Multiple Pathways Are Co-regulated by the Protein Kinase Snf1 and the Transcription Factors Adr1 and Cat8

ADR1 and CAT8 encode carbon source-responsive transcriptional regulators that cooperatively control expression of genes involved in ethanol utilization. These transcription factors are active only after the diauxic transition, when glucose is depleted and energy-generating metabolism has shifted to the aerobic oxidation of non-fermentable carbon sources. The Snf1 protein kinase complex is required for activation of their downstream target genes described previously. Using DNA microarrays, we determined the extent to which these three factors collaborate in regulating the expression of the yeast genome after glucose depletion. The expression of 108 genes is significantly decreased in the absence of ADR1. The importance of ADR1 during the diauxic transition is illustrated by the observation that expression of almost one-half of the 40 most highly glucose-repressed genes is ADR1-dependent. ADR1-dependent genes fall into a variety of functional classes with carbon metabolism containing the largest number of members. Most of the genes in this class are involved in the oxidation of different non-fermentable carbon sources. These microarray data show that ADR1 coordinates the biochemical pathways that generate acetyl-CoA and NADH from non-fermentable substrates. Only a small number of ADR1-dependent genes are also CAT8-dependent. However, nearly one-half of the ADR1-dependent genes are also dependent on the Snf1 protein kinase for derepression. Many more genes are SNF1-dependent than are either ADR1- or CAT8-dependent suggesting that SNF1 plays a broader role in gene expression than either ADR1 or CAT8. The largest class of SNF1-dependent genes encodes regulatory proteins that could extend SNF1 dependence to additional pathways.