Figure 1. The SAC controls Kar9 asymmetry independently of Cdk1/Clb4, but in a Cdk1/Clb5-dependent manner. (A) Representative images of metaphase cells expressing Kar9-YFP, Clb4-Venus or Clb5-Venus together with CFP-Tub1. Scale bar is 2 µm. (B) Representative images of metaphase cells expressing Kar9-YFP in various mutant backgrounds. (C and D) Quantification of Kar9 asymmetry in nnf1–17 mutant background in combination with mutations affecting Cdk1/Clb4-dependent phosphorylation of Kar9 (C) or Cdk1/Clb5 activity (D). Cells coexpressed Kar9-YFP and CFP-Tub1 and were either MAD2 or mad2∆. Quantification as described in the text, cells were shifted to 37°C for 50 min before imaging. Stars indicate p-values obtained from one-way ANOVA comparing “strong asymmetry” (3 clones with total n > 115). Scale bar is 2 µm. (E) Quantification of metaphase arrest in nnf1–17 and clb5∆ cells in either MAD2 or mad2∆ background. Percentage of metaphase cells over the total number of cells was determined. Stars indicate p-values obtained from one-way ANOVA comparing to WT or as indicated (three clones with total n > 1100).