Binding Characteristics and Regulatory Mechanisms of the Transcription Factors Controlling Oleate-responsive Genes in Saccharomyces cerevisiae

Transcriptional activation of many genes involved in peroxisome-related functions is regulated by the Oaf1p, Pip2p, and Adr1p transcription factors in Saccharomyces cerevisiae. We have analyzed the in vivo binding characteristics of Oaf1p-Pip2p and found that this complex is recruited to its target oleate-response element (ORE) under all growth conditions tested. In addition, this complex also binds to ORE-containing genes that do not appear to be regulated by these proteins, as well as to some genes lacking conventional OREs. The recruitment of the Oaf1p-Pip2p complex was greatly increased upon glucose derepression, possibly due to Oaf1p phosphorylation with only moderate increases upon oleate induction. Thus, this complex may receive a nutritional cue while it is already bound to DNA, suggesting that, in addition to the increase in Oaf1p-Pip2p binding, other mechanism(s) such as enhanced Adr1p association may drive the expression of highly inducible fatty acid-responsive genes. Adr1p binds to target genes in an oleate-dependent fashion and is involved in Oaf1p-Pip2p binding. In turn, the Oaf1p-Pip2p complex appears to be important for Adr1p binding to a subset of oleate-responsive genes. Adr1p is a positive regulator of ORE-containing genes, but it also acts as a negative factor in expression of some of these genes. Finally, we have also shown that Adr1p is directly involved in mediating oleate induction of Oaf1p-Pip2p target genes.