Data for paper on High Expression Levels of Hsp104 Cures the Yeast [PSI+] Prion by Dissolution of the Prion Seeds

The yeast Sup35 protein misfolds into the infectious [PSI+] prion, which is then propagated by the severing activity of the molecular chaperone, Hsp104. This prion is unique in that it is cured both by inactivation and overexpression of Hsp104. We previously proposed that the latter curing is due to the trimming activity of Hsp104 causing dissolution of the prion seeds. However, an alternative proposal is that this curing is due to Hsp104 causing asymmetric segregation of the prion seeds, which requires cell division. In support of the dissolution model, we find no difference in the extent of curing between mother and daughter cells when half of the cells are cured by Hsp104 overexpression in one generation. Furthermore, curing was not affected by the lack of expression of Sir2, a protein required for asymmetric segregation of misfolded proteins between mother and daughter cells. Even more importantly, when the curing of [PSI+] by Hsp104 overexpression was conducted in the presence of ethanol to arrest cell division, the Hsp104 expression still cured the [PSI+] prion. Therefore, the curing of [PSI+] by Hsp104 overexpression is not due to asymmetric segregation of the prion seeds, but rather to their dissolution by Hsp104.