(A, B) Ubiquitylation of the indicated HA-tagged Fzo1 mutant variants, expressed in wt and cdc48-2 cells in (A) or in ∆fzo1 and ∆fzo1cdc48-2 cells in (B). Total cell extracts were prepared and analyzed by SDS–PAGE and immunoblotting, using HA-specific antibodies. (C) Analysis of Cdc48-Fzo1 co-immunoprecipitation. The indicated HA-Fzo1 variants were expressed in Δfzo1 cells. Crude mitochondrial extracts were solubilized, subjected to co-immunoprecipitation, and analyzed by SDS–PAGE and Western blot using HA- and Cdc48-specific antibodies. (D) Localization of indicated Fzo1-GFP variants, expressed in ∆fzo1∆dnm1 and ∆fzo1∆dnm1cdc48-2 cells. Fzo1-GFP was co-expressed with Su9-mCherry. Fzo1-GFP foci were quantified as shown in Fig S3 in at least 100 cells showing a tubular mitochondrial network, including mean (bars) and individual experiments (circles, squares, and triangles). PoS, PonceauS staining.