{"gene":"SRF","run_date":"2026-06-10T07:46:41","timeline":{"discoveries":[{"year":1991,"finding":"SRF and yeast MCM1 share a conserved 90-amino-acid MADS-box domain that is sufficient for dimerization, DNA binding, and ternary complex formation with accessory proteins (p62TCF for SRF; STE12 and p62TCF for MCM1). Substitution of three specific residues in ARG80 with SRF equivalents (positions 198, 200, 203) conferred p62TCF recruitment, and substitution of four SRF residues with MCM1 equivalents (positions 73, 75, 77, 78) conferred STE12 recruitment, identifying specific amino acids within the shared domain that mediate distinct protein-protein interactions.","method":"In vitro gel retardation assays, chimeric protein domain swapping, site-directed mutagenesis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in vitro with mutagenesis and domain-swap experiments identifying specific residues; replicated across multiple constructs","pmids":["1756729"],"is_preprint":false},{"year":1991,"finding":"The N-terminal 98-amino-acid MADS-box domain of MCM1 (ortholog sharing 70% identity with SRF DNA-binding domain) is sufficient for DNA binding, dimerization, viability, and physical interaction with cofactors alpha1, alpha2, and STE12; a ~50 amino acid sub-region within this domain provides contacts with all three cofactors.","method":"In vitro binding studies with deletion constructs, in vivo reporter assays, yeast complementation","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in vitro combined with in vivo functional assays; multiple deletion and hybrid constructs tested","pmids":["1756728"],"is_preprint":false},{"year":1992,"finding":"SRF and MCM1 have related but distinct DNA-binding specificities: MCM1 selects a consensus (NotC)CCY(A/T)(A/T)(T/A)NN(A/G)G, distinct from the SRF consensus CC(A/T)6GG. Differences in specificity map largely to the N-terminal basic portion of their respective DNA-binding domains.","method":"In vitro selection of binding sites from random oligonucleotides, carboxylethylation interference analysis, comparative binding affinity assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro binding site selection with interference footprinting and comparative affinity measurements; multiple orthogonal methods in one study","pmids":["1630900"],"is_preprint":false},{"year":1992,"finding":"MCM1 sets the precise spacing and orientation of alpha2 homeodomain dimers on DNA: alpha2 dimers alone bind inverted, direct, and everted repeat arrangements with equal affinity, but MCM1 restricts binding to only the naturally occurring operator geometry, thereby raising target specificity of the homeodomain protein.","method":"In vitro DNA binding assays with artificial operators containing half-sites in different arrangements, affinity measurements","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with defined synthetic DNA substrates demonstrating mechanistic basis for specificity; multiple orthogonal binding conditions tested","pmids":["1732062"],"is_preprint":false},{"year":1992,"finding":"The Elk-1 ETS domain is necessary and sufficient for direct DNA binding, while both the ETS domain and flanking sequences up to amino acid 169 (including a protein-protein interaction region spanning residues 137–169) are required for ternary complex formation with SRF at the c-fos serum response element. A single amino acid substitution in the ETS domain can dramatically alter direct DNA-binding affinity without severely affecting SRF-assisted binding.","method":"In vitro gel retardation assays with Elk-1 deletion and point-mutant constructs","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic deletion and point mutagenesis with in vitro binding reconstitution; multiple mutant constructs tested in one study","pmids":["1630903"],"is_preprint":false},{"year":1993,"finding":"SAP-1 (isolated by yeast genetic screen) and Elk-1 both function as SRF accessory proteins (p62/TCF class) that form ternary complexes with SRF at the serum response element; only two of the three Elk-1-homologous regions in SAP-1 are required for cooperative interactions with SRF, while the third contains conserved MAP kinase phosphorylation sites.","method":"Yeast genetic screen for cDNAs with p62/TCF DNA-binding properties, gel retardation ternary complex assays, sequence analysis of conserved phosphorylation sites","journal":"Philosophical transactions of the Royal Society of London. Series B, Biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast screen plus in vitro ternary complex assays; single lab but two methods","pmids":["8103935"],"is_preprint":false},{"year":1998,"finding":"Crystal structure of yeast MATalpha2/MCM1/DNA ternary complex at 2.25 Å reveals that the otherwise flexible N-terminal extension of the alpha2 homeodomain forms a beta-hairpin gripping the MCM1 surface via parallel beta-strand hydrogen bonds and hydrophobic side chains; MCM1-induced DNA bending brings the two proteins closer, facilitating their interaction. A 'chameleon' sequence in alpha2 adopts alpha-helical conformation in one monomer and beta-strand in the other.","method":"X-ray crystallography at 2.25 Å resolution","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution crystal structure directly revealing protein-protein and protein-DNA contacts","pmids":["9490409"],"is_preprint":false},{"year":1997,"finding":"MCM1 uses a DNA-contact mechanism distinct from SRF: 5-bromouracil photo-cross-linking shows MCM1 contacts the major groove at the center of its recognition site (not observed for SRF), and Mcm1-dependent DNA bending requires bases outside the conserved CC(A/T)6GG site that do not affect SRF bending, indicating DNA bending by Mcm1 is sequence-dependent and transcriptionally important even when binding affinity is minimally affected.","method":"5-bromouracil-mediated photo-cross-linking, gel retardation with extensive base-pair substitution series, in vivo transcriptional reporter assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biochemical methods (cross-linking, binding, bending, transcription) in one study","pmids":["9121436"],"is_preprint":false},{"year":1997,"finding":"Mcm1 is phosphorylated in vivo at multiple sites (>8 isoforms by isoelectric focusing), with two major phosphorylation sites in the N-terminal 17 amino acids adjacent to the MADS-box. A unique Mcm1 isoform is induced by osmotic stress (NaCl or KCl), establishing that Mcm1 itself is a target of osmotic stress signal transduction; deletion of the N-terminus or mutation of the primary phosphorylation site impairs growth on high-salt medium.","method":"Isoelectric focusing of in vivo-labeled protein, deletion and point mutant analysis on high-salt medium, induction experiments with NaCl/KCl","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo phosphorylation detected by IEF with supporting genetic evidence; single lab, two orthogonal methods","pmids":["9001236"],"is_preprint":false},{"year":1994,"finding":"Specific residues within the MCM1 MADS-box domain (positions 69–81) mediate interaction with alpha1 and STE12 cofactors (a subset also affecting STE12 binding), while interaction with alpha2 requires a distinct mechanism, as nonconservative substitutions at alpha2-contact residues do not significantly affect alpha2-mediated repression. Most lethal mutations affect DNA-binding affinity, and lethality of many such mutations is suppressed by high-copy MCM1.","method":"In vitro DNA-binding cooperative binding assays, in vivo reporter gene assays, alanine-scanning mutagenesis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic point mutagenesis combined with in vitro cooperative binding assays and in vivo reporters; comprehensive mutant series","pmids":["8139556"],"is_preprint":false},{"year":1996,"finding":"A hydrophobic patch in the region preceding the alpha2 homeodomain mediates direct protein-protein interaction with Mcm1 (in the absence of DNA), is required for cooperative DNA binding in vitro and transcriptional repression in vivo. A conserved YPWM motif found in homeodomain proteins of insects and mammals can partially substitute for this patch in alpha2, suggesting evolutionary conservation of the interaction mechanism.","method":"In vitro cooperative DNA-binding assays with alpha2 mutants, in vivo repression assays, comparison with heterologous YPWM-containing peptides","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — domain identification by mutagenesis with in vitro reconstitution and in vivo validation; cross-species comparison","pmids":["8628280"],"is_preprint":false},{"year":2000,"finding":"In Saccharomyces cerevisiae arginine metabolism, the putative alpha-helix within the MADS-box domain of Mcm1 (and ArgRI) is its primary interaction surface with ArgRIII. Purified GST-ArgRI and ArgRII1-180, or Mcm1 and ArgRII1-180, reconstitute an arginine-dependent DNA-binding activity in mobility shift analysis; ArgRIII stability is required for Mcm1 stability and Mcm1-dependent gene expression.","method":"Yeast two-hybrid, affinity chromatography with purified proteins, in vitro EMSA reconstitution, in vivo gene expression assays","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of complex from purified components combined with affinity chromatography and in vivo assays; multiple orthogonal methods","pmids":["10632874"],"is_preprint":false},{"year":2000,"finding":"ArgRII (zinc cluster protein) is the arginine sensor in the ArgR-Mcm1 complex: purified ArgRI and ArgRII1-180 (or Mcm1 and ArgRII1-180) reconstitute arginine-dependent DNA binding in EMSA, and the arginine-binding site maps to the region downstream of ArgRII's zinc cluster domain, sharing identity with bacterial arginine repressor arginine-binding domains.","method":"In vitro EMSA reconstitution with purified recombinant proteins, arginine-dependence assays, domain deletion analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical reconstitution from purified components with defined domain requirements; arginine-dependence directly tested","pmids":["10688655"],"is_preprint":false},{"year":2000,"finding":"SRF-null (Srf−/−) embryonic stem cells show impaired mesodermal differentiation in vitro (failure to activate T/Brachyury), but this impairment is non-cell-autonomous: retinoic acid rescues T activation, SRF re-expression rescues differentiation, and in nude mice Srf−/− ES cells readily form mesodermal derivatives, demonstrating that SRF contributes to mesodermal gene expression in a context-dependent manner.","method":"Conditional Srf knockout ES cells, in vitro differentiation assays, retinoic acid rescue, teratoma formation in nude mice","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple rescue conditions and in vivo complementation; replicated across several experimental contexts","pmids":["11060034"],"is_preprint":false},{"year":2002,"finding":"Mcm1 alanine substitutions in the MADS-box reveal that interaction with alpha2 requires different residues than interaction with alpha1 or Ste12 cofactors: most mutations affecting alpha1/Ste12 binding do not affect alpha2-mediated repression, indicating distinct interaction surfaces within the same domain for different cofactors.","method":"Systematic alanine-scanning mutagenesis of MADS-box, in vivo transcriptional reporter assays, in vitro DNA-binding assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic mutagenesis with in vitro binding and in vivo transcription assays; comprehensive mutant series","pmids":["12052870"],"is_preprint":false},{"year":2003,"finding":"Mcm7 (MCM helicase subunit) acts as a novel cofactor of Mcm1 in transcriptional regulation: Mcm7 stimulates Mcm1 binding to early cell cycle box (ECB) elements upstream of MCM7, CDC6, and MCM5 promoters; Mcm7 is recruited to these promoters during late M phase while Mcm1 binds constitutively, suggesting Mcm7 modulates periodic expression of early cell cycle genes through Mcm1.","method":"Gel retardation assays with purified proteins, chromatin immunoprecipitation, in vivo reporter assays, analysis of mcm7 and mcm1 mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus in vitro binding reconstitution; single lab, two methods","pmids":["12738768"],"is_preprint":false},{"year":2002,"finding":"Mcm1 associates globally with chromatin in a punctate pattern, binds cooperatively to multiple sites at autonomously replicating sequences (ARS), and is localized at replication origins in vivo, supporting a direct role for Mcm1 in replication initiation beyond transcriptional regulation of replication genes.","method":"Chromatin immunoprecipitation, in vivo chromatin association assay, in vitro binding with purified Mcm1, loss-of-function analysis at chromosomal origin","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus in vitro binding; single lab, two orthogonal methods","pmids":["12473677"],"is_preprint":false},{"year":2004,"finding":"SRF directly binds the Bcl-2 promoter in vivo (ChIP) and activates Bcl-2 transcription; reconstitution of Bcl-2 in Srf−/− ES cells rescues apoptosis, demonstrating that SRF-dependent Bcl-2 expression is required for ES cell survival. SRF deficiency also impairs Bcl-xl expression and leads to inappropriate apoptosis in embryoid bodies and pre-gastrulation embryos.","method":"Chromatin immunoprecipitation, luciferase reporter assays, genetic rescue (Bcl-2 re-expression in Srf−/− ES cells), apoptosis assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP demonstrating direct promoter binding plus genetic rescue experiment; multiple orthogonal methods in one study","pmids":["15057274"],"is_preprint":false},{"year":2004,"finding":"FHL2, an SRF target gene, physically interacts with SRF protein and binds promoters of SRF-responsive smooth muscle genes (but not immediate-early gene promoters) in response to RhoA activation. FHL2 antagonizes smooth muscle gene induction by competing with MAL/MRTF-A for SRF binding, creating a negative autoregulatory feedback loop selectively controlling a subset of RhoA-activated SRF targets.","method":"Large-scale expression profiling, co-immunoprecipitation, chromatin immunoprecipitation, RhoA activation assays, competitive binding assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP plus ChIP demonstrating in vivo promoter occupancy plus functional competition assays; multiple orthogonal methods","pmids":["15610731"],"is_preprint":false},{"year":2004,"finding":"Alpha1 cofactor increases the DNA bend induced by Mcm1 at alpha-specific gene binding sites; this enhanced bending is required for full transcriptional activation. Mcm1 binds alpha-specific gene promoters even in the absence of alpha1 (shown by ChIP), indicating alpha1's function extends beyond Mcm1 recruitment to modulating DNA architecture.","method":"Chromatin immunoprecipitation, circular permutation DNA-bending assays, in vivo transcriptional reporter assays with bending-defective mutants","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus DNA bending assays with functional validation; single lab, two orthogonal methods","pmids":["15118075"],"is_preprint":false},{"year":2008,"finding":"Disruption of epithelial cell-cell junctions activates SRF-mediated transcription via a Rac1-monomeric actin-MAL/MRTF signaling axis in epithelial cells, distinct from the RhoA-dependent pathway in serum-stimulated fibroblasts. Using clostridial cytotoxins, Rac (but not RhoA) was shown to be required for SRF and target gene induction upon junction dissociation; actomyosin contractility is a prerequisite but not sufficient.","method":"RNAi knockdown, clostridial cytotoxin-mediated Rho GTPase inhibition, reporter gene assays, dominant-negative and constitutively active GTPase constructs","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and genetic manipulation of specific GTPases with reporter readout; single lab, multiple inhibitor approaches","pmids":["18334560"],"is_preprint":false},{"year":2009,"finding":"RNAi depletion of MRTFs or SRF in breast carcinoma and melanoma cells reduces cell adhesion, spreading, invasion, and motility (without affecting proliferation or inducing apoptosis); MRTF-depleted xenografts show reduced cell motility but normal proliferation. Depletion of MRTFs or SRF prevents lung colonization after intravenous injection. MYH9 (NMHCIIa) and MYL9 (MLC2) are identified as MRTF-dependent SRF target genes also required for invasion and lung colonization. Activated MAL/MRTF-A expression increases lung colonization by poorly metastatic cells.","method":"RNA interference, xenograft tumor models, intravital imaging, lung colonization assays, gene expression profiling","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi knockdown and gain-of-function in multiple cell lines with in vivo xenograft and colonization readouts; multiple orthogonal methods replicated in two cell types","pmids":["19198601"],"is_preprint":false},{"year":2008,"finding":"In Alzheimer's disease patients and mouse models, SRF and myocardin are overexpressed in cerebral vascular smooth muscle cells; SRF/MYOCD overexpression transactivates SREBP-2, which downregulates LRP-1 (a key Abeta clearance receptor), generating an Abeta non-clearing VSMC phenotype. Hypoxia stimulates SRF/MYOCD expression in human cerebral VSMCs.","method":"Immunohistochemistry, overexpression studies in VSMCs, promoter/reporter assays for SREBP-2 transactivation, LRP-1 expression analysis, hypoxia experiments","journal":"Nature cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional overexpression with defined transcriptional readout; single lab with multiple cell-based methods","pmids":["19098903"],"is_preprint":false},{"year":2011,"finding":"Conditional epidermal ablation of Srf in mice leads to reduced cortical actin network in basal cells, failure of mitotic cell rounding, altered phospho-ERM and cortical myosin-IIA distribution, and defects in spindle orientation, asymmetric cell divisions, stratification, and differentiation. Low-dose actin inhibitors in vivo and shRNA knockdown in vitro recapitulate the cortical network loss and rounding defects, linking Srf-driven actin gene expression to cortical actomyosin organization and mitotic shape changes.","method":"Conditional epidermal Srf knockout mice, low-dose actin inhibitor treatment in vivo, shRNA knockdown in vitro, immunofluorescence of phospho-ERM and myosin-IIA, spindle orientation measurements","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo combined with pharmacological and RNAi recapitulation; multiple orthogonal readouts across in vivo and in vitro systems","pmids":["21336301"],"is_preprint":false},{"year":2013,"finding":"Inducible endothelial-specific deletion of Srf in postnatal mice abolishes filopodia formation and contractility in tip cells during sprouting angiogenesis, while leaving vascular remodeling intact. VEGF-A induces nuclear accumulation of MRTFs and regulates MRTF/SRF-dependent target genes including Myl9, which is required for endothelial cell migration in vitro.","method":"Inducible endothelial-specific Srf conditional KO mice, retinal angiogenesis assays, VEGF stimulation, MRTF nuclear localization imaging, in vitro migration assays","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo with defined cellular phenotype plus VEGF-MRTF-SRF pathway dissection; multiple methods","pmids":["23674601"],"is_preprint":false},{"year":2014,"finding":"GSK-3 directly phosphorylates SRF on a highly conserved serine residue and binds SRF; this serine phosphorylation is required for SRF transcriptional activity and for SRF's interaction with MKL-family cofactors (MKL1 and MKL2) but not with TCF cofactor ELK-1. Axonal growth deficits from GSK-3 inhibition are rescued by constitutively active SRF; the SRF target gene vinculin is sufficient to overcome axonal growth deficits of SRF-deficient and GSK-3-inhibited neurons.","method":"In vitro kinase assay, co-immunoprecipitation of GSK-3/SRF, site-directed mutagenesis of phosphorylation site, shRNA knockdown, constitutively active SRF rescue, axon outgrowth assays in hippocampal neurons","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay plus mutagenesis plus co-IP plus genetic rescue in neurons; multiple orthogonal methods in one study","pmids":["24623780"],"is_preprint":false},{"year":2015,"finding":"Endothelial-specific depletion of SRF or MRTF-A/-B in mice causes loss of blood-brain barrier integrity and intracerebral hemorrhagic stroke. At the molecular level, SRF/MRTF directly regulate expression of tight junction components (Claudins, ZO proteins), adherens junction components (VE-cadherin, α-Actinin), and basement membrane constituents (Collagen IV), which are downregulated upon SRF depletion.","method":"Conditional endothelial-specific Srf and Mrtf knockout mice, in vivo MRI for hemorrhage detection, immunofluorescence, gene expression analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo with defined molecular targets, replicated with SRF and MRTF knockouts; in vivo imaging confirmation","pmids":["26221020"],"is_preprint":false},{"year":2016,"finding":"TCF (ternary complex factor) cofactors act as general antagonists of MRTF-dependent SRF target gene expression by competing directly with MRTFs for access to SRF. TCF inactivation in MEFs inhibits >60% of TPA-inducible gene transcription and impairs cell proliferation; TCF-deficient MEFs exhibit hypercontractile and pro-invasive behavior. SRF ChIP-seq combined with Hi-C identifies over 700 TCF-dependent SRF direct target genes.","method":"TCF triple inactivation in MEFs, ChIP-seq, Hi-C, RNA-seq, competitive binding assays between TCFs and MRTFs for SRF","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide ChIP-seq and Hi-C plus functional competition assays with genetic loss-of-function; multiple orthogonal methods","pmids":["27867007"],"is_preprint":false},{"year":2017,"finding":"Serum response factor (SRF) binds to the CArG box in the MYH9 promoter and drives its expression; miR-647 directly binds the 3' UTR of SRF mRNA to suppress SRF levels, which in turn reduces MYH9 expression and suppresses gastric cancer metastasis.","method":"Luciferase 3'UTR reporter assays, ChIP for SRF at MYH9 promoter, overexpression/knockdown experiments, orthotopic GC mouse models","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating direct SRF-MYH9 promoter binding plus 3'UTR reporter validation; single lab, two orthogonal methods","pmids":["28900514"],"is_preprint":false},{"year":2017,"finding":"Satellite cell-specific Srf deletion abolishes myoblast fusion (required in both fusion partners) without affecting proliferation or differentiation. Srf-null myoblasts lack actin-based finger-like protrusions at fusion sites. Overexpression of an α-actin isoform in Srf-null satellite cells restores actin polymerization and rescues fusion in vitro and in vivo, demonstrating that SRF controls myoblast fusion through maintenance of actin cytoskeleton architecture.","method":"Satellite cell-specific Srf conditional KO, live imaging of fusion sites, α-actin overexpression rescue, in vivo overload-induced hypertrophy model","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with genetic rescue in vivo and in vitro; multiple orthogonal readouts","pmids":["29269426"],"is_preprint":false},{"year":2018,"finding":"SRF and its coactivator MKL1 bind DNA near hedgehog target genes and form a protein complex with the hedgehog transcription factor GLI1, amplifying GLI1 transcriptional activity. Cytoskeletal activation through Rho and the formin mDia is required for SRF-MKL-driven GLI1 activation. This constitutes a noncanonical hedgehog pathway enabling drug resistance in basal cell carcinomas.","method":"Multidimensional genomics of human/mouse BCCs, ChIP for SRF/MKL1 near hedgehog target genes, co-immunoprecipitation of SRF-MKL1-GLI1 complex, Rho/mDia inhibition experiments","journal":"Nature medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating SRF-MKL1-GLI1 complex plus ChIP and functional inhibitor studies; single lab, multiple methods","pmids":["29400712"],"is_preprint":false},{"year":2018,"finding":"HDAC6 co-immunoprecipitates with MRTF-A and regulates its acetylation and protein level; HDAC6 inhibition (tubastatin A) or knockdown increases MRTF-A acetylation, total MRTF-A protein, and nuclear SRF transcriptional activity, preserving contractile gene (α-SMA) expression in VSMCs. This is the first demonstration of HDAC6 regulation of the MRTF-A/SRF axis.","method":"Co-immunoprecipitation, HDAC6 knockdown, pharmacological inhibition (tubastatin A), SRF luciferase reporter, in vivo rat carotid injury model","journal":"JACC. Basic to translational science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating HDAC6-MRTF-A interaction plus functional reporter and in vivo model; single lab","pmids":["30623138"],"is_preprint":false},{"year":2019,"finding":"IGF2BP1 promotes SRF expression in cancer cells by binding SRF mRNA and impairing miRNA-directed decay in an m6A-dependent manner, resulting in enhanced SRF-dependent transcriptional activity and upregulation of SRF target genes (including PDLIM7 and FOXK1) that promote tumor cell growth and invasion.","method":"RNA immunoprecipitation, m6A sequencing, miRNA-reporter assays, RNAi knockdown, gene expression profiling","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP demonstrating IGF2BP1-SRF mRNA interaction plus m6A and functional assays; single lab, multiple methods","pmids":["30371874"],"is_preprint":false},{"year":2020,"finding":"SENP1 deficiency in vascular smooth muscle cells increases SUMOylation of SRF at lysine 143, which reduces SRF lysosomal localization and increases nuclear accumulation, and switches the SRF complex from a contractile phenotype-responsive SRF-myocardin complex to a synthetic phenotype-responsive SRF-ELK1 complex, promoting vascular remodeling and neointimal formation.","method":"VSMC-specific Senp1 knockout mice, site-directed mutagenesis of SRF K143, co-immunoprecipitation of SRF complexes, subcellular fractionation, ELK inhibitor (AZD6244) treatment, neointima formation assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — site-specific mutagenesis identifying SUMOylation site combined with Co-IP of SRF complexes, KO mouse model, and pharmacological rescue; multiple orthogonal methods","pmids":["39134547"],"is_preprint":false},{"year":2021,"finding":"Sarcomere disorganization (via Actn2 mutation) increases monomeric cardiac α-actin, which sequesters the SRF cofactor MRTF-A in the cytoplasm and prevents SRF activation. Overexpression of a dominant-negative MRTF-A mutant recapitulates the morphological and transcriptional defects of both Actn2 and Srf mutant cardiomyocytes, placing MRTF-A/SRF downstream of sarcomere integrity in the control of cardiomyocyte maturation.","method":"Cardiomyocyte-specific Actn2 mutant mice, Srf conditional KO, dominant-negative MRTF-A overexpression, G-actin/F-actin fractionation, MRTF-A nuclear localization imaging, transcriptomic analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO plus dominant-negative overexpression with epistasis; actin fractionation mechanistically linking sarcomere to MRTF-A/SRF; multiple orthogonal methods","pmids":["33361330"],"is_preprint":false},{"year":2022,"finding":"In LMNA-mutant muscle cells, ERK1/2-phosphorylated cofilin-1 (at T25) binds MRTF-A in the cytoplasm, preventing MRTF-A nuclear entry and SRF stimulation. Reduced MRTF-A/SRF activity decreases expression of ATAT1 (α-tubulin acetyltransferase 1), leading to decreased α-tubulin acetylation and Connexin 43 mislocalization in cardiomyocytes, driving dilated cardiomyopathy.","method":"Co-immunoprecipitation of phospho-cofilin-1 with MRTF-A, MRTF-A nuclear localization imaging, Atat1 KO mice, tubastatin A treatment of Lmna mutant mice, Cx43 immunofluorescence, cardiac function measurements","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP demonstrating cofilin-1-MRTF-A interaction with phosphorylation-dependent mechanism; in vivo KO and pharmacological rescue; multiple orthogonal methods","pmids":["36550158"],"is_preprint":false},{"year":2022,"finding":"Mural cell-specific inducible Srf deletion demonstrates that SRF directs pericyte migration downstream of PDGFRB signaling via MRTF cofactors (PDGFB-dependent SRF activation is MRTF-mediated), and is essential in VSMCs for expression of the contractile machinery; SRF deletion in VSMCs triggers arteriovenous shunt formation.","method":"Inducible mural cell-specific Srf KO mice, retinal angiogenesis assays, RNA-sequencing, in vivo live imaging, in vitro MRTF-SRF reporter assays with PDGFB stimulation, immunohistology","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO in vivo with defined pathway (PDGFB-MRTF-SRF) via reporter assays; RNA-seq plus imaging; multiple orthogonal methods","pmids":["35862101"],"is_preprint":false},{"year":2020,"finding":"Exercise induces phosphorylation of a new site on MRTF-B (SRF cofactor), required for its nuclear translocation and subsequent transcription of SRF target gene Fos. High-intensity exercise also phosphorylates histone H3 at serine 10 at SRF target gene loci via MSK1/2; ablation of MSK1/2 prevents this histone phosphorylation, reduces SRF-target gene induction, and prevents increases in protein synthesis after exercise.","method":"Phosphoproteomics screen in exercised mice, MSK1/2 KO mice, chromatin immunoprecipitation (H3S10p), muscle biopsies from human exercise subjects","journal":"Acta physiologica (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphoproteomics plus ChIP and KO model; replicated in human samples; single lab","pmids":["32408395"],"is_preprint":false},{"year":2022,"finding":"The actin cytoskeleton-MRTF-A/SRF signaling cascade transduces extracellular matrix physical cues to modulate circadian clock function. Pharmacological or genetic inhibition of SRF or MRTF-A lengthens circadian period; actin polymerization shortens period. SRF-null or Mrtfa-null cells mimic actin-depolymerizing effects. Per2, Nr1d1, and Nfil3 are identified as direct transcriptional targets of MRTF-A/SRF that mediate the actin dynamics-induced clock response.","method":"Srf and Mrtfa conditional knockouts, pharmacological inhibition of ROCK/actin polymerization, circadian bioluminescence reporter assays, ChIP identifying Per2/Nr1d1/Nfil3 as direct MRTF-A/SRF targets, integrin/FAK inhibition","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus ChIP plus pharmacological dissection; single lab with multiple orthogonal methods","pmids":["36093830"],"is_preprint":false},{"year":2010,"finding":"SRF directly binds the frataxin (FXN) promoter (demonstrated by ChIP and EMSA); mutagenesis of the predicted SRF binding site significantly decreases FXN promoter activity; SRF overexpression significantly increases frataxin mRNA and protein levels in HEK293 and SH-SY5Y cells and in Friedreich ataxia patient lymphoblasts.","method":"Chromatin immunoprecipitation, electrophoretic mobility shift assay, site-directed mutagenesis of SRF binding site, luciferase reporter assays, SRF overexpression in cell lines and patient cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus EMSA plus mutagenesis plus overexpression; single lab, multiple orthogonal methods","pmids":["20808827"],"is_preprint":false},{"year":2003,"finding":"B cell receptor activation of SRF occurs via a Src-Syk-Tec-PLCγ-Ca2+ (Lyn-Syk-Btk-PLCγ-Ca2+) pathway. SRF responds to lower Ca2+ concentrations than NFAT and is less dependent on IP3R expression. Calcineurin plays a partial role in SRF activation (in combination with DAG), while calcineurin is fully required for NFAT. Both SRF and NFAT require Rac, Rho, CDC42, and actin; SRF but not NFAT is independent of JNK.","method":"Pharmacological and dominant-negative inhibition of signaling components, calcium chelation, IP3R-deficient cell lines, reporter assays for SRF and NFAT","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic pharmacological/genetic pathway dissection with reporter assays; single lab, multiple inhibitor/genetic conditions","pmids":["12912915"],"is_preprint":false},{"year":1999,"finding":"The SRF gene is activated by serum/LPA through a bipartite promoter mechanism requiring both an Sp1-factor binding site (targeted by Ras signaling) and CArG box motifs (targeted by Rho-mediated signals), demonstrating that SRF auto-regulates its own transcription through its CArG binding sites.","method":"Promoter-reporter assays with mutated SRE/CArG and Sp1 sites, LPA and serum stimulation, dominant-negative Ras and Rho constructs","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-directed mutagenesis of promoter elements with pathway-specific dominant-negative constructs; single lab","pmids":["10602487"],"is_preprint":false}],"current_model":"SRF is a dimeric MADS-box transcription factor that binds CC(A/T)6GG (CArG box) sequences and functions as a transcriptional hub regulated by two competing families of cofactors: MRTF/myocardin-family proteins (activated by Rho-dependent actin polymerization, which releases G-actin-sequestered MRTFs to translocate to the nucleus and activate SRF-driven cytoskeletal/contractile gene programs) and TCF/ternary complex factors such as Elk-1 and SAP-1 (activated by MAP kinase/ERK signaling to drive immediate-early and proliferative gene programs); competition between MRTFs and TCFs for SRF binding determines the balance between contractile and proliferative transcriptional programs, while SRF activity is further modulated by SUMOylation (at K143, switching SRF between myocardin and ELK1 complexes), GSK-3-mediated phosphorylation (required for MKL cofactor interaction and axon growth), and by autoregulation of the SRF gene itself through Ras/Sp1 and Rho/CArG pathways."},"narrative":{"mechanistic_narrative":"SRF is a MADS-box transcription factor that binds CArG box (CC(A/T)6GG) sequences and serves as a transcriptional hub controlling cytoskeletal, contractile, and immediate-early gene programs [PMID:1630900, PMID:27867007]. Its conserved 90-residue MADS-box domain is sufficient for dimerization, DNA binding, and assembly of ternary complexes with accessory proteins, with discrete residue sets within this single domain mediating recruitment of distinct cofactor classes [PMID:1756729]. SRF activity is governed by competition between two cofactor families that dock on this domain: ternary complex factors (TCFs) such as Elk-1 and SAP-1, whose ETS domains and flanking interaction regions form ternary complexes at the c-fos serum response element and drive proliferative, MAP-kinase-responsive transcription [PMID:1630903, PMID:8103935, PMID:27867007], and the MRTF/myocardin family, which couples SRF to actin dynamics — actin polymerization releases G-actin-sequestered MRTFs for nuclear entry to activate cytoskeletal and contractile targets, and TCFs act as general antagonists of MRTF-dependent SRF transcription by competing for SRF access [PMID:27867007, PMID:33361330]. This actin-MRTF-SRF axis transduces diverse upstream signals — RhoA in serum-stimulated fibroblasts, Rac1 upon epithelial junction disruption, VEGF in endothelial tip cells, and PDGFRB in pericytes [PMID:18334560, PMID:23674601, PMID:35862101] — into programs that build cortical and contractile actin architecture, demonstrated by SRF requirements for mitotic cell rounding and spindle orientation in epidermis, myoblast fusion, angiogenic filopodia, and blood-brain-barrier integrity, all rescuable through restoration of actin-cytoskeletal targets [PMID:21336301, PMID:29269426, PMID:23674601, PMID:26221020]. SRF additionally directly activates survival and contractile target genes including Bcl-2, MYH9/MYL9, FHL2, and frataxin [PMID:15057274, PMID:19198601, PMID:15610731, PMID:20808827], and FHL2 feeds back as an MRTF-competing antagonist of a subset of RhoA-induced targets [PMID:15610731]. SRF output is further tuned by post-translational control: GSK-3 phosphorylates a conserved serine required for MKL/MRTF (but not ELK-1) interaction and axon growth [PMID:24623780], and SUMOylation at K143 switches SRF between myocardin and ELK1 complexes to toggle contractile versus synthetic phenotypes in vascular smooth muscle [PMID:39134547]. SRF also autoregulates its own gene through Sp1/Ras and CArG/Rho promoter elements [PMID:10602487]. Much of the detailed structural and cofactor-residue mechanism derives from the yeast ortholog MCM1, which shares the MADS-box and analogous combinatorial cofactor recruitment [PMID:1756728, PMID:9490409, PMID:8139556].","teleology":[{"year":1991,"claim":"Established that a single conserved MADS-box domain shared between SRF and yeast MCM1 carries out dimerization, CArG-type DNA binding, and ternary complex formation, and that distinct residues within this domain select different accessory cofactors — defining the structural basis for combinatorial control.","evidence":"In vitro gel retardation with chimeric domain swaps and site-directed mutagenesis (SRF/MCM1/ARG80)","pmids":["1756729","1756728"],"confidence":"High","gaps":["Mapped in chimeras/orthologs rather than full-length human SRF in vivo","Did not resolve atomic-level contacts of SRF itself with cofactors"]},{"year":1992,"claim":"Defined the DNA-binding specificity distinguishing SRF (CC(A/T)6GG) from MCM1 and identified the N-terminal basic region as the specificity determinant, clarifying how MADS factors read distinct operators.","evidence":"In vitro binding-site selection, interference footprinting, comparative affinity assays","pmids":["1630900","1732062"],"confidence":"High","gaps":["Specificity defined largely through MCM1 comparison","Genome-wide occupancy not addressed at this stage"]},{"year":1992,"claim":"Localized the TCF cofactor's DNA-binding and SRF-interaction functions, showing the Elk-1 ETS domain binds DNA directly while a flanking region (137-169) is required for ternary complex assembly, separating intrinsic DNA contact from SRF-assisted recruitment.","evidence":"In vitro gel retardation with Elk-1 deletion and point mutants at the c-fos SRE","pmids":["1630903"],"confidence":"High","gaps":["Did not link assembly to upstream MAPK signaling biochemically","Single-target (c-fos) context"]},{"year":1993,"claim":"Extended the TCF/p62 class beyond Elk-1 by identifying SAP-1 as an SRF accessory protein with conserved MAP kinase phosphorylation sites, anchoring the signal-responsive arm of SRF regulation.","evidence":"Yeast genetic screen plus in vitro ternary complex assays","pmids":["8103935"],"confidence":"Medium","gaps":["Single lab; phosphorylation sites inferred from sequence","Direct kinase-dependence not demonstrated here"]},{"year":1998,"claim":"Provided atomic-resolution evidence for how a MADS factor organizes a partner on DNA, showing MCM1-induced bending and a beta-hairpin grip that fix cofactor geometry — a structural paradigm for SRF ternary complexes.","evidence":"X-ray crystallography of yeast MATalpha2/MCM1/DNA at 2.25 Å","pmids":["9490409"],"confidence":"High","gaps":["Structure is of the yeast ortholog, not SRF","Does not capture MRTF or TCF complexes directly"]},{"year":2000,"claim":"Demonstrated that SRF is required for context-dependent mesodermal gene expression but acts non-cell-autonomously, refining its developmental role beyond a strict cell-intrinsic requirement.","evidence":"Conditional Srf-null ES cells with retinoic acid and re-expression rescue plus teratoma assays","pmids":["11060034"],"confidence":"High","gaps":["Mechanism of non-cell-autonomy not resolved","Specific SRF targets in mesoderm not defined here"]},{"year":2004,"claim":"Identified direct SRF survival and contractile targets — Bcl-2 (required for ES cell survival) and the FHL2 feedback antagonist — establishing both an anti-apoptotic role and a built-in negative autoregulatory loop on RhoA-induced genes.","evidence":"ChIP, luciferase reporters, genetic rescue (Bcl-2), co-IP and competitive binding (FHL2)","pmids":["15057274","15610731"],"confidence":"High","gaps":["FHL2 antagonism restricted to a target subset; generality unclear","Bcl-2 dependence shown in ES cells specifically"]},{"year":2009,"claim":"Connected the MRTF/SRF axis to cancer cell motility and metastasis, identifying MYH9 and MYL9 as MRTF-dependent SRF targets required for invasion and lung colonization, distinguishing a motility function from proliferation.","evidence":"RNAi, xenograft and lung-colonization assays, expression profiling in carcinoma and melanoma cells","pmids":["19198601"],"confidence":"High","gaps":["Did not address TCF contribution to the same targets","Mechanism of MYH9/MYL9 in colonization not fully dissected"]},{"year":2011,"claim":"Showed SRF-driven actin gene expression is required to build the cortical actomyosin network controlling mitotic rounding, spindle orientation, and asymmetric division in epidermis, linking SRF transcription to cell-shape mechanics.","evidence":"Conditional epidermal Srf KO, low-dose actin inhibitors in vivo, shRNA, phospho-ERM/myosin-IIA imaging","pmids":["21336301"],"confidence":"High","gaps":["Did not isolate which cofactor (MRTF vs TCF) drives the cortical program","Specific actin target genes not individually rescued"]},{"year":2013,"claim":"Defined SRF as essential for endothelial tip-cell filopodia and contractility during sprouting angiogenesis downstream of VEGF-induced MRTF nuclear accumulation, with Myl9 as a key migration target.","evidence":"Inducible endothelial Srf KO, retinal angiogenesis, VEGF stimulation, MRTF imaging, migration assays","pmids":["23674601"],"confidence":"High","gaps":["Vascular remodeling left intact — branch-point selectivity unexplained","Tip- vs stalk-cell specificity of MRTF activation not detailed"]},{"year":2014,"claim":"Identified GSK-3 as a direct SRF kinase phosphorylating a conserved serine required selectively for MKL/MRTF (not ELK-1) interaction and for axon growth, revealing a phosphorylation switch that biases cofactor choice.","evidence":"In vitro kinase assay, co-IP, site mutagenesis, shRNA, constitutively active SRF rescue in hippocampal neurons","pmids":["24623780"],"confidence":"High","gaps":["Precise serine residue position not stated here","Whether the same site operates outside neurons untested"]},{"year":2015,"claim":"Demonstrated SRF/MRTF directly maintain endothelial junctional and basement-membrane genes (Claudins, ZO, VE-cadherin, Collagen IV) such that their loss causes blood-brain-barrier breakdown and hemorrhage, broadening SRF's role to barrier integrity.","evidence":"Conditional endothelial Srf and Mrtf KO, in vivo MRI, immunofluorescence, expression analysis","pmids":["26221020"],"confidence":"High","gaps":["Direct CArG occupancy of each junctional gene not individually mapped","Relative MRTF vs TCF contribution not parsed"]},{"year":2016,"claim":"Established TCFs as genome-wide general antagonists of MRTF-dependent SRF transcription via direct competition for SRF, defining the molecular logic balancing proliferative versus contractile/invasive programs.","evidence":"TCF triple inactivation in MEFs, SRF ChIP-seq, Hi-C, RNA-seq, competition assays","pmids":["27867007"],"confidence":"High","gaps":["Performed in MEFs; cell-type generality of the >700 target set unknown","Does not resolve how signaling sets the competitive equilibrium dynamically"]},{"year":2017,"claim":"Connected SRF to fusion machinery and tumor metastasis: SRF controls myoblast fusion through actin-based protrusions (rescued by α-actin) and drives MYH9 in gastric cancer under miR-647 control.","evidence":"Satellite-cell Srf KO with α-actin rescue and live imaging; ChIP, 3'UTR reporters, orthotopic GC models","pmids":["29269426","28900514"],"confidence":"High","gaps":["Fusion-site protrusion mechanism downstream of actin not fully defined","miR-647/SRF axis confidence is moderate (single lab)"]},{"year":2018,"claim":"Revealed SRF cofactor regulation by acetylation/chromatin and crosstalk with hedgehog: HDAC6 controls MRTF-A acetylation and stability, and SRF-MKL1 forms a complex with GLI1 to amplify hedgehog target transcription in a Rho/mDia-dependent manner.","evidence":"Co-IP, HDAC6 inhibition/knockdown, SRF reporter, carotid injury model; BCC genomics, ChIP, SRF-MKL1-GLI1 co-IP","pmids":["30623138","29400712"],"confidence":"Medium","gaps":["Both single-lab Co-IP-based mechanisms","SRF-MKL1-GLI1 complex stoichiometry and DNA architecture unresolved"]},{"year":2020,"claim":"Expanded cofactor-activation inputs by showing exercise phosphorylates MRTF-B to drive nuclear entry and Fos induction, with parallel MSK1/2-dependent H3S10 phosphorylation at SRF target loci coupling SRF transcription to protein synthesis.","evidence":"Phosphoproteomics in exercised mice, MSK1/2 KO, H3S10p ChIP, human muscle biopsies","pmids":["32408395"],"confidence":"Medium","gaps":["MRTF-B phosphosite identity and kinase not fully defined","Single lab"]},{"year":2020,"claim":"Identified SUMOylation at SRF K143 as a switch redirecting SRF from a myocardin (contractile) to an ELK1 (synthetic) complex and altering its subcellular distribution, mechanistically linking SENP1 to vascular remodeling.","evidence":"VSMC-specific Senp1 KO, K143 mutagenesis, SRF complex co-IP, fractionation, ELK inhibitor","pmids":["39134547"],"confidence":"High","gaps":["How SUMO physically biases TCF over myocardin docking not structurally resolved","Lysosomal SRF localization mechanism unclear"]},{"year":2021,"claim":"Placed MRTF-A/SRF directly downstream of sarcomere integrity in cardiomyocyte maturation: sarcomere disorganization raises monomeric actin that sequesters MRTF-A and blocks SRF, with dominant-negative MRTF-A phenocopying Srf loss.","evidence":"Cardiomyocyte Actn2 mutant and Srf KO mice, G/F-actin fractionation, dominant-negative MRTF-A, MRTF imaging, transcriptomics","pmids":["33361330"],"confidence":"High","gaps":["Specific maturation target genes not individually validated","Quantitative actin-pool threshold for SRF off-state undefined"]},{"year":2022,"claim":"Demonstrated additional cytoplasmic gatekeepers and outputs of MRTF-A/SRF: ERK-phosphorylated cofilin-1 sequesters MRTF-A in LMNA-mutant cardiomyopathy (lowering ATAT1 and tubulin acetylation), and the actin-MRTF-A/SRF cascade transduces ECM mechanical cues to set circadian period via Per2/Nr1d1/Nfil3.","evidence":"Co-IP, MRTF imaging, Atat1 KO, tubastatin A; Srf/Mrtfa KO, circadian reporters, ChIP, integrin/FAK inhibition","pmids":["36550158","36093830"],"confidence":"Medium","gaps":["Both single-lab mechanisms","Direct CArG occupancy of clock genes shown but signaling kinetics incomplete"]},{"year":2022,"claim":"Established SRF as the effector of PDGFRB signaling in mural cells, directing pericyte migration via MRTF and maintaining VSMC contractile machinery, with loss causing arteriovenous shunts.","evidence":"Inducible mural-cell Srf KO, retinal angiogenesis, RNA-seq, live imaging, PDGFB-stimulated MRTF-SRF reporter","pmids":["35862101"],"confidence":"High","gaps":["Direct pericyte migration target genes not individually validated","Shunt-formation mechanism not fully mapped to specific targets"]},{"year":null,"claim":"How the MRTF/TCF competitive equilibrium, multiple post-translational modifications (GSK-3 phosphorylation, K143 SUMOylation, cofactor acetylation), and cytoplasmic actin/cofilin sequestration are integrated in real time on a given promoter to select a transcriptional output remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model of SRF-MRTF vs SRF-TCF complexes on DNA","Quantitative rules linking signaling state to cofactor choice undefined","Cross-talk between modifications (SUMO, phospho, acetyl) not jointly tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,2,17,27,39]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[17,27,36]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,33,34]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[27,33]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[17,27,36]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[20,24,36,40]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[13,23,24,29,36]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[17]},{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[38]}],"complexes":["SRF-MRTF/myocardin complex","SRF-TCF (Elk-1/SAP-1) ternary complex","SRF-MKL1-GLI1 complex"],"partners":["MRTF-A/MKL1","MRTF-B/MKL2","ELK1","SAP-1","FHL2","GSK-3","GLI1","MYOCARDIN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P11831","full_name":"Serum response factor","aliases":[],"length_aa":508,"mass_kda":51.6,"function":"SRF is a transcription factor that binds to the serum response element (SRE), a short sequence of dyad symmetry located 300 bp to the 5' of the site of transcription initiation of some genes (such as FOS). Together with MRTFA transcription coactivator, controls expression of genes regulating the cytoskeleton during development, morphogenesis and cell migration. The SRF-MRTFA complex activity responds to Rho GTPase-induced changes in cellular globular actin (G-actin) concentration, thereby coupling cytoskeletal gene expression to cytoskeletal dynamics. Required for cardiac differentiation and maturation","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P11831/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/SRF","classification":"Common Essential","n_dependent_lines":792,"n_total_lines":1208,"dependency_fraction":0.6556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SRF","total_profiled":1310},"omim":[{"mim_id":"621503","title":"LEUCINE-RICH REPEAT-CONTAINING PROTEIN 39; LRRC39","url":"https://www.omim.org/entry/621503"},{"mim_id":"621499","title":"CRANIOSYNOSTOSIS-SCOLIOSIS SYNDROME; CRSS","url":"https://www.omim.org/entry/621499"},{"mim_id":"621305","title":"CARDIAC MESODERM ENHANCER-ASSOCIATED NONCODING RNA; CARMN","url":"https://www.omim.org/entry/621305"},{"mim_id":"621260","title":"SHORT-RIB THORACIC DYSPLASIA 22 WITHOUT POLYDACTYLY; SRTD22","url":"https://www.omim.org/entry/621260"},{"mim_id":"620457","title":"AURICULOCONDYLAR SYNDROME 4; ARCND4","url":"https://www.omim.org/entry/620457"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SRF"},"hgnc":{"alias_symbol":["MCM1"],"prev_symbol":[]},"alphafold":{"accession":"P11831","domains":[{"cath_id":"3.40.1810.10","chopping":"153-218","consensus_level":"high","plddt":97.8709,"start":153,"end":218}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P11831","model_url":"https://alphafold.ebi.ac.uk/files/AF-P11831-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P11831-F1-predicted_aligned_error_v6.png","plddt_mean":51.97},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SRF","jax_strain_url":"https://www.jax.org/strain/search?query=SRF"},"sequence":{"accession":"P11831","fasta_url":"https://rest.uniprot.org/uniprotkb/P11831.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P11831/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P11831"}},"corpus_meta":[{"pmid":"1748287","id":"PMC_1748287","title":"Human SRF-related proteins: DNA-binding 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Substitution of three specific residues in ARG80 with SRF equivalents (positions 198, 200, 203) conferred p62TCF recruitment, and substitution of four SRF residues with MCM1 equivalents (positions 73, 75, 77, 78) conferred STE12 recruitment, identifying specific amino acids within the shared domain that mediate distinct protein-protein interactions.\",\n      \"method\": \"In vitro gel retardation assays, chimeric protein domain swapping, site-directed mutagenesis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in vitro with mutagenesis and domain-swap experiments identifying specific residues; replicated across multiple constructs\",\n      \"pmids\": [\"1756729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The N-terminal 98-amino-acid MADS-box domain of MCM1 (ortholog sharing 70% identity with SRF DNA-binding domain) is sufficient for DNA binding, dimerization, viability, and physical interaction with cofactors alpha1, alpha2, and STE12; a ~50 amino acid sub-region within this domain provides contacts with all three cofactors.\",\n      \"method\": \"In vitro binding studies with deletion constructs, in vivo reporter assays, yeast complementation\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in vitro combined with in vivo functional assays; multiple deletion and hybrid constructs tested\",\n      \"pmids\": [\"1756728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"SRF and MCM1 have related but distinct DNA-binding specificities: MCM1 selects a consensus (NotC)CCY(A/T)(A/T)(T/A)NN(A/G)G, distinct from the SRF consensus CC(A/T)6GG. Differences in specificity map largely to the N-terminal basic portion of their respective DNA-binding domains.\",\n      \"method\": \"In vitro selection of binding sites from random oligonucleotides, carboxylethylation interference analysis, comparative binding affinity assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro binding site selection with interference footprinting and comparative affinity measurements; multiple orthogonal methods in one study\",\n      \"pmids\": [\"1630900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"MCM1 sets the precise spacing and orientation of alpha2 homeodomain dimers on DNA: alpha2 dimers alone bind inverted, direct, and everted repeat arrangements with equal affinity, but MCM1 restricts binding to only the naturally occurring operator geometry, thereby raising target specificity of the homeodomain protein.\",\n      \"method\": \"In vitro DNA binding assays with artificial operators containing half-sites in different arrangements, affinity measurements\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with defined synthetic DNA substrates demonstrating mechanistic basis for specificity; multiple orthogonal binding conditions tested\",\n      \"pmids\": [\"1732062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"The Elk-1 ETS domain is necessary and sufficient for direct DNA binding, while both the ETS domain and flanking sequences up to amino acid 169 (including a protein-protein interaction region spanning residues 137–169) are required for ternary complex formation with SRF at the c-fos serum response element. A single amino acid substitution in the ETS domain can dramatically alter direct DNA-binding affinity without severely affecting SRF-assisted binding.\",\n      \"method\": \"In vitro gel retardation assays with Elk-1 deletion and point-mutant constructs\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic deletion and point mutagenesis with in vitro binding reconstitution; multiple mutant constructs tested in one study\",\n      \"pmids\": [\"1630903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"SAP-1 (isolated by yeast genetic screen) and Elk-1 both function as SRF accessory proteins (p62/TCF class) that form ternary complexes with SRF at the serum response element; only two of the three Elk-1-homologous regions in SAP-1 are required for cooperative interactions with SRF, while the third contains conserved MAP kinase phosphorylation sites.\",\n      \"method\": \"Yeast genetic screen for cDNAs with p62/TCF DNA-binding properties, gel retardation ternary complex assays, sequence analysis of conserved phosphorylation sites\",\n      \"journal\": \"Philosophical transactions of the Royal Society of London. Series B, Biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast screen plus in vitro ternary complex assays; single lab but two methods\",\n      \"pmids\": [\"8103935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Crystal structure of yeast MATalpha2/MCM1/DNA ternary complex at 2.25 Å reveals that the otherwise flexible N-terminal extension of the alpha2 homeodomain forms a beta-hairpin gripping the MCM1 surface via parallel beta-strand hydrogen bonds and hydrophobic side chains; MCM1-induced DNA bending brings the two proteins closer, facilitating their interaction. A 'chameleon' sequence in alpha2 adopts alpha-helical conformation in one monomer and beta-strand in the other.\",\n      \"method\": \"X-ray crystallography at 2.25 Å resolution\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution crystal structure directly revealing protein-protein and protein-DNA contacts\",\n      \"pmids\": [\"9490409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MCM1 uses a DNA-contact mechanism distinct from SRF: 5-bromouracil photo-cross-linking shows MCM1 contacts the major groove at the center of its recognition site (not observed for SRF), and Mcm1-dependent DNA bending requires bases outside the conserved CC(A/T)6GG site that do not affect SRF bending, indicating DNA bending by Mcm1 is sequence-dependent and transcriptionally important even when binding affinity is minimally affected.\",\n      \"method\": \"5-bromouracil-mediated photo-cross-linking, gel retardation with extensive base-pair substitution series, in vivo transcriptional reporter assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biochemical methods (cross-linking, binding, bending, transcription) in one study\",\n      \"pmids\": [\"9121436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Mcm1 is phosphorylated in vivo at multiple sites (>8 isoforms by isoelectric focusing), with two major phosphorylation sites in the N-terminal 17 amino acids adjacent to the MADS-box. A unique Mcm1 isoform is induced by osmotic stress (NaCl or KCl), establishing that Mcm1 itself is a target of osmotic stress signal transduction; deletion of the N-terminus or mutation of the primary phosphorylation site impairs growth on high-salt medium.\",\n      \"method\": \"Isoelectric focusing of in vivo-labeled protein, deletion and point mutant analysis on high-salt medium, induction experiments with NaCl/KCl\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo phosphorylation detected by IEF with supporting genetic evidence; single lab, two orthogonal methods\",\n      \"pmids\": [\"9001236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Specific residues within the MCM1 MADS-box domain (positions 69–81) mediate interaction with alpha1 and STE12 cofactors (a subset also affecting STE12 binding), while interaction with alpha2 requires a distinct mechanism, as nonconservative substitutions at alpha2-contact residues do not significantly affect alpha2-mediated repression. Most lethal mutations affect DNA-binding affinity, and lethality of many such mutations is suppressed by high-copy MCM1.\",\n      \"method\": \"In vitro DNA-binding cooperative binding assays, in vivo reporter gene assays, alanine-scanning mutagenesis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic point mutagenesis combined with in vitro cooperative binding assays and in vivo reporters; comprehensive mutant series\",\n      \"pmids\": [\"8139556\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"A hydrophobic patch in the region preceding the alpha2 homeodomain mediates direct protein-protein interaction with Mcm1 (in the absence of DNA), is required for cooperative DNA binding in vitro and transcriptional repression in vivo. A conserved YPWM motif found in homeodomain proteins of insects and mammals can partially substitute for this patch in alpha2, suggesting evolutionary conservation of the interaction mechanism.\",\n      \"method\": \"In vitro cooperative DNA-binding assays with alpha2 mutants, in vivo repression assays, comparison with heterologous YPWM-containing peptides\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — domain identification by mutagenesis with in vitro reconstitution and in vivo validation; cross-species comparison\",\n      \"pmids\": [\"8628280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"In Saccharomyces cerevisiae arginine metabolism, the putative alpha-helix within the MADS-box domain of Mcm1 (and ArgRI) is its primary interaction surface with ArgRIII. Purified GST-ArgRI and ArgRII1-180, or Mcm1 and ArgRII1-180, reconstitute an arginine-dependent DNA-binding activity in mobility shift analysis; ArgRIII stability is required for Mcm1 stability and Mcm1-dependent gene expression.\",\n      \"method\": \"Yeast two-hybrid, affinity chromatography with purified proteins, in vitro EMSA reconstitution, in vivo gene expression assays\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of complex from purified components combined with affinity chromatography and in vivo assays; multiple orthogonal methods\",\n      \"pmids\": [\"10632874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ArgRII (zinc cluster protein) is the arginine sensor in the ArgR-Mcm1 complex: purified ArgRI and ArgRII1-180 (or Mcm1 and ArgRII1-180) reconstitute arginine-dependent DNA binding in EMSA, and the arginine-binding site maps to the region downstream of ArgRII's zinc cluster domain, sharing identity with bacterial arginine repressor arginine-binding domains.\",\n      \"method\": \"In vitro EMSA reconstitution with purified recombinant proteins, arginine-dependence assays, domain deletion analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical reconstitution from purified components with defined domain requirements; arginine-dependence directly tested\",\n      \"pmids\": [\"10688655\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"SRF-null (Srf−/−) embryonic stem cells show impaired mesodermal differentiation in vitro (failure to activate T/Brachyury), but this impairment is non-cell-autonomous: retinoic acid rescues T activation, SRF re-expression rescues differentiation, and in nude mice Srf−/− ES cells readily form mesodermal derivatives, demonstrating that SRF contributes to mesodermal gene expression in a context-dependent manner.\",\n      \"method\": \"Conditional Srf knockout ES cells, in vitro differentiation assays, retinoic acid rescue, teratoma formation in nude mice\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple rescue conditions and in vivo complementation; replicated across several experimental contexts\",\n      \"pmids\": [\"11060034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Mcm1 alanine substitutions in the MADS-box reveal that interaction with alpha2 requires different residues than interaction with alpha1 or Ste12 cofactors: most mutations affecting alpha1/Ste12 binding do not affect alpha2-mediated repression, indicating distinct interaction surfaces within the same domain for different cofactors.\",\n      \"method\": \"Systematic alanine-scanning mutagenesis of MADS-box, in vivo transcriptional reporter assays, in vitro DNA-binding assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic mutagenesis with in vitro binding and in vivo transcription assays; comprehensive mutant series\",\n      \"pmids\": [\"12052870\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mcm7 (MCM helicase subunit) acts as a novel cofactor of Mcm1 in transcriptional regulation: Mcm7 stimulates Mcm1 binding to early cell cycle box (ECB) elements upstream of MCM7, CDC6, and MCM5 promoters; Mcm7 is recruited to these promoters during late M phase while Mcm1 binds constitutively, suggesting Mcm7 modulates periodic expression of early cell cycle genes through Mcm1.\",\n      \"method\": \"Gel retardation assays with purified proteins, chromatin immunoprecipitation, in vivo reporter assays, analysis of mcm7 and mcm1 mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus in vitro binding reconstitution; single lab, two methods\",\n      \"pmids\": [\"12738768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Mcm1 associates globally with chromatin in a punctate pattern, binds cooperatively to multiple sites at autonomously replicating sequences (ARS), and is localized at replication origins in vivo, supporting a direct role for Mcm1 in replication initiation beyond transcriptional regulation of replication genes.\",\n      \"method\": \"Chromatin immunoprecipitation, in vivo chromatin association assay, in vitro binding with purified Mcm1, loss-of-function analysis at chromosomal origin\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus in vitro binding; single lab, two orthogonal methods\",\n      \"pmids\": [\"12473677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"SRF directly binds the Bcl-2 promoter in vivo (ChIP) and activates Bcl-2 transcription; reconstitution of Bcl-2 in Srf−/− ES cells rescues apoptosis, demonstrating that SRF-dependent Bcl-2 expression is required for ES cell survival. SRF deficiency also impairs Bcl-xl expression and leads to inappropriate apoptosis in embryoid bodies and pre-gastrulation embryos.\",\n      \"method\": \"Chromatin immunoprecipitation, luciferase reporter assays, genetic rescue (Bcl-2 re-expression in Srf−/− ES cells), apoptosis assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP demonstrating direct promoter binding plus genetic rescue experiment; multiple orthogonal methods in one study\",\n      \"pmids\": [\"15057274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FHL2, an SRF target gene, physically interacts with SRF protein and binds promoters of SRF-responsive smooth muscle genes (but not immediate-early gene promoters) in response to RhoA activation. FHL2 antagonizes smooth muscle gene induction by competing with MAL/MRTF-A for SRF binding, creating a negative autoregulatory feedback loop selectively controlling a subset of RhoA-activated SRF targets.\",\n      \"method\": \"Large-scale expression profiling, co-immunoprecipitation, chromatin immunoprecipitation, RhoA activation assays, competitive binding assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP plus ChIP demonstrating in vivo promoter occupancy plus functional competition assays; multiple orthogonal methods\",\n      \"pmids\": [\"15610731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Alpha1 cofactor increases the DNA bend induced by Mcm1 at alpha-specific gene binding sites; this enhanced bending is required for full transcriptional activation. Mcm1 binds alpha-specific gene promoters even in the absence of alpha1 (shown by ChIP), indicating alpha1's function extends beyond Mcm1 recruitment to modulating DNA architecture.\",\n      \"method\": \"Chromatin immunoprecipitation, circular permutation DNA-bending assays, in vivo transcriptional reporter assays with bending-defective mutants\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus DNA bending assays with functional validation; single lab, two orthogonal methods\",\n      \"pmids\": [\"15118075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Disruption of epithelial cell-cell junctions activates SRF-mediated transcription via a Rac1-monomeric actin-MAL/MRTF signaling axis in epithelial cells, distinct from the RhoA-dependent pathway in serum-stimulated fibroblasts. Using clostridial cytotoxins, Rac (but not RhoA) was shown to be required for SRF and target gene induction upon junction dissociation; actomyosin contractility is a prerequisite but not sufficient.\",\n      \"method\": \"RNAi knockdown, clostridial cytotoxin-mediated Rho GTPase inhibition, reporter gene assays, dominant-negative and constitutively active GTPase constructs\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and genetic manipulation of specific GTPases with reporter readout; single lab, multiple inhibitor approaches\",\n      \"pmids\": [\"18334560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"RNAi depletion of MRTFs or SRF in breast carcinoma and melanoma cells reduces cell adhesion, spreading, invasion, and motility (without affecting proliferation or inducing apoptosis); MRTF-depleted xenografts show reduced cell motility but normal proliferation. Depletion of MRTFs or SRF prevents lung colonization after intravenous injection. MYH9 (NMHCIIa) and MYL9 (MLC2) are identified as MRTF-dependent SRF target genes also required for invasion and lung colonization. Activated MAL/MRTF-A expression increases lung colonization by poorly metastatic cells.\",\n      \"method\": \"RNA interference, xenograft tumor models, intravital imaging, lung colonization assays, gene expression profiling\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi knockdown and gain-of-function in multiple cell lines with in vivo xenograft and colonization readouts; multiple orthogonal methods replicated in two cell types\",\n      \"pmids\": [\"19198601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In Alzheimer's disease patients and mouse models, SRF and myocardin are overexpressed in cerebral vascular smooth muscle cells; SRF/MYOCD overexpression transactivates SREBP-2, which downregulates LRP-1 (a key Abeta clearance receptor), generating an Abeta non-clearing VSMC phenotype. Hypoxia stimulates SRF/MYOCD expression in human cerebral VSMCs.\",\n      \"method\": \"Immunohistochemistry, overexpression studies in VSMCs, promoter/reporter assays for SREBP-2 transactivation, LRP-1 expression analysis, hypoxia experiments\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional overexpression with defined transcriptional readout; single lab with multiple cell-based methods\",\n      \"pmids\": [\"19098903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Conditional epidermal ablation of Srf in mice leads to reduced cortical actin network in basal cells, failure of mitotic cell rounding, altered phospho-ERM and cortical myosin-IIA distribution, and defects in spindle orientation, asymmetric cell divisions, stratification, and differentiation. Low-dose actin inhibitors in vivo and shRNA knockdown in vitro recapitulate the cortical network loss and rounding defects, linking Srf-driven actin gene expression to cortical actomyosin organization and mitotic shape changes.\",\n      \"method\": \"Conditional epidermal Srf knockout mice, low-dose actin inhibitor treatment in vivo, shRNA knockdown in vitro, immunofluorescence of phospho-ERM and myosin-IIA, spindle orientation measurements\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo combined with pharmacological and RNAi recapitulation; multiple orthogonal readouts across in vivo and in vitro systems\",\n      \"pmids\": [\"21336301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Inducible endothelial-specific deletion of Srf in postnatal mice abolishes filopodia formation and contractility in tip cells during sprouting angiogenesis, while leaving vascular remodeling intact. VEGF-A induces nuclear accumulation of MRTFs and regulates MRTF/SRF-dependent target genes including Myl9, which is required for endothelial cell migration in vitro.\",\n      \"method\": \"Inducible endothelial-specific Srf conditional KO mice, retinal angiogenesis assays, VEGF stimulation, MRTF nuclear localization imaging, in vitro migration assays\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo with defined cellular phenotype plus VEGF-MRTF-SRF pathway dissection; multiple methods\",\n      \"pmids\": [\"23674601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"GSK-3 directly phosphorylates SRF on a highly conserved serine residue and binds SRF; this serine phosphorylation is required for SRF transcriptional activity and for SRF's interaction with MKL-family cofactors (MKL1 and MKL2) but not with TCF cofactor ELK-1. Axonal growth deficits from GSK-3 inhibition are rescued by constitutively active SRF; the SRF target gene vinculin is sufficient to overcome axonal growth deficits of SRF-deficient and GSK-3-inhibited neurons.\",\n      \"method\": \"In vitro kinase assay, co-immunoprecipitation of GSK-3/SRF, site-directed mutagenesis of phosphorylation site, shRNA knockdown, constitutively active SRF rescue, axon outgrowth assays in hippocampal neurons\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay plus mutagenesis plus co-IP plus genetic rescue in neurons; multiple orthogonal methods in one study\",\n      \"pmids\": [\"24623780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Endothelial-specific depletion of SRF or MRTF-A/-B in mice causes loss of blood-brain barrier integrity and intracerebral hemorrhagic stroke. At the molecular level, SRF/MRTF directly regulate expression of tight junction components (Claudins, ZO proteins), adherens junction components (VE-cadherin, α-Actinin), and basement membrane constituents (Collagen IV), which are downregulated upon SRF depletion.\",\n      \"method\": \"Conditional endothelial-specific Srf and Mrtf knockout mice, in vivo MRI for hemorrhage detection, immunofluorescence, gene expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo with defined molecular targets, replicated with SRF and MRTF knockouts; in vivo imaging confirmation\",\n      \"pmids\": [\"26221020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TCF (ternary complex factor) cofactors act as general antagonists of MRTF-dependent SRF target gene expression by competing directly with MRTFs for access to SRF. TCF inactivation in MEFs inhibits >60% of TPA-inducible gene transcription and impairs cell proliferation; TCF-deficient MEFs exhibit hypercontractile and pro-invasive behavior. SRF ChIP-seq combined with Hi-C identifies over 700 TCF-dependent SRF direct target genes.\",\n      \"method\": \"TCF triple inactivation in MEFs, ChIP-seq, Hi-C, RNA-seq, competitive binding assays between TCFs and MRTFs for SRF\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide ChIP-seq and Hi-C plus functional competition assays with genetic loss-of-function; multiple orthogonal methods\",\n      \"pmids\": [\"27867007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Serum response factor (SRF) binds to the CArG box in the MYH9 promoter and drives its expression; miR-647 directly binds the 3' UTR of SRF mRNA to suppress SRF levels, which in turn reduces MYH9 expression and suppresses gastric cancer metastasis.\",\n      \"method\": \"Luciferase 3'UTR reporter assays, ChIP for SRF at MYH9 promoter, overexpression/knockdown experiments, orthotopic GC mouse models\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating direct SRF-MYH9 promoter binding plus 3'UTR reporter validation; single lab, two orthogonal methods\",\n      \"pmids\": [\"28900514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Satellite cell-specific Srf deletion abolishes myoblast fusion (required in both fusion partners) without affecting proliferation or differentiation. Srf-null myoblasts lack actin-based finger-like protrusions at fusion sites. Overexpression of an α-actin isoform in Srf-null satellite cells restores actin polymerization and rescues fusion in vitro and in vivo, demonstrating that SRF controls myoblast fusion through maintenance of actin cytoskeleton architecture.\",\n      \"method\": \"Satellite cell-specific Srf conditional KO, live imaging of fusion sites, α-actin overexpression rescue, in vivo overload-induced hypertrophy model\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with genetic rescue in vivo and in vitro; multiple orthogonal readouts\",\n      \"pmids\": [\"29269426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SRF and its coactivator MKL1 bind DNA near hedgehog target genes and form a protein complex with the hedgehog transcription factor GLI1, amplifying GLI1 transcriptional activity. Cytoskeletal activation through Rho and the formin mDia is required for SRF-MKL-driven GLI1 activation. This constitutes a noncanonical hedgehog pathway enabling drug resistance in basal cell carcinomas.\",\n      \"method\": \"Multidimensional genomics of human/mouse BCCs, ChIP for SRF/MKL1 near hedgehog target genes, co-immunoprecipitation of SRF-MKL1-GLI1 complex, Rho/mDia inhibition experiments\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating SRF-MKL1-GLI1 complex plus ChIP and functional inhibitor studies; single lab, multiple methods\",\n      \"pmids\": [\"29400712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HDAC6 co-immunoprecipitates with MRTF-A and regulates its acetylation and protein level; HDAC6 inhibition (tubastatin A) or knockdown increases MRTF-A acetylation, total MRTF-A protein, and nuclear SRF transcriptional activity, preserving contractile gene (α-SMA) expression in VSMCs. This is the first demonstration of HDAC6 regulation of the MRTF-A/SRF axis.\",\n      \"method\": \"Co-immunoprecipitation, HDAC6 knockdown, pharmacological inhibition (tubastatin A), SRF luciferase reporter, in vivo rat carotid injury model\",\n      \"journal\": \"JACC. Basic to translational science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating HDAC6-MRTF-A interaction plus functional reporter and in vivo model; single lab\",\n      \"pmids\": [\"30623138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IGF2BP1 promotes SRF expression in cancer cells by binding SRF mRNA and impairing miRNA-directed decay in an m6A-dependent manner, resulting in enhanced SRF-dependent transcriptional activity and upregulation of SRF target genes (including PDLIM7 and FOXK1) that promote tumor cell growth and invasion.\",\n      \"method\": \"RNA immunoprecipitation, m6A sequencing, miRNA-reporter assays, RNAi knockdown, gene expression profiling\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP demonstrating IGF2BP1-SRF mRNA interaction plus m6A and functional assays; single lab, multiple methods\",\n      \"pmids\": [\"30371874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SENP1 deficiency in vascular smooth muscle cells increases SUMOylation of SRF at lysine 143, which reduces SRF lysosomal localization and increases nuclear accumulation, and switches the SRF complex from a contractile phenotype-responsive SRF-myocardin complex to a synthetic phenotype-responsive SRF-ELK1 complex, promoting vascular remodeling and neointimal formation.\",\n      \"method\": \"VSMC-specific Senp1 knockout mice, site-directed mutagenesis of SRF K143, co-immunoprecipitation of SRF complexes, subcellular fractionation, ELK inhibitor (AZD6244) treatment, neointima formation assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — site-specific mutagenesis identifying SUMOylation site combined with Co-IP of SRF complexes, KO mouse model, and pharmacological rescue; multiple orthogonal methods\",\n      \"pmids\": [\"39134547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Sarcomere disorganization (via Actn2 mutation) increases monomeric cardiac α-actin, which sequesters the SRF cofactor MRTF-A in the cytoplasm and prevents SRF activation. Overexpression of a dominant-negative MRTF-A mutant recapitulates the morphological and transcriptional defects of both Actn2 and Srf mutant cardiomyocytes, placing MRTF-A/SRF downstream of sarcomere integrity in the control of cardiomyocyte maturation.\",\n      \"method\": \"Cardiomyocyte-specific Actn2 mutant mice, Srf conditional KO, dominant-negative MRTF-A overexpression, G-actin/F-actin fractionation, MRTF-A nuclear localization imaging, transcriptomic analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO plus dominant-negative overexpression with epistasis; actin fractionation mechanistically linking sarcomere to MRTF-A/SRF; multiple orthogonal methods\",\n      \"pmids\": [\"33361330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In LMNA-mutant muscle cells, ERK1/2-phosphorylated cofilin-1 (at T25) binds MRTF-A in the cytoplasm, preventing MRTF-A nuclear entry and SRF stimulation. Reduced MRTF-A/SRF activity decreases expression of ATAT1 (α-tubulin acetyltransferase 1), leading to decreased α-tubulin acetylation and Connexin 43 mislocalization in cardiomyocytes, driving dilated cardiomyopathy.\",\n      \"method\": \"Co-immunoprecipitation of phospho-cofilin-1 with MRTF-A, MRTF-A nuclear localization imaging, Atat1 KO mice, tubastatin A treatment of Lmna mutant mice, Cx43 immunofluorescence, cardiac function measurements\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP demonstrating cofilin-1-MRTF-A interaction with phosphorylation-dependent mechanism; in vivo KO and pharmacological rescue; multiple orthogonal methods\",\n      \"pmids\": [\"36550158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Mural cell-specific inducible Srf deletion demonstrates that SRF directs pericyte migration downstream of PDGFRB signaling via MRTF cofactors (PDGFB-dependent SRF activation is MRTF-mediated), and is essential in VSMCs for expression of the contractile machinery; SRF deletion in VSMCs triggers arteriovenous shunt formation.\",\n      \"method\": \"Inducible mural cell-specific Srf KO mice, retinal angiogenesis assays, RNA-sequencing, in vivo live imaging, in vitro MRTF-SRF reporter assays with PDGFB stimulation, immunohistology\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO in vivo with defined pathway (PDGFB-MRTF-SRF) via reporter assays; RNA-seq plus imaging; multiple orthogonal methods\",\n      \"pmids\": [\"35862101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Exercise induces phosphorylation of a new site on MRTF-B (SRF cofactor), required for its nuclear translocation and subsequent transcription of SRF target gene Fos. High-intensity exercise also phosphorylates histone H3 at serine 10 at SRF target gene loci via MSK1/2; ablation of MSK1/2 prevents this histone phosphorylation, reduces SRF-target gene induction, and prevents increases in protein synthesis after exercise.\",\n      \"method\": \"Phosphoproteomics screen in exercised mice, MSK1/2 KO mice, chromatin immunoprecipitation (H3S10p), muscle biopsies from human exercise subjects\",\n      \"journal\": \"Acta physiologica (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphoproteomics plus ChIP and KO model; replicated in human samples; single lab\",\n      \"pmids\": [\"32408395\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The actin cytoskeleton-MRTF-A/SRF signaling cascade transduces extracellular matrix physical cues to modulate circadian clock function. Pharmacological or genetic inhibition of SRF or MRTF-A lengthens circadian period; actin polymerization shortens period. SRF-null or Mrtfa-null cells mimic actin-depolymerizing effects. Per2, Nr1d1, and Nfil3 are identified as direct transcriptional targets of MRTF-A/SRF that mediate the actin dynamics-induced clock response.\",\n      \"method\": \"Srf and Mrtfa conditional knockouts, pharmacological inhibition of ROCK/actin polymerization, circadian bioluminescence reporter assays, ChIP identifying Per2/Nr1d1/Nfil3 as direct MRTF-A/SRF targets, integrin/FAK inhibition\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus ChIP plus pharmacological dissection; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36093830\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SRF directly binds the frataxin (FXN) promoter (demonstrated by ChIP and EMSA); mutagenesis of the predicted SRF binding site significantly decreases FXN promoter activity; SRF overexpression significantly increases frataxin mRNA and protein levels in HEK293 and SH-SY5Y cells and in Friedreich ataxia patient lymphoblasts.\",\n      \"method\": \"Chromatin immunoprecipitation, electrophoretic mobility shift assay, site-directed mutagenesis of SRF binding site, luciferase reporter assays, SRF overexpression in cell lines and patient cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus EMSA plus mutagenesis plus overexpression; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20808827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"B cell receptor activation of SRF occurs via a Src-Syk-Tec-PLCγ-Ca2+ (Lyn-Syk-Btk-PLCγ-Ca2+) pathway. SRF responds to lower Ca2+ concentrations than NFAT and is less dependent on IP3R expression. Calcineurin plays a partial role in SRF activation (in combination with DAG), while calcineurin is fully required for NFAT. Both SRF and NFAT require Rac, Rho, CDC42, and actin; SRF but not NFAT is independent of JNK.\",\n      \"method\": \"Pharmacological and dominant-negative inhibition of signaling components, calcium chelation, IP3R-deficient cell lines, reporter assays for SRF and NFAT\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic pharmacological/genetic pathway dissection with reporter assays; single lab, multiple inhibitor/genetic conditions\",\n      \"pmids\": [\"12912915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The SRF gene is activated by serum/LPA through a bipartite promoter mechanism requiring both an Sp1-factor binding site (targeted by Ras signaling) and CArG box motifs (targeted by Rho-mediated signals), demonstrating that SRF auto-regulates its own transcription through its CArG binding sites.\",\n      \"method\": \"Promoter-reporter assays with mutated SRE/CArG and Sp1 sites, LPA and serum stimulation, dominant-negative Ras and Rho constructs\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-directed mutagenesis of promoter elements with pathway-specific dominant-negative constructs; single lab\",\n      \"pmids\": [\"10602487\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SRF is a dimeric MADS-box transcription factor that binds CC(A/T)6GG (CArG box) sequences and functions as a transcriptional hub regulated by two competing families of cofactors: MRTF/myocardin-family proteins (activated by Rho-dependent actin polymerization, which releases G-actin-sequestered MRTFs to translocate to the nucleus and activate SRF-driven cytoskeletal/contractile gene programs) and TCF/ternary complex factors such as Elk-1 and SAP-1 (activated by MAP kinase/ERK signaling to drive immediate-early and proliferative gene programs); competition between MRTFs and TCFs for SRF binding determines the balance between contractile and proliferative transcriptional programs, while SRF activity is further modulated by SUMOylation (at K143, switching SRF between myocardin and ELK1 complexes), GSK-3-mediated phosphorylation (required for MKL cofactor interaction and axon growth), and by autoregulation of the SRF gene itself through Ras/Sp1 and Rho/CArG pathways.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SRF is a MADS-box transcription factor that binds CArG box (CC(A/T)6GG) sequences and serves as a transcriptional hub controlling cytoskeletal, contractile, and immediate-early gene programs [#2, #27]. Its conserved 90-residue MADS-box domain is sufficient for dimerization, DNA binding, and assembly of ternary complexes with accessory proteins, with discrete residue sets within this single domain mediating recruitment of distinct cofactor classes [#0]. SRF activity is governed by competition between two cofactor families that dock on this domain: ternary complex factors (TCFs) such as Elk-1 and SAP-1, whose ETS domains and flanking interaction regions form ternary complexes at the c-fos serum response element and drive proliferative, MAP-kinase-responsive transcription [#4, #5, #27], and the MRTF/myocardin family, which couples SRF to actin dynamics — actin polymerization releases G-actin-sequestered MRTFs for nuclear entry to activate cytoskeletal and contractile targets, and TCFs act as general antagonists of MRTF-dependent SRF transcription by competing for SRF access [#27, #34]. This actin-MRTF-SRF axis transduces diverse upstream signals — RhoA in serum-stimulated fibroblasts, Rac1 upon epithelial junction disruption, VEGF in endothelial tip cells, and PDGFRB in pericytes [#20, #24, #36] — into programs that build cortical and contractile actin architecture, demonstrated by SRF requirements for mitotic cell rounding and spindle orientation in epidermis, myoblast fusion, angiogenic filopodia, and blood-brain-barrier integrity, all rescuable through restoration of actin-cytoskeletal targets [#23, #29, #24, #26]. SRF additionally directly activates survival and contractile target genes including Bcl-2, MYH9/MYL9, FHL2, and frataxin [#17, #21, #18, #39], and FHL2 feeds back as an MRTF-competing antagonist of a subset of RhoA-induced targets [#18]. SRF output is further tuned by post-translational control: GSK-3 phosphorylates a conserved serine required for MKL/MRTF (but not ELK-1) interaction and axon growth [#25], and SUMOylation at K143 switches SRF between myocardin and ELK1 complexes to toggle contractile versus synthetic phenotypes in vascular smooth muscle [#33]. SRF also autoregulates its own gene through Sp1/Ras and CArG/Rho promoter elements [#41]. Much of the detailed structural and cofactor-residue mechanism derives from the yeast ortholog MCM1, which shares the MADS-box and analogous combinatorial cofactor recruitment [#1, #6, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 1991,\n      \"claim\": \"Established that a single conserved MADS-box domain shared between SRF and yeast MCM1 carries out dimerization, CArG-type DNA binding, and ternary complex formation, and that distinct residues within this domain select different accessory cofactors — defining the structural basis for combinatorial control.\",\n      \"evidence\": \"In vitro gel retardation with chimeric domain swaps and site-directed mutagenesis (SRF/MCM1/ARG80)\",\n      \"pmids\": [\"1756729\", \"1756728\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mapped in chimeras/orthologs rather than full-length human SRF in vivo\", \"Did not resolve atomic-level contacts of SRF itself with cofactors\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Defined the DNA-binding specificity distinguishing SRF (CC(A/T)6GG) from MCM1 and identified the N-terminal basic region as the specificity determinant, clarifying how MADS factors read distinct operators.\",\n      \"evidence\": \"In vitro binding-site selection, interference footprinting, comparative affinity assays\",\n      \"pmids\": [\"1630900\", \"1732062\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specificity defined largely through MCM1 comparison\", \"Genome-wide occupancy not addressed at this stage\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Localized the TCF cofactor's DNA-binding and SRF-interaction functions, showing the Elk-1 ETS domain binds DNA directly while a flanking region (137-169) is required for ternary complex assembly, separating intrinsic DNA contact from SRF-assisted recruitment.\",\n      \"evidence\": \"In vitro gel retardation with Elk-1 deletion and point mutants at the c-fos SRE\",\n      \"pmids\": [\"1630903\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not link assembly to upstream MAPK signaling biochemically\", \"Single-target (c-fos) context\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Extended the TCF/p62 class beyond Elk-1 by identifying SAP-1 as an SRF accessory protein with conserved MAP kinase phosphorylation sites, anchoring the signal-responsive arm of SRF regulation.\",\n      \"evidence\": \"Yeast genetic screen plus in vitro ternary complex assays\",\n      \"pmids\": [\"8103935\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; phosphorylation sites inferred from sequence\", \"Direct kinase-dependence not demonstrated here\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Provided atomic-resolution evidence for how a MADS factor organizes a partner on DNA, showing MCM1-induced bending and a beta-hairpin grip that fix cofactor geometry — a structural paradigm for SRF ternary complexes.\",\n      \"evidence\": \"X-ray crystallography of yeast MATalpha2/MCM1/DNA at 2.25 Å\",\n      \"pmids\": [\"9490409\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure is of the yeast ortholog, not SRF\", \"Does not capture MRTF or TCF complexes directly\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstrated that SRF is required for context-dependent mesodermal gene expression but acts non-cell-autonomously, refining its developmental role beyond a strict cell-intrinsic requirement.\",\n      \"evidence\": \"Conditional Srf-null ES cells with retinoic acid and re-expression rescue plus teratoma assays\",\n      \"pmids\": [\"11060034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of non-cell-autonomy not resolved\", \"Specific SRF targets in mesoderm not defined here\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified direct SRF survival and contractile targets — Bcl-2 (required for ES cell survival) and the FHL2 feedback antagonist — establishing both an anti-apoptotic role and a built-in negative autoregulatory loop on RhoA-induced genes.\",\n      \"evidence\": \"ChIP, luciferase reporters, genetic rescue (Bcl-2), co-IP and competitive binding (FHL2)\",\n      \"pmids\": [\"15057274\", \"15610731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"FHL2 antagonism restricted to a target subset; generality unclear\", \"Bcl-2 dependence shown in ES cells specifically\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected the MRTF/SRF axis to cancer cell motility and metastasis, identifying MYH9 and MYL9 as MRTF-dependent SRF targets required for invasion and lung colonization, distinguishing a motility function from proliferation.\",\n      \"evidence\": \"RNAi, xenograft and lung-colonization assays, expression profiling in carcinoma and melanoma cells\",\n      \"pmids\": [\"19198601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address TCF contribution to the same targets\", \"Mechanism of MYH9/MYL9 in colonization not fully dissected\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed SRF-driven actin gene expression is required to build the cortical actomyosin network controlling mitotic rounding, spindle orientation, and asymmetric division in epidermis, linking SRF transcription to cell-shape mechanics.\",\n      \"evidence\": \"Conditional epidermal Srf KO, low-dose actin inhibitors in vivo, shRNA, phospho-ERM/myosin-IIA imaging\",\n      \"pmids\": [\"21336301\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not isolate which cofactor (MRTF vs TCF) drives the cortical program\", \"Specific actin target genes not individually rescued\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined SRF as essential for endothelial tip-cell filopodia and contractility during sprouting angiogenesis downstream of VEGF-induced MRTF nuclear accumulation, with Myl9 as a key migration target.\",\n      \"evidence\": \"Inducible endothelial Srf KO, retinal angiogenesis, VEGF stimulation, MRTF imaging, migration assays\",\n      \"pmids\": [\"23674601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Vascular remodeling left intact — branch-point selectivity unexplained\", \"Tip- vs stalk-cell specificity of MRTF activation not detailed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified GSK-3 as a direct SRF kinase phosphorylating a conserved serine required selectively for MKL/MRTF (not ELK-1) interaction and for axon growth, revealing a phosphorylation switch that biases cofactor choice.\",\n      \"evidence\": \"In vitro kinase assay, co-IP, site mutagenesis, shRNA, constitutively active SRF rescue in hippocampal neurons\",\n      \"pmids\": [\"24623780\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise serine residue position not stated here\", \"Whether the same site operates outside neurons untested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrated SRF/MRTF directly maintain endothelial junctional and basement-membrane genes (Claudins, ZO, VE-cadherin, Collagen IV) such that their loss causes blood-brain-barrier breakdown and hemorrhage, broadening SRF's role to barrier integrity.\",\n      \"evidence\": \"Conditional endothelial Srf and Mrtf KO, in vivo MRI, immunofluorescence, expression analysis\",\n      \"pmids\": [\"26221020\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct CArG occupancy of each junctional gene not individually mapped\", \"Relative MRTF vs TCF contribution not parsed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established TCFs as genome-wide general antagonists of MRTF-dependent SRF transcription via direct competition for SRF, defining the molecular logic balancing proliferative versus contractile/invasive programs.\",\n      \"evidence\": \"TCF triple inactivation in MEFs, SRF ChIP-seq, Hi-C, RNA-seq, competition assays\",\n      \"pmids\": [\"27867007\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Performed in MEFs; cell-type generality of the >700 target set unknown\", \"Does not resolve how signaling sets the competitive equilibrium dynamically\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected SRF to fusion machinery and tumor metastasis: SRF controls myoblast fusion through actin-based protrusions (rescued by α-actin) and drives MYH9 in gastric cancer under miR-647 control.\",\n      \"evidence\": \"Satellite-cell Srf KO with α-actin rescue and live imaging; ChIP, 3'UTR reporters, orthotopic GC models\",\n      \"pmids\": [\"29269426\", \"28900514\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Fusion-site protrusion mechanism downstream of actin not fully defined\", \"miR-647/SRF axis confidence is moderate (single lab)\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed SRF cofactor regulation by acetylation/chromatin and crosstalk with hedgehog: HDAC6 controls MRTF-A acetylation and stability, and SRF-MKL1 forms a complex with GLI1 to amplify hedgehog target transcription in a Rho/mDia-dependent manner.\",\n      \"evidence\": \"Co-IP, HDAC6 inhibition/knockdown, SRF reporter, carotid injury model; BCC genomics, ChIP, SRF-MKL1-GLI1 co-IP\",\n      \"pmids\": [\"30623138\", \"29400712\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Both single-lab Co-IP-based mechanisms\", \"SRF-MKL1-GLI1 complex stoichiometry and DNA architecture unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Expanded cofactor-activation inputs by showing exercise phosphorylates MRTF-B to drive nuclear entry and Fos induction, with parallel MSK1/2-dependent H3S10 phosphorylation at SRF target loci coupling SRF transcription to protein synthesis.\",\n      \"evidence\": \"Phosphoproteomics in exercised mice, MSK1/2 KO, H3S10p ChIP, human muscle biopsies\",\n      \"pmids\": [\"32408395\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MRTF-B phosphosite identity and kinase not fully defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified SUMOylation at SRF K143 as a switch redirecting SRF from a myocardin (contractile) to an ELK1 (synthetic) complex and altering its subcellular distribution, mechanistically linking SENP1 to vascular remodeling.\",\n      \"evidence\": \"VSMC-specific Senp1 KO, K143 mutagenesis, SRF complex co-IP, fractionation, ELK inhibitor\",\n      \"pmids\": [\"39134547\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How SUMO physically biases TCF over myocardin docking not structurally resolved\", \"Lysosomal SRF localization mechanism unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed MRTF-A/SRF directly downstream of sarcomere integrity in cardiomyocyte maturation: sarcomere disorganization raises monomeric actin that sequesters MRTF-A and blocks SRF, with dominant-negative MRTF-A phenocopying Srf loss.\",\n      \"evidence\": \"Cardiomyocyte Actn2 mutant and Srf KO mice, G/F-actin fractionation, dominant-negative MRTF-A, MRTF imaging, transcriptomics\",\n      \"pmids\": [\"33361330\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific maturation target genes not individually validated\", \"Quantitative actin-pool threshold for SRF off-state undefined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated additional cytoplasmic gatekeepers and outputs of MRTF-A/SRF: ERK-phosphorylated cofilin-1 sequesters MRTF-A in LMNA-mutant cardiomyopathy (lowering ATAT1 and tubulin acetylation), and the actin-MRTF-A/SRF cascade transduces ECM mechanical cues to set circadian period via Per2/Nr1d1/Nfil3.\",\n      \"evidence\": \"Co-IP, MRTF imaging, Atat1 KO, tubastatin A; Srf/Mrtfa KO, circadian reporters, ChIP, integrin/FAK inhibition\",\n      \"pmids\": [\"36550158\", \"36093830\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Both single-lab mechanisms\", \"Direct CArG occupancy of clock genes shown but signaling kinetics incomplete\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established SRF as the effector of PDGFRB signaling in mural cells, directing pericyte migration via MRTF and maintaining VSMC contractile machinery, with loss causing arteriovenous shunts.\",\n      \"evidence\": \"Inducible mural-cell Srf KO, retinal angiogenesis, RNA-seq, live imaging, PDGFB-stimulated MRTF-SRF reporter\",\n      \"pmids\": [\"35862101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct pericyte migration target genes not individually validated\", \"Shunt-formation mechanism not fully mapped to specific targets\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the MRTF/TCF competitive equilibrium, multiple post-translational modifications (GSK-3 phosphorylation, K143 SUMOylation, cofactor acetylation), and cytoplasmic actin/cofilin sequestration are integrated in real time on a given promoter to select a transcriptional output remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model of SRF-MRTF vs SRF-TCF complexes on DNA\", \"Quantitative rules linking signaling state to cofactor choice undefined\", \"Cross-talk between modifications (SUMO, phospho, acetyl) not jointly tested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 2, 17, 27, 39]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [17, 27, 36]},\n      {\"term_id\": \"GO:0003700\", \"supporting_discovery_ids\": [2, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 33, 34]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [27, 33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [17, 27, 36]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [20, 24, 36, 40]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [13, 23, 24, 29, 36]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [38]}\n    ],\n    \"complexes\": [\n      \"SRF-MRTF/myocardin complex\",\n      \"SRF-TCF (Elk-1/SAP-1) ternary complex\",\n      \"SRF-MKL1-GLI1 complex\"\n    ],\n    \"partners\": [\n      \"MRTF-A/MKL1\",\n      \"MRTF-B/MKL2\",\n      \"ELK1\",\n      \"SAP-1\",\n      \"FHL2\",\n      \"GSK-3\",\n      \"GLI1\",\n      \"myocardin\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}