Role of Fapy glycosylase and UvrABC excinuclease in the repair of UVA (320-400 nm)-mediated DNA damage in Escherichia coli.
In contrast to the damage caused by far-UV, the damage caused by UVA (320-400 nm) is largely oxygen dependent, suggesting near-UV-mediated DNA damage involves reactive oxygen species. The DNA repair enzymes that recognize oxidized bases may, therefore, be an important part of the cell's near-UV defense repertoire. To evaluate the relative importance of Fpg (Fapy) glycosylase (an enzyme known to remove oxidized bases) and the DNA damage-inducible UvrABC excinuclease in recovery from near-UV-induced stress, we have constructed fpg- and uvrA- derivatives of Escherichia coli and tested the response (survival) of these strains to both UVA and far-UV radiation. Relative to control strains, the fpg- derivatives were found to be consistently more sensitive to the lethal effects of UVA, but not far-UV radiation. In contrast, uvrA- mutants were more sensitive than control strains to both UVA and far-UV radiation. Thymine dimers, known to be produced by far-UV and corrected by UvrABC, were not generated by the UVA fluences used in this study, suggesting that some other UVA-induced lesion(s) is recognized and repaired by this excinuclease.
Shennan
M G
MG
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Palmer
C M
CM
Schellhorn
H E
HE
D004249:DNA Damage; D043382:DNA-Formamidopyrimidine Glycosylase; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects*; D029968:Escherichia coli Proteins; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D013045:Species Specificity; D014466:Ultraviolet Rays
D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli