Regulation of the PIS1-encoded Phosphatidylinositol Synthase in Saccharomyces cerevisiae by Zinc

In the yeast Saccharomyces cerevisiae, the mineral zinc is essential for growth and metabolism. Depletion of zinc from the growth medium of wild type cells results in changes in phospholipid metabolism, including an increase in phosphatidylinositol content (Iwanyshyn, W. M., Han, G.-S., and Carman, G. M. (2004) J. Biol. Chem. 279, 21976–21983). We examined the effects of zinc depletion on the regulation of the PIS1-encoded phosphatidylinositol synthase, the enzyme that catalyzes the formation of phosphatidylinositol from CDP-diacylglycerol and inositol. Phosphatidylinositol synthase activity increased when zinc was depleted from the growth medium. Analysis of a zrt1Δ zrt2Δ mutant defective in plasma membrane zinc transport indicated that the cytoplasmic levels of zinc were responsible for the regulation of phosphatidylinositol synthase. PIS1 mRNA, its encoded protein Pis1p, and the β-galactosidase activity driven by the PPIS1-lacZ reporter gene were elevated in zinc-depleted cells. This indicated that the increase in phosphatidylinositol synthase activity was the result of a transcriptional mechanism. The zinc-mediated induction of the PPIS1-lacZ reporter gene, Pis1p, and phosphatidylinositol synthase activity was lost in zap1Δ mutant cells. These data indicated that the regulation of PIS1 gene expression by zinc depletion was mediated by the zinc-regulated transcription factor Zap1p. Direct interaction between glutathione S-transferase (GST)-Zap1p687–880 and a putative upstream activating sequence (UAS) zinc-responsive element in the PIS1 promoter was demonstrated by electrophoretic mobility shift assays. Mutations in the UAS zinc-responsive element in the PIS1 promoter abolished the GST-Zap1p687–880-DNA interaction in vitro and abolished the zinc-mediated regulation of the PIS1 gene in vivo. This work advances understanding of phospholipid synthesis regulation by zinc and the transcription control of the PIS1 gene.