{"gene":"FAF1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1995,"finding":"FAF1 was identified as a protein that specifically interacts with the cytoplasmic domain of wild-type Fas but not the lprcg-mutated Fas, and potentiates Fas-induced apoptosis when transiently expressed in L cells.","method":"Yeast two-hybrid screen, mammalian co-immunoprecipitation, transient overexpression with apoptosis readout","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — yeast two-hybrid plus mammalian cell validation, replicated in multiple subsequent studies","pmids":["8524870"],"is_preprint":false},{"year":2003,"finding":"FAF1 is a member of the Fas-DISC, interacting with FADD and caspase-8 via their death effector domains (DEDs) binding the amino acid 181-381 region of FAF1. FAF1 colocalizes with Fas at the cytoplasmic membrane before Fas activation and moves to the cytoplasm after activation. A dominant-negative FAF1 deletion mutant lacking the N-terminus protects cells from Fas-induced apoptosis, and FAF1-mediated cell death is suppressed in FADD- and caspase-8-deficient cells, placing FAF1 upstream of caspase-8.","method":"Co-immunoprecipitation (in vivo and in vitro), confocal microscopy, dominant-negative overexpression, genetic epistasis in FADD/caspase-8-deficient Jurkat cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis, localization, and dominant-negative experiments in multiple cell systems","pmids":["12702723"],"is_preprint":false},{"year":1999,"finding":"Human FAF1 (hFAF1) was identified and characterized; the N-terminal region (amino acids 1–201) including the upstream ubiquitin homology domain binds to the death domain of Fas but not to the lprcg mutant Fas.","method":"GST pulldown with in vitro translation product of Fas, cDNA cloning","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — GST pulldown with defined domain mapping, single lab but consistent with other reports","pmids":["10462485"],"is_preprint":false},{"year":2001,"finding":"Apoptosis induced by hFAF1 overexpression requires its ubiquitin homologous domain (UB2) and adjacent nuclear localization signal, but not the Fas-binding domain, indicating an intrinsic apoptotic activity independent of Fas binding.","method":"Transient overexpression of deletion mutants, apoptosis assays (membrane blebbing, phosphatidylserine exposure, caspase-3 activation)","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis with multiple orthogonal apoptosis readouts, single lab","pmids":["11527403"],"is_preprint":false},{"year":2001,"finding":"Protein kinase CK2 phosphorylates FAF1 in vitro at Ser289 and Ser291, and CK2 is the major cellular kinase responsible for FAF1 phosphorylation in cell extracts.","method":"In vitro kinase assay with recombinant CK2, MALDI-MS identification of phosphorylation sites, tissue extract kinase assay","journal":"The international journal of biochemistry & cell biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with site identification by MS, plus in-cell evidence; single lab but multiple orthogonal methods","pmids":["11378439"],"is_preprint":false},{"year":2003,"finding":"CK2 phosphorylates FAF1 at Ser289 and Ser291 in vivo (at least one site confirmed), and phosphorylation-deficient FAF1 mutants show delayed nuclear import compared to wild-type FAF1, without affecting FAF1's ability to potentiate Fas-induced apoptosis.","method":"In vivo phosphorylation analysis, nuclear import assay with phosphorylation-deficient mutants","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional mutagenesis with localization readout, single lab, consistent with prior in vitro findings","pmids":["12832043"],"is_preprint":false},{"year":2004,"finding":"FAF1 selectively coactivates mineralocorticoid receptor (MR)-mediated transcription but does not transactivate glucocorticoid receptor (GR), as shown by yeast two-hybrid interaction and transient transactivation assays in mouse hippocampal cells.","method":"Yeast two-hybrid screen, transient transactivation assays in mammalian neural cells","journal":"Molecular pharmacology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid plus mammalian reporter assay, single lab, two orthogonal methods","pmids":["14978255"],"is_preprint":false},{"year":2007,"finding":"FAF1 suppresses IKK activation by interacting with IKKβ via its leucine-zipper domain, disrupting IKK heterocomplex and homocomplex formation and attenuating IKKγ recruitment to IKKβ, thereby inhibiting NF-κB signaling in response to TNF-α, IL-1β, and LPS.","method":"Co-immunoprecipitation, overexpression and siRNA knockdown with IKK kinase activity assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown, overexpression with kinase activity readout; replicated by other labs in the NF-κB context","pmids":["17684021"],"is_preprint":false},{"year":2013,"finding":"FAF1 interacts with VCP complexed with Npl4-Ufd1 heterodimer via its C-terminal UBX domain, and with polyubiquitinated proteins via its N-terminal UBA domain (which recognizes Lys48-linked ubiquitin), promoting endoplasmic reticulum-associated degradation (ERAD). VCP association to the UBX domain regulates ubiquitin binding to the UBA domain.","method":"Co-immunoprecipitation, structural and biochemical analysis, ERAD functional assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural and biochemical analysis combined with functional ERAD assays; consistent with multiple independent studies on FAF1-VCP interaction","pmids":["23293021"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of human FAF1 UBX domain at 2.9 Å resolution reveals a conserved FcisP touch-turn motif in the p97/VCP-binding region, with two conformations of this motif suggesting a conformational change upon binding to p97/VCP N domain.","method":"X-ray crystallography","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure determination, single lab but atomic-resolution structural data","pmids":["21414298"],"is_preprint":false},{"year":2014,"finding":"FAF1 binds p97 stably in a stoichiometry of 3–6 FAF1 per p97 hexamer; cryo-EM reconstruction at 17 Å shows FAF1 positioned above the p97 ring.","method":"Cryo-EM, native mass spectrometry, analytical ultracentrifugation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure plus biochemical stoichiometry determination, single lab with multiple orthogonal methods","pmids":["24619421"],"is_preprint":false},{"year":2013,"finding":"Parkin acts as an E3 ubiquitin ligase that ubiquitinates FAF1 both in vitro and in cells; PD-linked parkin mutations disrupt FAF1 ubiquitination and degradation, elevating FAF1 expression. Wild-type parkin abolishes FAF1-mediated cell death, but PD-linked mutants do not. FAF1 accumulates in the substantia nigra in MPTP-treated mice, and FAF1-deficient mice show attenuated MPTP-induced dopaminergic cell loss.","method":"In vitro ubiquitination assay, cell-based ubiquitination assay, mouse model (gene trap and MPTP treatment), behavioral and biochemical readouts","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of ubiquitination plus in vivo mouse model with multiple readouts","pmids":["23307929"],"is_preprint":false},{"year":2013,"finding":"The UAS domain of FAF1 polymerizes upon interaction with long-chain unsaturated fatty acids; specific mutations in positively charged surface residues of the UAS domain prevent this polymerization.","method":"In vitro polymerization assay, site-directed mutagenesis, cell-based fatty acid regulation assay","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis identifying critical residues, single lab","pmids":["23720822"],"is_preprint":false},{"year":2014,"finding":"FAF1 contains a non-canonical FFAT motif that allows direct interaction with the MSP domain of VAPB, thereby mediating VAPB interaction with p97. FAF1 knockdown strongly reduces VAPB interaction with ubiquitinated proteins.","method":"Co-immunoprecipitation, direct binding assays, siRNA knockdown","journal":"BMC biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assays plus siRNA knockdown, single lab with two orthogonal methods","pmids":["24885147"],"is_preprint":false},{"year":2016,"finding":"FAF1/UBXN-3 binds to the licensing factor CDT-1 and ubiquitylated proteins to promote CDC-48/p97-dependent turnover and disassembly of DNA replication factor complexes at the fork. Inactivation of FAF1/UBXN-3 stabilizes CDT-1 and CDC-45/GINS on chromatin, causing replication fork defects, replication stress, and genome instability.","method":"Genetic knockdown/knockout in C. elegans and human cells, chromatin fractionation, replication fork dynamics assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis and direct substrate identification across two model organisms (C. elegans and human cells) with multiple orthogonal readouts","pmids":["26842564"],"is_preprint":false},{"year":2016,"finding":"Upon oxidative stress, FAF1 translocates from the cytoplasm to the nucleus and promotes catalytic activation of PARP1 through direct physical interaction, driving PARP1-dependent necrotic cell death (energetic collapse, mitochondrial depolarization, AIF nuclear translocation). FAF1 overexpression in mouse ventral midbrain promotes PARP1 activation and dopaminergic neurodegeneration in the MPTP model.","method":"Subcellular fractionation and immunofluorescence, co-immunoprecipitation, siRNA knockdown with cell death assays, AAV-mediated overexpression in mouse brain","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — localization, direct physical interaction, siRNA knockdown, and in vivo mouse model with multiple mechanistic readouts","pmids":["27662363"],"is_preprint":false},{"year":2017,"finding":"FAF1 destabilizes TGF-β type II receptor (TβRII) on the cell surface by recruiting the VCP/E3 ligase complex. AKT directly phosphorylates FAF1 at Ser582, disrupting the FAF1-VCP complex and reducing FAF1 at the plasma membrane, resulting in increased TβRII surface levels and enhanced TGF-β signaling.","method":"Co-immunoprecipitation, in vitro kinase assay, FAF1 knockout mouse model, EMT and metastasis assays, MMTV-PyMT transgenic mouse model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay establishing direct AKT phosphorylation, multiple in vivo models, and reconstitution of the FAF1-VCP-TβRII regulatory axis","pmids":["28443643"],"is_preprint":false},{"year":2018,"finding":"FAF1 forms aggregates that negatively regulate MAVS by competing with TRIM31 for MAVS association, thereby antagonizing K63-linked polyubiquitination and aggregation of MAVS. Upon viral infection, IKKε directly phosphorylates FAF1 at Ser556, triggering FAF1 de-aggregation and lysosomal degradation, relieving FAF1-dependent suppression of MAVS. FAF1 knockout mice show enhanced innate antiviral signaling and reduced viral load.","method":"Co-immunoprecipitation, in vitro kinase assay, FAF1 knockout mice, viral infection models, ubiquitination assays","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay establishing direct IKKε phosphorylation, KO mouse model, multiple orthogonal mechanistic experiments","pmids":["30472208"],"is_preprint":false},{"year":2019,"finding":"FAF1 contains two SUMO-interacting motifs (SIMs) that are crucial for interaction with sumoylated mineralocorticoid receptor (MR) and for repressing aldosterone-activated MR transactivation. FAF1/SIM-mediated MR repression involves inhibition of MR N/C interactions and promotion of MR polyubiquitination and degradation. Silencing FAF1 increases aldosterone-induced MR target gene expression.","method":"Mutagenesis of SIM motifs, co-immunoprecipitation, transactivation reporter assays, siRNA knockdown","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis combined with functional transcription assays and siRNA knockdown, single lab","pmids":["30935967"],"is_preprint":false},{"year":2020,"finding":"FAF1 missense variants (p.Asp371Asn and p.Arg85Pro) encode unstable FAF1 proteins; expression of these variants in CRC cells causes resistance to apoptosis, accumulation of β-catenin in the cytoplasm, and NF-κB nuclear translocation, establishing FAF1 as a functional regulator of both apoptosis and Wnt/NF-κB pathways.","method":"CRISPR/Cas9 gene editing, transfection of missense variants, apoptosis assays, Western blot, NF-κB and Wnt reporter assays","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with variant rescue, multiple functional assays, single lab","pmids":["32179092"],"is_preprint":false},{"year":2021,"finding":"VCP/FAF1 facilitates extraction of SUMOylated and ubiquitylated DNA replication proteins from chromatin. FAF1 inactivation combined with USP7 inactivation is synthetically lethal in C. elegans and mammalian cells, and USP7/VCP inhibitors show synergistic toxicity, establishing a functional cooperation between FAF1-dependent chromatin extraction and USP7-mediated deubiquitylation at replication forks.","method":"Genetic epistasis (double KO/KD), chromatin fractionation, proteasome inhibitor treatment, pharmacological synergy assays in C. elegans and mammalian cells","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — synthetic lethality epistasis replicated across two organisms with pharmacological validation","pmids":["34644576"],"is_preprint":false},{"year":2022,"finding":"FAF1 assembles a globular structure that sequesters free polyunsaturated fatty acids (PUFAs) into a hydrophobic core via its UAS domain interaction, preventing PUFA peroxidation by limiting iron access. FAF1 knockout mice develop hepatic injury on PUFA-enriched diet, and FAF1-deficient cells become sensitive to ferroptosis upon PUFA exposure, placing FAF1 upstream of GPX4 in ferroptosis protection.","method":"FAF1 knockout cell lines and mice, ferroptosis assays, structural biochemistry (globular assembly), lipid peroxidation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO animal model plus mechanistic in vitro characterization and multiple cellular assays","pmids":["35467977"],"is_preprint":false},{"year":2014,"finding":"FAF1 interacts with CD40 via its N-terminal FID domain, binding to the TRAF6-binding domain of CD40's cytoplasmic tail. CD40 ligation induces FAF1 expression in an NF-κB-dependent manner, and FAF1 in turn suppresses CD40-induced NF-κB activation via a negative feedback loop; FAF1 knockdown prolongs CD40-induced NF-κB activation.","method":"Yeast two-hybrid, in vitro and in vivo co-immunoprecipitation, siRNA knockdown, NF-κB reporter assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus mammalian Co-IP and functional siRNA knockdown; single lab, two orthogonal methods","pmids":["24810049"],"is_preprint":false},{"year":2015,"finding":"HSP70 interacts with FAF1 via its N-terminal 1–120 amino acid sequence and competitively inhibits FAF1 binding to Fas, suppressing caspase-8 activation and apoptosis. An N-terminal HSP70 deletion mutant (HSP70-ΔN) cannot interact with FAF1 and fails to attenuate stress-induced apoptosis.","method":"Co-immunoprecipitation, competitive binding assays, overexpression of domain deletion mutants, caspase activity assays","journal":"Cell stress & chaperones","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus domain deletion functional analysis, single lab, mechanistically coherent but limited to pulldown-level evidence","pmids":["25935138"],"is_preprint":false},{"year":2017,"finding":"XIAP interacts with FAF1, promotes ubiquitination of FAF1, blocks FAF1-mediated cell death by interfering with the caspase cascade, and directly interferes with FAF1's inhibition of NF-κB. Conversely, FAF1 attenuates XIAP-mediated NF-κB activation without affecting XIAP's anti-apoptotic activity.","method":"Co-immunoprecipitation, domain mapping, ubiquitination assay, cell death assays, NF-κB reporter assays","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with domain mapping and functional assays, single lab","pmids":["28414080"],"is_preprint":false},{"year":2018,"finding":"FAF1 functions upstream of JNK1 upon ischemic insult; FAF1 physically interacts with JNK1 and promotes JNK1-mediated mitochondrial dysfunction and necrotic cell death. Conditional FAF1 knockout in retinal cells (Dkk3-Cre;Faf1flox/flox mice) attenuates JNK1 activation and ameliorates ischemic retinal cell death.","method":"Immunoprecipitation, conditional KO mouse model, retinal ischemia model with IOP elevation, JNK1 activity assays","journal":"Cell communication and signaling","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO mouse model plus direct protein interaction and kinase activation readouts","pmids":["30200976"],"is_preprint":false},{"year":2020,"finding":"FAF1 is secreted from neuronal cells via both BFA-resistant secretory pathways (vesicle-free form) and as exosome cargo. Extracellular FAF1 is taken up by neighboring cells via endocytosis and induces cell death through apoptotic and necrotic pathways. FAF1 also increases the number of exosomes, suggesting a regulatory role in exosome biogenesis.","method":"Conditioned medium analysis, ultracentrifugation exosome isolation, electron microscopy, nanoparticle tracking analysis, transwell transmission assay, flow cytometry","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods for secretion and uptake characterization, single lab","pmids":["32831099"],"is_preprint":false},{"year":2024,"finding":"VCP controls ubiquitin-proteasomal degradation of KCC2 dependent on FAF1 recruitment; propofol-induced degradation of KCC2 is inhibited by FAF1 knockout, demonstrating that FAF1 is required for VCP-mediated targeting of ubiquitinated KCC2 to the proteasome.","method":"VCP inhibitor (DBeQ), VCP and FAF1 knockout (sgRNA), co-immunoprecipitation, in vivo VPM microinjection in mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO and pharmacological inhibition with in vivo validation, single lab","pmids":["39793039"],"is_preprint":false},{"year":2024,"finding":"SAP130 sumoylation at Lys794, Lys878, and Lys932 is required for its interaction with FAF1; FAF1 promotes SAP130 polyubiquitination and degradation in a sumoylation-dependent manner, thereby counteracting SAP130's transcriptional repression activity.","method":"In vitro and in vivo sumoylation assays, mutagenesis of SUMO acceptor sites, co-immunoprecipitation, polyubiquitination assay, transcriptional reporter assays","journal":"BMC molecular and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo sumoylation assays with mutagenesis and functional readouts, single lab","pmids":["38172660"],"is_preprint":false},{"year":2025,"finding":"Extracellular GMFB activates FAF1 via the FAS receptor to promote degradation of the H+-ATPase ATP6V1A, leading to lysosomal dysfunction in retinal pigment epithelial cells. FAS siRNA and antagonist partially reverse GMFB-induced lysosomal damage, establishing a FAS-FAF1-ATP6V1A signaling axis.","method":"siRNA library screening, immunofluorescence, molecular docking, co-immunoprecipitation, intravitreal injection in vivo","journal":"International journal of biological macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA screening plus co-IP and in vivo validation, single lab, multiple methods","pmids":["40490177"],"is_preprint":false},{"year":2026,"finding":"FAF1 accelerates p97/VCP-mediated unfolding of K48-ubiquitinated substrates by using its p97-bound C-terminal UBX domain to anchor a long helix that braces the UT3 domain of Ufd1, stabilizing the Ufd1-Npl4 cofactor for ubiquitin unfolding and engagement by the ATPase motor. This mechanism stimulates proteasomal degradation.","method":"In vitro reconstituted unfolding system with human components, FRET-based assays, cryo-EM structure determination, mutagenesis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution, cryo-EM structure, mutagenesis, and FRET assays all in one study; independently replicated in a concurrent publication (PMID:41790892)","pmids":["42228561","41790892"],"is_preprint":false},{"year":2017,"finding":"FAF1 regulates CD40-induced NF-κB activation via a negative feedback loop: CD40 ligation induces FAF1 expression in an NF-κB-dependent manner, and FAF1 in turn suppresses CD40-induced NF-κB activation through interaction with CD40 via its FID domain. (Note: this finding overlaps with PMID:24810049 above and is the same discovery.)","method":"Yeast two-hybrid, Co-IP, NF-κB reporter, siRNA knockdown","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods but single lab","pmids":["24810049"],"is_preprint":false},{"year":2011,"finding":"FAF1 expression is required for cranial neural crest (CNC) differentiation in zebrafish; faf1 knockdown causes pharyngeal cartilage defects and jaw abnormality due to failure of CNC to differentiate and express cartilage markers sox9a and col2a1. Rescue with faf1 mRNA restores the phenotype.","method":"Zebrafish morpholino knockdown, mRNA rescue, in situ hybridization for cartilage markers","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino knockdown with mRNA rescue in zebrafish, single lab, defined molecular markers","pmids":["21295280"],"is_preprint":false},{"year":2017,"finding":"FAF1 impairs autophagic flux in dopaminergic neurons, leading to α-synuclein accumulation; pharmacological targeting of FAF1 with KM-819 restores autophagic flux and reduces α-synuclein accumulation in FAF1-overexpressing neuronal cells and in A53T α-synuclein transgenic mice.","method":"FAF1 overexpression via AAV, pharmacological inhibition (KM-819), autophagic flux assays, α-synuclein quantification, transgenic mouse model","journal":"ACS chemical neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mouse model with pharmacological and genetic manipulation, single lab","pmids":["35230076"],"is_preprint":false},{"year":2017,"finding":"NLRP2 protein physically interacts with FAF1 in mouse oocytes and preimplantation embryos; knockdown of either Nlrp2 or Faf1 interferes with NLRP2-FAF1 complex formation and causes developmental arrest in early embryogenesis.","method":"Co-immunoprecipitation from oocytes and embryos, immunofluorescence colocalization, zygote knockdown","journal":"Reproduction (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP plus functional knockdown in zygotes, single lab","pmids":["28630100"],"is_preprint":false}],"current_model":"FAF1 is a multi-domain scaffold protein that promotes apoptosis as a component of the Fas-DISC (binding Fas, FADD, and caspase-8 upstream of caspase-8 activation), suppresses NF-κB by disrupting IKK complex assembly, regulates ubiquitin-proteasomal and ERAD pathways by bridging K48-polyubiquitinated substrates to the VCP/p97-Ufd1-Npl4 complex (with its UBX domain anchoring a helix that stabilizes Ufd1 to accelerate substrate unfolding), facilitates DNA replication fork progression by promoting CDC-48/p97-dependent removal of CDT-1 and other ubiquitylated replication factors from chromatin, protects against ferroptosis by sequestering free PUFAs in a hydrophobic core via its UAS domain, and modulates antiviral immunity by competing with TRIM31 for MAVS association—a suppressive activity itself regulated by IKKε-mediated phosphorylation at Ser556 triggering FAF1 lysosomal degradation; additionally, AKT phosphorylates FAF1 at Ser582 to disrupt its VCP recruitment function at the plasma membrane, elevating TGF-β receptor levels, while parkin E3 ligase ubiquitinates FAF1 to limit its pro-death activity in dopaminergic neurons."},"narrative":{"mechanistic_narrative":"FAF1 is a multi-domain scaffold protein that integrates apoptotic signaling, ubiquitin-dependent protein extraction, and lipid sequestration to govern cell death and proteostasis [PMID:12702723, PMID:23293021, PMID:35467977]. It was first defined as a Fas-associated protein that binds the cytoplasmic domain of wild-type Fas and potentiates Fas-induced apoptosis [PMID:8524870], and it operates within the Fas-DISC by associating with FADD and caspase-8 through their death-effector domains, placing it upstream of caspase-8 activation [PMID:12702723]. In parallel, FAF1 acts as a UBX-domain cofactor of the p97/VCP-Ufd1-Npl4 segregase: its N-terminal UBA domain recognizes K48-linked polyubiquitin while its C-terminal UBX domain docks onto p97, and a helix anchored by the p97-bound UBX domain braces the Ufd1 UT3 domain to accelerate substrate unfolding and proteasomal degradation [PMID:23293021, PMID:42228561, PMID:41790892]. Through this VCP-coupling activity FAF1 drives ERAD and the chromatin extraction of ubiquitylated and SUMOylated replication factors such as CDT-1, promoting replication-fork progression and genome stability, an activity that cooperates with USP7-mediated deubiquitylation [PMID:26842564, PMID:34644576]. FAF1 suppresses NF-κB by binding IKKβ through its leucine-zipper and disrupting IKK complex assembly [PMID:17684021], and antagonizes innate antiviral immunity by competing with TRIM31 for MAVS, a suppressive function relieved by IKKε phosphorylation at Ser556 that triggers FAF1 lysosomal degradation [PMID:30472208]. Its UAS domain sequesters free polyunsaturated fatty acids into a hydrophobic core, protecting cells from ferroptosis upstream of GPX4 [PMID:35467977]. FAF1 abundance and activity are tuned by post-translational control: parkin ubiquitinates FAF1 to limit its pro-death role in dopaminergic neurons [PMID:23307929], and AKT phosphorylation at Ser582 disrupts the FAF1-VCP complex to stabilize the TGF-β type II receptor and enhance TGF-β signaling [PMID:28443643].","teleology":[{"year":1995,"claim":"Established FAF1 as a physical partner of the Fas death receptor and a potentiator of apoptosis, defining its founding role in death-receptor signaling.","evidence":"Yeast two-hybrid against the Fas cytoplasmic domain, co-IP, and transient overexpression apoptosis assay in L cells","pmids":["8524870"],"confidence":"High","gaps":["Did not define the molecular step at which FAF1 acts in the apoptotic cascade","Did not map the FAF1 domains responsible for Fas binding"]},{"year":1999,"claim":"Mapped the Fas-binding activity of human FAF1 to its N-terminal ubiquitin-homology-containing region, localizing the interaction surface.","evidence":"GST pulldown with in vitro translated Fas and cDNA cloning","pmids":["10462485"],"confidence":"Medium","gaps":["Pulldown-level evidence without functional consequence","Did not address whether N-terminal binding is required for apoptosis"]},{"year":2001,"claim":"Distinguished an intrinsic, Fas-independent apoptotic activity residing in the ubiquitin-homology domain, and identified CK2 as the major FAF1 kinase.","evidence":"Deletion-mutant overexpression with apoptosis readouts; in vitro CK2 kinase assay with MS site mapping (Ser289/Ser291)","pmids":["11527403","11378439"],"confidence":"Medium","gaps":["Functional role of CK2 phosphorylation not yet linked to apoptosis","Mechanism of the Fas-independent death activity unresolved"]},{"year":2003,"claim":"Resolved FAF1's position in the Fas-DISC upstream of caspase-8 and showed CK2 phosphorylation controls its nuclear import rather than its apoptotic potency.","evidence":"Reciprocal co-IP, confocal localization, dominant-negative and genetic epistasis in FADD/caspase-8-deficient Jurkat cells; in vivo phosphorylation and nuclear import assays","pmids":["12702723","12832043"],"confidence":"High","gaps":["Stoichiometry of FAF1 within the assembled DISC not defined","How nuclear import relates to FAF1's cytoplasmic death function unclear"]},{"year":2007,"claim":"Defined FAF1 as a negative regulator of NF-κB acting by disrupting IKK complex assembly, extending its role from apoptosis into inflammatory signaling.","evidence":"Reciprocal co-IP, siRNA knockdown and overexpression with IKK kinase activity assays","pmids":["17684021"],"confidence":"High","gaps":["Whether IKK regulation is stimulus-specific not fully resolved","Structural basis of leucine-zipper-mediated IKKβ binding undefined"]},{"year":2013,"claim":"Established the bipartite ubiquitin/p97-binding architecture of FAF1 as a VCP cofactor driving ERAD, and placed parkin as the E3 ligase restraining its pro-death activity in dopaminergic neurons.","evidence":"Co-IP and biochemical analysis of UBA/UBX binding with ERAD assays; in vitro and cell-based ubiquitination plus FAF1-deficient/MPTP mouse models; UAS-domain PUFA polymerization assays","pmids":["23293021","23307929","23720822"],"confidence":"High","gaps":["Functional consequence of UAS-domain fatty-acid polymerization not yet defined","How parkin loss and FAF1 accumulation drive neurodegeneration mechanistically unclear"]},{"year":2014,"claim":"Defined the structural stoichiometry and accessory interactions of the FAF1-p97 segregase module, including bridging VAPB to p97.","evidence":"Cryo-EM, native MS and analytical ultracentrifugation of p97-FAF1; FFAT-motif binding to VAPB MSP domain with siRNA knockdown","pmids":["24619421","24885147"],"confidence":"High","gaps":["Functional output of VAPB bridging to ubiquitinated proteins not fully resolved","How FAF1 stoichiometry on p97 tunes substrate processing unknown"]},{"year":2016,"claim":"Identified FAF1/UBXN-3 as the p97 adaptor that extracts CDT-1 and other ubiquitylated replication factors from chromatin to safeguard fork progression, and uncovered a stress-induced nuclear PARP1-activating necrotic function.","evidence":"Cross-species genetic depletion (C. elegans/human), chromatin fractionation and fork dynamics; subcellular fractionation, co-IP, siRNA and in vivo midbrain overexpression for PARP1 axis","pmids":["26842564","27662363"],"confidence":"High","gaps":["How FAF1 selects replication-factor substrates not defined","Switch between PARP1-necrotic and proteostatic functions of nuclear FAF1 unclear"]},{"year":2017,"claim":"Connected FAF1 to growth-factor and stress signaling through AKT phosphorylation-controlled VCP recruitment regulating TβRII, and through JNK1-dependent ischemic cell death.","evidence":"Co-IP, in vitro AKT kinase assay, FAF1 KO and MMTV-PyMT mouse models; conditional retinal KO with JNK1 activity readouts","pmids":["28443643","30200976"],"confidence":"High","gaps":["Whether Ser582 phosphorylation regulates VCP functions beyond TβRII unknown","Direct vs. indirect basis of FAF1-JNK1 coupling not resolved"]},{"year":2018,"claim":"Established FAF1 as a brake on antiviral innate immunity through aggregation-dependent competition with TRIM31 at MAVS, relieved by IKKε phosphorylation-triggered lysosomal degradation.","evidence":"Co-IP, in vitro IKKε kinase assay, ubiquitination assays and FAF1 KO mice in viral infection models","pmids":["30472208"],"confidence":"High","gaps":["Structural basis of FAF1 aggregate competition with TRIM31 undefined","How Ser556 phosphorylation drives de-aggregation mechanistically unclear"]},{"year":2021,"claim":"Revealed that FAF1-VCP extracts SUMOylated as well as ubiquitylated replication proteins and functionally cooperates with USP7 deubiquitylation at forks, exposing a synthetic-lethal vulnerability.","evidence":"Double-KO/KD epistasis and pharmacological synergy in C. elegans and mammalian cells with chromatin fractionation","pmids":["34644576"],"confidence":"High","gaps":["Mechanism coupling SUMO recognition to extraction not defined","Therapeutic window of USP7/VCP synergy untested clinically"]},{"year":2022,"claim":"Defined a non-enzymatic ferroptosis-protective mechanism in which FAF1 sequesters free PUFAs into a hydrophobic core, acting upstream of GPX4.","evidence":"FAF1 KO cells and mice, ferroptosis and lipid-peroxidation assays, structural biochemistry of globular PUFA-sequestering assembly","pmids":["35467977"],"confidence":"High","gaps":["Regulation of FAF1 PUFA sequestration in vivo not defined","Relationship between lipid-binding and proteostatic functions unresolved"]},{"year":2026,"claim":"Provided the mechanistic basis for FAF1's stimulation of p97-driven proteolysis, showing its UBX-anchored helix braces the Ufd1 UT3 domain to accelerate K48-ubiquitin unfolding.","evidence":"In vitro reconstitution with human components, FRET assays, cryo-EM and mutagenesis (independently 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Section F, Structural biology and crystallization communications","url":"https://pubmed.ncbi.nlm.nih.gov/22102026","citation_count":1,"is_preprint":false},{"pmid":"38065537","id":"PMC_38065537","title":"FAF1 Gene Involvement in Pituitary Corticotroph Tumors.","date":"2023","source":"Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme","url":"https://pubmed.ncbi.nlm.nih.gov/38065537","citation_count":0,"is_preprint":false},{"pmid":"41278724","id":"PMC_41278724","title":"Faf1 accelerates p97-mediated protein unfolding by promoting ubiquitin engagement.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41278724","citation_count":0,"is_preprint":false},{"pmid":"41790892","id":"PMC_41790892","title":"The accessory adapters FAF1, FAF2, and UBXN7 accelerate proteasomal degradation by increasing prior p97-mediated substrate unfolding.","date":"2026","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/41790892","citation_count":0,"is_preprint":false},{"pmid":"42228561","id":"PMC_42228561","title":"Faf1 accelerates p97-mediated protein unfolding by promoting ubiquitin engagement.","date":"2026","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/42228561","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":30002,"output_tokens":8412,"usd":0.108093,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":18259,"output_tokens":4858,"usd":0.106372,"stage2_stop_reason":"end_turn"},"total_usd":0.214465,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"FAF1 was identified as a protein that specifically interacts with the cytoplasmic domain of wild-type Fas but not the lprcg-mutated Fas, and potentiates Fas-induced apoptosis when transiently expressed in L cells.\",\n      \"method\": \"Yeast two-hybrid screen, mammalian co-immunoprecipitation, transient overexpression with apoptosis readout\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — yeast two-hybrid plus mammalian cell validation, replicated in multiple subsequent studies\",\n      \"pmids\": [\"8524870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"FAF1 is a member of the Fas-DISC, interacting with FADD and caspase-8 via their death effector domains (DEDs) binding the amino acid 181-381 region of FAF1. FAF1 colocalizes with Fas at the cytoplasmic membrane before Fas activation and moves to the cytoplasm after activation. A dominant-negative FAF1 deletion mutant lacking the N-terminus protects cells from Fas-induced apoptosis, and FAF1-mediated cell death is suppressed in FADD- and caspase-8-deficient cells, placing FAF1 upstream of caspase-8.\",\n      \"method\": \"Co-immunoprecipitation (in vivo and in vitro), confocal microscopy, dominant-negative overexpression, genetic epistasis in FADD/caspase-8-deficient Jurkat cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis, localization, and dominant-negative experiments in multiple cell systems\",\n      \"pmids\": [\"12702723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human FAF1 (hFAF1) was identified and characterized; the N-terminal region (amino acids 1–201) including the upstream ubiquitin homology domain binds to the death domain of Fas but not to the lprcg mutant Fas.\",\n      \"method\": \"GST pulldown with in vitro translation product of Fas, cDNA cloning\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — GST pulldown with defined domain mapping, single lab but consistent with other reports\",\n      \"pmids\": [\"10462485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Apoptosis induced by hFAF1 overexpression requires its ubiquitin homologous domain (UB2) and adjacent nuclear localization signal, but not the Fas-binding domain, indicating an intrinsic apoptotic activity independent of Fas binding.\",\n      \"method\": \"Transient overexpression of deletion mutants, apoptosis assays (membrane blebbing, phosphatidylserine exposure, caspase-3 activation)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis with multiple orthogonal apoptosis readouts, single lab\",\n      \"pmids\": [\"11527403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Protein kinase CK2 phosphorylates FAF1 in vitro at Ser289 and Ser291, and CK2 is the major cellular kinase responsible for FAF1 phosphorylation in cell extracts.\",\n      \"method\": \"In vitro kinase assay with recombinant CK2, MALDI-MS identification of phosphorylation sites, tissue extract kinase assay\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with site identification by MS, plus in-cell evidence; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"11378439\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CK2 phosphorylates FAF1 at Ser289 and Ser291 in vivo (at least one site confirmed), and phosphorylation-deficient FAF1 mutants show delayed nuclear import compared to wild-type FAF1, without affecting FAF1's ability to potentiate Fas-induced apoptosis.\",\n      \"method\": \"In vivo phosphorylation analysis, nuclear import assay with phosphorylation-deficient mutants\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional mutagenesis with localization readout, single lab, consistent with prior in vitro findings\",\n      \"pmids\": [\"12832043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FAF1 selectively coactivates mineralocorticoid receptor (MR)-mediated transcription but does not transactivate glucocorticoid receptor (GR), as shown by yeast two-hybrid interaction and transient transactivation assays in mouse hippocampal cells.\",\n      \"method\": \"Yeast two-hybrid screen, transient transactivation assays in mammalian neural cells\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid plus mammalian reporter assay, single lab, two orthogonal methods\",\n      \"pmids\": [\"14978255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"FAF1 suppresses IKK activation by interacting with IKKβ via its leucine-zipper domain, disrupting IKK heterocomplex and homocomplex formation and attenuating IKKγ recruitment to IKKβ, thereby inhibiting NF-κB signaling in response to TNF-α, IL-1β, and LPS.\",\n      \"method\": \"Co-immunoprecipitation, overexpression and siRNA knockdown with IKK kinase activity assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown, overexpression with kinase activity readout; replicated by other labs in the NF-κB context\",\n      \"pmids\": [\"17684021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FAF1 interacts with VCP complexed with Npl4-Ufd1 heterodimer via its C-terminal UBX domain, and with polyubiquitinated proteins via its N-terminal UBA domain (which recognizes Lys48-linked ubiquitin), promoting endoplasmic reticulum-associated degradation (ERAD). VCP association to the UBX domain regulates ubiquitin binding to the UBA domain.\",\n      \"method\": \"Co-immunoprecipitation, structural and biochemical analysis, ERAD functional assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural and biochemical analysis combined with functional ERAD assays; consistent with multiple independent studies on FAF1-VCP interaction\",\n      \"pmids\": [\"23293021\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of human FAF1 UBX domain at 2.9 Å resolution reveals a conserved FcisP touch-turn motif in the p97/VCP-binding region, with two conformations of this motif suggesting a conformational change upon binding to p97/VCP N domain.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure determination, single lab but atomic-resolution structural data\",\n      \"pmids\": [\"21414298\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FAF1 binds p97 stably in a stoichiometry of 3–6 FAF1 per p97 hexamer; cryo-EM reconstruction at 17 Å shows FAF1 positioned above the p97 ring.\",\n      \"method\": \"Cryo-EM, native mass spectrometry, analytical ultracentrifugation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure plus biochemical stoichiometry determination, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"24619421\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Parkin acts as an E3 ubiquitin ligase that ubiquitinates FAF1 both in vitro and in cells; PD-linked parkin mutations disrupt FAF1 ubiquitination and degradation, elevating FAF1 expression. Wild-type parkin abolishes FAF1-mediated cell death, but PD-linked mutants do not. FAF1 accumulates in the substantia nigra in MPTP-treated mice, and FAF1-deficient mice show attenuated MPTP-induced dopaminergic cell loss.\",\n      \"method\": \"In vitro ubiquitination assay, cell-based ubiquitination assay, mouse model (gene trap and MPTP treatment), behavioral and biochemical readouts\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of ubiquitination plus in vivo mouse model with multiple readouts\",\n      \"pmids\": [\"23307929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The UAS domain of FAF1 polymerizes upon interaction with long-chain unsaturated fatty acids; specific mutations in positively charged surface residues of the UAS domain prevent this polymerization.\",\n      \"method\": \"In vitro polymerization assay, site-directed mutagenesis, cell-based fatty acid regulation assay\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis identifying critical residues, single lab\",\n      \"pmids\": [\"23720822\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FAF1 contains a non-canonical FFAT motif that allows direct interaction with the MSP domain of VAPB, thereby mediating VAPB interaction with p97. FAF1 knockdown strongly reduces VAPB interaction with ubiquitinated proteins.\",\n      \"method\": \"Co-immunoprecipitation, direct binding assays, siRNA knockdown\",\n      \"journal\": \"BMC biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assays plus siRNA knockdown, single lab with two orthogonal methods\",\n      \"pmids\": [\"24885147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FAF1/UBXN-3 binds to the licensing factor CDT-1 and ubiquitylated proteins to promote CDC-48/p97-dependent turnover and disassembly of DNA replication factor complexes at the fork. Inactivation of FAF1/UBXN-3 stabilizes CDT-1 and CDC-45/GINS on chromatin, causing replication fork defects, replication stress, and genome instability.\",\n      \"method\": \"Genetic knockdown/knockout in C. elegans and human cells, chromatin fractionation, replication fork dynamics assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis and direct substrate identification across two model organisms (C. elegans and human cells) with multiple orthogonal readouts\",\n      \"pmids\": [\"26842564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Upon oxidative stress, FAF1 translocates from the cytoplasm to the nucleus and promotes catalytic activation of PARP1 through direct physical interaction, driving PARP1-dependent necrotic cell death (energetic collapse, mitochondrial depolarization, AIF nuclear translocation). FAF1 overexpression in mouse ventral midbrain promotes PARP1 activation and dopaminergic neurodegeneration in the MPTP model.\",\n      \"method\": \"Subcellular fractionation and immunofluorescence, co-immunoprecipitation, siRNA knockdown with cell death assays, AAV-mediated overexpression in mouse brain\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — localization, direct physical interaction, siRNA knockdown, and in vivo mouse model with multiple mechanistic readouts\",\n      \"pmids\": [\"27662363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FAF1 destabilizes TGF-β type II receptor (TβRII) on the cell surface by recruiting the VCP/E3 ligase complex. AKT directly phosphorylates FAF1 at Ser582, disrupting the FAF1-VCP complex and reducing FAF1 at the plasma membrane, resulting in increased TβRII surface levels and enhanced TGF-β signaling.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, FAF1 knockout mouse model, EMT and metastasis assays, MMTV-PyMT transgenic mouse model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay establishing direct AKT phosphorylation, multiple in vivo models, and reconstitution of the FAF1-VCP-TβRII regulatory axis\",\n      \"pmids\": [\"28443643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FAF1 forms aggregates that negatively regulate MAVS by competing with TRIM31 for MAVS association, thereby antagonizing K63-linked polyubiquitination and aggregation of MAVS. Upon viral infection, IKKε directly phosphorylates FAF1 at Ser556, triggering FAF1 de-aggregation and lysosomal degradation, relieving FAF1-dependent suppression of MAVS. FAF1 knockout mice show enhanced innate antiviral signaling and reduced viral load.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, FAF1 knockout mice, viral infection models, ubiquitination assays\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay establishing direct IKKε phosphorylation, KO mouse model, multiple orthogonal mechanistic experiments\",\n      \"pmids\": [\"30472208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FAF1 contains two SUMO-interacting motifs (SIMs) that are crucial for interaction with sumoylated mineralocorticoid receptor (MR) and for repressing aldosterone-activated MR transactivation. FAF1/SIM-mediated MR repression involves inhibition of MR N/C interactions and promotion of MR polyubiquitination and degradation. Silencing FAF1 increases aldosterone-induced MR target gene expression.\",\n      \"method\": \"Mutagenesis of SIM motifs, co-immunoprecipitation, transactivation reporter assays, siRNA knockdown\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis combined with functional transcription assays and siRNA knockdown, single lab\",\n      \"pmids\": [\"30935967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FAF1 missense variants (p.Asp371Asn and p.Arg85Pro) encode unstable FAF1 proteins; expression of these variants in CRC cells causes resistance to apoptosis, accumulation of β-catenin in the cytoplasm, and NF-κB nuclear translocation, establishing FAF1 as a functional regulator of both apoptosis and Wnt/NF-κB pathways.\",\n      \"method\": \"CRISPR/Cas9 gene editing, transfection of missense variants, apoptosis assays, Western blot, NF-κB and Wnt reporter assays\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with variant rescue, multiple functional assays, single lab\",\n      \"pmids\": [\"32179092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"VCP/FAF1 facilitates extraction of SUMOylated and ubiquitylated DNA replication proteins from chromatin. FAF1 inactivation combined with USP7 inactivation is synthetically lethal in C. elegans and mammalian cells, and USP7/VCP inhibitors show synergistic toxicity, establishing a functional cooperation between FAF1-dependent chromatin extraction and USP7-mediated deubiquitylation at replication forks.\",\n      \"method\": \"Genetic epistasis (double KO/KD), chromatin fractionation, proteasome inhibitor treatment, pharmacological synergy assays in C. elegans and mammalian cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — synthetic lethality epistasis replicated across two organisms with pharmacological validation\",\n      \"pmids\": [\"34644576\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FAF1 assembles a globular structure that sequesters free polyunsaturated fatty acids (PUFAs) into a hydrophobic core via its UAS domain interaction, preventing PUFA peroxidation by limiting iron access. FAF1 knockout mice develop hepatic injury on PUFA-enriched diet, and FAF1-deficient cells become sensitive to ferroptosis upon PUFA exposure, placing FAF1 upstream of GPX4 in ferroptosis protection.\",\n      \"method\": \"FAF1 knockout cell lines and mice, ferroptosis assays, structural biochemistry (globular assembly), lipid peroxidation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO animal model plus mechanistic in vitro characterization and multiple cellular assays\",\n      \"pmids\": [\"35467977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FAF1 interacts with CD40 via its N-terminal FID domain, binding to the TRAF6-binding domain of CD40's cytoplasmic tail. CD40 ligation induces FAF1 expression in an NF-κB-dependent manner, and FAF1 in turn suppresses CD40-induced NF-κB activation via a negative feedback loop; FAF1 knockdown prolongs CD40-induced NF-κB activation.\",\n      \"method\": \"Yeast two-hybrid, in vitro and in vivo co-immunoprecipitation, siRNA knockdown, NF-κB reporter assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus mammalian Co-IP and functional siRNA knockdown; single lab, two orthogonal methods\",\n      \"pmids\": [\"24810049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HSP70 interacts with FAF1 via its N-terminal 1–120 amino acid sequence and competitively inhibits FAF1 binding to Fas, suppressing caspase-8 activation and apoptosis. An N-terminal HSP70 deletion mutant (HSP70-ΔN) cannot interact with FAF1 and fails to attenuate stress-induced apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, competitive binding assays, overexpression of domain deletion mutants, caspase activity assays\",\n      \"journal\": \"Cell stress & chaperones\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus domain deletion functional analysis, single lab, mechanistically coherent but limited to pulldown-level evidence\",\n      \"pmids\": [\"25935138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"XIAP interacts with FAF1, promotes ubiquitination of FAF1, blocks FAF1-mediated cell death by interfering with the caspase cascade, and directly interferes with FAF1's inhibition of NF-κB. Conversely, FAF1 attenuates XIAP-mediated NF-κB activation without affecting XIAP's anti-apoptotic activity.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, ubiquitination assay, cell death assays, NF-κB reporter assays\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with domain mapping and functional assays, single lab\",\n      \"pmids\": [\"28414080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"FAF1 functions upstream of JNK1 upon ischemic insult; FAF1 physically interacts with JNK1 and promotes JNK1-mediated mitochondrial dysfunction and necrotic cell death. Conditional FAF1 knockout in retinal cells (Dkk3-Cre;Faf1flox/flox mice) attenuates JNK1 activation and ameliorates ischemic retinal cell death.\",\n      \"method\": \"Immunoprecipitation, conditional KO mouse model, retinal ischemia model with IOP elevation, JNK1 activity assays\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO mouse model plus direct protein interaction and kinase activation readouts\",\n      \"pmids\": [\"30200976\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FAF1 is secreted from neuronal cells via both BFA-resistant secretory pathways (vesicle-free form) and as exosome cargo. Extracellular FAF1 is taken up by neighboring cells via endocytosis and induces cell death through apoptotic and necrotic pathways. FAF1 also increases the number of exosomes, suggesting a regulatory role in exosome biogenesis.\",\n      \"method\": \"Conditioned medium analysis, ultracentrifugation exosome isolation, electron microscopy, nanoparticle tracking analysis, transwell transmission assay, flow cytometry\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods for secretion and uptake characterization, single lab\",\n      \"pmids\": [\"32831099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"VCP controls ubiquitin-proteasomal degradation of KCC2 dependent on FAF1 recruitment; propofol-induced degradation of KCC2 is inhibited by FAF1 knockout, demonstrating that FAF1 is required for VCP-mediated targeting of ubiquitinated KCC2 to the proteasome.\",\n      \"method\": \"VCP inhibitor (DBeQ), VCP and FAF1 knockout (sgRNA), co-immunoprecipitation, in vivo VPM microinjection in mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO and pharmacological inhibition with in vivo validation, single lab\",\n      \"pmids\": [\"39793039\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SAP130 sumoylation at Lys794, Lys878, and Lys932 is required for its interaction with FAF1; FAF1 promotes SAP130 polyubiquitination and degradation in a sumoylation-dependent manner, thereby counteracting SAP130's transcriptional repression activity.\",\n      \"method\": \"In vitro and in vivo sumoylation assays, mutagenesis of SUMO acceptor sites, co-immunoprecipitation, polyubiquitination assay, transcriptional reporter assays\",\n      \"journal\": \"BMC molecular and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo sumoylation assays with mutagenesis and functional readouts, single lab\",\n      \"pmids\": [\"38172660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Extracellular GMFB activates FAF1 via the FAS receptor to promote degradation of the H+-ATPase ATP6V1A, leading to lysosomal dysfunction in retinal pigment epithelial cells. FAS siRNA and antagonist partially reverse GMFB-induced lysosomal damage, establishing a FAS-FAF1-ATP6V1A signaling axis.\",\n      \"method\": \"siRNA library screening, immunofluorescence, molecular docking, co-immunoprecipitation, intravitreal injection in vivo\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA screening plus co-IP and in vivo validation, single lab, multiple methods\",\n      \"pmids\": [\"40490177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"FAF1 accelerates p97/VCP-mediated unfolding of K48-ubiquitinated substrates by using its p97-bound C-terminal UBX domain to anchor a long helix that braces the UT3 domain of Ufd1, stabilizing the Ufd1-Npl4 cofactor for ubiquitin unfolding and engagement by the ATPase motor. This mechanism stimulates proteasomal degradation.\",\n      \"method\": \"In vitro reconstituted unfolding system with human components, FRET-based assays, cryo-EM structure determination, mutagenesis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution, cryo-EM structure, mutagenesis, and FRET assays all in one study; independently replicated in a concurrent publication (PMID:41790892)\",\n      \"pmids\": [\"42228561\", \"41790892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FAF1 regulates CD40-induced NF-κB activation via a negative feedback loop: CD40 ligation induces FAF1 expression in an NF-κB-dependent manner, and FAF1 in turn suppresses CD40-induced NF-κB activation through interaction with CD40 via its FID domain. (Note: this finding overlaps with PMID:24810049 above and is the same discovery.)\",\n      \"method\": \"Yeast two-hybrid, Co-IP, NF-κB reporter, siRNA knockdown\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods but single lab\",\n      \"pmids\": [\"24810049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FAF1 expression is required for cranial neural crest (CNC) differentiation in zebrafish; faf1 knockdown causes pharyngeal cartilage defects and jaw abnormality due to failure of CNC to differentiate and express cartilage markers sox9a and col2a1. Rescue with faf1 mRNA restores the phenotype.\",\n      \"method\": \"Zebrafish morpholino knockdown, mRNA rescue, in situ hybridization for cartilage markers\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino knockdown with mRNA rescue in zebrafish, single lab, defined molecular markers\",\n      \"pmids\": [\"21295280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FAF1 impairs autophagic flux in dopaminergic neurons, leading to α-synuclein accumulation; pharmacological targeting of FAF1 with KM-819 restores autophagic flux and reduces α-synuclein accumulation in FAF1-overexpressing neuronal cells and in A53T α-synuclein transgenic mice.\",\n      \"method\": \"FAF1 overexpression via AAV, pharmacological inhibition (KM-819), autophagic flux assays, α-synuclein quantification, transgenic mouse model\",\n      \"journal\": \"ACS chemical neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mouse model with pharmacological and genetic manipulation, single lab\",\n      \"pmids\": [\"35230076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"NLRP2 protein physically interacts with FAF1 in mouse oocytes and preimplantation embryos; knockdown of either Nlrp2 or Faf1 interferes with NLRP2-FAF1 complex formation and causes developmental arrest in early embryogenesis.\",\n      \"method\": \"Co-immunoprecipitation from oocytes and embryos, immunofluorescence colocalization, zygote knockdown\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP plus functional knockdown in zygotes, single lab\",\n      \"pmids\": [\"28630100\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FAF1 is a multi-domain scaffold protein that promotes apoptosis as a component of the Fas-DISC (binding Fas, FADD, and caspase-8 upstream of caspase-8 activation), suppresses NF-κB by disrupting IKK complex assembly, regulates ubiquitin-proteasomal and ERAD pathways by bridging K48-polyubiquitinated substrates to the VCP/p97-Ufd1-Npl4 complex (with its UBX domain anchoring a helix that stabilizes Ufd1 to accelerate substrate unfolding), facilitates DNA replication fork progression by promoting CDC-48/p97-dependent removal of CDT-1 and other ubiquitylated replication factors from chromatin, protects against ferroptosis by sequestering free PUFAs in a hydrophobic core via its UAS domain, and modulates antiviral immunity by competing with TRIM31 for MAVS association—a suppressive activity itself regulated by IKKε-mediated phosphorylation at Ser556 triggering FAF1 lysosomal degradation; additionally, AKT phosphorylates FAF1 at Ser582 to disrupt its VCP recruitment function at the plasma membrane, elevating TGF-β receptor levels, while parkin E3 ligase ubiquitinates FAF1 to limit its pro-death activity in dopaminergic neurons.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FAF1 is a multi-domain scaffold protein that integrates apoptotic signaling, ubiquitin-dependent protein extraction, and lipid sequestration to govern cell death and proteostasis [#1, #8, #21]. It was first defined as a Fas-associated protein that binds the cytoplasmic domain of wild-type Fas and potentiates Fas-induced apoptosis [#0], and it operates within the Fas-DISC by associating with FADD and caspase-8 through their death-effector domains, placing it upstream of caspase-8 activation [#1]. In parallel, FAF1 acts as a UBX-domain cofactor of the p97/VCP-Ufd1-Npl4 segregase: its N-terminal UBA domain recognizes K48-linked polyubiquitin while its C-terminal UBX domain docks onto p97, and a helix anchored by the p97-bound UBX domain braces the Ufd1 UT3 domain to accelerate substrate unfolding and proteasomal degradation [#8, #30]. Through this VCP-coupling activity FAF1 drives ERAD and the chromatin extraction of ubiquitylated and SUMOylated replication factors such as CDT-1, promoting replication-fork progression and genome stability, an activity that cooperates with USP7-mediated deubiquitylation [#14, #20]. FAF1 suppresses NF-\\u03baB by binding IKK\\u03b2 through its leucine-zipper and disrupting IKK complex assembly [#7], and antagonizes innate antiviral immunity by competing with TRIM31 for MAVS, a suppressive function relieved by IKK\\u03b5 phosphorylation at Ser556 that triggers FAF1 lysosomal degradation [#17]. Its UAS domain sequesters free polyunsaturated fatty acids into a hydrophobic core, protecting cells from ferroptosis upstream of GPX4 [#21]. FAF1 abundance and activity are tuned by post-translational control: parkin ubiquitinates FAF1 to limit its pro-death role in dopaminergic neurons [#11], and AKT phosphorylation at Ser582 disrupts the FAF1-VCP complex to stabilize the TGF-\\u03b2 type II receptor and enhance TGF-\\u03b2 signaling [#16].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established FAF1 as a physical partner of the Fas death receptor and a potentiator of apoptosis, defining its founding role in death-receptor signaling.\",\n      \"evidence\": \"Yeast two-hybrid against the Fas cytoplasmic domain, co-IP, and transient overexpression apoptosis assay in L cells\",\n      \"pmids\": [\"8524870\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular step at which FAF1 acts in the apoptotic cascade\", \"Did not map the FAF1 domains responsible for Fas binding\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Mapped the Fas-binding activity of human FAF1 to its N-terminal ubiquitin-homology-containing region, localizing the interaction surface.\",\n      \"evidence\": \"GST pulldown with in vitro translated Fas and cDNA cloning\",\n      \"pmids\": [\"10462485\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pulldown-level evidence without functional consequence\", \"Did not address whether N-terminal binding is required for apoptosis\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Distinguished an intrinsic, Fas-independent apoptotic activity residing in the ubiquitin-homology domain, and identified CK2 as the major FAF1 kinase.\",\n      \"evidence\": \"Deletion-mutant overexpression with apoptosis readouts; in vitro CK2 kinase assay with MS site mapping (Ser289/Ser291)\",\n      \"pmids\": [\"11527403\", \"11378439\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of CK2 phosphorylation not yet linked to apoptosis\", \"Mechanism of the Fas-independent death activity unresolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Resolved FAF1's position in the Fas-DISC upstream of caspase-8 and showed CK2 phosphorylation controls its nuclear import rather than its apoptotic potency.\",\n      \"evidence\": \"Reciprocal co-IP, confocal localization, dominant-negative and genetic epistasis in FADD/caspase-8-deficient Jurkat cells; in vivo phosphorylation and nuclear import assays\",\n      \"pmids\": [\"12702723\", \"12832043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of FAF1 within the assembled DISC not defined\", \"How nuclear import relates to FAF1's cytoplasmic death function unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined FAF1 as a negative regulator of NF-\\u03baB acting by disrupting IKK complex assembly, extending its role from apoptosis into inflammatory signaling.\",\n      \"evidence\": \"Reciprocal co-IP, siRNA knockdown and overexpression with IKK kinase activity assays\",\n      \"pmids\": [\"17684021\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IKK regulation is stimulus-specific not fully resolved\", \"Structural basis of leucine-zipper-mediated IKK\\u03b2 binding undefined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established the bipartite ubiquitin/p97-binding architecture of FAF1 as a VCP cofactor driving ERAD, and placed parkin as the E3 ligase restraining its pro-death activity in dopaminergic neurons.\",\n      \"evidence\": \"Co-IP and biochemical analysis of UBA/UBX binding with ERAD assays; in vitro and cell-based ubiquitination plus FAF1-deficient/MPTP mouse models; UAS-domain PUFA polymerization assays\",\n      \"pmids\": [\"23293021\", \"23307929\", \"23720822\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of UAS-domain fatty-acid polymerization not yet defined\", \"How parkin loss and FAF1 accumulation drive neurodegeneration mechanistically unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the structural stoichiometry and accessory interactions of the FAF1-p97 segregase module, including bridging VAPB to p97.\",\n      \"evidence\": \"Cryo-EM, native MS and analytical ultracentrifugation of p97-FAF1; FFAT-motif binding to VAPB MSP domain with siRNA knockdown\",\n      \"pmids\": [\"24619421\", \"24885147\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of VAPB bridging to ubiquitinated proteins not fully resolved\", \"How FAF1 stoichiometry on p97 tunes substrate processing unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified FAF1/UBXN-3 as the p97 adaptor that extracts CDT-1 and other ubiquitylated replication factors from chromatin to safeguard fork progression, and uncovered a stress-induced nuclear PARP1-activating necrotic function.\",\n      \"evidence\": \"Cross-species genetic depletion (C. elegans/human), chromatin fractionation and fork dynamics; subcellular fractionation, co-IP, siRNA and in vivo midbrain overexpression for PARP1 axis\",\n      \"pmids\": [\"26842564\", \"27662363\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FAF1 selects replication-factor substrates not defined\", \"Switch between PARP1-necrotic and proteostatic functions of nuclear FAF1 unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected FAF1 to growth-factor and stress signaling through AKT phosphorylation-controlled VCP recruitment regulating T\\u03b2RII, and through JNK1-dependent ischemic cell death.\",\n      \"evidence\": \"Co-IP, in vitro AKT kinase assay, FAF1 KO and MMTV-PyMT mouse models; conditional retinal KO with JNK1 activity readouts\",\n      \"pmids\": [\"28443643\", \"30200976\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Ser582 phosphorylation regulates VCP functions beyond T\\u03b2RII unknown\", \"Direct vs. indirect basis of FAF1-JNK1 coupling not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established FAF1 as a brake on antiviral innate immunity through aggregation-dependent competition with TRIM31 at MAVS, relieved by IKK\\u03b5 phosphorylation-triggered lysosomal degradation.\",\n      \"evidence\": \"Co-IP, in vitro IKK\\u03b5 kinase assay, ubiquitination assays and FAF1 KO mice in viral infection models\",\n      \"pmids\": [\"30472208\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of FAF1 aggregate competition with TRIM31 undefined\", \"How Ser556 phosphorylation drives de-aggregation mechanistically unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed that FAF1-VCP extracts SUMOylated as well as ubiquitylated replication proteins and functionally cooperates with USP7 deubiquitylation at forks, exposing a synthetic-lethal vulnerability.\",\n      \"evidence\": \"Double-KO/KD epistasis and pharmacological synergy in C. elegans and mammalian cells with chromatin fractionation\",\n      \"pmids\": [\"34644576\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism coupling SUMO recognition to extraction not defined\", \"Therapeutic window of USP7/VCP synergy untested clinically\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a non-enzymatic ferroptosis-protective mechanism in which FAF1 sequesters free PUFAs into a hydrophobic core, acting upstream of GPX4.\",\n      \"evidence\": \"FAF1 KO cells and mice, ferroptosis and lipid-peroxidation assays, structural biochemistry of globular PUFA-sequestering assembly\",\n      \"pmids\": [\"35467977\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulation of FAF1 PUFA sequestration in vivo not defined\", \"Relationship between lipid-binding and proteostatic functions unresolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Provided the mechanistic basis for FAF1's stimulation of p97-driven proteolysis, showing its UBX-anchored helix braces the Ufd1 UT3 domain to accelerate K48-ubiquitin unfolding.\",\n      \"evidence\": \"In vitro reconstitution with human components, FRET assays, cryo-EM and mutagenesis (independently replicated)\",\n      \"pmids\": [\"42228561\", \"41790892\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How this acceleration is regulated by FAF1 phosphorylation not addressed\", \"Substrate-specificity determinants of the accelerated unfolding undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FAF1's distinct activities\\u2014DISC scaffolding, p97-segregase cofactor function, lipid sequestration, and signaling regulation\\u2014are coordinately switched within a single cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No integrated model linking phosphorylation state to choice among FAF1 functions\", \"Unclear how domain-specific activities are spatially partitioned across nucleus, cytosol, ER and plasma membrane\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 8, 30]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 30]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [12, 21]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [6, 18, 28]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 16]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 15]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 15]},\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [14, 20]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 15, 21]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [8, 30, 27]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [14, 20]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [7, 17]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 22]}\n    ],\n    \"complexes\": [\"Fas-DISC\", \"p97/VCP-Ufd1-Npl4 complex\"],\n    \"partners\": [\"FAS\", \"FADD\", \"CASP8\", \"VCP\", \"IKBKB\", \"MAVS\", \"VAPB\", \"CDT1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}