{"gene":"HCFC2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1999,"finding":"HCF-2 was identified as a second HCF-like protein sharing three regions of strong amino acid sequence homology with HCF-1, including the beta-propeller (kelch repeat) domain. HCF-2 associates with VP16 and can support complex assembly with Oct-1 and DNA, but is significantly less efficient than HCF-1. Chimeric protein analysis showed that differences between the fifth and sixth kelch repeats of the beta-propeller domains from HCF-1 and HCF-2 dictate this selectivity. HCF-2 shows a more dynamic pattern of subcellular localization than HCF-1 and is expressed especially in the testis.","method":"Sequence analysis, in vitro complex assembly assays, chimeric protein construction, subcellular localization studies","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (binding assays, chimeric protein analysis, localization) in a focused mechanistic study of HCFC2","pmids":["10196288"],"is_preprint":false},{"year":2000,"finding":"HCF-2, like HCF-1, contains a functional SAS1 self-association element (a short ~43-amino-acid region) in its N-terminal subunit. Unlike HCF-1, HCF-2 is not proteolyzed, yet still retains this association element, suggesting SAS1 does not function solely to maintain subunit association after cleavage.","method":"Domain mapping, protein-protein interaction assays, sequence analysis of HCF-1 and HCF-2","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding/interaction assays with domain mapping, single lab study","pmids":["10958670"],"is_preprint":false},{"year":2001,"finding":"The C-terminal WYF domain of HCF-1 interacts with the MYND domain of PDCD2, and this interaction is conserved between human HCF-2 and C. elegans HCF. Overexpression of PDCD2 suppresses HCF-1 complementation of a temperature-sensitive cell-cycle lesion, and overexpression of interfering domains of either PDCD2 or HCF-1 enhances complementation, establishing PDCD2 as a negative regulator of HCF-1 (and by conservation, HCF-2).","method":"Co-immunoprecipitation, domain interaction mapping, functional complementation assay with temperature-sensitive HCF-1 mutant cells","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction mapping and functional rescue assay, conservation across HCF-2 noted but not directly validated by separate experiment for HCF-2","pmids":["12149646"],"is_preprint":false},{"year":2001,"finding":"All three HCF family members (HCF-1, HCF-2, and C. elegans CeHCF) can promote VP16-induced complex formation, indicating VP16 targets a highly conserved function. However, unlike HCF-1 and CeHCF, HCF-2 fails to support VP16 transcriptional activation effectively, demonstrating that HCF-2 can stabilize the VP16-induced complex but cannot mediate its transcriptional activity.","method":"In vitro complex assembly, transcriptional activation assays comparing HCF-1, HCF-2, and CeHCF","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional comparison using transcriptional assays and complex assembly, single lab with two orthogonal methods","pmids":["11711630"],"is_preprint":false},{"year":2003,"finding":"C. elegans CeHCF (which is structurally more related to HCF-2 than HCF-1) undergoes developmental and cell-cycle-regulated phosphorylation. Phosphorylation occurs at four clustered CDC2/CDK2 consensus sites in a non-conserved region. Phosphorylation of CeHCF or human HCF-1 is dispensable for association with VP16.","method":"Phosphorylation-site mapping of endogenous CeHCF, cell-cycle synchronization experiments, in vitro kinase assays","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphorylation site mapping with functional testing (VP16 binding), single lab, two orthogonal readouts","pmids":["11341844"],"is_preprint":false},{"year":2003,"finding":"A C-terminal targeting signal of CeHCF (last 23 amino acids) contains interdigitated amino acids involved in both nuclear and mitochondrial targeting. Critically, this signal is sufficient to redirect HCF-2 into mitochondria when transferred, demonstrating that HCF-2 can be targeted to mitochondria via a heterologous signal.","method":"GFP fusion constructs, live imaging in transgenic worms and mammalian cells, domain deletion/transfer experiments","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with domain-transfer validation showing functional consequence for HCF-2 targeting, single lab","pmids":["14629117"],"is_preprint":false},{"year":2017,"finding":"HCFC2 is required for IRF1- and IRF2-dependent transcription of Tlr3 in macrophages. Three independent ENU-induced mutations in Hcfc2 specifically abrogated macrophage responses to poly(I:C). HCFC2 promotes binding of IRF1 and IRF2 to the Tlr3 promoter; without this, inflammatory cytokine and type I IFN responses are reduced. HCFC2 is also necessary for transcription of a large subset of other IRF2-dependent interferon-regulated genes. Hcfc2 mutations compromised survival during influenza virus and herpes simplex virus 1 infections in mice.","method":"ENU mutagenesis screen, chromatin immunoprecipitation (ChIP) showing IRF1/IRF2 binding to Tlr3 promoter, cytokine response assays in macrophages, in vivo infection survival experiments","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — three independent loss-of-function alleles converge on same phenotype, ChIP demonstrates direct mechanistic link, replicated across multiple infectious models","pmids":["28970238"],"is_preprint":false}],"current_model":"HCFC2 (HCF-2) is a nuclear protein containing a beta-propeller (kelch repeat) domain that associates with the herpes simplex virus transactivator VP16 and supports VP16-induced complex formation with Oct-1, but unlike HCF-1 cannot mediate transcriptional activation from this complex; in innate immunity, HCFC2 acts as a co-factor that promotes IRF1 and IRF2 binding to the Tlr3 promoter, thereby enabling transcription of Tlr3 and a broad set of IRF2-dependent interferon-regulated genes in macrophages, and its loss results in susceptibility to viral infections."},"narrative":{"mechanistic_narrative":"HCFC2 (HCF-2) is a nuclear, kelch-repeat (beta-propeller) protein originally defined as a second member of the host cell factor family that, like HCF-1, associates with the herpes simplex virus transactivator VP16 and supports assembly of the VP16–Oct-1–DNA complex [PMID:10196288, PMID:11711630]. Functional comparison establishes a key divergence from HCF-1: HCFC2 stabilizes the VP16-induced complex but cannot mediate transcriptional activation from it, and residue differences between the fifth and sixth kelch repeats of the beta-propeller dictate this selectivity [PMID:10196288, PMID:11711630]. Beyond its viral cofactor role, HCFC2 is required for IRF1- and IRF2-dependent transcription, acting at the Tlr3 promoter to promote IRF1 and IRF2 binding and thereby enabling Tlr3 expression and a broad set of IRF2-dependent interferon-regulated genes in macrophages; loss-of-function compromises inflammatory cytokine and type I IFN responses and survival during influenza and herpes simplex virus 1 infection [PMID:28970238]. HCFC2 retains an N-terminal SAS1 self-association element yet, unlike HCF-1, is not proteolytically processed [PMID:10958670].","teleology":[{"year":1999,"claim":"Established HCFC2 as a distinct HCF family protein and asked whether it shares HCF-1's VP16 cofactor function, showing it associates with VP16 and assembles the Oct-1/DNA complex but less efficiently, with selectivity localized to its beta-propeller kelch repeats.","evidence":"Sequence analysis, in vitro complex assembly, and chimeric protein construction comparing HCF-1 and HCF-2 beta-propeller domains","pmids":["10196288"],"confidence":"High","gaps":["Functional consequence of dynamic subcellular localization not resolved","Testis-enriched expression not mechanistically explained","No structural model of the HCF-2 beta-propeller"]},{"year":2000,"claim":"Tested whether the SAS1 self-association element functions only to hold cleaved subunits together, finding HCFC2 retains a functional SAS1 element despite not being proteolyzed, decoupling self-association from cleavage.","evidence":"Domain mapping and protein-protein interaction assays on HCF-1 and HCF-2","pmids":["10958670"],"confidence":"Medium","gaps":["Physiological role of unprocessed HCF-2 self-association unknown","Why HCF-2 escapes proteolysis not established"]},{"year":2001,"claim":"Defined a conserved WYF–MYND interaction with the negative regulator PDCD2 and asked whether it extends to HCF-2, noting conservation of the interaction across human HCF-2 and C. elegans HCF.","evidence":"Co-immunoprecipitation, reciprocal domain interaction mapping, and functional complementation with temperature-sensitive HCF-1 cells","pmids":["12149646"],"confidence":"Medium","gaps":["PDCD2 regulation of HCF-2 inferred from conservation, not directly tested for HCF-2","Functional consequence of PDCD2 binding to HCF-2 unmeasured"]},{"year":2001,"claim":"Resolved whether HCFC2's stabilization of the VP16 complex translates into transcriptional output, demonstrating HCF-2 stabilizes the VP16-induced complex but fails to support transcriptional activation, separating complex assembly from activation function.","evidence":"In vitro complex assembly and transcriptional activation assays comparing HCF-1, HCF-2, and CeHCF","pmids":["11711630"],"confidence":"Medium","gaps":["Molecular basis of activation deficiency not mapped","No identification of activation cofactors HCF-2 fails to recruit"]},{"year":2003,"claim":"Addressed post-translational and targeting regulation of HCF family members using CeHCF (structurally closer to HCF-2), mapping cell-cycle CDC2/CDK2 phosphorylation sites and showing a C-terminal signal sufficient to redirect HCF-2 into mitochondria.","evidence":"Phosphorylation-site mapping, cell-cycle synchronization, in vitro kinase assays, and GFP-fusion localization/domain-transfer experiments","pmids":["11341844","14629117"],"confidence":"Medium","gaps":["Whether endogenous HCF-2 is phosphorylated or mitochondrially localized not shown","Functional significance of dual targeting unknown"]},{"year":2017,"claim":"Defined an in vivo physiological function distinct from the VP16 role, showing HCFC2 is required for IRF1/IRF2 binding at the Tlr3 promoter and for IRF2-dependent interferon-regulated gene expression, with loss causing viral susceptibility.","evidence":"ENU mutagenesis with three independent alleles, ChIP for IRF1/IRF2 promoter binding, macrophage cytokine assays, and in vivo influenza/HSV-1 infection survival","pmids":["28970238"],"confidence":"High","gaps":["Direct biochemical interaction between HCFC2 and IRF1/IRF2 not shown","Mechanism by which HCFC2 promotes IRF promoter binding unresolved","Relationship between VP16 cofactor activity and IRF2 cofactor activity unexplored"]},{"year":null,"claim":"How HCFC2's beta-propeller cofactor activity is mechanistically reconciled across its VP16/Oct-1 and IRF1/IRF2 roles, and what direct molecular partners mediate the immune function, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct structural or biochemical link between HCFC2 and IRF transcription factors","Unknown whether transcription cofactor and chromatin recruitment mechanisms are shared with HCF-1"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[6]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,6]}],"complexes":["VP16-induced complex (VP16-Oct-1-DNA)"],"partners":["VP16","POU2F1","IRF1","IRF2","PDCD2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y5Z7","full_name":"Host cell factor 2","aliases":["C2 factor"],"length_aa":792,"mass_kda":86.8,"function":"","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9Y5Z7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HCFC2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HIST2H2BE","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/HCFC2","total_profiled":1310},"omim":[{"mim_id":"607926","title":"HOST CELL FACTOR C2; HCFC2","url":"https://www.omim.org/entry/607926"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HCFC2"},"hgnc":{"alias_symbol":["HCF-2"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y5Z7","domains":[{"cath_id":"2.120.10.80","chopping":"16-181","consensus_level":"medium","plddt":94.6505,"start":16,"end":181},{"cath_id":"2.120.10.80","chopping":"200-208_236-268_280-356","consensus_level":"medium","plddt":88.3434,"start":200,"end":356},{"cath_id":"2.60.40.10","chopping":"357-395_598-620_637-675","consensus_level":"medium","plddt":90.3171,"start":357,"end":675},{"cath_id":"2.60.40.10","chopping":"686-783","consensus_level":"high","plddt":84.6582,"start":686,"end":783}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y5Z7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y5Z7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y5Z7-F1-predicted_aligned_error_v6.png","plddt_mean":72.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HCFC2","jax_strain_url":"https://www.jax.org/strain/search?query=HCFC2"},"sequence":{"accession":"Q9Y5Z7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y5Z7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y5Z7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y5Z7"}},"corpus_meta":[{"pmid":"21392734","id":"PMC_21392734","title":"Genetic 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HCF-2 associates with VP16 and can support complex assembly with Oct-1 and DNA, but is significantly less efficient than HCF-1. Chimeric protein analysis showed that differences between the fifth and sixth kelch repeats of the beta-propeller domains from HCF-1 and HCF-2 dictate this selectivity. HCF-2 shows a more dynamic pattern of subcellular localization than HCF-1 and is expressed especially in the testis.\",\n      \"method\": \"Sequence analysis, in vitro complex assembly assays, chimeric protein construction, subcellular localization studies\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (binding assays, chimeric protein analysis, localization) in a focused mechanistic study of HCFC2\",\n      \"pmids\": [\"10196288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"HCF-2, like HCF-1, contains a functional SAS1 self-association element (a short ~43-amino-acid region) in its N-terminal subunit. Unlike HCF-1, HCF-2 is not proteolyzed, yet still retains this association element, suggesting SAS1 does not function solely to maintain subunit association after cleavage.\",\n      \"method\": \"Domain mapping, protein-protein interaction assays, sequence analysis of HCF-1 and HCF-2\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding/interaction assays with domain mapping, single lab study\",\n      \"pmids\": [\"10958670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The C-terminal WYF domain of HCF-1 interacts with the MYND domain of PDCD2, and this interaction is conserved between human HCF-2 and C. elegans HCF. Overexpression of PDCD2 suppresses HCF-1 complementation of a temperature-sensitive cell-cycle lesion, and overexpression of interfering domains of either PDCD2 or HCF-1 enhances complementation, establishing PDCD2 as a negative regulator of HCF-1 (and by conservation, HCF-2).\",\n      \"method\": \"Co-immunoprecipitation, domain interaction mapping, functional complementation assay with temperature-sensitive HCF-1 mutant cells\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction mapping and functional rescue assay, conservation across HCF-2 noted but not directly validated by separate experiment for HCF-2\",\n      \"pmids\": [\"12149646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"All three HCF family members (HCF-1, HCF-2, and C. elegans CeHCF) can promote VP16-induced complex formation, indicating VP16 targets a highly conserved function. However, unlike HCF-1 and CeHCF, HCF-2 fails to support VP16 transcriptional activation effectively, demonstrating that HCF-2 can stabilize the VP16-induced complex but cannot mediate its transcriptional activity.\",\n      \"method\": \"In vitro complex assembly, transcriptional activation assays comparing HCF-1, HCF-2, and CeHCF\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional comparison using transcriptional assays and complex assembly, single lab with two orthogonal methods\",\n      \"pmids\": [\"11711630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"C. elegans CeHCF (which is structurally more related to HCF-2 than HCF-1) undergoes developmental and cell-cycle-regulated phosphorylation. Phosphorylation occurs at four clustered CDC2/CDK2 consensus sites in a non-conserved region. Phosphorylation of CeHCF or human HCF-1 is dispensable for association with VP16.\",\n      \"method\": \"Phosphorylation-site mapping of endogenous CeHCF, cell-cycle synchronization experiments, in vitro kinase assays\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphorylation site mapping with functional testing (VP16 binding), single lab, two orthogonal readouts\",\n      \"pmids\": [\"11341844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A C-terminal targeting signal of CeHCF (last 23 amino acids) contains interdigitated amino acids involved in both nuclear and mitochondrial targeting. Critically, this signal is sufficient to redirect HCF-2 into mitochondria when transferred, demonstrating that HCF-2 can be targeted to mitochondria via a heterologous signal.\",\n      \"method\": \"GFP fusion constructs, live imaging in transgenic worms and mammalian cells, domain deletion/transfer experiments\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with domain-transfer validation showing functional consequence for HCF-2 targeting, single lab\",\n      \"pmids\": [\"14629117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HCFC2 is required for IRF1- and IRF2-dependent transcription of Tlr3 in macrophages. Three independent ENU-induced mutations in Hcfc2 specifically abrogated macrophage responses to poly(I:C). HCFC2 promotes binding of IRF1 and IRF2 to the Tlr3 promoter; without this, inflammatory cytokine and type I IFN responses are reduced. HCFC2 is also necessary for transcription of a large subset of other IRF2-dependent interferon-regulated genes. Hcfc2 mutations compromised survival during influenza virus and herpes simplex virus 1 infections in mice.\",\n      \"method\": \"ENU mutagenesis screen, chromatin immunoprecipitation (ChIP) showing IRF1/IRF2 binding to Tlr3 promoter, cytokine response assays in macrophages, in vivo infection survival experiments\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three independent loss-of-function alleles converge on same phenotype, ChIP demonstrates direct mechanistic link, replicated across multiple infectious models\",\n      \"pmids\": [\"28970238\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HCFC2 (HCF-2) is a nuclear protein containing a beta-propeller (kelch repeat) domain that associates with the herpes simplex virus transactivator VP16 and supports VP16-induced complex formation with Oct-1, but unlike HCF-1 cannot mediate transcriptional activation from this complex; in innate immunity, HCFC2 acts as a co-factor that promotes IRF1 and IRF2 binding to the Tlr3 promoter, thereby enabling transcription of Tlr3 and a broad set of IRF2-dependent interferon-regulated genes in macrophages, and its loss results in susceptibility to viral infections.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HCFC2 (HCF-2) is a nuclear, kelch-repeat (beta-propeller) protein originally defined as a second member of the host cell factor family that, like HCF-1, associates with the herpes simplex virus transactivator VP16 and supports assembly of the VP16–Oct-1–DNA complex [#0, #3]. Functional comparison establishes a key divergence from HCF-1: HCFC2 stabilizes the VP16-induced complex but cannot mediate transcriptional activation from it, and residue differences between the fifth and sixth kelch repeats of the beta-propeller dictate this selectivity [#0, #3]. Beyond its viral cofactor role, HCFC2 is required for IRF1- and IRF2-dependent transcription, acting at the Tlr3 promoter to promote IRF1 and IRF2 binding and thereby enabling Tlr3 expression and a broad set of IRF2-dependent interferon-regulated genes in macrophages; loss-of-function compromises inflammatory cytokine and type I IFN responses and survival during influenza and herpes simplex virus 1 infection [#6]. HCFC2 retains an N-terminal SAS1 self-association element yet, unlike HCF-1, is not proteolytically processed [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established HCFC2 as a distinct HCF family protein and asked whether it shares HCF-1's VP16 cofactor function, showing it associates with VP16 and assembles the Oct-1/DNA complex but less efficiently, with selectivity localized to its beta-propeller kelch repeats.\",\n      \"evidence\": \"Sequence analysis, in vitro complex assembly, and chimeric protein construction comparing HCF-1 and HCF-2 beta-propeller domains\",\n      \"pmids\": [\"10196288\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of dynamic subcellular localization not resolved\", \"Testis-enriched expression not mechanistically explained\", \"No structural model of the HCF-2 beta-propeller\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Tested whether the SAS1 self-association element functions only to hold cleaved subunits together, finding HCFC2 retains a functional SAS1 element despite not being proteolyzed, decoupling self-association from cleavage.\",\n      \"evidence\": \"Domain mapping and protein-protein interaction assays on HCF-1 and HCF-2\",\n      \"pmids\": [\"10958670\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological role of unprocessed HCF-2 self-association unknown\", \"Why HCF-2 escapes proteolysis not established\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined a conserved WYF–MYND interaction with the negative regulator PDCD2 and asked whether it extends to HCF-2, noting conservation of the interaction across human HCF-2 and C. elegans HCF.\",\n      \"evidence\": \"Co-immunoprecipitation, reciprocal domain interaction mapping, and functional complementation with temperature-sensitive HCF-1 cells\",\n      \"pmids\": [\"12149646\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PDCD2 regulation of HCF-2 inferred from conservation, not directly tested for HCF-2\", \"Functional consequence of PDCD2 binding to HCF-2 unmeasured\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Resolved whether HCFC2's stabilization of the VP16 complex translates into transcriptional output, demonstrating HCF-2 stabilizes the VP16-induced complex but fails to support transcriptional activation, separating complex assembly from activation function.\",\n      \"evidence\": \"In vitro complex assembly and transcriptional activation assays comparing HCF-1, HCF-2, and CeHCF\",\n      \"pmids\": [\"11711630\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of activation deficiency not mapped\", \"No identification of activation cofactors HCF-2 fails to recruit\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Addressed post-translational and targeting regulation of HCF family members using CeHCF (structurally closer to HCF-2), mapping cell-cycle CDC2/CDK2 phosphorylation sites and showing a C-terminal signal sufficient to redirect HCF-2 into mitochondria.\",\n      \"evidence\": \"Phosphorylation-site mapping, cell-cycle synchronization, in vitro kinase assays, and GFP-fusion localization/domain-transfer experiments\",\n      \"pmids\": [\"11341844\", \"14629117\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether endogenous HCF-2 is phosphorylated or mitochondrially localized not shown\", \"Functional significance of dual targeting unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined an in vivo physiological function distinct from the VP16 role, showing HCFC2 is required for IRF1/IRF2 binding at the Tlr3 promoter and for IRF2-dependent interferon-regulated gene expression, with loss causing viral susceptibility.\",\n      \"evidence\": \"ENU mutagenesis with three independent alleles, ChIP for IRF1/IRF2 promoter binding, macrophage cytokine assays, and in vivo influenza/HSV-1 infection survival\",\n      \"pmids\": [\"28970238\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical interaction between HCFC2 and IRF1/IRF2 not shown\", \"Mechanism by which HCFC2 promotes IRF promoter binding unresolved\", \"Relationship between VP16 cofactor activity and IRF2 cofactor activity unexplored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HCFC2's beta-propeller cofactor activity is mechanistically reconciled across its VP16/Oct-1 and IRF1/IRF2 roles, and what direct molecular partners mediate the immune function, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct structural or biochemical link between HCFC2 and IRF transcription factors\", \"Unknown whether transcription cofactor and chromatin recruitment mechanisms are shared with HCF-1\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 6]}\n    ],\n    \"complexes\": [\"VP16-induced complex (VP16-Oct-1-DNA)\"],\n    \"partners\": [\"VP16\", \"POU2F1\", \"IRF1\", \"IRF2\", \"PDCD2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":4,"faith_total":4,"faith_pct":100.0}}