FIG. 1.

Hsp90 mutants stimulate GCN4-lacZ expression under repressed conditions. (A) β-Galactosidase activity assayed in extracts prepared from the different yeast strains expressing Hsp90 mutants transformed with the GCN4-lacZ reporter plasmid p180 (schematically represented). Enzyme activities are given in units. (B) β-Galactosidase activity assayed for the panel A strains transformed with the control reporter plasmid p227 containing point mutations (×) in the ATGs of the four uORFs in the 5′-untranslated region of the GCN4 mRNA. The values are the means of three to four independent experiments. + a.a., with amino acids; − a.a., without amino acids; hHsp90, human Hsp90β; 10%, strain 10% Hsp82wt; G313N, HH1a-pHCA/Hsp82 G313N; T525I, HH1a-pHCA/Hsp82 T525I.