{"gene":"MED29","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2004,"finding":"MED29 (IXL) was identified as a new subunit of the mammalian Mediator complex. When fused to the Gal4 DNA-binding domain and co-transfected with VP-16, IXL/MED29 functions as a transcriptional suppressor. Overexpression in COS-7 cells inhibited transcriptional activities of SRE and AP-1, suggesting it acts as a transcriptional suppressor in the MAPK signaling pathway.","method":"Gal4 fusion transcriptional repression assay, co-transfection with VP-16, overexpression in COS-7 cells with SRE/AP-1 reporter assays; nuclear/cytoplasmic localization by subcellular fractionation","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — reporter assays with single lab, multiple readouts but no structural or in vitro reconstitution validation","pmids":["15555573"],"is_preprint":false},{"year":2004,"finding":"A stable endogenous CRSP/Med2 complex specifically lacking both Med220 and Med70 subunits was isolated. Electron microscopy and single-particle reconstruction determined its 3D structure at 31 Å resolution. CRSP/Med2 retains potent activator-dependent coactivator function with VP16, Sp1, and Sp1/SREBP-1a on chromatin templates in vitro, but cannot support vitamin D receptor (VDR)-directed activated transcription, which requires Med220 for coactivator recruitment. This demonstrates a combinatorial assembly mechanism allowing promoter-selective function.","method":"Biochemical purification of endogenous complex, electron microscopy single-particle reconstruction, in vitro transcription on chromatin templates with multiple activators","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — structure determination by EM, in vitro reconstitution with chromatin templates, multiple activator conditions, functional distinction from full complex established","pmids":["15175162"],"is_preprint":false},{"year":2007,"finding":"MED29 (IXL) is amplified and overexpressed in pancreatic cancer cells harboring a 19q13 amplicon. RNAi-mediated silencing of IXL/MED29 in PANC-1 (amplified) cells significantly decreased cell viability, caused G0-G1 cell cycle arrest, and increased apoptosis, but had no significant effect in non-amplified MiaPaCa-2 cells, establishing MED29 as required for survival specifically in amplified cancer cells.","method":"Fluorescence in situ hybridization for copy number, quantitative RT-PCR for expression, high-throughput RNAi loss-of-function screen, cell viability assay, flow cytometry for cell cycle and apoptosis","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi knockdown with multiple phenotypic readouts (viability, cell cycle, apoptosis) in paired amplified/non-amplified lines, single lab","pmids":["17332321"],"is_preprint":false},{"year":2011,"finding":"MED29 silencing in PANC-1 cells (high MED29 expression) decreased migration, invasion, and colony formation. Conversely, lentiviral overexpression of MED29 in NIH/3T3 and MIAPaCa-2 cells (low endogenous expression) decreased proliferation, and subcutaneous xenograft experiments showed dramatic tumor suppression with decreased tumor incidence and size. Gene expression analysis revealed differential expression of cell cycle and cell division genes consistent with reduced cell growth, indicating MED29 has context-dependent oncogenic and tumor-suppressive roles.","method":"RNAi knockdown (migration, invasion, colony formation assays), lentiviral overexpression, in vivo subcutaneous xenograft in immunocompromised mice, gene expression microarray analysis","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro assays plus in vivo xenograft, gene expression analysis, single lab but orthogonal methods","pmids":["21225629"],"is_preprint":false},{"year":2022,"finding":"The tRF AS-tDR-007333 activates MED29 expression through two distinct mechanisms: (1) binding to HSPB1, which enhances H3K4me1 and H3K27ac histone marks at the MED29 promoter; (2) stimulating expression of transcription factor ELK4, which binds the MED29 promoter and increases its transcription. MED29 upregulation downstream of these axes promotes NSCLC cell proliferation and migration.","method":"ChIP assay, luciferase reporter assay, RNA pulldown, mass spectrometry, RNA immunoprecipitation (RIP), co-immunoprecipitation (Co-IP), Western blot, gain- and loss-of-function experiments, in vivo tumor growth assay","journal":"Journal of hematology & oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP, luciferase, RIP, Co-IP) in single lab establishing two regulatory axes for MED29 transcription","pmids":["35526007"],"is_preprint":false},{"year":2024,"finding":"MED29 promotes epithelial-mesenchymal transition (EMT), migration, and invasion in oral squamous cell carcinoma (OSCC) cells. CHRDL1 inhibits MED29 expression via suppression of the MAPK signaling pathway, thereby restraining EMT and reducing OSCC cell invasion and metastasis in vitro and in a tail-vein lung metastasis nude mouse model.","method":"RT-qPCR, Western blot, scratch/wound healing assay, Transwell invasion assay, immunofluorescence, in vivo tail-vein lung metastasis model in nude mice, MED29 overexpression and knockdown","journal":"Molecular medicine (Cambridge, Mass.)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — multiple assays in vitro and in vivo but single lab; MAPK pathway link is inferred from pathway inhibition, not direct biochemical reconstitution","pmids":["39462350"],"is_preprint":false},{"year":2025,"finding":"Biallelic loss-of-function MED29 variants (homozygous c.416T>C, p.Leu139Pro) cause pontocerebellar hypoplasia with cataracts in humans. Morpholino knockdown of MED29 in zebrafish impaired locomotion and cerebellar GABAergic neuron development, rescued by human wild-type MED29. shRNA knockdown in mouse hippocampal neurons decreased neurite length and arborization in vitro and caused defective embryonic neuronal migration in vivo. Overexpression of the p.Leu139Pro variant was consistent with loss-of-function.","method":"Whole-exome sequencing with Sanger validation, morpholino knockdown in zebrafish with wild-type rescue, shRNA knockdown in mouse hippocampal cultures (neurite morphology), in utero electroporation in mouse embryos (neuronal migration), overexpression of mutant protein","journal":"European journal of human genetics : EJHG","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple model systems (zebrafish, mouse neurons in vitro and in vivo), wild-type rescue, and mutant overexpression validating loss-of-function, replicated across orthogonal experimental approaches","pmids":["40745490"],"is_preprint":false},{"year":2025,"finding":"In C. elegans, endogenously-tagged MDT-29/MED29 is ubiquitously expressed and concentrated in discrete foci within germ cell nuclei. Germline depletion of MDT-29 during larval development increased fecundity by expanding the germline stem cell pool and decreasing germ cell apoptosis, establishing MED29 as a regulator of germline stem cell number and germ cell apoptosis.","method":"Endogenous tagging and live imaging for subcellular localization, germline-specific RNAi depletion, quantification of germline stem cell pool size and germ cell apoptosis","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — preprint, single lab, germline-specific depletion with defined phenotype but limited mechanistic pathway placement","pmids":[],"is_preprint":true}],"current_model":"MED29 (also known as IXL) is a subunit of the multi-subunit Mediator transcriptional coactivator complex that bridges gene-specific activators and RNA polymerase II machinery; it functions as a context-dependent transcriptional suppressor/coactivator, is required for cancer cell survival when amplified at 19q13, promotes EMT and migration in cancer cells downstream of MAPK signaling, is regulated transcriptionally by HSPB1/ELK4 axes via chromatin modifications, and is essential for neuronal development and migration—as demonstrated by loss-of-function causing pontocerebellar hypoplasia in humans and neurodevelopmental defects in zebrafish and mouse models."},"narrative":{"mechanistic_narrative":"MED29 (IXL) is a subunit of the multi-subunit Mediator transcriptional coactivator complex that modulates RNA polymerase II–dependent transcription in a promoter- and activator-selective manner [PMID:15555573, PMID:15175162]. As part of the endogenous CRSP/Mediator complex, it contributes to a combinatorial assembly in which subunit composition dictates which activators the complex can support, retaining coactivator function with VP16, Sp1, and SREBP-1a on chromatin templates [PMID:15175162]; in isolation as a Gal4 fusion, MED29 acts as a context-dependent transcriptional suppressor and dampens SRE- and AP-1-driven, MAPK-responsive transcription [PMID:15555573]. MED29 is required for neuronal development and migration: biallelic loss-of-function variants cause pontocerebellar hypoplasia with cataracts in humans, and depletion produces cerebellar GABAergic neuron, neurite outgrowth, and neuronal migration defects across zebrafish and mouse models with wild-type rescue [PMID:40745490]. In cancer, MED29 has context-dependent roles—it is amplified at 19q13 and required for survival of amplified pancreatic cancer cells [PMID:17332321], yet behaves as both an oncogenic driver of EMT, migration, and invasion downstream of MAPK signaling and a tumor suppressor depending on cellular context [PMID:21225629, PMID:39462350], and its transcription is upregulated through HSPB1-dependent histone modification and ELK4 binding at its promoter [PMID:35526007].","teleology":[{"year":2004,"claim":"Establishing MED29 as a Mediator subunit and asking what it does to transcription positioned it as a context-dependent regulator rather than a generic coactivator.","evidence":"Gal4 fusion repression assays and SRE/AP-1 reporter assays in COS-7 cells with subcellular fractionation","pmids":["15555573"],"confidence":"Medium","gaps":["No structural placement within Mediator","Suppressor activity inferred from overexpression/fusion, not endogenous complex behavior"]},{"year":2004,"claim":"Structural and biochemical dissection of the CRSP/Mediator complex showed that subunit composition governs activator selectivity, framing how individual subunits like MED29 confer promoter specificity.","evidence":"Biochemical purification, EM single-particle reconstruction at 31 Å, and in vitro transcription on chromatin templates with multiple activators","pmids":["15175162"],"confidence":"High","gaps":["MED29's specific contribution to the complex not isolated","Does not define MED29 contact surfaces or activator interactions directly"]},{"year":2007,"claim":"The question of whether 19q13 amplification creates a dependency was answered by showing MED29 is selectively required for survival of amplified cancer cells.","evidence":"FISH copy number, RNAi knockdown, viability/cell cycle/apoptosis readouts in paired amplified (PANC-1) and non-amplified (MiaPaCa-2) lines","pmids":["17332321"],"confidence":"Medium","gaps":["Transcriptional targets mediating survival dependency unidentified","Single lab, single tumor type"]},{"year":2011,"claim":"Opposing knockdown and overexpression phenotypes resolved that MED29 has context-dependent oncogenic and tumor-suppressive roles rather than a single directional effect.","evidence":"RNAi knockdown, lentiviral overexpression, subcutaneous xenografts, and gene expression microarrays in pancreatic and fibroblast lines","pmids":["21225629"],"confidence":"Medium","gaps":["Molecular basis of context-dependence not defined","Cell cycle gene changes correlative, not mechanistically linked"]},{"year":2022,"claim":"Identifying how MED29 is transcriptionally upregulated revealed two converging regulatory axes controlling its expression in lung cancer.","evidence":"ChIP, luciferase reporters, RNA pulldown/MS, RIP, Co-IP, and gain/loss-of-function with in vivo tumor growth in NSCLC","pmids":["35526007"],"confidence":"Medium","gaps":["Whether HSPB1 and ELK4 act independently or cooperatively unresolved","Downstream effectors of MED29 in proliferation/migration not mapped"]},{"year":2024,"claim":"Linking MED29 to EMT downstream of MAPK signaling connected its transcriptional regulatory role to an invasive/metastatic program in solid tumors.","evidence":"Overexpression/knockdown with migration, invasion, and EMT readouts plus a tail-vein lung metastasis model, with CHRDL1/MAPK pathway manipulation in OSCC","pmids":["39462350"],"confidence":"Medium","gaps":["MAPK link inferred from pathway inhibition, not direct biochemistry","Direct transcriptional targets driving EMT unidentified"]},{"year":2025,"claim":"Human genetics combined with cross-species modeling established MED29 as essential for neuronal development and migration and as a cause of pontocerebellar hypoplasia.","evidence":"Whole-exome sequencing, zebrafish morpholino with WT rescue, mouse hippocampal shRNA neurite assays, and in utero electroporation migration assays; mutant overexpression","pmids":["40745490"],"confidence":"High","gaps":["Neuronal transcriptional targets of MED29 unknown","How p.Leu139Pro disrupts Mediator function at the molecular level undefined"]},{"year":2025,"claim":"An invertebrate model raised the question of MED29's role in stem cell homeostasis, implicating it in germline stem cell number and germ cell apoptosis.","evidence":"Endogenous tagging/live imaging and germline-specific RNAi depletion in C. elegans (preprint)","pmids":[],"confidence":"Low","gaps":["Preprint, single lab, not peer-reviewed","No mechanistic pathway placement for the germline phenotype","Conservation of this role in mammals untested"]},{"year":null,"claim":"The direct transcriptional targets and Mediator contacts through which MED29 exerts its context-dependent suppressor/coactivator activity across neurons and tumors remain undefined.","evidence":"No direct target identification or structural MED29-activator interaction mapping in the corpus","pmids":[],"confidence":"Low","gaps":["No defined gene targets bridging MED29 to its developmental and oncogenic phenotypes","No structural model of MED29 within Mediator"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,7]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6]}],"complexes":["Mediator complex","CRSP/Med complex"],"partners":["HSPB1","ELK4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NX70","full_name":"Mediator of RNA polymerase II transcription subunit 29","aliases":["Intersex-like protein","Mediator complex subunit 29"],"length_aa":200,"mass_kda":21.1,"function":"Component of the Mediator complex, a coactivator involved in the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator functions as a bridge to convey information from gene-specific regulatory proteins to the basal RNA polymerase II transcription machinery. Mediator is recruited to promoters by direct interactions with regulatory proteins and serves as a scaffold for the assembly of a functional preinitiation complex with RNA polymerase II and the general transcription factors","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9NX70/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/MED29","classification":"Common Essential","n_dependent_lines":1166,"n_total_lines":1208,"dependency_fraction":0.9652317880794702},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000063322","cell_line_id":"CID000254","localizations":[{"compartment":"nuclear_punctae","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"MED27","stoichiometry":10.0},{"gene":"MED4","stoichiometry":10.0},{"gene":"MED9","stoichiometry":10.0},{"gene":"MED30","stoichiometry":10.0},{"gene":"MED8","stoichiometry":10.0},{"gene":"MED15","stoichiometry":10.0},{"gene":"MED28","stoichiometry":10.0},{"gene":"MED20","stoichiometry":10.0},{"gene":"MED10","stoichiometry":10.0},{"gene":"MED18","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000254","total_profiled":1310},"omim":[{"mim_id":"612915","title":"MEDIATOR COMPLEX SUBUNIT 20; MED20","url":"https://www.omim.org/entry/612915"},{"mim_id":"612914","title":"MEDIATOR COMPLEX SUBUNIT 29; MED29","url":"https://www.omim.org/entry/612914"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MED29"},"hgnc":{"alias_symbol":["DKFZp434H247","MED2"],"prev_symbol":["IXL"]},"alphafold":{"accession":"Q9NX70","domains":[{"cath_id":"1.10.287","chopping":"54-137","consensus_level":"high","plddt":89.2051,"start":54,"end":137}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NX70","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NX70-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NX70-F1-predicted_aligned_error_v6.png","plddt_mean":72.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MED29","jax_strain_url":"https://www.jax.org/strain/search?query=MED29"},"sequence":{"accession":"Q9NX70","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NX70.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NX70/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NX70"}},"corpus_meta":[{"pmid":"35526007","id":"PMC_35526007","title":"A novel tRNA-derived fragment AS-tDR-007333 promotes the malignancy of NSCLC via the HSPB1/MED29 and ELK4/MED29 axes.","date":"2022","source":"Journal of hematology & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/35526007","citation_count":98,"is_preprint":false},{"pmid":"17332321","id":"PMC_17332321","title":"Intersex-like (IXL) is a cell survival regulator in pancreatic cancer with 19q13 amplification.","date":"2007","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/17332321","citation_count":63,"is_preprint":false},{"pmid":"15175162","id":"PMC_15175162","title":"Structure and function of CRSP/Med2; a promoter-selective transcriptional coactivator complex.","date":"2004","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/15175162","citation_count":55,"is_preprint":false},{"pmid":"29203634","id":"PMC_29203634","title":"Mediator Complex Subunits MED2, MED5, MED16, and MED23 Genetically Interact in the Regulation of Phenylpropanoid Biosynthesis.","date":"2017","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/29203634","citation_count":50,"is_preprint":false},{"pmid":"29630599","id":"PMC_29630599","title":"Functional diversification accompanies gene family expansion of MED2 homologs in Candida albicans.","date":"2018","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29630599","citation_count":29,"is_preprint":false},{"pmid":"15998721","id":"PMC_15998721","title":"Reevaluation of the role of the med-1 and med-2 genes in specifying the Caenorhabditis elegans endoderm.","date":"2005","source":"Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15998721","citation_count":26,"is_preprint":false},{"pmid":"21225629","id":"PMC_21225629","title":"MED29, a component of the mediator complex, possesses both oncogenic and tumor suppressive characteristics in pancreatic cancer.","date":"2011","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/21225629","citation_count":24,"is_preprint":false},{"pmid":"15555573","id":"PMC_15555573","title":"IXL, a new subunit of the mammalian Mediator complex, functions as a transcriptional suppressor.","date":"2004","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15555573","citation_count":10,"is_preprint":false},{"pmid":"33036991","id":"PMC_33036991","title":"Candida glabrata Yap6 Recruits Med2 To Alter Glycerophospholipid Composition and Develop Acid pH Stress Resistance.","date":"2020","source":"Applied and environmental microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/33036991","citation_count":9,"is_preprint":false},{"pmid":"39462350","id":"PMC_39462350","title":"CHRDL1 inhibits OSCC metastasis via MAPK signaling-mediated inhibition of MED29.","date":"2024","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/39462350","citation_count":7,"is_preprint":false},{"pmid":"10487928","id":"PMC_10487928","title":"Disruption and functional analysis of seven ORFs on chromosome IV: YDL057w, YDL012c, YDL010w, YDL009c, YDL008w (APC11), YDL005c (MED2) and YDL003w (MCD1).","date":"1999","source":"Yeast (Chichester, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10487928","citation_count":6,"is_preprint":false},{"pmid":"39589925","id":"PMC_39589925","title":"ERD14 regulation by the HY5- or HY5-MED2 module mediates the cold signal transduction of asparagus bean.","date":"2024","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/39589925","citation_count":6,"is_preprint":false},{"pmid":"33045248","id":"PMC_33045248","title":"Yeast MED2 is involved in the endoplasmic reticulum stress response and modulation of the replicative lifespan.","date":"2020","source":"Mechanisms of ageing and development","url":"https://pubmed.ncbi.nlm.nih.gov/33045248","citation_count":4,"is_preprint":false},{"pmid":"40745490","id":"PMC_40745490","title":"Biallelic MED29 variants cause pontocerebellar hypoplasia with cataracts.","date":"2025","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/40745490","citation_count":2,"is_preprint":false},{"pmid":"16939003","id":"PMC_16939003","title":"mED2--a novel gene involved in mouse embryonic development.","date":"2006","source":"Yi chuan xue bao = Acta genetica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/16939003","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.10.25333392","title":"Identification and Validation of a Lipid Metabolism-associated Gene Signature for Predicting Survival in Sepsis 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Devices","date":"2025-04-11","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.07.646993","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11590,"output_tokens":2533,"usd":0.036382,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9703,"output_tokens":2772,"usd":0.058908,"stage2_stop_reason":"end_turn"},"total_usd":0.09529,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"MED29 (IXL) was identified as a new subunit of the mammalian Mediator complex. When fused to the Gal4 DNA-binding domain and co-transfected with VP-16, IXL/MED29 functions as a transcriptional suppressor. Overexpression in COS-7 cells inhibited transcriptional activities of SRE and AP-1, suggesting it acts as a transcriptional suppressor in the MAPK signaling pathway.\",\n      \"method\": \"Gal4 fusion transcriptional repression assay, co-transfection with VP-16, overexpression in COS-7 cells with SRE/AP-1 reporter assays; nuclear/cytoplasmic localization by subcellular fractionation\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — reporter assays with single lab, multiple readouts but no structural or in vitro reconstitution validation\",\n      \"pmids\": [\"15555573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"A stable endogenous CRSP/Med2 complex specifically lacking both Med220 and Med70 subunits was isolated. Electron microscopy and single-particle reconstruction determined its 3D structure at 31 Å resolution. CRSP/Med2 retains potent activator-dependent coactivator function with VP16, Sp1, and Sp1/SREBP-1a on chromatin templates in vitro, but cannot support vitamin D receptor (VDR)-directed activated transcription, which requires Med220 for coactivator recruitment. This demonstrates a combinatorial assembly mechanism allowing promoter-selective function.\",\n      \"method\": \"Biochemical purification of endogenous complex, electron microscopy single-particle reconstruction, in vitro transcription on chromatin templates with multiple activators\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structure determination by EM, in vitro reconstitution with chromatin templates, multiple activator conditions, functional distinction from full complex established\",\n      \"pmids\": [\"15175162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MED29 (IXL) is amplified and overexpressed in pancreatic cancer cells harboring a 19q13 amplicon. RNAi-mediated silencing of IXL/MED29 in PANC-1 (amplified) cells significantly decreased cell viability, caused G0-G1 cell cycle arrest, and increased apoptosis, but had no significant effect in non-amplified MiaPaCa-2 cells, establishing MED29 as required for survival specifically in amplified cancer cells.\",\n      \"method\": \"Fluorescence in situ hybridization for copy number, quantitative RT-PCR for expression, high-throughput RNAi loss-of-function screen, cell viability assay, flow cytometry for cell cycle and apoptosis\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi knockdown with multiple phenotypic readouts (viability, cell cycle, apoptosis) in paired amplified/non-amplified lines, single lab\",\n      \"pmids\": [\"17332321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MED29 silencing in PANC-1 cells (high MED29 expression) decreased migration, invasion, and colony formation. Conversely, lentiviral overexpression of MED29 in NIH/3T3 and MIAPaCa-2 cells (low endogenous expression) decreased proliferation, and subcutaneous xenograft experiments showed dramatic tumor suppression with decreased tumor incidence and size. Gene expression analysis revealed differential expression of cell cycle and cell division genes consistent with reduced cell growth, indicating MED29 has context-dependent oncogenic and tumor-suppressive roles.\",\n      \"method\": \"RNAi knockdown (migration, invasion, colony formation assays), lentiviral overexpression, in vivo subcutaneous xenograft in immunocompromised mice, gene expression microarray analysis\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro assays plus in vivo xenograft, gene expression analysis, single lab but orthogonal methods\",\n      \"pmids\": [\"21225629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The tRF AS-tDR-007333 activates MED29 expression through two distinct mechanisms: (1) binding to HSPB1, which enhances H3K4me1 and H3K27ac histone marks at the MED29 promoter; (2) stimulating expression of transcription factor ELK4, which binds the MED29 promoter and increases its transcription. MED29 upregulation downstream of these axes promotes NSCLC cell proliferation and migration.\",\n      \"method\": \"ChIP assay, luciferase reporter assay, RNA pulldown, mass spectrometry, RNA immunoprecipitation (RIP), co-immunoprecipitation (Co-IP), Western blot, gain- and loss-of-function experiments, in vivo tumor growth assay\",\n      \"journal\": \"Journal of hematology & oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP, luciferase, RIP, Co-IP) in single lab establishing two regulatory axes for MED29 transcription\",\n      \"pmids\": [\"35526007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MED29 promotes epithelial-mesenchymal transition (EMT), migration, and invasion in oral squamous cell carcinoma (OSCC) cells. CHRDL1 inhibits MED29 expression via suppression of the MAPK signaling pathway, thereby restraining EMT and reducing OSCC cell invasion and metastasis in vitro and in a tail-vein lung metastasis nude mouse model.\",\n      \"method\": \"RT-qPCR, Western blot, scratch/wound healing assay, Transwell invasion assay, immunofluorescence, in vivo tail-vein lung metastasis model in nude mice, MED29 overexpression and knockdown\",\n      \"journal\": \"Molecular medicine (Cambridge, Mass.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — multiple assays in vitro and in vivo but single lab; MAPK pathway link is inferred from pathway inhibition, not direct biochemical reconstitution\",\n      \"pmids\": [\"39462350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Biallelic loss-of-function MED29 variants (homozygous c.416T>C, p.Leu139Pro) cause pontocerebellar hypoplasia with cataracts in humans. Morpholino knockdown of MED29 in zebrafish impaired locomotion and cerebellar GABAergic neuron development, rescued by human wild-type MED29. shRNA knockdown in mouse hippocampal neurons decreased neurite length and arborization in vitro and caused defective embryonic neuronal migration in vivo. Overexpression of the p.Leu139Pro variant was consistent with loss-of-function.\",\n      \"method\": \"Whole-exome sequencing with Sanger validation, morpholino knockdown in zebrafish with wild-type rescue, shRNA knockdown in mouse hippocampal cultures (neurite morphology), in utero electroporation in mouse embryos (neuronal migration), overexpression of mutant protein\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple model systems (zebrafish, mouse neurons in vitro and in vivo), wild-type rescue, and mutant overexpression validating loss-of-function, replicated across orthogonal experimental approaches\",\n      \"pmids\": [\"40745490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In C. elegans, endogenously-tagged MDT-29/MED29 is ubiquitously expressed and concentrated in discrete foci within germ cell nuclei. Germline depletion of MDT-29 during larval development increased fecundity by expanding the germline stem cell pool and decreasing germ cell apoptosis, establishing MED29 as a regulator of germline stem cell number and germ cell apoptosis.\",\n      \"method\": \"Endogenous tagging and live imaging for subcellular localization, germline-specific RNAi depletion, quantification of germline stem cell pool size and germ cell apoptosis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — preprint, single lab, germline-specific depletion with defined phenotype but limited mechanistic pathway placement\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"MED29 (also known as IXL) is a subunit of the multi-subunit Mediator transcriptional coactivator complex that bridges gene-specific activators and RNA polymerase II machinery; it functions as a context-dependent transcriptional suppressor/coactivator, is required for cancer cell survival when amplified at 19q13, promotes EMT and migration in cancer cells downstream of MAPK signaling, is regulated transcriptionally by HSPB1/ELK4 axes via chromatin modifications, and is essential for neuronal development and migration—as demonstrated by loss-of-function causing pontocerebellar hypoplasia in humans and neurodevelopmental defects in zebrafish and mouse models.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MED29 (IXL) is a subunit of the multi-subunit Mediator transcriptional coactivator complex that modulates RNA polymerase II–dependent transcription in a promoter- and activator-selective manner [#0, #1]. As part of the endogenous CRSP/Mediator complex, it contributes to a combinatorial assembly in which subunit composition dictates which activators the complex can support, retaining coactivator function with VP16, Sp1, and SREBP-1a on chromatin templates [#1]; in isolation as a Gal4 fusion, MED29 acts as a context-dependent transcriptional suppressor and dampens SRE- and AP-1-driven, MAPK-responsive transcription [#0]. MED29 is required for neuronal development and migration: biallelic loss-of-function variants cause pontocerebellar hypoplasia with cataracts in humans, and depletion produces cerebellar GABAergic neuron, neurite outgrowth, and neuronal migration defects across zebrafish and mouse models with wild-type rescue [#6]. In cancer, MED29 has context-dependent roles—it is amplified at 19q13 and required for survival of amplified pancreatic cancer cells [#2], yet behaves as both an oncogenic driver of EMT, migration, and invasion downstream of MAPK signaling and a tumor suppressor depending on cellular context [#3, #5], and its transcription is upregulated through HSPB1-dependent histone modification and ELK4 binding at its promoter [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing MED29 as a Mediator subunit and asking what it does to transcription positioned it as a context-dependent regulator rather than a generic coactivator.\",\n      \"evidence\": \"Gal4 fusion repression assays and SRE/AP-1 reporter assays in COS-7 cells with subcellular fractionation\",\n      \"pmids\": [\"15555573\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural placement within Mediator\", \"Suppressor activity inferred from overexpression/fusion, not endogenous complex behavior\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Structural and biochemical dissection of the CRSP/Mediator complex showed that subunit composition governs activator selectivity, framing how individual subunits like MED29 confer promoter specificity.\",\n      \"evidence\": \"Biochemical purification, EM single-particle reconstruction at 31 Å, and in vitro transcription on chromatin templates with multiple activators\",\n      \"pmids\": [\"15175162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"MED29's specific contribution to the complex not isolated\", \"Does not define MED29 contact surfaces or activator interactions directly\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The question of whether 19q13 amplification creates a dependency was answered by showing MED29 is selectively required for survival of amplified cancer cells.\",\n      \"evidence\": \"FISH copy number, RNAi knockdown, viability/cell cycle/apoptosis readouts in paired amplified (PANC-1) and non-amplified (MiaPaCa-2) lines\",\n      \"pmids\": [\"17332321\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcriptional targets mediating survival dependency unidentified\", \"Single lab, single tumor type\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Opposing knockdown and overexpression phenotypes resolved that MED29 has context-dependent oncogenic and tumor-suppressive roles rather than a single directional effect.\",\n      \"evidence\": \"RNAi knockdown, lentiviral overexpression, subcutaneous xenografts, and gene expression microarrays in pancreatic and fibroblast lines\",\n      \"pmids\": [\"21225629\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of context-dependence not defined\", \"Cell cycle gene changes correlative, not mechanistically linked\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identifying how MED29 is transcriptionally upregulated revealed two converging regulatory axes controlling its expression in lung cancer.\",\n      \"evidence\": \"ChIP, luciferase reporters, RNA pulldown/MS, RIP, Co-IP, and gain/loss-of-function with in vivo tumor growth in NSCLC\",\n      \"pmids\": [\"35526007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HSPB1 and ELK4 act independently or cooperatively unresolved\", \"Downstream effectors of MED29 in proliferation/migration not mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linking MED29 to EMT downstream of MAPK signaling connected its transcriptional regulatory role to an invasive/metastatic program in solid tumors.\",\n      \"evidence\": \"Overexpression/knockdown with migration, invasion, and EMT readouts plus a tail-vein lung metastasis model, with CHRDL1/MAPK pathway manipulation in OSCC\",\n      \"pmids\": [\"39462350\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MAPK link inferred from pathway inhibition, not direct biochemistry\", \"Direct transcriptional targets driving EMT unidentified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Human genetics combined with cross-species modeling established MED29 as essential for neuronal development and migration and as a cause of pontocerebellar hypoplasia.\",\n      \"evidence\": \"Whole-exome sequencing, zebrafish morpholino with WT rescue, mouse hippocampal shRNA neurite assays, and in utero electroporation migration assays; mutant overexpression\",\n      \"pmids\": [\"40745490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Neuronal transcriptional targets of MED29 unknown\", \"How p.Leu139Pro disrupts Mediator function at the molecular level undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"An invertebrate model raised the question of MED29's role in stem cell homeostasis, implicating it in germline stem cell number and germ cell apoptosis.\",\n      \"evidence\": \"Endogenous tagging/live imaging and germline-specific RNAi depletion in C. elegans (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Preprint, single lab, not peer-reviewed\", \"No mechanistic pathway placement for the germline phenotype\", \"Conservation of this role in mammals untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct transcriptional targets and Mediator contacts through which MED29 exerts its context-dependent suppressor/coactivator activity across neurons and tumors remain undefined.\",\n      \"evidence\": \"No direct target identification or structural MED29-activator interaction mapping in the corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No defined gene targets bridging MED29 to its developmental and oncogenic phenotypes\", \"No structural model of MED29 within Mediator\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [\"Mediator complex\", \"CRSP/Med complex\"],\n    \"partners\": [\"HSPB1\", \"ELK4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}