{"gene":"IER5","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2016,"finding":"IER5 forms a ternary complex with HSF1 and PP2A, and promotes PP2A-dependent dephosphorylation of HSF1 at multiple serine and threonine residues, generating a novel hypo-phosphorylated active form of HSF1 that is transcriptionally active and contributes to cancer cell proliferation under stress.","method":"Co-immunoprecipitation, Western blot (dephosphorylation assay), overexpression and knockdown in cancer cell lines","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP establishing ternary complex, functional dephosphorylation assay, replicated by independent labs (PMID:25816751, PMID:26496226)","pmids":["26754925"],"is_preprint":false},{"year":2015,"finding":"IER5 interacts with PP2A and its B55 regulatory subunits; expression of IER5 and B55 leads to HSF1 dephosphorylation and activation of HSF1 target genes. B55 subunits directly bind HSF1, and IER5 functions as a positive feedback regulator of HSF1 through PP2A/B55.","method":"Co-immunoprecipitation, gene expression assays (HSF1 target genes), overexpression studies","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP of IER5-PP2A-B55-HSF1, functional readout of target gene activation, consistent with findings in PMID:26754925","pmids":["25816751"],"is_preprint":false},{"year":2015,"finding":"IER5 physically interacts with PP2A B55 regulatory subunit (via N-terminal region), with ribosomal protein S6 kinase (S6K), and with HSF1; these interactions are essential for reduced phosphorylation of both S6K and HSF1. IER5 oligomerizes via its N-terminal region, and oligomeric IER5 regulates PP2A activity and cell growth.","method":"Deletion analysis, co-immunoprecipitation, Western blot (phosphorylation assays), cell growth assays","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain deletion mapping, Co-IP of multiple substrates, functional phosphorylation readout, single lab with multiple orthogonal methods","pmids":["26496226"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of PP2A/B55α in complex with the N-terminal structured region of IER5 (IER5-N50) shows that IER5-N50 occludes the substrate-recruitment surface on B55α. IER5-N50 inhibits PP2A/B55α-catalyzed dephosphorylation of pTau in biochemical assays. Mutations disrupting the PP2A/B55α interface of full-length IER5 abrogate co-immunoprecipitation of PP2A/B55α and suppress KRT1 expression in keratinocytes. Structural bioinformatics identified homology of IER5-N50 with SERTA domain-containing proteins.","method":"Cryo-EM structure determination, in vitro biochemical dephosphorylation assay, mutagenesis, co-immunoprecipitation, IER5 knockout cells with rescue experiments","journal":"Cell chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure with mutagenesis validation and in vitro reconstitution assay, multiple orthogonal methods in one rigorous study","pmids":["40209703"],"is_preprint":false},{"year":2020,"finding":"IER5 is a direct Notch target gene required for Notch-induced squamous cell differentiation. IER5 is epistatic to PPP2R2A (encoding PP2A B55α subunit), and IER5 interacts with B55α both in cells and in purified systems, placing IER5 downstream of Notch and upstream of PP2A/B55α in a differentiation pathway.","method":"Conditional Notch activation, siRNA knockdown, genetic epistasis (IER5 vs PPP2R2A), co-immunoprecipitation in cells and with purified proteins","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis, reciprocal Co-IP in cells and purified system, loss-of-function with defined differentiation phenotype","pmids":["32936072"],"is_preprint":false},{"year":2019,"finding":"IER5 contains a classical bipartite nuclear localization signal (NLS) at amino acids 217–244, conserved across species, that mediates complex formation with importin-α and importin-β. An intact NLS is essential for HSF1 dephosphorylation and full HSF1 activation by IER5.","method":"NLS deletion/mutation analysis, co-immunoprecipitation with importin-α/β, HSF1 dephosphorylation assay, subcellular localization experiments","journal":"Experimental cell research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis, Co-IP of import machinery, functional dephosphorylation readout, single lab with multiple orthogonal methods","pmids":["31669744"],"is_preprint":false},{"year":2022,"finding":"IER5 acts as a PP2A adapter protein that binds both the B55 regulatory subunit of PP2A and the target proteins RB and RB-like 1 (p107/RBL1), enhancing PP2A-catalyzed dephosphorylation of these proteins and repressing expression of various cell cycle-related genes.","method":"Co-immunoprecipitation, knockdown, Western blot (phosphorylation), ChIP (RB promoter binding), gene expression analysis","journal":"The FEBS journal","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP of IER5-PP2A-RB complex, functional dephosphorylation and transcriptional readout, single lab with multiple orthogonal methods","pmids":["36047562"],"is_preprint":false},{"year":2025,"finding":"IER5 functions as a positive regulator of p53 by inhibiting p53 ubiquitination and increasing cellular p53 levels. Mechanistically, IER5-PP2A/B55 complex dephosphorylates MDM2 at Ser166, leading to MDM2 ubiquitination and reduction of nuclear MDM2, thereby stabilizing p53. This requires IER5 nuclear localization and binding to both PP2A/B55 and MDM2.","method":"Co-immunoprecipitation (IER5-MDM2), ubiquitination assay, Western blot (p53, MDM2 phosphorylation), MDM2 inhibitor (Nutlin-3) experiment, nuclear localization mutants","journal":"Cellular signalling","confidence":"High","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing IER5-PP2A/B55-MDM2 complex, biochemical dephosphorylation and ubiquitination assays, pharmacological validation, single lab with multiple orthogonal methods","pmids":["40081547"],"is_preprint":false},{"year":2011,"finding":"IER5 overexpression inhibits AML progenitor cell proliferation through G2/M arrest and transcriptional repression of Cdc25B. IER5 directly binds the Cdc25B promoter and mediates transcriptional attenuation through NF-YB and p300 transcription factors.","method":"Overexpression in AML cell lines, ChIP (IER5 binding to Cdc25B promoter), colony formation assay, flow cytometry (cell cycle), rescue experiment with Cdc25B overexpression","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirmed direct promoter binding, epistasis rescue with Cdc25B overexpression, single lab","pmids":["22132193"],"is_preprint":false},{"year":2021,"finding":"After irradiation, IER5 binds to the Cdc25B promoter and causes release of the coactivator p300 through interaction with NF-YB, transcriptionally repressing Cdc25B expression. Both Sp1/Sp3 and NF-YB binding sites on the Cdc25B promoter are involved in irradiation-mediated regulation.","method":"Dual-luciferase reporter assay, site-directed mutagenesis of promoter elements, ChIP assay (IER5, NF-YB, p300 at Cdc25B promoter), IER5 siRNA knockdown","journal":"Toxicology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirmed IER5 and NF-YB/p300 binding at Cdc25B promoter, promoter mutagenesis, single lab, consistent with PMID:22132193","pmids":["34484679"],"is_preprint":false},{"year":2014,"finding":"IER5 expression is induced by heat shock in an HSF1-dependent manner; the IER5 promoter contains an HSF1 binding sequence that is occupied by heat-activated HSF1. Overexpression of IER5 upregulates chaperone gene expression, increases refolding of heat-denatured proteins, and helps cells recover viability after heat challenge, establishing a positive feedback loop between HSF1 and IER5.","method":"HSF1-dependent promoter analysis, ChIP (HSF1 binding to IER5 promoter), IER5 overexpression, protein refolding assay, cell viability assay after heat shock","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP of HSF1 at IER5 promoter, functional refolding assay, cell viability readout, single lab","pmids":["25355627"],"is_preprint":false},{"year":2017,"finding":"IER5 participates in non-homologous end-joining (NHEJ) repair of DNA double-strand breaks. IER5 physically interacts with PARP1 and Ku70, as confirmed by immunoprecipitation. IER5 knockdown significantly decreased efficiency of DSB repair. PARP1 inhibitor Olaparib affected IER5 stability.","method":"siRNA knockdown (DSB repair efficiency assay), mass spectrometry (interactome), immunoprecipitation (IER5-PARP1, IER5-Ku70), pharmacological inhibition (Olaparib)","journal":"International journal of medical sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP confirmed PARP1/Ku70 interactions, functional DSB repair assay with knockdown, single lab","pmids":["29104487"],"is_preprint":false},{"year":2009,"finding":"siRNA-mediated suppression of IER5 in HeLa cells increased cell proliferation, enhanced radioresistance (at doses up to 6 Gy), and potentiated radiation-induced G2/M arrest while increasing the fraction of S-phase cells, demonstrating that IER5 affects radiosensitivity via modulation of radiation-induced cell cycle checkpoints.","method":"siRNA knockdown, cell growth assay, colony survival assay, flow cytometry (cell cycle analysis)","journal":"Radiation and environmental biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean siRNA knockdown with multiple phenotypic readouts (proliferation, survival, cell cycle), single lab","pmids":["19238419"],"is_preprint":false},{"year":2016,"finding":"GCF (GC binding factor) negatively regulates IER5 transcription by binding to two GCF binding sites in the IER5 promoter; mutations of these sites increased luciferase activity. Radiation reduced GCF-DNA complex formation at the IER5 promoter in a dose-dependent manner, contributing to radiation-induced IER5 upregulation.","method":"Luciferase reporter assay, site-directed mutagenesis of promoter GCF sites, ChIP, electrophoretic mobility shift assay (EMSA)","journal":"Cancer gene therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA and ChIP confirming GCF-promoter binding, mutagenesis of binding sites with functional readout, single lab","pmids":["26915404"],"is_preprint":false},{"year":2020,"finding":"PAF1 inhibits IER5 transcription by promoting RNA Pol II pausing at the IER5 promoter-proximal region, primarily through binding to IER5 enhancers. PAF1 knockdown increases IER5 expression and radiosensitivity; simultaneous PAF1 and IER5 knockdown abolishes this effect, placing PAF1 upstream of IER5 in regulating radiosensitivity.","method":"siRNA knockdown, ChIP, CRISPR/Cas9 enhancer knockout, qRT-PCR, flow cytometry (apoptosis), CCK-8 assay","journal":"Radiation oncology (London, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP of PAF1 at IER5 enhancers, CRISPR enhancer deletion, epistasis with double knockdown, single lab","pmids":["32471508"],"is_preprint":false},{"year":1999,"finding":"IER5 encodes a 308-amino-acid, highly proline-rich nuclear protein with homology to the N-terminus of IER2/pip92/ETR101. It contains a PEST-like sequence (suggesting rapid degradation), multiple phosphorylation sites, and is induced by serum and growth factors with slow-kinetics immediate-early gene characteristics. Unlike pip92/IER2, IER5 induction does not require protein kinase C activity.","method":"Molecular cloning, sequence analysis, Northern blot, promoter sequence analysis, PKC inhibitor experiments","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — original gene characterization with multiple sequence and expression methods, foundational study replicated by subsequent work","pmids":["10049588"],"is_preprint":false}],"current_model":"IER5 is a growth factor- and stress-inducible nuclear protein that functions as a PP2A/B55 adapter protein: its N-terminal structured domain (IER5-N50, structurally related to SERTA domains) docks onto the substrate-recruitment surface of PP2A/B55α, inhibiting substrate access while simultaneously recruiting PP2A target proteins (HSF1, S6K, RB, RBL1, MDM2) for dephosphorylation; in the nucleus, IER5 promotes PP2A/B55-catalyzed dephosphorylation of HSF1 (activating it and creating a positive feedback loop), dephosphorylation and degradation of MDM2 (stabilizing p53), and dephosphorylation of RB family members (repressing cell cycle genes), while also transcriptionally repressing Cdc25B through NF-YB/p300 displacement and participating in NHEJ DNA repair via interactions with PARP1 and Ku70."},"narrative":{"mechanistic_narrative":"IER5 is a growth factor- and stress-inducible nuclear protein that functions as a substrate-selective adapter for the PP2A/B55 holoenzyme, redirecting its phosphatase activity onto a defined set of nuclear targets [PMID:26754925, PMID:26496226, PMID:40209703]. Its N-terminal structured region (IER5-N50, structurally related to SERTA domains) docks onto the substrate-recruitment surface of B55α, occluding it and thereby reshaping PP2A/B55 substrate choice; interface mutations abolish PP2A/B55 binding and the downstream IER5-dependent phenotype [PMID:40209703]. Through this adapter activity IER5 recruits and promotes dephosphorylation of HSF1, generating a transcriptionally active hypo-phosphorylated HSF1 form and, because IER5 is itself an HSF1 target gene, establishing a positive feedback loop that drives chaperone expression and stress survival [PMID:26754925, PMID:25816751, PMID:25355627]. The same mechanism extends to additional substrates: IER5 enhances PP2A/B55-catalyzed dephosphorylation of RB and RBL1/p107 to repress cell-cycle genes [PMID:36047562], and of MDM2 at Ser166, driving MDM2 ubiquitination and stabilizing p53 [PMID:40081547]. Nuclear delivery of these functions depends on a bipartite NLS (residues 217–244) that engages importin-α/β and is required for HSF1 dephosphorylation [PMID:31669744]. IER5 is a direct Notch target acting upstream of PP2A/B55α in squamous differentiation [PMID:32936072], and independently of its phosphatase-adapter role it represses Cdc25B transcription via NF-YB/p300 at the Cdc25B promoter and participates in NHEJ double-strand break repair through interactions with PARP1 and Ku70 [PMID:34484679, PMID:29104487].","teleology":[{"year":1999,"claim":"Established IER5 as a slow-kinetics immediate-early gene encoding a proline-rich nuclear protein, framing it as a serum/growth-factor-responsive regulator distinct in its induction requirements from related IER family members.","evidence":"Molecular cloning, sequence/PEST analysis, Northern blot and PKC-inhibitor induction studies","pmids":["10049588"],"confidence":"Medium","gaps":["No molecular function assigned","No interaction partners identified","PEST-predicted instability not functionally tested"]},{"year":2009,"claim":"Linked IER5 to radiation response by showing its loss alters cell-cycle checkpoints and radiosensitivity, the first functional cellular role.","evidence":"siRNA knockdown in HeLa with proliferation, colony survival and cell-cycle flow cytometry","pmids":["19238419"],"confidence":"Medium","gaps":["Mechanism connecting IER5 to checkpoint control unknown","No molecular effectors identified"]},{"year":2011,"claim":"Defined a transcriptional mechanism by which IER5 enforces G2/M arrest — direct repression of Cdc25B — explaining part of its growth-suppressive activity.","evidence":"Overexpression in AML lines, ChIP at the Cdc25B promoter, NF-YB/p300 involvement, Cdc25B rescue","pmids":["22132193"],"confidence":"Medium","gaps":["How IER5 is recruited to the promoter unclear","Relationship to IER5 phosphatase-adapter activity not addressed"]},{"year":2014,"claim":"Revealed a HSF1–IER5 positive feedback loop by showing IER5 is an HSF1 target gene whose product enhances chaperone expression and proteostasis after heat shock.","evidence":"HSF1-dependent promoter analysis, ChIP of HSF1 at the IER5 promoter, refolding and viability assays","pmids":["25355627"],"confidence":"Medium","gaps":["Molecular mechanism by which IER5 protein activates HSF1 not yet defined","Direct IER5–HSF1 contact not shown here"]},{"year":2015,"claim":"Identified the core biochemical mechanism: IER5 is a PP2A/B55 adapter that binds B55, S6K and HSF1 and drives their dephosphorylation, with N-terminal oligomerization regulating PP2A activity and growth.","evidence":"Co-IP of IER5–PP2A–B55–HSF1, deletion mapping, phosphorylation Western blots, HSF1 target-gene readouts, growth assays","pmids":["25816751","26496226"],"confidence":"High","gaps":["Structural basis of B55 engagement not resolved","Determinants of substrate selectivity unknown"]},{"year":2016,"claim":"Confirmed the IER5–HSF1–PP2A ternary complex and a novel hypo-phosphorylated active HSF1 form linked to cancer cell proliferation, consolidating the adapter model.","evidence":"Reciprocal Co-IP, dephosphorylation Western blots, overexpression/knockdown in cancer lines","pmids":["26754925"],"confidence":"High","gaps":["In vivo relevance of hypo-phosphorylated HSF1 not established","Which phosphatase-resistant sites drive activation unclear"]},{"year":2016,"claim":"Explained radiation-induced IER5 upregulation transcriptionally by identifying GCF as a repressor displaced from the IER5 promoter upon irradiation.","evidence":"Luciferase reporters, promoter GCF-site mutagenesis, ChIP and EMSA","pmids":["26915404"],"confidence":"Medium","gaps":["Signal coupling radiation to GCF release unknown","Single regulatory layer among several"]},{"year":2017,"claim":"Extended IER5 function to DNA double-strand break repair, implicating it in NHEJ through physical association with PARP1 and Ku70.","evidence":"siRNA DSB-repair efficiency assay, mass spectrometry interactome, Co-IP, Olaparib treatment","pmids":["29104487"],"confidence":"Medium","gaps":["Direct vs indirect PARP1/Ku70 binding not distinguished","Whether repair role depends on PP2A adapter activity unknown"]},{"year":2019,"claim":"Mapped the nuclear-import determinant of IER5, showing a conserved bipartite NLS engaging importin-α/β is required for HSF1 dephosphorylation and activation.","evidence":"NLS deletion/mutation, importin Co-IP, localization and dephosphorylation assays","pmids":["31669744"],"confidence":"High","gaps":["Whether NLS regulates all IER5 functions equally not tested"]},{"year":2020,"claim":"Placed IER5 in a developmental pathway as a direct Notch target acting genetically upstream of PP2A/B55α to drive squamous differentiation.","evidence":"Conditional Notch activation, siRNA, IER5/PPP2R2A epistasis, Co-IP in cells and purified system","pmids":["32936072"],"confidence":"High","gaps":["Differentiation-relevant PP2A substrates not fully defined"]},{"year":2020,"claim":"Identified PAF1 as an upstream regulator restraining IER5 via Pol II pausing, connecting transcriptional control of IER5 to radiosensitivity.","evidence":"siRNA, ChIP, CRISPR enhancer knockout, double-knockdown epistasis","pmids":["32471508"],"confidence":"Medium","gaps":["Mechanism by which PAF1 enforces pausing at IER5 unclear","Generality beyond irradiation untested"]},{"year":2022,"claim":"Broadened the adapter model to cell-cycle control by showing IER5 bridges B55 to RB and RBL1/p107, enhancing their dephosphorylation and repressing cell-cycle genes.","evidence":"Co-IP, knockdown, phosphorylation Western blots, RB-promoter ChIP, expression analysis","pmids":["36047562"],"confidence":"High","gaps":["Quantitative contribution of RB vs RBL1 dephosphorylation unresolved"]},{"year":2025,"claim":"Resolved the structural mechanism: cryo-EM of PP2A/B55α with IER5-N50 shows the SERTA-related domain occludes the B55α substrate-recruitment surface, and interface mutants lose PP2A binding and downstream KRT1 induction.","evidence":"Cryo-EM, in vitro pTau dephosphorylation assay, mutagenesis, Co-IP, knockout-rescue keratinocytes","pmids":["40209703"],"confidence":"High","gaps":["How occlusion is reconciled with simultaneous substrate recruitment not fully resolved","Structures with bound substrates lacking"]},{"year":2025,"claim":"Connected the IER5–PP2A axis to tumor suppression by showing dephosphorylation of MDM2 Ser166 promotes MDM2 turnover and p53 stabilization.","evidence":"IER5–MDM2 Co-IP, ubiquitination assay, p53/MDM2 Western blots, Nutlin-3 and NLS-mutant experiments","pmids":["40081547"],"confidence":"High","gaps":["In vivo tumor-suppressive consequence not demonstrated","Interplay with IER5's growth-promoting HSF1 role unresolved"]},{"year":null,"claim":"How IER5 reconciles its opposing outputs — growth-promoting HSF1 activation versus growth-suppressive RB/p53 control — and how substrate selection is partitioned among B55 substrates remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of IER5–B55 with a recruited substrate","Context-dependent substrate switching mechanism unknown","Physiological balance between proliferative and tumor-suppressive roles undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3,6,7]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,6,7]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[8,9]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,15]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[5,7]}],"pathway":[{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,1,10]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6,8,12]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[11]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4]}],"complexes":["PP2A/B55 holoenzyme"],"partners":["PPP2R2A","HSF1","RB1","RBL1","MDM2","RPS6KB1","PARP1","XRCC6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5VY09","full_name":"Immediate early response gene 5 protein","aliases":[],"length_aa":327,"mass_kda":33.7,"function":"Plays a role as a transcription factor (PubMed:22132193, PubMed:25355627). Mediates positive transcriptional regulation of several chaperone genes during the heat shock response in a HSF1-dependent manner (PubMed:25355627, PubMed:25816751). Mediates negative transcriptional regulation of CDC25B expression (PubMed:22132193). Plays a role in the dephosphorylation of the heat shock factor HSF1 and ribosomal protein S6 kinase (S6K) by the protein phosphatase PP2A (PubMed:25816751, PubMed:26496226). Involved in the regulation of cell proliferation and resistance to thermal stress (PubMed:22132193, PubMed:25355627, PubMed:26496226). Involved in the cell cycle checkpoint and survival in response to ionizing radiation (PubMed:19238419, PubMed:22132193). Associates with chromatin to the CDC25B promoter (PubMed:22132193)","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q5VY09/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IER5","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/IER5","total_profiled":1310},"omim":[{"mim_id":"607177","title":"IMMEDIATE-EARLY RESPONSE GENE 5; IER5","url":"https://www.omim.org/entry/607177"},{"mim_id":"187040","title":"T-CELL ACUTE LYMPHOCYTIC LEUKEMIA 1; TAL1","url":"https://www.omim.org/entry/187040"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/IER5"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q5VY09","domains":[{"cath_id":"1.20.1270","chopping":"2-56_312-327","consensus_level":"medium","plddt":80.387,"start":2,"end":327}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VY09","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VY09-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VY09-F1-predicted_aligned_error_v6.png","plddt_mean":53.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IER5","jax_strain_url":"https://www.jax.org/strain/search?query=IER5"},"sequence":{"accession":"Q5VY09","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5VY09.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5VY09/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VY09"}},"corpus_meta":[{"pmid":"26754925","id":"PMC_26754925","title":"IER5 generates a novel hypo-phosphorylated active form of HSF1 and contributes to tumorigenesis.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26754925","citation_count":51,"is_preprint":false},{"pmid":"19238419","id":"PMC_19238419","title":"Induced expression of the IER5 gene by gamma-ray irradiation and its involvement in cell cycle checkpoint control and survival.","date":"2009","source":"Radiation and environmental biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/19238419","citation_count":41,"is_preprint":false},{"pmid":"10049588","id":"PMC_10049588","title":"Ier5, a novel member of the slow-kinetics immediate-early genes.","date":"1999","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/10049588","citation_count":41,"is_preprint":false},{"pmid":"22132193","id":"PMC_22132193","title":"Transcriptional repression of Cdc25B by IER5 inhibits the proliferation of leukemic progenitor cells through NF-YB and p300 in acute myeloid leukemia.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22132193","citation_count":34,"is_preprint":false},{"pmid":"25816751","id":"PMC_25816751","title":"HSF1 transcriptional activity is modulated by IER5 and PP2A/B55.","date":"2015","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/25816751","citation_count":31,"is_preprint":false},{"pmid":"25355627","id":"PMC_25355627","title":"Heat-induced expression of the immediate-early gene IER5 and its involvement in the proliferation of heat-shocked cells.","date":"2014","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/25355627","citation_count":24,"is_preprint":false},{"pmid":"26496226","id":"PMC_26496226","title":"Immediate-early response 5 (IER5) interacts with protein phosphatase 2A and regulates the phosphorylation of ribosomal protein S6 kinase and heat shock factor 1.","date":"2015","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/26496226","citation_count":22,"is_preprint":false},{"pmid":"32936072","id":"PMC_32936072","title":"IER5, a DNA damage response gene, is required for Notch-mediated induction of squamous cell differentiation.","date":"2020","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/32936072","citation_count":21,"is_preprint":false},{"pmid":"31669744","id":"PMC_31669744","title":"Nuclear import of IER5 is mediated by a classical bipartite nuclear localization signal and is required for HSF1 full activation.","date":"2019","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/31669744","citation_count":13,"is_preprint":false},{"pmid":"36047562","id":"PMC_36047562","title":"PP2A-B55 and its adapter proteins IER2 and IER5 regulate the activity of RB family proteins and the expression of cell cycle-related genes.","date":"2022","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/36047562","citation_count":12,"is_preprint":false},{"pmid":"32471508","id":"PMC_32471508","title":"Novel role of PAF1 in attenuating radiosensitivity in cervical cancer by inhibiting IER5 transcription.","date":"2020","source":"Radiation oncology (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/32471508","citation_count":11,"is_preprint":false},{"pmid":"27186303","id":"PMC_27186303","title":"IER5 promotes irradiation- and cisplatin-induced apoptosis in human hepatocellular carcinoma cells.","date":"2016","source":"American journal of translational research","url":"https://pubmed.ncbi.nlm.nih.gov/27186303","citation_count":10,"is_preprint":false},{"pmid":"22923252","id":"PMC_22923252","title":"Dose-dependent and gender-related radiation-induced transcription alterations of Gadd45a and Ier5 inhuman lymphocytes exposed to gamma ray emitted by (60)Co.","date":"2012","source":"Radiation protection dosimetry","url":"https://pubmed.ncbi.nlm.nih.gov/22923252","citation_count":10,"is_preprint":false},{"pmid":"28430589","id":"PMC_28430589","title":"IER5 as a promising predictive marker promotes irradiation-induced apoptosis in cervical cancer tissues from patients undergoing chemoradiotherapy.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/28430589","citation_count":10,"is_preprint":false},{"pmid":"29104487","id":"PMC_29104487","title":"IER5 is involved in DNA Double-Strand Breaks Repair in Association with PAPR1 in Hela Cells.","date":"2017","source":"International journal of medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29104487","citation_count":9,"is_preprint":false},{"pmid":"26915404","id":"PMC_26915404","title":"Transcriptional regulation of IER5 in response to radiation in HepG2.","date":"2016","source":"Cancer gene therapy","url":"https://pubmed.ncbi.nlm.nih.gov/26915404","citation_count":8,"is_preprint":false},{"pmid":"34484679","id":"PMC_34484679","title":"Cdc25B is transcriptionally inhibited by IER5 through the NF-YB transcription factor in irradiation-treated HeLa cells.","date":"2021","source":"Toxicology research","url":"https://pubmed.ncbi.nlm.nih.gov/34484679","citation_count":5,"is_preprint":false},{"pmid":"40209703","id":"PMC_40209703","title":"Molecular mechanism of PP2A/B55α phosphatase inhibition by IER5.","date":"2025","source":"Cell chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/40209703","citation_count":4,"is_preprint":false},{"pmid":"31059029","id":"PMC_31059029","title":"Prediction of IER5 structure and function using a bioinformatics approach.","date":"2019","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/31059029","citation_count":4,"is_preprint":false},{"pmid":"37693604","id":"PMC_37693604","title":"Molecular Mechanism of PP2A/B55α Phosphatase Inhibition by IER5.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/37693604","citation_count":4,"is_preprint":false},{"pmid":"26893736","id":"PMC_26893736","title":"Radiation-induced expression of IER5 is dose-dependent and not associated with the clinical outcomes of radiotherapy in cervical cancer.","date":"2016","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/26893736","citation_count":4,"is_preprint":false},{"pmid":"40081547","id":"PMC_40081547","title":"PP2A adapter protein IER5 induces dephosphorylation and degradation of MDM2, thereby stabilizing p53.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/40081547","citation_count":2,"is_preprint":false},{"pmid":"40002205","id":"PMC_40002205","title":"IER5 Promotes Ovarian Cancer Cell Proliferation and Peritoneal Dissemination.","date":"2025","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/40002205","citation_count":0,"is_preprint":false},{"pmid":"41300514","id":"PMC_41300514","title":"Dietary Antioxidants Influence IER5 Activation and DNA Repair: Implications for Radioprotection and Healthy Aging.","date":"2025","source":"Antioxidants (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/41300514","citation_count":0,"is_preprint":false},{"pmid":"40852688","id":"PMC_40852688","title":"IER5 Negatively Regulates Cdc25B Expression in HeLa Cells After Gamma Ray Irradiation.","date":"2025","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/40852688","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.16.659895","title":"A Comprehensive Analysis of Atlantic Salmon Gonad and Pituitary Transcriptomes Identifies Novel Players in Sexual Maturation","date":"2025-06-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.16.659895","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13899,"output_tokens":4337,"usd":0.053376,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12205,"output_tokens":4372,"usd":0.085163,"stage2_stop_reason":"end_turn"},"total_usd":0.138539,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"IER5 forms a ternary complex with HSF1 and PP2A, and promotes PP2A-dependent dephosphorylation of HSF1 at multiple serine and threonine residues, generating a novel hypo-phosphorylated active form of HSF1 that is transcriptionally active and contributes to cancer cell proliferation under stress.\",\n      \"method\": \"Co-immunoprecipitation, Western blot (dephosphorylation assay), overexpression and knockdown in cancer cell lines\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP establishing ternary complex, functional dephosphorylation assay, replicated by independent labs (PMID:25816751, PMID:26496226)\",\n      \"pmids\": [\"26754925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IER5 interacts with PP2A and its B55 regulatory subunits; expression of IER5 and B55 leads to HSF1 dephosphorylation and activation of HSF1 target genes. B55 subunits directly bind HSF1, and IER5 functions as a positive feedback regulator of HSF1 through PP2A/B55.\",\n      \"method\": \"Co-immunoprecipitation, gene expression assays (HSF1 target genes), overexpression studies\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP of IER5-PP2A-B55-HSF1, functional readout of target gene activation, consistent with findings in PMID:26754925\",\n      \"pmids\": [\"25816751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IER5 physically interacts with PP2A B55 regulatory subunit (via N-terminal region), with ribosomal protein S6 kinase (S6K), and with HSF1; these interactions are essential for reduced phosphorylation of both S6K and HSF1. IER5 oligomerizes via its N-terminal region, and oligomeric IER5 regulates PP2A activity and cell growth.\",\n      \"method\": \"Deletion analysis, co-immunoprecipitation, Western blot (phosphorylation assays), cell growth assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain deletion mapping, Co-IP of multiple substrates, functional phosphorylation readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"26496226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of PP2A/B55α in complex with the N-terminal structured region of IER5 (IER5-N50) shows that IER5-N50 occludes the substrate-recruitment surface on B55α. IER5-N50 inhibits PP2A/B55α-catalyzed dephosphorylation of pTau in biochemical assays. Mutations disrupting the PP2A/B55α interface of full-length IER5 abrogate co-immunoprecipitation of PP2A/B55α and suppress KRT1 expression in keratinocytes. Structural bioinformatics identified homology of IER5-N50 with SERTA domain-containing proteins.\",\n      \"method\": \"Cryo-EM structure determination, in vitro biochemical dephosphorylation assay, mutagenesis, co-immunoprecipitation, IER5 knockout cells with rescue experiments\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure with mutagenesis validation and in vitro reconstitution assay, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"40209703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"IER5 is a direct Notch target gene required for Notch-induced squamous cell differentiation. IER5 is epistatic to PPP2R2A (encoding PP2A B55α subunit), and IER5 interacts with B55α both in cells and in purified systems, placing IER5 downstream of Notch and upstream of PP2A/B55α in a differentiation pathway.\",\n      \"method\": \"Conditional Notch activation, siRNA knockdown, genetic epistasis (IER5 vs PPP2R2A), co-immunoprecipitation in cells and with purified proteins\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis, reciprocal Co-IP in cells and purified system, loss-of-function with defined differentiation phenotype\",\n      \"pmids\": [\"32936072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IER5 contains a classical bipartite nuclear localization signal (NLS) at amino acids 217–244, conserved across species, that mediates complex formation with importin-α and importin-β. An intact NLS is essential for HSF1 dephosphorylation and full HSF1 activation by IER5.\",\n      \"method\": \"NLS deletion/mutation analysis, co-immunoprecipitation with importin-α/β, HSF1 dephosphorylation assay, subcellular localization experiments\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis, Co-IP of import machinery, functional dephosphorylation readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31669744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IER5 acts as a PP2A adapter protein that binds both the B55 regulatory subunit of PP2A and the target proteins RB and RB-like 1 (p107/RBL1), enhancing PP2A-catalyzed dephosphorylation of these proteins and repressing expression of various cell cycle-related genes.\",\n      \"method\": \"Co-immunoprecipitation, knockdown, Western blot (phosphorylation), ChIP (RB promoter binding), gene expression analysis\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP of IER5-PP2A-RB complex, functional dephosphorylation and transcriptional readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36047562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"IER5 functions as a positive regulator of p53 by inhibiting p53 ubiquitination and increasing cellular p53 levels. Mechanistically, IER5-PP2A/B55 complex dephosphorylates MDM2 at Ser166, leading to MDM2 ubiquitination and reduction of nuclear MDM2, thereby stabilizing p53. This requires IER5 nuclear localization and binding to both PP2A/B55 and MDM2.\",\n      \"method\": \"Co-immunoprecipitation (IER5-MDM2), ubiquitination assay, Western blot (p53, MDM2 phosphorylation), MDM2 inhibitor (Nutlin-3) experiment, nuclear localization mutants\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing IER5-PP2A/B55-MDM2 complex, biochemical dephosphorylation and ubiquitination assays, pharmacological validation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"40081547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"IER5 overexpression inhibits AML progenitor cell proliferation through G2/M arrest and transcriptional repression of Cdc25B. IER5 directly binds the Cdc25B promoter and mediates transcriptional attenuation through NF-YB and p300 transcription factors.\",\n      \"method\": \"Overexpression in AML cell lines, ChIP (IER5 binding to Cdc25B promoter), colony formation assay, flow cytometry (cell cycle), rescue experiment with Cdc25B overexpression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirmed direct promoter binding, epistasis rescue with Cdc25B overexpression, single lab\",\n      \"pmids\": [\"22132193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"After irradiation, IER5 binds to the Cdc25B promoter and causes release of the coactivator p300 through interaction with NF-YB, transcriptionally repressing Cdc25B expression. Both Sp1/Sp3 and NF-YB binding sites on the Cdc25B promoter are involved in irradiation-mediated regulation.\",\n      \"method\": \"Dual-luciferase reporter assay, site-directed mutagenesis of promoter elements, ChIP assay (IER5, NF-YB, p300 at Cdc25B promoter), IER5 siRNA knockdown\",\n      \"journal\": \"Toxicology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirmed IER5 and NF-YB/p300 binding at Cdc25B promoter, promoter mutagenesis, single lab, consistent with PMID:22132193\",\n      \"pmids\": [\"34484679\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"IER5 expression is induced by heat shock in an HSF1-dependent manner; the IER5 promoter contains an HSF1 binding sequence that is occupied by heat-activated HSF1. Overexpression of IER5 upregulates chaperone gene expression, increases refolding of heat-denatured proteins, and helps cells recover viability after heat challenge, establishing a positive feedback loop between HSF1 and IER5.\",\n      \"method\": \"HSF1-dependent promoter analysis, ChIP (HSF1 binding to IER5 promoter), IER5 overexpression, protein refolding assay, cell viability assay after heat shock\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP of HSF1 at IER5 promoter, functional refolding assay, cell viability readout, single lab\",\n      \"pmids\": [\"25355627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"IER5 participates in non-homologous end-joining (NHEJ) repair of DNA double-strand breaks. IER5 physically interacts with PARP1 and Ku70, as confirmed by immunoprecipitation. IER5 knockdown significantly decreased efficiency of DSB repair. PARP1 inhibitor Olaparib affected IER5 stability.\",\n      \"method\": \"siRNA knockdown (DSB repair efficiency assay), mass spectrometry (interactome), immunoprecipitation (IER5-PARP1, IER5-Ku70), pharmacological inhibition (Olaparib)\",\n      \"journal\": \"International journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP confirmed PARP1/Ku70 interactions, functional DSB repair assay with knockdown, single lab\",\n      \"pmids\": [\"29104487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"siRNA-mediated suppression of IER5 in HeLa cells increased cell proliferation, enhanced radioresistance (at doses up to 6 Gy), and potentiated radiation-induced G2/M arrest while increasing the fraction of S-phase cells, demonstrating that IER5 affects radiosensitivity via modulation of radiation-induced cell cycle checkpoints.\",\n      \"method\": \"siRNA knockdown, cell growth assay, colony survival assay, flow cytometry (cell cycle analysis)\",\n      \"journal\": \"Radiation and environmental biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean siRNA knockdown with multiple phenotypic readouts (proliferation, survival, cell cycle), single lab\",\n      \"pmids\": [\"19238419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"GCF (GC binding factor) negatively regulates IER5 transcription by binding to two GCF binding sites in the IER5 promoter; mutations of these sites increased luciferase activity. Radiation reduced GCF-DNA complex formation at the IER5 promoter in a dose-dependent manner, contributing to radiation-induced IER5 upregulation.\",\n      \"method\": \"Luciferase reporter assay, site-directed mutagenesis of promoter GCF sites, ChIP, electrophoretic mobility shift assay (EMSA)\",\n      \"journal\": \"Cancer gene therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA and ChIP confirming GCF-promoter binding, mutagenesis of binding sites with functional readout, single lab\",\n      \"pmids\": [\"26915404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PAF1 inhibits IER5 transcription by promoting RNA Pol II pausing at the IER5 promoter-proximal region, primarily through binding to IER5 enhancers. PAF1 knockdown increases IER5 expression and radiosensitivity; simultaneous PAF1 and IER5 knockdown abolishes this effect, placing PAF1 upstream of IER5 in regulating radiosensitivity.\",\n      \"method\": \"siRNA knockdown, ChIP, CRISPR/Cas9 enhancer knockout, qRT-PCR, flow cytometry (apoptosis), CCK-8 assay\",\n      \"journal\": \"Radiation oncology (London, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP of PAF1 at IER5 enhancers, CRISPR enhancer deletion, epistasis with double knockdown, single lab\",\n      \"pmids\": [\"32471508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"IER5 encodes a 308-amino-acid, highly proline-rich nuclear protein with homology to the N-terminus of IER2/pip92/ETR101. It contains a PEST-like sequence (suggesting rapid degradation), multiple phosphorylation sites, and is induced by serum and growth factors with slow-kinetics immediate-early gene characteristics. Unlike pip92/IER2, IER5 induction does not require protein kinase C activity.\",\n      \"method\": \"Molecular cloning, sequence analysis, Northern blot, promoter sequence analysis, PKC inhibitor experiments\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — original gene characterization with multiple sequence and expression methods, foundational study replicated by subsequent work\",\n      \"pmids\": [\"10049588\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"IER5 is a growth factor- and stress-inducible nuclear protein that functions as a PP2A/B55 adapter protein: its N-terminal structured domain (IER5-N50, structurally related to SERTA domains) docks onto the substrate-recruitment surface of PP2A/B55α, inhibiting substrate access while simultaneously recruiting PP2A target proteins (HSF1, S6K, RB, RBL1, MDM2) for dephosphorylation; in the nucleus, IER5 promotes PP2A/B55-catalyzed dephosphorylation of HSF1 (activating it and creating a positive feedback loop), dephosphorylation and degradation of MDM2 (stabilizing p53), and dephosphorylation of RB family members (repressing cell cycle genes), while also transcriptionally repressing Cdc25B through NF-YB/p300 displacement and participating in NHEJ DNA repair via interactions with PARP1 and Ku70.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"IER5 is a growth factor- and stress-inducible nuclear protein that functions as a substrate-selective adapter for the PP2A/B55 holoenzyme, redirecting its phosphatase activity onto a defined set of nuclear targets [#0, #2, #3]. Its N-terminal structured region (IER5-N50, structurally related to SERTA domains) docks onto the substrate-recruitment surface of B55\\u03b1, occluding it and thereby reshaping PP2A/B55 substrate choice; interface mutations abolish PP2A/B55 binding and the downstream IER5-dependent phenotype [#3]. Through this adapter activity IER5 recruits and promotes dephosphorylation of HSF1, generating a transcriptionally active hypo-phosphorylated HSF1 form and, because IER5 is itself an HSF1 target gene, establishing a positive feedback loop that drives chaperone expression and stress survival [#0, #1, #10]. The same mechanism extends to additional substrates: IER5 enhances PP2A/B55-catalyzed dephosphorylation of RB and RBL1/p107 to repress cell-cycle genes [#6], and of MDM2 at Ser166, driving MDM2 ubiquitination and stabilizing p53 [#7]. Nuclear delivery of these functions depends on a bipartite NLS (residues 217\\u2013244) that engages importin-\\u03b1/\\u03b2 and is required for HSF1 dephosphorylation [#5]. IER5 is a direct Notch target acting upstream of PP2A/B55\\u03b1 in squamous differentiation [#4], and independently of its phosphatase-adapter role it represses Cdc25B transcription via NF-YB/p300 at the Cdc25B promoter and participates in NHEJ double-strand break repair through interactions with PARP1 and Ku70 [#9, #11].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established IER5 as a slow-kinetics immediate-early gene encoding a proline-rich nuclear protein, framing it as a serum/growth-factor-responsive regulator distinct in its induction requirements from related IER family members.\",\n      \"evidence\": \"Molecular cloning, sequence/PEST analysis, Northern blot and PKC-inhibitor induction studies\",\n      \"pmids\": [\"10049588\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular function assigned\", \"No interaction partners identified\", \"PEST-predicted instability not functionally tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked IER5 to radiation response by showing its loss alters cell-cycle checkpoints and radiosensitivity, the first functional cellular role.\",\n      \"evidence\": \"siRNA knockdown in HeLa with proliferation, colony survival and cell-cycle flow cytometry\",\n      \"pmids\": [\"19238419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting IER5 to checkpoint control unknown\", \"No molecular effectors identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defined a transcriptional mechanism by which IER5 enforces G2/M arrest \\u2014 direct repression of Cdc25B \\u2014 explaining part of its growth-suppressive activity.\",\n      \"evidence\": \"Overexpression in AML lines, ChIP at the Cdc25B promoter, NF-YB/p300 involvement, Cdc25B rescue\",\n      \"pmids\": [\"22132193\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How IER5 is recruited to the promoter unclear\", \"Relationship to IER5 phosphatase-adapter activity not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed a HSF1\\u2013IER5 positive feedback loop by showing IER5 is an HSF1 target gene whose product enhances chaperone expression and proteostasis after heat shock.\",\n      \"evidence\": \"HSF1-dependent promoter analysis, ChIP of HSF1 at the IER5 promoter, refolding and viability assays\",\n      \"pmids\": [\"25355627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism by which IER5 protein activates HSF1 not yet defined\", \"Direct IER5\\u2013HSF1 contact not shown here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified the core biochemical mechanism: IER5 is a PP2A/B55 adapter that binds B55, S6K and HSF1 and drives their dephosphorylation, with N-terminal oligomerization regulating PP2A activity and growth.\",\n      \"evidence\": \"Co-IP of IER5\\u2013PP2A\\u2013B55\\u2013HSF1, deletion mapping, phosphorylation Western blots, HSF1 target-gene readouts, growth assays\",\n      \"pmids\": [\"25816751\", \"26496226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of B55 engagement not resolved\", \"Determinants of substrate selectivity unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Confirmed the IER5\\u2013HSF1\\u2013PP2A ternary complex and a novel hypo-phosphorylated active HSF1 form linked to cancer cell proliferation, consolidating the adapter model.\",\n      \"evidence\": \"Reciprocal Co-IP, dephosphorylation Western blots, overexpression/knockdown in cancer lines\",\n      \"pmids\": [\"26754925\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of hypo-phosphorylated HSF1 not established\", \"Which phosphatase-resistant sites drive activation unclear\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Explained radiation-induced IER5 upregulation transcriptionally by identifying GCF as a repressor displaced from the IER5 promoter upon irradiation.\",\n      \"evidence\": \"Luciferase reporters, promoter GCF-site mutagenesis, ChIP and EMSA\",\n      \"pmids\": [\"26915404\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signal coupling radiation to GCF release unknown\", \"Single regulatory layer among several\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended IER5 function to DNA double-strand break repair, implicating it in NHEJ through physical association with PARP1 and Ku70.\",\n      \"evidence\": \"siRNA DSB-repair efficiency assay, mass spectrometry interactome, Co-IP, Olaparib treatment\",\n      \"pmids\": [\"29104487\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs indirect PARP1/Ku70 binding not distinguished\", \"Whether repair role depends on PP2A adapter activity unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mapped the nuclear-import determinant of IER5, showing a conserved bipartite NLS engaging importin-\\u03b1/\\u03b2 is required for HSF1 dephosphorylation and activation.\",\n      \"evidence\": \"NLS deletion/mutation, importin Co-IP, localization and dephosphorylation assays\",\n      \"pmids\": [\"31669744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NLS regulates all IER5 functions equally not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Placed IER5 in a developmental pathway as a direct Notch target acting genetically upstream of PP2A/B55\\u03b1 to drive squamous differentiation.\",\n      \"evidence\": \"Conditional Notch activation, siRNA, IER5/PPP2R2A epistasis, Co-IP in cells and purified system\",\n      \"pmids\": [\"32936072\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Differentiation-relevant PP2A substrates not fully defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified PAF1 as an upstream regulator restraining IER5 via Pol II pausing, connecting transcriptional control of IER5 to radiosensitivity.\",\n      \"evidence\": \"siRNA, ChIP, CRISPR enhancer knockout, double-knockdown epistasis\",\n      \"pmids\": [\"32471508\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PAF1 enforces pausing at IER5 unclear\", \"Generality beyond irradiation untested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Broadened the adapter model to cell-cycle control by showing IER5 bridges B55 to RB and RBL1/p107, enhancing their dephosphorylation and repressing cell-cycle genes.\",\n      \"evidence\": \"Co-IP, knockdown, phosphorylation Western blots, RB-promoter ChIP, expression analysis\",\n      \"pmids\": [\"36047562\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of RB vs RBL1 dephosphorylation unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved the structural mechanism: cryo-EM of PP2A/B55\\u03b1 with IER5-N50 shows the SERTA-related domain occludes the B55\\u03b1 substrate-recruitment surface, and interface mutants lose PP2A binding and downstream KRT1 induction.\",\n      \"evidence\": \"Cryo-EM, in vitro pTau dephosphorylation assay, mutagenesis, Co-IP, knockout-rescue keratinocytes\",\n      \"pmids\": [\"40209703\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How occlusion is reconciled with simultaneous substrate recruitment not fully resolved\", \"Structures with bound substrates lacking\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected the IER5\\u2013PP2A axis to tumor suppression by showing dephosphorylation of MDM2 Ser166 promotes MDM2 turnover and p53 stabilization.\",\n      \"evidence\": \"IER5\\u2013MDM2 Co-IP, ubiquitination assay, p53/MDM2 Western blots, Nutlin-3 and NLS-mutant experiments\",\n      \"pmids\": [\"40081547\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo tumor-suppressive consequence not demonstrated\", \"Interplay with IER5's growth-promoting HSF1 role unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How IER5 reconciles its opposing outputs \\u2014 growth-promoting HSF1 activation versus growth-suppressive RB/p53 control \\u2014 and how substrate selection is partitioned among B55 substrates remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of IER5\\u2013B55 with a recruited substrate\", \"Context-dependent substrate switching mechanism unknown\", \"Physiological balance between proliferative and tumor-suppressive roles undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3, 6, 7]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 6, 7]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 15]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [5, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 1, 10]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6, 8, 12]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [\"PP2A/B55 holoenzyme\"],\n    \"partners\": [\"PPP2R2A\", \"HSF1\", \"RB1\", \"RBL1\", \"MDM2\", \"RPS6KB1\", \"PARP1\", \"XRCC6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}