{"gene":"DNAJB4","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":2016,"finding":"HLJ1/DNAJB4 directly binds to the catalytic and protein-binding domains of Src kinase through its amino acid Y172 and the P301/P304 motif, suppressing Src catalytic activity. Src-induced phosphorylation of HLJ1 at Y172 elevates the HLJ1-Src interaction, resulting in Src inhibition. HLJ1 also downregulates formation of oncogenic complexes involving EGFR, FAK, and STAT3 signaling pathways, thereby inhibiting epithelial-mesenchymal transition and lung cancer metastasis.","method":"shRNA silencing, ectopic expression, co-immunoprecipitation, site-directed mutagenesis (Y172, P301/P304), HLJ1-knockout mouse specimens, lung cancer patient specimens","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, mutagenesis of specific residues, KO mouse validation, patient specimen correlation, multiple orthogonal methods in single study","pmids":["27065329"],"is_preprint":false},{"year":2013,"finding":"DNAJB4 directly interacts with both wild-type (WT) and mutant E-cadherin (Ecad). Increased DNAJB4 expression stabilizes WT Ecad at the plasma membrane while inducing premature proteasomal degradation of unfolded HDGC-associated mutant Ecad (e.g., E757K), acting as a molecular mediator of endoplasmic reticulum-associated degradation (ERAD). The interaction is enhanced in the context of the unfolded mutant when proteasome degradation is inhibited.","method":"Drosophila genetic screen (DnaJ-1/Ecad interaction in vivo), co-immunoprecipitation (direct interaction), overexpression/knockdown in cells, proteasome inhibition, chick embryo chorioallantoic membrane assay","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods including in vivo genetic screen, direct binding assay, functional cellular assays, and in vivo tumor model","pmids":["24293545"],"is_preprint":false},{"year":2010,"finding":"HLJ1 specifically interacts with nucleophosmin (NPM1), forming a multiprotein complex that alters the nucleolar distribution and oligomerization state of NPM1. HLJ1 prevents NPM1 oligomerization by forming HLJ1-NPM1 heterodimers, and this complex recruits the transcriptional corepressor AP-2alpha to the MMP-2 promoter, suppressing MMP-2 expression and STAT3 activity. Silencing HLJ1 accelerates NPM1 oligomerization and increases MMP-2 and STAT3 activities.","method":"Co-immunoprecipitation, overexpression, siRNA knockdown, promoter reporter assay, western blotting","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP, functional KD and OE, promoter assay, single lab with multiple orthogonal methods","pmids":["20145123"],"is_preprint":false},{"year":2010,"finding":"Under acidic extracellular pH (pHe 6.4), HLJ1 undergoes tyrosine phosphorylation, and this tyrosine-phosphorylated form of HLJ1 markedly enhances interaction with beta-actin. The association between HLJ1 and beta-actin is tyrosine phosphorylation-dependent and is linked to impaired cell migration under acidic stress.","method":"Acidic culture conditions, co-immunoprecipitation, subcellular fractionation, phosphorylation site identification, migration assay","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP demonstrating phosphorylation-dependent binding, single lab, multiple methods","pmids":["20615403"],"is_preprint":false},{"year":2010,"finding":"HLJ1 is a substrate of caspase-3 during UV-induced apoptosis, cleaved at a non-typical caspase-3 cleavage site (MEID) at amino acids 125–128. HLJ1 overexpression promotes UV-induced apoptosis by enhancing JNK and caspase-3 activation. Caspase inhibitors (zVAD-fmk, DEVD-fmk) prevent UV-induced HLJ1 degradation.","method":"Flow cytometry, caspase-specific inhibitors, site identification by mutagenesis, enforced HLJ1 expression, western blotting","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — caspase cleavage site identified by mutagenesis, inhibitor rescue experiments, single lab with multiple orthogonal methods","pmids":["20494979"],"is_preprint":false},{"year":2006,"finding":"HLJ1 inhibits lung cancer cell proliferation, anchorage-independent growth, tumorigenesis, cell motility, and invasion, and slows cell cycle progression through a STAT1/P21(WAF1) pathway that is independent of P53 and interferon.","method":"HLJ1 overexpression and knockdown in CL1-5 cells, DNA microarray, pathway analysis, western blotting, in vivo tumorigenesis assay, cell cycle analysis","journal":"Journal of the National Cancer Institute","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD and OE with defined pathway readout, microarray, in vivo experiments, single lab","pmids":["16788156"],"is_preprint":false},{"year":2005,"finding":"Transcription factor YY1 directly upregulates HLJ1 basal promoter activity by binding to YY1-binding sites within the HLJ1 promoter region (-232 to +176). YY1-driven HLJ1 upregulation increases E-cadherin expression and suppresses cancer cell invasion; these effects are reversed by HLJ1 siRNA.","method":"Luciferase reporter assay, serial promoter deletion, site-directed mutagenesis, EMSA, co-transfection, YY1 overexpression, siRNA knockdown, invasion assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — EMSA confirming direct YY1 binding, mutagenesis of binding sites, luciferase reporter, epistasis via HLJ1 siRNA rescue, multiple orthogonal methods","pmids":["15782117"],"is_preprint":false},{"year":2007,"finding":"An enhancer segment (-2125 to -1039 bp upstream of transcription start site) controls HLJ1 expression. A minimal 50-bp element (-1492 to -1443 bp) contains an AP-1 site (-1457 to -1451 bp) that binds transcription factors FosB, JunB, and JunD in vivo. YY1 at the promoter and AP-1 at the enhancer act synergistically via DNA bending and multiprotein complex formation with coactivator p300 to upregulate HLJ1 expression >5-fold and inhibit cancer cell invasion.","method":"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), overexpression experiments, promoter deletion analysis, co-transfection","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — ChIP confirming in vivo AP-1 binding, promoter deletion mapping, multiple TF overexpression, multiple orthogonal methods in single study","pmids":["17510411"],"is_preprint":false},{"year":2008,"finding":"Curcumin transcriptionally upregulates HLJ1 through an AP-1 site within the HLJ1 enhancer, via the JNK/JunD signaling pathway. JNK phosphorylation by curcumin leads to JunD upregulation, which drives HLJ1 expression. HLJ1 induction then upregulates E-cadherin and suppresses lung cancer cell invasion and metastasis. JNK inhibitor SP-600125 attenuates curcumin-induced JunD and HLJ1 expression.","method":"Luciferase reporter assay, siRNA knockdown, JNK inhibitor treatment, in vitro invasion assay, in vivo metastasis assay, western blotting","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — pathway epistasis via inhibitor and siRNA, reporter assay, in vivo validation, single lab","pmids":["18794131"],"is_preprint":false},{"year":2022,"finding":"HLJ1/DNAJB4 acts as a molecular chaperone that converts misfolded IL-12p35 homodimers to monomers in LPS-stimulated macrophages, thereby maintaining bioactive IL-12p70 heterodimerization and secretion. This promotes IFN-γ production by NK cells and amplifies sepsis severity. HLJ1-deleted macrophages adoptively transferred into LPS-treated mice reduce IL-12 and IFN-γ levels and protect from IFN-γ-dependent mortality.","method":"HLJ1 knockout mice, adoptive macrophage transfer, CLP sepsis model, single-cell RNA sequencing, IL-12 and IFN-γ measurement, functional chaperone assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic chaperone function established with KO mice, adoptive transfer (epistasis), scRNA-seq, multiple orthogonal methods across multiple model systems","pmids":["35983991"],"is_preprint":false},{"year":2022,"finding":"DNAJB4 normally localizes to the Z-disc in skeletal muscle. Loss-of-function variants (stop gain p.Lys286Ter, missense p.Leu262Ser causing rapid degradation; missense p.Arg25Gln which is stable but functionally null) cause myopathy with early respiratory failure. DNAJB4 knockout mice develop muscle weakness, fiber atrophy, myofibrillar disorganization, and accumulation of Z-disc proteins and protein chaperones, establishing DNAJB4 as essential for skeletal muscle proteostasis.","method":"Exome sequencing, patient muscle biopsy, immunofluorescence localization, DNAJB4 KO mouse model, yeast complementation assay, protein disaggregation assay, heat shock protection assay","journal":"Acta neuropathologica","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple patient variants functionally validated in yeast and KO mouse model with multiple orthogonal cellular/histological readouts","pmids":["36264506"],"is_preprint":false},{"year":2022,"finding":"A dominant heterozygous DNAJB4 variant (p.F90L) causes a distal myopathy with cytoplasmic inclusions and accumulation of desmin, p62, HSP70, and DNAJB4 predominantly in type 1 muscle fibers. Both Dnajb4(F90L) knockin and Dnajb4 knockout mice develop muscle weakness and recapitulate the muscle pathology in soleus muscle, indicating defective chaperone function leads to selective muscle degeneration.","method":"Whole-exome sequencing, patient muscle biopsy, knockin mouse model, knockout mouse model, immunofluorescence, muscle function testing","journal":"Acta neuropathologica","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockin and KO mouse models both recapitulating pathology, patient validation, multiple histological readouts","pmids":["36512060"],"is_preprint":false},{"year":2006,"finding":"The carboxyl-terminal portion of HLJ1 directly binds the carboxyl tail of the human mu opioid receptor (but not the third cytoplasmic loop), as demonstrated by yeast two-hybrid, in vitro overlay (His-fusion HLJ1 + GST-fusion receptor tail), and co-immunoprecipitation in HEK cell lysates. Confocal microscopy shows co-localization of HLJ1 and the mu opioid receptor at the cell membrane.","method":"Yeast two-hybrid screen, overlay assay (in vitro direct binding), co-immunoprecipitation, confocal immunofluorescence","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — direct binding confirmed by overlay assay and Co-IP, co-localization shown, single lab with three orthogonal methods","pmids":["16542645"],"is_preprint":false},{"year":2011,"finding":"SDIM1, a novel neuronal membrane protein, physically interacts with DNAJB4 (both in vitro and in vivo by yeast two-hybrid and co-immunoprecipitation). Co-overexpression of SDIM1 attenuates cell death caused by DNAJB4 overexpression in neuro-progenitor cells, suggesting SDIM1 sequesters DNAJB4 to increase cell viability.","method":"Yeast two-hybrid, co-immunoprecipitation, overexpression in neuro-progenitor cells, cell viability assay","journal":"Molecular neurodegeneration","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and yeast two-hybrid for interaction, functional rescue by co-overexpression, single lab","pmids":["21255413"],"is_preprint":false},{"year":2018,"finding":"DNAJB4 is down-regulated in metastatic melanoma cells compared to primary melanoma cells. Overexpression of DNAJB4 suppresses invasion of melanoma cells through diminished expression and activities of MMP-2 and MMP-9.","method":"Targeted LC-MS/MS proteomics (parallel-reaction monitoring), cell invasion assay, MMP-2/MMP-9 activity assay","journal":"Analytical chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, proteomics quantification and functional invasion assay without detailed mechanistic pathway dissection","pmids":["29722524"],"is_preprint":false},{"year":2019,"finding":"DNAJB4 expression increases during epithelial-mesenchymal transition (EMT) in human mammary epithelial cells. Suppression of DNAJB4 in mesenchymal breast cancer cells decreases cell migration in vitro and reduces primary tumor growth, extravasation, and lung metastasis in vivo.","method":"Quantitative mass spectrometry proteomics, DNAJB4 knockdown, in vitro migration assay, in vivo xenograft and metastasis model","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — KD with in vitro and in vivo phenotypic readouts, proteomics discovery, single lab","pmids":["31221721"],"is_preprint":false},{"year":2011,"finding":"Hepatitis B virus (HBV) protein upregulates HLJ1 expression through the transcription factor YY1 sites within the HLJ1 promoter. YY1 expression is upregulated by HBV in a concentration-dependent manner, and knockdown of YY1 partially reduces HBV-induced HLJ1 activation.","method":"Transient and stable HBV expression in HepG2 cells, HLJ1 promoter activity assay, YY1 siRNA knockdown, western blotting","journal":"Virus research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — promoter reporter assay and siRNA, single lab, limited mechanistic depth","pmids":["21345358"],"is_preprint":false},{"year":2024,"finding":"DNAJB4/HLJ1 physically interacts with HSP70 (validated by AlphaFold-Multimer modeling and co-immunoprecipitation) and attenuates ER stress in APAP-induced liver injury. DNAJB4-deficient mice show exacerbated hepatic necrosis, elevated liver enzymes, enhanced c-jun/JNK activation, altered APAP metabolism with GSH depletion, and upregulated ER stress markers (ATF6, XBP1, CHOP). Restoration of DNAJB4 expression attenuates ER stress and liver injury.","method":"DNAJB4 KO mouse model (Dnajb4-/-), co-immunoprecipitation, AlphaFold-Multimer structural modeling, transcriptomic analysis, pharmacological ER stress inhibition, metabolic profiling","journal":"Cell biology and toxicology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse model with multiple readouts, Co-IP validating interaction with HSP70, multiple orthogonal methods, single lab","pmids":["42065820"],"is_preprint":false},{"year":2026,"finding":"AHSA1 binds to DNAJB4 (confirmed by co-immunoprecipitation) and promotes DNAJB4 protein production. The AHSA1-DNAJB4 complex suppresses ERAD pathway activity (reducing XBP-1s, ATF4, CHOP, GADD34 expression) and promotes endometrial cancer cell colony formation and survival. Knockdown of DNAJB4 negates the pro-tumorigenic effects of AHSA1 overexpression, placing DNAJB4 downstream of AHSA1 in this ERAD regulatory axis.","method":"Co-immunoprecipitation, DNAJB4 knockdown, AHSA1 overexpression, colony formation assay, flow cytometry apoptosis assay, western blot for ERAD proteins","journal":"Journal of reproductive immunology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — Co-IP, genetic epistasis by KD/OE combination, multiple pathway readouts, single lab","pmids":["41990440"],"is_preprint":false},{"year":2024,"finding":"DNAJB4 loss-of-function missense variants in the J-domain (p.K35N, p.R61G) produce stable proteins that fail to complement DNAJB4 function in yeast and fail to disaggregate TDP-43 client proteins, establishing the J-domain as essential for chaperone client-protein processing activity.","method":"Yeast complementation assay, TDP-43 disaggregation assay, protein stability assessment, whole-exome sequencing, patient clinical data","journal":"Acta neuropathologica communications","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro/yeast functional assays for chaperone activity, multiple variant characterization, single lab","pmids":["39468638"],"is_preprint":false},{"year":2013,"finding":"Andrographolide upregulates HLJ1 via JunB activation; HLJ1 induction then modulates AP-2alpha binding at the MMP-2 promoter to repress MMP-2 expression. Silencing of HLJ1 partially reverses the inhibition of cancer cell invasion by andrographolide.","method":"Drug screening using HLJ1 promoter-enhancer reporter, siRNA knockdown, MMP-2 promoter reporter, in vitro invasion assay, in vivo tumorigenesis","journal":"Carcinogenesis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — reporter assay and siRNA epistasis, limited mechanistic detail for JunB/AP-2α pathway, single lab","pmids":["23306212"],"is_preprint":false},{"year":2024,"finding":"HLJ1 deficiency in mice leads to altered gene signatures enriched in IL-6/STAT3 signaling, and DEN-induced STAT3 and H2AX phosphorylation is amplified. Long-term DEN treatment in HLJ1 KO mice enhances tumor proliferation with pronounced STAT3 phosphorylation in peritumoral normal tissues. Transplantation of HLJ1-wildtype cancer cells into HLJ1-deficient mice augments tumorigenesis, confirming a tumor-suppressive role for HLJ1 in the peritumoral microenvironment via STAT3 pathway suppression.","method":"HLJ1 KO mice, DEN carcinogenesis model, whole-genome transcriptomics, syngeneic transplantation assay, phospho-STAT3 and phospho-H2AX immunostaining","journal":"Cell biology and toxicology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse model with transcriptomics, epistasis via syngeneic transplantation, multiple readouts, single lab","pmids":["39738726"],"is_preprint":false},{"year":2023,"finding":"DNAJB4 overexpression activates the Hippo signaling pathway in triple-negative breast cancer (TNBC) cells, promoting apoptosis. DNAJB4 knockdown suppresses Hippo pathway activity and inhibits TNBC cell apoptosis.","method":"Gain- and loss-of-function in vitro and in vivo assays, western blot for Hippo pathway components, flow cytometry apoptosis assay, xenograft model","journal":"Discover oncology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — KD/OE with pathway protein readout only, no direct mechanistic link between DNAJB4 and Hippo components identified, single lab","pmids":["37012515"],"is_preprint":false},{"year":2008,"finding":"HLJ1 protein localizes to the cytoplasm of human embryonic liver cells, as determined by immunohistochemistry with validated monoclonal antibodies.","method":"Immunohistochemistry with anti-HLJ1 monoclonal antibodies on human embryonic liver tissue","journal":"Sheng wu gong cheng xue bao = Chinese journal of biotechnology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single localization method, no functional consequence linked","pmids":["18837411"],"is_preprint":false},{"year":2022,"finding":"Genetic deletion of HLJ1 does not alter blood loss, activity of extrinsic and intrinsic coagulation pathways, or blood clot formation in mice, despite HLJ1 being detectable in plasma and co-localizing with CD41 (platelet/megakaryocyte marker) in bone marrow. This is a negative result establishing no role for HLJ1 in blood coagulation under normal physiological conditions.","method":"HLJ1 KO mouse (HLJ1-/-), tail bleeding assay, coagulation pathway activity tests, thromboelastography, western blot, immunohistochemistry","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse model with multiple coagulation readouts, clear negative result across multiple assays, single lab","pmids":["35216179"],"is_preprint":false}],"current_model":"DNAJB4/HLJ1 is an HSP40/DNAJ family co-chaperone that functions in multiple cellular contexts: it acts as an endogenous Src kinase inhibitor by directly binding Src through Y172 and P301/P304 motifs (with Src-induced Y172 phosphorylation enhancing inhibitory interaction), modulates E-cadherin stability and ERAD by distinguishing folded from misfolded client proteins, forms inhibitory heterodimers with NPM1 to recruit AP-2alpha and suppress MMP-2/STAT3, interacts with HSP70 to attenuate ER stress, promotes IL-12p70 heterodimerization in macrophages to amplify sepsis-associated IFN-γ responses, localizes to the Z-disc in skeletal muscle where it is required for myofibrillar proteostasis, and is transcriptionally regulated by YY1 (at its promoter) and AP-1 family members (FosB, JunB, JunD at its enhancer) acting synergistically with the coactivator p300."},"narrative":{"mechanistic_narrative":"DNAJB4 (HLJ1) is an HSP40/DNAJ-family co-chaperone whose J-domain-dependent chaperone activity governs client-protein triage across proteostasis, tissue homeostasis, and tumor suppression [PMID:36264506, PMID:39468638]. Its central biochemical function is to distinguish folded from misfolded clients: it stabilizes correctly folded proteins while routing aberrant species toward proteasomal clearance, exemplified by its direct binding to E-cadherin, where it preserves wild-type protein at the plasma membrane but drives ERAD of misfolded HDGC mutant E-cadherin [PMID:24293545]. This client-triage activity depends on an intact J-domain, since loss-of-function J-domain variants produce stable proteins that fail to disaggregate TDP-43 and fail to complement DNAJB4 in yeast [PMID:39468638], and operates in concert with the HSP70 chaperone system to limit ER stress [PMID:42065820]. In skeletal muscle DNAJB4 localizes to the Z-disc and is essential for myofibrillar proteostasis; loss-of-function and dominant variants cause myopathy with accumulation of Z-disc and chaperone proteins and selective fiber degeneration, establishing a direct Mendelian disease link [PMID:36264506, PMID:36512060]. As a chaperone DNAJB4 also remodels the oligomeric/assembly state of partner proteins—maintaining bioactive IL-12p70 heterodimers in LPS-stimulated macrophages to amplify NK-cell IFN-γ and sepsis severity [PMID:35983991], and forming heterodimers with NPM1 that recruit AP-2alpha to repress MMP-2 and STAT3 [PMID:20145123]. Across epithelial cancers DNAJB4 acts as a tumor suppressor, directly binding and inhibiting Src kinase through its Y172 and P301/P304 motifs to dismantle EGFR/FAK/STAT3 oncogenic signaling and block EMT and metastasis [PMID:27065329], and suppressing the peritumoral IL-6/STAT3 axis [PMID:39738726]. Its expression is controlled by YY1 at the promoter acting synergistically with AP-1 factors (FosB, JunB, JunD) and p300 at an upstream enhancer [PMID:15782117, PMID:17510411].","teleology":[{"year":2006,"claim":"Established DNAJB4/HLJ1 as a functional tumor suppressor, answering whether this chaperone has a direct role in cancer cell behavior rather than being a passive marker.","evidence":"overexpression/knockdown in CL1-5 lung cancer cells with in vivo tumorigenesis and a defined STAT1/p21 pathway readout","pmids":["16788156"],"confidence":"Medium","gaps":["Molecular mechanism linking DNAJB4 chaperone activity to STAT1/p21 not defined","p53/interferon-independence shown but upstream trigger unknown"]},{"year":2005,"claim":"Identified the transcriptional driver of DNAJB4, showing YY1 directly activates its promoter and that this circuit controls E-cadherin and invasion.","evidence":"luciferase reporters, promoter deletion, EMSA and site-directed mutagenesis with HLJ1 siRNA epistasis","pmids":["15782117"],"confidence":"High","gaps":["Did not address enhancer-level regulation","Mechanism by which DNAJB4 raises E-cadherin not resolved"]},{"year":2007,"claim":"Resolved the full regulatory architecture, showing an upstream enhancer with an AP-1 site cooperates with the YY1 promoter via p300 to amplify DNAJB4 expression.","evidence":"ChIP for in vivo FosB/JunB/JunD binding, promoter/enhancer deletion mapping and TF overexpression","pmids":["17510411"],"confidence":"High","gaps":["Physiological signals engaging this enhancer not defined here","DNA-bending/synergy model not structurally confirmed"]},{"year":2010,"claim":"Defined a chaperone-based transcriptional control mechanism whereby DNAJB4 heterodimerizes with NPM1 to repress MMP-2 and STAT3.","evidence":"Co-IP, siRNA/overexpression and MMP-2 promoter reporter assays mapping AP-2alpha recruitment","pmids":["20145123"],"confidence":"Medium","gaps":["Direct vs indirect AP-2alpha recruitment not fully resolved","Stoichiometry of HLJ1-NPM1 heterodimer not determined"]},{"year":2010,"claim":"Showed DNAJB4 is itself regulated post-translationally, being a caspase-3 substrate that promotes UV-induced apoptosis.","evidence":"caspase inhibitor rescue, mutagenesis of a non-canonical MEID cleavage site, enforced expression","pmids":["20494979"],"confidence":"Medium","gaps":["Functional consequence of cleaved fragments unknown","Link between cleavage and chaperone activity not tested"]},{"year":2013,"claim":"Established the core client-triage chaperone function: DNAJB4 distinguishes folded from misfolded E-cadherin and mediates ERAD of mutant client.","evidence":"Drosophila genetic screen, direct Co-IP binding, proteasome inhibition and CAM tumor assay","pmids":["24293545"],"confidence":"High","gaps":["Recognition determinants for misfolded client not defined","HSP70 cooperation not addressed in this study"]},{"year":2016,"claim":"Defined the direct molecular basis of DNAJB4 tumor suppression: it binds and inhibits Src kinase through specific residues, collapsing downstream oncogenic signaling.","evidence":"reciprocal Co-IP, Y172 and P301/P304 mutagenesis, KO mouse and patient specimens","pmids":["27065329"],"confidence":"High","gaps":["Whether Src inhibition requires chaperone/J-domain activity not resolved","Relationship to NPM1/STAT3 axis not integrated"]},{"year":2022,"claim":"Generalized the chaperone assembly-control function to immunity, showing DNAJB4 converts misfolded IL-12p35 to enable bioactive IL-12p70 and drive IFN-γ in sepsis.","evidence":"KO mice, adoptive macrophage transfer, CLP model, scRNA-seq and chaperone assays","pmids":["35983991"],"confidence":"High","gaps":["Structural basis of p35 remodeling not determined","Whether the same mechanism operates in human macrophages not shown"]},{"year":2022,"claim":"Established DNAJB4 as a Mendelian disease gene, localizing it to the muscle Z-disc and showing loss-of-function and dominant variants cause myopathy through proteostatic failure.","evidence":"exome sequencing, patient biopsies, KO and knockin mouse models, yeast complementation and disaggregation assays","pmids":["36264506","36512060"],"confidence":"High","gaps":["Specific endogenous muscle clients of DNAJB4 not identified","Why type 1 fibers are selectively vulnerable unexplained"]},{"year":2024,"claim":"Mapped the chaperone activity to the J-domain, showing disease variants there preserve protein stability but abolish client disaggregation.","evidence":"yeast complementation and TDP-43 disaggregation assays with J-domain missense variants","pmids":["39468638"],"confidence":"Medium","gaps":["HSP70 ATPase coupling by the J-domain not directly measured","TDP-43 used as proxy client; native clients not tested"]},{"year":2024,"claim":"Linked DNAJB4 to ER-stress control via HSP70, showing its loss exacerbates drug-induced liver injury through unresolved ER stress.","evidence":"Dnajb4-/- mice, Co-IP and AlphaFold-Multimer modeling of HSP70 interaction, ER-stress marker profiling","pmids":["42065820"],"confidence":"Medium","gaps":["Direct HSP70 binding interface not experimentally resolved","Whether ER-stress effect is cell-autonomous unclear"]},{"year":2024,"claim":"Extended tumor suppression to the microenvironment, showing HLJ1 restrains IL-6/STAT3 signaling in peritumoral tissue.","evidence":"KO mice, DEN carcinogenesis, transcriptomics and syngeneic transplantation","pmids":["39738726"],"confidence":"Medium","gaps":["Cell type mediating peritumoral STAT3 suppression not pinpointed","Direct DNAJB4-STAT3 molecular link not established"]},{"year":null,"claim":"How DNAJB4 mechanistically reconciles its dual roles—tumor suppressor in epithelial cancers versus EMT/metastasis promoter in some breast and mesenchymal contexts—remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["Context-dependent client repertoire not defined","No unifying structural or regulatory model for opposing phenotypes","Whether HSP70 partnering differs across tissues unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0044183","term_label":"protein folding chaperone","supporting_discovery_ids":[1,9,10,19]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[23]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[10]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1,17]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,10,19]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[17]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[10,11]}],"complexes":[],"partners":["SRC","CDH1","NPM1","HSPA1A","AHSA1","OPRM1","ACTB","SDIM1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9UDY4","full_name":"DnaJ homolog subfamily B member 4","aliases":["Heat shock 40 kDa protein 1 homolog","HSP40 homolog","Heat shock protein 40 homolog","Human liver DnaJ-like protein"],"length_aa":337,"mass_kda":37.8,"function":"Probable chaperone. Stimulates ATP hydrolysis and the folding of unfolded proteins mediated by HSPA1A/B (in vitro) (PubMed:24318877)","subcellular_location":"Cytoplasm; Cell membrane; Cytoplasm, myofibril, sarcomere, Z line","url":"https://www.uniprot.org/uniprotkb/Q9UDY4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DNAJB4","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000162616","cell_line_id":"CID000018","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"HSPH1","stoichiometry":0.2},{"gene":"HSPA8","stoichiometry":0.2},{"gene":"GSTP1","stoichiometry":0.2},{"gene":"GDI2","stoichiometry":0.2},{"gene":"HSPA4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000018","total_profiled":1310},"omim":[{"mim_id":"620326","title":"CONGENITAL MYOPATHY 21 WITH EARLY RESPIRATORY FAILURE; CMYO21","url":"https://www.omim.org/entry/620326"},{"mim_id":"619089","title":"GIPC PDZ DOMAIN-CONTAINING FAMILY, MEMBER 2; GIPC2","url":"https://www.omim.org/entry/619089"},{"mim_id":"611327","title":"DNAJ/HSP40 HOMOLOG, SUBFAMILY B, MEMBER 4; DNAJB4","url":"https://www.omim.org/entry/611327"},{"mim_id":"117000","title":"CONGENITAL MYOPATHY 1A, AUTOSOMAL DOMINANT, WITH SUSCEPTIBILITY TO MALIGNANT HYPERTHERMIA; CMYO1A","url":"https://www.omim.org/entry/117000"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Plasma membrane","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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and protein-binding domains of Src kinase through its amino acid Y172 and the P301/P304 motif, suppressing Src catalytic activity. Src-induced phosphorylation of HLJ1 at Y172 elevates the HLJ1-Src interaction, resulting in Src inhibition. HLJ1 also downregulates formation of oncogenic complexes involving EGFR, FAK, and STAT3 signaling pathways, thereby inhibiting epithelial-mesenchymal transition and lung cancer metastasis.\",\n      \"method\": \"shRNA silencing, ectopic expression, co-immunoprecipitation, site-directed mutagenesis (Y172, P301/P304), HLJ1-knockout mouse specimens, lung cancer patient specimens\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, mutagenesis of specific residues, KO mouse validation, patient specimen correlation, multiple orthogonal methods in single study\",\n      \"pmids\": [\"27065329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"DNAJB4 directly interacts with both wild-type (WT) and mutant E-cadherin (Ecad). Increased DNAJB4 expression stabilizes WT Ecad at the plasma membrane while inducing premature proteasomal degradation of unfolded HDGC-associated mutant Ecad (e.g., E757K), acting as a molecular mediator of endoplasmic reticulum-associated degradation (ERAD). The interaction is enhanced in the context of the unfolded mutant when proteasome degradation is inhibited.\",\n      \"method\": \"Drosophila genetic screen (DnaJ-1/Ecad interaction in vivo), co-immunoprecipitation (direct interaction), overexpression/knockdown in cells, proteasome inhibition, chick embryo chorioallantoic membrane assay\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods including in vivo genetic screen, direct binding assay, functional cellular assays, and in vivo tumor model\",\n      \"pmids\": [\"24293545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HLJ1 specifically interacts with nucleophosmin (NPM1), forming a multiprotein complex that alters the nucleolar distribution and oligomerization state of NPM1. HLJ1 prevents NPM1 oligomerization by forming HLJ1-NPM1 heterodimers, and this complex recruits the transcriptional corepressor AP-2alpha to the MMP-2 promoter, suppressing MMP-2 expression and STAT3 activity. Silencing HLJ1 accelerates NPM1 oligomerization and increases MMP-2 and STAT3 activities.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, siRNA knockdown, promoter reporter assay, western blotting\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP, functional KD and OE, promoter assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"20145123\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Under acidic extracellular pH (pHe 6.4), HLJ1 undergoes tyrosine phosphorylation, and this tyrosine-phosphorylated form of HLJ1 markedly enhances interaction with beta-actin. The association between HLJ1 and beta-actin is tyrosine phosphorylation-dependent and is linked to impaired cell migration under acidic stress.\",\n      \"method\": \"Acidic culture conditions, co-immunoprecipitation, subcellular fractionation, phosphorylation site identification, migration assay\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP demonstrating phosphorylation-dependent binding, single lab, multiple methods\",\n      \"pmids\": [\"20615403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HLJ1 is a substrate of caspase-3 during UV-induced apoptosis, cleaved at a non-typical caspase-3 cleavage site (MEID) at amino acids 125–128. HLJ1 overexpression promotes UV-induced apoptosis by enhancing JNK and caspase-3 activation. Caspase inhibitors (zVAD-fmk, DEVD-fmk) prevent UV-induced HLJ1 degradation.\",\n      \"method\": \"Flow cytometry, caspase-specific inhibitors, site identification by mutagenesis, enforced HLJ1 expression, western blotting\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — caspase cleavage site identified by mutagenesis, inhibitor rescue experiments, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"20494979\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HLJ1 inhibits lung cancer cell proliferation, anchorage-independent growth, tumorigenesis, cell motility, and invasion, and slows cell cycle progression through a STAT1/P21(WAF1) pathway that is independent of P53 and interferon.\",\n      \"method\": \"HLJ1 overexpression and knockdown in CL1-5 cells, DNA microarray, pathway analysis, western blotting, in vivo tumorigenesis assay, cell cycle analysis\",\n      \"journal\": \"Journal of the National Cancer Institute\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD and OE with defined pathway readout, microarray, in vivo experiments, single lab\",\n      \"pmids\": [\"16788156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Transcription factor YY1 directly upregulates HLJ1 basal promoter activity by binding to YY1-binding sites within the HLJ1 promoter region (-232 to +176). YY1-driven HLJ1 upregulation increases E-cadherin expression and suppresses cancer cell invasion; these effects are reversed by HLJ1 siRNA.\",\n      \"method\": \"Luciferase reporter assay, serial promoter deletion, site-directed mutagenesis, EMSA, co-transfection, YY1 overexpression, siRNA knockdown, invasion assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — EMSA confirming direct YY1 binding, mutagenesis of binding sites, luciferase reporter, epistasis via HLJ1 siRNA rescue, multiple orthogonal methods\",\n      \"pmids\": [\"15782117\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"An enhancer segment (-2125 to -1039 bp upstream of transcription start site) controls HLJ1 expression. A minimal 50-bp element (-1492 to -1443 bp) contains an AP-1 site (-1457 to -1451 bp) that binds transcription factors FosB, JunB, and JunD in vivo. YY1 at the promoter and AP-1 at the enhancer act synergistically via DNA bending and multiprotein complex formation with coactivator p300 to upregulate HLJ1 expression >5-fold and inhibit cancer cell invasion.\",\n      \"method\": \"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), overexpression experiments, promoter deletion analysis, co-transfection\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — ChIP confirming in vivo AP-1 binding, promoter deletion mapping, multiple TF overexpression, multiple orthogonal methods in single study\",\n      \"pmids\": [\"17510411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Curcumin transcriptionally upregulates HLJ1 through an AP-1 site within the HLJ1 enhancer, via the JNK/JunD signaling pathway. JNK phosphorylation by curcumin leads to JunD upregulation, which drives HLJ1 expression. HLJ1 induction then upregulates E-cadherin and suppresses lung cancer cell invasion and metastasis. JNK inhibitor SP-600125 attenuates curcumin-induced JunD and HLJ1 expression.\",\n      \"method\": \"Luciferase reporter assay, siRNA knockdown, JNK inhibitor treatment, in vitro invasion assay, in vivo metastasis assay, western blotting\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — pathway epistasis via inhibitor and siRNA, reporter assay, in vivo validation, single lab\",\n      \"pmids\": [\"18794131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HLJ1/DNAJB4 acts as a molecular chaperone that converts misfolded IL-12p35 homodimers to monomers in LPS-stimulated macrophages, thereby maintaining bioactive IL-12p70 heterodimerization and secretion. This promotes IFN-γ production by NK cells and amplifies sepsis severity. HLJ1-deleted macrophages adoptively transferred into LPS-treated mice reduce IL-12 and IFN-γ levels and protect from IFN-γ-dependent mortality.\",\n      \"method\": \"HLJ1 knockout mice, adoptive macrophage transfer, CLP sepsis model, single-cell RNA sequencing, IL-12 and IFN-γ measurement, functional chaperone assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic chaperone function established with KO mice, adoptive transfer (epistasis), scRNA-seq, multiple orthogonal methods across multiple model systems\",\n      \"pmids\": [\"35983991\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DNAJB4 normally localizes to the Z-disc in skeletal muscle. Loss-of-function variants (stop gain p.Lys286Ter, missense p.Leu262Ser causing rapid degradation; missense p.Arg25Gln which is stable but functionally null) cause myopathy with early respiratory failure. DNAJB4 knockout mice develop muscle weakness, fiber atrophy, myofibrillar disorganization, and accumulation of Z-disc proteins and protein chaperones, establishing DNAJB4 as essential for skeletal muscle proteostasis.\",\n      \"method\": \"Exome sequencing, patient muscle biopsy, immunofluorescence localization, DNAJB4 KO mouse model, yeast complementation assay, protein disaggregation assay, heat shock protection assay\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple patient variants functionally validated in yeast and KO mouse model with multiple orthogonal cellular/histological readouts\",\n      \"pmids\": [\"36264506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A dominant heterozygous DNAJB4 variant (p.F90L) causes a distal myopathy with cytoplasmic inclusions and accumulation of desmin, p62, HSP70, and DNAJB4 predominantly in type 1 muscle fibers. Both Dnajb4(F90L) knockin and Dnajb4 knockout mice develop muscle weakness and recapitulate the muscle pathology in soleus muscle, indicating defective chaperone function leads to selective muscle degeneration.\",\n      \"method\": \"Whole-exome sequencing, patient muscle biopsy, knockin mouse model, knockout mouse model, immunofluorescence, muscle function testing\",\n      \"journal\": \"Acta neuropathologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockin and KO mouse models both recapitulating pathology, patient validation, multiple histological readouts\",\n      \"pmids\": [\"36512060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The carboxyl-terminal portion of HLJ1 directly binds the carboxyl tail of the human mu opioid receptor (but not the third cytoplasmic loop), as demonstrated by yeast two-hybrid, in vitro overlay (His-fusion HLJ1 + GST-fusion receptor tail), and co-immunoprecipitation in HEK cell lysates. Confocal microscopy shows co-localization of HLJ1 and the mu opioid receptor at the cell membrane.\",\n      \"method\": \"Yeast two-hybrid screen, overlay assay (in vitro direct binding), co-immunoprecipitation, confocal immunofluorescence\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — direct binding confirmed by overlay assay and Co-IP, co-localization shown, single lab with three orthogonal methods\",\n      \"pmids\": [\"16542645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"SDIM1, a novel neuronal membrane protein, physically interacts with DNAJB4 (both in vitro and in vivo by yeast two-hybrid and co-immunoprecipitation). Co-overexpression of SDIM1 attenuates cell death caused by DNAJB4 overexpression in neuro-progenitor cells, suggesting SDIM1 sequesters DNAJB4 to increase cell viability.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, overexpression in neuro-progenitor cells, cell viability assay\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and yeast two-hybrid for interaction, functional rescue by co-overexpression, single lab\",\n      \"pmids\": [\"21255413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"DNAJB4 is down-regulated in metastatic melanoma cells compared to primary melanoma cells. Overexpression of DNAJB4 suppresses invasion of melanoma cells through diminished expression and activities of MMP-2 and MMP-9.\",\n      \"method\": \"Targeted LC-MS/MS proteomics (parallel-reaction monitoring), cell invasion assay, MMP-2/MMP-9 activity assay\",\n      \"journal\": \"Analytical chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, proteomics quantification and functional invasion assay without detailed mechanistic pathway dissection\",\n      \"pmids\": [\"29722524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DNAJB4 expression increases during epithelial-mesenchymal transition (EMT) in human mammary epithelial cells. Suppression of DNAJB4 in mesenchymal breast cancer cells decreases cell migration in vitro and reduces primary tumor growth, extravasation, and lung metastasis in vivo.\",\n      \"method\": \"Quantitative mass spectrometry proteomics, DNAJB4 knockdown, in vitro migration assay, in vivo xenograft and metastasis model\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — KD with in vitro and in vivo phenotypic readouts, proteomics discovery, single lab\",\n      \"pmids\": [\"31221721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Hepatitis B virus (HBV) protein upregulates HLJ1 expression through the transcription factor YY1 sites within the HLJ1 promoter. YY1 expression is upregulated by HBV in a concentration-dependent manner, and knockdown of YY1 partially reduces HBV-induced HLJ1 activation.\",\n      \"method\": \"Transient and stable HBV expression in HepG2 cells, HLJ1 promoter activity assay, YY1 siRNA knockdown, western blotting\",\n      \"journal\": \"Virus research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — promoter reporter assay and siRNA, single lab, limited mechanistic depth\",\n      \"pmids\": [\"21345358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DNAJB4/HLJ1 physically interacts with HSP70 (validated by AlphaFold-Multimer modeling and co-immunoprecipitation) and attenuates ER stress in APAP-induced liver injury. DNAJB4-deficient mice show exacerbated hepatic necrosis, elevated liver enzymes, enhanced c-jun/JNK activation, altered APAP metabolism with GSH depletion, and upregulated ER stress markers (ATF6, XBP1, CHOP). Restoration of DNAJB4 expression attenuates ER stress and liver injury.\",\n      \"method\": \"DNAJB4 KO mouse model (Dnajb4-/-), co-immunoprecipitation, AlphaFold-Multimer structural modeling, transcriptomic analysis, pharmacological ER stress inhibition, metabolic profiling\",\n      \"journal\": \"Cell biology and toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse model with multiple readouts, Co-IP validating interaction with HSP70, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"42065820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"AHSA1 binds to DNAJB4 (confirmed by co-immunoprecipitation) and promotes DNAJB4 protein production. The AHSA1-DNAJB4 complex suppresses ERAD pathway activity (reducing XBP-1s, ATF4, CHOP, GADD34 expression) and promotes endometrial cancer cell colony formation and survival. Knockdown of DNAJB4 negates the pro-tumorigenic effects of AHSA1 overexpression, placing DNAJB4 downstream of AHSA1 in this ERAD regulatory axis.\",\n      \"method\": \"Co-immunoprecipitation, DNAJB4 knockdown, AHSA1 overexpression, colony formation assay, flow cytometry apoptosis assay, western blot for ERAD proteins\",\n      \"journal\": \"Journal of reproductive immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — Co-IP, genetic epistasis by KD/OE combination, multiple pathway readouts, single lab\",\n      \"pmids\": [\"41990440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"DNAJB4 loss-of-function missense variants in the J-domain (p.K35N, p.R61G) produce stable proteins that fail to complement DNAJB4 function in yeast and fail to disaggregate TDP-43 client proteins, establishing the J-domain as essential for chaperone client-protein processing activity.\",\n      \"method\": \"Yeast complementation assay, TDP-43 disaggregation assay, protein stability assessment, whole-exome sequencing, patient clinical data\",\n      \"journal\": \"Acta neuropathologica communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro/yeast functional assays for chaperone activity, multiple variant characterization, single lab\",\n      \"pmids\": [\"39468638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Andrographolide upregulates HLJ1 via JunB activation; HLJ1 induction then modulates AP-2alpha binding at the MMP-2 promoter to repress MMP-2 expression. Silencing of HLJ1 partially reverses the inhibition of cancer cell invasion by andrographolide.\",\n      \"method\": \"Drug screening using HLJ1 promoter-enhancer reporter, siRNA knockdown, MMP-2 promoter reporter, in vitro invasion assay, in vivo tumorigenesis\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — reporter assay and siRNA epistasis, limited mechanistic detail for JunB/AP-2α pathway, single lab\",\n      \"pmids\": [\"23306212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HLJ1 deficiency in mice leads to altered gene signatures enriched in IL-6/STAT3 signaling, and DEN-induced STAT3 and H2AX phosphorylation is amplified. Long-term DEN treatment in HLJ1 KO mice enhances tumor proliferation with pronounced STAT3 phosphorylation in peritumoral normal tissues. Transplantation of HLJ1-wildtype cancer cells into HLJ1-deficient mice augments tumorigenesis, confirming a tumor-suppressive role for HLJ1 in the peritumoral microenvironment via STAT3 pathway suppression.\",\n      \"method\": \"HLJ1 KO mice, DEN carcinogenesis model, whole-genome transcriptomics, syngeneic transplantation assay, phospho-STAT3 and phospho-H2AX immunostaining\",\n      \"journal\": \"Cell biology and toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse model with transcriptomics, epistasis via syngeneic transplantation, multiple readouts, single lab\",\n      \"pmids\": [\"39738726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"DNAJB4 overexpression activates the Hippo signaling pathway in triple-negative breast cancer (TNBC) cells, promoting apoptosis. DNAJB4 knockdown suppresses Hippo pathway activity and inhibits TNBC cell apoptosis.\",\n      \"method\": \"Gain- and loss-of-function in vitro and in vivo assays, western blot for Hippo pathway components, flow cytometry apoptosis assay, xenograft model\",\n      \"journal\": \"Discover oncology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — KD/OE with pathway protein readout only, no direct mechanistic link between DNAJB4 and Hippo components identified, single lab\",\n      \"pmids\": [\"37012515\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HLJ1 protein localizes to the cytoplasm of human embryonic liver cells, as determined by immunohistochemistry with validated monoclonal antibodies.\",\n      \"method\": \"Immunohistochemistry with anti-HLJ1 monoclonal antibodies on human embryonic liver tissue\",\n      \"journal\": \"Sheng wu gong cheng xue bao = Chinese journal of biotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single localization method, no functional consequence linked\",\n      \"pmids\": [\"18837411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Genetic deletion of HLJ1 does not alter blood loss, activity of extrinsic and intrinsic coagulation pathways, or blood clot formation in mice, despite HLJ1 being detectable in plasma and co-localizing with CD41 (platelet/megakaryocyte marker) in bone marrow. This is a negative result establishing no role for HLJ1 in blood coagulation under normal physiological conditions.\",\n      \"method\": \"HLJ1 KO mouse (HLJ1-/-), tail bleeding assay, coagulation pathway activity tests, thromboelastography, western blot, immunohistochemistry\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse model with multiple coagulation readouts, clear negative result across multiple assays, single lab\",\n      \"pmids\": [\"35216179\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DNAJB4/HLJ1 is an HSP40/DNAJ family co-chaperone that functions in multiple cellular contexts: it acts as an endogenous Src kinase inhibitor by directly binding Src through Y172 and P301/P304 motifs (with Src-induced Y172 phosphorylation enhancing inhibitory interaction), modulates E-cadherin stability and ERAD by distinguishing folded from misfolded client proteins, forms inhibitory heterodimers with NPM1 to recruit AP-2alpha and suppress MMP-2/STAT3, interacts with HSP70 to attenuate ER stress, promotes IL-12p70 heterodimerization in macrophages to amplify sepsis-associated IFN-γ responses, localizes to the Z-disc in skeletal muscle where it is required for myofibrillar proteostasis, and is transcriptionally regulated by YY1 (at its promoter) and AP-1 family members (FosB, JunB, JunD at its enhancer) acting synergistically with the coactivator p300.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DNAJB4 (HLJ1) is an HSP40/DNAJ-family co-chaperone whose J-domain-dependent chaperone activity governs client-protein triage across proteostasis, tissue homeostasis, and tumor suppression [#10, #19]. Its central biochemical function is to distinguish folded from misfolded clients: it stabilizes correctly folded proteins while routing aberrant species toward proteasomal clearance, exemplified by its direct binding to E-cadherin, where it preserves wild-type protein at the plasma membrane but drives ERAD of misfolded HDGC mutant E-cadherin [#1]. This client-triage activity depends on an intact J-domain, since loss-of-function J-domain variants produce stable proteins that fail to disaggregate TDP-43 and fail to complement DNAJB4 in yeast [#19], and operates in concert with the HSP70 chaperone system to limit ER stress [#17]. In skeletal muscle DNAJB4 localizes to the Z-disc and is essential for myofibrillar proteostasis; loss-of-function and dominant variants cause myopathy with accumulation of Z-disc and chaperone proteins and selective fiber degeneration, establishing a direct Mendelian disease link [#10, #11]. As a chaperone DNAJB4 also remodels the oligomeric/assembly state of partner proteins—maintaining bioactive IL-12p70 heterodimers in LPS-stimulated macrophages to amplify NK-cell IFN-\\u03b3 and sepsis severity [#9], and forming heterodimers with NPM1 that recruit AP-2alpha to repress MMP-2 and STAT3 [#2]. Across epithelial cancers DNAJB4 acts as a tumor suppressor, directly binding and inhibiting Src kinase through its Y172 and P301/P304 motifs to dismantle EGFR/FAK/STAT3 oncogenic signaling and block EMT and metastasis [#0], and suppressing the peritumoral IL-6/STAT3 axis [#21]. Its expression is controlled by YY1 at the promoter acting synergistically with AP-1 factors (FosB, JunB, JunD) and p300 at an upstream enhancer [#6, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established DNAJB4/HLJ1 as a functional tumor suppressor, answering whether this chaperone has a direct role in cancer cell behavior rather than being a passive marker.\",\n      \"evidence\": \"overexpression/knockdown in CL1-5 lung cancer cells with in vivo tumorigenesis and a defined STAT1/p21 pathway readout\",\n      \"pmids\": [\"16788156\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking DNAJB4 chaperone activity to STAT1/p21 not defined\", \"p53/interferon-independence shown but upstream trigger unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified the transcriptional driver of DNAJB4, showing YY1 directly activates its promoter and that this circuit controls E-cadherin and invasion.\",\n      \"evidence\": \"luciferase reporters, promoter deletion, EMSA and site-directed mutagenesis with HLJ1 siRNA epistasis\",\n      \"pmids\": [\"15782117\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address enhancer-level regulation\", \"Mechanism by which DNAJB4 raises E-cadherin not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved the full regulatory architecture, showing an upstream enhancer with an AP-1 site cooperates with the YY1 promoter via p300 to amplify DNAJB4 expression.\",\n      \"evidence\": \"ChIP for in vivo FosB/JunB/JunD binding, promoter/enhancer deletion mapping and TF overexpression\",\n      \"pmids\": [\"17510411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signals engaging this enhancer not defined here\", \"DNA-bending/synergy model not structurally confirmed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined a chaperone-based transcriptional control mechanism whereby DNAJB4 heterodimerizes with NPM1 to repress MMP-2 and STAT3.\",\n      \"evidence\": \"Co-IP, siRNA/overexpression and MMP-2 promoter reporter assays mapping AP-2alpha recruitment\",\n      \"pmids\": [\"20145123\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect AP-2alpha recruitment not fully resolved\", \"Stoichiometry of HLJ1-NPM1 heterodimer not determined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed DNAJB4 is itself regulated post-translationally, being a caspase-3 substrate that promotes UV-induced apoptosis.\",\n      \"evidence\": \"caspase inhibitor rescue, mutagenesis of a non-canonical MEID cleavage site, enforced expression\",\n      \"pmids\": [\"20494979\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of cleaved fragments unknown\", \"Link between cleavage and chaperone activity not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established the core client-triage chaperone function: DNAJB4 distinguishes folded from misfolded E-cadherin and mediates ERAD of mutant client.\",\n      \"evidence\": \"Drosophila genetic screen, direct Co-IP binding, proteasome inhibition and CAM tumor assay\",\n      \"pmids\": [\"24293545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recognition determinants for misfolded client not defined\", \"HSP70 cooperation not addressed in this study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the direct molecular basis of DNAJB4 tumor suppression: it binds and inhibits Src kinase through specific residues, collapsing downstream oncogenic signaling.\",\n      \"evidence\": \"reciprocal Co-IP, Y172 and P301/P304 mutagenesis, KO mouse and patient specimens\",\n      \"pmids\": [\"27065329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Src inhibition requires chaperone/J-domain activity not resolved\", \"Relationship to NPM1/STAT3 axis not integrated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Generalized the chaperone assembly-control function to immunity, showing DNAJB4 converts misfolded IL-12p35 to enable bioactive IL-12p70 and drive IFN-\\u03b3 in sepsis.\",\n      \"evidence\": \"KO mice, adoptive macrophage transfer, CLP model, scRNA-seq and chaperone assays\",\n      \"pmids\": [\"35983991\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of p35 remodeling not determined\", \"Whether the same mechanism operates in human macrophages not shown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established DNAJB4 as a Mendelian disease gene, localizing it to the muscle Z-disc and showing loss-of-function and dominant variants cause myopathy through proteostatic failure.\",\n      \"evidence\": \"exome sequencing, patient biopsies, KO and knockin mouse models, yeast complementation and disaggregation assays\",\n      \"pmids\": [\"36264506\", \"36512060\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific endogenous muscle clients of DNAJB4 not identified\", \"Why type 1 fibers are selectively vulnerable unexplained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapped the chaperone activity to the J-domain, showing disease variants there preserve protein stability but abolish client disaggregation.\",\n      \"evidence\": \"yeast complementation and TDP-43 disaggregation assays with J-domain missense variants\",\n      \"pmids\": [\"39468638\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"HSP70 ATPase coupling by the J-domain not directly measured\", \"TDP-43 used as proxy client; native clients not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked DNAJB4 to ER-stress control via HSP70, showing its loss exacerbates drug-induced liver injury through unresolved ER stress.\",\n      \"evidence\": \"Dnajb4-/- mice, Co-IP and AlphaFold-Multimer modeling of HSP70 interaction, ER-stress marker profiling\",\n      \"pmids\": [\"42065820\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct HSP70 binding interface not experimentally resolved\", \"Whether ER-stress effect is cell-autonomous unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended tumor suppression to the microenvironment, showing HLJ1 restrains IL-6/STAT3 signaling in peritumoral tissue.\",\n      \"evidence\": \"KO mice, DEN carcinogenesis, transcriptomics and syngeneic transplantation\",\n      \"pmids\": [\"39738726\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell type mediating peritumoral STAT3 suppression not pinpointed\", \"Direct DNAJB4-STAT3 molecular link not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DNAJB4 mechanistically reconciles its dual roles—tumor suppressor in epithelial cancers versus EMT/metastasis promoter in some breast and mesenchymal contexts—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Context-dependent client repertoire not defined\", \"No unifying structural or regulatory model for opposing phenotypes\", \"Whether HSP70 partnering differs across tissues unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0044183\", \"supporting_discovery_ids\": [1, 9, 10, 19]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": []}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [23]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1, 17]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 10, 19]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [10, 11]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SRC\", \"CDH1\", \"NPM1\", \"HSPA1A\", \"AHSA1\", \"OPRM1\", \"ACTB\", \"SDIM1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}