FAILURE TO DETECT AN ANTIMUTATOR PHENOTYPE FOLLOWING DISRUPTION OF THE SACCHAROMYCES-CEREVISIAE DDR48 GENE

The antimutator phenotype, reportedly conferred by disruption of the S accharomyces cerevisiae DDR48 gene, was suggested to affect only a spe cific spontaneous mutational pathway. We attempted to identify the typ es of mutation that are DDR48-dependent by determining the specificity of the ddr48 antimutator. However, disruption of DDR48 did not decrea se the rates of spontaneous forward mutation in a plasmid-borne copy o f the yeast SUP4-o gene, the reversion or suppression of the lys2-1 al lele, or forward mutation at the CAN1 locus. Interestingly, the latter gene had been reported previously to be subject to the antimutator ef fect, DNA sequence analysis of spontaneous SUP4-o mutations arising in DDR48 and ddr48 backgrounds provided no evidence for a reduction in t he rates of individual mutational classes. Thus, we were unable to ver ify that disruption of DDR48 causes an antimutator phenotype.