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- Title
N-Terminal Domain of Yeast Hsp 104 Chaperone Is Dispensable for Thermotolerance and Prion Propagation but Necessary for Curing Prions by Hsp 104 Overexpression.
- Authors
Guo-Chiuan Hung; Masison, Daniel C.
- Abstract
Hsp104 is a hexameric protein chaperone that resolubilizes stress-damaged proteins from aggregates. Hsp104 promotes [PS1+] prion propagation by breaking prion aggregates, which propagate as amyloid fibers, into more numerous prion ‘seeds.’ Inactivating Hsp104 cures cells of [PS1+] and other amyloid-like yeast prions. Overexpressing Hsp104 also eliminates [PS1+], presumably by completely resolubilizing prion aggregates. Inexplicably, however, excess Hsp104 does not cure the other prions. Here we identify missense mutations in Hsp104's amino-terminal domain (NTD), which is conserved among Hsp100 proteins but whose function is unknown, that improve [PS1+] propagation. Hsp104Δ47, engineered to lack the NTD, supported [PS1+] and functioned normally in thermotolerance and protein disaggregation. Hsp104Δ147 failed to cure [PS1+] when overexpressed, however, implying that excess Hsp104 does not eliminate [PS1+] by direct dissolution of prion aggregates. Curing of [PS1+] by overexpressing catalytically inactive Hsp104 (Hsp104KT), which interferes with endogenous Hsp104, did not require the NTD. We further found that Hsp104 mutants defective in threading peptides through the hexamer pore had reduced ability to support [PS1+] in proportion to protein resolubilization defects, suggesting that [PS+] propagation depends on this threading and that Hsp104 ‘breaks’ prion aggregates by extracting protein monomers from the amyloid fibers.
- Subjects
PRIONS; MOLECULAR chaperones; AMYLOID beta-protein; PRION diseases; MUTAGENESIS; GENETIC mutation
- Publication
Genetics, 2006, Vol 173, Issue 2, p611
- ISSN
0016-6731
- Publication type
Article
- DOI
10.1534/genetics.106.056820