Septin2

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0000281 mitotic cytokinesis	IDA PMID:40171709 Septin complexes: Ahead of the curve.	ACCEPT	Summary: Member of the Sep1-Sep2-Pnut septin complex that acts in cytokinesis. Reason: Curator annotation from the Nakamura and Parkhurst review; the Sep1-Sep2-Pnut complex localizes to the cleavage furrow and the septin complex is required for cytokinesis. Single-subunit requirements are partly masked by redundancy (Sep2 with Sep5), but the function is consistent with the complex. Supporting Evidence: PMID:8636235 The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1. PMID:24433211 Sep2 Sep5 double mutants have an early pupal lethal phenotype and lack imaginal discs, suggesting that these genes have redundant functions during imaginal cell proliferation
GO:0003924 GTPase activity	IBA GO_REF:0000033	REMOVE	Summary: Phylogenetic/sequence transfer of GTPase activity to Sep2. Reason: Contradicted by direct evidence: individual recombinant Sep2 showed no GTPase activity and does not exchange bound GTP (PMID:25355953). Sep2 is a SEPT6-class septin (PMID:38728140), a class generally regarded as catalytically inactive; the IBA transfer from the septin family node (donors include Pnut and Sep1) does not hold for this subclass. Supporting Evidence: PMID:25355953 Sep2 protein, on the other hand, did not possess any noticeable GTPase activity (Table 1). PMID:38728140 Drosophila has 5 Septins that are grouped into three classes: Sep2 and Sep5 (SEPT6 class), Sep1 and Sep4 (SEPT2 class), and Pnut (SEPT7 class)
GO:0003924 GTPase activity	IDA NOT PMID:25355953 Functional insight into the role of Orc6 in septin complex f...	ACCEPT	Summary: Sep2 alone shows no detectable GTP hydrolysis. Reason: This NOT annotation is supported by direct GTPase assays of the individual recombinant septins: Sep2, a SEPT6-class septin, did not hydrolyse GTP and appears to hold non-exchangeable GTP, consistent with a structural rather than catalytic role in the hexamer. Supporting Evidence: PMID:25355953 Sep2 protein, on the other hand, did not possess any noticeable GTPase activity (Table 1). PMID:25355953 supporting a structural rather than regulatory role for Sep2 in Drosophila septin complex assembly
GO:0003924 GTPase activity	IDA PMID:8636235 A purified Drosophila septin complex forms filaments and exh...	REMOVE	Summary: GTPase activity measured for the purified Pnut-Sep2-Sep1 complex, attributed to each subunit. Reason: PMID:8636235 measured GTP binding and hydrolysis by the whole embryo-purified complex, not by Sep2 alone. Later assays of individual recombinant subunits (PMID:25355953) found no detectable GTPase activity for Sep2, which is also captured by the NOT annotation in GOA. The catalytic activity belongs to Pnut and Sep1; Sep2 is a GTP-binding structural subunit. Because Sep2 GTPase activity was directly measured and found absent, this is a contradicted function rather than a matter of interpretation, consistent with the accepted NOT row and the removal of the IBA/ISS rows. Supporting Evidence: PMID:8636235 It binds and hydrolyzes exogenously added GTP. PMID:25355953 Sep2 protein, on the other hand, did not possess any noticeable GTPase activity (Table 1).
GO:0003924 GTPase activity	ISS GO_REF:0000024	REMOVE	Summary: Phylogenetic/sequence transfer of GTPase activity to Sep2. Reason: Contradicted by direct evidence: individual recombinant Sep2 showed no GTPase activity and does not exchange bound GTP (PMID:25355953). Sep2 is a SEPT6-class septin (PMID:38728140), a class generally regarded as catalytically inactive; the ISS transfer from the septin family node (donors include Pnut and Sep1) does not hold for this subclass. Supporting Evidence: PMID:25355953 Sep2 protein, on the other hand, did not possess any noticeable GTPase activity (Table 1). PMID:38728140 Drosophila has 5 Septins that are grouped into three classes: Sep2 and Sep5 (SEPT6 class), Sep1 and Sep4 (SEPT2 class), and Pnut (SEPT7 class)
GO:0005515 protein binding	IPI PMID:11884525 Identification of septin-interacting proteins and characteri...	REMOVE	Summary: Two-hybrid interaction with a SUMO-pathway protein. Reason: Generic protein binding from a yeast two-hybrid screen for septin-interacting proteins (PMID:11884525) is uninformative and there is no specific binding term that captures the reported interactor; removal per curation policy on protein binding.
GO:0005525 GTP binding	IEA GO_REF:0000002	ACCEPT	Summary: GTP binding predicted from the septin-type G domain. Reason: Septins bind guanine nucleotide stably; the purified Drosophila complex copurifies with one bound guanine nucleotide per subunit. This holds even for the SEPT6-class subunits (Sep2/Sep5), which bind but do not exchange or hydrolyse GTP. Supporting Evidence: PMID:8636235 The complex copurifies with one molecule of bound guanine nucleotide per septin polypeptide.
GO:0005737 cytoplasm	IEA GO_REF:0000044	MODIFY	Summary: Septins are cytoplasmic proteins that assemble at the cortex. Reason: Correct but general; this septin is a subunit of a hetero-oligomeric septin complex, and the gene already carries the more specific cytoplasmic term GO:0031105 septin complex (a descendant of cytoplasm). Proposed replacements: septin complex Supporting Evidence: file:DROME/Septin2/Septin2-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Cytoplasm, cytoskeleton, spindle PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair.
GO:0005819 spindle	IEA GO_REF:0000044	MARK AS OVER ANNOTATED	Summary: Spindle localization transferred from mammalian septins via UniProt. Reason: The UniProt subcellular location is by similarity (ECO:0000250) to mammalian SEPTIN6/7, which have been seen on spindle microtubules. Drosophila Sep2 localizes to the cortex, cleavage furrow and wound edge; no fly data place it on the spindle. Supporting Evidence: file:DROME/Septin2/Septin2-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Cytoplasm, cytoskeleton, spindle
GO:0005940 septin ring	IBA GO_REF:0000033	ACCEPT	Summary: Septin ring localization inherited from the septin family. Reason: IBA from PANTHER node PTN000430171 with broad fungal, mammalian, worm and Drosophila donors. Drosophila septins form ring structures at the cleavage furrow and around cell wounds. Supporting Evidence: PMID:8181057 Pnut protein is localized to the cleavage furrow of dividing cells during cytokinesis and to the intercellular bridge connecting postmitotic daughter cells.
GO:0005940 septin ring	IPI PMID:40171709 Septin complexes: Ahead of the curve.	ACCEPT	Summary: Septins assemble into ring structures at the wound edge and division site. Reason: Curator annotation from the Nakamura and Parkhurst review, which describes septin complexes organised as rings at the wound edge; Drosophila septins also form rings at the cleavage furrow. Supporting Evidence: PMID:40171709 Taken together, our study demonstrated that the bending of actin filaments by two distinct Septin complexes regulates the assembly and disassembly of the actomyosin ring during cell wound repair
GO:0007295 growth of a germarium-derived egg chamber	IMP PMID:24433211 The Drosophila melanogaster septin gene Sep2 has a redundant...	KEEP AS NON CORE	Summary: Sep2 is required for normal egg chamber formation. Reason: Sep2 mutant females are semisterile with egg chambers containing abnormal nurse cell numbers, a phenotype only partly rescued by Sep5. Tissue-specific developmental requirement, plausibly reflecting germline cyst divisions; non-core. Supporting Evidence: PMID:24433211 Their ovaries have egg chambers containing abnormal numbers of nurse cells.
GO:0007298 border follicle cell migration	IMP PMID:37329886 Septins regulate border cell surface geometry, shape, and mo...	KEEP AS NON CORE	Summary: Septins regulate border cell cluster shape and motility. Reason: RNAi against Sep1, Sep2 or Pnut impairs border cell migration; septins act downstream of Rho to tune cluster surface deformability. Developmental, context-specific role; non-core. Supporting Evidence: PMID:37329886 Expressing RNAi against Sep1, Sep2, or Pnut impaired migration (Figures 2B–2D).
GO:0007349 cellularization	TAS PMID:12386932 How one becomes many: blastoderm cellularization in Drosophi...	KEEP AS NON CORE	Summary: Septins localise to the cellularization front. Reason: TAS from a review of blastoderm cellularization. Septins concentrate at the leading edge of cellularization furrows and the septin complex was purified from cellularizing embryos; cellularization is a specialised cytokinesis, retained as non-core. Supporting Evidence: PMID:11076973 Seven (Anillin, KLP3A, Dynamin A and B, Peanut, Septin 1, and Septin 2) have been previously implicated in cellularization and/or cytokinesis, suggesting that the screen has enriched for the desired class of proteins.
GO:0007444 imaginal disc development	IGI PMID:24433211 The Drosophila melanogaster septin gene Sep2 has a redundant...	KEEP AS NON CORE	Summary: Sep2 and Sep5 act redundantly for imaginal disc formation. Reason: IGI: Sep2 Sep5 double mutants lack imaginal discs, attributed to failed imaginal cell proliferation, most likely reflecting the septin role in cytokinesis. Developmental consequence; non-core. Supporting Evidence: PMID:24433211 Sep2 Sep5 double mutants have an early pupal lethal phenotype and lack imaginal discs, suggesting that these genes have redundant functions during imaginal cell proliferation
GO:0008104 intracellular protein localization	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Septin scaffolds localise other proteins to the cell cortex. Reason: IBA from PANTHER node PTN000430171 with fungal donors (yeast Shs1/Cdc11, Candida septins) and human SEPTIN14, where septin collars restrict and recruit proteins. Plausible for Drosophila septin scaffolds but not directly shown for this gene; retained as non-core.
GO:0015630 microtubule cytoskeleton	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Septin association with microtubules inherited from mammalian/yeast septins. Reason: IBA from PANTHER node PTN000430171 with donors including human SEPTIN2, SEPTIN7, SEPTIN9 and SEPTIN12. Septins do associate with microtubules in some cell types, and Drosophila Pnut/Sep1/Sep2 were recovered in a microtubule/microfilament-associated protein screen, but the primary Drosophila septin structures are cortical and actin-associated. Basis: phylogenetic inference only; no cached Drosophila paper directly shows this septin on microtubules.
GO:0031105 septin complex	IBA GO_REF:0000033	ACCEPT	Summary: Septin complex membership inherited across the septin family. Reason: IBA from PANTHER node PTN000430171 with very broad donors, including all Drosophila septins in the curated set. Experimental evidence confirms membership of this subunit in a hetero-oligomeric septin complex. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair.
GO:0031105 septin complex	IDA PMID:18987337 Drosophila Orc6 facilitates GTPase activity and filament for...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: Direct biochemical evidence that this subunit assembles into a hetero-oligomeric septin complex (Sep1/Sep2/Pnut and/or Sep4/Sep5/Pnut). Core location. Supporting Evidence: PMID:18987337 Septin complex was purified from Drosophila embryos and also reconstituted from recombinant proteins.
GO:0031105 septin complex	IGI PMID:37329886 Septins regulate border cell surface geometry, shape, and mo...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: IGI: Sep1 or Sep2 knockdown reduces Pnut protein levels in follicle cells, consistent with mutual stabilisation within a complex. Membership is independently established biochemically (PMID:8636235). Supporting Evidence: PMID:37329886 Expressing RNAi against Sep1, Sep2, or Pnut impaired migration (Figures 2B–2D). PMID:8636235 The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1.
GO:0031105 septin complex	IPI PMID:24633326 Septins promote F-actin ring formation by crosslinking actin...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: IPI (curator-supplied; abstract-only cache): septins were studied as a complex bundling actin into rings during cellularization. Membership of Pnut, Sep1 and Sep2 in one complex is independently established by immunopurification (PMID:8636235). Supporting Evidence: PMID:24633326 In vitro reconstitution assays show that septins alone bundle actin filaments into rings PMID:8636235 The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1.
GO:0031105 septin complex	IPI PMID:25355953 Functional insight into the role of Orc6 in septin complex f...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: Direct biochemical evidence that this subunit assembles into a hetero-oligomeric septin complex (Sep1/Sep2/Pnut and/or Sep4/Sep5/Pnut). Core location. Supporting Evidence: PMID:25355953 We reconstituted a recombinant Drosophila septin complex and compared activities of the wild-type and several mutant septin complex variants both in vitro and in vivo.
GO:0031105 septin complex	IPI PMID:8636235 A purified Drosophila septin complex forms filaments and exh...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: Direct biochemical evidence that this subunit assembles into a hetero-oligomeric septin complex (Sep1/Sep2/Pnut and/or Sep4/Sep5/Pnut). Core location. Supporting Evidence: PMID:8636235 The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1.
GO:0031105 septin complex	TAS PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun...	ACCEPT	Summary: Subunit of the hetero-oligomeric septin complex. Reason: Direct biochemical evidence that this subunit assembles into a hetero-oligomeric septin complex (Sep1/Sep2/Pnut and/or Sep4/Sep5/Pnut). Core location. Supporting Evidence: PMID:38728140 Taken together, our findings further suggest that Sep1/Sep2/Pnut and Sep4/Sep5/Pnut are functioning as distinct complexes within the context of cell wound repair.
GO:0032153 cell division site	IBA GO_REF:0000033	ACCEPT	Summary: Septins accumulate at the cell division site. Reason: IBA from PANTHER node PTN000430171 with broad donors; consistent with Drosophila septin localization to the cleavage furrow.
GO:0042060 wound healing	IMP PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun...	ACCEPT	Summary: Septins are required for efficient cell wound repair. Reason: All five septins are required for efficient wound repair of the syncytial embryo; Sep1/Sep2 and Sep4/Sep5 loss give distinct actin-ring phenotypes. Direct IMP evidence; this is single-cell (plasma membrane/cortex) wound repair. Supporting Evidence: PMID:38728140 we show that all five Drosophila Septins are required for efficient cell wound repair PMID:38728140 Sep1 knockdown and Sep2 mutant embryos exhibit delayed wound closure, reduced recruitment of actin to the actomyosin ring, and premature actomyosin ring disassembly
GO:0042461 photoreceptor cell development	NAS PMID:8181057 The Drosophila peanut gene is required for cytokinesis and e...	MARK AS OVER ANNOTATED	Summary: Photoreceptor development inferred from a genetic interaction with seven in absentia. Reason: The only basis is a dominant genetic interaction between pnut and sina noted in PMID:8181057, which the authors interpret as possible pleiotropy. No septin was shown to act in photoreceptor development; for Sep1, Sep2 and Sep4 the NAS row simply extends this pnut observation to paralogs. Supporting Evidence: PMID:8181057 pnut displays genetic interactions with seven in absentia, a gene required for neuronal fate determination in the compound eye
GO:0042803 protein homodimerization activity	IDA PMID:8636235 A purified Drosophila septin complex forms filaments and exh...	KEEP AS NON CORE	Summary: Septin subunits proposed to be present as homodimers in the purified complex. Reason: The 1996 hydrodynamic data suggested a heterotrimer of homodimers; current models describe a palindromic hexamer assembled through alternating G- and NC-interfaces. Homotypic septin contacts are real but describe complex architecture rather than a distinct function; non-core. Supporting Evidence: PMID:8636235 Hydrodynamic and sequence data suggest that the complex is composed of a heterotrimer of homodimers.
GO:0044837 actomyosin contractile ring organization	IMP PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun...	ACCEPT	Summary: Septins organise the actomyosin ring during single-cell wound repair. Reason: In the Drosophila embryo cell-wound model, knockdown or mutation of each septin perturbs actomyosin ring assembly, contraction or disassembly; the two complexes bend actin bundles to different curvatures. Core process for the septin complexes. Supporting Evidence: PMID:38728140 Sep1 knockdown and Sep2 mutant embryos exhibit delayed wound closure, reduced recruitment of actin to the actomyosin ring, and premature actomyosin ring disassembly PMID:38728140 Interestingly, we observe curved F-actin bundles induced by two separate Septin complexes, whereas individual Septins can only bind to and bundle F-actin.
GO:0051015 actin filament binding	IDA PMID:38728140 Two Septin complexes mediate actin dynamics during cell woun...	ACCEPT	Summary: Purified septin subunits and complexes bind and bundle actin filaments. Reason: Each of the five Drosophila septins, purified individually, binds and bundles F-actin in vitro, and the assembled Sep1/Sep2/Pnut and Sep4/Sep5/Pnut complexes additionally bend the bundles into rings. Direct F-actin binding is a core activity linking septins to the actomyosin cytoskeleton. Supporting Evidence: PMID:38728140 Strikingly, we find that all five Drosophila Septins can bind to and bundle actin filaments PMID:38728140 Interestingly, we observe curved F-actin bundles induced by two separate Septin complexes, whereas individual Septins can only bind to and bundle F-actin.
GO:0051726 regulation of cell cycle	IGI PMID:24433211 The Drosophila melanogaster septin gene Sep2 has a redundant...	MARK AS OVER ANNOTATED	Summary: Imaginal cell proliferation defect of Sep2 Sep5 double mutants. Reason: The double mutant lacks imaginal discs, which the authors attribute to failed imaginal cell proliferation. There is no evidence that Sep2 or Sep5 regulate cell-cycle progression as such; the proliferation defect is best explained by the septin requirement for cytokinesis. 'Regulation of cell cycle' over-interprets the phenotype. Supporting Evidence: PMID:24433211 Sep2 Sep5 double mutants have an early pupal lethal phenotype and lack imaginal discs, suggesting that these genes have redundant functions during imaginal cell proliferation
GO:0060090 molecular adaptor activity	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Septin filaments act as scaffolds that recruit other proteins. Reason: IBA from PANTHER node PTN000430171 with donors yeast Cdc3 and Cdc12 (SGD:S000000595, SGD:S000001149), where septin collars scaffold bud-neck proteins. Drosophila septins also act as cortical scaffolds (e.g. with Anillin), but the documented fly activities are actin filament binding and bundling; the generic adaptor term is retained as non-core.
GO:0061640 cytoskeleton-dependent cytokinesis	IBA GO_REF:0000033	MODIFY	Summary: Septin role in cytoskeleton-dependent cytokinesis inherited from the septin family. Reason: IBA from PANTHER node PTN000430171 with broad donors (yeast, fission yeast, mouse, worm and the Drosophila septins Pnut, Sep1, Sep2, Sep4 and Sep5; the gene appearing among the donors is expected, not circular). The process is correct but more general than the evidence supports: this gene already carries the more specific child term GO:0000281 mitotic cytokinesis from experimental annotations, so the IBA is better expressed with that term. Proposed replacements: mitotic cytokinesis Supporting Evidence: PMID:8181057 We find that pnut is also required for cytokinesis

Gene Description

Existing Annotations Review

Core Functions

Sep2 is a non-catalytic, GTP-bound structural subunit of the Sep1-Sep2-Pnut septin complex; it binds and bundles actin filaments and the complex bends F-actin bundles to organise the actomyosin ring during wound repair and cytokinesis.

References

Deep Research

Falcon

📚 Additional Documentation

Notes

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