{"gene":"MX1","run_date":"2026-06-10T05:19:51","timeline":{"discoveries":[{"year":1990,"finding":"Constitutive expression of human MxA in transfected 3T3 cells conferred resistance to influenza A virus and vesicular stomatitis virus (VSV), but not to picornaviruses, togavirus, or herpes simplex virus type 1, establishing MxA as a specific cytoplasmic antiviral effector. The related MxB protein failed to confer resistance, confirming specificity.","method":"Stable transfection of 3T3 cells with MxA or MxB cDNA, followed by viral infection and yield assays","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean cell-based loss/gain-of-function, replicated across multiple virus families, confirmed by MxB negative control","pmids":["2161946"],"is_preprint":false},{"year":1992,"finding":"MxA protein has intrinsic GTPase activity (hydrolyzes GTP→GDP with Km ~0.1 mM, requires Mg2+, ~70 GTP molecules/min/molecule); amino acid substitution within the GTP-binding domain abolished activity. MxA also transiently binds cytoskeletal components including actin and tubulins.","method":"Immunoprecipitation of native MxA with polyclonal antibodies followed by GTPase activity assay; site-directed mutagenesis in transfected CHO cells","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic assay with mutagenesis, replicated in multiple studies","pmids":["1629950"],"is_preprint":false},{"year":1992,"finding":"MxA mutant MxA(R645), carrying a Glu→Arg substitution near the carboxy terminus, retains anti-influenza activity but loses anti-VSV activity, defining the C-terminal region as a determinant of antiviral specificity. When relocated to the nucleus, MxA(R645) blocked influenza primary transcription like murine Mx1, demonstrating that nuclear localization shifts the step of inhibition.","method":"Site-directed mutagenesis; nuclear targeting with heterologous NLS; viral RNA accumulation assays","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis combined with subcellular relocalization and mechanistic assays in one rigorous study","pmids":["1314172"],"is_preprint":false},{"year":1991,"finding":"Mouse Mx1 protein purified from E. coli has GTPase activity; amino acid substitution within the GTP-binding motif reduced activity. Mx1 is homologous to dynamin and yeast Vps1 not only in the GTPase motif but also over ~300 N-terminal amino acids, placing Mx proteins in the dynamin superfamily.","method":"Purification of recombinant Mx1 from E. coli; in vitro GTPase assay; site-directed mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis, foundational biochemical characterization","pmids":["1657964"],"is_preprint":false},{"year":1993,"finding":"Mouse Mx1 self-assembles into polymeric 'horseshoe'-like structures in vitro; GTP treatment induces conversion to larger tightly stacked helical forms. The main self-assembly motif maps to residues 51–99, conserved across Mx family and Mx-related proteins.","method":"Gel filtration; negative-stain electron microscopy of purified Mx1; deletion mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural characterization with EM and mutagenesis, GTP-dependent conformational change directly shown","pmids":["8325879"],"is_preprint":false},{"year":1995,"finding":"Purified recombinant His-MxA directly inhibited VSV in vitro transcription catalyzed by viral RNP complexes; inhibition of both leader RNA and mRNA synthesis indicates interference with transcription initiation. GTP binding (not hydrolysis) was required for anti-VSV activity, as GTP analogs non-hydrolyzable by MxA still abolished VSV inhibition. The C-terminal mutant MxA(E645R), despite normal GTPase activity, showed no inhibition of VSV in vitro transcription.","method":"In vitro VSV transcription assay with purified His-MxA; GTP analog experiments; mutant MxA proteins","journal":"Virology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro reconstitution assay with purified protein, mutagenesis, and analog experiments","pmids":["7831809"],"is_preprint":false},{"year":1995,"finding":"MxA expressed in the cytoplasm inhibits Thogoto virus accumulation of viral RNA and proteins; MxA(R645) remains active against Thogoto virus from both cytoplasm and nucleus, indicating a nuclear step is targeted. MxB had no antiviral activity against Thogoto or Dhori virus. Dhori virus is uniquely resistant to MxA but sensitive to murine Mx1.","method":"Stable transfection with MxA, MxA(R645), or MxB; viral RNA/protein accumulation assays; nuclear-targeted mutant","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean cell-based assays with multiple MxA variants, replicated findings, mechanistic distinction between cytoplasmic and nuclear targeting","pmids":["7745744"],"is_preprint":false},{"year":1995,"finding":"MxA GTPase activity has Km ~260 µM for GTP with turnover ~27 min⁻¹; MxA binds GTP with higher affinity (Kd ~20 µM) than GDP (Kd ~100 µM), suggesting a high proportion of GTP-loaded MxA in vivo. Guanine nucleotides do not co-purify with MxA, and it forms high-molecular-weight oligomers in solution.","method":"Recombinant His-MxA expressed in E. coli; fluorescent nucleotide binding assays; gel filtration","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — detailed in vitro enzymatic and binding characterization with purified recombinant protein","pmids":["7539429"],"is_preprint":false},{"year":1996,"finding":"MxA inhibits representative members of all four genera of Bunyaviridae (Hantaan virus, La Crosse virus, Rift Valley fever virus, sandfly fever virus) by interfering with an early step in virus replication, preventing accumulation of viral transcripts and proteins; viral titers were reduced up to 10⁴-fold.","method":"Stable transfection of Vero cells with MxA cDNA; viral RNA/protein detection; plaque assays","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean cell-based assays across multiple virus families, replicated across independent studies","pmids":["8551631"],"is_preprint":false},{"year":1998,"finding":"MxA interacts with Thogoto virus RNP complexes in a GTPγS-dependent cosedimentation assay, demonstrating the first direct physical interaction between MxA GTPase and a viral target structure. MxA also forms oligomers in vivo as shown by nuclear translocation assay in mammalian cells.","method":"In vitro cosedimentation assay with purified MxA and viral RNP; nuclear translocation assay in intact cells","journal":"Methods (San Diego, Calif.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay with purified components, single lab, two methods","pmids":["9735310"],"is_preprint":false},{"year":1998,"finding":"MxA C-terminus (downstream of aa 564) folds back to interact with an internal domain (aa 372–540); this intramolecular interaction requires Phe382 and Leu612 (part of a leucine zipper). Intermolecular oligomerization uses the same interaction surfaces; the outcome (monomer vs. oligomer) depends on whether the interaction is intra- or intermolecular.","method":"Yeast two-hybrid mapping; mammalian nuclear transport assay; site-directed mutagenesis of Phe382 and Leu612","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — yeast two-hybrid with multiple deletion/point mutants, validated in mammalian cells, two orthogonal assay systems","pmids":["9774462"],"is_preprint":false},{"year":1998,"finding":"Human MxA confers resistance to Semliki Forest virus (SFV), a positive-strand RNA togavirus, reducing viral yield up to 1,700-fold. MxA inhibited accumulation of 49S and 26S SFV RNA, indicating block early in replication. MxA inhibited an SFV replicon lacking structural proteins, showing the target is among viral nonstructural components.","method":"Stable MxA-transfected HEp-2 and U937 cells; SFV replicon transfection; viral RNA northern blot","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — replicon approach dissects structural from nonstructural target, multiple cell lines, clean mechanistic readout","pmids":["9445055"],"is_preprint":false},{"year":2000,"finding":"Monomeric MxA(L612K), which lacks GTPase activity and fails to oligomerize, retains antiviral activity against Thogoto virus and VSV in transient transfection. This indicates that GTP hydrolysis is not required for antiviral function and that MxA monomers are antivirally active. Wild-type MxA high-molecular-weight oligomers serve as a stable intracellular pool from which active monomers are recruited.","method":"Site-directed mutagenesis (L612K); transient transfection in Vero cells; Thogoto minireplicon assay; GTPase activity measurement","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with multiple functional readouts, minireplicon system, single lab","pmids":["10933733"],"is_preprint":false},{"year":2002,"finding":"MxA binds to the La Crosse virus (LACV) nucleocapsid (N) protein via its C-terminal GTPase effector domain (carboxy terminus), sequesters it into perinuclear fibrillary complexes visible by electron microscopy, and thereby prevents incorporation into new virions. The C-terminal mutant MxA(E645R) neither binds N protein nor causes complex formation.","method":"Co-immunoprecipitation; confocal microscopy co-localization; electron microscopy; C-terminal point mutant MxA(E645R)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — co-IP plus EM structural analysis plus mutagenesis, multiple orthogonal methods in one study","pmids":["11880649"],"is_preprint":false},{"year":2002,"finding":"Recombinant MxA protein assembles in vitro at physiological salt into ~20 nm-diameter filamentous structures; in the presence of guanosine nucleotides these rearrange into rings and compact helical arrays, indicating that GTP binding/hydrolysis drives conformational changes critical for antiviral function.","method":"Recombinant MxA production; sedimentation assay; negative-stain electron microscopy; nucleotide titration","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with EM structural characterization, nucleotide-dependent assembly directly demonstrated","pmids":["11847228"],"is_preprint":false},{"year":2004,"finding":"MxA colocalizes with and co-immunoprecipitates the nucleocapsid protein (NP) of Crimean-Congo hemorrhagic fever virus (CCHFV) in perinuclear regions; the E645R mutation in the C-terminal domain abolishes both antiviral activity and NP interaction, confirming C-terminal GED mediates target recognition.","method":"Confocal microscopy; co-immunoprecipitation; C-terminal mutant MxA(E645R); plaque assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP combined with mutagenesis and functional assay, independently validates LACV mechanism for a different nairovirus","pmids":["15047845"],"is_preprint":false},{"year":2005,"finding":"MxA physically interacts with the second ankyrin-like repeat domain of TRPC channels (TRPC1, -3, -4, -5, -6, -7) in yeast two-hybrid, GST pull-down, and co-immunoprecipitation assays. Co-expression of MxA with TRPC6 enhances agonist/OAG-induced Ca²⁺ entry; GTP binding (not hydrolysis) is required for this potentiation. Endogenous MxA upregulated by IFN-α also regulated TRPC6 activity.","method":"Yeast two-hybrid; GST pull-down; co-immunoprecipitation; Ca²⁺ imaging in HEK293T cells; GTP-binding mutants","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — three binding assays plus functional Ca²⁺ readout, single lab","pmids":["15757897"],"is_preprint":false},{"year":2006,"finding":"MxA localizes to a subcompartment of the smooth endoplasmic reticulum positive for Syntaxin17; overexpression causes redistribution of Hook3, mannose-6-phosphate receptor, and Lamp-1 to this MxA-positive compartment, but does not functionally affect endocytosis or the secretory pathway.","method":"Immunofluorescence co-localization with ER/Golgi markers; functional endocytosis assays; live-cell imaging","journal":"Journal of interferon & cytokine research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization by immunofluorescence with multiple markers, functional negative result for secretory pathway, single lab","pmids":["16978069"],"is_preprint":false},{"year":2008,"finding":"Human MxA inhibits African swine fever virus (ASFV), a large double-stranded DNA virus, reducing replication 100-fold. MxA was recruited to perinuclear ASFV assembly sites surrounding virus factories, and a C-terminal MxA mutant lost this activity, extending MxA's known antiviral range to large dsDNA viruses.","method":"Stable MxA-transfected Vero cells; plaque assay; immunofluorescence co-localization with viral assembly sites; mutant MxA","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean cell-based assay, localization data, mutant confirmation, single lab","pmids":["19109387"],"is_preprint":false},{"year":2009,"finding":"MxA inhibits tumor cell motility and invasion in a GTPase-dependent manner. Co-immunoprecipitation showed MxA associates with tubulin, and a GTPase-inactivating mutation abolished both tubulin association and anti-motility activity. In vivo expression reduced hepatic metastases.","method":"Stable MxA expression in PC-3M and LOX cells; in vitro motility/invasion assays; co-immunoprecipitation with tubulin; GTPase mutant; intrasplenic injection mouse model","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus mutagenesis plus in vivo model, single lab, multiple orthogonal methods","pmids":["19297326"],"is_preprint":false},{"year":2010,"finding":"MxA belongs to the dynamin superfamily: crystal structures of its oligomerized stalk (middle domain + GTPase effector domain) revealed the architecture of MxA oligomers and provided structural basis for antiviral function, including formation of ring-like structures around liposomes and liposome tubulation.","method":"Crystal structure determination (X-ray crystallography); liposome tubulation assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with functional validation of liposome interaction, foundational structural study","pmids":["20538602"],"is_preprint":false},{"year":2011,"finding":"MxA directly interacts with cellular RNA helicases UAP56 and URH49 via in vitro binding with purified recombinant proteins; the MxA–UAP56/URH49 complex localizes to the perinuclear region in the cytoplasm. Mouse Mx1 also binds UAP56 and URH49, with the complex forming in distinct nuclear dots. These helicases are required for efficient IAV replication.","method":"Co-immunoprecipitation; in vitro binding with purified recombinant proteins; confocal microscopy co-localization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro binding with purified proteins plus cell-based co-IP and co-localization, single lab","pmids":["21859714"],"is_preprint":false},{"year":2011,"finding":"MxA enhances ER stress signaling in influenza virus-infected cells and promotes tunicamycin-induced cell death. MxA interacts with the ER chaperone BiP, and BiP overexpression reduces MxA-promoted ER stress signaling.","method":"Co-immunoprecipitation of MxA with BiP; ER stress markers (BiP mRNA, XBP1 splicing); cell death assay with tunicamycin","journal":"Journal of interferon & cytokine research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single co-IP, multiple ER stress readouts, single lab","pmids":["21992152"],"is_preprint":false},{"year":2012,"finding":"siRNA knockdown of MxA in IFN-α-treated primate cells abolished IFN-α-mediated suppression of influenza A virus replication. In MxA-stable Vero cells, strand-specific RT-PCR showed that MxA blocked viral replication at a step prior to primary transcription of gRNA into mRNA (suppressed mRNA, cRNA, and gRNA accumulation at 8 h post-infection).","method":"siRNA knockdown of MxA in A549 and LLC-MK2 cells; stable MxA-Vero cells; strand-specific RT-PCR; plaque assay","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 / Strong — RNAi loss-of-function in IFN context plus stable overexpression, strand-specific RNA analysis, replicates earlier findings with new mechanistic detail","pmids":["23152507"],"is_preprint":false},{"year":2014,"finding":"MxA is SUMOylated at Lys48 by SUMO2/3; it also interacts with SUMO1 via its CID-GED domain in a SIM-independent manner and with the SUMO E2 enzyme Ubc9 via its GTPase domain. Mutation of putative SIM motifs (SIMa, SIMb) reduced MxA antiviral activity. However, the SUMOylation-deficient mutant MxA(K48R) retained full antiviral activity against VSV and IAV, indicating SUMOylation itself is not required for antiviral function.","method":"Yeast two-hybrid screen; co-immunoprecipitation; confocal co-localization; site-directed mutagenesis; antiviral activity assays","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus co-IP plus mutagenesis plus functional assay, single lab","pmids":["25447205"],"is_preprint":false},{"year":2015,"finding":"SUMO expression stabilizes MxA protein and increases the level of MxA oligomers in cells, providing a larger intracellular pool of MxA. Depletion of MxA in SUMO-expressing cells abolished SUMO-mediated resistance to VSV, demonstrating that MxA mediates SUMO-induced intrinsic anti-VSV resistance.","method":"Stable SUMO expression; MxA depletion by siRNA; MxA oligomer analysis; VSV replication assay","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi epistasis, oligomer analysis, functional rescue, single lab","pmids":["27170750"],"is_preprint":false},{"year":2015,"finding":"Dimeric MxA (produced by GTPγS-induced disassembly of oligomers) forms stable complexes with influenza A virus nucleoprotein (NP). Dimeric MxA binds NP from MxA-sensitive IAV strains but interacts much more weakly with NP from the MxA-resistant H1N1/1918 PR8 strain. Monomeric MxA restricted IAV replication but could not form stable NP complexes, suggesting dimers are the active NP-binding unit.","method":"GTPγS-induced MxA disassembly; native gel and analytical ultracentrifugation for stoichiometry; co-immunoprecipitation of MxA with viral NP; influenza infection assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of defined MxA oligomeric states, co-IP with NP, multiple mutants, single lab with multiple orthogonal methods","pmids":["26507657"],"is_preprint":false},{"year":2017,"finding":"Single-molecule FRET revealed that MxA GTPase domain–BSE can adopt 'open' or 'closed' conformations; GTP loading shifts preference to the 'closed' state and activates domain movement. Frequent movements between BSE and stalk via hinge 1 occur during GTP hydrolysis cycles, generating torque in the MxA helical polymer that may underlie its mechanochemical antiviral mechanism.","method":"Single-molecule FRET (smFRET) with MxA labeled at defined positions; nucleotide-loading experiments; FRAP","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — single-molecule structural dynamics with multiple nucleotide states, rigorous smFRET methodology, single lab","pmids":["28548099"],"is_preprint":false},{"year":2019,"finding":"MxA forms membraneless metastable cytoplasmic condensates (not ER/Golgi-associated membranes as previously believed); condensates undergo rapid reversible disassembly/reassembly driven by changes in extracellular tonicity. VSV nucleocapsid (N) protein associates with GFP-MxA condensates in infected cells showing antiviral effect. FRAP showed a mobile fraction of ~0.24, consistent with a higher-order network.","method":"Live-cell fluorescence microscopy; FRAP; 1,6-hexanediol treatment; tonicity manipulation; co-localization with VSV N protein","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging with multiple probes and perturbations, FRAP, functional antiviral correlation, single lab; contradicts prior ER localization data","pmids":["31484749"],"is_preprint":false},{"year":2021,"finding":"Rare heterozygous single-nucleotide variants in MX1 were strongly associated with human susceptibility to zoonotic H7N9 influenza. Most identified MxA variants lost antiviral activity against avian IAVs, and nearly all exerted dominant-negative effects on wild-type MxA function, indicating an effective MxA null phenotype in heterozygous carriers.","method":"Whole-genome sequencing case-control study; functional assays in transfected human cell lines with wild-type and variant MxA; dominant-negative co-expression experiments","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — human genetic association validated by cell-based functional assays with multiple variants and dominant-negative tests, single lab with rigorous controls","pmids":["34413236"],"is_preprint":false},{"year":1994,"finding":"Insect cell-purified murine Mx1 and human MxA both hydrolyze GTP with Km ~65 µM (Mx1) and ~62 µM (MxA); activity is strictly Mg2+-dependent and specific for guanine nucleotides. Mx1 is thermolabile at 10°C lower than MxA, and Mx1 shows ~340-fold higher affinity for GTPγS than GDP while MxA shows only ~30-fold difference, indicating distinct enzymatic properties.","method":"Purification of baculovirus-expressed Mx1 and MxA; GTPase kinetics; filter-binding nucleotide affinity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — comparative biochemical characterization of both proteins with purified recombinant material","pmids":["7507489"],"is_preprint":false},{"year":2015,"finding":"IFNλ induces MxA expression in primary human dermal fibroblasts via a MAPK-dependent (p38 and p42/44) but STAT1-independent mechanism; inhibition of MAPK blocked MxA induction in fibroblasts but not in keratinocytes. This defines a cell-type-specific signaling pathway for MxA induction.","method":"IFNλ stimulation of primary dermal fibroblasts and keratinocytes; MAPK inhibitors (p38, MEK); STAT1 phosphorylation western blot; MxA western blot","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological inhibition with mechanistic pathway dissection, two cell types compared, single lab","pmids":["26288353"],"is_preprint":false}],"current_model":"Human MxA (MX1) is an interferon-α/β-induced dynamin-like GTPase that self-assembles into oligomeric rings and helical polymers; it sequesters the nucleocapsid proteins of diverse RNA (and some DNA) viruses—via its C-terminal GTPase effector domain—into perinuclear complexes, directly inhibits viral RNP transcription in vitro in a GTP-binding-dependent manner, undergoes nucleotide-driven conformational changes that generate mechanical force within the polymer, and interacts with cellular cofactors (UAP56/URH49, tubulin, TRPC channels, SUMO machinery) to exert broad antiviral and anti-motility activities; rare dominant-negative MX1 variants in humans increase susceptibility to zoonotic influenza, confirming its essential role in innate antiviral defense."},"narrative":{"mechanistic_narrative":"MX1 (MxA) is an interferon-induced, dynamin-superfamily GTPase that acts as a broad cytoplasmic antiviral effector, restricting RNA and some DNA viruses by recognizing and sequestering their nucleocapsid structures [PMID:2161946, PMID:1657964, PMID:11880649]. It possesses intrinsic, Mg2+-dependent GTPase activity localized to an N-terminal domain whose mutation abolishes catalysis, and it binds GTP with higher affinity than GDP [PMID:1629950, PMID:7539429, PMID:7507489]. MxA self-assembles into oligomeric horseshoe, ring, and helical polymers, an assembly that is remodeled by guanine nucleotides; crystallography of the oligomerized stalk and GTPase effector domain (GED) defines this architecture and its capacity to tubulate liposomes [PMID:8325879, PMID:11847228, PMID:20538602]. Single-molecule analysis shows that GTP loading drives conformational shifts between the GTPase domain and the bundle-signaling element, generating torque within the polymer that underlies a mechanochemical mode of action [PMID:28548099]. Antiviral target recognition is mediated by the C-terminal GED: MxA binds the nucleocapsid proteins of La Crosse, Crimean-Congo hemorrhagic fever, influenza A, and VSV and sequesters them into perinuclear complexes, and the C-terminal E645R mutation abolishes both target binding and restriction [PMID:11880649, PMID:15047845, PMID:26507657]. GTP binding rather than hydrolysis is required for antiviral activity, and MxA monomers/dimers extracted from the oligomeric pool are the active species, with dimers forming the stable nucleoprotein-binding unit [PMID:7831809, PMID:10933733, PMID:26507657]. Through this mechanism MxA blocks viral replication at an early step preceding primary transcription, acting against influenza A, VSV, Thogoto, Bunyaviridae, Semliki Forest virus, and African swine fever virus [PMID:2161946, PMID:8551631, PMID:9445055, PMID:19109387, PMID:23152507]. Beyond direct antiviral defense MxA engages cellular partners including the RNA helicases UAP56/URH49, tubulin, and TRPC channels, and it inhibits tumor cell motility in a GTPase-dependent manner [PMID:15757897, PMID:19297326, PMID:21859714]. Rare heterozygous dominant-negative MX1 variants that abolish antiviral activity increase human susceptibility to zoonotic H7N9 influenza, confirming its essential role in innate antiviral immunity [PMID:34413236].","teleology":[{"year":1990,"claim":"Established that MxA is a specific antiviral effector by showing it confers cytoplasmic resistance to defined virus families but not others, distinguishing it functionally from MxB.","evidence":"Stable transfection of 3T3 cells with MxA or MxB cDNA followed by viral yield assays","pmids":["2161946"],"confidence":"High","gaps":["Did not define the molecular target or mechanism of restriction","Basis of virus-family specificity unknown"]},{"year":1991,"claim":"Placed Mx proteins in the dynamin superfamily and showed they are GTP-hydrolyzing enzymes, providing the biochemical framework for their mechanism.","evidence":"Recombinant mouse Mx1 purified from E. coli, in vitro GTPase assay, site-directed mutagenesis of the GTP-binding motif","pmids":["1657964"],"confidence":"High","gaps":["Did not connect GTPase activity to antiviral function","No structural model"]},{"year":1992,"claim":"Defined GTPase catalysis and the C-terminal region as separable determinants, with the C-terminus controlling antiviral specificity and subcellular site of inhibition.","evidence":"GTPase assays on immunoprecipitated MxA with mutagenesis; nuclear-targeted MxA(R645) and viral RNA accumulation assays","pmids":["1629950","1314172"],"confidence":"High","gaps":["Did not identify the C-terminal binding partner","Mechanism linking localization to inhibition step unresolved"]},{"year":1995,"claim":"Demonstrated that purified MxA directly inhibits viral RNP transcription and that GTP binding, not hydrolysis, is the requirement, dissociating catalytic turnover from antiviral output.","evidence":"In vitro VSV transcription assays with purified His-MxA, GTP analog experiments, and the E645R mutant; fluorescent nucleotide binding kinetics","pmids":["7831809","7539429","7745744"],"confidence":"High","gaps":["The direct viral target structure not yet physically identified","How GTP-bound MxA interferes with initiation mechanistically unclear"]},{"year":1993,"claim":"Showed MxA/Mx1 self-assembly into polymers is nucleotide-responsive, mapping a conserved N-terminal self-assembly motif and revealing GTP-driven conformational reorganization.","evidence":"Gel filtration, negative-stain EM, and deletion/point mutagenesis of purified Mx protein; intramolecular fold-back mapping by yeast two-hybrid","pmids":["8325879","9774462","11847228"],"confidence":"High","gaps":["Functional role of oligomers vs. monomers in restriction unsettled","Polymer geometry not defined at atomic resolution"]},{"year":1996,"claim":"Broadened the antiviral spectrum to all Bunyaviridae genera and positive-strand togaviruses, showing MxA blocks an early replication step prior to transcript accumulation.","evidence":"Stable MxA-transfected Vero/HEp-2/U937 cells, plaque assays, replicon transfection, and northern/RT-PCR RNA analysis","pmids":["8551631","9445055"],"confidence":"High","gaps":["Common molecular target across diverse viruses not yet defined","Whether a single mechanism explains all families unknown"]},{"year":1998,"claim":"Provided the first direct physical evidence that MxA engages a viral RNP target, in a GTP-dependent manner, while clarifying intramolecular versus intermolecular oligomerization surfaces.","evidence":"GTPgammaS-dependent cosedimentation of purified MxA with Thogoto RNP; yeast two-hybrid and mutagenesis of fold-back/leucine-zipper residues","pmids":["9735310","9774462"],"confidence":"Medium","gaps":["Cosedimentation from single lab without reciprocal in-cell validation at the time","Stoichiometry of the MxA-RNP interaction undefined"]},{"year":2000,"claim":"Resolved the active species question by showing GTPase-dead, monomeric MxA(L612K) retains antiviral activity, defining oligomers as a storage pool and monomers as functional.","evidence":"L612K mutagenesis, transient transfection, Thogoto minireplicon assay, and GTPase measurement in Vero cells","pmids":["10933733"],"confidence":"High","gaps":["Apparent tension with later dimer-as-active-unit data","How monomer recruitment from oligomer pool is regulated unknown"]},{"year":2002,"claim":"Identified the mechanism of restriction as C-terminal GED-mediated capture of viral nucleocapsid protein into perinuclear complexes, blocking virion incorporation.","evidence":"Co-IP, confocal and electron microscopy of MxA-LACV N complexes, with the E645R C-terminal mutant; in vitro filament/ring assembly by EM","pmids":["11880649","11847228"],"confidence":"High","gaps":["Whether sequestration is the sole mechanism across all viruses unclear","Structural basis of N-protein recognition not solved"]},{"year":2004,"claim":"Generalized the nucleocapsid-sequestration mechanism to a second nairovirus (CCHFV), confirming the C-terminal GED as the conserved target-recognition determinant.","evidence":"Confocal co-localization, co-IP, plaque assay, and the E645R mutant in CCHFV-infected cells","pmids":["15047845"],"confidence":"High","gaps":["Did not establish whether all sensitive viruses share an identical binding interface"]},{"year":2010,"claim":"Provided the structural basis for MxA oligomerization by solving the stalk/GED architecture and demonstrating membrane-tubulating capacity.","evidence":"X-ray crystallography of the oligomerized MxA stalk plus liposome tubulation assays","pmids":["20538602"],"confidence":"High","gaps":["Full-length nucleotide-bound structure not captured","Direct structural snapshot of MxA bound to a viral target absent"]},{"year":2011,"claim":"Expanded the interactome to cellular RNA helicases UAP56/URH49 and the ER chaperone BiP, linking MxA to host RNA processing and ER stress responses during infection.","evidence":"Co-IP, in vitro binding with purified recombinant proteins, confocal co-localization, and ER stress markers in IAV-infected cells","pmids":["21859714","21992152"],"confidence":"Medium","gaps":["Functional consequence of helicase binding for restriction not isolated","BiP interaction rests on single co-IP"]},{"year":2012,"claim":"Confirmed MxA as the effector of IFN-alpha-mediated influenza suppression by loss-of-function and pinpointed the block to a step before primary transcription.","evidence":"siRNA knockdown in IFN-treated primate cells and strand-specific RT-PCR in stable MxA-Vero cells","pmids":["23152507"],"confidence":"High","gaps":["Precise molecular event blocked before transcription not defined","Relationship to NP sequestration in this assay not directly shown"]},{"year":2015,"claim":"Refined the active antiviral unit as the MxA dimer for nucleoprotein capture and linked strain resistance (1918 PR8) to weakened NP binding; established SUMO as a stabilizer of the MxA oligomer pool.","evidence":"GTPgammaS-induced disassembly, analytical ultracentrifugation, co-IP with IAV NP; SUMO co-expression with MxA oligomer analysis and siRNA epistasis","pmids":["26507657","27170750","25447205"],"confidence":"Medium","gaps":["Reconciliation of dimer-active model with earlier monomer-active data incomplete","SUMOylation per se shown dispensable, leaving its in vivo role unclear"]},{"year":2017,"claim":"Defined the mechanochemical basis of MxA action by showing GTP-driven open/closed conformational cycling generates torque within the helical polymer.","evidence":"Single-molecule FRET with site-specific labeling under different nucleotide states, plus FRAP","pmids":["28548099"],"confidence":"High","gaps":["Direct demonstration that torque disrupts viral RNP not yet shown","Link between polymer mechanics and monomer/dimer active units unresolved"]},{"year":2019,"claim":"Reinterpreted MxA cytoplasmic organization as membraneless, tonicity-responsive condensates that recruit viral nucleocapsid, revising earlier ER/Golgi localization models.","evidence":"Live-cell imaging, FRAP, 1,6-hexanediol and tonicity perturbation, and co-localization with VSV N protein","pmids":["31484749","16978069"],"confidence":"Medium","gaps":["Single-lab condensate model conflicts with prior smooth-ER localization data","Functional necessity of condensate formation for restriction not isolated"]},{"year":2021,"claim":"Established human in vivo relevance by linking dominant-negative MX1 variants to susceptibility to zoonotic H7N9 influenza, confirming MxA as essential for antiviral defense.","evidence":"Whole-genome sequencing case-control study with cell-based functional and dominant-negative co-expression assays of variant MxA","pmids":["34413236"],"confidence":"High","gaps":["Penetrance and contribution to seasonal influenza not addressed","Mechanism of dominant-negative interference at the polymer level not detailed"]},{"year":null,"claim":"How GTP-driven polymer mechanics, the monomer/dimer active species, and condensate formation integrate into a single physical mechanism for disrupting viral RNPs remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No atomic-resolution structure of MxA bound to a viral nucleocapsid","Unified reconciliation of monomer-, dimer-, and condensate-based models lacking","Functional roles of TRPC, tubulin, and SUMO interactions in physiology vs. antiviral defense undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,3,7,30]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[13,15,26]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,19]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,13,21,28]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[17,22]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,23,29]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,18,29]}],"complexes":[],"partners":["UAP56","URH49","TRPC6","BIP","UBC9","TUBULIN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P20591","full_name":"Interferon-induced GTP-binding protein Mx1","aliases":["Interferon-induced protein p78","IFI-78K","Interferon-regulated resistance GTP-binding protein MxA","Myxoma resistance protein 1","Myxovirus resistance protein 1"],"length_aa":662,"mass_kda":75.5,"function":"Interferon-induced dynamin-like GTPase with antiviral activity against a wide range of RNA viruses and some DNA viruses. Its target viruses include negative-stranded RNA viruses and HBV through binding and inactivation of their ribonucleocapsid. May also antagonize reoviridae and asfarviridae replication. Inhibits thogoto virus (THOV) replication by preventing the nuclear import of viral nucleocapsids. Inhibits La Crosse virus (LACV) replication by sequestering viral nucleoprotein in perinuclear complexes, preventing genome amplification, budding, and egress. Inhibits influenza A virus (IAV) replication by decreasing or delaying NP synthesis and by blocking endocytic traffic of incoming virus particles. Enhances ER stress-mediated cell death after influenza virus infection. 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NRAV","url":"https://www.omim.org/entry/616207"},{"mim_id":"615326","title":"INTERFERON, KAPPA; IFNK","url":"https://www.omim.org/entry/615326"},{"mim_id":"612176","title":"MYB-LIKE, SWIRM, AND MPN DOMAINS-CONTAINING PROTEIN 1; MYSM1","url":"https://www.omim.org/entry/612176"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear membrane","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"salivary 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and children with respiratory tract infection.","date":"1996","source":"Acta paediatrica (Oslo, Norway : 1992)","url":"https://pubmed.ncbi.nlm.nih.gov/8640043","citation_count":26,"is_preprint":false},{"pmid":"21992152","id":"PMC_21992152","title":"Interferon-inducible antiviral protein MxA enhances cell death triggered by endoplasmic reticulum stress.","date":"2011","source":"Journal of interferon & cytokine research : the official journal of the International Society for Interferon and Cytokine Research","url":"https://pubmed.ncbi.nlm.nih.gov/21992152","citation_count":26,"is_preprint":false},{"pmid":"14729264","id":"PMC_14729264","title":"Genomic structure, organisation, and promoter analysis of the bovine (Bos taurus) Mx1 gene.","date":"2004","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/14729264","citation_count":26,"is_preprint":false},{"pmid":"30696001","id":"PMC_30696001","title":"Cell-Penetrating Mx1 Enhances Anti-Viral Resistance against Mucosal Influenza Viral 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prostate cancer and regulates cell cycle, invasion and Docetaxel induced apoptosis.","date":"2014","source":"The Prostate","url":"https://pubmed.ncbi.nlm.nih.gov/25327819","citation_count":23,"is_preprint":false},{"pmid":"28561372","id":"PMC_28561372","title":"MxA is a positive regulator of type I IFN signaling in HCV infection.","date":"2017","source":"Journal of medical virology","url":"https://pubmed.ncbi.nlm.nih.gov/28561372","citation_count":22,"is_preprint":false},{"pmid":"32445727","id":"PMC_32445727","title":"MxA suppresses TAK1-IKKα/β-NF-κB mediated inflammatory cytokine production to facilitate Mycobacterium tuberculosis infection.","date":"2020","source":"The Journal of infection","url":"https://pubmed.ncbi.nlm.nih.gov/32445727","citation_count":21,"is_preprint":false},{"pmid":"25408889","id":"PMC_25408889","title":"Production of transgenic pigs over-expressing the antiviral gene Mx1.","date":"2014","source":"Cell regeneration (London, 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immunology","url":"https://pubmed.ncbi.nlm.nih.gov/31465870","citation_count":19,"is_preprint":false},{"pmid":"20309637","id":"PMC_20309637","title":"IL-29 and IFN-α regulate the expression of MxA, 2',5'-OAS and PKR genes in association with the activation of Raf-MEK-ERK and PI3K-AKT signal pathways in HepG2.2.15 cells.","date":"2010","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/20309637","citation_count":19,"is_preprint":false},{"pmid":"11523057","id":"PMC_11523057","title":"Intrahepatic MxA expression is correlated with interferon-alpha expression in chronic and fulminant hepatitis.","date":"2001","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/11523057","citation_count":18,"is_preprint":false},{"pmid":"24085612","id":"PMC_24085612","title":"Association of functional polymorphisms in the MxA gene with susceptibility to enterovirus 71 infection.","date":"2013","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24085612","citation_count":18,"is_preprint":false},{"pmid":"16738935","id":"PMC_16738935","title":"Genomic structure, promoter analysis, and expression of the porcine (Sus scrofa) Mx1 gene.","date":"2006","source":"Immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/16738935","citation_count":17,"is_preprint":false},{"pmid":"30667074","id":"PMC_30667074","title":"Distinguishing pustular psoriasis and acute generalized exanthematous pustulosis on the basis of plasmacytoid dendritic cells and MxA protein.","date":"2019","source":"Journal of cutaneous pathology","url":"https://pubmed.ncbi.nlm.nih.gov/30667074","citation_count":16,"is_preprint":false},{"pmid":"38664395","id":"PMC_38664395","title":"Bat-borne H9N2 influenza virus evades MxA restriction and exhibits efficient replication and transmission in ferrets.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38664395","citation_count":15,"is_preprint":false},{"pmid":"17032164","id":"PMC_17032164","title":"Mx1 and IP-10: biomarkers to measure IFN-beta activity in mice following gene-based delivery.","date":"2006","source":"Journal of interferon & cytokine research : the official journal of the International Society for Interferon and Cytokine Research","url":"https://pubmed.ncbi.nlm.nih.gov/17032164","citation_count":15,"is_preprint":false},{"pmid":"8659121","id":"PMC_8659121","title":"Expression of the human MxA protein is associated with hyperphosphorylation of VSV P protein in human neural Cells.","date":"1996","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/8659121","citation_count":15,"is_preprint":false},{"pmid":"11222725","id":"PMC_11222725","title":"Expression of human MxA protein in mosquito cells interferes with LaCrosse virus replication.","date":"2001","source":"Journal of 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quantification and disability progression in interferon beta-treated multiple sclerosis patients.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24733382","citation_count":14,"is_preprint":false},{"pmid":"32329195","id":"PMC_32329195","title":"Effects of early pregnancy on expression of interferon-stimulated gene 15, STAT1, OAS1, MX1, and IP-10 in ovine liver.","date":"2020","source":"Animal science journal = Nihon chikusan Gakkaiho","url":"https://pubmed.ncbi.nlm.nih.gov/32329195","citation_count":14,"is_preprint":false},{"pmid":"16843495","id":"PMC_16843495","title":"Single nucleotide polymorphisms and functional analysis of MxA promoter region in multiple sclerosis.","date":"2006","source":"Journal of the neurological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/16843495","citation_count":14,"is_preprint":false},{"pmid":"26411585","id":"PMC_26411585","title":"Structural analysis of tumor-related single amino acid mutations in human MxA protein.","date":"2015","source":"Chinese journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26411585","citation_count":14,"is_preprint":false},{"pmid":"24294956","id":"PMC_24294956","title":"Expression of bovine Mx1 protein inhibits the replication of foot-and-mouth disease virus in BHK-21 cells.","date":"2013","source":"Acta virologica","url":"https://pubmed.ncbi.nlm.nih.gov/24294956","citation_count":13,"is_preprint":false},{"pmid":"12858204","id":"PMC_12858204","title":"MxA expression in patients with viral infection after allogeneic stem cell transplantation.","date":"2003","source":"Bone marrow transplantation","url":"https://pubmed.ncbi.nlm.nih.gov/12858204","citation_count":13,"is_preprint":false},{"pmid":"31421628","id":"PMC_31421628","title":"MicroRNA-29b variants and MxA expression change during interferon beta therapy in patients with relapsing-remitting multiple sclerosis.","date":"2019","source":"Multiple sclerosis and related disorders","url":"https://pubmed.ncbi.nlm.nih.gov/31421628","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48946,"output_tokens":7854,"usd":0.132324,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17229,"output_tokens":5200,"usd":0.108073,"stage2_stop_reason":"end_turn"},"total_usd":0.240397,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1990,\n      \"finding\": \"Constitutive expression of human MxA in transfected 3T3 cells conferred resistance to influenza A virus and vesicular stomatitis virus (VSV), but not to picornaviruses, togavirus, or herpes simplex virus type 1, establishing MxA as a specific cytoplasmic antiviral effector. The related MxB protein failed to confer resistance, confirming specificity.\",\n      \"method\": \"Stable transfection of 3T3 cells with MxA or MxB cDNA, followed by viral infection and yield assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean cell-based loss/gain-of-function, replicated across multiple virus families, confirmed by MxB negative control\",\n      \"pmids\": [\"2161946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"MxA protein has intrinsic GTPase activity (hydrolyzes GTP→GDP with Km ~0.1 mM, requires Mg2+, ~70 GTP molecules/min/molecule); amino acid substitution within the GTP-binding domain abolished activity. MxA also transiently binds cytoskeletal components including actin and tubulins.\",\n      \"method\": \"Immunoprecipitation of native MxA with polyclonal antibodies followed by GTPase activity assay; site-directed mutagenesis in transfected CHO cells\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic assay with mutagenesis, replicated in multiple studies\",\n      \"pmids\": [\"1629950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"MxA mutant MxA(R645), carrying a Glu→Arg substitution near the carboxy terminus, retains anti-influenza activity but loses anti-VSV activity, defining the C-terminal region as a determinant of antiviral specificity. When relocated to the nucleus, MxA(R645) blocked influenza primary transcription like murine Mx1, demonstrating that nuclear localization shifts the step of inhibition.\",\n      \"method\": \"Site-directed mutagenesis; nuclear targeting with heterologous NLS; viral RNA accumulation assays\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis combined with subcellular relocalization and mechanistic assays in one rigorous study\",\n      \"pmids\": [\"1314172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Mouse Mx1 protein purified from E. coli has GTPase activity; amino acid substitution within the GTP-binding motif reduced activity. Mx1 is homologous to dynamin and yeast Vps1 not only in the GTPase motif but also over ~300 N-terminal amino acids, placing Mx proteins in the dynamin superfamily.\",\n      \"method\": \"Purification of recombinant Mx1 from E. coli; in vitro GTPase assay; site-directed mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis, foundational biochemical characterization\",\n      \"pmids\": [\"1657964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Mouse Mx1 self-assembles into polymeric 'horseshoe'-like structures in vitro; GTP treatment induces conversion to larger tightly stacked helical forms. The main self-assembly motif maps to residues 51–99, conserved across Mx family and Mx-related proteins.\",\n      \"method\": \"Gel filtration; negative-stain electron microscopy of purified Mx1; deletion mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural characterization with EM and mutagenesis, GTP-dependent conformational change directly shown\",\n      \"pmids\": [\"8325879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Purified recombinant His-MxA directly inhibited VSV in vitro transcription catalyzed by viral RNP complexes; inhibition of both leader RNA and mRNA synthesis indicates interference with transcription initiation. GTP binding (not hydrolysis) was required for anti-VSV activity, as GTP analogs non-hydrolyzable by MxA still abolished VSV inhibition. The C-terminal mutant MxA(E645R), despite normal GTPase activity, showed no inhibition of VSV in vitro transcription.\",\n      \"method\": \"In vitro VSV transcription assay with purified His-MxA; GTP analog experiments; mutant MxA proteins\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro reconstitution assay with purified protein, mutagenesis, and analog experiments\",\n      \"pmids\": [\"7831809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"MxA expressed in the cytoplasm inhibits Thogoto virus accumulation of viral RNA and proteins; MxA(R645) remains active against Thogoto virus from both cytoplasm and nucleus, indicating a nuclear step is targeted. MxB had no antiviral activity against Thogoto or Dhori virus. Dhori virus is uniquely resistant to MxA but sensitive to murine Mx1.\",\n      \"method\": \"Stable transfection with MxA, MxA(R645), or MxB; viral RNA/protein accumulation assays; nuclear-targeted mutant\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean cell-based assays with multiple MxA variants, replicated findings, mechanistic distinction between cytoplasmic and nuclear targeting\",\n      \"pmids\": [\"7745744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"MxA GTPase activity has Km ~260 µM for GTP with turnover ~27 min⁻¹; MxA binds GTP with higher affinity (Kd ~20 µM) than GDP (Kd ~100 µM), suggesting a high proportion of GTP-loaded MxA in vivo. Guanine nucleotides do not co-purify with MxA, and it forms high-molecular-weight oligomers in solution.\",\n      \"method\": \"Recombinant His-MxA expressed in E. coli; fluorescent nucleotide binding assays; gel filtration\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — detailed in vitro enzymatic and binding characterization with purified recombinant protein\",\n      \"pmids\": [\"7539429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"MxA inhibits representative members of all four genera of Bunyaviridae (Hantaan virus, La Crosse virus, Rift Valley fever virus, sandfly fever virus) by interfering with an early step in virus replication, preventing accumulation of viral transcripts and proteins; viral titers were reduced up to 10⁴-fold.\",\n      \"method\": \"Stable transfection of Vero cells with MxA cDNA; viral RNA/protein detection; plaque assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean cell-based assays across multiple virus families, replicated across independent studies\",\n      \"pmids\": [\"8551631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MxA interacts with Thogoto virus RNP complexes in a GTPγS-dependent cosedimentation assay, demonstrating the first direct physical interaction between MxA GTPase and a viral target structure. MxA also forms oligomers in vivo as shown by nuclear translocation assay in mammalian cells.\",\n      \"method\": \"In vitro cosedimentation assay with purified MxA and viral RNP; nuclear translocation assay in intact cells\",\n      \"journal\": \"Methods (San Diego, Calif.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay with purified components, single lab, two methods\",\n      \"pmids\": [\"9735310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MxA C-terminus (downstream of aa 564) folds back to interact with an internal domain (aa 372–540); this intramolecular interaction requires Phe382 and Leu612 (part of a leucine zipper). Intermolecular oligomerization uses the same interaction surfaces; the outcome (monomer vs. oligomer) depends on whether the interaction is intra- or intermolecular.\",\n      \"method\": \"Yeast two-hybrid mapping; mammalian nuclear transport assay; site-directed mutagenesis of Phe382 and Leu612\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — yeast two-hybrid with multiple deletion/point mutants, validated in mammalian cells, two orthogonal assay systems\",\n      \"pmids\": [\"9774462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Human MxA confers resistance to Semliki Forest virus (SFV), a positive-strand RNA togavirus, reducing viral yield up to 1,700-fold. MxA inhibited accumulation of 49S and 26S SFV RNA, indicating block early in replication. MxA inhibited an SFV replicon lacking structural proteins, showing the target is among viral nonstructural components.\",\n      \"method\": \"Stable MxA-transfected HEp-2 and U937 cells; SFV replicon transfection; viral RNA northern blot\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — replicon approach dissects structural from nonstructural target, multiple cell lines, clean mechanistic readout\",\n      \"pmids\": [\"9445055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Monomeric MxA(L612K), which lacks GTPase activity and fails to oligomerize, retains antiviral activity against Thogoto virus and VSV in transient transfection. This indicates that GTP hydrolysis is not required for antiviral function and that MxA monomers are antivirally active. Wild-type MxA high-molecular-weight oligomers serve as a stable intracellular pool from which active monomers are recruited.\",\n      \"method\": \"Site-directed mutagenesis (L612K); transient transfection in Vero cells; Thogoto minireplicon assay; GTPase activity measurement\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with multiple functional readouts, minireplicon system, single lab\",\n      \"pmids\": [\"10933733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MxA binds to the La Crosse virus (LACV) nucleocapsid (N) protein via its C-terminal GTPase effector domain (carboxy terminus), sequesters it into perinuclear fibrillary complexes visible by electron microscopy, and thereby prevents incorporation into new virions. The C-terminal mutant MxA(E645R) neither binds N protein nor causes complex formation.\",\n      \"method\": \"Co-immunoprecipitation; confocal microscopy co-localization; electron microscopy; C-terminal point mutant MxA(E645R)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — co-IP plus EM structural analysis plus mutagenesis, multiple orthogonal methods in one study\",\n      \"pmids\": [\"11880649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Recombinant MxA protein assembles in vitro at physiological salt into ~20 nm-diameter filamentous structures; in the presence of guanosine nucleotides these rearrange into rings and compact helical arrays, indicating that GTP binding/hydrolysis drives conformational changes critical for antiviral function.\",\n      \"method\": \"Recombinant MxA production; sedimentation assay; negative-stain electron microscopy; nucleotide titration\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with EM structural characterization, nucleotide-dependent assembly directly demonstrated\",\n      \"pmids\": [\"11847228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"MxA colocalizes with and co-immunoprecipitates the nucleocapsid protein (NP) of Crimean-Congo hemorrhagic fever virus (CCHFV) in perinuclear regions; the E645R mutation in the C-terminal domain abolishes both antiviral activity and NP interaction, confirming C-terminal GED mediates target recognition.\",\n      \"method\": \"Confocal microscopy; co-immunoprecipitation; C-terminal mutant MxA(E645R); plaque assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP combined with mutagenesis and functional assay, independently validates LACV mechanism for a different nairovirus\",\n      \"pmids\": [\"15047845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MxA physically interacts with the second ankyrin-like repeat domain of TRPC channels (TRPC1, -3, -4, -5, -6, -7) in yeast two-hybrid, GST pull-down, and co-immunoprecipitation assays. Co-expression of MxA with TRPC6 enhances agonist/OAG-induced Ca²⁺ entry; GTP binding (not hydrolysis) is required for this potentiation. Endogenous MxA upregulated by IFN-α also regulated TRPC6 activity.\",\n      \"method\": \"Yeast two-hybrid; GST pull-down; co-immunoprecipitation; Ca²⁺ imaging in HEK293T cells; GTP-binding mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — three binding assays plus functional Ca²⁺ readout, single lab\",\n      \"pmids\": [\"15757897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MxA localizes to a subcompartment of the smooth endoplasmic reticulum positive for Syntaxin17; overexpression causes redistribution of Hook3, mannose-6-phosphate receptor, and Lamp-1 to this MxA-positive compartment, but does not functionally affect endocytosis or the secretory pathway.\",\n      \"method\": \"Immunofluorescence co-localization with ER/Golgi markers; functional endocytosis assays; live-cell imaging\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization by immunofluorescence with multiple markers, functional negative result for secretory pathway, single lab\",\n      \"pmids\": [\"16978069\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Human MxA inhibits African swine fever virus (ASFV), a large double-stranded DNA virus, reducing replication 100-fold. MxA was recruited to perinuclear ASFV assembly sites surrounding virus factories, and a C-terminal MxA mutant lost this activity, extending MxA's known antiviral range to large dsDNA viruses.\",\n      \"method\": \"Stable MxA-transfected Vero cells; plaque assay; immunofluorescence co-localization with viral assembly sites; mutant MxA\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean cell-based assay, localization data, mutant confirmation, single lab\",\n      \"pmids\": [\"19109387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MxA inhibits tumor cell motility and invasion in a GTPase-dependent manner. Co-immunoprecipitation showed MxA associates with tubulin, and a GTPase-inactivating mutation abolished both tubulin association and anti-motility activity. In vivo expression reduced hepatic metastases.\",\n      \"method\": \"Stable MxA expression in PC-3M and LOX cells; in vitro motility/invasion assays; co-immunoprecipitation with tubulin; GTPase mutant; intrasplenic injection mouse model\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus mutagenesis plus in vivo model, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"19297326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MxA belongs to the dynamin superfamily: crystal structures of its oligomerized stalk (middle domain + GTPase effector domain) revealed the architecture of MxA oligomers and provided structural basis for antiviral function, including formation of ring-like structures around liposomes and liposome tubulation.\",\n      \"method\": \"Crystal structure determination (X-ray crystallography); liposome tubulation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with functional validation of liposome interaction, foundational structural study\",\n      \"pmids\": [\"20538602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MxA directly interacts with cellular RNA helicases UAP56 and URH49 via in vitro binding with purified recombinant proteins; the MxA–UAP56/URH49 complex localizes to the perinuclear region in the cytoplasm. Mouse Mx1 also binds UAP56 and URH49, with the complex forming in distinct nuclear dots. These helicases are required for efficient IAV replication.\",\n      \"method\": \"Co-immunoprecipitation; in vitro binding with purified recombinant proteins; confocal microscopy co-localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro binding with purified proteins plus cell-based co-IP and co-localization, single lab\",\n      \"pmids\": [\"21859714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MxA enhances ER stress signaling in influenza virus-infected cells and promotes tunicamycin-induced cell death. MxA interacts with the ER chaperone BiP, and BiP overexpression reduces MxA-promoted ER stress signaling.\",\n      \"method\": \"Co-immunoprecipitation of MxA with BiP; ER stress markers (BiP mRNA, XBP1 splicing); cell death assay with tunicamycin\",\n      \"journal\": \"Journal of interferon & cytokine research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single co-IP, multiple ER stress readouts, single lab\",\n      \"pmids\": [\"21992152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"siRNA knockdown of MxA in IFN-α-treated primate cells abolished IFN-α-mediated suppression of influenza A virus replication. In MxA-stable Vero cells, strand-specific RT-PCR showed that MxA blocked viral replication at a step prior to primary transcription of gRNA into mRNA (suppressed mRNA, cRNA, and gRNA accumulation at 8 h post-infection).\",\n      \"method\": \"siRNA knockdown of MxA in A549 and LLC-MK2 cells; stable MxA-Vero cells; strand-specific RT-PCR; plaque assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — RNAi loss-of-function in IFN context plus stable overexpression, strand-specific RNA analysis, replicates earlier findings with new mechanistic detail\",\n      \"pmids\": [\"23152507\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MxA is SUMOylated at Lys48 by SUMO2/3; it also interacts with SUMO1 via its CID-GED domain in a SIM-independent manner and with the SUMO E2 enzyme Ubc9 via its GTPase domain. Mutation of putative SIM motifs (SIMa, SIMb) reduced MxA antiviral activity. However, the SUMOylation-deficient mutant MxA(K48R) retained full antiviral activity against VSV and IAV, indicating SUMOylation itself is not required for antiviral function.\",\n      \"method\": \"Yeast two-hybrid screen; co-immunoprecipitation; confocal co-localization; site-directed mutagenesis; antiviral activity assays\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus co-IP plus mutagenesis plus functional assay, single lab\",\n      \"pmids\": [\"25447205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SUMO expression stabilizes MxA protein and increases the level of MxA oligomers in cells, providing a larger intracellular pool of MxA. Depletion of MxA in SUMO-expressing cells abolished SUMO-mediated resistance to VSV, demonstrating that MxA mediates SUMO-induced intrinsic anti-VSV resistance.\",\n      \"method\": \"Stable SUMO expression; MxA depletion by siRNA; MxA oligomer analysis; VSV replication assay\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi epistasis, oligomer analysis, functional rescue, single lab\",\n      \"pmids\": [\"27170750\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Dimeric MxA (produced by GTPγS-induced disassembly of oligomers) forms stable complexes with influenza A virus nucleoprotein (NP). Dimeric MxA binds NP from MxA-sensitive IAV strains but interacts much more weakly with NP from the MxA-resistant H1N1/1918 PR8 strain. Monomeric MxA restricted IAV replication but could not form stable NP complexes, suggesting dimers are the active NP-binding unit.\",\n      \"method\": \"GTPγS-induced MxA disassembly; native gel and analytical ultracentrifugation for stoichiometry; co-immunoprecipitation of MxA with viral NP; influenza infection assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of defined MxA oligomeric states, co-IP with NP, multiple mutants, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"26507657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Single-molecule FRET revealed that MxA GTPase domain–BSE can adopt 'open' or 'closed' conformations; GTP loading shifts preference to the 'closed' state and activates domain movement. Frequent movements between BSE and stalk via hinge 1 occur during GTP hydrolysis cycles, generating torque in the MxA helical polymer that may underlie its mechanochemical antiviral mechanism.\",\n      \"method\": \"Single-molecule FRET (smFRET) with MxA labeled at defined positions; nucleotide-loading experiments; FRAP\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — single-molecule structural dynamics with multiple nucleotide states, rigorous smFRET methodology, single lab\",\n      \"pmids\": [\"28548099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MxA forms membraneless metastable cytoplasmic condensates (not ER/Golgi-associated membranes as previously believed); condensates undergo rapid reversible disassembly/reassembly driven by changes in extracellular tonicity. VSV nucleocapsid (N) protein associates with GFP-MxA condensates in infected cells showing antiviral effect. FRAP showed a mobile fraction of ~0.24, consistent with a higher-order network.\",\n      \"method\": \"Live-cell fluorescence microscopy; FRAP; 1,6-hexanediol treatment; tonicity manipulation; co-localization with VSV N protein\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging with multiple probes and perturbations, FRAP, functional antiviral correlation, single lab; contradicts prior ER localization data\",\n      \"pmids\": [\"31484749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Rare heterozygous single-nucleotide variants in MX1 were strongly associated with human susceptibility to zoonotic H7N9 influenza. Most identified MxA variants lost antiviral activity against avian IAVs, and nearly all exerted dominant-negative effects on wild-type MxA function, indicating an effective MxA null phenotype in heterozygous carriers.\",\n      \"method\": \"Whole-genome sequencing case-control study; functional assays in transfected human cell lines with wild-type and variant MxA; dominant-negative co-expression experiments\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human genetic association validated by cell-based functional assays with multiple variants and dominant-negative tests, single lab with rigorous controls\",\n      \"pmids\": [\"34413236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Insect cell-purified murine Mx1 and human MxA both hydrolyze GTP with Km ~65 µM (Mx1) and ~62 µM (MxA); activity is strictly Mg2+-dependent and specific for guanine nucleotides. Mx1 is thermolabile at 10°C lower than MxA, and Mx1 shows ~340-fold higher affinity for GTPγS than GDP while MxA shows only ~30-fold difference, indicating distinct enzymatic properties.\",\n      \"method\": \"Purification of baculovirus-expressed Mx1 and MxA; GTPase kinetics; filter-binding nucleotide affinity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — comparative biochemical characterization of both proteins with purified recombinant material\",\n      \"pmids\": [\"7507489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"IFNλ induces MxA expression in primary human dermal fibroblasts via a MAPK-dependent (p38 and p42/44) but STAT1-independent mechanism; inhibition of MAPK blocked MxA induction in fibroblasts but not in keratinocytes. This defines a cell-type-specific signaling pathway for MxA induction.\",\n      \"method\": \"IFNλ stimulation of primary dermal fibroblasts and keratinocytes; MAPK inhibitors (p38, MEK); STAT1 phosphorylation western blot; MxA western blot\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological inhibition with mechanistic pathway dissection, two cell types compared, single lab\",\n      \"pmids\": [\"26288353\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Human MxA (MX1) is an interferon-α/β-induced dynamin-like GTPase that self-assembles into oligomeric rings and helical polymers; it sequesters the nucleocapsid proteins of diverse RNA (and some DNA) viruses—via its C-terminal GTPase effector domain—into perinuclear complexes, directly inhibits viral RNP transcription in vitro in a GTP-binding-dependent manner, undergoes nucleotide-driven conformational changes that generate mechanical force within the polymer, and interacts with cellular cofactors (UAP56/URH49, tubulin, TRPC channels, SUMO machinery) to exert broad antiviral and anti-motility activities; rare dominant-negative MX1 variants in humans increase susceptibility to zoonotic influenza, confirming its essential role in innate antiviral defense.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MX1 (MxA) is an interferon-induced, dynamin-superfamily GTPase that acts as a broad cytoplasmic antiviral effector, restricting RNA and some DNA viruses by recognizing and sequestering their nucleocapsid structures [#0, #3, #13]. It possesses intrinsic, Mg2+-dependent GTPase activity localized to an N-terminal domain whose mutation abolishes catalysis, and it binds GTP with higher affinity than GDP [#1, #7, #30]. MxA self-assembles into oligomeric horseshoe, ring, and helical polymers, an assembly that is remodeled by guanine nucleotides; crystallography of the oligomerized stalk and GTPase effector domain (GED) defines this architecture and its capacity to tubulate liposomes [#4, #14, #20]. Single-molecule analysis shows that GTP loading drives conformational shifts between the GTPase domain and the bundle-signaling element, generating torque within the polymer that underlies a mechanochemical mode of action [#27]. Antiviral target recognition is mediated by the C-terminal GED: MxA binds the nucleocapsid proteins of La Crosse, Crimean-Congo hemorrhagic fever, influenza A, and VSV and sequesters them into perinuclear complexes, and the C-terminal E645R mutation abolishes both target binding and restriction [#13, #15, #26]. GTP binding rather than hydrolysis is required for antiviral activity, and MxA monomers/dimers extracted from the oligomeric pool are the active species, with dimers forming the stable nucleoprotein-binding unit [#5, #12, #26]. Through this mechanism MxA blocks viral replication at an early step preceding primary transcription, acting against influenza A, VSV, Thogoto, Bunyaviridae, Semliki Forest virus, and African swine fever virus [#0, #8, #11, #18, #23]. Beyond direct antiviral defense MxA engages cellular partners including the RNA helicases UAP56/URH49, tubulin, and TRPC channels, and it inhibits tumor cell motility in a GTPase-dependent manner [#16, #19, #21]. Rare heterozygous dominant-negative MX1 variants that abolish antiviral activity increase human susceptibility to zoonotic H7N9 influenza, confirming its essential role in innate antiviral immunity [#29].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established that MxA is a specific antiviral effector by showing it confers cytoplasmic resistance to defined virus families but not others, distinguishing it functionally from MxB.\",\n      \"evidence\": \"Stable transfection of 3T3 cells with MxA or MxB cDNA followed by viral yield assays\",\n      \"pmids\": [\"2161946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular target or mechanism of restriction\", \"Basis of virus-family specificity unknown\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Placed Mx proteins in the dynamin superfamily and showed they are GTP-hydrolyzing enzymes, providing the biochemical framework for their mechanism.\",\n      \"evidence\": \"Recombinant mouse Mx1 purified from E. coli, in vitro GTPase assay, site-directed mutagenesis of the GTP-binding motif\",\n      \"pmids\": [\"1657964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not connect GTPase activity to antiviral function\", \"No structural model\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Defined GTPase catalysis and the C-terminal region as separable determinants, with the C-terminus controlling antiviral specificity and subcellular site of inhibition.\",\n      \"evidence\": \"GTPase assays on immunoprecipitated MxA with mutagenesis; nuclear-targeted MxA(R645) and viral RNA accumulation assays\",\n      \"pmids\": [\"1629950\", \"1314172\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the C-terminal binding partner\", \"Mechanism linking localization to inhibition step unresolved\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Demonstrated that purified MxA directly inhibits viral RNP transcription and that GTP binding, not hydrolysis, is the requirement, dissociating catalytic turnover from antiviral output.\",\n      \"evidence\": \"In vitro VSV transcription assays with purified His-MxA, GTP analog experiments, and the E645R mutant; fluorescent nucleotide binding kinetics\",\n      \"pmids\": [\"7831809\", \"7539429\", \"7745744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The direct viral target structure not yet physically identified\", \"How GTP-bound MxA interferes with initiation mechanistically unclear\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Showed MxA/Mx1 self-assembly into polymers is nucleotide-responsive, mapping a conserved N-terminal self-assembly motif and revealing GTP-driven conformational reorganization.\",\n      \"evidence\": \"Gel filtration, negative-stain EM, and deletion/point mutagenesis of purified Mx protein; intramolecular fold-back mapping by yeast two-hybrid\",\n      \"pmids\": [\"8325879\", \"9774462\", \"11847228\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of oligomers vs. monomers in restriction unsettled\", \"Polymer geometry not defined at atomic resolution\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Broadened the antiviral spectrum to all Bunyaviridae genera and positive-strand togaviruses, showing MxA blocks an early replication step prior to transcript accumulation.\",\n      \"evidence\": \"Stable MxA-transfected Vero/HEp-2/U937 cells, plaque assays, replicon transfection, and northern/RT-PCR RNA analysis\",\n      \"pmids\": [\"8551631\", \"9445055\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Common molecular target across diverse viruses not yet defined\", \"Whether a single mechanism explains all families unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Provided the first direct physical evidence that MxA engages a viral RNP target, in a GTP-dependent manner, while clarifying intramolecular versus intermolecular oligomerization surfaces.\",\n      \"evidence\": \"GTPgammaS-dependent cosedimentation of purified MxA with Thogoto RNP; yeast two-hybrid and mutagenesis of fold-back/leucine-zipper residues\",\n      \"pmids\": [\"9735310\", \"9774462\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cosedimentation from single lab without reciprocal in-cell validation at the time\", \"Stoichiometry of the MxA-RNP interaction undefined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Resolved the active species question by showing GTPase-dead, monomeric MxA(L612K) retains antiviral activity, defining oligomers as a storage pool and monomers as functional.\",\n      \"evidence\": \"L612K mutagenesis, transient transfection, Thogoto minireplicon assay, and GTPase measurement in Vero cells\",\n      \"pmids\": [\"10933733\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Apparent tension with later dimer-as-active-unit data\", \"How monomer recruitment from oligomer pool is regulated unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified the mechanism of restriction as C-terminal GED-mediated capture of viral nucleocapsid protein into perinuclear complexes, blocking virion incorporation.\",\n      \"evidence\": \"Co-IP, confocal and electron microscopy of MxA-LACV N complexes, with the E645R C-terminal mutant; in vitro filament/ring assembly by EM\",\n      \"pmids\": [\"11880649\", \"11847228\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether sequestration is the sole mechanism across all viruses unclear\", \"Structural basis of N-protein recognition not solved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Generalized the nucleocapsid-sequestration mechanism to a second nairovirus (CCHFV), confirming the C-terminal GED as the conserved target-recognition determinant.\",\n      \"evidence\": \"Confocal co-localization, co-IP, plaque assay, and the E645R mutant in CCHFV-infected cells\",\n      \"pmids\": [\"15047845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish whether all sensitive viruses share an identical binding interface\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Provided the structural basis for MxA oligomerization by solving the stalk/GED architecture and demonstrating membrane-tubulating capacity.\",\n      \"evidence\": \"X-ray crystallography of the oligomerized MxA stalk plus liposome tubulation assays\",\n      \"pmids\": [\"20538602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length nucleotide-bound structure not captured\", \"Direct structural snapshot of MxA bound to a viral target absent\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Expanded the interactome to cellular RNA helicases UAP56/URH49 and the ER chaperone BiP, linking MxA to host RNA processing and ER stress responses during infection.\",\n      \"evidence\": \"Co-IP, in vitro binding with purified recombinant proteins, confocal co-localization, and ER stress markers in IAV-infected cells\",\n      \"pmids\": [\"21859714\", \"21992152\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of helicase binding for restriction not isolated\", \"BiP interaction rests on single co-IP\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Confirmed MxA as the effector of IFN-alpha-mediated influenza suppression by loss-of-function and pinpointed the block to a step before primary transcription.\",\n      \"evidence\": \"siRNA knockdown in IFN-treated primate cells and strand-specific RT-PCR in stable MxA-Vero cells\",\n      \"pmids\": [\"23152507\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise molecular event blocked before transcription not defined\", \"Relationship to NP sequestration in this assay not directly shown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Refined the active antiviral unit as the MxA dimer for nucleoprotein capture and linked strain resistance (1918 PR8) to weakened NP binding; established SUMO as a stabilizer of the MxA oligomer pool.\",\n      \"evidence\": \"GTPgammaS-induced disassembly, analytical ultracentrifugation, co-IP with IAV NP; SUMO co-expression with MxA oligomer analysis and siRNA epistasis\",\n      \"pmids\": [\"26507657\", \"27170750\", \"25447205\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reconciliation of dimer-active model with earlier monomer-active data incomplete\", \"SUMOylation per se shown dispensable, leaving its in vivo role unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the mechanochemical basis of MxA action by showing GTP-driven open/closed conformational cycling generates torque within the helical polymer.\",\n      \"evidence\": \"Single-molecule FRET with site-specific labeling under different nucleotide states, plus FRAP\",\n      \"pmids\": [\"28548099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct demonstration that torque disrupts viral RNP not yet shown\", \"Link between polymer mechanics and monomer/dimer active units unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Reinterpreted MxA cytoplasmic organization as membraneless, tonicity-responsive condensates that recruit viral nucleocapsid, revising earlier ER/Golgi localization models.\",\n      \"evidence\": \"Live-cell imaging, FRAP, 1,6-hexanediol and tonicity perturbation, and co-localization with VSV N protein\",\n      \"pmids\": [\"31484749\", \"16978069\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab condensate model conflicts with prior smooth-ER localization data\", \"Functional necessity of condensate formation for restriction not isolated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established human in vivo relevance by linking dominant-negative MX1 variants to susceptibility to zoonotic H7N9 influenza, confirming MxA as essential for antiviral defense.\",\n      \"evidence\": \"Whole-genome sequencing case-control study with cell-based functional and dominant-negative co-expression assays of variant MxA\",\n      \"pmids\": [\"34413236\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Penetrance and contribution to seasonal influenza not addressed\", \"Mechanism of dominant-negative interference at the polymer level not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GTP-driven polymer mechanics, the monomer/dimer active species, and condensate formation integrate into a single physical mechanism for disrupting viral RNPs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No atomic-resolution structure of MxA bound to a viral nucleocapsid\", \"Unified reconciliation of monomer-, dimer-, and condensate-based models lacking\", \"Functional roles of TRPC, tubulin, and SUMO interactions in physiology vs. antiviral defense undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 3, 7, 30]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [13, 15, 26]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 13, 21, 28]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [17, 22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 23, 29]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 18, 29]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"UAP56\", \"URH49\", \"TRPC6\", \"BiP\", \"Ubc9\", \"tubulin\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":9,"faith_total":9,"faith_pct":100.0}}