pis1 encodes the phosphatidylinositol synthase of Schizosaccharomyces pombe (CDP-diacylglycerol--inositol 3-phosphatidyltransferase, EC 2.7.8.11), the ortholog of S. cerevisiae Pis1 and human CDIPT. This multi-pass membrane enzyme of the CDP-alcohol phosphatidyltransferase family transfers the phosphatidyl group of CDP-diacylglycerol to myo-inositol, making phosphatidylinositol, the precursor of phosphoinositides, inositol-containing sphingolipids and GPI anchors. It competes with phosphatidylserine synthase (pps1) for ER CDP-DAG. In S. pombe, PI synthase activity peaks in exponential growth and rises quickly when inositol is added to inositol-starved cells. By homology to S. cerevisiae Pis1 it acts mainly in the ER membrane, with possible pools in the Golgi and mitochondrial outer membrane.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000139 Golgi membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt subcellular location (SL-0134), which UniProt assigns by similarity to S. cerevisiae Pis1 (P06197). Reason: Plausible by homology but without S. pombe data; the S. cerevisiae PIS1 review accepts Golgi on S. cerevisiae experimental evidence, which does not transfer automatically. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Golgi apparatus membrane |
| GO:0000139 Golgi membrane | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: PomBase curator transfer of Golgi membrane from S. cerevisiae Pis1 (P06197). Reason: Homology-based secondary location; the ER is the principal site. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Golgi apparatus membrane |
| GO:0003881 CDP-diacylglycerol-inositol 3-phosphatidyltransferase activity | EXP PMID:1324908 Regulation of CDP-diacylglycerol synthesis and utilization b... | ACCEPT | Summary: Gaynor and Greenberg (1992) measured PI synthase activity in S. pombe membrane extracts and its induction by inositol; pis1 (SPAC1D4.08) is the single PI synthase gene. Reason: Core activity; abstract-only, extract-level evidence later attributed to pis1 by PomBase and UniProt. Supporting Evidence: PMID:1324908 phosphatidylinositol (PI) synthase, and phosphatidylserine (PS) synthase in cell extracts of the fission yeast Schizosaccharomyces pombe PMID:1324908 Upon the addition of inositol to inositol-starved cells, there was a rapid and continued increase in PI synthase expression. file:SCHPO/pis1/pis1-uniprot.txt Catalyzes the synthesis of phosphatidylinositol (PtdIns). |
| GO:0003881 CDP-diacylglycerol-inositol 3-phosphatidyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA from PTN000394714 (PI synthase node: S. cerevisiae Pis1, human CDIPT, Arabidopsis PIS1 and pis1 itself). Reason: Correct. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Catalyzes the synthesis of phosphatidylinositol (PtdIns). |
| GO:0003881 CDP-diacylglycerol-inositol 3-phosphatidyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from RHEA:11580 and EC 2.7.8.11. Reason: Correct. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Reaction=a CDP-1,2-diacyl-sn-glycerol + myo-inositol = a 1,2-diacyl-sn- |
| GO:0005741 mitochondrial outer membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt subcellular location (SL-0172) assigned by similarity to S. cerevisiae Pis1. Reason: Homology-based; no S. pombe data. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Mitochondrion outer membrane |
| GO:0005741 mitochondrial outer membrane | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: PomBase curator transfer of mitochondrial outer membrane from S. cerevisiae Pis1 (P06197), which is a correctly matched ortholog (unlike the cho1 transfer from S. cerevisiae Cho1). Reason: Secondary location by homology. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Mitochondrion outer membrane |
| GO:0005789 endoplasmic reticulum membrane | IC GO_REF:0000111 | ACCEPT | Summary: PomBase curator inference of ER membrane from the PI synthase activity (with GO:0003881); used in the PomBase PI GO-CAM 663d668500002178. Reason: Core location, consistent with membrane-extract activity and with the S. cerevisiae ortholog. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location (SL-0097) by similarity to S. cerevisiae Pis1. Reason: Correct. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Endoplasmic reticulum membrane |
| GO:0005789 endoplasmic reticulum membrane | ISS GO_REF:0000024 | ACCEPT | Summary: Curator transfer from S. cerevisiae Pis1. Reason: Correct. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Endoplasmic reticulum membrane |
| GO:0005794 Golgi apparatus | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PANTHER IBA (PTN000394714) to Golgi apparatus, from S. cerevisiae Pis1 and Arabidopsis/trypanosome PI synthases. Reason: A real family-wide secondary site but not the principal ER location; non-core for S. pombe in the absence of local data. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Golgi apparatus membrane |
| GO:0006644 phospholipid metabolic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA00028721 mapping to phospholipid metabolic process. Reason: Correct but generic. |
| GO:0006661 phosphatidylinositol biosynthetic process | EXP PMID:1324908 Regulation of CDP-diacylglycerol synthesis and utilization b... | ACCEPT | Summary: PI synthase activity and its inositol regulation measured in S. pombe extracts. Reason: Core process. Supporting Evidence: PMID:1324908 phosphatidylinositol (PI) synthase, and phosphatidylserine (PS) synthase in cell extracts of the fission yeast Schizosaccharomyces pombe PMID:1324908 Upon the addition of inositol to inositol-starved cells, there was a rapid and continued increase in PI synthase expression. |
| GO:0006661 phosphatidylinositol biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PANTHER IBA (PTN000394714) to PI biosynthetic process. Reason: Core process. Supporting Evidence: file:SCHPO/pis1/pis1-uniprot.txt Catalyzes the synthesis of phosphatidylinositol (PtdIns). |
| GO:0008610 lipid biosynthetic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: ARBA00027236 mapping to lipid biosynthetic process. Reason: Correct but very general. |
| GO:0008654 phospholipid biosynthetic process | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro IPR000462 (CDP-alcohol phosphatidyltransferase) mapping to phospholipid biosynthetic process. Reason: Correct but generic. |
| GO:0016020 membrane | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro IPR000462 mapping to membrane. Reason: Correct but uninformative. |
| GO:0016780 phosphotransferase activity, for other substituted phosphate groups | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro IPR000462 mapping to phosphotransferase activity, for other substituted phosphate groups. Reason: Correct parent of GO:0003881, uninformative. |
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Download this section (compressed HTML)Q: Is pis1 expression and activity controlled by inositol at the transcriptional or post-translational level in S. pombe, given that its regulation of these enzymes differs from that of S. cerevisiae (PMID:1324908)?
Experiment: Localize functional, natively tagged pis1 relative to ER, Golgi and mitochondrial markers and test whether the S. cerevisiae Golgi and outer-membrane pools are conserved in S. pombe.
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