THE UPSTREAM REGION OF THE FOX3 GENE ENCODING PEROXISOMAL 3-OXOACYL-COENZYME-A THIOLASE IN SACCHAROMYCES-CEREVISIAE CONTAINS ABF1-BINDING AND REPLICATION PROTEIN-A-BINDING SITES THAT PARTICIPATE IN ITS REGULATION BY GLUCOSE REPRESSION

Expression of the FOX3 gene, which encodes yeast peroxisomal 3-oxoacyl -coenzyme A thiolase, can be induced by oleate and repressed by glucos e. Previously, we have shown that induction was mediated by an oleate response element. Just upstream of this element a negatively acting co ntrol region that mediated glucose repression was found. In order to s tudy this negative control region, we carried out DNA-binding assays a nd analyzed phenotypes of mutations in this region and in the trans-ac ting factor CAR80, which is identical to UME6. DNA-binding assays show ed that two multifunctional yeast proteins, ABF1 and RP-A, interacted with the negative control element independently of the transcriptional activity of the FOX3 gene. ABF1 and RP-A, the latter being identical to BUF, were able to bind to DNA independently of one another but also simultaneously, The phenotypes of mutations in either DNA-binding sit es of ABF1, RP-A, or both, which affected the DNA binding of these fac tors in vitro, indicated that these sites and the proteins that intera ct with them participate in glucose repression, The involvement of the RP-A site in glucose repression was Further supported by our observat ion that the CAR80 gene product, which is required for repression medi ated by the RP-A site, was essential for maintenance of glucose repres sion. In addition to the RP-A site in the FOX3 promoter, similar seque nces were observed in other genes involved in peroxisomal function, RP -A proved to bind to all of these sequences, albeit with various affin ities, From these results it is concluded that the ABF1 and RP-A sites are being required in concert to mediate glucose repression of the FO X3 gene. In addition, coordinated regulation of expression of genes in volved in peroxisomal function in response to glucose is mediated by p roteins associated with the RP-A site, probably RP-A and CAR80.