The Sup35 domains required for maintenance of weak, strong or undifferentiated yeast [PSI+] prions.
The Sup35 protein can exist in a non-infectious form or in various infectious forms called [PSI+] prion variants (or prion strains). Each of the different [PSI+] prion variants converts non-infectious Sup35 molecules into that prion variant's infectious form. One definition of a 'prion domain' is the minimal fragment of a prion protein that is necessary and sufficient to maintain the prion form. We now demonstrate that the Sup35 N region (residues 1-123), which is frequently referred to as the 'prion domain', is insufficient to maintain the weak or strong [PSI+] variants per se, but appears to maintain them in an 'undifferentiated' [PSI+] state that can differentiate into weak or strong [PSI+] variants when transferred to the full-length Sup35 protein. In contrast, Sup35 residues 1-137 are necessary and sufficient to faithfully maintain weak or strong [PSI+] variants. This implicates Sup35 residues 124-137 in the variant-specific maintenance of the weak or strong [PSI+] forms. Structure predictions indicate that the residues in the 124-137 region form an alpha-helix and that the 1-123 region may have beta structure. In view of these findings, we discuss a plausible molecular basis for the [PSI+] prion variants as well as the inherent difficulties in defining a 'prion domain'.
Bradley
Michael E
ME
Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, IL 60607, USA.
Liebman
Susan W
SW
D000818:Animals; D015153:Blotting, Western; D015966:Gene Expression Regulation, Fungal; D014644:Genetic Variation; D010454:Peptide Termination Factors; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011328:Prions / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins