FIG. 9.

The esa1 mutant G₂/M arrest is dependent on the RAD9 checkpoint gene. (A) rad9Δ (LPY3784), (B) esa1-L254P (LPY3785), (C) rad9Δ esa1-L254P (LPY3780), (D) mad3Δ esa1-L254P (LPY4223), and (E) mad3 (LPY4222) mutant cells were incubated at 37°C and then analyzed for DNA content by flow cytometry. The x and y axes represent relative fluorescence intensity and number of cells, respectively. The esa1-L254P and mad3Δ esa1-L254P mutants arrested after DNA replication with approximately 80% of the cells containing 2C DNA content, whereas the rad9Δ and mad3 cells have normal DNA content for dividing cells. The rad9Δ esa1-L254P double mutant had both 1C and 2C peaks, indicating that esa1-L254P cell cycle arrest is dependent on RAD9 but not on MAD3.