title: Repair of cytotoxic lesions introduced into DNA by methylating agents.
abstract: We have investigated the biological role of O6-methylguanine and methylphosphotriesters in the DNA of mammalian cells. Our approach has been to express Escherichia coli (E. coli) DNA repair activities of well-defined specificity in Chinese hamster cells. Expression of O6-methylguanine-DNA methyltransferase is necessary and sufficient to confer resistance to the cytotoxic action of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) indicating the potential involvement of O6-methylguanine in cell killing by this compound. We present evidence that methylphosphotriesters in DNA do not constitute a cytotoxic threat. Despite this, cell lines resistant to MNNG may display elevated expression of a methylphosphotriester repair function. This may be the result of fortuitous co-amplification of transfected sequences and indicates that care should be exercised in correlating resistance to methylating agents with particular DNA repair enzymes.
authors.forename: P
authors.initials: P
authors.lastname: Karran
authors.forename: J
authors.initials: J
authors.lastname: Hall
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D004249:DNA Damage; D004260:DNA Repair; D004926:Escherichia coli / Q000187:drug effects; D006147:Guanine / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D000477:Alkylating Agents; D006147:Guanine; C008449:O-(6)-methylguanine