Evidence for the excision repair of O6-n-butyldeoxyguanosine in human cells

Abstract
The persistence of O6 - n -butyldeoxyguanosine ( O6 -nBudG) in DNA, the presence of O6 -alkylguanine DNA alkyltransferase (AT) activity in cell extracts, and cell survival following exposure to N - n -butyl- N -nitrosourea (BNU), have been measured in normal and xeroderma pigmentosum cell strains, both transformed and untransformed. The rates of removal of O6 -nBudG did not correlate with AT activity but did correlate with the ability of strains to excise bulky DNA lesions. BNU and N -methyl- N -nitrosourea dose—response curves for cell killing suggests that both AT and excision may be involved in the repair of cytotoxic lesions.