The C-C (6-4) UV photoproduct is mutagenic in Escherichia coli.

AUTOR(ES)

Glickman, B W

RESUMO

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 X C to A X 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.

Documentos Relacionados

• The T-T pyrimidine (6-4) pyrimidinone UV photoproduct is much less mutagenic in yeast than in Escherichia coli.
• Kinetics of pyrimidine(6-4)pyrimidone photoproduct repair in Escherichia coli.
• The thymine-thymine pyrimidine-pyrimidone(6-4) ultraviolet light photoproduct is highly mutagenic and specifically induces 3' thymine-to-cytosine transitions in Escherichia coli.
• Purification of a novel UV-damaged-DNA binding protein highly specific for (6-4) photoproduct.
• The (6-4) photoproduct of thymine-thymine induces targeted substitution mutations in mammalian cells.