INDUCTION OF FRAMESHIFT MUTATIONS IN CULTURED-MAMMALIAN-CELLS WITHIN A TRANSFECTED SEQUENCE CONTAINING A POLY(DC-DA)CENTER-DOT-POLY(DT-DG) MICROSATELLITE

A cultured mouse cell line with an integrated copy of a plasmid that c ontains a short dinucleotide repeat sequence (microsatellite) has been used to determine the frequencies and types of mutation induced by tw o frameshift mutagens. The presence of the microsatellite, which consi sts of 17 repeats of a poly(dC-dA) . poly(dT-dG) sequence, disrupts th e reading fro me of a gene coding for neomycin resistance. Revertants were selected in G418, and mutations were analyzed by PCR. ICR-170 was found to increase the reversion frequency by ten- to 15-fold at its I D50, although most of the frameshifts that it induced were single-base insertions outside the microsatellite sequence. NA-AAF brought about a more modest increase in mutation frequency, but nearly all of the re vertants in the NA-AAF-treated cultures had insertions or deletions of multiples of two base pairs within the DNA segment that included the microsatellite. This system can be modified to include different short tandem repeat sequences as targets for testing of compounds that ore suspected of having frameshift-inducing activities. (C) 1996 Wiley-Lis s, Inc.