Figure 4.

Folding stressors activate the PSR via transcription of RPN4 and do not increase UPS substrate load. (A) Schematic of a HSR reporter (right) and its fold GFP induction in titrations of bortezomib, canavanine, and AZC (left). (B) Schematic of a pRPN4 reporter (right) and its fold GFP induction in titrations of bortezomib, canavanine, and AZC (left). (C) Schematic of the RPN4 locus in wild type or a pYEF3:RPN4 background (right), and measurements of fold PSR activity in stressor titrations for both strains (left). (D) Measurements of Cyto-Deg (top) and ERm-Deg (bottom) fold stability for titrations of bortezomib, canavanine, or AZC in either a wild type (solid) or pYEF3:RPN4 (dotted) background. Titrations of both strains are normalized to the no-treatment values of each reporter. (E) Mean fold activity of the HSR or PSR at 37°C relative to 30°C in wild-type cells. (F) Mean fold activity of the HSR (left) or PSR (right) relative to wild type upon deletion of HSC82, SSA2, HSP104, or UMP1. For titrations, significance was collectively tested across the three highest concentrations measured by combining data from these concentrations into one group per genetic context, then performing a paired two-sided Student’s t test. Error bars denote standard error for n ≥ 3 biological replicates. ns, P > 0.05; *, P < 0.05; **, P < 0.01; and ***, P < 0.001.