The Hsp42 PrLD is essential for CytoQ formation. (A) Hsp42 domain organization. Hsp42 consists of an NTE composed of two IDDs (PrLD and IDD) followed by the ACD and a CTE. Prediction of intrinsically unfolded protein segments according to Foldindex (Prilusky et al., 2005) and the relative abundance of specific amino acids within each Hsp42 domain are shown. The average amino acid abundance of the yeast proteome is included as reference. (B) Schematic diagrams of Hsp42 WT and deletion constructs. F, FLAG tag. (C) mCherry-VHL localization patterns in S. cerevisiae hsp42Δ cells expressing Hsp42 WT or the indicated Hsp42 deletion mutants and their superposition with the nuclear marker Htb1-cerulean upon control conditions (30°C) and proteotoxic stress (37°C + MG132) are shown. The number of cells showing CytoQ (mCherry-VHL foci distant from the Htb1-cerulean signal) or INQ (mCherry-VHL foci adjacent or overlapping with the Htb1-cerulean signal) inclusions was quantified (n > 50/sample). (D) Immunofluorescence images of Hsp42 WT and deletion mutants and their superposition with mCherry-VHL and DAPI upon control conditions (30°C) and proteotoxic stress (37°C for 30 min + MG132) are shown. Maximal projections of widefield z stack images are presented. Bars, 2 µm.