Affinage

MED14

Mediator of RNA polymerase II transcription subunit 14 · UniProt O60244

Length
1454 aa
Mass
160.6 kDa
Annotated
2026-06-10
22 papers in source corpus 15 papers cited in narrative 14 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MED14 is an architectural and functional backbone subunit of the Mediator coactivator complex that couples transcriptional regulators to RNA polymerase II (PMID:25383669, PMID:7479899). Its incorporation into the human core Mediator confers basal and coactivator-dependent transcription function on the head-middle bimodular complex and dramatically strengthens Mediator association with Pol II (PMID:25383669). This activity is concentrated in the MED14 N-terminal domain, which is sufficient to support basal and p53-activated transcription, directly contacts the RPB1 subunit of Pol II preferentially in its hypophosphorylated CTD state, and is required to recruit Pol II to core promoters (PMID:41110510). Consistent with this recruitment role, loss of MED14 function reduces Pol II and CDK8 occupancy and Pol II CTD phosphorylation at target promoters (PMID:24049075, PMID:12089139). Beyond its constitutive scaffolding function, MED14 acts as a gene-selective regulatory node: it directly binds the N-terminal domain of PPARγ to drive PPARγ-dependent transactivation and adipogenesis (PMID:20194623), is required for activation of specific glucocorticoid receptor target genes (PMID:16239257), and is post-translationally tuned by signaling—ERK phosphorylates Ser986 to promote mitogen-induced immediate-early gene transcription (PMID:24049075), while PKA phosphorylates Ser983 downstream of GLP-1 receptor signaling to enable beta cell-specific CREB-dependent enhancer programs (PMID:41779793, PMID:40667025). In multicellular organisms MED14 is additionally required cell-autonomously for stem/progenitor cell maintenance and for terminal differentiation of neural crest, where it genetically interacts with the BAF/SWI-SNF chromatin-remodeling complex (PMID:25772472, PMID:26553192). The yeast ortholog Rgr1 is an essential Mediator component that organizes chromatin and mediates both transcriptional repression and activation, establishing the deep conservation of these functions (PMID:7479899, PMID:7635307, PMID:2196447).

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 1990 Medium

    Established that the MED14 ortholog is an essential gene whose disruption causes pleiotropic defects, the first indication of a broad regulatory function.

    Evidence Gene cloning by complementation with null and truncation mutant analysis, EM, and carbohydrate assays in yeast

    PMID:2196447

    Open questions at the time
    • Molecular function not yet linked to transcription machinery
    • C-terminal truncation phenotypes not mechanistically resolved
  2. 1995 High

    Defined the MED14 ortholog Rgr1 as a physical subunit of the Mediator/Pol II holoenzyme that, with Sin4, organizes chromatin and governs both repression and activation, placing it within the transcription apparatus.

    Evidence Biochemical co-purification of Mediator/Pol II holoenzyme plus GST pulldown, genetic epistasis, and superhelical density assays in yeast

    PMID:7479899 PMID:7635307

    Open questions at the time
    • Architectural role within Mediator undefined
    • Direct Pol II contact not mapped
    • Mammalian equivalence not yet shown
  3. 1994 Medium

    Showed the ortholog functions in a defined transcriptional repression pathway downstream of a regulator, demonstrating gene-specific regulatory engagement.

    Evidence Genetic selection for repression-deficient mutants, reporter assays, and protein-level analysis (RME1/IME1) in yeast

    PMID:7851756

    Open questions at the time
    • Direct molecular target of repression unknown
    • Single-pathway readout
  4. 2002 Medium

    Connected the ortholog to an early step in Pol II function by showing it is required for both Ser-2 and Ser-5 CTD phosphorylation and broad mRNA transcription.

    Evidence RNAi knockdown in C. elegans embryos with immunofluorescence for CTD phosphorylation and transcription assays

    PMID:12089139

    Open questions at the time
    • Whether CTD phosphorylation effect is direct or downstream of recruitment unresolved
    • No biochemical mechanism
  5. 2005 Medium

    Refined the pathway logic by placing Rgr1/Sin4 Mediator in a common, non-redundant pathway with SWI/SNF chromatin remodeling at target genes.

    Evidence Genetic epistasis of double mutants and reporter assays at MAL genes in yeast

    PMID:15514050

    Open questions at the time
    • Physical basis of Mediator-SWI/SNF cooperation not shown
    • Single-locus analysis
  6. 2010 High

    Demonstrated a gene-selective, direct activator-tethering role by mapping a ligand-independent MED14–PPARγ N-terminal domain interaction required for transactivation and adipogenesis.

    Evidence siRNA knockdown, direct NTD binding assay, ChIP, and 3T3-L1 differentiation assay

    PMID:20194623

    Open questions at the time
    • MED14 region binding PPARγ-NTD not mapped
    • Structural basis of selective promoter vs enhancer occupancy unresolved
  7. 2006 Medium

    Extended gene-selective activation to the glucocorticoid receptor, showing MED14 is needed for some but not all GR targets and controls coactivator recruitment to GREs.

    Evidence siRNA knockdown of MED14/MED1 with RT-qPCR and ChIP for GR, MED14, MED1, Pol II

    PMID:16239257

    Open questions at the time
    • Determinant of gene selectivity unknown
    • Direct GR-MED14 contact not demonstrated
  8. 2013 High

    Identified MED14 as a signal-responsive node by showing ERK directly phosphorylates Ser986 to drive immediate-early gene transcription via enhanced CDK8/Pol II recruitment.

    Evidence In vitro ERK kinase assay, S986 phosphosite mapping by mutagenesis, RNAi/ChIP, reporter assays, and Elk-1 Co-IP

    PMID:24049075

    Open questions at the time
    • Structural consequence of S986 phosphorylation on Mediator undefined
    • Elk-1/MED14 interaction interface not mapped
  9. 2014 High

    Resolved MED14's core mechanistic role by showing its incorporation is required for the core Mediator to acquire transcription function and to associate strongly with Pol II, defining it as the complex's backbone.

    Evidence In vitro reconstitution of 15-subunit human core Mediator, functional transcription assays, CX-MS, and Pol II association assays

    PMID:25383669

    Open questions at the time
    • Atomic-resolution contacts to Pol II not yet defined
    • Which subdomain mediates Pol II binding not localized
  10. 2015 Medium

    Showed in vivo that MED14 has a cell-autonomous role in stem/progenitor maintenance and neural crest terminal differentiation, genetically interacting with the BAF complex, beyond global transcription.

    Evidence Zebrafish forward-genetic mutants, microarray transcriptomics, cell transplantation, planarian RNAi, and brg1 double-mutant epistasis

    PMID:25772472 PMID:26553192

    Open questions at the time
    • Specific MED14-dependent gene programs in stem cells not identified
    • Molecular basis of Mediator-BAF interaction not shown
  11. 2025 High

    Localized the functional and Pol II-binding activity to the MED14 N-terminal domain, which directly binds hypophosphorylated RPB1 and is sufficient for basal and p53-activated transcription and Pol II recruitment.

    Evidence MultiBac reconstitution of core Mediator subcomplexes, in vitro transcription, direct RPB1 binding/competition assay, LC-MS/MS CTD phospho-analysis, and cryo-EM reanalysis

    PMID:41110510

    Open questions at the time
    • Atomic structure of the MED14-NTD/RPB1 interface not solved
    • How CTD phosphorylation state is sensed mechanistically unresolved
  12. 2026 High

    Defined a second signaling input by showing PKA phosphorylates Ser983 downstream of GLP-1 receptor signaling to enable beta cell-specific CREB enhancer programs.

    Evidence Proteomic/phosphoproteomic screens identifying Ser983 and a Med14 S983A knock-in mouse with islet transcriptomics, ChIP, and beta-cell counts

    PMID:40667025 PMID:41779793

    Open questions at the time
    • How S983 phosphorylation distinguishes beta cell-specific from immediate-early CREB targets unresolved
    • Structural effect of phosphorylation not shown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How signaling-driven phosphorylation of the MED14 disordered region and its activator-binding surfaces are integrated to produce gene-selective output within the Mediator scaffold remains unresolved.
  • No atomic structure of MED14 phosphosite or activator interfaces
  • Mechanism linking phosphorylation to selective enhancer/promoter engagement unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 3 GO:0005198 structural molecule activity 2 GO:0060090 molecular adaptor activity 2
Localization
GO:0005634 nucleus 2
Pathway
R-HSA-1266738 Developmental Biology 2 R-HSA-162582 Signal Transduction 2 R-HSA-74160 Gene expression (Transcription) 2
Partners
ELK1MED1PPARGRPB1
Complex memberships
Mediator complexRNA polymerase II holoenzyme

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 Yeast Rgr1 (MED14 ortholog) and Sin4 are physical components of the Mediator complex and RNA polymerase II holoenzyme, forming a subcomplex together with Gal11 and a 50-kDa polypeptide, implicating the Mediator in both transcriptional repression and activation. Biochemical co-purification of Mediator/RNA Pol II holoenzyme; genetic deletion and truncation strains Proceedings of the National Academy of Sciences of the United States of America High 7479899
1995 Yeast Rgr1 and Sin4 proteins are physically associated in vivo (GST pulldown), act together to organize chromatin structure (shown by histone-mutation-like phenotypes and plasmid superhelical density), and thereby regulate transcription from multiple genes. GST-fusion pulldown in vivo; genetic epistasis; plasmid superhelical density assay; suppression genetics (Rgr1 overexpression suppresses sin4 temperature sensitivity) Genetics High 7635307
1990 Yeast Rgr1 (MED14 ortholog) is essential for viability; null mutation is lethal, while C-terminal truncation causes phenotypes including glucose repression defects, aberrant cell morphology (daughter cell wall remaining attached to mother), and reduced reserve carbohydrates. Gene cloning by complementation; null and truncation mutant analysis; electron microscopy; biochemical carbohydrate measurements Molecular and cellular biology Medium 2196447
1994 Yeast Rgr1 (MED14 ortholog) is required for RME1-dependent transcriptional repression of IME1; rgr1 mutations impair repression without reducing RME1 protein levels, placing Rgr1 downstream of or parallel to RME1 in the repression pathway. Genetic selection for repression-deficient mutants; reporter gene assays; complementation; protein level analysis Genetics Medium 7851756
2002 C. elegans RGR-1 (MED14 ortholog) is broadly required for mRNA transcription in the embryo, including for phosphorylation of both Ser-2 and Ser-5 of the RNA Pol II C-terminal domain repeat, suggesting a role at an early recruitment or initiation step. RNAi knockdown of rgr-1 in C. elegans embryos; immunofluorescence detection of RNA Pol II CTD phosphorylation; transcription assays The Journal of biological chemistry Medium 12089139
2004 Yeast Rgr1 (MED14 ortholog) and Sin4 act in a common Mediator pathway to repress basal MAL gene expression; genetic analysis places Rgr1 and Sin4 in the same pathway, with each Sin4-module component playing a distinct role. The Swi/Snf chromatin-remodeling complex is also required and acts non-redundantly with the Rgr1/Sin4 Mediator pathway. Genetic selection for constitutive mutants; complementation grouping; epistasis analysis of double mutants; reporter gene (HIS3, lacZ) assays Genetics Medium 15514050
2005 Human MED14 is required for glucocorticoid receptor (GR)-dependent transcriptional activation of specific target genes (IRF8, IGFBP1, ladinin 1) but not others (GILZ), demonstrating a gene-selective role for MED14 in GR-mediated transcription. MED14 knockdown reduces MED14 and MED1 recruitment to GREs; at IGFBP1, RNA Pol II occupies the promoter but not the GRE, whereas at GILZ, it occupies both. siRNA knockdown of MED14 and MED1; RT-qPCR for target gene mRNA; ChIP for GR, MED14, MED1, and RNA Pol II Molecular endocrinology (Baltimore, Md.) Medium 16239257
2010 Human MED14 directly interacts with the N-terminal domain (NTD) of PPARγ in a ligand-independent manner and is required for PPARγ-dependent transactivation; MED14 knockdown does not reduce PPARγ, MED6, or MED8 recruitment to the Fabp4 enhancer but does reduce their occupancy at the Fabp4 proximal promoter, impairing adipogenesis of 3T3-L1 cells. siRNA knockdown; direct interaction assay (GST/pull-down or equivalent binding assay with NTD of PPARγ); ChIP for PPARγ, MED6, MED8, TBP, RNA Pol II; adipogenesis differentiation assay Molecular and cellular biology High 20194623
2013 Human MED14 is a direct ERK substrate; Ser986 within a serine-proline-rich region is the major ERK phosphorylation site. Mitogens induce MED14 phosphorylation at S986 at immediate-early gene (IEG) promoters. MED14 knockdown reduces CDK8 and RNA Pol II recruitment and RNA Pol II CTD phosphorylation, impairing IEG transcription. S986A substitution selectively reduces Elk-1/Ras-dependent transcription. Elk-1 associates with MED14 independently of MED23. In vitro kinase assay with ERK; phosphosite mapping (S986 identified by mutagenesis); RNAi knockdown with ChIP for CDK8 and RNA Pol II; reporter assays with S986A mutant; Co-IP for Elk-1/MED14 interaction Nucleic acids research High 24049075
2014 Reconstituted 15-subunit human core Mediator acquires basal and coactivator transcription functions only after incorporation of MED14 into the head-middle bimodular complex, dramatically enhancing complex association with RNA Pol II. MED14 serves as both an architectural and functional backbone of the Mediator complex, as mapped by chemical cross-linking/MS. In vitro reconstitution of 15-subunit human core Mediator; functional transcription assays; chemical cross-linking coupled to mass spectrometry (CX-MS); Pol II association assays Nature structural & molecular biology High 25383669
2015 Zebrafish med14 mutation (logelei) causes morphological arrest and loss of multiple stem/progenitor cell populations by 2 days of development, without broadly affecting transcription; transplanted log cells survive in wild-type environments, indicating a cell-autonomous role for med14 in stem cell maintenance rather than global transcription. Forward genetic screen; zebrafish mutant characterization; microarray transcriptomics; cell transplantation assay; planarian RNAi knockdown Stem cell reports Medium 25772472
2015 Zebrafish med14 and brg1 (BAF/SWI-SNF subunit) genetically interact in neural crest differentiation: both are required for terminal differentiation (but not specification or migration) of jaw-forming neural crest cells; double mutant analysis reveals a strong genetic interaction between the Mediator and BAF complexes. Zebrafish genetic mutant analysis; cell transplantation (cell-autonomous requirement); double-mutant epistasis BMC developmental biology Medium 26553192
2025 The N-terminal domain (NTD) of human MED14 is sufficient for a reconstituted 15-subunit core Mediator to support both basal and p53-activated transcription; the MED14-NTD directly interacts with the RPB1 subunit of RNA Pol II (preferentially in the hypophosphorylated CTD state) and is required for recruiting Pol II to core promoters. Recombinant RPB1 can competitively reverse the Mediator–Pol II interaction. MultiBac baculovirus reconstitution of human core Mediator subcomplexes; in vitro transcription assay; direct binding assay with RPB1; LC-MS/MS analysis of CTD phosphorylation state; cryo-EM reanalysis of published structures The Journal of biological chemistry High 41110510
2026 PKA phosphorylates Med14 at Ser983 (within a conserved RRXS PKA recognition motif in an intrinsically disordered region) upon GLP-1 receptor agonist (Exendin-4) stimulation in pancreatic beta cells; S983A mutation blocks Exendin-4-induced activation of beta cell-specific CREB-dependent enhancers, reduces beta cell numbers, and impairs beta-cell-specific gene regulation without affecting immediate-early CREB targets. Proteomic screen for coregulators; phosphoproteomics identifying Ser983; Med14 S983A knock-in mouse islets; transcriptomics; ChIP for enhancer activity Proceedings of the National Academy of Sciences of the United States of America High 40667025 41779793

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1995 Yeast global transcriptional regulators Sin4 and Rgr1 are components of mediator complex/RNA polymerase II holoenzyme. Proceedings of the National Academy of Sciences of the United States of America 219 7479899
2005 MED14 and MED1 differentially regulate target-specific gene activation by the glucocorticoid receptor. Molecular endocrinology (Baltimore, Md.) 112 16239257
2014 Reconstitution of active human core Mediator complex reveals a critical role of the MED14 subunit. Nature structural & molecular biology 109 25383669
2007 The transcription corepressor LEUNIG interacts with the histone deacetylase HDA19 and mediator components MED14 (SWP) and CDK8 (HEN3) to repress transcription. Molecular and cellular biology 108 17526732
1995 Genetic and physical interactions between yeast RGR1 and SIN4 in chromatin organization and transcriptional regulation. Genetics 82 7635307
1990 Structure and molecular analysis of RGR1, a gene required for glucose repression of Saccharomyces cerevisiae. Molecular and cellular biology 77 2196447
2010 MED14 tethers mediator to the N-terminal domain of peroxisome proliferator-activated receptor gamma and is required for full transcriptional activity and adipogenesis. Molecular and cellular biology 67 20194623
1994 Requirement for RGR1 and SIN4 in RME1-dependent repression in Saccharomyces cerevisiae. Genetics 55 7851756
2004 Mutations in SIN4 and RGR1 cause constitutive expression of MAL structural genes in Saccharomyces cerevisiae. Genetics 21 15514050
2022 PHYTOCHROME-INTERACTING FACTOR 4/HEMERA-mediated thermosensory growth requires the Mediator subunit MED14. Plant physiology 20 36063057
2006 Differential roles of transcriptional mediator complex subunits Crsp34/Med27, Crsp150/Med14 and Trap100/Med24 during zebrafish retinal development. Genetics 17 16582438
2002 Broad requirement for the mediator subunit RGR-1 for transcription in the Caenorhabditis elegans embryo. The Journal of biological chemistry 17 12089139
2018 A role for MED14 and UVH6 in heterochromatin transcription upon destabilization of silencing. Life science alliance 15 30574575
2020 Differential requirement of MED14/17 recruitment for activation of heat inducible genes. The New phytologist 14 33251584
2013 ERK phosphorylation of MED14 in promoter complexes during mitogen-induced gene activation by Elk-1. Nucleic acids research 14 24049075
2015 An in vivo requirement for the mediator subunit med14 in the maintenance of stem cell populations. Stem cell reports 10 25772472
2015 Med14 cooperates with brg1 in the differentiation of skeletogenic neural crest. BMC developmental biology 8 26553192
2025 N-terminal half of MED14 is critical for Mediator-RNA polymerase II interaction and the resulting transcription. The Journal of biological chemistry 2 41110510
2021 A Recurrent Cryptic MED14-HOXA9 Rearrangement in an Adult Patient With Mixed-Phenotype Acute Leukemia, T/myeloid, NOS. Frontiers in oncology 2 34367969
2026 Med14 phosphorylation shapes genomic response to GLP-1 agonists. Proceedings of the National Academy of Sciences of the United States of America 1 41779793
2025 Med14 phosphorylation shapes genomic response to GLP-1 Agonist. bioRxiv : the preprint server for biology 1 40667025
2003 Refinement of the physical location and the genomic characterization of the CRSP2 (EXLM1) gene on Xp11.4. DNA sequence : the journal of DNA sequencing and mapping 1 12825353

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