Affinage

FIGNL1

Fidgetin-like protein 1 · UniProt Q6PIW4

Length
674 aa
Mass
74.1 kDa
Annotated
2026-06-09
22 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

FIGNL1 is an AAA+ ATPase that functions as an anti-recombinase, actively dismantling RAD51 (and the meiotic recombinase DMC1) nucleoprotein filaments to balance recombinase assembly and disassembly during homologous recombination, meiosis, and replication fork restart (PMID:30926776, PMID:37891173, PMID:39147779). It engages RAD51 through a conserved RAD51-binding domain and is recruited to DNA damage sites independently of BRCA2, RAD51, and RAD51 paralogs (PMID:23754376). Cryo-EM shows FIGNL1 assembles into a non-planar hexamer that encloses the RAD51 N-terminus within its central pore; both pore-loop engagement and ATPase catalysis are essential for filament removal and for viability in mouse embryonic stem cells (PMID:39636933). FIGNL1 disassembles RAD51 from both ssDNA and dsDNA, limiting non-productive recombinase assembly on native chromatin (PMID:37891173), and acts at a post-assembly step to alter filament structure and promote processing of recombination intermediates (PMID:39147779). FIGNL1 operates as a stable, mutually stabilizing complex with FIRRM/C1orf112/FLIP, which directly stimulates its filament-disassembly activity and is required for RAD51 dissociation following ICL damage and fork restart (PMID:37515771, PMID:37439366, PMID:38286805). Its activity is antagonized by upstream regulators: BRCA2 directly binds the FIGNL1-FIRRM complex to protect productive RAD51 filaments from premature dismantling (PMID:37515771, PMID:38133958), and the RAD51 paralog SWSAP1 inhibits FIGNL1-mediated RAD51 dissociation (PMID:30926776); loss of FIGNL1 restores RAD51 loading and viability in BRCA2-deficient cells, showing that unrestricted FIGNL1 activity, not defective loading, underlies the BRCA2 HR defect (PMID:41166468). By promoting post-replicative RAD51 disassembly, FIGNL1 prevents RAD51-dependent ultra-fine chromosome bridges and catastrophic genome instability (PMID:38597669). Compound heterozygous frameshift mutations in FIGNL1 abolish its nuclear foci and cause spontaneous and induced chromosomal breakage in a human patient (PMID:37740949).

Mechanistic history

Synthesis pass · year-by-year structured walk · 7 steps
  1. 2013 Medium

    Established FIGNL1 as a direct RAD51 interactor required for homologous recombination, distinguishing it from RAD51 loading factors by showing it acts without affecting RAD51 loading onto ssDNA.

    Evidence Co-IP, domain mapping, siRNA knockdown with HR reporter and foci analysis

    PMID:23754376

    Open questions at the time
    • Biochemical activity on RAD51 filaments not yet demonstrated
    • Functional role of the SPIDR/KIAA0146 complex partner unresolved
    • No structural basis for RAD51 engagement
  2. 2019 High

    Defined FIGNL1 biochemically as an anti-recombinase that dissociates RAD51 from ssDNA and identified SWSAP1 as a regulator that protects filaments by inhibiting this activity.

    Evidence In vitro RAD51-ssDNA dissociation with purified proteins, ATPase-dead mutagenesis, siRNA epistasis

    PMID:30926776

    Open questions at the time
    • Reported ATPase-independence of dismantling later refined by structural work
    • Mechanism of pore engagement not established
    • Activity on dsDNA-bound RAD51 not tested
  3. 2023 High

    Identified FIRRM/C1orf112/FLIP as the stable, mutually stabilizing partner that directly stimulates FIGNL1 filament-disassembly activity, and placed BRCA2 upstream as an antagonist protecting RAD51 filaments.

    Evidence Proximity proteomics, Co-IP, in vitro filament disassembly with purified FIGNL1/C1orf112/BRCA2/RAD51, CRISPR KO, ICL sensitivity

    PMID:37439366 PMID:37515771 PMID:37556550 PMID:37808755 PMID:38133958

    Open questions at the time
    • Stoichiometry of the FIGNL1-FIRRM-BRCA2 assembly not defined
    • FIGNL1-independent FIRRM functions only partially mapped
    • Regulation of complex assembly at damage sites unclear
  4. 2023 High

    Extended FIGNL1-FIRRM function to meiosis and replication, showing it dismantles both RAD51 and DMC1 and acts on dsDNA to limit non-productive recombinase assembly on intact chromatin.

    Evidence Germline-specific conditional KO mice, meiotic chromosome spreads, in vitro filament disassembly on dsDNA and ssDNA

    PMID:37439366 PMID:37891173

    Open questions at the time
    • How DMC1 versus RAD51 selectivity is controlled is unknown
    • Coupling to meiotic crossover designation not resolved
    • Substrate discrimination between productive and non-productive filaments unclear
  5. 2024 High

    Resolved the mechanism: FIGNL1 forms a non-planar hexamer that captures the RAD51 N-terminus in its pore, with pore-loop and ATPase residues essential for disassembly and for ES cell viability.

    Evidence Cryo-EM structure with pore-loop/ATPase mutagenesis, in vitro disassembly assay, mouse ES cell lethality

    PMID:39071279 PMID:39636933

    Open questions at the time
    • How FIRRM modulates the hexamer is not visualized
    • Conformational cycle during ATP hydrolysis not captured
    • Structure of the FIGNL1-FIRRM-BRCA2 assembly absent
  6. 2024 High

    Linked FIGNL1 anti-recombinase activity to genome stability by showing it prevents RAD51-dependent ultra-fine chromosome bridges after replication stress and processes recombination intermediates to promote strand invasion.

    Evidence FIGNL1 CRISPR KO human cells, UFB immunofluorescence, RAD51 foci after fork restart, in vitro strand invasion assay with FIGNL1ΔN, conditional KO mice

    PMID:38286805 PMID:38597669 PMID:39147779

    Open questions at the time
    • Temporal coordination of disassembly with fork restart not fully defined
    • Why some RAD51 filaments are productive and spared is unclear
  7. 2025 High

    Reinterpreted the BRCA2 HR defect by showing FIGNL1 loss restores RAD51 loading and viability in BRCA2-deficient cells, establishing unrestricted FIGNL1 activity as the primary cause of failed RAD51 retention.

    Evidence FIGNL1 KO in BRCA2-deficient mouse ES cells, RAD51 foci, HR reporter, Co-IP of MMS22L-TONSL-FIGNL1, viability assay

    PMID:41166468

    Open questions at the time
    • Role of MMS22L-TONSL in regulating FIGNL1 not mechanistically defined
    • Therapeutic implications for BRCA2-mutant tumors not tested
    • How BRCA2 spatially restricts FIGNL1 in normal cells unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How FIGNL1 distinguishes productive RAD51/DMC1 filaments to be spared from non-productive ones to be dismantled, and how its activity is spatiotemporally licensed by BRCA2, SWSAP1, FIRRM, and MMS22L-TONSL, remains unresolved.
  • No integrated structural model of the regulated complex
  • Substrate selectivity logic unknown
  • In vivo regulation across cell cycle not defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0008092 cytoskeletal protein binding 3 GO:0140657 ATP-dependent activity 3 GO:0098772 molecular function regulator activity 2
Localization
GO:0000228 nuclear chromosome 2 GO:0005634 nucleus 2
Pathway
R-HSA-1474165 Reproduction 3 R-HSA-73894 DNA Repair 3 R-HSA-69306 DNA Replication 2
Complex memberships
FIGNL1-FIRRM/C1orf112/FLIP complex

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2013 FIGNL1 specifically interacts with RAD51 through a conserved RAD51-binding domain. FIGNL1 is recruited to sites of DNA damage independently of BRCA2, RAD51, and RAD51 paralogs. FIGNL1 depletion causes defective HR repair but does not affect RAD51 loading onto ssDNA. FIGNL1 forms a complex with KIAA0146/SPIDR, which acts together with FIGNL1 in HR repair. Co-immunoprecipitation, domain mapping, siRNA knockdown, HR reporter assay, immunofluorescence foci analysis Proceedings of the National Academy of Sciences of the United States of America Medium 23754376
2019 Purified FIGNL1 promotes dissociation of RAD51 from ssDNA in vitro (anti-recombinase activity). This RAD51-dismantling activity does not require FIGNL1 ATPase activity but depends on RAD51-binding. The RAD51 paralogue SWSAP1 binds both RAD51 and FIGNL1, and purified SWSAP1 inhibits the RAD51-dismantling activity of FIGNL1, thereby protecting RAD51 filaments. Depletion of FIGNL1 suppresses the defective RAD51 assembly seen in SWSAP1-depleted cells (genetic epistasis). In vitro RAD51-ssDNA dissociation assay with purified proteins, ATPase-dead mutagenesis, siRNA epistasis, RAD51 foci immunofluorescence Nature communications High 30926776
2023 C1orf112/FLIP forms a stable complex with FIGNL1. Loss of FLIP leads to increased RAD51 amounts and foci on chromatin (with or without DNA damage), defective replication fork progression, and reduced HR competency, consistent with FLIP being required for RAD51 dissociation from nucleofilaments. Both proteins have epistatic roles in ICL repair. Co-immunoprecipitation, siRNA/CRISPR KO, RAD51 chromatin fractionation, replication fork assay, HR reporter assay bioRxivpreprint Medium 37808755
2023 C1orf112/FIRRM physically interacts with FIGNL1 and enhances FIGNL1 protein stability. The RAD51 filament disassembly activity of FIGNL1 is directly stimulated by C1orf112 in vitro. BRCA2 directly interacts with the C1orf112-FIGNL1 complex and functions upstream to protect RAD51 filament from premature disassembly. C1orf112- and FIGNL1-deficient cells are primarily sensitive to DNA ICL agents. RAD51 proximity proteomics, Co-IP, in vitro RAD51 filament disassembly assay with purified proteins, CRISPR KO, DNA damage sensitivity assays Cell reports High 37515771
2023 The FLIP-FIGNL1 complex regulates RAD51 and DMC1 dissociation to promote meiotic recombination and replication fork restart. FLIP interacts with FIGNL1; depletion of either protein destabilizes the other and impairs RAD51 dissociation. FLIP-null meiocytes accumulate massive RAD51 and DMC1 foci, arrested at a zygotene-like stage. Co-immunoprecipitation, germline-specific conditional knockout mice, RAD51/DMC1 immunofluorescence on meiotic spreads, replication fork restart assay Nucleic acids research High 37439366
2023 FIRRM (FIGNL1 Interacting Regulator of Recombination and Mitosis) was identified as a FIGNL1 partner required for RAD51 foci resolution at ICL-induced DSBs. FIGNL1 and FIRRM stability is interdependent. FIRRM binds preferentially to single-stranded DNA in vitro. A FIRRM mutant (ΔWCF) that is stable without FIGNL1 can rescue RAD51 foci resolution and cell survival, indicating FIRRM has FIGNL1-independent function in DNA repair. CRISPR screen, Co-IP, RAD51 foci immunofluorescence, in vitro ssDNA binding assay, domain mutagenesis, cell survival assay Science advances Medium 37556550
2023 FIGNL1 germline-specific conditional knockout male mice show defective chromosome synapsis, impaired meiotic DSB repair, and accumulation of RAD51/DMC1 on meiotic chromosomes. FIGNL1-cKO spermatocytes also accumulate RAD51/DMC1 in pre-meiotic S-phase independently of SPO11-generated DSBs. Purified FIGNL1 dismantles RAD51 filaments on double-stranded DNA as well as ssDNA, indicating a role in limiting non-productive RAD51/DMC1 assembly on native dsDNA. Germline-specific conditional knockout mouse, meiotic chromosome spread immunofluorescence, in vitro RAD51 filament disassembly assay with purified protein on dsDNA and ssDNA Nature communications High 37891173
2024 Cryo-EM structure of FIGNL1 in complex with RAD51 reveals that FIGNL1 forms a non-planar hexamer that encloses the RAD51 N-terminus within its hexamer pore. Mutations in FIGNL1 pore loop or catalytic (ATPase) residues abolish filament disassembly activity and are lethal in mouse embryonic stem cells, establishing that ATPase activity and pore loop engagement with RAD51 N-terminus are mechanistically essential for RAD51 removal. Cryo-EM structure determination, active-site mutagenesis (pore loop and ATPase mutants), in vitro RAD51 filament disassembly assay, mouse embryonic stem cell lethality assay Science (New York, N.Y.) High 39636933
2024 FIGNL1 knockout human cells accumulate ultra-fine chromosome bridges (UFBs) between sister chromatids at telomeres and centromeres after replication stress. These UFBs depend on RAD51 (not replication fork stalling per se), and are suppressed by FIGNL1, indicating that FIGNL1-mediated post-replicative RAD51 disassembly prevents recombination intermediate-like UFBs and catastrophic genome instability. FIGNL1 is defective in RAD51 dissociation after replication fork restart in its absence. FIGNL1 CRISPR KO human cells, ultra-fine bridge immunofluorescence (FANCD2/BLM markers), RAD51 foci after fork restart, epistasis with RAD51 inhibitor Nucleic acids research High 38597669
2024 The FIGNL1-FIRRM complex is required for completing meiotic prophase in mouse spermatocytes. Both proteins limit RAD51 and DMC1 accumulation on intact chromatin independently of SPO11-catalyzed DSB formation. Purified human FIGNL1ΔN alters the RAD51/DMC1 nucleoprotein filament structure and inhibits strand invasion in vitro, placing FIGNL1-FIRRM activity at a post-assembly step to promote strand invasion and processing of recombination intermediates. Male germline-specific conditional KO mice, meiotic chromosome spreads, in vitro RAD51/DMC1 filament alteration and strand invasion assay with purified FIGNL1ΔN Nature communications High 39147779
2024 FLIP (C1orf112) loss causes increased RAD51 chromatin association, defective replication fork progression, elevated chromosomal instability, and reduced HR competency. FLIP and FIGNL1 form a stable epistatic complex with co-dependent protein stability, and the complex is required for RAD51 dissociation from nucleofilaments upon ICL damage. CRISPR KO, RAD51 chromatin fractionation, replication fork progression assay (DNA fiber), HR reporter assay, Co-IP, chromosomal instability/micronuclei quantification Nature communications High 38286805
2024 Cryo-EM structure of FIGNL1-RAD51 complex (preprint version): FIGNL1 forms a non-planar hexamer enclosing RAD51 N-terminus in the hexamer pore. Pore loop and ATPase catalytic mutants are defective in RAD51 filament disassembly and lethal in mouse ES cells. Cryo-EM structure, mutagenesis, in vitro filament disassembly assay, mouse ES cell lethality bioRxivpreprint Medium 39071279
2025 Loss of FIGNL1 (anti-recombinase) restores RAD51 loading at DSBs in BRCA2-deficient cells, leading to genome stability, HR proficiency, and viability of BRCA2-deficient mouse embryonic stem cells. Mechanistically, HR defects upon BRCA2 loss arise primarily from unrestricted FIGNL1-mediated removal of RAD51 from DSBs rather than from defective RAD51 loading. The MMS22L-TONSL complex interacts with FIGNL1 and is critical for HR in BRCA2/FIGNL1 double-deficient cells. FIGNL1 KO in BRCA2-deficient mouse ES cells, RAD51 foci at DSBs, HR reporter assay, Co-IP (MMS22L-TONSL-FIGNL1 interaction), viability assay Science (New York, N.Y.) High 41166468
2023 In vitro reconstitution protocol established: purified C1orf112/FIRRM-FIGNL1 complex directly disassembles RAD51 filaments, and BRCA2 antagonizes this disassembly to protect RAD51 filament from premature dismantling. In vitro reconstitution with purified C1orf112/FIRRM, FIGNL1, mini-BRCA2, and RAD51 from E. coli or S. cerevisiae; RAD51 filament disassembly assay STAR protocols Medium 38133958
2023 Compound heterozygous frameshift mutations in FIGNL1 (c.189del and c.1519_1523del) in a human patient cause loss of FIGNL1 nuclear foci formation, fail to increase foci upon DNA damage (phleomycin), and result in increased chromosomal breakage spontaneously and after mitomycin C exposure, establishing FIGNL1 nuclear foci as functionally important for the DDR. Whole exome sequencing, transfection of DYK-tagged FIGNL1 mutant constructs in HEK293 cells, nuclear foci quantification, chromosomal breakage assay European journal of endocrinology Medium 37740949

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2013 FIGNL1-containing protein complex is required for efficient homologous recombination repair. Proceedings of the National Academy of Sciences of the United States of America 88 23754376
2019 Human RAD51 paralogue SWSAP1 fosters RAD51 filament by regulating the anti-recombinase FIGNL1 AAA+ ATPase. Nature communications 56 30926776
2024 FIGNL1 Promotes Hepatocellular Carcinoma Formation via Remodeling ECM-receptor Interaction Pathway Mediated by HMMR. Current gene therapy 26 37929733
2023 FIGNL1 AAA+ ATPase remodels RAD51 and DMC1 filaments in pre-meiotic DNA replication and meiotic recombination. Nature communications 23 37891173
2022 FIGNL1 Inhibits Non-homologous Chromosome Association and Crossover Formation. Frontiers in plant science 17 35898226
2017 FIGNL1 is overexpressed in small cell lung cancer patients and enhances NCI-H446 cell resistance to cisplatin and etoposide. Oncology reports 15 28260065
2024 FLIP(C1orf112)-FIGNL1 complex regulates RAD51 chromatin association to promote viability after replication stress. Nature communications 12 38286805
2023 The FLIP-FIGNL1 complex regulates the dissociation of RAD51/DMC1 in homologous recombination and replication fork restart. Nucleic acids research 12 37439366
2024 FIGNL1-FIRRM is essential for meiotic recombination and prevents DNA damage-independent RAD51 and DMC1 loading. Nature communications 11 39147779
2024 Molecular basis of FIGNL1 in dissociating RAD51 from DNA and chromatin. Science (New York, N.Y.) 11 39636933
2023 C1orf112 teams up with FIGNL1 to facilitate RAD51 filament disassembly and DNA interstrand cross-link repair. Cell reports 10 37515771
2023 FIRRM cooperates with FIGNL1 to promote RAD51 disassembly during DNA repair. Science advances 10 37556550
2020 FIGNL1 promotes non‑small cell lung cancer cell proliferation. International journal of oncology 10 33367932
2024 Human AAA+ ATPase FIGNL1 suppresses RAD51-mediated ultra-fine bridge formation. Nucleic acids research 9 38597669
2024 FIRRM and FIGNL1: partners in the regulation of homologous recombination. Trends in genetics : TIG 7 38494375
2022 FIGNL1 is a potential biomarker of cisplatin resistance in non-small cell lung cancer. The International journal of biological markers 7 35791674
2025 FIGNL1 inhibits homologous recombination in BRCA2 deficient cells by dissociating RAD51 filaments. Science (New York, N.Y.) 3 41166468
2023 Loss of function of FIGNL1, a DNA damage response gene, causes human ovarian dysgenesis. European journal of endocrinology 3 37740949
2025 FIGNL1 hexamer dissociates RAD51-filament: a new mechanism. Trends in biochemical sciences 1 39893069
2024 Molecular basis of FIGNL1 in dissociating RAD51 from DNA and chromatin. bioRxiv : the preprint server for biology 1 39071279
2023 RADIF(C1orf112)-FIGNL1 Complex Regulates RAD51 Chromatin Association to Promote Viability After Replication Stress. bioRxiv : the preprint server for biology 0 37808755
2023 Reconstitution of the antagonistic effect between C1orf112/FIRRM-FIGNL1 and BRCA2 on RAD51 filament stabilization. STAR protocols 0 38133958

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