{"gene":"HSPBP1","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2005,"finding":"Crystal structure of HspBP1 alone and in complex with the Hsp70 ATPase domain reveals an armadillo-repeat fold whose concave face embraces lobe II of the ATPase domain; steric conflict displaces lobe I, reducing nucleotide affinity — a mechanism distinct from BAG-1 or GrpE, which instead trigger a conformational change in lobe II.","method":"X-ray crystallography (crystal structure of HspBP1 alone and in complex with Hsp70 ATPase domain fragment); yeast genetics (Fes1p deletion showing requirement for protein folding at 37°C)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution crystal structure with functional validation in yeast, replicated across two organisms, multiple orthogonal methods in one rigorous study","pmids":["15694338"],"is_preprint":false},{"year":2002,"finding":"HspBP1 is a nucleotide exchange factor (NEF) for Hsc70; it promotes nucleotide dissociation from both yeast Ssa1p and mammalian Hsc70 in vitro, establishing it as a member of the eukaryotic NEF family homologous to yeast Fes1p.","method":"In vitro nucleotide dissociation assay; chaperone-mediated protein refolding assay","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay replicated with multiple Hsp70 orthologs, independently confirmed by subsequent structural study (PMID:15694338)","pmids":["12417338"],"is_preprint":false},{"year":2004,"finding":"HspBP1 inhibits the ubiquitin ligase activity of CHIP when HspBP1 is complexed with Hsc70, thereby interfering with CHIP-induced proteasomal degradation of immature CFTR and stimulating CFTR maturation.","method":"Co-immunoprecipitation; ubiquitin ligase activity assay; pulse-chase analysis of CFTR maturation; RNAi knockdown","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP combined with in vitro ubiquitin ligase assay and functional CFTR maturation readout, multiple orthogonal methods in a single focused study","pmids":["15215316"],"is_preprint":false},{"year":2003,"finding":"HspBP1 has two structural domains: an N-terminal largely unstructured domain I (aa 1–83) and a helical domain II (aa 84–359). Domain II is sufficient to bind Hsp70 and alter the conformation of the Hsp70 ATPase domain; domain I enhances both functions.","method":"Circular dichroism; limited proteolysis; truncation mutagenesis; Hsp70-binding assay in reticulocyte lysate; luciferase renaturation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical methods (CD, limited proteolysis, truncation mutants, functional assay) in a single lab","pmids":["12651857"],"is_preprint":false},{"year":2013,"finding":"Yeast Fes1 (ortholog of HspBP1) acts as a cytosolic triaging factor that selectively interacts with misfolded proteins bound to Hsp70 and triggers their release; in the absence of Fes1, misfolded proteins fail to undergo polyubiquitylation, aggregate, and induce a strong heat-shock response.","method":"Yeast genetics (FES1 deletion); polyubiquitylation assay; protein aggregation analysis; heat-shock reporter assay; binding assays with misfolded substrates","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with multiple orthogonal readouts (ubiquitylation, aggregation, stress reporter), placing Fes1/HspBP1 at a defined pathway node between Hsp70 and UPS degradation","pmids":["23530227"],"is_preprint":false},{"year":2018,"finding":"Fes1 and HspBP1 each contain a flexible N-terminal release domain (RD) with substrate-mimicking properties; the RD contacts the Hsp70 substrate-binding domain and competes with peptide substrate for binding, ensuring efficient release of persistent substrates. The armadillo domain triggers nucleotide exchange while the RD drives substrate release.","method":"In vitro peptide competition assays; mutagenesis of the release domain; yeast complementation; mammalian cell functional assays; NMR/structural analysis of RD","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — mechanistic dissection by mutagenesis, in vitro competition assays, and complementation in two organisms (yeast and mammalian cells) in a single rigorous study","pmids":["29323280"],"is_preprint":false},{"year":2016,"finding":"The FES1 transcript is alternatively spliced at its 3' end to produce two isoforms: Fes1L (targeted to the nucleus, the first identified nuclear Hsp70 NEF) and Fes1S (cytosolic). Fes1S is essential for proteasomal degradation of misfolded proteins and proteostasis; Fes1L localizes to the nucleus but cannot substitute for cytosolic Fes1S function.","method":"RNA-seq; isoform-specific expression constructs; fluorescence microscopy for localization; yeast genetics (isoform-specific deletions); ubiquitin-proteasome degradation assays; heat-shock reporter assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — isoform localization confirmed by microscopy linked directly to functional rescue of degradation phenotypes, multiple orthogonal methods","pmids":["26912797"],"is_preprint":false},{"year":2014,"finding":"HSPBP1 inhibits CHIP-mediated ubiquitylation and proteasomal degradation of inducible HSP70 family members (HSPA1L and HSPA2) in testes, thereby stabilizing these chaperones at the posttranslational level. Loss of HSPBP1 in mice leads to impaired meiosis and spermatocyte apoptosis due to reduced HSPA1L and HSPA2 levels.","method":"HSPBP1 knockout mice; Western blot analysis; ubiquitylation assays; meiotic phenotype analysis (immunofluorescence of synaptonemal complexes)","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO mouse model with defined mechanistic pathway (CHIP inhibition → HSP70 stabilization) supported by ubiquitylation assays and phenotypic rescue logic","pmids":["24899640"],"is_preprint":false},{"year":2017,"finding":"Neurons express abundant HspBP1 which suppresses CHIP ubiquitin ligase activity, resulting in low CHIP-mediated degradation of misfolded proteins. CRISPR-Cas9 silencing of HspBP1 in neurons increased CHIP activity and reduced mutant huntingtin aggregation and neuropathology in HD knock-in mice.","method":"CRISPR-Cas9 knockdown; CHIP ubiquitin ligase activity assay; Co-immunoprecipitation; immunofluorescence; Western blot; HD knock-in mouse model","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function by CRISPR in primary neurons and in vivo mouse model, with direct mechanistic link to CHIP ubiquitin ligase activity, multiple orthogonal approaches","pmids":["28847953"],"is_preprint":false},{"year":2003,"finding":"The inhibitory effect of HspBP1 on Hsp70-dependent protein folding can be reversed by the cooperative action of both Hsp40 and TPR1 together; neither cochaperone alone is sufficient to dissociate the Hsp70-HspBP1 complex.","method":"In vitro luciferase refolding assay; Kd measurement by competition assays; Hela cell tetracycline-inducible Hsp70 expression system","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution plus cell-based validation, single lab with two orthogonal approaches","pmids":["14503850"],"is_preprint":false},{"year":2019,"finding":"Fes1 undergoes reversible methionine oxidation at a cluster of three methionine residues in its core armadillo domain under oxidizing conditions; this oxidation inhibits NEF activity and consequently alters Hsp70 chaperone activity. Oxidation is reversed by cytoplasmic methionine sulfoxide reductases Mxr1 (MsrA) and Mxr2 (MsrB).","method":"In vitro oxidation and activity assays with recombinant proteins; site-directed mutagenesis; in-cell oxidation assays; genetic manipulation of Mxr1/Mxr2","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted in vitro assay with mutagenesis to map oxidation site, complemented by in-cell validation and identification of specific reductase erasers","pmids":["31806703"],"is_preprint":false},{"year":2007,"finding":"HspBP1 antagonizes the prosurvival function of Hsp70 by interfering with Hsp70-mediated stabilization of lysosomal membranes; ectopic HspBP1 promotes lysosomal membrane permeabilization, cathepsin release into cytosol, and caspase-3 activation in response to anticancer drugs, in a manner dependent on its ability to bind Hsp70.","method":"Ectopic expression; RNAi knockdown; lysosomal membrane permeability assay; cathepsin release assay; caspase-3 activation assay; Hsp70-binding mutant analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts with Hsp70-binding-dependent requirement established by mutant analysis, single lab","pmids":["17855353"],"is_preprint":false},{"year":2011,"finding":"HspBP1 binds directly to Tag7 (PGRP-S) as well as to Hsp70, thereby eliminating the cytotoxic activity of the Tag7-Hsp70 complex and lowering the ATP concentration required to dissociate Tag7 from the Hsp70 peptide-binding site.","method":"Co-immunoprecipitation; cytotoxicity assays; ATP-dependent dissociation assay; immunodetection in CD8+ lymphocytes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional cytotoxicity assay and biochemical dissociation assay, single lab","pmids":["21247889"],"is_preprint":false},{"year":2009,"finding":"Extracellular HspBP1 co-immunoprecipitates with extracellular Hsp72 in conditioned medium and synergistically augments Hsp72-mediated EGFR phosphorylation and downstream ERK1/2 activation; the N-terminal domain of HspBP1 is required for this activity.","method":"Co-immunoprecipitation from conditioned medium; EGFR phosphorylation assay; ERK1/2 activation assay; N-terminal deletion mutant analysis; chromogranin A co-localization","journal":"Biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP combined with functional signaling assay and domain-deletion analysis, single lab","pmids":["18986301"],"is_preprint":false},{"year":2020,"finding":"HspBP1 is an integral component of cytoplasmic stress granules (SGs) under oxidative stress, co-localizing with G3BP1, HuR, and TIA-1/TIAR; HspBP1 associates with polyA-RNA in vivo and binds RNA homopolymers directly in vitro. HspBP1 knockdown impairs SG assembly while overexpression promotes SG formation without stress, with the Hsp70-binding domain contributing to SG regulation.","method":"Immunofluorescence microscopy; co-immunoprecipitation; mass spectrometry; in vitro RNA binding assay; siRNA knockdown; overexpression; single-granule analysis","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (MS, Co-IP, in vitro RNA binding, KD, OE) in a single lab for a novel localization and function","pmids":["32235396"],"is_preprint":false},{"year":2014,"finding":"HspBP1 reduces Hsp70 binding to the GR ligand-binding domain and inhibits glucocorticoid, mineralocorticoid, and androgen receptor transcriptional activity, in contrast to BAG-1M which has dose-dependent stimulatory/inhibitory effects. Hsp40 and steroid receptors preferentially associate with BAG-1M rather than HspBP1 in pulldown assays.","method":"Co-immunoprecipitation; pulldown assays; reporter gene assays (GR, MR, AR activity); overexpression","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and pulldown plus reporter assay, single lab, functionally informative but mechanism not deeply dissected","pmids":["24454860"],"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 and enhancing IRF3 activation and IFN-β production upon Sendai virus infection.","method":"Overexpression; siRNA knockdown; CRISPR knockout; ubiquitination assay (K48-specific); IRF3 phosphorylation assay; IFN-β reporter assay","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple loss- and gain-of-function approaches with K48-specific ubiquitination assay, single lab","pmids":["33713958"],"is_preprint":false},{"year":2022,"finding":"HspBP1 interacts with BRCA1 and promotes BRCA1-mediated homologous recombination DNA repair; HspBP1 knockdown or overexpression in BRCA1-proficient breast cancer cells reduces HR repair efficiency and alters tumorigenicity. Independently, HspBP1 inhibits the association of Hsp70 with Apaf-1 to promote cell survival after ionizing radiation, regardless of BRCA1 status.","method":"Co-immunoprecipitation (HspBP1-BRCA1 interaction); HR repair assay; xenograft tumor model; siRNA knockdown; overexpression; Apaf-1/Hsp70 co-IP","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional HR assay and in vivo xenograft, plus Apaf-1 interaction dissected separately, single lab","pmids":["35387978"],"is_preprint":false},{"year":2019,"finding":"Yeast Fes1 has Hsp70-independent roles: Fes1 mutants defective for Hsp70 interaction retain the ability to support vacuole import and degradation (Vid pathway) degradation of gluconeogenic enzymes and cell wall integrity (CWI) signaling. Fes1 binds directly to the Vid substrate Fbp1 in vitro and captures the CWI kinase Slt2 from cell lysates via its armadillo domain.","method":"Hsp70-interaction-defective Fes1 mutants; in vitro binding assay (Fes1 + Fbp1); pulldown of Slt2 from lysate; yeast growth assays; Vid pathway assay","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding plus genetic mutant analysis in yeast, single lab, novel Hsp70-independent function established","pmids":["31242183"],"is_preprint":false},{"year":2026,"finding":"HSPBP1 Cys201 is identified as a target of the anti-necroptotic compound parthenolide (PTL); covalent modification at Cys201 contributes to necroptosis inhibition, and HSPBP1 knockdown confers partial resistance to necroptosis.","method":"Mass spectrometry (PTL-HSPBP1 covalent adduct at Cys201); co-incubation with purified HSPBP1; siRNA knockdown; necroptosis assay in HT-29 cells; mouse AAA model","journal":"Cell death & disease","confidence":"Low","confidence_rationale":"Tier 3 / Weak — mass spectrometry adduct mapping and KD phenotype, single study, mechanism at Cys201 not fully dissected beyond compound binding","pmids":["42014672"],"is_preprint":false}],"current_model":"HSPBP1 (and its yeast ortholog Fes1) is an armadillo-repeat nucleotide exchange factor for Hsp70/Hsc70 that uses a two-part mechanism: its concave armadillo domain embraces lobe II of the Hsp70 ATPase domain and sterically displaces lobe I to promote ADP release, while a flexible N-terminal release domain mimics substrate to compete with and evict persistent misfolded clients from the chaperone; released substrates are then triaged toward proteasomal degradation by the ubiquitin-proteasome system, a process requiring cytosolic Fes1S; additionally, HspBP1 inhibits the CHIP ubiquitin ligase when in complex with Hsc70 to protect selected clients (including CFTR and inducible Hsp70 family members) from degradation, regulates steroid receptor folding, localizes to stress granules where it binds RNA and interacts with SG proteins, and is subject to redox regulation via reversible methionine oxidation."},"narrative":{"mechanistic_narrative":"HSPBP1 (yeast ortholog Fes1) is an armadillo-repeat nucleotide exchange factor for Hsp70/Hsc70 that couples chaperone cycling to protein quality control [PMID:12417338, PMID:15694338]. Structurally it pairs a helical armadillo domain II, whose concave face embraces lobe II of the Hsp70 ATPase domain and sterically displaces lobe I to lower nucleotide affinity, with a flexible N-terminal release domain that mimics substrate and competes for the Hsp70 substrate-binding domain, so that nucleotide exchange and active eviction of persistent clients occur together [PMID:15694338, PMID:29323280, PMID:12651857]. Through this triaging activity HSPBP1 selectively releases misfolded proteins from Hsp70 and routes them toward polyubiquitylation and proteasomal degradation; loss of the factor causes substrate aggregation and a heightened heat-shock response, and a dedicated cytosolic isoform (Fes1S) is required for this degradative function [PMID:23530227, PMID:26912797]. In parallel, when complexed with Hsc70 HSPBP1 inhibits the CHIP ubiquitin ligase, stabilizing selected clients including immature CFTR and the inducible chaperones HSPA1L and HSPA2 in testes, where its loss in mice causes meiotic failure and spermatocyte apoptosis [PMID:15215316, PMID:24899640]. By the same CHIP-suppressing mechanism HSPBP1 limits clearance of mutant huntingtin in neurons [PMID:28847953]. HSPBP1 additionally antagonizes Hsp70 cytoprotection at lysosomes to promote membrane permeabilization and cell death [PMID:17855353], regulates steroid-receptor activity by reducing Hsp70 binding to the receptor ligand-binding domain [PMID:24454860], and is an integral RNA-binding component of oxidative-stress granules where it associates with G3BP1, HuR, and TIA-1/TIAR [PMID:32235396]. Its exchange activity is redox-tunable through reversible methionine oxidation of a cluster in the armadillo core, reversed by MsrA/MsrB [PMID:31806703].","teleology":[{"year":2002,"claim":"Established the core biochemical identity of HspBP1 by showing it is a nucleotide exchange factor that drives nucleotide dissociation from Hsp70-class chaperones, defining a eukaryotic NEF family with yeast Fes1p.","evidence":"In vitro nucleotide dissociation and refolding assays with yeast Ssa1p and mammalian Hsc70","pmids":["12417338"],"confidence":"High","gaps":["Structural basis of exchange not yet resolved","Did not address substrate release or downstream fate of clients"]},{"year":2003,"claim":"Mapped the two-domain architecture, showing the helical domain II suffices to bind Hsp70 and remodel its ATPase domain while the unstructured N-terminal domain enhances both functions.","evidence":"Circular dichroism, limited proteolysis, truncation mutagenesis, and luciferase renaturation assays","pmids":["12651857"],"confidence":"Medium","gaps":["Molecular role of domain I not defined","Single-lab biochemical study without structure"]},{"year":2003,"claim":"Showed how the inhibitory Hsp70-HspBP1 complex is resolved, requiring cooperative action of Hsp40 and TPR1 rather than either cochaperone alone.","evidence":"In vitro luciferase refolding, Kd competition assays, and inducible Hsp70 cell system","pmids":["14503850"],"confidence":"Medium","gaps":["Physiological context of TPR1/Hsp40 cooperation untested","Single lab"]},{"year":2004,"claim":"Identified a degradation-protective branch: when bound to Hsc70, HspBP1 inhibits CHIP ubiquitin ligase activity, sparing immature CFTR from proteasomal destruction and promoting its maturation.","evidence":"Reciprocal Co-IP, in vitro ubiquitin ligase assay, CFTR pulse-chase, and RNAi","pmids":["15215316"],"confidence":"High","gaps":["Selectivity of which clients are protected not defined","Reconciliation with the degradative NEF role not addressed"]},{"year":2005,"claim":"Provided the atomic mechanism of exchange, showing the armadillo concave face embraces ATPase lobe II and displaces lobe I to reduce nucleotide affinity, a mechanism distinct from BAG-1 and GrpE.","evidence":"X-ray crystallography of HspBP1 alone and with the Hsp70 ATPase domain, plus Fes1p yeast deletion genetics","pmids":["15694338"],"confidence":"High","gaps":["Did not capture substrate release contacts","Full-length complex structure not solved"]},{"year":2007,"claim":"Linked HspBP1 to cell-death decisions, showing it antagonizes Hsp70 stabilization of lysosomal membranes to promote permeabilization, cathepsin release, and caspase activation in a Hsp70-binding-dependent manner.","evidence":"Ectopic expression, RNAi, lysosomal permeability and cathepsin/caspase assays, Hsp70-binding mutant","pmids":["17855353"],"confidence":"Medium","gaps":["Direct lysosomal localization mechanism unclear","Single lab"]},{"year":2009,"claim":"Extended HspBP1 to extracellular signaling, showing secreted HspBP1 augments Hsp72-driven EGFR phosphorylation and ERK1/2 activation via its N-terminal domain.","evidence":"Co-IP from conditioned medium, EGFR/ERK signaling assays, N-terminal deletion analysis","pmids":["18986301"],"confidence":"Medium","gaps":["Receptor for the extracellular complex unidentified","Physiological relevance of secretion unclear"]},{"year":2011,"claim":"Showed HspBP1 binds Tag7 (PGRP-S) and Hsp70 to neutralize the cytotoxic Tag7-Hsp70 complex and lower the ATP needed for its dissociation.","evidence":"Co-IP, cytotoxicity and ATP-dependent dissociation assays in CD8+ lymphocytes","pmids":["21247889"],"confidence":"Medium","gaps":["Structural basis of Tag7 binding unknown","Single lab"]},{"year":2013,"claim":"Defined the triaging role, showing Fes1 selectively engages Hsp70-bound misfolded clients and triggers their release for polyubiquitylation; its loss causes aggregation and a strong stress response.","evidence":"FES1 deletion yeast genetics with polyubiquitylation, aggregation, and heat-shock reporter assays","pmids":["23530227"],"confidence":"High","gaps":["Molecular contacts driving release not yet resolved (addressed in 2018)","Coupling to specific E3 ligases not defined"]},{"year":2014,"claim":"Provided in vivo physiological context for CHIP inhibition, showing HSPBP1 stabilizes HSPA1L and HSPA2 in testes and is required for meiosis and spermatocyte survival.","evidence":"HSPBP1 knockout mice, Western blot, ubiquitylation assays, synaptonemal complex immunofluorescence","pmids":["24899640"],"confidence":"High","gaps":["Tissue-specific basis of client selection not defined","Relationship to the degradative NEF function unresolved"]},{"year":2014,"claim":"Identified a steroid-receptor regulatory role, showing HspBP1 reduces Hsp70 binding to the GR ligand-binding domain and inhibits GR/MR/AR transcriptional activity, unlike BAG-1M.","evidence":"Co-IP, pulldown, and GR/MR/AR reporter assays with overexpression","pmids":["24454860"],"confidence":"Medium","gaps":["Mechanism of receptor LBD effect not deeply dissected","Endogenous relevance untested"]},{"year":2016,"claim":"Revealed isoform-specific compartmentalization, defining a nuclear Fes1L and cytosolic Fes1S, with only Fes1S supporting proteasomal degradation of misfolded proteins.","evidence":"RNA-seq, isoform constructs, fluorescence localization, isoform-specific yeast deletions, degradation and heat-shock assays","pmids":["26912797"],"confidence":"High","gaps":["Function of nuclear Fes1L not defined","Human HSPBP1 isoform equivalence not established"]},{"year":2017,"claim":"Demonstrated disease-relevant CHIP suppression in brain, showing abundant neuronal HspBP1 dampens CHIP activity and its silencing reduces mutant huntingtin aggregation and neuropathology.","evidence":"CRISPR-Cas9 knockdown, CHIP ligase assays, Co-IP, and HD knock-in mouse model","pmids":["28847953"],"confidence":"High","gaps":["Whether HspBP1 lowering is broadly protective across proteinopathies unknown","Effect on global proteostasis in neurons not assessed"]},{"year":2018,"claim":"Resolved the substrate-release mechanism, showing a flexible N-terminal release domain mimics substrate and competes at the Hsp70 substrate-binding domain, distinct from armadillo-driven nucleotide exchange.","evidence":"In vitro peptide competition, release-domain mutagenesis, yeast and mammalian complementation, structural analysis of the RD","pmids":["29323280"],"confidence":"High","gaps":["Kinetic coupling of exchange and release not fully quantified","Client-specificity determinants of the RD unclear"]},{"year":2019,"claim":"Established redox regulation, showing reversible methionine oxidation of an armadillo-core cluster inhibits NEF activity, reversed by Mxr1/Mxr2 (MsrA/MsrB).","evidence":"In vitro and in-cell oxidation/activity assays, site-directed mutagenesis, and reductase genetics in yeast","pmids":["31806703"],"confidence":"High","gaps":["Physiological oxidative conditions triggering this in cells not defined","Conservation of the methionine cluster in human HSPBP1 not tested"]},{"year":2019,"claim":"Uncovered Hsp70-independent activities, showing Fes1 mutants unable to bind Hsp70 still support Vid-pathway degradation and CWI signaling by directly binding Fbp1 and capturing the kinase Slt2.","evidence":"Hsp70-interaction-defective mutants, in vitro Fbp1 binding, Slt2 pulldown, and yeast growth/Vid assays","pmids":["31242183"],"confidence":"Medium","gaps":["Mammalian equivalents of these moonlighting functions unknown","Single lab in yeast"]},{"year":2020,"claim":"Assigned a stress-granule and RNA-binding role, showing HspBP1 is an integral SG component that binds polyA-RNA and RNA homopolymers and regulates SG assembly.","evidence":"Immunofluorescence, Co-IP/MS, in vitro RNA binding, siRNA, and overexpression with single-granule analysis","pmids":["32235396"],"confidence":"Medium","gaps":["RNA-binding region not mapped","Relationship between SG role and NEF activity unresolved"]},{"year":2021,"claim":"Linked HspBP1 to innate immunity, showing it stabilizes RIG-I by inhibiting K48-linked ubiquitination, enhancing IRF3 activation and IFN-beta production.","evidence":"Overexpression, siRNA, CRISPR knockout, K48-specific ubiquitination, IRF3 phosphorylation, and IFN-beta reporter assays","pmids":["33713958"],"confidence":"Medium","gaps":["Direct E3 ligase antagonized not identified","Whether CHIP or another ligase is involved unclear"]},{"year":2022,"claim":"Connected HspBP1 to DNA repair and radioresistance, showing it interacts with BRCA1 to promote homologous recombination and separately inhibits Hsp70-Apaf-1 association to promote survival after irradiation.","evidence":"Co-IP, HR repair assay, xenograft model, siRNA/overexpression, and Apaf-1/Hsp70 co-IP","pmids":["35387978"],"confidence":"Medium","gaps":["Mechanism by which HspBP1 aids BRCA1 in HR undefined","Single lab"]},{"year":2026,"claim":"Identified a druggable cysteine, showing HSPBP1 Cys201 is covalently targeted by parthenolide and contributes to necroptosis inhibition.","evidence":"Mass spectrometry adduct mapping, purified-protein co-incubation, siRNA, necroptosis assay, and mouse AAA model","pmids":["42014672"],"confidence":"Low","gaps":["Mechanism downstream of Cys201 modification not dissected","Single study without independent confirmation"]},{"year":null,"claim":"How HSPBP1 reconciles its dual outputs — actively releasing clients for degradation versus protecting clients by inhibiting CHIP — and what determines client triage between these fates remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No defined switch governing degradative versus protective branches","Human full-length HSPBP1-Hsp70-client complex structure unsolved","Client-selection rules across tissues unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,0,5]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,7,8]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[14]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[13]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,4,2]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[4,10,14]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[11,17]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[16]}],"complexes":["stress granule"],"partners":["HSPA8","HSPA1L","HSPA2","STUB1","BRCA1","G3BP1","PGLYRP1","EGFR"],"other_free_text":[]}},"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 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Biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/38189890","citation_count":2,"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":17854,"output_tokens":5307,"usd":0.066584,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13576,"output_tokens":5778,"usd":0.106165,"stage2_stop_reason":"end_turn"},"total_usd":0.172749,"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\": 2005,\n      \"finding\": \"Crystal structure of HspBP1 alone and in complex with the Hsp70 ATPase domain reveals an armadillo-repeat fold whose concave face embraces lobe II of the ATPase domain; steric conflict displaces lobe I, reducing nucleotide affinity — a mechanism distinct from BAG-1 or GrpE, which instead trigger a conformational change in lobe II.\",\n      \"method\": \"X-ray crystallography (crystal structure of HspBP1 alone and in complex with Hsp70 ATPase domain fragment); yeast genetics (Fes1p deletion showing requirement for protein folding at 37°C)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution crystal structure with functional validation in yeast, replicated across two organisms, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"15694338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HspBP1 is a nucleotide exchange factor (NEF) for Hsc70; it promotes nucleotide dissociation from both yeast Ssa1p and mammalian Hsc70 in vitro, establishing it as a member of the eukaryotic NEF family homologous to yeast Fes1p.\",\n      \"method\": \"In vitro nucleotide dissociation assay; chaperone-mediated protein refolding assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay replicated with multiple Hsp70 orthologs, independently confirmed by subsequent structural study (PMID:15694338)\",\n      \"pmids\": [\"12417338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"HspBP1 inhibits the ubiquitin ligase activity of CHIP when HspBP1 is complexed with Hsc70, thereby interfering with CHIP-induced proteasomal degradation of immature CFTR and stimulating CFTR maturation.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitin ligase activity assay; pulse-chase analysis of CFTR maturation; RNAi knockdown\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP combined with in vitro ubiquitin ligase assay and functional CFTR maturation readout, multiple orthogonal methods in a single focused study\",\n      \"pmids\": [\"15215316\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HspBP1 has two structural domains: an N-terminal largely unstructured domain I (aa 1–83) and a helical domain II (aa 84–359). Domain II is sufficient to bind Hsp70 and alter the conformation of the Hsp70 ATPase domain; domain I enhances both functions.\",\n      \"method\": \"Circular dichroism; limited proteolysis; truncation mutagenesis; Hsp70-binding assay in reticulocyte lysate; luciferase renaturation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical methods (CD, limited proteolysis, truncation mutants, functional assay) in a single lab\",\n      \"pmids\": [\"12651857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Yeast Fes1 (ortholog of HspBP1) acts as a cytosolic triaging factor that selectively interacts with misfolded proteins bound to Hsp70 and triggers their release; in the absence of Fes1, misfolded proteins fail to undergo polyubiquitylation, aggregate, and induce a strong heat-shock response.\",\n      \"method\": \"Yeast genetics (FES1 deletion); polyubiquitylation assay; protein aggregation analysis; heat-shock reporter assay; binding assays with misfolded substrates\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with multiple orthogonal readouts (ubiquitylation, aggregation, stress reporter), placing Fes1/HspBP1 at a defined pathway node between Hsp70 and UPS degradation\",\n      \"pmids\": [\"23530227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Fes1 and HspBP1 each contain a flexible N-terminal release domain (RD) with substrate-mimicking properties; the RD contacts the Hsp70 substrate-binding domain and competes with peptide substrate for binding, ensuring efficient release of persistent substrates. The armadillo domain triggers nucleotide exchange while the RD drives substrate release.\",\n      \"method\": \"In vitro peptide competition assays; mutagenesis of the release domain; yeast complementation; mammalian cell functional assays; NMR/structural analysis of RD\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mechanistic dissection by mutagenesis, in vitro competition assays, and complementation in two organisms (yeast and mammalian cells) in a single rigorous study\",\n      \"pmids\": [\"29323280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The FES1 transcript is alternatively spliced at its 3' end to produce two isoforms: Fes1L (targeted to the nucleus, the first identified nuclear Hsp70 NEF) and Fes1S (cytosolic). Fes1S is essential for proteasomal degradation of misfolded proteins and proteostasis; Fes1L localizes to the nucleus but cannot substitute for cytosolic Fes1S function.\",\n      \"method\": \"RNA-seq; isoform-specific expression constructs; fluorescence microscopy for localization; yeast genetics (isoform-specific deletions); ubiquitin-proteasome degradation assays; heat-shock reporter assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — isoform localization confirmed by microscopy linked directly to functional rescue of degradation phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"26912797\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HSPBP1 inhibits CHIP-mediated ubiquitylation and proteasomal degradation of inducible HSP70 family members (HSPA1L and HSPA2) in testes, thereby stabilizing these chaperones at the posttranslational level. Loss of HSPBP1 in mice leads to impaired meiosis and spermatocyte apoptosis due to reduced HSPA1L and HSPA2 levels.\",\n      \"method\": \"HSPBP1 knockout mice; Western blot analysis; ubiquitylation assays; meiotic phenotype analysis (immunofluorescence of synaptonemal complexes)\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO mouse model with defined mechanistic pathway (CHIP inhibition → HSP70 stabilization) supported by ubiquitylation assays and phenotypic rescue logic\",\n      \"pmids\": [\"24899640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Neurons express abundant HspBP1 which suppresses CHIP ubiquitin ligase activity, resulting in low CHIP-mediated degradation of misfolded proteins. CRISPR-Cas9 silencing of HspBP1 in neurons increased CHIP activity and reduced mutant huntingtin aggregation and neuropathology in HD knock-in mice.\",\n      \"method\": \"CRISPR-Cas9 knockdown; CHIP ubiquitin ligase activity assay; Co-immunoprecipitation; immunofluorescence; Western blot; HD knock-in mouse model\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function by CRISPR in primary neurons and in vivo mouse model, with direct mechanistic link to CHIP ubiquitin ligase activity, multiple orthogonal approaches\",\n      \"pmids\": [\"28847953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The inhibitory effect of HspBP1 on Hsp70-dependent protein folding can be reversed by the cooperative action of both Hsp40 and TPR1 together; neither cochaperone alone is sufficient to dissociate the Hsp70-HspBP1 complex.\",\n      \"method\": \"In vitro luciferase refolding assay; Kd measurement by competition assays; Hela cell tetracycline-inducible Hsp70 expression system\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution plus cell-based validation, single lab with two orthogonal approaches\",\n      \"pmids\": [\"14503850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Fes1 undergoes reversible methionine oxidation at a cluster of three methionine residues in its core armadillo domain under oxidizing conditions; this oxidation inhibits NEF activity and consequently alters Hsp70 chaperone activity. Oxidation is reversed by cytoplasmic methionine sulfoxide reductases Mxr1 (MsrA) and Mxr2 (MsrB).\",\n      \"method\": \"In vitro oxidation and activity assays with recombinant proteins; site-directed mutagenesis; in-cell oxidation assays; genetic manipulation of Mxr1/Mxr2\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted in vitro assay with mutagenesis to map oxidation site, complemented by in-cell validation and identification of specific reductase erasers\",\n      \"pmids\": [\"31806703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"HspBP1 antagonizes the prosurvival function of Hsp70 by interfering with Hsp70-mediated stabilization of lysosomal membranes; ectopic HspBP1 promotes lysosomal membrane permeabilization, cathepsin release into cytosol, and caspase-3 activation in response to anticancer drugs, in a manner dependent on its ability to bind Hsp70.\",\n      \"method\": \"Ectopic expression; RNAi knockdown; lysosomal membrane permeability assay; cathepsin release assay; caspase-3 activation assay; Hsp70-binding mutant analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts with Hsp70-binding-dependent requirement established by mutant analysis, single lab\",\n      \"pmids\": [\"17855353\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"HspBP1 binds directly to Tag7 (PGRP-S) as well as to Hsp70, thereby eliminating the cytotoxic activity of the Tag7-Hsp70 complex and lowering the ATP concentration required to dissociate Tag7 from the Hsp70 peptide-binding site.\",\n      \"method\": \"Co-immunoprecipitation; cytotoxicity assays; ATP-dependent dissociation assay; immunodetection in CD8+ lymphocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional cytotoxicity assay and biochemical dissociation assay, single lab\",\n      \"pmids\": [\"21247889\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Extracellular HspBP1 co-immunoprecipitates with extracellular Hsp72 in conditioned medium and synergistically augments Hsp72-mediated EGFR phosphorylation and downstream ERK1/2 activation; the N-terminal domain of HspBP1 is required for this activity.\",\n      \"method\": \"Co-immunoprecipitation from conditioned medium; EGFR phosphorylation assay; ERK1/2 activation assay; N-terminal deletion mutant analysis; chromogranin A co-localization\",\n      \"journal\": \"Biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP combined with functional signaling assay and domain-deletion analysis, single lab\",\n      \"pmids\": [\"18986301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HspBP1 is an integral component of cytoplasmic stress granules (SGs) under oxidative stress, co-localizing with G3BP1, HuR, and TIA-1/TIAR; HspBP1 associates with polyA-RNA in vivo and binds RNA homopolymers directly in vitro. HspBP1 knockdown impairs SG assembly while overexpression promotes SG formation without stress, with the Hsp70-binding domain contributing to SG regulation.\",\n      \"method\": \"Immunofluorescence microscopy; co-immunoprecipitation; mass spectrometry; in vitro RNA binding assay; siRNA knockdown; overexpression; single-granule analysis\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (MS, Co-IP, in vitro RNA binding, KD, OE) in a single lab for a novel localization and function\",\n      \"pmids\": [\"32235396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HspBP1 reduces Hsp70 binding to the GR ligand-binding domain and inhibits glucocorticoid, mineralocorticoid, and androgen receptor transcriptional activity, in contrast to BAG-1M which has dose-dependent stimulatory/inhibitory effects. Hsp40 and steroid receptors preferentially associate with BAG-1M rather than HspBP1 in pulldown assays.\",\n      \"method\": \"Co-immunoprecipitation; pulldown assays; reporter gene assays (GR, MR, AR activity); overexpression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and pulldown plus reporter assay, single lab, functionally informative but mechanism not deeply dissected\",\n      \"pmids\": [\"24454860\"],\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 and enhancing IRF3 activation and IFN-β production upon Sendai virus infection.\",\n      \"method\": \"Overexpression; siRNA knockdown; CRISPR knockout; ubiquitination assay (K48-specific); IRF3 phosphorylation assay; IFN-β reporter assay\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple loss- and gain-of-function approaches with K48-specific ubiquitination assay, 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; HspBP1 knockdown or overexpression in BRCA1-proficient breast cancer cells reduces HR repair efficiency and alters tumorigenicity. Independently, HspBP1 inhibits the association of Hsp70 with Apaf-1 to promote cell survival after ionizing radiation, regardless of BRCA1 status.\",\n      \"method\": \"Co-immunoprecipitation (HspBP1-BRCA1 interaction); HR repair assay; xenograft tumor model; siRNA knockdown; overexpression; Apaf-1/Hsp70 co-IP\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional HR assay and in vivo xenograft, plus Apaf-1 interaction dissected separately, single lab\",\n      \"pmids\": [\"35387978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Yeast Fes1 has Hsp70-independent roles: Fes1 mutants defective for Hsp70 interaction retain the ability to support vacuole import and degradation (Vid pathway) degradation of gluconeogenic enzymes and cell wall integrity (CWI) signaling. Fes1 binds directly to the Vid substrate Fbp1 in vitro and captures the CWI kinase Slt2 from cell lysates via its armadillo domain.\",\n      \"method\": \"Hsp70-interaction-defective Fes1 mutants; in vitro binding assay (Fes1 + Fbp1); pulldown of Slt2 from lysate; yeast growth assays; Vid pathway assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding plus genetic mutant analysis in yeast, single lab, novel Hsp70-independent function established\",\n      \"pmids\": [\"31242183\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"HSPBP1 Cys201 is identified as a target of the anti-necroptotic compound parthenolide (PTL); covalent modification at Cys201 contributes to necroptosis inhibition, and HSPBP1 knockdown confers partial resistance to necroptosis.\",\n      \"method\": \"Mass spectrometry (PTL-HSPBP1 covalent adduct at Cys201); co-incubation with purified HSPBP1; siRNA knockdown; necroptosis assay in HT-29 cells; mouse AAA model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — mass spectrometry adduct mapping and KD phenotype, single study, mechanism at Cys201 not fully dissected beyond compound binding\",\n      \"pmids\": [\"42014672\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HSPBP1 (and its yeast ortholog Fes1) is an armadillo-repeat nucleotide exchange factor for Hsp70/Hsc70 that uses a two-part mechanism: its concave armadillo domain embraces lobe II of the Hsp70 ATPase domain and sterically displaces lobe I to promote ADP release, while a flexible N-terminal release domain mimics substrate to compete with and evict persistent misfolded clients from the chaperone; released substrates are then triaged toward proteasomal degradation by the ubiquitin-proteasome system, a process requiring cytosolic Fes1S; additionally, HspBP1 inhibits the CHIP ubiquitin ligase when in complex with Hsc70 to protect selected clients (including CFTR and inducible Hsp70 family members) from degradation, regulates steroid receptor folding, localizes to stress granules where it binds RNA and interacts with SG proteins, and is subject to redox regulation via reversible methionine oxidation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HSPBP1 (yeast ortholog Fes1) is an armadillo-repeat nucleotide exchange factor for Hsp70/Hsc70 that couples chaperone cycling to protein quality control [#1, #0]. Structurally it pairs a helical armadillo domain II, whose concave face embraces lobe II of the Hsp70 ATPase domain and sterically displaces lobe I to lower nucleotide affinity, with a flexible N-terminal release domain that mimics substrate and competes for the Hsp70 substrate-binding domain, so that nucleotide exchange and active eviction of persistent clients occur together [#0, #5, #3]. Through this triaging activity HSPBP1 selectively releases misfolded proteins from Hsp70 and routes them toward polyubiquitylation and proteasomal degradation; loss of the factor causes substrate aggregation and a heightened heat-shock response, and a dedicated cytosolic isoform (Fes1S) is required for this degradative function [#4, #6]. In parallel, when complexed with Hsc70 HSPBP1 inhibits the CHIP ubiquitin ligase, stabilizing selected clients including immature CFTR and the inducible chaperones HSPA1L and HSPA2 in testes, where its loss in mice causes meiotic failure and spermatocyte apoptosis [#2, #7]. By the same CHIP-suppressing mechanism HSPBP1 limits clearance of mutant huntingtin in neurons [#8]. HSPBP1 additionally antagonizes Hsp70 cytoprotection at lysosomes to promote membrane permeabilization and cell death [#11], regulates steroid-receptor activity by reducing Hsp70 binding to the receptor ligand-binding domain [#15], and is an integral RNA-binding component of oxidative-stress granules where it associates with G3BP1, HuR, and TIA-1/TIAR [#14]. Its exchange activity is redox-tunable through reversible methionine oxidation of a cluster in the armadillo core, reversed by MsrA/MsrB [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established the core biochemical identity of HspBP1 by showing it is a nucleotide exchange factor that drives nucleotide dissociation from Hsp70-class chaperones, defining a eukaryotic NEF family with yeast Fes1p.\",\n      \"evidence\": \"In vitro nucleotide dissociation and refolding assays with yeast Ssa1p and mammalian Hsc70\",\n      \"pmids\": [\"12417338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of exchange not yet resolved\", \"Did not address substrate release or downstream fate of clients\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped the two-domain architecture, showing the helical domain II suffices to bind Hsp70 and remodel its ATPase domain while the unstructured N-terminal domain enhances both functions.\",\n      \"evidence\": \"Circular dichroism, limited proteolysis, truncation mutagenesis, and luciferase renaturation assays\",\n      \"pmids\": [\"12651857\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular role of domain I not defined\", \"Single-lab biochemical study without structure\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Showed how the inhibitory Hsp70-HspBP1 complex is resolved, requiring cooperative action of Hsp40 and TPR1 rather than either cochaperone alone.\",\n      \"evidence\": \"In vitro luciferase refolding, Kd competition assays, and inducible Hsp70 cell system\",\n      \"pmids\": [\"14503850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological context of TPR1/Hsp40 cooperation untested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified a degradation-protective branch: when bound to Hsc70, HspBP1 inhibits CHIP ubiquitin ligase activity, sparing immature CFTR from proteasomal destruction and promoting its maturation.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro ubiquitin ligase assay, CFTR pulse-chase, and RNAi\",\n      \"pmids\": [\"15215316\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Selectivity of which clients are protected not defined\", \"Reconciliation with the degradative NEF role not addressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Provided the atomic mechanism of exchange, showing the armadillo concave face embraces ATPase lobe II and displaces lobe I to reduce nucleotide affinity, a mechanism distinct from BAG-1 and GrpE.\",\n      \"evidence\": \"X-ray crystallography of HspBP1 alone and with the Hsp70 ATPase domain, plus Fes1p yeast deletion genetics\",\n      \"pmids\": [\"15694338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture substrate release contacts\", \"Full-length complex structure not solved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Linked HspBP1 to cell-death decisions, showing it antagonizes Hsp70 stabilization of lysosomal membranes to promote permeabilization, cathepsin release, and caspase activation in a Hsp70-binding-dependent manner.\",\n      \"evidence\": \"Ectopic expression, RNAi, lysosomal permeability and cathepsin/caspase assays, Hsp70-binding mutant\",\n      \"pmids\": [\"17855353\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct lysosomal localization mechanism unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Extended HspBP1 to extracellular signaling, showing secreted HspBP1 augments Hsp72-driven EGFR phosphorylation and ERK1/2 activation via its N-terminal domain.\",\n      \"evidence\": \"Co-IP from conditioned medium, EGFR/ERK signaling assays, N-terminal deletion analysis\",\n      \"pmids\": [\"18986301\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor for the extracellular complex unidentified\", \"Physiological relevance of secretion unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed HspBP1 binds Tag7 (PGRP-S) and Hsp70 to neutralize the cytotoxic Tag7-Hsp70 complex and lower the ATP needed for its dissociation.\",\n      \"evidence\": \"Co-IP, cytotoxicity and ATP-dependent dissociation assays in CD8+ lymphocytes\",\n      \"pmids\": [\"21247889\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of Tag7 binding unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the triaging role, showing Fes1 selectively engages Hsp70-bound misfolded clients and triggers their release for polyubiquitylation; its loss causes aggregation and a strong stress response.\",\n      \"evidence\": \"FES1 deletion yeast genetics with polyubiquitylation, aggregation, and heat-shock reporter assays\",\n      \"pmids\": [\"23530227\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular contacts driving release not yet resolved (addressed in 2018)\", \"Coupling to specific E3 ligases not defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided in vivo physiological context for CHIP inhibition, showing HSPBP1 stabilizes HSPA1L and HSPA2 in testes and is required for meiosis and spermatocyte survival.\",\n      \"evidence\": \"HSPBP1 knockout mice, Western blot, ubiquitylation assays, synaptonemal complex immunofluorescence\",\n      \"pmids\": [\"24899640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific basis of client selection not defined\", \"Relationship to the degradative NEF function unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified a steroid-receptor regulatory role, showing HspBP1 reduces Hsp70 binding to the GR ligand-binding domain and inhibits GR/MR/AR transcriptional activity, unlike BAG-1M.\",\n      \"evidence\": \"Co-IP, pulldown, and GR/MR/AR reporter assays with overexpression\",\n      \"pmids\": [\"24454860\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of receptor LBD effect not deeply dissected\", \"Endogenous relevance untested\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed isoform-specific compartmentalization, defining a nuclear Fes1L and cytosolic Fes1S, with only Fes1S supporting proteasomal degradation of misfolded proteins.\",\n      \"evidence\": \"RNA-seq, isoform constructs, fluorescence localization, isoform-specific yeast deletions, degradation and heat-shock assays\",\n      \"pmids\": [\"26912797\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Function of nuclear Fes1L not defined\", \"Human HSPBP1 isoform equivalence not established\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated disease-relevant CHIP suppression in brain, showing abundant neuronal HspBP1 dampens CHIP activity and its silencing reduces mutant huntingtin aggregation and neuropathology.\",\n      \"evidence\": \"CRISPR-Cas9 knockdown, CHIP ligase assays, Co-IP, and HD knock-in mouse model\",\n      \"pmids\": [\"28847953\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HspBP1 lowering is broadly protective across proteinopathies unknown\", \"Effect on global proteostasis in neurons not assessed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Resolved the substrate-release mechanism, showing a flexible N-terminal release domain mimics substrate and competes at the Hsp70 substrate-binding domain, distinct from armadillo-driven nucleotide exchange.\",\n      \"evidence\": \"In vitro peptide competition, release-domain mutagenesis, yeast and mammalian complementation, structural analysis of the RD\",\n      \"pmids\": [\"29323280\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetic coupling of exchange and release not fully quantified\", \"Client-specificity determinants of the RD unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established redox regulation, showing reversible methionine oxidation of an armadillo-core cluster inhibits NEF activity, reversed by Mxr1/Mxr2 (MsrA/MsrB).\",\n      \"evidence\": \"In vitro and in-cell oxidation/activity assays, site-directed mutagenesis, and reductase genetics in yeast\",\n      \"pmids\": [\"31806703\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological oxidative conditions triggering this in cells not defined\", \"Conservation of the methionine cluster in human HSPBP1 not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Uncovered Hsp70-independent activities, showing Fes1 mutants unable to bind Hsp70 still support Vid-pathway degradation and CWI signaling by directly binding Fbp1 and capturing the kinase Slt2.\",\n      \"evidence\": \"Hsp70-interaction-defective mutants, in vitro Fbp1 binding, Slt2 pulldown, and yeast growth/Vid assays\",\n      \"pmids\": [\"31242183\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian equivalents of these moonlighting functions unknown\", \"Single lab in yeast\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Assigned a stress-granule and RNA-binding role, showing HspBP1 is an integral SG component that binds polyA-RNA and RNA homopolymers and regulates SG assembly.\",\n      \"evidence\": \"Immunofluorescence, Co-IP/MS, in vitro RNA binding, siRNA, and overexpression with single-granule analysis\",\n      \"pmids\": [\"32235396\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"RNA-binding region not mapped\", \"Relationship between SG role and NEF activity unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Linked HspBP1 to innate immunity, showing it stabilizes RIG-I by inhibiting K48-linked ubiquitination, enhancing IRF3 activation and IFN-beta production.\",\n      \"evidence\": \"Overexpression, siRNA, CRISPR knockout, K48-specific ubiquitination, IRF3 phosphorylation, and IFN-beta reporter assays\",\n      \"pmids\": [\"33713958\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct E3 ligase antagonized not identified\", \"Whether CHIP or another ligase is involved unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected HspBP1 to DNA repair and radioresistance, showing it interacts with BRCA1 to promote homologous recombination and separately inhibits Hsp70-Apaf-1 association to promote survival after irradiation.\",\n      \"evidence\": \"Co-IP, HR repair assay, xenograft model, siRNA/overexpression, and Apaf-1/Hsp70 co-IP\",\n      \"pmids\": [\"35387978\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which HspBP1 aids BRCA1 in HR undefined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified a druggable cysteine, showing HSPBP1 Cys201 is covalently targeted by parthenolide and contributes to necroptosis inhibition.\",\n      \"evidence\": \"Mass spectrometry adduct mapping, purified-protein co-incubation, siRNA, necroptosis assay, and mouse AAA model\",\n      \"pmids\": [\"42014672\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Mechanism downstream of Cys201 modification not dissected\", \"Single study without independent confirmation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HSPBP1 reconciles its dual outputs — actively releasing clients for degradation versus protecting clients by inhibiting CHIP — and what determines client triage between these fates remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No defined switch governing degradative versus protective branches\", \"Human full-length HSPBP1-Hsp70-client complex structure unsolved\", \"Client-selection rules across tissues unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 0, 5]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 7, 8]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 4, 2]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [4, 10, 14]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [11, 17]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"complexes\": [\"stress granule\"],\n    \"partners\": [\"HSPA8\", \"HSPA1L\", \"HSPA2\", \"STUB1\", \"BRCA1\", \"G3BP1\", \"PGLYRP1\", \"EGFR\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":7,"faith_total":7,"faith_pct":100.0}}