Tuning Hsp70 Function: Investigating the Ability of Hsp40/Hsp70 Extragenic Suppressors to Promote Prion Propagation in Yeast

Abstract

Hsp70s are a versatile class of molecular chaperones, essential for a variety of cellular functions ranging from protein folding and transport to iron‐sulfur cluster biogenesis. Hsp70s function with obligate Hsp40 co‐chaperones, also called J‐proteins, which stimulate Hsp70 ATPase activity via their characteristic J‐domains. In Saccharomyces cerevisiae, the J‐protein Sis1 is essential for cell viability and the propagation of prions. However, the means by which Sis1 drives specific functions of Hsp70 are largely unknown. We recently reported the discovery of gain‐of‐function substitutions in both the J‐protein Ydj1 and the Hsp70 Ssa1 which allow cell survival without Sis1. Here we present additional data that support the ability of the suppressor mutants to substitute for Sis1‐dependent roles, specifically the maintenance of yeast prions. Specifically, we tested the ability of the two most robust suppressor mutations in both Ydj1 and Ssa1 to maintain two prions, [PSI‐+] and [RNQ+], and included both phenotypically strong and weak variants of [PSI‐+] in our analysis. Interestingly, we found similar results for all mutants: both Ydj1 mutants could substitute for the propagation of strong [PSI‐+], but not weak [PSI‐+] nor [RNQ+]. Similarly, we found that the Ssa1 mutants could not support the maintenance of weak [PSI‐+] nor [RNQ+]. Unfortunately, due to the severe [PSI‐+] toxicity in the compromised strain bearing strong [PSI‐+], we could not confidently determine the ability of the Ssa1 mutants to support strong [PSI‐+] propagation. Further investigation of additional Ydj1 and Ssa1 mutants may provide greater resolution regarding the specific functions required of J‐proteins by distinct prions for propagation.Support or Funding InformationThis work was supported by National Institutes of Health (https://www.nih.gov/) grants GM31107 and GM27870 (EAC) and R15GM110606 (JKH). This work was also supported by the Lafayette College Chemistry Department, the EXCEL research scholarship program, and the John F and Dorothy M Dorflinger Summer Research Endowment Fund (JKH).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.