| Aspect | Evidence-based details | Key citations (pqac IDs) | Primary source (with year) |
|---|---|---|---|
| Catalytic reaction | S. pombe CTPS/Cts1 catalyzes the ATP-dependent conversion of UTP to CTP; like other CTPS enzymes, it uses glutamine hydrolysis in a C-terminal glutamine amidotransferase domain to supply ammonia to the synthase domain through an intramolecular tunnel. GTP is the allosteric activator for efficient glutamine hydrolysis, and CTP provides feedback inhibition. | (pqac-00000000, pqac-00000013, pqac-00000016) | Deng et al., 2024; Bearne et al., 2022; Zhou et al., 2021 |
| Domain architecture | The fission-yeast enzyme is a two-domain CTPS family protein: N-terminal CTP synthase/synthase domain plus C-terminal glutamine amidotransferase (GATase) domain; S. pombe carries a single essential CTPS gene at the cts1 locus, and the cited work used UniProt O42644 for sequence/structure reference. | (pqac-00000008, pqac-00000009, pqac-00000010) | Zhang, 2018 |
| Cytoophidia formation and prevalence | CTPS/Cts1 forms filamentous cytoophidia in the cytoplasm of S. pombe. During logarithmic growth, cytoophidia are highly prevalent, reported in >90% of cells. | (pqac-00000000, pqac-00000002, pqac-00000004, pqac-00000019) | Deng et al., 2024; Zhang & Liu, 2019 |
| Growth-phase dynamics | Cytoophidia are abundant in early-to-mid exponential/log phase but disperse or disappear in stationary phase; this is reversible when cells are returned to rich medium. CTPS protein drops in stationary phase while mRNA is comparatively unchanged, consistent with regulation at protein stability/turnover level. | (pqac-00000002, pqac-00000004, pqac-00000007, pqac-00000019) | Deng et al., 2024; Zhang & Liu, 2019 |
| Temperature sensitivity | Unlike some reports in budding yeast, S. pombe cytoophidia are temperature-sensitive: both cold shock and heat shock rapidly shorten/disassemble cytoophidia, with reversibility after return to permissive conditions. Small heat-shock proteins are required for normal assembly. | (pqac-00000004, pqac-00000007) | Zhang & Liu, 2019 |
| DON effect | The glutamine analog DON irreversibly targets the glutamine amidotransferase chemistry of CTPS and promotes cytoophidium assembly in S. pombe, increasing filament length without changing total CTPS protein level; DON-induced filaments can also be reversed by cold treatment. | (pqac-00000007, pqac-00000012) | Zhang & Liu, 2019; Bearne et al., 2022 |
| H359A loss-filament phenotype | Mutation of conserved His359 to Ala abolishes cytoophidium formation without lethality. Loss of filamentation causes slower growth, prolonged G2/cell-cycle duration, increased cell length, and reduced CTPS protein despite unchanged mRNA, supporting a protein-stabilizing role for cytoophidia. | (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000019) | Deng et al., 2024 |
| Cell-cycle/growth linkage | In the 2024 study, filament loss or CTPS reduction decreased expression of G2/M- and growth-related genes including slm9; slm9 overexpression partially rescued the extended G2 phase and enlarged-cell phenotype, linking cytoophidia to proliferation control rather than only enzyme storage. | (pqac-00000000, pqac-00000001) | Deng et al., 2024 |
| Stress, nitrogen deprivation, and protein turnover regulation | CTPS/cts1 levels are reported to decline under heat, oxidative, and osmotic stress and after cadmium sulfate or methyl methanesulfonate treatment. Nitrogen-deprivation-induced G1 arrest reduces CTPS RNA about 5-fold, and S phase shows ~10% lower CTPS levels than G1/G2/M. The protein is also reported to undergo ubiquitin-mediated degradation/ubiquitin-linked regulation. | (pqac-00000003, pqac-00000005, pqac-00000006) | Zhang, 2018 |
| Quantitative highlights | Notable quantitative observations include: cytoophidia in >90% of log-phase cells; nitrogen deprivation lowering CTPS RNA ~5-fold; S phase showing ~10% lower CTPS levels; heat/cold shock effects occurring within minutes; H359A and CRISPRi-based CTPS reduction both increasing cell size and slowing growth/cell-cycle progression. | (pqac-00000000, pqac-00000002, pqac-00000004, pqac-00000007) | Deng et al., 2024; Zhang & Liu, 2019; Zhang, 2018 |


*Table: This table summarizes the main functional annotation points for Schizosaccharomyces pombe CTPS/Cts1 (UniProt O42644), including enzymatic function, domain organization, localization into cytoophidia, regulatory inputs, and mutant phenotypes. It is useful as a compact evidence map linking each annotation point to specific context IDs and primary sources.*