{"gene":"NELFB","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2009,"finding":"NELF-B (COBRA1) is a subunit of the four-subunit NELF complex that controls RNA polymerase II pausing in transcription; knockout of mouse NELF-B causes inner cell mass deficiency and embryonic lethality, and ChIP shows COBRA1 binds to the Lef1 promoter to modulate promoter-bound RNA polymerase abundance, preventing unscheduled expression of developmental genes in embryonic stem cells.","method":"Knockout mouse model, knockdown in mESCs, chromatin immunoprecipitation (ChIP)","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined phenotype + ChIP demonstrating direct promoter occupancy, multiple orthogonal methods","pmids":["19340312"],"is_preprint":false},{"year":2004,"finding":"COBRA1 physically interacts with BRCA1 in the nucleus of human breast cancer cells, as shown by co-immunoprecipitation of endogenous proteins, and localizes to the nucleus.","method":"Co-immunoprecipitation of endogenous proteins, immunofluorescence","journal":"IUBMB life","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP with localization, single lab","pmids":["15185750"],"is_preprint":false},{"year":2004,"finding":"COBRA1 inhibits AP-1 transcriptional activity in a dose-dependent manner by physically interacting with c-Jun and c-Fos; the middle region of COBRA1 binds c-Fos, and deletion of the c-Fos binding site abolishes COBRA1-mediated AP-1 inhibition.","method":"Transfection/overexpression, siRNA knockdown, reporter assay, co-immunoprecipitation, deletion mutagenesis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — gain/loss-of-function + Co-IP + mutagenesis, single lab","pmids":["15530430"],"is_preprint":false},{"year":2013,"finding":"NELF-B attenuates glucocorticoid receptor (GR)-mediated gene induction, reduces partial agonist activity, and increases agonist EC50; ChIP shows NELF-B diminishes GR recruitment to promoter regions; NELF-A and NELF-B each act independently as competitive decelerators after the site of GR action; a conserved motif in each subunit is required for full modulatory activity.","method":"Stable knockdown, ChIP, competition assay, mutagenesis of conserved motif","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KD, ChIP, competition assay, mutagenesis), mechanistic placement in GR induction sequence","pmids":["24097989"],"is_preprint":false},{"year":2013,"finding":"The neurotrophin receptor TrkC killer fragment (TrkC KF) interacts with COBRA1 (NELF-B); COBRA1 shuttles TrkC KF to the mitochondria where it promotes Bax activation, cytochrome c release, and apoptosome-dependent apoptosis. Cobra1 silencing rescues neuroepithelial cell death caused by NT-3 silencing in chick neural tube.","method":"Co-immunoprecipitation, subcellular fractionation, in vivo silencing in chick neural tube, Bax/cytochrome c release assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, mitochondrial fractionation, in vivo rescue, multiple orthogonal methods","pmids":["24034695"],"is_preprint":false},{"year":2016,"finding":"Tissue-specific deletion of Cobra1 in mouse mammary gland blocks ductal morphogenesis, alveologenesis, and lactogenesis; additional loss of full-length Brca1 largely rescues these defects and restores developmental transcription, demonstrating that BRCA1 antagonizes COBRA1-dependent transcription programme in a DNA repair-independent manner.","method":"Conditional (tissue-specific) knockout, genetic epistasis (double KO), transcriptional profiling","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — clean conditional KO + genetic suppression (double KO rescue) with defined phenotypic and transcriptional readouts","pmids":["26941120"],"is_preprint":false},{"year":2018,"finding":"The genetic interaction between Brca1 and Cobra1 in mammary gland development is domain-specific: separation-of-function mutations abrogating either BRCA1 RING E3 ligase activity or BRCT phospho-recognition fail to rescue Cobra1 KO mammary defects, and deletion of Palb2 does not rescue Cobra1 KO, placing the interaction specifically with full-length BRCA1.","method":"Conditional knockout, separation-of-function mutations, genetic epistasis","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — multiple separation-of-function alleles tested in vivo with defined phenotypic readout","pmids":["29426838"],"is_preprint":false},{"year":2023,"finding":"Crystal structure of the human NELF-B/C/E ternary complex was solved at high resolution, revealing detailed inter-subunit interaction surfaces and residues important for the association between NELF-B and NELF-E.","method":"X-ray crystallography","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with identification of key interaction residues","pmids":["37591184"],"is_preprint":false},{"year":2023,"finding":"Cytoplasmic NELFB supports cell proliferation independently of Pol II pausing: separation-of-function mutations that sequester NELFB in the cytoplasm decouple its role in cell proliferation from Pol II pausing. Cytoplasmic NELFB physically and functionally interacts with PI3K/AKT prosurvival kinases, and ectopic membrane-tethered PI3K/AKT partially bypasses the proliferative role of NELFB but not its effect on Pol II occupancy.","method":"Separation-of-function mutations, subcellular localization experiments, co-immunoprecipitation, AKT ectopic expression rescue, Pol II ChIP","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (mutational uncoupling, Co-IP, ChIP, genetic rescue) in single rigorous study","pmids":["37717699"],"is_preprint":false},{"year":2025,"finding":"Nelfb deletion from preadipocyte lineages in mice causes failure of dermal white adipose tissue and other fat depot formation; Nelfb promotes open chromatin and stabilizes RNA Polymerase II binding at Pparg, Cebpa, Krox20, and Stat3 promoters; retroviral Pparg expression or rosiglitazone (Pparg agonist) treatment rescues adipocyte differentiation in Nelfb-depleted cells or mice, placing Nelfb upstream of Pparg in the adipogenic gene regulatory hierarchy.","method":"Conditional knockout, ChIP (Pol II, chromatin accessibility), retroviral rescue, pharmacological rescue (rosiglitazone)","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — clean conditional KO, ChIP, and multiple rescue experiments placing NELFB upstream of Pparg in adipogenesis","pmids":["40960263"],"is_preprint":false}],"current_model":"NELF-B (COBRA1) is a subunit of the four-subunit NELF complex that stabilizes promoter-proximal RNA polymerase II pausing and regulates transcription elongation; it physically interacts with BRCA1 (antagonistically), AP-1 components (c-Jun/c-Fos), the glucocorticoid receptor, and PI3K/AKT kinases, and can shuttle apoptotic signals to mitochondria via TrkC killer fragment—with its nuclear Pol II pausing function and its cytoplasmic PI3K/AKT signaling function being genetically separable."},"narrative":{"teleology":[{"year":2004,"claim":"Establishing that NELF-B (COBRA1) functions as a nuclear transcriptional coregulator: prior to this, its molecular role was undefined; co-immunoprecipitation showed it interacts with BRCA1 in the nucleus and physically binds AP-1 components (c-Jun/c-Fos) to dose-dependently inhibit AP-1-driven transcription via a mappable c-Fos-binding domain.","evidence":"Co-IP of endogenous proteins, reporter assays, deletion mutagenesis in human breast cancer and other cell lines","pmids":["15185750","15530430"],"confidence":"Medium","gaps":["BRCA1–COBRA1 interaction shown by single Co-IP without reciprocal validation or functional consequence defined","AP-1 inhibition demonstrated only by overexpression/reporter, lacking genome-wide or endogenous target validation","Relationship to Pol II pausing not yet established"]},{"year":2009,"claim":"Demonstrating that NELF-B is an essential NELF complex subunit required for Pol II pausing in vivo: knockout causes embryonic lethality due to inner cell mass failure, and ChIP showed direct promoter occupancy modulating Pol II abundance at developmental genes in embryonic stem cells.","evidence":"Nelfb knockout mouse, knockdown in mESCs, chromatin immunoprecipitation","pmids":["19340312"],"confidence":"High","gaps":["Genome-wide target repertoire of NELF-B in ESCs not determined","Whether ICM deficiency reflects specific gene derepression or general transcription failure not resolved"]},{"year":2013,"claim":"Revealing two previously unknown functions — attenuation of glucocorticoid receptor signaling and cytoplasmic apoptotic signaling: NELF-B acts as a competitive decelerator of GR-driven gene induction via a conserved motif, and separately shuttles the TrkC killer fragment to mitochondria to initiate Bax/cytochrome c-dependent apoptosis in neural progenitors.","evidence":"Stable knockdown with ChIP and competition assay for GR; reciprocal Co-IP, mitochondrial fractionation, and in vivo silencing in chick neural tube for TrkC KF","pmids":["24097989","24034695"],"confidence":"High","gaps":["Mechanism by which NELF-B recognizes and transports TrkC KF to mitochondria not structurally defined","Whether GR attenuation requires the intact NELF tetrameric complex or only NELF-B is unclear","Relationship between cytoplasmic apoptotic role and nuclear Pol II pausing function not addressed"]},{"year":2016,"claim":"Establishing a functional antagonism between BRCA1 and NELF-B in tissue development: conditional Cobra1 deletion blocked mammary gland morphogenesis and lactogenesis, and co-deletion of full-length Brca1 rescued these defects, demonstrating that BRCA1 counteracts NELF-B-dependent transcriptional control independently of DNA repair.","evidence":"Tissue-specific conditional knockout, double-KO genetic epistasis, transcriptional profiling in mouse mammary gland","pmids":["26941120"],"confidence":"High","gaps":["Molecular mechanism by which BRCA1 antagonizes NELF-B-dependent pausing not identified","Whether this genetic interaction extends to non-mammary tissues not tested"]},{"year":2018,"claim":"Refining the BRCA1–NELF-B genetic interaction to require full-length BRCA1: separation-of-function mutations in BRCA1 RING or BRCT domains and Palb2 deletion all failed to rescue Cobra1 KO mammary defects, demonstrating specificity beyond BRCA1's known enzymatic activities.","evidence":"Conditional knockout with multiple separation-of-function alleles and Palb2 deletion in vivo","pmids":["29426838"],"confidence":"High","gaps":["Which BRCA1 domain or activity mediates the antagonism remains unidentified","No biochemical reconstitution of BRCA1-mediated NELF eviction or pausing release"]},{"year":2023,"claim":"Solving the structural basis of the NELF core and uncoupling nuclear from cytoplasmic functions: the NELF-B/C/E crystal structure revealed inter-subunit interaction surfaces, while separation-of-function mutations demonstrated that cytoplasmic NELF-B promotes proliferation via PI3K/AKT independently of Pol II pausing.","evidence":"X-ray crystallography of NELF-B/C/E; separation-of-function mutants, Co-IP with PI3K/AKT, ectopic AKT rescue, Pol II ChIP","pmids":["37591184","37717699"],"confidence":"High","gaps":["How cytoplasmic NELF-B activates PI3K/AKT at the molecular level is unknown","Whether NELF-B's cytoplasmic pool is regulated by signaling-dependent nuclear-cytoplasmic shuttling not addressed","Full tetrameric NELF complex structure (with NELF-A and RNA Pol II) not yet available"]},{"year":2025,"claim":"Extending NELF-B's developmental role to adipogenesis: conditional Nelfb deletion from preadipocytes abolished fat depot formation, and ChIP showed NELF-B maintains open chromatin and Pol II binding at Pparg, Cebpa, Krox20, and Stat3 promoters; Pparg re-expression or pharmacological activation rescued differentiation, placing NELF-B upstream of the master adipogenic regulator.","evidence":"Conditional knockout in preadipocyte lineage, ChIP for Pol II and chromatin accessibility, retroviral Pparg rescue, rosiglitazone treatment in vivo and in vitro","pmids":["40960263"],"confidence":"High","gaps":["Whether NELF-B's role in adipogenesis is separable from the cytoplasmic PI3K/AKT function not tested","Genome-wide pausing landscape in preadipocytes not characterized"]},{"year":null,"claim":"Key open questions include: the molecular mechanism by which BRCA1 antagonizes NELF-B–dependent pausing, how cytoplasmic NELF-B engages and activates PI3K/AKT, and whether the nuclear pausing and cytoplasmic signaling functions are coordinately regulated during development and disease.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No reconstituted biochemical system for BRCA1-mediated pausing release at NELF-B targets","Structural basis of cytoplasmic NELF-B–PI3K/AKT interaction unknown","Regulation of nuclear-cytoplasmic partitioning of NELF-B not characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3,9]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,9]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1,3,9]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4,8]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,3,5,9]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[4]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,5,9]}],"complexes":["NELF complex (NELF-A/B/C/E)"],"partners":["BRCA1","NELF-E","NELF-C","NELF-A","FOS","JUN","AKT1","NTRK3"],"other_free_text":[]},"mechanistic_narrative":"NELF-B (COBRA1) is a core subunit of the four-subunit NELF complex that enforces promoter-proximal RNA polymerase II pausing, thereby gating the expression of developmental and differentiation genes. Knockout studies demonstrate that NELF-B is essential for embryonic viability, mammary gland morphogenesis, and adipogenesis, where it stabilizes Pol II occupancy and maintains open chromatin at key regulatory promoters such as Pparg and Cebpa; BRCA1 genetically antagonizes this NELF-B–dependent transcriptional programme in a DNA-repair-independent, domain-specific manner [PMID:19340312, PMID:26941120, PMID:29426838, PMID:40960263]. Beyond its nuclear Pol II-pausing function, NELF-B possesses a genetically separable cytoplasmic role in which it physically engages PI3K/AKT pro-survival kinases to promote cell proliferation, and it can shuttle the TrkC killer fragment to mitochondria to trigger Bax-dependent apoptosis [PMID:37717699, PMID:24034695]. The high-resolution crystal structure of the NELF-B/C/E ternary complex reveals the inter-subunit contacts that organize the NELF core [PMID:37591184]."},"prefetch_data":{"uniprot":{"accession":"Q8WX92","full_name":"Negative elongation factor B","aliases":["Cofactor of BRCA1"],"length_aa":580,"mass_kda":65.7,"function":"Essential component of the NELF complex, a complex that negatively regulates the elongation of transcription by RNA polymerase II (PubMed:12612062). The NELF complex, which acts via an association with the DSIF complex and causes transcriptional pausing, is counteracted by the P-TEFb kinase complex (PubMed:10199401). May be able to induce chromatin unfolding (PubMed:11739404). Essential for early embryogenesis; plays an important role in maintaining the undifferentiated state of embryonic stem cells (ESCs) by preventing unscheduled expression of developmental genes (By similarity). Plays a key role in establishing the responsiveness of stem cells to developmental cues; facilitates plasticity and cell fate commitment in ESCs by establishing the appropriate expression level of signaling molecules (By similarity). Supports the transcription of genes involved in energy metabolism in cardiomyocytes; facilitates the association of transcription initiation factors with the promoters of the metabolism-related genes (By similarity) (Microbial infection) The NELF complex is involved in HIV-1 latency possibly involving recruitment of PCF11 to paused RNA polymerase II (PubMed:23884411). In vitro, binds weakly to the HIV-1 TAR RNA which is located in the long terminal repeat (LTR) of HIV-1 (PubMed:23884411)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q8WX92/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/NELFB","classification":"Common Essential","n_dependent_lines":1170,"n_total_lines":1208,"dependency_fraction":0.9685430463576159},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"INTS9","stoichiometry":10.0},{"gene":"POLR2B","stoichiometry":4.0},{"gene":"POLR2E","stoichiometry":0.2},{"gene":"POLR2F","stoichiometry":0.2},{"gene":"POLR2H","stoichiometry":0.2},{"gene":"POLR2I","stoichiometry":0.2},{"gene":"POLR2J","stoichiometry":0.2},{"gene":"POLR2K","stoichiometry":0.2},{"gene":"PPP2CA","stoichiometry":0.2},{"gene":"SSRP1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/NELFB","total_profiled":1310},"omim":[{"mim_id":"611180","title":"NEGATIVE ELONGATION FACTOR COMPLEX, MEMBER B; NELFB","url":"https://www.omim.org/entry/611180"},{"mim_id":"606026","title":"NEGATIVE ELONGATION FACTOR COMPLEX, MEMBER A; NELFA","url":"https://www.omim.org/entry/606026"},{"mim_id":"605297","title":"NEGATIVE ELONGATION FACTOR COMPLEX, MEMBER C/D; NELFCD","url":"https://www.omim.org/entry/605297"},{"mim_id":"154040","title":"NEGATIVE ELONGATION FACTOR COMPLEX, MEMBER E; NELFE","url":"https://www.omim.org/entry/154040"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NELFB"},"hgnc":{"alias_symbol":["KIAA1182","NELF-B"],"prev_symbol":["COBRA1"]},"alphafold":{"accession":"Q8WX92","domains":[{"cath_id":"-","chopping":"1-37","consensus_level":"medium","plddt":78.9592,"start":1,"end":37},{"cath_id":"-","chopping":"42-149","consensus_level":"high","plddt":90.2576,"start":42,"end":149},{"cath_id":"-","chopping":"153-366","consensus_level":"medium","plddt":95.6712,"start":153,"end":366},{"cath_id":"1.25.40","chopping":"410-549","consensus_level":"high","plddt":94.638,"start":410,"end":549}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WX92","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WX92-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WX92-F1-predicted_aligned_error_v6.png","plddt_mean":89.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NELFB","jax_strain_url":"https://www.jax.org/strain/search?query=NELFB"},"sequence":{"accession":"Q8WX92","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WX92.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WX92/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WX92"}},"corpus_meta":[{"pmid":"19340312","id":"PMC_19340312","title":"Mouse cofactor of BRCA1 (Cobra1) is required for early embryogenesis.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19340312","citation_count":52,"is_preprint":false},{"pmid":"34705606","id":"PMC_34705606","title":"NSUN6, an RNA methyltransferase of 5-mC controls glioblastoma response to temozolomide (TMZ) via NELFB and RPS6KB2 interaction.","date":"2021","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/34705606","citation_count":32,"is_preprint":false},{"pmid":"26941120","id":"PMC_26941120","title":"Genetic suppression reveals DNA repair-independent antagonism between BRCA1 and COBRA1 in mammary gland development.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/26941120","citation_count":22,"is_preprint":false},{"pmid":"24034695","id":"PMC_24034695","title":"The dependence receptor TrkC triggers mitochondria-dependent apoptosis upon Cobra-1 recruitment.","date":"2013","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/24034695","citation_count":20,"is_preprint":false},{"pmid":"18071589","id":"PMC_18071589","title":"Concerted transcriptional regulation by BRCA1 and COBRA1 in breast cancer cells.","date":"2007","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/18071589","citation_count":16,"is_preprint":false},{"pmid":"15530430","id":"PMC_15530430","title":"COBRA1 inhibits AP-1 transcriptional activity in transfected cells.","date":"2004","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15530430","citation_count":12,"is_preprint":false},{"pmid":"24097989","id":"PMC_24097989","title":"A conserved protein motif is required for full modulatory activity of negative elongation factor subunits NELF-A and NELF-B in modifying glucocorticoid receptor-regulated gene induction properties.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24097989","citation_count":11,"is_preprint":false},{"pmid":"28112367","id":"PMC_28112367","title":"Knockdown of COBRA1 decreases the proliferation and migration of hepatocellular carcinoma cells.","date":"2017","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/28112367","citation_count":9,"is_preprint":false},{"pmid":"30036938","id":"PMC_30036938","title":"BRCA1 Interacting Protein COBRA1 Facilitates Adaptation to Castrate-Resistant Growth Conditions.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/30036938","citation_count":5,"is_preprint":false},{"pmid":"15185750","id":"PMC_15185750","title":"Characterization of COBRA1 in human breast cancer cell lines using a new polyclonal antibody against COBRA1.","date":"2004","source":"IUBMB 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NELF-B causes inner cell mass deficiency and embryonic lethality, and ChIP shows COBRA1 binds to the Lef1 promoter to modulate promoter-bound RNA polymerase abundance, preventing unscheduled expression of developmental genes in embryonic stem cells.\",\n      \"method\": \"Knockout mouse model, knockdown in mESCs, chromatin immunoprecipitation (ChIP)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined phenotype + ChIP demonstrating direct promoter occupancy, multiple orthogonal methods\",\n      \"pmids\": [\"19340312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"COBRA1 physically interacts with BRCA1 in the nucleus of human breast cancer cells, as shown by co-immunoprecipitation of endogenous proteins, and localizes to the nucleus.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins, immunofluorescence\",\n      \"journal\": \"IUBMB life\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP with localization, single lab\",\n      \"pmids\": [\"15185750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"COBRA1 inhibits AP-1 transcriptional activity in a dose-dependent manner by physically interacting with c-Jun and c-Fos; the middle region of COBRA1 binds c-Fos, and deletion of the c-Fos binding site abolishes COBRA1-mediated AP-1 inhibition.\",\n      \"method\": \"Transfection/overexpression, siRNA knockdown, reporter assay, co-immunoprecipitation, deletion mutagenesis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain/loss-of-function + Co-IP + mutagenesis, single lab\",\n      \"pmids\": [\"15530430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NELF-B attenuates glucocorticoid receptor (GR)-mediated gene induction, reduces partial agonist activity, and increases agonist EC50; ChIP shows NELF-B diminishes GR recruitment to promoter regions; NELF-A and NELF-B each act independently as competitive decelerators after the site of GR action; a conserved motif in each subunit is required for full modulatory activity.\",\n      \"method\": \"Stable knockdown, ChIP, competition assay, mutagenesis of conserved motif\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KD, ChIP, competition assay, mutagenesis), mechanistic placement in GR induction sequence\",\n      \"pmids\": [\"24097989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The neurotrophin receptor TrkC killer fragment (TrkC KF) interacts with COBRA1 (NELF-B); COBRA1 shuttles TrkC KF to the mitochondria where it promotes Bax activation, cytochrome c release, and apoptosome-dependent apoptosis. Cobra1 silencing rescues neuroepithelial cell death caused by NT-3 silencing in chick neural tube.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation, in vivo silencing in chick neural tube, Bax/cytochrome c release assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, mitochondrial fractionation, in vivo rescue, multiple orthogonal methods\",\n      \"pmids\": [\"24034695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Tissue-specific deletion of Cobra1 in mouse mammary gland blocks ductal morphogenesis, alveologenesis, and lactogenesis; additional loss of full-length Brca1 largely rescues these defects and restores developmental transcription, demonstrating that BRCA1 antagonizes COBRA1-dependent transcription programme in a DNA repair-independent manner.\",\n      \"method\": \"Conditional (tissue-specific) knockout, genetic epistasis (double KO), transcriptional profiling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean conditional KO + genetic suppression (double KO rescue) with defined phenotypic and transcriptional readouts\",\n      \"pmids\": [\"26941120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The genetic interaction between Brca1 and Cobra1 in mammary gland development is domain-specific: separation-of-function mutations abrogating either BRCA1 RING E3 ligase activity or BRCT phospho-recognition fail to rescue Cobra1 KO mammary defects, and deletion of Palb2 does not rescue Cobra1 KO, placing the interaction specifically with full-length BRCA1.\",\n      \"method\": \"Conditional knockout, separation-of-function mutations, genetic epistasis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple separation-of-function alleles tested in vivo with defined phenotypic readout\",\n      \"pmids\": [\"29426838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Crystal structure of the human NELF-B/C/E ternary complex was solved at high resolution, revealing detailed inter-subunit interaction surfaces and residues important for the association between NELF-B and NELF-E.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with identification of key interaction residues\",\n      \"pmids\": [\"37591184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cytoplasmic NELFB supports cell proliferation independently of Pol II pausing: separation-of-function mutations that sequester NELFB in the cytoplasm decouple its role in cell proliferation from Pol II pausing. Cytoplasmic NELFB physically and functionally interacts with PI3K/AKT prosurvival kinases, and ectopic membrane-tethered PI3K/AKT partially bypasses the proliferative role of NELFB but not its effect on Pol II occupancy.\",\n      \"method\": \"Separation-of-function mutations, subcellular localization experiments, co-immunoprecipitation, AKT ectopic expression rescue, Pol II ChIP\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (mutational uncoupling, Co-IP, ChIP, genetic rescue) in single rigorous study\",\n      \"pmids\": [\"37717699\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Nelfb deletion from preadipocyte lineages in mice causes failure of dermal white adipose tissue and other fat depot formation; Nelfb promotes open chromatin and stabilizes RNA Polymerase II binding at Pparg, Cebpa, Krox20, and Stat3 promoters; retroviral Pparg expression or rosiglitazone (Pparg agonist) treatment rescues adipocyte differentiation in Nelfb-depleted cells or mice, placing Nelfb upstream of Pparg in the adipogenic gene regulatory hierarchy.\",\n      \"method\": \"Conditional knockout, ChIP (Pol II, chromatin accessibility), retroviral rescue, pharmacological rescue (rosiglitazone)\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean conditional KO, ChIP, and multiple rescue experiments placing NELFB upstream of Pparg in adipogenesis\",\n      \"pmids\": [\"40960263\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NELF-B (COBRA1) is a subunit of the four-subunit NELF complex that stabilizes promoter-proximal RNA polymerase II pausing and regulates transcription elongation; it physically interacts with BRCA1 (antagonistically), AP-1 components (c-Jun/c-Fos), the glucocorticoid receptor, and PI3K/AKT kinases, and can shuttle apoptotic signals to mitochondria via TrkC killer fragment—with its nuclear Pol II pausing function and its cytoplasmic PI3K/AKT signaling function being genetically separable.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NELF-B (COBRA1) is a core subunit of the four-subunit NELF complex that enforces promoter-proximal RNA polymerase II pausing, thereby gating the expression of developmental and differentiation genes. Knockout studies demonstrate that NELF-B is essential for embryonic viability, mammary gland morphogenesis, and adipogenesis, where it stabilizes Pol II occupancy and maintains open chromatin at key regulatory promoters such as Pparg and Cebpa; BRCA1 genetically antagonizes this NELF-B–dependent transcriptional programme in a DNA-repair-independent, domain-specific manner [PMID:19340312, PMID:26941120, PMID:29426838, PMID:40960263]. Beyond its nuclear Pol II-pausing function, NELF-B possesses a genetically separable cytoplasmic role in which it physically engages PI3K/AKT pro-survival kinases to promote cell proliferation, and it can shuttle the TrkC killer fragment to mitochondria to trigger Bax-dependent apoptosis [PMID:37717699, PMID:24034695]. The high-resolution crystal structure of the NELF-B/C/E ternary complex reveals the inter-subunit contacts that organize the NELF core [PMID:37591184].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing that NELF-B (COBRA1) functions as a nuclear transcriptional coregulator: prior to this, its molecular role was undefined; co-immunoprecipitation showed it interacts with BRCA1 in the nucleus and physically binds AP-1 components (c-Jun/c-Fos) to dose-dependently inhibit AP-1-driven transcription via a mappable c-Fos-binding domain.\",\n      \"evidence\": \"Co-IP of endogenous proteins, reporter assays, deletion mutagenesis in human breast cancer and other cell lines\",\n      \"pmids\": [\"15185750\", \"15530430\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"BRCA1–COBRA1 interaction shown by single Co-IP without reciprocal validation or functional consequence defined\",\n        \"AP-1 inhibition demonstrated only by overexpression/reporter, lacking genome-wide or endogenous target validation\",\n        \"Relationship to Pol II pausing not yet established\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that NELF-B is an essential NELF complex subunit required for Pol II pausing in vivo: knockout causes embryonic lethality due to inner cell mass failure, and ChIP showed direct promoter occupancy modulating Pol II abundance at developmental genes in embryonic stem cells.\",\n      \"evidence\": \"Nelfb knockout mouse, knockdown in mESCs, chromatin immunoprecipitation\",\n      \"pmids\": [\"19340312\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Genome-wide target repertoire of NELF-B in ESCs not determined\",\n        \"Whether ICM deficiency reflects specific gene derepression or general transcription failure not resolved\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Revealing two previously unknown functions — attenuation of glucocorticoid receptor signaling and cytoplasmic apoptotic signaling: NELF-B acts as a competitive decelerator of GR-driven gene induction via a conserved motif, and separately shuttles the TrkC killer fragment to mitochondria to initiate Bax/cytochrome c-dependent apoptosis in neural progenitors.\",\n      \"evidence\": \"Stable knockdown with ChIP and competition assay for GR; reciprocal Co-IP, mitochondrial fractionation, and in vivo silencing in chick neural tube for TrkC KF\",\n      \"pmids\": [\"24097989\", \"24034695\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which NELF-B recognizes and transports TrkC KF to mitochondria not structurally defined\",\n        \"Whether GR attenuation requires the intact NELF tetrameric complex or only NELF-B is unclear\",\n        \"Relationship between cytoplasmic apoptotic role and nuclear Pol II pausing function not addressed\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Establishing a functional antagonism between BRCA1 and NELF-B in tissue development: conditional Cobra1 deletion blocked mammary gland morphogenesis and lactogenesis, and co-deletion of full-length Brca1 rescued these defects, demonstrating that BRCA1 counteracts NELF-B-dependent transcriptional control independently of DNA repair.\",\n      \"evidence\": \"Tissue-specific conditional knockout, double-KO genetic epistasis, transcriptional profiling in mouse mammary gland\",\n      \"pmids\": [\"26941120\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism by which BRCA1 antagonizes NELF-B-dependent pausing not identified\",\n        \"Whether this genetic interaction extends to non-mammary tissues not tested\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Refining the BRCA1–NELF-B genetic interaction to require full-length BRCA1: separation-of-function mutations in BRCA1 RING or BRCT domains and Palb2 deletion all failed to rescue Cobra1 KO mammary defects, demonstrating specificity beyond BRCA1's known enzymatic activities.\",\n      \"evidence\": \"Conditional knockout with multiple separation-of-function alleles and Palb2 deletion in vivo\",\n      \"pmids\": [\"29426838\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Which BRCA1 domain or activity mediates the antagonism remains unidentified\",\n        \"No biochemical reconstitution of BRCA1-mediated NELF eviction or pausing release\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Solving the structural basis of the NELF core and uncoupling nuclear from cytoplasmic functions: the NELF-B/C/E crystal structure revealed inter-subunit interaction surfaces, while separation-of-function mutations demonstrated that cytoplasmic NELF-B promotes proliferation via PI3K/AKT independently of Pol II pausing.\",\n      \"evidence\": \"X-ray crystallography of NELF-B/C/E; separation-of-function mutants, Co-IP with PI3K/AKT, ectopic AKT rescue, Pol II ChIP\",\n      \"pmids\": [\"37591184\", \"37717699\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How cytoplasmic NELF-B activates PI3K/AKT at the molecular level is unknown\",\n        \"Whether NELF-B's cytoplasmic pool is regulated by signaling-dependent nuclear-cytoplasmic shuttling not addressed\",\n        \"Full tetrameric NELF complex structure (with NELF-A and RNA Pol II) not yet available\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extending NELF-B's developmental role to adipogenesis: conditional Nelfb deletion from preadipocytes abolished fat depot formation, and ChIP showed NELF-B maintains open chromatin and Pol II binding at Pparg, Cebpa, Krox20, and Stat3 promoters; Pparg re-expression or pharmacological activation rescued differentiation, placing NELF-B upstream of the master adipogenic regulator.\",\n      \"evidence\": \"Conditional knockout in preadipocyte lineage, ChIP for Pol II and chromatin accessibility, retroviral Pparg rescue, rosiglitazone treatment in vivo and in vitro\",\n      \"pmids\": [\"40960263\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether NELF-B's role in adipogenesis is separable from the cytoplasmic PI3K/AKT function not tested\",\n        \"Genome-wide pausing landscape in preadipocytes not characterized\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: the molecular mechanism by which BRCA1 antagonizes NELF-B–dependent pausing, how cytoplasmic NELF-B engages and activates PI3K/AKT, and whether the nuclear pausing and cytoplasmic signaling functions are coordinately regulated during development and disease.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No reconstituted biochemical system for BRCA1-mediated pausing release at NELF-B targets\",\n        \"Structural basis of cytoplasmic NELF-B–PI3K/AKT interaction unknown\",\n        \"Regulation of nuclear-cytoplasmic partitioning of NELF-B not characterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3, 9]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1, 3, 9]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4, 8]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 3, 5, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 5, 9]}\n    ],\n    \"complexes\": [\n      \"NELF complex (NELF-A/B/C/E)\"\n    ],\n    \"partners\": [\n      \"BRCA1\",\n      \"NELF-E\",\n      \"NELF-C\",\n      \"NELF-A\",\n      \"FOS\",\n      \"JUN\",\n      \"AKT1\",\n      \"NTRK3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}