Fig. 2. Activity of the Ire1 mutants as measured by a UPRE-lacZ reporter. KMY1015 (ire1 null mutant) cells carrying both pCZY1 (UPRE-lacZ reporter plasmid) and pRS315-Ire1-HA or mutant alleles were cultured with (+) or without (–) 2 µg/ml tunicamycin (Tun) for 4 hours and subjected to -galactosidase assay. For the empty vector control (ire1), pRS315 was used instead of pRS315-Ire1-HA. In all three panels, each value is the mean ± s.d. for three independent clones and was normalized to that of the Tun+ wild-type Ire1-HA control, which was set at 100.