Septin1 (Sep1) is a Drosophila SEPT2-class septin GTPase that assembles with Peanut and Septin2 into the Sep1-Sep2-Pnut hetero-oligomer purified from embryos. Sep1 binds and hydrolyses GTP, and intact GTP-binding/hydrolysis motifs of Sep1 are needed for complex function. It concentrates at the leading edge of cleavage and cellularization furrows and at other cortical sites, and directly binds and bundles actin filaments. In the Sep1-Sep2-Pnut complex, recruited by Anillin, it bends F-actin into tight rings and is required for assembly and maintenance of the actomyosin ring during cell wound repair; it also contributes to border cell migration.
| 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:8590810 The protein is concentrated at the leading edge of the cleavage furrows of dividing cells and cellularizing embryos |
| GO:0003924 GTPase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Septin GTPase activity inherited from the septin family node. Reason: IBA from PANTHER node PTN000430171 (donors include Pnut, Sep1, yeast Cdc3/Cdc12 and human SEPTIN4). The gene itself has direct experimental support (IDA). Supporting Evidence: PMID:25355953 We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2. |
| GO:0003924 GTPase activity | IDA PMID:25355953 Functional insight into the role of Orc6 in septin complex f... | ACCEPT | Summary: Septin complex binds and hydrolyses GTP; this subunit carries catalytic activity. Reason: Direct biochemical evidence: the Pnut-Sep2-Sep1 complex hydrolyses GTP, and mutational analysis shows complex function depends on intact GTP-binding/hydrolysis domains of Pnut and Sep1 (Sep2 alone is inactive). GTP hydrolysis is a core intrinsic activity of this septin subunit. Supporting Evidence: PMID:25355953 We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2. |
| GO:0003924 GTPase activity | IDA PMID:8636235 A purified Drosophila septin complex forms filaments and exh... | ACCEPT | Summary: Septin complex binds and hydrolyses GTP; this subunit carries catalytic activity. Reason: Direct biochemical evidence: the Pnut-Sep2-Sep1 complex hydrolyses GTP, and mutational analysis shows complex function depends on intact GTP-binding/hydrolysis domains of Pnut and Sep1 (Sep2 alone is inactive). GTP hydrolysis is a core intrinsic activity of this septin subunit. Supporting Evidence: PMID:8636235 It binds and hydrolyzes exogenously added GTP. |
| GO:0003924 GTPase activity | ISS GO_REF:0000024 | ACCEPT | Summary: GTPase activity by similarity to Pnut. Reason: Transfer supported by direct assays of the complex and its subunits. Supporting Evidence: PMID:25355953 We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2. |
| 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 | IDA PMID:25355953 Functional insight into the role of Orc6 in septin complex f... | ACCEPT | Summary: Septin subunits copurify with bound guanine nucleotide and bind GTP. Reason: Direct evidence that the septin complex and its subunits bind guanine nucleotide; GTP binding is the defining biochemical property of the septin GTPase fold. Supporting Evidence: PMID:25355953 We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2. |
| 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 | EXP PMID:8590810 Localization and possible functions of Drosophila septins. | MODIFY | Summary: Sep1 is a cytoplasmic/cortical protein. Reason: Correct but general. Immunolocalization shows Sep1 concentrated at cleavage furrow leading edges and other cortical sites, and biochemically associated with Pnut in the septin complex; the more specific cytoplasmic location the gene already carries is GO:0031105 septin complex (a cytoplasmic, cytoskeletal complex). Proposed replacements: septin complex Supporting Evidence: PMID:8590810 The protein is concentrated at the leading edge of the cleavage furrows of dividing cells and cellularizing embryos PMID:8590810 Both immunolocalization and biochemical experiments show that Sep1 is intimately associated with Pnut |
| GO:0005737 cytoplasm | IEA GO_REF:0000120 | 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/Septin1/Septin1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm 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: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: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:8590810 The protein is concentrated at the leading edge of the cleavage furrows of dividing cells and cellularizing embryos |
| GO:0007476 imaginal disc-derived wing morphogenesis | IMP PMID:34496252 Atypical laminin spots and pull-generated microtubule-actin ... | KEEP AS NON CORE | Summary: Septins required for microtubule-actin cables that mediate wing surface adhesion. Reason: IMP from a study of wing adhesion during metamorphosis, in which septins are needed to form pressure-resistant microtubule-actin projections. Tissue-level morphogenesis that likely reflects the general septin role in cortical cytoskeletal organisation; non-core. Supporting Evidence: PMID:34496252 Formation of cables resistant to pressure requires spectraplakin, Patronin, septins, and Sdb |
| 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:0031625 ubiquitin protein ligase binding | IPI PMID:17456438 Drosophila melanogaster Parkin ubiquitinates peanut and sept... | KEEP AS NON CORE | Summary: Septin interacts with, and is ubiquitinated by, the E3 ligase Parkin. Reason: Pnut and Sep1 are substrates of Parkin E3 ligase activity; binding the ligase is a property of a substrate, not a function the septin performs. Informative binding term, retained as non-core. Supporting Evidence: PMID:17456438 peanut and septin1, D. melanogaster septin proteins, were also ubiquitinated by D. melanogaster Parkin |
| GO:0032153 cell division site | IBA GO_REF:0000033 | MODIFY | Summary: Septins accumulate at the cell division site. Reason: IBA from PANTHER node PTN000430171 with broad donors. Correct but general: direct immunolocalization places this septin at the cleavage furrow, and the gene already carries the more specific child term GO:0032154 cleavage furrow. Proposed replacements: cleavage furrow Supporting Evidence: PMID:8590810 The protein is concentrated at the leading edge of the cleavage furrows of dividing cells and cellularizing embryos |
| GO:0032154 cleavage furrow | IDA PMID:33037125 A novel coordinated function of Myosin II with GOLPH3 contro... | ACCEPT | Summary: Septin localizes to the cleavage furrow during cytokinesis. Reason: Septins are recruited to the cleavage furrow of dividing cells; direct immunolocalization in multiple Drosophila cell types. Core location for the cytokinetic role. Supporting Evidence: PMID:8590810 The protein is concentrated at the leading edge of the cleavage furrows of dividing cells and cellularizing embryos |
| 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:0043065 positive regulation of apoptotic process | IDA PMID:17456438 Drosophila melanogaster Parkin ubiquitinates peanut and sept... | KEEP AS NON CORE | Summary: Septins enhance p53-dependent apoptosis in a cell-based assay. Reason: Abstract-only reference; the assay reports higher p53-dependent apoptosis in the presence of septins and dopamine, in a Parkin-substrate context. Deferring to the curator, but this is a peripheral, context-specific observation; non-core. Supporting Evidence: PMID:17456438 the rate and efficiency of p53-dependent apoptosis were significantly higher |
| 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: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 |
| GO:0070938 contractile ring | HDA PMID:25294944 Subcellular localisations of the CPTI collection of YFP-tagg... | ACCEPT | Summary: YFP-tagged Sep1 colocalizes with the contractile ring. Reason: High-throughput CPTI localization placed Sep1 with myosin II at the closing contractile structures, consistent with septin association with actomyosin rings. Supporting Evidence: PMID:25294944 These include Category I proteins Zipper, Msn and Septin 1 and 5 other lines |
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Download this section (compressed HTML)Septin 1 (Septin1) encodes a member of the septin family of GTP-binding proteins. Septins form hetero-oligomeric filaments and rings that associate with filamentous actin. Septin1, together with Septin5 and pnut, is required for the bundling of actin filaments into compact cytoskeleton cables during dorsoventral wing adhesion.
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