In vivo formation and repair of cyclobutane pyrimidine dimers and 6-4 photoproducts measured at the gene and nucleotide level in Escherichia coli

摘要: In vivo formation and repair of the major UV-induced DNA photoproducts, cyclobutane pyrimidine dimers (CPDs) 6-4 pyrimidine-pyrimidone photoproducts (6-4 PPs), have been examined at gene nucleotide level in Escherichia coli. Each type photoproduct has individually studied using photoreactivation two newly developed assays; multiplex QPCR assay for damage detection reiterative primer extension (PE) level. E. coli lacI lacZ genes, CPDs PPs form a 2:1 ratio, respectively, during UV irradiation. Repair is more efficient than since, on average, 42% are repaired both genes first 40 min following 200 J/m(2) irradiation, while 1% repaired. The location, relative frequency formation, efficiency each was 52 codons Hotspots were found lesion. Most sites where formed. Allowing recovery shows that about fourfold CPDs. Comparison lesion-specific distribution with mutation spectrum from wild-type cells most mutational hotspots correlated majority CPD formation. However, also formed some these relatively high frequency. This information, taken together observation faster CPDs, suggest cause mutagenic inefficient