S. cerevisiae Sup35p inhabits two metastable states: functional translation termination factor; and prion-like aggregate [PSI+], which propagates by converting soluble Sup35p to its own misfolded form. Once initiated, Sup35p polymerization in [PSI+] cells is spontaneous, but [PSI+] prion inheritance depends on the Hsp104p disaggregase. To identify Hsp104-interacting sequences, Sup35p was subjected to a systematic deletion screen. [PSI+] maintenance by mutant Sup35p was assessed in both presence and absence of plasmid-encoded WT Sup35p in haploid sup35 cells. Large deletions abolished [PSI+], implying perturbations of prion structure, while others imparted [PSI+]-dependent toxicity. Removal of a single 25aa segment destabilised [PSI+] inheritance, resulting in enhanced rates of prion loss. This is consistent with the expected prion propagation defect in response to reduced Hsp104p interaction. However, several mutants containing this 25aa segment share the destabilised prion phenotype, suggesting chaperone/prion interactions are strongly context-dependent, and no one Sup35p region is solely responsible for Hsp104p recognition.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/17160 |
| Date | 24 February 2009 |
| Creators | Davies, Linda Emily |
| Contributors | Glover, John R. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
| Format | 2200588 bytes, application/pdf |
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