Figure 2.

The protein kinase foci disassemble upon the reinitiation of growth. (A) The protein kinase foci disassemble upon the addition of fresh medium to growth-arrested cells. Cells expressing the indicated GFP fusion proteins were grown for several days in minimal medium to induce protein kinase foci and then transferred to fresh medium for 90 min. The cells were examined by fluorescence microscopy before (0 min) and after (90 min) the incubation in fresh medium. (B) The protein kinase-GFP fusion proteins were not degraded upon the resumption of growth. The relative level of each of the fusion proteins was assessed by Western blotting with cell extracts prepared before (0 min) and after 45 or 90 min of incubation with fresh medium containing the translation elongation inhibitor, cycloheximide (35 μg/ml). The levels of phosphoglycerate kinase (PGK) served as a loading control for this experiment.