Generation of a strong mutator phenotype in yeast by imbalanced base excision repair.
Increased spontaneous mutation is associated with increased cancer risk. Here, by using a model system, we show that spontaneous mutation can be increased several hundred-fold by a simple imbalance between the first two enzymes involved in DNA base excision repair. The Saccharomyces cerevisiae MAG1 3-methyladenine (3MeA) DNA glycosylase, when expressed at high levels relative to the apurinic/apyrimidinic endonuclease, increases spontaneous mutation by up to approximately 600-fold in S. cerevisiae and approximately 200-fold in Escherichia coli. Genetic evidence suggests that, in yeast, the increased spontaneous mutation requires the generation of abasic sites and the processing of these sites by the REV1/REV3/REV7 lesion bypass pathway. Comparison of the mutator activity produced by Mag1, which has a broad substrate range, with that produced by the E. coli Tag 3MeA DNA glycosylase, which has a narrow substrate range, indicates that the removal of endogenously produced 3MeA is unlikely to be responsible for the mutator effect of Mag1. Finally, the human AAG 3-MeA DNA glycosylase also can produce a small (approximately 2-fold) but statistically significant increase in spontaneous mutation, a result which could have important implications for carcinogenesis.
Glassner
B J
BJ
Department of Cancer Cell Biology, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA.
Rasmussen
L J
LJ
Najarian
M T
MT
Posnick
L M
LM
Samson
L D
LD
D019757:Carbon-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D045647:DNA Glycosylases; D004260:DNA Repair / Q000235:genetics*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D043223:Deoxyribonuclease IV (Phage T4-Induced); D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D015870:Gene Expression; D005800:Genes, Fungal; D006801:Humans; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000209:etiology / Q000235:genetics; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*
D029968:Escherichia coli Proteins; D009153:Mutagens; D008741:Methyl Methanesulfonate; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; C021565:3-methyladenine-DNA glycosylase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase