MUTATION-SPECTRUM OF A TRUE ABASIC SITE IN CODON 12 OF A C-HA-RAS GENE IN MAMMALIAN-CELLS

An abasic site is postulated to be a premutagenic lesion. We previousl y reported that a c-Ha-ras gene with an abasic site analogue at either the first or the second position of codon 12 induced the formation of foci by point-mutational activation of the gene [Kamiya et al. (1992) Nucleic Acids Res. 20, 4409-4415]. In this study we constructed c-Ha- ras genes with a true abasic site in codon 12. The ras genes were foun d to be activated in NIH3T3 cells by a mutation to A at the modified a nd flanking positions, and the flanking mutations were detected more f requently.