Apc2 is the cullin-family subunit of the Schizosaccharomyces pombe anaphase-promoting complex/cyclosome (APC/C), the 20S, 13-subunit cullin-RING E3 ubiquitin ligase (Apc1, Apc2, Nuc2, Lid1/Apc4, Apc5, Cut9, Cut23/Apc8, Apc10, Apc11, Hcn1, Apc13, Apc14 and Apc15) that triggers the metaphase-to-anaphase transition and exit from mitosis. It is the orthologue of budding yeast Apc2 and human ANAPC2. The 681-residue protein carries N-terminal cullin repeats and a C-terminal cullin-homology domain that anchors the RING-H2 subunit Apc11 to the complex; together the Apc2-Apc11 pair forms the catalytic module of the ligase, analogous to Cul1-Rbx1 of the SCF, which binds and positions the ubiquitin-charged E2 enzymes Ubc4 and Ubc11 (UbcP4) over substrates that are recognised through their D-box and KEN-box degrons by the coactivators Slp1 (Cdc20) in mitosis, Ste9/Srw1 (Cdh1) in G1 and Mfr1 in meiosis, together with Apc10/Doc1. Apc2 has no ubiquitin-thioester chemistry or substrate specificity of its own: the RING partner carries the E2-activating function, and a minimal Apc2-Apc11 module ubiquitinates substrates without degron selectivity. In the purified mitotic APC/C-Slp1 particle Apc2 is present at one copy and the Apc2-Apc11-Apc10 catalytic region maps to the lower side of the tricorn-shaped complex, next to the coactivator. Through the complex, Apc2 supports ubiquitination and proteasomal destruction of the securin Cut2 (releasing separase for sister-chromatid separation) and of the mitotic cyclin Cdc13 (lowering Cdc2 activity for mitotic exit and the G1 state). Fission yeast has a closed mitosis and the APC/C acts on nuclear substrates; YFP-tagged Apc2 is detected in both the nucleus and the cytosol. Whether the fission yeast complex builds K11- or K48-linked ubiquitin chains has not been determined, and the zinc-binding insert of metazoan ANAPC2 has not been demonstrated in the fungal protein.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000151 ubiquitin ligase complex | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA machine-learning mapping to the generic ubiquitin ligase complex term, a parent of the anaphase-promoting complex (GO:0005680) that Apc2 is annotated to experimentally (PMID:12477395, PMID:15060174) and by PAINT. Reason: Correct, if general. The APC/C is by definition a ubiquitin ligase complex (a conserved multisubunit ubiquitin ligase) and Apc2 is one of its 13 core subunits, so the electronic parent-term annotation is accurate and consistent with the specific GO:0005680 rows; it adds no new claim. Supporting Evidence: PMID:12477395 The anaphase-promoting complex (APC) is a conserved multisubunit ubiquitin ligase required for the degradation of key cell cycle regulators. file:SCHPO/apc2/apc2-uniprot.txt The APC/C is composed of at least 13 subunits: apc1, apc2, |
| GO:0003674 molecular_function | ND GO_REF:0000015 | ACCEPT | Summary: Root molecular function ND annotation: when it was made, no molecular function had been curated for this gene product from literature. Reason: ACCEPT under the ND acceptance rule (projects/NO_DATA.md). The evidence this review cites for the molecular function is inferred (from orthologs, family membership or sequence features) or comes from other species; none of it is literature on this gene product in this species. This was judged from the review's own content during the NO_DATA re-action pass, not from a new literature search. Earlier action: MODIFY. The S. pombe papers cited (PMID:20924356, PMID:15060174) state the Apc2 scaffold role as background; the biochemistry behind it is on human and budding-yeast APC/C. The term the earlier MODIFY proposed, ubiquitin ligase complex scaffold activity, is kept as its own NEW row. |
| GO:0005634 nucleus | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | ACCEPT | Summary: High-throughput localisation from the Matsuyama et al. 2006 ORFeome study, in which each S. pombe ORF was C-terminally tagged with YFP and imaged (4,431 proteins); Apc2-YFP was scored in the nucleus (and cytosol). The cached record is abstract-only, so the Apc2 image itself cannot be inspected. Reason: Fission yeast undergoes a closed mitosis and the obligatory APC/C substrates Cut2/securin and Cdc13/cyclin B are nuclear at metaphase, so the nucleus is the compartment in which the Apc2-containing ligase performs its core function; the atlas observation agrees with the UniProt/ARBA nuclear mapping and with the biology. Accepted as the core site of activity, with the caveat that the evidence is a tagged-overexpression screen rather than an endogenous, cell-cycle-resolved study. Supporting Evidence: PMID:16823372 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. PMID:9264466 We show here that the fission yeast gene products Cut9 and Nuc2 are the subunits of the 20S complex, the putative APC (anaphase promoting complex)/cyclosome which contains ubiquitin ligase activity required for cyclin and Cut2 destruction. |
| GO:0005634 nucleus | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA electronic nuclear-localisation prediction, consistent with the HDA nucleus row from the ORFeome YFP atlas (PMID:16823372) and with the nuclear substrates of the APC/C in the closed mitosis of fission yeast. Reason: Correct and consistent with the direct HDA row; the electronic annotation adds no new claim but is accurate for the compartment in which the Apc2-containing APC/C ubiquitinates Cut2 and Cdc13. Supporting Evidence: PMID:16823372 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. |
| GO:0005680 anaphase-promoting complex | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from ancestral node PTN000231994 of the ANAPC2 family (PTHR45957), with experimental descendants in human ANAPC2, fly, budding yeast Apc2 and fission yeast apc2 itself. APC/C membership is the defining, ancestral property of this cullin-family lineage. Reason: Apc2 is a constitutive core subunit of the 13-subunit fission yeast APC/C, recovered by mass spectrometry from Lid1-TAP, Apc13-TAP and Cut9-TAP purifications and present at one copy per particle in the mitotic APC/C-Slp1 complex. The IBA is a sound phylogenetic judgment; PomBase:SPBP23A10.04 (apc2 itself) appearing in the WITH/FROM list is expected, because its own IDA evidence was one of the descendant annotations used to place the IBD node. Supporting Evidence: PMID:12477395 Our data increase the total number of identified APC subunits to 13 in both yeasts and indicate that previous approaches were biased against the identification of small subunits. file:SCHPO/apc2/apc2-deep-research-falcon.md Apc2 yielded 19 unique tryptic peptides in a Lid1-TAP preparation and 24 in an independent Apc13-TAP preparation. file:SCHPO/apc2/apc2-deep-research-falcon.md differently tagged Apc2 molecules did not self-coimmunoprecipitate |
| GO:0005680 anaphase-promoting complex | IDA PMID:12477395 Proteomics analysis identifies new components of the fission... | ACCEPT | Summary: Yoon et al. 2002 tandem-affinity purified the S. pombe APC/C and analysed it by DALPC mass spectrometry, raising the subunit count to 13; Apc2 (SPBP23A10.04) was recovered with 19 and 24 unique peptides from Lid1-TAP and Apc13-TAP preparations. This is the founding identification of fission yeast Apc2 as an APC/C subunit and the source of the UniProt SUBUNIT statement. Reason: Direct biochemical evidence for complex membership in the gene's own organism; the cached record is abstract-only, but the abstract states the purification approach and the 13-subunit result, and the deep research reports the Apc2 peptide counts. Core. Supporting Evidence: PMID:12477395 Here, we have applied a tandem affinity purification approach coupled with direct analysis of the purified complexes by mass spectrometry (DALPC) to reveal additional subunits of both the S. pombe and S. cerevisiae APCs. file:SCHPO/apc2/apc2-deep-research-falcon.md Apc2 yielded 19 unique tryptic peptides in a Lid1-TAP preparation and 24 in an independent Apc13-TAP preparation. file:SCHPO/apc2/apc2-uniprot.txt The APC/C is composed of at least 13 subunits: apc1, apc2, |
| GO:0005680 anaphase-promoting complex | IDA PMID:15060174 Swm1/Apc13 is an evolutionarily conserved subunit of the ana... | ACCEPT | Summary: Schwickart et al. 2004 purified TAP-tagged Cut9 and Apc13 from fission yeast and identified by mass spectrometry the set of known or predicted APC/C subunits (plus Apc13, Apc14 and Apc15) in both preparations; the full text is cached and the S. pombe purifications are described explicitly. Reason: Independent co-purification of Apc2 with two different tagged APC/C subunits in the gene's own organism confirms constitutive membership of the complex. Core. Supporting Evidence: PMID:15060174 Mass spectrometric analysis of the Cut9-TAP purification identified 10 proteins known or predicted to be APC/C subunits PMID:15060174 purification of a TAP-tagged version of Apc13 yielded the same set of APC/C subunits as Cut9-TAP |
| GO:0005680 anaphase-promoting complex | IPI PMID:12477395 Proteomics analysis identifies new components of the fission... | ACCEPT | Summary: ComplexPortal-derived IPI for the fission yeast APC/C (CPX-763 and its Slp1, Srw1/Ste9 and Mfr1 coactivator variants), citing the Yoon et al. 2002 proteomic definition of the 13-subunit complex. Reason: Duplicates the PomBase IDA from the same paper with a different evidence code; the underlying evidence (co-purification and mass-spectrometric identification of Apc2 in the TAP-purified complex) is sound. Core. Supporting Evidence: PMID:12477395 Our data increase the total number of identified APC subunits to 13 in both yeasts and indicate that previous approaches were biased against the identification of small subunits. |
| GO:0005829 cytosol | HDA PMID:16823372 ORFeome cloning and global analysis of protein localization ... | KEEP AS NON CORE | Summary: Second localisation call from the Matsuyama et al. 2006 ORFeome YFP atlas, which scored Apc2-YFP in the cytosol as well as the nucleus. The APC/C is a soluble, roughly 1 MDa particle and a cytosolic pool is expected, but no fission yeast study links Apc2 to a cytosolic substrate or activity. Reason: The observation is credible for a soluble complex and is not contradicted by any other data, so it is retained; but the core function of Apc2 (ubiquitination of the nuclear substrates Cut2 and Cdc13 during the closed mitosis of fission yeast) is executed in the nucleus, and the deep research explicitly cautions that no exclusive or activity-linked localisation for Apc2 itself is established by the species-specific evidence. Kept as a non-core location. Supporting Evidence: PMID:16823372 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. |
| GO:0006511 ubiquitin-dependent protein catabolic process | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA electronic mapping to the general ubiquitin-dependent proteolysis term; the specific descendants anaphase-promoting complex-dependent catabolic process (GO:0031145) and proteasome-mediated ubiquitin-dependent protein catabolic process (GO:0043161) are annotated from the literature. Reason: Correct but general. The Apc2-containing APC/C is a ubiquitin ligase whose activity is required for the destruction of cyclin and Cut2, so the parent-term inference is accurate; it is subsumed by the more specific GO:0031145 row and adds no independent claim. Supporting Evidence: PMID:9264466 We show here that the fission yeast gene products Cut9 and Nuc2 are the subunits of the 20S complex, the putative APC (anaphase promoting complex)/cyclosome which contains ubiquitin ligase activity required for cyclin and Cut2 destruction. PMID:12477395 The anaphase-promoting complex (APC) is a conserved multisubunit ubiquitin ligase required for the degradation of key cell cycle regulators. |
| GO:0007091 metaphase/anaphase transition of mitotic cell cycle | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from node PTN000231994, seeded by the budding yeast APC2 genetic evidence (rsi1/apc2 ts mutants arrest in metaphase and are rescued by deleting the securin PDS1). APC/C-Cdc20-driven destruction of securin is the ancestral trigger of the metaphase/anaphase transition across eukaryotes, and in fission yeast the 20S APC/cyclosome supplies the ligase activity required for Cut2/securin and cyclin destruction. Reason: Apc2 forms the catalytic centre of the ligase (with Apc11) that ubiquitinates Cut2/securin under Slp1/Cdc20 control, which is precisely the process the term defines; the fission yeast complex is placed by cryo-EM with Slp1 adjacent to the Apc2-Apc11-Apc10 catalytic region. The IBA correctly reflects a conserved, ancestral function and there is no evidence of divergence in this lineage. Core. Supporting Evidence: PMID:9264466 We show here that the fission yeast gene products Cut9 and Nuc2 are the subunits of the 20S complex, the putative APC (anaphase promoting complex)/cyclosome which contains ubiquitin ligase activity required for cyclin and Cut2 destruction. PMID:20924356 The catalytic centre of the APC/C is formed from the cullin and RING subunits Apc2 and Apc11, analogous to Cul1 and Rbx1, respectively, of the SCF cullin RING ligase. file:SCHPO/apc2/apc2-deep-research-falcon.md Securin destruction activates separase and sister-chromatid separation; cyclin-B destruction lowers Cdk activity and permits mitotic exit. |
| GO:0031145 anaphase-promoting complex-dependent catabolic process | NAS PMID:12477395 Proteomics analysis identifies new components of the fission... | ACCEPT | Summary: ComplexPortal NAS assigned to every subunit of the fission yeast APC/C (CPX-763 and coactivator variants), citing the Yoon et al. 2002 proteomic definition of the complex. The process (ubiquitination by the APC/C followed by proteasomal destruction of securin and B-type cyclins) is established for the fission yeast 20S complex and for purified S. pombe APC/C used in in vitro ubiquitination assays. Reason: GO:0031145 is the most precise process term for what the Apc2-containing ligase does, and Apc2 does the work as the cullin scaffold of the catalytic module rather than merely being required for it. The NAS code reflects a complex-level assignment, but the assertion is correct and is grounded experimentally on the fission yeast complex. Core. Supporting Evidence: PMID:9264466 We show here that the fission yeast gene products Cut9 and Nuc2 are the subunits of the 20S complex, the putative APC (anaphase promoting complex)/cyclosome which contains ubiquitin ligase activity required for cyclin and Cut2 destruction. PMID:15060174 The anaphase-promoting complex (APC/C) is a large ubiquitin-protein ligase which controls progression through anaphase by triggering the degradation of cell cycle regulators such as securin and B-type cyclins. file:SCHPO/apc2/apc2-deep-research-falcon.md In fission yeast, Ubc4 and Ubc11 contribute to different aspects of cyclin-B ubiquitylation. |
| GO:0043161 proteasome-mediated ubiquitin-dependent protein catabolic process | IC PMID:12477395 Proteomics analysis identifies new components of the fission... | ACCEPT | Summary: PomBase curator inference from APC/C membership (GO:0005680, PMID:12477395) to the general process of proteasome-mediated, ubiquitin-dependent proteolysis; a parent of the ComplexPortal GO:0031145 row. Reason: The inference is sound - the APC/C is a ubiquitin ligase whose products are degraded by the 26S proteasome, and Apc2 is one of its two catalytic-module subunits - and the term is accurate though less specific than GO:0031145. Both rows describe the same core activity. Supporting Evidence: PMID:12477395 The anaphase-promoting complex (APC) is a conserved multisubunit ubiquitin ligase required for the degradation of key cell cycle regulators. PMID:9264466 We show here that the fission yeast gene products Cut9 and Nuc2 are the subunits of the 20S complex, the putative APC (anaphase promoting complex)/cyclosome which contains ubiquitin ligase activity required for cyclin and Cut2 destruction. |
| GO:0070979 protein K11-linked ubiquitination | IBA GO_REF:0000033 | MODIFY | Summary: PAINT IBA from node PTN000231994 whose only experimental donor for this term is human ANAPC2 (UniProtKB:Q9UJX6). K11-linked chain assembly by the human APC/C depends on the chain-elongating E2 UBE2S working after UBE2C/UbcH10. The characterised E2s of the fission yeast APC/C are Ubc4 and Ubc11 (the UbcH10/UBE2C orthologue); no UBE2S-type elongating E2 has been described for the S. pombe complex, and the linkage of the chains it builds has not been determined. In budding yeast, whose APC/C uses Ubc4 and Ubc1, the chains are K48-linked. Reason: The IBD placement propagates a metazoan, UBE2S-dependent linkage specificity to the whole ANAPC2 family. The lineage-independent claim that is actually supported for fission yeast is that the Apc2-containing APC/C assembles polyubiquitin chains that target Cut2/securin and Cdc13/cyclin B to the proteasome (Ubc4- and Ubc11-dependent cyclin ubiquitylation by purified S. pombe APC/C). Because the linkage type in S. pombe is undetermined (and the closest characterised fungal system, budding yeast, makes K48 rather than K11 chains), the row should be re-expressed with the linkage-agnostic term protein polyubiquitination (GO:0000209), and the K11 IBD should be re-placed at the node where UBE2S-dependent chain elongation arose. Propagation Review Root cause: PROPAGATION BAD Failure modes: LINEAGE OR TAXON MISMATCH GRANULARITY MISMATCH Sources checked: PANTHER:PTN000231994 SUPPORTS SOURCE BUT NOT TARGET IBD node in PTHR45957 carrying GO:0070979 on the strength of human ANAPC2 K11 evidence; K11 specificity depends on the elongating E2 UBE2S, which has not been described for the fission yeast APC/C, so the node is placed too deep for this term. UniProtKB:Q9UJX6 · ANAPC2 SUPPORTS SOURCE BUT NOT TARGET Human ANAPC2 has direct IDA evidence for K11-linked chains built by UBE2C/UBE2S; the fission yeast APC/C uses Ubc4 and Ubc11 and its chain linkage is undetermined. Proposed replacements: protein polyubiquitination Supporting Evidence: PMID:19822757 The cooperation between Ube2S and UbcH10 is reminiscent of yeast APC/C, which uses a chain-initiating E2, Ubc4, and a chain-elongating E2, Ubc1 PMID:19822757 However, Ubc4 and Ubc1 function sequentially to assemble K48-linked ubiquitin chains, whereas human UbcH10 and Ube2S most likely bind APC/C at the same time. file:SCHPO/apc2/apc2-deep-research-falcon.md In fission yeast, Ubc4 and Ubc11 contribute to different aspects of cyclin-B ubiquitylation. |
| GO:0160072 ubiquitin ligase complex scaffold activity | ISS PMID:20924356 The APC/C subunit Cdc16/Cut9 is a contiguous tetratricopepti... | NEW | Summary: Inferred ubiquitin ligase complex scaffold activity for this gene product, proposed during the NO_DATA re-action pass. Reason: Ubiquitin ligase complex scaffold activity is inferred for this gene product (ISS), not shown for it experimentally; the ND row for the aspect therefore stays (projects/NO_DATA.md). A molecular function can now be stated for this protein: the conserved cullin scaffold role, GO:0160072 ubiquitin ligase complex scaffold activity (the binding activity that brings together a ubiquitin ligase and its substrate adaptor so that they act in a coordinated way). The fission yeast evidence is complex-level (Apc2 and Apc11 form the catalytic centre; the Apc2-Apc11-Apc10 region maps next to the Slp1 coactivator in the S. pombe cryo-EM reconstruction), and the tethering mechanism is established in the orthologues (APC11 and UbcH10 bind the C-terminal cullin homology domain of APC2; Apc2 is not required for ubiquitin transfer in a minimal system but tethers and positions Apc11), so the term would be supported by ISS/IC rather than by a fission-yeast IDA. The term is the one carried by the canonical cullins CUL1-5 in GOA and adopted for human ANAPC2 and budding yeast Apc2 in this repository; Apc2 contributes to, but does not itself enable, ubiquitin protein ligase activity (GO:0061630), which belongs to the Apc11 RING. Supporting Evidence: PMID:20924356 The catalytic centre of the APC/C is formed from the cullin and RING subunits Apc2 and Apc11, analogous to Cul1 and Rbx1, respectively, of the SCF cullin RING ligase. PMID:20924356 In combination, Apc2 and Apc11 are competent to catalyse protein ubiquitylation, although lack substrate selectivity PMID:15060174 Apc11 is anchored to the complex through Apc2, a subunit distantly related to cullins PMID:11739784 Both APC11 and UbcH10 bind to the C-terminal cullin homology domain of APC2, whereas Ubc4 interacts with APC11 directly. PMID:10888670 While Apc2p was not required to effect ubiquitin transfer in vitro, it may function in a cellular context to tether Apc11p to APC core proteins, and to properly position the Apc11p RING-H2 finger with respect to its substrates. file:SCHPO/apc2/apc2-deep-research-falcon.md Mapping placed the Apc2–Apc11–Apc10 catalytic region along the right/lower side of the complex, with Apc11 near the cavity lip and Slp1 near the lower horn-like region. file:SCHPO/apc2/apc2-deep-research-falcon.md Apc11 supplies the RING element that activates or positions the E2–ubiquitin conjugate; Apc2 supplies the cullin-like scaffold. file:SCHPO/apc2/apc2-uniprot.txt Belongs to the cullin family. |
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Download this section (compressed HTML)Q: Which ubiquitin-chain linkages does the fission yeast APC/C build on Cut2 and Cdc13 with Ubc4 and Ubc11 - K48-linked chains as in budding yeast, K11-linked chains as in the UBE2S-dependent human system, or mixed chains - and should the PAINT K11 IBD for the ANAPC2 family be re-placed at a metazoan node?
Q: Does deletion or conditional inactivation of fission yeast apc2 remove Apc11 and Apc10 from the purified complex, as apc2 delta does in budding yeast, i.e. is the cullin tethering function that underlies the proposed ubiquitin ligase complex scaffold activity conserved in S. pombe?
Q: Is the zinc-binding module found in human APC2 (absent from budding yeast Apc2) present in fission yeast Apc2, and does it contribute to complex stability?
Experiment: Build a conditional (auxin-degron or ts) apc2 allele in a Lid1-TAP or Cut9-TAP background, purify the complex after Apc2 depletion, score retention of Apc11, Apc10 and Slp1 by mass spectrometry and immunoblot, and assay ubiquitination of Cut2 and Cdc13 in vitro with recombinant Uba1, Ubc4 and Ubc11.
Hypothesis: Fission yeast Apc2 independently tethers Apc11 and Apc10 to the APC/C core, and loss of Apc2 abolishes ligase activity of the purified complex.
Type: conditional depletion with TAP purification and in vitro ubiquitination
Experiment: Reconstitute ubiquitination of Cut2 and Cdc13 with purified S. pombe APC/C, Slp1, Uba1, Ubc4 and Ubc11 using wild-type and lysine-to-arginine ubiquitin mutants, and quantify linkage types by ubiquitin-AQUA mass spectrometry; compare with chains on Cdc13 immunopurified from metaphase-arrested cells.
Hypothesis: The ubiquitin chains assembled on Cut2 and Cdc13 by the Apc2-containing fission yeast APC/C are predominantly K48-linked, with no substantial K11 component.
Type: in vitro reconstitution with quantitative ubiquitin linkage mass spectrometry
Experiment: Tag apc2 at its chromosomal locus with a fluorescent protein, confirm the fusion is functional, and image it live through the cell cycle alongside a spindle-pole-body and a nuclear-envelope marker, including in cells arrested at metaphase by the spindle assembly checkpoint.
Hypothesis: Endogenous Apc2 is predominantly nuclear during the closed mitosis of fission yeast, with a cytosolic pool in interphase.
Type: endogenous tagging and live-cell imaging
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