Uracil-DNA glycosylase causes 5-bromodeoxyuridine photosensitization in Escherichia coli K-12.
An Escherichia coli uracil-DNA glycosylase-defective mutant (ung-1 thyA) was more resistant than its wild-type counterpart (ung+ thyA) to the killing effect of UV light when cultured in medium containing 5-bromouracil or 5-bromo-2'-deoxyuridine (BrdUrd). The phenotype of resistance to BrdUrd photosensitization and the uracil-DNA glycosylase deficiency appeared to be 100% cotransduced by P1 phage. During growth with BrdUrd, both strains exhibited similar growth rates and 5-bromouracil incorporation into DNA. The resistant phenotype of the ung-1 mutant was observed primarily during the stationary phase. In cells carrying 5-bromouracil-substituted DNA, mutations causing resistance to rifampin and valine were induced by UV irradiation at a higher frequency in the wild type than in the ung-1 mutant. This Ung-dependent UV mutagenesis required UmuC function. These results suggest that the action of the uracil-DNA glycosylase on UV-irradiated 5-bromouracil-substituted DNA produces lethal and mutagenic lesions. The BrdUrd photosensitization-resistant phenotype allowed us to develop a new, efficient method for enriching and screening ung mutants.
Department of Radiation Biophysics, Kobe University School of Medicine, Japan.
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Yamamoto
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Fujiwara
D001973:Bromodeoxyuridine / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D045647:DNA Glycosylases; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D014466:Ultraviolet Rays; D051981:Uracil-DNA Glycosidase
D004269:DNA, Bacterial; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D001973:Bromodeoxyuridine