Destabilizing Interactions Among [PSI⁺] and [PIN⁺] Yeast Prion Variants

Corresponding author: Susan W. Liebman, University of Illinois, 900 S. Ashland Ave., Chicago, IL 60607., suel{at}uic.edu (E-mail)

Communicating editor: F. WINSTON

The yeast Sup35 and Rnq1 proteins can exist in either the noninfectious soluble forms, [psi^-] or [pin^-], respectively, or the multiple infectious amyloid-like forms called [PSI⁺] or [PIN⁺] prion variants (or prion strains). It was previously shown that [PSI⁺] and [PIN⁺] prions enhance one another's de novo appearance. Here we show that specific prion variants of [PSI⁺] and [PIN⁺] disrupt each other's stable inheritance. Acquiring [PSI⁺] often impedes the inheritance of particular [PIN⁺] variants. Conversely, the presence of some [PIN⁺] variants impairs the inheritance of weak [PSI⁺] but not strong [PSI⁺] variants. These same [PIN⁺] variants generate a single-dot fluorescence pattern when a fusion of Rnq1 and green fluorescent protein is expressed. Another [PIN⁺] variant, which forms a distinctly different multiple-dot fluorescence pattern, does not impair [PSI⁺] inheritance. Thus, destabilization of prions by heterologous prions depends upon the variants involved. These findings may have implications for understanding interactions among other amyloid-forming proteins, including those associated with certain human diseases.

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