Enhanced restriction site mutation (RSM) analysis of 1,2-dimethylhydrazine induced mutations, using endogenous p53 intron sequences

The restriction site mutation (RSM) assay was used to studythe mutational sensitivities of three target regions of themurine p53 gene. The non-coding intron 6 target region was comparedwith the coding regions exon 4 and exon 5 with respect to theirrelative sensitivity to the induction of mutations by 1,2-dimethylhydrazine(DMH). Our results demonstrated that the majority of inducedmutations detected were in the intron 6 gene region. A totalof 15 enzyme-resistant restriction sites were detected in DMHtreated mice, nine of these in the intron 6 region, four inthe exon 4 region and two in the exon 5 region. The elevated sensitivity of the intron 6 region was exemplified by our detectionof spontaneous mutations in this region; two resistant restrictionsites were detected in untreated animals. No spontaneous mutationswere detected in either of the exon sequences studied here,nor have any been detected in exon targets in our previous invivo RSM analyses. The mutations induced by DMH were mostlyGC