title: The transcription factor GCN4 regulates PHM8 and alters triacylglycerol metabolism in Saccharomyces cerevisiae.
abstract: PHM8 is a very important enzyme in nonpolar lipid metabolism because of its role in triacylglycerol (TAG) biosynthesis under phosphate stress conditions. It is positively regulated by the PHO4 transcription factor under low phosphate conditions; however, its regulation has not been explored under normal physiological conditions. General control nonderepressible (GCN4), a basic leucine-zipper transcription factor activates the transcription of amino acids, purine biosynthesis genes and many stress response genes under various stress conditions. In this study, we demonstrate that the level of TAG is regulated by the transcription factor GCN4. GCN4 directly binds to its consensus recognition sequence (TGACTC) in the PHM8 promoter and controls its expression. The analysis of cells expressing the PPHM8-lacZ reporter gene showed that mutations (TGACTC-GGGCCC) in the GCN4-binding sequence caused a significant increase in β-galactosidase activity. Mutation in the GCN4 binding sequence causes an increase in PHM8 expression, lysophosphatidic acid phosphatase activity and TAG level. PHM8, in conjunction with DGA1, a mono- and diacylglycerol transferase, controls the level of TAG. These results revealed that GCN4 negatively regulates PHM8 and that deletion of GCN4 causes de-repression of PHM8, which is responsible for the increased TAG content in gcn4∆ cells.
authors.affiliation: Lipidomic Centre, Department of Lipid Science, CSIR-Central Food Technological Research Institute, Mysore, Karnataka, 570020, India.|Academy of Scientific and Innovative Research, CSIR-CFTRI, Mysore, India.
authors.forename: Kamlesh Kumar
authors.initials: KK
authors.lastname: Yadav
authors.affiliation: Lipidomic Centre, Department of Lipid Science, CSIR-Central Food Technological Research Institute, Mysore, Karnataka, 570020, India. ram@cftri.com.|Academy of Scientific and Innovative Research, CSIR-CFTRI, Mysore, India. ram@cftri.com.
authors.forename: Ram
authors.initials: R
authors.lastname: Rajasekharan
mesh_terms: D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D055786:Gene Knockout Techniques; D050356:Lipid Metabolism; D055432:Metabolomics / Q000379:methods; D009154:Mutation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; C501391:GCN4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014280:Triglycerides
keywords: Lipid droplets; Lysophosphatidic acid phosphatase; Repressor; Transcriptional regulation; Triacylglycerol