
authors.initials: S
authors.lastname: Broyde
mesh_terms: D018736:DNA Adducts / Q000737:chemistry* / Q000378:metabolism; D003838:Deoxyadenine Nucleotides / Q000737:chemistry / Q000378:metabolism; D003845:Deoxycytosine Nucleotides / Q000737:chemistry / Q000378:metabolism; D003848:Deoxyguanine Nucleotides / Q000737:chemistry / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000737:chemistry* / Q000378:metabolism; D004855:Equilenin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism; D045166:Estradiol Congeners / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D018736:DNA Adducts; D003838:Deoxyadenine Nucleotides; D003845:Deoxycytosine Nucleotides; D003848:Deoxyguanine Nucleotides; D003854:Deoxyribonucleotides; D045166:Estradiol Congeners; C065250:4-hydroxy-equilenin; D004855:Equilenin