id: Q9NXK8
gene_symbol: FBXL12
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  FBXL12 (F-box/LRR-repeat protein 12; FBL12) is a substrate-recognition
  subunit of an SCF (SKP1-CUL1-RBX1) E3 ubiquitin ligase complex. Its N-terminal
  F-box motif binds SKP1, linking it to the CUL1-RBX1 catalytic core, and its
  leucine-rich repeats confer substrate selectivity, so that SCF(FBXL12) directs
  substrate-specific (often K48-linked) polyubiquitination and proteasomal
  degradation. Several physiological substrates have been defined in distinct
  cellular programs, with substrate selection frequently gated by substrate
  phosphorylation. SCF(FBXL12) degrades calcium/calmodulin-dependent protein
  kinase I (CAMK1; acceptor Lys59), which lowers CAMK1-driven p27 phosphorylation,
  disrupts cyclin D1/CDK4 complex assembly, and triggers G1 cell-cycle arrest in
  lung epithelia. It targets the cyclin-dependent kinase inhibitors p57KIP2/CDKN1C
  (TGF-beta1-induced, phosphorylation-dependent turnover linked to osteoblast
  differentiation) and CDKN1B/p27 (Lys165 acceptor; degraded together with
  SCF(FBXL1)/SKP2 downstream of pre-TCR and Notch signaling to license the
  proliferative burst of thymocyte beta-selection). It promotes
  CHK1-phosphorylation-dependent degradation of chromatin-associated FANCD2 to
  support replication-fork recovery and cancer-cell survival under replication
  stress, and degrades the aldehyde dehydrogenases ALDH3A1/ALDH3A2 to permit
  trophoblast differentiation during placental development. An SCF complex
  containing FBXL12 also mediates DNA-damage-induced K48-linked ubiquitination
  and removal of the NHEJ factor Ku80 from DNA ends (shown in Xenopus extracts,
  with conservation to human inferred). FBXL12 acts in both the cytoplasm (where
  it co-localizes with CAMK1) and the nucleus/chromatin (FANCD2, Ku80). Many of
  its catalogued interactions derive from high-throughput proteomic screens and
  are not established functional substrates.
alternative_products:
- name: '1'
  id: Q9NXK8-1
- name: '2'
  id: Q9NXK8-2
  sequence_note: VSP_008859
existing_annotations:
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:18660753
  qualifier: enables
  review:
    summary: Interactions with CDKN1C/p57KIP2 (P49918) and SKP1 (P63208) from the study showing SCF(FBL12) directly ubiquitinates p57KIP2. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records functionally important substrate (CDKN1C) and SKP1 interactions, but bare protein binding is uninformative per curation guidelines; the substrate relationship is captured by the catabolic-process annotations.
    supported_by:
    - reference_id: PMID:18660753
      supporting_text: FBL12 formed an SCF(FBL12) complex and directly ubiquitinated p57(KIP2) in a phosphorylation-dependent manner
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:21163940
  qualifier: enables
  review:
    summary: Interaction with RNF32 (Q9H0A6) from an Alzheimer's-disease interactome map. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interaction of uncertain functional significance; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; Q9H0A6: RNF32; NbExp=2; IntAct=EBI-719790, EBI-724829;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: High-throughput interactions (e.g. DOCK8, LNX1) from a proteome-scale interactome. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactions of uncertain functional significance; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; Q8TBB1: LNX1; NbExp=3; IntAct=EBI-719790, EBI-739832;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:27705803
  qualifier: enables
  review:
    summary: Interaction with SKP1 (P63208) from a Polycomb complexome map. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records the FBXL12-SKP1 association required for SCF assembly, but bare protein binding is uninformative; captured by the ubiquitin ligase complex annotation.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; P63208: SKP1; NbExp=11; IntAct=EBI-719790, EBI-307486;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: Interactions (GEMIN4, SKP1) from a binary interactome reference map. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactions; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; P57678: GEMIN4; NbExp=3; IntAct=EBI-719790, EBI-356700;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: Interaction with SKP1 (P63208) from a cell-specific proteome-scale interactome. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput SKP1 interaction; bare protein binding is uninformative and is subsumed by the ubiquitin ligase complex annotation.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; P63208: SKP1; NbExp=11; IntAct=EBI-719790, EBI-307486;'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:40205054
  qualifier: enables
  review:
    summary: Interaction with SKP1 (P63208) from a multimodal cell-map genomics study. Bare protein binding is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput SKP1 interaction; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: 'Q9NXK8; P63208: SKP1; NbExp=11; IntAct=EBI-719790, EBI-307486;'
- term:
    id: GO:0000151
    label: ubiquitin ligase complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: part_of
  review:
    summary: Ortholog-based electronic assignment of ubiquitin ligase complex membership, consistent with FBXL12 being an SCF substrate-recognition subunit.
    action: ACCEPT
    reason: Correct core cellular component; FBXL12 assembles into SCF(FBXL12). A more specific SCF complex term would be preferable.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Combined automated electronic assignment of cytoplasmic localization, consistent with the cytosolic Reactome annotations.
    action: ACCEPT
    reason: Plausible localization for a cytosolic SCF substrate receptor; consistent with TAS cytosol annotations.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0016567
    label: protein ubiquitination
  evidence_type: IEA
  original_reference_id: GO_REF:0000041
  qualifier: involved_in
  review:
    summary: UniPathway-derived general protein ubiquitination process, consistent with FBXL12's role in substrate ubiquitination.
    action: ACCEPT
    reason: Correct but generic; the SCF-dependent catabolic process term better captures the role. Supported by direct ubiquitination of p57KIP2.
    supported_by:
    - reference_id: PMID:18660753
      supporting_text: FBL12 formed an SCF(FBL12) complex and directly ubiquitinated p57(KIP2) in a phosphorylation-dependent manner
- term:
    id: GO:0031146
    label: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process
  evidence_type: NAS
  original_reference_id: PMID:33234069
  qualifier: involved_in
  review:
    summary: ComplexPortal author statement that FBXL12 functions in SCF-dependent proteasomal protein catabolism. Captures the core biological process.
    action: ACCEPT
    reason: Core biological process for an SCF F-box substrate receptor; directly supported by p57KIP2 degradation (PMID:18660753).
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0051726
    label: regulation of cell cycle
  evidence_type: NAS
  original_reference_id: PMID:33234069
  qualifier: involved_in
  review:
    summary: ComplexPortal author statement linking FBXL12 to cell-cycle regulation, consistent with degradation of the CDK inhibitors p57KIP2/CDKN1C and CDKN1B/p27 and of CAMK1 (G1 arrest; thymocyte beta-selection proliferation).
    action: KEEP_AS_NON_CORE
    reason: Supported downstream regulatory role (via CAMK1, p57KIP2/CDKN1C and CDKN1B/p27 turnover) but a generic process distinct from the core substrate-receptor activity.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: disruption of cyclin D1/CDK4 complex assembly which results in G1 cell cycle arrest in lung epithelia
    - reference_id: file:human/FBXL12/FBXL12-deep-research-falcon.md
      supporting_text: >-
        SCF-Fbxl12 promoted **K48-linked polyubiquitination** of Cdkn1b, with a key
        ubiquitination site identified at **K165**; Cdkn1b(K165R) strongly reduced
        polyubiquitination
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8952618
  qualifier: located_in
  review:
    summary: Reactome curation of cytosolic localization within generic CRL1/NEDD8-cycle reactions. Plausible localization, though derived from pathway context.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation (NEDD8 transfer); reflects the shared cytosolic CRL machinery rather than FBXL12-specific function.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8952620
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic CRL1 NEDD8-binding reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation; reflects shared cytosolic CRL machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8955241
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic CAND1/CRL reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation; reflects shared cytosolic CRL machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8955289
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic COMMD/CAND1/CRL reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation; reflects shared cytosolic CRL machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8956040
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic COP9-signalosome deneddylation reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation; reflects shared cytosolic CRL machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-8956200
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic DCUN1D3/CRL1 reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic CRL-cycle pathway annotation; reflects shared cytosolic CRL machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-983140
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic E2-to-substrate ubiquitin-transfer reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic ubiquitination pathway annotation; reflects shared cytosolic machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-983147
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic E3-release reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic ubiquitination pathway annotation; reflects shared cytosolic machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-983156
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic substrate-polyubiquitination reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic ubiquitination pathway annotation; reflects shared cytosolic machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-983157
  qualifier: located_in
  review:
    summary: Reactome cytosolic localization within a generic E3-substrate-E2 interaction reaction.
    action: KEEP_AS_NON_CORE
    reason: Generic ubiquitination pathway annotation; reflects shared cytosolic machinery.
    supported_by:
    - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
      supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
- term:
    id: GO:1990756
    label: ubiquitin-like ligase-substrate adaptor activity
  evidence_type: IDA
  original_reference_id: PMID:18660753
  qualifier: enables
  review:
    summary: Proposed core molecular function. As the LRR substrate-recognition subunit of SCF(FBXL12), FBXL12 selects substrates such as p57KIP2/CDKN1C (and CAMK1) for SCF-dependent ubiquitination. This more informative MF term is not in the GOA.
    action: NEW
    reason: Captures the precise molecular function of FBXL12 as an SCF substrate-recognition adaptor, more informative than the bare protein binding annotations.
    supported_by:
    - reference_id: PMID:18660753
      supporting_text: FBL12 formed an SCF(FBL12) complex and directly ubiquitinated p57(KIP2) in a phosphorylation-dependent manner
references:
- id: GO_REF:0000041
  title: Gene Ontology annotation based on UniPathway vocabulary mapping
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to
    orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:18660753
  title: A new ubiquitin ligase involved in p57KIP2 proteolysis regulates osteoblast
    cell differentiation.
  findings:
  - statement: FBL12/FBXL12 forms an SCF(FBL12) complex and directly ubiquitinates p57KIP2/CDKN1C in a phosphorylation-dependent manner downstream of TGF-beta1, regulating osteoblast differentiation.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (EMBO Rep 2008), full text available; establishes p57KIP2/CDKN1C as a direct SCF(FBXL12) substrate.
- id: PMID:21163940
  title: Interactome mapping suggests new mechanistic details underlying Alzheimer's
    disease.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput interactome; source of a bare protein binding (RNF32) annotation.
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput interactome; source of bare protein binding annotations.
- id: PMID:27705803
  title: A High-Density Map for Navigating the Human Polycomb Complexome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput complexome map; source of an SKP1 interaction (bare protein binding).
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Binary interactome reference map; source of bare protein binding annotations.
- id: PMID:33234069
  title: 'The FBXL family of F-box proteins: variations on a theme.'
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Review of the FBXL family; basis for the ComplexPortal NAS SCF-catabolic-process and cell-cycle annotations.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human
    interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput interactome; source of an SKP1 interaction (bare protein binding).
- id: PMID:40205054
  title: Multimodal cell maps as a foundation for structural and functional genomics.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput cell-map genomics; source of an SKP1 interaction (bare protein binding).
- id: PMID:23707388
  title: Fbxl12 triggers G1 arrest by mediating degradation of calmodulin kinase I.
  findings:
  - statement: FBXL12 mediates polyubiquitination and proteasomal degradation of CAMK1, disrupting cyclin D1/CDK4 complex assembly and causing G1 cell-cycle arrest in lung epithelia.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Cited in UniProt FUNCTION as the source of the CAMK1-degradation role (Cell Signal 2013); not in the publications cache, so supporting quotes for this claim are drawn from the UniProt entry.
- id: Reactome:R-HSA-8952618
  title: AcM-UBE2M transfers NEDD8 to CRL1 E3 ubiquitin ligase complex
  findings: []
- id: Reactome:R-HSA-8952620
  title: NEDD8:AcM-UBE2M binds CRL1 E3 ubiquitin ligase complex
  findings: []
- id: Reactome:R-HSA-8955241
  title: CAND1 binds cytosolic CRL E3 ubiquitin ligases
  findings: []
- id: Reactome:R-HSA-8955289
  title: COMMDs displace CAND1 from cytosolic CRL E3 ubiquitin ligase complexes
  findings: []
- id: Reactome:R-HSA-8956040
  title: COP9 signalosome deneddylates cytosolic CRL E3 ubiquitin ligase complexes
  findings: []
- id: Reactome:R-HSA-8956200
  title: MyrG-DCUN1D3 binds CRL1 E3 ubiquitin ligase complex
  findings: []
- id: Reactome:R-HSA-983140
  title: Transfer of Ub from E2 to substrate and release of E2
  findings: []
- id: Reactome:R-HSA-983147
  title: Release of E3 from polyubiquitinated substrate
  findings: []
- id: Reactome:R-HSA-983156
  title: Polyubiquitination of substrate
  findings: []
- id: Reactome:R-HSA-983157
  title: Interaction of E3 with substrate and E2-Ub complex
  findings: []
- id: file:human/FBXL12/FBXL12-deep-research-falcon.md
  title: Falcon deep research report for human FBXL12
  findings:
  - statement: FBXL12 is an SCF (SKP1-CUL1-RBX1) substrate-recognition subunit whose biology is best defined by its substrates in different cellular programs, including FANCD2, CaMKI, ALDH3A1/2, and CDKN1B/p27.
    supporting_text: >-
      SCF substrate-recognition subunit that drives ubiquitin-dependent remodeling
      of protein abundance (often proteasomal degradation) for specific substrates
      in distinct biological programs: replication stress recovery (FANCD2),
      cell-cycle gating (CaMKI; CDKN1B/p27), and differentiation programs (ALDH3A1/2).
  - statement: Human SCF(FBXL12) promotes CHK1-phosphorylation-dependent proteasomal degradation of chromatin-associated FANCD2 to enable replication-fork recovery and cancer-cell survival under replication stress.
    supporting_text: >-
      FANCD2 becomes a substrate of SCF^FBXL12 following **CHK1-dependent
      phosphorylation**, creating a phosphodegron that triggers FBXL12-dependent
      turnover, thereby helping clear "chromatin-trapped" FANCD2 at stalled forks
      and enabling replication restart
  - statement: SCF(FBXL12) targets ALDH3A1 and ALDH3A2 for ubiquitin-dependent degradation, which is essential for trophoblast differentiation during placental development.
    supporting_text: >-
      SCF^FBXL12 targets **ALDH3A1 and ALDH3A2** for ubiquitin-dependent degradation
      and that this is **essential for trophoblast differentiation** and proper
      placental development
  - statement: SCF(FBXL12) directly K48-polyubiquitinates CDKN1B/p27 (acceptor K165) to license the proliferative burst of thymocyte beta-selection downstream of pre-TCR and Notch signaling.
    supporting_text: >-
      SCF-Fbxl12 promoted **K48-linked polyubiquitination** of Cdkn1b, with a key
      ubiquitination site identified at **K165**; Cdkn1b(K165R) strongly reduced
      polyubiquitination
  - statement: An SCF complex containing Fbxl12 mediates DNA-damage-induced ubiquitination of Ku80 and its removal from DNA ends (Xenopus extracts, human conservation inferred).
    supporting_text: >-
      an **SCF complex containing Fbxl12** was required for **DNA damage-induced
      Ku80 ubiquitylation**, removal from DNA ends, and subsequent degradation
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Falcon synthesis cross-checked against UniProt (CAMK1 FUNCTION; CDKN1C IntAct)
      and the cached PMID:18660753 (p57KIP2). Additional substrate axes (FANCD2 /
      Brunner 2023 Mol Cell; ALDH3A1-2 / Nishiyama 2015 Stem Cells; CDKN1B-p27 /
      Zhao 2019 Nat Immunol; Ku80 / Postow 2013 Cell Cycle) are reported via
      author-year DOIs not in the PMID cache, so treated as leads but drawn from
      peer-reviewed primary studies; not added as new GOA terms.
core_functions:
- description: Substrate-recognition subunit of an SCF (SKP1-CUL1-RBX1) E3 ubiquitin ligase complex that selects (frequently phosphorylation-gated) substrates, including the CDK inhibitors p57KIP2/CDKN1C and CDKN1B/p27 and the kinase CAMK1, for SCF-dependent polyubiquitination and proteasomal degradation.
  molecular_function:
    id: GO:1990756
    label: ubiquitin-like ligase-substrate adaptor activity
  locations:
  - id: GO:0005829
    label: cytosol
  - id: GO:0005634
    label: nucleus
  supported_by:
  - reference_id: PMID:18660753
    supporting_text: FBL12 formed an SCF(FBL12) complex and directly ubiquitinated p57(KIP2) in a phosphorylation-dependent manner
  - reference_id: file:human/FBXL12/FBXL12-uniprot.txt
    supporting_text: Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex
  directly_involved_in:
  - id: GO:0031146
    label: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process
- description: As the SCF(FBXL12) substrate receptor, promotes CHK1-phosphorylation-dependent proteasomal degradation of chromatin-associated FANCD2, clearing replication-stalled FANCD2 to support replication-fork recovery and cancer-cell survival under replication stress.
  molecular_function:
    id: GO:1990756
    label: ubiquitin-like ligase-substrate adaptor activity
  locations:
  - id: GO:0005634
    label: nucleus
  supported_by:
  - reference_id: file:human/FBXL12/FBXL12-deep-research-falcon.md
    supporting_text: >-
      FANCD2 becomes a substrate of SCF^FBXL12 following **CHK1-dependent
      phosphorylation**, creating a phosphodegron that triggers FBXL12-dependent
      turnover, thereby helping clear "chromatin-trapped" FANCD2 at stalled forks
      and enabling replication restart
  directly_involved_in:
  - id: GO:0031146
    label: SCF-dependent proteasomal ubiquitin-dependent protein catabolic process
proposed_new_terms: []
suggested_questions:
- question: What is the complete physiological substrate repertoire of SCF(FBXL12), and what degron/phosphodegron features (e.g. CHK1, CK2, TGF-beta-driven) does its LRR domain recognize across substrates?
- question: How is FBXL12 partitioned between cytoplasmic (CAMK1) and nuclear/chromatin (FANCD2, Ku80, p27) substrate pools, and what determines context-specific substrate choice in cell cycle, replication stress, development, and immunity?
suggested_experiments:
- description: Reconstitute SCF(FBXL12)-mediated ubiquitination in vitro with purified SKP1-CUL1-RBX1-FBXL12, an E2, and phosphorylated versus unphosphorylated substrates (p57KIP2, CAMK1, CDKN1B/p27, CHK1-phosphorylated FANCD2) to define the phosphodegron requirement and map ubiquitination sites.
- description: Perform quantitative ubiquitinome/proteome profiling in FBXL12-knockout versus control cells (including replication-stressed cancer models and differentiating trophoblast/thymocyte systems) to define the endogenous substrate landscape and validate the cell-cycle, replication-stress, and developmental consequences.