(A–B) Atg8 is required for localization of Ccz1 to autophagosomes. Graphs show percentage of colocalization of Ccz1 puncta (A) or Ypt7 puncta (B) relative to Ape1 puncta in wild-type and the different mutants. Cells were grown and analyzed as in Figure 1. Ape1 dots (n ≥ 50), Ccz1 dots (n ≥ 300), and Ypt7 dots (n ≥ 200) were quantified by Image J. Error bars represent SD. (C–E) Interaction analysis of Atg8 with Mon1-Ccz1. (C) Immunoprecipitation of TAP-tagged Ccz1 from wild-type and atg4∆ strain co-expressing GFP-Atg8. The strain was grown in YPD or in SD-N for 3 hr before preparing cell extracts. GFP-Atg8 was subsequently immunoprecipitated using GFP-trap beads. Finally, immunoprecipitates were analyzed by Western blotting against GFP and CbP-tag. The graph is the quantification of three independent experiments, where the interaction observed in unstarved cells from wild-type is set as 1. Error bars are SD. (D) Interaction of Atg8 with Mon1-Ccz1 or purified Ccz1. TAP-tagged proteins (shown as purified proteins on Coomassie stained gels to left) were incubated with GST, GST-ubiquitin, and GST-Atg8 immobilized on GSH-Sepharose. Eluted proteins were resolved by SDS-PAGE and analyzed by Western blotting against the CbP-tag (top) or by Coomassie staining (bottom). Load, 10%. (E) Interaction of Atg8 mutants with Mon1-Ccz1. Analysis was done as in (D) with the indicated GST-tagged Atg8 truncation mutants. (F) Interaction of Mon1-Ccz1∆C with Atg8. Mon1-Ccz1∆C was purified as wild-type and analyzed for interaction with GST-tagged Atg8 as before. Top, Western blot against the CbP tag. A star indicates the additional decoration of GST-Atg8 by the antibody; bottom, Coomassie staining and quantification of three experiments. (G) Requirements of Mon1 and Ccz1 domains for autophagy. The indicated truncations were analyzed in cells expressing mCherry-tagged Atg8. Vacuoles were stained with CMAC, and cells grown in SD-N medium were then analyzed by fluorescence microscopy as in Figure 1B. Size bar, 5 µm.