Coordinate regulation of phospholipid biosynthesis in Saccharomyces cerevisiae: pleiotropically constitutive opi1 mutant

Abstract

Phospholipid metabolism in the Saccharomyces cerevisiae opil mutant, which excretes inositol and is constitutive for the biosynthetic enzyme inositol-l-phosphate synthase (M. Greenberg, P. Goldwasser, and S. Henry, Mol. Gen. Genet. 186:157-163, 1982), was examined and compared to that of a wild-type strain. In wild-type S. cerevisiae, the phospholipid composition and the relative rates of synthesis of individual phospholipids change in response to the availability of exogenous supplies of soluble phospholipid precursors, particularly inositol. The opil mutant, in contrast, displays a relatively invariant phospholipid composition, and its pattern of phospholipid synthesis does not change in response to exogenous phospholipid precursors. Phosphatidylinositol synthase was not found to be regulated in either wild-type or opil cells. In wild-type cells, phosphatidylserine synthase and the phospholipid N-methyltransferases are coordinately repressed in response to a combination of inositol and choline. However, in opil cells these activities are expressed constitutively. These results suggest that the gene product of the OPIJ locus participates in the coordinate regulation of phospholipid synthesis.

Inositol biosynthesis: Candida albicans and Saccharomyces cerevisiae genes share common regulation

“…I N 0 2 and IN04 are positive regulators (activators) of the ZNOI gene Loewy and Henry, 1984); however, it is not yet known if their action is direct or indirect. Many of the inositol-excreting strains are defective in phospholipid biosynthesis (Greenberg et al, 1983;Klig et al, 1985;Summers et al, 1988;McGraw and Henry, 1989). One of the inositol-excreting strains, opil, appears to have a defect in a negative regulator (repressor) of INOI (Greenberg et al, 1982a;Klig et al, 1985).…”

“…They were grown at 30°C for five to six generations in the presence of the label and harvested while the cells were still in the logarithmic growth phase (at a density of 1-2 x lo7 cells/ml). Labeling for additional generations altered neither the percentage distribution of the label into lipid classes nor the specific activity of the lipid extracted, so it appears that a steady-state labeling condition was achieved (Atkinson et al, 1980;Klig et al, 1985).…”

“…This regulation is reflected in the steady-state levels of the corresponding RNA (Hirsch and Henry, 1986) and in the amount of inositol-1-phosphate synthase found in the cells (Donahue and Henry, 1981). Genetic studies, analysing mutant yeast strains, revealed that inositol biosynthesis is also regulated coordinately with the synthesis of phosphatidylcholine (Greenberg et al, 1983;Loewy and Henry, 1984;Klig et al, 1985;McGraw and Henry, 1989).…”

“…C . albicans does not require exogenous inositol for growth, yet it synthesizes phosphatidylinositol (Klig et al, 1990), so it appears to have the capacity to syntehsize inositol. To examine inositol biosynthesis in C .…”

Yeast sequencing reports. Comparison of INO1 gene sequences and products in Candida albicans and Saccharomyces cerevisiae

“…This regulation is reflected in the steady-state levels of the corresponding RNA (Hirsch and Henry, 1986) and in the amount of inositol-1-phosphate synthase found in the cells (Donahue and Henry, 1981). Studies have been shown that inositol biosynthesis is regulated coordinately with the synthesis of phosphatidylcholine (Greenberg et al, 1983;Loewy and Henry, 1984;Klig et al, 1985;McGraw and Henry, 1989). Protein regulatory factors were demonstrated to affect this regulation by binding to a 10 base pair sequence, the inositoy choline regulatory element, present 5' to phospholipid and phospholipid precursor biosynthetic genes (Carman and Henry, 1989;Lopes et al, 1991;Nikoloff et al, 1992;Paltauf et al, 1992).…”