Sites of preferential induction of cyclobutane pyrimidine dimers in the nontranscribed strand of lacI correspond with sites of UV-induced mutation in Escherichia coli.
An approach utilizing fluorescence-activated DNA sequencing technology was used to study the position and frequency of UV-induced lesions in the lacI gene of Escherichia coli. The spectrum of sites of UV damage in the NC+ region of the gene was compared with a published spectrum of UV-induced mutation in lacI (Schaaper, R.M., Dunn, R.L., and Glickman, B.W. (1987) J. Mol. Biol. 198, 187-202). On average, the frequency of UV-induced lesions in the nontranscribed strand was higher than that in the transcribed strand in the region analyzed. A large fraction of mutations occurs at sites of UV-induced lesions in the nontranscribed strand, but not in the transcribed strand. This bias is reduced in an excision repair deficient (UvrB-) strain. In addition, mutations occur overwhelmingly at sites where a dipyrimidine sequence is present in the nontranscribed strand. This bias is also markedly reduced in the UvrB- strain. In light of recent work Mellon and Hanawalt (Mellon, I., and Hanawalt, P.C. (1989) Nature 342, 95-98) describing the preferential removal of cyclobutane dimers from the transcribed strand of the expressed lacZ gene in E. coli, our data suggest that preferential strand repair may have a significant effect on mutagenesis.
Koehler
D R
DR
Department of Biology, York University, North York, Ontario, Canada.
Awadallah
S S
SS
Glickman
B W
BW
D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects; D005453:Fluorescence; D005798:Genes, Bacterial; D009154:Mutation; D011740:Pyrimidine Dimers / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
D011740:Pyrimidine Dimers