Comparative repair of the endogenous lesions 8-oxo-7, 8-dihydroguanine (8-oxoG), uracil and abasic site by mammalian cell extracts: 8-oxoG is poorly repaired by human cell extracts.
The repair of the endogenous lesions 8-oxo-7,8-dihydroguanine (8-oxoG), uracil (U) and natural abasic site (AP site) was investigated using an in vitro base excision repair assay in which a plasmid substrate containing a single lesion at a defined position was repaired by mammalian cell extracts. Repair replication of an 8-oxoG/cytosine base pair performed by normal human cell extracts was approximately 5-fold less efficient than repair of a U/adenine base pair and, in turn, the latter was repaired approximately 10-fold less efficiently than an AP site placed in front of an adenine. A similar pattern of repair capacity for the three lesions was observed in Chinese hamster extracts. Repair of 8-oxoG was performed by the one nucleotide insertion pathway only. The lower repair replication ability of 8-oxoG with respect to U was linked to a lower DNA glycosylase (base removal) activity rather than to inability to process the beta-elimination cleaved strand left by the AP lyase activity associated with human oxoguanine DNA glycosylase 1. The data show that DNA repair of 8-oxoG is poor in human cells in comparison with other frequent endogenous lesions.
Cappelli
E
E
DNA Repair Unit and Mutagenesis Laboratory, Istituto Nazionale Ricerca Cancro, Largo Rosanna Benzi n. 10, 16132 Genova, Italy.
Degan
P
P
Frosina
G
G
D000818:Animals; D001483:Base Sequence; D002457:Cell Extracts; D006224:Cricetinae; D045647:DNA Glycosylases; D017931:DNA Primers; D004260:DNA Repair; D006151:Guanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D006801:Humans; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D010957:Plasmids; D014498:Uracil / Q000378:metabolism*
D002457:Cell Extracts; D017931:DNA Primers; D006151:Guanosine; C046215:8-hydroxyguanosine; D014498:Uracil; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases