{"gene":"HEY1","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2000,"finding":"HEY1 (Hey1) promoter is directly activated by all four mammalian Notch receptors via two functional RBP-Jκ binding sites, establishing Hey1 as a direct Notch target gene.","method":"Cotransfection/promoter reporter assays with activated Notch constructs and site-directed mutagenesis of RBP-Jκ binding sites","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — promoter mutagenesis with functional reporter assay, all four Notch receptors tested","pmids":["10964718"],"is_preprint":false},{"year":2000,"finding":"HESR1/HEY1 overexpression in endothelial cells downregulates VEGFR2 mRNA levels and blocks endothelial cell proliferation, migration, and capillary-like network formation in vitro.","method":"Overexpression and antisense oligonucleotide knockdown in primary endothelial cells with tube formation, proliferation, and migration assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — bidirectional manipulation (OE and KD) with multiple functional readouts in a defined cellular model","pmids":["11069914"],"is_preprint":false},{"year":2001,"finding":"CHF2/HEY1 inhibits MyoD-dependent myogenin promoter activation, blocks myogenic conversion, and forms an inactive heterodimeric complex with MyoD; the repressive activity maps to a hydrophobic C-terminal region, not the bHLH or YRPW motifs.","method":"Transient transfection reporter assays, EMSA, co-immunoprecipitation, and mutational analysis in 10T1/2 fibroblasts and C2C12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding assay (EMSA, Co-IP) combined with domain mutagenesis and functional myogenic conversion assay","pmids":["11279181"],"is_preprint":false},{"year":2002,"finding":"Notch signaling activation during endothelial capillary network formation induces HESR1/HEY1 expression, which in turn downregulates VEGFR2, reducing VEGF-mediated EC proliferation but not bFGF-mediated proliferation.","method":"Dominant-negative and constitutively active Notch constructs in endothelial cells; reporter assays and RT-PCR for VEGFR2 and HESR1","journal":"Microvascular research","confidence":"Medium","confidence_rationale":"Tier 2 — genetic manipulation of Notch pathway with downstream gene expression and functional readouts, single lab","pmids":["12453432"],"is_preprint":false},{"year":2003,"finding":"Hey1 (Hesr1) misexpression in mouse brain transiently maintains neural precursor cells by negatively regulating neuronal bHLH genes Mash1 and Math3, increasing late-born superficial-layer neurons; at later stages it inhibits neurogenesis and promotes astroglial fate.","method":"In utero electroporation of mouse brain; transient transfection reporter assays for Mash1/Math3 transcription","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — gain-of-function in vivo with mechanistic reporter assay validation, multiple outcomes measured","pmids":["12947105"],"is_preprint":false},{"year":2003,"finding":"BOIP, a conserved protein, interacts with the Orange domain of HEY1/HRT1, and this interaction recruits BOIP to the nucleus, identifying Orange-domain binding as a mechanism for regulating HEY1 activity.","method":"Yeast two-hybrid screen, co-localization studies showing nuclear recruitment upon binding","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 3 — yeast two-hybrid plus localization data, single lab, no enzymatic readout","pmids":["14648848"],"is_preprint":false},{"year":2004,"finding":"Combined knockout of Hey1 and Hey2 in mice results in embryonic lethality with failure of vascular remodeling, loss of arterial endothelial markers (CD44, neuropilin1, ephrin-B2), establishing Hey1/Hey2 as essential downstream transducers of Notch signals in arterial cell fate specification.","method":"Mouse double-knockout genetics; comparison with Notch1 and Jagged1 knockout phenotypes (genetic epistasis); immunostaining for arterial markers","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — double KO mouse model with epistasis analysis, replicated across multiple genetic backgrounds","pmids":["15107403"],"is_preprint":false},{"year":2004,"finding":"Hey1 completely abrogates Runx2 transcriptional activity via direct interaction, and siRNA-mediated inhibition of Hey1 increases osteoblast matrix mineralization, identifying Hey1 as a negative regulator of osteoblast differentiation acting through Runx2.","method":"siRNA knockdown, reporter assays for Runx2 transcriptional activity, mineralization assays in MC3T3 and C2C12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function siRNA with mechanistic reporter assay demonstrating Runx2 interaction, multiple cell types","pmids":["15178686"],"is_preprint":false},{"year":2005,"finding":"Hey1 functions as a corepressor for AF1 in the androgen receptor (AR), inhibiting transcription from androgen-dependent target genes; activated Notch represses endogenous AR transactivation through Hey1. Hey1 co-localizes with AR in prostate epithelium and is excluded from the nucleus in most prostate cancers.","method":"Transient transfection reporter assays, coactivator/corepressor assays; immunofluorescence colocalization; constitutively active Notch constructs","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — functional corepressor assay with Notch epistasis and subcellular localization data with pathological relevance","pmids":["15684393"],"is_preprint":false},{"year":2005,"finding":"Hesr1/Hey1 and Hesr2/Hey2 are redundantly required for cardiovascular Notch signaling: double knockout mice exhibit embryonic lethality recapitulating most cardiovascular phenotypes of Notch pathway mutants including arterial-venous specification defects, septation, and cushion formation defects.","method":"Hesr1/Hesr2 double-knockout mouse genetics; phenotypic and molecular analysis of cardiovascular defects","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — double KO mouse with comprehensive phenotypic analysis, independently corroborating Fischer et al. 2004","pmids":["15680351"],"is_preprint":false},{"year":2006,"finding":"HESR1/HEY1 represses VEGFR2 transcription not through direct E-box binding but through interactions with GC-box/SP1-like binding proteins; the bHLH and Orange domains are sufficient for repression; the YRPW motif is dispensable; a TATA box renders the promoter resistant to HESR1 repression.","method":"Promoter reporter assays with HESR1 domain mutants, protein-DNA binding studies, promoter comparison across TATA vs. non-TATA promoters","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — domain mutagenesis with mechanistic dissection of promoter requirements","pmids":["16782059"],"is_preprint":false},{"year":2006,"finding":"KSHV RTA induces HEY1 expression; HEY1 represses the RTA promoter as part of a repressor complex (without direct DNA binding), interacts with co-repressor mSin3A, and this interaction is abolished by RTA, suggesting a feedback repression mechanism in KSHV latency.","method":"Luciferase reporter assays, ChIP, co-immunoprecipitation of HEY1 with mSin3A, siRNA knockdown","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, co-IP and ChIP with reporter assay but RTA-mediated indirect complex not fully reconstituted","pmids":["16678790"],"is_preprint":false},{"year":2006,"finding":"HESR1/HEY1 directly binds the 3′ non-coding region of the dopamine transporter (DAT1) gene and represses its expression; Hesr1 knockout mice show upregulation of multiple dopamine-related genes and altered dopaminergic behavior.","method":"Direct DNA-binding assay; RT-PCR gene expression in knockout mice; behavioral testing","journal":"Journal of neuroscience research","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding plus in vivo KO phenotype, but single lab","pmids":["16998899"],"is_preprint":false},{"year":2007,"finding":"Combined loss of Hey1 and HeyL causes impaired epithelial-to-mesenchymal transition (EMT) in atrioventricular endocardial explants, accompanied by reduced MMP-2 expression and reduced mesenchymal cell density, resulting in ventricular septal defects and valve dysplasia.","method":"Hey1/HeyL double-knockout mouse genetics; AV explant EMT assay; MMP-2 expression analysis; comparison with Hey2 and Notch1 knockouts (genetic epistasis)","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — double KO with mechanistic ex vivo EMT assay and epistasis to Notch1","pmids":["17303760"],"is_preprint":false},{"year":2007,"finding":"Forced expression of Hesr1/Hey1 in the cardiac lineage suppresses AV canal boundary formation and reduces Bmp2 and Tbx2 expression, indicating that Hey1 directly suppresses Tbx2 to regulate AV boundary formation, independently of Notch2 signaling.","method":"Cardiac lineage-specific transgenic misexpression; in situ hybridization and immunostaining for AV markers; pharmacological Notch2 inhibition","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 — in vivo gain-of-function with molecular phenotyping and Notch2 independence established","pmids":["17259303"],"is_preprint":false},{"year":2008,"finding":"HEY1 binds to N-box domains adjacent to the SOX9 enhancer site in intron 1 of COL2A1, repressing SOX9-mediated transcriptional activation of COL2A1 and AGGRECAN to block chondrogenic differentiation; overexpression of HEY1 represses COL2A1 ~80-fold.","method":"ChIP for endogenous HEY1 binding to COL2A1 intron 1; transfection reporter assays; qPCR for COL2A1 and AGGRECAN","journal":"Arthritis and rheumatism","confidence":"High","confidence_rationale":"Tier 1 — ChIP identifying endogenous binding site, corroborated by overexpression reporter assays","pmids":["18759300"],"is_preprint":false},{"year":2008,"finding":"Hey1 is a direct target of BMP9-induced Smad signaling (ChIP evidence); Hey1 loss diminishes BMP9-induced osteogenesis and promotes chondrogenic fate; Hey1 and Runx2 act synergistically, with Runx2 downstream of Hey1, and exogenous Runx2 rescues Hey1-knockdown osteogenic defects.","method":"ChIP for Smad binding to Hey1 locus; siRNA knockdown with in vitro/in vivo osteogenesis assays; Runx2 rescue experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — ChIP plus siRNA KD with rescue experiment, multiple osteogenic readouts in vitro and in vivo","pmids":["18986983"],"is_preprint":false},{"year":2009,"finding":"Hey1 is recruited to the promoter regions of myogenin and Mef2C in myoblasts, correlating with reduced MyoD recruitment to these promoters, establishing that Hey1 represses myogenesis by blocking key myogenic target gene expression rather than directly inhibiting MyoD intrinsic activity.","method":"ChIP in C2C12 myoblasts for Hey1 and MyoD at myogenin and Mef2C promoters; Hey1 overexpression with differentiation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — ChIP with mechanistic promoter occupancy data showing displacement of MyoD, multiple evidence lines","pmids":["19917614"],"is_preprint":false},{"year":2009,"finding":"KSHV RTA acts as an E3 ubiquitin ligase targeting HEY1 for ubiquitination and proteasomal degradation; a Cys-plus-His-rich region of RTA is required; HEY1 interacts with co-repressor mSin3A; RTA disrupts the HEY1-mSin3A interaction.","method":"Ubiquitination assay, proteasome inhibitor rescue, co-immunoprecipitation of HEY1 with mSin3A, domain mutant analysis of RTA","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 — in vitro ubiquitination assay with domain mutagenesis and mechanistic co-IP","pmids":["19369342"],"is_preprint":false},{"year":2009,"finding":"A naturally occurring Leu94Met polymorphism in HEY1 converts it from an AR corepressor to an AR co-activator and abolishes HEY1-mediated p53 activation and p53-dependent cell-cycle arrest, without affecting its intrinsic transcriptional repressive domains.","method":"Transient transfection reporter assays, cell-cycle analysis, sensitivity assays to p53-activating drugs; mutagenesis of HEY1 localization motifs","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 — domain/point mutagenesis with multiple functional assays (AR corepressor, p53 activation, cell-cycle arrest)","pmids":["19802006"],"is_preprint":false},{"year":2011,"finding":"Hesr1/Hey1 and Hesr3/HeyL are required together for the generation of undifferentiated quiescent satellite cells during postnatal muscle development; double knockout leads to premature myogenic differentiation (MyoD, myogenin, Ki67 expression in satellite cells) and age-dependent loss of satellite cells.","method":"Hesr1/Hesr3 double-knockout mouse analysis; in vitro myoblast culture showing loss of Pax7+/MyoD− undifferentiated cells; in vivo satellite cell counts and regeneration assays","journal":"Development","confidence":"High","confidence_rationale":"Tier 2 — double KO mouse with cell-autonomous in vitro validation and multiple molecular markers","pmids":["21989910"],"is_preprint":false},{"year":2014,"finding":"HEY1-NCOA2 fusion protein (derived from t(8;8) in mesenchymal chondrosarcoma) results from fusion of HEY1 exon 4 to NCOA2 exon 13 and is present in virtually all mesenchymal chondrosarcomas, defining this as the diagnostic gene fusion for this sarcoma.","method":"5' RACE, RT-PCR, FISH in clinical tumor specimens; genome-wide exon array expression screening","journal":"Genes, chromosomes & cancer","confidence":"High","confidence_rationale":"Tier 2 — fusion junction molecularly characterized in multiple independent tumor samples","pmids":["22034177"],"is_preprint":false},{"year":2014,"finding":"KSHV LANA stabilizes HEY1 protein by inhibiting its degradation, and HEY1 stabilized by LANA promotes neoplastic vasculature; HEY1 knockdown reduces new blood vessel formation in vivo (Matrigel plug assay).","method":"Whole-transcriptome sequencing, IHC on patient specimens, Matrigel plug angiogenesis assay in mice, siRNA knockdown of HEY1","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo angiogenesis assay with genetic manipulation, single lab","pmids":["24523441"],"is_preprint":false},{"year":2015,"finding":"Hey1 expression in endothelial cells is induced by BMP9 (an Alk1 ligand) in serum, independent of canonical Notch/γ-secretase signaling; soluble Alk1 (but not Alk3) receptor abolishes this induction.","method":"Gamma-secretase inhibition, dominant-negative MAML1 expression, soluble BMP receptor pretreatment, RT-PCR for Hey1 in primary human endothelial cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — pharmacological and genetic Notch blockade combined with receptor-specific BMP inhibition, single lab","pmids":["25799559"],"is_preprint":false},{"year":2016,"finding":"HEY1 is a direct downstream effector of FRA1 in the c-Met/HGF signaling pathway; CAF-derived HGF activates FRA1 in an ERK1/2-dependent manner, which in turn drives HEY1 expression to regulate liver tumor-initiating cells.","method":"Functional shRNA knockdown and overexpression assays; ChIP/reporter assays placing HEY1 downstream of FRA1; STAM NASH-HCC mouse model validation","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — ChIP/reporter placing HEY1 downstream of FRA1, in vivo mouse model corroboration","pmids":["27134167"],"is_preprint":false},{"year":2016,"finding":"HEY1 phosphorylation at Ser-68 by STK38 and STK38L increases HEY1 protein stability but inhibits its ability to enhance p53 transcriptional activity; the phosphomimetic S68D mutant fails to induce p53-dependent cell-cycle arrest. HEY1 also interacts with MDM2 and is subject to MDM2-mediated degradation, and this interaction is prevented by Ser-68 phosphorylation.","method":"MALDI-TOF/TOF MS identification of phosphorylation site; mutagenesis (S68D phosphomimetic); kinase interaction and phosphorylation assays; co-immunoprecipitation with RPL11 and MDM2; p53 reporter assays; cell-cycle analysis","journal":"Bioscience reports","confidence":"High","confidence_rationale":"Tier 1 — MS identification + mutagenesis + kinase assay + multiple functional readouts","pmids":["27129302"],"is_preprint":false},{"year":2019,"finding":"Hey1 and HeyL function cell-autonomously and redundantly in muscle stem cells (satellite cells); HeyL requires Hes1 to form heterodimers that bind Hey1 target sites in chromatin with high affinity; HeyL-Hes1 heterodimer and Hey1 act synergistically to suppress myogenin promoter activity.","method":"Conditional and genetic null mice; cultured satellite cell assays; ChIP-seq for HeyL and HeyL-Hes1; myogenin promoter reporter assay","journal":"Development","confidence":"High","confidence_rationale":"Tier 1 — ChIP-seq with genome-wide binding analysis plus functional reporter assay and conditional KO mice","pmids":["30745427"],"is_preprint":false},{"year":2019,"finding":"BMP9 specifically induces Hey1 expression; Hey1 forms complexes with Id4 in osteoblasts; BMP9-induced overexpression of Hey1 overcomes Id4 inhibition and suppresses osteopontin (Opn) promoter activity, preventing OPN-type osteoblast differentiation.","method":"ChIP, immunoprecipitation (Hey1-Id4 complex), site-directed mutagenesis of Opn promoter, Opn promoter reporter assays","journal":"International journal of biochemistry & cell biology","confidence":"High","confidence_rationale":"Tier 1 — ChIP + Co-IP + promoter mutagenesis identifying Hey1-Id4 complex mechanism","pmids":["31550547"],"is_preprint":false},{"year":2019,"finding":"HIF-1α directly binds a hypoxia response element (HRE) in the HEY1 promoter under hypoxia; HEY1 then directly represses PINK1 transcription; HCC cells with HEY1 knockdown re-express PINK1, and HEY1 overexpression reduces mitochondrial mass and oxidative stress.","method":"ChIP and luciferase reporter assays for HRE in HEY1 promoter; ChIP-seq and transcriptome sequencing to identify PINK1 as HEY1 target; siRNA knockdown of HEY1 with mitochondrial phenotype readouts","journal":"Cell death & disease","confidence":"High","confidence_rationale":"Tier 1 — ChIP plus ChIP-seq with transcriptome validation and functional knockdown","pmids":["31819034"],"is_preprint":false},{"year":2021,"finding":"Hey1 displays non-oscillatory stationary expression in slowly dividing neural progenitors (in contrast to oscillatory Hes1/Hes5 in fast-cycling progenitors), contributing to long-term maintenance of adult neural stem cells downstream of Notch; cell cycle arrest biases Notch effector selection toward Hey1.","method":"Live imaging of Hey1 expression dynamics; comparison with Hes1/Hes5 oscillations; Notch manipulation in embryonic NPCs; adult NSC lineage tracing","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — live imaging with Notch genetic manipulation revealing non-oscillatory expression, multiple complementary approaches","pmids":["34772946"],"is_preprint":false},{"year":2022,"finding":"HEY1-NCOA2 fusion protein preferentially binds promoter regions of canonical HEY1 targets (ChIP-seq) but converts them from repressed to transactivated; the fusion directly targets and upregulates PDGFB and PDGFRA, and dramatically increases phospho-AKT (Ser473).","method":"ChIP-seq and RNA-seq in iPSC-derived MSCs with inducible HEY1-NCOA2 expression; comparison with wildtype HEY1 and NCOA2","journal":"The Journal of pathology","confidence":"High","confidence_rationale":"Tier 1 — genome-wide ChIP-seq + transcriptome in appropriate cell context with isogenic controls","pmids":["35342947"],"is_preprint":false},{"year":2023,"finding":"HEY1-NCOA2 expression in embryonic superficial zone chondrocyte precursors induces mesenchymal chondrosarcoma in mice; the fusion protein physically interacts with Runx2 via NCOA2 C-terminal domains; Runx2 knockout delays but does not abolish tumor onset; HDAC inhibitor panobinostat suppresses tumor growth by abrogating HEY1-NCOA2/Runx2-downstream gene expression.","method":"Mouse mesenchymal chondrosarcoma model via gene transduction and transplantation; ChIP-seq; co-immunoprecipitation of HEY1-NCOA2 with Runx2; Runx2 conditional knockout; in vitro and in vivo panobinostat treatment","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1 — in vivo tumor model + ChIP-seq + Co-IP with domain identification + drug rescue experiment","pmids":["37212282"],"is_preprint":false},{"year":2024,"finding":"HEY1 is SUMOylated at conserved lysines by the E3 ligase TRIM28 in endothelial cells; SUMOylation facilitates HEY1 homodimer formation and preserves E-box promoter binding capability, maintaining HEY1's repressive activity on angiogenic RTK and Notch pathway genes. Proangiogenic stimuli induce HEY1 deSUMOylation, causing heterodimerization with HES1, loss of DNA binding, and relief of repression.","method":"Immunoprecipitation + mass spectrometry identifying SUMOylation sites; ChIP, dual luciferase, EMSA for DNA binding; co-immunoprecipitation for dimerization; SUMOylation-deficient mutant mice; multiple in vivo angiogenesis models (embryonic vascular growth, matrigel plug, wound healing, OIR, tumor angiogenesis)","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 1 — MS identification + mutagenesis + structural dimerization analysis + multiple in vivo models, single rigorous study with orthogonal methods","pmids":["38166414"],"is_preprint":false},{"year":2018,"finding":"Hey1 interacts directly with the TrkC intracellular domain and importin-α3/KPNA4; the cleaved TrkC killer-fragment is translocated to the nucleus by importins and interacts with Hey1 there; Hey1 and TrkC-KF together transcriptionally silence MDM2, contributing to p53 stabilization and induction of apoptosis in neuroblastoma.","method":"Co-immunoprecipitation identifying TrkC-Hey1 and TrkC-KPNA4 interactions; MDM2 promoter reporter assays; Hey1 and p53 knockdown/overexpression; avian neuroblastoma in vivo model","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1 — reconstituted nuclear interaction with promoter reporter and in vivo rescue experiment","pmids":["29750782"],"is_preprint":false},{"year":2015,"finding":"Hey1 null mice on C57BL/6N background exhibit perinatal lethality due to abnormal fourth pharyngeal arch artery (PAA4) development, resulting in aortic arch malformations; endothelial cells in PAA4 differentiate normally but are structurally disorganized and vascular smooth muscle cells are absent, associated with downregulation of endothelial Jag1.","method":"Hrt1/Hey1 knockout mouse analysis; histology, immunostaining for endothelial and VSMC markers; Jag1 expression analysis","journal":"Mechanisms of development","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with cellular and molecular phenotyping revealing specific endothelial-VSMC signaling defect","pmids":["26577899"],"is_preprint":false},{"year":2020,"finding":"Hey1 expression in vascular endothelial cells (not smooth muscle cells) is essential for pharyngeal arch artery development and great vessel morphogenesis; endothelial-specific Tek-Cre-mediated Hey1 deletion impairs endothelial tube formation and smooth muscle differentiation. A distal endothelial enhancer controlling Hey1 expression is conserved, specific to large-caliber arteries, and regulated by Notch (not ALK1) signaling.","method":"Cell type-specific conditional knockout (Tek-Cre); enhancer identification and functional testing in vivo; Notch vs ALK1 signaling manipulations","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with cell-type specificity established plus enhancer mechanistic dissection","pmids":["33454003"],"is_preprint":false},{"year":2022,"finding":"Babam2 interacts with Hey1 to inhibit Nfatc1 transcription, negatively regulating osteoclastogenesis; silencing Hey1 largely abolishes the anti-osteoclastogenic effects of Babam2 overexpression.","method":"Co-immunoprecipitation (Babam2-Hey1 interaction); Nfatc1 promoter reporter assays; Babam2 transgenic mice; siRNA knockdown epistasis experiments","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP with functional reporter and epistasis, single lab","pmids":["35864959"],"is_preprint":false}],"current_model":"HEY1 is a bHLH-Orange transcriptional repressor that is directly activated downstream of Notch (via RBP-Jκ) and BMP/Smad/Alk1 signaling; its repressive activity is modulated by SUMOylation (mediated by TRIM28, promoting homodimerization and E-box binding) and phosphorylation at Ser-68 (by STK38/STK38L, stabilizing the protein but blocking p53 activation), as well as by KSHV RTA-mediated ubiquitination and proteasomal degradation; mechanistically, HEY1 represses target gene promoters through interactions with SP1-like factors (for VEGFR2), direct N-box binding (COL2A1), or by forming inactive heterodimers with MyoD, and it acts as a corepressor for the androgen receptor AF1 domain; HEY1 is essential for arterial cell fate specification, endothelial tube formation and vascular remodeling, cardiac EMT and AV boundary formation (via Tbx2 suppression), maintenance of muscle satellite cells and neural progenitors, and osteoblast differentiation (by antagonizing Runx2), while the oncogenic HEY1-NCOA2 fusion converts its canonical target-gene repressor function into transcriptional activation, upregulating PDGFB/PDGFRA and PI3K/AKT signaling, driving mesenchymal chondrosarcoma."},"narrative":{"teleology":[{"year":2000,"claim":"Identifying HEY1 as a direct Notch transcriptional target resolved how Notch receptor activation is decoded by a specific bHLH repressor, placing HEY1 immediately downstream of RBP-Jκ.","evidence":"Promoter reporter assays with all four activated Notch receptors and RBP-Jκ site mutagenesis","pmids":["10964718"],"confidence":"High","gaps":["Whether Notch-independent inputs also regulate HEY1 promoter in vivo was not addressed","Chromatin context of RBP-Jκ binding not examined"]},{"year":2000,"claim":"Demonstrating that HEY1 overexpression suppresses VEGFR2 and blocks endothelial tube formation established its first functional role as an anti-angiogenic transcriptional repressor.","evidence":"Bidirectional manipulation (overexpression and antisense knockdown) in primary endothelial cells with proliferation, migration, and tube formation assays","pmids":["11069914"],"confidence":"High","gaps":["Mechanism of VEGFR2 repression (direct vs. indirect) not resolved","In vivo angiogenic relevance not tested"]},{"year":2001,"claim":"Showing that HEY1 sequesters MyoD into transcriptionally inactive heterodimers via a C-terminal domain (not bHLH or YRPW) revealed a dominant-negative mechanism for blocking myogenesis distinct from canonical bHLH repression.","evidence":"Co-IP, EMSA, and domain mutagenesis in 10T1/2 and C2C12 myogenic conversion assays","pmids":["11279181"],"confidence":"High","gaps":["Structural basis of HEY1-MyoD heterodimer inactivity unknown","In vivo relevance to satellite cell biology not yet tested"]},{"year":2003,"claim":"In utero electroporation experiments showed that HEY1 maintains neural precursor identity by repressing proneural bHLH genes Mash1 and Math3, expanding the repertoire of HEY1-regulated cell fate decisions beyond the vasculature.","evidence":"In utero electroporation in mouse brain with reporter assay validation for Mash1/Math3 promoters","pmids":["12947105"],"confidence":"High","gaps":["Whether HEY1 binds Mash1/Math3 promoters directly was not shown","Redundancy with Hey2/HeyL in neural progenitors not addressed"]},{"year":2004,"claim":"Hey1/Hey2 double-knockout lethality with loss of arterial markers phenocopying Notch1 and Jagged1 mutants established these factors as the essential downstream mediators of Notch-driven arterial cell fate specification.","evidence":"Double-knockout mouse genetics with genetic epistasis to Notch1/Jagged1 knockouts and arterial marker immunostaining","pmids":["15107403","15680351"],"confidence":"High","gaps":["Individual contributions of Hey1 vs. Hey2 to specific arterial genes not dissected","Downstream direct target genes mediating arterial fate unknown"]},{"year":2004,"claim":"Identification of Runx2 as a direct interaction partner whose transcriptional activity is completely blocked by HEY1 revealed a mechanism for HEY1-mediated inhibition of osteoblast differentiation.","evidence":"siRNA knockdown, Runx2 reporter assays, and mineralization assays in MC3T3 and C2C12 cells","pmids":["15178686"],"confidence":"High","gaps":["Whether HEY1 binds Runx2 on chromatin or sequesters it off-DNA not determined","In vivo skeletal phenotype of Hey1 single KO not examined"]},{"year":2005,"claim":"Demonstration that HEY1 acts as a corepressor for the androgen receptor AF1 domain, with Notch signaling suppressing AR transactivation through HEY1, linked Notch-HEY1 signaling to androgen-dependent gene regulation in prostate.","evidence":"Reporter assays, corepressor assays, activated Notch constructs, and AR-HEY1 colocalization in prostate epithelium","pmids":["15684393"],"confidence":"High","gaps":["Genome-wide AR target gene regulation by HEY1 not mapped","Mechanism of HEY1 nuclear exclusion in prostate cancer not defined"]},{"year":2006,"claim":"Mechanistic dissection of VEGFR2 repression showed HEY1 acts through SP1-like factors at GC-box elements rather than direct E-box binding, and that bHLH plus Orange domains suffice while the YRPW motif is dispensable, defining a non-canonical repression mode for TATA-less promoters.","evidence":"Promoter reporter assays with domain mutants; protein-DNA binding studies; TATA vs. non-TATA promoter comparisons","pmids":["16782059"],"confidence":"High","gaps":["Identity of the SP1-like factor mediating HEY1 tethering not determined","Whether this mechanism applies genome-wide to other TATA-less targets unknown"]},{"year":2007,"claim":"Hey1/HeyL double knockouts revealed that these factors are redundantly required for endocardial EMT and AV valve morphogenesis, while forced Hey1 expression suppresses Tbx2 to regulate AV boundary formation, expanding HEY1's role to cardiac cushion development.","evidence":"Double-knockout mouse with AV explant EMT assays and MMP-2 analysis; cardiac-specific transgenic misexpression with in situ hybridization","pmids":["17303760","17259303"],"confidence":"High","gaps":["Whether Hey1 directly binds the Tbx2 promoter not shown","Relative contributions of Hey1 vs. HeyL to EMT not separated"]},{"year":2008,"claim":"ChIP identification of HEY1 binding to N-box elements in COL2A1 intron 1, where it antagonizes SOX9-mediated activation, established direct N-box binding as a distinct mode of HEY1-mediated transcriptional repression controlling chondrogenesis.","evidence":"ChIP for endogenous HEY1 at COL2A1 intron 1; reporter assays; qPCR for COL2A1 and AGGRECAN","pmids":["18759300"],"confidence":"High","gaps":["Whether HEY1 physically interacts with SOX9 or merely competes for adjacent cis-elements unknown","Genome-wide N-box occupancy not mapped"]},{"year":2008,"claim":"ChIP evidence that Smad signaling directly activates the Hey1 locus downstream of BMP9 established a Notch-independent route for Hey1 induction, with Runx2 rescue of Hey1 knockdown confirming Hey1 acts upstream of Runx2 in osteogenesis.","evidence":"Smad ChIP at Hey1 locus; siRNA knockdown with in vitro/in vivo osteogenesis assays; Runx2 rescue","pmids":["18986983"],"confidence":"High","gaps":["How Hey1 simultaneously represses and cooperates with Runx2 in different osteogenic contexts not reconciled"]},{"year":2009,"claim":"ChIP showing Hey1 occupies myogenin and Mef2C promoters with concomitant displacement of MyoD refined the myogenic repression mechanism from simple MyoD sequestration to active promoter-level competition.","evidence":"ChIP in C2C12 myoblasts for Hey1 and MyoD at myogenin/Mef2C promoters","pmids":["19917614"],"confidence":"High","gaps":["Whether Hey1 recruits specific co-repressors at these promoters not addressed"]},{"year":2009,"claim":"Identification of KSHV RTA as an E3 ubiquitin ligase that targets HEY1 for proteasomal degradation and disrupts the HEY1-mSin3A co-repressor complex revealed a viral strategy to overcome HEY1-mediated repression of lytic reactivation.","evidence":"In vitro ubiquitination assay, proteasome inhibitor rescue, Co-IP with mSin3A, RTA domain mutagenesis","pmids":["19369342"],"confidence":"High","gaps":["Whether endogenous cellular E3 ligases regulate HEY1 turnover similarly not explored","In vivo relevance to KSHV latency-lytic switch not confirmed"]},{"year":2009,"claim":"The Leu94Met polymorphism converting HEY1 from AR corepressor to co-activator while abolishing p53 activation demonstrated that a single residue switch can invert HEY1's functional output, linking HEY1 to p53-dependent cell cycle control.","evidence":"Point mutagenesis with AR corepressor, p53 reporter, and cell-cycle arrest assays","pmids":["19802006"],"confidence":"High","gaps":["Structural basis of how L94M inverts corepressor to co-activator function unknown","Population frequency and clinical significance of L94M not established"]},{"year":2011,"claim":"Hey1/HeyL double knockout causing premature satellite cell differentiation and age-dependent satellite cell depletion established HEY1 as essential for maintaining muscle stem cell quiescence, linking Notch-HEY1 signaling to adult tissue regeneration.","evidence":"Double-knockout mouse; in vitro myoblast culture showing loss of Pax7+/MyoD− undifferentiated cells; satellite cell counts and regeneration assays","pmids":["21989910"],"confidence":"High","gaps":["Direct chromatin targets of Hey1 in satellite cells not identified genome-wide"]},{"year":2014,"claim":"Molecular characterization of the HEY1-NCOA2 fusion in mesenchymal chondrosarcoma identified the diagnostic translocation for this tumor type, implicating conversion of HEY1 repressor function into aberrant transcriptional activation as an oncogenic mechanism.","evidence":"5' RACE, RT-PCR, FISH in multiple clinical tumor specimens; genome-wide exon array","pmids":["22034177"],"confidence":"High","gaps":["Oncogenic mechanism of the fusion not yet defined","Target genes of HEY1-NCOA2 unknown"]},{"year":2016,"claim":"Identification of Ser-68 phosphorylation by STK38/STK38L as a modification that stabilizes HEY1 protein but blocks p53 activation revealed a phospho-switch controlling HEY1's pro-apoptotic function, with MDM2 identified as a degradation-promoting interactor opposed by this phosphorylation.","evidence":"MALDI-TOF MS; S68D phosphomimetic mutagenesis; kinase assays; Co-IP with RPL11 and MDM2; p53 reporter and cell-cycle assays","pmids":["27129302"],"confidence":"High","gaps":["In vivo significance of Ser-68 phosphorylation not tested","Whether STK38 regulation is context-specific (e.g., tissue type) unknown"]},{"year":2018,"claim":"Demonstration that the TrkC killer-fragment is imported to the nucleus via importin-β3/KPNA4 and cooperates with HEY1 to silence MDM2, stabilizing p53 and inducing apoptosis, established a dependence-receptor signaling pathway converging on HEY1-mediated transcriptional repression.","evidence":"Co-IP of TrkC-Hey1 and TrkC-KPNA4; MDM2 promoter reporter; Hey1/p53 knockdown/overexpression; avian neuroblastoma in vivo model","pmids":["29750782"],"confidence":"High","gaps":["Whether HEY1 directly binds the MDM2 promoter not shown by ChIP","Generality beyond neuroblastoma not tested"]},{"year":2019,"claim":"ChIP-seq revealing that HeyL requires Hes1 to form heterodimers that bind Hey1 target sites showed how combinatorial bHLH pairing determines genome-wide occupancy, explaining the functional redundancy between Hey1 and HeyL in satellite cells.","evidence":"Conditional knockout mice; ChIP-seq for HeyL and HeyL-Hes1; myogenin promoter reporter assay","pmids":["30745427"],"confidence":"High","gaps":["Whether Hey1 also requires a heterodimeric partner for full chromatin occupancy not determined"]},{"year":2020,"claim":"Endothelial-specific conditional deletion proved that Hey1 function in pharyngeal arch artery morphogenesis is cell-autonomous to endothelial cells, and identified a distal Notch-responsive enhancer specific to large arteries, defining the cis-regulatory logic of vascular Hey1 expression.","evidence":"Tek-Cre conditional knockout; enhancer identification and functional testing in vivo; Notch vs. ALK1 signaling manipulations","pmids":["33454003"],"confidence":"High","gaps":["Transcription factors binding the distal enhancer besides Notch not identified","Whether the enhancer is relevant to non-pharyngeal arteries unknown"]},{"year":2021,"claim":"Live imaging revealed that Hey1 is expressed in a non-oscillatory, stationary pattern in slowly dividing neural progenitors, contrasting with oscillatory Hes1/Hes5, establishing expression dynamics as a mechanism by which Notch effector choice biases stem cell maintenance vs. proliferation.","evidence":"Live imaging of Hey1 dynamics; comparison with Hes1/Hes5 oscillations; Notch manipulation in embryonic NPCs; adult NSC lineage tracing","pmids":["34772946"],"confidence":"High","gaps":["Molecular basis for why Hey1 does not oscillate unknown","Whether stationary expression is intrinsic to the Hey1 mRNA/protein or imposed by cell cycle state not resolved"]},{"year":2022,"claim":"Genome-wide ChIP-seq and RNA-seq of the HEY1-NCOA2 fusion showed it binds canonical HEY1 target promoters but converts them from repressed to activated, directly upregulating PDGFB/PDGFRA and hyperactivating PI3K/AKT, providing the mechanistic basis for how the fusion drives mesenchymal chondrosarcoma.","evidence":"ChIP-seq and RNA-seq in iPSC-derived MSCs with inducible HEY1-NCOA2 vs. wildtype HEY1/NCOA2 isogenic controls","pmids":["35342947"],"confidence":"High","gaps":["Whether PDGFB/PDGFRA are necessary and sufficient for transformation not tested","Structural basis of repressor-to-activator conversion not resolved"]},{"year":2023,"claim":"An in vivo mesenchymal chondrosarcoma mouse model showed that the HEY1-NCOA2 fusion physically interacts with Runx2 and that Runx2 contributes to but is not solely required for tumorigenesis, while HDAC inhibition suppresses fusion-driven gene expression and tumor growth.","evidence":"Mouse tumor model; ChIP-seq; Co-IP of HEY1-NCOA2 with Runx2; Runx2 conditional KO; panobinostat treatment in vitro and in vivo","pmids":["37212282"],"confidence":"High","gaps":["Which Runx2-independent pathways sustain tumor growth unknown","Mechanism by which HDAC inhibition specifically disrupts fusion activity not defined"]},{"year":2024,"claim":"Discovery that TRIM28-mediated SUMOylation stabilizes HEY1 homodimers and E-box binding while proangiogenic deSUMOylation switches HEY1 to inactive HES1 heterodimers provided a unified post-translational mechanism governing the angiogenic switch through HEY1 dimerization control.","evidence":"IP-MS identifying SUMOylation sites; ChIP, EMSA, dual luciferase for DNA binding; Co-IP for dimerization; SUMOylation-deficient mutant mice; multiple in vivo angiogenesis models","pmids":["38166414"],"confidence":"High","gaps":["The deSUMOylase responsible for proangiogenic HEY1 modification not identified","Whether SUMOylation regulates HEY1 in non-endothelial contexts unknown","Structural basis of how SUMOylation favors homodimer over heterodimer not resolved"]},{"year":null,"claim":"Key unresolved questions include the structural basis for HEY1 dimerization switching, genome-wide direct target identification across multiple tissue contexts, the identity of endogenous E3 ligases and deSUMOylases regulating HEY1 turnover outside viral contexts, and the precise mechanism by which the HEY1-NCOA2 fusion converts repression to activation.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of HEY1 or its complexes","Comprehensive genome-wide binding data for wildtype HEY1 across tissues lacking","Endogenous ubiquitin ligases for HEY1 turnover not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,2,7,8,10,15,17,28,30]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[10,12,15,32]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,8,33]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4,6,9,13,14,34,35]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,10,15,17,28,30]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[21,30,31]}],"complexes":["HEY1-mSin3A co-repressor complex","HEY1-HES1 heterodimer","HEY1-MyoD heterodimer"],"partners":["RBPJ","MYOD1","RUNX2","AR","TRIM28","HES1","NTRK3","BABAM2"],"other_free_text":[]},"mechanistic_narrative":"HEY1 is a bHLH-Orange transcriptional repressor that functions as a central effector of Notch and BMP/Smad signaling to control cell fate decisions in vascular, cardiac, neural, skeletal, and muscle progenitor compartments. HEY1 represses target genes through multiple mechanisms: direct N-box binding (e.g., COL2A1), interaction with SP1-like factors at GC-box elements (e.g., VEGFR2), sequestration of tissue-specific activators such as MyoD into inactive heterodimers, and recruitment of the mSin3A co-repressor complex; its repressive activity on angiogenic genes is maintained by TRIM28-mediated SUMOylation, which stabilizes DNA-binding homodimers, while proangiogenic signals trigger deSUMOylation and heterodimerization with HES1, relieving repression [PMID:38166414, PMID:10964718, PMID:16782059, PMID:11279181, PMID:19369342]. In vascular development, Hey1 and Hey2 are redundantly required downstream of Notch for arterial identity specification and great vessel morphogenesis, while Hey1 and HeyL together govern cardiac atrioventricular EMT and muscle satellite cell quiescence [PMID:15107403, PMID:17303760, PMID:21989910]. The HEY1-NCOA2 fusion, the defining translocation of mesenchymal chondrosarcoma, retains HEY1 target-gene binding but converts repression into transactivation, upregulating PDGFB/PDGFRA and PI3K/AKT signaling to drive tumorigenesis [PMID:35342947, PMID:37212282]."},"prefetch_data":{"uniprot":{"accession":"Q9Y5J3","full_name":"Hairy/enhancer-of-split related with YRPW motif protein 1","aliases":["Cardiovascular helix-loop-helix factor 2","CHF-2","Class B basic helix-loop-helix protein 31","bHLHb31","HES-related repressor protein 1","Hairy and enhancer of split-related protein 1","HESR-1","Hairy-related transcription factor 1","HRT-1","hHRT1"],"length_aa":304,"mass_kda":32.6,"function":"Transcriptional repressor which binds preferentially to the canonical E box sequence 5'-CACGTG-3' (PubMed:11095750). Downstream effector of Notch signaling required for cardiovascular development. Specifically required for the Notch-induced endocardial epithelial to mesenchymal transition, which is itself criticial for cardiac valve and septum development. May be required in conjunction with HEY2 to specify arterial cell fate or identity. Promotes maintenance of neuronal precursor cells and glial versus neuronal fate specification. Represses transcription by the cardiac transcriptional activators GATA4 and GATA6 and by the neuronal bHLH factors ASCL1/MASH1 and NEUROD4/MATH3 (PubMed:15485867). Involved in the regulation of liver cancer cells self-renewal (PubMed:25985737)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q9Y5J3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HEY1","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HEY1","total_profiled":1310},"omim":[{"mim_id":"621120","title":"DELTA-LIKE NONCANONICAL NOTCH LIGAND 2; DLK2","url":"https://www.omim.org/entry/621120"},{"mim_id":"618111","title":"ZINC FINGER PROTEIN 64; ZFP64","url":"https://www.omim.org/entry/618111"},{"mim_id":"614301","title":"ATAXIN 1-LIKE; ATXN1L","url":"https://www.omim.org/entry/614301"},{"mim_id":"609034","title":"HES-RELATED bHLH TRANSCRIPTION FACTOR WITH YRPW MOTIF-LIKE PROTEIN; HEYL","url":"https://www.omim.org/entry/609034"},{"mim_id":"608677","title":"MIB E3 UBIQUITIN PROTEIN LIGASE 1; MIB1","url":"https://www.omim.org/entry/608677"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nuclear membrane","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":48.2}],"url":"https://www.proteinatlas.org/search/HEY1"},"hgnc":{"alias_symbol":["HESR-1","CHF2","HESR1","HRT-1","CHF-2","HERP2","bHLHb31"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y5J3","domains":[{"cath_id":"4.10.280.10","chopping":"45-112","consensus_level":"medium","plddt":90.046,"start":45,"end":112},{"cath_id":"1.20.58","chopping":"114-170","consensus_level":"medium","plddt":92.896,"start":114,"end":170}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y5J3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y5J3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y5J3-F1-predicted_aligned_error_v6.png","plddt_mean":66.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HEY1","jax_strain_url":"https://www.jax.org/strain/search?query=HEY1"},"sequence":{"accession":"Q9Y5J3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y5J3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y5J3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y5J3"}},"corpus_meta":[{"pmid":"15107403","id":"PMC_15107403","title":"The Notch target genes Hey1 and Hey2 are required for embryonic vascular development.","date":"2004","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/15107403","citation_count":538,"is_preprint":false},{"pmid":"27134167","id":"PMC_27134167","title":"Cancer-Associated Fibroblasts Regulate Tumor-Initiating Cell Plasticity in Hepatocellular Carcinoma through c-Met/FRA1/HEY1 Signaling.","date":"2016","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/27134167","citation_count":273,"is_preprint":false},{"pmid":"22034177","id":"PMC_22034177","title":"Identification of a novel, recurrent HEY1-NCOA2 fusion in mesenchymal chondrosarcoma based on a genome-wide screen of exon-level expression data.","date":"2011","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/22034177","citation_count":244,"is_preprint":false},{"pmid":"10964718","id":"PMC_10964718","title":"Comparative analysis of the human and mouse Hey1 promoter: Hey genes are new Notch target genes.","date":"2000","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/10964718","citation_count":208,"is_preprint":false},{"pmid":"15178686","id":"PMC_15178686","title":"Coordinated activation of notch, Wnt, and transforming growth factor-beta signaling pathways in bone morphogenic protein 2-induced osteogenesis. 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the repressive activity maps to a hydrophobic C-terminal region, not the bHLH or YRPW motifs.\",\n      \"method\": \"Transient transfection reporter assays, EMSA, co-immunoprecipitation, and mutational analysis in 10T1/2 fibroblasts and C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding assay (EMSA, Co-IP) combined with domain mutagenesis and functional myogenic conversion assay\",\n      \"pmids\": [\"11279181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Notch signaling activation during endothelial capillary network formation induces HESR1/HEY1 expression, which in turn downregulates VEGFR2, reducing VEGF-mediated EC proliferation but not bFGF-mediated proliferation.\",\n      \"method\": \"Dominant-negative and constitutively active Notch constructs in endothelial cells; reporter assays and RT-PCR for VEGFR2 and HESR1\",\n      \"journal\": \"Microvascular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic manipulation of Notch pathway with downstream gene expression and functional readouts, single lab\",\n      \"pmids\": [\"12453432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Hey1 (Hesr1) misexpression in mouse brain transiently maintains neural precursor cells by negatively regulating neuronal bHLH genes Mash1 and Math3, increasing late-born superficial-layer neurons; at later stages it inhibits neurogenesis and promotes astroglial fate.\",\n      \"method\": \"In utero electroporation of mouse brain; transient transfection reporter assays for Mash1/Math3 transcription\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function in vivo with mechanistic reporter assay validation, multiple outcomes measured\",\n      \"pmids\": [\"12947105\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"BOIP, a conserved protein, interacts with the Orange domain of HEY1/HRT1, and this interaction recruits BOIP to the nucleus, identifying Orange-domain binding as a mechanism for regulating HEY1 activity.\",\n      \"method\": \"Yeast two-hybrid screen, co-localization studies showing nuclear recruitment upon binding\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — yeast two-hybrid plus localization data, single lab, no enzymatic readout\",\n      \"pmids\": [\"14648848\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Combined knockout of Hey1 and Hey2 in mice results in embryonic lethality with failure of vascular remodeling, loss of arterial endothelial markers (CD44, neuropilin1, ephrin-B2), establishing Hey1/Hey2 as essential downstream transducers of Notch signals in arterial cell fate specification.\",\n      \"method\": \"Mouse double-knockout genetics; comparison with Notch1 and Jagged1 knockout phenotypes (genetic epistasis); immunostaining for arterial markers\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — double KO mouse model with epistasis analysis, replicated across multiple genetic backgrounds\",\n      \"pmids\": [\"15107403\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Hey1 completely abrogates Runx2 transcriptional activity via direct interaction, and siRNA-mediated inhibition of Hey1 increases osteoblast matrix mineralization, identifying Hey1 as a negative regulator of osteoblast differentiation acting through Runx2.\",\n      \"method\": \"siRNA knockdown, reporter assays for Runx2 transcriptional activity, mineralization assays in MC3T3 and C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function siRNA with mechanistic reporter assay demonstrating Runx2 interaction, multiple cell types\",\n      \"pmids\": [\"15178686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Hey1 functions as a corepressor for AF1 in the androgen receptor (AR), inhibiting transcription from androgen-dependent target genes; activated Notch represses endogenous AR transactivation through Hey1. Hey1 co-localizes with AR in prostate epithelium and is excluded from the nucleus in most prostate cancers.\",\n      \"method\": \"Transient transfection reporter assays, coactivator/corepressor assays; immunofluorescence colocalization; constitutively active Notch constructs\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — functional corepressor assay with Notch epistasis and subcellular localization data with pathological relevance\",\n      \"pmids\": [\"15684393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Hesr1/Hey1 and Hesr2/Hey2 are redundantly required for cardiovascular Notch signaling: double knockout mice exhibit embryonic lethality recapitulating most cardiovascular phenotypes of Notch pathway mutants including arterial-venous specification defects, septation, and cushion formation defects.\",\n      \"method\": \"Hesr1/Hesr2 double-knockout mouse genetics; phenotypic and molecular analysis of cardiovascular defects\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — double KO mouse with comprehensive phenotypic analysis, independently corroborating Fischer et al. 2004\",\n      \"pmids\": [\"15680351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HESR1/HEY1 represses VEGFR2 transcription not through direct E-box binding but through interactions with GC-box/SP1-like binding proteins; the bHLH and Orange domains are sufficient for repression; the YRPW motif is dispensable; a TATA box renders the promoter resistant to HESR1 repression.\",\n      \"method\": \"Promoter reporter assays with HESR1 domain mutants, protein-DNA binding studies, promoter comparison across TATA vs. non-TATA promoters\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — domain mutagenesis with mechanistic dissection of promoter requirements\",\n      \"pmids\": [\"16782059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"KSHV RTA induces HEY1 expression; HEY1 represses the RTA promoter as part of a repressor complex (without direct DNA binding), interacts with co-repressor mSin3A, and this interaction is abolished by RTA, suggesting a feedback repression mechanism in KSHV latency.\",\n      \"method\": \"Luciferase reporter assays, ChIP, co-immunoprecipitation of HEY1 with mSin3A, siRNA knockdown\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, co-IP and ChIP with reporter assay but RTA-mediated indirect complex not fully reconstituted\",\n      \"pmids\": [\"16678790\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"HESR1/HEY1 directly binds the 3′ non-coding region of the dopamine transporter (DAT1) gene and represses its expression; Hesr1 knockout mice show upregulation of multiple dopamine-related genes and altered dopaminergic behavior.\",\n      \"method\": \"Direct DNA-binding assay; RT-PCR gene expression in knockout mice; behavioral testing\",\n      \"journal\": \"Journal of neuroscience research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding plus in vivo KO phenotype, but single lab\",\n      \"pmids\": [\"16998899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Combined loss of Hey1 and HeyL causes impaired epithelial-to-mesenchymal transition (EMT) in atrioventricular endocardial explants, accompanied by reduced MMP-2 expression and reduced mesenchymal cell density, resulting in ventricular septal defects and valve dysplasia.\",\n      \"method\": \"Hey1/HeyL double-knockout mouse genetics; AV explant EMT assay; MMP-2 expression analysis; comparison with Hey2 and Notch1 knockouts (genetic epistasis)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — double KO with mechanistic ex vivo EMT assay and epistasis to Notch1\",\n      \"pmids\": [\"17303760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Forced expression of Hesr1/Hey1 in the cardiac lineage suppresses AV canal boundary formation and reduces Bmp2 and Tbx2 expression, indicating that Hey1 directly suppresses Tbx2 to regulate AV boundary formation, independently of Notch2 signaling.\",\n      \"method\": \"Cardiac lineage-specific transgenic misexpression; in situ hybridization and immunostaining for AV markers; pharmacological Notch2 inhibition\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gain-of-function with molecular phenotyping and Notch2 independence established\",\n      \"pmids\": [\"17259303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HEY1 binds to N-box domains adjacent to the SOX9 enhancer site in intron 1 of COL2A1, repressing SOX9-mediated transcriptional activation of COL2A1 and AGGRECAN to block chondrogenic differentiation; overexpression of HEY1 represses COL2A1 ~80-fold.\",\n      \"method\": \"ChIP for endogenous HEY1 binding to COL2A1 intron 1; transfection reporter assays; qPCR for COL2A1 and AGGRECAN\",\n      \"journal\": \"Arthritis and rheumatism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP identifying endogenous binding site, corroborated by overexpression reporter assays\",\n      \"pmids\": [\"18759300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Hey1 is a direct target of BMP9-induced Smad signaling (ChIP evidence); Hey1 loss diminishes BMP9-induced osteogenesis and promotes chondrogenic fate; Hey1 and Runx2 act synergistically, with Runx2 downstream of Hey1, and exogenous Runx2 rescues Hey1-knockdown osteogenic defects.\",\n      \"method\": \"ChIP for Smad binding to Hey1 locus; siRNA knockdown with in vitro/in vivo osteogenesis assays; Runx2 rescue experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP plus siRNA KD with rescue experiment, multiple osteogenic readouts in vitro and in vivo\",\n      \"pmids\": [\"18986983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Hey1 is recruited to the promoter regions of myogenin and Mef2C in myoblasts, correlating with reduced MyoD recruitment to these promoters, establishing that Hey1 represses myogenesis by blocking key myogenic target gene expression rather than directly inhibiting MyoD intrinsic activity.\",\n      \"method\": \"ChIP in C2C12 myoblasts for Hey1 and MyoD at myogenin and Mef2C promoters; Hey1 overexpression with differentiation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP with mechanistic promoter occupancy data showing displacement of MyoD, multiple evidence lines\",\n      \"pmids\": [\"19917614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"KSHV RTA acts as an E3 ubiquitin ligase targeting HEY1 for ubiquitination and proteasomal degradation; a Cys-plus-His-rich region of RTA is required; HEY1 interacts with co-repressor mSin3A; RTA disrupts the HEY1-mSin3A interaction.\",\n      \"method\": \"Ubiquitination assay, proteasome inhibitor rescue, co-immunoprecipitation of HEY1 with mSin3A, domain mutant analysis of RTA\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro ubiquitination assay with domain mutagenesis and mechanistic co-IP\",\n      \"pmids\": [\"19369342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"A naturally occurring Leu94Met polymorphism in HEY1 converts it from an AR corepressor to an AR co-activator and abolishes HEY1-mediated p53 activation and p53-dependent cell-cycle arrest, without affecting its intrinsic transcriptional repressive domains.\",\n      \"method\": \"Transient transfection reporter assays, cell-cycle analysis, sensitivity assays to p53-activating drugs; mutagenesis of HEY1 localization motifs\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — domain/point mutagenesis with multiple functional assays (AR corepressor, p53 activation, cell-cycle arrest)\",\n      \"pmids\": [\"19802006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Hesr1/Hey1 and Hesr3/HeyL are required together for the generation of undifferentiated quiescent satellite cells during postnatal muscle development; double knockout leads to premature myogenic differentiation (MyoD, myogenin, Ki67 expression in satellite cells) and age-dependent loss of satellite cells.\",\n      \"method\": \"Hesr1/Hesr3 double-knockout mouse analysis; in vitro myoblast culture showing loss of Pax7+/MyoD− undifferentiated cells; in vivo satellite cell counts and regeneration assays\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — double KO mouse with cell-autonomous in vitro validation and multiple molecular markers\",\n      \"pmids\": [\"21989910\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HEY1-NCOA2 fusion protein (derived from t(8;8) in mesenchymal chondrosarcoma) results from fusion of HEY1 exon 4 to NCOA2 exon 13 and is present in virtually all mesenchymal chondrosarcomas, defining this as the diagnostic gene fusion for this sarcoma.\",\n      \"method\": \"5' RACE, RT-PCR, FISH in clinical tumor specimens; genome-wide exon array expression screening\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — fusion junction molecularly characterized in multiple independent tumor samples\",\n      \"pmids\": [\"22034177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KSHV LANA stabilizes HEY1 protein by inhibiting its degradation, and HEY1 stabilized by LANA promotes neoplastic vasculature; HEY1 knockdown reduces new blood vessel formation in vivo (Matrigel plug assay).\",\n      \"method\": \"Whole-transcriptome sequencing, IHC on patient specimens, Matrigel plug angiogenesis assay in mice, siRNA knockdown of HEY1\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo angiogenesis assay with genetic manipulation, single lab\",\n      \"pmids\": [\"24523441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Hey1 expression in endothelial cells is induced by BMP9 (an Alk1 ligand) in serum, independent of canonical Notch/γ-secretase signaling; soluble Alk1 (but not Alk3) receptor abolishes this induction.\",\n      \"method\": \"Gamma-secretase inhibition, dominant-negative MAML1 expression, soluble BMP receptor pretreatment, RT-PCR for Hey1 in primary human endothelial cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological and genetic Notch blockade combined with receptor-specific BMP inhibition, single lab\",\n      \"pmids\": [\"25799559\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HEY1 is a direct downstream effector of FRA1 in the c-Met/HGF signaling pathway; CAF-derived HGF activates FRA1 in an ERK1/2-dependent manner, which in turn drives HEY1 expression to regulate liver tumor-initiating cells.\",\n      \"method\": \"Functional shRNA knockdown and overexpression assays; ChIP/reporter assays placing HEY1 downstream of FRA1; STAM NASH-HCC mouse model validation\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ChIP/reporter placing HEY1 downstream of FRA1, in vivo mouse model corroboration\",\n      \"pmids\": [\"27134167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"HEY1 phosphorylation at Ser-68 by STK38 and STK38L increases HEY1 protein stability but inhibits its ability to enhance p53 transcriptional activity; the phosphomimetic S68D mutant fails to induce p53-dependent cell-cycle arrest. HEY1 also interacts with MDM2 and is subject to MDM2-mediated degradation, and this interaction is prevented by Ser-68 phosphorylation.\",\n      \"method\": \"MALDI-TOF/TOF MS identification of phosphorylation site; mutagenesis (S68D phosphomimetic); kinase interaction and phosphorylation assays; co-immunoprecipitation with RPL11 and MDM2; p53 reporter assays; cell-cycle analysis\",\n      \"journal\": \"Bioscience reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — MS identification + mutagenesis + kinase assay + multiple functional readouts\",\n      \"pmids\": [\"27129302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Hey1 and HeyL function cell-autonomously and redundantly in muscle stem cells (satellite cells); HeyL requires Hes1 to form heterodimers that bind Hey1 target sites in chromatin with high affinity; HeyL-Hes1 heterodimer and Hey1 act synergistically to suppress myogenin promoter activity.\",\n      \"method\": \"Conditional and genetic null mice; cultured satellite cell assays; ChIP-seq for HeyL and HeyL-Hes1; myogenin promoter reporter assay\",\n      \"journal\": \"Development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP-seq with genome-wide binding analysis plus functional reporter assay and conditional KO mice\",\n      \"pmids\": [\"30745427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"BMP9 specifically induces Hey1 expression; Hey1 forms complexes with Id4 in osteoblasts; BMP9-induced overexpression of Hey1 overcomes Id4 inhibition and suppresses osteopontin (Opn) promoter activity, preventing OPN-type osteoblast differentiation.\",\n      \"method\": \"ChIP, immunoprecipitation (Hey1-Id4 complex), site-directed mutagenesis of Opn promoter, Opn promoter reporter assays\",\n      \"journal\": \"International journal of biochemistry & cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP + Co-IP + promoter mutagenesis identifying Hey1-Id4 complex mechanism\",\n      \"pmids\": [\"31550547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"HIF-1α directly binds a hypoxia response element (HRE) in the HEY1 promoter under hypoxia; HEY1 then directly represses PINK1 transcription; HCC cells with HEY1 knockdown re-express PINK1, and HEY1 overexpression reduces mitochondrial mass and oxidative stress.\",\n      \"method\": \"ChIP and luciferase reporter assays for HRE in HEY1 promoter; ChIP-seq and transcriptome sequencing to identify PINK1 as HEY1 target; siRNA knockdown of HEY1 with mitochondrial phenotype readouts\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP plus ChIP-seq with transcriptome validation and functional knockdown\",\n      \"pmids\": [\"31819034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Hey1 displays non-oscillatory stationary expression in slowly dividing neural progenitors (in contrast to oscillatory Hes1/Hes5 in fast-cycling progenitors), contributing to long-term maintenance of adult neural stem cells downstream of Notch; cell cycle arrest biases Notch effector selection toward Hey1.\",\n      \"method\": \"Live imaging of Hey1 expression dynamics; comparison with Hes1/Hes5 oscillations; Notch manipulation in embryonic NPCs; adult NSC lineage tracing\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — live imaging with Notch genetic manipulation revealing non-oscillatory expression, multiple complementary approaches\",\n      \"pmids\": [\"34772946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HEY1-NCOA2 fusion protein preferentially binds promoter regions of canonical HEY1 targets (ChIP-seq) but converts them from repressed to transactivated; the fusion directly targets and upregulates PDGFB and PDGFRA, and dramatically increases phospho-AKT (Ser473).\",\n      \"method\": \"ChIP-seq and RNA-seq in iPSC-derived MSCs with inducible HEY1-NCOA2 expression; comparison with wildtype HEY1 and NCOA2\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — genome-wide ChIP-seq + transcriptome in appropriate cell context with isogenic controls\",\n      \"pmids\": [\"35342947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"HEY1-NCOA2 expression in embryonic superficial zone chondrocyte precursors induces mesenchymal chondrosarcoma in mice; the fusion protein physically interacts with Runx2 via NCOA2 C-terminal domains; Runx2 knockout delays but does not abolish tumor onset; HDAC inhibitor panobinostat suppresses tumor growth by abrogating HEY1-NCOA2/Runx2-downstream gene expression.\",\n      \"method\": \"Mouse mesenchymal chondrosarcoma model via gene transduction and transplantation; ChIP-seq; co-immunoprecipitation of HEY1-NCOA2 with Runx2; Runx2 conditional knockout; in vitro and in vivo panobinostat treatment\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vivo tumor model + ChIP-seq + Co-IP with domain identification + drug rescue experiment\",\n      \"pmids\": [\"37212282\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HEY1 is SUMOylated at conserved lysines by the E3 ligase TRIM28 in endothelial cells; SUMOylation facilitates HEY1 homodimer formation and preserves E-box promoter binding capability, maintaining HEY1's repressive activity on angiogenic RTK and Notch pathway genes. Proangiogenic stimuli induce HEY1 deSUMOylation, causing heterodimerization with HES1, loss of DNA binding, and relief of repression.\",\n      \"method\": \"Immunoprecipitation + mass spectrometry identifying SUMOylation sites; ChIP, dual luciferase, EMSA for DNA binding; co-immunoprecipitation for dimerization; SUMOylation-deficient mutant mice; multiple in vivo angiogenesis models (embryonic vascular growth, matrigel plug, wound healing, OIR, tumor angiogenesis)\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — MS identification + mutagenesis + structural dimerization analysis + multiple in vivo models, single rigorous study with orthogonal methods\",\n      \"pmids\": [\"38166414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Hey1 interacts directly with the TrkC intracellular domain and importin-α3/KPNA4; the cleaved TrkC killer-fragment is translocated to the nucleus by importins and interacts with Hey1 there; Hey1 and TrkC-KF together transcriptionally silence MDM2, contributing to p53 stabilization and induction of apoptosis in neuroblastoma.\",\n      \"method\": \"Co-immunoprecipitation identifying TrkC-Hey1 and TrkC-KPNA4 interactions; MDM2 promoter reporter assays; Hey1 and p53 knockdown/overexpression; avian neuroblastoma in vivo model\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted nuclear interaction with promoter reporter and in vivo rescue experiment\",\n      \"pmids\": [\"29750782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Hey1 null mice on C57BL/6N background exhibit perinatal lethality due to abnormal fourth pharyngeal arch artery (PAA4) development, resulting in aortic arch malformations; endothelial cells in PAA4 differentiate normally but are structurally disorganized and vascular smooth muscle cells are absent, associated with downregulation of endothelial Jag1.\",\n      \"method\": \"Hrt1/Hey1 knockout mouse analysis; histology, immunostaining for endothelial and VSMC markers; Jag1 expression analysis\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with cellular and molecular phenotyping revealing specific endothelial-VSMC signaling defect\",\n      \"pmids\": [\"26577899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Hey1 expression in vascular endothelial cells (not smooth muscle cells) is essential for pharyngeal arch artery development and great vessel morphogenesis; endothelial-specific Tek-Cre-mediated Hey1 deletion impairs endothelial tube formation and smooth muscle differentiation. A distal endothelial enhancer controlling Hey1 expression is conserved, specific to large-caliber arteries, and regulated by Notch (not ALK1) signaling.\",\n      \"method\": \"Cell type-specific conditional knockout (Tek-Cre); enhancer identification and functional testing in vivo; Notch vs ALK1 signaling manipulations\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with cell-type specificity established plus enhancer mechanistic dissection\",\n      \"pmids\": [\"33454003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Babam2 interacts with Hey1 to inhibit Nfatc1 transcription, negatively regulating osteoclastogenesis; silencing Hey1 largely abolishes the anti-osteoclastogenic effects of Babam2 overexpression.\",\n      \"method\": \"Co-immunoprecipitation (Babam2-Hey1 interaction); Nfatc1 promoter reporter assays; Babam2 transgenic mice; siRNA knockdown epistasis experiments\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP with functional reporter and epistasis, single lab\",\n      \"pmids\": [\"35864959\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HEY1 is a bHLH-Orange transcriptional repressor that is directly activated downstream of Notch (via RBP-Jκ) and BMP/Smad/Alk1 signaling; its repressive activity is modulated by SUMOylation (mediated by TRIM28, promoting homodimerization and E-box binding) and phosphorylation at Ser-68 (by STK38/STK38L, stabilizing the protein but blocking p53 activation), as well as by KSHV RTA-mediated ubiquitination and proteasomal degradation; mechanistically, HEY1 represses target gene promoters through interactions with SP1-like factors (for VEGFR2), direct N-box binding (COL2A1), or by forming inactive heterodimers with MyoD, and it acts as a corepressor for the androgen receptor AF1 domain; HEY1 is essential for arterial cell fate specification, endothelial tube formation and vascular remodeling, cardiac EMT and AV boundary formation (via Tbx2 suppression), maintenance of muscle satellite cells and neural progenitors, and osteoblast differentiation (by antagonizing Runx2), while the oncogenic HEY1-NCOA2 fusion converts its canonical target-gene repressor function into transcriptional activation, upregulating PDGFB/PDGFRA and PI3K/AKT signaling, driving mesenchymal chondrosarcoma.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"HEY1 is a bHLH-Orange transcriptional repressor that functions as a central effector of Notch and BMP/Smad signaling to control cell fate decisions in vascular, cardiac, neural, skeletal, and muscle progenitor compartments. HEY1 represses target genes through multiple mechanisms: direct N-box binding (e.g., COL2A1), interaction with SP1-like factors at GC-box elements (e.g., VEGFR2), sequestration of tissue-specific activators such as MyoD into inactive heterodimers, and recruitment of the mSin3A co-repressor complex; its repressive activity on angiogenic genes is maintained by TRIM28-mediated SUMOylation, which stabilizes DNA-binding homodimers, while proangiogenic signals trigger deSUMOylation and heterodimerization with HES1, relieving repression [PMID:38166414, PMID:10964718, PMID:16782059, PMID:11279181, PMID:19369342]. In vascular development, Hey1 and Hey2 are redundantly required downstream of Notch for arterial identity specification and great vessel morphogenesis, while Hey1 and HeyL together govern cardiac atrioventricular EMT and muscle satellite cell quiescence [PMID:15107403, PMID:17303760, PMID:21989910]. The HEY1-NCOA2 fusion, the defining translocation of mesenchymal chondrosarcoma, retains HEY1 target-gene binding but converts repression into transactivation, upregulating PDGFB/PDGFRA and PI3K/AKT signaling to drive tumorigenesis [PMID:35342947, PMID:37212282].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Identifying HEY1 as a direct Notch transcriptional target resolved how Notch receptor activation is decoded by a specific bHLH repressor, placing HEY1 immediately downstream of RBP-Jκ.\",\n      \"evidence\": \"Promoter reporter assays with all four activated Notch receptors and RBP-Jκ site mutagenesis\",\n      \"pmids\": [\"10964718\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Notch-independent inputs also regulate HEY1 promoter in vivo was not addressed\", \"Chromatin context of RBP-Jκ binding not examined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstrating that HEY1 overexpression suppresses VEGFR2 and blocks endothelial tube formation established its first functional role as an anti-angiogenic transcriptional repressor.\",\n      \"evidence\": \"Bidirectional manipulation (overexpression and antisense knockdown) in primary endothelial cells with proliferation, migration, and tube formation assays\",\n      \"pmids\": [\"11069914\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of VEGFR2 repression (direct vs. indirect) not resolved\", \"In vivo angiogenic relevance not tested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showing that HEY1 sequesters MyoD into transcriptionally inactive heterodimers via a C-terminal domain (not bHLH or YRPW) revealed a dominant-negative mechanism for blocking myogenesis distinct from canonical bHLH repression.\",\n      \"evidence\": \"Co-IP, EMSA, and domain mutagenesis in 10T1/2 and C2C12 myogenic conversion assays\",\n      \"pmids\": [\"11279181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of HEY1-MyoD heterodimer inactivity unknown\", \"In vivo relevance to satellite cell biology not yet tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"In utero electroporation experiments showed that HEY1 maintains neural precursor identity by repressing proneural bHLH genes Mash1 and Math3, expanding the repertoire of HEY1-regulated cell fate decisions beyond the vasculature.\",\n      \"evidence\": \"In utero electroporation in mouse brain with reporter assay validation for Mash1/Math3 promoters\",\n      \"pmids\": [\"12947105\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HEY1 binds Mash1/Math3 promoters directly was not shown\", \"Redundancy with Hey2/HeyL in neural progenitors not addressed\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Hey1/Hey2 double-knockout lethality with loss of arterial markers phenocopying Notch1 and Jagged1 mutants established these factors as the essential downstream mediators of Notch-driven arterial cell fate specification.\",\n      \"evidence\": \"Double-knockout mouse genetics with genetic epistasis to Notch1/Jagged1 knockouts and arterial marker immunostaining\",\n      \"pmids\": [\"15107403\", \"15680351\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contributions of Hey1 vs. Hey2 to specific arterial genes not dissected\", \"Downstream direct target genes mediating arterial fate unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identification of Runx2 as a direct interaction partner whose transcriptional activity is completely blocked by HEY1 revealed a mechanism for HEY1-mediated inhibition of osteoblast differentiation.\",\n      \"evidence\": \"siRNA knockdown, Runx2 reporter assays, and mineralization assays in MC3T3 and C2C12 cells\",\n      \"pmids\": [\"15178686\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HEY1 binds Runx2 on chromatin or sequesters it off-DNA not determined\", \"In vivo skeletal phenotype of Hey1 single KO not examined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstration that HEY1 acts as a corepressor for the androgen receptor AF1 domain, with Notch signaling suppressing AR transactivation through HEY1, linked Notch-HEY1 signaling to androgen-dependent gene regulation in prostate.\",\n      \"evidence\": \"Reporter assays, corepressor assays, activated Notch constructs, and AR-HEY1 colocalization in prostate epithelium\",\n      \"pmids\": [\"15684393\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide AR target gene regulation by HEY1 not mapped\", \"Mechanism of HEY1 nuclear exclusion in prostate cancer not defined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Mechanistic dissection of VEGFR2 repression showed HEY1 acts through SP1-like factors at GC-box elements rather than direct E-box binding, and that bHLH plus Orange domains suffice while the YRPW motif is dispensable, defining a non-canonical repression mode for TATA-less promoters.\",\n      \"evidence\": \"Promoter reporter assays with domain mutants; protein-DNA binding studies; TATA vs. non-TATA promoter comparisons\",\n      \"pmids\": [\"16782059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the SP1-like factor mediating HEY1 tethering not determined\", \"Whether this mechanism applies genome-wide to other TATA-less targets unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Hey1/HeyL double knockouts revealed that these factors are redundantly required for endocardial EMT and AV valve morphogenesis, while forced Hey1 expression suppresses Tbx2 to regulate AV boundary formation, expanding HEY1's role to cardiac cushion development.\",\n      \"evidence\": \"Double-knockout mouse with AV explant EMT assays and MMP-2 analysis; cardiac-specific transgenic misexpression with in situ hybridization\",\n      \"pmids\": [\"17303760\", \"17259303\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Hey1 directly binds the Tbx2 promoter not shown\", \"Relative contributions of Hey1 vs. HeyL to EMT not separated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"ChIP identification of HEY1 binding to N-box elements in COL2A1 intron 1, where it antagonizes SOX9-mediated activation, established direct N-box binding as a distinct mode of HEY1-mediated transcriptional repression controlling chondrogenesis.\",\n      \"evidence\": \"ChIP for endogenous HEY1 at COL2A1 intron 1; reporter assays; qPCR for COL2A1 and AGGRECAN\",\n      \"pmids\": [\"18759300\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HEY1 physically interacts with SOX9 or merely competes for adjacent cis-elements unknown\", \"Genome-wide N-box occupancy not mapped\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"ChIP evidence that Smad signaling directly activates the Hey1 locus downstream of BMP9 established a Notch-independent route for Hey1 induction, with Runx2 rescue of Hey1 knockdown confirming Hey1 acts upstream of Runx2 in osteogenesis.\",\n      \"evidence\": \"Smad ChIP at Hey1 locus; siRNA knockdown with in vitro/in vivo osteogenesis assays; Runx2 rescue\",\n      \"pmids\": [\"18986983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Hey1 simultaneously represses and cooperates with Runx2 in different osteogenic contexts not reconciled\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"ChIP showing Hey1 occupies myogenin and Mef2C promoters with concomitant displacement of MyoD refined the myogenic repression mechanism from simple MyoD sequestration to active promoter-level competition.\",\n      \"evidence\": \"ChIP in C2C12 myoblasts for Hey1 and MyoD at myogenin/Mef2C promoters\",\n      \"pmids\": [\"19917614\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Hey1 recruits specific co-repressors at these promoters not addressed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identification of KSHV RTA as an E3 ubiquitin ligase that targets HEY1 for proteasomal degradation and disrupts the HEY1-mSin3A co-repressor complex revealed a viral strategy to overcome HEY1-mediated repression of lytic reactivation.\",\n      \"evidence\": \"In vitro ubiquitination assay, proteasome inhibitor rescue, Co-IP with mSin3A, RTA domain mutagenesis\",\n      \"pmids\": [\"19369342\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether endogenous cellular E3 ligases regulate HEY1 turnover similarly not explored\", \"In vivo relevance to KSHV latency-lytic switch not confirmed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The Leu94Met polymorphism converting HEY1 from AR corepressor to co-activator while abolishing p53 activation demonstrated that a single residue switch can invert HEY1's functional output, linking HEY1 to p53-dependent cell cycle control.\",\n      \"evidence\": \"Point mutagenesis with AR corepressor, p53 reporter, and cell-cycle arrest assays\",\n      \"pmids\": [\"19802006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of how L94M inverts corepressor to co-activator function unknown\", \"Population frequency and clinical significance of L94M not established\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Hey1/HeyL double knockout causing premature satellite cell differentiation and age-dependent satellite cell depletion established HEY1 as essential for maintaining muscle stem cell quiescence, linking Notch-HEY1 signaling to adult tissue regeneration.\",\n      \"evidence\": \"Double-knockout mouse; in vitro myoblast culture showing loss of Pax7+/MyoD− undifferentiated cells; satellite cell counts and regeneration assays\",\n      \"pmids\": [\"21989910\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct chromatin targets of Hey1 in satellite cells not identified genome-wide\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Molecular characterization of the HEY1-NCOA2 fusion in mesenchymal chondrosarcoma identified the diagnostic translocation for this tumor type, implicating conversion of HEY1 repressor function into aberrant transcriptional activation as an oncogenic mechanism.\",\n      \"evidence\": \"5' RACE, RT-PCR, FISH in multiple clinical tumor specimens; genome-wide exon array\",\n      \"pmids\": [\"22034177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Oncogenic mechanism of the fusion not yet defined\", \"Target genes of HEY1-NCOA2 unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of Ser-68 phosphorylation by STK38/STK38L as a modification that stabilizes HEY1 protein but blocks p53 activation revealed a phospho-switch controlling HEY1's pro-apoptotic function, with MDM2 identified as a degradation-promoting interactor opposed by this phosphorylation.\",\n      \"evidence\": \"MALDI-TOF MS; S68D phosphomimetic mutagenesis; kinase assays; Co-IP with RPL11 and MDM2; p53 reporter and cell-cycle assays\",\n      \"pmids\": [\"27129302\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo significance of Ser-68 phosphorylation not tested\", \"Whether STK38 regulation is context-specific (e.g., tissue type) unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstration that the TrkC killer-fragment is imported to the nucleus via importin-β3/KPNA4 and cooperates with HEY1 to silence MDM2, stabilizing p53 and inducing apoptosis, established a dependence-receptor signaling pathway converging on HEY1-mediated transcriptional repression.\",\n      \"evidence\": \"Co-IP of TrkC-Hey1 and TrkC-KPNA4; MDM2 promoter reporter; Hey1/p53 knockdown/overexpression; avian neuroblastoma in vivo model\",\n      \"pmids\": [\"29750782\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HEY1 directly binds the MDM2 promoter not shown by ChIP\", \"Generality beyond neuroblastoma not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"ChIP-seq revealing that HeyL requires Hes1 to form heterodimers that bind Hey1 target sites showed how combinatorial bHLH pairing determines genome-wide occupancy, explaining the functional redundancy between Hey1 and HeyL in satellite cells.\",\n      \"evidence\": \"Conditional knockout mice; ChIP-seq for HeyL and HeyL-Hes1; myogenin promoter reporter assay\",\n      \"pmids\": [\"30745427\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Hey1 also requires a heterodimeric partner for full chromatin occupancy not determined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Endothelial-specific conditional deletion proved that Hey1 function in pharyngeal arch artery morphogenesis is cell-autonomous to endothelial cells, and identified a distal Notch-responsive enhancer specific to large arteries, defining the cis-regulatory logic of vascular Hey1 expression.\",\n      \"evidence\": \"Tek-Cre conditional knockout; enhancer identification and functional testing in vivo; Notch vs. ALK1 signaling manipulations\",\n      \"pmids\": [\"33454003\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Transcription factors binding the distal enhancer besides Notch not identified\", \"Whether the enhancer is relevant to non-pharyngeal arteries unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Live imaging revealed that Hey1 is expressed in a non-oscillatory, stationary pattern in slowly dividing neural progenitors, contrasting with oscillatory Hes1/Hes5, establishing expression dynamics as a mechanism by which Notch effector choice biases stem cell maintenance vs. proliferation.\",\n      \"evidence\": \"Live imaging of Hey1 dynamics; comparison with Hes1/Hes5 oscillations; Notch manipulation in embryonic NPCs; adult NSC lineage tracing\",\n      \"pmids\": [\"34772946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for why Hey1 does not oscillate unknown\", \"Whether stationary expression is intrinsic to the Hey1 mRNA/protein or imposed by cell cycle state not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Genome-wide ChIP-seq and RNA-seq of the HEY1-NCOA2 fusion showed it binds canonical HEY1 target promoters but converts them from repressed to activated, directly upregulating PDGFB/PDGFRA and hyperactivating PI3K/AKT, providing the mechanistic basis for how the fusion drives mesenchymal chondrosarcoma.\",\n      \"evidence\": \"ChIP-seq and RNA-seq in iPSC-derived MSCs with inducible HEY1-NCOA2 vs. wildtype HEY1/NCOA2 isogenic controls\",\n      \"pmids\": [\"35342947\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PDGFB/PDGFRA are necessary and sufficient for transformation not tested\", \"Structural basis of repressor-to-activator conversion not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"An in vivo mesenchymal chondrosarcoma mouse model showed that the HEY1-NCOA2 fusion physically interacts with Runx2 and that Runx2 contributes to but is not solely required for tumorigenesis, while HDAC inhibition suppresses fusion-driven gene expression and tumor growth.\",\n      \"evidence\": \"Mouse tumor model; ChIP-seq; Co-IP of HEY1-NCOA2 with Runx2; Runx2 conditional KO; panobinostat treatment in vitro and in vivo\",\n      \"pmids\": [\"37212282\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which Runx2-independent pathways sustain tumor growth unknown\", \"Mechanism by which HDAC inhibition specifically disrupts fusion activity not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Discovery that TRIM28-mediated SUMOylation stabilizes HEY1 homodimers and E-box binding while proangiogenic deSUMOylation switches HEY1 to inactive HES1 heterodimers provided a unified post-translational mechanism governing the angiogenic switch through HEY1 dimerization control.\",\n      \"evidence\": \"IP-MS identifying SUMOylation sites; ChIP, EMSA, dual luciferase for DNA binding; Co-IP for dimerization; SUMOylation-deficient mutant mice; multiple in vivo angiogenesis models\",\n      \"pmids\": [\"38166414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The deSUMOylase responsible for proangiogenic HEY1 modification not identified\", \"Whether SUMOylation regulates HEY1 in non-endothelial contexts unknown\", \"Structural basis of how SUMOylation favors homodimer over heterodimer not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for HEY1 dimerization switching, genome-wide direct target identification across multiple tissue contexts, the identity of endogenous E3 ligases and deSUMOylases regulating HEY1 turnover outside viral contexts, and the precise mechanism by which the HEY1-NCOA2 fusion converts repression to activation.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal or cryo-EM structure of HEY1 or its complexes\", \"Comprehensive genome-wide binding data for wildtype HEY1 across tissues lacking\", \"Endogenous ubiquitin ligases for HEY1 turnover not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 2, 7, 8, 10, 15, 17, 28, 30]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [10, 12, 15, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 8, 33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [0, 3, 6, 9, 24, 29]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4, 6, 9, 13, 14, 34, 35]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 10, 15, 17, 28, 30]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [21, 30, 31]}\n    ],\n    \"complexes\": [\n      \"HEY1-mSin3A co-repressor complex\",\n      \"HEY1-HES1 heterodimer\",\n      \"HEY1-MyoD heterodimer\"\n    ],\n    \"partners\": [\n      \"RBPJ\",\n      \"MYOD1\",\n      \"RUNX2\",\n      \"AR\",\n      \"TRIM28\",\n      \"HES1\",\n      \"NTRK3\",\n      \"BABAM2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}