{"gene":"ERN1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1997,"finding":"Ire1p is a bifunctional enzyme with both kinase and site-specific endoribonuclease activities; it cleaves HAC1 mRNA specifically at both splice junctions to initiate unconventional mRNA splicing, and addition of purified tRNA ligase completes splicing in vitro from purified components.","method":"In vitro reconstitution of HAC1 mRNA splicing from purified components; site-specific endonuclease assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components, established bifunctional enzymatic mechanism, replicated across multiple studies","pmids":["9323131"],"is_preprint":false},{"year":1996,"finding":"Ire1p oligomerizes in response to ER stress and undergoes trans-autophosphorylation as a result of oligomerization; both oligomerization and a C-terminal tail domain beyond the kinase domain are required for UPR induction.","method":"Molecular genetics and biochemical studies; in vivo and in vitro oligomerization assays; kinase activity assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — biochemical reconstitution plus genetic analysis, replicated independently","pmids":["8670804"],"is_preprint":false},{"year":1996,"finding":"The cytoplasmic domain of yeast Ire1p (Ern1p) has intrinsic Ser/Thr kinase activity; oligomerization of cytoplasmic domains is required for trans-phosphorylation and kinase activation; the last 130 amino acids mediate oligomerization but are dispensable for in vitro kinase activity.","method":"In vitro kinase activity assay; in vivo and in vitro oligomerization assays; deletion mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay with mutagenesis, oligomerization biochemistry, replicated","pmids":["8663458"],"is_preprint":false},{"year":1998,"finding":"Human IRE1 (hIre1p) is a type I ER transmembrane protein with intrinsic autophosphorylation activity and endoribonuclease activity that cleaves the 5' splice site of yeast HAC1 mRNA; overexpressed hIre1p localizes to the ER with concentration around the nuclear envelope; a catalytically inactive kinase mutant acts as a dominant-negative to block BiP promoter activation; Ire1p mRNA autoregulation requires functional kinase activity.","method":"Autophosphorylation assay; endoribonuclease activity assay; immunofluorescence localization; dominant-negative overexpression; reporter gene (BiP promoter) assay","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (kinase assay, RNase assay, localization, reporter assay, dominant-negative genetics) in one study","pmids":["9637683"],"is_preprint":false},{"year":2001,"finding":"In mammalian cells, IRE1 splices XBP1 mRNA unconventionally in response to ER stress (analogous to yeast HAC1 splicing), producing an active transcription factor; XBP1 is a direct target of ATF6, placing IRE1-dependent XBP1 splicing downstream of ATF6 in the mammalian UPR.","method":"Identification of XBP1 mRNA splicing by IRE1; reporter assays; epistasis analysis placing ATF6 upstream of XBP1","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — identified mammalian substrate (XBP1 mRNA), epistasis established pathway position, highly replicated","pmids":["11779464"],"is_preprint":false},{"year":2000,"finding":"The yeast ER chaperone Kar2p/BiP directly binds the luminal domain of Ire1p and keeps Ire1p in an inactive, unphosphorylated state; ER stress causes Kar2p to dissociate from Ire1p, triggering Ire1p activation.","method":"Direct protein interaction assay; co-immunoprecipitation; demonstration of Kar2p-dependent Ire1p phosphorylation state","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct binding demonstrated, functional consequence (Ire1p activation state) established, replicated in subsequent studies","pmids":["11118306"],"is_preprint":false},{"year":1998,"finding":"The serine/threonine phosphatase Ptc2p directly dephosphorylates Ire1p in an Mg2+-dependent manner; the Ptc2p–Ire1p interaction is specific, direct, phosphorylation-dependent, and mediated through a kinase interaction domain in Ptc2p; Ptc2p negatively regulates the UPR by downregulating HAC1 splicing.","method":"In vitro dephosphorylation assay; two-hybrid and direct interaction assays; genetic deletion/overexpression with HAC1 splicing readout","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro phosphatase assay, direct binding, genetic epistasis, multiple orthogonal methods","pmids":["9528768"],"is_preprint":false},{"year":2001,"finding":"Mammalian IRE1 is intimately associated with RNA in vivo (detected by UV crosslinking); the IRE1-associated RNA fragments are different in stressed vs. unstressed cells and shorter in stressed cells; complex formation requires both the kinase and endonuclease domains of IRE1.","method":"In vivo UV crosslinking; domain mutant analysis","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo crosslinking with domain mutants, single lab, two methods","pmids":["11590247"],"is_preprint":false},{"year":2006,"finding":"The phosphatase Dcr2 physically interacts with phosphorylated Ire1 (mimicked by Ire1-S840E/S841E) and dephosphorylates Ire1 in vitro; Dcr2 overexpression delays HAC1 splicing and sensitizes cells to ER stress in a phosphatase-activity-dependent manner.","method":"In vitro dephosphorylation assay; in vivo co-immunoprecipitation; genetic overexpression/deletion with HAC1 splicing readout","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro phosphatase assay, in vivo interaction, genetic functional evidence, single lab","pmids":["16990850"],"is_preprint":false},{"year":2007,"finding":"The ATP-bound conformation of Kar2p/BiP (substrate-free) interacts with Ire1p via lobe IB of its ATPase domain (around residue Q88); substitution Q88E abolishes the Kar2p–Ire1p interaction, identifying the binding interface.","method":"Oligosaccharide-shielding mapping; site-directed mutagenesis; co-immunoprecipitation","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis combined with binding assay, single lab, two methods","pmids":["17276461"],"is_preprint":false},{"year":2006,"finding":"Yeast Ire1p contains a nuclear localization sequence (NLS) in its linker region (residues ~642–657) recognized by importin-alpha (classical NLS) and multiple importin-beta homologues; NLS-dependent nuclear localization of Ire1p is required for ER stress-induced HAC1 mRNA splicing and UPR signaling.","method":"GFP-NLS fusion localization; importin binding studies (kinetic data); site-directed mutagenesis of NLS; UPR reporter and HAC1 splicing assays","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — localization by live imaging, importin binding, mutagenesis with functional readout, single lab","pmids":["17035634"],"is_preprint":false},{"year":2007,"finding":"Sustained IRE1 signaling during persistent ER stress promotes cell survival, whereas attenuation of IRE1 (and ATF6) activity while PERK signaling is maintained correlates with apoptosis; artificial sustaining of IRE1 activity enhanced cell survival, establishing a causal link between IRE1 signaling duration and cell fate.","method":"Chemical-genetic activation of IRE1 (analog-sensitive kinase allele); cell viability/apoptosis assays; animal model (retinitis pigmentosa)","journal":"Science (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — chemical-genetic strategy, recapitulated in vivo, replicated in cell culture and animal model","pmids":["17991856"],"is_preprint":false},{"year":2009,"finding":"Sustained IRE1 signaling (uncoupled from ER stress by chemical-genetic strategy) enhances cell proliferation without promoting apoptosis, whereas equivalent PERK signaling impairs proliferation and promotes apoptosis; IRE1 and PERK thus have opposite effects on cell viability.","method":"Chemical-genetic individual activation of IRE1 or PERK; cell proliferation and apoptosis assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Moderate — chemical-genetic strategy enables clean separation of pathways, orthogonal viability/proliferation readouts, single lab","pmids":["19137072"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of Ire1 RNase domain define the active site: H1061 and Y1043 act as general acid-base pair (contributing ≥7.6 and 1.4 kcal/mol to transition state stabilization respectively), with N1057 and R1056 coordinating the scissile phosphate; two RNase subunits contribute to RNA stem-loop docking while each monomer contains a separate catalytic apparatus; Ire1 can also cleave anticodon stem-loops of tRNA.","method":"X-ray crystallography (two new structures); active-site mutagenesis with quantitative kinetic analysis; in vitro RNase assays","journal":"BMC biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures plus mutagenesis with thermodynamic quantification, mechanistic assignment of catalytic residues","pmids":["21729333"],"is_preprint":false},{"year":2014,"finding":"IRE1 uses two mechanistically distinct modes of RNA cleavage: XBP1/HAC1 intron excision requires cooperative action of IRE1 subunits within oligomers, whereas RIDD cleavage is performed by a single IRE1 subunit without cooperativity; these activities can be separated by mutations at oligomerization interfaces or by complementation with catalytically inactive RNase mutants.","method":"In vitro IRE1 cleavage assays; complementation with RNase-inactive mutants; oligomerization interface mutations; IRE1 RNase inhibitor (STF-083010)","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro cleavage reconstitution, mutagenesis of oligomerization interfaces, pharmacological separation, single lab multiple orthogonal approaches","pmids":["25437541"],"is_preprint":false},{"year":2014,"finding":"Phosphorylation within the kinase activation loop of Ire1 significantly increases RNase splicing activity in vitro; Ire1 mutants that cannot be phosphorylated on the activation loop show decreased XBP1 and promiscuous RNase splicing activity in cells, coupling kinase phosphorylation to RNase activation.","method":"Isolation of distinct phosphorylated Ire1 species; in vitro RNase splicing assays; activation-loop phosphorylation-deficient mutants; in-cell XBP1 splicing assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro biochemistry with defined phosphorylated species, mutagenesis, cellular validation, single lab multiple orthogonal methods","pmids":["24704861"],"is_preprint":false},{"year":2017,"finding":"Human IRE1α luminal domain (hIRE1α LD) directly binds peptides with characteristic amino acid bias via an MHC-like groove; unfolded protein/peptide binding induces allosteric changes that drive oligomerization; mutation of a hydrophobic patch at the oligomerization interface decouples peptide binding from oligomerization; impairing oligomerization abolishes IRE1 activity in living cells.","method":"Peptide binding assays; NMR/biochemical characterization of allosteric changes; site-directed mutagenesis of oligomerization interface; cell-based IRE1 activity assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (binding assays, mutagenesis, cellular activity assays), mechanistically defines sensing mechanism","pmids":["28971800"],"is_preprint":false},{"year":2019,"finding":"Reconstitution of human UPR components reveals that BiP binding to the luminal domains of IRE1 (and PERK) switches BiP from its chaperone cycle to an ER stress sensor cycle by preventing co-chaperone binding and abolishing ATPase stimulation; misfolded protein-dependent dissociation of BiP from IRE1 is primed by ATP but not ADP.","method":"In vitro reconstitution with purified human UPR and chaperone components; ATPase assays; co-chaperone binding assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with purified components, multiple orthogonal assays, mechanistically defines BiP–IRE1 cycle","pmids":["31695187"],"is_preprint":false},{"year":2022,"finding":"AKT directly phosphorylates IRE1 at serine 724 in response to insulin, promoting XBP1u mRNA splicing and generation of XBP1s in liver, linking insulin signaling to IRE1-dependent lipogenesis.","method":"In vitro kinase assay (AKT phosphorylating IRE1 S724); mutagenesis; hepatocyte and mouse liver experiments with XBP1 isoform measurement","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro kinase assay, mutagenesis, cellular and in vivo validation, single lab","pmids":["35863429"],"is_preprint":false},{"year":2022,"finding":"BRCA1 acts as an E3 ubiquitin ligase that ubiquitinates IRE1 (and PERK) in the ER, targeting them for proteasome-mediated degradation; BRCA1 deficiency leads to elevated IRE1 protein levels and constitutively activated UPR.","method":"Co-immunoprecipitation; ubiquitination assays; proteasome inhibition; BRCA1 knockdown/depletion with IRE1 protein level measurement","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay, co-IP, functional depletion phenotype, single lab","pmids":["36471805"],"is_preprint":false},{"year":2022,"finding":"ER transmembrane protein EI24 binds to the kinase domain of IRE1 under non-stressed conditions to inhibit its activation; upon ER stress, EI24 dissociates from IRE1 to permit UPR activation.","method":"Co-immunoprecipitation; domain mapping; EI24 knockout with IRE1 activation readout","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP with domain mapping, KO phenotype, single lab","pmids":["35005829"],"is_preprint":false},{"year":2022,"finding":"The RNA ligase RtcB is tyrosine-phosphorylated by c-Abl and dephosphorylated by PTP1B; phosphorylation of RtcB at Y306 perturbs its interaction with IRE1α and attenuates XBP1 mRNA splicing, providing a mechanism that tunes adaptive vs. pro-death IRE1 outputs.","method":"Phosphoproteomics; co-immunoprecipitation; site-directed mutagenesis (Y306); kinase/phosphatase inhibitor treatments; XBP1 splicing assays","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — identification of modification writer (c-Abl) and eraser (PTP1B), mutagenesis, interaction assay, single lab","pmids":["35193953"],"is_preprint":false},{"year":2021,"finding":"IRE1 kinase activity (but not RNase activity) is required for inflammation-induced adipocyte lipolysis; IRE1 kinase-mediated NF-κB activation and IL-6 secretion are part of this inflammatory lipolytic program; IRE1 kinase activity is dispensable for adrenergic/cAMP-induced lipolysis; adipocyte-specific IRE1 knockout mice confirmed IRE1 is required for endotoxin-induced blood triglyceride increase.","method":"IRE1 kinase inhibitors; IRE1 RNase inhibitors; adiponectin-Cre IRE1 conditional knockout mice; adipose tissue explants; in vivo endotoxin challenge","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — pharmacological and genetic separation of kinase vs RNase activities, conditional KO in vivo model, multiple readouts","pmids":["33610548"],"is_preprint":false},{"year":2022,"finding":"ER stress-induced activation of IRE1 kinase leads to phosphorylation of FMRP (Fragile X Mental Retardation Protein), suppressing macrophage cholesterol efflux and efferocytosis; pharmacological IRE1 kinase inhibition or FMRP deficiency enhances efflux and reduces atherosclerosis in mice.","method":"Mass spectrometry (phosphoproteomics); co-immunoprecipitation; IRE1 kinase inhibitors; FMRP knockout mice; atherosclerosis in vivo model","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — MS identification of phosphorylation, in vivo genetic and pharmacological validation, multiple orthogonal methods","pmids":["35191199"],"is_preprint":false},{"year":2015,"finding":"IRE1 kinase signaling prevents ER membrane permeabilization by suppressing accumulation of the BH3-domain protein Bnip3; without IRE1, Bnip3 accumulates, triggering Bax/Bak oligomerization in the ER membrane, ER membrane permeabilization, mitochondrial calcium accumulation, cytosolic oxidative stress, and cell death.","method":"IRE1 kinase inhibition; IRE1 knockout/knockdown; Bnip3 overexpression/knockdown; Bax/Bak oligomerization assay; ER calcium leak measurement","journal":"Science signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with defined mechanistic pathway, multiple pathway intermediates tested, single lab","pmids":["26106220"],"is_preprint":false},{"year":2018,"finding":"Constitutive IRE1 RNase activity contributes to basal production of pro-tumorigenic cytokines (IL-6, IL-8, CXCL1, GM-CSF, TGFβ2) in triple-negative breast cancer cells; paclitaxel enhances IRE1 RNase activity and expands tumor-initiating cells via this pathway; IRE1 RNase inhibition increases paclitaxel efficacy in xenograft models.","method":"IRE1 RNase inhibitor; IRE1 knockdown; xenograft mouse model; cytokine measurements","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic perturbation, in vivo xenograft, multiple cytokine readouts, single lab","pmids":["30111846"],"is_preprint":false},{"year":2018,"finding":"MYC directly controls IRE1 transcription by binding to its promoter and enhancer; MYC forms a transcriptional complex with XBP1 and enhances XBP1 transcriptional activity; XBP1 is a synthetic lethal partner of MYC hyperactivation.","method":"ChIP (MYC binding to IRE1 promoter/enhancer); co-IP (MYC-XBP1 complex); siRNA knockdown; in vivo xenograft and GEMM models","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and co-IP establish direct regulatory interaction, genetic and pharmacological in vivo validation, single lab","pmids":["29480818"],"is_preprint":false},{"year":2023,"finding":"IRE1 endoribonuclease activity degrades pre-miR-301a during ER stress; loss of pre-miR-301a elevates GADD45A mRNA (a proapoptotic factor targeted by miR-301a-3p), promoting apoptosis; this is XBP1s-independent, identifying IRE1 RNase-mediated pre-miRNA decay as a distinct pro-death output.","method":"Next-generation sequencing; IRE1 inhibitor; nuclear-cytosolic fractionation; miRNA target protector; XBP1s overexpression; cell death assays","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — NGS plus functional validation with target protector and inhibitor, single lab multiple methods","pmids":["37946177"],"is_preprint":false},{"year":2018,"finding":"IRE1 RNase signaling in glioblastoma controls expression of UBE2D3 (a ubiquitin-conjugating E2 enzyme) through both XBP1s and RIDD; UBE2D3 activates the NF-κB pathway, resulting in chemokine production and myeloid cell infiltration into tumors.","method":"Genetic and pharmacological IRE1 invalidation; RNA-seq; pathway reporter assays; xenograft mouse models; human GBM dataset analysis","journal":"Neuro-oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus pharmacological inhibition, in vivo model, pathway epistasis, single lab","pmids":["38153426"],"is_preprint":false},{"year":2019,"finding":"IRE1α deletion in mouse pancreatic β cells reduces expression of five protein disulfide isomerases (PDI, PDIR, P5, ERp44, ERp46) and impairs oxidative folding of proinsulin; reconstitution of the IRE1α-XBP1 pathway restores PDI expression, proinsulin/insulin content, and insulin secretion.","method":"β cell-specific Ire1α conditional knockout mice; Ire1α-deleted insulinoma cell lines; reconstitution of IRE1α-XBP1 pathway; insulin secretion assays; protein disulfide isomerase expression analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO plus reconstitution experiment in two model systems, defined molecular mechanism and cellular phenotype","pmids":["29507125"],"is_preprint":false},{"year":2022,"finding":"IRE1 signaling (via XBP1s) cross-talks with PERK to sustain PERK expression during prolonged ER stress, providing a mechanism for UPR branch coordination during chronic stress.","method":"IRE1 and XBP1s inhibitors; XBP1s overexpression; PERK protein/mRNA quantification under ER stress; genetic epistasis","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological perturbation with defined molecular readout, single lab","pmids":["38637497"],"is_preprint":false},{"year":2022,"finding":"Pumilio, an RNA-binding protein, is phosphorylated by hIRE1 kinase during ER stress; phosphorylated Pumilio protects spliced Xbp1 mRNA from RIDD degradation, providing a mechanism for selective Xbp1 mRNA sparing.","method":"In vitro phosphorylation assay (hIRE1 phosphorylating Pumilio); Pumilio phosphorylation-site mutagenesis; RNA immunoprecipitation; Xbp1 mRNA stability assays in Drosophila eye","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay demonstrating direct phosphorylation, mutagenesis, RNA binding assays, single lab","pmids":["35332141"],"is_preprint":false},{"year":1997,"finding":"Yeast Ire1p interacts with the transcriptional coactivator Gcn5p (Ada4p); the Gcn5/Ada complex is selectively required for the UPR but not the heat shock response, suggesting Ire1p recruits this histone acetyltransferase complex to activate UPR target genes.","method":"Two-hybrid and co-immunoprecipitation; genetic requirement analysis (ada/gcn5 mutants vs. UPR and heat shock reporters)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP interaction, genetic epistasis, single lab","pmids":["9113982"],"is_preprint":false},{"year":2001,"finding":"RNase L and Ire1p have mutually exclusive RNA substrate specificities despite being in the same superfamily; comparison of conserved active-site residues by mutagenesis identifies overlapping but not identical requirements, establishing functional distinctions between family members.","method":"In vitro RNA cleavage assays with wild-type and mutant RNase L and Ire1p; comparative mutagenesis of conserved nuclease domain residues","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with mutagenesis, single study defining active-site distinctions","pmids":["11333017"],"is_preprint":false},{"year":2022,"finding":"In the context of alveolar type 2 cell ER stress, IRE1α signaling (via XBP1) drives a cell-autonomous reprogrammed cell state and promotes granulocyte recruitment; an IRE1α inhibitor reduces the reprogrammed state, granulocyte recruitment, alveolitis, and lung injury.","method":"Single-cell RNA sequencing; organoid-based modeling; IRE1α inhibitor treatment; in vivo SP-C mutation mouse models","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with defined cellular phenotype, scRNA-seq, in vivo model, single lab","pmids":["36252035"],"is_preprint":false}],"current_model":"ERN1/IRE1 is a bifunctional ER-transmembrane serine/threonine kinase and endoribonuclease that senses unfolded proteins via its MHC-like luminal domain (which binds unfolded peptides, releasing inhibitory BiP and driving oligomerization), then undergoes trans-autophosphorylation on its activation loop (which allosterically activates the RNase domain) to execute two distinct RNA cleavage programs: cooperative oligomeric cleavage for unconventional splicing of XBP1 mRNA (generating the pro-survival transcription factor XBP1s) and monomeric, non-cooperative RIDD activity that degrades ER-targeted mRNAs and pre-miRNAs to modulate proteostasis and cell fate; its kinase activity also drives downstream signaling including JNK/MAPK8 activation, FMRP phosphorylation for lipid homeostasis, and NF-κB-dependent inflammatory outputs, while its activity is negatively regulated by BiP binding to the luminal domain, by phosphatases Ptc2p/Dcr2 that dephosphorylate the activation loop, by XBP1s-mediated transcriptional repression of IRE1 itself, and by BRCA1-mediated ubiquitination and proteasomal degradation."},"narrative":{"mechanistic_narrative":"ERN1/IRE1 is the central ER-transmembrane sensor of the unfolded protein response (UPR), coupling detection of ER protein-folding stress to transcriptional and post-transcriptional reprogramming of the secretory pathway [PMID:9637683, PMID:11779464]. Its luminal MHC-like domain directly binds unfolded peptides with a characteristic amino-acid bias, an event that drives allosteric oligomerization; impairing the oligomerization interface decouples peptide binding from activation and abolishes IRE1 activity in cells [PMID:28971800]. In the resting state IRE1 is held inactive by the ER chaperone BiP/Kar2p, which binds the luminal domain and is released upon stress, switching BiP from its chaperone cycle to a stress-sensor cycle and priming dissociation in an ATP-dependent manner [PMID:11118306, PMID:31695187]. IRE1 is bifunctional: it is a Ser/Thr kinase that trans-autophosphorylates upon oligomerization, and a site-specific endoribonuclease [PMID:9323131, PMID:8670804, PMID:8663458]. Activation-loop phosphorylation allosterically licenses the RNase domain, whose catalytic apparatus (general acid-base pair His1061/Tyr1043 with Asn1057/Arg1056 coordinating the scissile phosphate) executes two distinct cleavage programs [PMID:21729333, PMID:24704861]: cooperative cleavage by oligomeric subunits performs the unconventional splicing of HAC1/XBP1 mRNA to generate the active transcription factor XBP1s, completed in vivo by tRNA/RNA ligase, while a non-cooperative single-subunit mode mediates regulated IRE1-dependent decay (RIDD) of ER-targeted mRNAs and pre-miRNAs [PMID:9323131, PMID:11779464, PMID:25437541, PMID:37946177]. Through XBP1s the pathway supports oxidative protein folding, exemplified by its control of protein disulfide isomerases required for proinsulin folding in pancreatic β cells [PMID:29507125]. Beyond RNase signaling, IRE1 kinase activity drives NF-κB-dependent inflammatory outputs and phosphorylates substrates including FMRP to control lipid homeostasis, and prevents ER membrane permeabilization by suppressing Bnip3 [PMID:33610548, PMID:35191199, PMID:26106220]. The duration and balance of IRE1 signaling dictate cell fate, with sustained IRE1 activity promoting survival and proliferation while its RNase-mediated pre-miRNA decay and inflammatory programs can drive death or tumor progression [PMID:17991856, PMID:19137072, PMID:30111846, PMID:37946177]. IRE1 output is tuned by multiple regulators: phosphatases Ptc2p and Dcr2 that dephosphorylate the activation loop, the kinase-domain inhibitor EI24, and BRCA1-mediated ubiquitination targeting IRE1 for proteasomal degradation [PMID:9528768, PMID:16990850, PMID:35005829, PMID:36471805].","teleology":[{"year":1996,"claim":"Established that IRE1's cytoplasmic kinase activity depends on oligomerization-driven trans-phosphorylation, defining how an ER-resident sensor converts luminal stress into a catalytic signal.","evidence":"In vitro kinase assays, oligomerization assays, and deletion mutagenesis in yeast Ire1p","pmids":["8663458","8670804"],"confidence":"High","gaps":["Did not identify physiological RNase substrates","Did not define the luminal stress-sensing mechanism"]},{"year":1997,"claim":"Resolved that IRE1 is a single bifunctional enzyme whose endoribonuclease cleaves HAC1 mRNA at both splice junctions, with ligation completing unconventional splicing — the founding mechanism of the UPR.","evidence":"In vitro reconstitution of HAC1 splicing from purified components plus site-specific endonuclease assay","pmids":["9323131"],"confidence":"High","gaps":["Mammalian substrate unknown at this stage","Coupling between kinase and RNase domains not defined"]},{"year":1998,"claim":"Extended the mechanism to humans and showed IRE1 autoregulates its own expression in a kinase-dependent manner, while identifying the first negative regulator (phosphatase Ptc2p).","evidence":"Autophosphorylation/RNase assays, dominant-negative and reporter assays in human cells; in vitro dephosphorylation and genetics in yeast","pmids":["9637683","9528768"],"confidence":"High","gaps":["Mammalian RNase substrate still unidentified","How phosphorylation state controls RNase activity not yet quantified"]},{"year":2000,"claim":"Identified BiP/Kar2p as the luminal-domain brake whose stress-induced dissociation triggers IRE1 activation, providing a model for stress detection.","evidence":"Direct binding, co-IP, and phosphorylation-state assays in yeast; later interface mapping (Q88) by mutagenesis","pmids":["11118306","17276461"],"confidence":"High","gaps":["Whether BiP release alone is sufficient versus direct unfolded-protein sensing unresolved at this point"]},{"year":2001,"claim":"Defined the mammalian arm by identifying XBP1 mRNA as the conserved splicing substrate and placing IRE1-XBP1 downstream of ATF6, and showed IRE1 associates with stress-dependent RNA in vivo.","evidence":"XBP1 splicing identification, epistasis, reporter assays; in vivo UV crosslinking with domain mutants","pmids":["11779464","11590247"],"confidence":"High","gaps":["Catalytic mechanism of cleavage not yet structurally defined","RIDD activity not yet recognized"]},{"year":2006,"claim":"Showed IRE1 must localize to the nucleus via an importin-recognized NLS for HAC1 splicing, and identified a second activation-loop phosphatase (Dcr2) tuning the response.","evidence":"GFP-NLS localization, importin binding, mutagenesis with HAC1 readout; in vitro dephosphorylation and phospho-mimetic Co-IP","pmids":["17035634","16990850"],"confidence":"Medium","gaps":["Generality of nuclear localization requirement across species unclear","How dephosphorylation timing shapes signal duration not defined"]},{"year":2007,"claim":"Established that the duration of IRE1 signaling is a determinant of cell fate, with sustained activity favoring survival — linking UPR kinetics to apoptosis decisions.","evidence":"Analog-sensitive kinase chemical-genetics, viability assays, retinitis pigmentosa animal model","pmids":["17991856"],"confidence":"High","gaps":["Molecular effectors converting signal duration into fate not identified here"]},{"year":2009,"claim":"Cleanly separated IRE1 from PERK, demonstrating opposite effects on proliferation and viability and clarifying UPR branch division of labor.","evidence":"Chemical-genetic individual activation of IRE1 versus PERK with proliferation/apoptosis readouts","pmids":["19137072"],"confidence":"High","gaps":["Downstream targets driving proliferation versus death not delineated"]},{"year":2011,"claim":"Provided atomic-level assignment of the RNase active site, identifying the catalytic acid-base residues and the two-subunit RNA docking architecture.","evidence":"X-ray crystallography plus active-site mutagenesis with quantitative kinetics and in vitro RNase assays","pmids":["21729333"],"confidence":"High","gaps":["How oligomeric state selects between substrate classes not yet resolved"]},{"year":2014,"claim":"Distinguished two RNase modes — cooperative oligomeric XBP1/HAC1 splicing versus single-subunit non-cooperative RIDD — and showed activation-loop phosphorylation licenses splicing activity, explaining how a single enzyme runs distinct programs.","evidence":"In vitro cleavage and complementation assays, oligomerization-interface mutants, RNase inhibitor; phospho-species isolation with cellular XBP1 splicing","pmids":["25437541","24704861"],"confidence":"High","gaps":["In-cell determinants selecting splicing versus RIDD not fully defined","Full RIDD substrate repertoire not enumerated"]},{"year":2017,"claim":"Defined the luminal sensing mechanism directly: the MHC-like groove binds unfolded peptides and drives oligomerization required for activity, establishing peptide binding as the proximal trigger.","evidence":"Peptide binding assays, allostery characterization, oligomerization-interface mutagenesis, cell-based activity assays of human IRE1α LD","pmids":["28971800"],"confidence":"High","gaps":["Relative contributions of direct peptide binding versus BiP release in cells not quantified"]},{"year":2019,"claim":"Reconstituted the human BiP-IRE1 cycle, showing BiP switches from chaperone to sensor mode at IRE1, and connected XBP1s output to a concrete folding function (PDI-dependent proinsulin folding).","evidence":"In vitro reconstitution with purified human components, ATPase/co-chaperone assays; β-cell conditional KO and pathway reconstitution","pmids":["31695187","29507125"],"confidence":"High","gaps":["How sensor-mode switching is reversed during recovery not defined"]},{"year":2022,"claim":"Expanded IRE1 regulation and output: input kinases (AKT at S724), degradation control (BRCA1 ubiquitination), kinase-domain inhibition (EI24), output protection (Pumilio shielding spliced Xbp1 from RIDD), ligase regulation (RtcB phosphorylation), and kinase-driven inflammatory/lipid programs (FMRP, NF-κB).","evidence":"In vitro kinase/ubiquitination assays, Co-IP and domain mapping, phosphoproteomics, conditional KO mice, and in vivo disease models (atherosclerosis, adipose lipolysis)","pmids":["35863429","36471805","35005829","35332141","35193953","35191199","33610548"],"confidence":"Medium","gaps":["Most regulators validated in single labs","Interplay among the multiple regulatory inputs in vivo not integrated"]},{"year":2023,"claim":"Demonstrated an XBP1s-independent pro-death output: IRE1 RNase degrades pre-miR-301a to derepress GADD45A and promote apoptosis, broadening the RIDD repertoire to pre-miRNAs.","evidence":"NGS, IRE1 inhibitor, fractionation, miRNA target protector, XBP1s overexpression, cell death assays","pmids":["37946177"],"confidence":"Medium","gaps":["Single-lab finding","Generality of pre-miRNA decay across cell types not established"]},{"year":null,"claim":"How the combined inputs (peptide sensing, BiP release, activation-loop phosphorylation, kinase inputs, and degradation) are quantitatively integrated to set the splicing-versus-RIDD balance and ultimately the survival-versus-death decision in vivo remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking signal strength/duration to RNase mode selection","In vivo substrate hierarchies for RIDD largely uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,13,14,27,33]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,15,23,31]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,13]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,2,15]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[7,13]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[2,17]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[16,5]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[3,17,20]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[10]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,3,4,16,17]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,4,14,27]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[29,17]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[11,24,27]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[22,25,28]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,26,32]}],"complexes":[],"partners":["BIP/KAR2","XBP1","PTC2","DCR2","EI24","BRCA1","RTCB","FMRP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O75460","full_name":"Serine/threonine-protein kinase/endoribonuclease IRE1","aliases":["Endoplasmic reticulum-to-nucleus signaling 1","Inositol-requiring protein 1","hIRE1p","Ire1-alpha","IRE1a"],"length_aa":977,"mass_kda":109.7,"function":"Serine/threonine-protein kinase and endoribonuclease that acts as a key sensor for the endoplasmic reticulum unfolded protein response (UPR) (PubMed:11175748, PubMed:11779464, PubMed:12637535, PubMed:19328063, PubMed:21317875, PubMed:28128204, PubMed:30118681, PubMed:36739529, PubMed:9637683). 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molecular bases to IRE1 activity modulation.","date":"2021","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/34375386","citation_count":15,"is_preprint":false},{"pmid":"39002476","id":"PMC_39002476","title":"GRP78/IRE1 and cGAS/STING pathway crosstalk through CHOP facilitates iodoacetic acid-mediated testosterone decline.","date":"2024","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/39002476","citation_count":15,"is_preprint":false},{"pmid":"36471805","id":"PMC_36471805","title":"BRCA1 mediates protein homeostasis through the ubiquitination of PERK and IRE1.","date":"2022","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/36471805","citation_count":15,"is_preprint":false},{"pmid":"35193953","id":"PMC_35193953","title":"Stress-induced tyrosine phosphorylation of RtcB modulates IRE1 activity and signaling outputs.","date":"2022","source":"Life science 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splice junctions to initiate unconventional mRNA splicing, and addition of purified tRNA ligase completes splicing in vitro from purified components.\",\n      \"method\": \"In vitro reconstitution of HAC1 mRNA splicing from purified components; site-specific endonuclease assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components, established bifunctional enzymatic mechanism, replicated across multiple studies\",\n      \"pmids\": [\"9323131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Ire1p oligomerizes in response to ER stress and undergoes trans-autophosphorylation as a result of oligomerization; both oligomerization and a C-terminal tail domain beyond the kinase domain are required for UPR induction.\",\n      \"method\": \"Molecular genetics and biochemical studies; in vivo and in vitro oligomerization assays; kinase activity assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — biochemical reconstitution plus genetic analysis, replicated independently\",\n      \"pmids\": [\"8670804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The cytoplasmic domain of yeast Ire1p (Ern1p) has intrinsic Ser/Thr kinase activity; oligomerization of cytoplasmic domains is required for trans-phosphorylation and kinase activation; the last 130 amino acids mediate oligomerization but are dispensable for in vitro kinase activity.\",\n      \"method\": \"In vitro kinase activity assay; in vivo and in vitro oligomerization assays; deletion mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay with mutagenesis, oligomerization biochemistry, replicated\",\n      \"pmids\": [\"8663458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human IRE1 (hIre1p) is a type I ER transmembrane protein with intrinsic autophosphorylation activity and endoribonuclease activity that cleaves the 5' splice site of yeast HAC1 mRNA; overexpressed hIre1p localizes to the ER with concentration around the nuclear envelope; a catalytically inactive kinase mutant acts as a dominant-negative to block BiP promoter activation; Ire1p mRNA autoregulation requires functional kinase activity.\",\n      \"method\": \"Autophosphorylation assay; endoribonuclease activity assay; immunofluorescence localization; dominant-negative overexpression; reporter gene (BiP promoter) assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (kinase assay, RNase assay, localization, reporter assay, dominant-negative genetics) in one study\",\n      \"pmids\": [\"9637683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In mammalian cells, IRE1 splices XBP1 mRNA unconventionally in response to ER stress (analogous to yeast HAC1 splicing), producing an active transcription factor; XBP1 is a direct target of ATF6, placing IRE1-dependent XBP1 splicing downstream of ATF6 in the mammalian UPR.\",\n      \"method\": \"Identification of XBP1 mRNA splicing by IRE1; reporter assays; epistasis analysis placing ATF6 upstream of XBP1\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — identified mammalian substrate (XBP1 mRNA), epistasis established pathway position, highly replicated\",\n      \"pmids\": [\"11779464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The yeast ER chaperone Kar2p/BiP directly binds the luminal domain of Ire1p and keeps Ire1p in an inactive, unphosphorylated state; ER stress causes Kar2p to dissociate from Ire1p, triggering Ire1p activation.\",\n      \"method\": \"Direct protein interaction assay; co-immunoprecipitation; demonstration of Kar2p-dependent Ire1p phosphorylation state\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct binding demonstrated, functional consequence (Ire1p activation state) established, replicated in subsequent studies\",\n      \"pmids\": [\"11118306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The serine/threonine phosphatase Ptc2p directly dephosphorylates Ire1p in an Mg2+-dependent manner; the Ptc2p–Ire1p interaction is specific, direct, phosphorylation-dependent, and mediated through a kinase interaction domain in Ptc2p; Ptc2p negatively regulates the UPR by downregulating HAC1 splicing.\",\n      \"method\": \"In vitro dephosphorylation assay; two-hybrid and direct interaction assays; genetic deletion/overexpression with HAC1 splicing readout\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro phosphatase assay, direct binding, genetic epistasis, multiple orthogonal methods\",\n      \"pmids\": [\"9528768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mammalian IRE1 is intimately associated with RNA in vivo (detected by UV crosslinking); the IRE1-associated RNA fragments are different in stressed vs. unstressed cells and shorter in stressed cells; complex formation requires both the kinase and endonuclease domains of IRE1.\",\n      \"method\": \"In vivo UV crosslinking; domain mutant analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo crosslinking with domain mutants, single lab, two methods\",\n      \"pmids\": [\"11590247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The phosphatase Dcr2 physically interacts with phosphorylated Ire1 (mimicked by Ire1-S840E/S841E) and dephosphorylates Ire1 in vitro; Dcr2 overexpression delays HAC1 splicing and sensitizes cells to ER stress in a phosphatase-activity-dependent manner.\",\n      \"method\": \"In vitro dephosphorylation assay; in vivo co-immunoprecipitation; genetic overexpression/deletion with HAC1 splicing readout\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro phosphatase assay, in vivo interaction, genetic functional evidence, single lab\",\n      \"pmids\": [\"16990850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The ATP-bound conformation of Kar2p/BiP (substrate-free) interacts with Ire1p via lobe IB of its ATPase domain (around residue Q88); substitution Q88E abolishes the Kar2p–Ire1p interaction, identifying the binding interface.\",\n      \"method\": \"Oligosaccharide-shielding mapping; site-directed mutagenesis; co-immunoprecipitation\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis combined with binding assay, single lab, two methods\",\n      \"pmids\": [\"17276461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Yeast Ire1p contains a nuclear localization sequence (NLS) in its linker region (residues ~642–657) recognized by importin-alpha (classical NLS) and multiple importin-beta homologues; NLS-dependent nuclear localization of Ire1p is required for ER stress-induced HAC1 mRNA splicing and UPR signaling.\",\n      \"method\": \"GFP-NLS fusion localization; importin binding studies (kinetic data); site-directed mutagenesis of NLS; UPR reporter and HAC1 splicing assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — localization by live imaging, importin binding, mutagenesis with functional readout, single lab\",\n      \"pmids\": [\"17035634\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Sustained IRE1 signaling during persistent ER stress promotes cell survival, whereas attenuation of IRE1 (and ATF6) activity while PERK signaling is maintained correlates with apoptosis; artificial sustaining of IRE1 activity enhanced cell survival, establishing a causal link between IRE1 signaling duration and cell fate.\",\n      \"method\": \"Chemical-genetic activation of IRE1 (analog-sensitive kinase allele); cell viability/apoptosis assays; animal model (retinitis pigmentosa)\",\n      \"journal\": \"Science (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — chemical-genetic strategy, recapitulated in vivo, replicated in cell culture and animal model\",\n      \"pmids\": [\"17991856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Sustained IRE1 signaling (uncoupled from ER stress by chemical-genetic strategy) enhances cell proliferation without promoting apoptosis, whereas equivalent PERK signaling impairs proliferation and promotes apoptosis; IRE1 and PERK thus have opposite effects on cell viability.\",\n      \"method\": \"Chemical-genetic individual activation of IRE1 or PERK; cell proliferation and apoptosis assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — chemical-genetic strategy enables clean separation of pathways, orthogonal viability/proliferation readouts, single lab\",\n      \"pmids\": [\"19137072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of Ire1 RNase domain define the active site: H1061 and Y1043 act as general acid-base pair (contributing ≥7.6 and 1.4 kcal/mol to transition state stabilization respectively), with N1057 and R1056 coordinating the scissile phosphate; two RNase subunits contribute to RNA stem-loop docking while each monomer contains a separate catalytic apparatus; Ire1 can also cleave anticodon stem-loops of tRNA.\",\n      \"method\": \"X-ray crystallography (two new structures); active-site mutagenesis with quantitative kinetic analysis; in vitro RNase assays\",\n      \"journal\": \"BMC biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures plus mutagenesis with thermodynamic quantification, mechanistic assignment of catalytic residues\",\n      \"pmids\": [\"21729333\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"IRE1 uses two mechanistically distinct modes of RNA cleavage: XBP1/HAC1 intron excision requires cooperative action of IRE1 subunits within oligomers, whereas RIDD cleavage is performed by a single IRE1 subunit without cooperativity; these activities can be separated by mutations at oligomerization interfaces or by complementation with catalytically inactive RNase mutants.\",\n      \"method\": \"In vitro IRE1 cleavage assays; complementation with RNase-inactive mutants; oligomerization interface mutations; IRE1 RNase inhibitor (STF-083010)\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro cleavage reconstitution, mutagenesis of oligomerization interfaces, pharmacological separation, single lab multiple orthogonal approaches\",\n      \"pmids\": [\"25437541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Phosphorylation within the kinase activation loop of Ire1 significantly increases RNase splicing activity in vitro; Ire1 mutants that cannot be phosphorylated on the activation loop show decreased XBP1 and promiscuous RNase splicing activity in cells, coupling kinase phosphorylation to RNase activation.\",\n      \"method\": \"Isolation of distinct phosphorylated Ire1 species; in vitro RNase splicing assays; activation-loop phosphorylation-deficient mutants; in-cell XBP1 splicing assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro biochemistry with defined phosphorylated species, mutagenesis, cellular validation, single lab multiple orthogonal methods\",\n      \"pmids\": [\"24704861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human IRE1α luminal domain (hIRE1α LD) directly binds peptides with characteristic amino acid bias via an MHC-like groove; unfolded protein/peptide binding induces allosteric changes that drive oligomerization; mutation of a hydrophobic patch at the oligomerization interface decouples peptide binding from oligomerization; impairing oligomerization abolishes IRE1 activity in living cells.\",\n      \"method\": \"Peptide binding assays; NMR/biochemical characterization of allosteric changes; site-directed mutagenesis of oligomerization interface; cell-based IRE1 activity assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (binding assays, mutagenesis, cellular activity assays), mechanistically defines sensing mechanism\",\n      \"pmids\": [\"28971800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Reconstitution of human UPR components reveals that BiP binding to the luminal domains of IRE1 (and PERK) switches BiP from its chaperone cycle to an ER stress sensor cycle by preventing co-chaperone binding and abolishing ATPase stimulation; misfolded protein-dependent dissociation of BiP from IRE1 is primed by ATP but not ADP.\",\n      \"method\": \"In vitro reconstitution with purified human UPR and chaperone components; ATPase assays; co-chaperone binding assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with purified components, multiple orthogonal assays, mechanistically defines BiP–IRE1 cycle\",\n      \"pmids\": [\"31695187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"AKT directly phosphorylates IRE1 at serine 724 in response to insulin, promoting XBP1u mRNA splicing and generation of XBP1s in liver, linking insulin signaling to IRE1-dependent lipogenesis.\",\n      \"method\": \"In vitro kinase assay (AKT phosphorylating IRE1 S724); mutagenesis; hepatocyte and mouse liver experiments with XBP1 isoform measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro kinase assay, mutagenesis, cellular and in vivo validation, single lab\",\n      \"pmids\": [\"35863429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"BRCA1 acts as an E3 ubiquitin ligase that ubiquitinates IRE1 (and PERK) in the ER, targeting them for proteasome-mediated degradation; BRCA1 deficiency leads to elevated IRE1 protein levels and constitutively activated UPR.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assays; proteasome inhibition; BRCA1 knockdown/depletion with IRE1 protein level measurement\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay, co-IP, functional depletion phenotype, single lab\",\n      \"pmids\": [\"36471805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ER transmembrane protein EI24 binds to the kinase domain of IRE1 under non-stressed conditions to inhibit its activation; upon ER stress, EI24 dissociates from IRE1 to permit UPR activation.\",\n      \"method\": \"Co-immunoprecipitation; domain mapping; EI24 knockout with IRE1 activation readout\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP with domain mapping, KO phenotype, single lab\",\n      \"pmids\": [\"35005829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The RNA ligase RtcB is tyrosine-phosphorylated by c-Abl and dephosphorylated by PTP1B; phosphorylation of RtcB at Y306 perturbs its interaction with IRE1α and attenuates XBP1 mRNA splicing, providing a mechanism that tunes adaptive vs. pro-death IRE1 outputs.\",\n      \"method\": \"Phosphoproteomics; co-immunoprecipitation; site-directed mutagenesis (Y306); kinase/phosphatase inhibitor treatments; XBP1 splicing assays\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — identification of modification writer (c-Abl) and eraser (PTP1B), mutagenesis, interaction assay, single lab\",\n      \"pmids\": [\"35193953\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IRE1 kinase activity (but not RNase activity) is required for inflammation-induced adipocyte lipolysis; IRE1 kinase-mediated NF-κB activation and IL-6 secretion are part of this inflammatory lipolytic program; IRE1 kinase activity is dispensable for adrenergic/cAMP-induced lipolysis; adipocyte-specific IRE1 knockout mice confirmed IRE1 is required for endotoxin-induced blood triglyceride increase.\",\n      \"method\": \"IRE1 kinase inhibitors; IRE1 RNase inhibitors; adiponectin-Cre IRE1 conditional knockout mice; adipose tissue explants; in vivo endotoxin challenge\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — pharmacological and genetic separation of kinase vs RNase activities, conditional KO in vivo model, multiple readouts\",\n      \"pmids\": [\"33610548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ER stress-induced activation of IRE1 kinase leads to phosphorylation of FMRP (Fragile X Mental Retardation Protein), suppressing macrophage cholesterol efflux and efferocytosis; pharmacological IRE1 kinase inhibition or FMRP deficiency enhances efflux and reduces atherosclerosis in mice.\",\n      \"method\": \"Mass spectrometry (phosphoproteomics); co-immunoprecipitation; IRE1 kinase inhibitors; FMRP knockout mice; atherosclerosis in vivo model\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — MS identification of phosphorylation, in vivo genetic and pharmacological validation, multiple orthogonal methods\",\n      \"pmids\": [\"35191199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IRE1 kinase signaling prevents ER membrane permeabilization by suppressing accumulation of the BH3-domain protein Bnip3; without IRE1, Bnip3 accumulates, triggering Bax/Bak oligomerization in the ER membrane, ER membrane permeabilization, mitochondrial calcium accumulation, cytosolic oxidative stress, and cell death.\",\n      \"method\": \"IRE1 kinase inhibition; IRE1 knockout/knockdown; Bnip3 overexpression/knockdown; Bax/Bak oligomerization assay; ER calcium leak measurement\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with defined mechanistic pathway, multiple pathway intermediates tested, single lab\",\n      \"pmids\": [\"26106220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Constitutive IRE1 RNase activity contributes to basal production of pro-tumorigenic cytokines (IL-6, IL-8, CXCL1, GM-CSF, TGFβ2) in triple-negative breast cancer cells; paclitaxel enhances IRE1 RNase activity and expands tumor-initiating cells via this pathway; IRE1 RNase inhibition increases paclitaxel efficacy in xenograft models.\",\n      \"method\": \"IRE1 RNase inhibitor; IRE1 knockdown; xenograft mouse model; cytokine measurements\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic perturbation, in vivo xenograft, multiple cytokine readouts, single lab\",\n      \"pmids\": [\"30111846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MYC directly controls IRE1 transcription by binding to its promoter and enhancer; MYC forms a transcriptional complex with XBP1 and enhances XBP1 transcriptional activity; XBP1 is a synthetic lethal partner of MYC hyperactivation.\",\n      \"method\": \"ChIP (MYC binding to IRE1 promoter/enhancer); co-IP (MYC-XBP1 complex); siRNA knockdown; in vivo xenograft and GEMM models\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and co-IP establish direct regulatory interaction, genetic and pharmacological in vivo validation, single lab\",\n      \"pmids\": [\"29480818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"IRE1 endoribonuclease activity degrades pre-miR-301a during ER stress; loss of pre-miR-301a elevates GADD45A mRNA (a proapoptotic factor targeted by miR-301a-3p), promoting apoptosis; this is XBP1s-independent, identifying IRE1 RNase-mediated pre-miRNA decay as a distinct pro-death output.\",\n      \"method\": \"Next-generation sequencing; IRE1 inhibitor; nuclear-cytosolic fractionation; miRNA target protector; XBP1s overexpression; cell death assays\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — NGS plus functional validation with target protector and inhibitor, single lab multiple methods\",\n      \"pmids\": [\"37946177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"IRE1 RNase signaling in glioblastoma controls expression of UBE2D3 (a ubiquitin-conjugating E2 enzyme) through both XBP1s and RIDD; UBE2D3 activates the NF-κB pathway, resulting in chemokine production and myeloid cell infiltration into tumors.\",\n      \"method\": \"Genetic and pharmacological IRE1 invalidation; RNA-seq; pathway reporter assays; xenograft mouse models; human GBM dataset analysis\",\n      \"journal\": \"Neuro-oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus pharmacological inhibition, in vivo model, pathway epistasis, single lab\",\n      \"pmids\": [\"38153426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IRE1α deletion in mouse pancreatic β cells reduces expression of five protein disulfide isomerases (PDI, PDIR, P5, ERp44, ERp46) and impairs oxidative folding of proinsulin; reconstitution of the IRE1α-XBP1 pathway restores PDI expression, proinsulin/insulin content, and insulin secretion.\",\n      \"method\": \"β cell-specific Ire1α conditional knockout mice; Ire1α-deleted insulinoma cell lines; reconstitution of IRE1α-XBP1 pathway; insulin secretion assays; protein disulfide isomerase expression analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO plus reconstitution experiment in two model systems, defined molecular mechanism and cellular phenotype\",\n      \"pmids\": [\"29507125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IRE1 signaling (via XBP1s) cross-talks with PERK to sustain PERK expression during prolonged ER stress, providing a mechanism for UPR branch coordination during chronic stress.\",\n      \"method\": \"IRE1 and XBP1s inhibitors; XBP1s overexpression; PERK protein/mRNA quantification under ER stress; genetic epistasis\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological perturbation with defined molecular readout, single lab\",\n      \"pmids\": [\"38637497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Pumilio, an RNA-binding protein, is phosphorylated by hIRE1 kinase during ER stress; phosphorylated Pumilio protects spliced Xbp1 mRNA from RIDD degradation, providing a mechanism for selective Xbp1 mRNA sparing.\",\n      \"method\": \"In vitro phosphorylation assay (hIRE1 phosphorylating Pumilio); Pumilio phosphorylation-site mutagenesis; RNA immunoprecipitation; Xbp1 mRNA stability assays in Drosophila eye\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay demonstrating direct phosphorylation, mutagenesis, RNA binding assays, single lab\",\n      \"pmids\": [\"35332141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Yeast Ire1p interacts with the transcriptional coactivator Gcn5p (Ada4p); the Gcn5/Ada complex is selectively required for the UPR but not the heat shock response, suggesting Ire1p recruits this histone acetyltransferase complex to activate UPR target genes.\",\n      \"method\": \"Two-hybrid and co-immunoprecipitation; genetic requirement analysis (ada/gcn5 mutants vs. UPR and heat shock reporters)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP interaction, genetic epistasis, single lab\",\n      \"pmids\": [\"9113982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"RNase L and Ire1p have mutually exclusive RNA substrate specificities despite being in the same superfamily; comparison of conserved active-site residues by mutagenesis identifies overlapping but not identical requirements, establishing functional distinctions between family members.\",\n      \"method\": \"In vitro RNA cleavage assays with wild-type and mutant RNase L and Ire1p; comparative mutagenesis of conserved nuclease domain residues\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with mutagenesis, single study defining active-site distinctions\",\n      \"pmids\": [\"11333017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In the context of alveolar type 2 cell ER stress, IRE1α signaling (via XBP1) drives a cell-autonomous reprogrammed cell state and promotes granulocyte recruitment; an IRE1α inhibitor reduces the reprogrammed state, granulocyte recruitment, alveolitis, and lung injury.\",\n      \"method\": \"Single-cell RNA sequencing; organoid-based modeling; IRE1α inhibitor treatment; in vivo SP-C mutation mouse models\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with defined cellular phenotype, scRNA-seq, in vivo model, single lab\",\n      \"pmids\": [\"36252035\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ERN1/IRE1 is a bifunctional ER-transmembrane serine/threonine kinase and endoribonuclease that senses unfolded proteins via its MHC-like luminal domain (which binds unfolded peptides, releasing inhibitory BiP and driving oligomerization), then undergoes trans-autophosphorylation on its activation loop (which allosterically activates the RNase domain) to execute two distinct RNA cleavage programs: cooperative oligomeric cleavage for unconventional splicing of XBP1 mRNA (generating the pro-survival transcription factor XBP1s) and monomeric, non-cooperative RIDD activity that degrades ER-targeted mRNAs and pre-miRNAs to modulate proteostasis and cell fate; its kinase activity also drives downstream signaling including JNK/MAPK8 activation, FMRP phosphorylation for lipid homeostasis, and NF-κB-dependent inflammatory outputs, while its activity is negatively regulated by BiP binding to the luminal domain, by phosphatases Ptc2p/Dcr2 that dephosphorylate the activation loop, by XBP1s-mediated transcriptional repression of IRE1 itself, and by BRCA1-mediated ubiquitination and proteasomal degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ERN1/IRE1 is the central ER-transmembrane sensor of the unfolded protein response (UPR), coupling detection of ER protein-folding stress to transcriptional and post-transcriptional reprogramming of the secretory pathway [#3, #4]. Its luminal MHC-like domain directly binds unfolded peptides with a characteristic amino-acid bias, an event that drives allosteric oligomerization; impairing the oligomerization interface decouples peptide binding from activation and abolishes IRE1 activity in cells [#16]. In the resting state IRE1 is held inactive by the ER chaperone BiP/Kar2p, which binds the luminal domain and is released upon stress, switching BiP from its chaperone cycle to a stress-sensor cycle and priming dissociation in an ATP-dependent manner [#5, #17]. IRE1 is bifunctional: it is a Ser/Thr kinase that trans-autophosphorylates upon oligomerization, and a site-specific endoribonuclease [#0, #1, #2]. Activation-loop phosphorylation allosterically licenses the RNase domain, whose catalytic apparatus (general acid-base pair His1061/Tyr1043 with Asn1057/Arg1056 coordinating the scissile phosphate) executes two distinct cleavage programs [#13, #15]: cooperative cleavage by oligomeric subunits performs the unconventional splicing of HAC1/XBP1 mRNA to generate the active transcription factor XBP1s, completed in vivo by tRNA/RNA ligase, while a non-cooperative single-subunit mode mediates regulated IRE1-dependent decay (RIDD) of ER-targeted mRNAs and pre-miRNAs [#0, #4, #14, #27]. Through XBP1s the pathway supports oxidative protein folding, exemplified by its control of protein disulfide isomerases required for proinsulin folding in pancreatic β cells [#29]. Beyond RNase signaling, IRE1 kinase activity drives NF-κB-dependent inflammatory outputs and phosphorylates substrates including FMRP to control lipid homeostasis, and prevents ER membrane permeabilization by suppressing Bnip3 [#22, #23, #24]. The duration and balance of IRE1 signaling dictate cell fate, with sustained IRE1 activity promoting survival and proliferation while its RNase-mediated pre-miRNA decay and inflammatory programs can drive death or tumor progression [#11, #12, #25, #27]. IRE1 output is tuned by multiple regulators: phosphatases Ptc2p and Dcr2 that dephosphorylate the activation loop, the kinase-domain inhibitor EI24, and BRCA1-mediated ubiquitination targeting IRE1 for proteasomal degradation [#6, #8, #20, #19].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established that IRE1's cytoplasmic kinase activity depends on oligomerization-driven trans-phosphorylation, defining how an ER-resident sensor converts luminal stress into a catalytic signal.\",\n      \"evidence\": \"In vitro kinase assays, oligomerization assays, and deletion mutagenesis in yeast Ire1p\",\n      \"pmids\": [\"8663458\", \"8670804\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify physiological RNase substrates\", \"Did not define the luminal stress-sensing mechanism\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Resolved that IRE1 is a single bifunctional enzyme whose endoribonuclease cleaves HAC1 mRNA at both splice junctions, with ligation completing unconventional splicing — the founding mechanism of the UPR.\",\n      \"evidence\": \"In vitro reconstitution of HAC1 splicing from purified components plus site-specific endonuclease assay\",\n      \"pmids\": [\"9323131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian substrate unknown at this stage\", \"Coupling between kinase and RNase domains not defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Extended the mechanism to humans and showed IRE1 autoregulates its own expression in a kinase-dependent manner, while identifying the first negative regulator (phosphatase Ptc2p).\",\n      \"evidence\": \"Autophosphorylation/RNase assays, dominant-negative and reporter assays in human cells; in vitro dephosphorylation and genetics in yeast\",\n      \"pmids\": [\"9637683\", \"9528768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian RNase substrate still unidentified\", \"How phosphorylation state controls RNase activity not yet quantified\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identified BiP/Kar2p as the luminal-domain brake whose stress-induced dissociation triggers IRE1 activation, providing a model for stress detection.\",\n      \"evidence\": \"Direct binding, co-IP, and phosphorylation-state assays in yeast; later interface mapping (Q88) by mutagenesis\",\n      \"pmids\": [\"11118306\", \"17276461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether BiP release alone is sufficient versus direct unfolded-protein sensing unresolved at this point\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the mammalian arm by identifying XBP1 mRNA as the conserved splicing substrate and placing IRE1-XBP1 downstream of ATF6, and showed IRE1 associates with stress-dependent RNA in vivo.\",\n      \"evidence\": \"XBP1 splicing identification, epistasis, reporter assays; in vivo UV crosslinking with domain mutants\",\n      \"pmids\": [\"11779464\", \"11590247\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic mechanism of cleavage not yet structurally defined\", \"RIDD activity not yet recognized\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Showed IRE1 must localize to the nucleus via an importin-recognized NLS for HAC1 splicing, and identified a second activation-loop phosphatase (Dcr2) tuning the response.\",\n      \"evidence\": \"GFP-NLS localization, importin binding, mutagenesis with HAC1 readout; in vitro dephosphorylation and phospho-mimetic Co-IP\",\n      \"pmids\": [\"17035634\", \"16990850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Generality of nuclear localization requirement across species unclear\", \"How dephosphorylation timing shapes signal duration not defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that the duration of IRE1 signaling is a determinant of cell fate, with sustained activity favoring survival — linking UPR kinetics to apoptosis decisions.\",\n      \"evidence\": \"Analog-sensitive kinase chemical-genetics, viability assays, retinitis pigmentosa animal model\",\n      \"pmids\": [\"17991856\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular effectors converting signal duration into fate not identified here\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Cleanly separated IRE1 from PERK, demonstrating opposite effects on proliferation and viability and clarifying UPR branch division of labor.\",\n      \"evidence\": \"Chemical-genetic individual activation of IRE1 versus PERK with proliferation/apoptosis readouts\",\n      \"pmids\": [\"19137072\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream targets driving proliferation versus death not delineated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided atomic-level assignment of the RNase active site, identifying the catalytic acid-base residues and the two-subunit RNA docking architecture.\",\n      \"evidence\": \"X-ray crystallography plus active-site mutagenesis with quantitative kinetics and in vitro RNase assays\",\n      \"pmids\": [\"21729333\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How oligomeric state selects between substrate classes not yet resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguished two RNase modes — cooperative oligomeric XBP1/HAC1 splicing versus single-subunit non-cooperative RIDD — and showed activation-loop phosphorylation licenses splicing activity, explaining how a single enzyme runs distinct programs.\",\n      \"evidence\": \"In vitro cleavage and complementation assays, oligomerization-interface mutants, RNase inhibitor; phospho-species isolation with cellular XBP1 splicing\",\n      \"pmids\": [\"25437541\", \"24704861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In-cell determinants selecting splicing versus RIDD not fully defined\", \"Full RIDD substrate repertoire not enumerated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the luminal sensing mechanism directly: the MHC-like groove binds unfolded peptides and drives oligomerization required for activity, establishing peptide binding as the proximal trigger.\",\n      \"evidence\": \"Peptide binding assays, allostery characterization, oligomerization-interface mutagenesis, cell-based activity assays of human IRE1α LD\",\n      \"pmids\": [\"28971800\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of direct peptide binding versus BiP release in cells not quantified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Reconstituted the human BiP-IRE1 cycle, showing BiP switches from chaperone to sensor mode at IRE1, and connected XBP1s output to a concrete folding function (PDI-dependent proinsulin folding).\",\n      \"evidence\": \"In vitro reconstitution with purified human components, ATPase/co-chaperone assays; β-cell conditional KO and pathway reconstitution\",\n      \"pmids\": [\"31695187\", \"29507125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How sensor-mode switching is reversed during recovery not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Expanded IRE1 regulation and output: input kinases (AKT at S724), degradation control (BRCA1 ubiquitination), kinase-domain inhibition (EI24), output protection (Pumilio shielding spliced Xbp1 from RIDD), ligase regulation (RtcB phosphorylation), and kinase-driven inflammatory/lipid programs (FMRP, NF-κB).\",\n      \"evidence\": \"In vitro kinase/ubiquitination assays, Co-IP and domain mapping, phosphoproteomics, conditional KO mice, and in vivo disease models (atherosclerosis, adipose lipolysis)\",\n      \"pmids\": [\"35863429\", \"36471805\", \"35005829\", \"35332141\", \"35193953\", \"35191199\", \"33610548\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Most regulators validated in single labs\", \"Interplay among the multiple regulatory inputs in vivo not integrated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated an XBP1s-independent pro-death output: IRE1 RNase degrades pre-miR-301a to derepress GADD45A and promote apoptosis, broadening the RIDD repertoire to pre-miRNAs.\",\n      \"evidence\": \"NGS, IRE1 inhibitor, fractionation, miRNA target protector, XBP1s overexpression, cell death assays\",\n      \"pmids\": [\"37946177\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding\", \"Generality of pre-miRNA decay across cell types not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the combined inputs (peptide sensing, BiP release, activation-loop phosphorylation, kinase inputs, and degradation) are quantitatively integrated to set the splicing-versus-RIDD balance and ultimately the survival-versus-death decision in vivo remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking signal strength/duration to RNase mode selection\", \"In vivo substrate hierarchies for RIDD largely uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 13, 14, 27, 33]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 15, 23, 31]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 13]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 2, 15]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [7, 13]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [2, 17]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [16, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [3, 17, 20]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 3, 4, 16, 17]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 4, 14, 27]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [29, 17]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [11, 24, 27]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [22, 25, 28]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 26, 32]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"BiP/KAR2\", \"XBP1\", \"PTC2\", \"DCR2\", \"EI24\", \"BRCA1\", \"RTCB\", \"FMRP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}