title: In vitro replication and repair studies of tandem lesions containing neighboring thymidine glycol and 8-oxo-7,8-dihydro-2'-deoxyguanosine.
abstract: Reactive oxygen species can induce the formation of tandem DNA lesions. We recently showed that the treatment of calf thymus DNA with Cu2+/H2O2/ascorbate could result in the efficient formation of a tandem lesion where a 5,6-dihydroxy-5,6-dihydrothymidine (or thymidine glycol) is situated on the 5' side of an 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG). In the present study, we assessed how the 5'-Tg-(8-oxodG)-3' and 5'-(8-oxodG)-Tg-3' tandem lesions are replicated by purified DNA polymerases and how they are recognized by base excision repair enzymes. Our results revealed that the tandem lesions blocked primer extension mediated by the Klenow fragment and yeast polymerase eta more readily than when the Tg or 8-oxodG was present alone. The mutagenic properties of Tg or 8-oxodG differed while they were present alone or in tandem. Moreover, the human 8-oxoguanine-DNA glycosylase (hOGG1)-mediated cleavage of 8-oxodG was compromised considerably by the presence of a neighboring 5' Tg, whereas the presence of Tg as the adjacent 3' nucleoside enhanced 8-oxodG cleavage by hOGG1. The efficiency for the cleavage of Tg by endonuclease III was not affected by the presence of an adjoining 8-oxodG. These results supported the notion that the replication and repair of tandem single-nucleobase lesions depend on the types of lesions involved and their spatial arrangement.
authors.affiliation: Environmental Toxicology Graduate Program and Department of Chemistry, University of California, Riverside, California 92521-0403, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Jiang
authors.forename: Yuesong
authors.initials: Y
authors.lastname: Wang
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004261:DNA Replication; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D006801:Humans; D017382:Reactive Oxygen Species / Q000378:metabolism; D013936:Thymidine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; C029390:thymidine glycol; C024829:8-hydroxyguanine; D006147:Guanine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; C427203:calf thymus DNA; D043224:Deoxyribonuclease (Pyrimidine Dimer); D045643:DNA Repair Enzymes; D003849:Deoxyguanosine; D013936:Thymidine