{"gene":"FAAP100","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2007,"finding":"FAAP100 is an essential component of the FA core complex that directly interacts with FANCB and FANCL to form a stable subcomplex; this subcomplex protects each component from proteolytic degradation and allows their coregulation by FANCA and FANCM during nuclear localization. FAAP100 depletion (siRNA) or knockout abolishes FANCD2 monoubiquitination, causes hypersensitivity to DNA crosslinking agents, and produces genomic instability.","method":"Co-immunoprecipitation, siRNA depletion, gene knockout, FANCD2 monoubiquitination assay, nuclear localization imaging","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP identifying direct FANCB-FANCL interaction, siRNA and gene knockout with multiple orthogonal phenotypic readouts, replicated in subsequent studies","pmids":["17396147"],"is_preprint":false},{"year":2014,"finding":"FANCB, FANCL, and FAAP100 form a minimal catalytic subcomplex (the monoubiquitination module) that is sufficient for FANCD2 monoubiquitination in vitro; embedding FANCL within this subcomplex is required for maximal activity and site specificity. Cells lacking other FA core complex subunits (outside this trimer) retain residual FANCD2 monoubiquitination activity.","method":"Purification of native avian FA core complex, biochemical reconstitution of FANCD2 monoubiquitination in vitro, genetic epistasis in cells deficient for individual subunits","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components plus genetic epistasis; independently replicated by multiple labs","pmids":["24905007"],"is_preprint":false},{"year":2014,"finding":"Epistasis analysis identifies three functional modules in the FA core complex: a catalytic module of FANCL, FANCB, and FAAP100 that is absolutely required for E3 ligase function; disruption of this catalytic module causes complete loss of core complex function, whereas loss of ancillary module components (FANCA-FANCG-FAAP20 or FANCC-FANCE-FANCF) does not abolish activity.","method":"Genetic epistasis analysis, FANCD2 monoubiquitination assays in cells with individual subunit knockouts/knockdowns","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic epistasis across multiple genetic backgrounds, consistent with independent biochemical reconstitution data","pmids":["24910428"],"is_preprint":false},{"year":2016,"finding":"The FA core complex contains two spatially separate FANCL molecules that are dimerized by FANCB and FAAP100, forming a dimer-of-trimers (two copies of FANCB-FANCL-FAAP100). This homodimeric catalytic module is poised to symmetrically monoubiquitinate both FANCI and FANCD2; FANCC-FANCE-FANCF bridge between this module and the FANCI-FANCD2 substrate and transiently alter the FANCI-FANCD2 configuration to stabilize its dimerization interface.","method":"Structural electron microscopy (EM), crosslink-coupled mass spectrometry, in vitro ubiquitination assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural EM combined with XL-MS and functional ubiquitination assays in a single study, independently confirmed by cryo-EM in 2019","pmids":["27986592"],"is_preprint":false},{"year":2016,"finding":"Purified recombinant FA core complex contains two spatially separate FANCL molecules dimerized by FANCB and FAAP100; FANCC and FANCE act as substrate receptors restricting monoubiquitination to the FANCD2:FANCI heterodimer in only its DNA-bound form; FANCA and FANCG are dispensable for maximal in vitro ubiquitination. Deubiquitination by USP1:UAF1 only occurs when DNA is disengaged.","method":"Recombinant FA core complex purification, in vitro ubiquitination and deubiquitination assays, substrate specificity experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — fully reconstituted recombinant complex with mechanistic substrate and DNA-dependency assays, consistent with parallel structural study","pmids":["27986371"],"is_preprint":false},{"year":2019,"finding":"Cryo-EM structure of the reconstituted FA core complex reveals that FANCB and FAAP100 form two central dimers that flank two copies of FANCL, creating a scaffold for the remaining five subunits in an extended asymmetric structure. Despite lacking sequence homology, FANCB and FAAP100 adopt similar structures. The two FANCL subunits are in different conformations at opposite ends of the complex, suggesting each has a distinct role; destabilization of this scaffold disrupts the entire complex.","method":"Cryo-electron microscopy, mass spectrometry, recombinant FA core complex reconstitution","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM structure of reconstituted active complex with MS validation, published in Nature","pmids":["31666700"],"is_preprint":false},{"year":2023,"finding":"FAAP100 plays an essential role in R-loop resolution and replication fork protection to counteract transcription-replication conflicts (TRCs) during mouse primordial germ cell (PGC) proliferation. FAAP100 deletion inactivates the FA pathway, increases TRCs and cotranscriptional R-loops, causes replication fork collapse and DNA damage, activates p53 signaling, and leads to PGC proliferation defects and insufficient reproductive reserve establishment.","method":"FAAP100 conditional knockout in mice, R-loop detection, replication fork protection assays, p53 pathway analysis, fertility phenotyping","journal":"BMC biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — mouse knockout with multiple molecular readouts (R-loops, fork protection, p53) but single lab, no rescue experiment described in abstract","pmids":["37580696"],"is_preprint":false},{"year":2025,"finding":"The FAAP100 missense variant T542P prevents BLP100 (FANCB-FANCL-FAAP100) subcomplex formation, impairs E3 ligase activity, and causes defective FAAP100 nuclear translocation and chromatin recruitment, establishing that subcomplex assembly is required for FAAP100 nuclear import and chromatin association. Homozygous Faap100-/- mice exhibit embryonic lethality, microsomia, malformations, and gonadal atrophy. FAAP100 is designated a causative FA gene (FANCX).","method":"Patient-derived cell complementation assay, engineered FAAP100-inactivated human/avian/zebrafish/mouse cells, ICL sensitivity assays, FAAP100T542P functional characterization, mouse knockout model","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal systems (human cells, avian cells, zebrafish, mouse KO), rescue with WT vs. mutant, specific mechanism (subcomplex disruption → nuclear translocation failure) across multiple independent labs","pmids":["40232843"],"is_preprint":false},{"year":2025,"finding":"Homozygous loss-of-function variants in FAAP100 cause severe Fanconi anemia (designated FANCX) in humans; patient-derived cells show defective FANCD2/FANCI monoubiquitination and ICL hypersensitivity. Expression of WT FAAP100 cDNA rescues cellular phenotypes, but patient-derived variants do not.","method":"Patient-derived cell lines, complementation assay with WT vs. patient variant cDNA, FANCD2 monoubiquitination assay, ICL sensitivity assay","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — human patient cells with direct complementation rescue, two independent families, consistent with parallel mechanistic study","pmids":["40244696"],"is_preprint":false}],"current_model":"FAAP100 is a core structural and catalytic component of the FA core complex that directly associates with FANCB and FANCL to form the minimal BLP100 catalytic trimer (monoubiquitination module); two copies of this trimer dimerize via FANCB-FAAP100 contacts to form the homodimeric scaffold of the entire FA core complex, positioning two FANCL molecules for symmetric monoubiquitination of the FANCD2-FANCI heterodimer in a DNA-dependent manner, while also being required for FANCL stability and nuclear localization; loss of FAAP100 abolishes FANCD2/FANCI monoubiquitination, causes ICL hypersensitivity and genomic instability, and in vivo disrupts R-loop resolution in primordial germ cells, with germline loss-of-function variants in humans causing a severe form of Fanconi anemia (FANCX)."},"narrative":{"mechanistic_narrative":"FAAP100 is an essential structural and catalytic component of the Fanconi anemia (FA) core complex, the multisubunit E3 ubiquitin ligase that monoubiquitinates the FANCD2-FANCI heterodimer to activate DNA interstrand crosslink (ICL) repair [PMID:17396147, PMID:24910428]. FAAP100 directly associates with FANCB and FANCL to form the minimal catalytic trimer (the BLP100 monoubiquitination module) that is sufficient to monoubiquitinate FANCD2 in vitro and is absolutely required for E3 ligase function, whereas ancillary modules (FANCA-FANCG-FAAP20 and FANCC-FANCE-FANCF) are dispensable for residual activity [PMID:24905007, PMID:24910428, PMID:27986371]. Structurally, FANCB and FAAP100 form two central dimers that flank and dimerize two copies of FANCL, building a dimer-of-trimers scaffold that symmetrically positions both FANCL molecules to monoubiquitinate the DNA-bound FANCD2-FANCI heterodimer; despite lacking sequence homology, FANCB and FAAP100 adopt similar folds, and destabilizing this scaffold collapses the entire complex [PMID:27986592, PMID:31666700]. FAAP100 is required for FANCL stability and for nuclear translocation and chromatin recruitment, and its incorporation into the BLP100 subcomplex is itself the prerequisite for its own nuclear import [PMID:17396147, PMID:40232843]. Loss of FAAP100 abolishes FANCD2/FANCI monoubiquitination, causes ICL hypersensitivity and genomic instability [PMID:17396147], and in mouse primordial germ cells disrupts R-loop resolution and replication fork protection, driving transcription-replication conflicts and p53-dependent proliferation defects [PMID:37580696]. Germline loss-of-function variants in FAAP100 cause a severe form of Fanconi anemia designated FANCX, with patient cells showing defective monoubiquitination and ICL hypersensitivity rescued by wild-type but not variant cDNA [PMID:40232843, PMID:40244696].","teleology":[{"year":2007,"claim":"Established that FAAP100 is a bona fide FA core complex component by showing it directly binds FANCB and FANCL and is required for FANCD2 monoubiquitination, defining its place in the ICL repair pathway.","evidence":"Co-IP, siRNA depletion and knockout with FANCD2 monoubiquitination, crosslink sensitivity, and nuclear localization readouts","pmids":["17396147"],"confidence":"High","gaps":["Did not resolve whether the FANCB-FANCL-FAAP100 trimer is catalytically sufficient on its own","No structural basis for the interactions"]},{"year":2014,"claim":"Defined the FANCB-FANCL-FAAP100 trimer as the minimal catalytic monoubiquitination module sufficient for FANCD2 modification and showed ancillary modules are not required for activity, isolating the catalytic core.","evidence":"In vitro reconstitution with purified native avian FA core complex plus genetic epistasis in subunit-deficient cells (two parallel studies)","pmids":["24905007","24910428"],"confidence":"High","gaps":["Stoichiometry and architecture of the trimer within the full complex not resolved","Mechanism of substrate engagement not defined"]},{"year":2016,"claim":"Revealed that FANCB and FAAP100 dimerize two FANCL molecules into a dimer-of-trimers poised for symmetric monoubiquitination, and that DNA-bound FANCD2-FANCI is the restricted substrate, explaining the architecture underlying catalysis.","evidence":"EM/XL-MS with in vitro ubiquitination, plus fully recombinant complex reconstitution with substrate-specificity and DNA-dependency assays (two parallel studies)","pmids":["27986592","27986371"],"confidence":"High","gaps":["Atomic-resolution fold of FAAP100 not yet determined","Functional asymmetry between the two FANCL copies unexplained"]},{"year":2019,"claim":"Provided a high-resolution scaffold model in which FANCB-FAAP100 central dimers organize the entire complex and showed FAAP100 adopts a FANCB-like fold despite no sequence homology, establishing FAAP100 as a structural keystone.","evidence":"Cryo-EM of reconstituted active complex with MS validation","pmids":["31666700"],"confidence":"High","gaps":["Conformational dynamics of the two distinct FANCL states not mechanistically dissected","Does not address in vivo regulation of complex assembly"]},{"year":2023,"claim":"Extended FAAP100 function to an in vivo physiological role, showing it counteracts transcription-replication conflicts via R-loop resolution and fork protection during germ cell development.","evidence":"FAAP100 conditional knockout mice with R-loop detection, fork protection assays, p53 pathway analysis, and fertility phenotyping","pmids":["37580696"],"confidence":"Medium","gaps":["No rescue experiment described","Single lab","Whether R-loop phenotype is direct or secondary to loss of FANCD2 ubiquitination not separated"]},{"year":2025,"claim":"Identified FAAP100 as a human Fanconi anemia gene (FANCX) and mechanistically tied disease variants to failure of BLP100 subcomplex assembly, linking subcomplex formation to FAAP100 nuclear import and chromatin recruitment.","evidence":"Patient-derived cell complementation with WT vs. variant cDNA, engineered multi-organism cell models, ICL sensitivity, T542P functional characterization, and mouse knockout (two parallel studies)","pmids":["40232843","40244696"],"confidence":"High","gaps":["Full spectrum of pathogenic variants not catalogued","Genotype-phenotype correlations across patients not established"]},{"year":null,"claim":"How FAAP100-dependent conformational asymmetry between the two FANCL copies is functionally exploited, and how nuclear import of the BLP100 subcomplex is regulated, remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No mechanism for the distinct roles of the two FANCL conformations","Regulation of subcomplex-coupled nuclear import not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[3,5]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[1,4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,7]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,2,4]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,8]}],"complexes":["FA core complex","BLP100 subcomplex (FANCB-FANCL-FAAP100)"],"partners":["FANCB","FANCL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q0VG06","full_name":"Fanconi anemia core complex-associated protein 100","aliases":["Fanconi anemia-associated protein of 100 kDa"],"length_aa":881,"mass_kda":93.4,"function":"Plays a role in Fanconi anemia-associated DNA damage response network. Regulates FANCD2 monoubiquitination and the stability of the FA core complex. Induces chromosomal instability as well as hypersensitivity to DNA cross-linking agents, when repressed","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q0VG06/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FAAP100","classification":"Not Classified","n_dependent_lines":225,"n_total_lines":1208,"dependency_fraction":0.18625827814569537},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FAAP100","total_profiled":1310},"omim":[{"mim_id":"621258","title":"FANCONI ANEMIA, COMPLEMENTATION GROUP X; FANCX","url":"https://www.omim.org/entry/621258"},{"mim_id":"611301","title":"FA CORE COMPLEX-ASSOCIATED PROTEIN 100; FAAP100","url":"https://www.omim.org/entry/611301"},{"mim_id":"608111","title":"FANCL GENE; FANCL","url":"https://www.omim.org/entry/608111"},{"mim_id":"300515","title":"FANCB GENE; FANCB","url":"https://www.omim.org/entry/300515"},{"mim_id":"227650","title":"FANCONI ANEMIA, COMPLEMENTATION GROUP A; FANCA","url":"https://www.omim.org/entry/227650"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FAAP100"},"hgnc":{"alias_symbol":["FLJ22175"],"prev_symbol":["C17orf70"]},"alphafold":{"accession":"Q0VG06","domains":[{"cath_id":"2.60.40.10","chopping":"480-615_637-646","consensus_level":"medium","plddt":79.6345,"start":480,"end":646},{"cath_id":"3.30.310","chopping":"701-826","consensus_level":"high","plddt":82.3918,"start":701,"end":826}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q0VG06","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q0VG06-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q0VG06-F1-predicted_aligned_error_v6.png","plddt_mean":73.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FAAP100","jax_strain_url":"https://www.jax.org/strain/search?query=FAAP100"},"sequence":{"accession":"Q0VG06","fasta_url":"https://rest.uniprot.org/uniprotkb/Q0VG06.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q0VG06/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q0VG06"}},"corpus_meta":[{"pmid":"19622404","id":"PMC_19622404","title":"Cellular and molecular consequences of defective Fanconi anemia proteins in replication-coupled DNA repair: mechanistic insights.","date":"2009","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/19622404","citation_count":128,"is_preprint":false},{"pmid":"17396147","id":"PMC_17396147","title":"FAAP100 is essential for activation of the Fanconi anemia-associated DNA damage response pathway.","date":"2007","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/17396147","citation_count":120,"is_preprint":false},{"pmid":"27986371","id":"PMC_27986371","title":"Mechanism of Ubiquitination and Deubiquitination in the Fanconi Anemia Pathway.","date":"2016","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/27986371","citation_count":105,"is_preprint":false},{"pmid":"24905007","id":"PMC_24905007","title":"The genetic and biochemical basis of FANCD2 monoubiquitination.","date":"2014","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/24905007","citation_count":102,"is_preprint":false},{"pmid":"31666700","id":"PMC_31666700","title":"Structure of the Fanconi anaemia monoubiquitin ligase complex.","date":"2019","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/31666700","citation_count":85,"is_preprint":false},{"pmid":"24910428","id":"PMC_24910428","title":"Modularized functions of the Fanconi anemia core complex.","date":"2014","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24910428","citation_count":80,"is_preprint":false},{"pmid":"22396592","id":"PMC_22396592","title":"Fanconi anemia (FA) binding protein FAAP20 stabilizes FA complementation group A (FANCA) and participates in interstrand cross-link repair.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22396592","citation_count":70,"is_preprint":false},{"pmid":"30540754","id":"PMC_30540754","title":"Multiplexed CRISPR/Cas9-mediated knockout of 19 Fanconi anemia pathway genes in zebrafish revealed their roles in growth, sexual development and fertility.","date":"2018","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30540754","citation_count":52,"is_preprint":false},{"pmid":"27986592","id":"PMC_27986592","title":"The FA Core Complex Contains a Homo-dimeric Catalytic Module for the Symmetric Mono-ubiquitination of FANCI-FANCD2.","date":"2016","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/27986592","citation_count":51,"is_preprint":false},{"pmid":"30201439","id":"PMC_30201439","title":"The radiotherapy-sensitization effect of cantharidin: Mechanisms involving cell cycle regulation, enhanced DNA damage, and inhibited DNA damage repair.","date":"2018","source":"Pancreatology : official journal of the International Association of Pancreatology (IAP) ... [et al.]","url":"https://pubmed.ncbi.nlm.nih.gov/30201439","citation_count":33,"is_preprint":false},{"pmid":"19379763","id":"PMC_19379763","title":"FANCM-FAAP24 and FANCJ: FA proteins that metabolize DNA.","date":"2009","source":"Mutation research","url":"https://pubmed.ncbi.nlm.nih.gov/19379763","citation_count":25,"is_preprint":false},{"pmid":"19405097","id":"PMC_19405097","title":"Identification and characterization of mutations in FANCL gene: a second case of Fanconi anemia belonging to FA-L complementation group.","date":"2009","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/19405097","citation_count":24,"is_preprint":false},{"pmid":"40244696","id":"PMC_40244696","title":"Deficiency of the Fanconi anemia core complex protein FAAP100 results in severe Fanconi anemia.","date":"2025","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40244696","citation_count":16,"is_preprint":false},{"pmid":"40232843","id":"PMC_40232843","title":"Genetic inactivation of FAAP100 causes Fanconi anemia due to disruption of the monoubiquitin ligase core complex.","date":"2025","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40232843","citation_count":13,"is_preprint":false},{"pmid":"37580696","id":"PMC_37580696","title":"FAAP100 is required for the resolution of transcription-replication conflicts in primordial germ cells.","date":"2023","source":"BMC biology","url":"https://pubmed.ncbi.nlm.nih.gov/37580696","citation_count":7,"is_preprint":false},{"pmid":"39421870","id":"PMC_39421870","title":"Somatic gene mutations involved in DNA damage response/Fanconi anemia signaling are tissue- and cell-type specific in human solid tumors.","date":"2024","source":"Frontiers in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39421870","citation_count":5,"is_preprint":false},{"pmid":"40454474","id":"PMC_40454474","title":"Another Fanconi anemia gene joins the club.","date":"2025","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/40454474","citation_count":1,"is_preprint":false},{"pmid":"28672922","id":"PMC_28672922","title":"Combining affinity propagation clustering and mutual information network to investigate key genes in fibroid.","date":"2017","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28672922","citation_count":1,"is_preprint":false},{"pmid":"40541815","id":"PMC_40541815","title":"FAAP100:A biomarker based on pan-cancer analysis, promotes the progression of lung adenocarcinoma.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/40541815","citation_count":0,"is_preprint":false},{"pmid":"41517999","id":"PMC_41517999","title":"Genomic comparisons and the adaptive basis of brain size plasticity and chromosomal instability in the Eurasian common shrew.","date":"2026","source":"Molecular biology and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/41517999","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.11.648246","title":"Genomic comparisons shed light on the adaptive basis of brain size plasticity and chromosomal instability in the Eurasian common shrew","date":"2025-04-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.11.648246","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12191,"output_tokens":2630,"usd":0.038011,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9796,"output_tokens":2810,"usd":0.059615,"stage2_stop_reason":"end_turn"},"total_usd":0.097626,"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\": 2007,\n      \"finding\": \"FAAP100 is an essential component of the FA core complex that directly interacts with FANCB and FANCL to form a stable subcomplex; this subcomplex protects each component from proteolytic degradation and allows their coregulation by FANCA and FANCM during nuclear localization. FAAP100 depletion (siRNA) or knockout abolishes FANCD2 monoubiquitination, causes hypersensitivity to DNA crosslinking agents, and produces genomic instability.\",\n      \"method\": \"Co-immunoprecipitation, siRNA depletion, gene knockout, FANCD2 monoubiquitination assay, nuclear localization imaging\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP identifying direct FANCB-FANCL interaction, siRNA and gene knockout with multiple orthogonal phenotypic readouts, replicated in subsequent studies\",\n      \"pmids\": [\"17396147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FANCB, FANCL, and FAAP100 form a minimal catalytic subcomplex (the monoubiquitination module) that is sufficient for FANCD2 monoubiquitination in vitro; embedding FANCL within this subcomplex is required for maximal activity and site specificity. Cells lacking other FA core complex subunits (outside this trimer) retain residual FANCD2 monoubiquitination activity.\",\n      \"method\": \"Purification of native avian FA core complex, biochemical reconstitution of FANCD2 monoubiquitination in vitro, genetic epistasis in cells deficient for individual subunits\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components plus genetic epistasis; independently replicated by multiple labs\",\n      \"pmids\": [\"24905007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Epistasis analysis identifies three functional modules in the FA core complex: a catalytic module of FANCL, FANCB, and FAAP100 that is absolutely required for E3 ligase function; disruption of this catalytic module causes complete loss of core complex function, whereas loss of ancillary module components (FANCA-FANCG-FAAP20 or FANCC-FANCE-FANCF) does not abolish activity.\",\n      \"method\": \"Genetic epistasis analysis, FANCD2 monoubiquitination assays in cells with individual subunit knockouts/knockdowns\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic epistasis across multiple genetic backgrounds, consistent with independent biochemical reconstitution data\",\n      \"pmids\": [\"24910428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The FA core complex contains two spatially separate FANCL molecules that are dimerized by FANCB and FAAP100, forming a dimer-of-trimers (two copies of FANCB-FANCL-FAAP100). This homodimeric catalytic module is poised to symmetrically monoubiquitinate both FANCI and FANCD2; FANCC-FANCE-FANCF bridge between this module and the FANCI-FANCD2 substrate and transiently alter the FANCI-FANCD2 configuration to stabilize its dimerization interface.\",\n      \"method\": \"Structural electron microscopy (EM), crosslink-coupled mass spectrometry, in vitro ubiquitination assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural EM combined with XL-MS and functional ubiquitination assays in a single study, independently confirmed by cryo-EM in 2019\",\n      \"pmids\": [\"27986592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Purified recombinant FA core complex contains two spatially separate FANCL molecules dimerized by FANCB and FAAP100; FANCC and FANCE act as substrate receptors restricting monoubiquitination to the FANCD2:FANCI heterodimer in only its DNA-bound form; FANCA and FANCG are dispensable for maximal in vitro ubiquitination. Deubiquitination by USP1:UAF1 only occurs when DNA is disengaged.\",\n      \"method\": \"Recombinant FA core complex purification, in vitro ubiquitination and deubiquitination assays, substrate specificity experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — fully reconstituted recombinant complex with mechanistic substrate and DNA-dependency assays, consistent with parallel structural study\",\n      \"pmids\": [\"27986371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cryo-EM structure of the reconstituted FA core complex reveals that FANCB and FAAP100 form two central dimers that flank two copies of FANCL, creating a scaffold for the remaining five subunits in an extended asymmetric structure. Despite lacking sequence homology, FANCB and FAAP100 adopt similar structures. The two FANCL subunits are in different conformations at opposite ends of the complex, suggesting each has a distinct role; destabilization of this scaffold disrupts the entire complex.\",\n      \"method\": \"Cryo-electron microscopy, mass spectrometry, recombinant FA core complex reconstitution\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM structure of reconstituted active complex with MS validation, published in Nature\",\n      \"pmids\": [\"31666700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FAAP100 plays an essential role in R-loop resolution and replication fork protection to counteract transcription-replication conflicts (TRCs) during mouse primordial germ cell (PGC) proliferation. FAAP100 deletion inactivates the FA pathway, increases TRCs and cotranscriptional R-loops, causes replication fork collapse and DNA damage, activates p53 signaling, and leads to PGC proliferation defects and insufficient reproductive reserve establishment.\",\n      \"method\": \"FAAP100 conditional knockout in mice, R-loop detection, replication fork protection assays, p53 pathway analysis, fertility phenotyping\",\n      \"journal\": \"BMC biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — mouse knockout with multiple molecular readouts (R-loops, fork protection, p53) but single lab, no rescue experiment described in abstract\",\n      \"pmids\": [\"37580696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The FAAP100 missense variant T542P prevents BLP100 (FANCB-FANCL-FAAP100) subcomplex formation, impairs E3 ligase activity, and causes defective FAAP100 nuclear translocation and chromatin recruitment, establishing that subcomplex assembly is required for FAAP100 nuclear import and chromatin association. Homozygous Faap100-/- mice exhibit embryonic lethality, microsomia, malformations, and gonadal atrophy. FAAP100 is designated a causative FA gene (FANCX).\",\n      \"method\": \"Patient-derived cell complementation assay, engineered FAAP100-inactivated human/avian/zebrafish/mouse cells, ICL sensitivity assays, FAAP100T542P functional characterization, mouse knockout model\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal systems (human cells, avian cells, zebrafish, mouse KO), rescue with WT vs. mutant, specific mechanism (subcomplex disruption → nuclear translocation failure) across multiple independent labs\",\n      \"pmids\": [\"40232843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Homozygous loss-of-function variants in FAAP100 cause severe Fanconi anemia (designated FANCX) in humans; patient-derived cells show defective FANCD2/FANCI monoubiquitination and ICL hypersensitivity. Expression of WT FAAP100 cDNA rescues cellular phenotypes, but patient-derived variants do not.\",\n      \"method\": \"Patient-derived cell lines, complementation assay with WT vs. patient variant cDNA, FANCD2 monoubiquitination assay, ICL sensitivity assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human patient cells with direct complementation rescue, two independent families, consistent with parallel mechanistic study\",\n      \"pmids\": [\"40244696\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FAAP100 is a core structural and catalytic component of the FA core complex that directly associates with FANCB and FANCL to form the minimal BLP100 catalytic trimer (monoubiquitination module); two copies of this trimer dimerize via FANCB-FAAP100 contacts to form the homodimeric scaffold of the entire FA core complex, positioning two FANCL molecules for symmetric monoubiquitination of the FANCD2-FANCI heterodimer in a DNA-dependent manner, while also being required for FANCL stability and nuclear localization; loss of FAAP100 abolishes FANCD2/FANCI monoubiquitination, causes ICL hypersensitivity and genomic instability, and in vivo disrupts R-loop resolution in primordial germ cells, with germline loss-of-function variants in humans causing a severe form of Fanconi anemia (FANCX).\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FAAP100 is an essential structural and catalytic component of the Fanconi anemia (FA) core complex, the multisubunit E3 ubiquitin ligase that monoubiquitinates the FANCD2-FANCI heterodimer to activate DNA interstrand crosslink (ICL) repair [#0, #2]. FAAP100 directly associates with FANCB and FANCL to form the minimal catalytic trimer (the BLP100 monoubiquitination module) that is sufficient to monoubiquitinate FANCD2 in vitro and is absolutely required for E3 ligase function, whereas ancillary modules (FANCA-FANCG-FAAP20 and FANCC-FANCE-FANCF) are dispensable for residual activity [#1, #2, #4]. Structurally, FANCB and FAAP100 form two central dimers that flank and dimerize two copies of FANCL, building a dimer-of-trimers scaffold that symmetrically positions both FANCL molecules to monoubiquitinate the DNA-bound FANCD2-FANCI heterodimer; despite lacking sequence homology, FANCB and FAAP100 adopt similar folds, and destabilizing this scaffold collapses the entire complex [#3, #5]. FAAP100 is required for FANCL stability and for nuclear translocation and chromatin recruitment, and its incorporation into the BLP100 subcomplex is itself the prerequisite for its own nuclear import [#0, #7]. Loss of FAAP100 abolishes FANCD2/FANCI monoubiquitination, causes ICL hypersensitivity and genomic instability [#0], and in mouse primordial germ cells disrupts R-loop resolution and replication fork protection, driving transcription-replication conflicts and p53-dependent proliferation defects [#6]. Germline loss-of-function variants in FAAP100 cause a severe form of Fanconi anemia designated FANCX, with patient cells showing defective monoubiquitination and ICL hypersensitivity rescued by wild-type but not variant cDNA [#7, #8].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that FAAP100 is a bona fide FA core complex component by showing it directly binds FANCB and FANCL and is required for FANCD2 monoubiquitination, defining its place in the ICL repair pathway.\",\n      \"evidence\": \"Co-IP, siRNA depletion and knockout with FANCD2 monoubiquitination, crosslink sensitivity, and nuclear localization readouts\",\n      \"pmids\": [\"17396147\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether the FANCB-FANCL-FAAP100 trimer is catalytically sufficient on its own\", \"No structural basis for the interactions\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the FANCB-FANCL-FAAP100 trimer as the minimal catalytic monoubiquitination module sufficient for FANCD2 modification and showed ancillary modules are not required for activity, isolating the catalytic core.\",\n      \"evidence\": \"In vitro reconstitution with purified native avian FA core complex plus genetic epistasis in subunit-deficient cells (two parallel studies)\",\n      \"pmids\": [\"24905007\", \"24910428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and architecture of the trimer within the full complex not resolved\", \"Mechanism of substrate engagement not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed that FANCB and FAAP100 dimerize two FANCL molecules into a dimer-of-trimers poised for symmetric monoubiquitination, and that DNA-bound FANCD2-FANCI is the restricted substrate, explaining the architecture underlying catalysis.\",\n      \"evidence\": \"EM/XL-MS with in vitro ubiquitination, plus fully recombinant complex reconstitution with substrate-specificity and DNA-dependency assays (two parallel studies)\",\n      \"pmids\": [\"27986592\", \"27986371\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution fold of FAAP100 not yet determined\", \"Functional asymmetry between the two FANCL copies unexplained\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided a high-resolution scaffold model in which FANCB-FAAP100 central dimers organize the entire complex and showed FAAP100 adopts a FANCB-like fold despite no sequence homology, establishing FAAP100 as a structural keystone.\",\n      \"evidence\": \"Cryo-EM of reconstituted active complex with MS validation\",\n      \"pmids\": [\"31666700\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conformational dynamics of the two distinct FANCL states not mechanistically dissected\", \"Does not address in vivo regulation of complex assembly\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended FAAP100 function to an in vivo physiological role, showing it counteracts transcription-replication conflicts via R-loop resolution and fork protection during germ cell development.\",\n      \"evidence\": \"FAAP100 conditional knockout mice with R-loop detection, fork protection assays, p53 pathway analysis, and fertility phenotyping\",\n      \"pmids\": [\"37580696\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No rescue experiment described\", \"Single lab\", \"Whether R-loop phenotype is direct or secondary to loss of FANCD2 ubiquitination not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified FAAP100 as a human Fanconi anemia gene (FANCX) and mechanistically tied disease variants to failure of BLP100 subcomplex assembly, linking subcomplex formation to FAAP100 nuclear import and chromatin recruitment.\",\n      \"evidence\": \"Patient-derived cell complementation with WT vs. variant cDNA, engineered multi-organism cell models, ICL sensitivity, T542P functional characterization, and mouse knockout (two parallel studies)\",\n      \"pmids\": [\"40232843\", \"40244696\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full spectrum of pathogenic variants not catalogued\", \"Genotype-phenotype correlations across patients not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FAAP100-dependent conformational asymmetry between the two FANCL copies is functionally exploited, and how nuclear import of the BLP100 subcomplex is regulated, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No mechanism for the distinct roles of the two FANCL conformations\", \"Regulation of subcomplex-coupled nuclear import not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 8]}\n    ],\n    \"complexes\": [\n      \"FA core complex\",\n      \"BLP100 subcomplex (FANCB-FANCL-FAAP100)\"\n    ],\n    \"partners\": [\n      \"FANCB\",\n      \"FANCL\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}