[URE3] prion propagation in Saccharomyces cerevisiae: Requirement for chaperone Hsp104 and curing by overexpressed chaperone Ydj1p

The [URE3] nonchromosomal genetic element is an infectious form (prion) of the Ure2 protein, apparently a self-propagating amyloidosis. We find that a n insertion mutation or deletion of HSP104 results in inability to propagat e the [URE3] prion. Our results indicate that Hsp104 is a common factor in the maintenance of two independent yeast prions. However, overproduction of Hsp104 does not affect the stability of [URE3], in contrast to what is fou nd for the [PSI+] prion, which is known to be cured by either overproductio n or deficiency of Hsp104. Like Hsp104, the Hsp40 class chaperone Ydj1p, wi th the Hsp70 class Ssa1p, can renature proteins. We find that overproductio n of Ydj1p results in a gradual complete loss of [URE3]. The involvement of protein chaperones in the propagation of [URE3] indicates a role for prote in conformation in inheritance.