TABLE 1

The drug sensitivity profile of JN394 top2–4 expressing βwt or βE522K in the presence of different cytotoxics at 35°C The yeast strain JN394 top2–4 was transformed with recombinant plasmid encoding either βwt or βE522K. The transformed strains were tested for drug sensitivity to different concentrations of topo II poisons. Equal amounts of each transformant as determined by optical density were plated in a series of dilutions onto adenine-supplemented yeast extract/peptone/dextrose with drug and were grown at 35°C for 5 days. After 5 days, the extent of growth was assessed by comparing the number of yeast colonies to the wt. The results shown here are the amount of growth of yeast colonies: ++++, very good growth (e.g., growth at all dilutions); +++, good growth; ++, reasonable growth; +, poor growth (e.g. growth at just the most concentrated plating); and -, no growth. Comparisons of the level of growth from several dilutions on plates containing several different drug concentrations allowed approximate fold resistance values to be determined. The experiment was performed in duplicate.