DCTP MISINCORPORATION IN A CHINESE-HAMSTER MUTATOR PHENOTYPE - THE ROLE OF GGA GENETIC CONTEXT

Clone CSA7 is a CHEF18 hamster cell line that shows an increased intra cellular accumulation of dCTP. To localize the mutations that accumula te spontaneously in a functional gene of such a mutator phenotype, ind ependent CSA7 mutants of the hypoxanthine-guanine phosphoribosyl trans ferase (hprt) gene were isolated and screened by a polymerase chain re action-single strand conformation polymorphism technique, Sixty-two pe rcent of mutants produced detectable changes of the strand migration p rofile and the mutations were preferentially localized in the exons 3 (31%) and 6 (62%), The sequencing of such exons revealed that the rate of C base incorporation was the major mutation pathway and that the A base of a GGA sequence was the preferential site of misincorporation.