cellular bud tip polarisome

GO:0031561 · Other · Multiprotein complex · Proposed

Protein complex that has a role in determining cell polarity, found at the tip of a growing fungal bud. [GO:0031561]

Part of: cellular bud tip (GO:0005934)

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Spa2/Pea2 polarisome scaffold	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	SPA2, PEA2		CONDITIONAL	Scaffold proteins that localize to budding growth sites and form a stable pair in the Saccharomyces 12S polarisome. `DOI:10.1083/jcb.135.3.725` Valtz and Herskowitz 1996 showed that Pea2 and Spa2 localize to polarized-growth sites in budding and mating cells and depend on one another for stable localization. `DOI:10.1128/MCB.18.7.4053` Sheu et al. 1998 found that Spa2 interacts with Pea2 in two-hybrid and coimmunoprecipitation experiments.
Bud6/Aip3 actin-associated polarity protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	BUD6, AIP3		CONDITIONAL	Actin-associated polarity protein that cosediments with Spa2 and Pea2 in the budding-yeast 12S polarisome. `DOI:10.1128/MCB.18.7.4053` Sheu et al. 1998 showed that Spa2 interacts with Bud6/Aip3 by two-hybrid analysis and that a significant portion of Spa2, Pea2, and Bud6 cosediments as a 12S multiprotein complex.

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast Spa2, Pea2, and Bud6/Aip3 proteins localize to polarized growth sites, including small bud tips, and form a 12S polarisome complex. [DOI:10.1128/MCB.18.7.4053]

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which Spa2, Pea2, and Bud6/Aip3 were connected by two-hybrid, coimmunoprecipitation, and velocity-sedimentation assays. [DOI:10.1128/MCB.18.7.4053]

bud-tip polarized morphogenesis — The cellular bud tip polarisome concentrates Spa2, Pea2, and Bud6/Aip3 at budding growth sites to support polarized morphogenesis in Saccharomyces cerevisiae.
- GO:0031561 GO:0031561 defines the cellular bud tip polarisome by its role in determining cell polarity at the tip of a growing fungal bud.
- DOI:10.1128/MCB.18.7.4053 Sheu et al. 1998 proposed that Spa2, Pea2, and Bud6 act together in a complex to promote polarized morphogenesis.

Spa2 and Pea2 form a stable scaffold and Bud6/Aip3 cosediments with that scaffold in the Saccharomyces 12S polarisome found at budding growth sites.

Subject	Predicate	Object	Evidence
Spa2/Pea2 polarisome scaffold	forms scaffold for	cellular bud tip polarisome	`DOI:10.1083/jcb.135.3.725` Valtz and Herskowitz 1996 found that Pea2 and Spa2 localize in a similar pattern and depend on one another for stable localization. `DOI:10.1128/MCB.18.7.4053` Sheu et al. 1998 showed that Spa2 and Pea2 interact by two-hybrid analysis and coimmunoprecipitate in vivo.
Bud6/Aip3 actin-associated polarity protein	cosediments with	Spa2/Pea2 polarisome scaffold	`DOI:10.1128/MCB.18.7.4053` Sheu et al. 1998 found that a significant portion of Bud6 cosediments with Spa2 and Pea2 by velocity sedimentation.
cellular bud tip polarisome	localizes to	cellular bud tip	`GO:0031561` GO:0031561 defines this structure as the polarisome at the tip of a growing fungal bud.
cellular bud tip polarisome	supports	bud-tip polarized morphogenesis	`DOI:10.1128/MCB.18.7.4053` Sheu et al. 1998 proposed that Spa2, Pea2, and Bud6 function together, perhaps as a complex, to promote polarized morphogenesis.

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for Spa2, Pea2, and Bud6/Aip3 at the cellular bud tip. This localized record deliberately reuses the reviewed-label-only Saccharomyces polarisome cohorts from the broader polarisome record instead of guessing InterPro, Pfam, NCBIfam, or UniProtKB family groundings whose broader homologous families do not exactly delimit the bud-tip complex.
INTERPRETATION (RESOLVED): Keep Bni1, Aip5, the exocyst, and MAPK signaling proteins outside the first cellular-bud-tip polarisome component boundary. GO:0000133 and later Saccharomyces polarisome studies implicate Bni1, Aip5, and other actin-assembly factors in the broader polarisome, but Sheu et al. 1998 directly support a Spa2/Pea2/Bud6 12S complex and discuss Bni1 only as a possible additional component. The exocyst is a separate bud-tip-localized complex and the MAPK factors tested by Sheu et al. are interacting signaling proteins, not curated constituents of the GO:0031561 structure.

GO:0031561 Gene Ontology cellular-component term for the cellular bud tip polarisome.
GO:0000133 Gene Ontology cellular-component term for polarisome.
GO:0005934 Gene Ontology cellular-component term for the cellular bud tip.
DOI:10.1128/MCB.18.7.4053 Sheu et al. 1998, 'Spa2p interacts with cell polarity proteins and signaling components involved in yeast cell morphogenesis', Molecular and Cellular Biology.
DOI:10.1083/jcb.135.3.725 Valtz and Herskowitz 1996, 'Pea2 protein of yeast is localized to sites of polarized growth and is required for efficient mating and bipolar budding', Journal of Cell Biology.

2026-09-28T19:36:57Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T19:40:49Z codex · EXPANDED_RECORD — Added polarisome parentage, cellular-bud-tip parthood, Spa2/Pea2 and Bud6/Aip3 constituents, Saccharomyces distribution and canonical example evidence, a bud-tip morphogenesis function, a nonmechanistic 12S polarisome topology graph, and grounding and component-boundary discussions.
2026-09-28T19:57:58Z codex · ADDRESSED_REVIEW — Resolved #1738 by renaming the Bud6/Aip3 component and graph node from an actin nucleation-promoting factor to an actin-associated polarity protein.