The eukaryotic 9 fatty acid desaturate, which catalyzes the initial conversion of saturated to unsaturated fatty acids is a highly regulated enzyme. It responds to diverse array of stimuli to meet cellular requirements for balanced synthesis of membrane lipids and the optimal use of nutrients lipids. This laboratory clone and sequenced the Saccharomyces OLE1 gene, which encodes that enzyme. Expression of rat- yeast chimeric desaturates in ole1 gene-disrupted cells demonstrated that there is functional homology between the animal and fungal enzyme systems. OLE1 was found to be regulated by a number of specific nutritional and physiological conditions. Transcriptional controls were identified that are triggered by exogenous fatty acids, by changes in carbon source and by carbon starvation. A second set of controls was found to independently act to regulate OLE1 mRNA stability. These studies also suggested that there are similarities between its expression and the less well defined animal systems. The central working hypothesis of this research is that proteins that regulate desaturate activity also control other genes involved in lipid utilization. These include sterol biosynthetic enzymes and fatty acid chain elongation enzymes. This proposal is to define the regulators of OLE1 expression. Modified regulatory genes will then be used to identify connections that lead to the coordinated control of lipid synthesis and utilization. Regulatory DNA sequences in the OLE1 promoter will be identified and modified to be used to clone and characterize genes encoding members of that regulatory circuit. Regulation of OLE1 mRNA stability will be characterized by locating the stability determinants within the mRNA. That information will be used to identify trans-acting regulators at that level of OLE1 expression. These studies will lead to new information concerning the regulation and cellular functions of unsaturated fatty acids in yeast. They are also expected to be relevant to desaturate regulation in higher eukaryotes, including the homologous 9 enzymes in liver and adipose cells, and the biochemically uncharacterized desaturates that form eicosanoids and other polyunsaturated fatty acids.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM045768-05
Application #
2392139
Study Section
Microbial Physiology and Genetics Subcommittee 2 (MBC)
Project Start
1992-09-30
Project End
1999-06-30
Budget Start
1997-04-01
Budget End
1999-06-30
Support Year
5
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Rutgers University
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
038633251
City
New Brunswick
State
NJ
Country
United States
Zip Code
08901
Martin, Charles E; Oh, Chan-Seok; Jiang, Yide (2007) Regulation of long chain unsaturated fatty acid synthesis in yeast. Biochim Biophys Acta 1771:271-85
Oh, Chan-Seok; Martin, Charles E (2006) Candida albicans Spt23p controls the expression of the Ole1p Delta9 fatty acid desaturase and regulates unsaturated fatty acid biosynthesis. J Biol Chem 281:7030-9
Kandasamy, Pitchaimani; Vemula, Muralikrishna; Oh, Chan-Seok et al. (2004) Regulation of unsaturated fatty acid biosynthesis in Saccharomyces: the endoplasmic reticulum membrane protein, Mga2p, a transcription activator of the OLE1 gene, regulates the stability of the OLE1 mRNA through exosome-mediated mechanisms. J Biol Chem 279:36586-92
Vemula, Muralikrishna; Kandasamy, Pitchaimani; Oh, Chan-Seok et al. (2003) Maintenance and regulation of mRNA stability of the Saccharomyces cerevisiae OLE1 gene requires multiple elements within the transcript that act through translation-independent mechanisms. J Biol Chem 278:45269-79
Jiang, Yide; Vasconcelles, Michael J; Wretzel, Sharon et al. (2002) Mga2p processing by hypoxia and unsaturated fatty acids in Saccharomyces cerevisiae: impact on LORE-dependent gene expression. Eukaryot Cell 1:481-90
Martin, C E; Oh, C-S; Kandasamy, P et al. (2002) Yeast desaturases. Biochem Soc Trans 30:1080-2
Jiang, Y; Vasconcelles, M J; Wretzel, S et al. (2001) MGA2 is involved in the low-oxygen response element-dependent hypoxic induction of genes in Saccharomyces cerevisiae. Mol Cell Biol 21:6161-9
Kohlwein, S D; Eder, S; Oh, C S et al. (2001) Tsc13p is required for fatty acid elongation and localizes to a novel structure at the nuclear-vacuolar interface in Saccharomyces cerevisiae. Mol Cell Biol 21:109-25
Vasconcelles, M J; Jiang, Y; McDaid, K et al. (2001) Identification and characterization of a low oxygen response element involved in the hypoxic induction of a family of Saccharomyces cerevisiae genes. Implications for the conservation of oxygen sensing in eukaryotes. J Biol Chem 276:14374-84
Chellappa, R; Kandasamy, P; Oh, C S et al. (2001) The membrane proteins, Spt23p and Mga2p, play distinct roles in the activation of Saccharomyces cerevisiae OLE1 gene expression. Fatty acid-mediated regulation of Mga2p activity is independent of its proteolytic processing into a soluble transcription act J Biol Chem 276:43548-56

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