FBF1 (Fas-binding factor 1, also Albatross) is a coiled-coil protein of the distal appendages (ciliary transition fibers) of the mother centriole and ciliary basal body. Recruited downstream of CEP83 and SCLT1 (with LRRC45), FBF1 occupies the distal appendage matrix between the appendage blades, close to the ciliary membrane. Rather than being a core scaffold for appendage assembly, it acts at the ciliary base to control entry into the cilium: the C. elegans orthologue DYF-19 binds IFT-B and is needed for assembled IFT particles to pass the ciliary base, and human FBF1 is required for gating of ciliary transmembrane proteins. In FBF1-knockout cells CP110 removal and TTBK2 recruitment proceed but few cilia form. In epithelial cells FBF1/Albatross also binds keratin filaments and PARD3 and is needed for apical junctional complex formation and epithelial polarity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000922 spindle pole | IDA PMID:21399614 Novel asymmetrically localizing components of human centroso... | KEEP AS NON CORE | Summary: IDA spindle pole from the Jakobsen et al. screen, which noted cell-cycle-variable centrosome association of Albatross/FBF1. Reason: FBF1 stays with the mother centriole, which occupies a spindle pole in mitosis; the observation is plausible but reflects centriole position rather than a spindle function. Supporting Evidence: PMID:21399614 We observed by fluorescence microscopy that C14orf145, Albatross, and C3orf34 localize to the mature mother centriole, akin to CEP170 and CEP164 that localize to the appendage structures of the mature centriole. |
| GO:0000922 spindle pole | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: IEA spindle pole from UniProt subcellular location. Reason: As for the IDA row. Supporting Evidence: PMID:21399614 We observed by fluorescence microscopy that C14orf145, Albatross, and C3orf34 localize to the mature mother centriole, akin to CEP170 and CEP164 that localize to the appendage structures of the mature centriole. |
| GO:0005515 protein binding | IPI PMID:18838552 The keratin-binding protein Albatross regulates polarization... | REMOVE | Summary: IPI with PARD3 (Q8TEW0): Albatross/FBF1 forms a complex with Par3. Reason: Bare protein binding is uninformative; the Par3 association is captured by the apical junction assembly and epithelial polarity annotations. No specific MF follows from the interaction alone. Removal does not dispute the interaction. Supporting Evidence: PMID:18838552 Here, we show that Albatross complexes with Par3 to regulate formation of the apical junctional complex (AJC) and maintain lateral membrane identity. |
| GO:0005813 centrosome | IDA GO_REF:0000052 | ACCEPT | Summary: HPA immunofluorescence (GO_REF:0000052): centrosome (HPA grade Supported). Reason: Consistent with FBF1 being a mother-centriole distal appendage protein. Supporting Evidence: PMID:21399614 We observed by fluorescence microscopy that C14orf145, Albatross, and C3orf34 localize to the mature mother centriole, akin to CEP170 and CEP164 that localize to the appendage structures of the mature centriole. PMID:23348840 we identified five DAP components, including one previously described (CEP164), one partially characterized (CEP89 [ccdc123]), and three novel (CEP83 [ccdc41], SCLT1, and FBF1) DAP proteins |
| GO:0005814 centriole | IBA GO_REF:0000033 | ACCEPT | Summary: IBA centriole; FBF1 among the sources. Reason: FBF1 is at the distal appendages of the mother centriole. Supporting Evidence: PMID:23348840 we identified five DAP components, including one previously described (CEP164), one partially characterized (CEP89 [ccdc123]), and three novel (CEP83 [ccdc41], SCLT1, and FBF1) DAP proteins |
| GO:0005814 centriole | IDA PMID:23348840 Centriole distal appendages promote membrane docking, leadin... | ACCEPT | Summary: IDA: FBF1 identified as a distal appendage component. Reason: Direct localization. Supporting Evidence: PMID:23348840 we identified five DAP components, including one previously described (CEP164), one partially characterized (CEP89 [ccdc123]), and three novel (CEP83 [ccdc41], SCLT1, and FBF1) DAP proteins |
| GO:0005814 centriole | IEA GO_REF:0000120 | ACCEPT | Summary: IEA centriole location. Reason: Consistent with direct evidence. Supporting Evidence: PMID:23348840 we identified five DAP components, including one previously described (CEP164), one partially characterized (CEP89 [ccdc123]), and three novel (CEP83 [ccdc41], SCLT1, and FBF1) DAP proteins |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5617816 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5626223 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5626227 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5626228 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5626681 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5626699 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0005829 cytosol | TAS Reactome:R-HSA-5638009 | KEEP AS NON CORE | Summary: Reactome places this distal appendage protein in its 'cytosol' compartment for a ciliogenesis reaction; Reactome has no centriole/distal-appendage compartment, so centrosomal reactions are modelled in cytosol. Reason: This TAS row reflects a Reactome compartment convention rather than an independent localization experiment. The protein is a structural component of the centriolar distal appendages (ciliary transition fibers), which are part of the centrosome in the cytoplasm rather than the soluble cytosol. The location is broadly compatible (the centrosome lies in the cytoplasm and is not membrane-bounded) but uninformative, so it is retained only as non-core; the informative location is ciliary transition fiber. |
| GO:0036064 ciliary basal body | IBA GO_REF:0000033 | ACCEPT | Summary: IBA ciliary basal body, including C. elegans DYF-19 as a source. Reason: FBF1/DYF-19 localizes to the transition fibers of the basal body in worms and human cells. Supporting Evidence: PMID:24231678 DYF-19 localizes specifically to transition fibres and interacts directly with the IFT-B component DYF-11/IFT54. PMID:24231678 Furthermore, we found that human FBF1 shares conserved localization and function with its worm counterpart. |
| GO:0036064 ciliary basal body | IDA GO_REF:0000052 | ACCEPT | Summary: HPA immunofluorescence (GO_REF:0000052): basal body (HPA grade Supported), a main HPA location. Reason: Consistent with transition fiber localization at the basal body. Supporting Evidence: PMID:24231678 Furthermore, we found that human FBF1 shares conserved localization and function with its worm counterpart. |
| GO:0043296 apical junction complex | IDA PMID:18838552 The keratin-binding protein Albatross regulates polarization... | KEEP AS NON CORE | Summary: IDA colocalizes_with apical junction complex in polarized epithelial cells. Reason: Supported by the Albatross study, but the epithelial junction role has not been extensively replicated and is distinct from the well-supported distal appendage role. Retained as non-core. Supporting Evidence: PMID:18838552 In nonpolarized epithelial cells, Albatross localizes with keratin filaments, whereas in polarized epithelial cells, Albatross is primarily localized in the vicinity of the AJC. |
| GO:0043297 apical junction assembly | IMP PMID:18838552 The keratin-binding protein Albatross regulates polarization... | KEEP AS NON CORE | Summary: IMP: Albatross knockdown causes loss of apical junction complex components from cell-cell borders. Reason: Experimental evidence from a single study supports a role in AJC formation via Par3. Plausible and retained, but peripheral to the core centriolar role. Supporting Evidence: PMID:18838552 Knockdown of Albatross in polarized cells causes a disappearance of key components of the AJC at cell-cell borders and keratin filament reorganization. PMID:18838552 Here, we show that Albatross complexes with Par3 to regulate formation of the apical junctional complex (AJC) and maintain lateral membrane identity. |
| GO:0045095 keratin filament | IDA PMID:18838552 The keratin-binding protein Albatross regulates polarization... | KEEP AS NON CORE | Summary: IDA colocalizes_with keratin filament in non-polarized epithelial cells. Reason: Supported by the cited study (keratin-binding protein Albatross); non-core. Supporting Evidence: PMID:18838552 In nonpolarized epithelial cells, Albatross localizes with keratin filaments, whereas in polarized epithelial cells, Albatross is primarily localized in the vicinity of the AJC. PMID:18838552 We propose that keratins and the keratin-binding protein Albatross are important for epithelial cell polarization. |
| GO:0060271 cilium assembly | IBA GO_REF:0000033 | ACCEPT | Summary: IBA cilium assembly with human, fly and worm (DYF-19) sources. Reason: FBF1 orthologues are required for ciliary entry of IFT particles and for normal cilium formation in worms, and human FBF1 depletion impairs ciliogenesis. Supporting Evidence: PMID:24231678 Here we report that FBF1, a highly conserved transition fibre protein, is required for the ciliary import of assembled IFT particles at the ciliary base. PMID:23348840 All five DAP components are essential for ciliogenesis; loss of CEP83 specifically blocks centriole-to-membrane docking. |
| GO:0060271 cilium assembly | IEA GO_REF:0000002 | ACCEPT | Summary: IEA (InterPro2GO) cilium assembly. Reason: Consistent with experimental evidence. Supporting Evidence: PMID:24231678 Here we report that FBF1, a highly conserved transition fibre protein, is required for the ciliary import of assembled IFT particles at the ciliary base. |
| GO:0060271 cilium assembly | IMP PMID:23348840 Centriole distal appendages promote membrane docking, leadin... | ACCEPT | Summary: IMP: FBF1 depletion impairs ciliogenesis (Tanos et al.). Reason: Supported by the Tanos abstract and by the conserved role in IFT entry. In FBF1-knockout cells the initiation steps (CP110 removal, TTBK2 recruitment) occur normally, yet few cells form cilia, so FBF1 acts after licensing of the mother centriole, at the IFT-entry/axoneme-extension step, rather than in initiation. Supporting Evidence: PMID:23348840 All five DAP components are essential for ciliogenesis; loss of CEP83 specifically blocks centriole-to-membrane docking. PMID:29789620 Both CP110 removal and TTBK2 recruitment occurred normally in FBF1−/− cells (~ 70%), compared with WT cells (~ 80%) and yet cilia were detected in only ~ 14% of the population |
| GO:0060271 cilium assembly | IMP PMID:23348840 Centriole distal appendages promote membrane docking, leadin... | ACCEPT | Summary: IMP: FBF1 depletion impairs ciliogenesis (involved_in row). Reason: As above. Supporting Evidence: PMID:23348840 All five DAP components are essential for ciliogenesis; loss of CEP83 specifically blocks centriole-to-membrane docking. PMID:24231678 Here we report that FBF1, a highly conserved transition fibre protein, is required for the ciliary import of assembled IFT particles at the ciliary base. |
| GO:0070161 anchoring junction | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: IEA anchoring junction from UniProt subcellular location (cell junction). Reason: Reflects the Albatross localization near the apical junctional complex; non-core. Supporting Evidence: PMID:18838552 In nonpolarized epithelial cells, Albatross localizes with keratin filaments, whereas in polarized epithelial cells, Albatross is primarily localized in the vicinity of the AJC. |
| GO:0090162 establishment of epithelial cell polarity | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: IEA (InterPro2GO) establishment of epithelial cell polarity. Reason: Family-wide mapping derived from the Albatross study; plausible but non-core. Supporting Evidence: PMID:18838552 We propose that keratins and the keratin-binding protein Albatross are important for epithelial cell polarization. |
| GO:0090162 establishment of epithelial cell polarity | IMP PMID:18838552 The keratin-binding protein Albatross regulates polarization... | KEEP AS NON CORE | Summary: IMP: Albatross knockdown mislocalizes lateral proteins to the apical side in polarized epithelial cells. Reason: Experimental support from a single study; retained as a non-core function. Supporting Evidence: PMID:18838552 Here, we show that Albatross complexes with Par3 to regulate formation of the apical junctional complex (AJC) and maintain lateral membrane identity. PMID:18838552 We propose that keratins and the keratin-binding protein Albatross are important for epithelial cell polarization. |
| GO:0097539 ciliary transition fiber | IDA PMID:23348840 Centriole distal appendages promote membrane docking, leadin... | ACCEPT | Summary: IDA: FBF1 is one of five distal appendage (transition fiber) components. Reason: Defining location; super-resolution places FBF1 in the distal appendage matrix near the ciliary membrane. Supporting Evidence: PMID:23348840 we identified five DAP components, including one previously described (CEP164), one partially characterized (CEP89 [ccdc123]), and three novel (CEP83 [ccdc41], SCLT1, and FBF1) DAP proteins PMID:29789620 By contrast, FBF1 marks the distal end of the DAM near the ciliary membrane. Strikingly, unlike CEP164, which is essential for ciliogenesis, FBF1 is required for ciliary gating of transmembrane proteins |
| GO:0097539 ciliary transition fiber | IEA GO_REF:0000002 | ACCEPT | Summary: IEA (InterPro2GO) ciliary transition fiber. Reason: Conserved transition fiber localization in worms and humans. Supporting Evidence: PMID:24231678 DYF-19 localizes specifically to transition fibres and interacts directly with the IFT-B component DYF-11/IFT54. |
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Download this section (compressed HTML)Q: In FBF1-knockout cells CP110 removal and TTBK2 recruitment occur but cilia rarely form; is the block caused by failed IFT entry, failed ciliary membrane-protein retention, or instability of nascent axonemes?
Q: Are the epithelial junction/keratin and distal appendage functions of FBF1 carried out by distinct pools or isoforms?
Experiment: In FBF1-knockout RPE-1 cells, quantify IFT-B entry and ciliary transmembrane protein diffusion barriers by live imaging and FRAP, and rescue with FBF1 mutants lacking the IFT54-binding region to test the direct gating mechanism.
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