Excision repair reduces doxorubicin-induced genotoxicity.
LacI mutations induced by doxorubicin in a wild-type, uvr(A)BC repair-proficient E. coli strain were analyzed by DNA sequencing. These mutations were contrasted with mutations previously recovered from doxorubicin-treated uvrB- organisms in order to assess the role of excision repair in doxorubicin-induced genotoxicity. After a 30-min exposure of wild-type E. coli to 330 microM doxorubicin, survival was 34% and the overall lacI mutation frequency increased 1.8-fold to 340 x 10(-8). The distribution of doxorubicin-induced mutants among subclasses of mutation involving the i-d and lac operator regions differed significantly between repair-proficient and -deficient strains. Distributional differences appeared to result both from a decrease in deletions involving the lac operator and an increase in base substitutions involving the i-d region in repair proficient organisms. However, elements of the doxorubicin-induced mutation spectrum in uvrB- E. coli are still discernable in wild-type organisms. These elements include the remarkable shift of 3'-deletion endpoints to palindromic sequence within the lac operator and the recovery of multiple isolates of T:A-->A:T transversions at position 96 in doxorubicin-treated cultures. These observations suggest that components of the uvr(A)BC nucleotide excision repair system function through a general mechanism prior to fixation of mutations to reduce, but not completely eliminate, the genotoxic effects of doxorubicin.
Anderson
R D
RD
Ireland Cancer Center Research Laboratories/Case Western Reserve University, Cleveland, OH 44106.
Veigl
M L
ML
Baxter
J
J
Sedwick
W D
WD
D001483:Base Sequence; D004252:DNA Mutational Analysis; D004260:DNA Repair; D004269:DNA, Bacterial; D004317:Doxorubicin / Q000633:toxicity*; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009153:Mutagens / Q000633:toxicity*
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D009153:Mutagens; D004317:Doxorubicin; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC