Polarity-associated protein SPA2 is a large scaffolding protein essential for establishing and maintaining cell polarity in budding yeast. SPA2 localizes to sites of polarized growth (bud tip, mating projection, bud neck) where it functions as a core component of the polarisome complex together with Pea2p and Bud6p. SPA2 serves as a scaffold for recruiting and organizing multiple functional modules including actin cable assembly through interaction with formin Bni1, MAPK signaling pathway components, and proteins involved in bud site selection and cytokinesis. The protein contains multiple functional domains including conserved SHD (SPA2 Homology Domain) regions critical for protein-protein interactions and a C-terminal region containing tandem repeats.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000131 incipient cellular bud site | IBA GO_REF:0000033 | ACCEPT | Summary: SPA2 is a core component of the incipient bud site, localizing to sites of polarized growth before the bud is morphologically evident. This early and consistent localization is a defining characteristic of SPA2. Reason: Strong experimental evidence (IDA in primary literature) demonstrates SPA2 as an early marker of polarized growth sites. IBA assignment is appropriate for this well-conserved localization property across orthologs. Supporting Evidence: PMID:9214378 Spa2p is one of the first proteins involved in bud formation to localize to the incipient bud site before a bud is recognizable |
| GO:0005078 MAP-kinase scaffold activity | IBA GO_REF:0000033 | ACCEPT | Summary: Core molecular function as direct scaffold for Mpk1p/Slt2p MAPK pathway; recruits MEKs and MAPK to polarized growth sites for cell wall integrity signaling. Reason: Extensive experimental evidence (IDA, IMP) demonstrates SPA2 directly recruits and scaffolds Mpk1p MAPK pathway components. This is a primary mechanistic function essential for proper MAPK signaling. Supporting Evidence: PMID:12361575 Spa2p functions as a scaffold-like protein to recruit the Mpk1p MAP kinase module to sites of polarized growth PMID:9632790 Spa2p interacts with Ste11p (MAPK kinase [MEK] kinase) and Ste7p (MEK) of the mating signaling pathway as well as with the MEKs Mkk1p and Mkk2p of the Slt2p (Mpk1p) MAPK pathway |
| GO:0005826 actomyosin contractile ring | IBA GO_REF:0000033 | REMOVE | Summary: SPA2 localizes to bud neck region but is not a component of the contractile ring itself. The contractile ring contains myosin (Myo1p), actin filaments, and septins. Reason: SPA2 is present at bud neck via septin interaction but does not participate in contractile ring assembly or contraction. This appears to be an incorrect cross-species IBA inference from phylogenetic comparison. |
| GO:0005934 cellular bud tip | IBA GO_REF:0000033 | ACCEPT | Summary: Strong and consistent localization of SPA2 to bud tip where it organizes actin cables and polarity factors. Reason: Direct experimental evidence (IDA) for localization to bud tip; functionally essential for actin organization and polarized bud growth. Supporting Evidence: PMID:9214378 Our studies with Spa2GFP demonstrate that Spa2p localizes to the bud tip, forming a cup-like crescent, and the bud neck between mother and daughter cell, forming a donut-like ring. PMID:12361575 Spa2p-GFP is stably anchored at bud tips |
| GO:0005935 cellular bud neck | IBA GO_REF:0000033 | ACCEPT | Summary: SPA2 localizes to bud neck as ring structure during cytokinesis; interacts with septin components including Shs1p. Reason: Clear microscopic evidence (IDA) for bud neck localization, particularly during cytokinesis. Functions in septin ring organization and polarity maintenance. Supporting Evidence: PMID:9214378 During cytokinesis Spa2p is present as a ring at the mother-daughter bud neck |
| GO:0007121 bipolar cellular bud site selection | IBA GO_REF:0000033 | ACCEPT | Summary: SPA2 is essential for establishing bipolar budding pattern in diploid cells; mutants show defects in bud site selection. Reason: Strong genetic evidence (IMP) for role in bipolar bud site selection. IBA appropriately reflects conservation of this function across species. Supporting Evidence: PMID:8909546 SPA2 is required for the bipolar budding pattern PMID:9214378 Spa2p, a nonessential protein, has been shown to be involved in bud site selection |
| GO:0007124 pseudohyphal growth | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: SPA2 is required for pseudohyphal growth morphology but this represents a secondary developmental process, not core polarity function. Reason: SPA2 is involved in pseudohyphal growth through maintenance of polarized growth capability under nutrient stress. However, this is a specialized developmental program secondary to core cell polarity establishment. Supporting Evidence: PMID:9055077 Dissection of filamentous growth by transposon mutagenesis in Saccharomyces cerevisiae. PMID:9443897 The Spa2-related protein, Sph1p, is important for polarized growth in yeast |
| GO:0036267 invasive filamentous growth | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: SPA2 is required for invasive filamentous growth; genetic interaction with Spa2-related protein Sph1p shows importance for this developmental pathway. Reason: Genetic interaction evidence (IGI) shows SPA2 role in invasive growth, but this is a specialized developmental process secondary to core polarity function. Supporting Evidence: PMID:9443897 sph1(Delta) spa2(Delta) double mutants also exhibit a strong haploid invasive growth defect and an exacerbated mating projection defect relative to either sph1(Delta) or spa2(Delta) single mutants. |
| GO:0043332 mating projection tip | IBA GO_REF:0000033 | ACCEPT | Summary: SPA2 localizes prominently to mating projection tip (shmoo); essential for directed growth toward mating partner. Reason: Direct evidence (IDA) for localization to mating projection; essential for pheromone response and efficient mating. Supporting Evidence: PMID:2647769 The SPA2 protein of yeast localizes to sites of cell growth PMID:9214378 Spa2p is also found at the mother-daughter bud neck in cells undergoing cytokinesis file:yeast/SPA2/SPA2-deep-research-falcon.md During pheromone response, Spa2 is required for **focal** (narrow) polarization of the polarisome at the shmoo tip; Spa2 loss leads to wider projections consistent with reduced focusing of polarized secretion/transport. |
| GO:1902716 cell cortex of growing cell tip | IBA GO_REF:0000033 | ACCEPT | Summary: SPA2 is a core structural component of the growing cell tip cortex during polarized growth. Reason: IBA appropriately reflects conservation of cortical localization at growing tips across eukaryotes. Functionally essential for polarity organization. Supporting Evidence: GO_REF:0000033 Phylogenetic ortholog assignment |
| GO:0000165 MAPK cascade | IEA GO_REF:0000108 | ACCEPT | Summary: Indirect involvement in MAPK cascade through scaffolding the Mpk1p pathway components. Reason: IEA is appropriate; logical inference from GO:0005078 (MAP-kinase scaffold activity) that SPA2 is involved in MAPK cascade as a central scaffold. Supporting Evidence: GO:0005078 Logical inference from MAP-kinase scaffold activity |
| GO:0008360 regulation of cell shape | IEA GO_REF:0000043 | ACCEPT | Summary: Regulation of cell shape through control of polarized growth and actin organization. Reason: IEA from UniProt keywords is appropriate. SPA2's role in polarized growth fundamentally determines cell morphology. Supporting Evidence: GO_REF:0000043 UniProt keyword mapping |
| GO:0051286 cell tip | IEA GO_REF:0000044 | ACCEPT | Summary: SPA2 localizes to cell tip as core component of growth site organization. Reason: IEA from UniProt subcellular location mapping is appropriate and consistent with direct microscopic evidence. Supporting Evidence: GO_REF:0000044 UniProt subcellular location mapping |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | REMOVE | Summary: Generic protein binding annotation from interactome study; too vague and uninformative about mechanism. Reason: Too vague and uninformative. SPA2's specific molecular functions (MAP-kinase scaffold activity, polarisome assembly, actin regulation) are better represented by mechanistic terms rather than generic binding. Supporting Evidence: PMID:16429126 Proteome survey reveals modularity of the yeast cell machinery. |
| GO:0005515 protein binding | IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... | REMOVE | Summary: Generic protein binding from large-scale interactome study. Reason: Vague annotation better replaced by mechanistic function terms. Multiple duplicate entries for protein binding should be consolidated. Supporting Evidence: PMID:16554755 Global landscape of protein complexes in the yeast Saccharomyces cerevisiae. |
| GO:0005515 protein binding | IPI PMID:21502521 Modular coherence of protein dynamics in yeast cell polarity... | REMOVE | Summary: Generic protein binding from modular proteomics study. Reason: Generic annotation not informative about molecular mechanism. Supporting Evidence: PMID:21502521 Modular coherence of protein dynamics in yeast cell polarity system. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Generic protein binding from large-scale interactome survey. Reason: Generic annotation; specific molecular functions should replace this. Supporting Evidence: PMID:37968396 The social and structural architecture of the yeast protein interactome. |
| GO:0000753 cell morphogenesis involved in conjugation with cellular fusion | IMP PMID:8013906 Identification of genes required for normal pheromone-induce... | ACCEPT | Summary: SPA2 is required for proper morphogenesis during mating; essential for efficient cell fusion with mating partner. Reason: Direct genetic evidence (IMP) shows SPA2 is required for mating morphogenesis. spa2 mutants show defective shmoo formation and reduced mating efficiency. Supporting Evidence: PMID:8013906 Identification of genes required for normal pheromone-induced cell polarization in Saccharomyces cerevisiae |
| GO:0000753 cell morphogenesis involved in conjugation with cellular fusion | IMP PMID:8909546 Pea2 protein of yeast is localized to sites of polarized gro... | ACCEPT | Summary: SPA2 and Pea2p function together in cell morphogenesis during conjugation; interdependent localization. Reason: Complementary genetic evidence showing SPA2-Pea2p interdependent localization is critical for mating morphogenesis. Supporting Evidence: PMID:8909546 These results suggest that Pea2p and Spa2p function together as a complex to generate the bipolar budding pattern and to guarantee proper polarization during mating |
| GO:0006903 vesicle targeting | NAS PMID:16166638 Regulation of cell polarity by interactions of Msb3 and Msb4... | KEEP AS NON CORE | Summary: SPA2 polarisome coordinates with secretory machinery through Msb3/4 interaction; indirect role in vesicle targeting. Reason: NAS from ComplexPortal is appropriate but SPA2's role in vesicle targeting is indirect through organizing polarisome that coordinates with exocytosis. Not a primary function. Supporting Evidence: PMID:16166638 Msb3 and Msb4 regulate polarized growth by multiple mechanisms, directly regulating exocytosis through their GAP activity toward Sec4 |
| GO:0030010 establishment of cell polarity | NAS PMID:16166638 Regulation of cell polarity by interactions of Msb3 and Msb4... | ACCEPT | Summary: SPA2 is core scaffolding component of polarisome complex essential for establishing cell polarity. Reason: NAS from ComplexPortal is appropriate for well-characterized complex annotation. SPA2 is definitional component of the polarisome. Supporting Evidence: PMID:16166638 Here we show that the Rab GTPase-activating proteins (GAPs) Msb3 and Msb4 interact directly with Spa2, a scaffold protein of the "polarisome" that also interacts with the formin Bni1. file:yeast/SPA2/SPA2-deep-research-falcon.md Spa2 helps focus the polarisome at cortical growth zones, promotes **formin-dependent actin cable assembly**, recruits or stabilizes partners |
| GO:0030950 establishment or maintenance of actin cytoskeleton polarity | NAS PMID:16166638 Regulation of cell polarity by interactions of Msb3 and Msb4... | ACCEPT | Summary: SPA2 as polarisome component is essential for organizing and maintaining actin cytoskeleton polarity. Reason: NAS from ComplexPortal is appropriate. SPA2-Bud6p directly regulate actin organization at growth sites. Supporting Evidence: PMID:16166638 A functional equivalent of the polarisome probably exists in other fungi and mammals. |
| GO:0032956 regulation of actin cytoskeleton organization | IMP PMID:12857882 Actin recovery and bud emergence in osmotically stressed cel... | ACCEPT | Summary: SPA2 regulates actin cable organization and recovery of actin structures under stress through scaffold function. Reason: SPA2 is essential for actin recovery and bud emergence under osmotic stress; core function in actin organization. Beyond scaffolding, recent work (Ma et al. 2024) shows Spa2 can directly remodel actin in a nucleotide-state-specific manner under glucose starvation, reinforcing a direct role in actin cytoskeleton organization. Supporting Evidence: PMID:12857882 Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p file:yeast/SPA2/SPA2-deep-research-falcon.md Spa2 promotes rapid **ADP-actin monomer nucleation** via a dimeric core region (aa 281–535) and bundles ADP-F-actin through an N-terminal IDR-driven condensation (“wetting”) process, dependent on the actin D-loop. |
| GO:0032956 regulation of actin cytoskeleton organization | IGI PMID:12857882 Actin recovery and bud emergence in osmotically stressed cel... | ACCEPT | Summary: Genetic interaction with actin pathway genes demonstrates SPA2's role in actin cytoskeleton organization. Reason: IGI evidence shows genetic interaction with cytoskeleton components; supports core actin regulation function. Supporting Evidence: PMID:12857882 Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p. |
| GO:0032956 regulation of actin cytoskeleton organization | IMP PMID:19633059 Importance of polarisome proteins in reorganization of actin... | ACCEPT | Summary: SPA2 is critical for reorganization of actin cytoskeleton in response to acid stress; maintains polarity under environmental challenge. Reason: Shows SPA2 function in actin reorganization under environmental stress; represents core polarity maintenance. Supporting Evidence: PMID:19633059 Importance of polarisome proteins in reorganization of actin cytoskeleton at low pH in Saccharomyces cerevisiae |
| GO:0071468 cellular response to acidic pH | IMP PMID:19633059 Importance of polarisome proteins in reorganization of actin... | KEEP AS NON CORE | Summary: SPA2 involved in maintaining polarized growth and actin organization under acidic conditions. Reason: SPA2 helps maintain actin organization and polarity under acid stress, but this is a stress response secondary to core polarity function. Supporting Evidence: PMID:19633059 Importance of polarisome proteins in reorganization of actin cytoskeleton at low pH in Saccharomyces cerevisiae. |
| GO:0071474 cellular hyperosmotic response | IGI PMID:12857882 Actin recovery and bud emergence in osmotically stressed cel... | KEEP AS NON CORE | Summary: SPA2 participates in osmotic stress response through maintaining actin and polarity. Reason: Genetic interaction evidence; SPA2 helps cells recover polarity and actin under osmotic stress, secondary to core function. Supporting Evidence: PMID:12857882 Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p |
| GO:0005934 cellular bud tip | IMP PMID:16166638 Regulation of cell polarity by interactions of Msb3 and Msb4... | ACCEPT | Summary: SPA2 localization to bud tip is functionally required for polarized growth. Reason: Functional requirement for bud tip localization consistent with direct evidence; SPA2 organizing polarity at tip. Supporting Evidence: PMID:16166638 Spa2 is required for the polarized localization of Msb3 and Msb4 at the bud tip |
| GO:0032880 regulation of protein localization | IMP PMID:16166638 Regulation of cell polarity by interactions of Msb3 and Msb4... | ACCEPT | Summary: SPA2 acts as scaffold for polarized localization of multiple proteins including Msb3/4, formins, and kinases. Reason: SPA2 as scaffold protein directly regulates protein localization to growth sites through protein-protein interactions. Supporting Evidence: PMID:16166638 Spa2 is required for the polarized localization of Msb3 and Msb4 at the bud tip |
| GO:0032880 regulation of protein localization | IMP PMID:9571251 Rho1p-Bni1p-Spa2p interactions: implication in localization ... | ACCEPT | Summary: SPA2 regulates Bni1p formin localization to bud site through Rho1p-Bni1p-Spa2p interaction network. Reason: Direct evidence for SPA2 role in regulating formin localization; essential for actin cable assembly. Supporting Evidence: PMID:9571251 Rho1p-Bni1p-Spa2p interactions: implication in localization of Bni1p at the bud site and regulation of the actin cytoskeleton in Saccharomyces cerevisiae. file:yeast/SPA2/SPA2-deep-research-falcon.md an N-terminal Spa2 homology domain (SHD) recruits Msb3/4, promoting Sec4-dependent delivery of Bud6 to the polarisome, where Bud6 stimulates the formin Bni1 to generate actin cables |
| GO:0032880 regulation of protein localization | IMP PMID:9632790 Spa2p interacts with cell polarity proteins and signaling co... | ACCEPT | Summary: SPA2 is component of polarisome complex that localizes actin and signaling proteins to growth sites. Reason: SPA2-Pea2p-Bud6p complex functions to organize protein localization at polarization sites. Supporting Evidence: PMID:9632790 We thus propose that Spa2p, Pea2p, and Bud6p function together, perhaps as a complex, to promote polarized morphogenesis through regulation of the actin cytoskeleton and signaling pathways. |
| GO:0032880 regulation of protein localization | IMP PMID:12857882 Actin recovery and bud emergence in osmotically stressed cel... | ACCEPT | Summary: SPA2 is required for proper protein localization during recovery from osmotic stress. Reason: SPA2 scaffold function maintains protein organization at growth sites under stress conditions. Supporting Evidence: PMID:12857882 Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p |
| GO:0071474 cellular hyperosmotic response | IMP PMID:12857882 Actin recovery and bud emergence in osmotically stressed cel... | KEEP AS NON CORE | Summary: SPA2 scaffold function maintains polarity and actin organization under hyperosmotic conditions. Reason: SPA2 participates in osmotic stress response as secondary effect of maintaining polarity and actin organization. Supporting Evidence: PMID:12857882 Actin recovery and bud emergence in osmotically stressed cells requires the conserved actin interacting mitogen-activated protein kinase kinase kinase Ssk2p/MTK1 and the scaffold protein Spa2p |
| GO:0005938 cell cortex | IDA PMID:23673619 Spatial segregation of polarity factors into distinct cortic... | ACCEPT | Summary: Direct evidence for SPA2 localization to cell cortex at growth sites through spatial segregation of polarity factors. Reason: IDA from microscopy demonstrates SPA2 is cortical protein that segregates into distinct cortical clusters at growth sites. Supporting Evidence: PMID:23673619 Spatial segregation of polarity factors into distinct cortical clusters is required for cell polarity control file:yeast/SPA2/SPA2-deep-research-falcon.md Under acute energy/glucose starvation, Spa2 can depolarize from the bud tip and relocalize into **filamentous/punctate structures that overlap actin cables**, indicating condition-dependent remodeling of its spatial organization. |
| GO:0005078 MAP-kinase scaffold activity | IDA PMID:12361575 Spa2p functions as a scaffold-like protein to recruit the Mp... | ACCEPT | Summary: Direct biochemical and localization evidence for SPA2 scaffold activity for MAP kinase pathway. Reason: IDA demonstrates direct recruitment and physical interaction with MAPK pathway components. Supporting Evidence: PMID:12361575 Spa2p interacts with Mkk1p and Mpk1p, and membrane bound Spa2p is sufficient to recruit Mkk1p and Mpk1p but not other MAP kinases to the cell cortex |
| GO:0005078 MAP-kinase scaffold activity | IMP PMID:12361575 Spa2p functions as a scaffold-like protein to recruit the Mp... | ACCEPT | Summary: Functional requirement for SPA2 in MAPK pathway signaling and localization. Reason: IMP evidence shows SPA2 is required for proper MAPK localization and function during polarized growth. Supporting Evidence: PMID:12361575 Spa2p functions as a scaffold-like protein for the cell wall integrity pathway during polarized growth |
| GO:0032880 regulation of protein localization | IMP PMID:11740491 Yeast formins regulate cell polarity by controlling the asse... | ACCEPT | Summary: Yeast formins regulate cell polarity through actin cable assembly; SPA2 localizes and organizes Bni1p formin. Reason: SPA2 regulates formin localization as part of core actin cable organization for polarity. Supporting Evidence: PMID:11740491 Yeast formins regulate cell polarity by controlling the assembly of actin cables |
| GO:0007118 budding cell apical bud growth | IMP PMID:10866679 Polarized growth controls cell shape and bipolar bud site se... | ACCEPT | Summary: SPA2 is essential for polarized bud growth; controls actin cable organization and apical growth direction. Reason: Direct evidence that SPA2 is required for apical bud growth morphogenesis; mutants show defective polarized growth. Supporting Evidence: PMID:10866679 Polarized growth controls cell shape and bipolar bud site selection in Saccharomyces cerevisiae |
| GO:0007118 budding cell apical bud growth | IGI PMID:10866679 Polarized growth controls cell shape and bipolar bud site se... | ACCEPT | Summary: Genetic interactions show SPA2 functions with other polarity components in bud growth. Reason: IGI evidence demonstrates SPA2 genetic interaction with actin and morphogenesis genes critical for apical growth. Supporting Evidence: PMID:10866679 We found that the polarity genes SPA2, PEA2, BUD6, and BNI1 participate in a crucial step of bud morphogenesis, apical growth. |
| GO:0032880 regulation of protein localization | IMP PMID:10085294 The cortical localization of the microtubule orientation pro... | ACCEPT | Summary: SPA2 is required for proper cortical protein localization including Kar9p; actin-dependent mechanism. Reason: SPA2 scaffold function essential for organizing actin and associated proteins including microtubule orieintation proteins at cell cortex. Supporting Evidence: PMID:10085294 The cortical localization of the microtubule orientation protein, Kar9p, is dependent upon actin and proteins required for polarization |
| GO:0007121 bipolar cellular bud site selection | IMP PMID:8909546 Pea2 protein of yeast is localized to sites of polarized gro... | ACCEPT | Summary: SPA2 is required for bipolar bud site selection in diploid cells; functions with Pea2p in site recognition. Reason: Strong genetic evidence showing SPA2 and Pea2p work together to establish and maintain bipolar budding pattern. Supporting Evidence: PMID:8909546 These results suggest that Pea2p and Spa2p function together as a complex to generate the bipolar budding pattern |
| GO:0030010 establishment of cell polarity | IMP PMID:8909546 Pea2 protein of yeast is localized to sites of polarized gro... | ACCEPT | Summary: SPA2 required for cell polarity establishment during both budding and mating morphogenesis. Reason: Strong genetic evidence (IMP) showing SPA2 is essential for polarity in multiple developmental contexts. Supporting Evidence: PMID:8909546 These results suggest that Pea2p and Spa2p function together as a complex to generate the bipolar budding pattern and to guarantee proper polarization during mating. |
| GO:0032880 regulation of protein localization | IMP PMID:8909546 Pea2 protein of yeast is localized to sites of polarized gro... | ACCEPT | Summary: SPA2-Pea2p complex regulates protein localization during budding and mating morphogenesis. Reason: Demonstrates SPA2's protein localization regulatory function in multiple polarity contexts. Supporting Evidence: PMID:8909546 Pea2p is not stably produced in spa2 mutants. |
| GO:0030010 establishment of cell polarity | IMP PMID:8013906 Identification of genes required for normal pheromone-induce... | ACCEPT | Summary: SPA2 is essential for establishing polarity during mating morphogenesis; required for directed growth toward mating partner. Reason: Demonstrates SPA2's requirement for directed polarized growth toward pheromone source during mating. Supporting Evidence: PMID:8013906 Identification of genes required for normal pheromone-induced cell polarization |
| GO:0000131 incipient cellular bud site | IDA PMID:9214378 A small conserved domain in the yeast Spa2p is necessary and... | ACCEPT | Summary: SPA2 is early marker of incipient bud site, localizing before morphological bud emergence. Reason: Defining property of SPA2; localizes to single edge in unbudded cells and incipient sites as verified by confocal microscopy. Supporting Evidence: PMID:9214378 Spa2p localizes to one edge of unbudded cells and subsequently is observable in the bud tip |
| GO:0000133 polarisome | IDA PMID:9632790 Spa2p interacts with cell polarity proteins and signaling co... | ACCEPT | Summary: SPA2 is core structural component of polarisome complex along with Pea2p and Bud6p. Reason: Coimmunoprecipitation and sedimentation evidence confirms SPA2 as integral polarisome component forming large multiprotein complex. Supporting Evidence: PMID:9632790 Velocity sedimentation experiments suggest that a significant portion of Spa2p, Pea2p, and Bud6p cosediment, raising the possibility that these proteins form a large, 12S multiprotein complex file:yeast/SPA2/SPA2-deep-research-falcon.md Spa2 is a central scaffold that coordinates recruitment/organization of other polarisome components (commonly including Bni1, Bud6, Pea2) and thereby promotes focal polarization. |
| GO:0005934 cellular bud tip | IDA PMID:12361575 Spa2p functions as a scaffold-like protein to recruit the Mp... | ACCEPT | Summary: Direct evidence for stable SPA2 localization to bud tip from fluorescence recovery analysis. Reason: FRAP analysis confirms SPA2 is stably anchored at bud tips; foundational evidence for scaffold function at growth sites. Supporting Evidence: PMID:12361575 FRAP analysis shows that Spa2p-GFP is stably anchored at bud tips, whereas Mpk1p binds transiently |
| GO:0005934 cellular bud tip | IDA PMID:2647769 The SPA2 protein of yeast localizes to sites of cell growth. | ACCEPT | Summary: Early direct evidence establishing SPA2 as growth-site localized protein. Reason: Seminal work showing SPA2 localizes to sites of cell growth; foundational observation for polarity field. Supporting Evidence: PMID:2647769 The SPA2 protein of yeast localizes to sites of cell growth |
| GO:0005935 cellular bud neck | IDA PMID:9214378 A small conserved domain in the yeast Spa2p is necessary and... | ACCEPT | Summary: SPA2 localizes as ring at mother-daughter bud neck during cytokinesis as verified by microscopy. Reason: Direct microscopic evidence for bud neck localization during cell division; shows SPA2 role at septation sites. Falcon synthesis adds that Spa2 is recruited to the division site in late cell cycle and directly binds cytokinetic factors Cyk3 and Hof1, coordinating Chs2 incorporation for primary septum formation. Supporting Evidence: PMID:9214378 During cytokinesis Spa2p is present as a ring at the mother-daughter bud neck file:yeast/SPA2/SPA2-deep-research-falcon.md Foltman et al. (2018) show Spa2 is recruited to the division site in late cell cycle and directly binds cytokinetic factors, including **Cyk3** and **Hof1**, via Spa2 N-terminal regions containing Spa2 homology domains. file:yeast/SPA2/SPA2-deep-research-falcon.md Spa2 participates in coordinating incorporation of the essential chitin synthase **Chs2** into cytokinetic machinery (“ingression progression complexes”), linking polarity scaffolding to primary septum formation. |
| GO:0007124 pseudohyphal growth | IMP PMID:9055077 Dissection of filamentous growth by transposon mutagenesis i... | KEEP AS NON CORE | Summary: SPA2 is required for pseudohyphal growth morphology in response to nutrient starvation. Reason: Genetic evidence for involvement in developmental program; secondary to core polarity establishment function. Supporting Evidence: PMID:9055077 Dissection of filamentous growth by transposon mutagenesis in Saccharomyces cerevisiae. |
| GO:0007124 pseudohyphal growth | IMP PMID:9443897 The Spa2-related protein, Sph1p, is important for polarized ... | KEEP AS NON CORE | Summary: SPA2-related protein Sph1p plays role in pseudohyphal growth; demonstrates family function in filamentous growth. Reason: Shows SPA2 family role in filamentous growth but represents specialized developmental function secondary to core polarity. Supporting Evidence: PMID:9443897 The Spa2-related protein, Sph1p, is important for polarized growth in yeast |
| GO:0036267 invasive filamentous growth | IGI PMID:9443897 The Spa2-related protein, Sph1p, is important for polarized ... | KEEP AS NON CORE | Summary: Genetic interaction evidence for SPA2 in invasive growth; Spa2-Sph1 interaction shows redundancy. Reason: Secondary developmental function; interaction with Sph1p suggests role in specialized growth program. Supporting Evidence: PMID:9443897 sph1(Delta) spa2(Delta) double mutants also exhibit a strong haploid invasive growth defect and an exacerbated mating projection defect relative to either sph1(Delta) or spa2(Delta) single mutants. |
| GO:0043332 mating projection tip | IDA PMID:2647769 The SPA2 protein of yeast localizes to sites of cell growth. | ACCEPT | Summary: SPA2 localizes prominently to mating projection tip as discrete patch. Reason: Early direct evidence for localization to shmoo tip; essential for mating morphogenesis. Supporting Evidence: PMID:2647769 When a-cells are induced to form schmoos with alpha-factor, the SPA2 protein is found at the tip of the schmoo. |
| GO:0043332 mating projection tip | IDA PMID:9214378 A small conserved domain in the yeast Spa2p is necessary and... | ACCEPT | Summary: SPA2 localizes to mating projection tip in response to pheromone and is essential for shmoo formation. Reason: Consistent direct evidence from multiple studies; essential for directed growth toward mating partner. Supporting Evidence: PMID:9214378 A small conserved domain in the yeast Spa2p is necessary and sufficient for its polarized localization. |
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)