Fig. 2.
Model for the biochemical regulation of phospholipid synthesis. The upper portion of the diagram shows the major steps in the synthesis of phospholipids. The key enzymes (PMT, CHO2-encoded PE methyltransferase and OPI3-encoded phospholipid methyltransferase; PIS, PIS1-encoded PI synthase; PSS, CHO1-encoded PS synthase; PAP, PAH1-encoded PA phosphatase; DGK, DGK1-encoded DAG kinase) that are biochemically regulated by phospholipid precursors and products are highlighted by the blue ellipses. The bottom portion of the diagram shows the transcriptional activation of UASINO-containing genes (blue) by the Ino2-Ino4 complex. Elevated PA (highlighted in yellow) content prevents the translocation of Opi1 into the nucleus, and thus its repressor function of UASINO-containing phospholipid synthesis genes. The color green designates stimulation, whereas the color red designates inhibition.