The repair of UV-damaged DNA in Escherichia coli is controlled by the uvr genes (A, B and C)1,2. These genes are also thought to be involved in the repair of chemically damaged DNA3-5, however their specific roles in repairing the multiplicity of different adducts that can be produced by chemical carcinogens are not well understood. We have investigated the repair of DNA damaged by different chemical carcinogens and transfected into E. coli strains with mutations in different uvr genes. The major product of DNA damage by N-acetoxy-2-acetylaminofluorene (NA-AAF) is N-(guanin-C8-yl)-2- acetylaminofluorene (G-C8-AAF)6. Our results suggest that, like UV-induced pyrimidine dimers, the repair of this adduct requires all three uvr genes. However, the repair of DNA damaged by N-hydroxy-aminofluorene (N-OH-AF, the major adduct of which is N-(guanin-C8-yl)-2-aminofluorene, G-C8-AF) seems only to require the uvrC gene.
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