{"gene":"HAUS8","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2008,"finding":"HAUS8 (Hice1) is a microtubule-associated protein that localizes to interphase centrosomes and mitotic spindles (preferentially at spindle pole vicinity). Its N-terminal region (first 149 aa) directly binds, bundles, and stabilizes microtubules in vitro. Depletion by RNAi causes abnormal/unstable spindle configurations, mitotic delay at prometaphase/metaphase, and elevated aneuploidy, without affecting interphase centrosome duplication.","method":"RNA interference (siRNA depletion), immunofluorescence localization, in vitro microtubule bundling/stabilization assays with recombinant protein fragments, nocodazole/cold-treatment resistance assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro microtubule binding/bundling reconstitution with domain mapping, complemented by RNAi loss-of-function with defined cellular phenotypes, single lab but multiple orthogonal methods","pmids":["18362163"],"is_preprint":false},{"year":2009,"finding":"Hice1 (HAUS8) directly interacts with Hec1 via its coiled-coil domain 1; this interaction is required for centrosome-directed microtubule growth. Depletion of Hice1 reduces Hec1 levels at centrosomes; antibody neutralization of either protein impairs microtubule aster formation from purified mitotic centrosomes in vitro; overexpression of a Hice1 mutant lacking the Hec1-binding coiled-coil domain phenocopies Hec1/Hice1 depletion spindle defects.","method":"Co-immunoprecipitation, siRNA depletion, in vitro microtubule aster formation assay from purified centrosomes, antibody neutralization, overexpression of deletion mutants","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct binding mapped to specific domains, in vitro centrosome aster assay, reciprocal functional rescue experiments, single lab with multiple orthogonal methods","pmids":["19776357"],"is_preprint":false},{"year":2011,"finding":"Aurora-A kinase directly binds and phosphorylates HAUS8 (Hice1) at an N-terminal Ser/Thr-17-21 cluster, which reduces Hice1 microtubule binding activity in vitro and diminishes spindle localization in vivo. This phosphorylation (detected by phospho-Ser-19/20 antibody) occurs predominantly at spindle poles from prophase to metaphase. A phospho-mimic 17-21E mutant reduces microtubule binding and decreases Fam29a (Augmin component) association with spindles; a phospho-deficient 17-21A mutant permits intraspindle nucleation but delays spindle pole separation and mitotic progression.","method":"In vitro kinase assay, phospho-specific antibody, immunostaining, in vitro microtubule binding assay with phospho-mutants, spindle pole separation timing assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay with domain mapping, phospho-specific antibody validation, in vitro MT binding with phospho-mutants, in vivo spindle localization, single lab with multiple orthogonal methods","pmids":["21705324"],"is_preprint":false},{"year":2011,"finding":"Plk1 phosphorylates the Hice1 (HAUS8) subunit of the Augmin complex to promote the Augmin-MT interaction and MT-based MT nucleation from within the spindle. This is enabled by Cdc2-dependent phosphorylation of Nedd1 at S460, which recruits Plk1 to spindles. Loss of Plk1-dependent Hice1 phosphorylation impairs the Augmin-MT interaction, γ-tubulin recruitment to spindles, and results in improper bipolar spindle formation, mitotic arrest, and apoptosis.","method":"In vitro kinase assay, phospho-mutant rescue experiments, MT co-sedimentation/Augmin-MT interaction assay, immunofluorescence for γ-tubulin spindle recruitment, flow cytometry for mitotic arrest/apoptosis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro kinase assay, MT interaction assay, phospho-mutant functional rescue with defined molecular and cellular readouts, single lab with multiple orthogonal methods","pmids":["21690413"],"is_preprint":false},{"year":2023,"finding":"The Haus8 subunit of augmin contains two nuclear localization sequences (NLS) that overlap with its MT-binding site. Importin-α and importin-β directly bind augmin through these NLS sequences on Haus8, preventing augmin from binding microtubules; RanGTP relieves this inhibition, releasing augmin to bind MTs and promote branching MT nucleation. This was demonstrated in vitro with pulldowns and TIRF microscopy, and confirmed in Xenopus egg extract.","method":"In vitro pulldown assays, total internal reflection fluorescence (TIRF) microscopy, Xenopus egg extract, NLS mapping on Haus8 subunit","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with defined domain mapping, TIRF microscopy, Xenopus egg extract validation, replicated by independent lab (PMID:37357828)","pmids":["37086784"],"is_preprint":false},{"year":2023,"finding":"Human augmin complex is directly inhibited by importins binding to HAUS8 (among other subunits), which prevents augmin from binding microtubules. RanGTP relieves this inhibition in vitro, providing a mechanism for direct Ran-GTP regulation of branched MT nucleation around chromosomes.","method":"In vitro reconstitution of Ran-GTP-regulated MT binding, importin binding assays, biochemical pulldowns","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution, independently replicated by Kraus et al. 2023 (PMID:37086784) using orthogonal methods","pmids":["37357828"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of an augmin subcomplex on the microtubule reveals that the disordered N-terminus of Haus8 constitutes a second MT-binding site (in addition to the Haus6 CH domain). This Haus8 N-terminal site contributes to augmin's MT affinity and helps establish the shallow branch angle of branching MT nucleation.","method":"Cryo-electron microscopy structure determination, domain mutagenesis, in vitro MT binding assays, branching MT nucleation assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure with domain-level resolution, mutagenesis of MT-binding sites, functional branching angle assay, single study with multiple orthogonal methods","pmids":["41173848"],"is_preprint":false},{"year":2018,"finding":"HAUS8 co-immunoprecipitates with VISA (MAVS), RIG-I, and TBK1 upon Sendai virus infection, and overexpression of HAUS8 promotes NF-κB, IRF3, and IFN-β promoter activity while increasing polyubiquitination of VISA, RIG-I, and TBK1. Knockdown of HAUS8 inhibits IRF3, NF-κB, and IFN-β activation. Thus HAUS8 acts as a positive regulator of RLR-VISA antiviral signaling.","method":"Co-immunoprecipitation, overexpression/knockdown, luciferase reporter assays for NF-κB/IRF3/IFN-β promoter, ubiquitination assay","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and functional reporter assays, single lab, multiple complementary methods but no structural or reconstitution validation; role is unexpected given the protein's canonical function","pmids":["29916539"],"is_preprint":false},{"year":2024,"finding":"Co-depletion of HAUS8 in KIF18A-depleted RPE-1 cells rescues mitotic errors (lagging chromosomes, micronuclei) by shortening antiparallel MT overlaps, slowing microtubule poleward flux, and improving chromosome alignment. Speckle microscopy showed slower growth and flux of kinetochore MTs in the rescue condition, placing HAUS8 as a contributor to spindle flux and chromosome alignment fidelity.","method":"siRNA co-depletion, live-cell imaging, speckle microscopy, measurement of MT overlap length and poleward flux rates","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (co-depletion rescue), speckle microscopy with quantitative flux measurements, single study but multiple quantitative readouts","pmids":["39541344"],"is_preprint":false}],"current_model":"HAUS8 (Hice1) is a subunit of the eight-subunit augmin complex that binds microtubules via its disordered N-terminus (establishing branch angle in cooperation with the Haus6 CH domain), is recruited to spindles through a Ran-GTP/importin-regulated mechanism (importins bind the Haus8 NLS, blocking MT interaction until released by RanGTP), and is phosphorylated by Aurora-A (at Ser17-21) and Plk1 to fine-tune its MT-binding activity and Augmin complex recruitment during bipolar spindle assembly; it also interacts with Hec1 at the spindle pole to support centrosomal MT nucleation, and loss of HAUS8 causes spindle instability, chromosome segregation errors, and mitotic arrest."},"narrative":{"mechanistic_narrative":"HAUS8 (Hice1) is a microtubule-associated subunit of the augmin complex that drives microtubule-based microtubule nucleation during bipolar spindle assembly [PMID:18362163, PMID:41173848]. Its disordered N-terminal region directly binds, bundles, and stabilizes microtubules and constitutes a second MT-binding site within augmin (alongside the Haus6 CH domain), where it contributes to MT affinity and establishes the shallow branch angle characteristic of branching nucleation [PMID:18362163, PMID:41173848]. Augmin engagement with microtubules is spatially gated by the Ran system: importin-α/β bind NLS sequences on HAUS8 that overlap its MT-binding site, blocking MT interaction until RanGTP releases the inhibition near chromosomes [PMID:37086784, PMID:37357828]. This activity is further tuned by mitotic kinases—Aurora-A phosphorylates an N-terminal Ser/Thr-17-21 cluster to reduce MT binding and spindle localization, while Plk1 phosphorylation promotes the augmin-MT interaction and γ-tubulin recruitment to spindles [PMID:21705324, PMID:21690413]. HAUS8 also interacts with Hec1 through its first coiled-coil domain to support centrosome-directed microtubule growth, and contributes to spindle poleward flux and chromosome alignment fidelity [PMID:19776357, PMID:39541344]. Depletion produces unstable spindles, mitotic delay, and aneuploidy [PMID:18362163]. Beyond its mitotic role, HAUS8 has been reported as a positive regulator of RIG-I/MAVS antiviral signaling [PMID:29916539].","teleology":[{"year":2008,"claim":"Established HAUS8 as a microtubule-associated protein with intrinsic MT-binding activity and a mitotic spindle function, answering whether the protein acts directly on microtubules.","evidence":"RNAi depletion with spindle phenotyping plus in vitro MT bundling/stabilization with recombinant N-terminal fragments","pmids":["18362163"],"confidence":"High","gaps":["Did not place HAUS8 within the augmin complex","Mechanism of spindle recruitment unknown"]},{"year":2009,"claim":"Identified a direct Hice1-Hec1 interaction required for centrosome-directed MT growth, linking HAUS8 to centrosomal nucleation.","evidence":"Co-IP, domain-mapped binding via coiled-coil 1, in vitro centrosome aster assay with antibody neutralization and deletion-mutant rescue","pmids":["19776357"],"confidence":"High","gaps":["Structural basis of the coiled-coil interaction not resolved","Relationship to augmin-dependent branching nucleation not addressed"]},{"year":2011,"claim":"Showed that Aurora-A and Plk1 phosphorylation tune HAUS8 MT-binding and augmin recruitment, establishing kinase control over branching nucleation timing.","evidence":"In vitro kinase assays, phospho-specific antibodies, phospho-mimic/deficient mutants in MT binding and spindle localization, MT co-sedimentation and γ-tubulin recruitment readouts","pmids":["21705324","21690413"],"confidence":"High","gaps":["Interplay between Aurora-A and Plk1 inputs not integrated","Quantitative contribution of each phospho-site to spindle assembly in vivo unclear"]},{"year":2023,"claim":"Defined the Ran-GTP/importin mechanism that spatially restricts augmin MT binding via NLS sequences on HAUS8, explaining how branching nucleation is targeted near chromosomes.","evidence":"In vitro pulldowns, TIRF microscopy, NLS mapping on Haus8, and Xenopus egg extract validation; independently replicated","pmids":["37086784","37357828"],"confidence":"High","gaps":["Crosstalk between importin gating and kinase phosphorylation not resolved","In-cell quantification of the RanGTP gradient effect on HAUS8 limited"]},{"year":2025,"claim":"Provided structural evidence that the disordered HAUS8 N-terminus forms a second MT-binding site shaping the augmin branch angle, defining its mechanical role in branching geometry.","evidence":"Cryo-EM of an augmin subcomplex on microtubules with domain mutagenesis and branching nucleation assays","pmids":["41173848"],"confidence":"High","gaps":["Full-complex structure with all subunits not resolved","How phosphorylation and importin binding alter this interface structurally unknown"]},{"year":2024,"claim":"Positioned HAUS8 as a contributor to spindle poleward flux and chromosome alignment through epistasis with KIF18A.","evidence":"siRNA co-depletion rescue in RPE-1 cells with live-cell and speckle microscopy measuring MT overlap and flux","pmids":["39541344"],"confidence":"Medium","gaps":["Direct molecular link between HAUS8 and flux machinery not established","Single-study epistasis without reconstitution"]},{"year":2018,"claim":"Reported a non-mitotic role for HAUS8 as a positive regulator of RIG-I/MAVS antiviral innate immune signaling.","evidence":"Co-IP with VISA/RIG-I/TBK1, overexpression/knockdown, luciferase reporters, and ubiquitination assays after Sendai virus infection","pmids":["29916539"],"confidence":"Medium","gaps":["Single lab, no structural or reconstitution validation","Mechanism linking augmin function to antiviral signaling unexplained","Role unexpected given canonical spindle function"]},{"year":null,"claim":"How importin gating, Aurora-A/Plk1 phosphorylation, and the structural MT-binding interface are integrated into a single regulated nucleation event remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No unified model coordinating spatial (Ran) and temporal (kinase) control","Reconciliation of mitotic and antiviral functions absent"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,6]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,6]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,6]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[4,6]}],"complexes":["augmin"],"partners":["HAUS6","NDC80","KPNA","KPNB1","AURKA","PLK1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BT25","full_name":"HAUS augmin-like complex subunit 8","aliases":["HEC1/NDC80-interacting centrosome-associated protein 1","Sarcoma antigen NY-SAR-48"],"length_aa":410,"mass_kda":44.9,"function":"Contributes to mitotic spindle assembly, maintenance of centrosome integrity and completion of cytokinesis as part of the HAUS augmin-like complex","subcellular_location":"Cytoplasm; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cytoplasm, cytoskeleton, spindle; Cytoplasm, cytoskeleton, spindle pole","url":"https://www.uniprot.org/uniprotkb/Q9BT25/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/HAUS8","classification":"Common Essential","n_dependent_lines":1004,"n_total_lines":1208,"dependency_fraction":0.8311258278145696},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HAUS8","total_profiled":1310},"omim":[{"mim_id":"613434","title":"HAUS AUGMIN-LIKE COMPLEX, SUBUNIT 8; HAUS8","url":"https://www.omim.org/entry/613434"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HAUS8"},"hgnc":{"alias_symbol":["MGC20533","NY-SAR-48"],"prev_symbol":["HICE1"]},"alphafold":{"accession":"Q9BT25","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BT25","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BT25-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BT25-F1-predicted_aligned_error_v6.png","plddt_mean":68.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HAUS8","jax_strain_url":"https://www.jax.org/strain/search?query=HAUS8"},"sequence":{"accession":"Q9BT25","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BT25.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BT25/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BT25"}},"corpus_meta":[{"pmid":"21690413","id":"PMC_21690413","title":"Regulation of microtubule-based microtubule nucleation by mammalian polo-like kinase 1.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21690413","citation_count":71,"is_preprint":false},{"pmid":"28709640","id":"PMC_28709640","title":"Genome-wide identification of genes essential for podocyte cytoskeletons based on single-cell RNA sequencing.","date":"2017","source":"Kidney international","url":"https://pubmed.ncbi.nlm.nih.gov/28709640","citation_count":69,"is_preprint":false},{"pmid":"18362163","id":"PMC_18362163","title":"Hice1, a novel microtubule-associated protein required for maintenance of spindle integrity and chromosomal stability in human cells.","date":"2008","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18362163","citation_count":57,"is_preprint":false},{"pmid":"26061684","id":"PMC_26061684","title":"Alterations of the spindle checkpoint pathway in clinicopathologically aggressive CpG island methylator phenotype clear cell renal cell carcinomas.","date":"2015","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26061684","citation_count":37,"is_preprint":false},{"pmid":"21705324","id":"PMC_21705324","title":"Aurora-A phosphorylates Augmin complex component Hice1 protein at an N-terminal serine/threonine cluster to modulate its microtubule binding activity during spindle assembly.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21705324","citation_count":30,"is_preprint":false},{"pmid":"37357828","id":"PMC_37357828","title":"Microtubule binding of the human augmin complex is directly controlled by importins and Ran-GTP.","date":"2023","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/37357828","citation_count":20,"is_preprint":false},{"pmid":"29916539","id":"PMC_29916539","title":"HAUS8 regulates RLR‑VISA antiviral signaling positively by targeting VISA.","date":"2018","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/29916539","citation_count":19,"is_preprint":false},{"pmid":"19776357","id":"PMC_19776357","title":"Hec1 contributes to mitotic centrosomal microtubule growth for proper spindle assembly through interaction with Hice1.","date":"2009","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19776357","citation_count":18,"is_preprint":false},{"pmid":"37086784","id":"PMC_37086784","title":"Augmin is a Ran-regulated spindle assembly factor.","date":"2023","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/37086784","citation_count":17,"is_preprint":false},{"pmid":"38616878","id":"PMC_38616878","title":"Genome-wide association studies to identify quantitative trait loci and positional candidate genes affecting meat quality-related traits in pigs.","date":"2023","source":"Journal of animal science and technology","url":"https://pubmed.ncbi.nlm.nih.gov/38616878","citation_count":5,"is_preprint":false},{"pmid":"39541344","id":"PMC_39541344","title":"Microtubule poleward flux as a target for modifying chromosome segregation errors.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/39541344","citation_count":2,"is_preprint":false},{"pmid":"35954157","id":"PMC_35954157","title":"Kidney Cancer Biomarker Selection Using Regularized Survival Models.","date":"2022","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/35954157","citation_count":1,"is_preprint":false},{"pmid":"41173848","id":"PMC_41173848","title":"How augmin establishes the angle of the microtubule branch site.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/41173848","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8741,"output_tokens":2845,"usd":0.034449,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10131,"output_tokens":2654,"usd":0.058502,"stage2_stop_reason":"end_turn"},"total_usd":0.092951,"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\": 2008,\n      \"finding\": \"HAUS8 (Hice1) is a microtubule-associated protein that localizes to interphase centrosomes and mitotic spindles (preferentially at spindle pole vicinity). Its N-terminal region (first 149 aa) directly binds, bundles, and stabilizes microtubules in vitro. Depletion by RNAi causes abnormal/unstable spindle configurations, mitotic delay at prometaphase/metaphase, and elevated aneuploidy, without affecting interphase centrosome duplication.\",\n      \"method\": \"RNA interference (siRNA depletion), immunofluorescence localization, in vitro microtubule bundling/stabilization assays with recombinant protein fragments, nocodazole/cold-treatment resistance assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro microtubule binding/bundling reconstitution with domain mapping, complemented by RNAi loss-of-function with defined cellular phenotypes, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"18362163\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Hice1 (HAUS8) directly interacts with Hec1 via its coiled-coil domain 1; this interaction is required for centrosome-directed microtubule growth. Depletion of Hice1 reduces Hec1 levels at centrosomes; antibody neutralization of either protein impairs microtubule aster formation from purified mitotic centrosomes in vitro; overexpression of a Hice1 mutant lacking the Hec1-binding coiled-coil domain phenocopies Hec1/Hice1 depletion spindle defects.\",\n      \"method\": \"Co-immunoprecipitation, siRNA depletion, in vitro microtubule aster formation assay from purified centrosomes, antibody neutralization, overexpression of deletion mutants\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct binding mapped to specific domains, in vitro centrosome aster assay, reciprocal functional rescue experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19776357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Aurora-A kinase directly binds and phosphorylates HAUS8 (Hice1) at an N-terminal Ser/Thr-17-21 cluster, which reduces Hice1 microtubule binding activity in vitro and diminishes spindle localization in vivo. This phosphorylation (detected by phospho-Ser-19/20 antibody) occurs predominantly at spindle poles from prophase to metaphase. A phospho-mimic 17-21E mutant reduces microtubule binding and decreases Fam29a (Augmin component) association with spindles; a phospho-deficient 17-21A mutant permits intraspindle nucleation but delays spindle pole separation and mitotic progression.\",\n      \"method\": \"In vitro kinase assay, phospho-specific antibody, immunostaining, in vitro microtubule binding assay with phospho-mutants, spindle pole separation timing assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay with domain mapping, phospho-specific antibody validation, in vitro MT binding with phospho-mutants, in vivo spindle localization, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"21705324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Plk1 phosphorylates the Hice1 (HAUS8) subunit of the Augmin complex to promote the Augmin-MT interaction and MT-based MT nucleation from within the spindle. This is enabled by Cdc2-dependent phosphorylation of Nedd1 at S460, which recruits Plk1 to spindles. Loss of Plk1-dependent Hice1 phosphorylation impairs the Augmin-MT interaction, γ-tubulin recruitment to spindles, and results in improper bipolar spindle formation, mitotic arrest, and apoptosis.\",\n      \"method\": \"In vitro kinase assay, phospho-mutant rescue experiments, MT co-sedimentation/Augmin-MT interaction assay, immunofluorescence for γ-tubulin spindle recruitment, flow cytometry for mitotic arrest/apoptosis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro kinase assay, MT interaction assay, phospho-mutant functional rescue with defined molecular and cellular readouts, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"21690413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The Haus8 subunit of augmin contains two nuclear localization sequences (NLS) that overlap with its MT-binding site. Importin-α and importin-β directly bind augmin through these NLS sequences on Haus8, preventing augmin from binding microtubules; RanGTP relieves this inhibition, releasing augmin to bind MTs and promote branching MT nucleation. This was demonstrated in vitro with pulldowns and TIRF microscopy, and confirmed in Xenopus egg extract.\",\n      \"method\": \"In vitro pulldown assays, total internal reflection fluorescence (TIRF) microscopy, Xenopus egg extract, NLS mapping on Haus8 subunit\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with defined domain mapping, TIRF microscopy, Xenopus egg extract validation, replicated by independent lab (PMID:37357828)\",\n      \"pmids\": [\"37086784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Human augmin complex is directly inhibited by importins binding to HAUS8 (among other subunits), which prevents augmin from binding microtubules. RanGTP relieves this inhibition in vitro, providing a mechanism for direct Ran-GTP regulation of branched MT nucleation around chromosomes.\",\n      \"method\": \"In vitro reconstitution of Ran-GTP-regulated MT binding, importin binding assays, biochemical pulldowns\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution, independently replicated by Kraus et al. 2023 (PMID:37086784) using orthogonal methods\",\n      \"pmids\": [\"37357828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of an augmin subcomplex on the microtubule reveals that the disordered N-terminus of Haus8 constitutes a second MT-binding site (in addition to the Haus6 CH domain). This Haus8 N-terminal site contributes to augmin's MT affinity and helps establish the shallow branch angle of branching MT nucleation.\",\n      \"method\": \"Cryo-electron microscopy structure determination, domain mutagenesis, in vitro MT binding assays, branching MT nucleation assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure with domain-level resolution, mutagenesis of MT-binding sites, functional branching angle assay, single study with multiple orthogonal methods\",\n      \"pmids\": [\"41173848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HAUS8 co-immunoprecipitates with VISA (MAVS), RIG-I, and TBK1 upon Sendai virus infection, and overexpression of HAUS8 promotes NF-κB, IRF3, and IFN-β promoter activity while increasing polyubiquitination of VISA, RIG-I, and TBK1. Knockdown of HAUS8 inhibits IRF3, NF-κB, and IFN-β activation. Thus HAUS8 acts as a positive regulator of RLR-VISA antiviral signaling.\",\n      \"method\": \"Co-immunoprecipitation, overexpression/knockdown, luciferase reporter assays for NF-κB/IRF3/IFN-β promoter, ubiquitination assay\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and functional reporter assays, single lab, multiple complementary methods but no structural or reconstitution validation; role is unexpected given the protein's canonical function\",\n      \"pmids\": [\"29916539\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Co-depletion of HAUS8 in KIF18A-depleted RPE-1 cells rescues mitotic errors (lagging chromosomes, micronuclei) by shortening antiparallel MT overlaps, slowing microtubule poleward flux, and improving chromosome alignment. Speckle microscopy showed slower growth and flux of kinetochore MTs in the rescue condition, placing HAUS8 as a contributor to spindle flux and chromosome alignment fidelity.\",\n      \"method\": \"siRNA co-depletion, live-cell imaging, speckle microscopy, measurement of MT overlap length and poleward flux rates\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (co-depletion rescue), speckle microscopy with quantitative flux measurements, single study but multiple quantitative readouts\",\n      \"pmids\": [\"39541344\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HAUS8 (Hice1) is a subunit of the eight-subunit augmin complex that binds microtubules via its disordered N-terminus (establishing branch angle in cooperation with the Haus6 CH domain), is recruited to spindles through a Ran-GTP/importin-regulated mechanism (importins bind the Haus8 NLS, blocking MT interaction until released by RanGTP), and is phosphorylated by Aurora-A (at Ser17-21) and Plk1 to fine-tune its MT-binding activity and Augmin complex recruitment during bipolar spindle assembly; it also interacts with Hec1 at the spindle pole to support centrosomal MT nucleation, and loss of HAUS8 causes spindle instability, chromosome segregation errors, and mitotic arrest.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HAUS8 (Hice1) is a microtubule-associated subunit of the augmin complex that drives microtubule-based microtubule nucleation during bipolar spindle assembly [#0, #6]. Its disordered N-terminal region directly binds, bundles, and stabilizes microtubules and constitutes a second MT-binding site within augmin (alongside the Haus6 CH domain), where it contributes to MT affinity and establishes the shallow branch angle characteristic of branching nucleation [#0, #6]. Augmin engagement with microtubules is spatially gated by the Ran system: importin-\\u03b1/\\u03b2 bind NLS sequences on HAUS8 that overlap its MT-binding site, blocking MT interaction until RanGTP releases the inhibition near chromosomes [#4, #5]. This activity is further tuned by mitotic kinases\\u2014Aurora-A phosphorylates an N-terminal Ser/Thr-17-21 cluster to reduce MT binding and spindle localization, while Plk1 phosphorylation promotes the augmin-MT interaction and \\u03b3-tubulin recruitment to spindles [#2, #3]. HAUS8 also interacts with Hec1 through its first coiled-coil domain to support centrosome-directed microtubule growth, and contributes to spindle poleward flux and chromosome alignment fidelity [#1, #8]. Depletion produces unstable spindles, mitotic delay, and aneuploidy [#0]. Beyond its mitotic role, HAUS8 has been reported as a positive regulator of RIG-I/MAVS antiviral signaling [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established HAUS8 as a microtubule-associated protein with intrinsic MT-binding activity and a mitotic spindle function, answering whether the protein acts directly on microtubules.\",\n      \"evidence\": \"RNAi depletion with spindle phenotyping plus in vitro MT bundling/stabilization with recombinant N-terminal fragments\",\n      \"pmids\": [\"18362163\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not place HAUS8 within the augmin complex\", \"Mechanism of spindle recruitment unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified a direct Hice1-Hec1 interaction required for centrosome-directed MT growth, linking HAUS8 to centrosomal nucleation.\",\n      \"evidence\": \"Co-IP, domain-mapped binding via coiled-coil 1, in vitro centrosome aster assay with antibody neutralization and deletion-mutant rescue\",\n      \"pmids\": [\"19776357\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the coiled-coil interaction not resolved\", \"Relationship to augmin-dependent branching nucleation not addressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed that Aurora-A and Plk1 phosphorylation tune HAUS8 MT-binding and augmin recruitment, establishing kinase control over branching nucleation timing.\",\n      \"evidence\": \"In vitro kinase assays, phospho-specific antibodies, phospho-mimic/deficient mutants in MT binding and spindle localization, MT co-sedimentation and \\u03b3-tubulin recruitment readouts\",\n      \"pmids\": [\"21705324\", \"21690413\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Interplay between Aurora-A and Plk1 inputs not integrated\", \"Quantitative contribution of each phospho-site to spindle assembly in vivo unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the Ran-GTP/importin mechanism that spatially restricts augmin MT binding via NLS sequences on HAUS8, explaining how branching nucleation is targeted near chromosomes.\",\n      \"evidence\": \"In vitro pulldowns, TIRF microscopy, NLS mapping on Haus8, and Xenopus egg extract validation; independently replicated\",\n      \"pmids\": [\"37086784\", \"37357828\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crosstalk between importin gating and kinase phosphorylation not resolved\", \"In-cell quantification of the RanGTP gradient effect on HAUS8 limited\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided structural evidence that the disordered HAUS8 N-terminus forms a second MT-binding site shaping the augmin branch angle, defining its mechanical role in branching geometry.\",\n      \"evidence\": \"Cryo-EM of an augmin subcomplex on microtubules with domain mutagenesis and branching nucleation assays\",\n      \"pmids\": [\"41173848\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-complex structure with all subunits not resolved\", \"How phosphorylation and importin binding alter this interface structurally unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Positioned HAUS8 as a contributor to spindle poleward flux and chromosome alignment through epistasis with KIF18A.\",\n      \"evidence\": \"siRNA co-depletion rescue in RPE-1 cells with live-cell and speckle microscopy measuring MT overlap and flux\",\n      \"pmids\": [\"39541344\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link between HAUS8 and flux machinery not established\", \"Single-study epistasis without reconstitution\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Reported a non-mitotic role for HAUS8 as a positive regulator of RIG-I/MAVS antiviral innate immune signaling.\",\n      \"evidence\": \"Co-IP with VISA/RIG-I/TBK1, overexpression/knockdown, luciferase reporters, and ubiquitination assays after Sendai virus infection\",\n      \"pmids\": [\"29916539\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab, no structural or reconstitution validation\", \"Mechanism linking augmin function to antiviral signaling unexplained\", \"Role unexpected given canonical spindle function\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How importin gating, Aurora-A/Plk1 phosphorylation, and the structural MT-binding interface are integrated into a single regulated nucleation event remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No unified model coordinating spatial (Ran) and temporal (kinase) control\", \"Reconciliation of mitotic and antiviral functions absent\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [4, 6]}\n    ],\n    \"complexes\": [\"augmin\"],\n    \"partners\": [\"HAUS6\", \"NDC80\", \"KPNA\", \"KPNB1\", \"AURKA\", \"PLK1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}