FIG. 5.

The pph21-102 and tap42-11 cells display a normal PP2A activity at both the permissive and nonpermissive temperatures. Yeast cells of strains Y162 (PPH21 PPH22), Y176 (tap42-11), Y648 (PPH21 pph22), Y638 (pph21-102 pph22), and Y531 (pph21 pph22) were grown to early log phase at 23°C and then shifted to 37°C for 2 h. Cells before and after the shift were lysed, and phosphatase activity in the lysates was determined by an in vitro phosphatase assay using phosphorylated H1 histone as the substrate. The H1 histone phosphatase activity was measured in the presence (solid bars) or absence (open bars) of 10 nM type 1 phosphatase inhibitor 2 (I-2). PP2A activity was defined as the activity that was insensitive to I-2. The activities shown are the averages of three independent experiments. Units shown are arbitrary.