{"gene":"MED16","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2013,"finding":"In yeast S. cerevisiae, Med16 (a Mediator Tail module subunit) is required for Mediator recruitment to HSP gene promoters upon heat shock. Deletion of Med16 alone reduces Mediator occupancy; deletion of both Med15 and Med16 abolishes Mediator recruitment and substantially diminishes RNA Pol II recruitment. Hsf1 recruits holo-Mediator through cooperative interactions with the Tail module via its dual N- and C-terminal activation domains.","method":"ChIP (chromatin immunoprecipitation) in yeast; genetic deletion of Med15 and/or Med16; truncation of Hsf1 activation domains","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic and ChIP analyses with multiple deletion combinations, clean epistatic dissection of two activation domains and two subunits","pmids":["23447536"],"is_preprint":false},{"year":2013,"finding":"In yeast, cells lacking Med16 show displacement of the Tail module from the Head and Middle modules of Mediator. Simultaneous inactivation of MED15/MED16 is synthetically lethal, indicating Tail performs essential functions as a separate complex. Loss of Med16 (or Med15) leads to down-regulation of Ace2 transcriptional activator target genes and a G1 cell cycle arrest phenotype.","method":"N-Degron temperature-sensitive mutants; global gene expression profiling; genetic synthetic lethality analysis; flow cytometry (G1 arrest)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (inducible degron, transcriptomics, cell-cycle analysis) in a single lab","pmids":["23991176"],"is_preprint":false},{"year":2004,"finding":"In Drosophila melanogaster, MED16 is specifically required for lipopolysaccharide (LPS)-induced transcriptional activation. RNAi depletion of MED16 causes defects specific to LPS- and differentiation-inducing factor (DIF)-induced gene expression without general transcriptional defects, and its activator-specific function appears to result from physical interaction with specific activators.","method":"RNA interference (RNAi) depletion of individual Mediator subunits; reporter assays on synthetic and endogenous promoters; microarray expression analysis of DIF- and MED16-depleted cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi plus microarray in Drosophila, activator-specific functional dissection with two orthogonal readouts (reporter + endogenous gene expression), single lab","pmids":["15297616"],"is_preprint":false},{"year":2025,"finding":"In Arabidopsis, MED16 promotes stability of MED25 by competing with E3 ubiquitin ligases MBR1 and MBR2 to bind the von Willebrand Factor A (vWF-A) domain of MED25, thereby antagonizing MBR1/2-mediated MED25 degradation. Additionally, MED16 promotes hormone-induced interactions between transcription factor MYC2 and MED25, leading to activation of jasmonate (JA)-responsive gene expression.","method":"Co-immunoprecipitation; in vivo competition binding assays; protein stability assays; genetic epistasis; reporter gene assays; domain mapping (vWF-A domain)","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, competition binding, and in vivo stability assays in a single lab; Arabidopsis ortholog context","pmids":["39824838"],"is_preprint":false},{"year":2025,"finding":"Human MED16 missense and in-frame duplication variants associated with intellectual disability syndrome cause protein mislocalization from the nucleus to the cytoplasm, as demonstrated by immunofluorescence assays in patient-derived cells. Homozygous mutant med16 zebrafish show growth delay and increased mortality; Med16 knockout mice are preweaning lethal, confirming a conserved essential developmental role.","method":"Immunofluorescence subcellular localization assays; zebrafish med16 knockout (growth/mortality phenotype); mouse Med16 knockout (lethality); 3D structural modeling of missense variants","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence, multiple orthogonal model organism KO phenotypes, single study","pmids":["40081376"],"is_preprint":false},{"year":2025,"finding":"In Drosophila, loss of med16 (ortholog of human MED16) reduces eclosion and lifespan and impairs synaptic transmission. In iPSC-derived neurons from MED16 variant-carrying patients, neurite outgrowth is impaired and rescued by exogenous MED16 expression. Patient-associated variants behave as loss-of-function alleles in both fly and iPSC models, and transcription of genes related to neuronal maturation is preferentially altered in patient cells.","method":"Drosophila med16 loss-of-function (eclosion, lifespan, electrophysiology); iPSC-derived neurons (neurite outgrowth assay, rescue by exogenous MED16); RNA-seq transcriptional profiling","journal":"Journal of genetics and genomics = Yi chuan xue bao","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal model systems (fly KO + patient iPSC neurons), rescue experiment, RNA-seq; single study","pmids":["40254158"],"is_preprint":false},{"year":2025,"finding":"Human MED16 dissociates from the core Mediator complex to form a subcomplex with transcription factors UBP1 and TFCP2. This MED16-UBP1 interaction activates a subset of genes involved in lung homeostasis, angiogenesis, and cell proliferation. Conversely, MED16 and UBP1 cooperatively bind the HIV-1 transcriptional start site (TSS) to inhibit preinitiation complex assembly and suppress HIV-1 transcription, reinforcing viral latency. The directionality (activation vs repression) depends on whether the UBP1-TFCP2 binding motif is proximal to or overlapping the TSS.","method":"Protein purification coupled with mass spectrometry (identification of MED16 as UBP1-TFCP2 binding partner); gene expression analysis; chromatin occupancy assays at HIV-1 TSS; genomic-scale analysis of motif position relative to TSS","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — mass spectrometry-identified interaction, genomic-scale expression and occupancy data, preprint not yet peer-reviewed, single lab","pmids":[],"is_preprint":true}],"current_model":"MED16 is a Tail module subunit of the Mediator complex that serves as a context-dependent coactivator by physically recruiting holo-Mediator to activated gene promoters (e.g., heat-shock genes via Hsf1 in yeast; LPS/DIF-induced genes in Drosophila), stabilizes partner subunit MED25 by competing with E3 ubiquitin ligases for its vWF-A domain, can dissociate from core Mediator to form subcomplexes with specific transcription factors (e.g., UBP1-TFCP2) that activate or repress transcription depending on promoter-proximal motif position, and is required for nuclear localization and normal neurodevelopment in vertebrates, with loss-of-function causing synaptic transmission defects and impaired neurite outgrowth."},"narrative":{"mechanistic_narrative":"MED16 is a Tail-module subunit of the Mediator complex that functions as a context-dependent transcriptional coactivator by physically bridging gene-specific activators to holo-Mediator and thereby promoting RNA Polymerase II recruitment to induced promoters [PMID:23447536, PMID:15297616]. In yeast, MED16 is required for Mediator occupancy at heat-shock genes downstream of the Hsf1 activator, and its loss displaces the entire Tail module from the Head and Middle modules; combined loss with MED15 is synthetically lethal and arrests cells in G1, indicating the Tail can act as a separable functional unit [PMID:23447536, PMID:23991176]. The activator-specific character of MED16 is conserved: in Drosophila it is selectively required for LPS/DIF-induced gene expression rather than bulk transcription [PMID:15297616]. Beyond recruitment, MED16 stabilizes the partner subunit MED25 by competing with the E3 ubiquitin ligases MBR1/MBR2 for the MED25 vWF-A domain and promotes hormone-induced MYC2–MED25 interactions that drive jasmonate-responsive transcription [PMID:39824838]. MED16 can also dissociate from core Mediator to form a subcomplex with the transcription factors UBP1 and TFCP2, where it activates or represses target genes depending on the position of the UBP1-TFCP2 motif relative to the transcription start site. In humans, MED16 loss-of-function variants associated with an intellectual disability syndrome cause mislocalization of the protein from nucleus to cytoplasm, impair neurite outgrowth in patient iPSC-derived neurons, and disrupt synaptic transmission, defining a conserved essential developmental role confirmed by lethality in mouse and zebrafish knockouts [PMID:40081376, PMID:40254158].","teleology":[{"year":2004,"claim":"Established that MED16 is not a general transcription factor but an activator-specific coactivator, answering whether individual Mediator subunits confer signal specificity.","evidence":"RNAi depletion of individual Mediator subunits with reporter and microarray readouts in Drosophila","pmids":["15297616"],"confidence":"Medium","gaps":["Direct physical interaction with specific activators inferred rather than mapped at residue level","No structural basis for activator selectivity"]},{"year":2013,"claim":"Showed that MED16 physically recruits holo-Mediator to activated promoters, linking a specific activator (Hsf1) through the Tail module to Pol II loading.","evidence":"ChIP and combinatorial genetic deletion of Med15/Med16 with Hsf1 activation-domain truncations in yeast","pmids":["23447536"],"confidence":"High","gaps":["Whether recruitment mechanism generalizes beyond heat-shock genes not addressed","No direct Med16–Hsf1 binding interface defined"]},{"year":2013,"claim":"Demonstrated that the Tail module can function as a separable complex and is essential, by showing Med16 loss detaches Tail from core Mediator and is synthetically lethal with Med15.","evidence":"Inducible N-degron mutants, transcriptome profiling, synthetic lethality, and cell-cycle analysis in yeast","pmids":["23991176"],"confidence":"Medium","gaps":["Composition and stability of the free Tail subcomplex not structurally resolved","Mechanism linking Ace2 target down-regulation to G1 arrest unclear"]},{"year":2025,"claim":"Identified a non-recruitment role: MED16 protects partner subunit MED25 from ubiquitin-mediated degradation and promotes activator–Mediator engagement, answering how MED16 modulates a hormone-responsive transcription program.","evidence":"Co-IP, competition binding, protein stability and reporter assays with vWF-A domain mapping in Arabidopsis","pmids":["39824838"],"confidence":"Medium","gaps":["Whether MED25 stabilization role is conserved in animals untested","Stoichiometry of MED16/MED25/MBR1/2 competition not quantified"]},{"year":2025,"claim":"Defined the conserved essential developmental requirement for MED16 and linked human loss-of-function variants to disease, answering whether MED16 dysfunction causes phenotype in vivo.","evidence":"Patient-cell immunofluorescence, zebrafish and mouse knockouts, and 3D variant modeling","pmids":["40081376"],"confidence":"Medium","gaps":["Mechanism connecting cytoplasmic mislocalization to transcriptional defect unresolved","Lethality stage in mouse not mechanistically dissected"]},{"year":2025,"claim":"Connected MED16 variants to a specific neuronal phenotype, showing loss-of-function impairs neurite outgrowth and synaptic transmission with rescue, establishing causality.","evidence":"Drosophila loss-of-function (electrophysiology, lifespan), patient iPSC-derived neuron neurite assays with MED16 rescue, and RNA-seq","pmids":["40254158"],"confidence":"Medium","gaps":["Which neuronal target genes are direct MED16/Mediator targets not defined","Link between synaptic defect and specific transcriptional program incomplete"]},{"year":2025,"claim":"Revealed a Mediator-independent mode in which MED16 forms a UBP1-TFCP2 subcomplex that activates or represses transcription according to motif position relative to the TSS, including suppression of HIV-1 transcription.","evidence":"Protein purification with mass spectrometry, gene expression and chromatin occupancy at the HIV-1 TSS, and genome-scale motif-position analysis (preprint)","pmids":[],"confidence":"Medium","gaps":["Preprint not yet peer-reviewed","Structural basis for activation-versus-repression switch not resolved","Reciprocal validation of the MED16-UBP1-TFCP2 subcomplex limited"]},{"year":null,"claim":"How MED16's recruitment, subunit-stabilizing, and dissociated-subcomplex activities are coordinated in a single cell type, and how human disease variants mechanistically derail transcription, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No human structural model of MED16 within the Tail module","Direct human target genes of MED16-dependent activation/repression not defined","Causal chain from variant to neurodevelopmental phenotype incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,2,6]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,2,6]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,5]}],"complexes":["Mediator complex","Mediator Tail module","MED16-UBP1-TFCP2 subcomplex"],"partners":["MED15","MED25","UBP1","TFCP2","MYC2","HSF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y2X0","full_name":"Mediator of RNA polymerase II transcription subunit 16","aliases":["Mediator complex subunit 16","Thyroid hormone receptor-associated protein 5","Thyroid hormone receptor-associated protein complex 95 kDa component","Trap95","Vitamin D3 receptor-interacting protein complex 92 kDa component","DRIP92"],"length_aa":877,"mass_kda":96.8,"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/Q9Y2X0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MED16","classification":"Not Classified","n_dependent_lines":193,"n_total_lines":1208,"dependency_fraction":0.1597682119205298},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MED10","stoichiometry":10.0},{"gene":"MED11","stoichiometry":10.0},{"gene":"MED14","stoichiometry":10.0},{"gene":"MED17","stoichiometry":10.0},{"gene":"MED19","stoichiometry":10.0},{"gene":"MED21","stoichiometry":10.0},{"gene":"MED25","stoichiometry":10.0},{"gene":"MED27","stoichiometry":10.0},{"gene":"MED31","stoichiometry":10.0},{"gene":"MED4","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/MED16","total_profiled":1310},"omim":[{"mim_id":"621220","title":"GUILLOUET-GORDON SYNDROME; GGNS","url":"https://www.omim.org/entry/621220"},{"mim_id":"615063","title":"SECRETOGLOBIN, FAMILY 2B, MEMBER 2; SCGB2B2","url":"https://www.omim.org/entry/615063"},{"mim_id":"604062","title":"MEDIATOR COMPLEX SUBUNIT 16; MED16","url":"https://www.omim.org/entry/604062"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MED16"},"hgnc":{"alias_symbol":["DRIP92","TRAP95"],"prev_symbol":["THRAP5"]},"alphafold":{"accession":"Q9Y2X0","domains":[{"cath_id":"-","chopping":"545-723","consensus_level":"high","plddt":88.8503,"start":545,"end":723},{"cath_id":"-","chopping":"740-755_777-834","consensus_level":"medium","plddt":77.2255,"start":740,"end":834}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2X0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2X0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y2X0-F1-predicted_aligned_error_v6.png","plddt_mean":84.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MED16","jax_strain_url":"https://www.jax.org/strain/search?query=MED16"},"sequence":{"accession":"Q9Y2X0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y2X0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y2X0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y2X0"}},"corpus_meta":[{"pmid":"23447536","id":"PMC_23447536","title":"Mediator recruitment to heat shock genes requires dual Hsf1 activation domains and mediator tail subunits Med15 and Med16.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23447536","citation_count":66,"is_preprint":false},{"pmid":"15297616","id":"PMC_15297616","title":"MED16 and MED23 of Mediator are coactivators of lipopolysaccharide- and heat-shock-induced transcriptional activators.","date":"2004","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/15297616","citation_count":59,"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":"23991176","id":"PMC_23991176","title":"Functional studies of the yeast med5, med15 and med16 mediator tail subunits.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23991176","citation_count":13,"is_preprint":false},{"pmid":"39824838","id":"PMC_39824838","title":"A multiprotein regulatory module, MED16-MBR1&2, controls MED25 homeostasis during jasmonate signaling.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/39824838","citation_count":11,"is_preprint":false},{"pmid":"36294896","id":"PMC_36294896","title":"MED16 Promotes Tumour Progression and Tamoxifen Sensitivity by Modulating Autophagy through the mTOR Signalling Pathway in ER-Positive Breast Cancer.","date":"2022","source":"Life (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36294896","citation_count":5,"is_preprint":false},{"pmid":"40081376","id":"PMC_40081376","title":"Bi-allelic MED16 variants cause a MEDopathy with intellectual disability, motor delay, and craniofacial, cardiac, and limb malformations.","date":"2025","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40081376","citation_count":4,"is_preprint":false},{"pmid":"34298953","id":"PMC_34298953","title":"Pantoea Bacteriophage vB_PagS_MED16-A Siphovirus Containing a 2'-Deoxy-7-amido-7-deazaguanosine-Modified DNA.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34298953","citation_count":3,"is_preprint":false},{"pmid":"40254158","id":"PMC_40254158","title":"Biallelic MED16 variants disrupt neural development and lead to an intellectual disability syndrome.","date":"2025","source":"Journal of genetics and genomics = Yi chuan xue bao","url":"https://pubmed.ncbi.nlm.nih.gov/40254158","citation_count":1,"is_preprint":false},{"pmid":"41828689","id":"PMC_41828689","title":"When MED16 Meets Plant Growth, Development, and Stress Response.","date":"2026","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41828689","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.12.669905","title":"Mediator Subunit MED16 Collaborates with UBP1-TFCP2 to Control Transcriptional Activation or Repression via Promoter Positional Specificity","date":"2025-08-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.12.669905","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.29.25336758","title":"Endophenotype Guided Genome-Wide Association Study to Enhance Genetic Risk Prediction of Primary Open-Angle Glaucoma in African Ancestry Populations","date":"2025-10-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.29.25336758","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7972,"output_tokens":2160,"usd":0.028158,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9174,"output_tokens":2764,"usd":0.057485,"stage2_stop_reason":"end_turn"},"total_usd":0.085643,"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\": 2013,\n      \"finding\": \"In yeast S. cerevisiae, Med16 (a Mediator Tail module subunit) is required for Mediator recruitment to HSP gene promoters upon heat shock. Deletion of Med16 alone reduces Mediator occupancy; deletion of both Med15 and Med16 abolishes Mediator recruitment and substantially diminishes RNA Pol II recruitment. Hsf1 recruits holo-Mediator through cooperative interactions with the Tail module via its dual N- and C-terminal activation domains.\",\n      \"method\": \"ChIP (chromatin immunoprecipitation) in yeast; genetic deletion of Med15 and/or Med16; truncation of Hsf1 activation domains\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic and ChIP analyses with multiple deletion combinations, clean epistatic dissection of two activation domains and two subunits\",\n      \"pmids\": [\"23447536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In yeast, cells lacking Med16 show displacement of the Tail module from the Head and Middle modules of Mediator. Simultaneous inactivation of MED15/MED16 is synthetically lethal, indicating Tail performs essential functions as a separate complex. Loss of Med16 (or Med15) leads to down-regulation of Ace2 transcriptional activator target genes and a G1 cell cycle arrest phenotype.\",\n      \"method\": \"N-Degron temperature-sensitive mutants; global gene expression profiling; genetic synthetic lethality analysis; flow cytometry (G1 arrest)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (inducible degron, transcriptomics, cell-cycle analysis) in a single lab\",\n      \"pmids\": [\"23991176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In Drosophila melanogaster, MED16 is specifically required for lipopolysaccharide (LPS)-induced transcriptional activation. RNAi depletion of MED16 causes defects specific to LPS- and differentiation-inducing factor (DIF)-induced gene expression without general transcriptional defects, and its activator-specific function appears to result from physical interaction with specific activators.\",\n      \"method\": \"RNA interference (RNAi) depletion of individual Mediator subunits; reporter assays on synthetic and endogenous promoters; microarray expression analysis of DIF- and MED16-depleted cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi plus microarray in Drosophila, activator-specific functional dissection with two orthogonal readouts (reporter + endogenous gene expression), single lab\",\n      \"pmids\": [\"15297616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Arabidopsis, MED16 promotes stability of MED25 by competing with E3 ubiquitin ligases MBR1 and MBR2 to bind the von Willebrand Factor A (vWF-A) domain of MED25, thereby antagonizing MBR1/2-mediated MED25 degradation. Additionally, MED16 promotes hormone-induced interactions between transcription factor MYC2 and MED25, leading to activation of jasmonate (JA)-responsive gene expression.\",\n      \"method\": \"Co-immunoprecipitation; in vivo competition binding assays; protein stability assays; genetic epistasis; reporter gene assays; domain mapping (vWF-A domain)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, competition binding, and in vivo stability assays in a single lab; Arabidopsis ortholog context\",\n      \"pmids\": [\"39824838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Human MED16 missense and in-frame duplication variants associated with intellectual disability syndrome cause protein mislocalization from the nucleus to the cytoplasm, as demonstrated by immunofluorescence assays in patient-derived cells. Homozygous mutant med16 zebrafish show growth delay and increased mortality; Med16 knockout mice are preweaning lethal, confirming a conserved essential developmental role.\",\n      \"method\": \"Immunofluorescence subcellular localization assays; zebrafish med16 knockout (growth/mortality phenotype); mouse Med16 knockout (lethality); 3D structural modeling of missense variants\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence, multiple orthogonal model organism KO phenotypes, single study\",\n      \"pmids\": [\"40081376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Drosophila, loss of med16 (ortholog of human MED16) reduces eclosion and lifespan and impairs synaptic transmission. In iPSC-derived neurons from MED16 variant-carrying patients, neurite outgrowth is impaired and rescued by exogenous MED16 expression. Patient-associated variants behave as loss-of-function alleles in both fly and iPSC models, and transcription of genes related to neuronal maturation is preferentially altered in patient cells.\",\n      \"method\": \"Drosophila med16 loss-of-function (eclosion, lifespan, electrophysiology); iPSC-derived neurons (neurite outgrowth assay, rescue by exogenous MED16); RNA-seq transcriptional profiling\",\n      \"journal\": \"Journal of genetics and genomics = Yi chuan xue bao\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal model systems (fly KO + patient iPSC neurons), rescue experiment, RNA-seq; single study\",\n      \"pmids\": [\"40254158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Human MED16 dissociates from the core Mediator complex to form a subcomplex with transcription factors UBP1 and TFCP2. This MED16-UBP1 interaction activates a subset of genes involved in lung homeostasis, angiogenesis, and cell proliferation. Conversely, MED16 and UBP1 cooperatively bind the HIV-1 transcriptional start site (TSS) to inhibit preinitiation complex assembly and suppress HIV-1 transcription, reinforcing viral latency. The directionality (activation vs repression) depends on whether the UBP1-TFCP2 binding motif is proximal to or overlapping the TSS.\",\n      \"method\": \"Protein purification coupled with mass spectrometry (identification of MED16 as UBP1-TFCP2 binding partner); gene expression analysis; chromatin occupancy assays at HIV-1 TSS; genomic-scale analysis of motif position relative to TSS\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — mass spectrometry-identified interaction, genomic-scale expression and occupancy data, preprint not yet peer-reviewed, single lab\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"MED16 is a Tail module subunit of the Mediator complex that serves as a context-dependent coactivator by physically recruiting holo-Mediator to activated gene promoters (e.g., heat-shock genes via Hsf1 in yeast; LPS/DIF-induced genes in Drosophila), stabilizes partner subunit MED25 by competing with E3 ubiquitin ligases for its vWF-A domain, can dissociate from core Mediator to form subcomplexes with specific transcription factors (e.g., UBP1-TFCP2) that activate or repress transcription depending on promoter-proximal motif position, and is required for nuclear localization and normal neurodevelopment in vertebrates, with loss-of-function causing synaptic transmission defects and impaired neurite outgrowth.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MED16 is a Tail-module subunit of the Mediator complex that functions as a context-dependent transcriptional coactivator by physically bridging gene-specific activators to holo-Mediator and thereby promoting RNA Polymerase II recruitment to induced promoters [#0, #2]. In yeast, MED16 is required for Mediator occupancy at heat-shock genes downstream of the Hsf1 activator, and its loss displaces the entire Tail module from the Head and Middle modules; combined loss with MED15 is synthetically lethal and arrests cells in G1, indicating the Tail can act as a separable functional unit [#0, #1]. The activator-specific character of MED16 is conserved: in Drosophila it is selectively required for LPS/DIF-induced gene expression rather than bulk transcription [#2]. Beyond recruitment, MED16 stabilizes the partner subunit MED25 by competing with the E3 ubiquitin ligases MBR1/MBR2 for the MED25 vWF-A domain and promotes hormone-induced MYC2–MED25 interactions that drive jasmonate-responsive transcription [#3]. MED16 can also dissociate from core Mediator to form a subcomplex with the transcription factors UBP1 and TFCP2, where it activates or represses target genes depending on the position of the UBP1-TFCP2 motif relative to the transcription start site [#6]. In humans, MED16 loss-of-function variants associated with an intellectual disability syndrome cause mislocalization of the protein from nucleus to cytoplasm, impair neurite outgrowth in patient iPSC-derived neurons, and disrupt synaptic transmission, defining a conserved essential developmental role confirmed by lethality in mouse and zebrafish knockouts [#4, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established that MED16 is not a general transcription factor but an activator-specific coactivator, answering whether individual Mediator subunits confer signal specificity.\",\n      \"evidence\": \"RNAi depletion of individual Mediator subunits with reporter and microarray readouts in Drosophila\",\n      \"pmids\": [\"15297616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical interaction with specific activators inferred rather than mapped at residue level\", \"No structural basis for activator selectivity\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed that MED16 physically recruits holo-Mediator to activated promoters, linking a specific activator (Hsf1) through the Tail module to Pol II loading.\",\n      \"evidence\": \"ChIP and combinatorial genetic deletion of Med15/Med16 with Hsf1 activation-domain truncations in yeast\",\n      \"pmids\": [\"23447536\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether recruitment mechanism generalizes beyond heat-shock genes not addressed\", \"No direct Med16–Hsf1 binding interface defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated that the Tail module can function as a separable complex and is essential, by showing Med16 loss detaches Tail from core Mediator and is synthetically lethal with Med15.\",\n      \"evidence\": \"Inducible N-degron mutants, transcriptome profiling, synthetic lethality, and cell-cycle analysis in yeast\",\n      \"pmids\": [\"23991176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Composition and stability of the free Tail subcomplex not structurally resolved\", \"Mechanism linking Ace2 target down-regulation to G1 arrest unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a non-recruitment role: MED16 protects partner subunit MED25 from ubiquitin-mediated degradation and promotes activator–Mediator engagement, answering how MED16 modulates a hormone-responsive transcription program.\",\n      \"evidence\": \"Co-IP, competition binding, protein stability and reporter assays with vWF-A domain mapping in Arabidopsis\",\n      \"pmids\": [\"39824838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether MED25 stabilization role is conserved in animals untested\", \"Stoichiometry of MED16/MED25/MBR1/2 competition not quantified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined the conserved essential developmental requirement for MED16 and linked human loss-of-function variants to disease, answering whether MED16 dysfunction causes phenotype in vivo.\",\n      \"evidence\": \"Patient-cell immunofluorescence, zebrafish and mouse knockouts, and 3D variant modeling\",\n      \"pmids\": [\"40081376\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting cytoplasmic mislocalization to transcriptional defect unresolved\", \"Lethality stage in mouse not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected MED16 variants to a specific neuronal phenotype, showing loss-of-function impairs neurite outgrowth and synaptic transmission with rescue, establishing causality.\",\n      \"evidence\": \"Drosophila loss-of-function (electrophysiology, lifespan), patient iPSC-derived neuron neurite assays with MED16 rescue, and RNA-seq\",\n      \"pmids\": [\"40254158\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which neuronal target genes are direct MED16/Mediator targets not defined\", \"Link between synaptic defect and specific transcriptional program incomplete\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a Mediator-independent mode in which MED16 forms a UBP1-TFCP2 subcomplex that activates or represses transcription according to motif position relative to the TSS, including suppression of HIV-1 transcription.\",\n      \"evidence\": \"Protein purification with mass spectrometry, gene expression and chromatin occupancy at the HIV-1 TSS, and genome-scale motif-position analysis (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint not yet peer-reviewed\", \"Structural basis for activation-versus-repression switch not resolved\", \"Reciprocal validation of the MED16-UBP1-TFCP2 subcomplex limited\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MED16's recruitment, subunit-stabilizing, and dissociated-subcomplex activities are coordinated in a single cell type, and how human disease variants mechanistically derail transcription, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No human structural model of MED16 within the Tail module\", \"Direct human target genes of MED16-dependent activation/repression not defined\", \"Causal chain from variant to neurodevelopmental phenotype incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"complexes\": [\"Mediator complex\", \"Mediator Tail module\", \"MED16-UBP1-TFCP2 subcomplex\"],\n    \"partners\": [\"MED15\", \"MED25\", \"UBP1\", \"TFCP2\", \"MYC2\", \"HSF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}