期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1993
卷号：90
期号：6
页码：2117-2121
DOI：10.1073/pnas.90.6.2117
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Three genes that participate in the repair of DNA alkylation damage were recently cloned from Saccharomyces cerevisiae: the MGT1 O6-methylguanine DNA methyltransferase gene, the MAG 3-methyladenine DNA glycosylase gene, and the APN1 apurinic/apyrimidinic (AP) endonuclease gene. Altering the expression levels of these three genes produced significant changes in the S. cerevisiae spontaneous mutation rate. Spontaneous mutation increased in the absence of the MGT1 DNA methyltransferase, presumably because unrepaired, spontaneously produced, O6-alkylguanine lesions mispair during replication. Moreover, changing the ratios of the MAG 3-methyladenine DNA glycosylase and the APN1 AP endonuclease had profound effects on spontaneous mutation rates. In the absence of APN1, the overexpression of MAG increased spontaneous mutation, and the underexpression of MAG decreased spontaneous mutation. We infer that the MAG glycosylase acts upon spontaneously produced 3-alkyladenine and 7-alkylguanine DNA lesions to produce mutagenic abasic sites, and that if the repair of these abasic sites is not initiated by the APN1 AP endonuclease they cause mutations during replication. Our results indicate that eukaryotic cells harbor endogenous metabolites that alkylate nuclear DNA at both oxygens and nitrogens.
