{"gene":"SNRPD1","run_date":"2026-06-10T07:46:37","timeline":{"discoveries":[{"year":2001,"finding":"Purified U7 snRNPs from HeLa cells specifically lack Sm proteins D1 (SNRPD1) and D2, despite containing other conventional Sm proteins; this absence is largely dictated by the special Sm binding site of U7 snRNA, and the vacant D1 position is instead occupied by a novel Sm-like protein Lsm10.","method":"Biochemical fractionation and affinity purification of U7 snRNPs with biotinylated oligonucleotide, followed by microsequencing of associated polypeptides; functional mapping via U7 snRNA Sm-site analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct biochemical purification with microsequencing, mechanistically mapped to the RNA Sm-binding site, single rigorous study with multiple orthogonal methods","pmids":["11574479"],"is_preprint":false},{"year":1997,"finding":"The SNRPD1 gene (encoding Sm-D1) is the single functional gene among a multigene family; it contains three introns and its promoter activity was localized to a 0.38 kb PstI fragment by CAT reporter gene fusion assays. Two other family members are processed pseudogenes.","method":"Southern blotting, DNA sequencing, CAT reporter gene fusion assays in cell transfection","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional promoter mapping by reporter assay with sequence analysis, single lab study","pmids":["9168134"],"is_preprint":false},{"year":1997,"finding":"Recombinant Sm-D1 (SNRPD1) expressed in a baculovirus eukaryotic system retains antigenicity equivalent to native Sm-D1, demonstrating that the C-terminal GR-repeat region (containing dimethylarginine post-translational modifications) constitutes immunoreactive determinants recognized by SLE patient anti-Sm sera and anti-Sm monoclonal antibodies.","method":"Baculovirus expression and purification of recombinant Sm-D1; direct antibody-binding ELISA comparing recombinant vs. native protein; testing with patient sera and monoclonal antibodies","journal":"Clinical immunology and immunopathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — recombinant protein expression with functional ELISA validation against multiple serum sources, single lab","pmids":["9175921"],"is_preprint":false},{"year":2003,"finding":"HCV nonstructural protein NS3 physically binds to SNRPD1 (Sm-D1) via the C-terminal GR-repeat region of Sm-D1; co-expression of NS3 alters the subcellular localization of NS3 from cytoplasm to nucleus, and changes the expression pattern of Sm-D1.","method":"Yeast two-hybrid assay to identify interaction; deletion mutant mapping of the binding region; immunostaining to assess co-localization and subcellular redistribution","journal":"Microbiology and immunology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid plus deletion mapping plus immunostaining, single lab, no in vitro reconstitution","pmids":["14524621"],"is_preprint":false},{"year":2017,"finding":"SNRPD1 physically interacts with SNRPA1 and PNN within human pluripotent stem cell spliceosomes; depletion of SNRPD1 causes loss of pluripotency, blocks hiPS generation, and reduces hPS spliceosome abundance, placing SNRPD1 as a required component for pluripotency-specific spliceosome assembly.","method":"Co-immunoprecipitation (physical interaction); co-localization with hPS spliceosomes; siRNA knockdown with pluripotency marker loss and reprogramming efficiency assays","journal":"Stem cell research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — reciprocal Co-IP plus KD phenotype in two cell systems, single lab, multiple orthogonal methods","pmids":["28595116"],"is_preprint":false},{"year":2021,"finding":"SNRPD1 knockdown in breast cancer cells causes cell cycle arrest at G0/G1 phase and halted tumor cell growth; reduced SNRPD1 expression also reduces sensitivity to doxorubicin specifically in triple-negative breast cancer cells.","method":"siRNA knockdown, flow cytometry cell cycle analysis, qPCR, western blotting, drug response assay","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined cell cycle phenotype confirmed by multiple methods (flow cytometry, western blot, qPCR), single lab","pmids":["33879154"],"is_preprint":false},{"year":2023,"finding":"SNRPD1 knockdown in hepatocellular carcinoma cells induces autophagy (increased autophagic vacuoles, upregulation of ATG5, ATG7, ATG12) and blocks the PI3K/AKT/mTOR/4EBP1 signaling pathway; SNRPD1 inhibition also suppresses tumor growth in vivo.","method":"siRNA knockdown in vitro and xenograft in vivo; western blotting for PI3K/AKT/mTOR/4EBP1 pathway proteins; autophagy gene expression and vacuole detection; Ki67 immunostaining in vivo","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with pathway analysis validated in vitro and in vivo with multiple readouts, single lab","pmids":["37268273"],"is_preprint":false},{"year":2024,"finding":"IGF2BP2, an m6A reader RNA-binding protein, binds SNRPD1 mRNA and enhances its stability through m6A-dependent mechanisms, thereby increasing SNRPD1 protein expression; IGF2BP2 overexpression reverses the anti-tumor effects of SNRPD1 knockdown in TNBC cells.","method":"RIP (RNA immunoprecipitation) assay to detect IGF2BP2-SNRPD1 mRNA interaction; methylated RNA immunoprecipitation (MeRIP) for m6A; qRT-PCR for RNA stability; functional rescue by co-transfection","journal":"Breast cancer (Dove Medical Press)","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — RIP and MeRIP assays plus functional rescue, single lab, mechanistic pathway established","pmids":["39411513"],"is_preprint":false}],"current_model":"SNRPD1 (Sm-D1) is a core Sm protein of canonical snRNPs (U1, U2, U4/U6, U5) but is specifically excluded from U7 snRNPs due to the unique Sm-binding site of U7 snRNA; its C-terminal GR-repeat region, which carries dimethylarginine post-translational modifications, mediates interactions with viral proteins (HCV NS3) and constitutes the major SLE autoantibody epitope; in pluripotent stem cells it physically associates with SNRPA1 and PNN to support pluripotency-specific spliceosome assembly; in cancer cells it promotes cell cycle progression (G1/S transition) and suppresses autophagy via the PI3K/AKT/mTOR/4EBP1 pathway, with its mRNA stability regulated post-transcriptionally by the m6A reader IGF2BP2."},"narrative":{"mechanistic_narrative":"SNRPD1 (Sm-D1) is a core Sm protein of canonical snRNPs whose assembly into spliceosomal particles underlies its role in pre-mRNA splicing across diverse cellular contexts [PMID:11574479, PMID:28595116]. It is encoded by the single functional gene of a multigene family, two other members being processed pseudogenes [PMID:9168134]. SNRPD1 is incorporated into canonical snRNPs but is specifically excluded from U7 snRNPs, where the special Sm-binding site of U7 snRNA dictates that its position is instead occupied by the Sm-like protein Lsm10 [PMID:11574479]. In human pluripotent stem cells SNRPD1 physically associates with SNRPA1 and PNN to support a pluripotency-specific spliceosome, and its depletion causes loss of pluripotency and blocks reprogramming [PMID:28595116]. Its C-terminal GR-repeat region, bearing dimethylarginine modifications, forms the major SLE autoantibody epitope recognized by anti-Sm sera and also mediates a direct interaction with the HCV nonstructural protein NS3 that redistributes NS3 to the nucleus [PMID:9175921, PMID:14524621]. In cancer cells SNRPD1 promotes proliferation and G1/S cell cycle progression and suppresses autophagy through the PI3K/AKT/mTOR/4EBP1 pathway, and its mRNA is stabilized post-transcriptionally by the m6A reader IGF2BP2 [PMID:33879154, PMID:37268273, PMID:39411513].","teleology":[{"year":1997,"claim":"Establishing that SNRPD1 is the sole functional gene of its family clarified that a single locus produces the Sm-D1 protein, distinguishing it from non-coding processed pseudogenes.","evidence":"Southern blotting, sequencing and CAT reporter promoter mapping in transfected cells","pmids":["9168134"],"confidence":"Medium","gaps":["Promoter regulation in physiological contexts not defined","No link to protein function established here"]},{"year":1997,"claim":"Identifying the C-terminal GR-repeat region with dimethylarginine modifications as the immunoreactive determinant explained why Sm-D1 is a dominant SLE autoantigen.","evidence":"Baculovirus-expressed recombinant Sm-D1 tested by ELISA against patient anti-Sm sera and monoclonal antibodies","pmids":["9175921"],"confidence":"Medium","gaps":["Does not establish the role of this modification in normal snRNP function","Mechanism of autoantibody generation not addressed"]},{"year":2001,"claim":"Showing that SNRPD1 is specifically excluded from U7 snRNPs and replaced by Lsm10 demonstrated that the RNA Sm-binding site selects which Sm proteins are incorporated, distinguishing canonical from specialized snRNPs.","evidence":"Affinity purification of U7 snRNPs with microsequencing and Sm-site functional mapping","pmids":["11574479"],"confidence":"High","gaps":["Structural basis of D1 exclusion not resolved at atomic level","Functional consequence of substitution for histone mRNA processing not detailed here"]},{"year":2003,"claim":"Identifying a direct HCV NS3–Sm-D1 interaction via the GR-repeat region linked the autoantigenic domain to a viral protein and to altered NS3 subcellular localization.","evidence":"Yeast two-hybrid, deletion mapping and immunostaining co-localization","pmids":["14524621"],"confidence":"Medium","gaps":["No in vitro reconstitution of the interaction","Functional consequence for splicing or viral replication not established"]},{"year":2017,"claim":"Demonstrating that SNRPD1 associates with SNRPA1 and PNN and is required for pluripotency placed it within a pluripotency-specific spliceosome rather than only housekeeping splicing.","evidence":"Reciprocal Co-IP, co-localization with hPS spliceosomes, and siRNA knockdown with reprogramming/pluripotency assays","pmids":["28595116"],"confidence":"Medium","gaps":["Specific splicing targets supporting pluripotency not defined","Single lab, no in vivo validation"]},{"year":2021,"claim":"Knockdown causing G0/G1 arrest in breast cancer linked SNRPD1 to cell cycle progression and chemosensitivity beyond its housekeeping splicing role.","evidence":"siRNA knockdown with flow cytometry, qPCR, western blot and doxorubicin response assays","pmids":["33879154"],"confidence":"Medium","gaps":["Molecular link between splicing function and cell cycle control not defined","Mechanism of altered drug sensitivity unresolved"]},{"year":2023,"claim":"Showing that SNRPD1 knockdown induces autophagy and blocks PI3K/AKT/mTOR/4EBP1 signaling defined a signaling pathway through which it supports tumor growth.","evidence":"siRNA knockdown in vitro and xenograft in vivo with pathway western blots, autophagy markers and Ki67 staining","pmids":["37268273"],"confidence":"Medium","gaps":["Direct molecular connection between SNRPD1 and PI3K/AKT/mTOR not established","Whether effect depends on splicing activity unknown"]},{"year":2024,"claim":"Identifying IGF2BP2 as an m6A reader that stabilizes SNRPD1 mRNA established a post-transcriptional mechanism controlling SNRPD1 protein levels in cancer.","evidence":"RIP and MeRIP assays, mRNA stability qRT-PCR, and functional rescue by co-transfection in TNBC cells","pmids":["39411513"],"confidence":"Medium","gaps":["Specific m6A sites on SNRPD1 mRNA not mapped","Upstream regulation of IGF2BP2 in this context unknown"]},{"year":null,"claim":"How SNRPD1's core spliceosomal function mechanistically connects to its cancer-associated cell cycle, autophagy, and signaling phenotypes remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No identified splicing targets bridging spliceosome assembly and proliferation/autophagy","Whether oncogenic effects require splicing activity is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,4]}],"complexes":["spliceosomal snRNP"],"partners":["SNRPA1","PNN","NS3","IGF2BP2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P62316","full_name":"Small nuclear ribonucleoprotein Sm D2","aliases":["snRNP core protein D2"],"length_aa":118,"mass_kda":13.5,"function":"Plays a role in pre-mRNA splicing as a core component of the spliceosomal U1, U2, U4 and U5 small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome (PubMed:11991638, PubMed:18984161, PubMed:19325628, PubMed:23333303, PubMed:25555158, PubMed:26912367, PubMed:28076346, PubMed:28502770, PubMed:28781166, PubMed:32494006). Component of both the pre-catalytic spliceosome B complex and activated spliceosome C complexes (PubMed:11991638, PubMed:28076346, PubMed:28502770, PubMed:28781166). As a component of the minor spliceosome, involved in the splicing of U12-type introns in pre-mRNAs (PubMed:15146077)","subcellular_location":"Cytoplasm, cytosol; Nucleus","url":"https://www.uniprot.org/uniprotkb/P62316/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/SNRPD1","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RBM17","stoichiometry":10.0},{"gene":"SF3A2","stoichiometry":10.0},{"gene":"SF3A3","stoichiometry":10.0},{"gene":"SF3B1","stoichiometry":10.0},{"gene":"SF3B6","stoichiometry":10.0},{"gene":"SNRPB","stoichiometry":10.0},{"gene":"SNRPC","stoichiometry":10.0},{"gene":"SNRPD2","stoichiometry":10.0},{"gene":"SNRPF","stoichiometry":10.0},{"gene":"RBM39","stoichiometry":4.0}],"url":"https://opencell.sf.czbiohub.org/search/SNRPD1","total_profiled":1310},"omim":[{"mim_id":"617909","title":"LSM10, U7 SMALL NUCLEAR RNA-ASSOCIATED PROTEIN; LSM10","url":"https://www.omim.org/entry/617909"},{"mim_id":"616587","title":"SIR2 ANTIPHAGE-LIKE PROTEIN 1; SIRAL1","url":"https://www.omim.org/entry/616587"},{"mim_id":"603542","title":"SMALL NUCLEAR RIBONUCLEOPROTEIN POLYPEPTIDE G; SNRPG","url":"https://www.omim.org/entry/603542"},{"mim_id":"603541","title":"SMALL NUCLEAR RIBONUCLEOPROTEIN POLYPEPTIDE F; SNRPF","url":"https://www.omim.org/entry/603541"},{"mim_id":"601063","title":"SMALL NUCLEAR RIBONUCLEOPROTEIN POLYPEPTIDE D1; SNRPD1","url":"https://www.omim.org/entry/601063"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SNRPD1"},"hgnc":{"alias_symbol":["HsT2456","Sm-D1"],"prev_symbol":["SNRPD"]},"alphafold":{"accession":"P62316","domains":[{"cath_id":"2.30.30.100","chopping":"2-110","consensus_level":"medium","plddt":92.5073,"start":2,"end":110}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P62316","model_url":"https://alphafold.ebi.ac.uk/files/AF-P62316-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P62316-F1-predicted_aligned_error_v6.png","plddt_mean":90.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SNRPD1","jax_strain_url":"https://www.jax.org/strain/search?query=SNRPD1"},"sequence":{"accession":"P62316","fasta_url":"https://rest.uniprot.org/uniprotkb/P62316.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P62316/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P62316"}},"corpus_meta":[{"pmid":"11574479","id":"PMC_11574479","title":"Purified U7 snRNPs lack the Sm proteins D1 and D2 but contain Lsm10, a new 14 kDa Sm D1-like protein.","date":"2001","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/11574479","citation_count":138,"is_preprint":false},{"pmid":"28595116","id":"PMC_28595116","title":"The unique spliceosome signature of human pluripotent stem cells is mediated by SNRPA1, SNRPD1, and PNN.","date":"2017","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/28595116","citation_count":26,"is_preprint":false},{"pmid":"33879154","id":"PMC_33879154","title":"SNRPD1 confers diagnostic and therapeutic values on breast cancers through cell cycle regulation.","date":"2021","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/33879154","citation_count":19,"is_preprint":false},{"pmid":"9175921","id":"PMC_9175921","title":"Screening of SLE sera using purified recombinant Sm-D1 protein from a baculovirus expression system.","date":"1997","source":"Clinical immunology and immunopathology","url":"https://pubmed.ncbi.nlm.nih.gov/9175921","citation_count":17,"is_preprint":false},{"pmid":"14524621","id":"PMC_14524621","title":"Hepatitis C virus nonstructural protein NS3 binds to Sm-D1, a small nuclear ribonucleoprotein associated with autoimmune disease.","date":"2003","source":"Microbiology and immunology","url":"https://pubmed.ncbi.nlm.nih.gov/14524621","citation_count":11,"is_preprint":false},{"pmid":"37268273","id":"PMC_37268273","title":"SNRPD1 inhibition suppresses the proliferation of hepatocellular carcinoma and promotes autophagy through the PI3K/AKT/mTOR/4EBP1 pathway.","date":"2023","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/37268273","citation_count":10,"is_preprint":false},{"pmid":"39411513","id":"PMC_39411513","title":"The Potential Role of SNRPD1 Stabilized by IGF2BP2 in the Progression of Triple-Negative Breast Cancer.","date":"2024","source":"Breast cancer (Dove Medical Press)","url":"https://pubmed.ncbi.nlm.nih.gov/39411513","citation_count":1,"is_preprint":false},{"pmid":"9168134","id":"PMC_9168134","title":"Analysis of genes for human snRNP Sm-D1 protein and identification of the promoter sequence which shows segmental homology to the promoters of Sm-E and U1 snRNA genes.","date":"1997","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/9168134","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6103,"output_tokens":2159,"usd":0.025347,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9163,"output_tokens":2687,"usd":0.056495,"stage2_stop_reason":"end_turn"},"total_usd":0.081842,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"Purified U7 snRNPs from HeLa cells specifically lack Sm proteins D1 (SNRPD1) and D2, despite containing other conventional Sm proteins; this absence is largely dictated by the special Sm binding site of U7 snRNA, and the vacant D1 position is instead occupied by a novel Sm-like protein Lsm10.\",\n      \"method\": \"Biochemical fractionation and affinity purification of U7 snRNPs with biotinylated oligonucleotide, followed by microsequencing of associated polypeptides; functional mapping via U7 snRNA Sm-site analysis\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct biochemical purification with microsequencing, mechanistically mapped to the RNA Sm-binding site, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"11574479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The SNRPD1 gene (encoding Sm-D1) is the single functional gene among a multigene family; it contains three introns and its promoter activity was localized to a 0.38 kb PstI fragment by CAT reporter gene fusion assays. Two other family members are processed pseudogenes.\",\n      \"method\": \"Southern blotting, DNA sequencing, CAT reporter gene fusion assays in cell transfection\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional promoter mapping by reporter assay with sequence analysis, single lab study\",\n      \"pmids\": [\"9168134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Recombinant Sm-D1 (SNRPD1) expressed in a baculovirus eukaryotic system retains antigenicity equivalent to native Sm-D1, demonstrating that the C-terminal GR-repeat region (containing dimethylarginine post-translational modifications) constitutes immunoreactive determinants recognized by SLE patient anti-Sm sera and anti-Sm monoclonal antibodies.\",\n      \"method\": \"Baculovirus expression and purification of recombinant Sm-D1; direct antibody-binding ELISA comparing recombinant vs. native protein; testing with patient sera and monoclonal antibodies\",\n      \"journal\": \"Clinical immunology and immunopathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — recombinant protein expression with functional ELISA validation against multiple serum sources, single lab\",\n      \"pmids\": [\"9175921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"HCV nonstructural protein NS3 physically binds to SNRPD1 (Sm-D1) via the C-terminal GR-repeat region of Sm-D1; co-expression of NS3 alters the subcellular localization of NS3 from cytoplasm to nucleus, and changes the expression pattern of Sm-D1.\",\n      \"method\": \"Yeast two-hybrid assay to identify interaction; deletion mutant mapping of the binding region; immunostaining to assess co-localization and subcellular redistribution\",\n      \"journal\": \"Microbiology and immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid plus deletion mapping plus immunostaining, single lab, no in vitro reconstitution\",\n      \"pmids\": [\"14524621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SNRPD1 physically interacts with SNRPA1 and PNN within human pluripotent stem cell spliceosomes; depletion of SNRPD1 causes loss of pluripotency, blocks hiPS generation, and reduces hPS spliceosome abundance, placing SNRPD1 as a required component for pluripotency-specific spliceosome assembly.\",\n      \"method\": \"Co-immunoprecipitation (physical interaction); co-localization with hPS spliceosomes; siRNA knockdown with pluripotency marker loss and reprogramming efficiency assays\",\n      \"journal\": \"Stem cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — reciprocal Co-IP plus KD phenotype in two cell systems, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28595116\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SNRPD1 knockdown in breast cancer cells causes cell cycle arrest at G0/G1 phase and halted tumor cell growth; reduced SNRPD1 expression also reduces sensitivity to doxorubicin specifically in triple-negative breast cancer cells.\",\n      \"method\": \"siRNA knockdown, flow cytometry cell cycle analysis, qPCR, western blotting, drug response assay\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined cell cycle phenotype confirmed by multiple methods (flow cytometry, western blot, qPCR), single lab\",\n      \"pmids\": [\"33879154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SNRPD1 knockdown in hepatocellular carcinoma cells induces autophagy (increased autophagic vacuoles, upregulation of ATG5, ATG7, ATG12) and blocks the PI3K/AKT/mTOR/4EBP1 signaling pathway; SNRPD1 inhibition also suppresses tumor growth in vivo.\",\n      \"method\": \"siRNA knockdown in vitro and xenograft in vivo; western blotting for PI3K/AKT/mTOR/4EBP1 pathway proteins; autophagy gene expression and vacuole detection; Ki67 immunostaining in vivo\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with pathway analysis validated in vitro and in vivo with multiple readouts, single lab\",\n      \"pmids\": [\"37268273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"IGF2BP2, an m6A reader RNA-binding protein, binds SNRPD1 mRNA and enhances its stability through m6A-dependent mechanisms, thereby increasing SNRPD1 protein expression; IGF2BP2 overexpression reverses the anti-tumor effects of SNRPD1 knockdown in TNBC cells.\",\n      \"method\": \"RIP (RNA immunoprecipitation) assay to detect IGF2BP2-SNRPD1 mRNA interaction; methylated RNA immunoprecipitation (MeRIP) for m6A; qRT-PCR for RNA stability; functional rescue by co-transfection\",\n      \"journal\": \"Breast cancer (Dove Medical Press)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — RIP and MeRIP assays plus functional rescue, single lab, mechanistic pathway established\",\n      \"pmids\": [\"39411513\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SNRPD1 (Sm-D1) is a core Sm protein of canonical snRNPs (U1, U2, U4/U6, U5) but is specifically excluded from U7 snRNPs due to the unique Sm-binding site of U7 snRNA; its C-terminal GR-repeat region, which carries dimethylarginine post-translational modifications, mediates interactions with viral proteins (HCV NS3) and constitutes the major SLE autoantibody epitope; in pluripotent stem cells it physically associates with SNRPA1 and PNN to support pluripotency-specific spliceosome assembly; in cancer cells it promotes cell cycle progression (G1/S transition) and suppresses autophagy via the PI3K/AKT/mTOR/4EBP1 pathway, with its mRNA stability regulated post-transcriptionally by the m6A reader IGF2BP2.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SNRPD1 (Sm-D1) is a core Sm protein of canonical snRNPs whose assembly into spliceosomal particles underlies its role in pre-mRNA splicing across diverse cellular contexts [#0, #4]. It is encoded by the single functional gene of a multigene family, two other members being processed pseudogenes [#1]. SNRPD1 is incorporated into canonical snRNPs but is specifically excluded from U7 snRNPs, where the special Sm-binding site of U7 snRNA dictates that its position is instead occupied by the Sm-like protein Lsm10 [#0]. In human pluripotent stem cells SNRPD1 physically associates with SNRPA1 and PNN to support a pluripotency-specific spliceosome, and its depletion causes loss of pluripotency and blocks reprogramming [#4]. Its C-terminal GR-repeat region, bearing dimethylarginine modifications, forms the major SLE autoantibody epitope recognized by anti-Sm sera and also mediates a direct interaction with the HCV nonstructural protein NS3 that redistributes NS3 to the nucleus [#2, #3]. In cancer cells SNRPD1 promotes proliferation and G1/S cell cycle progression and suppresses autophagy through the PI3K/AKT/mTOR/4EBP1 pathway, and its mRNA is stabilized post-transcriptionally by the m6A reader IGF2BP2 [#5, #6, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing that SNRPD1 is the sole functional gene of its family clarified that a single locus produces the Sm-D1 protein, distinguishing it from non-coding processed pseudogenes.\",\n      \"evidence\": \"Southern blotting, sequencing and CAT reporter promoter mapping in transfected cells\",\n      \"pmids\": [\"9168134\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Promoter regulation in physiological contexts not defined\", \"No link to protein function established here\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identifying the C-terminal GR-repeat region with dimethylarginine modifications as the immunoreactive determinant explained why Sm-D1 is a dominant SLE autoantigen.\",\n      \"evidence\": \"Baculovirus-expressed recombinant Sm-D1 tested by ELISA against patient anti-Sm sera and monoclonal antibodies\",\n      \"pmids\": [\"9175921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not establish the role of this modification in normal snRNP function\", \"Mechanism of autoantibody generation not addressed\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showing that SNRPD1 is specifically excluded from U7 snRNPs and replaced by Lsm10 demonstrated that the RNA Sm-binding site selects which Sm proteins are incorporated, distinguishing canonical from specialized snRNPs.\",\n      \"evidence\": \"Affinity purification of U7 snRNPs with microsequencing and Sm-site functional mapping\",\n      \"pmids\": [\"11574479\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of D1 exclusion not resolved at atomic level\", \"Functional consequence of substitution for histone mRNA processing not detailed here\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identifying a direct HCV NS3–Sm-D1 interaction via the GR-repeat region linked the autoantigenic domain to a viral protein and to altered NS3 subcellular localization.\",\n      \"evidence\": \"Yeast two-hybrid, deletion mapping and immunostaining co-localization\",\n      \"pmids\": [\"14524621\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of the interaction\", \"Functional consequence for splicing or viral replication not established\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating that SNRPD1 associates with SNRPA1 and PNN and is required for pluripotency placed it within a pluripotency-specific spliceosome rather than only housekeeping splicing.\",\n      \"evidence\": \"Reciprocal Co-IP, co-localization with hPS spliceosomes, and siRNA knockdown with reprogramming/pluripotency assays\",\n      \"pmids\": [\"28595116\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific splicing targets supporting pluripotency not defined\", \"Single lab, no in vivo validation\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Knockdown causing G0/G1 arrest in breast cancer linked SNRPD1 to cell cycle progression and chemosensitivity beyond its housekeeping splicing role.\",\n      \"evidence\": \"siRNA knockdown with flow cytometry, qPCR, western blot and doxorubicin response assays\",\n      \"pmids\": [\"33879154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between splicing function and cell cycle control not defined\", \"Mechanism of altered drug sensitivity unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showing that SNRPD1 knockdown induces autophagy and blocks PI3K/AKT/mTOR/4EBP1 signaling defined a signaling pathway through which it supports tumor growth.\",\n      \"evidence\": \"siRNA knockdown in vitro and xenograft in vivo with pathway western blots, autophagy markers and Ki67 staining\",\n      \"pmids\": [\"37268273\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular connection between SNRPD1 and PI3K/AKT/mTOR not established\", \"Whether effect depends on splicing activity unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identifying IGF2BP2 as an m6A reader that stabilizes SNRPD1 mRNA established a post-transcriptional mechanism controlling SNRPD1 protein levels in cancer.\",\n      \"evidence\": \"RIP and MeRIP assays, mRNA stability qRT-PCR, and functional rescue by co-transfection in TNBC cells\",\n      \"pmids\": [\"39411513\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific m6A sites on SNRPD1 mRNA not mapped\", \"Upstream regulation of IGF2BP2 in this context unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SNRPD1's core spliceosomal function mechanistically connects to its cancer-associated cell cycle, autophagy, and signaling phenotypes remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No identified splicing targets bridging spliceosome assembly and proliferation/autophagy\", \"Whether oncogenic effects require splicing activity is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\"spliceosomal snRNP\"],\n    \"partners\": [\"SNRPA1\", \"PNN\", \"NS3\", \"IGF2BP2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"loss","faith_supported":6,"faith_total":6,"faith_pct":100.0}}