FIGURE 5.
UPR induction in arv1Δ mutants is synergistic with the detection of unfolded proteins in the ER lumen. A, plasmids mutated at interface 1 (IFIL) or interface 2 (IFIIL) of the Ire1p core luminal domain rescue arv1Δ ire1Δ synthetic lethality, as represented by growth on a URA-based selection medium. Counterselection for the plasmid by growth on 5-fluoroortic acid (5-FOA) restores the synthetic lethal phenotype. The empty vector control (pRS416) in the arv1Δ ire1Δ strains was inviable. Control genotype refers to yeast strains in the same genetic background as the double mutants. B, Northern blot analysis of HAC1 mRNA in ire1Δ and arv1Δ ire1Δ strains expressing control Ire1p, IFIL Ire1p, or IFIIL Ire1p with or without 2 mm DTT treatment. EV, empty vector control. Unspliced HAC1u and spliced (induced) HAC1i are indicated; lower bands are splicing intermediates. HAC1 splicing was calculated as HAC1i/(HAC1i + HAC1u) based on densitometry.