| Function/role in pathway | Molecular interactions/complex membership | Localization | Key experimental evidence (assay type; quantitative where available) | Notes on conservation/differences vs mammals | Primary citations with year and URL |
|---|---|---|---|---|---|
| Upstream autophagy-initiation factor in the fission yeast Atg1 complex; best-supported direct role is to stabilize Atg13 HORMA and support Atg1-complex assembly rather than to activate Atg1 kinase directly (pqac-00000000, pqac-00000002, pqac-00000010) | Core subunit of the S. pombe Atg1 complex; binds Atg13 HORMA, contacts Atg1 C-terminal domain, but does **not** bind Atg17 (pqac-00000003, pqac-00000004) | S. pombe-specific localization is not directly established in the retrieved primary evidence; by complex membership, function is inferred at the pre-autophagosomal/autophagosome-initiation site (pqac-00000000, pqac-00000003) | Affinity isolation/coprecipitation mapped Atg13–Atg101 and Atg1CTD–Atg101 interactions; crosslinking/biochemistry support Atg101 incorporation into the complex (pqac-00000003, pqac-00000013) | Complex composition resembles mammalian ULK more than budding yeast because S. pombe contains Atg101; unlike mammals, S. pombe Atg101 is not required for Atg1 kinase activity in vitro (pqac-00000000, pqac-00000010) | Nanji et al., 2017, https://doi.org/10.1080/15548627.2017.1382782; Pan et al., 2020, https://doi.org/10.7554/eLife.58073 |
| Structural adaptor/stabilizer of Atg13 HORMA heterodimer | Obligatory heterodimer with Atg13 HORMA; Atg101 does not homodimerize; Atg13–Atg101 interaction enhances stability of both proteins (pqac-00000012) | Not directly measured here (pqac-00000012) | Differential scanning fluorimetry: Atg13HORMA Tm ~43°C, Atg101 Tm ~48°C, Atg13HORMA–Atg101 complex Tm ~63°C, showing strong stabilization upon heterodimerization (pqac-00000012) | S. pombe Atg101 adopts a HORMA-fold architecture similar to human ATG101; Atg13 resembles a complementary HORMA partner, consistent with conserved HORMA-pairing logic (pqac-00000004, pqac-00000012) | Nanji et al., 2017, https://doi.org/10.1080/15548627.2017.1382782 |
| Accessory factor with functions beyond Atg13 stabilization, likely helping recruit other partners/downstream factors through the WF finger (pqac-00000008) | Atg101-GFP purifications recovered Atg1, Atg13, and Atg4 peptides; Atg101 also directly bound Fkh1 in thesis work; WF finger projects away from the Atg13-binding site (pqac-00000001, pqac-00000008) | Atg101-GFP was expressed from a chromosomally tagged strain for proteomic analysis, but a discrete subcellular localization pattern was not reported in the retrieved excerpt (pqac-00000005, pqac-00000006) | IP-MS from Atg101-GFP identified 625 prey genes across conditions; WF-finger mutant W110A/P111A/F112A impaired autophagy while preserving Atg13 binding, arguing for separable functions (pqac-00000001, pqac-00000008) | Mirrors mammalian models where the WF finger contributes to downstream factor recruitment, but the S. pombe thesis emphasizes additional context-dependent interactors and possible non-autophagy roles (pqac-00000008) | Nanji, 2021 thesis, https://doi.org/10.14288/1.0378352 |
| Not required for Atg1 catalytic activation in the tested fission-yeast system | Atg1 kinase activation depends mainly on Atg11-mediated dimerization/cis-autophosphorylation, not on Atg101, Atg13, or Atg17 in the in vitro kinase assays reported (pqac-00000010) | Not addressed (pqac-00000010) | Immunopurified YFP-Atg1 from atg101Δ cells showed autophosphorylation and peptide-substrate phosphorylation similar to wild type under rich and nitrogen-starvation conditions; by contrast atg11Δ Atg1 was nearly inactive (pqac-00000010) | Important divergence from mammalian ATG101, which is generally considered essential for ULK-complex stability and autophagy; in S. pombe, Atg101 appears less central to Atg1 kinase activation itself (pqac-00000008, pqac-00000010) | Pan et al., 2020, https://doi.org/10.7554/eLife.58073 |
| Gene originally identified as mug66, linked genetically to sporulation/meiosis-associated phenotypes and later recognized as the S. pombe Atg101 ortholog (pqac-00000007) | Homolog of mammalian Atg101/ATG101; supports assignment of mug66/SPAC25H1.03 to the ATG101 family (pqac-00000007) | Mammalian ATG101 localizes to the isolation membrane/phagophore, but equivalent S. pombe localization was not shown in the retrieved paper set (pqac-00000007) | Hosokawa et al. cite prior work that mug66 mutants are defective in spore formation; because autophagy is required for sporulation in yeasts, this phenotype is consistent with an autophagy-related role, but indirect for S. pombe Atg101 specifically (pqac-00000007) | Mammalian ATG101 is directly required for autophagy and for stability/phosphorylation of ATG13 and ULK1; S. pombe evidence is stronger for complex assembly/stability than for direct kinase activation control (pqac-00000007, pqac-00000010) | Hosokawa et al., 2009, https://doi.org/10.4161/auto.5.7.9296; Pan et al., 2020, https://doi.org/10.7554/eLife.58073 |
| Evolutionary note: S. pombe Atg101 is **not** a functional replacement for budding-yeast Atg29/Atg31 | Does not bind Atg17, and S. pombe Atg101 failed to rescue S. cerevisiae atg29Δ atg31Δ defects; co-expression with S. pombe Atg17 also failed to complement S. cerevisiae atg17Δ (pqac-00000004, pqac-00000012) | Not addressed (pqac-00000004) | Cross-species complementation assays negative; interaction maps show Atg17 scaffolding is conserved but Atg101 wiring is distinct (pqac-00000004, pqac-00000013) | Places S. pombe between budding yeast and mammals: it has ATG101 like mammals, but Atg101 wiring and requirements are not identical to either system (pqac-00000000, pqac-00000012) | Nanji et al., 2017, https://doi.org/10.1080/15548627.2017.1382782 |


*Table: This table compacts the main functional-annotation evidence for Schizosaccharomyces pombe Atg101/Mug66, emphasizing pathway role, experimentally supported interactions, and key differences from mammalian ATG101. It is useful for distinguishing what is directly shown in fission yeast from what is inferred by conservation.*