{"gene":"MED8","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2006,"finding":"Med8, Med18, and Med20 form a head subcomplex with two submodules: (1) the N-terminal domain of Med8 binds TBP in vitro and is essential in vivo, and (2) Med8C/Med18/Med20 where Med18 and Med20 adopt related beta-barrel folds. X-ray crystal structure of the Med8C/18/20 submodule revealed a conserved putative protein-interaction face that includes sites altered by srb mutations, which counteract defects from Pol II truncation.","method":"X-ray crystallography, in vitro TBP-binding assay, in vivo genetic complementation, structural mutagenesis analysis","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure resolved with functional validation (TBP binding in vitro, essential in vivo), multiple orthogonal methods in a single rigorous study","pmids":["16964259"],"is_preprint":false},{"year":2009,"finding":"Med8, Med18, and Med20 are interdependent for proper folding and trimer complex formation; all three subunits must be present simultaneously during renaturation to achieve correct folding, though they can also form soluble monomers and pairwise subcomplexes when renatured separately.","method":"Immunoprecipitation, far-UV circular dichroism, fluorescence spectroscopy on recombinant denatured/renatured proteins in various combinations","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal biophysical methods (CD, fluorescence, IP), single lab","pmids":["19934057"],"is_preprint":false},{"year":1999,"finding":"Yeast Med8 (p27) directly binds to regulatory elements of SUC2 (upstream activating sequences) and HXK2 (downstream repressing sequences) genes, as demonstrated by purification of the endogenous protein and in vitro binding of recombinant Med8 expressed in E. coli. Med8 also binds the CTD of RNA polymerase II.","method":"Biochemical purification, N-terminal protein sequencing, recombinant protein expression in E. coli, in vitro DNA-binding assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct biochemical binding assay with recombinant protein, corroborated by AFM in a companion paper, single lab","pmids":["9918841"],"is_preprint":false},{"year":1999,"finding":"Atomic force microscopy directly visualized Med8 binding to the UAS of the SUC2 promoter and the DRS of the HXK2 gene, showing Med8 fully covers one of two 7 bp motifs (consensus (A/C)(A/G)GAAAT) in each fragment with no preference between the two available sites.","method":"Atomic force microscopy (AFM) of DNA-protein complexes","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct visualization of protein-DNA complexes by AFM, corroborating in vitro biochemical data, single lab","pmids":["10526178"],"is_preprint":false},{"year":2006,"finding":"Bunyamwera virus NSs protein interacts with the MED8 component of Mediator to inhibit host transcription and the interferon response; the interacting domain on NSs maps to the C-terminal region conserved among orthobunyavirus NSs proteins, and deletion of this domain strongly reduced inhibition of host protein expression and abrogated interferon antagonism.","method":"Protein interaction mapping, recombinant virus with domain deletion, host transcription and interferon response assays","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain deletion in recombinant virus with defined functional readouts, single lab","pmids":["16973571"],"is_preprint":false},{"year":2009,"finding":"In S. pombe, Med8 interacts with Rpb4 (a subunit of RNA polymerase II) and with the transcriptional activator Ace2; the C-terminal region of Med8 is required for the Med8-Rpb4 interaction and can partially complement the sep15-598 mutant, suggesting Med8 transmits regulatory information from Ace2 to Pol II via Rpb4.","method":"Genetic epistasis, co-immunoprecipitation, domain-mapping biochemical assays, complementation assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction mapping with domain delineation plus genetic complementation, single lab","pmids":["19720063"],"is_preprint":false},{"year":2025,"finding":"Human MED8 interacts with TRIP4, reduces its ubiquitination, and stabilizes TRIP4 protein levels, thereby promoting epithelial-mesenchymal transition and sorafenib resistance in hepatocellular carcinoma cells.","method":"Co-immunoprecipitation, ubiquitination assay, MED8 knockdown/overexpression functional assays, TRIP4 overexpression rescue experiment","journal":"Journal of enzyme inhibition and medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — co-IP and ubiquitination assay with rescue experiment demonstrate mechanism, single lab, no independent replication","pmids":["41117311"],"is_preprint":false},{"year":2026,"finding":"Human MED8 cooperates with CDK7 to bind and activate super-enhancers of PDGFRA, sustaining high transcriptional output of this oncogene in glioma; mechanistic evidence from ChIP, CUT&TAG, co-immunoprecipitation, mass spectrometry, protein fragment complementation, and dual-luciferase reporter assays.","method":"CUT&TAG, chromatin immunoprecipitation, co-immunoprecipitation, mass spectrometry, protein fragment complementation assay, dual-luciferase reporter assay, xenograft and organoid models","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (ChIP, Co-IP, MS, functional reporter) in a single study, single lab","pmids":["42157323"],"is_preprint":false}],"current_model":"MED8 is an essential subunit of the Mediator head module that (i) directly binds TBP through its conserved N-terminal domain, (ii) forms a structurally defined subcomplex with Med18 and Med20 (whose beta-barrel folds are resolved by X-ray crystallography) that is required for initiation-complex assembly, (iii) binds DNA regulatory elements (UAS/DRS) of specific target genes and the RNA Pol II CTD, (iv) transmits activator signals (e.g., from Ace2) to Pol II via Rpb4 in fission yeast, (v) is exploited by bunyavirus NSs protein to suppress host transcription and the interferon response, and (vi) in human cancer cells cooperates with CDK7 to sustain super-enhancer-driven oncogene (PDGFRA) transcription and stabilizes TRIP4 by reducing its ubiquitination to promote EMT and drug resistance."},"narrative":{"mechanistic_narrative":"MED8 is a subunit of the Mediator head module that couples gene-specific regulatory signals to the RNA polymerase II general transcription machinery [PMID:16964259, PMID:9918841]. Its conserved N-terminal domain directly binds TBP and is essential in vivo, while its C-terminal region nucleates a structurally defined submodule with Med18 and Med20 — both adopting beta-barrel folds — that is required for proper trimer folding and bears a conserved protein-interaction surface whose mutation counteracts defects from Pol II truncation [PMID:16964259, PMID:19934057]. MED8 also engages transcription directly at two levels: it binds defined DNA regulatory elements, covering a (A/C)(A/G)GAAAT motif within the upstream activating sequence of SUC2 and the downstream repressing sequence of HXK2, and it contacts the RNA Pol II CTD [PMID:9918841, PMID:10526178]. In fission yeast, MED8 transmits activator input from Ace2 to Pol II through an interaction with Rpb4 mediated by its C-terminal region [PMID:19720063]. The protein is targeted by Bunyamwera virus NSs, which binds MED8 to shut down host transcription and antagonize the interferon response [PMID:16973571]. In human cancer, MED8 sustains oncogenic transcription: it cooperates with CDK7 to bind and activate PDGFRA super-enhancers in glioma [PMID:42157323], and it stabilizes TRIP4 by reducing its ubiquitination to drive epithelial-mesenchymal transition and sorafenib resistance in hepatocellular carcinoma [PMID:41117311].","teleology":[{"year":1999,"claim":"Established that Med8 is not merely a structural scaffold but contacts both promoter DNA and the polymerase directly, answering how a Mediator subunit might confer gene specificity.","evidence":"Biochemical purification of endogenous yeast Med8, recombinant protein DNA-binding and CTD-binding assays, with AFM visualization of Med8 occupying defined sequence motifs at SUC2 UAS and HXK2 DRS","pmids":["9918841","10526178"],"confidence":"Medium","gaps":["Whether sequence-specific DNA binding occurs in the context of intact Mediator in vivo is not resolved","Functional consequence of CTD binding not dissected"]},{"year":2006,"claim":"Defined the architecture and essential function of the Med8/Med18/Med20 head submodule, showing Med8's N-terminal domain binds TBP and identifying a conserved interaction surface linked to Pol II function.","evidence":"X-ray crystallography of the Med8C/18/20 submodule, in vitro TBP-binding assay, in vivo genetic complementation, and srb-mutation analysis","pmids":["16964259"],"confidence":"High","gaps":["Structure of the TBP-binding N-terminal domain itself not resolved","Does not establish how the submodule engages the holo-Mediator or Pol II in vivo"]},{"year":2006,"claim":"Revealed that MED8 is a host vulnerability exploited by a pathogen, with Bunyamwera NSs targeting it to suppress transcription and interferon responses.","evidence":"Protein interaction mapping and recombinant virus carrying an NSs C-terminal domain deletion with host transcription and interferon antagonism readouts","pmids":["16973571"],"confidence":"Medium","gaps":["The MED8 surface contacted by NSs is not mapped","Whether NSs disrupts Mediator assembly or only its activity is unknown"]},{"year":2009,"claim":"Showed MED8 acts as a signal conduit from a specific activator to the polymerase, and clarified the folding hierarchy of the head submodule.","evidence":"Co-IP and domain mapping of Med8-Rpb4 and Med8-Ace2 interactions with complementation in S. pombe; in vitro renaturation of recombinant subunits monitored by CD, fluorescence, and IP","pmids":["19720063","19934057"],"confidence":"Medium","gaps":["Direct evidence that Ace2 signal physically routes through Med8 to Rpb4 in a single chain is incomplete","Folding interdependence shown in vitro; in vivo assembly order not established"]},{"year":2026,"claim":"Extended MED8 function to human oncogenic transcription, showing cooperation with CDK7 at super-enhancers to sustain a driver oncogene.","evidence":"CUT&TAG, ChIP, co-IP, mass spectrometry, protein fragment complementation, dual-luciferase reporter, plus xenograft and organoid models in glioma","pmids":["42157323"],"confidence":"Medium","gaps":["Whether MED8-CDK7 cooperation generalizes beyond PDGFRA super-enhancers is untested","Single lab without independent replication"]},{"year":2025,"claim":"Identified a non-canonical, transcription-independent role: MED8 stabilizing a partner protein by limiting its ubiquitination to drive a cancer phenotype.","evidence":"Co-IP, ubiquitination assay, MED8 knockdown/overexpression and TRIP4 rescue in hepatocellular carcinoma cells","pmids":["41117311"],"confidence":"Medium","gaps":["The E3 ligase MED8 antagonizes on TRIP4 is not identified","Whether this function requires Mediator association is unknown","Single lab, no independent replication"]},{"year":null,"claim":"How MED8's structural role in the Mediator head integrates with its emerging functions in super-enhancer regulation and partner stabilization in human cells remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of human MED8 within holo-Mediator","No unifying model linking DNA binding, TBP/Rpb4 contacts, and oncogenic super-enhancer activity"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[2,3]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,7]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,7]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,2,7]}],"complexes":["Mediator head module (Med8/Med18/Med20 submodule)"],"partners":["TBP","MED18","MED20","RPB4","ACE2","CDK7","TRIP4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96G25","full_name":"Mediator of RNA polymerase II transcription subunit 8","aliases":["Activator-recruited cofactor 32 kDa component","ARC32","Mediator complex subunit 8"],"length_aa":268,"mass_kda":29.1,"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. May play a role as a target recruitment subunit in E3 ubiquitin-protein ligase complexes and thus in ubiquitination and subsequent proteasomal degradation of target proteins","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q96G25/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/MED8","classification":"Common Essential","n_dependent_lines":1189,"n_total_lines":1208,"dependency_fraction":0.984271523178808},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000159479","cell_line_id":"CID000237","localizations":[{"compartment":"nuclear_punctae","grade":3},{"compartment":"nucleoplasm","grade":3}],"interactors":[{"gene":"MED10","stoichiometry":10.0},{"gene":"MED11","stoichiometry":10.0},{"gene":"MED14","stoichiometry":10.0},{"gene":"MED18","stoichiometry":10.0},{"gene":"MED19","stoichiometry":10.0},{"gene":"MED20","stoichiometry":10.0},{"gene":"MED21","stoichiometry":10.0},{"gene":"MED22","stoichiometry":10.0},{"gene":"MED27","stoichiometry":10.0},{"gene":"MED28","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000237","total_profiled":1310},"omim":[{"mim_id":"615463","title":"SZT2 SUBUNIT OF KICSTOR COMPLEX; SZT2","url":"https://www.omim.org/entry/615463"},{"mim_id":"608667","title":"NIPPED-B-LIKE; NIPBL","url":"https://www.omim.org/entry/608667"},{"mim_id":"607956","title":"MEDIATOR COMPLEX SUBUNIT 8; MED8","url":"https://www.omim.org/entry/607956"},{"mim_id":"300040","title":"STRUCTURAL MAINTENANCE OF CHROMOSOMES 1A; SMC1A","url":"https://www.omim.org/entry/300040"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MED8"},"hgnc":{"alias_symbol":["MGC17544","MGC19641","ARC32"],"prev_symbol":[]},"alphafold":{"accession":"Q96G25","domains":[{"cath_id":"1.20.58","chopping":"1-74","consensus_level":"medium","plddt":93.1416,"start":1,"end":74},{"cath_id":"-","chopping":"78-111","consensus_level":"medium","plddt":93.3035,"start":78,"end":111},{"cath_id":"1.20.5","chopping":"114-162","consensus_level":"medium","plddt":91.398,"start":114,"end":162}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96G25","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96G25-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96G25-F1-predicted_aligned_error_v6.png","plddt_mean":75.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MED8","jax_strain_url":"https://www.jax.org/strain/search?query=MED8"},"sequence":{"accession":"Q96G25","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96G25.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96G25/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96G25"}},"corpus_meta":[{"pmid":"16964259","id":"PMC_16964259","title":"Structure and TBP binding of the Mediator head subcomplex Med8-Med18-Med20.","date":"2006","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16964259","citation_count":94,"is_preprint":false},{"pmid":"16973571","id":"PMC_16973571","title":"Interaction of Bunyamwera Orthobunyavirus NSs protein with mediator protein MED8: a mechanism for inhibiting the interferon response.","date":"2006","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/16973571","citation_count":72,"is_preprint":false},{"pmid":"9918841","id":"PMC_9918841","title":"Med8, a subunit of the mediator CTD complex of RNA polymerase II, directly binds to regulatory elements of SUC2 and HXK2 genes.","date":"1999","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/9918841","citation_count":30,"is_preprint":false},{"pmid":"10526178","id":"PMC_10526178","title":"Analysis by atomic force microscopy of Med8 binding to cis-acting regulatory elements of the SUC2 and HXK2 genes of saccharomyces cerevisiae.","date":"1999","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/10526178","citation_count":23,"is_preprint":false},{"pmid":"11191205","id":"PMC_11191205","title":"The Schizosaccharomyces pombe sep15+ gene encodes a protein homologous to the Med8 subunit of the Saccharomyces cerevisiae transcriptional mediator complex.","date":"2000","source":"Current genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11191205","citation_count":23,"is_preprint":false},{"pmid":"17922236","id":"PMC_17922236","title":"Genomic expression patterns in cell separation mutants of Schizosaccharomyces pombe defective in the genes sep10 ( + ) and sep15 ( + ) coding for the Mediator subunits Med31 and Med8.","date":"2007","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/17922236","citation_count":17,"is_preprint":false},{"pmid":"19720063","id":"PMC_19720063","title":"The Med8 mediator subunit interacts with the Rpb4 subunit of RNA polymerase II and Ace2 transcriptional activator in Schizosaccharomyces pombe.","date":"2009","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/19720063","citation_count":13,"is_preprint":false},{"pmid":"21744120","id":"PMC_21744120","title":"Knockdown of NtMed8, a Med8-like gene, causes abnormal development of vegetative and floral organs in tobacco (Nicotiana tabacum L.).","date":"2011","source":"Plant cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/21744120","citation_count":9,"is_preprint":false},{"pmid":"19934057","id":"PMC_19934057","title":"Med8, Med18, and Med20 subunits of the Mediator head domain are interdependent upon each other for folding and complex formation.","date":"2009","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/19934057","citation_count":7,"is_preprint":false},{"pmid":"38062856","id":"PMC_38062856","title":"Mediator subunit MED8 interacts with heat shock transcription factor HSF3 to promote fucoxanthin synthesis in the diatom Phaeodactylum tricornutum.","date":"2023","source":"The New phytologist","url":"https://pubmed.ncbi.nlm.nih.gov/38062856","citation_count":4,"is_preprint":false},{"pmid":"34601339","id":"PMC_34601339","title":"The tomato Mediator subunit MED8 positively regulates plant response to Botrytis cinerea.","date":"2021","source":"Journal of plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/34601339","citation_count":3,"is_preprint":false},{"pmid":"41117311","id":"PMC_41117311","title":"Targeting MED8 enhances sorafenib sensitivity in hepatocellular carcinoma by disrupting epithelial-mesenchymal transition mechanisms.","date":"2025","source":"Journal of enzyme inhibition and medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41117311","citation_count":0,"is_preprint":false},{"pmid":"42157323","id":"PMC_42157323","title":"Disrupting MED8-dependent epigenetic reprogramming augments avapritinib sensitivity in PDGFRA-driven glioma.","date":"2026","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/42157323","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7173,"output_tokens":2089,"usd":0.026427,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9067,"output_tokens":2689,"usd":0.05628,"stage2_stop_reason":"end_turn"},"total_usd":0.082707,"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\": 2006,\n      \"finding\": \"Med8, Med18, and Med20 form a head subcomplex with two submodules: (1) the N-terminal domain of Med8 binds TBP in vitro and is essential in vivo, and (2) Med8C/Med18/Med20 where Med18 and Med20 adopt related beta-barrel folds. X-ray crystal structure of the Med8C/18/20 submodule revealed a conserved putative protein-interaction face that includes sites altered by srb mutations, which counteract defects from Pol II truncation.\",\n      \"method\": \"X-ray crystallography, in vitro TBP-binding assay, in vivo genetic complementation, structural mutagenesis analysis\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure resolved with functional validation (TBP binding in vitro, essential in vivo), multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"16964259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Med8, Med18, and Med20 are interdependent for proper folding and trimer complex formation; all three subunits must be present simultaneously during renaturation to achieve correct folding, though they can also form soluble monomers and pairwise subcomplexes when renatured separately.\",\n      \"method\": \"Immunoprecipitation, far-UV circular dichroism, fluorescence spectroscopy on recombinant denatured/renatured proteins in various combinations\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with multiple orthogonal biophysical methods (CD, fluorescence, IP), single lab\",\n      \"pmids\": [\"19934057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Yeast Med8 (p27) directly binds to regulatory elements of SUC2 (upstream activating sequences) and HXK2 (downstream repressing sequences) genes, as demonstrated by purification of the endogenous protein and in vitro binding of recombinant Med8 expressed in E. coli. Med8 also binds the CTD of RNA polymerase II.\",\n      \"method\": \"Biochemical purification, N-terminal protein sequencing, recombinant protein expression in E. coli, in vitro DNA-binding assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct biochemical binding assay with recombinant protein, corroborated by AFM in a companion paper, single lab\",\n      \"pmids\": [\"9918841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Atomic force microscopy directly visualized Med8 binding to the UAS of the SUC2 promoter and the DRS of the HXK2 gene, showing Med8 fully covers one of two 7 bp motifs (consensus (A/C)(A/G)GAAAT) in each fragment with no preference between the two available sites.\",\n      \"method\": \"Atomic force microscopy (AFM) of DNA-protein complexes\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct visualization of protein-DNA complexes by AFM, corroborating in vitro biochemical data, single lab\",\n      \"pmids\": [\"10526178\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Bunyamwera virus NSs protein interacts with the MED8 component of Mediator to inhibit host transcription and the interferon response; the interacting domain on NSs maps to the C-terminal region conserved among orthobunyavirus NSs proteins, and deletion of this domain strongly reduced inhibition of host protein expression and abrogated interferon antagonism.\",\n      \"method\": \"Protein interaction mapping, recombinant virus with domain deletion, host transcription and interferon response assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain deletion in recombinant virus with defined functional readouts, single lab\",\n      \"pmids\": [\"16973571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In S. pombe, Med8 interacts with Rpb4 (a subunit of RNA polymerase II) and with the transcriptional activator Ace2; the C-terminal region of Med8 is required for the Med8-Rpb4 interaction and can partially complement the sep15-598 mutant, suggesting Med8 transmits regulatory information from Ace2 to Pol II via Rpb4.\",\n      \"method\": \"Genetic epistasis, co-immunoprecipitation, domain-mapping biochemical assays, complementation assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction mapping with domain delineation plus genetic complementation, single lab\",\n      \"pmids\": [\"19720063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Human MED8 interacts with TRIP4, reduces its ubiquitination, and stabilizes TRIP4 protein levels, thereby promoting epithelial-mesenchymal transition and sorafenib resistance in hepatocellular carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, MED8 knockdown/overexpression functional assays, TRIP4 overexpression rescue experiment\",\n      \"journal\": \"Journal of enzyme inhibition and medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — co-IP and ubiquitination assay with rescue experiment demonstrate mechanism, single lab, no independent replication\",\n      \"pmids\": [\"41117311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Human MED8 cooperates with CDK7 to bind and activate super-enhancers of PDGFRA, sustaining high transcriptional output of this oncogene in glioma; mechanistic evidence from ChIP, CUT&TAG, co-immunoprecipitation, mass spectrometry, protein fragment complementation, and dual-luciferase reporter assays.\",\n      \"method\": \"CUT&TAG, chromatin immunoprecipitation, co-immunoprecipitation, mass spectrometry, protein fragment complementation assay, dual-luciferase reporter assay, xenograft and organoid models\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (ChIP, Co-IP, MS, functional reporter) in a single study, single lab\",\n      \"pmids\": [\"42157323\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MED8 is an essential subunit of the Mediator head module that (i) directly binds TBP through its conserved N-terminal domain, (ii) forms a structurally defined subcomplex with Med18 and Med20 (whose beta-barrel folds are resolved by X-ray crystallography) that is required for initiation-complex assembly, (iii) binds DNA regulatory elements (UAS/DRS) of specific target genes and the RNA Pol II CTD, (iv) transmits activator signals (e.g., from Ace2) to Pol II via Rpb4 in fission yeast, (v) is exploited by bunyavirus NSs protein to suppress host transcription and the interferon response, and (vi) in human cancer cells cooperates with CDK7 to sustain super-enhancer-driven oncogene (PDGFRA) transcription and stabilizes TRIP4 by reducing its ubiquitination to promote EMT and drug resistance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MED8 is a subunit of the Mediator head module that couples gene-specific regulatory signals to the RNA polymerase II general transcription machinery [#0, #2]. Its conserved N-terminal domain directly binds TBP and is essential in vivo, while its C-terminal region nucleates a structurally defined submodule with Med18 and Med20 — both adopting beta-barrel folds — that is required for proper trimer folding and bears a conserved protein-interaction surface whose mutation counteracts defects from Pol II truncation [#0, #1]. MED8 also engages transcription directly at two levels: it binds defined DNA regulatory elements, covering a (A/C)(A/G)GAAAT motif within the upstream activating sequence of SUC2 and the downstream repressing sequence of HXK2, and it contacts the RNA Pol II CTD [#2, #3]. In fission yeast, MED8 transmits activator input from Ace2 to Pol II through an interaction with Rpb4 mediated by its C-terminal region [#5]. The protein is targeted by Bunyamwera virus NSs, which binds MED8 to shut down host transcription and antagonize the interferon response [#4]. In human cancer, MED8 sustains oncogenic transcription: it cooperates with CDK7 to bind and activate PDGFRA super-enhancers in glioma [#7], and it stabilizes TRIP4 by reducing its ubiquitination to drive epithelial-mesenchymal transition and sorafenib resistance in hepatocellular carcinoma [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that Med8 is not merely a structural scaffold but contacts both promoter DNA and the polymerase directly, answering how a Mediator subunit might confer gene specificity.\",\n      \"evidence\": \"Biochemical purification of endogenous yeast Med8, recombinant protein DNA-binding and CTD-binding assays, with AFM visualization of Med8 occupying defined sequence motifs at SUC2 UAS and HXK2 DRS\",\n      \"pmids\": [\n        \"9918841\",\n        \"10526178\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether sequence-specific DNA binding occurs in the context of intact Mediator in vivo is not resolved\",\n        \"Functional consequence of CTD binding not dissected\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined the architecture and essential function of the Med8/Med18/Med20 head submodule, showing Med8's N-terminal domain binds TBP and identifying a conserved interaction surface linked to Pol II function.\",\n      \"evidence\": \"X-ray crystallography of the Med8C/18/20 submodule, in vitro TBP-binding assay, in vivo genetic complementation, and srb-mutation analysis\",\n      \"pmids\": [\n        \"16964259\"\n      ],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structure of the TBP-binding N-terminal domain itself not resolved\",\n        \"Does not establish how the submodule engages the holo-Mediator or Pol II in vivo\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed that MED8 is a host vulnerability exploited by a pathogen, with Bunyamwera NSs targeting it to suppress transcription and interferon responses.\",\n      \"evidence\": \"Protein interaction mapping and recombinant virus carrying an NSs C-terminal domain deletion with host transcription and interferon antagonism readouts\",\n      \"pmids\": [\n        \"16973571\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The MED8 surface contacted by NSs is not mapped\",\n        \"Whether NSs disrupts Mediator assembly or only its activity is unknown\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed MED8 acts as a signal conduit from a specific activator to the polymerase, and clarified the folding hierarchy of the head submodule.\",\n      \"evidence\": \"Co-IP and domain mapping of Med8-Rpb4 and Med8-Ace2 interactions with complementation in S. pombe; in vitro renaturation of recombinant subunits monitored by CD, fluorescence, and IP\",\n      \"pmids\": [\n        \"19720063\",\n        \"19934057\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct evidence that Ace2 signal physically routes through Med8 to Rpb4 in a single chain is incomplete\",\n        \"Folding interdependence shown in vitro; in vivo assembly order not established\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended MED8 function to human oncogenic transcription, showing cooperation with CDK7 at super-enhancers to sustain a driver oncogene.\",\n      \"evidence\": \"CUT&TAG, ChIP, co-IP, mass spectrometry, protein fragment complementation, dual-luciferase reporter, plus xenograft and organoid models in glioma\",\n      \"pmids\": [\n        \"42157323\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether MED8-CDK7 cooperation generalizes beyond PDGFRA super-enhancers is untested\",\n        \"Single lab without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a non-canonical, transcription-independent role: MED8 stabilizing a partner protein by limiting its ubiquitination to drive a cancer phenotype.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, MED8 knockdown/overexpression and TRIP4 rescue in hepatocellular carcinoma cells\",\n      \"pmids\": [\n        \"41117311\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The E3 ligase MED8 antagonizes on TRIP4 is not identified\",\n        \"Whether this function requires Mediator association is unknown\",\n        \"Single lab, no independent replication\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MED8's structural role in the Mediator head integrates with its emerging functions in super-enhancer regulation and partner stabilization in human cells remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structure of human MED8 within holo-Mediator\",\n        \"No unifying model linking DNA binding, TBP/Rpb4 contacts, and oncogenic super-enhancer activity\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0003677\",\n        \"supporting_discovery_ids\": [\n          2,\n          3\n        ]\n      },\n      {\n        \"term_id\": \"GO:0140110\",\n        \"supporting_discovery_ids\": [\n          0,\n          7\n        ]\n      },\n      {\n        \"term_id\": \"GO:0060090\",\n        \"supporting_discovery_ids\": [\n          0,\n          5\n        ]\n      }\n    ],\n    \"localization\": [\n      {\n        \"term_id\": \"GO:0005634\",\n        \"supporting_discovery_ids\": [\n          2,\n          7\n        ]\n      }\n    ],\n    \"pathway\": [\n      {\n        \"term_id\": \"R-HSA-74160\",\n        \"supporting_discovery_ids\": [\n          0,\n          2,\n          7\n        ]\n      }\n    ],\n    \"complexes\": [\n      \"Mediator head module (Med8/Med18/Med20 submodule)\"\n    ],\n    \"partners\": [\n      \"TBP\",\n      \"MED18\",\n      \"MED20\",\n      \"Rpb4\",\n      \"Ace2\",\n      \"CDK7\",\n      \"TRIP4\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}