{"gene":"CASC3","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2004,"finding":"MLN51 (CASC3) is an RNA-binding protein that associates with the exon junction complex (EJC) core components Magoh, Y14, and NFX1/TAP via its conserved SELOR (speckle localizer and RNA binding module) domain. It co-precipitates with spliced mRNAs at the EJC deposition position both in nucleus and cytoplasm, and transiently co-localizes with Magoh in nuclear speckles.","method":"Co-immunoprecipitation of endogenous proteins, co-precipitation with spliced mRNAs, subcellular localization studies, domain mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP of endogenous proteins, mRNA co-precipitation, subcellular localization with domain-level functional mapping, replicated across nuclear and cytoplasmic compartments","pmids":["15166247"],"is_preprint":false},{"year":2007,"finding":"MLN51 (CASC3) stimulates both the ATPase and RNA-helicase activities of eIF4AIII: it decreases the KM for ATP by an order of magnitude and increases kcat ~30-fold, and the ATP-bound eIF4AIII–MLN51 complex shows ~100-fold higher RNA affinity than the unbound form. The Y14–Magoh heterodimer partially inhibits MLN51-stimulated ATPase activity but does not return it to background levels.","method":"In vitro ATPase assay, RNA-helicase assay, kinetic analysis of eIF4AIII–MLN51 complex","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstituted enzymatic assays with quantitative kinetic parameters, single lab but multiple biochemical readouts","pmids":["17375189"],"is_preprint":false},{"year":2013,"finding":"MLN51 (CASC3) directly interacts with eukaryotic translation initiation factor eIF3 and ribosomal subunits, and functions as a translation enhancer: overexpression preferentially increases translation of intron-containing reporters via the EJC, silencing MLN51 decreases translation, and modulation in cell-free extracts confirms a direct role in protein synthesis.","method":"Immunoprecipitation, in vitro binding assays, cell-free translation extracts, reporter translation assays, siRNA knockdown","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro binding, cell-free assays, reporter assays, KD) in a single study establishing direct interaction and functional role","pmids":["23530232"],"is_preprint":false},{"year":2014,"finding":"MLN51 (CASC3) is a component of cytoplasmic processing bodies (P-bodies) and its overexpression triggers P-body disassembly and formation of novel small cytoplasmic RNA-containing foci with directed movements distinct from stress granules and P-bodies. A similar reduction in P-body count is observed in HER2+ breast cancer cells naturally overexpressing MLN51.","method":"Fluorescence microscopy, live-cell imaging, co-localization assays, RNA staining, P-body marker analysis","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence (P-body disassembly), single lab, multiple imaging approaches","pmids":["25205763"],"is_preprint":false},{"year":2016,"finding":"In vivo mouse studies show CASC3 is not an essential EJC core component for brain development: homozygous Casc3 null embryos are smaller with proportionately reduced brain size due to developmental delay (fewer neurons and progenitors, no apoptosis), contrasting sharply with severe microcephaly and apoptosis caused by haploinsufficiency of other EJC cores (Magoh, Eif4a3, Rbm8a). CASC3 protein is substoichiometric relative to other EJC cores in the developing brain.","method":"Genetic mouse models (null and hypomorphic alleles), brain histology, cell counting, protein expression quantification by western blot","journal":"RNA (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent Casc3 alleles with orthogonal phenotypic readouts, direct comparison to other EJC mutants, quantitative protein stoichiometry","pmids":["27780844"],"is_preprint":false},{"year":2020,"finding":"CASC3 is required for transcriptome-wide promotion of nonsense-mediated mRNA decay (NMD): CASC3 knockout cells show upregulation of hundreds of NMD-targeted mRNA isoforms without changes in overall EJC composition or EJC-dependent splicing. Tethering CASC3 to reporter mRNAs stimulates mRNA decay and endonucleolytic cleavage at the termination codon. CASC3 functions as a peripheral (not constitutive) EJC component that equips the EJC with cytoplasmic NMD-communicating ability.","method":"CASC3 knockout cell lines, transcriptome-wide RNA-seq, tethering assays, endonucleolytic cleavage assays, mass spectrometry of EJC composition","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO cell lines, transcriptome-wide analysis, mechanistic tethering and cleavage assays, EJC composition analysis, multiple orthogonal methods","pmids":["32621609"],"is_preprint":false},{"year":2006,"finding":"MLN51 (CASC3) is required downstream of GM-CSF signaling for proliferation of fibroblast-like synoviocytes: siRNA knockdown of MLN51 completely blocks GM-CSF/synovial fluid-mediated proliferation of rheumatoid arthritis FLSs.","method":"siRNA knockdown, cell proliferation assay, cytokine treatment","journal":"Arthritis research & therapy","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA KD with specific proliferation phenotype, replicated across GM-CSF and synovial fluid conditions, single lab","pmids":["17101062"],"is_preprint":false},{"year":2008,"finding":"In rheumatoid arthritis FLSs, GM-CSF-mediated MLN51 (CASC3) upregulation is controlled at both transcriptional and post-translational levels via p38 MAPK. MLN51 acts upstream of FLICE-inhibitory protein (FLIP) upregulation, which mediates FLS hyperproliferation.","method":"siRNA knockdown, MAPK inhibition, western blot, transcriptional analysis","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — epistasis via pharmacological inhibition and siRNA, pathway ordering established, single lab","pmids":["18513326"],"is_preprint":false},{"year":2025,"finding":"CASC3 is a substrate of the E3 ubiquitin ligase Smurf2: Smurf2 interacts with CASC3 and promotes its ubiquitination and proteasomal degradation. The degradation depends on the CASC3 137–283 domain and lysine residue K254. Smurf2-mediated CASC3 degradation reduces leukemia cell viability and tumor growth.","method":"Co-immunoprecipitation, ubiquitination assay, domain mapping, lysine mutagenesis, mouse tumor models","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, site-directed mutagenesis (K254), in vivo mouse model, single lab","pmids":["40978141"],"is_preprint":false}],"current_model":"CASC3 (MLN51/BTZ) is a peripheral component of the exon junction complex (EJC) that binds spliced mRNAs via its conserved SELOR domain; it stimulates eIF4AIII ATPase and RNA-helicase activities, directly interacts with eIF3 to enhance translation, and promotes cytoplasmic nonsense-mediated mRNA decay by equipping the EJC with persistent NMD-signaling capacity, while its protein levels are regulated by Smurf2-mediated ubiquitination and proteasomal degradation."},"narrative":{"mechanistic_narrative":"CASC3 (MLN51/BTZ) is an RNA-binding protein that functions as a peripheral component of the exon junction complex (EJC), coupling spliced-mRNA marking to downstream cytoplasmic gene-expression control [PMID:15166247]. Through its conserved SELOR domain it associates with the EJC core components Magoh, Y14, and NFX1/TAP and co-precipitates with spliced mRNAs in both nucleus and cytoplasm [PMID:15166247]. CASC3 acts as a potent allosteric activator of the EJC helicase eIF4AIII, lowering its KM for ATP and increasing kcat to enhance ATPase and RNA-helicase activity and clamp the complex onto RNA [PMID:17375189]. Beyond core assembly, CASC3 directly contacts eIF3 and ribosomal subunits to enhance translation of intron-containing mRNAs via the EJC [PMID:23530232], and it is required transcriptome-wide for nonsense-mediated mRNA decay, equipping the EJC with persistent NMD-signaling capability such that tethered CASC3 stimulates mRNA decay and endonucleolytic cleavage at the termination codon [PMID:32621609]. Genetic studies establish that CASC3 is a substoichiometric, non-constitutive EJC subunit whose loss causes developmental delay rather than the severe microcephaly and apoptosis seen with core EJC haploinsufficiency [PMID:27780844]. CASC3 protein levels are controlled by Smurf2-mediated ubiquitination at K254 and proteasomal degradation, a route that constrains leukemia cell viability [PMID:40978141]. CASC3 has additional cytoplasmic roles in processing-body dynamics [PMID:25205763] and in GM-CSF-driven synoviocyte proliferation [PMID:17101062, PMID:18513326].","teleology":[{"year":2004,"claim":"Established CASC3 as an EJC-associated RNA-binding protein, answering whether it physically links to the spliced-mRNA-marking machinery and through what module.","evidence":"Co-immunoprecipitation of endogenous proteins, mRNA co-precipitation, and SELOR-domain mapping in human cells","pmids":["15166247"],"confidence":"High","gaps":["Did not resolve whether CASC3 is constitutive or peripheral to the EJC","Functional consequence of EJC association not yet defined"]},{"year":2007,"claim":"Defined a biochemical mechanism for CASC3 within the EJC by showing it allosterically activates the eIF4AIII helicase, explaining how it could stabilize the complex on RNA.","evidence":"In vitro reconstituted ATPase and RNA-helicase assays with kinetic analysis of the eIF4AIII–MLN51 complex","pmids":["17375189"],"confidence":"High","gaps":["In vitro kinetics not linked to a cellular phenotype","Interplay with Y14–Magoh inhibition in vivo unresolved"]},{"year":2013,"claim":"Extended CASC3 function to translation, answering whether the EJC-bound protein influences protein synthesis and through which factor.","evidence":"Co-IP, in vitro binding to eIF3 and ribosomal subunits, cell-free translation extracts, and reporter assays with siRNA knockdown","pmids":["23530232"],"confidence":"High","gaps":["Structural basis of the eIF3 contact not defined","Selectivity for intron-containing mRNAs mechanistically unexplained"]},{"year":2014,"claim":"Connected CASC3 to cytoplasmic RNA granule dynamics, showing its abundance influences P-body composition.","evidence":"Fluorescence microscopy, live-cell imaging, and P-body/stress-granule marker analysis, including HER2+ breast cancer cells","pmids":["25205763"],"confidence":"Medium","gaps":["Mechanism of P-body disassembly unknown","Identity and function of the novel CASC3 foci undefined"]},{"year":2016,"claim":"Resolved the in vivo status of CASC3 within the EJC, showing it is substoichiometric and non-essential relative to core subunits.","evidence":"Two Casc3 mouse alleles with brain histology, cell counting, and protein stoichiometry by western blot","pmids":["27780844"],"confidence":"High","gaps":["Molecular basis of milder phenotype versus core EJC loss not defined","Tissue-specific requirements beyond brain unaddressed"]},{"year":2020,"claim":"Established CASC3 as a peripheral EJC factor that confers NMD-signaling competence, clarifying its distinct role from core assembly and splicing.","evidence":"CASC3 knockout cells, transcriptome-wide RNA-seq, tethering and endonucleolytic cleavage assays, and EJC composition mass spectrometry","pmids":["32621609"],"confidence":"High","gaps":["How CASC3 communicates with NMD effectors not detailed","Determinants of CASC3 loading onto specific EJCs unknown"]},{"year":2008,"claim":"Placed CASC3 in a signaling-driven proliferation pathway, showing GM-CSF/p38 MAPK regulation and action upstream of FLIP in rheumatoid arthritis synoviocytes.","evidence":"siRNA knockdown, pharmacological MAPK inhibition, transcriptional analysis, and western blot in FLSs (extending 2006 proliferation findings)","pmids":["18513326","17101062"],"confidence":"Medium","gaps":["Molecular link between EJC/RNA functions and FLIP regulation unclear","Confined to a single disease cell type"]},{"year":2025,"claim":"Identified the post-translational control of CASC3 abundance, showing Smurf2-mediated ubiquitination and degradation with functional consequences in leukemia.","evidence":"Co-IP, ubiquitination assay, domain mapping (137–283), K254 mutagenesis, and mouse tumor models","pmids":["40978141"],"confidence":"Medium","gaps":["Signals triggering Smurf2-mediated turnover unknown","Whether degradation reshapes EJC/NMD output not tested"]},{"year":null,"claim":"How CASC3 abundance and Smurf2-mediated turnover dynamically select which EJCs become NMD-competent, and how this is integrated with its translation and granule roles, remains open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the CASC3–EJC–NMD effector interface","Determinants of CASC3 loading onto specific transcripts undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,2]},{"term_id":"GO:0045182","term_label":"translation regulator activity","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,3]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,5]}],"complexes":["exon junction complex (EJC)"],"partners":["EIF4A3","MAGOH","RBM8A","NXF1","EIF3","SMURF2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O15234","full_name":"Protein CASC3","aliases":["Cancer susceptibility candidate gene 3 protein","Metastatic lymph node gene 51 protein","MLN 51","Protein barentsz","Btz"],"length_aa":703,"mass_kda":76.3,"function":"Required for pre-mRNA splicing as component of the spliceosome (PubMed:28502770, PubMed:29301961). Core component of the splicing-dependent multiprotein exon junction complex (EJC) deposited at splice junctions on mRNAs. The EJC is a dynamic structure consisting of core proteins and several peripheral nuclear and cytoplasmic associated factors that join the complex only transiently either during EJC assembly or during subsequent mRNA metabolism. The EJC marks the position of the exon-exon junction in the mature mRNA for the gene expression machinery and the core components remain bound to spliced mRNAs throughout all stages of mRNA metabolism thereby influencing downstream processes including nuclear mRNA export, subcellular mRNA localization, translation efficiency and nonsense-mediated mRNA decay (NMD). Stimulates the ATPase and RNA-helicase activities of EIF4A3. Plays a role in the stress response by participating in cytoplasmic stress granules assembly and by favoring cell recovery following stress. Component of the dendritic ribonucleoprotein particles (RNPs) in hippocampal neurons. May play a role in mRNA transport. Binds spliced mRNA in sequence-independent manner, 20-24 nucleotides upstream of mRNA exon-exon junctions. Binds poly(G) and poly(U) RNA homomer","subcellular_location":"Cytoplasm; Cytoplasm, perinuclear region; Nucleus; Nucleus speckle; Cytoplasm, Stress granule; Cytoplasm, Cytoplasmic ribonucleoprotein granule; Cell projection, dendrite","url":"https://www.uniprot.org/uniprotkb/O15234/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CASC3","classification":"Not Classified","n_dependent_lines":506,"n_total_lines":1208,"dependency_fraction":0.41887417218543044},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CAPZB","stoichiometry":0.2},{"gene":"DDX21","stoichiometry":0.2},{"gene":"DDX6","stoichiometry":0.2},{"gene":"EIF4A3","stoichiometry":0.2},{"gene":"GSPT1","stoichiometry":0.2},{"gene":"NPM1","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"RBM8A","stoichiometry":0.2},{"gene":"RPS16","stoichiometry":0.2},{"gene":"SRP9","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CASC3","total_profiled":1310},"omim":[{"mim_id":"606504","title":"CANCER SUSCEPTIBILITY CANDIDATE 3; CASC3","url":"https://www.omim.org/entry/606504"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear membrane","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CASC3"},"hgnc":{"alias_symbol":["MLN51","BTZ"],"prev_symbol":[]},"alphafold":{"accession":"O15234","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O15234","model_url":"https://alphafold.ebi.ac.uk/files/AF-O15234-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O15234-F1-predicted_aligned_error_v6.png","plddt_mean":53.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CASC3","jax_strain_url":"https://www.jax.org/strain/search?query=CASC3"},"sequence":{"accession":"O15234","fasta_url":"https://rest.uniprot.org/uniprotkb/O15234.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O15234/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O15234"}},"corpus_meta":[{"pmid":"15166247","id":"PMC_15166247","title":"Association of the breast cancer protein MLN51 with the exon junction complex via its speckle localizer and RNA binding module.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15166247","citation_count":95,"is_preprint":false},{"pmid":"23530232","id":"PMC_23530232","title":"EJC core component MLN51 interacts with eIF3 and activates translation.","date":"2013","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23530232","citation_count":62,"is_preprint":false},{"pmid":"32621609","id":"PMC_32621609","title":"CASC3 promotes transcriptome-wide activation of nonsense-mediated decay by the exon junction complex.","date":"2020","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/32621609","citation_count":45,"is_preprint":false},{"pmid":"17375189","id":"PMC_17375189","title":"MLN51 stimulates the RNA-helicase activity of eIF4AIII.","date":"2007","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/17375189","citation_count":44,"is_preprint":false},{"pmid":"33131409","id":"PMC_33131409","title":"Depletion of circ_0007841 inhibits multiple myeloma development and BTZ resistance via miR-129-5p/JAG1 axis.","date":"2020","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/33131409","citation_count":37,"is_preprint":false},{"pmid":"27029030","id":"PMC_27029030","title":"Methylation-regulated miR-124-1 suppresses tumorigenesis in hepatocellular carcinoma by targeting CASC3.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/27029030","citation_count":34,"is_preprint":false},{"pmid":"32673066","id":"PMC_32673066","title":"Circular RNA circ_0091579 Promotes Hepatocellular Carcinoma Proliferation, Migration, Invasion, and Glycolysis Through miR-490-5p/CASC3 Axis.","date":"2020","source":"Cancer biotherapy & radiopharmaceuticals","url":"https://pubmed.ncbi.nlm.nih.gov/32673066","citation_count":24,"is_preprint":false},{"pmid":"25205763","id":"PMC_25205763","title":"Overexpression of MLN51 triggers P-body disassembly and formation of a new type of RNA granules.","date":"2014","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/25205763","citation_count":24,"is_preprint":false},{"pmid":"17101062","id":"PMC_17101062","title":"MLN51 and GM-CSF involvement in the proliferation of fibroblast-like synoviocytes in the pathogenesis of rheumatoid arthritis.","date":"2006","source":"Arthritis research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/17101062","citation_count":24,"is_preprint":false},{"pmid":"37019286","id":"PMC_37019286","title":"Guanidine-modified nanoparticles as robust BTZ delivery carriers and activators of immune responses.","date":"2023","source":"Journal of controlled release : official journal of the Controlled Release Society","url":"https://pubmed.ncbi.nlm.nih.gov/37019286","citation_count":19,"is_preprint":false},{"pmid":"37791784","id":"PMC_37791784","title":"Drug distribution and efficacy of the DprE1 inhibitor BTZ-043 in the C3HeB/FeJ mouse tuberculosis model.","date":"2023","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/37791784","citation_count":19,"is_preprint":false},{"pmid":"34729247","id":"PMC_34729247","title":"circ-NOL10 regulated by MTDH/CASC3 inhibits breast cancer progression and metastasis via multiple miRNAs and PDCD4.","date":"2021","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/34729247","citation_count":19,"is_preprint":false},{"pmid":"24847525","id":"PMC_24847525","title":"Development of P22 viral capsid nanocomposites as anti-cancer drug, bortezomib (BTZ), delivery nanoplatforms.","date":"2014","source":"Macromolecular bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/24847525","citation_count":19,"is_preprint":false},{"pmid":"27780844","id":"PMC_27780844","title":"Mouse models of Casc3 reveal developmental functions distinct from other components of the exon junction complex.","date":"2016","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/27780844","citation_count":17,"is_preprint":false},{"pmid":"36642157","id":"PMC_36642157","title":"CASC3 Biomolecular Condensates Restrict Turnip Crinkle Virus by Limiting Host Factor Availability.","date":"2023","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/36642157","citation_count":11,"is_preprint":false},{"pmid":"36975792","id":"PMC_36975792","title":"Pharmacokinetics and Efficacy of the Benzothiazinone BTZ-043 against Tuberculous Mycobacteria inside Granulomas in the Guinea Pig Model.","date":"2023","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/36975792","citation_count":10,"is_preprint":false},{"pmid":"18513326","id":"PMC_18513326","title":"FLIP and MAPK play crucial roles in the MLN51-mediated hyperproliferation of fibroblast-like synoviocytes in the pathogenesis of rheumatoid arthritis.","date":"2008","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/18513326","citation_count":9,"is_preprint":false},{"pmid":"35358540","id":"PMC_35358540","title":"CTCF-activated SNHG16 facilitates gastrointestinal stromal tumor by targeting miR-128-3p/CASC3 axis.","date":"2022","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/35358540","citation_count":6,"is_preprint":false},{"pmid":"29262899","id":"PMC_29262899","title":"[Icaritin Reverses Multidrug Resistance of Multiple Myeloma Cell Line KM3/BTZ].","date":"2017","source":"Zhongguo shi yan xue ye xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/29262899","citation_count":3,"is_preprint":false},{"pmid":"34504427","id":"PMC_34504427","title":"Cell-Penetrating Peptides Predicted From CASC3, AKIP1, and AHRR Proteins.","date":"2021","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34504427","citation_count":1,"is_preprint":false},{"pmid":"40978141","id":"PMC_40978141","title":"Smurf2 enhances ubiquitin-mediated degradation of CASC3 and attenuates leukemia progression.","date":"2025","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/40978141","citation_count":0,"is_preprint":false},{"pmid":"40381606","id":"PMC_40381606","title":"Identification of CASC3 as a novel SADS-CoV restriction factor through liquid-liquid phase separation inhibiting viral replication.","date":"2025","source":"Veterinary microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/40381606","citation_count":0,"is_preprint":false},{"pmid":"41858529","id":"PMC_41858529","title":"MLN51 (Metastatic Lymph Node Gene 51)/CASC3 (Cancer Susceptibility Candidate Gene 3), A Putative Tumour Suppressor in Breast Cancer, the Clinical and Therapeutic Connections.","date":"2026","source":"Breast cancer (Dove Medical Press)","url":"https://pubmed.ncbi.nlm.nih.gov/41858529","citation_count":0,"is_preprint":false},{"pmid":"30998158","id":"PMC_30998158","title":"[Effect of Bushen Yanggu Decoction on Multidrug Resistance of Multiple Myeloma Cell Line KM3/BTZ].","date":"2019","source":"Zhongguo shi yan xue ye xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/30998158","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13738,"output_tokens":2431,"usd":0.038839,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9526,"output_tokens":2868,"usd":0.059665,"stage2_stop_reason":"end_turn"},"total_usd":0.098504,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"MLN51 (CASC3) is an RNA-binding protein that associates with the exon junction complex (EJC) core components Magoh, Y14, and NFX1/TAP via its conserved SELOR (speckle localizer and RNA binding module) domain. It co-precipitates with spliced mRNAs at the EJC deposition position both in nucleus and cytoplasm, and transiently co-localizes with Magoh in nuclear speckles.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins, co-precipitation with spliced mRNAs, subcellular localization studies, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP of endogenous proteins, mRNA co-precipitation, subcellular localization with domain-level functional mapping, replicated across nuclear and cytoplasmic compartments\",\n      \"pmids\": [\"15166247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MLN51 (CASC3) stimulates both the ATPase and RNA-helicase activities of eIF4AIII: it decreases the KM for ATP by an order of magnitude and increases kcat ~30-fold, and the ATP-bound eIF4AIII–MLN51 complex shows ~100-fold higher RNA affinity than the unbound form. The Y14–Magoh heterodimer partially inhibits MLN51-stimulated ATPase activity but does not return it to background levels.\",\n      \"method\": \"In vitro ATPase assay, RNA-helicase assay, kinetic analysis of eIF4AIII–MLN51 complex\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstituted enzymatic assays with quantitative kinetic parameters, single lab but multiple biochemical readouts\",\n      \"pmids\": [\"17375189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MLN51 (CASC3) directly interacts with eukaryotic translation initiation factor eIF3 and ribosomal subunits, and functions as a translation enhancer: overexpression preferentially increases translation of intron-containing reporters via the EJC, silencing MLN51 decreases translation, and modulation in cell-free extracts confirms a direct role in protein synthesis.\",\n      \"method\": \"Immunoprecipitation, in vitro binding assays, cell-free translation extracts, reporter translation assays, siRNA knockdown\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (co-IP, in vitro binding, cell-free assays, reporter assays, KD) in a single study establishing direct interaction and functional role\",\n      \"pmids\": [\"23530232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MLN51 (CASC3) is a component of cytoplasmic processing bodies (P-bodies) and its overexpression triggers P-body disassembly and formation of novel small cytoplasmic RNA-containing foci with directed movements distinct from stress granules and P-bodies. A similar reduction in P-body count is observed in HER2+ breast cancer cells naturally overexpressing MLN51.\",\n      \"method\": \"Fluorescence microscopy, live-cell imaging, co-localization assays, RNA staining, P-body marker analysis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence (P-body disassembly), single lab, multiple imaging approaches\",\n      \"pmids\": [\"25205763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In vivo mouse studies show CASC3 is not an essential EJC core component for brain development: homozygous Casc3 null embryos are smaller with proportionately reduced brain size due to developmental delay (fewer neurons and progenitors, no apoptosis), contrasting sharply with severe microcephaly and apoptosis caused by haploinsufficiency of other EJC cores (Magoh, Eif4a3, Rbm8a). CASC3 protein is substoichiometric relative to other EJC cores in the developing brain.\",\n      \"method\": \"Genetic mouse models (null and hypomorphic alleles), brain histology, cell counting, protein expression quantification by western blot\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent Casc3 alleles with orthogonal phenotypic readouts, direct comparison to other EJC mutants, quantitative protein stoichiometry\",\n      \"pmids\": [\"27780844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CASC3 is required for transcriptome-wide promotion of nonsense-mediated mRNA decay (NMD): CASC3 knockout cells show upregulation of hundreds of NMD-targeted mRNA isoforms without changes in overall EJC composition or EJC-dependent splicing. Tethering CASC3 to reporter mRNAs stimulates mRNA decay and endonucleolytic cleavage at the termination codon. CASC3 functions as a peripheral (not constitutive) EJC component that equips the EJC with cytoplasmic NMD-communicating ability.\",\n      \"method\": \"CASC3 knockout cell lines, transcriptome-wide RNA-seq, tethering assays, endonucleolytic cleavage assays, mass spectrometry of EJC composition\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO cell lines, transcriptome-wide analysis, mechanistic tethering and cleavage assays, EJC composition analysis, multiple orthogonal methods\",\n      \"pmids\": [\"32621609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MLN51 (CASC3) is required downstream of GM-CSF signaling for proliferation of fibroblast-like synoviocytes: siRNA knockdown of MLN51 completely blocks GM-CSF/synovial fluid-mediated proliferation of rheumatoid arthritis FLSs.\",\n      \"method\": \"siRNA knockdown, cell proliferation assay, cytokine treatment\",\n      \"journal\": \"Arthritis research & therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA KD with specific proliferation phenotype, replicated across GM-CSF and synovial fluid conditions, single lab\",\n      \"pmids\": [\"17101062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In rheumatoid arthritis FLSs, GM-CSF-mediated MLN51 (CASC3) upregulation is controlled at both transcriptional and post-translational levels via p38 MAPK. MLN51 acts upstream of FLICE-inhibitory protein (FLIP) upregulation, which mediates FLS hyperproliferation.\",\n      \"method\": \"siRNA knockdown, MAPK inhibition, western blot, transcriptional analysis\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — epistasis via pharmacological inhibition and siRNA, pathway ordering established, single lab\",\n      \"pmids\": [\"18513326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CASC3 is a substrate of the E3 ubiquitin ligase Smurf2: Smurf2 interacts with CASC3 and promotes its ubiquitination and proteasomal degradation. The degradation depends on the CASC3 137–283 domain and lysine residue K254. Smurf2-mediated CASC3 degradation reduces leukemia cell viability and tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, domain mapping, lysine mutagenesis, mouse tumor models\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, site-directed mutagenesis (K254), in vivo mouse model, single lab\",\n      \"pmids\": [\"40978141\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CASC3 (MLN51/BTZ) is a peripheral component of the exon junction complex (EJC) that binds spliced mRNAs via its conserved SELOR domain; it stimulates eIF4AIII ATPase and RNA-helicase activities, directly interacts with eIF3 to enhance translation, and promotes cytoplasmic nonsense-mediated mRNA decay by equipping the EJC with persistent NMD-signaling capacity, while its protein levels are regulated by Smurf2-mediated ubiquitination and proteasomal degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CASC3 (MLN51/BTZ) is an RNA-binding protein that functions as a peripheral component of the exon junction complex (EJC), coupling spliced-mRNA marking to downstream cytoplasmic gene-expression control [#0]. Through its conserved SELOR domain it associates with the EJC core components Magoh, Y14, and NFX1/TAP and co-precipitates with spliced mRNAs in both nucleus and cytoplasm [#0]. CASC3 acts as a potent allosteric activator of the EJC helicase eIF4AIII, lowering its KM for ATP and increasing kcat to enhance ATPase and RNA-helicase activity and clamp the complex onto RNA [#1]. Beyond core assembly, CASC3 directly contacts eIF3 and ribosomal subunits to enhance translation of intron-containing mRNAs via the EJC [#2], and it is required transcriptome-wide for nonsense-mediated mRNA decay, equipping the EJC with persistent NMD-signaling capability such that tethered CASC3 stimulates mRNA decay and endonucleolytic cleavage at the termination codon [#5]. Genetic studies establish that CASC3 is a substoichiometric, non-constitutive EJC subunit whose loss causes developmental delay rather than the severe microcephaly and apoptosis seen with core EJC haploinsufficiency [#4]. CASC3 protein levels are controlled by Smurf2-mediated ubiquitination at K254 and proteasomal degradation, a route that constrains leukemia cell viability [#8]. CASC3 has additional cytoplasmic roles in processing-body dynamics [#3] and in GM-CSF-driven synoviocyte proliferation [#6, #7].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established CASC3 as an EJC-associated RNA-binding protein, answering whether it physically links to the spliced-mRNA-marking machinery and through what module.\",\n      \"evidence\": \"Co-immunoprecipitation of endogenous proteins, mRNA co-precipitation, and SELOR-domain mapping in human cells\",\n      \"pmids\": [\"15166247\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether CASC3 is constitutive or peripheral to the EJC\", \"Functional consequence of EJC association not yet defined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined a biochemical mechanism for CASC3 within the EJC by showing it allosterically activates the eIF4AIII helicase, explaining how it could stabilize the complex on RNA.\",\n      \"evidence\": \"In vitro reconstituted ATPase and RNA-helicase assays with kinetic analysis of the eIF4AIII–MLN51 complex\",\n      \"pmids\": [\"17375189\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro kinetics not linked to a cellular phenotype\", \"Interplay with Y14–Magoh inhibition in vivo unresolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended CASC3 function to translation, answering whether the EJC-bound protein influences protein synthesis and through which factor.\",\n      \"evidence\": \"Co-IP, in vitro binding to eIF3 and ribosomal subunits, cell-free translation extracts, and reporter assays with siRNA knockdown\",\n      \"pmids\": [\"23530232\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the eIF3 contact not defined\", \"Selectivity for intron-containing mRNAs mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected CASC3 to cytoplasmic RNA granule dynamics, showing its abundance influences P-body composition.\",\n      \"evidence\": \"Fluorescence microscopy, live-cell imaging, and P-body/stress-granule marker analysis, including HER2+ breast cancer cells\",\n      \"pmids\": [\"25205763\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of P-body disassembly unknown\", \"Identity and function of the novel CASC3 foci undefined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved the in vivo status of CASC3 within the EJC, showing it is substoichiometric and non-essential relative to core subunits.\",\n      \"evidence\": \"Two Casc3 mouse alleles with brain histology, cell counting, and protein stoichiometry by western blot\",\n      \"pmids\": [\"27780844\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of milder phenotype versus core EJC loss not defined\", \"Tissue-specific requirements beyond brain unaddressed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established CASC3 as a peripheral EJC factor that confers NMD-signaling competence, clarifying its distinct role from core assembly and splicing.\",\n      \"evidence\": \"CASC3 knockout cells, transcriptome-wide RNA-seq, tethering and endonucleolytic cleavage assays, and EJC composition mass spectrometry\",\n      \"pmids\": [\"32621609\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CASC3 communicates with NMD effectors not detailed\", \"Determinants of CASC3 loading onto specific EJCs unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Placed CASC3 in a signaling-driven proliferation pathway, showing GM-CSF/p38 MAPK regulation and action upstream of FLIP in rheumatoid arthritis synoviocytes.\",\n      \"evidence\": \"siRNA knockdown, pharmacological MAPK inhibition, transcriptional analysis, and western blot in FLSs (extending 2006 proliferation findings)\",\n      \"pmids\": [\"18513326\", \"17101062\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between EJC/RNA functions and FLIP regulation unclear\", \"Confined to a single disease cell type\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified the post-translational control of CASC3 abundance, showing Smurf2-mediated ubiquitination and degradation with functional consequences in leukemia.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, domain mapping (137–283), K254 mutagenesis, and mouse tumor models\",\n      \"pmids\": [\"40978141\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signals triggering Smurf2-mediated turnover unknown\", \"Whether degradation reshapes EJC/NMD output not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CASC3 abundance and Smurf2-mediated turnover dynamically select which EJCs become NMD-competent, and how this is integrated with its translation and granule roles, remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the CASC3–EJC–NMD effector interface\", \"Determinants of CASC3 loading onto specific transcripts undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0045182\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-72766\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [\"exon junction complex (EJC)\"],\n    \"partners\": [\"EIF4A3\", \"MAGOH\", \"RBM8A\", \"NXF1\", \"EIF3\", \"SMURF2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}