Site specific cleavage of φX-174 replicative form DNA after modification by N-acetoxy-N-2-acetylaminofluorene

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Abstract
Three kinds of structural disturbances were found in an 88 base pair (bp) fragment of φX-174 DNA after exposure to N-acetoxy-N-2-acetylaminofluorene (N-Aco-AAF). (i) Frequent strand scissions at two specific guanine sites on the 5′ 32P-end-labeled fragment were identified by base sequence analysis. Scissions at these two sites were induced at neutral pH and they were not increased by treatment with apurinic endonuclease. They are an immediate consequence of N-Aco-AAF action and are not primarily apurinic sites, (ii) Alkali treatment with 1 M piperidine at 90°C induced strand scissions at every guanine, demonstrating adduct slices, depurination and strand scissions, (iii) Adducted DNA was sensitive to single-strand specific nuciease digestion, suggesting unwound DNA. These studies indicate the prediliction of N-Aco-AAF for certain DNA sites and they suggest three kinds of DNA modifications which can be expected after adduction by this carcinogen. Some of the sites may be premutational carcinogen-induced DNA structural modifications.