The Ste5-8A mutant disrupts cell cycle periodicity of pheromone response. Cells (
cdc15-2 or
cdc15-2 STE5-8A) were synchronized in late M phase by arrest at 36°C, and then transferred to 25°C. At various times, response to brief treatment with α factor was monitored (see Experimental Procedures). Top,
FUS1-lacZ induction (mean of 4 trials). Bottom, Fus3 activation (phospho-Fus3) was measured using phospho-specific antibodies (mean of 6 trials). Arrows mark the times of bud emergence (see Figures
S1D and
5G).