Nucleotide Exchange Factors for Hsp70s Are Required for [URE3] Prion Propagation in Saccharomyces cerevisiae

The [URE3] and [PSI+] prions are infectious amyloid forms of Ure2p and Sup35p. Several chaperones influence prion propagation: Hsp104p overproduction destabilizes [PSI+], whereas [URE3] is sensitive to excess of Ssa1p or Ydj1p. Here, we show that overproduction of the chaperone, Sse1p, can efficiently cure [URE3]. Sse1p and Fes1p are nucleotide exchange factors for Ssa1p. Interestingly, deletion of either SSE1 or FES1 completely blocked [URE3] propagation. In addition, deletion of SSE1 also interfered with [PSI+] propagation