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Journal of Bacteriology, January 2001, p. 745-751, Vol. 183, No. 2
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.2.745-751.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

O2R, a Novel Regulatory Element Mediating Rox1p-Independent O2 and Unsaturated Fatty Acid Repression of OLE1 in Saccharomyces cerevisiae

Youji Nakagawa, Shigemi Sugioka, Yoshinobu Kaneko, and Satoshi Harashima*

Department of Biotechnology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan

Received 17 July 2000/Accepted 13 October 2000

Fatty acid desaturation catalyzed by fatty acid desaturases requires molecular oxygen (O2). Saccharomyces cerevisiae cells derepress expression of OLE1 encoding Delta 9 fatty acid desaturase under hypoxic conditions to allow more-efficient use of limited O2. It has been proposed that aerobic conditions lead to repression of OLE1 by well-established O2-responsive repressor Rox1p, since putative binding sequences for Rox1p are present in the promoter of OLE1. However, we revealed in this study that disruption of ROX1 unexpectedly did not affect the O2 repression of OLE1, indicating that a Rox1p-independent novel mechanism operates for this repression. We identified by promoter deletion analysis the 50-bp O2-regulated (O2R) element in the OLE1 promoter approximately 360 bp upstream of the start codon. Site-directed mutagenesis of the O2R element showed that the putative binding motif (5'-GATAA-3') for the GATA family of transcriptional factors is important for O2 repression. Anaerobic derepression of OLE1 transcription was repressed by unsaturated fatty acids (UFAs), and interestingly the O2R element was responsible for this UFA repression despite not being included within the fatty acid-regulated (FAR) element previously reported. The fact that such a short 50-bp O2R element responds to both O2 and UFA signals implies that O2 and UFA signals merge in the ultimate step of the pathways. We discuss the differential roles of FAR and O2R elements in the transcriptional regulation of OLE1.

* Corresponding author. Mailing address: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. Phone: 81-6-6879-7420. Fax: 81-6-6879-7421. E-mail: harashima{at}gen.bio.eng.osaka-u.ac.jp.

Journal of Bacteriology, January 2001, p. 745-751, Vol. 183, No. 2
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.2.745-751.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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