title: Efficiency of excision of 8-oxo-guanine within DNA clustered damage by XRS5 nuclear extracts and purified human OGG1 protein.
abstract: A major DNA lesion is the strongly mutagenic 8-oxo-7,8-dihydroguanine (8-oxoG) base, formed by oxidative attack at guanine and which leads to a high level of G.C-->T.A transversions. Clustered DNA damages are formed in DNA following exposure to ionizing radiation or radiomimetic anticancer agents and are thought to be biologically severe. The presence of 8-oxoG within clustered DNA damage may present a challenge to the repair machinery of the cell, if the OGG1 DNA glycosylase/AP lyase protein, present in eukaryotic cells, does not efficiently excise its substrate, 8-oxoG. In this study, specific oligonucleotide constructs containing an 8-oxoG located in several positions opposite to another damage (5,6-dihydrothymine (DHT), uracil, 8-oxoG, AP site, or various types of single strand breaks) were used to determine the relative efficiency of purified human OGG1 and mammalian XRS5 nuclear extracts to excise 8-oxoG from clustered damages. A base damage (DHT, uracil, and 8-oxoG) on the opposite strand has little or no influence on the rate of excision of 8-oxoG whereas the presence of either an AP site or various types of single strand breaks has a strong inhibitory effect on the formation of a SSB due to the excision of 8-oxoG by both hOGG1 and the nuclear extract. The binding of hOGG1 to 8-oxoG is not significantly affected by the presence of a neighboring lesion.
authors.affiliation: Medical Research Council, Radiation and Genome Stability Unit, Harwell, Didcot, Oxon OX11 0RD, United Kingdom.
authors.forename: M H
authors.initials: MH
authors.lastname: David-Cordonnier
authors.forename: S
authors.initials: S
authors.lastname: Boiteux
authors.forename: P
authors.initials: P
authors.lastname: O'Neill
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D002467:Cell Nucleus / Q000378:metabolism*; D004249:DNA Damage; D043382:DNA-Formamidopyrimidine Glycosylase; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*
chemical_list: D000080242:8-Hydroxy-2'-Deoxyguanosine; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D003849:Deoxyguanosine