{"gene":"GEMIN2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2011,"finding":"Crystal structure (2.5 Å) of Gemin2 bound to the SmD1/D2/F/E/G pentamer and SMN's Gemin2-binding domain revealed that Gemin2 adopts an extended conformation wrapping around the crescent-shaped pentamer, interacting with all five Sm proteins, gripping both sides and the outer perimeter, and reaching into the RNA-binding pocket to prevent RNA binding. An SMA-causing mutation in an SMN helix that mediates Gemin2 binding abrogates SMN-Gemin2 interaction.","method":"X-ray crystallography (2.5 Å), structure-guided mutagenesis, biochemical binding assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution crystal structure with mutagenesis validation, published in high-impact journal, single rigorous study with multiple orthogonal methods","pmids":["21816274"],"is_preprint":false},{"year":2020,"finding":"Crystallographic and biochemical analyses showed that Gemin2 constrains the horseshoe-shaped SmD1/D2/F/E/G pentamer in a narrow state via negative cooperativity with RNA, enhancing RNA specificity. RNA binding inside the pentamer widens it, allosterically releasing Gemin2/SMN; subsequent SmD3/B joining further facilitates Gemin2/SMN release. This reveals the mechanism of snRNA selection and SMN complex release during snRNP assembly.","method":"X-ray crystallography, biochemical binding and assembly assays, mutational analysis","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with biochemical assays, single lab but multiple orthogonal methods","pmids":["31799625"],"is_preprint":false},{"year":2012,"finding":"NMR solution structure of Gemin2 bound to the Gemin2-binding domain of SMN revealed how Gemin2 is stabilized by SMN and identified conserved SMN residues at the binding interface. Notably, several conserved SMN residues including sites of two SMA patient mutations are not required for Gemin2 binding but form a conserved SMN/Gemin2 surface likely important for snRNP assembly.","method":"NMR spectroscopy, biochemical binding assays","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structure with functional mutagenesis validation, single lab, multiple methods","pmids":["22607171"],"is_preprint":false},{"year":2010,"finding":"Human GEMIN2 directly binds RAD51 and stimulates RAD51-mediated homologous pairing by inhibiting RAD51 dissociation from DNA and enhancing the RAD51-mediated strand exchange when RPA is pre-bound to ssDNA. Depletion of GEMIN2 in chicken DT40 cells and human cells reduced homologous recombination efficiency and decreased RAD51 subnuclear foci formation, establishing GEMIN2 as a novel RAD51 mediator.","method":"Biochemical binding assays (direct binding), in vitro recombination assays, siRNA knockdown, RAD51 focus formation assay, GEMIN2-knockout cell line","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal biochemical assays plus genetic loss-of-function with defined cellular phenotype, single lab, multiple orthogonal methods","pmids":["20403813"],"is_preprint":false},{"year":2011,"finding":"The purified SMN-GEMIN2 fusion complex stimulates RAD51-mediated homologous pairing more efficiently than GEMIN2 alone. SMN-GEMIN2, but not GEMIN2 alone, possesses DNA-binding activity and significantly stimulates secondary duplex DNA capture by the RAD51-ssDNA complex during homologous pairing, establishing a role for the SMN-GEMIN2 complex in homologous recombination.","method":"Protein purification, in vitro recombination and DNA-binding assays, complementation of GEMIN2-knockout cells","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified proteins, multiple biochemical assays, cell-based complementation, single lab","pmids":["21732698"],"is_preprint":false},{"year":2007,"finding":"Gemin2 undergoes self-association (homodimerization) detected by mammalian two-hybrid and in vitro pull-down assays. Gemin2 stabilizes SMN oligomer formation; in vitro dissociation assays showed that Gemin2 presence stabilizes SMN amino-terminal self-interaction. Gemin2 knockdown by siRNA drastically decreases SMN oligomer formation and snRNP assembly activity.","method":"Mammalian two-hybrid, in vitro pull-down, in vitro dissociation assay, siRNA knockdown, snRNP assembly assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical and cell-based methods, single lab","pmids":["17308308"],"is_preprint":false},{"year":2000,"finding":"Depletion of SMN protein in DT40 cells leads to a significant decrease in Gemin2 protein levels, demonstrating that SMN stabilizes Gemin2 and that SMN and Gemin2 form a stable complex in vivo.","method":"Tet-repressible SMN expression system in DT40 cells (homologous recombination-based SMN gene disruption), western blotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function system with direct protein-level readout, single lab, clean experimental system","pmids":["11121410"],"is_preprint":false},{"year":2002,"finding":"In vivo genetic evidence that reduced Smn/Gemin2 protein levels disturb U snRNP assembly (indicated by reduced nuclear accumulation of Sm proteins) and that this correlates with enhanced motoneuron degeneration in Gemin2(+/-)/Smn(+/-) double heterozygous mice.","method":"Mouse gene targeting (Gemin2 heterozygous knockout), Sm protein localization by immunofluorescence, histological assessment of motoneuron degeneration","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with defined molecular and cellular phenotypes, single lab","pmids":["12091709"],"is_preprint":false},{"year":2006,"finding":"GEMIN2/SIP1 binds HIV-1 integrase (IN), identified by yeast two-hybrid, and siRNA depletion of Gemin2 in human monocyte-derived macrophages dramatically reduces HIV-1 infection and viral cDNA synthesis without affecting expression from integrated proviral DNA. Co-immunoprecipitation suggested Gemin2 interacts with the incoming viral genome through IN.","method":"Yeast two-hybrid, siRNA knockdown, HIV-1 infection assay, co-immunoprecipitation with FLAG-tagged Gemin2","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus co-IP plus functional siRNA knockdown, single lab, multiple methods","pmids":["16731905"],"is_preprint":false},{"year":2009,"finding":"Gemin2/SIP1 stabilizes HIV-1 integrase (IN) multimer formation by preventing proteasome-mediated degradation of IN. The SMN-interacting protein 1 (SIP1/Gemin2)-IN interaction promotes assembly of IN and reverse transcriptase on viral RNA, augmenting reverse transcriptase activity in vitro. Synthetic peptides mimicking IN binding motifs that disrupt IN-SIP1 interaction abrogated reverse transcription in vitro and in vivo.","method":"In vitro reverse transcription assay, siRNA knockdown, co-immunoprecipitation, synthetic peptide inhibition, proteasome inhibitor experiments","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical and cell-based methods, single lab, follows up on prior yeast two-hybrid identification","pmids":["19915660"],"is_preprint":false},{"year":2015,"finding":"SMN·Gemin2 complexes from humans form oligomers spanning the dimer-to-octamer range, with the YG box oligomerization domain of SMN being both necessary and sufficient for oligomerization. Fission yeast SMN·Gemin2 exists as a dimer-tetramer equilibrium (Kd = 1.0 ± 0.9 µM). A 1.9 Å crystal structure of the yeast SMN YG box confirmed high structural conservation with the human ortholog. Disulfide cross-linking showed SMN tetramers form by self-association of stable dimers.","method":"X-ray crystallography (1.9 Å), analytical ultracentrifugation, disulfide cross-linking, size-exclusion chromatography","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with multiple biophysical methods, single lab","pmids":["26092730"],"is_preprint":false},{"year":2010,"finding":"Drosophila Gemin2 (CG10419) colocalizes with SMN in cytoplasmic U bodies in Drosophila egg chambers. Gemin2 is excluded from P bodies but consistently found associated with them due to the invariant U body–P body association.","method":"Immunofluorescence/confocal microscopy in Drosophila egg chambers","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct subcellular localization by immunofluorescence in a model organism, replicated for multiple Gemin proteins","pmids":["20452345"],"is_preprint":false},{"year":2010,"finding":"SMN, Gemin2 and Gemin3 associate with beta-actin mRNA in cytoplasmic complexes in human SHSY5Y neuroblastoma cells, providing the first direct evidence of beta-actin mRNA in SMN cytoplasmic complexes.","method":"Targeted mRNA screen (immunoprecipitation of SMN/Gemin2/Gemin3 complexes followed by RT-PCR for beta-actin mRNA)","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct co-immunoprecipitation of mRNA with Gemin2 complex, single lab, single method","pmids":["20620147"],"is_preprint":false},{"year":2008,"finding":"Gemin2 knockdown specifically in motoneurons in zebrafish using two separate approaches (cell-autonomous knockdown) did not cause motor axon outgrowth defects, in contrast to SMN knockdown. Motor axon defects observed with global Gemin2 morpholino knockdown were secondary to body morphology defects, as shown by wild-type neuron transplantation experiments. This establishes that Gemin2 reduction does not directly cause motor axon phenotypes, dissociating snRNP function from SMN's motor axon role.","method":"Morpholino knockdown in zebrafish, cell-autonomous knockdown in motoneurons, neuronal transplantation assay, motor axon imaging","journal":"Developmental neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic approaches with clear negative result compared to SMN, single lab, epistatic dissection","pmids":["18000835"],"is_preprint":false},{"year":2023,"finding":"p70S6 kinase (ribosomal protein S6 kinase beta-1, p70S6K) directly binds and phosphorylates Gemin2. The phosphorylation status of Gemin2 influences the capacity of the SMN complex to condense in Cajal bodies in vivo. p70S6K knockdown reduced the number of Cajal bodies and inhibited in vivo UsnRNP synthesis. Gemin2 also functions as a connecting element between the 6S complex and the SMN complex, as shown by size exclusion chromatography.","method":"Co-immunoprecipitation, in vitro kinase assay (p70S6K phosphorylating Gemin2), size exclusion chromatography, siRNA knockdown of p70S6K, Cajal body counting by immunofluorescence","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding and phosphorylation demonstrated biochemically with functional readout (Cajal body condensation), single lab, multiple methods","pmids":["37958537"],"is_preprint":false},{"year":2006,"finding":"C. elegans SMI-1 (orthologue of Gemin2) directly interacts with SMN-1 protein, shown by yeast two-hybrid and demonstrated conservation of the SMN-Gemin2 interaction in C. elegans.","method":"Yeast two-hybrid, cloning and sequencing of smi-1, RNAi phenotypic analysis","journal":"Invertebrate neuroscience : IN","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single method (yeast two-hybrid) for direct interaction, single lab","pmids":["16964508"],"is_preprint":false},{"year":2016,"finding":"In S. cerevisiae, the Gemin2 homolog Brr1 is required for snRNP Sm ring assembly in specific Sm protein mutant backgrounds. The N-terminal segment of Brr1 (amino acids 24-47) corresponding to the Gemin2 α1 helix that interacts with SmF, and a C-terminal peptide (336QKDLIE341) that in Gemin2 interacts with SmD2, are essential for Brr1 function. Specific SmE, SmF, SmD2, and SmD1 subunit mutations are synthetically lethal with brr1Δ, but not SmG, SmD3, and SmB mutations, defining the subset of the ring that requires Brr1/Gemin2 for assembly.","method":"Yeast genetics (synthetic lethality screen, complementation assay), site-directed mutagenesis of Sm proteins and Brr1","journal":"RNA (New York, N.Y.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with defined mutants, multiple pairwise combinations tested, single lab, model-organism ortholog","pmids":["27974620"],"is_preprint":false}],"current_model":"GEMIN2 is a core subunit of the SMN complex that wraps around the SmD1/D2/F/E/G pentamer in an extended conformation, blocking RNA access and imposing specificity during snRNP assembly; RNA binding allosterically widens the pentamer to release GEMIN2/SMN, a process regulated by p70S6K-mediated phosphorylation of GEMIN2 and by GEMIN2 self-association that stabilizes SMN oligomers. Independently of snRNP assembly, GEMIN2 acts as a RAD51 mediator in homologous recombination by stabilizing RAD51-DNA complexes and stimulating strand exchange, and it facilitates HIV-1 reverse transcription by stabilizing integrase multimers."},"narrative":{"mechanistic_narrative":"GEMIN2 is a core subunit of the SMN complex that imposes specificity and ordered assembly during the biogenesis of spliceosomal U snRNPs [PMID:21816274, PMID:31799625]. Structurally, GEMIN2 adopts an extended conformation that wraps around the crescent-shaped SmD1/D2/F/E/G pentamer, contacting all five Sm proteins and reaching into the RNA-binding pocket to block premature RNA access [PMID:21816274]; it constrains the pentamer in a narrow state through negative cooperativity with RNA so that snRNA binding allosterically widens the ring and releases GEMIN2/SMN, with subsequent SmD3/B joining completing the handoff [PMID:31799625]. GEMIN2 is anchored to a defined helix of SMN, an interaction abolished by an SMA-causing SMN mutation [PMID:21816274, PMID:22607171], and reciprocally SMN stabilizes GEMIN2 protein levels in vivo [PMID:11121410]; GEMIN2 in turn self-associates and stabilizes SMN amino-terminal oligomerization, with SMN·GEMIN2 forming dimer-to-octamer assemblies governed by the SMN YG box [PMID:17308308, PMID:26092730]. The complex's condensation in Cajal bodies and snRNP output are regulated by p70S6K, which directly binds and phosphorylates GEMIN2 [PMID:37958537]. Independently of snRNP assembly, GEMIN2 acts as a RAD51 mediator in homologous recombination: it binds RAD51 directly, inhibits RAD51 dissociation from DNA, and stimulates strand exchange, with the SMN-GEMIN2 complex further enhancing duplex DNA capture, and its depletion reduces recombination efficiency and RAD51 foci [PMID:20403813, PMID:21732698]. GEMIN2 also facilitates HIV-1 replication by binding integrase, stabilizing integrase multimers against proteasomal degradation, and promoting reverse transcription [PMID:16731905, PMID:19915660]. Genetic dissociation in zebrafish shows that GEMIN2 reduction, unlike SMN loss, does not directly cause motor axon defects [PMID:18000835].","teleology":[{"year":2000,"claim":"Established that GEMIN2 is an obligate partner of SMN in vivo, framing it as a stable component of the SMN complex rather than an independent factor.","evidence":"Tet-repressible SMN disruption in DT40 cells with western blotting for GEMIN2 levels","pmids":["11121410"],"confidence":"Medium","gaps":["Did not define GEMIN2's molecular contribution to the complex","Stabilization mechanism not resolved structurally"]},{"year":2002,"claim":"Linked reduced Smn/Gemin2 dosage to a snRNP-assembly defect and motoneuron degeneration, connecting the complex to SMA-relevant pathology.","evidence":"Gemin2 heterozygous knockout mice crossed to Smn heterozygotes, Sm protein localization and motoneuron histology","pmids":["12091709"],"confidence":"Medium","gaps":["Correlative link between snRNP defect and neurodegeneration","Cell-autonomy in motoneurons not tested"]},{"year":2006,"claim":"Identified a non-canonical role for GEMIN2 in HIV-1 biology by showing it binds viral integrase and is required for early infection.","evidence":"Yeast two-hybrid, siRNA depletion in macrophages, HIV-1 infection and viral cDNA assays, co-IP","pmids":["16731905"],"confidence":"Medium","gaps":["Mechanism by which GEMIN2 aids cDNA synthesis not defined here","Co-IP with viral genome indirect"]},{"year":2007,"claim":"Showed GEMIN2 self-associates and stabilizes SMN oligomers, providing a mechanism for how it promotes assembly-competent SMN complexes.","evidence":"Mammalian two-hybrid, in vitro pull-down and dissociation assays, siRNA knockdown with snRNP assembly readout","pmids":["17308308"],"confidence":"Medium","gaps":["Structural basis of self-association not determined","Stoichiometry of oligomers unresolved at this stage"]},{"year":2008,"claim":"Dissociated GEMIN2 from SMN's motor axon function by demonstrating cell-autonomous GEMIN2 knockdown does not cause axon defects, separating snRNP assembly from the axonal phenotype.","evidence":"Morpholino and cell-autonomous knockdown plus neuron transplantation in zebrafish, motor axon imaging","pmids":["18000835"],"confidence":"Medium","gaps":["Negative result; residual GEMIN2 function not excluded","Does not address mammalian motoneurons"]},{"year":2009,"claim":"Defined the mechanism of GEMIN2's pro-viral role: it stabilizes integrase multimers against proteasomal degradation and promotes reverse transcription.","evidence":"In vitro reverse transcription assays, co-IP, synthetic peptide inhibition, proteasome inhibitor experiments","pmids":["19915660"],"confidence":"Medium","gaps":["Structural detail of IN-GEMIN2 contact unknown","Relevance to integrated provirus stages not addressed"]},{"year":2010,"claim":"Established GEMIN2 as a direct RAD51 mediator in homologous recombination, expanding its role beyond snRNP assembly.","evidence":"Direct binding assays, in vitro recombination assays, siRNA and knockout cells, RAD51 focus assays","pmids":["20403813"],"confidence":"High","gaps":["Whether HR role depends on the full SMN complex not resolved here","In vivo HR contribution in differentiated cells unclear"]},{"year":2010,"claim":"Placed GEMIN2 in cytoplasmic U bodies and in mRNA-associated complexes, indicating subcellular contexts for its activity.","evidence":"Immunofluorescence in Drosophila egg chambers; IP of SMN/Gemin2/Gemin3 complexes with RT-PCR for beta-actin mRNA in neuroblastoma cells","pmids":["20452345","20620147"],"confidence":"Medium","gaps":["Functional consequence of mRNA association unknown","Direct vs indirect mRNA binding not distinguished"]},{"year":2011,"claim":"Provided the atomic-resolution mechanism for GEMIN2's specificity function: it wraps the Sm pentamer and occludes the RNA-binding pocket, and an SMA mutation disrupts SMN-GEMIN2 binding.","evidence":"2.5 A crystal structure of Gemin2-pentamer-SMN, structure-guided mutagenesis, binding assays","pmids":["21816274"],"confidence":"High","gaps":["Did not capture the RNA-bound release intermediate","Dynamics of the assembly transition inferred not observed"]},{"year":2011,"claim":"Showed the SMN-GEMIN2 complex outperforms GEMIN2 alone in HR by conferring DNA-binding and stimulating duplex capture, integrating the two activities.","evidence":"Purified SMN-GEMIN2 fusion, in vitro recombination and DNA-binding assays, knockout complementation","pmids":["21732698"],"confidence":"High","gaps":["Physiological SMN-GEMIN2 stoichiometry at DSBs unknown","Relationship to snRNP pool not defined"]},{"year":2012,"claim":"Refined the SMN-GEMIN2 interface and identified a conserved SMN/GEMIN2 surface, distinct from the binding contact, likely needed for assembly.","evidence":"NMR solution structure of GEMIN2 bound to SMN GEMIN2-binding domain, mutagenesis","pmids":["22607171"],"confidence":"High","gaps":["Functional role of the conserved surface not directly tested","SMA mutation effects on assembly not measured here"]},{"year":2015,"claim":"Defined the oligomeric architecture of SMN·GEMIN2 and the SMN YG box as the necessary and sufficient oligomerization determinant, conserved from yeast to human.","evidence":"1.9 A crystal structure of yeast SMN YG box, analytical ultracentrifugation, disulfide cross-linking, SEC","pmids":["26092730"],"confidence":"High","gaps":["Functional output of higher-order oligomers in assembly not quantified","Regulation of oligomer state not addressed"]},{"year":2016,"claim":"Defined which Sm ring subunits genetically require the GEMIN2 ortholog Brr1, mapping the assembly steps that depend on GEMIN2.","evidence":"Yeast synthetic lethality screen and complementation with Sm and Brr1 mutants","pmids":["27974620"],"confidence":"Medium","gaps":["Yeast genetics may not fully reflect human assembly order","Biochemical reconstitution of the subset dependence not shown"]},{"year":2020,"claim":"Revealed the allosteric logic of snRNP assembly: GEMIN2 enforces a narrow pentamer state via negative cooperativity with RNA, and RNA binding widens the ring to release GEMIN2/SMN.","evidence":"X-ray crystallography, biochemical binding and assembly assays, mutational analysis","pmids":["31799625"],"confidence":"High","gaps":["Kinetics of the release transition in cells not measured","Coupling to downstream snRNP maturation not detailed"]},{"year":2023,"claim":"Identified upstream regulation of GEMIN2 by p70S6K phosphorylation controlling SMN complex condensation in Cajal bodies and snRNP output.","evidence":"Co-IP, in vitro kinase assay, SEC, p70S6K knockdown, Cajal body counting","pmids":["37958537"],"confidence":"Medium","gaps":["Phosphosites and their structural effect not mapped","Signaling context driving p70S6K activity not defined"]},{"year":null,"claim":"How GEMIN2's distinct roles in snRNP assembly, homologous recombination, and HIV-1 reverse transcription are coordinated, partitioned, or regulated within a cell remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of GEMIN2-RAD51 or GEMIN2-integrase complexes","Determinants directing GEMIN2 to HR versus snRNP pools unknown","Physiological signals coupling p70S6K regulation to each function undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,4,9]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,12]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[4]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11,12]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[14,7]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,9]}],"complexes":["SMN complex"],"partners":["SMN1","RAD51","RPS6KB1","HIV-1 INTEGRASE"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O14893","full_name":"Gem-associated protein 2","aliases":["Component of gems 2","Survival of motor neuron protein-interacting protein 1","SMN-interacting protein 1"],"length_aa":280,"mass_kda":31.6,"function":"The SMN complex catalyzes the assembly of small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome, and thereby plays an important role in the splicing of cellular pre-mRNAs (PubMed:18984161, PubMed:9323129). Most spliceosomal snRNPs contain a common set of Sm proteins SNRPB, SNRPD1, SNRPD2, SNRPD3, SNRPE, SNRPF and SNRPG that assemble in a heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP (Sm core) (PubMed:18984161). In the cytosol, the Sm proteins SNRPD1, SNRPD2, SNRPE, SNRPF and SNRPG (5Sm) are trapped in an inactive 6S pICln-Sm complex by the chaperone CLNS1A that controls the assembly of the core snRNP (PubMed:18984161). To assemble core snRNPs, the SMN complex accepts the trapped 5Sm proteins from CLNS1A (PubMed:18984161, PubMed:9323129). Binding of snRNA inside 5Sm ultimately triggers eviction of the SMN complex, thereby allowing binding of SNRPD3 and SNRPB to complete assembly of the core snRNP (PubMed:31799625). Within the SMN complex, GEMIN2 constrains the conformation of 5Sm, thereby promoting 5Sm binding to snRNA containing the snRNP code (a nonameric Sm site and a 3'-adjacent stem-loop), thus preventing progression of assembly until a cognate substrate is bound (PubMed:16314521, PubMed:21816274, PubMed:31799625)","subcellular_location":"Nucleus, gem; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/O14893/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GEMIN2","classification":"Common Essential","n_dependent_lines":963,"n_total_lines":1208,"dependency_fraction":0.7971854304635762},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SMN1","stoichiometry":10.0},{"gene":"SNRPA","stoichiometry":0.2},{"gene":"SNRPB","stoichiometry":0.2},{"gene":"SNRPC","stoichiometry":0.2},{"gene":"SNRPD2","stoichiometry":0.2},{"gene":"SNRPF","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GEMIN2","total_profiled":1310},"omim":[{"mim_id":"607419","title":"GEM NUCLEAR ORGANELLE-ASSOCIATED PROTEIN 7; GEMIN7","url":"https://www.omim.org/entry/607419"},{"mim_id":"607006","title":"GEM NUCLEAR ORGANELLE-ASSOCIATED PROTEIN 6; GEMIN6","url":"https://www.omim.org/entry/607006"},{"mim_id":"607005","title":"GEM NUCLEAR ORGANELLE-ASSOCIATED PROTEIN 5; GEMIN5","url":"https://www.omim.org/entry/607005"},{"mim_id":"606969","title":"GEM NUCLEAR ORGANELLE-ASSOCIATED PROTEIN 4; GEMIN4","url":"https://www.omim.org/entry/606969"},{"mim_id":"606229","title":"ARGONAUTE RISC COMPONENT 2; AGO2","url":"https://www.omim.org/entry/606229"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Supported"},{"location":"Nucleoli","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GEMIN2"},"hgnc":{"alias_symbol":[],"prev_symbol":["SIP1"]},"alphafold":{"accession":"O14893","domains":[{"cath_id":"1.20.58.1070","chopping":"99-125_137-156_171-274","consensus_level":"high","plddt":90.0035,"start":99,"end":274}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O14893","model_url":"https://alphafold.ebi.ac.uk/files/AF-O14893-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O14893-F1-predicted_aligned_error_v6.png","plddt_mean":80.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GEMIN2","jax_strain_url":"https://www.jax.org/strain/search?query=GEMIN2"},"sequence":{"accession":"O14893","fasta_url":"https://rest.uniprot.org/uniprotkb/O14893.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O14893/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O14893"}},"corpus_meta":[{"pmid":"21816274","id":"PMC_21816274","title":"Structure of a key intermediate of the SMN complex reveals Gemin2's crucial function in snRNP assembly.","date":"2011","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21816274","citation_count":107,"is_preprint":false},{"pmid":"12091709","id":"PMC_12091709","title":"Gene targeting of Gemin2 in mice reveals a correlation between defects in the biogenesis of U snRNPs and motoneuron cell death.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12091709","citation_count":67,"is_preprint":false},{"pmid":"11121410","id":"PMC_11121410","title":"A cell system with targeted disruption of the SMN gene: functional conservation of the SMN protein and dependence of Gemin2 on SMN.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11121410","citation_count":52,"is_preprint":false},{"pmid":"17308308","id":"PMC_17308308","title":"Gemin2 plays an important role in stabilizing the survival of motor neuron complex.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17308308","citation_count":49,"is_preprint":false},{"pmid":"16731905","id":"PMC_16731905","title":"Identification of a novel human immunodeficiency virus type 1 integrase interactor, Gemin2, that facilitates efficient viral cDNA synthesis in vivo.","date":"2006","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/16731905","citation_count":49,"is_preprint":false},{"pmid":"20452345","id":"PMC_20452345","title":"Drosophila SMN complex proteins Gemin2, Gemin3, and Gemin5 are components of U bodies.","date":"2010","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/20452345","citation_count":37,"is_preprint":false},{"pmid":"20403813","id":"PMC_20403813","title":"GEMIN2 promotes accumulation of RAD51 at double-strand breaks in homologous recombination.","date":"2010","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/20403813","citation_count":33,"is_preprint":false},{"pmid":"19915660","id":"PMC_19915660","title":"Augmentation of reverse transcription by integrase through an interaction with host factor, SIP1/Gemin2 Is critical for HIV-1 infection.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19915660","citation_count":29,"is_preprint":false},{"pmid":"20620147","id":"PMC_20620147","title":"SMN, Gemin2 and Gemin3 associate with beta-actin mRNA in the cytoplasm of neuronal cells in vitro.","date":"2010","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/20620147","citation_count":28,"is_preprint":false},{"pmid":"26092730","id":"PMC_26092730","title":"Oligomeric Properties of Survival Motor Neuron·Gemin2 Complexes.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26092730","citation_count":27,"is_preprint":false},{"pmid":"18000835","id":"PMC_18000835","title":"The SMN binding protein Gemin2 is not involved in motor axon outgrowth.","date":"2008","source":"Developmental neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/18000835","citation_count":24,"is_preprint":false},{"pmid":"22607171","id":"PMC_22607171","title":"Solution structure of the core SMN-Gemin2 complex.","date":"2012","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/22607171","citation_count":22,"is_preprint":false},{"pmid":"21732698","id":"PMC_21732698","title":"Purification of the human SMN-GEMIN2 complex and assessment of its stimulation of RAD51-mediated DNA recombination reactions.","date":"2011","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21732698","citation_count":19,"is_preprint":false},{"pmid":"16964508","id":"PMC_16964508","title":"Caenorhabditis elegans in the study of SMN-interacting proteins: a role for SMI-1, an orthologue of human Gemin2 and the identification of novel components of the SMN complex.","date":"2006","source":"Invertebrate neuroscience : IN","url":"https://pubmed.ncbi.nlm.nih.gov/16964508","citation_count":19,"is_preprint":false},{"pmid":"31799625","id":"PMC_31799625","title":"Negative cooperativity between Gemin2 and RNA provides insights into RNA selection and the SMN complex's release in snRNP assembly.","date":"2020","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/31799625","citation_count":13,"is_preprint":false},{"pmid":"27974620","id":"PMC_27974620","title":"Will the circle be unbroken: specific mutations in the yeast Sm protein ring expose a requirement for assembly factor Brr1, a homolog of Gemin2.","date":"2016","source":"RNA (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/27974620","citation_count":8,"is_preprint":false},{"pmid":"38715801","id":"PMC_38715801","title":"Interaction between MARK3 (rs11623869), PLCB4 (rs6086746) and GEMIN2 (rs2277458) variants with bone mineral density and serum 25-hidroxivitamin D levels in Mexican Mestizo women.","date":"2024","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/38715801","citation_count":2,"is_preprint":false},{"pmid":"23939045","id":"PMC_23939045","title":"The gemin2-binding site on SMN protein: accessibility to antibody.","date":"2013","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/23939045","citation_count":1,"is_preprint":false},{"pmid":"37958537","id":"PMC_37958537","title":"The Impact of p70S6 Kinase-Dependent Phosphorylation of Gemin2 in UsnRNP Biogenesis.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37958537","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.07.09.602679","title":"A unique mechanism of snRNP core assembly","date":"2024-07-10","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.09.602679","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11130,"output_tokens":4401,"usd":0.049702,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12471,"output_tokens":4525,"usd":0.08774,"stage2_stop_reason":"end_turn"},"total_usd":0.137442,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structure (2.5 Å) of Gemin2 bound to the SmD1/D2/F/E/G pentamer and SMN's Gemin2-binding domain revealed that Gemin2 adopts an extended conformation wrapping around the crescent-shaped pentamer, interacting with all five Sm proteins, gripping both sides and the outer perimeter, and reaching into the RNA-binding pocket to prevent RNA binding. An SMA-causing mutation in an SMN helix that mediates Gemin2 binding abrogates SMN-Gemin2 interaction.\",\n      \"method\": \"X-ray crystallography (2.5 Å), structure-guided mutagenesis, biochemical binding assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution crystal structure with mutagenesis validation, published in high-impact journal, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"21816274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Crystallographic and biochemical analyses showed that Gemin2 constrains the horseshoe-shaped SmD1/D2/F/E/G pentamer in a narrow state via negative cooperativity with RNA, enhancing RNA specificity. RNA binding inside the pentamer widens it, allosterically releasing Gemin2/SMN; subsequent SmD3/B joining further facilitates Gemin2/SMN release. This reveals the mechanism of snRNA selection and SMN complex release during snRNP assembly.\",\n      \"method\": \"X-ray crystallography, biochemical binding and assembly assays, mutational analysis\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with biochemical assays, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"31799625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NMR solution structure of Gemin2 bound to the Gemin2-binding domain of SMN revealed how Gemin2 is stabilized by SMN and identified conserved SMN residues at the binding interface. Notably, several conserved SMN residues including sites of two SMA patient mutations are not required for Gemin2 binding but form a conserved SMN/Gemin2 surface likely important for snRNP assembly.\",\n      \"method\": \"NMR spectroscopy, biochemical binding assays\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structure with functional mutagenesis validation, single lab, multiple methods\",\n      \"pmids\": [\"22607171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Human GEMIN2 directly binds RAD51 and stimulates RAD51-mediated homologous pairing by inhibiting RAD51 dissociation from DNA and enhancing the RAD51-mediated strand exchange when RPA is pre-bound to ssDNA. Depletion of GEMIN2 in chicken DT40 cells and human cells reduced homologous recombination efficiency and decreased RAD51 subnuclear foci formation, establishing GEMIN2 as a novel RAD51 mediator.\",\n      \"method\": \"Biochemical binding assays (direct binding), in vitro recombination assays, siRNA knockdown, RAD51 focus formation assay, GEMIN2-knockout cell line\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal biochemical assays plus genetic loss-of-function with defined cellular phenotype, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"20403813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The purified SMN-GEMIN2 fusion complex stimulates RAD51-mediated homologous pairing more efficiently than GEMIN2 alone. SMN-GEMIN2, but not GEMIN2 alone, possesses DNA-binding activity and significantly stimulates secondary duplex DNA capture by the RAD51-ssDNA complex during homologous pairing, establishing a role for the SMN-GEMIN2 complex in homologous recombination.\",\n      \"method\": \"Protein purification, in vitro recombination and DNA-binding assays, complementation of GEMIN2-knockout cells\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified proteins, multiple biochemical assays, cell-based complementation, single lab\",\n      \"pmids\": [\"21732698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Gemin2 undergoes self-association (homodimerization) detected by mammalian two-hybrid and in vitro pull-down assays. Gemin2 stabilizes SMN oligomer formation; in vitro dissociation assays showed that Gemin2 presence stabilizes SMN amino-terminal self-interaction. Gemin2 knockdown by siRNA drastically decreases SMN oligomer formation and snRNP assembly activity.\",\n      \"method\": \"Mammalian two-hybrid, in vitro pull-down, in vitro dissociation assay, siRNA knockdown, snRNP assembly assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical and cell-based methods, single lab\",\n      \"pmids\": [\"17308308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Depletion of SMN protein in DT40 cells leads to a significant decrease in Gemin2 protein levels, demonstrating that SMN stabilizes Gemin2 and that SMN and Gemin2 form a stable complex in vivo.\",\n      \"method\": \"Tet-repressible SMN expression system in DT40 cells (homologous recombination-based SMN gene disruption), western blotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function system with direct protein-level readout, single lab, clean experimental system\",\n      \"pmids\": [\"11121410\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In vivo genetic evidence that reduced Smn/Gemin2 protein levels disturb U snRNP assembly (indicated by reduced nuclear accumulation of Sm proteins) and that this correlates with enhanced motoneuron degeneration in Gemin2(+/-)/Smn(+/-) double heterozygous mice.\",\n      \"method\": \"Mouse gene targeting (Gemin2 heterozygous knockout), Sm protein localization by immunofluorescence, histological assessment of motoneuron degeneration\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with defined molecular and cellular phenotypes, single lab\",\n      \"pmids\": [\"12091709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"GEMIN2/SIP1 binds HIV-1 integrase (IN), identified by yeast two-hybrid, and siRNA depletion of Gemin2 in human monocyte-derived macrophages dramatically reduces HIV-1 infection and viral cDNA synthesis without affecting expression from integrated proviral DNA. Co-immunoprecipitation suggested Gemin2 interacts with the incoming viral genome through IN.\",\n      \"method\": \"Yeast two-hybrid, siRNA knockdown, HIV-1 infection assay, co-immunoprecipitation with FLAG-tagged Gemin2\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus co-IP plus functional siRNA knockdown, single lab, multiple methods\",\n      \"pmids\": [\"16731905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Gemin2/SIP1 stabilizes HIV-1 integrase (IN) multimer formation by preventing proteasome-mediated degradation of IN. The SMN-interacting protein 1 (SIP1/Gemin2)-IN interaction promotes assembly of IN and reverse transcriptase on viral RNA, augmenting reverse transcriptase activity in vitro. Synthetic peptides mimicking IN binding motifs that disrupt IN-SIP1 interaction abrogated reverse transcription in vitro and in vivo.\",\n      \"method\": \"In vitro reverse transcription assay, siRNA knockdown, co-immunoprecipitation, synthetic peptide inhibition, proteasome inhibitor experiments\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical and cell-based methods, single lab, follows up on prior yeast two-hybrid identification\",\n      \"pmids\": [\"19915660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"SMN·Gemin2 complexes from humans form oligomers spanning the dimer-to-octamer range, with the YG box oligomerization domain of SMN being both necessary and sufficient for oligomerization. Fission yeast SMN·Gemin2 exists as a dimer-tetramer equilibrium (Kd = 1.0 ± 0.9 µM). A 1.9 Å crystal structure of the yeast SMN YG box confirmed high structural conservation with the human ortholog. Disulfide cross-linking showed SMN tetramers form by self-association of stable dimers.\",\n      \"method\": \"X-ray crystallography (1.9 Å), analytical ultracentrifugation, disulfide cross-linking, size-exclusion chromatography\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with multiple biophysical methods, single lab\",\n      \"pmids\": [\"26092730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Drosophila Gemin2 (CG10419) colocalizes with SMN in cytoplasmic U bodies in Drosophila egg chambers. Gemin2 is excluded from P bodies but consistently found associated with them due to the invariant U body–P body association.\",\n      \"method\": \"Immunofluorescence/confocal microscopy in Drosophila egg chambers\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct subcellular localization by immunofluorescence in a model organism, replicated for multiple Gemin proteins\",\n      \"pmids\": [\"20452345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SMN, Gemin2 and Gemin3 associate with beta-actin mRNA in cytoplasmic complexes in human SHSY5Y neuroblastoma cells, providing the first direct evidence of beta-actin mRNA in SMN cytoplasmic complexes.\",\n      \"method\": \"Targeted mRNA screen (immunoprecipitation of SMN/Gemin2/Gemin3 complexes followed by RT-PCR for beta-actin mRNA)\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct co-immunoprecipitation of mRNA with Gemin2 complex, single lab, single method\",\n      \"pmids\": [\"20620147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Gemin2 knockdown specifically in motoneurons in zebrafish using two separate approaches (cell-autonomous knockdown) did not cause motor axon outgrowth defects, in contrast to SMN knockdown. Motor axon defects observed with global Gemin2 morpholino knockdown were secondary to body morphology defects, as shown by wild-type neuron transplantation experiments. This establishes that Gemin2 reduction does not directly cause motor axon phenotypes, dissociating snRNP function from SMN's motor axon role.\",\n      \"method\": \"Morpholino knockdown in zebrafish, cell-autonomous knockdown in motoneurons, neuronal transplantation assay, motor axon imaging\",\n      \"journal\": \"Developmental neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic approaches with clear negative result compared to SMN, single lab, epistatic dissection\",\n      \"pmids\": [\"18000835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"p70S6 kinase (ribosomal protein S6 kinase beta-1, p70S6K) directly binds and phosphorylates Gemin2. The phosphorylation status of Gemin2 influences the capacity of the SMN complex to condense in Cajal bodies in vivo. p70S6K knockdown reduced the number of Cajal bodies and inhibited in vivo UsnRNP synthesis. Gemin2 also functions as a connecting element between the 6S complex and the SMN complex, as shown by size exclusion chromatography.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay (p70S6K phosphorylating Gemin2), size exclusion chromatography, siRNA knockdown of p70S6K, Cajal body counting by immunofluorescence\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding and phosphorylation demonstrated biochemically with functional readout (Cajal body condensation), single lab, multiple methods\",\n      \"pmids\": [\"37958537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"C. elegans SMI-1 (orthologue of Gemin2) directly interacts with SMN-1 protein, shown by yeast two-hybrid and demonstrated conservation of the SMN-Gemin2 interaction in C. elegans.\",\n      \"method\": \"Yeast two-hybrid, cloning and sequencing of smi-1, RNAi phenotypic analysis\",\n      \"journal\": \"Invertebrate neuroscience : IN\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single method (yeast two-hybrid) for direct interaction, single lab\",\n      \"pmids\": [\"16964508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In S. cerevisiae, the Gemin2 homolog Brr1 is required for snRNP Sm ring assembly in specific Sm protein mutant backgrounds. The N-terminal segment of Brr1 (amino acids 24-47) corresponding to the Gemin2 α1 helix that interacts with SmF, and a C-terminal peptide (336QKDLIE341) that in Gemin2 interacts with SmD2, are essential for Brr1 function. Specific SmE, SmF, SmD2, and SmD1 subunit mutations are synthetically lethal with brr1Δ, but not SmG, SmD3, and SmB mutations, defining the subset of the ring that requires Brr1/Gemin2 for assembly.\",\n      \"method\": \"Yeast genetics (synthetic lethality screen, complementation assay), site-directed mutagenesis of Sm proteins and Brr1\",\n      \"journal\": \"RNA (New York, N.Y.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with defined mutants, multiple pairwise combinations tested, single lab, model-organism ortholog\",\n      \"pmids\": [\"27974620\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GEMIN2 is a core subunit of the SMN complex that wraps around the SmD1/D2/F/E/G pentamer in an extended conformation, blocking RNA access and imposing specificity during snRNP assembly; RNA binding allosterically widens the pentamer to release GEMIN2/SMN, a process regulated by p70S6K-mediated phosphorylation of GEMIN2 and by GEMIN2 self-association that stabilizes SMN oligomers. Independently of snRNP assembly, GEMIN2 acts as a RAD51 mediator in homologous recombination by stabilizing RAD51-DNA complexes and stimulating strand exchange, and it facilitates HIV-1 reverse transcription by stabilizing integrase multimers.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GEMIN2 is a core subunit of the SMN complex that imposes specificity and ordered assembly during the biogenesis of spliceosomal U snRNPs [#0, #1]. Structurally, GEMIN2 adopts an extended conformation that wraps around the crescent-shaped SmD1/D2/F/E/G pentamer, contacting all five Sm proteins and reaching into the RNA-binding pocket to block premature RNA access [#0]; it constrains the pentamer in a narrow state through negative cooperativity with RNA so that snRNA binding allosterically widens the ring and releases GEMIN2/SMN, with subsequent SmD3/B joining completing the handoff [#1]. GEMIN2 is anchored to a defined helix of SMN, an interaction abolished by an SMA-causing SMN mutation [#0, #2], and reciprocally SMN stabilizes GEMIN2 protein levels in vivo [#6]; GEMIN2 in turn self-associates and stabilizes SMN amino-terminal oligomerization, with SMN·GEMIN2 forming dimer-to-octamer assemblies governed by the SMN YG box [#5, #10]. The complex's condensation in Cajal bodies and snRNP output are regulated by p70S6K, which directly binds and phosphorylates GEMIN2 [#14]. Independently of snRNP assembly, GEMIN2 acts as a RAD51 mediator in homologous recombination: it binds RAD51 directly, inhibits RAD51 dissociation from DNA, and stimulates strand exchange, with the SMN-GEMIN2 complex further enhancing duplex DNA capture, and its depletion reduces recombination efficiency and RAD51 foci [#3, #4]. GEMIN2 also facilitates HIV-1 replication by binding integrase, stabilizing integrase multimers against proteasomal degradation, and promoting reverse transcription [#8, #9]. Genetic dissociation in zebrafish shows that GEMIN2 reduction, unlike SMN loss, does not directly cause motor axon defects [#13].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established that GEMIN2 is an obligate partner of SMN in vivo, framing it as a stable component of the SMN complex rather than an independent factor.\",\n      \"evidence\": \"Tet-repressible SMN disruption in DT40 cells with western blotting for GEMIN2 levels\",\n      \"pmids\": [\"11121410\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define GEMIN2's molecular contribution to the complex\", \"Stabilization mechanism not resolved structurally\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Linked reduced Smn/Gemin2 dosage to a snRNP-assembly defect and motoneuron degeneration, connecting the complex to SMA-relevant pathology.\",\n      \"evidence\": \"Gemin2 heterozygous knockout mice crossed to Smn heterozygotes, Sm protein localization and motoneuron histology\",\n      \"pmids\": [\"12091709\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Correlative link between snRNP defect and neurodegeneration\", \"Cell-autonomy in motoneurons not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified a non-canonical role for GEMIN2 in HIV-1 biology by showing it binds viral integrase and is required for early infection.\",\n      \"evidence\": \"Yeast two-hybrid, siRNA depletion in macrophages, HIV-1 infection and viral cDNA assays, co-IP\",\n      \"pmids\": [\"16731905\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which GEMIN2 aids cDNA synthesis not defined here\", \"Co-IP with viral genome indirect\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Showed GEMIN2 self-associates and stabilizes SMN oligomers, providing a mechanism for how it promotes assembly-competent SMN complexes.\",\n      \"evidence\": \"Mammalian two-hybrid, in vitro pull-down and dissociation assays, siRNA knockdown with snRNP assembly readout\",\n      \"pmids\": [\"17308308\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of self-association not determined\", \"Stoichiometry of oligomers unresolved at this stage\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Dissociated GEMIN2 from SMN's motor axon function by demonstrating cell-autonomous GEMIN2 knockdown does not cause axon defects, separating snRNP assembly from the axonal phenotype.\",\n      \"evidence\": \"Morpholino and cell-autonomous knockdown plus neuron transplantation in zebrafish, motor axon imaging\",\n      \"pmids\": [\"18000835\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative result; residual GEMIN2 function not excluded\", \"Does not address mammalian motoneurons\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined the mechanism of GEMIN2's pro-viral role: it stabilizes integrase multimers against proteasomal degradation and promotes reverse transcription.\",\n      \"evidence\": \"In vitro reverse transcription assays, co-IP, synthetic peptide inhibition, proteasome inhibitor experiments\",\n      \"pmids\": [\"19915660\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural detail of IN-GEMIN2 contact unknown\", \"Relevance to integrated provirus stages not addressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established GEMIN2 as a direct RAD51 mediator in homologous recombination, expanding its role beyond snRNP assembly.\",\n      \"evidence\": \"Direct binding assays, in vitro recombination assays, siRNA and knockout cells, RAD51 focus assays\",\n      \"pmids\": [\"20403813\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HR role depends on the full SMN complex not resolved here\", \"In vivo HR contribution in differentiated cells unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed GEMIN2 in cytoplasmic U bodies and in mRNA-associated complexes, indicating subcellular contexts for its activity.\",\n      \"evidence\": \"Immunofluorescence in Drosophila egg chambers; IP of SMN/Gemin2/Gemin3 complexes with RT-PCR for beta-actin mRNA in neuroblastoma cells\",\n      \"pmids\": [\"20452345\", \"20620147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of mRNA association unknown\", \"Direct vs indirect mRNA binding not distinguished\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Provided the atomic-resolution mechanism for GEMIN2's specificity function: it wraps the Sm pentamer and occludes the RNA-binding pocket, and an SMA mutation disrupts SMN-GEMIN2 binding.\",\n      \"evidence\": \"2.5 A crystal structure of Gemin2-pentamer-SMN, structure-guided mutagenesis, binding assays\",\n      \"pmids\": [\"21816274\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture the RNA-bound release intermediate\", \"Dynamics of the assembly transition inferred not observed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed the SMN-GEMIN2 complex outperforms GEMIN2 alone in HR by conferring DNA-binding and stimulating duplex capture, integrating the two activities.\",\n      \"evidence\": \"Purified SMN-GEMIN2 fusion, in vitro recombination and DNA-binding assays, knockout complementation\",\n      \"pmids\": [\"21732698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological SMN-GEMIN2 stoichiometry at DSBs unknown\", \"Relationship to snRNP pool not defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Refined the SMN-GEMIN2 interface and identified a conserved SMN/GEMIN2 surface, distinct from the binding contact, likely needed for assembly.\",\n      \"evidence\": \"NMR solution structure of GEMIN2 bound to SMN GEMIN2-binding domain, mutagenesis\",\n      \"pmids\": [\"22607171\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of the conserved surface not directly tested\", \"SMA mutation effects on assembly not measured here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the oligomeric architecture of SMN·GEMIN2 and the SMN YG box as the necessary and sufficient oligomerization determinant, conserved from yeast to human.\",\n      \"evidence\": \"1.9 A crystal structure of yeast SMN YG box, analytical ultracentrifugation, disulfide cross-linking, SEC\",\n      \"pmids\": [\"26092730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of higher-order oligomers in assembly not quantified\", \"Regulation of oligomer state not addressed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined which Sm ring subunits genetically require the GEMIN2 ortholog Brr1, mapping the assembly steps that depend on GEMIN2.\",\n      \"evidence\": \"Yeast synthetic lethality screen and complementation with Sm and Brr1 mutants\",\n      \"pmids\": [\"27974620\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Yeast genetics may not fully reflect human assembly order\", \"Biochemical reconstitution of the subset dependence not shown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed the allosteric logic of snRNP assembly: GEMIN2 enforces a narrow pentamer state via negative cooperativity with RNA, and RNA binding widens the ring to release GEMIN2/SMN.\",\n      \"evidence\": \"X-ray crystallography, biochemical binding and assembly assays, mutational analysis\",\n      \"pmids\": [\"31799625\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinetics of the release transition in cells not measured\", \"Coupling to downstream snRNP maturation not detailed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified upstream regulation of GEMIN2 by p70S6K phosphorylation controlling SMN complex condensation in Cajal bodies and snRNP output.\",\n      \"evidence\": \"Co-IP, in vitro kinase assay, SEC, p70S6K knockdown, Cajal body counting\",\n      \"pmids\": [\"37958537\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphosites and their structural effect not mapped\", \"Signaling context driving p70S6K activity not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GEMIN2's distinct roles in snRNP assembly, homologous recombination, and HIV-1 reverse transcription are coordinated, partitioned, or regulated within a cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of GEMIN2-RAD51 or GEMIN2-integrase complexes\", \"Determinants directing GEMIN2 to HR versus snRNP pools unknown\", \"Physiological signals coupling p70S6K regulation to each function undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 4, 9]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 12]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11, 12]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [14, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"complexes\": [\n      \"SMN complex\"\n    ],\n    \"partners\": [\n      \"SMN1\",\n      \"RAD51\",\n      \"RPS6KB1\",\n      \"HIV-1 integrase\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}