A) Growth of wild-type and ire1Δ strains expressing an empty vector, IRE1 wild-type, and ire1-C832S, as indicated. Cells were spotted in three-fold serial dilutions onto plates containing no drug, tunicamycin (1 μg/ml), or sodium arsenite (1 mM) and cultured for 2-4 days at 30°C.
B) Arsenite-induced activation of the Hog1 is unaffected in the ire1Δ mutant. Cells were treated with sodium arsenite (1 mM) for hour. Whole cell extracts were prepared and analyzed by SDS-PAGE followed by immunoblotting for phosphorylated and total Hog1. Lower panel, Pgk1 (loading control). A parallel treatment with osmotic stress (0.4 M NaCl for 5 min) confirms the assignment of the phosphorylated Hog1 species. Parallel analysis of the hog1Δ strain confirms the accuracy of the Hog1 antibodies.