FIGURE 4:

Loss of repressors only partially derepresses transcription. G1/S transcripts were assayed at a fixed time corresponding to the transition from G1 to S phase. The P_GAL1-CDC20 arrest/release experiments shown in Figure 3 were repeated three times, and mRNA levels were measured before and 60 min after release in either the presence or absence of α factor. Bars, mRNA levels (mean ± SD; n = 3) at the 60-min time points, expressed relative to the levels in the M-phase–arrested cells. The effects of Whi5 and Stb1 were compared in FAR1 cln2∆ (left) and far1∆ cln2∆ (right) backgrounds. Statistical analysis of all 120 pairwise comparisons, using the Benjamini–Hochberg false discovery rate method, is provided in Supplemental Table S1. The most pertinent points are 1) the inhibition by α factor is statistically significant (q < 0.05) for each of the eight individual genotypes and 2) the derepression due to removal of Whi5/Stb1 is significant in most cases except for comparisons involving the far1∆ cln2∆ whi5∆ strain, for which greater variability prevents a firm conclusion, but the effect of Whi5 is separately supported by comparing far1∆ cln2∆ stb1∆ with far1∆ cln2∆ stb1∆ whi5∆ (e.g., q = 0.007 for CLN1 mRNA).