Selfish prion of Rnq1 mutant in yeast

Abstract

[PIN+]is a prion form of Rnq1 in Saccharomyces cerevisiae and is necessary for the de novo induction of a second prion, [PSI+]. We previously isolated a truncated form of Rnq1, named Rnq1Δ100, as a [PSI+]-eliminating factor in S. cerevisiae. Rnq1Δ100 deletes the N-terminal non-prion domain of Rnq1, and eliminates [PSI+]in [PIN+]yeast. Here we found that [PIN+] is transmissible to Rnq1Δ100 in the absence of full-length Rnq1, forming a novel prion variant [RNQ1Δ100+]. [RNQ1Δ100+]has similar [PIN+]properties as it stimulates the de novo induction of [PSI+] and is eliminated by the null hsp104Δ mutation, but not by Hsp104 overproduction. In contrast, [RNQ1Δ100+] inherits the inhibitory activity and hampers the maintenance of [PSI+] though less efficiently than [PIN+]made of Rnq1-Rnq1Δ100 co-aggregates. Interestingly, [RNQ1Δ100+] prion was eliminated by de novo [PSI+] induction. Thus, the [RNQ1Δ100+] prion demonstrates selfish activity to eliminate a heterologous prion in S. cerevisiae, showing the first instance of a selfish prion variant in living organisms. © 2009 The Authors Journal compilation © 2009 by the Molecular Biology Society of Japan/Blackwell Publishing Ltd.