Transcriptional control of genes involved in yeast phospholipid biosynthesis.

Phospholipid biosynthetic genes encode enzymes responsible for phospholipid biosynthesis. They are coordinately regulated by the availability of phospholipid precursors through the inositol-sensitive upstream activating sequence (UAS(INO)). However, not all phospholipid genes are UAS(INO)-containing genes and not all UAS(INO)-containing genes have the same response to the phospholipid precursors. Therefore, the transcriptional regulation of phospholipid genes in response to the availability of phospholipid precursors is still unclear. Here, 22 out of 47 phospholipid biosynthetic genes were identified as UAS(INO)-containing genes, including EKI1, EPT1, INM1, IPK2, KCS1, PAH1, and PIK1 which have never been reported before. We also showed, using qRT-PCR technique, that 12 UAS(INO)-containing genes are down-regulated by 100 μM inositol in the wild type cells and up-regulated by 100 μM inositol in the ino2Δ cells. Therefore, it is possible that these genes are transcriptionally regulated by the UAS(INO) through the negative response of Ino2p to inositol. One other UAS(INO)-containing gene might be regulated by the positive response of Ino2p to 100 μM inositol. Surprisingly, we found 9 UAS(INO)-containing genes are not dependent on the response of Ino2p to 100 μM inositol, indicating that they may be regulated by other pathway. Furthermore, we identified 9 and 3 non-UAS(INO)-containing genes that are possibly regulated by the negative and positive response of Ino2p to 100 μM inositol, respectively. Therefore, these observations provide insight into the understanding of the co-regulated phospholipid biosynthetic genes expression.