Respective weights of RPN4 , PDR1 , PDR3 or YAP1 in the selenite response. (A) Hierarchical clustering of the genes dependent on one or several of the four transcription factors studied for selenite induction. DNA microarrays were used to compare gene expression levels between wild-type and rpn4Δ, pdr1Δ, pdr3Δ or yap1Δ exposed to selenite (times 40, 60 and 80 minutes) or mock-treated (time 0). The 175 genes displaying an alteration of selenite induction in at least one mutant strain were clustered into 5 groups (see additional files 5 and 6). (B): Schematic representation of the importance of each transcription factor in the regulation of the five clusters defined in (A). The arrows symbolize the positive regulation of each cluster by the transcription factor: the width of the arrows indicates the importance of the regulation (large arrows: strong effect, thin arrows: weak effect). Dashed arrows indicate that the transcription factor controls the expression of only some of the genes present in the cluster. Solid arrows mean that all the genes present in the cluster are regulated. The relevance of the Gene Ontology categories and regulatory relationships in each of the clusters was investigated with the SGD GO term finder and Yeastract tools [33, 34]. Only the main GO category with a p-value < 0.0001 and the main transcription factor known to regulate the genes in one cluster were indicated. (C): Enlargement of the part of cluster 1 containing the genes most sensitive to the deletion of PDR1 and PDR3. Gene names are indicated. The presence of a PDRE in the promoters of these genes is indicated by black dots.