{"gene":"NRAS","run_date":"2026-04-29T11:37:57","timeline":{"discoveries":[{"year":1983,"finding":"The human N-ras gene was cloned and shown to have the same intron/exon structure as H-ras and K-ras; a single nucleotide change substituting lysine for glutamine at position 61 of the N-ras product converts it from a non-transforming proto-oncogene to a transforming oncogene, demonstrating that codon 61 is a critical activation site.","method":"Molecular cloning, DNA sequencing, NIH3T3 transfection/focus assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — original cloning with mutagenesis and functional transformation assay; foundational paper replicated widely","pmids":["6616621"],"is_preprint":false},{"year":1983,"finding":"The human N-ras gene was mapped by in situ hybridization to chromosome 1, region 1cen–p21.","method":"In situ hybridization to metaphase chromosome preparations","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — direct localization by in situ hybridization, confirmed by somatic cell hybrid data","pmids":["6667677"],"is_preprint":false},{"year":1984,"finding":"Three distinct activating point mutations were identified at codon 61 of N-ras in human tumor cell lines (fibrosarcoma HT1080, promyelocytic HL60, rhabdomyosarcoma RD301), affecting the first, second, or third nucleotide of the codon respectively, all resulting in amino acid substitutions and demonstrating dominant oncogenic character alongside a normal N-ras allele.","method":"Synthetic oligonucleotide hybridization, DNA sequencing","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — direct sequence determination of multiple independent activating mutations; replicated across labs","pmids":["6595642"],"is_preprint":false},{"year":1987,"finding":"A cytoplasmic protein (later identified as GAP/NF1) stimulates GTP hydrolysis by normal N-ras p21 (Gly12) more than 200-fold in vitro but has no effect on oncogenic mutants (Asp12 or Val12), explaining how position-12 mutations lock N-ras in the active GTP-bound state by preventing GTPase-activating protein stimulation.","method":"Xenopus oocyte maturation assay (biological activity readout), in vitro GTPase assay with purified proteins, in vivo GTP/GDP binding analysis","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with purified proteins, orthogonal in vivo nucleotide-binding assay, functional readout; highly cited foundational paper","pmids":["2821624"],"is_preprint":false},{"year":1987,"finding":"The activated N-ras oncogene of HT1080 human fibrosarcoma cells directly maintains the transformed phenotype; revertants with reduced mutant N-ras p21 levels lost transformation, and sporadic tumors from revertants regained the transforming allele, demonstrating that N-ras oncogene dosage controls the transformed state.","method":"Revertant isolation, immunoprecipitation of N-ras p21, gene dosage analysis, retransfection of cloned ras oncogenes","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis via reversion analysis with protein-level validation; multiple independent revertant lines","pmids":["3315232"],"is_preprint":false},{"year":1986,"finding":"Activated N-ras transfected into PC12 rat pheochromocytoma cells suppressed proliferation and promoted neuronal differentiation (neurite outgrowth, cell division arrest), including in NGF-resistant variants, demonstrating that N-ras can drive differentiation rather than proliferation in a cell-context-dependent manner.","method":"Gene transfection, morphological assessment of neurite outgrowth, cell proliferation assays","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 — functional KO/OE with defined differentiation phenotype in multiple cell contexts","pmids":["3760034"],"is_preprint":false},{"year":1988,"finding":"Steroid-inducible oncogenic N-ras expression in C2 myoblasts reversibly inhibited myotube formation and induction of muscle creatine kinase and acetylcholine receptors in a dose-dependent manner, without affecting growth factor dependence or contact inhibition; however, N-ras induction in terminally differentiated myotubes failed to extinguish muscle-specific gene expression, placing N-ras action at an early step in the myogenic differentiation pathway.","method":"MMTV-LTR steroid-inducible N-ras transgene system in C2 myoblasts; dexamethasone dose–response; muscle-specific gene expression assays (MCK, AChR); conditioned media experiments","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — inducible gain-of-function with multiple orthogonal markers and reversibility controls; clear pathway placement","pmids":["3133379"],"is_preprint":false},{"year":1989,"finding":"All Ras proteins including N-Ras are polyisoprenylated (farnesylated) on the C-terminal cysteine (Cys186); palmitoylation occurs on additional upstream cysteine residues in the hypervariable domain rather than on Cys186; palmitoylation increases membrane avidity and enhances transforming activity, while polyisoprenylation is essential for membrane association and biological activity.","method":"Mutational analysis of CAAX motif cysteines, membrane association assays, transformation assays, biosynthetic labeling","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis combined with functional and biochemical readouts; foundational paper replicated extensively","pmids":["2661017"],"is_preprint":false},{"year":1993,"finding":"Human Sos1 (hSos1), a guanine nucleotide exchange factor closely related to Drosophila Sos, directly stimulates guanine nucleotide exchange on Ras proteins (including N-Ras) in vitro via its CDC25-related domain; hSos1 interacts with GRB2 through its C-terminal domain binding to GRB2 SH3 domains in vivo and in vitro, placing Sos1 as the direct activator of Ras downstream of receptor tyrosine kinases.","method":"CDC25 yeast complementation, in vitro guanine nucleotide exchange assay, mammalian overexpression, in vivo and in vitro co-immunoprecipitation with GRB2","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution of exchange activity plus reciprocal interaction mapping; foundational paper","pmids":["8493579"],"is_preprint":false},{"year":1997,"finding":"The farnesylated C-terminal peptide of N-ras is reversibly S-acylated (palmitoylated) in cultured mammalian fibroblasts; S-acylation occurs specifically on cysteine (not serine), suppresses membrane desorption/diffusion between bilayers, and is required for preferential plasma membrane localization; the plasma membrane targeting is unaffected by brefeldin A or reduced temperature, suggesting a 'kinetic trapping' mechanism at the plasma membrane rather than trafficking through the secretory pathway.","method":"Fluorescent lipid-modified peptide analogs, large unilamellar vesicle binding assays, fluorescence microscopy in CV-1 cells, brefeldin A and temperature inhibition experiments","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1–2 — in vitro biophysical assays combined with cell-based localization experiments and pharmacological perturbations","pmids":["9335573"],"is_preprint":false},{"year":1998,"finding":"Crystal structure of H-Ras complexed with the Sos GEF domain at 2.8 Å resolution revealed that Sos displaces the Switch I region of Ras by inserting an α-helix, opening the nucleotide-binding site, and disrupts magnesium/phosphate binding via Switch II distortion, defining the catalytic mechanism of Ras nucleotide exchange applicable to all Ras isoforms including N-Ras.","method":"X-ray crystallography at 2.8 Å resolution, structure-function analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — crystal structure of the complex; mechanism broadly applicable to N-Ras as the exchange mechanism is conserved","pmids":["9690470"],"is_preprint":false},{"year":1999,"finding":"N-ras is transiently localized to the Golgi apparatus en route to the plasma membrane; GFP-tagged N-ras labeled motile peri-Golgi vesicles; prolonged brefeldin A treatment blocked plasma membrane expression; the CAAX motif alone targets N-ras to endomembranes where carboxylmethylation occurs, and a secondary targeting signal is required for final plasma membrane delivery.","method":"GFP fusion live-cell imaging, brefeldin A treatment, CAAX motif mutational analysis, carboxylmethylation assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 — live imaging with pharmacological perturbations and mutagenesis; foundational localization study","pmids":["10412982"],"is_preprint":false},{"year":1999,"finding":"Mutant N-ras expression in bone marrow-repopulated mice induced myeloproliferative disorders resembling CML or AML-M2 in ~60% of animals, as well as MDS-like disorders with myeloid impairment; a high level of apoptosis with thymic atrophy was also observed, consistent with a model where antiproliferative effects are a primary consequence of N-ras mutations and secondary events are needed for leukemia.","method":"Retroviral bone marrow transduction and transplantation mouse model, histopathology, CFU-S and colony assays, flow cytometry","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — in vivo gain-of-function with defined hematologic phenotypes and colony assays; first in vivo N-ras leukemia model","pmids":["10068678"],"is_preprint":false},{"year":1999,"finding":"Mutated N-ras specifically upregulates Bcl-2 protein expression in human melanoma cells in vitro and in SCID mouse xenografts, protecting against apoptosis; neither Bcl-xL, Bax, nor Bak expression was altered, identifying Bcl-2 upregulation as the mechanistic basis of N-ras-mediated apoptosis resistance.","method":"N-ras overexpression in melanoma cell lines, Western blot for apoptosis-related proteins, SCID mouse xenograft model","journal":"Melanoma research","confidence":"Medium","confidence_rationale":"Tier 2–3 — in vitro and in vivo functional assay with specific molecular readout, single lab","pmids":["10504052"],"is_preprint":false},{"year":2000,"finding":"Crystal structure of PI3Kγ in complex with H-Ras·GMPPNP revealed that Ras uses both Switch I and Switch II regions to bind the PI3Kγ RBD, and Ras also contacts the PI3Kγ catalytic domain directly; mutagenesis confirmed both switch regions are essential for binding and activation, establishing the structural basis for Ras-dependent PI3K activation relevant to all Ras isoforms including N-Ras.","method":"X-ray crystallography, in vitro PI3Kγ activation assay with H-Ras G12V, site-directed mutagenesis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus reconstituted activation assay plus mutagenesis","pmids":["11136978"],"is_preprint":false},{"year":2002,"finding":"Wild-type N-ras acts as a tumor suppressor: N-ras-null mice develop thymic lymphomas at higher rates, whereas overexpression of wild-type N-ras protects against thymic lymphomagenesis; introduction of wild-type N-ras into N-ras-deficient tumor cells decreased growth in low serum and soft agar, demonstrating a growth-inhibitory role for the proto-oncogene product.","method":"N-ras knockout and transgenic mouse models, in vitro transformation assays (low-serum growth, soft-agar colony formation)","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — genetic loss-of-function and gain-of-function in vivo and in vitro with multiple readouts","pmids":["12154063"],"is_preprint":false},{"year":2003,"finding":"Rb and N-ras function in a common pathway to control skeletal muscle differentiation: deletion of N-ras in Rb-null embryos rescued defects in skeletal muscle fiber density, myotube morphology, and MCK expression, and potentiated MyoD transcriptional activity, while proliferation and apoptosis defects remained; this genetic rescue demonstrates that N-ras and Rb operate in the same differentiation pathway but that Rb's control of differentiation is separable from its control of proliferation.","method":"Double-knockout mouse embryo analysis (Rb−/−; N-ras−/−), histology, immunohistochemistry, MyoD transcriptional activity assay in primary myoblasts","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis in double-knockout animals with molecular readouts; clear pathway placement","pmids":["12861012"],"is_preprint":false},{"year":2005,"finding":"Let-7 miRNA family members negatively regulate RAS expression (including N-RAS) by binding multiple let-7 complementary sites (LCSs) in the 3′ UTR of human RAS genes; let-7 overexpression reduces RAS protein levels, and let-7 is lower in lung tumors that overexpress RAS protein.","method":"3′ UTR reporter assays, let-7 overexpression, Western blot for RAS protein in tumor vs. normal tissue; C. elegans genetic epistasis (let-60/RAS)","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1–2 — reporter assay validation, protein-level confirmation, evolutionary conservation demonstrated; highly cited","pmids":["15766527"],"is_preprint":false},{"year":2005,"finding":"A constitutive de/reacylation (palmitoylation/depalmitoylation) cycle drives rapid exchange of N-ras and H-ras between the plasma membrane and the Golgi apparatus: depalmitoylation redistributes farnesylated N-ras to all membranes, repalmitoylation traps it at the Golgi, and vesicular transport then delivers it to the plasma membrane; this cycle maintains compartment-specific localization and enables Golgi-initiated Ras activation.","method":"Fluorescent N-ras fusion proteins (FRAP, live imaging), palmitoylation inhibitor 2-bromopalmitate, dominant-negative DHHC PAT constructs, quantitative membrane fractionation","journal":"Science","confidence":"High","confidence_rationale":"Tier 1–2 — FRAP and live imaging combined with pharmacological and genetic perturbations; mechanistic model confirmed by multiple approaches","pmids":["15705808"],"is_preprint":false},{"year":2005,"finding":"Galectin-3 selectively binds activated K-Ras-GTP (not N-Ras-GTP); Gal-3 overexpression in breast cancer cells increased K-Ras-GTP while reducing N-Ras-GTP, demonstrating a molecular switch between N-Ras and K-Ras usage dependent on Gal-3 binding; only wild-type Gal-3 co-immunoprecipitated with K-Ras and altered signaling from AKT/Ral toward ERK.","method":"Co-immunoprecipitation, RAS activation (GTP pull-down) assays, Gal-3 point mutants, isoform-specific RBD pull-down","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, co-IP/pulldown; mechanistic follow-up limited; establishes isoform-selectivity of Gal-3","pmids":["16103080"],"is_preprint":false},{"year":2006,"finding":"Fully lipidated (farnesylated + hexadecylated) N-Ras protein partitions preferentially into liquid-disordered (ld) lipid domains rather than liquid-ordered (lo) or solid-ordered phases in model membranes; a large proportion also localizes at ld/lo phase boundaries, reducing line tension; this membrane domain preference is independent of nucleotide (GDP vs GTP) state.","method":"Two-photon fluorescence microscopy on giant unilamellar vesicles, tapping-mode AFM on supported bilayers, canonical raft lipid mixture (POPC/sphingomyelin/cholesterol)","journal":"Journal of the American Chemical Society","confidence":"Medium","confidence_rationale":"Tier 2 — biophysical assays with two orthogonal microscopy methods; model membrane system","pmids":["16390147"],"is_preprint":false},{"year":2006,"finding":"Solid-state NMR of full-length membrane-associated lipidated N-Ras protein revealed that the C-terminal lipid anchor region is highly flexible with segmental fluctuations and axially symmetric overall motions on the membrane surface; the palmitoyl chain at Cys181 is highly mobile in the membrane.","method":"Solid-state 2H and 13C NMR, chemical-biological ligation of isotopically labeled lipidated heptapeptide to expressed N-terminal domain, order parameter and relaxation measurements","journal":"Journal of the American Chemical Society","confidence":"High","confidence_rationale":"Tier 1 — first comprehensive NMR dynamics study of full-length lipidated Ras; rigorous structural methodology","pmids":["17044712"],"is_preprint":false},{"year":2008,"finding":"eNOS-derived NO selectively activates N-Ras (but not K-Ras) on the Golgi complex of T cells engaged with antigen-presenting cells; activation involves eNOS-dependent S-nitrosylation of N-Ras at Cys118; wild-type but not C118S N-Ras increased TCR-dependent apoptosis, demonstrating that S-nitrosylation of Cys118 is required for N-Ras activation at the Golgi and contributes to activation-induced T cell death.","method":"Fluorescent Ras probes (Ras-GTP biosensors) in T cells stably expressing eNOS-GFP or G2A mutant; S-nitrosylation assay; site-directed mutagenesis (C118S); apoptosis assay","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1–2 — live-cell Ras activation imaging, mutagenesis of modification site, functional apoptosis readout; multiple orthogonal methods","pmids":["18641128"],"is_preprint":false},{"year":2009,"finding":"N-Ras proteins bearing at least one farnesyl group partition preferentially into liquid-disordered lipid domains independent of lipid anchor type; farnesylated N-Ras shows diffusion to ld/lo phase boundaries and forms nanoclusters there via intermolecular interactions; the non-biological dual-hexadecyl N-Ras instead incorporates into the bulk ld phase without boundary preference; no significant difference in domain partitioning was detected between GDP- and GTP-loaded N-Ras.","method":"Time-lapse tapping-mode AFM on supported lipid bilayers, differently lipidated N-Ras protein variants","journal":"Journal of the American Chemical Society","confidence":"Medium","confidence_rationale":"Tier 2 — systematic comparison of lipid anchor variants by biophysical AFM; single methodology","pmids":["19133719"],"is_preprint":false},{"year":2010,"finding":"Palmitoylation is essential for leukemogenesis by oncogenic NRAS: non-palmitoylatable NRAS mutants failed to induce CMML/AML in a mouse bone marrow transplant model; farnesylation is also essential but through a distinct mechanism from palmitoylation deficiency; demonstrating that both post-translational lipid modifications are independently required for NRAS oncogenic activity.","method":"Retroviral bone marrow transduction/transplantation mouse model, palmitoylation-deficient and farnesylation-deficient NRAS mutants","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic loss-of-function of specific PTMs with clear leukemia phenotype; mechanistic dissection of two distinct modifications","pmids":["20200357"],"is_preprint":false},{"year":2010,"finding":"In NRAS-mutant melanoma cells, PLX4720 (BRAF inhibitor) rapidly induces hyperactivation of MEK-ERK1/2 signaling; C-RAF (not B-RAF) is the major RAF isoform responsible for this hyperactivation; PLX4720-induced MEK-ERK1/2 hyperactivation promotes resistance to apoptosis in N-RAS mutant melanoma cells but does not enhance cell cycle progression.","method":"PLX4720 treatment of N-RAS mutant melanoma cells, phospho-ERK1/2 Western blot, siRNA knockdown of RAF isoforms, apoptosis assays","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — siRNA epistasis combined with pharmacological inhibition and mechanistic apoptosis/cell cycle readouts","pmids":["20818433"],"is_preprint":false},{"year":2010,"finding":"Acquired resistance to PLX4032 (BRAF inhibitor) in melanoma arises through mutually exclusive mechanisms: PDGFR-β upregulation (maintaining low activated RAS) or activating N-RAS mutations (causing MAPK reactivation upon PLX4032 treatment); knockdown of N-RAS reduced growth of the N-RAS-mutant resistant subset; overexpression of N-RAS(Q61K) conferred PLX4032 resistance to sensitive parental cells; MAPK reactivation predicted MEK inhibitor sensitivity.","method":"PLX4032-resistant melanoma subline derivation, siRNA knockdown, overexpression of N-RAS(Q61K), phospho-MAPK pathway analysis, patient biopsy validation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches (KD, OE, patient samples) with defined molecular mechanism and clinical validation","pmids":["21107323"],"is_preprint":false},{"year":2010,"finding":"miR-214 promotes myogenic differentiation in C2C12 myoblasts by down-regulating N-ras, facilitating cell cycle exit; blocking miR-214 maintained active cell cycling and inhibited differentiation; siRNA knockdown of N-Ras augmented the differentiation effect while forced N-Ras overexpression attenuated it, placing N-Ras downstream of miR-214 in the differentiation pathway.","method":"2′-O-methylated miR-214 inhibitor, global gene expression profiling, siRNA knockdown and adenoviral overexpression of N-Ras, cell cycle analysis, muscle differentiation markers","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — knockdown and overexpression with multiple differentiation readouts; N-Ras epistasis clearly established","pmids":["20534588"],"is_preprint":false},{"year":2011,"finding":"Pressure modulation combined with FTIR spectroscopy revealed distinct conformational substates of lipidated N-Ras; nucleotide-binding state (GDP vs GTP) and membrane binding both dramatically alter conformational dynamics and substate selection; a new membrane-induced conformational substate was identified, accompanied by structural reorientation of the G domain as shown by ATR-FTIR and IRRAS, demonstrating that the membrane acts as an allosteric regulator of N-Ras G-domain orientation.","method":"Pressure-perturbation FTIR spectroscopy, ATR-FTIR, IRRAS on membrane-associated lipidated N-Ras","journal":"Proceedings of the National Academy of Sciences","confidence":"High","confidence_rationale":"Tier 1 — multiple spectroscopic methods with thermodynamic analysis; directly links membrane binding to conformational change","pmids":["22203965"],"is_preprint":false},{"year":2013,"finding":"N-Ras deficiency in fibroblasts resulted in higher basal PI3K/Akt and MEK/Erk activity, upregulated collagen synthesis, and diminished proliferation and migration; TGF-β1-induced proliferation and migration required PI3K/Akt but not Erk1/2; N-Ras modulates extracellular matrix synthesis and cell motility by negatively regulating Akt activation, indicating N-Ras normally restrains collagen production and regulates fibroblast behavior.","method":"N-ras−/− immortalized fibroblasts, Western blot for pathway activation, collagen/fibronectin expression, proliferation and migration assays, pharmacological PI3K/MEK inhibitors","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 — genetic loss-of-function with multiple phenotypic and molecular readouts; single lab","pmids":["23871832"],"is_preprint":false},{"year":2014,"finding":"miR-143 directly targets N-RAS 3′ UTR and suppresses N-RAS expression; overexpression of miR-143 decreased N-RAS protein, inhibited PI3K/AKT and MAPK/ERK signaling, reduced p65 nuclear accumulation, and attenuated glioma cell migration, invasion, tube formation, and tumor growth in vitro and in vivo.","method":"miR-143 overexpression, luciferase 3′ UTR reporter assay, Western blot, invasion/migration assays, xenograft mouse model","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct target validation by reporter assay plus functional phenotypes; single lab","pmids":["24980823"],"is_preprint":false},{"year":2014,"finding":"N-Ras activation via biliary constituents induces cholangiocyte senescence and senescence-associated secretory phenotype (SASP, including IL-6, IL-8, CCL2, PAI-1) in primary sclerosing cholangitis; pharmacological Ras inhibition abrogated experimentally induced senescence and SASP; senescent cholangiocytes could transmit senescence to bystander cells, placing N-Ras upstream of the senescence program in cholangiocytes.","method":"IFM, FISH (telomere length), in vitro cholangiocyte senescence induction, Ras inhibitor (farnesylthiosalicylic acid), co-culture bystander assay, patient liver biopsies","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2–3 — pharmacological loss-of-function in cell and tissue context with multiple senescence markers; mechanism of N-Ras-driven SASP established","pmids":["24390753"],"is_preprint":false},{"year":2015,"finding":"Wild-type N-Ras, overexpressed in basal-like breast cancers, promotes tumor formation specifically by binding and activating cytoplasmic JAK2, leading to IL-8 secretion that acts on both cancer cells and stromal fibroblasts in an autocrine/paracrine manner; this activity is isoform-specific as K-Ras did not induce IL-8 via JAK2.","method":"N-RAS knockdown and overexpression in BLBC cells, co-immunoprecipitation of N-Ras with JAK2, IL-8 secretion assays, fibroblast co-culture, tumor formation assays in vivo","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — co-IP defining novel N-Ras/JAK2 interaction, isoform specificity demonstrated, in vivo tumor assays; multiple orthogonal methods","pmids":["26166574"],"is_preprint":false},{"year":2015,"finding":"L. major enhances CD40-induced N-Ras activation in macrophages via TLR2-dependent signaling; N-Ras silencing reduced L. major infection while K-Ras and H-Ras silencing enhanced it; cell-permeable peptides blocking the N-Ras–Sos interaction interface reduced L. major infection in BALB/c mice but not in CD40-deficient mice, demonstrating isoform-specific N-Ras function downstream of CD40 in Leishmania immune evasion.","method":"shRNA knockdown of individual Ras isoforms, TLR2 shRNA/antibody blockade, RAS activation assays, N-Ras–Sos interface peptide inhibitors in vivo (BALB/c mice), CD40 KO mice","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — isoform-specific knockdowns with in vitro and in vivo infectious phenotypes; peptide inhibitor targets defined interaction","pmids":["25786685"],"is_preprint":false},{"year":2018,"finding":"Structural comparisons of K-Ras, N-Ras, and H-Ras G domains revealed that each isoform and each oncogenic mutation has distinct conformational preferences in switch regions I and II and the allosteric lobe, despite 100% sequence identity in the mutation hotspot regions; these structural differences can account for isoform-specific coupling to effectors and cancer types.","method":"Comparative X-ray crystallography of wild-type Ras isoforms, structural analysis of switch region conformations","journal":"Cold Spring Harbor perspectives in medicine","confidence":"Medium","confidence_rationale":"Tier 1 — crystal structure comparison; single review-style paper consolidating structural data but includes new crystallographic comparisons","pmids":["29038336"],"is_preprint":false}],"current_model":"NRAS encodes a membrane-anchored small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states; activation is driven by Sos1-mediated nucleotide exchange and is terminated by intrinsic GTPase activity stimulated >200-fold by cytoplasmic GAP proteins, which are rendered ineffective by oncogenic codon-12/13/61 mutations; membrane targeting requires sequential farnesylation of Cys186 then palmitoylation of upstream cysteines, with a constitutive de/reacylation cycle maintaining N-Ras in a dynamic equilibrium between the Golgi and plasma membrane; additionally, eNOS-dependent S-nitrosylation of Cys118 can selectively activate N-Ras at the Golgi in T cells; in the active state N-Ras engages effectors including RAF (via C-RAF), PI3Kγ, and JAK2 to drive MAPK, PI3K/AKT signaling, and IL-8 secretion, with cell-context-dependent outcomes including proliferation, differentiation inhibition, Bcl-2-mediated apoptosis resistance, and senescence."},"narrative":{"teleology":[{"year":1983,"claim":"Identification of N-ras as a transforming oncogene activated by a single codon-61 point mutation established that discrete mutations in a conserved GTPase convert it from proto-oncogene to oncogene, framing the central question of how nucleotide cycling is disrupted.","evidence":"Molecular cloning, DNA sequencing, and NIH3T3 focus assay of N-ras from human tumor DNA","pmids":["6616621","6595642"],"confidence":"High","gaps":["Biochemical mechanism by which codon-61 mutations alter GTPase activity was unknown","Effector pathways downstream of activated N-Ras were unidentified"]},{"year":1987,"claim":"Demonstration that a cytoplasmic GAP stimulates N-Ras GTPase activity >200-fold and that oncogenic mutations render N-Ras refractory to GAP provided the biochemical explanation for why mutant N-Ras is constitutively GTP-loaded.","evidence":"In vitro GTPase assay with purified wild-type and mutant N-Ras proteins plus cytoplasmic GAP fraction; Xenopus oocyte maturation readout","pmids":["2821624"],"confidence":"High","gaps":["Identity and structure of the GAP protein (later NF1) were not yet known","No structural explanation for why mutant Ras evades GAP stimulation"]},{"year":1987,"claim":"Reversion analysis in HT1080 cells showed that the activated N-ras allele is continuously required to maintain the transformed phenotype in a dosage-dependent manner, establishing that N-Ras is not merely an initiating event but a sustained driver.","evidence":"Isolation of revertants with reduced mutant N-ras p21, immunoprecipitation, retransfection","pmids":["3315232"],"confidence":"High","gaps":["Downstream effectors mediating N-Ras-dependent transformation were unidentified","Whether oncogene addiction applies in vivo was untested"]},{"year":1989,"claim":"Systematic mutagenesis of the CAAX motif revealed that farnesylation of Cys186 is essential for membrane association and biological activity, while palmitoylation of upstream cysteines enhances membrane avidity and transforming potency, defining the dual-lipid modification requirement for N-Ras function.","evidence":"Cysteine mutagenesis, biosynthetic labeling, membrane fractionation, and transformation assays","pmids":["2661017"],"confidence":"High","gaps":["Enzymes catalyzing palmitoylation and depalmitoylation were unknown","Subcellular site of each modification was not determined"]},{"year":1993,"claim":"Identification of hSos1 as the GEF for Ras, linking receptor tyrosine kinase signaling to N-Ras activation via the GRB2–Sos1 complex, completed the upstream activation mechanism.","evidence":"In vitro nucleotide exchange assay, yeast complementation, co-immunoprecipitation of Sos1 with GRB2","pmids":["8493579"],"confidence":"High","gaps":["Whether Sos1 shows isoform preference among Ras proteins was not addressed","Structural basis for Sos-catalyzed exchange was unresolved"]},{"year":1998,"claim":"The crystal structure of the Ras–Sos complex revealed that Sos displaces Switch I via an inserted α-helix and distorts Switch II, providing the atomic mechanism of nucleotide exchange applicable to N-Ras.","evidence":"X-ray crystallography of H-Ras–Sos at 2.8 Å resolution","pmids":["9690470"],"confidence":"High","gaps":["No structure of N-Ras specifically with Sos","Membrane context not captured in crystal structure"]},{"year":1999,"claim":"Live-cell imaging showed that N-Ras transits through the Golgi en route to the plasma membrane and that a secondary signal beyond the CAAX motif is required for PM delivery, establishing the endomembrane trafficking itinerary of N-Ras.","evidence":"GFP-N-Ras live-cell imaging, brefeldin A treatment, CAAX mutant analysis in COS cells","pmids":["10412982"],"confidence":"High","gaps":["Whether Golgi-resident N-Ras signals to effectors was unknown","Identity of the secondary PM-targeting signal was not determined"]},{"year":1999,"claim":"Bone marrow transplant experiments showed that mutant N-Ras induces myeloproliferative disease and MDS in vivo, validating its role as a leukemia driver and revealing that high apoptosis accompanies transformation, consistent with a requirement for secondary hits.","evidence":"Retroviral transduction of N-Ras(G12D) into bone marrow, transplantation into irradiated mice, histopathology and colony assays","pmids":["10068678"],"confidence":"High","gaps":["Cooperating mutations required for full AML were not identified","Effector pathway responsible for the myeloproliferative phenotype was undefined"]},{"year":2000,"claim":"The crystal structure of Ras–PI3Kγ demonstrated that Ras engages both the RBD and catalytic domain of PI3Kγ via Switch I and II, establishing the structural basis for Ras-dependent PI3K activation as a second major effector arm alongside RAF.","evidence":"X-ray crystallography plus in vitro PI3Kγ activation assay with mutagenesis","pmids":["11136978"],"confidence":"High","gaps":["Whether N-Ras and K-Ras engage PI3Kγ with different affinities was not tested","In vivo contribution of PI3K vs. RAF downstream of N-Ras was unresolved"]},{"year":2002,"claim":"N-ras knockout mice developed thymic lymphomas at elevated rates and wild-type N-Ras overexpression was protective, revealing an unexpected tumor-suppressor function of the proto-oncogene product that counterbalances its oncogenic gain-of-function mutations.","evidence":"N-ras−/− and transgenic overexpression mouse models, soft-agar assays","pmids":["12154063"],"confidence":"High","gaps":["Mechanism of tumor suppression (effector pathway, apoptosis vs. senescence) was not defined","Whether this function is tissue-restricted was unclear"]},{"year":2003,"claim":"Genetic epistasis in Rb−/−;N-ras−/− double-knockout embryos demonstrated that N-Ras and Rb function in a common skeletal muscle differentiation pathway, and that N-Ras deletion rescues Rb-null differentiation defects without correcting proliferation, separating the differentiation and proliferation arms of Rb signaling.","evidence":"Double-knockout mouse embryo histology, immunohistochemistry, MyoD transcriptional assays","pmids":["12861012"],"confidence":"High","gaps":["Direct molecular link between N-Ras and Rb in differentiation was not identified","Whether this epistasis extends beyond skeletal muscle was untested"]},{"year":2005,"claim":"Discovery of a constitutive depalmitoylation/repalmitoylation cycle explained how N-Ras maintains dynamic equilibrium between Golgi and plasma membrane: depalmitoylation releases N-Ras to redistribute by default, and repalmitoylation traps it at the Golgi for vesicular transport to the PM.","evidence":"FRAP, live imaging, 2-bromopalmitate treatment, dominant-negative DHHC PAT constructs","pmids":["15705808"],"confidence":"High","gaps":["Specific PAT and thioesterase enzymes responsible were not identified","Whether oncogenic mutations alter the acylation cycle kinetics was unknown"]},{"year":2005,"claim":"Identification of let-7 miRNA as a negative regulator of RAS expression via 3′ UTR binding sites provided the first post-transcriptional regulatory layer controlling N-Ras abundance, with reduced let-7 in tumors correlating with RAS overexpression.","evidence":"3′ UTR reporter assay, let-7 overexpression/Western blot, C. elegans genetic epistasis","pmids":["15766527"],"confidence":"High","gaps":["Relative contribution of let-7 to N-Ras vs. K-Ras regulation was not quantified","In vivo therapeutic relevance of let-7 restoration was not tested"]},{"year":2008,"claim":"eNOS-derived NO was shown to selectively activate N-Ras (not K-Ras) at the Golgi of T cells via S-nitrosylation of Cys118, linking the previously identified Golgi-localized pool to a specific activation mechanism and functional outcome — TCR-dependent apoptosis.","evidence":"Ras-GTP biosensors in T cells expressing eNOS-GFP, S-nitrosylation assay, C118S mutagenesis, apoptosis assay","pmids":["18641128"],"confidence":"High","gaps":["Whether S-nitrosylation of N-Ras occurs in non-immune cell types was unknown","Structural basis for isoform selectivity of Cys118 nitrosylation was not defined"]},{"year":2010,"claim":"In vivo demonstration that non-palmitoylatable NRAS mutants completely fail to induce leukemia, while farnesylation-deficient mutants also fail through a distinct mechanism, established that both lipid modifications are independently required for N-Ras oncogenic signaling in hematopoietic cells.","evidence":"Retroviral bone marrow transduction/transplantation with palmitoylation-deficient and farnesylation-deficient NRAS mutants","pmids":["20200357"],"confidence":"High","gaps":["Downstream signaling differences between palmitoylation-deficient and farnesylation-deficient N-Ras were not characterized","Whether palmitoylation inhibition is therapeutically tractable was untested"]},{"year":2010,"claim":"Identification of activating N-RAS mutations as a mechanism of acquired resistance to BRAF inhibitors in melanoma, mediated by C-RAF-dependent MAPK reactivation, placed N-Ras at the center of therapeutic resistance and established the N-Ras–C-RAF axis as a clinically relevant signaling route.","evidence":"Resistant melanoma subline derivation, siRNA knockdown, N-RAS(Q61K) overexpression, patient biopsy validation","pmids":["21107323","20818433"],"confidence":"High","gaps":["Whether combined MEK + BRAF inhibition fully overcomes N-RAS-driven resistance was not resolved","Contribution of PI3K signaling to resistance in N-RAS-mutant context was not addressed"]},{"year":2015,"claim":"Discovery that wild-type N-Ras directly binds and activates cytoplasmic JAK2 to induce IL-8 secretion in basal-like breast cancer — an isoform-specific function not shared by K-Ras — expanded the effector repertoire of N-Ras beyond canonical RAF and PI3K pathways.","evidence":"Co-immunoprecipitation of N-Ras with JAK2, IL-8 secretion assays, isoform-specific knockdown/overexpression, in vivo tumor formation","pmids":["26166574"],"confidence":"High","gaps":["Structural basis for N-Ras isoform selectivity in JAK2 binding was not determined","Whether this mechanism operates in non-breast cancer contexts was unknown"]},{"year":2018,"claim":"Comparative crystallography revealed that K-Ras, N-Ras, and H-Ras G domains adopt isoform-specific conformational preferences in switch regions despite identical sequences at mutation hotspots, providing a structural rationale for isoform-selective effector coupling and cancer-type associations.","evidence":"Comparative X-ray crystallography of wild-type Ras isoform G domains","pmids":["29038336"],"confidence":"Medium","gaps":["Functional validation that these conformational differences dictate isoform-specific effector selection was lacking","No structure of full-length lipidated N-Ras in a membrane context"]},{"year":null,"claim":"Despite detailed knowledge of N-Ras lipid modification, trafficking, and oncogenic signaling, no isoform-selective direct inhibitor of N-Ras exists; the specific PAT and thioesterase enzymes governing N-Ras palmitoylation cycling remain incompletely defined, and how N-Ras isoform-specific conformational dynamics translate into selective effector engagement in vivo is unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No direct small-molecule inhibitor of N-Ras GTPase","Identity and regulation of the specific DHHC palmitoyltransferase(s) and thioesterase(s) for N-Ras","Full-length membrane-bound N-Ras structure at atomic resolution"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[0,3,10]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[15,16,29]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[7,9,20,21]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[9,11,18]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[11,18,22]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,8,10,14,25,26,32]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,2,12,24,26]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,6,16,27]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13,22]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[17,30]}],"complexes":[],"partners":["SOS1","GRB2","CRAF","PIK3CG","JAK2","RASA1"],"other_free_text":[]},"mechanistic_narrative":"NRAS encodes a membrane-anchored small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) conformations to transduce mitogenic, differentiation, and survival signals through effectors including C-RAF/MAPK, PI3Kγ/AKT, and JAK2/IL-8 pathways [PMID:20818433, PMID:11136978, PMID:26166574]. Activation is driven by Sos1-mediated nucleotide exchange [PMID:8493579], while intrinsic GTPase activity is accelerated >200-fold by cytoplasmic GAP proteins — a stimulation abolished by oncogenic codon-12, -13, or -61 mutations that lock N-Ras in the GTP-bound state [PMID:2821624, PMID:6616621]. Membrane targeting requires C-terminal farnesylation of Cys186 followed by palmitoylation of upstream cysteines, establishing a constitutive deacylation/reacylation cycle that dynamically partitions N-Ras between the Golgi apparatus and the plasma membrane; both lipid modifications are independently essential for leukemogenic activity [PMID:15705808, PMID:20200357]. Beyond its oncogenic role, wild-type N-Ras restrains proliferation and functions as a tumor suppressor in thymocytes [PMID:12154063], operates in an Rb-dependent differentiation pathway in skeletal muscle [PMID:12861012], and drives cellular senescence and senescence-associated secretory phenotype in cholangiocytes [PMID:24390753]."},"prefetch_data":{"uniprot":{"accession":"P01111","full_name":"GTPase NRas","aliases":["Transforming protein N-Ras"],"length_aa":189,"mass_kda":21.2,"function":"Ras proteins bind GDP/GTP and possess intrinsic GTPase activity","subcellular_location":"Cell membrane; Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/P01111/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NRAS","classification":"Not Classified","n_dependent_lines":103,"n_total_lines":1208,"dependency_fraction":0.08526490066225166},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CD9","stoichiometry":0.2},{"gene":"SLC16A1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/NRAS","total_profiled":1310},"omim":[{"mim_id":"621092","title":"IQ MOTIF-CONTAINING GTPase-ACTIVATING PROTEIN 3; IQGAP3","url":"https://www.omim.org/entry/621092"},{"mim_id":"620963","title":"ZDHHC PALMITOYLTRANSFERASE 18; ZDHHC18","url":"https://www.omim.org/entry/620963"},{"mim_id":"619767","title":"PULMONARY FIBROSIS AND/OR BONE MARROW FAILURE SYNDROME, TELOMERE-RELATED, 6; PFBMFT6","url":"https://www.omim.org/entry/619767"},{"mim_id":"618499","title":"NOONAN SYNDROME 11; NS11","url":"https://www.omim.org/entry/618499"},{"mim_id":"617944","title":"ABHYDROLASE DOMAIN-CONTAINING PROTEIN 17C, DEPALMITOYLASE; ABHD17C","url":"https://www.omim.org/entry/617944"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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Ras.","date":"2017","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/28162770","citation_count":485,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44986,"output_tokens":4704,"usd":0.102759},"stage2":{"model":"claude-opus-4-6","input_tokens":8218,"output_tokens":2888,"usd":0.169935},"total_usd":0.693936,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":58058,"output_tokens":9059,"usd":0.155029},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":13030,"output_tokens":4493,"usd":0.266213}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1987,\n      \"finding\": \"A cytoplasmic protein (later identified as GAP/NF1) stimulates GTP hydrolysis by normal N-ras p21 more than 200-fold in vitro but has no effect on oncogenic Asp12 or Val12 mutants, explaining why position-12 mutations maintain N-ras in an active GTP-bound state.\",\n      \"method\": \"Xenopus oocyte maturation assay, in vitro GTPase assay with purified protein, mammalian cell extracts\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified components, functional readout, replicated in mammalian extracts\",\n      \"pmids\": [\"2821624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The farnesylated C-terminal peptide of N-ras is reversibly S-acylated (palmitoylated) at a cysteine residue in mammalian fibroblasts; S-acylation suppresses membrane desorption and is required for stable plasma membrane localization, which is maintained by a 'kinetic trapping' mechanism at the plasma membrane rather than via the secretory pathway.\",\n      \"method\": \"Fluorescent lipid-modified peptide uptake, fluorescence microscopy, brefeldin A/temperature treatments, in-cell S-acylation assay with CV-1 cells\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including functional localization assay, chemical biology, and pharmacological inhibition controls\",\n      \"pmids\": [\"9335573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Palmitoylation of oncogenic NRAS is essential for leukemogenesis; loss of palmitoylation (but not farnesylation) prevents efficient plasma membrane targeting and abrogates NRAS-driven myeloid disease in a mouse bone marrow transplantation model.\",\n      \"method\": \"Bone marrow transduction and transplantation model with palmitoylation-deficient NRAS mutants, loss-of-function in vivo\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean in vivo loss-of-function with defined cellular/disease phenotype, genetic approach with mutagenesis\",\n      \"pmids\": [\"20200357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Fully lipidated (farnesylated and palmitoylated) N-Ras preferentially partitions into liquid-disordered (ld) lipid domains in model membranes, with some accumulation at ld/lo phase boundaries; this partitioning is distinct from lo (raft) domains.\",\n      \"method\": \"Two-photon fluorescence microscopy on giant unilamellar vesicles, tapping-mode atomic force microscopy (AFM)\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct biophysical imaging with orthogonal methods (fluorescence + AFM), replicated in subsequent study (PMID 19133719)\",\n      \"pmids\": [\"16390147\", \"19133719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"eNOS-derived NO selectively activates N-Ras (but not K-Ras) on the Golgi complex of antigen-stimulated T cells via S-nitrosylation of Cys118; this N-Ras activation promotes ERK signaling and contributes to activation-induced T cell death. The G2A eNOS mutant (defective in Golgi localization) fails to activate N-Ras.\",\n      \"method\": \"Fluorescent Ras activation probes in live T cells, Co-IP, site-directed mutagenesis (C118S N-Ras), eNOS-GFP vs G2A mutant expression, apoptosis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including live-cell imaging, mutagenesis, and functional consequence (apoptosis)\",\n      \"pmids\": [\"18641128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Membrane binding induces a new conformational substate in N-Ras that is not present in solution; the nucleotide-binding state (GDP vs GTP) and membrane interaction both modulate the conformational dynamics of the G domain, with structural reorientations relevant to effector interactions.\",\n      \"method\": \"FTIR spectroscopy with pressure perturbation, ATR-FTIR, IRRAS on lipid bilayer-associated N-Ras\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — biophysical structural approach, single study with multiple spectroscopic methods\",\n      \"pmids\": [\"22203965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Solid-state NMR reveals that the lipidated C-terminal membrane anchor of full-length N-Ras is highly dynamic on the membrane surface, with segmental fluctuations and axially symmetric overall motions; the palmitoyl chain at Cys181 is particularly flexible.\",\n      \"method\": \"Solid-state 2H and 13C NMR, chemical-biological synthesis of isotopically labeled lipidated N-Ras\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with isotopically labeled protein, quantitative NMR order parameters and relaxation measurements\",\n      \"pmids\": [\"17044712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In BRAF(V600E) melanoma cells acquiring PLX4032 resistance, N-RAS mutations lead to elevated activated N-RAS that reactivates the MAPK pathway; knockdown of N-RAS reduces growth of resistant cells, and overexpression of N-RAS(Q61K) confers PLX4032 resistance to sensitive parental lines.\",\n      \"method\": \"shRNA knockdown, overexpression in cell lines, analysis of resistant patient-derived tumor samples\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal gain- and loss-of-function experiments validated in patient-derived samples\",\n      \"pmids\": [\"21107323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PLX4720 (BRAF inhibitor) treatment of mutant N-RAS melanoma cells causes C-RAF-dependent hyperactivation of MEK-ERK1/2, promoting resistance to apoptosis.\",\n      \"method\": \"Western blot for pERK, siRNA knockdown of RAF isoforms, apoptosis assays in cell lines\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown identifies C-RAF as mediator, single lab\",\n      \"pmids\": [\"20818433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Wild-type N-Ras (but not K-Ras) induces IL-8 secretion in basal-like breast cancer cells by binding and activating the cytoplasmic pool of JAK2; IL-8 then acts in autocrine/paracrine fashion on cancer and stromal cells to promote tumor growth.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression, cytokine measurement, xenograft assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP showing N-Ras/JAK2 interaction with functional follow-up, single lab\",\n      \"pmids\": [\"26166574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Genetic epistasis in mice shows that deletion of N-ras rescues skeletal muscle differentiation defects (but not proliferation/apoptosis defects) in Rb-null embryos, demonstrating that N-ras acts downstream of or parallel to Rb in the differentiation pathway and that Rb-dependent control of differentiation and proliferation are genetically separable.\",\n      \"method\": \"Double-knockout mouse genetics, histology, gene expression analysis, myoblast culture\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — classical genetic epistasis in vivo with defined cellular phenotype\",\n      \"pmids\": [\"12861012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Activated N-ras oncogene expression in PC12 rat pheochromocytoma cells suppresses proliferation and promotes neuronal differentiation, establishing a role for N-ras in differentiation signaling distinct from its oncogenic proliferative activity.\",\n      \"method\": \"Gene transfection into PC12 cells, morphological and proliferation assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss/gain-of-function with defined cellular phenotype, early foundational study\",\n      \"pmids\": [\"3760034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"Inducible expression of activated N-ras in C2 myoblasts reversibly inhibits myogenic differentiation (myotube formation, muscle creatine kinase, acetylcholine receptor induction) in a dose-dependent manner; N-ras does not extinguish muscle-specific gene expression in already-differentiated myotubes, placing N-ras action at an early step in the myogenic differentiation pathway.\",\n      \"method\": \"Steroid-inducible MMTV-N-ras transgene in C2 cells, dexamethasone induction/withdrawal, muscle-specific gene expression assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — inducible system with reversible phenotype and pathway placement, single lab\",\n      \"pmids\": [\"3133379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"miR-214 promotes myogenic differentiation in C2C12 myoblasts by directly targeting N-ras mRNA; manipulation of N-Ras levels by siRNA or forced expression augments or attenuates miR-214 effects respectively, placing N-Ras downstream of miR-214 in myogenic exit from the cell cycle.\",\n      \"method\": \"miRNA inhibitor, siRNA knockdown, adenoviral overexpression, global gene expression profiling in C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis between miR-214 and N-Ras with reciprocal gain/loss-of-function\",\n      \"pmids\": [\"20534588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"N-ras antisense oligodeoxynucleotides inhibit GM-CSF/IL-3/M-CSF-driven but not G-CSF-driven granulocyte/macrophage colony formation from human CD34+ progenitors, demonstrating that N-ras expression is required specifically for growth factor-dependent hematopoietic progenitor proliferation through certain cytokine receptor pathways.\",\n      \"method\": \"Antisense oligodeoxynucleotide treatment of CD34+ cells, semisolid colony assays with defined cytokines\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with specific pathway/cytokine discrimination\",\n      \"pmids\": [\"1371302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mutant N-ras upregulates Bcl-2 expression (but not Bcl-xL, Bax, or Bak) in human melanoma cells in vitro and in SCID mouse xenografts, providing a mechanistic basis for N-ras-driven resistance to apoptosis and chemotherapy.\",\n      \"method\": \"Western blot, in vitro apoptosis assays, SCID mouse xenotransplantation, overexpression of mutant N-ras\",\n      \"journal\": \"Melanoma research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — in vitro and in vivo validation, specific Bcl-2 upregulation identified, single lab\",\n      \"pmids\": [\"10504052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Expression of constitutively active N-ras (Q61R) in the IL-6-dependent myeloma cell line ANBL6 confers IL-6-independent growth and suppresses apoptosis, through a mechanism independent of autocrine IL-6 production.\",\n      \"method\": \"Stable transfection, IL-6 withdrawal/neutralizing antibody assays, DNA synthesis and apoptosis assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with pharmacological dissection of mechanism\",\n      \"pmids\": [\"7627974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"N-Ras-deficient fibroblasts exhibit elevated basal PI3K/Akt and MEK/ERK activity, increased collagen synthesis, and reduced proliferation and migration; N-Ras normally suppresses ECM synthesis and promotes proliferation/migration by modulating Akt activation.\",\n      \"method\": \"N-ras(-/-) immortalized fibroblasts, Western blot for pathway activation, collagen/fibronectin synthesis assays, proliferation and migration assays\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic null with multiple cellular readouts, single lab\",\n      \"pmids\": [\"23871832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"UV irradiation activates the N-ras proto-oncogene by inducing point mutations predominantly at codon 61 (TT doublet); cyclobutane dimers (not 6-4 photoproducts) are the major premutagenic lesions, as photoreactivating enzyme treatment abolishes N-ras activation.\",\n      \"method\": \"UV irradiation of cloned N-ras plasmid, NIH 3T3 transformation assay, photoreactivating enzyme treatment, oligonucleotide probe hybridization, sequencing\",\n      \"journal\": \"Oncogene research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic dissection of UV mutagenesis using enzymatic specificity controls\",\n      \"pmids\": [\"3060800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"The activated N-ras oncogene of HT1080 fibrosarcoma cells directly maintains the transformed phenotype; revertants with reduced mutant N-ras p21 levels lose transformation, and re-amplification of the transforming allele restores tumorigenicity.\",\n      \"method\": \"Flat revertant isolation, immunoprecipitation, chromosomal ploidy analysis, transfection of cloned ras oncogenes\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic approaches in isogenic lines, reciprocal gain/loss-of-function\",\n      \"pmids\": [\"3315232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Galectin-3 overexpression causes a molecular switch from N-Ras-GTP to K-Ras-GTP usage in breast cancer cells; wild-type Gal-3 (but not non-oncogenic mutants) co-immunoprecipitates with K-Ras and selectively reduces N-Ras-GTP levels, shifting downstream signaling from AKT/Ral to ERK.\",\n      \"method\": \"Co-immunoprecipitation, RAS-GTP pull-down assays, Gal-3 mutant overexpression, pharmacological inhibitors\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP and active RAS measurements with mutant controls, single lab\",\n      \"pmids\": [\"16103080\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NRAS is a membrane-associated small GTPase that cycles between inactive GDP-bound and active GTP-bound states; a cytoplasmic GAP protein stimulates GTP hydrolysis by wild-type NRAS >200-fold but cannot act on oncogenic codon-12/13/61 mutants, which thereby remain constitutively GTP-bound and activate MAPK/ERK and PI3K/AKT effector pathways. Proper plasma membrane localization requires sequential farnesylation and palmitoylation (at Cys181), with S-acylation providing kinetic trapping at the plasma membrane; both modifications are essential for leukemogenic activity. Additionally, NRAS can be selectively activated at the Golgi by eNOS-dependent S-nitrosylation of Cys118 in T cells, and wild-type NRAS engages a cytoplasmic JAK2 pool to drive IL-8 secretion in breast cancer cells, illustrating isoform-specific signaling distinct from KRAS.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper and extract discoveries only from KEEP papers.\n\n**Key exclusions to note:**\n- Papers [75], [84], [86], [91] from main corpus and additional [this pattern] describe \"Upstream of N-ras\" (UNR/Unr), a separate gene — EXCLUDE (alias collision)\n- Papers about general RAS family without specific NRAS mechanistic content — mostly skip\n- Papers that are purely mutational surveys/clinical correlations without mechanistic content — skip (no discovery entry)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1983,\n      \"finding\": \"The human N-ras gene was cloned and shown to have the same intron/exon structure as H-ras and K-ras; a single nucleotide change substituting lysine for glutamine at position 61 of the N-ras product converts it from a non-transforming proto-oncogene to a transforming oncogene, demonstrating that codon 61 is a critical activation site.\",\n      \"method\": \"Molecular cloning, DNA sequencing, NIH3T3 transfection/focus assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original cloning with mutagenesis and functional transformation assay; foundational paper replicated widely\",\n      \"pmids\": [\"6616621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1983,\n      \"finding\": \"The human N-ras gene was mapped by in situ hybridization to chromosome 1, region 1cen–p21.\",\n      \"method\": \"In situ hybridization to metaphase chromosome preparations\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by in situ hybridization, confirmed by somatic cell hybrid data\",\n      \"pmids\": [\"6667677\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1984,\n      \"finding\": \"Three distinct activating point mutations were identified at codon 61 of N-ras in human tumor cell lines (fibrosarcoma HT1080, promyelocytic HL60, rhabdomyosarcoma RD301), affecting the first, second, or third nucleotide of the codon respectively, all resulting in amino acid substitutions and demonstrating dominant oncogenic character alongside a normal N-ras allele.\",\n      \"method\": \"Synthetic oligonucleotide hybridization, DNA sequencing\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct sequence determination of multiple independent activating mutations; replicated across labs\",\n      \"pmids\": [\"6595642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"A cytoplasmic protein (later identified as GAP/NF1) stimulates GTP hydrolysis by normal N-ras p21 (Gly12) more than 200-fold in vitro but has no effect on oncogenic mutants (Asp12 or Val12), explaining how position-12 mutations lock N-ras in the active GTP-bound state by preventing GTPase-activating protein stimulation.\",\n      \"method\": \"Xenopus oocyte maturation assay (biological activity readout), in vitro GTPase assay with purified proteins, in vivo GTP/GDP binding analysis\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with purified proteins, orthogonal in vivo nucleotide-binding assay, functional readout; highly cited foundational paper\",\n      \"pmids\": [\"2821624\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"The activated N-ras oncogene of HT1080 human fibrosarcoma cells directly maintains the transformed phenotype; revertants with reduced mutant N-ras p21 levels lost transformation, and sporadic tumors from revertants regained the transforming allele, demonstrating that N-ras oncogene dosage controls the transformed state.\",\n      \"method\": \"Revertant isolation, immunoprecipitation of N-ras p21, gene dosage analysis, retransfection of cloned ras oncogenes\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis via reversion analysis with protein-level validation; multiple independent revertant lines\",\n      \"pmids\": [\"3315232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"Activated N-ras transfected into PC12 rat pheochromocytoma cells suppressed proliferation and promoted neuronal differentiation (neurite outgrowth, cell division arrest), including in NGF-resistant variants, demonstrating that N-ras can drive differentiation rather than proliferation in a cell-context-dependent manner.\",\n      \"method\": \"Gene transfection, morphological assessment of neurite outgrowth, cell proliferation assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional KO/OE with defined differentiation phenotype in multiple cell contexts\",\n      \"pmids\": [\"3760034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"Steroid-inducible oncogenic N-ras expression in C2 myoblasts reversibly inhibited myotube formation and induction of muscle creatine kinase and acetylcholine receptors in a dose-dependent manner, without affecting growth factor dependence or contact inhibition; however, N-ras induction in terminally differentiated myotubes failed to extinguish muscle-specific gene expression, placing N-ras action at an early step in the myogenic differentiation pathway.\",\n      \"method\": \"MMTV-LTR steroid-inducible N-ras transgene system in C2 myoblasts; dexamethasone dose–response; muscle-specific gene expression assays (MCK, AChR); conditioned media experiments\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — inducible gain-of-function with multiple orthogonal markers and reversibility controls; clear pathway placement\",\n      \"pmids\": [\"3133379\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"All Ras proteins including N-Ras are polyisoprenylated (farnesylated) on the C-terminal cysteine (Cys186); palmitoylation occurs on additional upstream cysteine residues in the hypervariable domain rather than on Cys186; palmitoylation increases membrane avidity and enhances transforming activity, while polyisoprenylation is essential for membrane association and biological activity.\",\n      \"method\": \"Mutational analysis of CAAX motif cysteines, membrane association assays, transformation assays, biosynthetic labeling\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis combined with functional and biochemical readouts; foundational paper replicated extensively\",\n      \"pmids\": [\"2661017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human Sos1 (hSos1), a guanine nucleotide exchange factor closely related to Drosophila Sos, directly stimulates guanine nucleotide exchange on Ras proteins (including N-Ras) in vitro via its CDC25-related domain; hSos1 interacts with GRB2 through its C-terminal domain binding to GRB2 SH3 domains in vivo and in vitro, placing Sos1 as the direct activator of Ras downstream of receptor tyrosine kinases.\",\n      \"method\": \"CDC25 yeast complementation, in vitro guanine nucleotide exchange assay, mammalian overexpression, in vivo and in vitro co-immunoprecipitation with GRB2\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution of exchange activity plus reciprocal interaction mapping; foundational paper\",\n      \"pmids\": [\"8493579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The farnesylated C-terminal peptide of N-ras is reversibly S-acylated (palmitoylated) in cultured mammalian fibroblasts; S-acylation occurs specifically on cysteine (not serine), suppresses membrane desorption/diffusion between bilayers, and is required for preferential plasma membrane localization; the plasma membrane targeting is unaffected by brefeldin A or reduced temperature, suggesting a 'kinetic trapping' mechanism at the plasma membrane rather than trafficking through the secretory pathway.\",\n      \"method\": \"Fluorescent lipid-modified peptide analogs, large unilamellar vesicle binding assays, fluorescence microscopy in CV-1 cells, brefeldin A and temperature inhibition experiments\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro biophysical assays combined with cell-based localization experiments and pharmacological perturbations\",\n      \"pmids\": [\"9335573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Crystal structure of H-Ras complexed with the Sos GEF domain at 2.8 Å resolution revealed that Sos displaces the Switch I region of Ras by inserting an α-helix, opening the nucleotide-binding site, and disrupts magnesium/phosphate binding via Switch II distortion, defining the catalytic mechanism of Ras nucleotide exchange applicable to all Ras isoforms including N-Ras.\",\n      \"method\": \"X-ray crystallography at 2.8 Å resolution, structure-function analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure of the complex; mechanism broadly applicable to N-Ras as the exchange mechanism is conserved\",\n      \"pmids\": [\"9690470\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"N-ras is transiently localized to the Golgi apparatus en route to the plasma membrane; GFP-tagged N-ras labeled motile peri-Golgi vesicles; prolonged brefeldin A treatment blocked plasma membrane expression; the CAAX motif alone targets N-ras to endomembranes where carboxylmethylation occurs, and a secondary targeting signal is required for final plasma membrane delivery.\",\n      \"method\": \"GFP fusion live-cell imaging, brefeldin A treatment, CAAX motif mutational analysis, carboxylmethylation assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — live imaging with pharmacological perturbations and mutagenesis; foundational localization study\",\n      \"pmids\": [\"10412982\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mutant N-ras expression in bone marrow-repopulated mice induced myeloproliferative disorders resembling CML or AML-M2 in ~60% of animals, as well as MDS-like disorders with myeloid impairment; a high level of apoptosis with thymic atrophy was also observed, consistent with a model where antiproliferative effects are a primary consequence of N-ras mutations and secondary events are needed for leukemia.\",\n      \"method\": \"Retroviral bone marrow transduction and transplantation mouse model, histopathology, CFU-S and colony assays, flow cytometry\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo gain-of-function with defined hematologic phenotypes and colony assays; first in vivo N-ras leukemia model\",\n      \"pmids\": [\"10068678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Mutated N-ras specifically upregulates Bcl-2 protein expression in human melanoma cells in vitro and in SCID mouse xenografts, protecting against apoptosis; neither Bcl-xL, Bax, nor Bak expression was altered, identifying Bcl-2 upregulation as the mechanistic basis of N-ras-mediated apoptosis resistance.\",\n      \"method\": \"N-ras overexpression in melanoma cell lines, Western blot for apoptosis-related proteins, SCID mouse xenograft model\",\n      \"journal\": \"Melanoma research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — in vitro and in vivo functional assay with specific molecular readout, single lab\",\n      \"pmids\": [\"10504052\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Crystal structure of PI3Kγ in complex with H-Ras·GMPPNP revealed that Ras uses both Switch I and Switch II regions to bind the PI3Kγ RBD, and Ras also contacts the PI3Kγ catalytic domain directly; mutagenesis confirmed both switch regions are essential for binding and activation, establishing the structural basis for Ras-dependent PI3K activation relevant to all Ras isoforms including N-Ras.\",\n      \"method\": \"X-ray crystallography, in vitro PI3Kγ activation assay with H-Ras G12V, site-directed mutagenesis\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus reconstituted activation assay plus mutagenesis\",\n      \"pmids\": [\"11136978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Wild-type N-ras acts as a tumor suppressor: N-ras-null mice develop thymic lymphomas at higher rates, whereas overexpression of wild-type N-ras protects against thymic lymphomagenesis; introduction of wild-type N-ras into N-ras-deficient tumor cells decreased growth in low serum and soft agar, demonstrating a growth-inhibitory role for the proto-oncogene product.\",\n      \"method\": \"N-ras knockout and transgenic mouse models, in vitro transformation assays (low-serum growth, soft-agar colony formation)\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function and gain-of-function in vivo and in vitro with multiple readouts\",\n      \"pmids\": [\"12154063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Rb and N-ras function in a common pathway to control skeletal muscle differentiation: deletion of N-ras in Rb-null embryos rescued defects in skeletal muscle fiber density, myotube morphology, and MCK expression, and potentiated MyoD transcriptional activity, while proliferation and apoptosis defects remained; this genetic rescue demonstrates that N-ras and Rb operate in the same differentiation pathway but that Rb's control of differentiation is separable from its control of proliferation.\",\n      \"method\": \"Double-knockout mouse embryo analysis (Rb−/−; N-ras−/−), histology, immunohistochemistry, MyoD transcriptional activity assay in primary myoblasts\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in double-knockout animals with molecular readouts; clear pathway placement\",\n      \"pmids\": [\"12861012\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Let-7 miRNA family members negatively regulate RAS expression (including N-RAS) by binding multiple let-7 complementary sites (LCSs) in the 3′ UTR of human RAS genes; let-7 overexpression reduces RAS protein levels, and let-7 is lower in lung tumors that overexpress RAS protein.\",\n      \"method\": \"3′ UTR reporter assays, let-7 overexpression, Western blot for RAS protein in tumor vs. normal tissue; C. elegans genetic epistasis (let-60/RAS)\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reporter assay validation, protein-level confirmation, evolutionary conservation demonstrated; highly cited\",\n      \"pmids\": [\"15766527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"A constitutive de/reacylation (palmitoylation/depalmitoylation) cycle drives rapid exchange of N-ras and H-ras between the plasma membrane and the Golgi apparatus: depalmitoylation redistributes farnesylated N-ras to all membranes, repalmitoylation traps it at the Golgi, and vesicular transport then delivers it to the plasma membrane; this cycle maintains compartment-specific localization and enables Golgi-initiated Ras activation.\",\n      \"method\": \"Fluorescent N-ras fusion proteins (FRAP, live imaging), palmitoylation inhibitor 2-bromopalmitate, dominant-negative DHHC PAT constructs, quantitative membrane fractionation\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — FRAP and live imaging combined with pharmacological and genetic perturbations; mechanistic model confirmed by multiple approaches\",\n      \"pmids\": [\"15705808\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Galectin-3 selectively binds activated K-Ras-GTP (not N-Ras-GTP); Gal-3 overexpression in breast cancer cells increased K-Ras-GTP while reducing N-Ras-GTP, demonstrating a molecular switch between N-Ras and K-Ras usage dependent on Gal-3 binding; only wild-type Gal-3 co-immunoprecipitated with K-Ras and altered signaling from AKT/Ral toward ERK.\",\n      \"method\": \"Co-immunoprecipitation, RAS activation (GTP pull-down) assays, Gal-3 point mutants, isoform-specific RBD pull-down\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, co-IP/pulldown; mechanistic follow-up limited; establishes isoform-selectivity of Gal-3\",\n      \"pmids\": [\"16103080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Fully lipidated (farnesylated + hexadecylated) N-Ras protein partitions preferentially into liquid-disordered (ld) lipid domains rather than liquid-ordered (lo) or solid-ordered phases in model membranes; a large proportion also localizes at ld/lo phase boundaries, reducing line tension; this membrane domain preference is independent of nucleotide (GDP vs GTP) state.\",\n      \"method\": \"Two-photon fluorescence microscopy on giant unilamellar vesicles, tapping-mode AFM on supported bilayers, canonical raft lipid mixture (POPC/sphingomyelin/cholesterol)\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — biophysical assays with two orthogonal microscopy methods; model membrane system\",\n      \"pmids\": [\"16390147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Solid-state NMR of full-length membrane-associated lipidated N-Ras protein revealed that the C-terminal lipid anchor region is highly flexible with segmental fluctuations and axially symmetric overall motions on the membrane surface; the palmitoyl chain at Cys181 is highly mobile in the membrane.\",\n      \"method\": \"Solid-state 2H and 13C NMR, chemical-biological ligation of isotopically labeled lipidated heptapeptide to expressed N-terminal domain, order parameter and relaxation measurements\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — first comprehensive NMR dynamics study of full-length lipidated Ras; rigorous structural methodology\",\n      \"pmids\": [\"17044712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"eNOS-derived NO selectively activates N-Ras (but not K-Ras) on the Golgi complex of T cells engaged with antigen-presenting cells; activation involves eNOS-dependent S-nitrosylation of N-Ras at Cys118; wild-type but not C118S N-Ras increased TCR-dependent apoptosis, demonstrating that S-nitrosylation of Cys118 is required for N-Ras activation at the Golgi and contributes to activation-induced T cell death.\",\n      \"method\": \"Fluorescent Ras probes (Ras-GTP biosensors) in T cells stably expressing eNOS-GFP or G2A mutant; S-nitrosylation assay; site-directed mutagenesis (C118S); apoptosis assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — live-cell Ras activation imaging, mutagenesis of modification site, functional apoptosis readout; multiple orthogonal methods\",\n      \"pmids\": [\"18641128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"N-Ras proteins bearing at least one farnesyl group partition preferentially into liquid-disordered lipid domains independent of lipid anchor type; farnesylated N-Ras shows diffusion to ld/lo phase boundaries and forms nanoclusters there via intermolecular interactions; the non-biological dual-hexadecyl N-Ras instead incorporates into the bulk ld phase without boundary preference; no significant difference in domain partitioning was detected between GDP- and GTP-loaded N-Ras.\",\n      \"method\": \"Time-lapse tapping-mode AFM on supported lipid bilayers, differently lipidated N-Ras protein variants\",\n      \"journal\": \"Journal of the American Chemical Society\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic comparison of lipid anchor variants by biophysical AFM; single methodology\",\n      \"pmids\": [\"19133719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Palmitoylation is essential for leukemogenesis by oncogenic NRAS: non-palmitoylatable NRAS mutants failed to induce CMML/AML in a mouse bone marrow transplant model; farnesylation is also essential but through a distinct mechanism from palmitoylation deficiency; demonstrating that both post-translational lipid modifications are independently required for NRAS oncogenic activity.\",\n      \"method\": \"Retroviral bone marrow transduction/transplantation mouse model, palmitoylation-deficient and farnesylation-deficient NRAS mutants\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic loss-of-function of specific PTMs with clear leukemia phenotype; mechanistic dissection of two distinct modifications\",\n      \"pmids\": [\"20200357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In NRAS-mutant melanoma cells, PLX4720 (BRAF inhibitor) rapidly induces hyperactivation of MEK-ERK1/2 signaling; C-RAF (not B-RAF) is the major RAF isoform responsible for this hyperactivation; PLX4720-induced MEK-ERK1/2 hyperactivation promotes resistance to apoptosis in N-RAS mutant melanoma cells but does not enhance cell cycle progression.\",\n      \"method\": \"PLX4720 treatment of N-RAS mutant melanoma cells, phospho-ERK1/2 Western blot, siRNA knockdown of RAF isoforms, apoptosis assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA epistasis combined with pharmacological inhibition and mechanistic apoptosis/cell cycle readouts\",\n      \"pmids\": [\"20818433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Acquired resistance to PLX4032 (BRAF inhibitor) in melanoma arises through mutually exclusive mechanisms: PDGFR-β upregulation (maintaining low activated RAS) or activating N-RAS mutations (causing MAPK reactivation upon PLX4032 treatment); knockdown of N-RAS reduced growth of the N-RAS-mutant resistant subset; overexpression of N-RAS(Q61K) conferred PLX4032 resistance to sensitive parental cells; MAPK reactivation predicted MEK inhibitor sensitivity.\",\n      \"method\": \"PLX4032-resistant melanoma subline derivation, siRNA knockdown, overexpression of N-RAS(Q61K), phospho-MAPK pathway analysis, patient biopsy validation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches (KD, OE, patient samples) with defined molecular mechanism and clinical validation\",\n      \"pmids\": [\"21107323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"miR-214 promotes myogenic differentiation in C2C12 myoblasts by down-regulating N-ras, facilitating cell cycle exit; blocking miR-214 maintained active cell cycling and inhibited differentiation; siRNA knockdown of N-Ras augmented the differentiation effect while forced N-Ras overexpression attenuated it, placing N-Ras downstream of miR-214 in the differentiation pathway.\",\n      \"method\": \"2′-O-methylated miR-214 inhibitor, global gene expression profiling, siRNA knockdown and adenoviral overexpression of N-Ras, cell cycle analysis, muscle differentiation markers\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockdown and overexpression with multiple differentiation readouts; N-Ras epistasis clearly established\",\n      \"pmids\": [\"20534588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Pressure modulation combined with FTIR spectroscopy revealed distinct conformational substates of lipidated N-Ras; nucleotide-binding state (GDP vs GTP) and membrane binding both dramatically alter conformational dynamics and substate selection; a new membrane-induced conformational substate was identified, accompanied by structural reorientation of the G domain as shown by ATR-FTIR and IRRAS, demonstrating that the membrane acts as an allosteric regulator of N-Ras G-domain orientation.\",\n      \"method\": \"Pressure-perturbation FTIR spectroscopy, ATR-FTIR, IRRAS on membrane-associated lipidated N-Ras\",\n      \"journal\": \"Proceedings of the National Academy of Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple spectroscopic methods with thermodynamic analysis; directly links membrane binding to conformational change\",\n      \"pmids\": [\"22203965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"N-Ras deficiency in fibroblasts resulted in higher basal PI3K/Akt and MEK/Erk activity, upregulated collagen synthesis, and diminished proliferation and migration; TGF-β1-induced proliferation and migration required PI3K/Akt but not Erk1/2; N-Ras modulates extracellular matrix synthesis and cell motility by negatively regulating Akt activation, indicating N-Ras normally restrains collagen production and regulates fibroblast behavior.\",\n      \"method\": \"N-ras−/− immortalized fibroblasts, Western blot for pathway activation, collagen/fibronectin expression, proliferation and migration assays, pharmacological PI3K/MEK inhibitors\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with multiple phenotypic and molecular readouts; single lab\",\n      \"pmids\": [\"23871832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"miR-143 directly targets N-RAS 3′ UTR and suppresses N-RAS expression; overexpression of miR-143 decreased N-RAS protein, inhibited PI3K/AKT and MAPK/ERK signaling, reduced p65 nuclear accumulation, and attenuated glioma cell migration, invasion, tube formation, and tumor growth in vitro and in vivo.\",\n      \"method\": \"miR-143 overexpression, luciferase 3′ UTR reporter assay, Western blot, invasion/migration assays, xenograft mouse model\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct target validation by reporter assay plus functional phenotypes; single lab\",\n      \"pmids\": [\"24980823\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"N-Ras activation via biliary constituents induces cholangiocyte senescence and senescence-associated secretory phenotype (SASP, including IL-6, IL-8, CCL2, PAI-1) in primary sclerosing cholangitis; pharmacological Ras inhibition abrogated experimentally induced senescence and SASP; senescent cholangiocytes could transmit senescence to bystander cells, placing N-Ras upstream of the senescence program in cholangiocytes.\",\n      \"method\": \"IFM, FISH (telomere length), in vitro cholangiocyte senescence induction, Ras inhibitor (farnesylthiosalicylic acid), co-culture bystander assay, patient liver biopsies\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — pharmacological loss-of-function in cell and tissue context with multiple senescence markers; mechanism of N-Ras-driven SASP established\",\n      \"pmids\": [\"24390753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Wild-type N-Ras, overexpressed in basal-like breast cancers, promotes tumor formation specifically by binding and activating cytoplasmic JAK2, leading to IL-8 secretion that acts on both cancer cells and stromal fibroblasts in an autocrine/paracrine manner; this activity is isoform-specific as K-Ras did not induce IL-8 via JAK2.\",\n      \"method\": \"N-RAS knockdown and overexpression in BLBC cells, co-immunoprecipitation of N-Ras with JAK2, IL-8 secretion assays, fibroblast co-culture, tumor formation assays in vivo\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — co-IP defining novel N-Ras/JAK2 interaction, isoform specificity demonstrated, in vivo tumor assays; multiple orthogonal methods\",\n      \"pmids\": [\"26166574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"L. major enhances CD40-induced N-Ras activation in macrophages via TLR2-dependent signaling; N-Ras silencing reduced L. major infection while K-Ras and H-Ras silencing enhanced it; cell-permeable peptides blocking the N-Ras–Sos interaction interface reduced L. major infection in BALB/c mice but not in CD40-deficient mice, demonstrating isoform-specific N-Ras function downstream of CD40 in Leishmania immune evasion.\",\n      \"method\": \"shRNA knockdown of individual Ras isoforms, TLR2 shRNA/antibody blockade, RAS activation assays, N-Ras–Sos interface peptide inhibitors in vivo (BALB/c mice), CD40 KO mice\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — isoform-specific knockdowns with in vitro and in vivo infectious phenotypes; peptide inhibitor targets defined interaction\",\n      \"pmids\": [\"25786685\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Structural comparisons of K-Ras, N-Ras, and H-Ras G domains revealed that each isoform and each oncogenic mutation has distinct conformational preferences in switch regions I and II and the allosteric lobe, despite 100% sequence identity in the mutation hotspot regions; these structural differences can account for isoform-specific coupling to effectors and cancer types.\",\n      \"method\": \"Comparative X-ray crystallography of wild-type Ras isoforms, structural analysis of switch region conformations\",\n      \"journal\": \"Cold Spring Harbor perspectives in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure comparison; single review-style paper consolidating structural data but includes new crystallographic comparisons\",\n      \"pmids\": [\"29038336\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NRAS encodes a membrane-anchored small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states; activation is driven by Sos1-mediated nucleotide exchange and is terminated by intrinsic GTPase activity stimulated >200-fold by cytoplasmic GAP proteins, which are rendered ineffective by oncogenic codon-12/13/61 mutations; membrane targeting requires sequential farnesylation of Cys186 then palmitoylation of upstream cysteines, with a constitutive de/reacylation cycle maintaining N-Ras in a dynamic equilibrium between the Golgi and plasma membrane; additionally, eNOS-dependent S-nitrosylation of Cys118 can selectively activate N-Ras at the Golgi in T cells; in the active state N-Ras engages effectors including RAF (via C-RAF), PI3Kγ, and JAK2 to drive MAPK, PI3K/AKT signaling, and IL-8 secretion, with cell-context-dependent outcomes including proliferation, differentiation inhibition, Bcl-2-mediated apoptosis resistance, and senescence.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NRAS is a membrane-associated small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) states, functioning as a critical signaling switch in cell proliferation, differentiation, and survival. A cytoplasmic GAP stimulates GTP hydrolysis by wild-type NRAS over 200-fold, whereas oncogenic mutations at codons 12, 13, and 61 render NRAS insensitive to GAP-mediated inactivation, locking it in a constitutively active state that drives MAPK/ERK and PI3K/AKT signaling [PMID:2821624, PMID:21107323]. Proper plasma membrane targeting requires sequential farnesylation and palmitoylation at Cys181, with S-acylation providing kinetic trapping at the plasma membrane; palmitoylation is essential for NRAS-driven leukemogenesis in vivo [PMID:9335573, PMID:20200357]. Beyond canonical effector pathways, NRAS exhibits isoform-specific signaling: it is selectively activated at the Golgi by eNOS-dependent S-nitrosylation of Cys118 in T cells to promote ERK-dependent apoptosis, and engages a cytoplasmic JAK2 pool to drive IL-8 secretion in breast cancer cells [PMID:18641128, PMID:26166574].\",\n  \"teleology\": [\n    {\n      \"year\": 1987,\n      \"claim\": \"The biochemical basis of oncogenic NRAS activation was established: a cytoplasmic GAP accelerates GTP hydrolysis by wild-type NRAS >200-fold but is ineffective on codon-12 mutants, explaining their constitutive activity.\",\n      \"evidence\": \"In vitro GTPase assay with purified N-ras p21 and mammalian cell extracts, Xenopus oocyte maturation assay\",\n      \"pmids\": [\"2821624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the GAP (later NF1) not yet resolved\", \"No structural basis for why codon-12 mutants escape GAP-stimulated hydrolysis\", \"Effector pathways downstream of active NRAS not mapped\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Direct evidence that activated NRAS maintains the transformed phenotype was provided: revertants losing mutant N-ras expression lose tumorigenicity, and re-amplification restores it, while activated N-ras can also promote neuronal differentiation in PC12 cells.\",\n      \"evidence\": \"Flat revertant isolation and re-amplification in HT1080 cells; gene transfection and differentiation assays in PC12 cells\",\n      \"pmids\": [\"3315232\", \"3760034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No molecular effectors identified for the differentiation versus proliferation outputs\", \"Context-dependent effects (transformation vs. differentiation) not mechanistically explained\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Activated N-ras was shown to reversibly inhibit myogenic differentiation at an early commitment step, and UV-induced point mutations at codon 61 were identified as arising from cyclobutane pyrimidine dimers.\",\n      \"evidence\": \"Inducible MMTV-N-ras in C2 myoblasts with dexamethasone withdrawal; UV mutagenesis with photoreactivating enzyme treatment and NIH 3T3 transformation assay\",\n      \"pmids\": [\"3133379\", \"3060800\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream pathway linking N-ras to myogenic transcription factor inhibition unknown\", \"In vivo relevance of UV-induced codon-61 mutations for human cancer not established\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"N-ras was shown to be required selectively for GM-CSF/IL-3/M-CSF-driven but not G-CSF-driven hematopoietic colony formation, establishing pathway-specific dependence in normal hematopoiesis.\",\n      \"evidence\": \"Antisense oligodeoxynucleotide knockdown in CD34+ progenitors with defined cytokine colony assays\",\n      \"pmids\": [\"1371302\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antisense approach has incomplete knockdown and off-target concerns\", \"Which downstream effectors mediate cytokine-selective N-ras dependence is unknown\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"The membrane-targeting mechanism was resolved: farnesylated N-ras undergoes reversible S-acylation (palmitoylation) at Cys181, and this modification provides kinetic trapping at the plasma membrane rather than routing through the secretory pathway.\",\n      \"evidence\": \"Fluorescent lipid-modified peptide uptake, fluorescence microscopy, brefeldin A treatment in CV-1 fibroblasts\",\n      \"pmids\": [\"9335573\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Acyltransferase and thioesterase enzymes responsible not identified\", \"Whether palmitoylation cycling regulates signaling output not tested\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Genetic epistasis in mice revealed that N-ras acts downstream of or parallel to Rb specifically in the differentiation (not proliferation/apoptosis) arm, demonstrating genetically separable outputs of the Rb-N-ras axis.\",\n      \"evidence\": \"N-ras−/−; Rb−/− double-knockout mouse embryos, histology, and myoblast culture\",\n      \"pmids\": [\"12861012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction between Rb pathway components and N-ras not demonstrated\", \"Whether differentiation rescue reflects cell-autonomous signaling unclear\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Biophysical characterization established that fully lipidated N-Ras partitions into liquid-disordered membrane domains (not lipid rafts), and solid-state NMR revealed the C-terminal anchor is highly dynamic with the palmitoyl chain particularly flexible.\",\n      \"evidence\": \"Two-photon microscopy on GUVs, AFM; solid-state 2H/13C NMR on isotopically labeled lipidated N-Ras\",\n      \"pmids\": [\"16390147\", \"17044712\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of liquid-disordered partitioning for signaling not tested in cells\", \"Whether membrane domain preference changes with nucleotide state unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"A compartment-specific activation mechanism was uncovered: eNOS-derived NO selectively activates N-Ras (not K-Ras) at the Golgi via S-nitrosylation of Cys118, driving ERK signaling and activation-induced T cell death.\",\n      \"evidence\": \"Fluorescent Ras activation probes in live T cells, C118S mutagenesis, eNOS-GFP vs. G2A Golgi-targeting mutant\",\n      \"pmids\": [\"18641128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether S-nitrosylation directly blocks GAP interaction or alters effector binding not resolved\", \"Generality beyond T cells not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Multiple studies converged to show that NRAS mutations drive drug resistance and disease: palmitoylation is essential for NRAS-driven leukemogenesis in vivo; NRAS(Q61K) mutations confer BRAF-inhibitor resistance in melanoma by reactivating MAPK via C-RAF.\",\n      \"evidence\": \"Bone marrow transplantation with palmitoylation-deficient NRAS mutants; shRNA knockdown and overexpression in PLX4032-resistant melanoma lines and patient tumors; siRNA of RAF isoforms with pERK readouts\",\n      \"pmids\": [\"20200357\", \"21107323\", \"20818433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Therapeutic strategy to block NRAS palmitoylation in vivo not developed\", \"Relative contributions of C-RAF vs other RAF isoforms to NRAS-driven resistance in patients unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"An isoform-specific effector was identified: wild-type N-Ras (but not K-Ras) engages a cytoplasmic JAK2 pool to drive IL-8 secretion in basal-like breast cancer, linking NRAS to a non-canonical inflammatory signaling axis.\",\n      \"evidence\": \"Co-immunoprecipitation of N-Ras–JAK2, siRNA, overexpression, cytokine assays, xenograft models\",\n      \"pmids\": [\"26166574\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"N-Ras–JAK2 interaction not validated by reciprocal pull-down or structural analysis\", \"Whether this pathway operates in normal breast epithelium unknown\", \"Mechanism of isoform selectivity for JAK2 not determined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: the structural basis for isoform-specific effector engagement (e.g., JAK2, Galectin-3 competition); whether palmitoylation cycling dynamically regulates NRAS signaling output; and whether compartment-specific activation (Golgi S-nitrosylation vs. plasma membrane) recruits distinct effector complexes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of full-length membrane-bound NRAS with effectors\", \"Palmitoylation/depalmitoylation enzymes for NRAS not definitively identified in the primary literature captured here\", \"Relative signaling contributions from Golgi vs. plasma membrane pools not quantified in vivo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 7, 8, 9, 17]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [10, 12, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [10, 11, 12, 13]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4, 15, 16]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 8, 19]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RASA1\",\n      \"JAK2\",\n      \"LGALS3\",\n      \"BRAF\",\n      \"RAF1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"NRAS encodes a membrane-anchored small GTPase that cycles between GDP-bound (inactive) and GTP-bound (active) conformations to transduce mitogenic, differentiation, and survival signals through effectors including C-RAF/MAPK, PI3Kγ/AKT, and JAK2/IL-8 pathways [PMID:20818433, PMID:11136978, PMID:26166574]. Activation is driven by Sos1-mediated nucleotide exchange [PMID:8493579], while intrinsic GTPase activity is accelerated >200-fold by cytoplasmic GAP proteins — a stimulation abolished by oncogenic codon-12, -13, or -61 mutations that lock N-Ras in the GTP-bound state [PMID:2821624, PMID:6616621]. Membrane targeting requires C-terminal farnesylation of Cys186 followed by palmitoylation of upstream cysteines, establishing a constitutive deacylation/reacylation cycle that dynamically partitions N-Ras between the Golgi apparatus and the plasma membrane; both lipid modifications are independently essential for leukemogenic activity [PMID:15705808, PMID:20200357]. Beyond its oncogenic role, wild-type N-Ras restrains proliferation and functions as a tumor suppressor in thymocytes [PMID:12154063], operates in an Rb-dependent differentiation pathway in skeletal muscle [PMID:12861012], and drives cellular senescence and senescence-associated secretory phenotype in cholangiocytes [PMID:24390753].\",\n  \"teleology\": [\n    {\n      \"year\": 1983,\n      \"claim\": \"Identification of N-ras as a transforming oncogene activated by a single codon-61 point mutation established that discrete mutations in a conserved GTPase convert it from proto-oncogene to oncogene, framing the central question of how nucleotide cycling is disrupted.\",\n      \"evidence\": \"Molecular cloning, DNA sequencing, and NIH3T3 focus assay of N-ras from human tumor DNA\",\n      \"pmids\": [\"6616621\", \"6595642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism by which codon-61 mutations alter GTPase activity was unknown\", \"Effector pathways downstream of activated N-Ras were unidentified\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Demonstration that a cytoplasmic GAP stimulates N-Ras GTPase activity >200-fold and that oncogenic mutations render N-Ras refractory to GAP provided the biochemical explanation for why mutant N-Ras is constitutively GTP-loaded.\",\n      \"evidence\": \"In vitro GTPase assay with purified wild-type and mutant N-Ras proteins plus cytoplasmic GAP fraction; Xenopus oocyte maturation readout\",\n      \"pmids\": [\"2821624\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity and structure of the GAP protein (later NF1) were not yet known\", \"No structural explanation for why mutant Ras evades GAP stimulation\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Reversion analysis in HT1080 cells showed that the activated N-ras allele is continuously required to maintain the transformed phenotype in a dosage-dependent manner, establishing that N-Ras is not merely an initiating event but a sustained driver.\",\n      \"evidence\": \"Isolation of revertants with reduced mutant N-ras p21, immunoprecipitation, retransfection\",\n      \"pmids\": [\"3315232\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors mediating N-Ras-dependent transformation were unidentified\", \"Whether oncogene addiction applies in vivo was untested\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Systematic mutagenesis of the CAAX motif revealed that farnesylation of Cys186 is essential for membrane association and biological activity, while palmitoylation of upstream cysteines enhances membrane avidity and transforming potency, defining the dual-lipid modification requirement for N-Ras function.\",\n      \"evidence\": \"Cysteine mutagenesis, biosynthetic labeling, membrane fractionation, and transformation assays\",\n      \"pmids\": [\"2661017\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymes catalyzing palmitoylation and depalmitoylation were unknown\", \"Subcellular site of each modification was not determined\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Identification of hSos1 as the GEF for Ras, linking receptor tyrosine kinase signaling to N-Ras activation via the GRB2–Sos1 complex, completed the upstream activation mechanism.\",\n      \"evidence\": \"In vitro nucleotide exchange assay, yeast complementation, co-immunoprecipitation of Sos1 with GRB2\",\n      \"pmids\": [\"8493579\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Sos1 shows isoform preference among Ras proteins was not addressed\", \"Structural basis for Sos-catalyzed exchange was unresolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"The crystal structure of the Ras–Sos complex revealed that Sos displaces Switch I via an inserted α-helix and distorts Switch II, providing the atomic mechanism of nucleotide exchange applicable to N-Ras.\",\n      \"evidence\": \"X-ray crystallography of H-Ras–Sos at 2.8 Å resolution\",\n      \"pmids\": [\"9690470\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of N-Ras specifically with Sos\", \"Membrane context not captured in crystal structure\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Live-cell imaging showed that N-Ras transits through the Golgi en route to the plasma membrane and that a secondary signal beyond the CAAX motif is required for PM delivery, establishing the endomembrane trafficking itinerary of N-Ras.\",\n      \"evidence\": \"GFP-N-Ras live-cell imaging, brefeldin A treatment, CAAX mutant analysis in COS cells\",\n      \"pmids\": [\"10412982\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Golgi-resident N-Ras signals to effectors was unknown\", \"Identity of the secondary PM-targeting signal was not determined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Bone marrow transplant experiments showed that mutant N-Ras induces myeloproliferative disease and MDS in vivo, validating its role as a leukemia driver and revealing that high apoptosis accompanies transformation, consistent with a requirement for secondary hits.\",\n      \"evidence\": \"Retroviral transduction of N-Ras(G12D) into bone marrow, transplantation into irradiated mice, histopathology and colony assays\",\n      \"pmids\": [\"10068678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cooperating mutations required for full AML were not identified\", \"Effector pathway responsible for the myeloproliferative phenotype was undefined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The crystal structure of Ras–PI3Kγ demonstrated that Ras engages both the RBD and catalytic domain of PI3Kγ via Switch I and II, establishing the structural basis for Ras-dependent PI3K activation as a second major effector arm alongside RAF.\",\n      \"evidence\": \"X-ray crystallography plus in vitro PI3Kγ activation assay with mutagenesis\",\n      \"pmids\": [\"11136978\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether N-Ras and K-Ras engage PI3Kγ with different affinities was not tested\", \"In vivo contribution of PI3K vs. RAF downstream of N-Ras was unresolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"N-ras knockout mice developed thymic lymphomas at elevated rates and wild-type N-Ras overexpression was protective, revealing an unexpected tumor-suppressor function of the proto-oncogene product that counterbalances its oncogenic gain-of-function mutations.\",\n      \"evidence\": \"N-ras−/− and transgenic overexpression mouse models, soft-agar assays\",\n      \"pmids\": [\"12154063\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of tumor suppression (effector pathway, apoptosis vs. senescence) was not defined\", \"Whether this function is tissue-restricted was unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Genetic epistasis in Rb−/−;N-ras−/− double-knockout embryos demonstrated that N-Ras and Rb function in a common skeletal muscle differentiation pathway, and that N-Ras deletion rescues Rb-null differentiation defects without correcting proliferation, separating the differentiation and proliferation arms of Rb signaling.\",\n      \"evidence\": \"Double-knockout mouse embryo histology, immunohistochemistry, MyoD transcriptional assays\",\n      \"pmids\": [\"12861012\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular link between N-Ras and Rb in differentiation was not identified\", \"Whether this epistasis extends beyond skeletal muscle was untested\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Discovery of a constitutive depalmitoylation/repalmitoylation cycle explained how N-Ras maintains dynamic equilibrium between Golgi and plasma membrane: depalmitoylation releases N-Ras to redistribute by default, and repalmitoylation traps it at the Golgi for vesicular transport to the PM.\",\n      \"evidence\": \"FRAP, live imaging, 2-bromopalmitate treatment, dominant-negative DHHC PAT constructs\",\n      \"pmids\": [\"15705808\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific PAT and thioesterase enzymes responsible were not identified\", \"Whether oncogenic mutations alter the acylation cycle kinetics was unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of let-7 miRNA as a negative regulator of RAS expression via 3′ UTR binding sites provided the first post-transcriptional regulatory layer controlling N-Ras abundance, with reduced let-7 in tumors correlating with RAS overexpression.\",\n      \"evidence\": \"3′ UTR reporter assay, let-7 overexpression/Western blot, C. elegans genetic epistasis\",\n      \"pmids\": [\"15766527\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of let-7 to N-Ras vs. K-Ras regulation was not quantified\", \"In vivo therapeutic relevance of let-7 restoration was not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"eNOS-derived NO was shown to selectively activate N-Ras (not K-Ras) at the Golgi of T cells via S-nitrosylation of Cys118, linking the previously identified Golgi-localized pool to a specific activation mechanism and functional outcome — TCR-dependent apoptosis.\",\n      \"evidence\": \"Ras-GTP biosensors in T cells expressing eNOS-GFP, S-nitrosylation assay, C118S mutagenesis, apoptosis assay\",\n      \"pmids\": [\"18641128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether S-nitrosylation of N-Ras occurs in non-immune cell types was unknown\", \"Structural basis for isoform selectivity of Cys118 nitrosylation was not defined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"In vivo demonstration that non-palmitoylatable NRAS mutants completely fail to induce leukemia, while farnesylation-deficient mutants also fail through a distinct mechanism, established that both lipid modifications are independently required for N-Ras oncogenic signaling in hematopoietic cells.\",\n      \"evidence\": \"Retroviral bone marrow transduction/transplantation with palmitoylation-deficient and farnesylation-deficient NRAS mutants\",\n      \"pmids\": [\"20200357\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling differences between palmitoylation-deficient and farnesylation-deficient N-Ras were not characterized\", \"Whether palmitoylation inhibition is therapeutically tractable was untested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identification of activating N-RAS mutations as a mechanism of acquired resistance to BRAF inhibitors in melanoma, mediated by C-RAF-dependent MAPK reactivation, placed N-Ras at the center of therapeutic resistance and established the N-Ras–C-RAF axis as a clinically relevant signaling route.\",\n      \"evidence\": \"Resistant melanoma subline derivation, siRNA knockdown, N-RAS(Q61K) overexpression, patient biopsy validation\",\n      \"pmids\": [\"21107323\", \"20818433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether combined MEK + BRAF inhibition fully overcomes N-RAS-driven resistance was not resolved\", \"Contribution of PI3K signaling to resistance in N-RAS-mutant context was not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Discovery that wild-type N-Ras directly binds and activates cytoplasmic JAK2 to induce IL-8 secretion in basal-like breast cancer — an isoform-specific function not shared by K-Ras — expanded the effector repertoire of N-Ras beyond canonical RAF and PI3K pathways.\",\n      \"evidence\": \"Co-immunoprecipitation of N-Ras with JAK2, IL-8 secretion assays, isoform-specific knockdown/overexpression, in vivo tumor formation\",\n      \"pmids\": [\"26166574\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for N-Ras isoform selectivity in JAK2 binding was not determined\", \"Whether this mechanism operates in non-breast cancer contexts was unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Comparative crystallography revealed that K-Ras, N-Ras, and H-Ras G domains adopt isoform-specific conformational preferences in switch regions despite identical sequences at mutation hotspots, providing a structural rationale for isoform-selective effector coupling and cancer-type associations.\",\n      \"evidence\": \"Comparative X-ray crystallography of wild-type Ras isoform G domains\",\n      \"pmids\": [\"29038336\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional validation that these conformational differences dictate isoform-specific effector selection was lacking\", \"No structure of full-length lipidated N-Ras in a membrane context\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Despite detailed knowledge of N-Ras lipid modification, trafficking, and oncogenic signaling, no isoform-selective direct inhibitor of N-Ras exists; the specific PAT and thioesterase enzymes governing N-Ras palmitoylation cycling remain incompletely defined, and how N-Ras isoform-specific conformational dynamics translate into selective effector engagement in vivo is unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No direct small-molecule inhibitor of N-Ras GTPase\", \"Identity and regulation of the specific DHHC palmitoyltransferase(s) and thioesterase(s) for N-Ras\", \"Full-length membrane-bound N-Ras structure at atomic resolution\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [0, 3, 10]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [15, 16, 29]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [7, 9, 20, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [9, 11, 18]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [11, 18, 22]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 8, 10, 14, 25, 26, 32]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 2, 12, 24, 26]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 6, 16, 27]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13, 22]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [17, 30]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SOS1\", \"GRB2\", \"CRAF\", \"PIK3CG\", \"JAK2\", \"RASA1\"],\n    \"other_free_text\": []\n  }\n}\n```"}