Figure 6. Whi5^4E mutant anticipates entrance into S phase.

(a,b) Cell volume and protein distributions of wild type, whi5Δ and whi5^4E cells exponentially growing in glucose-supplemented medium. Data representative from three independent experiments are shown. Predicted (c) and experimental (d) kinetics of cell cycle entry for wild type (black), whi5Δ (red) and whi5^4E (blue) cells. Predicted (e-j) and experimental (k-p) transcriptional activation of selected genes of the G₁/S regulon in wild type (black), whi5Δ (red) and whi5^4E (blue) cells expressed as a function of cell size. Experimental data in k–p represent means±s.d.'s (n=3). Cell cycle entry and transcriptional activation are shown as a function of cell size; inserts in c,d show cell cycle entry expressed as a function of time (time 0 being reinoculation in fresh medium after elutriation). (j,p) summarize the time for which each gene anticipates the reaching of 50% expression in whi5Δ (red) and whi5^4E (blue) mutants in comparison with wild type.