Figure 4. Mutations in HSP90 confer resistance to azole and geldanamycin in two S. cerevisiae lineages and in one C. albicans lineage.

(A) Sc-G-12 (right panel) and Sc-G-14 (left panel) are both resistant to azole and geldanamycin and slightly cross-resistant to azole and radicicol, relative to their parental strains (above). (B) Resistance to azole and geldanamycin in Sc-G-14 is attributable to HSC82^I117N. Replacing the ancestral allele with the HSC82^I117N allele expressed on a plasmid increases resistance of the ancestral strain to the level observed in Sc-G-14, while replacing the HSC82^I117N allele with the ancestral allele on a plasmid abrogates resistance of Sc-G-14. (C) Deletion of HSC82 in Sc-G-12 or its parental strain phenocopies resistance of Sc-G-12, suggesting that HSC82^K385* confers resistance by loss of function of HSC82. (D) Ca-G-10 has increased resistance to azole and geldanamycin but no cross-resistance to azole and FK506 or azole and radicicol. (E) Resistance to azole and geldanamycin in Ca-G-10 is attributable to HSP90^D91Y. Replacing the native HSP90 allele in parental strain with HSP90^D91Y phenocopied resistance of Ca-G-10. Conversely, resistance of Ca-G-10 was abrogated when HSP90^D91Y was replaced with the ancestral HSP90 allele. Resistance assays were performed and analyzed is in Figure 2, after incubation at 30°C for 2 days (D) or 3 days (A–C, E). Assays were performed in YPD (A, C–E) or SD with amino acid supplements (B). GdA = geldanamycin; RAD = radicicol; and FL = fluconazole.