old mitotic spindle pole body
The spindle pole body that existed before the most recent spindle pole body duplication. In unperturbed Schizosaccharomyces pombe mitosis, septation initiation network activity becomes restricted to the new pole in late anaphase B, after activity at both poles earlier in mitosis. [DOI:10.1101/gad.296204]
Synonyms: old SPB
Taxonomic distribution
NCBITaxon:4896Schizosaccharomyces pombe — COMMON: Fission yeast is the model in which old and new mitotic spindle pole bodies were distinguished during asymmetric mitotic-exit signaling; no broader fungal distribution is asserted here. [DOI:10.1101/gad.296204]
Canonical examples
NCBITaxon:4896Schizosaccharomyces pombe — Reference fission-yeast system in which Pcp1-RFP inheritance distinguishes the pre-existing pole. Cdc7 is present at both poles in early anaphase B but becomes restricted to the new pole in late anaphase B; old-pole signaling is not constitutively absent. [DOI:10.1101/gad.296204]
Discussions
- INTERPRETATION (RESOLVED): Keep the GO age/asymmetry term for the old mitotic SPB narrower than the general mitotic SPB and distinct from local old/new SPB duplication placeholders. GO:0071957 denotes the pre-existing mitotic spindle pole body that lacks active mitotic-exit signaling proteins, whereas GO:0044732 denotes the broader mitotic SPB. The older ungrounded old_spb and new_spb causal-graph nodes on the general SPB record are generic duplication roles and are not exact records for the fission-yeast GO:0071957 and GO:0071958 age/asymmetry terms.
- CURATION_TODO (OPEN): Resolve exact source-neutral family groundings and exclusion evidence for fission-yeast SIN and NIMA-related proteins that distinguish the old mitotic SPB. This first GO-backed record captures the old mitotic SPB as an age/asymmetry structure without treating a lack of active fission-yeast-specific mitotic-exit proteins as positive component evidence or guessing InterPro, Pfam, NCBIfam, UniProtKB, or Complex Portal groundings.
- INTERPRETATION (RESOLVED): Separate old-pole identity from stage-dependent fission-yeast SIN activity and budding-yeast inheritance. The inherited GO definition and earlier boundary discussion used unqualified signaling-inactivity wording. Grallert et al. 2004 Figure 5 shows Cdc7 on both poles early in anaphase B and only on the new pole later; Fin1 remains associated with the old pole, and Fin1 perturbation can reactivate old-pole signaling. The paper discusses old-pole inheritance by the bud/daughter separately in Saccharomyces cerevisiae, not as the defining segregation pattern of symmetrically dividing S. pombe.
Evidence
GO:0071957Gene Ontology cellular-component term for the old mitotic spindle pole body, with old SPB as an exact synonym.GO:0044732Gene Ontology cellular-component parent term for mitotic spindle pole body.GO:0071958Gene Ontology cellular-component sibling term for the newly formed new mitotic spindle pole body.DOI:10.1101/gad.296204Grallert et al. 2004 distinguished old and new fission-yeast SPBs using Pcp1-RFP. Figure 5 shows Cdc7 at both poles in early anaphase B and its later restriction to the new pole. Figure 6 shows that compromised Fin1 function can restore Cdc7 to both poles. These experiments support stage-dependent SIN regulation, not permanent absence of signaling proteins from the old pole.
Curation history
2026-09-29T18:05:16Zcodex · CREATED_RECORD — Scaffolded by scripts/new_record.py2026-09-29T18:07:14Zcodex · EXPANDED_RECORD — Added the GO exact synonym, mitotic-SPB parentage, Schizosaccharomyces scope, GO and fission-yeast literature evidence, and boundary/component discussions for the old mitotic spindle pole body.2026-10-11T15:28:56Zcodex · ADDRESS_SAVED_REVIEW — Addressed #2220: Bound old-SPB SIN activity to the supported S. pombe cell-cycle context, replaced the unqualified definition with a literature-backed local definition, scoped the example, and appended a source-conflict clarification without rewriting prior discussions.
Source: data/structures/cytoskeleton/old_mitotic_spindle_pole_body.yaml