{"gene":"BTG1","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":1996,"finding":"BTG1 protein interacts with PRMT1 (protein-arginine N-methyltransferase 1) via yeast two-hybrid, and GST-BTG1 fusion protein quantitatively modulates endogenous PRMT1 methyltransferase activity, forming NG-monomethyl and asymmetric NG,NG-dimethylarginine on protein substrates.","method":"Yeast two-hybrid, GST pulldown, in vitro methyltransferase assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay with GST fusion proteins, modulation of endogenous activity demonstrated, replicated across multiple labs subsequently","pmids":["8663146"],"is_preprint":false},{"year":1992,"finding":"BTG1 expression is maximal in G0/G1 phases and is down-regulated as cells progress through G1; transfection of BTG1 into NIH3T3 cells negatively regulates cell proliferation.","method":"Northern blot (cell cycle staging), transient transfection with proliferation assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct cell cycle staging combined with functional loss/gain experiment; foundational paper replicated across many subsequent studies","pmids":["1373383"],"is_preprint":false},{"year":1998,"finding":"BTG1 and BTG2 physically interact with mCaf1 (mouse CCR4-associated factor 1) in vitro and in vivo (HeLa cells); the conserved box B domain of BTG1 is essential for this interaction, suggesting BTG proteins participate in transcriptional regulation of cell-cycle genes via the CCR4 complex.","method":"Yeast two-hybrid, GST pulldown, transient transfection/co-immunoprecipitation in HeLa cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP in cells plus in vitro pulldown plus domain mapping (box B mutagenesis); replicated by multiple labs","pmids":["9712883"],"is_preprint":false},{"year":1998,"finding":"Formation of the hCAF1/BTG1 complex in vitro requires phosphorylation of BTG1 at Ser-159 by CDK2/cyclin E or CDK2/cyclin A (but not CDK4/cyclin D1 or CDC2/cyclin B); the Ala-159 mutant fails to interact with hCAF1 in yeast; rCAF1 co-immunoprecipitates with BTG1 in the nucleus of contact-inhibited smooth muscle cells.","method":"Yeast two-hybrid with phosphorylation-site mutagenesis, in vitro kinase assay, co-immunoprecipitation, cell synchrony experiments","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinase assay with site-specific mutagenesis plus co-IP in primary cells; single lab but multiple orthogonal methods","pmids":["9820826"],"is_preprint":false},{"year":2000,"finding":"BTG1 and BTG2 physically associate with the homeodomain protein Hoxb9 and enhance Hoxb9-mediated transcriptional activation; BTG2 facilitates Hoxb9 binding to DNA; the interaction is mediated by the N-terminal activation domain of Hoxb9.","method":"Yeast two-hybrid, GST pulldown, transient transfection transcriptional reporter assays, EMSA (Hoxb9.Btg2 complex on responsive element)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal pulldown plus in-cell transcriptional assay plus DNA-binding assay; single lab, multiple orthogonal methods","pmids":["10617598"],"is_preprint":false},{"year":2001,"finding":"BTG1 interacts with hCAF1 and hPOP2 (human CAF1 paralogs) in vitro and in vivo; BTG1, through these interactions with a CCR4-like complex, can positively or negatively regulate estrogen receptor alpha (ERα)-mediated transcription; two LXXLL nuclear receptor boxes in BTG1 are required for regulation of ERα-mediated activation.","method":"Co-immunoprecipitation, GST pulldown, transient transfection transcriptional reporter assays, domain mapping (LXXLL motif mutagenesis)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP plus in-cell functional assay plus domain mutagenesis; single lab, multiple orthogonal methods","pmids":["11136725"],"is_preprint":false},{"year":2001,"finding":"The BTG1 B box drives nuclear localization and overlaps a functional Nuclear Export Signal (NES); the N-terminal 43 amino acids reduce nuclear accumulation; a nuclear-localized BTG1 mutant mimics BTG1's myogenic activity (enhanced G0/G1 arrest and terminal differentiation), while a cytoplasm-restricted mutant does not.","method":"Subcellular localization of BTG1-βGalactosidase fusion constructs by fluorescence imaging; functional differentiation assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with domain mutants plus functional differentiation readout; single lab","pmids":["11420681"],"is_preprint":false},{"year":2004,"finding":"BTG1 is a direct transcriptional target of FoxO3a in erythroid progenitors (promoter studies); BTG1 expression blocks erythroid colony outgrowth through a domain that binds PRMT1; inhibition of arginine methyltransferase activity blocks erythroid maturation, placing BTG1/PRMT1 in the FoxO3a-controlled erythroid differentiation pathway.","method":"Promoter-reporter assays (FoxO3a direct target), retroviral expression in primary mouse bone marrow cells, PRMT1-interaction domain mapping, pharmacological methyltransferase inhibition","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — promoter studies plus primary cell functional assay plus PRMT1 domain-dependency; single lab, multiple orthogonal methods","pmids":["14734530"],"is_preprint":false},{"year":2005,"finding":"BTG1 directly interacts (via GST pulldown and co-immunoprecipitation) with T3 and all-trans retinoic acid receptors and with avian MyoD (CMD1), acting as a transcriptional coactivator; interaction is mediated by the transactivation domain of each transcription factor and the A box plus C-terminal region of BTG1; nuclear-receptor corepressor NCoR induces ligand-dependency; deletion of BTG1 interaction domains abolishes its myogenic influence.","method":"GST pulldown, co-immunoprecipitation, transient transfection transcriptional assays, deletion/domain mutagenesis","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro GST pulldown plus reciprocal co-IP plus domain mutagenesis plus functional transcriptional assays; single lab, multiple orthogonal methods","pmids":["15674337"],"is_preprint":false},{"year":2007,"finding":"Btg1 induces G1 growth arrest in WEHI-231 B lymphoma cells via its box C region interaction with PRMT1; siRNA-mediated PRMT1 knockdown and methyltransferase inhibitor (AdOx) abrogate Btg1-induced growth inhibition, indicating that PRMT1 enzymatic activity is required for Btg1's antiproliferative function; anti-IgM stimulation triggers arginine methylation of a p36 substrate downstream of PRMT1.","method":"Retroviral overexpression, siRNA knockdown of PRMT1, pharmacological inhibition (AdOx), cell cycle analysis, immunoblot with asymmetric-methyl-arginine antibody","journal":"Experimental cell research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic (siRNA) and pharmacological rescue experiments with mechanistic readout; single lab, multiple orthogonal approaches","pmids":["17466295"],"is_preprint":false},{"year":2010,"finding":"BTG1 loss (by RNAi) causes glucocorticoid resistance by reducing glucocorticoid receptor (GR) expression and GR-mediated transcription; re-expression of BTG1 restores GR autoinduction; PRMT1 is recruited to the GR gene promoter in a BTG1-dependent manner, placing the BTG1/PRMT1 complex as a coactivator of GR-mediated gene expression.","method":"RNA interference, chromatin immunoprecipitation (ChIP), glucocorticoid response assays, reexpression rescue experiments","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating PRMT1 promoter recruitment plus RNAi loss-of-function plus rescue; single lab, multiple orthogonal methods","pmids":["20354172"],"is_preprint":false},{"year":2016,"finding":"BTG1 promotes PRMT1-mediated arginine methylation of ATF4 at residue R239, positively modulating ATF4 transcriptional activity under stress; BTG1 interacts with ATF4 (co-immunoprecipitation); loss of Btg1 in MEFs provides a survival advantage under stress conditions by altering ATF4-mediated stress responses.","method":"Co-immunoprecipitation, in vitro methylation assay with site-specific mutagenesis, Btg1 knockout MEFs, stress-survival assays","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — in vitro methylation assay identifying specific residue plus co-IP plus Btg1 knockout phenotype; single lab, multiple orthogonal methods","pmids":["26657730"],"is_preprint":false},{"year":2016,"finding":"BTG1 overexpression decreases triglyceride accumulation and ameliorates liver steatosis by suppressing ATF4 transcriptional activity, which in turn inhibits SCD1 expression; knockdown of SCD1 phenocopies BTG1 overexpression; ATF4 overexpression negates BTG1's anti-steatosis effect; BTG1 abundance is regulated by an mTOR/S6K1/CREB pathway in response to a high-carbohydrate diet.","method":"Adenovirus-mediated overexpression/knockdown in db/db mice and wild-type mice, transgenic BTG1 mice, in vitro hepatocyte assays, epistasis via ATF4 co-overexpression","journal":"Science signaling","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic epistasis (ATF4 rescue), in vivo mouse models, consistent in vitro and in vivo results; single lab, multiple orthogonal methods","pmids":["27188441"],"is_preprint":false},{"year":2015,"finding":"BTG1 regulates hepatic insulin sensitivity through upregulation of c-Jun expression; BTG1 stimulates c-Jun promoter activity and retinoic acid receptor activity; adenoviral c-Jun knockdown blocks BTG1-improved insulin signaling in vitro and in vivo, placing c-Jun downstream of BTG1 in this pathway.","method":"Adenovirus-mediated overexpression/knockdown, transgenic mice, in vitro signaling assays, epistasis via c-Jun knockdown rescue","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in vivo plus in vitro signaling; single lab","pmids":["26396236"],"is_preprint":false},{"year":2020,"finding":"BTG1 and BTG2 promote mRNA deadenylation and degradation, maintaining T cell quiescence; BTG1/2-deficient T cells show globally increased mRNA abundance and longer poly(A) tail length, lowering the activation threshold; BTG1/2 deficiency is specifically linked to increased polyadenylate tail length and mRNA half-life.","method":"Btg1/2 double-knockout mice, poly(A) tail length sequencing, mRNA half-life measurement, T cell activation assays","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with mechanistic readout (poly(A) tail measurement + mRNA half-life) plus functional cellular phenotype; rigorous study","pmids":["32165587"],"is_preprint":false},{"year":2021,"finding":"The boxC motif (conserved in BTG1 and BTG2 but not other APRO family members) is necessary and sufficient for interaction with the first RRM domain of cytoplasmic poly(A) binding protein PABPC1 and for stimulation of mRNA deadenylation in cellulo and in vitro; boxC is not required for BTG2 association with PRMT1, contrary to prior inference.","method":"NMR spectroscopy, mutagenesis of boxC motif, biochemical deadenylation assays in vitro and in cellulo","journal":"RNA biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure-guided mutagenesis plus in vitro reconstituted deadenylation assay; single lab, multiple orthogonal methods","pmids":["34060423"],"is_preprint":false},{"year":2020,"finding":"BTG1 variants found in non-Hodgkin lymphoma impair interaction with CNOT7 and CNOT8 (Caf1 subunits of the CCR4-NOT deadenylase complex) and reduce anti-proliferative activity, translational repression, and mRNA degradation, demonstrating that these protein-protein interactions are functionally critical for BTG1's tumor suppressor activity.","method":"Protein interaction assays (16 BTG1 variants), cell cycle progression assays, translational repression assays, mRNA degradation assays","journal":"Leukemia & lymphoma","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic variant-interaction-function correlation with multiple functional readouts; single lab","pmids":["33021411"],"is_preprint":false},{"year":2023,"finding":"BTG1 mutations in germinal center B cells confer a supercompetitor phenotype by altering MYC protein induction kinetics, disrupting a fitness-gating mechanism during antibody affinity maturation and promoting aggressive lymphomagenesis.","method":"Primary human lymphoma analysis, novel mouse models, MYC protein dynamics measurement","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Moderate — human and mouse genetic models with mechanistic readout (MYC kinetics); rigorous study with multiple orthogonal approaches","pmids":["36656933"],"is_preprint":false},{"year":2023,"finding":"BTG1 physically interacts with the scaffolding protein BCAR1; BTG1 deletion or expression of patient-derived BTG1 mutations leads to overactivation of the BCAR1-RAC1 pathway, conferring increased B cell migration in vitro and in vivo; this is targetable with the SRC inhibitor dasatinib.","method":"Co-immunoprecipitation (BTG1-BCAR1 interaction), BTG1 knockout mouse model, in vitro and in vivo migration assays, pharmacological rescue with dasatinib","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus genetic knockout with mechanistic pathway readout; single lab","pmids":["36375119"],"is_preprint":false},{"year":2022,"finding":"MD simulations reveal that the α2-α4 helix interface of BTG1 undergoes conformational transitions between closed and open metastable states; DLBCL mutations (Q36H, F40C, Q45P, E50K, A83T, A84E) in this region overstabilize one state or distort helices, disrupting the native dynamics required for productive interactions with binding partners.","method":"Atomistic molecular dynamics simulations, Markov state modeling","journal":"Biophysical journal","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational (MD/Markov state modeling) only, no experimental validation of conformational states","pmids":["35459639"],"is_preprint":false},{"year":2015,"finding":"Btg1 regulates proliferation of cerebellar granule cell precursors (GCPs) selectively through cyclin D1; gain- and loss-of-function in a GCP cell line demonstrate that Btg1 controls GCP proliferation via cyclin D1, and Btg1 knockout causes hyperplasia of the external granule layer with impaired motor coordination.","method":"Btg1 knockout mice, GCP cell line gain/loss-of-function, cyclin D1 expression analysis, motor coordination behavioral tests","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO phenotype plus in vitro gain/loss-of-function with specific molecular target (cyclin D1); single lab","pmids":["26524254"],"is_preprint":false},{"year":2012,"finding":"Ablation of Btg1 in mice causes premature exit of dentate gyrus and SVZ stem/progenitor cells from the cell cycle after S phase, followed by p53- and p21-dependent apoptosis, depleting the adult stem/progenitor pool and impairing contextual memory discrimination.","method":"Btg1 knockout mice, BrdU cell cycle analysis, p53/p21 immunostaining, TUNEL apoptosis assay, neurosphere self-renewal assays, behavioral tests","journal":"Frontiers in neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic KO with multiple mechanistic cellular readouts (cell cycle exit, p53/p21 induction, apoptosis, self-renewal); single lab","pmids":["22969701"],"is_preprint":false},{"year":2023,"finding":"Btg1 and Btg2 are required for neonatal cardiomyocyte cell cycle arrest; Btg1/2 double knockout and AAV9-mediated double knockdown mouse hearts show increased mitotic cardiomyocytes at postnatal day 7; RNAseq of Btg1/2-depleted NRVMs implicates Btg1/2 in inhibiting cell proliferation and modulating reactive oxygen species response pathways linked to cardiomyocyte cell cycle arrest.","method":"Constitutive double knockout mice, AAV9-mediated in vivo knockdown, siRNA in neonatal rat ventricular myocytes, EdU/pHH3 proliferation assays, RNAseq","journal":"Journal of molecular and cellular cardiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus in vivo AAV knockdown plus in vitro siRNA with transcriptomic readout; single lab","pmids":["37062247"],"is_preprint":false},{"year":2015,"finding":"Btg1 and Btg2 are required for normal vertebral patterning; Btg1-/- mice display partial posterior transformation of the seventh cervical vertebra; Btg1-/-;Btg2-/- double knockouts show stronger homeotic transformations, demonstrating Btg1 and Btg2 act synergistically in specifying axial skeleton identity, consistent with their roles as coregulators of Hox transcription factors.","method":"Single and double Btg1/Btg2 knockout mice, skeletal phenotype analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via double KO; single lab, clear phenotypic readout","pmids":["26218146"],"is_preprint":false},{"year":2018,"finding":"Combined loss of BTG1 and IKZF1 in mouse B cells increases glucocorticoid resistance beyond that caused by IKZF1 alone; BTG1 loss alone does not affect glucocorticoid sensitivity, but cooperates with IKZF1 loss specifically in this pathway; in vitro, Btg1/Ikzf1-deficient B cells show increased resistance to glucocorticoids but not other chemotherapy drugs.","method":"Btg1-knockout crossed onto Ikzf1-heterozygous mice, ex vivo glucocorticoid sensitivity assays, leukemia mouse model","journal":"Haematologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in mouse model with functional drug sensitivity readout; single lab","pmids":["27979924"],"is_preprint":false},{"year":2018,"finding":"BTG1 deficiency enhances the self-renewal capacity of ETV6-RUNX1-positive hematopoietic progenitors and drives upregulation of the proto-oncogene BCL6 and downregulation of BCL6 targets p19Arf and Tp53; ectopic BCL6 expression phenocopies BTG1 loss, identifying BTG1-mediated suppression of BCL6 as a mechanism limiting leukemogenesis.","method":"Btg1 knockout mouse fetal liver progenitors with ETV6-RUNX1 expression, self-renewal/clonogenic assays, gene expression analysis, ectopic BCL6 epistasis","journal":"Experimental hematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function plus ectopic epistasis with mechanistic pathway identification; single lab","pmids":["29408281"],"is_preprint":false},{"year":2020,"finding":"In medulloblastoma, Btg1 deletion increases apoptosis of cerebellar granule cell precursors (synergistically with Ptch1+/- mutation), associated with increased PRMT1 protein expression; Btg1 ablation also increases the proportion of CD15+ tumor stem cells, suggesting Btg1 regulates the balance between apoptosis and stem cell quiescence in medulloblastoma.","method":"Btg1/Ptch1 compound knockout mice, caspase-3 immunostaining, CD15 stem cell marker, PRMT1 protein quantification","journal":"Frontiers in oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic compound KO with multiple cellular readouts; single lab","pmids":["32231994"],"is_preprint":false},{"year":2026,"finding":"BTG1 suppresses β-catenin signaling by inhibiting formation of the β-catenin/TCF4 transcriptional complex, leading to reduced c-Myc and Cyclin D1 expression; BTG1 is required for HDAC inhibitor-induced cell cycle arrest and autophagy in DLBCL cells; in vivo antitumor efficacy of HDAC inhibition depends on the BTG1/β-catenin axis.","method":"BTG1 siRNA knockdown/overexpression, β-catenin co-immunoprecipitation (β-catenin/TCF4 complex), cell cycle/autophagy assays, DLBCL xenograft mouse model","journal":"Molecular carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP of complex plus genetic loss/gain-of-function plus in vivo xenograft; single lab","pmids":["41950351"],"is_preprint":false},{"year":1999,"finding":"T3 (triiodothyronine) and cAMP increase BTG1 nuclear accumulation in confluent myoblasts via increased nuclear import or retention, without direct transcriptional control of BTG1; AP-1 activity represses BTG1 expression via an AP-1-like sequence in the BTG1 promoter; BTG1 overexpression mimics T3/cAMP myogenic influence (inhibiting proliferation, promoting differentiation).","method":"Transient transfection reporter assays (BTG1 promoter), subcellular fractionation/immunolocalization, BTG1 overexpression functional assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter-reporter mapping plus localization plus functional overexpression; single lab","pmids":["10366433"],"is_preprint":false},{"year":2019,"finding":"PUM2 (RNA binding protein) directly binds the 3'UTR of BTG1 mRNA (RNA pulldown and RNA immunoprecipitation), repressing BTG1 expression; PUM2 knockdown increases BTG1 levels and suppresses glioblastoma cell proliferation and migration; BTG1 knockdown reverses the anti-proliferative effect of PUM2 knockdown, placing BTG1 downstream of PUM2.","method":"RNA pulldown, RNA immunoprecipitation, siRNA knockdown of PUM2 and BTG1, cell proliferation and migration assays","journal":"Cell structure and function","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct RNA-protein interaction (pulldown + RIP) plus genetic epistasis; single lab","pmids":["30787206"],"is_preprint":false}],"current_model":"BTG1 is an antiproliferative transcriptional cofactor that: (1) interacts with PRMT1 to modulate arginine methylation of substrates including ATF4 (R239) and promotes GR-mediated transcription; (2) recruits the CCR4-NOT deadenylase complex (via CAF1/CNOT7/CNOT8) and PABPC1 through its conserved boxB and boxC motifs to stimulate mRNA deadenylation and decay, thereby maintaining cellular quiescence; (3) acts as a coactivator of nuclear receptors (T3R, RARs), MyoD, and Hoxb9 through direct protein interactions mediated by its A box, C-terminal domain, and LXXLL motifs; (4) requires CDK2-dependent phosphorylation at Ser-159 for CAF1 interaction; (5) suppresses β-catenin/TCF4 complex formation; and (6) is regulated transcriptionally by FoxO3a and AP-1, and post-transcriptionally by PUM2 and multiple miRNAs targeting its 3'UTR."},"narrative":{"mechanistic_narrative":"BTG1 is an antiproliferative transcriptional cofactor and post-transcriptional regulator that enforces cellular quiescence and terminal differentiation across hematopoietic, neural, muscle, and cardiac lineages [PMID:1373383, PMID:32165587]. It operates through two convergent biochemical activities. First, BTG1 binds the arginine methyltransferase PRMT1 and modulates its enzymatic activity [PMID:8663146], a partnership required for BTG1's growth-arrest function in B lymphoma cells [PMID:17466295] and for arginine methylation of substrates including ATF4 at R239, which tunes the ATF4-dependent stress response [PMID:26657730]; through this PRMT1 axis BTG1 also acts as a coactivator, recruiting PRMT1 to the glucocorticoid receptor promoter to support GR autoinduction [PMID:20354172]. Second, BTG1 stimulates mRNA deadenylation and decay by recruiting the CCR4-NOT deadenylase via its CAF1 subunits (CNOT7/CNOT8) and engaging PABPC1, interactions mapped to its conserved boxB and boxC motifs; this deadenylation activity maintains lymphocyte quiescence by limiting global mRNA abundance and poly(A) tail length [PMID:9712883, PMID:32165587, PMID:34060423]. The CAF1 interaction is gated by CDK2/cyclin E- or A-dependent phosphorylation of BTG1 at Ser-159 [PMID:9820826]. BTG1 additionally functions as a transcriptional coregulator of nuclear receptors (T3R, RARs), MyoD, and the homeodomain protein Hoxb9 through its A box, C-terminal region, and LXXLL motifs [PMID:10617598, PMID:11136725, PMID:15674337], and it suppresses β-catenin/TCF4 complex formation to restrain c-Myc and Cyclin D1 [PMID:41950351]. BTG1 expression is itself controlled transcriptionally by FoxO3a and AP-1 and post-transcriptionally by PUM2 binding its 3'UTR [PMID:14734530, PMID:10366433, PMID:30787206]. Loss-of-function BTG1 variants in non-Hodgkin lymphoma impair CNOT7/CNOT8 binding and abolish antiproliferative activity, and BTG1 mutations drive a B-cell supercompetitor phenotype during affinity maturation by altering MYC induction kinetics, establishing BTG1 as a tumor suppressor in germinal-center lymphomagenesis [PMID:33021411, PMID:36656933].","teleology":[{"year":1992,"claim":"Established BTG1 as a cell-cycle-regulated antiproliferative gene, defining the phenotype that all later mechanism had to explain.","evidence":"Cell cycle staging by Northern blot plus gain-of-function transfection in NIH3T3 cells","pmids":["1373383"],"confidence":"High","gaps":["No molecular mechanism for growth inhibition identified","No binding partners known at this stage"]},{"year":1996,"claim":"Identified PRMT1 as a BTG1 partner and showed BTG1 modulates its methyltransferase activity, providing the first enzymatic axis for BTG1 function.","evidence":"Yeast two-hybrid, GST pulldown, in vitro methyltransferase assay","pmids":["8663146"],"confidence":"High","gaps":["Physiological substrates of the BTG1/PRMT1 complex not defined","Direction of modulation (activation vs inhibition) in cells unresolved"]},{"year":1998,"claim":"Connected BTG1 to the CCR4-NOT deadenylase by mapping the boxB-dependent CAF1 interaction, and showed CDK2 phosphorylation at Ser-159 gates that interaction, linking cell-cycle state to deadenylase recruitment.","evidence":"Yeast two-hybrid, GST pulldown, reciprocal co-IP, in vitro kinase assay with Ser159Ala mutagenesis, co-IP in primary cells","pmids":["9712883","9820826"],"confidence":"High","gaps":["Functional consequence of CAF1 recruitment on specific mRNAs not yet demonstrated","Kinase regulating Ser-159 in vivo context limited to in vitro CDK2 assays"]},{"year":2005,"claim":"Defined BTG1 as a coactivator of nuclear receptors, MyoD, and Hoxb9, showing its antiproliferative/differentiation role is partly transcriptional and domain-encoded.","evidence":"GST pulldown, co-IP, transcriptional reporter assays, LXXLL/A-box/C-terminal domain mutagenesis, EMSA across studies","pmids":["10617598","11136725","15674337"],"confidence":"High","gaps":["Whether coactivation requires the PRMT1 or CAF1 activities not dissected","Endogenous target genes of these complexes not mapped"]},{"year":2010,"claim":"Showed the BTG1/PRMT1 complex acts as a promoter-recruited coactivator of the glucocorticoid receptor, linking BTG1 loss to glucocorticoid resistance.","evidence":"RNAi loss-of-function, ChIP for PRMT1 promoter recruitment, rescue by BTG1 re-expression","pmids":["20354172"],"confidence":"High","gaps":["Methylation substrate at the GR locus not identified","Genome-wide BTG1/PRMT1 target set unknown"]},{"year":2016,"claim":"Identified ATF4 R239 as a specific BTG1/PRMT1 methylation target controlling stress transcription, linking the methylation axis to metabolic and stress phenotypes.","evidence":"Co-IP, in vitro methylation with site-specific mutagenesis, Btg1 knockout MEFs, in vivo liver steatosis and ATF4 epistasis models","pmids":["26657730","27188441"],"confidence":"High","gaps":["How ATF4 methylation alters its activity mechanistically not fully resolved","Relationship between ATF4 and SCD1 regulation and the deadenylase activity unexplored"]},{"year":2020,"claim":"Demonstrated genetically that BTG1 (with BTG2) drives global mRNA deadenylation and decay to maintain lymphocyte quiescence, establishing post-transcriptional control as a core antiproliferative mechanism.","evidence":"Btg1/2 double-knockout mice, poly(A) tail length sequencing, mRNA half-life measurement, T cell activation assays","pmids":["32165587"],"confidence":"High","gaps":["Specific target transcripts setting the activation threshold not enumerated","Redundancy and division of labor between BTG1 and BTG2 unresolved"]},{"year":2021,"claim":"Defined the boxC motif as necessary and sufficient for PABPC1 binding and deadenylation stimulation, structurally separating the RNA-decay function from PRMT1 association.","evidence":"NMR spectroscopy, boxC mutagenesis, in vitro and in cellulo deadenylation assays","pmids":["34060423"],"confidence":"High","gaps":["Full assembly of BTG1 with CCR4-NOT and PABPC1 on a substrate mRNA not structurally resolved","Whether boxB and boxC act on overlapping or distinct mRNA pools unknown"]},{"year":2023,"claim":"Established BTG1 as a germinal-center tumor suppressor whose lymphoma variants impair CNOT7/CNOT8 binding and alter MYC induction kinetics and BCAR1-RAC1 signaling, tying its biochemical activities to lymphomagenesis.","evidence":"Systematic variant-interaction-function correlation, primary human lymphoma analysis, knockout mouse models, MYC dynamics, BCAR1 co-IP, dasatinib rescue","pmids":["33021411","36656933","36375119"],"confidence":"High","gaps":["Direct mRNA targets linking deadenylase loss to MYC kinetics not defined","Whether BCAR1 regulation is independent of the CCR4-NOT activity unclear"]},{"year":null,"claim":"How BTG1's distinct activities — PRMT1-dependent methylation, CCR4-NOT deadenylation, nuclear-receptor coactivation, and β-catenin suppression — are coordinated or selectively deployed in a given cell type remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model integrating the transcriptional and post-transcriptional functions","Tissue-specific target mRNA and substrate repertoires not mapped","Conformational dynamics linking mutations to partner-binding defects only modeled computationally [#19]"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,5,8,10]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,9,15]},{"term_id":"GO:0060090","term_label":"molecular adaptor 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hematology","url":"https://pubmed.ncbi.nlm.nih.gov/29408281","citation_count":4,"is_preprint":false},{"pmid":"25297078","id":"PMC_25297078","title":"Molecular cloning, sequence analysis, and cadmium stress-rated expression changes of BTG1 in freshwater pearl mussel (Hyriopsis schlegelii).","date":"2014","source":"Dong wu xue yan jiu = Zoological research","url":"https://pubmed.ncbi.nlm.nih.gov/25297078","citation_count":4,"is_preprint":false},{"pmid":"37187949","id":"PMC_37187949","title":"Targeting a novel circITCH/miR-421/BTG1 axis is effective to suppress the malignant phenotypes in hepatocellular carcinoma (HCC) cells.","date":"2023","source":"Cytotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/37187949","citation_count":4,"is_preprint":false},{"pmid":"26662056","id":"PMC_26662056","title":"The tumor suppressor BTG1 is expressed in the developing digits and regulates skeletogenic differentiation of limb mesodermal progenitors in high density cultures.","date":"2015","source":"Cell and tissue research","url":"https://pubmed.ncbi.nlm.nih.gov/26662056","citation_count":3,"is_preprint":false},{"pmid":"28469801","id":"PMC_28469801","title":"Erratum: MiR-4295 promotes cell growth in bladder cancer by targeting BTG1.","date":"2017","source":"American journal of translational research","url":"https://pubmed.ncbi.nlm.nih.gov/28469801","citation_count":3,"is_preprint":false},{"pmid":"32166669","id":"PMC_32166669","title":"Identification of BTG1 Status in Solid Cancer for Future Researches Using a System Review and Meta-analysis.","date":"2020","source":"Current medical science","url":"https://pubmed.ncbi.nlm.nih.gov/32166669","citation_count":2,"is_preprint":false},{"pmid":"39095315","id":"PMC_39095315","title":"IKZF1 and BTG1 silencing reduces glucocorticoid response in B-cell precursor acute leukemia cell line.","date":"2024","source":"Hematology, transfusion and cell therapy","url":"https://pubmed.ncbi.nlm.nih.gov/39095315","citation_count":1,"is_preprint":false},{"pmid":"38254153","id":"PMC_38254153","title":"The predictive value of BTG1 for the response of newly diagnosed acute myeloid leukemia to decitabine.","date":"2024","source":"Clinical epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/38254153","citation_count":0,"is_preprint":false},{"pmid":"42080092","id":"PMC_42080092","title":"PC3/Tis21/BTG2 and BTG1 genes: regulators of the cell cycle and neurogenesis, as well as tumor suppressors in malignant brain tumors.","date":"2026","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/42080092","citation_count":0,"is_preprint":false},{"pmid":"36705483","id":"PMC_36705483","title":"Mutations in BTG1 Promote Germinal Center B-cell Malignant Transformation.","date":"2023","source":"Cancer discovery","url":"https://pubmed.ncbi.nlm.nih.gov/36705483","citation_count":0,"is_preprint":false},{"pmid":"34109351","id":"PMC_34109351","title":"[Expression and clinical significance of BTG-1 in 78 patients with oral squamous cell carcinoma].","date":"2021","source":"Shanghai kou qiang yi xue = Shanghai journal of stomatology","url":"https://pubmed.ncbi.nlm.nih.gov/34109351","citation_count":0,"is_preprint":false},{"pmid":"41950351","id":"PMC_41950351","title":"BTG1 Acts as a Critical Tumor Suppressor Link Between HDAC Inhibition and β-Catenin Signaling Suppression in Diffuse Large B-Cell Lymphoma.","date":"2026","source":"Molecular carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/41950351","citation_count":0,"is_preprint":false},{"pmid":"36746366","id":"PMC_36746366","title":"Expanding the phenotype of 12q21 deletions: A role of BTG1 in speech development?","date":"2023","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36746366","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.22.24315961","title":"Genomic Landscape and Molecular Subtypes of Primary Central Nervous System Lymphoma","date":"2024-10-23","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.22.24315961","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44849,"output_tokens":7553,"usd":0.123921,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":16987,"output_tokens":3823,"usd":0.090255,"stage2_stop_reason":"end_turn"},"total_usd":0.214176,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"BTG1 protein interacts with PRMT1 (protein-arginine N-methyltransferase 1) via yeast two-hybrid, and GST-BTG1 fusion protein quantitatively modulates endogenous PRMT1 methyltransferase activity, forming NG-monomethyl and asymmetric NG,NG-dimethylarginine on protein substrates.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, in vitro methyltransferase assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay with GST fusion proteins, modulation of endogenous activity demonstrated, replicated across multiple labs subsequently\",\n      \"pmids\": [\"8663146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"BTG1 expression is maximal in G0/G1 phases and is down-regulated as cells progress through G1; transfection of BTG1 into NIH3T3 cells negatively regulates cell proliferation.\",\n      \"method\": \"Northern blot (cell cycle staging), transient transfection with proliferation assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct cell cycle staging combined with functional loss/gain experiment; foundational paper replicated across many subsequent studies\",\n      \"pmids\": [\"1373383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"BTG1 and BTG2 physically interact with mCaf1 (mouse CCR4-associated factor 1) in vitro and in vivo (HeLa cells); the conserved box B domain of BTG1 is essential for this interaction, suggesting BTG proteins participate in transcriptional regulation of cell-cycle genes via the CCR4 complex.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, transient transfection/co-immunoprecipitation in HeLa cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP in cells plus in vitro pulldown plus domain mapping (box B mutagenesis); replicated by multiple labs\",\n      \"pmids\": [\"9712883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Formation of the hCAF1/BTG1 complex in vitro requires phosphorylation of BTG1 at Ser-159 by CDK2/cyclin E or CDK2/cyclin A (but not CDK4/cyclin D1 or CDC2/cyclin B); the Ala-159 mutant fails to interact with hCAF1 in yeast; rCAF1 co-immunoprecipitates with BTG1 in the nucleus of contact-inhibited smooth muscle cells.\",\n      \"method\": \"Yeast two-hybrid with phosphorylation-site mutagenesis, in vitro kinase assay, co-immunoprecipitation, cell synchrony experiments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinase assay with site-specific mutagenesis plus co-IP in primary cells; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"9820826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"BTG1 and BTG2 physically associate with the homeodomain protein Hoxb9 and enhance Hoxb9-mediated transcriptional activation; BTG2 facilitates Hoxb9 binding to DNA; the interaction is mediated by the N-terminal activation domain of Hoxb9.\",\n      \"method\": \"Yeast two-hybrid, GST pulldown, transient transfection transcriptional reporter assays, EMSA (Hoxb9.Btg2 complex on responsive element)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal pulldown plus in-cell transcriptional assay plus DNA-binding assay; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"10617598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"BTG1 interacts with hCAF1 and hPOP2 (human CAF1 paralogs) in vitro and in vivo; BTG1, through these interactions with a CCR4-like complex, can positively or negatively regulate estrogen receptor alpha (ERα)-mediated transcription; two LXXLL nuclear receptor boxes in BTG1 are required for regulation of ERα-mediated activation.\",\n      \"method\": \"Co-immunoprecipitation, GST pulldown, transient transfection transcriptional reporter assays, domain mapping (LXXLL motif mutagenesis)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP plus in-cell functional assay plus domain mutagenesis; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"11136725\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The BTG1 B box drives nuclear localization and overlaps a functional Nuclear Export Signal (NES); the N-terminal 43 amino acids reduce nuclear accumulation; a nuclear-localized BTG1 mutant mimics BTG1's myogenic activity (enhanced G0/G1 arrest and terminal differentiation), while a cytoplasm-restricted mutant does not.\",\n      \"method\": \"Subcellular localization of BTG1-βGalactosidase fusion constructs by fluorescence imaging; functional differentiation assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with domain mutants plus functional differentiation readout; single lab\",\n      \"pmids\": [\"11420681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"BTG1 is a direct transcriptional target of FoxO3a in erythroid progenitors (promoter studies); BTG1 expression blocks erythroid colony outgrowth through a domain that binds PRMT1; inhibition of arginine methyltransferase activity blocks erythroid maturation, placing BTG1/PRMT1 in the FoxO3a-controlled erythroid differentiation pathway.\",\n      \"method\": \"Promoter-reporter assays (FoxO3a direct target), retroviral expression in primary mouse bone marrow cells, PRMT1-interaction domain mapping, pharmacological methyltransferase inhibition\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter studies plus primary cell functional assay plus PRMT1 domain-dependency; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"14734530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"BTG1 directly interacts (via GST pulldown and co-immunoprecipitation) with T3 and all-trans retinoic acid receptors and with avian MyoD (CMD1), acting as a transcriptional coactivator; interaction is mediated by the transactivation domain of each transcription factor and the A box plus C-terminal region of BTG1; nuclear-receptor corepressor NCoR induces ligand-dependency; deletion of BTG1 interaction domains abolishes its myogenic influence.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation, transient transfection transcriptional assays, deletion/domain mutagenesis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro GST pulldown plus reciprocal co-IP plus domain mutagenesis plus functional transcriptional assays; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"15674337\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Btg1 induces G1 growth arrest in WEHI-231 B lymphoma cells via its box C region interaction with PRMT1; siRNA-mediated PRMT1 knockdown and methyltransferase inhibitor (AdOx) abrogate Btg1-induced growth inhibition, indicating that PRMT1 enzymatic activity is required for Btg1's antiproliferative function; anti-IgM stimulation triggers arginine methylation of a p36 substrate downstream of PRMT1.\",\n      \"method\": \"Retroviral overexpression, siRNA knockdown of PRMT1, pharmacological inhibition (AdOx), cell cycle analysis, immunoblot with asymmetric-methyl-arginine antibody\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic (siRNA) and pharmacological rescue experiments with mechanistic readout; single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"17466295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"BTG1 loss (by RNAi) causes glucocorticoid resistance by reducing glucocorticoid receptor (GR) expression and GR-mediated transcription; re-expression of BTG1 restores GR autoinduction; PRMT1 is recruited to the GR gene promoter in a BTG1-dependent manner, placing the BTG1/PRMT1 complex as a coactivator of GR-mediated gene expression.\",\n      \"method\": \"RNA interference, chromatin immunoprecipitation (ChIP), glucocorticoid response assays, reexpression rescue experiments\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating PRMT1 promoter recruitment plus RNAi loss-of-function plus rescue; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20354172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"BTG1 promotes PRMT1-mediated arginine methylation of ATF4 at residue R239, positively modulating ATF4 transcriptional activity under stress; BTG1 interacts with ATF4 (co-immunoprecipitation); loss of Btg1 in MEFs provides a survival advantage under stress conditions by altering ATF4-mediated stress responses.\",\n      \"method\": \"Co-immunoprecipitation, in vitro methylation assay with site-specific mutagenesis, Btg1 knockout MEFs, stress-survival assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro methylation assay identifying specific residue plus co-IP plus Btg1 knockout phenotype; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"26657730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"BTG1 overexpression decreases triglyceride accumulation and ameliorates liver steatosis by suppressing ATF4 transcriptional activity, which in turn inhibits SCD1 expression; knockdown of SCD1 phenocopies BTG1 overexpression; ATF4 overexpression negates BTG1's anti-steatosis effect; BTG1 abundance is regulated by an mTOR/S6K1/CREB pathway in response to a high-carbohydrate diet.\",\n      \"method\": \"Adenovirus-mediated overexpression/knockdown in db/db mice and wild-type mice, transgenic BTG1 mice, in vitro hepatocyte assays, epistasis via ATF4 co-overexpression\",\n      \"journal\": \"Science signaling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis (ATF4 rescue), in vivo mouse models, consistent in vitro and in vivo results; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"27188441\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"BTG1 regulates hepatic insulin sensitivity through upregulation of c-Jun expression; BTG1 stimulates c-Jun promoter activity and retinoic acid receptor activity; adenoviral c-Jun knockdown blocks BTG1-improved insulin signaling in vitro and in vivo, placing c-Jun downstream of BTG1 in this pathway.\",\n      \"method\": \"Adenovirus-mediated overexpression/knockdown, transgenic mice, in vitro signaling assays, epistasis via c-Jun knockdown rescue\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in vivo plus in vitro signaling; single lab\",\n      \"pmids\": [\"26396236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BTG1 and BTG2 promote mRNA deadenylation and degradation, maintaining T cell quiescence; BTG1/2-deficient T cells show globally increased mRNA abundance and longer poly(A) tail length, lowering the activation threshold; BTG1/2 deficiency is specifically linked to increased polyadenylate tail length and mRNA half-life.\",\n      \"method\": \"Btg1/2 double-knockout mice, poly(A) tail length sequencing, mRNA half-life measurement, T cell activation assays\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with mechanistic readout (poly(A) tail measurement + mRNA half-life) plus functional cellular phenotype; rigorous study\",\n      \"pmids\": [\"32165587\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The boxC motif (conserved in BTG1 and BTG2 but not other APRO family members) is necessary and sufficient for interaction with the first RRM domain of cytoplasmic poly(A) binding protein PABPC1 and for stimulation of mRNA deadenylation in cellulo and in vitro; boxC is not required for BTG2 association with PRMT1, contrary to prior inference.\",\n      \"method\": \"NMR spectroscopy, mutagenesis of boxC motif, biochemical deadenylation assays in vitro and in cellulo\",\n      \"journal\": \"RNA biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure-guided mutagenesis plus in vitro reconstituted deadenylation assay; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"34060423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"BTG1 variants found in non-Hodgkin lymphoma impair interaction with CNOT7 and CNOT8 (Caf1 subunits of the CCR4-NOT deadenylase complex) and reduce anti-proliferative activity, translational repression, and mRNA degradation, demonstrating that these protein-protein interactions are functionally critical for BTG1's tumor suppressor activity.\",\n      \"method\": \"Protein interaction assays (16 BTG1 variants), cell cycle progression assays, translational repression assays, mRNA degradation assays\",\n      \"journal\": \"Leukemia & lymphoma\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic variant-interaction-function correlation with multiple functional readouts; single lab\",\n      \"pmids\": [\"33021411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BTG1 mutations in germinal center B cells confer a supercompetitor phenotype by altering MYC protein induction kinetics, disrupting a fitness-gating mechanism during antibody affinity maturation and promoting aggressive lymphomagenesis.\",\n      \"method\": \"Primary human lymphoma analysis, novel mouse models, MYC protein dynamics measurement\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — human and mouse genetic models with mechanistic readout (MYC kinetics); rigorous study with multiple orthogonal approaches\",\n      \"pmids\": [\"36656933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"BTG1 physically interacts with the scaffolding protein BCAR1; BTG1 deletion or expression of patient-derived BTG1 mutations leads to overactivation of the BCAR1-RAC1 pathway, conferring increased B cell migration in vitro and in vivo; this is targetable with the SRC inhibitor dasatinib.\",\n      \"method\": \"Co-immunoprecipitation (BTG1-BCAR1 interaction), BTG1 knockout mouse model, in vitro and in vivo migration assays, pharmacological rescue with dasatinib\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus genetic knockout with mechanistic pathway readout; single lab\",\n      \"pmids\": [\"36375119\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MD simulations reveal that the α2-α4 helix interface of BTG1 undergoes conformational transitions between closed and open metastable states; DLBCL mutations (Q36H, F40C, Q45P, E50K, A83T, A84E) in this region overstabilize one state or distort helices, disrupting the native dynamics required for productive interactions with binding partners.\",\n      \"method\": \"Atomistic molecular dynamics simulations, Markov state modeling\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational (MD/Markov state modeling) only, no experimental validation of conformational states\",\n      \"pmids\": [\"35459639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Btg1 regulates proliferation of cerebellar granule cell precursors (GCPs) selectively through cyclin D1; gain- and loss-of-function in a GCP cell line demonstrate that Btg1 controls GCP proliferation via cyclin D1, and Btg1 knockout causes hyperplasia of the external granule layer with impaired motor coordination.\",\n      \"method\": \"Btg1 knockout mice, GCP cell line gain/loss-of-function, cyclin D1 expression analysis, motor coordination behavioral tests\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO phenotype plus in vitro gain/loss-of-function with specific molecular target (cyclin D1); single lab\",\n      \"pmids\": [\"26524254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Ablation of Btg1 in mice causes premature exit of dentate gyrus and SVZ stem/progenitor cells from the cell cycle after S phase, followed by p53- and p21-dependent apoptosis, depleting the adult stem/progenitor pool and impairing contextual memory discrimination.\",\n      \"method\": \"Btg1 knockout mice, BrdU cell cycle analysis, p53/p21 immunostaining, TUNEL apoptosis assay, neurosphere self-renewal assays, behavioral tests\",\n      \"journal\": \"Frontiers in neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with multiple mechanistic cellular readouts (cell cycle exit, p53/p21 induction, apoptosis, self-renewal); single lab\",\n      \"pmids\": [\"22969701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Btg1 and Btg2 are required for neonatal cardiomyocyte cell cycle arrest; Btg1/2 double knockout and AAV9-mediated double knockdown mouse hearts show increased mitotic cardiomyocytes at postnatal day 7; RNAseq of Btg1/2-depleted NRVMs implicates Btg1/2 in inhibiting cell proliferation and modulating reactive oxygen species response pathways linked to cardiomyocyte cell cycle arrest.\",\n      \"method\": \"Constitutive double knockout mice, AAV9-mediated in vivo knockdown, siRNA in neonatal rat ventricular myocytes, EdU/pHH3 proliferation assays, RNAseq\",\n      \"journal\": \"Journal of molecular and cellular cardiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus in vivo AAV knockdown plus in vitro siRNA with transcriptomic readout; single lab\",\n      \"pmids\": [\"37062247\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Btg1 and Btg2 are required for normal vertebral patterning; Btg1-/- mice display partial posterior transformation of the seventh cervical vertebra; Btg1-/-;Btg2-/- double knockouts show stronger homeotic transformations, demonstrating Btg1 and Btg2 act synergistically in specifying axial skeleton identity, consistent with their roles as coregulators of Hox transcription factors.\",\n      \"method\": \"Single and double Btg1/Btg2 knockout mice, skeletal phenotype analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via double KO; single lab, clear phenotypic readout\",\n      \"pmids\": [\"26218146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Combined loss of BTG1 and IKZF1 in mouse B cells increases glucocorticoid resistance beyond that caused by IKZF1 alone; BTG1 loss alone does not affect glucocorticoid sensitivity, but cooperates with IKZF1 loss specifically in this pathway; in vitro, Btg1/Ikzf1-deficient B cells show increased resistance to glucocorticoids but not other chemotherapy drugs.\",\n      \"method\": \"Btg1-knockout crossed onto Ikzf1-heterozygous mice, ex vivo glucocorticoid sensitivity assays, leukemia mouse model\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in mouse model with functional drug sensitivity readout; single lab\",\n      \"pmids\": [\"27979924\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"BTG1 deficiency enhances the self-renewal capacity of ETV6-RUNX1-positive hematopoietic progenitors and drives upregulation of the proto-oncogene BCL6 and downregulation of BCL6 targets p19Arf and Tp53; ectopic BCL6 expression phenocopies BTG1 loss, identifying BTG1-mediated suppression of BCL6 as a mechanism limiting leukemogenesis.\",\n      \"method\": \"Btg1 knockout mouse fetal liver progenitors with ETV6-RUNX1 expression, self-renewal/clonogenic assays, gene expression analysis, ectopic BCL6 epistasis\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function plus ectopic epistasis with mechanistic pathway identification; single lab\",\n      \"pmids\": [\"29408281\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In medulloblastoma, Btg1 deletion increases apoptosis of cerebellar granule cell precursors (synergistically with Ptch1+/- mutation), associated with increased PRMT1 protein expression; Btg1 ablation also increases the proportion of CD15+ tumor stem cells, suggesting Btg1 regulates the balance between apoptosis and stem cell quiescence in medulloblastoma.\",\n      \"method\": \"Btg1/Ptch1 compound knockout mice, caspase-3 immunostaining, CD15 stem cell marker, PRMT1 protein quantification\",\n      \"journal\": \"Frontiers in oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic compound KO with multiple cellular readouts; single lab\",\n      \"pmids\": [\"32231994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"BTG1 suppresses β-catenin signaling by inhibiting formation of the β-catenin/TCF4 transcriptional complex, leading to reduced c-Myc and Cyclin D1 expression; BTG1 is required for HDAC inhibitor-induced cell cycle arrest and autophagy in DLBCL cells; in vivo antitumor efficacy of HDAC inhibition depends on the BTG1/β-catenin axis.\",\n      \"method\": \"BTG1 siRNA knockdown/overexpression, β-catenin co-immunoprecipitation (β-catenin/TCF4 complex), cell cycle/autophagy assays, DLBCL xenograft mouse model\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP of complex plus genetic loss/gain-of-function plus in vivo xenograft; single lab\",\n      \"pmids\": [\"41950351\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"T3 (triiodothyronine) and cAMP increase BTG1 nuclear accumulation in confluent myoblasts via increased nuclear import or retention, without direct transcriptional control of BTG1; AP-1 activity represses BTG1 expression via an AP-1-like sequence in the BTG1 promoter; BTG1 overexpression mimics T3/cAMP myogenic influence (inhibiting proliferation, promoting differentiation).\",\n      \"method\": \"Transient transfection reporter assays (BTG1 promoter), subcellular fractionation/immunolocalization, BTG1 overexpression functional assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter-reporter mapping plus localization plus functional overexpression; single lab\",\n      \"pmids\": [\"10366433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PUM2 (RNA binding protein) directly binds the 3'UTR of BTG1 mRNA (RNA pulldown and RNA immunoprecipitation), repressing BTG1 expression; PUM2 knockdown increases BTG1 levels and suppresses glioblastoma cell proliferation and migration; BTG1 knockdown reverses the anti-proliferative effect of PUM2 knockdown, placing BTG1 downstream of PUM2.\",\n      \"method\": \"RNA pulldown, RNA immunoprecipitation, siRNA knockdown of PUM2 and BTG1, cell proliferation and migration assays\",\n      \"journal\": \"Cell structure and function\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct RNA-protein interaction (pulldown + RIP) plus genetic epistasis; single lab\",\n      \"pmids\": [\"30787206\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BTG1 is an antiproliferative transcriptional cofactor that: (1) interacts with PRMT1 to modulate arginine methylation of substrates including ATF4 (R239) and promotes GR-mediated transcription; (2) recruits the CCR4-NOT deadenylase complex (via CAF1/CNOT7/CNOT8) and PABPC1 through its conserved boxB and boxC motifs to stimulate mRNA deadenylation and decay, thereby maintaining cellular quiescence; (3) acts as a coactivator of nuclear receptors (T3R, RARs), MyoD, and Hoxb9 through direct protein interactions mediated by its A box, C-terminal domain, and LXXLL motifs; (4) requires CDK2-dependent phosphorylation at Ser-159 for CAF1 interaction; (5) suppresses β-catenin/TCF4 complex formation; and (6) is regulated transcriptionally by FoxO3a and AP-1, and post-transcriptionally by PUM2 and multiple miRNAs targeting its 3'UTR.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"BTG1 is an antiproliferative transcriptional cofactor and post-transcriptional regulator that enforces cellular quiescence and terminal differentiation across hematopoietic, neural, muscle, and cardiac lineages [#1, #14]. It operates through two convergent biochemical activities. First, BTG1 binds the arginine methyltransferase PRMT1 and modulates its enzymatic activity [#0], a partnership required for BTG1's growth-arrest function in B lymphoma cells [#9] and for arginine methylation of substrates including ATF4 at R239, which tunes the ATF4-dependent stress response [#11]; through this PRMT1 axis BTG1 also acts as a coactivator, recruiting PRMT1 to the glucocorticoid receptor promoter to support GR autoinduction [#10]. Second, BTG1 stimulates mRNA deadenylation and decay by recruiting the CCR4-NOT deadenylase via its CAF1 subunits (CNOT7/CNOT8) and engaging PABPC1, interactions mapped to its conserved boxB and boxC motifs; this deadenylation activity maintains lymphocyte quiescence by limiting global mRNA abundance and poly(A) tail length [#2, #14, #15]. The CAF1 interaction is gated by CDK2/cyclin E- or A-dependent phosphorylation of BTG1 at Ser-159 [#3]. BTG1 additionally functions as a transcriptional coregulator of nuclear receptors (T3R, RARs), MyoD, and the homeodomain protein Hoxb9 through its A box, C-terminal region, and LXXLL motifs [#4, #5, #8], and it suppresses β-catenin/TCF4 complex formation to restrain c-Myc and Cyclin D1 [#27]. BTG1 expression is itself controlled transcriptionally by FoxO3a and AP-1 and post-transcriptionally by PUM2 binding its 3'UTR [#7, #28, #29]. Loss-of-function BTG1 variants in non-Hodgkin lymphoma impair CNOT7/CNOT8 binding and abolish antiproliferative activity, and BTG1 mutations drive a B-cell supercompetitor phenotype during affinity maturation by altering MYC induction kinetics, establishing BTG1 as a tumor suppressor in germinal-center lymphomagenesis [#16, #17].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established BTG1 as a cell-cycle-regulated antiproliferative gene, defining the phenotype that all later mechanism had to explain.\",\n      \"evidence\": \"Cell cycle staging by Northern blot plus gain-of-function transfection in NIH3T3 cells\",\n      \"pmids\": [\"1373383\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No molecular mechanism for growth inhibition identified\", \"No binding partners known at this stage\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Identified PRMT1 as a BTG1 partner and showed BTG1 modulates its methyltransferase activity, providing the first enzymatic axis for BTG1 function.\",\n      \"evidence\": \"Yeast two-hybrid, GST pulldown, in vitro methyltransferase assay\",\n      \"pmids\": [\"8663146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates of the BTG1/PRMT1 complex not defined\", \"Direction of modulation (activation vs inhibition) in cells unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Connected BTG1 to the CCR4-NOT deadenylase by mapping the boxB-dependent CAF1 interaction, and showed CDK2 phosphorylation at Ser-159 gates that interaction, linking cell-cycle state to deadenylase recruitment.\",\n      \"evidence\": \"Yeast two-hybrid, GST pulldown, reciprocal co-IP, in vitro kinase assay with Ser159Ala mutagenesis, co-IP in primary cells\",\n      \"pmids\": [\"9712883\", \"9820826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of CAF1 recruitment on specific mRNAs not yet demonstrated\", \"Kinase regulating Ser-159 in vivo context limited to in vitro CDK2 assays\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined BTG1 as a coactivator of nuclear receptors, MyoD, and Hoxb9, showing its antiproliferative/differentiation role is partly transcriptional and domain-encoded.\",\n      \"evidence\": \"GST pulldown, co-IP, transcriptional reporter assays, LXXLL/A-box/C-terminal domain mutagenesis, EMSA across studies\",\n      \"pmids\": [\"10617598\", \"11136725\", \"15674337\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether coactivation requires the PRMT1 or CAF1 activities not dissected\", \"Endogenous target genes of these complexes not mapped\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showed the BTG1/PRMT1 complex acts as a promoter-recruited coactivator of the glucocorticoid receptor, linking BTG1 loss to glucocorticoid resistance.\",\n      \"evidence\": \"RNAi loss-of-function, ChIP for PRMT1 promoter recruitment, rescue by BTG1 re-expression\",\n      \"pmids\": [\"20354172\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Methylation substrate at the GR locus not identified\", \"Genome-wide BTG1/PRMT1 target set unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified ATF4 R239 as a specific BTG1/PRMT1 methylation target controlling stress transcription, linking the methylation axis to metabolic and stress phenotypes.\",\n      \"evidence\": \"Co-IP, in vitro methylation with site-specific mutagenesis, Btg1 knockout MEFs, in vivo liver steatosis and ATF4 epistasis models\",\n      \"pmids\": [\"26657730\", \"27188441\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How ATF4 methylation alters its activity mechanistically not fully resolved\", \"Relationship between ATF4 and SCD1 regulation and the deadenylase activity unexplored\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated genetically that BTG1 (with BTG2) drives global mRNA deadenylation and decay to maintain lymphocyte quiescence, establishing post-transcriptional control as a core antiproliferative mechanism.\",\n      \"evidence\": \"Btg1/2 double-knockout mice, poly(A) tail length sequencing, mRNA half-life measurement, T cell activation assays\",\n      \"pmids\": [\"32165587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific target transcripts setting the activation threshold not enumerated\", \"Redundancy and division of labor between BTG1 and BTG2 unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the boxC motif as necessary and sufficient for PABPC1 binding and deadenylation stimulation, structurally separating the RNA-decay function from PRMT1 association.\",\n      \"evidence\": \"NMR spectroscopy, boxC mutagenesis, in vitro and in cellulo deadenylation assays\",\n      \"pmids\": [\"34060423\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full assembly of BTG1 with CCR4-NOT and PABPC1 on a substrate mRNA not structurally resolved\", \"Whether boxB and boxC act on overlapping or distinct mRNA pools unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established BTG1 as a germinal-center tumor suppressor whose lymphoma variants impair CNOT7/CNOT8 binding and alter MYC induction kinetics and BCAR1-RAC1 signaling, tying its biochemical activities to lymphomagenesis.\",\n      \"evidence\": \"Systematic variant-interaction-function correlation, primary human lymphoma analysis, knockout mouse models, MYC dynamics, BCAR1 co-IP, dasatinib rescue\",\n      \"pmids\": [\"33021411\", \"36656933\", \"36375119\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mRNA targets linking deadenylase loss to MYC kinetics not defined\", \"Whether BCAR1 regulation is independent of the CCR4-NOT activity unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How BTG1's distinct activities — PRMT1-dependent methylation, CCR4-NOT deadenylation, nuclear-receptor coactivation, and β-catenin suppression — are coordinated or selectively deployed in a given cell type remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model integrating the transcriptional and post-transcriptional functions\", \"Tissue-specific target mRNA and substrate repertoires not mapped\", \"Conformational dynamics linking mutations to partner-binding defects only modeled computationally [#19]\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 5, 8, 10]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 9, 15]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 14, 15]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [14, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3, 6, 28]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [14, 15]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 3, 20]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 5, 8, 10]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [21, 22, 23]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [16, 17, 18]}\n    ],\n    \"complexes\": [\"CCR4-NOT deadenylase complex\"],\n    \"partners\": [\"PRMT1\", \"CNOT7\", \"CNOT8\", \"PABPC1\", \"ATF4\", \"BCAR1\", \"Hoxb9\", \"MyoD\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}