Variant-specific [PSI+] infection is transmitted by Sup35 polymers within [PSI+] aggregates with heterogeneous protein composition.
The [PSI(+)] prion is the aggregated self-propagating form of the Sup35 protein from the yeast Saccharomyces cerevisiae. Aggregates of Sup35 in [PSI(+)] cells exist in different heritable conformations, called "variants," and they are composed of detergent-resistant Sup35 polymers, which may be closely associated with themselves, other proteins, or both. Here, we report that disassembly of the aggregates into individual Sup35 polymers and non-Sup35 components increases their infectivity while retaining their variant specificity, showing that variant-specific [PSI(+)] infection can be transmitted by Sup35 polymers alone. Morphological analysis revealed that Sup35 isolated from [PSI(+)] yeast has the appearance of short barrels, and bundles, which seem to be composed of barrels. We show that the major components of two different variants of [PSI(+)] are interacting infectious Sup35 polymers and Ssa1/2. Using a candidate approach, we detected Hsp104, Ssb1/2, Sis1, Sse1, Ydj1, and Sla2 among minor components of the aggregates. We demonstrate that Ssa1/2 efficiently binds to the prion domain of Sup35 in [PSI(+)] cells, but that it interacts poorly with the nonaggregated Sup35 found in [psi(-)] cells. Hsp104, Sis1, and Sse1 interact preferentially with the prion versus nonprion form of Sup35, whereas Sla2 and Ssb1/2 interact with both forms of Sup35 with similar efficiency.
Bagriantsev
Sviatoslav N
SN
Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA.
Gracheva
Elena O
EO
Richmond
Janet E
JE
Liebman
Susan W
SW
D015151:Immunoblotting; D010454:Peptide Termination Factors; D011108:Polymers / Q000737:chemistry* / Q000378:metabolism*; D011328:Prions / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology
D010454:Peptide Termination Factors; D011108:Polymers; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012967:Sodium Dodecyl Sulfate