Figure 9.

Model for J‐protein involvement in prion fragmentation and Hsp104‐mediated curing of strong [PSI ⁺] and [URE3].

Model comes from Matveenko et al. (2018) with modifications. Abbreviations: 70, Hsp70; 104, Hsp104. J‐proteins Sis1 and Swa2 are required for [URE3] propagation, presumably for aggregate fragmentation to produce propagons (left side) (Higurashi et al., 2008; Troisi et al., 2015). [URE3] is relatively insensitive to Hsp104‐mediated curing so this process is omitted (Kryndushkin et al., 2011). Ydj1 overexpression potently cures [URE3] via competition with Sis1 (Higurashi et al., 2008; Reidy et al., 2014). For strong variants of [PSI ⁺] (right side), Sis1 and plausibly Ydj1 can participate in aggregate fragmentation (Higurashi et al., 2008; Tipton et al., 2008; Kirkland et al., 2011). As shown in this work, Apj1 and Sis1 are required for Hsp104‐mediated curing (shown here as malpartitioning of propagons), which Ydj1 potently inhibits (see Discussion for additional details).