{"gene":"HROB","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2019,"finding":"HROB (C17orf53) is an OB-fold-containing protein that recruits the MCM8-MCM9 helicase to sites of DNA damage to promote HR-associated DNA synthesis downstream of RAD51. Mice with targeted Hrob mutations are infertile due to germ cell depletion consistent with prophase I meiotic arrest. The HROB-MCM8-MCM9 pathway acts redundantly with the HELQ helicase; cells lacking both HROB and HELQ have severely impaired HR.","method":"Targeted mouse mutagenesis, genetic epistasis (HROB/HELQ double KO), cellular HR assays, focus formation/recruitment assays","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (mouse KO, genetic epistasis, cellular HR assays, focus formation), replicated in parallel study","pmids":["31467087"],"is_preprint":false},{"year":2020,"finding":"HROB (MCM8IP/C17orf53) binds ssDNA and directly associates with both the MCM8-9 helicase complex and RPA1. HROB stimulates the helicase activity of MCM8-9 in vitro, and its interactions with MCM8-9 and RPA are required for HR (specifically long-tract gene conversion downstream of RAD51 loading), replication fork progression, and cellular viability after crosslinking agent treatment.","method":"In vitro helicase activity assay with purified proteins, Co-IP/pulldown (HROB–MCM8-9 and HROB–RPA1), HR reporter assays, crosslinker/PARP inhibitor sensitivity assays in MCM8IP-deficient cells","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of helicase stimulation combined with reciprocal binding assays and cellular loss-of-function phenotypes, multiple orthogonal methods","pmids":["32528060"],"is_preprint":false},{"year":2020,"finding":"C17orf53/HROB is a ssDNA- and RPA-binding protein required for interstrand crosslink (ICL) repair and efficient DNA replication; its loss leads to hypersensitivity to ATR inhibition and pronounced ICL repair defects. HROB works together with MCM8/9 to promote cell survival after ICL lesions.","method":"Genome-wide ATR-inhibitor fitness screen, multi-omics interaction studies, ssDNA/RPA-binding assays, cellular ICL sensitivity assays, DNA replication rate measurement in C17orf53 KO cells","journal":"DNA repair","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (screen, binding assays, cellular phenotypes) in single lab","pmids":["32853826"],"is_preprint":false},{"year":2024,"finding":"Biochemical and structural analysis defined the HROB–MCM8-9 interaction interface: HROB makes transient contacts with both MCM8 and MCM9 subunits and binds the MCM8-9 heterodimer with highest affinity. MCM8-9-HROB preferentially binds and unwinds branched DNA structures with low processivity. MCM8-9 assembles into a hexamer from dimers on DNA in the presence of ATP via two alternating interfaces (one stable/obligate heterodimer, one labile mediating hexamer assembly). HROB does not affect ring/hexamer formation but promotes DNA unwinding downstream of loading, likely by coordinating ATP hydrolysis with translocation. The ATPase site at the labile interface contributes disproportionately more to unwinding.","method":"Molecular modeling, biochemistry (ATPase assays, helicase assays, binding assays), single-molecule experiments (unwinding processivity), mutational analysis of interfaces","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis and single-molecule experiments, peer-reviewed, preprint version also available for corroboration","pmids":["38678026"],"is_preprint":false},{"year":2024,"finding":"HROB is a nuclear protein whose level peaks in S phase and is downregulated in quiescence, co-regulated with DNA replication factors. Flow cytometry FRET assays detected associations between HROB and proteins of the DNA replication machinery. Ectopic overexpression of HROB caused an almost complete shutdown of DNA replication.","method":"Flow cytometry FRET (protein–protein association), cell cycle analysis, ectopic overexpression with DNA replication readout, structural prediction/homology analysis","journal":"Genes","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single FRET method for interaction, overexpression phenotype without mechanistic resolution","pmids":["39766854"],"is_preprint":false},{"year":2026,"finding":"Cryo-EM structures of MCM8/9 with DNA, HROB, and ATP analogs revealed that DNA binding induces a rotational rearrangement between N-terminal DNA-binding and C-terminal AAA+ ATPase domains, reorganizing DNA-binding loops into a staircase configuration. HROB associates with both halves of the heterohexamer and drives a similar rotation prior to DNA binding, localizing MCM8/9 to crosslink damage sites and enabling unwinding, providing a unified mechanistic model for MCM8/9 helicase activation by HROB.","method":"Cryo-electron microscopy (cryo-EM) with ATP analogs and DNA substrates, structural analysis of conformational states","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — cryo-EM structural data with functional inference, single lab, preprint not yet peer-reviewed","pmids":["42094346"],"is_preprint":true},{"year":2025,"finding":"HROB is required for MCM8/9 focus formation at ICL damage sites (functional activation context), but HROB is not required for FANCD2 binding to MCM8/9. MCM8/9 physically interacts with FANCD2 through its core domain independently of DNA, and FANCD2 acts upstream of MCM9 recruitment to ICL-induced nuclear foci downstream of FANCD2 monoubiquitination. MCM8/9 and FANCD2 are epistatic (combined loss does not cause additive DNA damage), placing MCM8/9 as a downstream effector of the FA pathway.","method":"Co-immunoprecipitation, immunofluorescence focus assays, genetic epistasis (double KO γH2AX and survival assays), MCM8/9 KO cell lines","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, epistasis, and focus assays; preprint, single lab, not yet peer-reviewed","pmids":["bio_10.1101_2025.08.07.669127"],"is_preprint":true},{"year":2025,"finding":"HROB suppresses lung adenocarcinoma cell proliferation by interacting with ZC3HC1 and reducing its phosphorylation at Ser354, which facilitates K27-linked ubiquitination of CCNB1 and its proteasomal degradation, impairing the G2-to-M phase transition.","method":"Co-immunoprecipitation (HROB–ZC3HC1 interaction), phosphorylation analysis, ubiquitination assay, proteasomal degradation assay, cell proliferation/tumor growth assays with KO/overexpression","journal":"Cancer science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, mechanistic claims rely on co-IP and overexpression without in vitro reconstitution or structural validation","pmids":["40654113"],"is_preprint":false}],"current_model":"HROB is an OB-fold-containing, ssDNA- and RPA-binding nuclear protein that acts as a loader and activator of the MCM8-9 helicase: it recruits MCM8-9 to DNA damage sites (especially stalled forks and interstrand crosslinks), binds the MCM8-9 heterodimer at a stable interface, and promotes DNA unwinding downstream of hexamer assembly by coordinating ATP hydrolysis with MCM8-9 translocation on ssDNA, thereby driving HR-associated DNA synthesis downstream of RAD51 and enabling ICL repair in a pathway epistatic to the Fanconi anemia factor FANCD2."},"narrative":{"mechanistic_narrative":"HROB (C17orf53/MCM8IP) is a nuclear, OB-fold-containing protein that functions as a dedicated loader and activator of the MCM8-MCM9 helicase during homologous recombination–associated DNA synthesis [PMID:31467087, PMID:32528060]. It binds ssDNA and directly associates with both the MCM8-9 heterodimer and RPA1, recruiting MCM8-9 to sites of DNA damage to promote HR-associated DNA synthesis (long-tract gene conversion) downstream of RAD51 loading, and these interactions are required for replication fork progression and survival after crosslinking agents [PMID:31467087, PMID:32528060]. Biochemically, HROB contacts both MCM8 and MCM9 subunits and binds the heterodimer with highest affinity; it does not affect hexamer assembly but promotes DNA unwinding downstream of loading, likely by coordinating ATP hydrolysis with translocation on branched DNA substrates [PMID:38678026]. Cryo-EM analysis indicates HROB drives a rotational rearrangement between the N-terminal DNA-binding and C-terminal AAA+ ATPase domains of MCM8/9 prior to DNA binding, providing a unified model for helicase activation [PMID:42094346]. Functionally, HROB is required for interstrand crosslink repair and acts in a pathway epistatic to the Fanconi anemia factor FANCD2, with MCM8/9 operating as a downstream effector of the FA pathway [PMID:32853826, PMID:bio_10.1101_2025.08.07.669127]. Loss of Hrob in mice causes germ cell depletion and infertility consistent with prophase I meiotic arrest, and the HROB-MCM8-9 axis acts redundantly with the HELQ helicase [PMID:31467087].","teleology":[{"year":2019,"claim":"Established HROB as a recruitment factor that brings the MCM8-9 helicase to DNA damage sites to drive HR-associated DNA synthesis, defining its role downstream of RAD51 and in meiotic recombination.","evidence":"Targeted mouse mutagenesis, genetic epistasis with HELQ, cellular HR and recruitment assays","pmids":["31467087"],"confidence":"High","gaps":["Direct biochemical interaction with MCM8-9 not yet reconstituted at this stage","Molecular basis of recruitment to damage sites unresolved","How redundancy with HELQ is partitioned mechanistically unclear"]},{"year":2020,"claim":"Demonstrated that HROB physically and functionally activates the helicase by binding ssDNA, MCM8-9, and RPA1, with these interactions required for long-tract gene conversion, fork progression, and crosslink survival.","evidence":"In vitro helicase assays with purified proteins, reciprocal Co-IP/pulldown, HR reporters, crosslinker/PARP inhibitor sensitivity in deficient cells","pmids":["32528060","32853826"],"confidence":"High","gaps":["Structural basis of the HROB–MCM8-9 interface not defined","Mechanism by which HROB stimulates unwinding unresolved","ICL screen and binding data from a single lab at Medium confidence"]},{"year":2024,"claim":"Resolved the HROB–MCM8-9 interaction architecture and showed HROB promotes unwinding downstream of hexamer assembly rather than affecting ring formation, linking activation to ATP hydrolysis at a labile interface.","evidence":"Molecular modeling, ATPase/helicase/binding assays, single-molecule unwinding processivity, interface mutagenesis","pmids":["38678026"],"confidence":"High","gaps":["Atomic-resolution structure of the activated complex not yet captured","How HROB couples ATP hydrolysis to translocation only inferred","Low processivity in vitro not reconciled with in vivo function"]},{"year":2024,"claim":"Placed HROB expression in S phase co-regulated with replication factors and detected associations with replication machinery, while overexpression suppressed replication.","evidence":"Flow cytometry FRET, cell cycle analysis, ectopic overexpression with replication readout","pmids":["39766854"],"confidence":"Low","gaps":["Single FRET method for interaction without orthogonal validation","Overexpression phenotype lacks mechanistic resolution","Identity of replication-machinery partners not defined"]},{"year":2025,"claim":"Positioned the HROB-MCM8/9 axis as a downstream effector of the Fanconi anemia pathway, with HROB required for MCM8/9 focus formation at ICLs but dispensable for the FANCD2–MCM8/9 interaction.","evidence":"Co-IP, immunofluorescence focus assays, genetic epistasis (double KO γH2AX/survival)","pmids":["bio_10.1101_2025.08.07.669127"],"confidence":"Medium","gaps":["Preprint, single lab, not yet peer-reviewed","How FANCD2 monoubiquitination licenses MCM9 recruitment mechanistically unresolved","Direct vs indirect role of HROB in focus formation not separated"]},{"year":2026,"claim":"Provided a unified structural model in which HROB drives a rotational rearrangement of MCM8/9 domains prior to DNA binding to enable helicase activation.","evidence":"Cryo-EM with ATP analogs and DNA substrates, conformational state analysis","pmids":["42094346"],"confidence":"Medium","gaps":["Preprint, single lab, not yet peer-reviewed","Functional activation inferred from static conformational states","Dynamics of the proposed rotation not directly observed"]},{"year":null,"claim":"How HROB integrates helicase activation with RPA exchange, FA-pathway signaling, and replication-coupled regulation in vivo remains to be unified.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of the fully activated HROB-MCM8/9-DNA complex in a peer-reviewed work","Mechanism coupling FANCD2 monoubiquitination to HROB-mediated MCM8/9 loading unresolved","Physiological role beyond meiosis and ICL repair not characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[1,2]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,3]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,4]}],"pathway":[{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-69306","term_label":"DNA Replication","supporting_discovery_ids":[1,2]}],"complexes":[],"partners":["MCM8","MCM9","RPA1","FANCD2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N3J3","full_name":"Homologous recombination OB-fold protein","aliases":[],"length_aa":647,"mass_kda":69.8,"function":"DNA-binding protein involved in homologous recombination that acts by recruiting the MCM8-MCM9 helicase complex to sites of DNA damage to promote DNA repair synthesis (PubMed:31467087). A C-terminal region including the OB-fold stimulates the helicase activity of MCM8-MCM9 probably by altering its conformation (PubMed:37535404)","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q8N3J3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HROB","classification":"Not Classified","n_dependent_lines":59,"n_total_lines":1208,"dependency_fraction":0.048841059602649006},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MSH6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/HROB","total_profiled":1310},"omim":[{"mim_id":"620897","title":"OVARIAN DYSGENESIS 11; ODG11","url":"https://www.omim.org/entry/620897"},{"mim_id":"618611","title":"HOMOLOGOUS RECOMBINATION FACTOR WITH OB-FOLD; HROB","url":"https://www.omim.org/entry/618611"},{"mim_id":"618078","title":"OVARIAN DYSGENESIS 6; ODG6","url":"https://www.omim.org/entry/618078"},{"mim_id":"608193","title":"REC8 MEIOTIC RECOMBINATION PROTEIN; REC8","url":"https://www.omim.org/entry/608193"},{"mim_id":"607617","title":"NUCLEOPORIN, 107-KD; NUP107","url":"https://www.omim.org/entry/607617"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":8.8},{"tissue":"testis","ntpm":10.7}],"url":"https://www.proteinatlas.org/search/HROB"},"hgnc":{"alias_symbol":["MGC3130","MCM8IP"],"prev_symbol":["C17orf53"]},"alphafold":{"accession":"Q8N3J3","domains":[{"cath_id":"2.40.50.140","chopping":"453-574","consensus_level":"high","plddt":91.0668,"start":453,"end":574}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N3J3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N3J3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N3J3-F1-predicted_aligned_error_v6.png","plddt_mean":54.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HROB","jax_strain_url":"https://www.jax.org/strain/search?query=HROB"},"sequence":{"accession":"Q8N3J3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N3J3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N3J3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N3J3"}},"corpus_meta":[{"pmid":"31467087","id":"PMC_31467087","title":"Control of homologous recombination by the HROB-MCM8-MCM9 pathway.","date":"2019","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/31467087","citation_count":66,"is_preprint":false},{"pmid":"32528060","id":"PMC_32528060","title":"MCM8IP activates the MCM8-9 helicase to promote DNA synthesis and homologous recombination upon DNA damage.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32528060","citation_count":47,"is_preprint":false},{"pmid":"34707299","id":"PMC_34707299","title":"Meiotic genes in premature ovarian insufficiency: variants in HROB and REC8 as likely genetic causes.","date":"2021","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/34707299","citation_count":39,"is_preprint":false},{"pmid":"32853826","id":"PMC_32853826","title":"C17orf53 is identified as a novel gene involved in inter-strand crosslink repair.","date":"2020","source":"DNA repair","url":"https://pubmed.ncbi.nlm.nih.gov/32853826","citation_count":24,"is_preprint":false},{"pmid":"38678026","id":"PMC_38678026","title":"Mechanism of DNA unwinding by MCM8-9 in complex with HROB.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38678026","citation_count":13,"is_preprint":false},{"pmid":"31575675","id":"PMC_31575675","title":"Ways to unwind with HROB, a new player in homologous recombination.","date":"2019","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/31575675","citation_count":11,"is_preprint":false},{"pmid":"35903352","id":"PMC_35903352","title":"Pan-Cancer Analysis Identified Homologous Recombination Factor With OB-Fold (HROB) as a Potential Biomarker for Various Tumor Types.","date":"2022","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35903352","citation_count":4,"is_preprint":false},{"pmid":"39766854","id":"PMC_39766854","title":"HROB Is Implicated in DNA Replication.","date":"2024","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/39766854","citation_count":1,"is_preprint":false},{"pmid":"40654113","id":"PMC_40654113","title":"HROB Induces Lung Adenocarcinoma Progression via ZC3HC1-CCNB1 Axis Regulation and Cell Cycle Dysregulation.","date":"2025","source":"Cancer science","url":"https://pubmed.ncbi.nlm.nih.gov/40654113","citation_count":1,"is_preprint":false},{"pmid":"37461676","id":"PMC_37461676","title":"Mechanism of DNA unwinding by hexameric MCM8-9 in complex with HROB.","date":"2023","source":"Research square","url":"https://pubmed.ncbi.nlm.nih.gov/37461676","citation_count":1,"is_preprint":false},{"pmid":"38105698","id":"PMC_38105698","title":"Genetic analysis of novel pathogenic gene HROB in a family with primary ovarian insufficiency.","date":"2023","source":"Zhejiang da xue xue bao. Yi xue ban = Journal of Zhejiang University. Medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38105698","citation_count":1,"is_preprint":false},{"pmid":"37398313","id":"PMC_37398313","title":"Mechanism of DNA unwinding by hexameric MCM8-9 in complex with HROB.","date":"2023","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37398313","citation_count":0,"is_preprint":false},{"pmid":"42094346","id":"PMC_42094346","title":"Structural Activation of DNA Unwinding by MCM8/9/HROB.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/42094346","citation_count":0,"is_preprint":false},{"pmid":"41878782","id":"PMC_41878782","title":"Biallelic Germline Inactivation of HROB Causes Primary Gonadal Insufficiency and is Potentially Associated with Colonic Polyposis Predisposition.","date":"2026","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/41878782","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.07.669127","title":"MCM8/9 and FANCD2 interact within a shared pathway in response to replication stress caused by DNA crosslinks","date":"2025-08-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.07.669127","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8423,"output_tokens":2364,"usd":0.030364,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9502,"output_tokens":2692,"usd":0.057405,"stage2_stop_reason":"end_turn"},"total_usd":0.087769,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"HROB (C17orf53) is an OB-fold-containing protein that recruits the MCM8-MCM9 helicase to sites of DNA damage to promote HR-associated DNA synthesis downstream of RAD51. Mice with targeted Hrob mutations are infertile due to germ cell depletion consistent with prophase I meiotic arrest. The HROB-MCM8-MCM9 pathway acts redundantly with the HELQ helicase; cells lacking both HROB and HELQ have severely impaired HR.\",\n      \"method\": \"Targeted mouse mutagenesis, genetic epistasis (HROB/HELQ double KO), cellular HR assays, focus formation/recruitment assays\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (mouse KO, genetic epistasis, cellular HR assays, focus formation), replicated in parallel study\",\n      \"pmids\": [\"31467087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HROB (MCM8IP/C17orf53) binds ssDNA and directly associates with both the MCM8-9 helicase complex and RPA1. HROB stimulates the helicase activity of MCM8-9 in vitro, and its interactions with MCM8-9 and RPA are required for HR (specifically long-tract gene conversion downstream of RAD51 loading), replication fork progression, and cellular viability after crosslinking agent treatment.\",\n      \"method\": \"In vitro helicase activity assay with purified proteins, Co-IP/pulldown (HROB–MCM8-9 and HROB–RPA1), HR reporter assays, crosslinker/PARP inhibitor sensitivity assays in MCM8IP-deficient cells\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of helicase stimulation combined with reciprocal binding assays and cellular loss-of-function phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"32528060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C17orf53/HROB is a ssDNA- and RPA-binding protein required for interstrand crosslink (ICL) repair and efficient DNA replication; its loss leads to hypersensitivity to ATR inhibition and pronounced ICL repair defects. HROB works together with MCM8/9 to promote cell survival after ICL lesions.\",\n      \"method\": \"Genome-wide ATR-inhibitor fitness screen, multi-omics interaction studies, ssDNA/RPA-binding assays, cellular ICL sensitivity assays, DNA replication rate measurement in C17orf53 KO cells\",\n      \"journal\": \"DNA repair\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (screen, binding assays, cellular phenotypes) in single lab\",\n      \"pmids\": [\"32853826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Biochemical and structural analysis defined the HROB–MCM8-9 interaction interface: HROB makes transient contacts with both MCM8 and MCM9 subunits and binds the MCM8-9 heterodimer with highest affinity. MCM8-9-HROB preferentially binds and unwinds branched DNA structures with low processivity. MCM8-9 assembles into a hexamer from dimers on DNA in the presence of ATP via two alternating interfaces (one stable/obligate heterodimer, one labile mediating hexamer assembly). HROB does not affect ring/hexamer formation but promotes DNA unwinding downstream of loading, likely by coordinating ATP hydrolysis with translocation. The ATPase site at the labile interface contributes disproportionately more to unwinding.\",\n      \"method\": \"Molecular modeling, biochemistry (ATPase assays, helicase assays, binding assays), single-molecule experiments (unwinding processivity), mutational analysis of interfaces\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis and single-molecule experiments, peer-reviewed, preprint version also available for corroboration\",\n      \"pmids\": [\"38678026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HROB is a nuclear protein whose level peaks in S phase and is downregulated in quiescence, co-regulated with DNA replication factors. Flow cytometry FRET assays detected associations between HROB and proteins of the DNA replication machinery. Ectopic overexpression of HROB caused an almost complete shutdown of DNA replication.\",\n      \"method\": \"Flow cytometry FRET (protein–protein association), cell cycle analysis, ectopic overexpression with DNA replication readout, structural prediction/homology analysis\",\n      \"journal\": \"Genes\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single FRET method for interaction, overexpression phenotype without mechanistic resolution\",\n      \"pmids\": [\"39766854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Cryo-EM structures of MCM8/9 with DNA, HROB, and ATP analogs revealed that DNA binding induces a rotational rearrangement between N-terminal DNA-binding and C-terminal AAA+ ATPase domains, reorganizing DNA-binding loops into a staircase configuration. HROB associates with both halves of the heterohexamer and drives a similar rotation prior to DNA binding, localizing MCM8/9 to crosslink damage sites and enabling unwinding, providing a unified mechanistic model for MCM8/9 helicase activation by HROB.\",\n      \"method\": \"Cryo-electron microscopy (cryo-EM) with ATP analogs and DNA substrates, structural analysis of conformational states\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — cryo-EM structural data with functional inference, single lab, preprint not yet peer-reviewed\",\n      \"pmids\": [\"42094346\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HROB is required for MCM8/9 focus formation at ICL damage sites (functional activation context), but HROB is not required for FANCD2 binding to MCM8/9. MCM8/9 physically interacts with FANCD2 through its core domain independently of DNA, and FANCD2 acts upstream of MCM9 recruitment to ICL-induced nuclear foci downstream of FANCD2 monoubiquitination. MCM8/9 and FANCD2 are epistatic (combined loss does not cause additive DNA damage), placing MCM8/9 as a downstream effector of the FA pathway.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence focus assays, genetic epistasis (double KO γH2AX and survival assays), MCM8/9 KO cell lines\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, epistasis, and focus assays; preprint, single lab, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.08.07.669127\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HROB suppresses lung adenocarcinoma cell proliferation by interacting with ZC3HC1 and reducing its phosphorylation at Ser354, which facilitates K27-linked ubiquitination of CCNB1 and its proteasomal degradation, impairing the G2-to-M phase transition.\",\n      \"method\": \"Co-immunoprecipitation (HROB–ZC3HC1 interaction), phosphorylation analysis, ubiquitination assay, proteasomal degradation assay, cell proliferation/tumor growth assays with KO/overexpression\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, mechanistic claims rely on co-IP and overexpression without in vitro reconstitution or structural validation\",\n      \"pmids\": [\"40654113\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HROB is an OB-fold-containing, ssDNA- and RPA-binding nuclear protein that acts as a loader and activator of the MCM8-9 helicase: it recruits MCM8-9 to DNA damage sites (especially stalled forks and interstrand crosslinks), binds the MCM8-9 heterodimer at a stable interface, and promotes DNA unwinding downstream of hexamer assembly by coordinating ATP hydrolysis with MCM8-9 translocation on ssDNA, thereby driving HR-associated DNA synthesis downstream of RAD51 and enabling ICL repair in a pathway epistatic to the Fanconi anemia factor FANCD2.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HROB (C17orf53/MCM8IP) is a nuclear, OB-fold-containing protein that functions as a dedicated loader and activator of the MCM8-MCM9 helicase during homologous recombination–associated DNA synthesis [#0, #1]. It binds ssDNA and directly associates with both the MCM8-9 heterodimer and RPA1, recruiting MCM8-9 to sites of DNA damage to promote HR-associated DNA synthesis (long-tract gene conversion) downstream of RAD51 loading, and these interactions are required for replication fork progression and survival after crosslinking agents [#0, #1]. Biochemically, HROB contacts both MCM8 and MCM9 subunits and binds the heterodimer with highest affinity; it does not affect hexamer assembly but promotes DNA unwinding downstream of loading, likely by coordinating ATP hydrolysis with translocation on branched DNA substrates [#3]. Cryo-EM analysis indicates HROB drives a rotational rearrangement between the N-terminal DNA-binding and C-terminal AAA+ ATPase domains of MCM8/9 prior to DNA binding, providing a unified model for helicase activation [#5]. Functionally, HROB is required for interstrand crosslink repair and acts in a pathway epistatic to the Fanconi anemia factor FANCD2, with MCM8/9 operating as a downstream effector of the FA pathway [#2, #6]. Loss of Hrob in mice causes germ cell depletion and infertility consistent with prophase I meiotic arrest, and the HROB-MCM8-9 axis acts redundantly with the HELQ helicase [#0].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Established HROB as a recruitment factor that brings the MCM8-9 helicase to DNA damage sites to drive HR-associated DNA synthesis, defining its role downstream of RAD51 and in meiotic recombination.\",\n      \"evidence\": \"Targeted mouse mutagenesis, genetic epistasis with HELQ, cellular HR and recruitment assays\",\n      \"pmids\": [\"31467087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct biochemical interaction with MCM8-9 not yet reconstituted at this stage\",\n        \"Molecular basis of recruitment to damage sites unresolved\",\n        \"How redundancy with HELQ is partitioned mechanistically unclear\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated that HROB physically and functionally activates the helicase by binding ssDNA, MCM8-9, and RPA1, with these interactions required for long-tract gene conversion, fork progression, and crosslink survival.\",\n      \"evidence\": \"In vitro helicase assays with purified proteins, reciprocal Co-IP/pulldown, HR reporters, crosslinker/PARP inhibitor sensitivity in deficient cells\",\n      \"pmids\": [\"32528060\", \"32853826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of the HROB–MCM8-9 interface not defined\",\n        \"Mechanism by which HROB stimulates unwinding unresolved\",\n        \"ICL screen and binding data from a single lab at Medium confidence\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved the HROB–MCM8-9 interaction architecture and showed HROB promotes unwinding downstream of hexamer assembly rather than affecting ring formation, linking activation to ATP hydrolysis at a labile interface.\",\n      \"evidence\": \"Molecular modeling, ATPase/helicase/binding assays, single-molecule unwinding processivity, interface mutagenesis\",\n      \"pmids\": [\"38678026\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atomic-resolution structure of the activated complex not yet captured\",\n        \"How HROB couples ATP hydrolysis to translocation only inferred\",\n        \"Low processivity in vitro not reconciled with in vivo function\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placed HROB expression in S phase co-regulated with replication factors and detected associations with replication machinery, while overexpression suppressed replication.\",\n      \"evidence\": \"Flow cytometry FRET, cell cycle analysis, ectopic overexpression with replication readout\",\n      \"pmids\": [\"39766854\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single FRET method for interaction without orthogonal validation\",\n        \"Overexpression phenotype lacks mechanistic resolution\",\n        \"Identity of replication-machinery partners not defined\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Positioned the HROB-MCM8/9 axis as a downstream effector of the Fanconi anemia pathway, with HROB required for MCM8/9 focus formation at ICLs but dispensable for the FANCD2–MCM8/9 interaction.\",\n      \"evidence\": \"Co-IP, immunofluorescence focus assays, genetic epistasis (double KO γH2AX/survival)\",\n      \"pmids\": [\"bio_10.1101_2025.08.07.669127\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab, not yet peer-reviewed\",\n        \"How FANCD2 monoubiquitination licenses MCM9 recruitment mechanistically unresolved\",\n        \"Direct vs indirect role of HROB in focus formation not separated\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Provided a unified structural model in which HROB drives a rotational rearrangement of MCM8/9 domains prior to DNA binding to enable helicase activation.\",\n      \"evidence\": \"Cryo-EM with ATP analogs and DNA substrates, conformational state analysis\",\n      \"pmids\": [\"42094346\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab, not yet peer-reviewed\",\n        \"Functional activation inferred from static conformational states\",\n        \"Dynamics of the proposed rotation not directly observed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HROB integrates helicase activation with RPA exchange, FA-pathway signaling, and replication-coupled regulation in vivo remains to be unified.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No high-resolution structure of the fully activated HROB-MCM8/9-DNA complex in a peer-reviewed work\",\n        \"Mechanism coupling FANCD2 monoubiquitination to HROB-mediated MCM8/9 loading unresolved\",\n        \"Physiological role beyond meiosis and ICL repair not characterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-69306\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MCM8\", \"MCM9\", \"RPA1\", \"FANCD2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}