Pop1p and Pop2p F-box requirements (4A) ClustalW alignment of the F-boxes of Pop1p, Pop2p, budding yeast Cdc4p, and human SKP2 and β-TRCP. Residues involved in the SKP1/F-box interaction are indicated with arrows . (4B) Schematic of Pop1p and Pop2p F-box mutants. (4C) The mutant proteins displayed in (B) were expressed in pop1 or pop2 deletion strains from pRep81 as indicated. Cells were fixed and processed for flow cytometry. Cells containing the normal 2C DNA content and cells with greater than 4C were quantified and results are presented in the diagram. Note that the polyploidy phenotype of Δpop2 mutants is mild  and, hence, the rescue observed with Pop2p proteins is less pronounced. (4D) The strains described in (C) were induced to express the indicated Myc-tagged Pop1p and Pop2p mutants for 20 h. Protein lysates were probed with antisera against Rum1p and tubulin as a loading control.