Figure 2.

Induction of Hac1p requires 3′UTR of HAC1 mRNA. The ERN⁺, ern1Δ, and hac1Δ strains with the UPRE-CYC1-lacZ reporter gene integrated into the respective chromosome (KMY1105, 1115, and 1145, respectively) were transformed with a vector alone (V) or a single-copy expression plasmid carrying the wild-type (WT) or a mutant (ΔHN or ΔHA) HAC1 gene, whose structures are schematically drawn at the bottom. bZIP and polyA denote the bZIP region and the polyadenylation site, respectively. Transformants were grown at 30°C in SC(−Ura, Leu) medium to a midlogarithmic phase, and aliquots were incubated in the presence (hatched bars) or absence (solid bars) of tunicamycin (TM). Samples taken after 3 h were used for β-galactosidase assays, and the activities are presented as the mean ± SD, based on duplicate determinations with three independent transformants. Separate samples taken after 1 h were used for extracting total proteins that were analyzed by immunoblotting with purified anti-Hac1p antibodies.