J Biol Chem, Vol. 274, Issue 15, 9969-9975, April 9, 1999

Transcriptional Regulation of the Schizosaccharomyces pombe Malic Enzyme Gene, mae2

Marinda Viljoen, Heinrich Volschenk, Richard A. Young^¶, and Hendrik J. J. van Vuuren

From the  Department of Microbiology, University of Stellenbosch, Stellenbosch 7600, South Africa, ^¶ Whitehead Institute for Biomedical Research and Massachusetts Institutes of Technology, Cambridge, Massachusetts 02142, and  Cool Climate Oenology and Viticulture Institute, Brock University, St. Catharines, Ontario L2S 3A1, Canada

The NAD-dependent malic enzyme from Schizosaccharomyces pombe catalyzes the oxidative decarboxylation of L-malate to pyruvate and CO₂. Transcription of the S. pombe malic enzyme gene, mae2, was studied to elucidate the regulatory mechanisms involved in the expression of the gene. No evidence for substrate-induced expression of mae2 was observed in the presence of 0.2% L-malate. However, transcription of mae2 was induced when cells were grown in high concentrations of glucose or under anaerobic conditions. The increased levels of malic enzyme may provide additional pyruvate or assist in maintaining the redox potential under fermentative conditions. Deletion and mutation analyses of the 5'-flanking region of the mae2 gene revealed the presence of three novel negative cis-acting elements, URS1, URS2, and URS3, that seem to function cooperatively to repress transcription of the mae2 gene. URS1 and URS2 are also present in the promoter region of the S. pombe malate transporter gene, suggesting co-regulation of their expression. Furthermore, two positive cis-acting elements in the mae2 promoter, UAS1 and UAS2, show homology with the DNA recognition sites of the cAMP-dependent transcription factors ADR1, AP-2, and ATF (activating transcription factor)/CREB (cAMP response element binding).