UV-INDUCED MUTATIONS OF SUPF GENE ON A SHUTTLE VECTOR PLASMID IN P53-DEFICIENT MOUSE CELLS ARE QUALITATIVELY DIFFERENT FROM THOSE IN WILD-TYPE CELLS

To verify the genetic instability of p53-deficient cells, UV-induced m utation of the supF gene on a shuttle vector was analyzed. UV-irradiat ed or non-irradiated shuttle vector plasmid carrying the supF gene as a target of mutation (pYZ289) was introduced into p53-deficient and p5 3-proficient mouse embryonic fibroblasts, and then the plasmid DNA rep licated in mouse cells was recovered. Survival of UV-irradiated plasmi d was almost equivalent in both p53-deficient and p53-proficient cells . The frequencies of UV-induced mutation of the supF gene were also th e same in both types of cells. However, the distributions of base chan ge mutations in the supF sequence were different between p53-deficient and p53-proficient cells; especially the locations of tandem CpC to T pT changes exhibited a marked difference. Since DNA repair activities of these two types of cell were almost the same, these qualitative dif ferences in UV-induced mutations were probably caused by as yet uniden tified differences in other than DNA repair activity.