FIG. 5.

In response to various stresses, Rpb4p and Rpb7p are exported to the cytoplasm at similar kinetics. (A to C) yMS4 (A), yMS18 (B), and yMS8 (C) cells expressing the indicated fluorescence-tagged proteins were allowed to proliferate for at least eight generations under optimal conditions in selective media at either 24°C (A) or 30°C (B, C, and D) until the mid-logarithmic phase (5 × 10⁶ cells/ml). Cultures were then challenged under the indicated stress condition as described for Fig. 1. Export kinetics experiments were performed as described for Fig. 2D. (D) Import kinetics of GFP-Rpb4p and Rpb7p-RFP are comparable. yRL82 cells were starved until both fluorescent proteins were localized in the cytoplasm in 80% or 90% of the cells. Cells were then collected by centrifugation and resuspended in synthetic complete medium (containing glucose and amino acids) supplemented with 50 μg/ml cycloheximide (similar results were obtained when cycloheximide was not added). Import kinetics results were determined as described for panels A to C.