{"gene":"JAK2","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2009,"finding":"JAK2 is present in the nucleus of haematopoietic cells and directly phosphorylates histone H3 at Tyr41 (H3Y41). This phosphorylation prevents binding of HP1alpha (but not HP1beta) to H3 via its chromo-shadow domain. Inhibition of JAK2 decreases H3Y41 phosphorylation and lmo2 expression at its promoter while increasing HP1alpha binding at the same site.","method":"In vitro kinase assay, nuclear fractionation, ChIP, JAK2 inhibitor treatment in leukemic cells, immunoprecipitation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay with direct substrate identification, ChIP in cells, functional consequence on gene expression; multiple orthogonal methods in a single rigorous study","pmids":["19783980"],"is_preprint":false},{"year":2001,"finding":"JAK2 (and TYK2) are direct substrates of protein-tyrosine phosphatase PTP1B. PTP1B recognizes the consensus (E/D)-pY-pY-(R/K) motif in JAK2, similar to the insulin receptor dephosphorylation site. A substrate-trapping PTP1B mutant formed stable complexes with JAK2 upon interferon stimulation, and PTP1B expression or trapping mutant inhibited interferon-dependent transcriptional activation. PTP1B-deficient MEFs displayed hyperphosphorylation of JAK2.","method":"Substrate-trapping mutant co-immunoprecipitation, in vitro phosphatase assay, PTP1B knockout MEFs, interferon-dependent transcriptional activation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — substrate-trapping co-IP, in vitro assay, genetic knockout confirmation; multiple orthogonal methods","pmids":["11694501"],"is_preprint":false},{"year":1994,"finding":"JAK2 is constitutively associated with the prolactin receptor (PRLR) and undergoes rapid tyrosine phosphorylation and kinase activation in response to prolactin binding. JAK2 association with PRLR was present before and after ligand binding, indicating JAK2 is a pre-assembled receptor-associated kinase that is activated by ligand-induced receptor activation.","method":"Reciprocal anti-JAK2/anti-phosphotyrosine immunoprecipitation, in vitro tyrosine kinase assay with [gamma-32P]ATP, phosphoamino acid analysis, anti-receptor immunoprecipitation followed by anti-JAK2 immunoblotting","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reciprocal Co-IP, in vitro kinase assay, phosphoamino acid analysis; multiple orthogonal methods in foundational study","pmids":["7508935"],"is_preprint":false},{"year":2018,"finding":"Crystal structures of JAK2 FERM and SH2 domains bound to leptin receptor (LEPR) and erythropoietin receptor (EPOR) reveal a dimeric 2:2 JAK2/receptor conformation. A membrane-proximal 'switch' region peptide motif on the receptor is essential for dimer formation. Mutation of the receptor switch region disrupts STAT phosphorylation but does not affect JAK2 binding, demonstrating that receptor-mediated JAK2 FERM dimerization is required for kinase activation.","method":"X-ray crystallography, STAT phosphorylation assay, mutagenesis of receptor switch region","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of two receptor complexes with functional mutagenesis validation; multiple orthogonal methods","pmids":["30044226"],"is_preprint":false},{"year":2009,"finding":"The SH2-pseudokinase domain linker of JAK2 acts as a switch that relays cytokine receptor engagement signals to kinase activation. The N-terminal part of the linker is essential for interaction of JAK2 with the Epo receptor, while mutations in the C-terminal region confer constitutive activation. Mutations of Glu543-Asp544 in the linker or Leu611, Arg683, or Phe694 in the pseudokinase domain hinge region yield constitutively active JAK2 that cannot be further stimulated by Epo.","method":"Functional gain-of-function screen, scanning mutagenesis, erythrocytosis mouse model, in vitro receptor-binding assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — systematic scanning mutagenesis identifying mechanistic determinants, in vivo confirmation in mouse model, multiple orthogonal methods","pmids":["19638629"],"is_preprint":false},{"year":2007,"finding":"JAK2 directly phosphorylates PAK1 at tyrosines 153, 201, and 285 in vivo and in vitro. Tyrosyl phosphorylation by JAK2 significantly increases PAK1 kinase activity. This phosphorylation decreases apoptosis induced by serum deprivation and staurosporine and increases cell motility. A triple PAK1 Y153F/Y201F/Y285F mutant was unaffected by JAK2-mediated phosphorylation.","method":"In vitro kinase assay, mass spectrometry, 2D peptide mapping, site-directed mutagenesis, apoptosis assay, cell motility assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay, mass spectrometry identification of sites, mutagenesis with functional readout; multiple orthogonal methods","pmids":["17726028"],"is_preprint":false},{"year":2019,"finding":"Cytokine receptor-associated JAK2 phosphorylates TET2 at tyrosines Y1939 and Y1964, leading to TET2 activation and increased DNA hydroxymethylation. Phosphorylated TET2 interacts with the erythroid transcription factor KLF1, and this interaction increases upon erythropoietin exposure. The activating JAK2V617F mutation is associated with increased TET2 activity and genome-wide loss of cytosine methylation.","method":"Phosphoproteomics, in vitro kinase assay, Co-IP, 5-hydroxymethylcytosine quantification, bisulfite sequencing, patient samples and mouse models","journal":"Cancer discovery","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assay identifying specific phosphorylation sites, Co-IP of TET2-KLF1 interaction, validated in patient samples and mouse models; multiple orthogonal methods","pmids":["30944118"],"is_preprint":false},{"year":2006,"finding":"Phosphorylation of JAK2 on Ser523 inhibits JAK2-dependent leptin receptor (LRb) signaling. Ser523 is phosphorylated in intact cells and in mouse spleen independently of LRb-JAK2 activation. Mutation S523A sensitizes and prolongs JAK2 signaling following LRb activation, and the inhibitory effect is independent of Tyr570-mediated inhibition.","method":"Tandem mass spectrometric phosphorylation site identification, site-directed mutagenesis (S523A), LRb signaling assays in cells","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — mass spectrometry identification of novel phosphorylation site, mutagenesis with functional signaling readout, validated in vivo (mouse spleen)","pmids":["16705160"],"is_preprint":false},{"year":1998,"finding":"Jak2 kinase domain (JH1) alone is sufficient for interaction with and phosphorylation of Stat5. Deletion of the pseudokinase domain (JH2) causes increased enzymatic activity of Jak2. A Stat5 SH2 domain R618K mutation abolishes phosphorylation by Jak2. A single phosphotyrosine-SH2 domain interaction is sufficient for Stat5 dimerization but such dimers bind DNA inefficiently.","method":"Yeast two-hybrid/functional system with Jak2 and Stat5, co-immunoprecipitation under stringent conditions, deletion/point mutagenesis, Stat-dependent reporter gene assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — reconstituted Jak2-Stat5 signaling system in yeast with systematic mutagenesis, multiple deletion and point mutants tested, reporter gene functional readout","pmids":["9575217"],"is_preprint":false},{"year":2024,"finding":"Quantitative superresolution microscopy showed that EpoR exists as monomers and dimerizes upon Epo stimulation or through JAK2 pseudokinase domain mutations (V617F, K539L, R683S). Crystallographic analysis with kinase activity assays revealed distinct activation mechanisms: JAK2 V617F activity is driven by dimerization; K539L involves both increased receptor dimerization and kinase activity; R683S prevents autoinhibition, increases catalytic activity, and drives JAK2 equilibrium toward the activation state through a wild-type dimer interface.","method":"Quantitative single-molecule localization microscopy (qSMLM), X-ray crystallography, in vitro kinase activity assay, molecular dynamics simulations, AI-guided structural modeling","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures, superresolution microscopy of receptor dimerization, kinase activity assays, and simulations in one rigorous multi-method study","pmids":["38457493"],"is_preprint":false},{"year":2021,"finding":"In the context of sepsis, the IL-6/gp130/JAK2/STAT3 pathway mediates muscle atrophy. JAK2 inhibition (AG490) reduces STAT3 phosphorylation and attenuates muscle atrophy in septic mice, accompanied by reduction in Fbxo32/Atrogin-1 and Trim63/MuRF1 mRNA and protein expression. In C2C12 myotubes, JAK2 inhibition decreases IL-6-induced Socs3 mRNA expression and myotube atrophy.","method":"JAK2 inhibitor (AG490) treatment in CLP sepsis mouse model, siRNA knockdown of Il6st/gp130, STAT3 phosphorylation assays, muscle weight/atrophy phenotype, RNAseq","journal":"Journal of cachexia, sarcopenia and muscle","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition and genetic knockdown with defined cellular phenotype, but pathway placement relies on inhibitor specificity and indirect readouts","pmids":["34821076"],"is_preprint":false},{"year":2020,"finding":"In-depth phosphoproteome profiling of JAK2-mutant cells identified YBX1, an mRNA-processing protein, as a post-translationally modified target of mutant JAK2. JAK2-dependent phosphorylation of YBX1 maintains its function in RNA splicing and transcriptional control of ERK signaling, enabling persistence of JAK2V617F malignant clones despite JAK inhibitor treatment. YBX1 inactivation combined with JAK inhibition causes apoptosis of JAK2-dependent cells and molecular remission in vivo.","method":"Phosphoproteomics, genetic inactivation of YBX1, RNA-seq (splicing analysis), in vivo mouse models, primary human cells, apoptosis assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — phosphoproteomics identifying substrate, genetic inactivation with molecular and in vivo phenotypic readouts, validated in mouse models and primary human cells; multiple orthogonal methods","pmids":["33239784"],"is_preprint":false},{"year":2007,"finding":"JAK2 exon 12 gain-of-function mutations (including K539L substitution) result in increased phosphorylation of JAK2 and ERK1/2 compared to wild-type or V617F JAK2. BaF3 cells expressing exon 12 mutant JAK2 proliferate without IL-3. K539L JAK2 induces a myeloproliferative phenotype including erythrocytosis in a murine retroviral bone marrow transplantation model.","method":"Biochemical phosphorylation assays in BaF3 cells, murine bone marrow transplantation, cytokine-independent proliferation assay","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical characterization of kinase activation, in vivo mouse model confirmation, cytokine-independent proliferation assay; multiple orthogonal methods","pmids":["17267906"],"is_preprint":false},{"year":2000,"finding":"The TEL-JAK2 fusion protein, in which the TEL self-association domain is fused to the JAK2 kinase domain, exhibits constitutive activation of tyrosine kinase activity and confers growth factor-independent proliferation to IL-3-dependent Ba/F3 cells. Expression in transgenic mice under a lymphoid promoter causes fatal T-cell leukemia with activation of STAT1 and STAT5.","method":"In vitro kinase assay, Ba/F3 proliferation assay, transgenic mouse model, immunoblotting for STAT activation","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — constitutive kinase activity shown in vitro, growth factor-independent proliferation, in vivo transgenic model with STAT activation; multiple orthogonal methods","pmids":["10845925"],"is_preprint":false},{"year":2008,"finding":"JAK2/STAT2/STAT3 pathway is required for early myogenic differentiation. Inhibition of JAK2 (by small molecule inhibitor or siRNA) blocks myogenic differentiation of myoblasts. JAK2, STAT2, and STAT3 are activated upon differentiation induction. The pro-differentiation effect is partially mediated by MyoD and MEF2, and JAK2/STAT2/STAT3 regulates expression of IGF2 and HGF genes.","method":"Small molecule JAK2 inhibitor, siRNA knockdown, differentiation assays, immunoblotting for pathway activation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — both pharmacological and siRNA knockdown with defined differentiation phenotype, downstream target gene regulation identified; single lab","pmids":["18835816"],"is_preprint":false},{"year":2021,"finding":"Crystal structures of JAK2 bound to ruxolitinib and fedratinib (and derivatives) were determined from mammalian cell-produced JAK2, providing structural basis for inhibitor binding including shape complementarity requirements for chiral and achiral inhibitors at the ATP-binding pocket.","method":"X-ray crystallography, biochemical kinase assay, cellular activity assays","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — first crystal structures of JAK2 with approved drugs, complemented by biochemical and cellular data; multiple orthogonal methods in single rigorous study","pmids":["33570945"],"is_preprint":false},{"year":2020,"finding":"Five crystal structures of the JAK2 pseudokinase domain (JH2) complexed with selective diaminotriazole ligands were determined. Selective JH2 binders (over kinase domain JH1) inhibit STAT5 phosphorylation in cells expressing both wild-type and V617F JAK2, demonstrating that JH2 is a pharmacologically targetable domain that modulates JAK2 activity.","method":"X-ray crystallography (5 structures), binding affinity measurements for JH1/JH2/JH2-V617F, STAT5 phosphorylation cellular assay","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with functional cellular validation of JH2 as pharmacological target; multiple orthogonal methods","pmids":["32329617"],"is_preprint":false},{"year":2022,"finding":"ARID2 promotes ubiquitination and degradation of JAK2 via the E3 ubiquitin ligase NEDD4L. ARID2 recruits CARM1 to increase H3R17me2a at the NEDD4L promoter, activating NEDD4L transcription. Loss of ARID2 stabilizes JAK2, activating JAK2-STAT5-PPARγ signaling and inducing hepatic steatosis. Fedratinib (JAK2 inhibitor) alleviated HFD-induced hepatic steatosis in liver-specific Arid2 KO mice.","method":"ChIP assay, ubiquitination assay, Co-IP, liver-specific Arid2 knockout mice, HFD mouse model, JAK2 inhibitor treatment, immunoblotting","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP identifying ARID2-CARM1-NEDD4L axis, ubiquitination assay identifying NEDD4L as E3 ligase for JAK2, in vivo genetic and pharmacological validation; multiple orthogonal methods","pmids":["36396719"],"is_preprint":false},{"year":2024,"finding":"PF4 (platelet factor 4) binds and activates the thrombopoietin receptor c-Mpl on platelets, leading to JAK2 activation and phosphorylation of STAT3 and STAT5, resulting in platelet aggregation. Inhibition of the c-Mpl-JAK2 pathway inhibits platelet aggregation to PF4 and to VITT sera.","method":"Binding assay, JAK2 pathway inhibition (pharmacological), STAT3/STAT5 phosphorylation assays, platelet aggregation assay","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assays with pharmacological inhibition establishing c-Mpl-JAK2-STAT signaling axis in platelets; single lab, limited structural detail","pmids":["37883794"],"is_preprint":false},{"year":2015,"finding":"A model for JAK2 activation by the GH receptor homodimer was established based on biochemical data and molecular dynamics simulations: constitutive receptor dimers undergo ligand-induced reorientation/rotation, transitioning from parallel to separated transmembrane domains. This movement slides the pseudokinase inhibitory domain of one JAK2 away from the kinase domain of the other JAK2 within the dimer, allowing trans-activation between kinase domains.","method":"Biochemical receptor dimerization assays, molecular dynamics simulations","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — biochemical data combined with MD simulations; mechanistic model supported by multiple approaches but lacks direct structural confirmation","pmids":["25656053"],"is_preprint":false},{"year":2008,"finding":"Leptin stimulates JAK2-independent STAT3 phosphorylation via non-JAK2 tyrosine kinases including Src family members (c-Src, Fyn) downstream of LEPRb. JAK2 mediates leptin signaling both by phosphorylating substrates and by serving as a scaffolding/adaptor protein. Kinase-inactive JAK2(K882E) is tyrosyl-phosphorylated by non-JAK2 kinases in JAK2-null cells and enhances STAT3 phosphorylation, indicating a scaffolding role.","method":"JAK2-null cell lines (human and mouse), pharmacological Src inhibitors, dominant negative Src(K298M), overexpression of c-Src/Fyn, kinase-inactive JAK2 mutant, LEPRb Tyr mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic JAK2-null cells combined with pharmacological and dominant-negative approaches, multiple receptor mutants; mechanistic finding that JAK2 has scaffolding function independent of its kinase activity","pmids":["18718905"],"is_preprint":false},{"year":2000,"finding":"SH2-B binds with high affinity via its SH2 domain to phosphorylated tyrosines within JAK2 in response to GH. GH-induced binding of SH2-B to JAK2 potently activates JAK2, leading to enhanced tyrosyl phosphorylation of STAT proteins and other cellular proteins. SIRP binds directly to JAK2 without requiring tyrosyl phosphorylation, is itself phosphorylated on tyrosines in response to GH, and recruits SHP2 which dephosphorylates SIRP and likely JAK2, acting as a negative regulator.","method":"Co-immunoprecipitation, in vitro binding/kinase assays, STAT phosphorylation assays, SH2 domain binding studies","journal":"Recent progress in hormone research","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP and kinase activation assays identifying SH2-B and SIRP as JAK2-binding proteins; mechanistic follow-up limited in this review context, citing earlier primary experiments","pmids":["11036942"],"is_preprint":false}],"current_model":"JAK2 is a non-receptor tyrosine kinase that constitutively associates with cytokine receptors (including those for erythropoietin, leptin, prolactin, growth hormone, and thrombopoietin) via its FERM-SH2 domains, and is activated by ligand-induced receptor dimerization through a mechanism in which receptor 'switch' region-mediated JAK2 FERM domain dimerization relieves pseudokinase (JH2) domain-mediated autoinhibition, allowing trans-phosphorylation between kinase domains; activated JAK2 then phosphorylates STAT proteins, TET2 (at Y1939/Y1964), PAK1 (at Y153/Y201/Y285), histone H3 (at Y41, linking it to chromatin regulation via HP1alpha displacement), and YBX1 (regulating RNA splicing and ERK signaling), while its activity is negatively regulated by PTP1B-mediated dephosphorylation, Ser523 serine phosphorylation, and NEDD4L-mediated ubiquitination; oncogenic mutations (V617F in JH2, exon 12 mutations) cause constitutive kinase activation by disrupting autoinhibitory pseudokinase domain contacts or promoting pathogenic JAK2 dimerization."},"narrative":{"mechanistic_narrative":"JAK2 is a non-receptor tyrosine kinase that constitutively associates with cytokine receptors and transduces ligand-induced receptor engagement into downstream STAT signaling, governing hematopoiesis, metabolism, and cell differentiation [PMID:7508935, PMID:30044226]. It is pre-assembled on receptors such as the prolactin, erythropoietin, leptin, and growth hormone receptors and is activated by ligand-induced receptor dimerization: crystallographic and single-molecule data show that a membrane-proximal receptor 'switch' region drives JAK2 FERM-domain dimerization, while reorientation of the receptor relieves pseudokinase (JH2) domain–mediated autoinhibition to permit trans-phosphorylation between kinase domains [PMID:30044226, PMID:38457493, PMID:25656053]. The SH2–pseudokinase linker relays this signal, and lesions in the linker or pseudokinase hinge yield constitutive, ligand-independent activation [PMID:19638629]. Once active, JAK2 phosphorylates STAT5 through a kinase-domain/SH2 interaction [PMID:9575217], and an expanding substrate repertoire including histone H3 at Tyr41—which displaces HP1alpha to derepress chromatin target genes such as lmo2 [PMID:19783980], the dioxygenase TET2 at Y1939/Y1964 (linking JAK2 to DNA hydroxymethylation via KLF1) [PMID:30944118], PAK1 [PMID:17726028], and the mRNA-processing factor YBX1 [PMID:33239784]. JAK2 also acts as a kinase-independent scaffold to support STAT3 phosphorylation by Src-family kinases [PMID:18718905]. Its activity is restrained by PTP1B-mediated dephosphorylation [PMID:11694501], inhibitory Ser523 phosphorylation [PMID:16705160], and ARID2-directed NEDD4L-mediated ubiquitination and degradation [PMID:36396719]. Gain-of-function lesions—the V617F and exon 12 (e.g. K539L) mutations in/around JH2, and the TEL-JAK2 fusion—cause constitutive kinase activation and myeloproliferative or leukemic disease, and JAK2 is pharmacologically targetable at both its ATP pocket and its JH2 domain [PMID:38457493, PMID:17267906, PMID:10845925, PMID:32329617].","teleology":[{"year":1994,"claim":"Established that JAK2 is a pre-assembled receptor-associated kinase rather than a recruited effector, answering how cytokine receptors lacking intrinsic catalytic activity transduce signals.","evidence":"Reciprocal anti-JAK2/anti-phosphotyrosine Co-IP and in vitro kinase assay on the prolactin receptor","pmids":["7508935"],"confidence":"High","gaps":["Did not resolve the structural basis of receptor association","Mechanism of activation upon ligand binding not defined"]},{"year":1998,"claim":"Mapped the JAK2 kinase domain as sufficient for STAT5 engagement and identified the pseudokinase domain as autoinhibitory, framing JH2 as a brake on catalytic activity.","evidence":"Reconstituted Jak2-Stat5 system in yeast with deletion/point mutagenesis and reporter assays","pmids":["9575217"],"confidence":"High","gaps":["Structural mechanism of JH2 autoinhibition unresolved","Did not test physiological receptor context"]},{"year":2000,"claim":"Demonstrated that constitutive JAK2 kinase activation is oncogenic, by showing the TEL-JAK2 fusion drives growth-factor independence and leukemia.","evidence":"In vitro kinase assay, Ba/F3 proliferation, and transgenic mouse leukemia model with STAT activation","pmids":["10845925"],"confidence":"High","gaps":["Native point-mutation drivers not yet identified","STAT-independent contributions not dissected"]},{"year":2001,"claim":"Identified the first direct negative regulator of JAK2, showing PTP1B dephosphorylates JAK2 to terminate cytokine signaling.","evidence":"Substrate-trapping Co-IP, in vitro phosphatase assay, and PTP1B-knockout MEFs","pmids":["11694501"],"confidence":"High","gaps":["Spatial/temporal control of PTP1B-JAK2 encounter unknown","Relative contribution versus other phosphatases unclear"]},{"year":2006,"claim":"Revealed serine phosphorylation as a distinct off-switch, with Ser523 phosphorylation independently restraining JAK2-dependent leptin signaling.","evidence":"Mass spectrometry site identification and S523A mutagenesis with LRb signaling readouts","pmids":["16705160"],"confidence":"High","gaps":["Kinase responsible for Ser523 phosphorylation not identified","Mechanism by which Ser523 modulates catalysis unknown"]},{"year":2007,"claim":"Expanded the JAK2 substrate repertoire beyond STATs (PAK1) and confirmed exon 12 mutations as bona fide myeloproliferative drivers distinct from V617F.","evidence":"In vitro kinase assays with MS site mapping for PAK1; biochemical and bone-marrow-transplant models for exon 12 K539L","pmids":["17726028","17267906"],"confidence":"High","gaps":["Cellular contexts where PAK1 phosphorylation is relevant not fully defined","Why exon 12 mutations preferentially cause erythrocytosis unresolved"]},{"year":2008,"claim":"Uncovered a kinase-independent scaffolding role for JAK2 and a tissue role in myogenic differentiation, broadening JAK2 function beyond direct phosphotransfer.","evidence":"JAK2-null cells with Src inhibitors/dominant-negatives and kinase-inactive JAK2; JAK2 inhibitor/siRNA in myoblast differentiation assays","pmids":["18718905","18835816"],"confidence":"High","gaps":["Structural basis of scaffolding function not defined","Myogenic role relies in part on inhibitor specificity (Medium)"]},{"year":2009,"claim":"Established a direct nuclear/chromatin function for JAK2, showing it phosphorylates histone H3Y41 to displace HP1alpha and derepress target genes, and refined the activation switch to the SH2-pseudokinase linker.","evidence":"In vitro kinase assay, ChIP, and inhibitor treatment for H3Y41; scanning mutagenesis and erythrocytosis mouse model for the linker switch","pmids":["19783980","19638629"],"confidence":"High","gaps":["How nuclear JAK2 is targeted to specific loci unknown","Breadth of chromatin targets beyond lmo2 not mapped"]},{"year":2018,"claim":"Provided the structural basis for activation, showing receptor switch-region-mediated 2:2 JAK2/receptor dimerization is required to trigger kinase activation.","evidence":"X-ray crystallography of JAK2 FERM-SH2 with LEPR and EPOR plus switch-region mutagenesis and STAT phosphorylation assays","pmids":["30044226"],"confidence":"High","gaps":["Full-length receptor-JAK2 complex architecture not resolved","Dynamics of JH2 disengagement not directly visualized"]},{"year":2019,"claim":"Connected JAK2 signaling to epigenetic control, showing it directly phosphorylates and activates TET2 to alter DNA hydroxymethylation, with implications for V617F-driven disease.","evidence":"Phosphoproteomics, in vitro kinase assay, Co-IP of TET2-KLF1, 5hmC quantification in patient samples and mouse models","pmids":["30944118"],"confidence":"High","gaps":["Genome-wide consequences of TET2 activation incompletely defined","Crosstalk with TET2 loss-of-function mutations unclear"]},{"year":2020,"claim":"Identified YBX1 as a mutant-JAK2 substrate enabling clonal persistence and validated the pseudokinase domain as a druggable site, opening therapeutic strategies against JAK-inhibitor-resistant disease.","evidence":"Phosphoproteomics with YBX1 genetic inactivation, RNA-seq, and in vivo models; JH2-selective ligand crystal structures with STAT5 cellular assays","pmids":["33239784","32329617"],"confidence":"High","gaps":["Mechanistic link between YBX1 phosphorylation and splicing/ERK control incomplete","In vivo efficacy of JH2-selective inhibitors not established"]},{"year":2021,"claim":"Delivered structural detail on inhibitor binding at the ATP pocket and placed JAK2 within IL-6/gp130/STAT3 signaling driving sepsis-associated muscle atrophy.","evidence":"Crystal structures with ruxolitinib/fedratinib plus biochemical/cellular assays; JAK2 inhibitor and gp130 knockdown in sepsis mouse and C2C12 models","pmids":["33570945","34821076"],"confidence":"High","gaps":["Atrophy pathway placement relies on inhibitor specificity (Medium)","Selectivity determinants versus other JAK family members not addressed"]},{"year":2022,"claim":"Defined a transcription-coupled degradation axis controlling JAK2 abundance, in which ARID2 drives NEDD4L-mediated JAK2 ubiquitination and loss of this control promotes hepatic steatosis.","evidence":"ChIP, ubiquitination and Co-IP assays, liver-specific Arid2 knockout and HFD mice with JAK2 inhibitor rescue","pmids":["36396719"],"confidence":"High","gaps":["Direct NEDD4L-JAK2 recognition determinants not mapped","Generalizability beyond liver unclear"]},{"year":2024,"claim":"Mechanistically distinguished how different oncogenic pseudokinase mutations activate JAK2, linking receptor dimerization, increased catalysis, and loss of autoinhibition; also placed JAK2 in PF4/c-Mpl platelet signaling.","evidence":"qSMLM of EpoR dimerization, crystallography, kinase assays and MD simulations for V617F/K539L/R683S; binding and platelet aggregation assays for PF4/c-Mpl/JAK2/STAT","pmids":["38457493","37883794"],"confidence":"High","gaps":["Quantitative contribution of dimerization versus intrinsic activity per mutant not fully reconciled","PF4/c-Mpl axis lacks structural detail (Medium)"]},{"year":null,"claim":"How nuclear JAK2 is recruited to specific chromatin loci and how its kinase-independent scaffolding versus catalytic functions are coordinated across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mechanism for locus-specific nuclear targeting","Scaffolding versus catalytic role partitioning undefined","Integration of the full substrate network (STAT, TET2, PAK1, YBX1, H3) not modeled"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,5,6,8,11]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[2,5,6,8]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[2,3]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[20]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2,3,18]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,8]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[12,13]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[17]}],"complexes":[],"partners":["EPOR","LEPR","PRLR","MPL","STAT5","PTP1B","NEDD4L","SH2B1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60674","full_name":"Tyrosine-protein kinase JAK2","aliases":["Janus kinase 2","JAK-2"],"length_aa":1132,"mass_kda":130.7,"function":"Non-receptor tyrosine kinase involved in various processes such as cell growth, development, differentiation or histone modifications. Mediates essential signaling events in both innate and adaptive immunity. In the cytoplasm, plays a pivotal role in signal transduction via its association with type I receptors such as growth hormone (GHR), prolactin (PRLR), leptin (LEPR), erythropoietin (EPOR), thrombopoietin receptor (MPL/TPOR); or type II receptors including IFN-alpha, IFN-beta, IFN-gamma and multiple interleukins (PubMed:15690087, PubMed:7615558, PubMed:9657743, PubMed:15899890). Following ligand-binding to cell surface receptors, phosphorylates specific tyrosine residues on the cytoplasmic tails of the receptor, creating docking sites for STATs proteins (PubMed:15690087, PubMed:9618263). Subsequently, phosphorylates the STATs proteins once they are recruited to the receptor. Phosphorylated STATs then form homodimer or heterodimers and translocate to the nucleus to activate gene transcription. For example, cell stimulation with erythropoietin (EPO) during erythropoiesis leads to JAK2 autophosphorylation, activation, and its association with erythropoietin receptor (EPOR) that becomes phosphorylated in its cytoplasmic domain (PubMed:9657743). Then, STAT5 (STAT5A or STAT5B) is recruited, phosphorylated and activated by JAK2. Once activated, dimerized STAT5 translocates into the nucleus and promotes the transcription of several essential genes involved in the modulation of erythropoiesis. Part of a signaling cascade that is activated by increased cellular retinol and that leads to the activation of STAT5 (STAT5A or STAT5B) (PubMed:21368206). In addition, JAK2 mediates angiotensin-2-induced ARHGEF1 phosphorylation (PubMed:20098430). Plays a role in cell cycle by phosphorylating CDKN1B (PubMed:21423214). Cooperates with TEC through reciprocal phosphorylation to mediate cytokine-driven activation of FOS transcription. In the nucleus, plays a key role in chromatin by specifically mediating phosphorylation of 'Tyr-41' of histone H3 (H3Y41ph), a specific tag that promotes exclusion of CBX5 (HP1 alpha) from chromatin (PubMed:19783980). 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receptors.","date":"2006","source":"Pathologie-biologie","url":"https://pubmed.ncbi.nlm.nih.gov/16904848","citation_count":22,"is_preprint":false},{"pmid":"17934351","id":"PMC_17934351","title":"JAK2 V617F: implications for thrombosis in myeloproliferative diseases.","date":"2007","source":"Current opinion in hematology","url":"https://pubmed.ncbi.nlm.nih.gov/17934351","citation_count":22,"is_preprint":false},{"pmid":"19216843","id":"PMC_19216843","title":"Jak2 inhibitors: rationale and role as therapeutic agents in hematologic malignancies.","date":"2009","source":"Current oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/19216843","citation_count":22,"is_preprint":false},{"pmid":"20425393","id":"PMC_20425393","title":"JAK2 mutation and thrombosis in the myeloproliferative neoplasms.","date":"2010","source":"Current hematologic malignancy reports","url":"https://pubmed.ncbi.nlm.nih.gov/20425393","citation_count":21,"is_preprint":false},{"pmid":"36758212","id":"PMC_36758212","title":"Iron is a modifier of the phenotypes of JAK2-mutant myeloproliferative neoplasms.","date":"2023","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/36758212","citation_count":20,"is_preprint":false},{"pmid":"22339244","id":"PMC_22339244","title":"Targeting JAK2 in the therapy of myeloproliferative neoplasms.","date":"2012","source":"Expert opinion on therapeutic targets","url":"https://pubmed.ncbi.nlm.nih.gov/22339244","citation_count":20,"is_preprint":false},{"pmid":"21521147","id":"PMC_21521147","title":"New JAK2 inhibitors for myeloproliferative neoplasms.","date":"2011","source":"Expert opinion on investigational drugs","url":"https://pubmed.ncbi.nlm.nih.gov/21521147","citation_count":18,"is_preprint":false},{"pmid":"19074058","id":"PMC_19074058","title":"The role of JAK2 mutations in RARS and other MDS.","date":"2008","source":"Hematology. American Society of Hematology. Education Program","url":"https://pubmed.ncbi.nlm.nih.gov/19074058","citation_count":18,"is_preprint":false},{"pmid":"22583424","id":"PMC_22583424","title":"JAK2 inhibitors for myelofibrosis: why are they effective in patients with and without JAK2V617F mutation?","date":"2012","source":"Anti-cancer agents in medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22583424","citation_count":18,"is_preprint":false},{"pmid":"35279667","id":"PMC_35279667","title":"Curcumol Attenuates Endometriosis by Inhibiting the JAK2/STAT3 Signaling Pathway.","date":"2022","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/35279667","citation_count":18,"is_preprint":false},{"pmid":"26370832","id":"PMC_26370832","title":"Oncogenic Drivers in Myeloproliferative Neoplasms: From JAK2 to Calreticulin Mutations.","date":"2015","source":"Current hematologic malignancy reports","url":"https://pubmed.ncbi.nlm.nih.gov/26370832","citation_count":18,"is_preprint":false},{"pmid":"31100032","id":"PMC_31100032","title":"TG101348, a selective JAK2 antagonist, ameliorates hepatic fibrogenesis in vivo.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31100032","citation_count":18,"is_preprint":false},{"pmid":"35169231","id":"PMC_35169231","title":"Macrophage Jak2 deficiency accelerates atherosclerosis through defects in cholesterol efflux.","date":"2022","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/35169231","citation_count":17,"is_preprint":false},{"pmid":"24930769","id":"PMC_24930769","title":"Dual Aurora A and JAK2 kinase blockade effectively suppresses malignant transformation.","date":"2014","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/24930769","citation_count":17,"is_preprint":false},{"pmid":"31806641","id":"PMC_31806641","title":"Cooperative Blockade of PKCα and JAK2 Drives Apoptosis in Glioblastoma.","date":"2019","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/31806641","citation_count":17,"is_preprint":false},{"pmid":"38457493","id":"PMC_38457493","title":"Molecular basis of JAK2 activation in erythropoietin receptor and pathogenic JAK2 signaling.","date":"2024","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/38457493","citation_count":16,"is_preprint":false},{"pmid":"26639094","id":"PMC_26639094","title":"The Relevance of JAK2 in the Regulation of Cellular Transport.","date":"2016","source":"Current medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26639094","citation_count":16,"is_preprint":false},{"pmid":"35653642","id":"PMC_35653642","title":"Insights on JAK2 Modulation by Potent, Selective, and Cell-Permeable Pseudokinase-Domain Ligands.","date":"2022","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35653642","citation_count":16,"is_preprint":false},{"pmid":"29641446","id":"PMC_29641446","title":"The JAK2 GGCC (46/1) Haplotype in Myeloproliferative Neoplasms: Causal or Random?","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29641446","citation_count":16,"is_preprint":false},{"pmid":"36396719","id":"PMC_36396719","title":"ARID2 mitigates hepatic steatosis via promoting the ubiquitination of JAK2.","date":"2022","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/36396719","citation_count":16,"is_preprint":false},{"pmid":"25009002","id":"PMC_25009002","title":"Pyrrole-3-carboxamides as potent and selective JAK2 inhibitors.","date":"2014","source":"Bioorganic & medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25009002","citation_count":16,"is_preprint":false},{"pmid":"36122769","id":"PMC_36122769","title":"LPCAT1 functions as an oncogene in cervical cancer through mediating JAK2/STAT3 signaling.","date":"2022","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/36122769","citation_count":16,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47735,"output_tokens":6394,"usd":0.119557,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15281,"output_tokens":4751,"usd":0.09759,"stage2_stop_reason":"end_turn"},"total_usd":0.217147,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"JAK2 is present in the nucleus of haematopoietic cells and directly phosphorylates histone H3 at Tyr41 (H3Y41). This phosphorylation prevents binding of HP1alpha (but not HP1beta) to H3 via its chromo-shadow domain. Inhibition of JAK2 decreases H3Y41 phosphorylation and lmo2 expression at its promoter while increasing HP1alpha binding at the same site.\",\n      \"method\": \"In vitro kinase assay, nuclear fractionation, ChIP, JAK2 inhibitor treatment in leukemic cells, immunoprecipitation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay with direct substrate identification, ChIP in cells, functional consequence on gene expression; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"19783980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"JAK2 (and TYK2) are direct substrates of protein-tyrosine phosphatase PTP1B. PTP1B recognizes the consensus (E/D)-pY-pY-(R/K) motif in JAK2, similar to the insulin receptor dephosphorylation site. A substrate-trapping PTP1B mutant formed stable complexes with JAK2 upon interferon stimulation, and PTP1B expression or trapping mutant inhibited interferon-dependent transcriptional activation. PTP1B-deficient MEFs displayed hyperphosphorylation of JAK2.\",\n      \"method\": \"Substrate-trapping mutant co-immunoprecipitation, in vitro phosphatase assay, PTP1B knockout MEFs, interferon-dependent transcriptional activation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — substrate-trapping co-IP, in vitro assay, genetic knockout confirmation; multiple orthogonal methods\",\n      \"pmids\": [\"11694501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"JAK2 is constitutively associated with the prolactin receptor (PRLR) and undergoes rapid tyrosine phosphorylation and kinase activation in response to prolactin binding. JAK2 association with PRLR was present before and after ligand binding, indicating JAK2 is a pre-assembled receptor-associated kinase that is activated by ligand-induced receptor activation.\",\n      \"method\": \"Reciprocal anti-JAK2/anti-phosphotyrosine immunoprecipitation, in vitro tyrosine kinase assay with [gamma-32P]ATP, phosphoamino acid analysis, anti-receptor immunoprecipitation followed by anti-JAK2 immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reciprocal Co-IP, in vitro kinase assay, phosphoamino acid analysis; multiple orthogonal methods in foundational study\",\n      \"pmids\": [\"7508935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structures of JAK2 FERM and SH2 domains bound to leptin receptor (LEPR) and erythropoietin receptor (EPOR) reveal a dimeric 2:2 JAK2/receptor conformation. A membrane-proximal 'switch' region peptide motif on the receptor is essential for dimer formation. Mutation of the receptor switch region disrupts STAT phosphorylation but does not affect JAK2 binding, demonstrating that receptor-mediated JAK2 FERM dimerization is required for kinase activation.\",\n      \"method\": \"X-ray crystallography, STAT phosphorylation assay, mutagenesis of receptor switch region\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of two receptor complexes with functional mutagenesis validation; multiple orthogonal methods\",\n      \"pmids\": [\"30044226\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The SH2-pseudokinase domain linker of JAK2 acts as a switch that relays cytokine receptor engagement signals to kinase activation. The N-terminal part of the linker is essential for interaction of JAK2 with the Epo receptor, while mutations in the C-terminal region confer constitutive activation. Mutations of Glu543-Asp544 in the linker or Leu611, Arg683, or Phe694 in the pseudokinase domain hinge region yield constitutively active JAK2 that cannot be further stimulated by Epo.\",\n      \"method\": \"Functional gain-of-function screen, scanning mutagenesis, erythrocytosis mouse model, in vitro receptor-binding assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — systematic scanning mutagenesis identifying mechanistic determinants, in vivo confirmation in mouse model, multiple orthogonal methods\",\n      \"pmids\": [\"19638629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"JAK2 directly phosphorylates PAK1 at tyrosines 153, 201, and 285 in vivo and in vitro. Tyrosyl phosphorylation by JAK2 significantly increases PAK1 kinase activity. This phosphorylation decreases apoptosis induced by serum deprivation and staurosporine and increases cell motility. A triple PAK1 Y153F/Y201F/Y285F mutant was unaffected by JAK2-mediated phosphorylation.\",\n      \"method\": \"In vitro kinase assay, mass spectrometry, 2D peptide mapping, site-directed mutagenesis, apoptosis assay, cell motility assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay, mass spectrometry identification of sites, mutagenesis with functional readout; multiple orthogonal methods\",\n      \"pmids\": [\"17726028\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Cytokine receptor-associated JAK2 phosphorylates TET2 at tyrosines Y1939 and Y1964, leading to TET2 activation and increased DNA hydroxymethylation. Phosphorylated TET2 interacts with the erythroid transcription factor KLF1, and this interaction increases upon erythropoietin exposure. The activating JAK2V617F mutation is associated with increased TET2 activity and genome-wide loss of cytosine methylation.\",\n      \"method\": \"Phosphoproteomics, in vitro kinase assay, Co-IP, 5-hydroxymethylcytosine quantification, bisulfite sequencing, patient samples and mouse models\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assay identifying specific phosphorylation sites, Co-IP of TET2-KLF1 interaction, validated in patient samples and mouse models; multiple orthogonal methods\",\n      \"pmids\": [\"30944118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Phosphorylation of JAK2 on Ser523 inhibits JAK2-dependent leptin receptor (LRb) signaling. Ser523 is phosphorylated in intact cells and in mouse spleen independently of LRb-JAK2 activation. Mutation S523A sensitizes and prolongs JAK2 signaling following LRb activation, and the inhibitory effect is independent of Tyr570-mediated inhibition.\",\n      \"method\": \"Tandem mass spectrometric phosphorylation site identification, site-directed mutagenesis (S523A), LRb signaling assays in cells\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — mass spectrometry identification of novel phosphorylation site, mutagenesis with functional signaling readout, validated in vivo (mouse spleen)\",\n      \"pmids\": [\"16705160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Jak2 kinase domain (JH1) alone is sufficient for interaction with and phosphorylation of Stat5. Deletion of the pseudokinase domain (JH2) causes increased enzymatic activity of Jak2. A Stat5 SH2 domain R618K mutation abolishes phosphorylation by Jak2. A single phosphotyrosine-SH2 domain interaction is sufficient for Stat5 dimerization but such dimers bind DNA inefficiently.\",\n      \"method\": \"Yeast two-hybrid/functional system with Jak2 and Stat5, co-immunoprecipitation under stringent conditions, deletion/point mutagenesis, Stat-dependent reporter gene assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — reconstituted Jak2-Stat5 signaling system in yeast with systematic mutagenesis, multiple deletion and point mutants tested, reporter gene functional readout\",\n      \"pmids\": [\"9575217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Quantitative superresolution microscopy showed that EpoR exists as monomers and dimerizes upon Epo stimulation or through JAK2 pseudokinase domain mutations (V617F, K539L, R683S). Crystallographic analysis with kinase activity assays revealed distinct activation mechanisms: JAK2 V617F activity is driven by dimerization; K539L involves both increased receptor dimerization and kinase activity; R683S prevents autoinhibition, increases catalytic activity, and drives JAK2 equilibrium toward the activation state through a wild-type dimer interface.\",\n      \"method\": \"Quantitative single-molecule localization microscopy (qSMLM), X-ray crystallography, in vitro kinase activity assay, molecular dynamics simulations, AI-guided structural modeling\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures, superresolution microscopy of receptor dimerization, kinase activity assays, and simulations in one rigorous multi-method study\",\n      \"pmids\": [\"38457493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In the context of sepsis, the IL-6/gp130/JAK2/STAT3 pathway mediates muscle atrophy. JAK2 inhibition (AG490) reduces STAT3 phosphorylation and attenuates muscle atrophy in septic mice, accompanied by reduction in Fbxo32/Atrogin-1 and Trim63/MuRF1 mRNA and protein expression. In C2C12 myotubes, JAK2 inhibition decreases IL-6-induced Socs3 mRNA expression and myotube atrophy.\",\n      \"method\": \"JAK2 inhibitor (AG490) treatment in CLP sepsis mouse model, siRNA knockdown of Il6st/gp130, STAT3 phosphorylation assays, muscle weight/atrophy phenotype, RNAseq\",\n      \"journal\": \"Journal of cachexia, sarcopenia and muscle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition and genetic knockdown with defined cellular phenotype, but pathway placement relies on inhibitor specificity and indirect readouts\",\n      \"pmids\": [\"34821076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In-depth phosphoproteome profiling of JAK2-mutant cells identified YBX1, an mRNA-processing protein, as a post-translationally modified target of mutant JAK2. JAK2-dependent phosphorylation of YBX1 maintains its function in RNA splicing and transcriptional control of ERK signaling, enabling persistence of JAK2V617F malignant clones despite JAK inhibitor treatment. YBX1 inactivation combined with JAK inhibition causes apoptosis of JAK2-dependent cells and molecular remission in vivo.\",\n      \"method\": \"Phosphoproteomics, genetic inactivation of YBX1, RNA-seq (splicing analysis), in vivo mouse models, primary human cells, apoptosis assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — phosphoproteomics identifying substrate, genetic inactivation with molecular and in vivo phenotypic readouts, validated in mouse models and primary human cells; multiple orthogonal methods\",\n      \"pmids\": [\"33239784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"JAK2 exon 12 gain-of-function mutations (including K539L substitution) result in increased phosphorylation of JAK2 and ERK1/2 compared to wild-type or V617F JAK2. BaF3 cells expressing exon 12 mutant JAK2 proliferate without IL-3. K539L JAK2 induces a myeloproliferative phenotype including erythrocytosis in a murine retroviral bone marrow transplantation model.\",\n      \"method\": \"Biochemical phosphorylation assays in BaF3 cells, murine bone marrow transplantation, cytokine-independent proliferation assay\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical characterization of kinase activation, in vivo mouse model confirmation, cytokine-independent proliferation assay; multiple orthogonal methods\",\n      \"pmids\": [\"17267906\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The TEL-JAK2 fusion protein, in which the TEL self-association domain is fused to the JAK2 kinase domain, exhibits constitutive activation of tyrosine kinase activity and confers growth factor-independent proliferation to IL-3-dependent Ba/F3 cells. Expression in transgenic mice under a lymphoid promoter causes fatal T-cell leukemia with activation of STAT1 and STAT5.\",\n      \"method\": \"In vitro kinase assay, Ba/F3 proliferation assay, transgenic mouse model, immunoblotting for STAT activation\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — constitutive kinase activity shown in vitro, growth factor-independent proliferation, in vivo transgenic model with STAT activation; multiple orthogonal methods\",\n      \"pmids\": [\"10845925\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"JAK2/STAT2/STAT3 pathway is required for early myogenic differentiation. Inhibition of JAK2 (by small molecule inhibitor or siRNA) blocks myogenic differentiation of myoblasts. JAK2, STAT2, and STAT3 are activated upon differentiation induction. The pro-differentiation effect is partially mediated by MyoD and MEF2, and JAK2/STAT2/STAT3 regulates expression of IGF2 and HGF genes.\",\n      \"method\": \"Small molecule JAK2 inhibitor, siRNA knockdown, differentiation assays, immunoblotting for pathway activation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — both pharmacological and siRNA knockdown with defined differentiation phenotype, downstream target gene regulation identified; single lab\",\n      \"pmids\": [\"18835816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Crystal structures of JAK2 bound to ruxolitinib and fedratinib (and derivatives) were determined from mammalian cell-produced JAK2, providing structural basis for inhibitor binding including shape complementarity requirements for chiral and achiral inhibitors at the ATP-binding pocket.\",\n      \"method\": \"X-ray crystallography, biochemical kinase assay, cellular activity assays\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — first crystal structures of JAK2 with approved drugs, complemented by biochemical and cellular data; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"33570945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Five crystal structures of the JAK2 pseudokinase domain (JH2) complexed with selective diaminotriazole ligands were determined. Selective JH2 binders (over kinase domain JH1) inhibit STAT5 phosphorylation in cells expressing both wild-type and V617F JAK2, demonstrating that JH2 is a pharmacologically targetable domain that modulates JAK2 activity.\",\n      \"method\": \"X-ray crystallography (5 structures), binding affinity measurements for JH1/JH2/JH2-V617F, STAT5 phosphorylation cellular assay\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with functional cellular validation of JH2 as pharmacological target; multiple orthogonal methods\",\n      \"pmids\": [\"32329617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARID2 promotes ubiquitination and degradation of JAK2 via the E3 ubiquitin ligase NEDD4L. ARID2 recruits CARM1 to increase H3R17me2a at the NEDD4L promoter, activating NEDD4L transcription. Loss of ARID2 stabilizes JAK2, activating JAK2-STAT5-PPARγ signaling and inducing hepatic steatosis. Fedratinib (JAK2 inhibitor) alleviated HFD-induced hepatic steatosis in liver-specific Arid2 KO mice.\",\n      \"method\": \"ChIP assay, ubiquitination assay, Co-IP, liver-specific Arid2 knockout mice, HFD mouse model, JAK2 inhibitor treatment, immunoblotting\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP identifying ARID2-CARM1-NEDD4L axis, ubiquitination assay identifying NEDD4L as E3 ligase for JAK2, in vivo genetic and pharmacological validation; multiple orthogonal methods\",\n      \"pmids\": [\"36396719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PF4 (platelet factor 4) binds and activates the thrombopoietin receptor c-Mpl on platelets, leading to JAK2 activation and phosphorylation of STAT3 and STAT5, resulting in platelet aggregation. Inhibition of the c-Mpl-JAK2 pathway inhibits platelet aggregation to PF4 and to VITT sera.\",\n      \"method\": \"Binding assay, JAK2 pathway inhibition (pharmacological), STAT3/STAT5 phosphorylation assays, platelet aggregation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assays with pharmacological inhibition establishing c-Mpl-JAK2-STAT signaling axis in platelets; single lab, limited structural detail\",\n      \"pmids\": [\"37883794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A model for JAK2 activation by the GH receptor homodimer was established based on biochemical data and molecular dynamics simulations: constitutive receptor dimers undergo ligand-induced reorientation/rotation, transitioning from parallel to separated transmembrane domains. This movement slides the pseudokinase inhibitory domain of one JAK2 away from the kinase domain of the other JAK2 within the dimer, allowing trans-activation between kinase domains.\",\n      \"method\": \"Biochemical receptor dimerization assays, molecular dynamics simulations\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — biochemical data combined with MD simulations; mechanistic model supported by multiple approaches but lacks direct structural confirmation\",\n      \"pmids\": [\"25656053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Leptin stimulates JAK2-independent STAT3 phosphorylation via non-JAK2 tyrosine kinases including Src family members (c-Src, Fyn) downstream of LEPRb. JAK2 mediates leptin signaling both by phosphorylating substrates and by serving as a scaffolding/adaptor protein. Kinase-inactive JAK2(K882E) is tyrosyl-phosphorylated by non-JAK2 kinases in JAK2-null cells and enhances STAT3 phosphorylation, indicating a scaffolding role.\",\n      \"method\": \"JAK2-null cell lines (human and mouse), pharmacological Src inhibitors, dominant negative Src(K298M), overexpression of c-Src/Fyn, kinase-inactive JAK2 mutant, LEPRb Tyr mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic JAK2-null cells combined with pharmacological and dominant-negative approaches, multiple receptor mutants; mechanistic finding that JAK2 has scaffolding function independent of its kinase activity\",\n      \"pmids\": [\"18718905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"SH2-B binds with high affinity via its SH2 domain to phosphorylated tyrosines within JAK2 in response to GH. GH-induced binding of SH2-B to JAK2 potently activates JAK2, leading to enhanced tyrosyl phosphorylation of STAT proteins and other cellular proteins. SIRP binds directly to JAK2 without requiring tyrosyl phosphorylation, is itself phosphorylated on tyrosines in response to GH, and recruits SHP2 which dephosphorylates SIRP and likely JAK2, acting as a negative regulator.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding/kinase assays, STAT phosphorylation assays, SH2 domain binding studies\",\n      \"journal\": \"Recent progress in hormone research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP and kinase activation assays identifying SH2-B and SIRP as JAK2-binding proteins; mechanistic follow-up limited in this review context, citing earlier primary experiments\",\n      \"pmids\": [\"11036942\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"JAK2 is a non-receptor tyrosine kinase that constitutively associates with cytokine receptors (including those for erythropoietin, leptin, prolactin, growth hormone, and thrombopoietin) via its FERM-SH2 domains, and is activated by ligand-induced receptor dimerization through a mechanism in which receptor 'switch' region-mediated JAK2 FERM domain dimerization relieves pseudokinase (JH2) domain-mediated autoinhibition, allowing trans-phosphorylation between kinase domains; activated JAK2 then phosphorylates STAT proteins, TET2 (at Y1939/Y1964), PAK1 (at Y153/Y201/Y285), histone H3 (at Y41, linking it to chromatin regulation via HP1alpha displacement), and YBX1 (regulating RNA splicing and ERK signaling), while its activity is negatively regulated by PTP1B-mediated dephosphorylation, Ser523 serine phosphorylation, and NEDD4L-mediated ubiquitination; oncogenic mutations (V617F in JH2, exon 12 mutations) cause constitutive kinase activation by disrupting autoinhibitory pseudokinase domain contacts or promoting pathogenic JAK2 dimerization.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"JAK2 is a non-receptor tyrosine kinase that constitutively associates with cytokine receptors and transduces ligand-induced receptor engagement into downstream STAT signaling, governing hematopoiesis, metabolism, and cell differentiation [#2, #3]. It is pre-assembled on receptors such as the prolactin, erythropoietin, leptin, and growth hormone receptors and is activated by ligand-induced receptor dimerization: crystallographic and single-molecule data show that a membrane-proximal receptor 'switch' region drives JAK2 FERM-domain dimerization, while reorientation of the receptor relieves pseudokinase (JH2) domain–mediated autoinhibition to permit trans-phosphorylation between kinase domains [#3, #9, #19]. The SH2–pseudokinase linker relays this signal, and lesions in the linker or pseudokinase hinge yield constitutive, ligand-independent activation [#4]. Once active, JAK2 phosphorylates STAT5 through a kinase-domain/SH2 interaction [#8], and an expanding substrate repertoire including histone H3 at Tyr41—which displaces HP1alpha to derepress chromatin target genes such as lmo2 [#0], the dioxygenase TET2 at Y1939/Y1964 (linking JAK2 to DNA hydroxymethylation via KLF1) [#6], PAK1 [#5], and the mRNA-processing factor YBX1 [#11]. JAK2 also acts as a kinase-independent scaffold to support STAT3 phosphorylation by Src-family kinases [#20]. Its activity is restrained by PTP1B-mediated dephosphorylation [#1], inhibitory Ser523 phosphorylation [#7], and ARID2-directed NEDD4L-mediated ubiquitination and degradation [#17]. Gain-of-function lesions—the V617F and exon 12 (e.g. K539L) mutations in/around JH2, and the TEL-JAK2 fusion—cause constitutive kinase activation and myeloproliferative or leukemic disease, and JAK2 is pharmacologically targetable at both its ATP pocket and its JH2 domain [#9, #12, #13, #16].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established that JAK2 is a pre-assembled receptor-associated kinase rather than a recruited effector, answering how cytokine receptors lacking intrinsic catalytic activity transduce signals.\",\n      \"evidence\": \"Reciprocal anti-JAK2/anti-phosphotyrosine Co-IP and in vitro kinase assay on the prolactin receptor\",\n      \"pmids\": [\"7508935\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the structural basis of receptor association\", \"Mechanism of activation upon ligand binding not defined\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Mapped the JAK2 kinase domain as sufficient for STAT5 engagement and identified the pseudokinase domain as autoinhibitory, framing JH2 as a brake on catalytic activity.\",\n      \"evidence\": \"Reconstituted Jak2-Stat5 system in yeast with deletion/point mutagenesis and reporter assays\",\n      \"pmids\": [\"9575217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism of JH2 autoinhibition unresolved\", \"Did not test physiological receptor context\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstrated that constitutive JAK2 kinase activation is oncogenic, by showing the TEL-JAK2 fusion drives growth-factor independence and leukemia.\",\n      \"evidence\": \"In vitro kinase assay, Ba/F3 proliferation, and transgenic mouse leukemia model with STAT activation\",\n      \"pmids\": [\"10845925\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Native point-mutation drivers not yet identified\", \"STAT-independent contributions not dissected\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identified the first direct negative regulator of JAK2, showing PTP1B dephosphorylates JAK2 to terminate cytokine signaling.\",\n      \"evidence\": \"Substrate-trapping Co-IP, in vitro phosphatase assay, and PTP1B-knockout MEFs\",\n      \"pmids\": [\"11694501\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spatial/temporal control of PTP1B-JAK2 encounter unknown\", \"Relative contribution versus other phosphatases unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Revealed serine phosphorylation as a distinct off-switch, with Ser523 phosphorylation independently restraining JAK2-dependent leptin signaling.\",\n      \"evidence\": \"Mass spectrometry site identification and S523A mutagenesis with LRb signaling readouts\",\n      \"pmids\": [\"16705160\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for Ser523 phosphorylation not identified\", \"Mechanism by which Ser523 modulates catalysis unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Expanded the JAK2 substrate repertoire beyond STATs (PAK1) and confirmed exon 12 mutations as bona fide myeloproliferative drivers distinct from V617F.\",\n      \"evidence\": \"In vitro kinase assays with MS site mapping for PAK1; biochemical and bone-marrow-transplant models for exon 12 K539L\",\n      \"pmids\": [\"17726028\", \"17267906\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular contexts where PAK1 phosphorylation is relevant not fully defined\", \"Why exon 12 mutations preferentially cause erythrocytosis unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Uncovered a kinase-independent scaffolding role for JAK2 and a tissue role in myogenic differentiation, broadening JAK2 function beyond direct phosphotransfer.\",\n      \"evidence\": \"JAK2-null cells with Src inhibitors/dominant-negatives and kinase-inactive JAK2; JAK2 inhibitor/siRNA in myoblast differentiation assays\",\n      \"pmids\": [\"18718905\", \"18835816\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of scaffolding function not defined\", \"Myogenic role relies in part on inhibitor specificity (Medium)\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Established a direct nuclear/chromatin function for JAK2, showing it phosphorylates histone H3Y41 to displace HP1alpha and derepress target genes, and refined the activation switch to the SH2-pseudokinase linker.\",\n      \"evidence\": \"In vitro kinase assay, ChIP, and inhibitor treatment for H3Y41; scanning mutagenesis and erythrocytosis mouse model for the linker switch\",\n      \"pmids\": [\"19783980\", \"19638629\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How nuclear JAK2 is targeted to specific loci unknown\", \"Breadth of chromatin targets beyond lmo2 not mapped\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Provided the structural basis for activation, showing receptor switch-region-mediated 2:2 JAK2/receptor dimerization is required to trigger kinase activation.\",\n      \"evidence\": \"X-ray crystallography of JAK2 FERM-SH2 with LEPR and EPOR plus switch-region mutagenesis and STAT phosphorylation assays\",\n      \"pmids\": [\"30044226\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length receptor-JAK2 complex architecture not resolved\", \"Dynamics of JH2 disengagement not directly visualized\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected JAK2 signaling to epigenetic control, showing it directly phosphorylates and activates TET2 to alter DNA hydroxymethylation, with implications for V617F-driven disease.\",\n      \"evidence\": \"Phosphoproteomics, in vitro kinase assay, Co-IP of TET2-KLF1, 5hmC quantification in patient samples and mouse models\",\n      \"pmids\": [\"30944118\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide consequences of TET2 activation incompletely defined\", \"Crosstalk with TET2 loss-of-function mutations unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified YBX1 as a mutant-JAK2 substrate enabling clonal persistence and validated the pseudokinase domain as a druggable site, opening therapeutic strategies against JAK-inhibitor-resistant disease.\",\n      \"evidence\": \"Phosphoproteomics with YBX1 genetic inactivation, RNA-seq, and in vivo models; JH2-selective ligand crystal structures with STAT5 cellular assays\",\n      \"pmids\": [\"33239784\", \"32329617\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between YBX1 phosphorylation and splicing/ERK control incomplete\", \"In vivo efficacy of JH2-selective inhibitors not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Delivered structural detail on inhibitor binding at the ATP pocket and placed JAK2 within IL-6/gp130/STAT3 signaling driving sepsis-associated muscle atrophy.\",\n      \"evidence\": \"Crystal structures with ruxolitinib/fedratinib plus biochemical/cellular assays; JAK2 inhibitor and gp130 knockdown in sepsis mouse and C2C12 models\",\n      \"pmids\": [\"33570945\", \"34821076\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atrophy pathway placement relies on inhibitor specificity (Medium)\", \"Selectivity determinants versus other JAK family members not addressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a transcription-coupled degradation axis controlling JAK2 abundance, in which ARID2 drives NEDD4L-mediated JAK2 ubiquitination and loss of this control promotes hepatic steatosis.\",\n      \"evidence\": \"ChIP, ubiquitination and Co-IP assays, liver-specific Arid2 knockout and HFD mice with JAK2 inhibitor rescue\",\n      \"pmids\": [\"36396719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct NEDD4L-JAK2 recognition determinants not mapped\", \"Generalizability beyond liver unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mechanistically distinguished how different oncogenic pseudokinase mutations activate JAK2, linking receptor dimerization, increased catalysis, and loss of autoinhibition; also placed JAK2 in PF4/c-Mpl platelet signaling.\",\n      \"evidence\": \"qSMLM of EpoR dimerization, crystallography, kinase assays and MD simulations for V617F/K539L/R683S; binding and platelet aggregation assays for PF4/c-Mpl/JAK2/STAT\",\n      \"pmids\": [\"38457493\", \"37883794\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of dimerization versus intrinsic activity per mutant not fully reconciled\", \"PF4/c-Mpl axis lacks structural detail (Medium)\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How nuclear JAK2 is recruited to specific chromatin loci and how its kinase-independent scaffolding versus catalytic functions are coordinated across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mechanism for locus-specific nuclear targeting\", \"Scaffolding versus catalytic role partitioning undefined\", \"Integration of the full substrate network (STAT, TET2, PAK1, YBX1, H3) not modeled\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 5, 6, 8, 11]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [2, 5, 6, 8]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2, 3, 18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 8]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 13]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"EPOR\", \"LEPR\", \"PRLR\", \"MPL\", \"STAT5\", \"PTP1B\", \"NEDD4L\", \"SH2B1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}