Reidy M and Masison DC (2010) Sti1 Regulation of Hsp70 and Hsp90 Is Critical for Curing of Saccharomyces cerevisiae [PSI+] Prions by Hsp104. Mol Cell Biol 30(14):3542-52
Abstract: Although propagation of yeast prions requires Hsp104 protein disaggregating activity, overproducing Hsp104 "cures" cells of [PSI(+)] prions. Earlier evidence suggests Hsp70 mutant Ssa1-21 impairs [PSI(+)] by a related mechanism. Here we confirm this link by finding deletion of STI1, which suppress Ssa1-21 impairment of [PSI(+)], blocks Hsp104 curing of [PSI(+)]. Hsp104's TPR interaction motif was dispensable for curing, but cells expressing Sti1 defective in Hsp70 or Hsp90 interaction cured less efficiently and the Hsp90 inhibitor radicicol abolished curing, implying Sti1 acts in curing through Hsp70 and Hsp90 interactions. Accordingly, strains lacking constitutive or inducible Hsp90 isoforms cured at reduced rates. We confirm an earlier finding that elevating free ubiquitin enhances curing, but it did not overcome inhibition of curing caused by Hsp90 defects, suggesting Hsp90 machinery is important for the contribution of ubiquitin to curing. We also find curing associated with cell division. Our findings point to crucial roles of Hsp70, Sti1 and Hsp90 for efficient curing by overexpressed Hsp104, and provide evidence supporting the earlier suggestion that destruction of prions by protein disaggregation does not adequately explain the curing.
|Status: Published||Type: Journal Article||PubMed ID: 20479121|
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