Figure 1.

Cross-seeding models to interpret [PSI⁺] and [PIN⁺] de novo formation promoted by [SWI⁺] and Swi1 overproduction. (A) [PSI⁺] inducibility by Swi1 overproduction. Swi1 aggregates formed upon overproduction are mostly non-inheritable. The small amounts of Swi1 aggregates that can be used to cross-seed de novo [PSI⁺] formation may explain the low efficiency of Swi1 overproduction in promoting [PSI⁺] de novo appearance. (B) [PSI⁺] inducibility by [SWI⁺]. Since the amyloidogenic [SWI⁺] aggregates can be used as an imperfect template to directly cross-seed Sup35 for [PSI⁺] de novo formation, [SWI⁺] is a better Pin⁺ factor than Swi1 overproduction as more templates are available for cross-seeding Sup35. (C) [PIN⁺] induction by [SWI⁺] without Rnq1 overproduction. Rnq1 has a complex prion domain with an amino acid composition more similar to that of Swi1 compared to that of Sup35. Thus, [SWI⁺] amyloids might have a higher cross-seeding ability to Rnq1 than to Sup35 resulting in [PIN⁺] formation even in the absence of Rnq1 overproduction.