{"gene":"MED29","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2004,"finding":"MED29 (IXL) was identified as a new subunit of the mammalian Mediator complex and functions as a transcriptional suppressor; IXL protein localizes to nucleus and cytoplasm in COS-7 cells, and overexpression inhibits transcriptional activities of SRE and AP-1, suggesting a role in suppressing MAP kinase signaling pathway-mediated transcription.","method":"Gal4-DBD fusion reporter assay, overexpression in COS-7 cells, Northern blot, subcellular localization","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, single method set, functional reporter assay with overexpression but no direct biochemical reconstitution of complex membership","pmids":["15555573"],"is_preprint":false},{"year":2004,"finding":"The human CRSP/Med complex exists in a stable endogenous form (CRSP/Med2) that specifically lacks Med220 and Med70 subunits; this sub-complex retains transcriptional coactivator activity for VP16, Sp1, and Sp1/SREBP-1a but cannot support vitamin D receptor-dependent transcription, demonstrating promoter-selective function via combinatorial subunit assembly.","method":"Biochemical isolation of endogenous complex, in vitro transcription on chromatin templates, electron microscopy and single-particle 3D reconstruction (31 Å resolution)","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro transcription, structural analysis by EM, multiple activators tested with rigorous controls","pmids":["15175162"],"is_preprint":false},{"year":2007,"finding":"MED29 (IXL) is amplified and overexpressed in pancreatic cancer cells with 19q13 amplification; RNAi-mediated silencing of MED29 in PANC-1 cells (amplified) but not MiaPaca-2 cells (non-amplified) significantly decreased cell viability and induced G0-G1 cell cycle arrest and increased apoptosis, establishing MED29 as a cell survival regulator in amplified cancer cells.","method":"High-throughput RNAi loss-of-function screen, FISH copy number analysis, qRT-PCR, cell viability assay, flow cytometry","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with defined cellular phenotype (cell cycle arrest, apoptosis), replicated across two cell lines","pmids":["17332321"],"is_preprint":false},{"year":2011,"finding":"MED29 silencing in PANC-1 pancreatic cancer cells (high MED29 expression) decreased migration, invasion, and colony formation; conversely, lentiviral MED29 overexpression in NIH/3T3 and MIAPaCa-2 cells (low endogenous expression) decreased proliferation and dramatically suppressed tumor growth in vivo, with gene expression analysis revealing differential regulation of cell cycle and cell division genes, indicating context-dependent oncogenic and tumor suppressive roles.","method":"RNAi knockdown, lentiviral overexpression, scratch/migration assay, invasion assay, colony formation assay, subcutaneous xenograft mouse model, gene expression microarray","journal":"International journal of cancer","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal cellular assays plus in vivo xenograft, gene expression analysis providing mechanistic pathway context","pmids":["21225629"],"is_preprint":false},{"year":2022,"finding":"The tRNA-derived fragment AS-tDR-007333 activates MED29 expression through two mechanisms: (1) binding to HSPB1, which enhances H3K4me1 and H3K27ac marks at the MED29 promoter; (2) stimulating ELK4 transcription factor expression, which directly binds the MED29 promoter and increases its transcription. Elevated MED29 expression downstream of these axes promotes NSCLC cell proliferation and migration.","method":"ChIP assay, luciferase reporter assay, RNA pulldown, mass spectrometry, RIP, Western blot, Co-IP, gain/loss-of-function experiments in vitro and in vivo","journal":"Journal of hematology & oncology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (ChIP, luciferase, Co-IP, pulldown, MS) in a single study demonstrating two distinct regulatory axes","pmids":["35526007"],"is_preprint":false},{"year":2024,"finding":"MED29 promotes epithelial-mesenchymal transition (EMT), invasion, and migration in oral squamous cell carcinoma (OSCC); CHRDL1 inhibits MED29 expression via suppression of the MAPK signaling pathway, thereby restraining EMT and metastasis in vitro and in vivo.","method":"RT-qPCR, Western blot, scratch assay, Transwell invasion/migration assay, immunofluorescence, tail vein lung metastasis nude mouse model","journal":"Molecular medicine (Cambridge, Mass.)","confidence":"Medium","confidence_rationale":"Tier 2 — defined cellular and in vivo phenotypes with pathway placement (MAPK-MED29-EMT axis), single lab","pmids":["39462350"],"is_preprint":false},{"year":2025,"finding":"Biallelic loss-of-function MED29 variants (p.Leu139Pro) cause pontocerebellar hypoplasia with cataracts; MED29 morpholino knockdown in zebrafish impaired cerebellar GABAergic neuron development and locomotion, 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.","method":"Whole-exome sequencing, Sanger validation, morpholino knockdown in zebrafish with wild-type rescue, shRNA knockdown in mouse hippocampal neurons (in vitro and in vivo electroporation), locomotion assay, immunostaining","journal":"European journal of human genetics : EJHG","confidence":"High","confidence_rationale":"Tier 2 — multiple model organisms, loss-of-function with wild-type rescue, in vitro and in vivo neuronal phenotypes, human genetic validation","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-specific depletion of MDT-29 during larval development increases fecundity by expanding the germline stem cell pool and decreasing germ cell apoptosis, establishing MED29 as a regulator of germ cell behavior and progeny production.","method":"Endogenous tagging, live imaging, germline-specific RNAi/depletion, germline stem cell counting, apoptosis assays, fecundity assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization with functional consequence, clean loss-of-function with defined cellular phenotypes, preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.02.14.638312"],"is_preprint":true}],"current_model":"MED29 is a subunit of the Mediator transcriptional coactivator complex that mediates signals between gene-specific activators and RNA polymerase II; it functions as a context-dependent regulator of transcription (acting as a suppressor or activator depending on cellular context), is required for cell survival, EMT, migration, and invasion in cancer cells, plays an essential role in neuronal migration and cerebellar development (with biallelic loss causing pontocerebellar hypoplasia in humans), and in C. elegans controls germline stem cell pool size and germ cell apoptosis by concentrating in discrete nuclear foci."},"narrative":{"teleology":[{"year":2004,"claim":"Establishing MED29 as a Mediator subunit with transcriptional suppressor activity resolved its molecular identity and initial function, showing it could inhibit SRE- and AP-1-dependent transcription linked to MAPK signaling.","evidence":"Gal4-DBD fusion reporter assays and overexpression in COS-7 cells","pmids":["15555573"],"confidence":"Medium","gaps":["Overexpression-only approach; endogenous loss-of-function not tested","No direct biochemical demonstration of incorporation into Mediator complex","Suppressor activity not tested on endogenous target genes"]},{"year":2004,"claim":"Demonstrating that an endogenous Mediator sub-complex (CRSP/Med2) retains coactivator function for certain activators but not others established the principle of promoter-selective transcription through combinatorial subunit composition, the framework within which MED29 operates.","evidence":"Biochemical purification of endogenous complex, in vitro transcription on chromatin templates, EM 3D reconstruction","pmids":["15175162"],"confidence":"High","gaps":["MED29-specific contribution to sub-complex selectivity not individually dissected","In vitro system may not capture full in vivo regulatory complexity"]},{"year":2007,"claim":"Linking MED29 amplification at 19q13 to pancreatic cancer cell survival established its first disease-relevant function, showing that silencing MED29 in amplified cells causes G0-G1 arrest and apoptosis while non-amplified cells are unaffected.","evidence":"High-throughput RNAi screen, FISH, flow cytometry in PANC-1 vs. MiaPaca-2 cells","pmids":["17332321"],"confidence":"Medium","gaps":["Mechanism by which MED29 drives survival (direct transcriptional targets) not identified","Amplicon contains other genes; MED29-specific contribution not fully isolated"]},{"year":2011,"claim":"Demonstrating that MED29 knockdown reduces migration and invasion while overexpression in low-expressing cells suppresses tumors in vivo resolved the apparent paradox by establishing context-dependent oncogenic and tumor-suppressive roles, with differential regulation of cell cycle and division genes.","evidence":"RNAi and lentiviral overexpression, migration/invasion/colony assays, xenograft model, gene expression microarray","pmids":["21225629"],"confidence":"High","gaps":["Direct transcriptional targets mediating context switch not identified by ChIP","Mechanism determining whether MED29 acts as activator vs. suppressor remains unclear"]},{"year":2022,"claim":"Delineating two upstream regulatory axes — tRNA fragment AS-tDR-007333 activating MED29 via HSPB1-dependent chromatin remodeling (H3K4me1/H3K27ac) and ELK4 transcription factor binding — revealed how MED29 expression is epigenetically and transcriptionally controlled to promote NSCLC proliferation.","evidence":"ChIP, luciferase reporter, RNA pulldown, mass spectrometry, RIP, Co-IP in NSCLC cells","pmids":["35526007"],"confidence":"High","gaps":["Whether these regulatory axes operate in non-lung cancer contexts is unknown","Downstream transcriptional program activated by MED29 in NSCLC not mapped"]},{"year":2024,"claim":"Placing MED29 downstream of CHRDL1-MAPK signaling as an EMT driver in oral squamous cell carcinoma extended the MAPK-MED29 regulatory axis to a new cancer type and directly linked MED29 to EMT and metastasis.","evidence":"RT-qPCR, Western blot, Transwell assays, tail vein lung metastasis model in nude mice","pmids":["39462350"],"confidence":"Medium","gaps":["Single lab study; independent confirmation in OSCC needed","Direct MED29 target genes driving EMT not identified","Whether MED29 directly or indirectly promotes EMT transcription factor expression is unresolved"]},{"year":2025,"claim":"Identifying biallelic MED29 loss-of-function as the cause of pontocerebellar hypoplasia with cataracts, validated by rescue in zebrafish and neuronal migration defects in mouse, established MED29 as essential for neurodevelopment and linked it to a Mendelian disorder.","evidence":"Whole-exome sequencing in human families, morpholino knockdown with WT rescue in zebrafish, shRNA in mouse hippocampal neurons with in utero electroporation","pmids":["40745490"],"confidence":"High","gaps":["Transcriptional targets of MED29 in developing neurons not identified","Whether the p.Leu139Pro variant disrupts Mediator complex assembly or specific activator interactions is unknown","Cataract mechanism not explored"]},{"year":2025,"claim":"Demonstrating that endogenously tagged C. elegans MDT-29 concentrates in discrete nuclear foci in germ cells and that its germline-specific depletion expands the stem cell pool and reduces apoptosis established a conserved role in restricting germ cell proliferation.","evidence":"Endogenous tagging, live imaging, germline-specific RNAi, stem cell counting and apoptosis assays in C. elegans (preprint)","pmids":["bio_10.1101_2025.02.14.638312"],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Nature of discrete nuclear foci (relationship to transcription sites or other condensates) uncharacterized","Whether germline stem cell regulation is Mediator complex-dependent or a moonlighting function is unknown"]},{"year":null,"claim":"The direct transcriptional targets and chromatin-level mechanism by which MED29 exerts its context-dependent activator versus suppressor function remain unresolved, as do the structural basis of its integration into Mediator sub-complexes and the determinants of its tissue-specific essentiality.","evidence":"","pmids":[],"confidence":"High","gaps":["No genome-wide ChIP-seq or CUT&RUN for MED29 occupancy at target promoters","No structural data for MED29 within the Mediator complex","Molecular basis of context-dependent oncogene vs. tumor suppressor switch uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,3,4]}],"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":[0,1,3,4]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,3,5]}],"complexes":["Mediator complex"],"partners":["HSPB1","ELK4","CHRDL1"],"other_free_text":[]},"mechanistic_narrative":"MED29 is a subunit of the Mediator transcriptional coactivator complex that functions as a context-dependent transcriptional regulator, acting as a suppressor of MAP kinase pathway-mediated transcription (via SRE and AP-1 reporters) in some settings and as a promoter of cell proliferation, migration, and epithelial-mesenchymal transition in cancers with MED29 amplification or upregulation [PMID:15555573, PMID:21225629, PMID:35526007, PMID:39462350]. In pancreatic cancer cells harboring 19q13 amplification, MED29 is required for cell viability, and its silencing causes G0-G1 arrest and apoptosis, whereas forced overexpression in low-expressing cells suppresses tumor growth in vivo, revealing dose- and context-dependent oncogenic versus tumor-suppressive activities [PMID:17332321, PMID:21225629]. MED29 is essential for neurodevelopment: biallelic loss-of-function variants cause pontocerebellar hypoplasia with cataracts in humans, and knockdown in zebrafish and mouse models impairs cerebellar GABAergic neuron development, neurite outgrowth, and embryonic neuronal migration [PMID:40745490]."},"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":95,"is_preprint":false},{"pmid":"24415770","id":"PMC_24415770","title":"The Arabidopsis mediator complex subunits MED16, MED14, and MED2 regulate mediator and RNA polymerase II recruitment to CBF-responsive cold-regulated genes.","date":"2014","source":"The Plant cell","url":"https://pubmed.ncbi.nlm.nih.gov/24415770","citation_count":95,"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":49,"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":28,"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":"33777083","id":"PMC_33777083","title":"Mediator Subunits MED16, MED14, and MED2 Are Required for Activation of ABRE-Dependent Transcription in Arabidopsis.","date":"2021","source":"Frontiers in plant science","url":"https://pubmed.ncbi.nlm.nih.gov/33777083","citation_count":15,"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":"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":"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":"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 : 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Encapsulation on the Receive Performance of PMUTs for Implantable 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":11698,"output_tokens":2224,"usd":0.034227},"stage2":{"model":"claude-opus-4-6","input_tokens":5498,"output_tokens":2390,"usd":0.13086},"total_usd":0.165087,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","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 and functions as a transcriptional suppressor; IXL protein localizes to nucleus and cytoplasm in COS-7 cells, and overexpression inhibits transcriptional activities of SRE and AP-1, suggesting a role in suppressing MAP kinase signaling pathway-mediated transcription.\",\n      \"method\": \"Gal4-DBD fusion reporter assay, overexpression in COS-7 cells, Northern blot, subcellular localization\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single method set, functional reporter assay with overexpression but no direct biochemical reconstitution of complex membership\",\n      \"pmids\": [\"15555573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The human CRSP/Med complex exists in a stable endogenous form (CRSP/Med2) that specifically lacks Med220 and Med70 subunits; this sub-complex retains transcriptional coactivator activity for VP16, Sp1, and Sp1/SREBP-1a but cannot support vitamin D receptor-dependent transcription, demonstrating promoter-selective function via combinatorial subunit assembly.\",\n      \"method\": \"Biochemical isolation of endogenous complex, in vitro transcription on chromatin templates, electron microscopy and single-particle 3D reconstruction (31 Å resolution)\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro transcription, structural analysis by EM, multiple activators tested with rigorous controls\",\n      \"pmids\": [\"15175162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MED29 (IXL) is amplified and overexpressed in pancreatic cancer cells with 19q13 amplification; RNAi-mediated silencing of MED29 in PANC-1 cells (amplified) but not MiaPaca-2 cells (non-amplified) significantly decreased cell viability and induced G0-G1 cell cycle arrest and increased apoptosis, establishing MED29 as a cell survival regulator in amplified cancer cells.\",\n      \"method\": \"High-throughput RNAi loss-of-function screen, FISH copy number analysis, qRT-PCR, cell viability assay, flow cytometry\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined cellular phenotype (cell cycle arrest, apoptosis), replicated across two cell lines\",\n      \"pmids\": [\"17332321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MED29 silencing in PANC-1 pancreatic cancer cells (high MED29 expression) decreased migration, invasion, and colony formation; conversely, lentiviral MED29 overexpression in NIH/3T3 and MIAPaCa-2 cells (low endogenous expression) decreased proliferation and dramatically suppressed tumor growth in vivo, with gene expression analysis revealing differential regulation of cell cycle and cell division genes, indicating context-dependent oncogenic and tumor suppressive roles.\",\n      \"method\": \"RNAi knockdown, lentiviral overexpression, scratch/migration assay, invasion assay, colony formation assay, subcutaneous xenograft mouse model, gene expression microarray\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal cellular assays plus in vivo xenograft, gene expression analysis providing mechanistic pathway context\",\n      \"pmids\": [\"21225629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The tRNA-derived fragment AS-tDR-007333 activates MED29 expression through two mechanisms: (1) binding to HSPB1, which enhances H3K4me1 and H3K27ac marks at the MED29 promoter; (2) stimulating ELK4 transcription factor expression, which directly binds the MED29 promoter and increases its transcription. Elevated MED29 expression downstream of these axes promotes NSCLC cell proliferation and migration.\",\n      \"method\": \"ChIP assay, luciferase reporter assay, RNA pulldown, mass spectrometry, RIP, Western blot, Co-IP, gain/loss-of-function experiments in vitro and in vivo\",\n      \"journal\": \"Journal of hematology & oncology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (ChIP, luciferase, Co-IP, pulldown, MS) in a single study demonstrating two distinct regulatory axes\",\n      \"pmids\": [\"35526007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MED29 promotes epithelial-mesenchymal transition (EMT), invasion, and migration in oral squamous cell carcinoma (OSCC); CHRDL1 inhibits MED29 expression via suppression of the MAPK signaling pathway, thereby restraining EMT and metastasis in vitro and in vivo.\",\n      \"method\": \"RT-qPCR, Western blot, scratch assay, Transwell invasion/migration assay, immunofluorescence, tail vein lung metastasis nude mouse model\",\n      \"journal\": \"Molecular medicine (Cambridge, Mass.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined cellular and in vivo phenotypes with pathway placement (MAPK-MED29-EMT axis), single lab\",\n      \"pmids\": [\"39462350\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Biallelic loss-of-function MED29 variants (p.Leu139Pro) cause pontocerebellar hypoplasia with cataracts; MED29 morpholino knockdown in zebrafish impaired cerebellar GABAergic neuron development and locomotion, 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.\",\n      \"method\": \"Whole-exome sequencing, Sanger validation, morpholino knockdown in zebrafish with wild-type rescue, shRNA knockdown in mouse hippocampal neurons (in vitro and in vivo electroporation), locomotion assay, immunostaining\",\n      \"journal\": \"European journal of human genetics : EJHG\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple model organisms, loss-of-function with wild-type rescue, in vitro and in vivo neuronal phenotypes, human genetic validation\",\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-specific depletion of MDT-29 during larval development increases fecundity by expanding the germline stem cell pool and decreasing germ cell apoptosis, establishing MED29 as a regulator of germ cell behavior and progeny production.\",\n      \"method\": \"Endogenous tagging, live imaging, germline-specific RNAi/depletion, germline stem cell counting, apoptosis assays, fecundity assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization with functional consequence, clean loss-of-function with defined cellular phenotypes, preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.02.14.638312\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"MED29 is a subunit of the Mediator transcriptional coactivator complex that mediates signals between gene-specific activators and RNA polymerase II; it functions as a context-dependent regulator of transcription (acting as a suppressor or activator depending on cellular context), is required for cell survival, EMT, migration, and invasion in cancer cells, plays an essential role in neuronal migration and cerebellar development (with biallelic loss causing pontocerebellar hypoplasia in humans), and in C. elegans controls germline stem cell pool size and germ cell apoptosis by concentrating in discrete nuclear foci.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MED29 is a subunit of the Mediator transcriptional coactivator complex that functions as a context-dependent transcriptional regulator, acting as a suppressor of MAP kinase pathway-mediated transcription (via SRE and AP-1 reporters) in some settings and as a promoter of cell proliferation, migration, and epithelial-mesenchymal transition in cancers with MED29 amplification or upregulation [PMID:15555573, PMID:21225629, PMID:35526007, PMID:39462350]. In pancreatic cancer cells harboring 19q13 amplification, MED29 is required for cell viability, and its silencing causes G0-G1 arrest and apoptosis, whereas forced overexpression in low-expressing cells suppresses tumor growth in vivo, revealing dose- and context-dependent oncogenic versus tumor-suppressive activities [PMID:17332321, PMID:21225629]. MED29 is essential for neurodevelopment: biallelic loss-of-function variants cause pontocerebellar hypoplasia with cataracts in humans, and knockdown in zebrafish and mouse models impairs cerebellar GABAergic neuron development, neurite outgrowth, and embryonic neuronal migration [PMID:40745490].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing MED29 as a Mediator subunit with transcriptional suppressor activity resolved its molecular identity and initial function, showing it could inhibit SRE- and AP-1-dependent transcription linked to MAPK signaling.\",\n      \"evidence\": \"Gal4-DBD fusion reporter assays and overexpression in COS-7 cells\",\n      \"pmids\": [\"15555573\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression-only approach; endogenous loss-of-function not tested\",\n        \"No direct biochemical demonstration of incorporation into Mediator complex\",\n        \"Suppressor activity not tested on endogenous target genes\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstrating that an endogenous Mediator sub-complex (CRSP/Med2) retains coactivator function for certain activators but not others established the principle of promoter-selective transcription through combinatorial subunit composition, the framework within which MED29 operates.\",\n      \"evidence\": \"Biochemical purification of endogenous complex, in vitro transcription on chromatin templates, EM 3D reconstruction\",\n      \"pmids\": [\"15175162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"MED29-specific contribution to sub-complex selectivity not individually dissected\",\n        \"In vitro system may not capture full in vivo regulatory complexity\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Linking MED29 amplification at 19q13 to pancreatic cancer cell survival established its first disease-relevant function, showing that silencing MED29 in amplified cells causes G0-G1 arrest and apoptosis while non-amplified cells are unaffected.\",\n      \"evidence\": \"High-throughput RNAi screen, FISH, flow cytometry in PANC-1 vs. MiaPaca-2 cells\",\n      \"pmids\": [\"17332321\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which MED29 drives survival (direct transcriptional targets) not identified\",\n        \"Amplicon contains other genes; MED29-specific contribution not fully isolated\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrating that MED29 knockdown reduces migration and invasion while overexpression in low-expressing cells suppresses tumors in vivo resolved the apparent paradox by establishing context-dependent oncogenic and tumor-suppressive roles, with differential regulation of cell cycle and division genes.\",\n      \"evidence\": \"RNAi and lentiviral overexpression, migration/invasion/colony assays, xenograft model, gene expression microarray\",\n      \"pmids\": [\"21225629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct transcriptional targets mediating context switch not identified by ChIP\",\n        \"Mechanism determining whether MED29 acts as activator vs. suppressor remains unclear\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Delineating two upstream regulatory axes — tRNA fragment AS-tDR-007333 activating MED29 via HSPB1-dependent chromatin remodeling (H3K4me1/H3K27ac) and ELK4 transcription factor binding — revealed how MED29 expression is epigenetically and transcriptionally controlled to promote NSCLC proliferation.\",\n      \"evidence\": \"ChIP, luciferase reporter, RNA pulldown, mass spectrometry, RIP, Co-IP in NSCLC cells\",\n      \"pmids\": [\"35526007\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether these regulatory axes operate in non-lung cancer contexts is unknown\",\n        \"Downstream transcriptional program activated by MED29 in NSCLC not mapped\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Placing MED29 downstream of CHRDL1-MAPK signaling as an EMT driver in oral squamous cell carcinoma extended the MAPK-MED29 regulatory axis to a new cancer type and directly linked MED29 to EMT and metastasis.\",\n      \"evidence\": \"RT-qPCR, Western blot, Transwell assays, tail vein lung metastasis model in nude mice\",\n      \"pmids\": [\"39462350\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab study; independent confirmation in OSCC needed\",\n        \"Direct MED29 target genes driving EMT not identified\",\n        \"Whether MED29 directly or indirectly promotes EMT transcription factor expression is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identifying biallelic MED29 loss-of-function as the cause of pontocerebellar hypoplasia with cataracts, validated by rescue in zebrafish and neuronal migration defects in mouse, established MED29 as essential for neurodevelopment and linked it to a Mendelian disorder.\",\n      \"evidence\": \"Whole-exome sequencing in human families, morpholino knockdown with WT rescue in zebrafish, shRNA in mouse hippocampal neurons with in utero electroporation\",\n      \"pmids\": [\"40745490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Transcriptional targets of MED29 in developing neurons not identified\",\n        \"Whether the p.Leu139Pro variant disrupts Mediator complex assembly or specific activator interactions is unknown\",\n        \"Cataract mechanism not explored\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrating that endogenously tagged C. elegans MDT-29 concentrates in discrete nuclear foci in germ cells and that its germline-specific depletion expands the stem cell pool and reduces apoptosis established a conserved role in restricting germ cell proliferation.\",\n      \"evidence\": \"Endogenous tagging, live imaging, germline-specific RNAi, stem cell counting and apoptosis assays in C. elegans (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.02.14.638312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint not yet peer-reviewed\",\n        \"Nature of discrete nuclear foci (relationship to transcription sites or other condensates) uncharacterized\",\n        \"Whether germline stem cell regulation is Mediator complex-dependent or a moonlighting function is unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct transcriptional targets and chromatin-level mechanism by which MED29 exerts its context-dependent activator versus suppressor function remain unresolved, as do the structural basis of its integration into Mediator sub-complexes and the determinants of its tissue-specific essentiality.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No genome-wide ChIP-seq or CUT&RUN for MED29 occupancy at target promoters\",\n        \"No structural data for MED29 within the Mediator complex\",\n        \"Molecular basis of context-dependent oncogene vs. tumor suppressor switch uncharacterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 3, 4]}\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, 3, 4]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3, 5]}\n    ],\n    \"complexes\": [\"Mediator complex\"],\n    \"partners\": [\"HSPB1\", \"ELK4\", \"CHRDL1\"],\n    \"other_free_text\": []\n  }\n}\n```"}