Figure 3. Radicicol sensitivity assay. A null mutation at the yeast STI1 locus confers sensitivity to the HSP90 inhibitor radicicol (RD) resulting in slow growth at 30 °C on rich media (asterisks). The glaucoma-associated STI1 variant K434R and the yeast-equivalent K470R do not alter growth on RD plates. Co-expression of yeast UTP21 mutations (L5P, S602F, D621G) which genetically interact with sti1^- does not affect sensitivity to RD, either alone or in combination with hSTI1(K434R).