Annotation inferences using phylogenetic trees
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
A large-scale screen in S. pombe identifies seven novel genes required for critical meiotic events.
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Systematic deletion of 175 meiotically upregulated genes (the source of the mug134 name); igo1/mug134 was not among the seven genes found to be critical for meiotic events.
"In the fission yeast Schizosaccharomyces pombe, we have deleted 175 meiotically upregulated genes and found seven genes not previously reported to be critical for meiotic events."
ORFeome cloning and global analysis of protein localization in the fission yeast Schizosaccharomyces pombe.
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Genome-wide YFP-tagged ORFeome localisation collection; Igo1-YFP scored in the cytosol and nucleus.
"Next, we determined the localization of 4,431 proteins, corresponding to approximately 90% of the fission yeast proteome, by tagging each ORF with the yellow fluorescent protein."
Nutritional Control of Cell Size by the Greatwall-Endosulfine-PP2A·B55 Pathway.
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The Ppk18-Igo1 pathway couples the nutritional environment to the cell cycle by regulating PP2A-B55 activity.
"Here we show that the greatwall-endosulfine (Ppk18-Igo1 in fission yeast) pathway couples the nutritional environment to the cell-cycle machinery by regulating the activity of PP2A·B55."
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Under nitrogen limitation, Ppk18 phosphorylates Igo1, which inhibits PP2A-B55 and allows full Cdk1-cyclin B activation and mitotic entry at a smaller size.
"When nutrients are limiting, TORC1 activity falls off, and the activation of greatwall (Ppk18) leads to the phosphorylation of endosulfine (Igo1) and inhibition of PP2A·B55, which in turn allows full activation of Cdk1·CyclinB and entry into mitosis with a smaller cell size."
TORC1 and TORC2 converge to regulate the SAGA co-activator in response to nutrient availability.
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Taf12 phosphorylation on starvation is set by PP2A (TORC1-activated) versus TORC2-Gad8; the full text shows that igo1 deletion and igo1-S64A fail to induce Taf12 phosphorylation and differentiation, and that pab1 deletion suppresses their sterility.
"Taf12 phosphorylation increases early upon starvation and is controlled by the opposing activities of the PP2A phosphatase, which is activated by TORC1, and the TORC2-activated Gad8AKT kinase."
The phosphatase inhibitor Sds23 regulates cell division symmetry in fission yeast.
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igo1 deletion alone has no cell-shape, size or division-symmetry defect; combined with sds23 deletion it increases bent cells and division size, while the division-symmetry trend is not significant.
"Lastly, the cell half ratio was even further reduced for double mutant cells, but we note that the double mutants were not significantly different from sds23∆ alone despite this trend (Figure 5E)."
UniProt entry P79058 (IGO1_SCHPO)
Deep research report for igo1 (S. pombe), Falcon provider
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Summarises the Ser64-dependent PP2A-B55 inhibition mechanism, the igo1 deletion G2/M and differentiation phenotypes, the TORC2-Gad8 crosstalk and the 2024 quiescence- translation study.
"**Ppk18 phosphorylation of Igo1 at Ser64** is the central activating event supported by the mechanistic literature. Loss of *igo1* causes abnormally high PP2A-B55 activity under nitrogen-poor or nitrogen-free conditions, while genetically reducing PP2A-B55 can rescue multiple *igo1Δ* phenotypes."
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Flags that the UniProt "mRNA stability protein" description is outdated relative to the fission-yeast evidence.
"The historical description “mRNA stability protein” is incomplete relative to current evidence."