. 2022 Jan 27;8(2):122. doi: 10.3390/jof8020122

Table 1.

Summary of the effects of PQC proteins on yeast prion propagation.

Protein	Perturbation	Variant	[PSI⁺]	[URE3]	[PIN⁺]	Comment	References
Hsp104
Hsp104	OE	FL	$↓ ↓$	↓/none	none		[49,62,63]
		KT *	$↓ ↓$	$↓ ↓$	$↓ ↓$		[49,50]
		$Δ$ N	↑	n.a.	n.a.	Increases [PSI⁺] induction rates	[42,65]
	$Δ$		$↓ ↓$	$↓ ↓$	$↓ ↓$		[49,51,103]
Hsp70
Ssa1	OE	FL	↑/none	↓/none	none	Prevents HSP104 OE curing of [PSI⁺]. Effects on [URE3-1] curing are not reproducible, the effect might be strain-specific	[62,73,78,104,105]
		SSA1-21	$↓ ↓$ /none	none	none	Dominant [PSI⁺] curing is strain-specific. The effect is more visible in the absence of either SSA1 or SSA2	[63,74,75,105],^†
Ssa2	OE	FL	↑/none	↓/none	n.a.	Prevents HSP104 OE curing	[62,79,104]
	Substitution	SSA2-21	$↓ ↓$	$↓ ↓$	n.a.		[63]
Ssa3	OE	FL	↑/none	none	n.a.	Prevents HSP104 OE curing	[62,79]
Ssa4	OE	FL	↑/↓	none	n.a.	Prevents HSP104 OE curing	[62,79]
Ssb1/2	OE	FL	↓	none	n.a.	Enhances HSP104 OE curing	[62,77,78]
	$Δ$		↑	n.a.	n.a.	Increases [PSI⁺] induction rates	[77,80]
Hsp40
Sis1	OE	FL	↓/none	none	none	Enhances HSP104 OE curing	[100,106,107]
	Depletion	FL	↑/↓	$↓ ↓$	$↓ ↓$	Effect on [PSI⁺] depends on depletion method (Tet-Off or relocalization)	[86,87,100,108]
	Substitution	$Δ$ DD	↓/none	↓	none	Prevents HSP104 OE curing	[44,89],^†
		$Δ$ CTD	↓	$↓ ↓$	$↓ ↓$	Prevents HSP104 OE curing	[44,89]
		JGF	↓	$↓ ↓$	$↓ ↓$	Prevents HSP104 OE curing	[44,89]
		K199A	↓	↓	n.a.	Prevents HSP104 OE curing	[44,89]
Ydj1	OE	FL	↑/↓/none	$↓ ↓$	none	Strain-dependent effect on [PSI⁺]	[51,78,100,109]
	$Δ$		none	none	none		[75,86,110]
Apj1	OE	FL	none	none	n.a.	Enhances HSP104 OE curing	[94,106,111]
	$Δ$		none	none	none		[86,110]
Zuo1	$Δ$		↑	none	none	Increases [PSI⁺] induction rates and rates of [PSI⁺] curing by mild heat shock	[40,80,86,110,112]
Swa2	$Δ$		none	↓	none		[86,110]
Protein-sorting factors
Cur1	OE	FL	↑/↓	↓	none	Strain-dependent effect on [PSI⁺]	[98,100,109]
	OE	$Δ$ 3-22	$↑ ↑$	$↓ ↓$	n.a.		[62,100]
	$Δ$		↓/none	↑	n.a.	Increases [URE3] induction rates; slightly weakens strong [PSI⁺] phenotype and enhances weak [PSI⁺] curing by mild heat shock	[98,100,113]
Btn2	OE	FL	none	$↓ ↓$	none		[98,100,113]
	$Δ$		↓	↑	n.a.	Increases [URE3] induction rates; enhances weak [PSI⁺] curing by mild heat shock	[98,100,113]
Hsp42	OE	FL	↑/↓/none	$↓ ↓$	n.a.		[100,113,114]

OE—overexpression, Δ—gene deletion or disruption, FL—full length protein. *—HSP104KT-a mutant allele of HSP104 containing two amino acid substitutions (K218T and K620T) (Figure 1b). Effects of chaperones on prions: ↑—subtle increase in strength of prion phenotype; ↑↑—substantial increase in strength of the prion phenotype; ↓—modest destabilization or weakening of prion phenotype; ↓↓—complete or near complete prion elimination. ^†—novel results presented in this work (Figure 2).