Differences in removal of acetylaminofluorene and pyrimidine dimers from the DNA of cultured mammalian cells.

Abstract

The rate and extent of disappearance of 2 DNA lesions (pyrimidine dimers and covalently bound acetylaminofluorene), both thought to be removed by the so-called wide-patch (approximately 100 nucleotides) repair process, were studied in a variety of cultured mammalian [human foreskin fibroblast Fu cells, El San human skin fibroblasts, human embryonic lung fibroblast WI-38 cells, Hartley guinea-pig embryo cells, NIH Swiss mouse embryo cells, BALB/c 3T3 cells, rat kangaroo (Potorous tridactylus) PT-K2 Kidney cells] cells. With the exception of mouse cells, dimers were removed more rapidly and extensively than covalently bound acetylaminofluorene. In human cells, e.g., about 50% of the dimers were excised from DNA in 1 h while only 25-50% of the chemically induced lesions were excised from DNA after 48 h. Mouse cells, which removed few dimers, were about as competent as control human fibroblasts at removing acetylaminofluorene lesions, but xeroderma pigmentosum cells (group D) removed fewer N-acetoxy-2-acetylaminofluorene-induced lesions than control human cells. There may be separate repair processes for these 2 types of lesions and their expression may be under similar genetic control in human cells.