INCREASED TRANSVERSIONS IN A NOVEL MUTATOR COLON-CANCER CELL-LINE

We describe a novel mutator phenotype in the Vaco411 colon cancer cell line which increases the spontaneous mutation rate 10-100-fold over b ackground, This mutator results primarily in transversion base substit utions which are found infrequently in repair competent cells, Of the four possible types of transversions, only three were principally reco vered, Spontaneous mutations recovered also included transitions and l arge deletions, but very few frameshifts were recovered, When compared to known mismatch repair defective colon cancer mutators, the distrib ution of mutations in Vaco411 is significantly different, Consistent w ith this difference, Vaco411 extracts are proficient in assays of mism atch repair, The Vaco411 mutator appears to be novel, and is not an ob vious human homologue of any of the previously characterized bacterial or yeast transversion phenotypes, Several hypotheses by which this mu tator may produce transversions are presented.