{"gene":"HSPBP1","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2005,"finding":"HspBP1 acts as a nucleotide exchange factor (NEF) for Hsp70 via a mechanism distinct from BAG-1 or GrpE: its curved, all alpha-helical armadillo-repeat fold embraces lobe II of the Hsp70 ATPase domain, and steric conflict displaces lobe I, reducing nucleotide affinity, rather than triggering a conformational change in lobe II as the other NEFs do.","method":"Crystal structure of HspBP1 alone and in complex with Hsp70 ATPase domain; in vitro nucleotide exchange assays; yeast genetic analysis (Fes1p deletion)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation, highly cited foundational paper","pmids":["15694338"],"is_preprint":false},{"year":2004,"finding":"HspBP1 inhibits the ubiquitin ligase activity of CHIP when complexed with Hsc70, thereby interfering with CHIP-induced proteasomal degradation of immature CFTR and stimulating CFTR maturation.","method":"Co-immunoprecipitation; in vitro ubiquitin ligase assays; CFTR maturation assays; overexpression and knockdown in cells","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (Co-IP, in vitro ubiquitylation, cellular CFTR maturation), highly cited","pmids":["15215316"],"is_preprint":false},{"year":2002,"finding":"HspBP1 is a nucleotide exchange factor that promotes nucleotide dissociation from mammalian Hsc70 (and yeast Ssa1p/BiP), and unlike its yeast ortholog Fes1p, inhibits chaperone-mediated protein refolding in vitro.","method":"In vitro nucleotide dissociation assays; in vitro luciferase refolding assays","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro NEF and refolding assays, replicated by multiple groups","pmids":["12417338"],"is_preprint":false},{"year":2018,"finding":"HspBP1 employs a flexible N-terminal release domain (RD) with substrate-mimicking properties that contacts the substrate-binding domain of Hsp70, competes with peptide substrate for binding, and is essential for efficient release of persistent substrates from Hsp70; the armadillo domain triggers nucleotide exchange while the RD safeguards substrate release.","method":"In vitro binding and competition assays with recombinant proteins; mutagenesis of the release domain; yeast and mammalian cell functional assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1-2 — reconstitution, domain mutagenesis, and cellular functional validation in two organisms","pmids":["29323280"],"is_preprint":false},{"year":2003,"finding":"HspBP1 has two structural domains: an unstructured N-terminal domain I (aa 1-83) and an alpha-helical domain II (aa 84-359); domain II alone is sufficient to bind Hsp70 and alter the conformation of its ATPase domain, and domain I augments these functions.","method":"Circular dichroism; limited proteolysis; truncation mutagenesis; in vitro luciferase refolding assay; reticulocyte lysate binding assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 — multiple in vitro methods, single lab","pmids":["12651857"],"is_preprint":false},{"year":2003,"finding":"Hsp40 and TPR1 cooperatively reverse HspBP1-mediated inhibition of Hsp70-dependent protein folding; the Hsp70-HspBP1 complex is dissociated only in the presence of both Hsp40 and TPR1 together, revealing a cooperative regulatory mechanism.","method":"In vitro luciferase refolding assays; Kd measurements; competition assays; tetracycline-inducible HeLa cell system","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (in vitro and cellular), single lab","pmids":["14503850"],"is_preprint":false},{"year":2014,"finding":"HSPBP1 inhibits ubiquitylation and proteasomal degradation of inducible HSP70 proteins (HSPA1L and HSPA2) at a posttranslational level; loss of HSPBP1 in mice causes male sterility due to impaired meiosis and massive spermatocyte apoptosis linked to loss of HSPA2-dependent synaptonemal complex disassembly.","method":"HSPBP1 knockout mouse generation; Western blot analysis of HSP70 protein levels; ubiquitylation assays; histological analysis of testes","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype plus mechanistic ubiquitylation assays","pmids":["24899640"],"is_preprint":false},{"year":2017,"finding":"Neurons express abundant HspBP1, which inhibits CHIP activity and thereby reduces CHIP-mediated K48-linked polyubiquitination and degradation of misfolded proteins including mutant huntingtin; CRISPR-Cas9 silencing of HspBP1 in neurons ameliorated mHtt aggregation and neuropathology in HD knockin mice.","method":"Western blot; co-immunoprecipitation; CHIP ubiquitination assays; CRISPR-Cas9 knockdown in neurons; HD knockin mouse model analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including in vivo CRISPR rescue experiment","pmids":["28847953"],"is_preprint":false},{"year":2014,"finding":"HspBP1 reduces Hsp70 binding to the ligand-binding domain of glucocorticoid receptor (GR) and inhibits GR, mineralocorticoid receptor (MR), and androgen receptor (AR) transcriptional activity, in contrast to BAG-1M which shows a dose-dependent biphasic effect; HspBP1 and BAG-1M differentially regulate the composition of steroid receptor-chaperone folding complexes.","method":"Co-immunoprecipitation; GST pull-down assays; reporter gene assays; overexpression in cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple assays (pull-down, co-IP, reporter), single lab","pmids":["24454860"],"is_preprint":false},{"year":2011,"finding":"HspBP1 binds both Hsp70 and Tag7 (PGRP-S innate immunity protein); this interaction eliminates the cytotoxic activity of the Tag7-Hsp70 complex, decreases the ATP concentration required to dissociate Tag7 from Hsp70's peptide-binding site, and inhibits cytotoxic activity secreted by CD8+ lymphocytes.","method":"Co-immunoprecipitation; cytotoxicity assays; biochemical binding assays with purified proteins","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct binding demonstrated plus functional consequence, single lab","pmids":["21247889"],"is_preprint":false},{"year":2007,"finding":"HspBP1 antagonizes the prosurvival function of Hsp70 in a manner dependent on its ability to bind Hsp70; ectopic HspBP1 expression promotes lysosomal membrane permeabilization, cathepsin release to cytosol, and caspase-3 activation in response to anticancer drugs.","method":"RNA interference; ectopic overexpression; lysosomal integrity assays; cathepsin release assays; caspase-3 activation assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple cellular assays with binding-deficient mutant controls, single lab","pmids":["17855353"],"is_preprint":false},{"year":2020,"finding":"HspBP1 is a component of stress granules (SGs) that regulates their formation: it colocalizes with G3BP1, HuR and TIA-1/TIAR in SGs, associates with these SG proteins by co-immunoprecipitation, binds polyA-RNA directly in vitro, and its knockdown impairs stress-induced SG assembly while overexpression promotes SG formation even in the absence of stress.","method":"Immunofluorescence microscopy; co-immunoprecipitation; mass spectrometry; in vitro RNA binding; siRNA knockdown and overexpression","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple orthogonal methods including direct RNA binding in vitro, single lab","pmids":["32235396"],"is_preprint":false},{"year":2021,"finding":"HSPBP1 promotes RIG-I-mediated antiviral signaling by inhibiting K48-linked ubiquitination of RIG-I, thereby stabilizing RIG-I protein levels and promoting IRF3 activation and IFN-β production in response to Sendai virus infection.","method":"Overexpression and knockdown/knockout; ubiquitination assays; co-immunoprecipitation; IRF3 phosphorylation assays; IFN-β reporter/ELISA","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple assays (ubiquitination, IRF3 activation, IFN-β) with KO/KD, single lab","pmids":["33713958"],"is_preprint":false},{"year":2022,"finding":"HspBP1 interacts with BRCA1 and promotes BRCA1-mediated homologous recombination DNA repair; independently of BRCA1 status, HspBP1 also interferes with the association of Hsp70 and Apaf-1 (apoptotic protease-activating factor-1), facilitating cell survival after ionizing radiation.","method":"Co-immunoprecipitation; homologous recombination reporter assays; knockdown and overexpression; xenograft tumor models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and functional HR assays, single lab","pmids":["35387978"],"is_preprint":false},{"year":2009,"finding":"Extracellular HspBP1 (e-HspBP1) co-immunoprecipitates with extracellular Hsp72 in conditioned medium; purified recombinant HspBP1 augments e-Hsp72-mediated phosphorylation of EGFR and downstream ERK1/2 in a concentration-dependent manner, and this activity requires the HspBP1 N-terminal domain.","method":"Co-immunoprecipitation from conditioned medium; EGFR and ERK phosphorylation assays; deletion mutant analysis; secretion assays","journal":"Biology of the cell","confidence":"Low","confidence_rationale":"Tier 3 — single co-IP plus downstream signaling assay, single lab","pmids":["18986301"],"is_preprint":false},{"year":2026,"finding":"HSPBP1 Cys201 was identified as an upstream cellular target contributing to necroptosis regulation; covalent modification of HSPBP1 at Cys201 by parthenolide (confirmed by mass spectrometry co-incubation) confers anti-necroptotic activity, and HSPBP1 knockdown reduces sensitivity to necroptosis.","method":"Mass spectrometry covalent modification mapping; HSPBP1 knockdown; co-incubation of purified HSPBP1 with parthenolide; necroptosis assays","journal":"Cell death & disease","confidence":"Low","confidence_rationale":"Tier 3 — single lab, mass spectrometry identification of modification site without full mechanistic follow-up of how HSPBP1 modulates the necroptosis pathway","pmids":["42014672"],"is_preprint":false}],"current_model":"HSPBP1 is an armadillo-repeat cochaperone that acts as a nucleotide exchange factor for Hsp70/Hsc70 by sterically displacing lobe I of the ATPase domain (distinct from the BAG-1/GrpE mechanism), and employs a flexible N-terminal release domain to mimic substrate and ensure efficient substrate release from Hsp70; it also inhibits the CHIP ubiquitin ligase when complexed with Hsc70, thereby promoting folding over degradation of client proteins such as CFTR and inducible HSP70 family members, regulates steroid receptor and RIG-I stability, participates in stress granule biogenesis, and its loss in mice causes spermatocyte apoptosis and male sterility."},"narrative":{"teleology":[{"year":2002,"claim":"Establishing that HSPBP1 is a nucleotide exchange factor for Hsc70 answered whether this cochaperone directly modulates the Hsp70 ATPase cycle, setting the stage for understanding its role in chaperone regulation.","evidence":"In vitro nucleotide dissociation and luciferase refolding assays with mammalian and yeast Hsp70 proteins","pmids":["12417338"],"confidence":"High","gaps":["No structural basis for NEF activity","Inhibition of refolding in vitro not reconciled with in vivo function"]},{"year":2003,"claim":"Defining the two-domain architecture of HSPBP1 — an unstructured N-terminal domain I and an alpha-helical domain II sufficient for Hsp70 binding — and identifying cooperative reversal of HspBP1 inhibition by Hsp40 plus TPR1 resolved how the cochaperone is structurally organized and dynamically regulated within the chaperone network.","evidence":"Circular dichroism, limited proteolysis, truncation mutagenesis, and in vitro cooperative refolding assays","pmids":["12651857","14503850"],"confidence":"Medium","gaps":["No atomic resolution structure of isolated HSPBP1","Cooperative mechanism of Hsp40/TPR1 reversal unclear at a structural level"]},{"year":2004,"claim":"Demonstrating that HSPBP1 inhibits CHIP ubiquitin ligase activity when complexed with Hsc70, thereby promoting CFTR maturation over degradation, established HSPBP1 as a triage factor that tips protein quality control toward folding.","evidence":"Co-immunoprecipitation, in vitro ubiquitin ligase assays, and cellular CFTR maturation assays with overexpression and knockdown","pmids":["15215316"],"confidence":"High","gaps":["Whether HSPBP1 directly contacts CHIP or acts indirectly through Hsc70 conformation not resolved","Range of CHIP substrates affected unknown"]},{"year":2005,"claim":"The crystal structure of HSPBP1 in complex with the Hsp70 ATPase domain revealed a novel NEF mechanism in which an armadillo-repeat fold embraces lobe II and sterically displaces lobe I, distinguishing HSPBP1 from all previously characterized NEFs.","evidence":"X-ray crystallography of HspBP1 alone and in complex with Hsp70 ATPase domain; in vitro nucleotide exchange assays; yeast Fes1p deletion complementation","pmids":["15694338"],"confidence":"High","gaps":["No structure of full-length HSPBP1 including the N-terminal domain","Dynamics of lobe I displacement not captured"]},{"year":2007,"claim":"Showing that HSPBP1 antagonizes the prosurvival function of Hsp70 by promoting lysosomal membrane permeabilization and caspase-3 activation broadened its role beyond protein folding to regulation of cell death pathways.","evidence":"RNA interference, overexpression with binding-deficient mutant controls, lysosomal integrity and cathepsin release assays in cancer cell lines","pmids":["17855353"],"confidence":"Medium","gaps":["Mechanism linking Hsp70 dissociation to lysosomal destabilization not defined","Relevance to physiological (non-drug-induced) cell death unclear"]},{"year":2014,"claim":"HSPBP1 knockout mice revealed an essential in vivo role: HSPBP1 prevents ubiquitin-dependent degradation of inducible HSP70 proteins (HSPA2), and its loss causes meiotic failure, spermatocyte apoptosis, and male sterility, establishing a physiological client-stabilization function.","evidence":"HSPBP1 knockout mouse; Western blot and ubiquitination assays; testis histology","pmids":["24899640"],"confidence":"High","gaps":["Whether HSPBP1 loss affects female fertility or other tissues not explored","Identity of the E3 ligase degrading HSPA2 in the absence of HSPBP1 not established"]},{"year":2014,"claim":"HSPBP1 modulates steroid receptor signaling by reducing Hsp70 binding to the ligand-binding domain of glucocorticoid, mineralocorticoid, and androgen receptors, revealing a nuclear-receptor-specific regulatory axis distinct from BAG-1M.","evidence":"Co-immunoprecipitation, GST pull-down, and reporter gene assays in cell lines","pmids":["24454860"],"confidence":"Medium","gaps":["Physiological relevance in endocrine tissues not tested in vivo","Structural basis for differential effects versus BAG-1M unknown"]},{"year":2017,"claim":"In neurons, abundant HSPBP1 suppresses CHIP-mediated K48-polyubiquitination of misfolded proteins including mutant huntingtin; CRISPR-Cas9 silencing of HSPBP1 in a Huntington's disease mouse model reduced mHtt aggregation and neuropathology, establishing HSPBP1 as a potential therapeutic target in neurodegeneration.","evidence":"Co-immunoprecipitation; CHIP ubiquitination assays; CRISPR-Cas9 knockdown in primary neurons; HD knockin mouse model","pmids":["28847953"],"confidence":"High","gaps":["Long-term safety of HSPBP1 depletion in neurons not assessed","Whether HSPBP1 inhibition affects other neurodegenerative disease proteins not tested"]},{"year":2018,"claim":"Discovery of the N-terminal release domain (RD) that mimics substrate and competes for the Hsp70 substrate-binding domain resolved a longstanding question: how HSPBP1 ensures substrate release after nucleotide exchange, showing a dual-domain mechanism — armadillo for NEF, RD for substrate eviction.","evidence":"In vitro binding and competition assays with recombinant proteins; release domain mutagenesis; functional assays in yeast and mammalian cells","pmids":["29323280"],"confidence":"High","gaps":["Atomic structure of the RD in complex with Hsp70 SBD not available","Whether RD competes equally with all substrate types not tested"]},{"year":2020,"claim":"Identification of HSPBP1 as a stress granule component that directly binds polyA-RNA and regulates stress granule assembly expanded its function beyond the Hsp70 chaperone cycle into RNA granule biology.","evidence":"Immunofluorescence colocalization with G3BP1/TIA-1; co-immunoprecipitation; in vitro RNA binding; siRNA knockdown and overexpression","pmids":["32235396"],"confidence":"Medium","gaps":["Whether stress granule role is Hsp70-dependent or independent not resolved","RNA targets of HSPBP1 not identified transcriptome-wide"]},{"year":2021,"claim":"HSPBP1 stabilizes RIG-I by inhibiting its K48-linked ubiquitination, thereby promoting innate antiviral IFN-β signaling, extending the anti-degradation paradigm to innate immunity.","evidence":"Overexpression and knockout; ubiquitination and IRF3 phosphorylation assays; IFN-β reporter and ELISA upon Sendai virus infection","pmids":["33713958"],"confidence":"Medium","gaps":["The E3 ligase targeting RIG-I that HSPBP1 antagonizes not identified","In vivo antiviral phenotype in HSPBP1 KO mice not tested"]},{"year":2022,"claim":"HSPBP1 promotes BRCA1-dependent homologous recombination repair and separately disrupts the Hsp70–Apaf-1 interaction to suppress apoptosis after DNA damage, adding a DNA repair dimension to its functions.","evidence":"Co-immunoprecipitation with BRCA1; HR reporter assays; knockdown/overexpression; xenograft tumor models","pmids":["35387978"],"confidence":"Medium","gaps":["Direct versus Hsp70-mediated mechanism of BRCA1 interaction not distinguished","Whether HSPBP1 affects other DNA repair pathways untested"]},{"year":null,"claim":"Key open questions include: (1) the full-length HSPBP1 structure with the release domain bound to Hsp70 SBD, (2) whether the stress granule and DNA repair functions are Hsp70-dependent or represent independent activities, and (3) the identity of the E3 ligase(s) antagonized by HSPBP1 beyond CHIP in different physiological contexts.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No full-length structure including the N-terminal release domain in complex","Hsp70 dependence of stress granule and HR functions not resolved","E3 ligases antagonized in innate immunity and spermatogenesis not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3,6,7]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[11]},{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[0,2,3]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1,7,11]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[14]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2,3,6,7]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[13]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[12]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[6,10]}],"complexes":[],"partners":["HSPA1A","HSPA8","STUB1","G3BP1","BRCA1","DDX58","HSPA2"],"other_free_text":[]},"mechanistic_narrative":"HSPBP1 is an armadillo-repeat cochaperone that functions as a nucleotide exchange factor (NEF) for Hsp70/Hsc70 and a critical regulator of protein quality control decisions between folding and degradation. Its curved alpha-helical core domain embraces lobe II of the Hsp70 ATPase domain, and steric displacement of lobe I reduces nucleotide affinity — a mechanism structurally distinct from BAG-1 or GrpE — while its flexible N-terminal release domain mimics substrate to ensure efficient client release from Hsp70 [PMID:15694338, PMID:29323280]. HSPBP1 inhibits the CHIP ubiquitin ligase in complex with Hsc70, thereby suppressing K48-linked ubiquitination and proteasomal degradation of clients including immature CFTR, inducible HSP70 family members, and RIG-I, and promoting BRCA1-mediated homologous recombination repair [PMID:15215316, PMID:24899640, PMID:33713958, PMID:35387978]. Loss of HSPBP1 in mice causes male sterility through spermatocyte apoptosis resulting from destabilization of HSPA2 and failure of synaptonemal complex disassembly [PMID:24899640]."},"prefetch_data":{"uniprot":{"accession":"Q9NZL4","full_name":"Hsp70-binding protein 1","aliases":["Heat shock protein-binding protein 1","Hsp70-binding protein 2","HspBP2","Hsp70-interacting protein 1","Hsp70-interacting protein 2"],"length_aa":359,"mass_kda":39.3,"function":"Inhibits HSPA1A chaperone activity by changing the conformation of the ATP-binding domain of HSPA1A and interfering with ATP binding. Interferes with ubiquitination mediated by STUB1 and inhibits chaperone-assisted degradation of immature CFTR","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q9NZL4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HSPBP1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000133265","cell_line_id":"CID000052","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"HSPA8","stoichiometry":0.2},{"gene":"ANXA11","stoichiometry":0.2},{"gene":"VIM","stoichiometry":0.2},{"gene":"HSPA1B;HSPA1A","stoichiometry":0.2},{"gene":"METAP2","stoichiometry":0.2},{"gene":"HSPA2","stoichiometry":0.2},{"gene":"EDRF1","stoichiometry":0.2},{"gene":"VCL","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000052","total_profiled":1310},"omim":[{"mim_id":"612939","title":"HEAT-SHOCK 70-KD PROTEIN-BINDING PROTEIN 1; HSPBP1","url":"https://www.omim.org/entry/612939"},{"mim_id":"612884","title":"MENOPAUSE, NATURAL, AGE AT, QUANTITATIVE TRAIT LOCUS 2; MENOQ2","url":"https://www.omim.org/entry/612884"},{"mim_id":"608005","title":"SIL1 NUCLEOTIDE EXCHANGE FACTOR; SIL1","url":"https://www.omim.org/entry/608005"},{"mim_id":"607207","title":"STIP1 HOMOLOGOUS AND U BOX-CONTAINING PROTEIN 1; STUB1","url":"https://www.omim.org/entry/607207"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":118.3}],"url":"https://www.proteinatlas.org/search/HSPBP1"},"hgnc":{"alias_symbol":["FES1"],"prev_symbol":[]},"alphafold":{"accession":"Q9NZL4","domains":[{"cath_id":"1.25.10.10","chopping":"84-102_115-230","consensus_level":"medium","plddt":95.549,"start":84,"end":230},{"cath_id":"1.25.10.10","chopping":"240-352","consensus_level":"medium","plddt":92.5796,"start":240,"end":352}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZL4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZL4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZL4-F1-predicted_aligned_error_v6.png","plddt_mean":83.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HSPBP1","jax_strain_url":"https://www.jax.org/strain/search?query=HSPBP1"},"sequence":{"accession":"Q9NZL4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NZL4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NZL4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZL4"}},"corpus_meta":[{"pmid":"15694338","id":"PMC_15694338","title":"Regulation of Hsp70 function by HspBP1: structural analysis reveals an alternate mechanism for Hsp70 nucleotide exchange.","date":"2005","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/15694338","citation_count":164,"is_preprint":false},{"pmid":"15215316","id":"PMC_15215316","title":"The cochaperone HspBP1 inhibits the CHIP ubiquitin ligase and stimulates the maturation of the cystic fibrosis transmembrane conductance regulator.","date":"2004","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/15215316","citation_count":138,"is_preprint":false},{"pmid":"12417338","id":"PMC_12417338","title":"HspBP1, a homologue of the yeast Fes1 and Sls1 proteins, is an Hsc70 nucleotide exchange factor.","date":"2002","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/12417338","citation_count":81,"is_preprint":false},{"pmid":"23530227","id":"PMC_23530227","title":"Hsp70 nucleotide exchange factor Fes1 is essential for ubiquitin-dependent degradation of misfolded cytosolic proteins.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23530227","citation_count":68,"is_preprint":false},{"pmid":"25487014","id":"PMC_25487014","title":"GrpE, Hsp110/Grp170, HspBP1/Sil1 and BAG domain proteins: nucleotide exchange factors for Hsp70 molecular chaperones.","date":"2015","source":"Sub-cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25487014","citation_count":48,"is_preprint":false},{"pmid":"29323280","id":"PMC_29323280","title":"Nucleotide exchange factors Fes1 and HspBP1 mimic substrate to release misfolded proteins from Hsp70.","date":"2018","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/29323280","citation_count":44,"is_preprint":false},{"pmid":"28847953","id":"PMC_28847953","title":"Differential HspBP1 expression accounts for the greater vulnerability of neurons than astrocytes to misfolded 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Formation.","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/32235396","citation_count":14,"is_preprint":false},{"pmid":"18986301","id":"PMC_18986301","title":"Extracellular HspBP1 and Hsp72 synergistically activate epidermal growth factor receptor.","date":"2009","source":"Biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/18986301","citation_count":12,"is_preprint":false},{"pmid":"23113305","id":"PMC_23113305","title":"Effect of exercise on the expression of HSPBP1, PGLYRP1, and HSPA1A genes in human leukocytes.","date":"2012","source":"Bulletin of experimental biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/23113305","citation_count":11,"is_preprint":false},{"pmid":"35387978","id":"PMC_35387978","title":"HspBP1 is a dual function regulatory protein that controls both DNA repair and apoptosis in breast cancer cells.","date":"2022","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/35387978","citation_count":11,"is_preprint":false},{"pmid":"15977250","id":"PMC_15977250","title":"Development of a sensitive assay for the measurement of antibodies against heat shock protein binding protein 1 (HspBP1): increased levels of anti-HspBP1 IgG are prevalent in HIV infected subjects.","date":"2005","source":"Journal of medical virology","url":"https://pubmed.ncbi.nlm.nih.gov/15977250","citation_count":11,"is_preprint":false},{"pmid":"31242183","id":"PMC_31242183","title":"Hsp70-nucleotide exchange factor (NEF) Fes1 has non-NEF roles in degradation of gluconeogenic enzymes and cell wall integrity.","date":"2019","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31242183","citation_count":9,"is_preprint":false},{"pmid":"16677834","id":"PMC_16677834","title":"Expression of the cochaperone HspBP1 is not coordinately regulated with Hsp70 expression.","date":"2006","source":"Cell biology 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HspBP1.","date":"2015","source":"PeerJ","url":"https://pubmed.ncbi.nlm.nih.gov/26713263","citation_count":4,"is_preprint":false},{"pmid":"22037021","id":"PMC_22037021","title":"Extracellular HspBP1 inhibits formation of a cytotoxic Tag7-Hsp70 complex in vitro and in human serum.","date":"2011","source":"Biochimie","url":"https://pubmed.ncbi.nlm.nih.gov/22037021","citation_count":4,"is_preprint":false},{"pmid":"21165407","id":"PMC_21165407","title":"Long-term exercises increase the concentration of HspBP1, a co-chaperone of 70-KDa heat shock protein.","date":"2010","source":"Bulletin of experimental biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/21165407","citation_count":4,"is_preprint":false},{"pmid":"10786638","id":"PMC_10786638","title":"Isolation and characterization of isoforms of HspBP1, inhibitors of Hsp70.","date":"2000","source":"Biochimica et biophysica 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Biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/38189890","citation_count":1,"is_preprint":false},{"pmid":"42014672","id":"PMC_42014672","title":"Identification of human MLKL Cys184 and HSPBP1 Cys201 as novel cellular targets for necroptosis.","date":"2026","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/42014672","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.23.604777","title":"SARS-CoV-2 S, M and E Structural Proteins Down-modulate HIV-1 LTR Activity and Modulate Endoplasmic Reticulum Stress Responses","date":"2024-07-23","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.23.604777","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17093,"output_tokens":3808,"usd":0.054199},"stage2":{"model":"claude-opus-4-6","input_tokens":7239,"output_tokens":3259,"usd":0.176505},"total_usd":0.230704,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"HspBP1 acts as a nucleotide exchange factor (NEF) for Hsp70 via a mechanism distinct from BAG-1 or GrpE: its curved, all alpha-helical armadillo-repeat fold embraces lobe II of the Hsp70 ATPase domain, and steric conflict displaces lobe I, reducing nucleotide affinity, rather than triggering a conformational change in lobe II as the other NEFs do.\",\n      \"method\": \"Crystal structure of HspBP1 alone and in complex with Hsp70 ATPase domain; in vitro nucleotide exchange assays; yeast genetic analysis (Fes1p deletion)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation, highly cited foundational paper\",\n      \"pmids\": [\"15694338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HspBP1 inhibits the ubiquitin ligase activity of CHIP when complexed with Hsc70, thereby interfering with CHIP-induced proteasomal degradation of immature CFTR and stimulating CFTR maturation.\",\n      \"method\": \"Co-immunoprecipitation; in vitro ubiquitin ligase assays; CFTR maturation assays; overexpression and knockdown in cells\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Co-IP, in vitro ubiquitylation, cellular CFTR maturation), highly cited\",\n      \"pmids\": [\"15215316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HspBP1 is a nucleotide exchange factor that promotes nucleotide dissociation from mammalian Hsc70 (and yeast Ssa1p/BiP), and unlike its yeast ortholog Fes1p, inhibits chaperone-mediated protein refolding in vitro.\",\n      \"method\": \"In vitro nucleotide dissociation assays; in vitro luciferase refolding assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro NEF and refolding assays, replicated by multiple groups\",\n      \"pmids\": [\"12417338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HspBP1 employs a flexible N-terminal release domain (RD) with substrate-mimicking properties that contacts the substrate-binding domain of Hsp70, competes with peptide substrate for binding, and is essential for efficient release of persistent substrates from Hsp70; the armadillo domain triggers nucleotide exchange while the RD safeguards substrate release.\",\n      \"method\": \"In vitro binding and competition assays with recombinant proteins; mutagenesis of the release domain; yeast and mammalian cell functional assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstitution, domain mutagenesis, and cellular functional validation in two organisms\",\n      \"pmids\": [\"29323280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HspBP1 has two structural domains: an unstructured N-terminal domain I (aa 1-83) and an alpha-helical domain II (aa 84-359); domain II alone is sufficient to bind Hsp70 and alter the conformation of its ATPase domain, and domain I augments these functions.\",\n      \"method\": \"Circular dichroism; limited proteolysis; truncation mutagenesis; in vitro luciferase refolding assay; reticulocyte lysate binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple in vitro methods, single lab\",\n      \"pmids\": [\"12651857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Hsp40 and TPR1 cooperatively reverse HspBP1-mediated inhibition of Hsp70-dependent protein folding; the Hsp70-HspBP1 complex is dissociated only in the presence of both Hsp40 and TPR1 together, revealing a cooperative regulatory mechanism.\",\n      \"method\": \"In vitro luciferase refolding assays; Kd measurements; competition assays; tetracycline-inducible HeLa cell system\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (in vitro and cellular), single lab\",\n      \"pmids\": [\"14503850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HSPBP1 inhibits ubiquitylation and proteasomal degradation of inducible HSP70 proteins (HSPA1L and HSPA2) at a posttranslational level; loss of HSPBP1 in mice causes male sterility due to impaired meiosis and massive spermatocyte apoptosis linked to loss of HSPA2-dependent synaptonemal complex disassembly.\",\n      \"method\": \"HSPBP1 knockout mouse generation; Western blot analysis of HSP70 protein levels; ubiquitylation assays; histological analysis of testes\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype plus mechanistic ubiquitylation assays\",\n      \"pmids\": [\"24899640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Neurons express abundant HspBP1, which inhibits CHIP activity and thereby reduces CHIP-mediated K48-linked polyubiquitination and degradation of misfolded proteins including mutant huntingtin; CRISPR-Cas9 silencing of HspBP1 in neurons ameliorated mHtt aggregation and neuropathology in HD knockin mice.\",\n      \"method\": \"Western blot; co-immunoprecipitation; CHIP ubiquitination assays; CRISPR-Cas9 knockdown in neurons; HD knockin mouse model analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including in vivo CRISPR rescue experiment\",\n      \"pmids\": [\"28847953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HspBP1 reduces Hsp70 binding to the ligand-binding domain of glucocorticoid receptor (GR) and inhibits GR, mineralocorticoid receptor (MR), and androgen receptor (AR) transcriptional activity, in contrast to BAG-1M which shows a dose-dependent biphasic effect; HspBP1 and BAG-1M differentially regulate the composition of steroid receptor-chaperone folding complexes.\",\n      \"method\": \"Co-immunoprecipitation; GST pull-down assays; reporter gene assays; overexpression in cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple assays (pull-down, co-IP, reporter), single lab\",\n      \"pmids\": [\"24454860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HspBP1 binds both Hsp70 and Tag7 (PGRP-S innate immunity protein); this interaction eliminates the cytotoxic activity of the Tag7-Hsp70 complex, decreases the ATP concentration required to dissociate Tag7 from Hsp70's peptide-binding site, and inhibits cytotoxic activity secreted by CD8+ lymphocytes.\",\n      \"method\": \"Co-immunoprecipitation; cytotoxicity assays; biochemical binding assays with purified proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct binding demonstrated plus functional consequence, single lab\",\n      \"pmids\": [\"21247889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"HspBP1 antagonizes the prosurvival function of Hsp70 in a manner dependent on its ability to bind Hsp70; ectopic HspBP1 expression promotes lysosomal membrane permeabilization, cathepsin release to cytosol, and caspase-3 activation in response to anticancer drugs.\",\n      \"method\": \"RNA interference; ectopic overexpression; lysosomal integrity assays; cathepsin release assays; caspase-3 activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple cellular assays with binding-deficient mutant controls, single lab\",\n      \"pmids\": [\"17855353\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HspBP1 is a component of stress granules (SGs) that regulates their formation: it colocalizes with G3BP1, HuR and TIA-1/TIAR in SGs, associates with these SG proteins by co-immunoprecipitation, binds polyA-RNA directly in vitro, and its knockdown impairs stress-induced SG assembly while overexpression promotes SG formation even in the absence of stress.\",\n      \"method\": \"Immunofluorescence microscopy; co-immunoprecipitation; mass spectrometry; in vitro RNA binding; siRNA knockdown and overexpression\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple orthogonal methods including direct RNA binding in vitro, single lab\",\n      \"pmids\": [\"32235396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HSPBP1 promotes RIG-I-mediated antiviral signaling by inhibiting K48-linked ubiquitination of RIG-I, thereby stabilizing RIG-I protein levels and promoting IRF3 activation and IFN-β production in response to Sendai virus infection.\",\n      \"method\": \"Overexpression and knockdown/knockout; ubiquitination assays; co-immunoprecipitation; IRF3 phosphorylation assays; IFN-β reporter/ELISA\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple assays (ubiquitination, IRF3 activation, IFN-β) with KO/KD, single lab\",\n      \"pmids\": [\"33713958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HspBP1 interacts with BRCA1 and promotes BRCA1-mediated homologous recombination DNA repair; independently of BRCA1 status, HspBP1 also interferes with the association of Hsp70 and Apaf-1 (apoptotic protease-activating factor-1), facilitating cell survival after ionizing radiation.\",\n      \"method\": \"Co-immunoprecipitation; homologous recombination reporter assays; knockdown and overexpression; xenograft tumor models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and functional HR assays, single lab\",\n      \"pmids\": [\"35387978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Extracellular HspBP1 (e-HspBP1) co-immunoprecipitates with extracellular Hsp72 in conditioned medium; purified recombinant HspBP1 augments e-Hsp72-mediated phosphorylation of EGFR and downstream ERK1/2 in a concentration-dependent manner, and this activity requires the HspBP1 N-terminal domain.\",\n      \"method\": \"Co-immunoprecipitation from conditioned medium; EGFR and ERK phosphorylation assays; deletion mutant analysis; secretion assays\",\n      \"journal\": \"Biology of the cell\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single co-IP plus downstream signaling assay, single lab\",\n      \"pmids\": [\"18986301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"HSPBP1 Cys201 was identified as an upstream cellular target contributing to necroptosis regulation; covalent modification of HSPBP1 at Cys201 by parthenolide (confirmed by mass spectrometry co-incubation) confers anti-necroptotic activity, and HSPBP1 knockdown reduces sensitivity to necroptosis.\",\n      \"method\": \"Mass spectrometry covalent modification mapping; HSPBP1 knockdown; co-incubation of purified HSPBP1 with parthenolide; necroptosis assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, mass spectrometry identification of modification site without full mechanistic follow-up of how HSPBP1 modulates the necroptosis pathway\",\n      \"pmids\": [\"42014672\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HSPBP1 is an armadillo-repeat cochaperone that acts as a nucleotide exchange factor for Hsp70/Hsc70 by sterically displacing lobe I of the ATPase domain (distinct from the BAG-1/GrpE mechanism), and employs a flexible N-terminal release domain to mimic substrate and ensure efficient substrate release from Hsp70; it also inhibits the CHIP ubiquitin ligase when complexed with Hsc70, thereby promoting folding over degradation of client proteins such as CFTR and inducible HSP70 family members, regulates steroid receptor and RIG-I stability, participates in stress granule biogenesis, and its loss in mice causes spermatocyte apoptosis and male sterility.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"HSPBP1 is an armadillo-repeat cochaperone that functions as a nucleotide exchange factor (NEF) for Hsp70/Hsc70 and a critical regulator of protein quality control decisions between folding and degradation. Its curved alpha-helical core domain embraces lobe II of the Hsp70 ATPase domain, and steric displacement of lobe I reduces nucleotide affinity — a mechanism structurally distinct from BAG-1 or GrpE — while its flexible N-terminal release domain mimics substrate to ensure efficient client release from Hsp70 [PMID:15694338, PMID:29323280]. HSPBP1 inhibits the CHIP ubiquitin ligase in complex with Hsc70, thereby suppressing K48-linked ubiquitination and proteasomal degradation of clients including immature CFTR, inducible HSP70 family members, and RIG-I, and promoting BRCA1-mediated homologous recombination repair [PMID:15215316, PMID:24899640, PMID:33713958, PMID:35387978]. Loss of HSPBP1 in mice causes male sterility through spermatocyte apoptosis resulting from destabilization of HSPA2 and failure of synaptonemal complex disassembly [PMID:24899640].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing that HSPBP1 is a nucleotide exchange factor for Hsc70 answered whether this cochaperone directly modulates the Hsp70 ATPase cycle, setting the stage for understanding its role in chaperone regulation.\",\n      \"evidence\": \"In vitro nucleotide dissociation and luciferase refolding assays with mammalian and yeast Hsp70 proteins\",\n      \"pmids\": [\"12417338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural basis for NEF activity\", \"Inhibition of refolding in vitro not reconciled with in vivo function\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defining the two-domain architecture of HSPBP1 — an unstructured N-terminal domain I and an alpha-helical domain II sufficient for Hsp70 binding — and identifying cooperative reversal of HspBP1 inhibition by Hsp40 plus TPR1 resolved how the cochaperone is structurally organized and dynamically regulated within the chaperone network.\",\n      \"evidence\": \"Circular dichroism, limited proteolysis, truncation mutagenesis, and in vitro cooperative refolding assays\",\n      \"pmids\": [\"12651857\", \"14503850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No atomic resolution structure of isolated HSPBP1\", \"Cooperative mechanism of Hsp40/TPR1 reversal unclear at a structural level\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that HSPBP1 inhibits CHIP ubiquitin ligase activity when complexed with Hsc70, thereby promoting CFTR maturation over degradation, established HSPBP1 as a triage factor that tips protein quality control toward folding.\",\n      \"evidence\": \"Co-immunoprecipitation, in vitro ubiquitin ligase assays, and cellular CFTR maturation assays with overexpression and knockdown\",\n      \"pmids\": [\"15215316\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HSPBP1 directly contacts CHIP or acts indirectly through Hsc70 conformation not resolved\", \"Range of CHIP substrates affected unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The crystal structure of HSPBP1 in complex with the Hsp70 ATPase domain revealed a novel NEF mechanism in which an armadillo-repeat fold embraces lobe II and sterically displaces lobe I, distinguishing HSPBP1 from all previously characterized NEFs.\",\n      \"evidence\": \"X-ray crystallography of HspBP1 alone and in complex with Hsp70 ATPase domain; in vitro nucleotide exchange assays; yeast Fes1p deletion complementation\",\n      \"pmids\": [\"15694338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of full-length HSPBP1 including the N-terminal domain\", \"Dynamics of lobe I displacement not captured\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showing that HSPBP1 antagonizes the prosurvival function of Hsp70 by promoting lysosomal membrane permeabilization and caspase-3 activation broadened its role beyond protein folding to regulation of cell death pathways.\",\n      \"evidence\": \"RNA interference, overexpression with binding-deficient mutant controls, lysosomal integrity and cathepsin release assays in cancer cell lines\",\n      \"pmids\": [\"17855353\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking Hsp70 dissociation to lysosomal destabilization not defined\", \"Relevance to physiological (non-drug-induced) cell death unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"HSPBP1 knockout mice revealed an essential in vivo role: HSPBP1 prevents ubiquitin-dependent degradation of inducible HSP70 proteins (HSPA2), and its loss causes meiotic failure, spermatocyte apoptosis, and male sterility, establishing a physiological client-stabilization function.\",\n      \"evidence\": \"HSPBP1 knockout mouse; Western blot and ubiquitination assays; testis histology\",\n      \"pmids\": [\"24899640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HSPBP1 loss affects female fertility or other tissues not explored\", \"Identity of the E3 ligase degrading HSPA2 in the absence of HSPBP1 not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"HSPBP1 modulates steroid receptor signaling by reducing Hsp70 binding to the ligand-binding domain of glucocorticoid, mineralocorticoid, and androgen receptors, revealing a nuclear-receptor-specific regulatory axis distinct from BAG-1M.\",\n      \"evidence\": \"Co-immunoprecipitation, GST pull-down, and reporter gene assays in cell lines\",\n      \"pmids\": [\"24454860\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological relevance in endocrine tissues not tested in vivo\", \"Structural basis for differential effects versus BAG-1M unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"In neurons, abundant HSPBP1 suppresses CHIP-mediated K48-polyubiquitination of misfolded proteins including mutant huntingtin; CRISPR-Cas9 silencing of HSPBP1 in a Huntington's disease mouse model reduced mHtt aggregation and neuropathology, establishing HSPBP1 as a potential therapeutic target in neurodegeneration.\",\n      \"evidence\": \"Co-immunoprecipitation; CHIP ubiquitination assays; CRISPR-Cas9 knockdown in primary neurons; HD knockin mouse model\",\n      \"pmids\": [\"28847953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Long-term safety of HSPBP1 depletion in neurons not assessed\", \"Whether HSPBP1 inhibition affects other neurodegenerative disease proteins not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Discovery of the N-terminal release domain (RD) that mimics substrate and competes for the Hsp70 substrate-binding domain resolved a longstanding question: how HSPBP1 ensures substrate release after nucleotide exchange, showing a dual-domain mechanism — armadillo for NEF, RD for substrate eviction.\",\n      \"evidence\": \"In vitro binding and competition assays with recombinant proteins; release domain mutagenesis; functional assays in yeast and mammalian cells\",\n      \"pmids\": [\"29323280\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the RD in complex with Hsp70 SBD not available\", \"Whether RD competes equally with all substrate types not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of HSPBP1 as a stress granule component that directly binds polyA-RNA and regulates stress granule assembly expanded its function beyond the Hsp70 chaperone cycle into RNA granule biology.\",\n      \"evidence\": \"Immunofluorescence colocalization with G3BP1/TIA-1; co-immunoprecipitation; in vitro RNA binding; siRNA knockdown and overexpression\",\n      \"pmids\": [\"32235396\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether stress granule role is Hsp70-dependent or independent not resolved\", \"RNA targets of HSPBP1 not identified transcriptome-wide\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"HSPBP1 stabilizes RIG-I by inhibiting its K48-linked ubiquitination, thereby promoting innate antiviral IFN-β signaling, extending the anti-degradation paradigm to innate immunity.\",\n      \"evidence\": \"Overexpression and knockout; ubiquitination and IRF3 phosphorylation assays; IFN-β reporter and ELISA upon Sendai virus infection\",\n      \"pmids\": [\"33713958\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The E3 ligase targeting RIG-I that HSPBP1 antagonizes not identified\", \"In vivo antiviral phenotype in HSPBP1 KO mice not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"HSPBP1 promotes BRCA1-dependent homologous recombination repair and separately disrupts the Hsp70–Apaf-1 interaction to suppress apoptosis after DNA damage, adding a DNA repair dimension to its functions.\",\n      \"evidence\": \"Co-immunoprecipitation with BRCA1; HR reporter assays; knockdown/overexpression; xenograft tumor models\",\n      \"pmids\": [\"35387978\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus Hsp70-mediated mechanism of BRCA1 interaction not distinguished\", \"Whether HSPBP1 affects other DNA repair pathways untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: (1) the full-length HSPBP1 structure with the release domain bound to Hsp70 SBD, (2) whether the stress granule and DNA repair functions are Hsp70-dependent or represent independent activities, and (3) the identity of the E3 ligase(s) antagonized by HSPBP1 beyond CHIP in different physiological contexts.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full-length structure including the N-terminal release domain in complex\", \"Hsp70 dependence of stress granule and HR functions not resolved\", \"E3 ligases antagonized in innate immunity and spermatogenesis not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3, 6, 7]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 7, 11]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2, 3, 6, 7]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6, 10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"HSPA1A\",\n      \"HSPA8\",\n      \"STUB1\",\n      \"G3BP1\",\n      \"BRCA1\",\n      \"DDX58\",\n      \"HSPA2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}