{"gene":"TSNAX","run_date":"2026-04-28T21:43:00","timeline":{"discoveries":[{"year":1997,"finding":"TRAX was identified as a protein partner of Translin via yeast two-hybrid interaction, and found to contain bipartite nuclear targeting sequences in its N-terminal region, suggesting a role in selective nuclear transport of Translin (which lacks nuclear targeting motifs).","method":"Yeast two-hybrid assay; sequence analysis of nuclear targeting signals","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 — single yeast two-hybrid identification with sequence-based functional inference, foundational paper","pmids":["9013868"],"is_preprint":false},{"year":1998,"finding":"Translin and Trax were identified as the protein components of the brain-enriched GS1 single-stranded DNA-binding complex, purified ~500,000-fold and identified by peptide sequencing after UV cross-linking.","method":"Biochemical purification, UV cross-linking, peptide sequencing","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted purification with UV cross-linking and peptide sequencing; direct identification","pmids":["9681436"],"is_preprint":false},{"year":1999,"finding":"TB-RBP (mouse Translin ortholog) forms complexes with Trax, the transitional endoplasmic reticulum ATPase, and cytoskeletal gamma actin in male germ cells; interaction with TER ATPase confirmed by in vitro binding and EM immunocytochemistry; TB-RBP colocalizes with actin in cytoplasm.","method":"Immunoprecipitation, in vitro binding assay, EM immunocytochemistry, confocal microscopy","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal co-IP and in vitro binding with multiple partners, but single lab","pmids":["10471275"],"is_preprint":false},{"year":2000,"finding":"Translin and Trax are somatodendritically localized in neurons (Purkinje cells, hippocampal, neocortical pyramidal neurons), enriched in the cytoplasmic fraction relative to nuclear extracts, supporting a role in dendritic RNA processing.","method":"In situ hybridization, subcellular fractionation, immunohistochemistry","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization by fractionation and immunohistochemistry; replicated across cell types","pmids":["10987859"],"is_preprint":false},{"year":2001,"finding":"Trax does not bind DNA or RNA on its own, forms heterodimers with TB-RBP (Translin) under reducing conditions; the Trax-TB-RBP heterodimer inhibits TB-RBP binding to RNA but enhances TB-RBP binding to specific single-stranded DNA sequences; Trax is predominantly cytoplasmic while TB-RBP shuttles between nucleus and cytoplasm using a nuclear export signal.","method":"In vitro binding assays, yeast two-hybrid, cell fractionation, confocal microscopy, domain mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (in vitro binding, mutagenesis, localization), single lab but comprehensive","pmids":["11278549"],"is_preprint":false},{"year":2002,"finding":"C1D (nuclear matrix protein/DNA-PK activator) interacts specifically with TRAX in a DNA damage-dependent manner; interaction in mammalian cells occurs only following gamma-irradiation; relative expression levels of TRAX and Translin affect their subcellular localization.","method":"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, fluorescent protein imaging","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal yeast and mammalian co-IP with damage-dependent specificity; single lab","pmids":["11801738"],"is_preprint":false},{"year":2002,"finding":"Trax is a component of the native Translin/Trax RNA-binding complex in brain; both GS1 (ssDNA) and protamine-2 (RNA) probes label the same heteromeric Translin/Trax complex as demonstrated by Trax antibody supershift and cross-competition.","method":"Gel-shift assay, antibody supershift, cross-competition, co-transfection in HEK293T cells","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — multiple gel-shift and supershift approaches; single lab","pmids":["12358744"],"is_preprint":false},{"year":2003,"finding":"The Translin/Trax heteromeric complex was identified as the glucose response element binding protein (GRBP) in liver that binds the MLTF-like site within the glucose response element of the L-PK gene; the complex exists as large polymers (~240 kDa nuclear, ~420 kDa cytosolic) with a 2:1 Translin:Trax molar ratio.","method":"Biochemical purification to homogeneity, partial amino acid sequencing, cDNA cloning, gel-shift assay","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1 — purification to homogeneity with sequencing; single lab","pmids":["14642810"],"is_preprint":false},{"year":2004,"finding":"The subcellular localization of TRAX and TB-RBP (Translin) in male germ cells is determined by their relative expression ratios: increased TRAX:TB-RBP ratio drives nuclear localization; elevated TB-RBP levels retain TRAX in the cytoplasm; this requires direct protein-protein interaction between the two.","method":"Immunohistochemistry, Western blot, co-expression in COS-1 cells and TB-RBP null MEFs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — demonstrated causally using null MEFs and co-expression system with multiple cell types","pmids":["15138261"],"is_preprint":false},{"year":2004,"finding":"The Translin/Trax complex recognizes clusters of G residues in RNA rather than the primary sequence of Y and H elements; high affinity binding is preserved after extensive mutation of Y and H elements as long as G clusters are retained.","method":"Truncation and mutagenesis of protamine-2 3'UTR combined with gel-shift binding assays","journal":"Brain research. Molecular brain research","confidence":"Medium","confidence_rationale":"Tier 2 — systematic mutagenesis with binding assay; single lab","pmids":["14741401"],"is_preprint":false},{"year":2005,"finding":"Co-expressed recombinant human Translin and Trax form a stable soluble heteromeric complex (~430 kDa, approximately equimolar subunit ratio by MALDI-TOF-MS) that binds both single- and double-stranded DNA; Trax alone aggregates into insoluble complexes.","method":"Co-expression, MALDI-TOF-MS, gel-shift assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 — reconstituted complex with mass spectrometry characterization; single lab","pmids":["15919079"],"is_preprint":false},{"year":2006,"finding":"In Drosophila, translin is essential for stabilizing the Trax protein (translin null mutants show dramatic loss of Trax); conversely, trax is not required for Translin stability; this asymmetric dependency is conserved throughout evolution.","method":"Translin null mutant generation, trax nonsense mutant isolation, protein level analysis","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic null mutants with direct protein level measurement; conserved finding replicated across organisms","pmids":["17028328"],"is_preprint":false},{"year":2007,"finding":"TRAX regulates GAP-43 transcription and axonal regeneration in rat retinal ganglion cells; siRNA-mediated silencing of Trax at P30 results in significant upregulation of GAP-43 transcript and protein and induces axon outgrowth.","method":"Proteomics identification, siRNA knockdown, transcript and protein analysis","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA KD with defined phenotypic readout; single lab","pmids":["17953615"],"is_preprint":false},{"year":2009,"finding":"C3PO, a complex of Translin and Trax, is a Mg2+-dependent endoribonuclease that promotes RISC activation by removing siRNA passenger strand cleavage products; identified using a reconstituted Drosophila long dsRNA- and duplex siRNA-initiated RISC system with recombinant Dicer-2, R2D2, and Ago2.","method":"In vitro RISC reconstitution with recombinant proteins, biochemical purification, endonuclease assay","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 — full in vitro reconstitution with recombinant proteins; landmark paper with 187 citations","pmids":["19661431"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of human C3PO reveals an asymmetric octamer barrel consisting of six Translin and two TRAX subunits; this asymmetric assembly is critical for endonuclease function, with cleavage occurring at the interior surface; C3PO activates human Ago2-RISC by degrading the Ago2-nicked passenger strand in a Dicer-independent mechanism.","method":"Crystal structure determination, in vitro RISC reconstitution with recombinant hAgo2 and C3PO, genetic depletion in mammalian cells","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus functional reconstitution plus cellular validation; replicated by companion paper","pmids":["21552258"],"is_preprint":false},{"year":2011,"finding":"Crystal structure of Drosophila C3PO formed by truncated Translin and Trax reveals hexameric assembly; Trax adopts the translin fold, possesses catalytic centers essential for C3PO endoRNase activity, and interacts extensively with Translin; catalytic pockets of Trax subunits are located within the interior chamber; cleavage leaves 3'-hydroxyl ends; full-length octameric C3PO characterized by EM and mass spectrometry.","method":"Crystal structure, electron microscopy, mass spectrometry, endoRNase activity assay, mutagenesis of Trax catalytic residues","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with mutagenesis of active site residues and kinetic measurements; multiple orthogonal methods","pmids":["21552261"],"is_preprint":false},{"year":2012,"finding":"C3PO (Translin/Trax complex) functions as an RNase that removes 5' pre-tRNA fragments after RNase P processing of pre-tRNAs in Neurospora crassa; this tRNA processing function is conserved in mouse embryonic fibroblast cells; translin and trax mutants have elevated tRNA levels and protein translation.","method":"Genetic mutant analysis in Neurospora, transcript analysis, mouse embryonic fibroblast cell studies","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 2 — identified endogenous RNA substrates in both fungal and mammalian cells using genetic mutants; two organism systems","pmids":["22773104"],"is_preprint":false},{"year":2012,"finding":"Both Translin and TRAX contribute to nucleic acid binding in the heteromeric complex; UV laser cross-linking identified TRAX-specific DNA contacts; mutation of the B3 motif in TRAX most severely impaired nucleic acid binding of the heteromeric complex.","method":"UV-laser cross-linking with radiolabeled ssDNA, site-directed mutagenesis of B2 and B3 motifs","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1 — UV cross-linking and mutagenesis; single lab","pmids":["22427937"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of Archaeoglobus fulgidus C3PO-like protein reveals an octamer that entirely encapsulates a 13-bp RNA duplex in its inner cavity; Trax-like-subunit catalytic sites target opposite strands separated by 7 base pairs for cleavage, explaining the mechanism of RNA recognition and cleavage.","method":"Crystal structure of C3PO bound to duplex RNA","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with substrate bound; clear mechanistic insight","pmids":["23353787"],"is_preprint":false},{"year":2013,"finding":"PLCβ binds to TRAX (the endonuclease subunit of C3PO) with high affinity; PLCβ binds approximately 5-fold more weakly to Translin than to TRAX, and ~2-fold more strongly to the assembled C3PO octamer; one PLCβ binds per C3PO octamer at an external site without altering TRAX/Translin assembly; PLCβ reduces C3PO hydrolysis rate of siRNA(GAPDH) to match that of the slowly hydrolyzed siRNA(Hsp90), providing mechanistic basis for gene-selective silencing reversal.","method":"Fluorescence-based binding assays, brightness/stoichiometry measurements, in vitro siRNA hydrolysis assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative binding and activity assays with purified proteins; mechanistically explanatory","pmids":["24338081"],"is_preprint":false},{"year":2015,"finding":"TRAX participates in ATM/H2AX-mediated DNA double-strand break repair by interacting with ATM and stabilizing the MRN complex at DSBs; nuclear localization of TRAX (via its NLS) is required for this function; TRAX-null MEFs show impaired ATM and H2AX phosphorylation and increased p53-mediated apoptosis after UV-C or gamma-irradiation.","method":"Co-immunoprecipitation, TRAX-null MEF rescue with WT vs. NLS-mutant TRAX, phosphorylation assays, irradiation experiments","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — null cell rescue with domain mutant plus multiple mechanistic readouts; single lab but comprehensive","pmids":["26096928"],"is_preprint":false},{"year":2016,"finding":"PLCβ association with TRAX is required for NGF-induced PC12 cell differentiation; PLCβ newly synthesized after NGF treatment associates with TRAX rather than Gαq, impacting RNA-induced silencing to switch cells to differentiated state; TRAX knockdown prevents differentiation.","method":"FRET, siRNA knockdown, Ca2+ signaling measurements, siRNA reversal assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — FRET and functional assays; single lab","pmids":["27624933"],"is_preprint":false},{"year":2016,"finding":"Crystal structures of Nanoarchaeum equitans C3PO reveal an open apo form with a substrate entryway, and closed forms with ssRNA and ssDNA captured at the inner cavity; the ssRNA complex represents the catalytic form; mutagenesis and in vitro cleavage assays establish a two-cation-assisted catalytic mechanism shared by eukaryotic C3POs.","method":"Crystal structure determination (apo, ssRNA-bound, ssDNA-bound), mutagenesis, in vitro cleavage assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — multiple crystal structures with mutagenesis and enzymatic validation","pmids":["27596600"],"is_preprint":false},{"year":2017,"finding":"Learning triggers the Translin/Trax RNase complex to degrade microRNAs targeting ACVR1C (activin A receptor type 1C); mice lacking translin/trax show increased disease-related microRNAs targeting ACVR1C after learning, loss of synaptic ACVR1C upregulation, and defects in synaptic tagging and long-term memory; ACVR1C inhibition phenocopies these deficits.","method":"Translin KO mice, microRNA profiling, synaptic tagging electrophysiology, behavioral memory tests, pharmacological ACVR1C inhibition","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — KO mice with multiple orthogonal approaches including electrophysiology, microRNA profiling, and pharmacological rescue","pmids":["28927503"],"is_preprint":false},{"year":2018,"finding":"GSK3β and DISC1 are novel interacting proteins of TRAX; GSK3β binds TRAX and negatively regulates its ability to facilitate non-homologous end-joining (NHEJ) DNA repair; A2A adenosine receptor stimulation inhibits GSK3β, dissociating the TRAX/DISC1/GSK3β complex and enhancing NHEJ via DNA-PK phosphorylation at Thr2609; pharmacological GSK3β inhibition mimics A2AR effects.","method":"Co-immunoprecipitation, PC12 cells, primary mouse neurons, iPSC-derived human neurons, DNA repair assays, pharmacological inhibition","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 — multiple cell systems, co-IP, pharmacological and genetic approaches; mechanistically coherent","pmids":["29298990"],"is_preprint":false},{"year":2018,"finding":"Cryo-EM structures of full-length Drosophila C3PO reveal a closed football-like octamer with a hollow interior; TRAX subunits form dynamic side ports (~25×30 Å) via anti-parallel α1 helices that mediate RNA substrate entry and release; stoichiometry of Drosophila C3PO is TRAX:Translin 4:4.","method":"Crystal structure (2.1 Å), cryo-EM structures at multiple resolutions, SUMO-tagging for stoichiometry determination","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus cryo-EM; multiple conformations captured with SUMO stoichiometry determination","pmids":["29860349"],"is_preprint":false},{"year":2019,"finding":"The Translin/Trax RNase complex degrades miR-181b in aortic vascular smooth muscle cells; TN knockout mice show elevated miR-181b in the aorta and are protected from high-salt-induced vascular stiffness; this identifies the TN/TX complex as a physiologically relevant microRNA-degrading enzyme in the vascular system.","method":"TN KO mice, high-salt water model, pulse wave velocity, tensile testing, microRNA quantification","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with physiological assays and miRNA measurement; causal link established","pmids":["31625778"],"is_preprint":false},{"year":2020,"finding":"Introduction of the E126A mutation in TRAX (Tsnax) abolishes microRNA-degrading activity of the TN/TX complex without impairing TN or TX protein expression or their co-precipitation; mice homozygous for Tsnax(E126A) display selectively elevated microRNAs and robust adiposity phenotype identical to Tsn KO mice, demonstrating that microRNA-degrading activity drives this metabolic phenotype.","method":"Knock-in mutagenesis (E126A), co-precipitation, microRNA profiling, body composition analysis, conditional KO in adipocytes and hepatocytes","journal":"Molecular metabolism","confidence":"High","confidence_rationale":"Tier 1–2 — active-site knock-in mutation with multiple orthogonal phenotypic and molecular validations","pmids":["32408014"],"is_preprint":false},{"year":2020,"finding":"Translin/Trax mediates a selective form of hippocampal long-term plasticity requiring postsynaptic PKA activity; translin KO mice show impaired NMDAR-dependent LTD but normal presynaptic PKA-dependent plasticity and normal mGluR-LTD, distinguishing the TN/TX pathway from FMRP.","method":"Translin KO mice, multiple hippocampal LTP/LTD electrophysiology paradigms, pharmacological dissection","journal":"Molecular brain","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with multiple electrophysiology paradigms; single lab","pmids":["33172471"],"is_preprint":false},{"year":2004,"finding":"Trax co-localizes with Golgi family protein Mea2 in the Golgi complex of mid-late pachytene spermatocytes; this Golgi localization is disrupted by a truncated Mea2 lacking the N-terminal region, suggesting TRAX-Mea2 interaction requires Mea2's N-terminus.","method":"Immunofluorescent staining, Mea2 mutant mouse analysis","journal":"The journal of histochemistry and cytochemistry","confidence":"Low","confidence_rationale":"Tier 3 — localization by immunostaining with partial mechanistic follow-up","pmids":["15314092"],"is_preprint":false}],"current_model":"TSNAX (Trax) forms an asymmetric hetero-octameric complex (C3PO) with six Translin and two Trax subunits, wherein Trax supplies the Mg2+-dependent endoribonuclease active sites within the interior chamber; this RNase complex promotes RISC activation by degrading siRNA passenger strand cleavage products, degrades microRNA precursors to reverse translational silencing at activated synapses (critical for synaptic plasticity and long-term memory), and processes pre-tRNA fragments, while outside the complex Trax also functions as a scaffold that binds ATM to facilitate non-homologous end-joining DNA repair, and the subcellular localization of Trax is regulated by its ratio to Translin (which stabilizes Trax and contains the nuclear export signal) and by interacting partners including DISC1 and GSK3β."},"narrative":{"teleology":[{"year":1997,"claim":"The identification of Trax as a Translin-interacting protein with nuclear targeting sequences established the first molecular partner of Translin and raised the question of whether Trax controls Translin's nuclear import.","evidence":"Yeast two-hybrid screen with Translin bait; sequence analysis of bipartite NLS in Trax N-terminus","pmids":["9013868"],"confidence":"Medium","gaps":["Single yeast two-hybrid interaction without reciprocal validation in mammalian cells","No functional assay for nuclear transport","Endogenous complex not yet characterized"]},{"year":1998,"claim":"Purification of the brain-enriched GS1 complex to near-homogeneity and identification of both Translin and Trax as its components established the endogenous Translin/Trax heteromeric complex as a nucleic-acid-binding entity.","evidence":"~500,000-fold biochemical purification from brain, UV cross-linking, peptide sequencing","pmids":["9681436"],"confidence":"High","gaps":["Enzymatic activity of the complex unknown","Stoichiometry not determined","Physiological RNA/DNA substrates unidentified"]},{"year":2001,"claim":"Demonstration that Trax alone cannot bind nucleic acids but modulates Translin's binding specificity—enhancing ssDNA binding while inhibiting RNA binding—resolved the functional asymmetry within the heterodimer and established that Trax is predominantly cytoplasmic while Translin shuttles between compartments.","evidence":"In vitro binding assays, yeast two-hybrid, cell fractionation, confocal microscopy, and domain mutagenesis","pmids":["11278549"],"confidence":"High","gaps":["Whether Trax contributes catalytic activity was unknown","Mechanism of nucleic acid substrate selectivity unresolved","In vivo relevance of the ssDNA vs RNA binding switch unclear"]},{"year":2004,"claim":"Experiments in Translin-null MEFs and co-expression systems causally demonstrated that the relative expression ratio of Trax to Translin determines their subcellular localization, with excess Translin retaining Trax cytoplasmically.","evidence":"Immunohistochemistry, Western blot, co-expression in COS-1 and TB-RBP-null MEFs","pmids":["15138261"],"confidence":"High","gaps":["How the ratio is physiologically regulated was unknown","Whether localization shift alters specific gene regulation unresolved"]},{"year":2006,"claim":"Genetic analysis in Drosophila revealed an asymmetric stability relationship—Translin is essential for Trax protein stability but not vice versa—establishing an evolutionarily conserved dependency.","evidence":"Translin-null and trax-nonsense Drosophila mutants with protein level analysis","pmids":["17028328"],"confidence":"High","gaps":["Molecular basis for asymmetric stabilization unknown","Whether the stability relationship holds in all mammalian tissues untested"]},{"year":2009,"claim":"Reconstitution of Drosophila RISC from purified components revealed that C3PO (Translin/Trax) is an Mg²⁺-dependent endoribonuclease that activates RISC by degrading passenger strand cleavage products, fundamentally redefining Trax as a catalytic enzyme rather than merely a binding partner.","evidence":"In vitro RISC reconstitution with recombinant Dicer-2, R2D2, Ago2, and purified C3PO; endonuclease assay","pmids":["19661431"],"confidence":"High","gaps":["Whether Trax or Translin supplies the active site was unresolved","Structural basis of the octamer unknown","In vivo endogenous RNA substrates unidentified"]},{"year":2011,"claim":"Crystal structures of human and Drosophila C3PO revealed an asymmetric 6 Translin:2 Trax octameric barrel in which Trax provides the interior catalytic centers, resolving which subunit is the nuclease and explaining why only two active sites exist per octamer.","evidence":"Crystal structures (human and Drosophila), active-site mutagenesis of Trax residues, EM, mass spectrometry, in vitro RISC reconstitution","pmids":["21552258","21552261"],"confidence":"High","gaps":["Mechanism of substrate entry into the chamber unknown","Whether stoichiometry varies across species unresolved","No structure with bound RNA substrate for eukaryotic C3PO"]},{"year":2012,"claim":"Discovery that C3PO degrades 5′ pre-tRNA fragments after RNase P cleavage—conserved from Neurospora to mouse—identified the first endogenous RNA substrate class beyond siRNA passenger strands.","evidence":"Genetic mutants in Neurospora crassa and mouse embryonic fibroblasts; tRNA and translation quantification","pmids":["22773104"],"confidence":"High","gaps":["Full repertoire of endogenous RNA substrates uncharacterized","Selectivity mechanism for tRNA vs other small RNAs unclear"]},{"year":2013,"claim":"Structures of archaeal C3PO bound to duplex RNA revealed that the Trax-like catalytic sites target opposite strands separated by 7 bp within a fully encapsulated substrate, and PLCβ was identified as a high-affinity external binding partner of TRAX that modulates C3PO's hydrolysis rate in a gene-selective manner.","evidence":"Crystal structure of A. fulgidus C3PO–RNA complex; fluorescence binding and siRNA hydrolysis assays with purified PLCβ and C3PO","pmids":["23353787","24338081"],"confidence":"High","gaps":["How PLCβ allosterically slows hydrolysis structurally unresolved","In vivo gene selectivity of PLCβ-C3PO not validated genome-wide"]},{"year":2015,"claim":"TRAX was shown to have a C3PO-independent nuclear function: interacting with ATM and stabilizing the MRN complex at DSBs to promote DNA repair; NLS-dependent nuclear localization of TRAX is required, and TRAX-null cells show impaired ATM/H2AX phosphorylation.","evidence":"Co-immunoprecipitation, TRAX-null MEF rescue with WT vs NLS-mutant TRAX, irradiation experiments","pmids":["26096928"],"confidence":"High","gaps":["Whether TRAX acts as scaffold or has enzymatic function in DNA repair unclear","Relationship between C3PO RNase activity and DNA repair function untested"]},{"year":2017,"claim":"Translin/Trax was demonstrated to degrade specific microRNAs (targeting ACVR1C) upon learning, linking C3PO's RNase activity to synaptic tagging, long-term potentiation, and memory consolidation.","evidence":"Translin KO mice, microRNA profiling, synaptic tagging electrophysiology, behavioral memory tests, pharmacological ACVR1C inhibition","pmids":["28927503"],"confidence":"High","gaps":["How learning signals activate C3PO-mediated microRNA degradation mechanistically unknown","Full set of learning-regulated microRNA substrates not defined"]},{"year":2018,"claim":"GSK3β and DISC1 were identified as TRAX interactors that negatively regulate TRAX-mediated NHEJ; A2A receptor signaling inhibits GSK3β, releasing TRAX from the complex to promote DNA-PK-dependent repair, integrating TRAX into a druggable signaling axis.","evidence":"Co-immunoprecipitation in PC12 cells, primary neurons, and iPSC-derived human neurons; pharmacological GSK3β and A2AR manipulation with DNA repair readouts","pmids":["29298990"],"confidence":"High","gaps":["Whether DISC1 mutations alter TRAX-dependent repair in disease contexts untested","Structural basis for the TRAX/DISC1/GSK3β ternary complex unknown"]},{"year":2018,"claim":"Cryo-EM and crystallography of full-length Drosophila C3PO revealed dynamic side ports formed by TRAX α1 helices that mediate RNA entry into the interior chamber, and established a 4:4 Trax:Translin stoichiometry in Drosophila—differing from the 2:6 human ratio.","evidence":"2.1 Å crystal structure, cryo-EM at multiple resolutions, SUMO-tagging stoichiometry determination","pmids":["29860349"],"confidence":"High","gaps":["Whether stoichiometric differences between species alter substrate selectivity unknown","Side port dynamics not captured in mammalian C3PO structures"]},{"year":2020,"claim":"The E126A active-site knock-in mutation in Trax cleanly separated the RNase function from protein complex integrity, proving that microRNA-degrading activity—not scaffolding—drives the metabolic (adiposity) phenotype of Translin/Trax loss; tissue-specific KO further localized the phenotype.","evidence":"E126A knock-in mice, co-precipitation confirming intact complex, microRNA profiling, body composition, conditional KO in adipocytes and hepatocytes","pmids":["32408014"],"confidence":"High","gaps":["Which specific microRNAs and target mRNAs drive adiposity unresolved","Whether E126A also impairs tRNA fragment processing not tested"]},{"year":null,"claim":"Major open questions include: (1) how synaptic or metabolic signals activate C3PO's microRNA-degrading activity, (2) the full substrate repertoire of C3PO across tissues, (3) structural basis for PLCβ regulation of C3PO, and (4) whether TRAX's DNA repair and RNA silencing functions are coordinated or independent.","evidence":"","pmids":[],"confidence":"Low","gaps":["Signal transduction pathway from neuronal activity to C3PO activation uncharacterized","No unbiased identification of all C3PO RNA substrates in mammalian cells","No structure of PLCβ–C3PO complex","Coordination between TRAX DNA repair and RNase functions untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[13,14,15,16,18,22,25,27]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[6,9,17]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,4,8]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,8,20]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[29]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[13,14,15,16,23,26,27]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[20,24]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[23,28]}],"complexes":["C3PO (Translin/Trax octamer)","TRAX/DISC1/GSK3β complex"],"partners":["TSN","DISC1","GSK3B","PLCB1","ATM","C1D","MEA2"],"other_free_text":[]},"mechanistic_narrative":"TSNAX (Trax) is the catalytic subunit of the C3PO endoribonuclease complex, an asymmetric octameric barrel formed with Translin that degrades RNA substrates within its interior chamber to regulate RNA silencing, tRNA processing, and microRNA turnover in diverse physiological contexts. Within C3PO, Trax supplies the Mg²⁺-dependent, two-cation-assisted catalytic sites that cleave siRNA passenger strand fragments to activate RISC [PMID:19661431, PMID:21552261], degrade pre-tRNA 5′ leader fragments after RNase P processing [PMID:22773104], and turn over specific microRNAs—including those targeting ACVR1C at activated synapses to enable synaptic tagging and long-term memory [PMID:28927503], and miR-181b in vascular smooth muscle to regulate arterial stiffness [PMID:31625778]; the E126A active-site knock-in mutation abolishes all microRNA-degrading activity and phenocopies Translin knockout metabolic defects [PMID:32408014]. Independent of its role in C3PO, nuclear-localized Trax interacts with ATM and stabilizes the MRN complex at DNA double-strand breaks to facilitate non-homologous end-joining repair, a function negatively regulated by GSK3β within a TRAX/DISC1/GSK3β complex [PMID:26096928, PMID:29298990]. Trax protein stability depends on Translin, and the subcellular distribution of the Translin/Trax complex is governed by their expression ratio, with excess Translin retaining Trax in the cytoplasm via its nuclear export signal [PMID:15138261, PMID:17028328]."},"prefetch_data":{"uniprot":{"accession":"Q99598","full_name":"Translin-associated protein X","aliases":["Translin-associated factor X"],"length_aa":290,"mass_kda":33.1,"function":"Acts in combination with TSN as an endonuclease involved in the activation of the RNA-induced silencing complex (RISC). Possible role in spermatogenesis","subcellular_location":"Cytoplasm, perinuclear region; Golgi apparatus; Nucleus","url":"https://www.uniprot.org/uniprotkb/Q99598/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TSNAX","classification":"Not Classified","n_dependent_lines":13,"n_total_lines":1208,"dependency_fraction":0.01076158940397351},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TSNAX","total_profiled":1310},"omim":[{"mim_id":"617246","title":"NSE2 (MMS21) HOMOLOG, SMC5-SMC6 COMPLEX SUMO LIGASE; NSMCE2","url":"https://www.omim.org/entry/617246"},{"mim_id":"607720","title":"TRANSLIN-ASSOCIATED FACTOR X-INTERACTING PROTEIN 1; TSNAXIP1","url":"https://www.omim.org/entry/607720"},{"mim_id":"605210","title":"DISC1 SCAFFOLD PROTEIN; DISC1","url":"https://www.omim.org/entry/605210"},{"mim_id":"602964","title":"TRANSLIN-ASSOCIATED FACTOR X; 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\"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single yeast two-hybrid identification with sequence-based functional inference, foundational paper\",\n      \"pmids\": [\"9013868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Translin and Trax were identified as the protein components of the brain-enriched GS1 single-stranded DNA-binding complex, purified ~500,000-fold and identified by peptide sequencing after UV cross-linking.\",\n      \"method\": \"Biochemical purification, UV cross-linking, peptide sequencing\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted purification with UV cross-linking and peptide sequencing; direct identification\",\n      \"pmids\": [\"9681436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"TB-RBP (mouse Translin ortholog) forms complexes with Trax, the transitional endoplasmic reticulum ATPase, and cytoskeletal gamma actin in male germ cells; interaction with TER ATPase confirmed by in vitro binding and EM immunocytochemistry; TB-RBP colocalizes with actin in cytoplasm.\",\n      \"method\": \"Immunoprecipitation, in vitro binding assay, EM immunocytochemistry, confocal microscopy\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP and in vitro binding with multiple partners, but single lab\",\n      \"pmids\": [\"10471275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Translin and Trax are somatodendritically localized in neurons (Purkinje cells, hippocampal, neocortical pyramidal neurons), enriched in the cytoplasmic fraction relative to nuclear extracts, supporting a role in dendritic RNA processing.\",\n      \"method\": \"In situ hybridization, subcellular fractionation, immunohistochemistry\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by fractionation and immunohistochemistry; replicated across cell types\",\n      \"pmids\": [\"10987859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Trax does not bind DNA or RNA on its own, forms heterodimers with TB-RBP (Translin) under reducing conditions; the Trax-TB-RBP heterodimer inhibits TB-RBP binding to RNA but enhances TB-RBP binding to specific single-stranded DNA sequences; Trax is predominantly cytoplasmic while TB-RBP shuttles between nucleus and cytoplasm using a nuclear export signal.\",\n      \"method\": \"In vitro binding assays, yeast two-hybrid, cell fractionation, confocal microscopy, domain mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (in vitro binding, mutagenesis, localization), single lab but comprehensive\",\n      \"pmids\": [\"11278549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"C1D (nuclear matrix protein/DNA-PK activator) interacts specifically with TRAX in a DNA damage-dependent manner; interaction in mammalian cells occurs only following gamma-irradiation; relative expression levels of TRAX and Translin affect their subcellular localization.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation in mammalian cells, fluorescent protein imaging\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal yeast and mammalian co-IP with damage-dependent specificity; single lab\",\n      \"pmids\": [\"11801738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Trax is a component of the native Translin/Trax RNA-binding complex in brain; both GS1 (ssDNA) and protamine-2 (RNA) probes label the same heteromeric Translin/Trax complex as demonstrated by Trax antibody supershift and cross-competition.\",\n      \"method\": \"Gel-shift assay, antibody supershift, cross-competition, co-transfection in HEK293T cells\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple gel-shift and supershift approaches; single lab\",\n      \"pmids\": [\"12358744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The Translin/Trax heteromeric complex was identified as the glucose response element binding protein (GRBP) in liver that binds the MLTF-like site within the glucose response element of the L-PK gene; the complex exists as large polymers (~240 kDa nuclear, ~420 kDa cytosolic) with a 2:1 Translin:Trax molar ratio.\",\n      \"method\": \"Biochemical purification to homogeneity, partial amino acid sequencing, cDNA cloning, gel-shift assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — purification to homogeneity with sequencing; single lab\",\n      \"pmids\": [\"14642810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The subcellular localization of TRAX and TB-RBP (Translin) in male germ cells is determined by their relative expression ratios: increased TRAX:TB-RBP ratio drives nuclear localization; elevated TB-RBP levels retain TRAX in the cytoplasm; this requires direct protein-protein interaction between the two.\",\n      \"method\": \"Immunohistochemistry, Western blot, co-expression in COS-1 cells and TB-RBP null MEFs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — demonstrated causally using null MEFs and co-expression system with multiple cell types\",\n      \"pmids\": [\"15138261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The Translin/Trax complex recognizes clusters of G residues in RNA rather than the primary sequence of Y and H elements; high affinity binding is preserved after extensive mutation of Y and H elements as long as G clusters are retained.\",\n      \"method\": \"Truncation and mutagenesis of protamine-2 3'UTR combined with gel-shift binding assays\",\n      \"journal\": \"Brain research. Molecular brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis with binding assay; single lab\",\n      \"pmids\": [\"14741401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Co-expressed recombinant human Translin and Trax form a stable soluble heteromeric complex (~430 kDa, approximately equimolar subunit ratio by MALDI-TOF-MS) that binds both single- and double-stranded DNA; Trax alone aggregates into insoluble complexes.\",\n      \"method\": \"Co-expression, MALDI-TOF-MS, gel-shift assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted complex with mass spectrometry characterization; single lab\",\n      \"pmids\": [\"15919079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"In Drosophila, translin is essential for stabilizing the Trax protein (translin null mutants show dramatic loss of Trax); conversely, trax is not required for Translin stability; this asymmetric dependency is conserved throughout evolution.\",\n      \"method\": \"Translin null mutant generation, trax nonsense mutant isolation, protein level analysis\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic null mutants with direct protein level measurement; conserved finding replicated across organisms\",\n      \"pmids\": [\"17028328\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TRAX regulates GAP-43 transcription and axonal regeneration in rat retinal ganglion cells; siRNA-mediated silencing of Trax at P30 results in significant upregulation of GAP-43 transcript and protein and induces axon outgrowth.\",\n      \"method\": \"Proteomics identification, siRNA knockdown, transcript and protein analysis\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with defined phenotypic readout; single lab\",\n      \"pmids\": [\"17953615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"C3PO, a complex of Translin and Trax, is a Mg2+-dependent endoribonuclease that promotes RISC activation by removing siRNA passenger strand cleavage products; identified using a reconstituted Drosophila long dsRNA- and duplex siRNA-initiated RISC system with recombinant Dicer-2, R2D2, and Ago2.\",\n      \"method\": \"In vitro RISC reconstitution with recombinant proteins, biochemical purification, endonuclease assay\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — full in vitro reconstitution with recombinant proteins; landmark paper with 187 citations\",\n      \"pmids\": [\"19661431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of human C3PO reveals an asymmetric octamer barrel consisting of six Translin and two TRAX subunits; this asymmetric assembly is critical for endonuclease function, with cleavage occurring at the interior surface; C3PO activates human Ago2-RISC by degrading the Ago2-nicked passenger strand in a Dicer-independent mechanism.\",\n      \"method\": \"Crystal structure determination, in vitro RISC reconstitution with recombinant hAgo2 and C3PO, genetic depletion in mammalian cells\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus functional reconstitution plus cellular validation; replicated by companion paper\",\n      \"pmids\": [\"21552258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure of Drosophila C3PO formed by truncated Translin and Trax reveals hexameric assembly; Trax adopts the translin fold, possesses catalytic centers essential for C3PO endoRNase activity, and interacts extensively with Translin; catalytic pockets of Trax subunits are located within the interior chamber; cleavage leaves 3'-hydroxyl ends; full-length octameric C3PO characterized by EM and mass spectrometry.\",\n      \"method\": \"Crystal structure, electron microscopy, mass spectrometry, endoRNase activity assay, mutagenesis of Trax catalytic residues\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with mutagenesis of active site residues and kinetic measurements; multiple orthogonal methods\",\n      \"pmids\": [\"21552261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"C3PO (Translin/Trax complex) functions as an RNase that removes 5' pre-tRNA fragments after RNase P processing of pre-tRNAs in Neurospora crassa; this tRNA processing function is conserved in mouse embryonic fibroblast cells; translin and trax mutants have elevated tRNA levels and protein translation.\",\n      \"method\": \"Genetic mutant analysis in Neurospora, transcript analysis, mouse embryonic fibroblast cell studies\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — identified endogenous RNA substrates in both fungal and mammalian cells using genetic mutants; two organism systems\",\n      \"pmids\": [\"22773104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Both Translin and TRAX contribute to nucleic acid binding in the heteromeric complex; UV laser cross-linking identified TRAX-specific DNA contacts; mutation of the B3 motif in TRAX most severely impaired nucleic acid binding of the heteromeric complex.\",\n      \"method\": \"UV-laser cross-linking with radiolabeled ssDNA, site-directed mutagenesis of B2 and B3 motifs\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — UV cross-linking and mutagenesis; single lab\",\n      \"pmids\": [\"22427937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of Archaeoglobus fulgidus C3PO-like protein reveals an octamer that entirely encapsulates a 13-bp RNA duplex in its inner cavity; Trax-like-subunit catalytic sites target opposite strands separated by 7 base pairs for cleavage, explaining the mechanism of RNA recognition and cleavage.\",\n      \"method\": \"Crystal structure of C3PO bound to duplex RNA\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with substrate bound; clear mechanistic insight\",\n      \"pmids\": [\"23353787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PLCβ binds to TRAX (the endonuclease subunit of C3PO) with high affinity; PLCβ binds approximately 5-fold more weakly to Translin than to TRAX, and ~2-fold more strongly to the assembled C3PO octamer; one PLCβ binds per C3PO octamer at an external site without altering TRAX/Translin assembly; PLCβ reduces C3PO hydrolysis rate of siRNA(GAPDH) to match that of the slowly hydrolyzed siRNA(Hsp90), providing mechanistic basis for gene-selective silencing reversal.\",\n      \"method\": \"Fluorescence-based binding assays, brightness/stoichiometry measurements, in vitro siRNA hydrolysis assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative binding and activity assays with purified proteins; mechanistically explanatory\",\n      \"pmids\": [\"24338081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TRAX participates in ATM/H2AX-mediated DNA double-strand break repair by interacting with ATM and stabilizing the MRN complex at DSBs; nuclear localization of TRAX (via its NLS) is required for this function; TRAX-null MEFs show impaired ATM and H2AX phosphorylation and increased p53-mediated apoptosis after UV-C or gamma-irradiation.\",\n      \"method\": \"Co-immunoprecipitation, TRAX-null MEF rescue with WT vs. NLS-mutant TRAX, phosphorylation assays, irradiation experiments\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — null cell rescue with domain mutant plus multiple mechanistic readouts; single lab but comprehensive\",\n      \"pmids\": [\"26096928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PLCβ association with TRAX is required for NGF-induced PC12 cell differentiation; PLCβ newly synthesized after NGF treatment associates with TRAX rather than Gαq, impacting RNA-induced silencing to switch cells to differentiated state; TRAX knockdown prevents differentiation.\",\n      \"method\": \"FRET, siRNA knockdown, Ca2+ signaling measurements, siRNA reversal assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FRET and functional assays; single lab\",\n      \"pmids\": [\"27624933\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structures of Nanoarchaeum equitans C3PO reveal an open apo form with a substrate entryway, and closed forms with ssRNA and ssDNA captured at the inner cavity; the ssRNA complex represents the catalytic form; mutagenesis and in vitro cleavage assays establish a two-cation-assisted catalytic mechanism shared by eukaryotic C3POs.\",\n      \"method\": \"Crystal structure determination (apo, ssRNA-bound, ssDNA-bound), mutagenesis, in vitro cleavage assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple crystal structures with mutagenesis and enzymatic validation\",\n      \"pmids\": [\"27596600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Learning triggers the Translin/Trax RNase complex to degrade microRNAs targeting ACVR1C (activin A receptor type 1C); mice lacking translin/trax show increased disease-related microRNAs targeting ACVR1C after learning, loss of synaptic ACVR1C upregulation, and defects in synaptic tagging and long-term memory; ACVR1C inhibition phenocopies these deficits.\",\n      \"method\": \"Translin KO mice, microRNA profiling, synaptic tagging electrophysiology, behavioral memory tests, pharmacological ACVR1C inhibition\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mice with multiple orthogonal approaches including electrophysiology, microRNA profiling, and pharmacological rescue\",\n      \"pmids\": [\"28927503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GSK3β and DISC1 are novel interacting proteins of TRAX; GSK3β binds TRAX and negatively regulates its ability to facilitate non-homologous end-joining (NHEJ) DNA repair; A2A adenosine receptor stimulation inhibits GSK3β, dissociating the TRAX/DISC1/GSK3β complex and enhancing NHEJ via DNA-PK phosphorylation at Thr2609; pharmacological GSK3β inhibition mimics A2AR effects.\",\n      \"method\": \"Co-immunoprecipitation, PC12 cells, primary mouse neurons, iPSC-derived human neurons, DNA repair assays, pharmacological inhibition\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple cell systems, co-IP, pharmacological and genetic approaches; mechanistically coherent\",\n      \"pmids\": [\"29298990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-EM structures of full-length Drosophila C3PO reveal a closed football-like octamer with a hollow interior; TRAX subunits form dynamic side ports (~25×30 Å) via anti-parallel α1 helices that mediate RNA substrate entry and release; stoichiometry of Drosophila C3PO is TRAX:Translin 4:4.\",\n      \"method\": \"Crystal structure (2.1 Å), cryo-EM structures at multiple resolutions, SUMO-tagging for stoichiometry determination\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus cryo-EM; multiple conformations captured with SUMO stoichiometry determination\",\n      \"pmids\": [\"29860349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The Translin/Trax RNase complex degrades miR-181b in aortic vascular smooth muscle cells; TN knockout mice show elevated miR-181b in the aorta and are protected from high-salt-induced vascular stiffness; this identifies the TN/TX complex as a physiologically relevant microRNA-degrading enzyme in the vascular system.\",\n      \"method\": \"TN KO mice, high-salt water model, pulse wave velocity, tensile testing, microRNA quantification\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with physiological assays and miRNA measurement; causal link established\",\n      \"pmids\": [\"31625778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Introduction of the E126A mutation in TRAX (Tsnax) abolishes microRNA-degrading activity of the TN/TX complex without impairing TN or TX protein expression or their co-precipitation; mice homozygous for Tsnax(E126A) display selectively elevated microRNAs and robust adiposity phenotype identical to Tsn KO mice, demonstrating that microRNA-degrading activity drives this metabolic phenotype.\",\n      \"method\": \"Knock-in mutagenesis (E126A), co-precipitation, microRNA profiling, body composition analysis, conditional KO in adipocytes and hepatocytes\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — active-site knock-in mutation with multiple orthogonal phenotypic and molecular validations\",\n      \"pmids\": [\"32408014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Translin/Trax mediates a selective form of hippocampal long-term plasticity requiring postsynaptic PKA activity; translin KO mice show impaired NMDAR-dependent LTD but normal presynaptic PKA-dependent plasticity and normal mGluR-LTD, distinguishing the TN/TX pathway from FMRP.\",\n      \"method\": \"Translin KO mice, multiple hippocampal LTP/LTD electrophysiology paradigms, pharmacological dissection\",\n      \"journal\": \"Molecular brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple electrophysiology paradigms; single lab\",\n      \"pmids\": [\"33172471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Trax co-localizes with Golgi family protein Mea2 in the Golgi complex of mid-late pachytene spermatocytes; this Golgi localization is disrupted by a truncated Mea2 lacking the N-terminal region, suggesting TRAX-Mea2 interaction requires Mea2's N-terminus.\",\n      \"method\": \"Immunofluorescent staining, Mea2 mutant mouse analysis\",\n      \"journal\": \"The journal of histochemistry and cytochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization by immunostaining with partial mechanistic follow-up\",\n      \"pmids\": [\"15314092\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TSNAX (Trax) forms an asymmetric hetero-octameric complex (C3PO) with six Translin and two Trax subunits, wherein Trax supplies the Mg2+-dependent endoribonuclease active sites within the interior chamber; this RNase complex promotes RISC activation by degrading siRNA passenger strand cleavage products, degrades microRNA precursors to reverse translational silencing at activated synapses (critical for synaptic plasticity and long-term memory), and processes pre-tRNA fragments, while outside the complex Trax also functions as a scaffold that binds ATM to facilitate non-homologous end-joining DNA repair, and the subcellular localization of Trax is regulated by its ratio to Translin (which stabilizes Trax and contains the nuclear export signal) and by interacting partners including DISC1 and GSK3β.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TSNAX (Trax) is the catalytic subunit of the C3PO endoribonuclease complex, an asymmetric octameric barrel formed with Translin that degrades RNA substrates within its interior chamber to regulate RNA silencing, tRNA processing, and microRNA turnover in diverse physiological contexts. Within C3PO, Trax supplies the Mg²⁺-dependent, two-cation-assisted catalytic sites that cleave siRNA passenger strand fragments to activate RISC [PMID:19661431, PMID:21552261], degrade pre-tRNA 5′ leader fragments after RNase P processing [PMID:22773104], and turn over specific microRNAs—including those targeting ACVR1C at activated synapses to enable synaptic tagging and long-term memory [PMID:28927503], and miR-181b in vascular smooth muscle to regulate arterial stiffness [PMID:31625778]; the E126A active-site knock-in mutation abolishes all microRNA-degrading activity and phenocopies Translin knockout metabolic defects [PMID:32408014]. Independent of its role in C3PO, nuclear-localized Trax interacts with ATM and stabilizes the MRN complex at DNA double-strand breaks to facilitate non-homologous end-joining repair, a function negatively regulated by GSK3β within a TRAX/DISC1/GSK3β complex [PMID:26096928, PMID:29298990]. Trax protein stability depends on Translin, and the subcellular distribution of the Translin/Trax complex is governed by their expression ratio, with excess Translin retaining Trax in the cytoplasm via its nuclear export signal [PMID:15138261, PMID:17028328].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"The identification of Trax as a Translin-interacting protein with nuclear targeting sequences established the first molecular partner of Translin and raised the question of whether Trax controls Translin's nuclear import.\",\n      \"evidence\": \"Yeast two-hybrid screen with Translin bait; sequence analysis of bipartite NLS in Trax N-terminus\",\n      \"pmids\": [\"9013868\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single yeast two-hybrid interaction without reciprocal validation in mammalian cells\", \"No functional assay for nuclear transport\", \"Endogenous complex not yet characterized\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Purification of the brain-enriched GS1 complex to near-homogeneity and identification of both Translin and Trax as its components established the endogenous Translin/Trax heteromeric complex as a nucleic-acid-binding entity.\",\n      \"evidence\": \"~500,000-fold biochemical purification from brain, UV cross-linking, peptide sequencing\",\n      \"pmids\": [\"9681436\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymatic activity of the complex unknown\", \"Stoichiometry not determined\", \"Physiological RNA/DNA substrates unidentified\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstration that Trax alone cannot bind nucleic acids but modulates Translin's binding specificity—enhancing ssDNA binding while inhibiting RNA binding—resolved the functional asymmetry within the heterodimer and established that Trax is predominantly cytoplasmic while Translin shuttles between compartments.\",\n      \"evidence\": \"In vitro binding assays, yeast two-hybrid, cell fractionation, confocal microscopy, and domain mutagenesis\",\n      \"pmids\": [\"11278549\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Trax contributes catalytic activity was unknown\", \"Mechanism of nucleic acid substrate selectivity unresolved\", \"In vivo relevance of the ssDNA vs RNA binding switch unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Experiments in Translin-null MEFs and co-expression systems causally demonstrated that the relative expression ratio of Trax to Translin determines their subcellular localization, with excess Translin retaining Trax cytoplasmically.\",\n      \"evidence\": \"Immunohistochemistry, Western blot, co-expression in COS-1 and TB-RBP-null MEFs\",\n      \"pmids\": [\"15138261\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the ratio is physiologically regulated was unknown\", \"Whether localization shift alters specific gene regulation unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Genetic analysis in Drosophila revealed an asymmetric stability relationship—Translin is essential for Trax protein stability but not vice versa—establishing an evolutionarily conserved dependency.\",\n      \"evidence\": \"Translin-null and trax-nonsense Drosophila mutants with protein level analysis\",\n      \"pmids\": [\"17028328\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for asymmetric stabilization unknown\", \"Whether the stability relationship holds in all mammalian tissues untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Reconstitution of Drosophila RISC from purified components revealed that C3PO (Translin/Trax) is an Mg²⁺-dependent endoribonuclease that activates RISC by degrading passenger strand cleavage products, fundamentally redefining Trax as a catalytic enzyme rather than merely a binding partner.\",\n      \"evidence\": \"In vitro RISC reconstitution with recombinant Dicer-2, R2D2, Ago2, and purified C3PO; endonuclease assay\",\n      \"pmids\": [\"19661431\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Trax or Translin supplies the active site was unresolved\", \"Structural basis of the octamer unknown\", \"In vivo endogenous RNA substrates unidentified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Crystal structures of human and Drosophila C3PO revealed an asymmetric 6 Translin:2 Trax octameric barrel in which Trax provides the interior catalytic centers, resolving which subunit is the nuclease and explaining why only two active sites exist per octamer.\",\n      \"evidence\": \"Crystal structures (human and Drosophila), active-site mutagenesis of Trax residues, EM, mass spectrometry, in vitro RISC reconstitution\",\n      \"pmids\": [\"21552258\", \"21552261\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of substrate entry into the chamber unknown\", \"Whether stoichiometry varies across species unresolved\", \"No structure with bound RNA substrate for eukaryotic C3PO\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Discovery that C3PO degrades 5′ pre-tRNA fragments after RNase P cleavage—conserved from Neurospora to mouse—identified the first endogenous RNA substrate class beyond siRNA passenger strands.\",\n      \"evidence\": \"Genetic mutants in Neurospora crassa and mouse embryonic fibroblasts; tRNA and translation quantification\",\n      \"pmids\": [\"22773104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full repertoire of endogenous RNA substrates uncharacterized\", \"Selectivity mechanism for tRNA vs other small RNAs unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Structures of archaeal C3PO bound to duplex RNA revealed that the Trax-like catalytic sites target opposite strands separated by 7 bp within a fully encapsulated substrate, and PLCβ was identified as a high-affinity external binding partner of TRAX that modulates C3PO's hydrolysis rate in a gene-selective manner.\",\n      \"evidence\": \"Crystal structure of A. fulgidus C3PO–RNA complex; fluorescence binding and siRNA hydrolysis assays with purified PLCβ and C3PO\",\n      \"pmids\": [\"23353787\", \"24338081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PLCβ allosterically slows hydrolysis structurally unresolved\", \"In vivo gene selectivity of PLCβ-C3PO not validated genome-wide\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"TRAX was shown to have a C3PO-independent nuclear function: interacting with ATM and stabilizing the MRN complex at DSBs to promote DNA repair; NLS-dependent nuclear localization of TRAX is required, and TRAX-null cells show impaired ATM/H2AX phosphorylation.\",\n      \"evidence\": \"Co-immunoprecipitation, TRAX-null MEF rescue with WT vs NLS-mutant TRAX, irradiation experiments\",\n      \"pmids\": [\"26096928\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TRAX acts as scaffold or has enzymatic function in DNA repair unclear\", \"Relationship between C3PO RNase activity and DNA repair function untested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Translin/Trax was demonstrated to degrade specific microRNAs (targeting ACVR1C) upon learning, linking C3PO's RNase activity to synaptic tagging, long-term potentiation, and memory consolidation.\",\n      \"evidence\": \"Translin KO mice, microRNA profiling, synaptic tagging electrophysiology, behavioral memory tests, pharmacological ACVR1C inhibition\",\n      \"pmids\": [\"28927503\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How learning signals activate C3PO-mediated microRNA degradation mechanistically unknown\", \"Full set of learning-regulated microRNA substrates not defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"GSK3β and DISC1 were identified as TRAX interactors that negatively regulate TRAX-mediated NHEJ; A2A receptor signaling inhibits GSK3β, releasing TRAX from the complex to promote DNA-PK-dependent repair, integrating TRAX into a druggable signaling axis.\",\n      \"evidence\": \"Co-immunoprecipitation in PC12 cells, primary neurons, and iPSC-derived human neurons; pharmacological GSK3β and A2AR manipulation with DNA repair readouts\",\n      \"pmids\": [\"29298990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether DISC1 mutations alter TRAX-dependent repair in disease contexts untested\", \"Structural basis for the TRAX/DISC1/GSK3β ternary complex unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Cryo-EM and crystallography of full-length Drosophila C3PO revealed dynamic side ports formed by TRAX α1 helices that mediate RNA entry into the interior chamber, and established a 4:4 Trax:Translin stoichiometry in Drosophila—differing from the 2:6 human ratio.\",\n      \"evidence\": \"2.1 Å crystal structure, cryo-EM at multiple resolutions, SUMO-tagging stoichiometry determination\",\n      \"pmids\": [\"29860349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether stoichiometric differences between species alter substrate selectivity unknown\", \"Side port dynamics not captured in mammalian C3PO structures\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The E126A active-site knock-in mutation in Trax cleanly separated the RNase function from protein complex integrity, proving that microRNA-degrading activity—not scaffolding—drives the metabolic (adiposity) phenotype of Translin/Trax loss; tissue-specific KO further localized the phenotype.\",\n      \"evidence\": \"E126A knock-in mice, co-precipitation confirming intact complex, microRNA profiling, body composition, conditional KO in adipocytes and hepatocytes\",\n      \"pmids\": [\"32408014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific microRNAs and target mRNAs drive adiposity unresolved\", \"Whether E126A also impairs tRNA fragment processing not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include: (1) how synaptic or metabolic signals activate C3PO's microRNA-degrading activity, (2) the full substrate repertoire of C3PO across tissues, (3) structural basis for PLCβ regulation of C3PO, and (4) whether TRAX's DNA repair and RNA silencing functions are coordinated or independent.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Signal transduction pathway from neuronal activity to C3PO activation uncharacterized\", \"No unbiased identification of all C3PO RNA substrates in mammalian cells\", \"No structure of PLCβ–C3PO complex\", \"Coordination between TRAX DNA repair and RNase functions untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [13, 14, 15, 16, 18, 22, 25, 27]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [6, 9, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 4, 8]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 8, 20]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [29]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [13, 14, 15, 16, 23, 26, 27]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [20, 24]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [23, 28]}\n    ],\n    \"complexes\": [\n      \"C3PO (Translin/Trax octamer)\",\n      \"TRAX/DISC1/GSK3β complex\"\n    ],\n    \"partners\": [\n      \"TSN\",\n      \"DISC1\",\n      \"GSK3B\",\n      \"PLCB1\",\n      \"ATM\",\n      \"C1D\",\n      \"MEA2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}