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  • Title: Specificity of unsaturated fatty acid-regulated expression of the Saccharomyces cerevisiae OLE1 gene.
    Author: McDonough VM, Stukey JE, Martin CE.
    Journal: J Biol Chem; 1992 Mar 25; 267(9):5931-6. PubMed ID: 1556107.
    Abstract:
    The Saccharomyces cerevisiae OLE1 gene encodes the delta-9 fatty acid desaturase, an enzyme which forms the monounsaturated palmitoleic (16:1) and oleic (18:1) fatty acids from palmitoyl (16:0) or stearoyl (18:0) CoA. Previous studies demonstrated that OLE1 mRNA levels and desaturase enzyme activity are repressed when either 16:1 delta-9 and 18:1 delta-9 are added to the growth medium (1). The polyunsaturate, linoleic acid (18:2, delta-9,12), which is not a product of the enzyme, is also a strong repressor. The specificity of the OLE1 transcriptional regulatory sensor was examined by testing the response of OLE1 promoter-lacZ fusion reporter genes to fatty acids that differ in chain length, degree of unsaturation and double bond positions. Monounsaturated and polyunsaturated fatty acids that contain a delta-9 double bond are strong repressors of reporter gene activity and native OLE1 mRNA levels. Monounsaturated fatty acids containing double bonds in the delta-10, delta-11, or delta-5 positions showed no repression of reporter enzyme levels although they were rapidly incorporated into membrane lipids and some supported growth of an OLE1 gene disrupted strain. Although 17:1 delta-10 does not repress OLE1 transcription, lipid analysis showed that it replaces almost all of the endogenous 16:1 delta-9 and 18:1 delta-9 in cellular lipids and OLE1 mRNA levels are strongly repressed. This suggests that additional systems regulate desaturase activity by post-transcriptional mechanisms that differ from the transcriptional sensor in their responses to specific fatty acids.
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