FIG. 1.

Persistent G₁ cell cycle arrest in hog1Δ cells during continuous exposure to arsenite. (A) The results of flow cytometry reveal accumulation of G₁ cells in asynchronously growing hog1Δ cells in the presence of 0.5 mM arsenite. (B) G₁-synchronized hog1Δ cells fail to restart the cell cycle under permanent arsenite stress. (C) The α-factor-nocodazole trap assay results confirm persistent G₁ arrest of hog1Δ cells. (D) Duration of G₂/M checkpoint delay in hog1Δ cells is not affected during arsenite exposure. (E) Lack of Hog1 kinase activity results in a persistent G₁ arrest, similar to that of hog1Δ cells. Cells with the analogue-sensitive HOG1-as allele were synchronized in G₁ with α-factor, exposed to 12 μM of the inhibitor 1-NM-PP1 for 5 min, washed in the presence of inhibitor, and released in fresh medium containing 12 μM 1-NM-PP1 in the presence or absence of 0.25 mM arsenite. In a control experiment, no inhibitor was added. At 10-min or 20-min intervals, samples were collected for the α-factor-nocodazole trap assay. As(III), arsenite; +, present; −, absent; 1C and 2C, values of DNA content; WT, wild type.