No abstract

The transcription factors Msn2 and Msn4 (multicopy suppressor of mutation proteins 2 and 4) bind the stress-response element in gene promoters in the yeast However, the roles of Msn2/4 in primary metabolic pathways such as fatty acid β-oxidation are unclear. Here, analysis revealed that the promoters of most genes involved in the biogenesis, function, and regulation of the peroxisome contain Msn2/4-binding sites. We also found that transcript levels of are increased in glucose-depletion conditions and that during growth in nonpreferred carbon sources, Msn2 is constantly localized to the nucleus in wild-type cells. Of note, the double mutant ΔΔ exhibited a severe growth defect when grown with oleic acid as the sole carbon source and had reduced transcript levels of major β-oxidation genes. ChIP indicated that Msn2 has increased occupancy on the promoters of β-oxidation genes in glucose-depleted conditions, and reporter gene analysis indicated reduced expression of these genes inΔΔ cells. Moreover, mobility shift assays revealed that Msn4 binds β-oxidation gene promoters. Immunofluorescence microscopy with anti-peroxisome membrane protein antibodies disclosed that the ΔΔ strain had fewer peroxisomes than the wild type, and lipid analysis indicated that the ΔΔ strain had increased triacylglycerol and steryl ester levels. Collectively, our data suggest that Msn2/Msn4 transcription factors activate expression of the genes involved in fatty acid oxidation. Because glucose sensing, signaling, and fatty acid β-oxidation pathways are evolutionarily conserved throughout eukaryotes, the ΔΔ strain could therefore be a good model system for further study of these critical processes.