Figure 7.

Pol I activity impacts the transcriptional regulation of r-protein genes during diauxic growth transition. Genome-wide analysis of expression levels of class II genes. Wild-type (WT) or CARA cells were grown in rich medium either to mid–log phase or 90 min after the end of the log phase at the diauxic transition (as indicated in Supplemental Fig. S1). After total RNA extraction, 20 μg of RNAs were labeled by reverse transcription in the presence of Cy5 dUTP (WT) or Cy3 dUTP (CARA) (see Materials and Methods) and used to probe a microarray harboring all yeast ORFs. Results were analyzed using the GeneSpring software (Silicon Genetics). For all mRNAs, the ratio of expression in CARA cells over WT cells (CARA/WT) was calculated. These values were transformed to a log2 scale, and the resulting distribution of ratios is depicted (r-protein genes, black histograms; non-r-protein genes, white histograms). During the mid–log phase, the distribution of expression ratios for r-protein genes is centered on zero, indicating that these genes are similarly expressed in both strains. During diauxic transition, mRNAs encoding r-protein are significantly overrepresented in CARA cells compared with WT cells.