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The C-C (6-4) UV Photoproduct is Mutagenic in Escherichia coli

Barry W. Glickman, Roel M. Schaaper, William A. Haseltine, Ronnie L. Dunn and Douglas E. Brash
Proceedings of the National Academy of Sciences of the United States of America
Vol. 83, No. 18 (Sep. 15, 1986), pp. 6945-6949
Stable URL: http://www.jstor.org/stable/28289
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The C-C (6-4) UV Photoproduct is Mutagenic in Escherichia coli
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Abstract

Mutation induced by ultraviolet light is predominantly targeted by UV photoproducts. Two primary candidates for the premutagenic lesion are the cyclobutane pyrimidine dimer and the less frequent (by a factor of 10) pyrimidine-pyrimidone (6-4) photoproduct. Methylation of the 3-cytosine in the sequence 5 CCAGG 3 reduces the yield of (6-4) lesions, but not of cyclobutane dimers, at these sites. By taking advantage of mutants deficient in cytosine methylation, we show here that at the three sites in the lacI gene of Escherichia coli having this sequence, the specific increase in the formation of the (6-4) photoproducts is accompanied by a concomitant increase in mutation. At each site, a G· C to A· T transition results in an amber mutation. In the unmethylated state, these sites become among the most frequent nonsense mutations recovered. We conclude that the (6-4) photoproduct constitutes a major premutagenic lesion in E. coli.

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