{"gene":"CIAO2B","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2010,"finding":"FAM96B (MIP18) was identified as a component of the MMXD complex (MMS19-MIP18-XPD) that localizes to the mitotic spindle during mitosis; siRNA-mediated knockdown of MIP18 led to improper chromosome segregation and accumulation of nuclei with abnormal shapes, establishing its role in chromosome segregation.","method":"Co-immunoprecipitation, siRNA knockdown, immunofluorescence localization to mitotic spindle, phenotypic analysis of chromosome segregation defects","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown with defined cellular phenotype, localization experiments; replicated in subsequent studies","pmids":["20797633"],"is_preprint":false},{"year":2012,"finding":"MIP18 (FAM96B) forms a core complex with MMS19 and CIAO1 in the cytoplasmic iron-sulfur cluster assembly (CIA) pathway; MIP18 interacts with both CIAO1 and Fe-S proteins by binding their Fe-S cluster-coordinating regions, functioning in Fe-S cluster delivery to cytoplasmic and nuclear proteins.","method":"Co-immunoprecipitation, pulldown assays, in vivo and in vitro binding experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus in vitro pulldown, replicated across multiple labs","pmids":["23150669"],"is_preprint":false},{"year":2012,"finding":"MMS19 forms a complex with CIA proteins CIAO1, IOP1, and MIP18 (FAM96B) in the cytoplasm; this complex binds multiple nuclear Fe-S proteins involved in DNA metabolism, and loss of MMS19 results in failure to transfer Fe-S clusters to target proteins and Fe-S protein instability.","method":"Co-immunoprecipitation, mass spectrometry, mouse knockout (preimplantation lethal), Fe-S protein stability assays","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, MS interactome, genetic knockout with defined phenotype; independently replicated","pmids":["22678361"],"is_preprint":false},{"year":2013,"finding":"CIA2B (FAM96B) associates with CIA1 (CIAO1) and MMS19 to form the CIA2B-CIA1-MMS19 complex, which binds to and facilitates Fe-S cluster assembly into most cytosolic-nuclear Fe-S proteins; depletion of CIA2B leads to stabilization of IRP2 (which lacks an Fe-S cluster), linking CIA2B to cellular iron regulation.","method":"Co-immunoprecipitation, 55Fe radiolabeling, siRNA knockdown, functional Fe-S assembly assays","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — Co-IP, 55Fe radiolabeling, siRNA knockdown with multiple orthogonal readouts; independent lab replication","pmids":["23891004"],"is_preprint":false},{"year":2013,"finding":"MMS19, MIP18 (FAM96B), and CIAO1 form a tight 'core' CIA complex; IOP1 is an 'external' component that interacts with the core complex both in vivo and in vitro but behaves differently—knockdown of core components leads to down-regulation of all core components, whereas IOP1 knockdown does not affect core component levels. MIP18 bridges MMS19 and CIAO1 within the core complex.","method":"siRNA knockdown, co-immunoprecipitation, in vitro binding assays, protein level analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, in vivo and in vitro binding, siRNA knockdown with multiple readouts in single lab","pmids":["23585563"],"is_preprint":false},{"year":2015,"finding":"The CIA targeting complex composed of MMS19, CIAO1, and FAM96B (CIA2B) is required for Fe-S cluster assembly onto XPD before its incorporation into TFIIH; XPD associates in a mutually exclusive fashion with either the CIA targeting complex (in the cytoplasm) or TFIIH (in the nucleus), establishing a sequential cytoplasmic Fe-S assembly step before nuclear TFIIH assembly.","method":"Co-immunoprecipitation, subcellular fractionation, iron depletion experiments, XPD point mutants defective in Fe-S or CIA complex binding","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis of active-site residues, subcellular fractionation, Co-IP, iron depletion; multiple orthogonal methods in single lab","pmids":["25897079"],"is_preprint":false},{"year":2017,"finding":"MIP18 (FAM96B) and CIAO1 associate with the C terminus of MMS19 to form a docking site for Fe-S client proteins; direct interaction between MMS19 and MIP18 is required to protect MIP18 from proteasomal degradation. XPD can interact with MMS19 independently of MIP18 and CIAO1, representing an exception.","method":"Co-immunoprecipitation, proteasomal inhibitor treatment, truncation/deletion mapping experiments","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, proteasome inhibitor rescue; single lab with multiple orthogonal approaches","pmids":["28178521"],"is_preprint":false},{"year":2017,"finding":"CIA2B (FAM96B) and MMS19 physically interact with the C terminus of viperin (RSAD2) using CIA1 as the primary viperin-interacting protein to facilitate Fe-S cluster insertion into viperin; CIA2A binds viperin's N terminus independently of CIA1, CIA2B, and MMS19. Depletion of CIA1, but not CIA2B or MMS19, predominantly impairs 55Fe/S cluster incorporation into viperin.","method":"Co-immunoprecipitation, 55Fe radiolabeling in human cells depleted of CIA factors by siRNA","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, 55Fe radiolabeling, siRNA depletion with multiple CIA factors; multiple orthogonal methods in single lab","pmids":["28615450"],"is_preprint":false},{"year":2018,"finding":"CIA2B (FAM96B) and MMS19, constituents of the CIA targeting complex, colocalize with components of the mitotic machinery; downregulation of CIA2B and MMS19 impairs the mitotic cycle. The chromokinesin KIF4A was identified as a mitotic Fe-S client—KIF4A binds an Fe-S cluster in vitro through its conserved cysteine-rich domain, and this domain is required for mitosis-related KIF4A localization, linking CIA2B-mediated Fe-S cluster delivery to mitotic defects.","method":"siRNA knockdown, in vitro Fe-S cluster binding assay, immunofluorescence colocalization, KIF4A knockout and cysteine-rich domain mutant analysis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro Fe-S binding, mutagenesis, KO with defined phenotype, localization experiments; multiple orthogonal methods","pmids":["29848660"],"is_preprint":false},{"year":2018,"finding":"Cytosolic HSC20 (C-HSC20) mediates complex formation between ISC pathway components (ISCU1, NFS1) and the CIA targeting complex (CIAO1, FAM96B, MMS19) to facilitate Fe-S cluster insertion into cytoplasmic and nuclear Fe-S recipient proteins, integrating de novo Fe-S biosynthesis with CIA targeting.","method":"Co-immunoprecipitation, siRNA knockdown, 55Fe radiolabeling","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and 55Fe radiolabeling, single lab with two orthogonal methods","pmids":["29309586"],"is_preprint":false},{"year":2019,"finding":"FBXL5 interacts with the CIA targeting complex (MMS19, FAM96B/CIA2B, and CIAO1); this interaction promotes FBXL5-mediated degradation of iron regulatory proteins (IRPs) and is regulated by oxygen tension—robust at 21% O2 but severely diminished at 1% O2, linking the CIA targeting complex to oxygen-dependent iron homeostasis.","method":"Co-immunoprecipitation, IRP degradation assays, oxygen tension manipulation experiments","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional IRP degradation assay and O2 manipulation; multiple orthogonal methods in single lab","pmids":["31229404"],"is_preprint":false},{"year":2020,"finding":"Crystal structures of the CIA targeting complex (CTC) revealed that CIAO2B (FAM96B) is centrally located and bridges CIAO1 and MMS19; cryo-EM reconstructions of CTC bound to primase or DNA2 revealed an evolutionarily conserved bipartite client recognition mode facilitated by CIAO1 and structural flexibility of MMS19. The primase Fe-S cluster is located ~70 Å from the CTC reactive cysteine, implicating conformational dynamics in Fe-S cluster transfer.","method":"X-ray crystallography, cryo-EM, biochemical assays, biophysical methods, yeast complementation assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure + cryo-EM + biochemical validation + yeast complementation; multiple orthogonal methods in single study","pmids":["32632277"],"is_preprint":false},{"year":2011,"finding":"FAM96B was identified as an interaction partner of the transcription factor E2-2 in endothelial cells; FAM96B interfered with E2-2-mediated transcriptional repression of a luciferase reporter and rescued E2-2-suppressed VEGFR2 promoter activity in a dose-dependent manner. FAM96B also decreased E2-2 protein expression, with the middle region of FAM96B required for this effect. FAM96B expression in endothelial cells potentiated migration, proliferation, and tube formation.","method":"Co-immunoprecipitation, luciferase reporter assays, FAM96B mutational analysis, endothelial cell functional assays (migration, proliferation, tube formation)","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP, reporter assay, mutagenesis, functional cell assays; single lab with multiple methods but unclear mechanistic link to CIA function","pmids":["21722264"],"is_preprint":false},{"year":2022,"finding":"Fam96b (MIP18) directly binds brain-type creatine kinase (CKB); this binding is independent of CKB substrates and does not interfere with CKB activity. Fam96b oligomerizes via intermolecular disulfide bonds, and enzymatically active CKB modulates Fam96b oligomerization. Oligomerized Fam96b recruits CKB and the MMXD complex to the mitotic spindle. Depletion of Fam96b by siRNA leads to mitotic defects, retarded proliferation, increased cell death, and aberrant cell cycle progression; both Fam96b oligomerization and CKB activity were required for proper mitotic spindle formation.","method":"Co-immunoprecipitation, pulldown, disulfide bond analysis, siRNA knockdown, rescue experiments, immunofluorescence","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP, biochemical characterization, siRNA with rescue; single lab with multiple orthogonal methods","pmids":["36503010"],"is_preprint":false},{"year":2022,"finding":"Iron availability regulates assembly of the CIA machinery: the CIA targeting complex (MMS19, CIAO1, CIAO2B/FAM96B) weakly associates with the CIA scaffold component NUBP2, suggesting a higher-order CIA metabolon. CIAO3 mutants defective in Fe-S cluster binding fail to integrate into higher-order CIA complexes but exhibit stronger associations with CIA substrates, indicating Fe-S cluster incorporation in CIAO3 is required for full CIA metabolon assembly.","method":"Targeted proteomics (PRM), co-immunoprecipitation, CIAO3 Fe-S binding mutants, iron supplementation/chelation experiments","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — targeted proteomics plus Co-IP and mutagenesis; single lab, multiple methods","pmids":["35654137"],"is_preprint":false},{"year":2024,"finding":"CIAO-2B is vital for DOG-1 (FANCJ/BRIP1) stability and DNA repair functions in C. elegans; unlike MMS-19, CIAO-2B has an essential role in C. elegans development. Loss of CIAO-2B results in DOG-1 instability and impaired genome integrity.","method":"C. elegans genetics (deletion mutants), DNA damage sensitivity assays, epistasis analysis, protein stability assays","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined phenotype in C. elegans ortholog; single lab","pmids":["39011897"],"is_preprint":false},{"year":2024,"finding":"Loss of CIAO1 function in patients impairs recruitment of Fe-S recipient proteins to the CIA core complex (CIAO1-MMS19-FAM96B), resulting in compromised activities of DNA helicases, polymerases, and repair enzymes; lentivirus-mediated restoration of CIAO1 expression reversed patient-derived cellular abnormalities, confirming FAM96B-containing CIA complex is essential for Fe-S delivery to DNA metabolism enzymes.","method":"Patient-derived cell studies, mutational analysis, functional Fe-S enzyme activity assays, lentiviral rescue experiments","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — functional enzyme assays, genetic rescue, multiple orthogonal readouts in human patient cells","pmids":["38950322"],"is_preprint":false},{"year":2019,"finding":"FAM96B was identified as a direct binding partner of selenoprotein W (SelW) in the brain; interaction confirmed by yeast two-hybrid screening, FRET analysis, pulldown assay with recombinant proteins, and co-immunoprecipitation from murine brain tissue.","method":"Yeast two-hybrid, FRET, pulldown assay, co-immunoprecipitation from brain tissue","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — interaction demonstrated by multiple methods but functional consequence not established; single lab","pmids":["30876693"],"is_preprint":false}],"current_model":"CIAO2B (FAM96B/MIP18/CIA2B) is a central scaffolding subunit of the cytosolic iron-sulfur cluster (CIA) targeting complex (CTC), where it bridges CIAO1 and MMS19 (as revealed by crystal structure and cryo-EM), forming a core complex that delivers Fe-S clusters to a broad range of cytosolic and nuclear client proteins involved in DNA replication, repair, and transcription (including XPD, DNA2, primase, and KIF4A); CIAO2B protects MMS19 binding partners from proteasomal degradation, participates in mitotic spindle organization, links Fe-S cluster biogenesis to IRP-mediated iron homeostasis via interaction with FBXL5, and is essential for organism viability, with loss of function in the CIA complex causing compromised DNA metabolism enzyme activities."},"narrative":{"mechanistic_narrative":"CIAO2B (FAM96B/MIP18/CIA2B) is the central scaffolding subunit of the cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) targeting complex, which delivers Fe-S clusters to a broad range of cytosolic and nuclear client proteins [PMID:23150669, PMID:23891004]. Within the core CIA targeting complex, CIAO2B is centrally located and bridges CIAO1 and MMS19, with crystal and cryo-EM structures defining a bipartite client recognition mode in which CIAO1 and the structural flexibility of MMS19 engage substrates such as primase and DNA2 [PMID:32632277]. The three core subunits are mutually stabilizing—knockdown of any one down-regulates the others, and direct MMS19 binding protects CIAO2B from proteasomal degradation [PMID:23585563, PMID:28178521]. Through this complex CIAO2B targets Fe-S clusters to DNA metabolism enzymes including XPD, which must be matured cytoplasmically by the CIA targeting complex before incorporation into nuclear TFIIH [PMID:25897079], and the chromokinesin KIF4A, an Fe-S client whose maturation links CIAO2B to mitotic spindle organization and faithful chromosome segregation [PMID:20797633, PMID:29848660]. CIAO2B also couples Fe-S biogenesis to cellular iron homeostasis: its depletion stabilizes IRP2, and the CIA targeting complex interacts with FBXL5 to promote oxygen-dependent degradation of iron regulatory proteins [PMID:23891004, PMID:31229404]. Loss of CIA core function compromises the activities of DNA helicases, polymerases, and repair enzymes, and the CIAO2B ortholog is essential for development and for stability of the FANCJ helicase DOG-1/BRIP1 [PMID:39011897, PMID:38950322].","teleology":[{"year":2010,"claim":"Established that CIAO2B (MIP18) is part of a spindle-associated complex with functional consequences, answering whether the protein had a defined cellular role.","evidence":"Co-IP, siRNA knockdown and mitotic spindle immunofluorescence defining the MMXD (MMS19-MIP18-XPD) complex","pmids":["20797633"],"confidence":"High","gaps":["Did not define the biochemical activity underlying the segregation defect","Connection to Fe-S cluster biology not yet established"]},{"year":2012,"claim":"Placed CIAO2B in the cytosolic Fe-S cluster assembly pathway, defining its molecular function as a delivery scaffold rather than a generic spindle factor.","evidence":"Co-IP, pulldown and in vitro binding showing MIP18 bridges CIAO1 and binds Fe-S coordinating regions of clients, within an MMS19-CIAO1-MIP18 complex","pmids":["23150669","22678361"],"confidence":"High","gaps":["Stoichiometry and architecture of the complex unresolved","Mechanism of cluster transfer not defined"]},{"year":2013,"claim":"Linked the CIAO2B complex to cellular iron regulation, showing its function extends beyond client maturation to iron homeostasis sensing.","evidence":"Co-IP, 55Fe radiolabeling and siRNA depletion showing CIA2B loss stabilizes IRP2 and impairs Fe-S assembly into most cytosolic-nuclear targets","pmids":["23891004"],"confidence":"High","gaps":["Mechanism connecting CIA2B loss to IRP2 stabilization not yet molecularly defined"]},{"year":2013,"claim":"Defined CIAO2B as the bridging subunit of a co-dependent core complex, clarifying complex topology and subunit interdependence.","evidence":"siRNA knockdown, Co-IP and in vitro binding distinguishing the tight MMS19-MIP18-CIAO1 core from the external IOP1 component","pmids":["23585563"],"confidence":"High","gaps":["High-resolution structure of the bridge interface not yet available"]},{"year":2015,"claim":"Demonstrated a sequential, compartmentalized maturation step, showing the CIA targeting complex acts cytoplasmically before nuclear client assembly.","evidence":"Co-IP, subcellular fractionation, iron depletion and XPD binding mutants showing mutually exclusive association of XPD with the CIA complex or TFIIH","pmids":["25897079"],"confidence":"High","gaps":["Spatial/temporal trigger for handoff to nuclear partners unresolved"]},{"year":2017,"claim":"Mapped the client docking site to the MMS19 C terminus and established that CIAO2B stability depends on MMS19 binding, explaining subunit co-regulation.","evidence":"Co-IP, truncation mapping and proteasome inhibitor rescue, with XPD shown to bind MMS19 independently of MIP18/CIAO1","pmids":["28178521"],"confidence":"Medium","gaps":["Single lab; degradation pathway and E3 ligase for unprotected MIP18 not identified"]},{"year":2017,"claim":"Refined client specificity, showing CIAO2B is not required for all CIA clients (e.g. viperin maturation depends predominantly on CIA1).","evidence":"Co-IP domain mapping and 55Fe radiolabeling with selective CIA factor depletion on viperin/RSAD2","pmids":["28615450"],"confidence":"High","gaps":["Determinants that route clients to CIAO2B-dependent vs independent paths unknown"]},{"year":2018,"claim":"Identified a defined mitotic Fe-S client (KIF4A), mechanistically connecting CIAO2B's Fe-S delivery to its long-known spindle phenotype.","evidence":"siRNA knockdown, in vitro Fe-S binding, immunofluorescence colocalization and KIF4A cysteine-rich domain mutants","pmids":["29848660"],"confidence":"High","gaps":["Whether spindle phenotypes arise solely through KIF4A or additional mitotic clients unresolved"]},{"year":2018,"claim":"Connected de novo Fe-S biosynthesis to CIA targeting, showing how clusters reach the CIAO2B complex.","evidence":"Co-IP, siRNA knockdown and 55Fe radiolabeling implicating cytosolic HSC20 in bridging ISC components to the CIA targeting complex","pmids":["29309586"],"confidence":"Medium","gaps":["Single lab; direct biochemical reconstitution of cluster transfer not shown"]},{"year":2019,"claim":"Mechanistically tied the CIAO2B complex to oxygen-dependent iron regulation via FBXL5.","evidence":"Co-IP, IRP degradation assays and oxygen tension manipulation showing FBXL5-CIA targeting complex interaction is oxygen-sensitive","pmids":["31229404"],"confidence":"High","gaps":["Structural basis of the FBXL5 interaction not defined"]},{"year":2020,"claim":"Provided atomic-level architecture, defining how CIAO2B bridges the complex and how clients are recognized and matured.","evidence":"X-ray crystallography, cryo-EM of CTC bound to primase/DNA2, biophysical assays and yeast complementation revealing a bipartite client recognition mode","pmids":["32632277"],"confidence":"High","gaps":["The ~70 Å separation between client cluster and reactive cysteine implies conformational dynamics not directly visualized","Transfer intermediate states unresolved"]},{"year":2022,"claim":"Extended CIAO2B's higher-order assembly, situating the targeting complex within an iron-regulated CIA metabolon.","evidence":"Targeted proteomics, Co-IP and CIAO3 Fe-S binding mutants with iron supplementation/chelation","pmids":["35654137"],"confidence":"Medium","gaps":["Weak NUBP2 association; functional role of metabolon assembly not established"]},{"year":2024,"claim":"Demonstrated organismal essentiality and a specific repair-enzyme client in vivo, distinguishing CIAO2B from MMS19.","evidence":"C. elegans deletion mutants, DNA damage sensitivity, epistasis and DOG-1 (FANCJ/BRIP1) stability assays","pmids":["39011897"],"confidence":"Medium","gaps":["Single ortholog system; whether human CIAO2B is similarly essential not directly tested here"]},{"year":2024,"claim":"Confirmed in human disease context that the CIAO2B-containing core complex is required to mature DNA metabolism enzymes.","evidence":"Patient-derived cells, functional Fe-S enzyme assays and lentiviral CIAO1 rescue showing impaired recruitment of Fe-S recipients to the CIAO1-MMS19-FAM96B complex","pmids":["38950322"],"confidence":"High","gaps":["Disease evidence centers on CIAO1; direct CIAO2B patient mutations not described here"]},{"year":null,"claim":"How conformational dynamics drive the actual Fe-S cluster transfer step from the CTC reactive cysteine to distant client clusters, and what governs client routing through CIAO2B-dependent versus independent paths, remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No captured transfer intermediate structure","Rules for client specificity not defined","Reconstituted transfer reaction not reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,4,11]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,5]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,8]}],"pathway":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[3]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,8]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[16,15]}],"complexes":["CIA targeting complex (CIAO1-MMS19-FAM96B)","MMXD complex (MMS19-MIP18-XPD)"],"partners":["CIAO1","MMS19","XPD","FBXL5","KIF4A","CKB","NUBP2","RSAD2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y3D0","full_name":"Cytosolic iron-sulfur assembly component 2B","aliases":["MSS19-interacting protein of 18 kDa","Mitotic spindle-associated MMXD complex subunit MIP18","Protein FAM96B"],"length_aa":163,"mass_kda":17.7,"function":"Component of the cytosolic iron-sulfur protein assembly (CIA) complex, a multiprotein complex that mediates the incorporation of iron-sulfur cluster into extramitochondrial Fe/S proteins (PubMed:22678361, PubMed:22678362, PubMed:23891004, PubMed:29848660). As a CIA complex component and in collaboration with CIAO1 and MMS19, binds to and facilitates the assembly of most cytosolic-nuclear Fe/S proteins (PubMed:23891004, PubMed:29848660). As part of the mitotic spindle-associated MMXD complex it plays a role in chromosome segregation, probably by facilitating iron-sulfur cluster assembly into ERCC2/XPD (PubMed:20797633). Together with MMS19, facilitates the transfer of Fe-S clusters to the motor protein KIF4A, which ensures proper localization of KIF4A to mitotic machinery components to promote the progression of mitosis (PubMed:29848660)","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, spindle; Midbody","url":"https://www.uniprot.org/uniprotkb/Q9Y3D0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/CIAO2B","classification":"Common Essential","n_dependent_lines":1176,"n_total_lines":1208,"dependency_fraction":0.9735099337748344},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CIAO2B","total_profiled":1310},"omim":[{"mim_id":"620960","title":"MULTIPLE MITOCHONDRIAL DYSFUNCTIONS SYNDROME 10; MMDS10","url":"https://www.omim.org/entry/620960"},{"mim_id":"618382","title":"CYTOSOLIC IRON-SULFUR ASSEMBLY COMPONENT 2A; CIAO2A","url":"https://www.omim.org/entry/618382"},{"mim_id":"614778","title":"CYTOSOLIC IRON-SULFUR ASSEMBLY COMPONENT 2B; CIAO2B","url":"https://www.omim.org/entry/614778"},{"mim_id":"604333","title":"WD40 REPEAT-CONTAINING PROTEIN CIAO1; CIAO1","url":"https://www.omim.org/entry/604333"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CIAO2B"},"hgnc":{"alias_symbol":["CGI-128","MIP18","CIA2B"],"prev_symbol":["FAM96B"]},"alphafold":{"accession":"Q9Y3D0","domains":[{"cath_id":"3.30.300.130","chopping":"42-158","consensus_level":"high","plddt":90.6451,"start":42,"end":158}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3D0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3D0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3D0-F1-predicted_aligned_error_v6.png","plddt_mean":84.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CIAO2B","jax_strain_url":"https://www.jax.org/strain/search?query=CIAO2B"},"sequence":{"accession":"Q9Y3D0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y3D0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y3D0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3D0"}},"corpus_meta":[{"pmid":"22678361","id":"PMC_22678361","title":"MMS19 links cytoplasmic iron-sulfur cluster assembly to DNA metabolism.","date":"2012","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/22678361","citation_count":194,"is_preprint":false},{"pmid":"23891004","id":"PMC_23891004","title":"Human CIA2A-FAM96A and CIA2B-FAM96B integrate iron homeostasis and maturation of different subsets of cytosolic-nuclear iron-sulfur proteins.","date":"2013","source":"Cell metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/23891004","citation_count":142,"is_preprint":false},{"pmid":"23898337","id":"PMC_23898337","title":"The iron-sulfur cluster assembly machineries in plants: current knowledge and open questions.","date":"2013","source":"Frontiers in plant science","url":"https://pubmed.ncbi.nlm.nih.gov/23898337","citation_count":129,"is_preprint":false},{"pmid":"32311335","id":"PMC_32311335","title":"Outlining the Complex Pathway of Mammalian Fe-S Cluster Biogenesis.","date":"2020","source":"Trends in biochemical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32311335","citation_count":109,"is_preprint":false},{"pmid":"20797633","id":"PMC_20797633","title":"MMXD, a TFIIH-independent XPD-MMS19 protein complex involved in chromosome segregation.","date":"2010","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/20797633","citation_count":104,"is_preprint":false},{"pmid":"23150669","id":"PMC_23150669","title":"The mammalian proteins MMS19, MIP18, and ANT2 are involved in cytoplasmic iron-sulfur cluster protein assembly.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23150669","citation_count":39,"is_preprint":false},{"pmid":"29309586","id":"PMC_29309586","title":"Cytosolic HSC20 integrates de novo iron-sulfur cluster biogenesis with the CIAO1-mediated transfer to recipients.","date":"2018","source":"Human molecular 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biology","url":"https://pubmed.ncbi.nlm.nih.gov/32632277","citation_count":33,"is_preprint":false},{"pmid":"28178521","id":"PMC_28178521","title":"The CIA Targeting Complex Is Highly Regulated and Provides Two Distinct Binding Sites for Client Iron-Sulfur Proteins.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/28178521","citation_count":29,"is_preprint":false},{"pmid":"32039527","id":"PMC_32039527","title":"FAM96B inhibits the senescence of dental pulp stem cells.","date":"2020","source":"Cell biology international","url":"https://pubmed.ncbi.nlm.nih.gov/32039527","citation_count":20,"is_preprint":false},{"pmid":"29848660","id":"PMC_29848660","title":"Fe-S cluster coordination of the chromokinesin KIF4A alters its subcellular localization during mitosis.","date":"2018","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/29848660","citation_count":17,"is_preprint":false},{"pmid":"25065591","id":"PMC_25065591","title":"Crumbs interacts with Xpd for nuclear division control in Drosophila.","date":"2014","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/25065591","citation_count":16,"is_preprint":false},{"pmid":"38950322","id":"PMC_38950322","title":"CIAO1 loss of function causes a neuromuscular disorder with compromise of nucleocytoplasmic Fe-S enzymes.","date":"2024","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/38950322","citation_count":13,"is_preprint":false},{"pmid":"35654137","id":"PMC_35654137","title":"Iron-regulated assembly of the cytosolic iron-sulfur cluster biogenesis machinery.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35654137","citation_count":13,"is_preprint":false},{"pmid":"34857765","id":"PMC_34857765","title":"The cytosolic iron-sulfur cluster assembly (CIA) pathway is required for replication stress tolerance of cancer cells to Chk1 and ATR inhibitors.","date":"2021","source":"NPJ breast cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34857765","citation_count":11,"is_preprint":false},{"pmid":"21722264","id":"PMC_21722264","title":"Interference of E2-2-mediated effect in endothelial cells by FAM96B through its limited expression of E2-2.","date":"2011","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/21722264","citation_count":10,"is_preprint":false},{"pmid":"30742009","id":"PMC_30742009","title":"Nkx2-5 Second Heart Field Target Gene Ccdc117 Regulates DNA Metabolism and Proliferation.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30742009","citation_count":10,"is_preprint":false},{"pmid":"36165859","id":"PMC_36165859","title":"FAM96A and FAM96B function as new tumor suppressor genes in breast cancer through regulation of the Wnt/β-catenin signaling pathway.","date":"2022","source":"Life 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Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/36503010","citation_count":3,"is_preprint":false},{"pmid":"39011897","id":"PMC_39011897","title":"The critical role of the iron-sulfur cluster and CTC components in DOG-1/BRIP1 function in Caenorhabditis elegans.","date":"2024","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/39011897","citation_count":1,"is_preprint":false},{"pmid":"42107644","id":"PMC_42107644","title":"Iron-sulfur cofactors in nucleic acid metabolism and protein synthesis: Assembly, delivery, and putative roles in cellular and viral systems.","date":"2026","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/42107644","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16795,"output_tokens":4620,"usd":0.059842,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12923,"output_tokens":4115,"usd":0.083745,"stage2_stop_reason":"end_turn"},"total_usd":0.143587,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"FAM96B (MIP18) was identified as a component of the MMXD complex (MMS19-MIP18-XPD) that localizes to the mitotic spindle during mitosis; siRNA-mediated knockdown of MIP18 led to improper chromosome segregation and accumulation of nuclei with abnormal shapes, establishing its role in chromosome segregation.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, immunofluorescence localization to mitotic spindle, phenotypic analysis of chromosome segregation defects\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown with defined cellular phenotype, localization experiments; replicated in subsequent studies\",\n      \"pmids\": [\"20797633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MIP18 (FAM96B) forms a core complex with MMS19 and CIAO1 in the cytoplasmic iron-sulfur cluster assembly (CIA) pathway; MIP18 interacts with both CIAO1 and Fe-S proteins by binding their Fe-S cluster-coordinating regions, functioning in Fe-S cluster delivery to cytoplasmic and nuclear proteins.\",\n      \"method\": \"Co-immunoprecipitation, pulldown assays, in vivo and in vitro binding experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus in vitro pulldown, replicated across multiple labs\",\n      \"pmids\": [\"23150669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"MMS19 forms a complex with CIA proteins CIAO1, IOP1, and MIP18 (FAM96B) in the cytoplasm; this complex binds multiple nuclear Fe-S proteins involved in DNA metabolism, and loss of MMS19 results in failure to transfer Fe-S clusters to target proteins and Fe-S protein instability.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, mouse knockout (preimplantation lethal), Fe-S protein stability assays\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, MS interactome, genetic knockout with defined phenotype; independently replicated\",\n      \"pmids\": [\"22678361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CIA2B (FAM96B) associates with CIA1 (CIAO1) and MMS19 to form the CIA2B-CIA1-MMS19 complex, which binds to and facilitates Fe-S cluster assembly into most cytosolic-nuclear Fe-S proteins; depletion of CIA2B leads to stabilization of IRP2 (which lacks an Fe-S cluster), linking CIA2B to cellular iron regulation.\",\n      \"method\": \"Co-immunoprecipitation, 55Fe radiolabeling, siRNA knockdown, functional Fe-S assembly assays\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — Co-IP, 55Fe radiolabeling, siRNA knockdown with multiple orthogonal readouts; independent lab replication\",\n      \"pmids\": [\"23891004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MMS19, MIP18 (FAM96B), and CIAO1 form a tight 'core' CIA complex; IOP1 is an 'external' component that interacts with the core complex both in vivo and in vitro but behaves differently—knockdown of core components leads to down-regulation of all core components, whereas IOP1 knockdown does not affect core component levels. MIP18 bridges MMS19 and CIAO1 within the core complex.\",\n      \"method\": \"siRNA knockdown, co-immunoprecipitation, in vitro binding assays, protein level analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, in vivo and in vitro binding, siRNA knockdown with multiple readouts in single lab\",\n      \"pmids\": [\"23585563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The CIA targeting complex composed of MMS19, CIAO1, and FAM96B (CIA2B) is required for Fe-S cluster assembly onto XPD before its incorporation into TFIIH; XPD associates in a mutually exclusive fashion with either the CIA targeting complex (in the cytoplasm) or TFIIH (in the nucleus), establishing a sequential cytoplasmic Fe-S assembly step before nuclear TFIIH assembly.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, iron depletion experiments, XPD point mutants defective in Fe-S or CIA complex binding\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis of active-site residues, subcellular fractionation, Co-IP, iron depletion; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"25897079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MIP18 (FAM96B) and CIAO1 associate with the C terminus of MMS19 to form a docking site for Fe-S client proteins; direct interaction between MMS19 and MIP18 is required to protect MIP18 from proteasomal degradation. XPD can interact with MMS19 independently of MIP18 and CIAO1, representing an exception.\",\n      \"method\": \"Co-immunoprecipitation, proteasomal inhibitor treatment, truncation/deletion mapping experiments\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, proteasome inhibitor rescue; single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"28178521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CIA2B (FAM96B) and MMS19 physically interact with the C terminus of viperin (RSAD2) using CIA1 as the primary viperin-interacting protein to facilitate Fe-S cluster insertion into viperin; CIA2A binds viperin's N terminus independently of CIA1, CIA2B, and MMS19. Depletion of CIA1, but not CIA2B or MMS19, predominantly impairs 55Fe/S cluster incorporation into viperin.\",\n      \"method\": \"Co-immunoprecipitation, 55Fe radiolabeling in human cells depleted of CIA factors by siRNA\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, 55Fe radiolabeling, siRNA depletion with multiple CIA factors; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"28615450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CIA2B (FAM96B) and MMS19, constituents of the CIA targeting complex, colocalize with components of the mitotic machinery; downregulation of CIA2B and MMS19 impairs the mitotic cycle. The chromokinesin KIF4A was identified as a mitotic Fe-S client—KIF4A binds an Fe-S cluster in vitro through its conserved cysteine-rich domain, and this domain is required for mitosis-related KIF4A localization, linking CIA2B-mediated Fe-S cluster delivery to mitotic defects.\",\n      \"method\": \"siRNA knockdown, in vitro Fe-S cluster binding assay, immunofluorescence colocalization, KIF4A knockout and cysteine-rich domain mutant analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro Fe-S binding, mutagenesis, KO with defined phenotype, localization experiments; multiple orthogonal methods\",\n      \"pmids\": [\"29848660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cytosolic HSC20 (C-HSC20) mediates complex formation between ISC pathway components (ISCU1, NFS1) and the CIA targeting complex (CIAO1, FAM96B, MMS19) to facilitate Fe-S cluster insertion into cytoplasmic and nuclear Fe-S recipient proteins, integrating de novo Fe-S biosynthesis with CIA targeting.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, 55Fe radiolabeling\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and 55Fe radiolabeling, single lab with two orthogonal methods\",\n      \"pmids\": [\"29309586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FBXL5 interacts with the CIA targeting complex (MMS19, FAM96B/CIA2B, and CIAO1); this interaction promotes FBXL5-mediated degradation of iron regulatory proteins (IRPs) and is regulated by oxygen tension—robust at 21% O2 but severely diminished at 1% O2, linking the CIA targeting complex to oxygen-dependent iron homeostasis.\",\n      \"method\": \"Co-immunoprecipitation, IRP degradation assays, oxygen tension manipulation experiments\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional IRP degradation assay and O2 manipulation; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"31229404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystal structures of the CIA targeting complex (CTC) revealed that CIAO2B (FAM96B) is centrally located and bridges CIAO1 and MMS19; cryo-EM reconstructions of CTC bound to primase or DNA2 revealed an evolutionarily conserved bipartite client recognition mode facilitated by CIAO1 and structural flexibility of MMS19. The primase Fe-S cluster is located ~70 Å from the CTC reactive cysteine, implicating conformational dynamics in Fe-S cluster transfer.\",\n      \"method\": \"X-ray crystallography, cryo-EM, biochemical assays, biophysical methods, yeast complementation assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure + cryo-EM + biochemical validation + yeast complementation; multiple orthogonal methods in single study\",\n      \"pmids\": [\"32632277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FAM96B was identified as an interaction partner of the transcription factor E2-2 in endothelial cells; FAM96B interfered with E2-2-mediated transcriptional repression of a luciferase reporter and rescued E2-2-suppressed VEGFR2 promoter activity in a dose-dependent manner. FAM96B also decreased E2-2 protein expression, with the middle region of FAM96B required for this effect. FAM96B expression in endothelial cells potentiated migration, proliferation, and tube formation.\",\n      \"method\": \"Co-immunoprecipitation, luciferase reporter assays, FAM96B mutational analysis, endothelial cell functional assays (migration, proliferation, tube formation)\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP, reporter assay, mutagenesis, functional cell assays; single lab with multiple methods but unclear mechanistic link to CIA function\",\n      \"pmids\": [\"21722264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Fam96b (MIP18) directly binds brain-type creatine kinase (CKB); this binding is independent of CKB substrates and does not interfere with CKB activity. Fam96b oligomerizes via intermolecular disulfide bonds, and enzymatically active CKB modulates Fam96b oligomerization. Oligomerized Fam96b recruits CKB and the MMXD complex to the mitotic spindle. Depletion of Fam96b by siRNA leads to mitotic defects, retarded proliferation, increased cell death, and aberrant cell cycle progression; both Fam96b oligomerization and CKB activity were required for proper mitotic spindle formation.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, disulfide bond analysis, siRNA knockdown, rescue experiments, immunofluorescence\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP, biochemical characterization, siRNA with rescue; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36503010\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Iron availability regulates assembly of the CIA machinery: the CIA targeting complex (MMS19, CIAO1, CIAO2B/FAM96B) weakly associates with the CIA scaffold component NUBP2, suggesting a higher-order CIA metabolon. CIAO3 mutants defective in Fe-S cluster binding fail to integrate into higher-order CIA complexes but exhibit stronger associations with CIA substrates, indicating Fe-S cluster incorporation in CIAO3 is required for full CIA metabolon assembly.\",\n      \"method\": \"Targeted proteomics (PRM), co-immunoprecipitation, CIAO3 Fe-S binding mutants, iron supplementation/chelation experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — targeted proteomics plus Co-IP and mutagenesis; single lab, multiple methods\",\n      \"pmids\": [\"35654137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CIAO-2B is vital for DOG-1 (FANCJ/BRIP1) stability and DNA repair functions in C. elegans; unlike MMS-19, CIAO-2B has an essential role in C. elegans development. Loss of CIAO-2B results in DOG-1 instability and impaired genome integrity.\",\n      \"method\": \"C. elegans genetics (deletion mutants), DNA damage sensitivity assays, epistasis analysis, protein stability assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined phenotype in C. elegans ortholog; single lab\",\n      \"pmids\": [\"39011897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of CIAO1 function in patients impairs recruitment of Fe-S recipient proteins to the CIA core complex (CIAO1-MMS19-FAM96B), resulting in compromised activities of DNA helicases, polymerases, and repair enzymes; lentivirus-mediated restoration of CIAO1 expression reversed patient-derived cellular abnormalities, confirming FAM96B-containing CIA complex is essential for Fe-S delivery to DNA metabolism enzymes.\",\n      \"method\": \"Patient-derived cell studies, mutational analysis, functional Fe-S enzyme activity assays, lentiviral rescue experiments\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional enzyme assays, genetic rescue, multiple orthogonal readouts in human patient cells\",\n      \"pmids\": [\"38950322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FAM96B was identified as a direct binding partner of selenoprotein W (SelW) in the brain; interaction confirmed by yeast two-hybrid screening, FRET analysis, pulldown assay with recombinant proteins, and co-immunoprecipitation from murine brain tissue.\",\n      \"method\": \"Yeast two-hybrid, FRET, pulldown assay, co-immunoprecipitation from brain tissue\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — interaction demonstrated by multiple methods but functional consequence not established; single lab\",\n      \"pmids\": [\"30876693\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CIAO2B (FAM96B/MIP18/CIA2B) is a central scaffolding subunit of the cytosolic iron-sulfur cluster (CIA) targeting complex (CTC), where it bridges CIAO1 and MMS19 (as revealed by crystal structure and cryo-EM), forming a core complex that delivers Fe-S clusters to a broad range of cytosolic and nuclear client proteins involved in DNA replication, repair, and transcription (including XPD, DNA2, primase, and KIF4A); CIAO2B protects MMS19 binding partners from proteasomal degradation, participates in mitotic spindle organization, links Fe-S cluster biogenesis to IRP-mediated iron homeostasis via interaction with FBXL5, and is essential for organism viability, with loss of function in the CIA complex causing compromised DNA metabolism enzyme activities.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CIAO2B (FAM96B/MIP18/CIA2B) is the central scaffolding subunit of the cytosolic iron-sulfur (Fe-S) cluster assembly (CIA) targeting complex, which delivers Fe-S clusters to a broad range of cytosolic and nuclear client proteins [#1, #3]. Within the core CIA targeting complex, CIAO2B is centrally located and bridges CIAO1 and MMS19, with crystal and cryo-EM structures defining a bipartite client recognition mode in which CIAO1 and the structural flexibility of MMS19 engage substrates such as primase and DNA2 [#11]. The three core subunits are mutually stabilizing—knockdown of any one down-regulates the others, and direct MMS19 binding protects CIAO2B from proteasomal degradation [#4, #6]. Through this complex CIAO2B targets Fe-S clusters to DNA metabolism enzymes including XPD, which must be matured cytoplasmically by the CIA targeting complex before incorporation into nuclear TFIIH [#5], and the chromokinesin KIF4A, an Fe-S client whose maturation links CIAO2B to mitotic spindle organization and faithful chromosome segregation [#0, #8]. CIAO2B also couples Fe-S biogenesis to cellular iron homeostasis: its depletion stabilizes IRP2, and the CIA targeting complex interacts with FBXL5 to promote oxygen-dependent degradation of iron regulatory proteins [#3, #10]. Loss of CIA core function compromises the activities of DNA helicases, polymerases, and repair enzymes, and the CIAO2B ortholog is essential for development and for stability of the FANCJ helicase DOG-1/BRIP1 [#15, #16].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established that CIAO2B (MIP18) is part of a spindle-associated complex with functional consequences, answering whether the protein had a defined cellular role.\",\n      \"evidence\": \"Co-IP, siRNA knockdown and mitotic spindle immunofluorescence defining the MMXD (MMS19-MIP18-XPD) complex\",\n      \"pmids\": [\"20797633\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the biochemical activity underlying the segregation defect\", \"Connection to Fe-S cluster biology not yet established\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Placed CIAO2B in the cytosolic Fe-S cluster assembly pathway, defining its molecular function as a delivery scaffold rather than a generic spindle factor.\",\n      \"evidence\": \"Co-IP, pulldown and in vitro binding showing MIP18 bridges CIAO1 and binds Fe-S coordinating regions of clients, within an MMS19-CIAO1-MIP18 complex\",\n      \"pmids\": [\"23150669\", \"22678361\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and architecture of the complex unresolved\", \"Mechanism of cluster transfer not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked the CIAO2B complex to cellular iron regulation, showing its function extends beyond client maturation to iron homeostasis sensing.\",\n      \"evidence\": \"Co-IP, 55Fe radiolabeling and siRNA depletion showing CIA2B loss stabilizes IRP2 and impairs Fe-S assembly into most cytosolic-nuclear targets\",\n      \"pmids\": [\"23891004\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting CIA2B loss to IRP2 stabilization not yet molecularly defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined CIAO2B as the bridging subunit of a co-dependent core complex, clarifying complex topology and subunit interdependence.\",\n      \"evidence\": \"siRNA knockdown, Co-IP and in vitro binding distinguishing the tight MMS19-MIP18-CIAO1 core from the external IOP1 component\",\n      \"pmids\": [\"23585563\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the bridge interface not yet available\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated a sequential, compartmentalized maturation step, showing the CIA targeting complex acts cytoplasmically before nuclear client assembly.\",\n      \"evidence\": \"Co-IP, subcellular fractionation, iron depletion and XPD binding mutants showing mutually exclusive association of XPD with the CIA complex or TFIIH\",\n      \"pmids\": [\"25897079\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial/temporal trigger for handoff to nuclear partners unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Mapped the client docking site to the MMS19 C terminus and established that CIAO2B stability depends on MMS19 binding, explaining subunit co-regulation.\",\n      \"evidence\": \"Co-IP, truncation mapping and proteasome inhibitor rescue, with XPD shown to bind MMS19 independently of MIP18/CIAO1\",\n      \"pmids\": [\"28178521\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; degradation pathway and E3 ligase for unprotected MIP18 not identified\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Refined client specificity, showing CIAO2B is not required for all CIA clients (e.g. viperin maturation depends predominantly on CIA1).\",\n      \"evidence\": \"Co-IP domain mapping and 55Fe radiolabeling with selective CIA factor depletion on viperin/RSAD2\",\n      \"pmids\": [\"28615450\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants that route clients to CIAO2B-dependent vs independent paths unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a defined mitotic Fe-S client (KIF4A), mechanistically connecting CIAO2B's Fe-S delivery to its long-known spindle phenotype.\",\n      \"evidence\": \"siRNA knockdown, in vitro Fe-S binding, immunofluorescence colocalization and KIF4A cysteine-rich domain mutants\",\n      \"pmids\": [\"29848660\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether spindle phenotypes arise solely through KIF4A or additional mitotic clients unresolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected de novo Fe-S biosynthesis to CIA targeting, showing how clusters reach the CIAO2B complex.\",\n      \"evidence\": \"Co-IP, siRNA knockdown and 55Fe radiolabeling implicating cytosolic HSC20 in bridging ISC components to the CIA targeting complex\",\n      \"pmids\": [\"29309586\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; direct biochemical reconstitution of cluster transfer not shown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mechanistically tied the CIAO2B complex to oxygen-dependent iron regulation via FBXL5.\",\n      \"evidence\": \"Co-IP, IRP degradation assays and oxygen tension manipulation showing FBXL5-CIA targeting complex interaction is oxygen-sensitive\",\n      \"pmids\": [\"31229404\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the FBXL5 interaction not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided atomic-level architecture, defining how CIAO2B bridges the complex and how clients are recognized and matured.\",\n      \"evidence\": \"X-ray crystallography, cryo-EM of CTC bound to primase/DNA2, biophysical assays and yeast complementation revealing a bipartite client recognition mode\",\n      \"pmids\": [\"32632277\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The ~70 \\u00c5 separation between client cluster and reactive cysteine implies conformational dynamics not directly visualized\", \"Transfer intermediate states unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended CIAO2B's higher-order assembly, situating the targeting complex within an iron-regulated CIA metabolon.\",\n      \"evidence\": \"Targeted proteomics, Co-IP and CIAO3 Fe-S binding mutants with iron supplementation/chelation\",\n      \"pmids\": [\"35654137\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Weak NUBP2 association; functional role of metabolon assembly not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated organismal essentiality and a specific repair-enzyme client in vivo, distinguishing CIAO2B from MMS19.\",\n      \"evidence\": \"C. elegans deletion mutants, DNA damage sensitivity, epistasis and DOG-1 (FANCJ/BRIP1) stability assays\",\n      \"pmids\": [\"39011897\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single ortholog system; whether human CIAO2B is similarly essential not directly tested here\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Confirmed in human disease context that the CIAO2B-containing core complex is required to mature DNA metabolism enzymes.\",\n      \"evidence\": \"Patient-derived cells, functional Fe-S enzyme assays and lentiviral CIAO1 rescue showing impaired recruitment of Fe-S recipients to the CIAO1-MMS19-FAM96B complex\",\n      \"pmids\": [\"38950322\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Disease evidence centers on CIAO1; direct CIAO2B patient mutations not described here\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How conformational dynamics drive the actual Fe-S cluster transfer step from the CTC reactive cysteine to distant client clusters, and what governs client routing through CIAO2B-dependent versus independent paths, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No captured transfer intermediate structure\", \"Rules for client specificity not defined\", \"Reconstituted transfer reaction not reported\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 4, 11]},\n      {\"term_id\": \"GO:0051536\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 5]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [16, 15]}\n    ],\n    \"complexes\": [\n      \"CIA targeting complex (CIAO1-MMS19-FAM96B)\",\n      \"MMXD complex (MMS19-MIP18-XPD)\"\n    ],\n    \"partners\": [\n      \"CIAO1\",\n      \"MMS19\",\n      \"XPD\",\n      \"FBXL5\",\n      \"KIF4A\",\n      \"CKB\",\n      \"NUBP2\",\n      \"RSAD2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}