clp1 (flp1; SPAC1782.09c; UniProt Q9P7H1) — curation notes

Session: 2026-09-26. Fission yeast Cdc14-family phosphatase. Inputs: clp1-uniprot.txt,
clp1-goa.tsv (75 rows), clp1-deep-research-falcon.md (Edison), cached publications.
Comparator: genes/yeast/CDC14/CDC14-ai-review.yaml (complete S. cerevisiae review).

Full-text availability

Abstract-only caches (curators read the full text; I did not): PMID:11448769, 15128870,
15265986, 15525536, 16085489, 16823372, 16950131, 18418059, 33176152, 37128864. Europe PMC
has no OA full text for any of these. Full text cached for the other 15 papers.

Holistic picture

• Founding paper: Clp1 is the S. pombe Cdc14 homolog, "not required for mitotic exit but rather
  functions together with the SIN in coordinating cytokinesis with the nuclear-division cycle"
  PMID:11448769. It leaves the nucleolus at mitotic entry (earlier than Cdc14)
  and goes to the spindle and division site; the SIN keeps it out of the nucleolus until cytokinesis
  is done PMID:11448769. clp1Δ enters mitosis early; overexpression delays G2/M
  PMID:11448769.
• Substrate specificity: Ser/Thr-Pro (Cdk1) sites. "belongs to a conserved family of
  serine-threonine-phosphatases" PMID:15128870; "proline-directed Cdc14-like phosphatase Clp1"
  PMID:21965289. Substrate-trap proteomics: >70 C286S-enriched candidates, Cdk1 sites in 44/73
  PMID:23297348. No phosphotyrosine substrate is known (deep research agrees). Clp1 affects
  Cdc2 Tyr15 only indirectly, via Cdc25.
• Mitotic exit / G2-M: Cdc25 is an in vitro substrate and Flp1 is needed for its rapid degradation
  at the end of mitosis [PMID:15128870 "Cdc25p is a substrate of Flp1p in vitro"; PMID:18418059
  "Flp1p is required for the rapid degradation of Cdc25p"]. Cdk1 phosphorylates and inhibits Clp1
  before anaphase; Clp1 autodephosphorylates as Cdk1 falls PMID:16950131. Pxl1 is
  dephosphorylated by Clp1 and Dis2 at mitotic exit PMID:34133210.
• Spindle: dephosphorylates Klp9 and Ase1 at anaphase B onset so they bind at the midzone; clp1off
  halves elongation velocity PMID:19686686. Also
  Dis1 PMID:34080538. Clp1
  concentrates at the midzone in anaphase B PMID:19686686. Meadows 2017: Klp9 C-terminus dephosphorylation by Clp1 is
  needed for Klp9-CPC interaction at the midzone; no change in pole-separation rate but more
  anaphase B spindle collapse in clp1Δ/C286S PMID:28178520.
• Kinetochores: Clp1 at kinetochores in prometaphase; clp1Δ cosegregates sisters when
  mono-orientation-prone; works with Aurora/Ark1 PMID:15525536. Nsk1 substrate: dephosphorylation
  needed for kinetochore-SPB junction localization [PMID:21965289; PMID:22065639 "purified MBP-Clp1
  but not catalytically inactive MBP-Clp1-C286S dephosphorylated Nsk1"]. Mde4 (monopolin) substrate
  PMID:19523829.
• IMPORTANT opposite sign: Choi & McCollum 2012 — clp1Δ reduces lagging chromosomes in mde4Δ and
  swi6Δ; Clp1-NLS increases them: "Clp1 antagonizes correction of merotelic attachments"
  PMID:22264609, mechanism = Klp9-dependent metaphase spindle length / tension.
• Cytokinesis: Mid1 tethers Clp1 at the contractile ring (Mid1 aa 331-534 binds Clp1 catalytic
  domain; 0/102 mid1Δ rings have Clp1); Clp1 dephosphorylates Cdc15 PMID:18378776. Cdc12 formin
  Cdk1 sites dephosphorylated by Clp1, allowing maximal Cdc12 at the ring PMID:29343550. FPALM:
  Clp1 at 136 nm, intermediate stratum PMID:28914606. Cdc11 (SIN scaffold) Cdk1 sites are
  Clp1 substrates PMID:23297348.
• Cytokinesis checkpoint: Clp1-dependent G2 delay and ring maintenance under mild cytokinetic
  perturbation; ectopic SIN activation bypasses the need for Clp1 PMID:15265986. Sid2 (SIN)
  phosphorylates Clp1 RxxS sites → 14-3-3 Rad24 binding → cytoplasmic retention [PMID:16085489;
  PMID:18951025 "Mutation of the Sid2 phosphorylation sites on Clp1 disrupts the Clp1-Rad24
  interaction and causes Clp1 to return prematurely to the nucleolus during cytokinesis"]. clp1-6A
  keeps the checkpoint but fails to complete cytokinesis under ring stress.
• Nuclear import via Sal3 (importin-β3); C-terminal basic NLS PMID:23297348.
• Stress: HU/H2O2 (not heat/osmotic) trigger interphase nucleoplasmic release via Cds1/Chk1, Pmk1
  and Cdk1 phosphorylation PMID:22918952. Deep research adds Cañete 2023 (Sci Rep; not in GOA):
  released Clp1 dephosphorylates Pcr1 and limits the oxidative-stress transcriptional response.
• Stress sequestration sites: heat-shock nucleolar rings (NuRs) PMID:33176152 and stationary
  phase nucleolar inclusions PMID:37128864 — GO:0140602 rows, abstract-only.

GO-CAM context

gocams/index.tsv has clp1 in three production models: SIN model 66187e4700002284 (Clp1 phosphatase
→ positive regulation of contractile ring assembly at the ring; phospho-Clp1 → cytokinesis checkpoint
at the mitotic SPB), ring-assembly model 67f85f2b00002096 (same MF/BP/CC), and G2/M model
69729a3800001390 (negative regulation of G2/M at the mitotic SPB). Core functions were aligned with
these. Module modules/metaphase_anaphase_transition_and_mitotic_exit.yaml uses Clp1 as the
fission-yeast exit-phosphatase variant (annoton clp1_spom, GO:0004722).

Decisions of note

• GO:0004725 protein tyrosine phosphatase activity (IEA, EC 3.1.3.48): MODIFY → GO:0008138
  protein tyrosine/serine/threonine phosphatase activity, mirroring the CDC14 review. No
  phosphotyrosine substrate; all substrates are Cdk1 pS/pT-P sites.
• GO:0005515 protein binding IPIs: Ark1 → MODIFY GO:0019901 protein kinase binding; Rad24 (two rows)
  → MODIFY GO:0071889 14-3-3 protein binding (evidence-backed, mechanistic); Mid1 → REMOVE (scaffold
  relationship already captured by the CR localization row); Mde4 → REMOVE (enzyme–substrate;
  belongs as has_input on the phosphatase activity).
• GO:0140429 IGI PMID:22264609 → MODIFY to GO:0051988 regulation of attachment of spindle
  microtubules to kinetochore. GO:0140429 has secondary ids GO:0098783 (repair of merotelic
  attachment defect) and GO:1990598 (repair of mono-orientation defect), merged 2020; the IGI row
  was presumably made to the former, but the paper shows Clp1 antagonizes merotelic correction, so
  the merged positive-regulation label misstates the direction. No negative-regulation term exists.
  The IMP row from PMID:15525536 (mono-orientation repair) is ACCEPTed. This creates a deliberate
  "inconsistent actions for the same term" validator warning.
• GO:0072479 response to SAC signaling (IMP, PMID:15525536): UNDECIDED — abstract-only; abstract
  supports biorientation, not a SAC-response process.
• GO:0006974 DNA damage response and GO:0033554 cellular response to stress: KEEP_AS_NON_CORE
  (real, kinase-dependent relocalization; downstream role undefined in the cited paper).
• GO:0140602 nucleolar peripheral inclusion body (two IDA rows): KEEP_AS_NON_CORE — sequestration
  under heat stress / stationary phase, not a site of activity.
• GO:1902846 EXP PMID:28178520: ACCEPT with caveat that this paper found no rate change, only more
  spindle collapse; rate effect is in PMID:19686686 and PMID:34080538.
• No NEW annotations proposed; the Pcr1/oxidative-stress function (Cañete 2023) is not in GOA and
  the paper is not cached, so it is noted here and in the GO:0033554 row only.

Validation

just validate SCHPO clp1: valid, 1 warning (deliberate GO:0140429 inconsistency). Rendered with
just render SCHPO clp1.