{"gene":"ZMAT2","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2017,"finding":"In the yeast pre-catalytic B complex spliceosome, Snu23 (ZMAT2 ortholog) together with Prp38 and Spp381 binds the Prp8 N-terminal domain and stabilizes U6 ACAGAGA stem–pre-mRNA and Brr2–U4 snRNA interactions, as revealed by cryo-EM structure at near-atomic resolution.","method":"Cryo-EM structure of yeast B complex spliceosome at near-atomic resolution","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — near-atomic cryo-EM structure with direct visualization of protein–RNA contacts, independently significant structural study","pmids":["28530653"],"is_preprint":false},{"year":2016,"finding":"ZMAT2/Snu23 contacts PRP38 via an ER/K motif-stabilized single α-helix; crystal structure and binding analyses demonstrated that Snu23, MFAP1, and Prp38 form a trimeric complex where Snu23 acts as an intermittent scaffold to facilitate spliceosome remodeling.","method":"Crystal structure determination, in vitro binding assays, mutational analysis of ER/K motifs","journal":"Structure","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with in vitro binding and mutagenesis in a single focused study","pmids":["27773687"],"is_preprint":false},{"year":2017,"finding":"Human SNU23 (ZMAT2) and yeast Snu23 both form higher-order complexes with their respective Prp38 proteins and with MFAP1/Spp381 via equivalent interfaces; cross-species interaction studies showed that these proteins constitute an evolutionarily conserved Snu23–Prp38–MFAP1/Spp381 sub-complex, repositioned from a tri-snRNP module in yeast to a B-specific module in metazoa.","method":"In vitro binding studies, cross-species pulldown experiments, bioinformatics ortholog inference","journal":"BMC evolutionary biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal binding studies across species with functional rescue assay, single lab","pmids":["28335716"],"is_preprint":false},{"year":2018,"finding":"ZMAT2 is an interactor of the pre-spliceosome required to maintain epidermal keratinocytes in an undifferentiated, proliferative state; RNA immunoprecipitation showed ZMAT2 associates with transcripts involved in cell adhesion, and siRNA knockdown of ZMAT2 caused aberrant splicing of cell adhesion-related transcripts, with functional interactions identified between ZMAT2 and epigenetic modifiers ING5, SMARCA5, BRD1, UHRF1, BPTF, and SMARCC2.","method":"siRNA knockdown, RNA immunoprecipitation (RIP), transcriptome-wide RNA splicing analysis, computational modeling, experimental validation of protein interactions","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RIP, transcriptome splicing, perturbation screen), single lab","pmids":["30380419"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structure of human B complex dimers revealed that SNU23 (ZMAT2) interacts with FBP21 and PRP38 at the U6/5′ splice site helix, contributing to 5′ splice site recognition; the structure also localized SNU23 within the molecular architecture of the human B complex.","method":"Cryo-EM structure of human spliceosomal B complex dimers","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structural determination with enhanced resolution providing direct visualization of SNU23 molecular contacts","pmids":["38383864"],"is_preprint":false},{"year":2024,"finding":"ZMAT2 undergoes phase separation to form liquid droplet condensates in HCC cells and forms protein–nucleic acid condensates with TRIM28 mRNA; ZMAT2 knockdown causes skipping of 25 bases in exon 11 of TRIM28 leading to nonsense-mediated decay, resulting in increased ROS accumulation and reduced cell proliferation.","method":"RNAseq, RIP-seq, ZMAT2 knockdown, phase separation assay (liquid droplet condensate imaging), ROS measurement, cell proliferation assay","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RNAseq, RIPseq, condensate imaging, functional rescue), single lab","pmids":["39164737"],"is_preprint":false},{"year":2020,"finding":"In zebrafish, zmat2 knockdown causes pectoral fin defects and embryo dorsalization consistent with reduced BMP signaling; these phenotypes were partially rescued by zbmp2b RNA overexpression and fully rescued by wild-type zzmat2 overexpression, but not by overexpression of the disease-associated mutant form, establishing ZMAT2 as a regulator of skeletal development through the BMP signaling pathway.","method":"Zebrafish morpholino knockdown, in situ hybridization, immunohistochemistry, mRNA rescue experiments with wild-type and mutant zmat2","journal":"Bone","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined phenotypic readout, epistasis via RNA rescue, single lab with multiple orthogonal methods","pmids":["32247068"],"is_preprint":false},{"year":2025,"finding":"Using single-molecule CoSMoS imaging, Snu23 (ZMAT2 ortholog) was shown to bind and release from spliceosomes simultaneously with Prp38 and Spp381 as a BCP subcomplex; BCP proteins associate with pre-mRNA after tri-snRNP binding and are released predominantly after U4 snRNP dissociation and NTC association; under low ATP, BCP pre-associates with the tri-snRNP. This recruitment pathway is conserved between yeast and humans.","method":"Colocalization Single Molecule Spectroscopy (CoSMoS) real-time imaging of splicing dynamics in yeast","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct real-time single-molecule visualization of binding dynamics with mechanistic resolution of assembly order, replicated in peer-reviewed publication","pmids":["39995036"],"is_preprint":false},{"year":2018,"finding":"Yeast Snu23 was identified as a direct substrate of the DNA damage checkpoint kinase Rad53, phosphorylated by Rad53 in vitro, placing ZMAT2/Snu23 as a target of the DNA damage response kinase cascade.","method":"Mass spectrometry-based phosphoproteomic screen, in vitro kinase assay","journal":"G3 (Bethesda, Md.)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro kinase assay confirmed phosphorylation, but functional consequence of this modification was not established for Snu23 specifically","pmids":["30377154"],"is_preprint":false}],"current_model":"ZMAT2 (hSNU23/Snu23) is a spliceosomal B complex protein that, together with PRP38 and MFAP1/Spp381, forms a conserved BCP subcomplex that binds the spliceosome after tri-snRNP association, stabilizes U6 ACAGAGA stem–pre-mRNA and Brr2–U4 snRNA interactions via contacts with the PRP8 N-terminal domain, and is released after U4 snRNP dissociation during catalytic activation; it additionally undergoes phase separation to form condensates that regulate alternative splicing of specific targets such as TRIM28, maintains epidermal progenitor cell identity by splicing cell adhesion transcripts in cooperation with chromatin modifiers, and modulates BMP signaling during skeletal development."},"narrative":{"mechanistic_narrative":"ZMAT2 (hSNU23/Snu23) is a spliceosomal protein that contributes to the assembly and catalytic activation of the pre-catalytic B complex [PMID:28530653, PMID:39995036]. It nucleates a conserved trimeric subcomplex with PRP38 and MFAP1/Spp381, contacting PRP38 through an ER/K-motif-stabilized single α-helix and acting as an intermittent scaffold that facilitates spliceosome remodeling [PMID:27773687, PMID:28335716]. Within the B complex, ZMAT2 binds the PRP8 N-terminal domain and stabilizes the U6 ACAGAGA stem–pre-mRNA and Brr2–U4 snRNA interactions [PMID:28530653], and in the human complex it interacts with FBP21 and PRP38 at the U6/5′ splice site helix to support 5′ splice site recognition [PMID:38383864]. Real-time single-molecule imaging established that ZMAT2 binds and releases from the spliceosome together with PRP38 and Spp381 as a single BCP module, associating after tri-snRNP binding and dissociating predominantly after U4 snRNP release upon NTC association [PMID:39995036]. Beyond core splicing, ZMAT2 maintains epidermal keratinocytes in an undifferentiated, proliferative state by binding and correctly splicing cell-adhesion transcripts in functional cooperation with chromatin modifiers [PMID:30380419], undergoes phase separation into condensates that regulate alternative splicing of TRIM28 mRNA to control ROS levels and proliferation [PMID:39164737], and acts as a regulator of skeletal development through the BMP signaling pathway [PMID:32247068].","teleology":[{"year":2016,"claim":"Established the structural basis by which ZMAT2 engages its splicing partners, answering how the protein is organized within a remodeling module.","evidence":"Crystal structure, in vitro binding, and ER/K-motif mutagenesis of the Snu23–Prp38–MFAP1 trimer","pmids":["27773687"],"confidence":"High","gaps":["Did not resolve how the trimer docks onto the full spliceosome","Functional consequence of disrupting the ER/K helix in cells not tested"]},{"year":2017,"claim":"Placed ZMAT2 within the pre-catalytic B complex and defined its RNA-stabilizing role, answering what the protein physically does during spliceosome assembly.","evidence":"Near-atomic cryo-EM of the yeast B complex spliceosome","pmids":["28530653"],"confidence":"High","gaps":["Static structure does not capture binding/release dynamics","Human complex architecture not directly resolved here"]},{"year":2017,"claim":"Demonstrated evolutionary conservation of the Snu23–Prp38–MFAP1/Spp381 subcomplex across yeast and metazoa, answering whether the module is repositioned between species.","evidence":"Cross-species in vitro binding and pulldown experiments with ortholog inference","pmids":["28335716"],"confidence":"Medium","gaps":["Binding assays in vitro, not in assembled spliceosomes","Single-lab data"]},{"year":2018,"claim":"Identified a tissue-level role for ZMAT2 in maintaining epidermal progenitor identity through splicing of adhesion transcripts, extending its function beyond generic core splicing.","evidence":"siRNA knockdown, RIP, transcriptome splicing analysis, and protein-interaction validation in keratinocytes","pmids":["30380419"],"confidence":"Medium","gaps":["Mechanistic link between adhesion-transcript splicing and chromatin modifiers not resolved","Direct vs indirect effects on individual transcripts unclear"]},{"year":2018,"claim":"Linked ZMAT2/Snu23 to the DNA damage response as a phosphorylation target of Rad53, raising the possibility that splicing assembly is regulated by checkpoint signaling.","evidence":"Phosphoproteomic screen and in vitro kinase assay in yeast","pmids":["30377154"],"confidence":"Medium","gaps":["Functional consequence of phosphorylation not established","In vitro phosphorylation only; physiological relevance untested"]},{"year":2020,"claim":"Established ZMAT2 as a regulator of skeletal development via BMP signaling, answering whether the gene has an organismal developmental function.","evidence":"Zebrafish morpholino knockdown with wild-type and mutant mRNA rescue","pmids":["32247068"],"confidence":"Medium","gaps":["Molecular link between ZMAT2 splicing activity and BMP pathway not defined","Morpholino approach without genetic mutant confirmation"]},{"year":2024,"claim":"Resolved ZMAT2 contacts in the human B complex and connected them to 5′ splice site recognition, extending the yeast structural model to humans.","evidence":"Cryo-EM of human spliceosomal B complex dimers","pmids":["38383864"],"confidence":"High","gaps":["Functional role of B-complex dimerization not established","Dynamics of FBP21–SNU23 contact not captured"]},{"year":2024,"claim":"Revealed a non-canonical condensate-forming behavior of ZMAT2 that regulates alternative splicing of TRIM28 and controls ROS and proliferation in cancer cells.","evidence":"RNAseq, RIP-seq, condensate imaging, ROS and proliferation assays in HCC cells","pmids":["39164737"],"confidence":"Medium","gaps":["Relationship between condensate formation and core spliceosome function unclear","Generality of phase separation beyond TRIM28 not assessed"]},{"year":2025,"claim":"Defined the real-time assembly order of the BCP module, answering when ZMAT2 binds and is released relative to tri-snRNP and U4 dissociation.","evidence":"Single-molecule CoSMoS imaging of splicing dynamics in yeast","pmids":["39995036"],"confidence":"High","gaps":["Whether human BCP follows identical kinetics not directly imaged","Regulation of the low-ATP pre-association state in vivo unknown"]},{"year":null,"claim":"How ZMAT2's core spliceosomal role mechanistically connects to its tissue-specific functions in epidermal identity, BMP-dependent skeletal development, and condensate-driven alternative splicing remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking core B-complex activity to selective target splicing","Physiological role of phosphorylation and phase separation not integrated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[3,5]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,4]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,4,5]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[0,4,7]}],"complexes":["spliceosomal B complex","Snu23-Prp38-MFAP1/Spp381 (BCP) subcomplex"],"partners":["PRP38","MFAP1","PRP8","FBP21","RAD53","TRIM28"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96NC0","full_name":"Zinc finger matrin-type protein 2","aliases":[],"length_aa":199,"mass_kda":23.6,"function":"Involved in pre-mRNA splicing as a component of the spliceosome","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q96NC0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/ZMAT2","classification":"Common Essential","n_dependent_lines":1207,"n_total_lines":1208,"dependency_fraction":0.9991721854304636},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"RBM39","stoichiometry":0.2},{"gene":"SF3A1","stoichiometry":0.2},{"gene":"SNRPA","stoichiometry":0.2},{"gene":"SNRPB","stoichiometry":0.2},{"gene":"SNRPC","stoichiometry":0.2},{"gene":"SSRP1","stoichiometry":0.2},{"gene":"TOP1","stoichiometry":0.2},{"gene":"XPO6","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ZMAT2","total_profiled":1310},"omim":[{"mim_id":"619930","title":"ZINC FINGER, MATRIN-TYPE 2; ZMAT2","url":"https://www.omim.org/entry/619930"},{"mim_id":"617031","title":"PRE-mRNA-PROCESSING FACTOR 38A; PRPF38A","url":"https://www.omim.org/entry/617031"},{"mim_id":"179300","title":"RADIOULNAR SYNOSTOSIS, NONSYNDROMIC, SUSCEPTIBILITY TO; RUS","url":"https://www.omim.org/entry/179300"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Mitochondria","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ZMAT2"},"hgnc":{"alias_symbol":["FLJ31121","hSNU23","Snu23"],"prev_symbol":[]},"alphafold":{"accession":"Q96NC0","domains":[{"cath_id":"-","chopping":"57-113","consensus_level":"medium","plddt":75.0239,"start":57,"end":113},{"cath_id":"1.20.5","chopping":"116-186","consensus_level":"medium","plddt":76.6073,"start":116,"end":186}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96NC0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96NC0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96NC0-F1-predicted_aligned_error_v6.png","plddt_mean":71.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ZMAT2","jax_strain_url":"https://www.jax.org/strain/search?query=ZMAT2"},"sequence":{"accession":"Q96NC0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96NC0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96NC0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96NC0"}},"corpus_meta":[{"pmid":"28530653","id":"PMC_28530653","title":"Structure of a pre-catalytic spliceosome.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28530653","citation_count":180,"is_preprint":false},{"pmid":"34021117","id":"PMC_34021117","title":"Transcriptome-wide association study identifies new susceptibility genes and pathways for depression.","date":"2021","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/34021117","citation_count":41,"is_preprint":false},{"pmid":"27773687","id":"PMC_27773687","title":"Scaffolding in the Spliceosome via Single α Helices.","date":"2016","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/27773687","citation_count":28,"is_preprint":false},{"pmid":"30380419","id":"PMC_30380419","title":"Splicing and Chromatin Factors Jointly Regulate Epidermal Differentiation.","date":"2018","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/30380419","citation_count":23,"is_preprint":false},{"pmid":"30377154","id":"PMC_30377154","title":"The Yeast DNA Damage Checkpoint Kinase Rad53 Targets the Exoribonuclease, Xrn1.","date":"2018","source":"G3 (Bethesda, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/30377154","citation_count":22,"is_preprint":false},{"pmid":"33194991","id":"PMC_33194991","title":"Proteomic Characterization of Proliferation Inhibition of Well-Differentiated Laryngeal Squamous Cell Carcinoma Cells Under Below-Background Radiation in a Deep Underground Environment.","date":"2020","source":"Frontiers in public health","url":"https://pubmed.ncbi.nlm.nih.gov/33194991","citation_count":18,"is_preprint":false},{"pmid":"28335716","id":"PMC_28335716","title":"Human MFAP1 is a cryptic ortholog of the Saccharomyces cerevisiae Spp381 splicing factor.","date":"2017","source":"BMC evolutionary biology","url":"https://pubmed.ncbi.nlm.nih.gov/28335716","citation_count":14,"is_preprint":false},{"pmid":"38383864","id":"PMC_38383864","title":"Cryo-EM analyses of dimerized spliceosomes provide new insights into the functions of B complex proteins.","date":"2024","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/38383864","citation_count":14,"is_preprint":false},{"pmid":"39164737","id":"PMC_39164737","title":"ZMAT2 condensates regulate the alternative splicing of TRIM28 to reduce cellular ROS accumulation, thereby promoting the proliferation of HCC cells.","date":"2024","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/39164737","citation_count":8,"is_preprint":false},{"pmid":"32247068","id":"PMC_32247068","title":"ZMAT2, a newly-identified potential disease-causing gene in congenital radioulnar synostosis, modulates BMP signaling.","date":"2020","source":"Bone","url":"https://pubmed.ncbi.nlm.nih.gov/32247068","citation_count":7,"is_preprint":false},{"pmid":"32952394","id":"PMC_32952394","title":"ZMAT2 in Humans and Other Primates: A Highly Conserved and Understudied Gene.","date":"2020","source":"Evolutionary bioinformatics online","url":"https://pubmed.ncbi.nlm.nih.gov/32952394","citation_count":5,"is_preprint":false},{"pmid":"39995036","id":"PMC_39995036","title":"Dynamics and evolutionary conservation of B complex protein recruitment during spliceosome activation.","date":"2025","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/39995036","citation_count":5,"is_preprint":false},{"pmid":"32005145","id":"PMC_32005145","title":"Zmat2 in mammals: conservation and diversification among genes and Pseudogenes.","date":"2020","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/32005145","citation_count":3,"is_preprint":false},{"pmid":"32463827","id":"PMC_32463827","title":"The Zmat2 gene in non-mammalian vertebrates: Organizational simplicity within a divergent locus in fish.","date":"2020","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/32463827","citation_count":1,"is_preprint":false},{"pmid":"39149324","id":"PMC_39149324","title":"Dynamics and Evolutionary Conservation of B Complex Protein Recruitment During Spliceosome Activation.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/39149324","citation_count":0,"is_preprint":false},{"pmid":"40634559","id":"PMC_40634559","title":"Integrated bioinformatics and experimental analysis of mitochondrial-associated membrane function and mechanism in acute respiratory distress syndrome​​.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/40634559","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10024,"output_tokens":2320,"usd":0.032436,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9466,"output_tokens":2896,"usd":0.059865,"stage2_stop_reason":"end_turn"},"total_usd":0.092301,"stage1_batch_id":"msgbatch_01UT1AahFPCAyn2uVweS7A9z","stage2_batch_id":"msgbatch_01HuKWtKNT4Pqj1bc8eEP5RV","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"In the yeast pre-catalytic B complex spliceosome, Snu23 (ZMAT2 ortholog) together with Prp38 and Spp381 binds the Prp8 N-terminal domain and stabilizes U6 ACAGAGA stem–pre-mRNA and Brr2–U4 snRNA interactions, as revealed by cryo-EM structure at near-atomic resolution.\",\n      \"method\": \"Cryo-EM structure of yeast B complex spliceosome at near-atomic resolution\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — near-atomic cryo-EM structure with direct visualization of protein–RNA contacts, independently significant structural study\",\n      \"pmids\": [\"28530653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ZMAT2/Snu23 contacts PRP38 via an ER/K motif-stabilized single α-helix; crystal structure and binding analyses demonstrated that Snu23, MFAP1, and Prp38 form a trimeric complex where Snu23 acts as an intermittent scaffold to facilitate spliceosome remodeling.\",\n      \"method\": \"Crystal structure determination, in vitro binding assays, mutational analysis of ER/K motifs\",\n      \"journal\": \"Structure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with in vitro binding and mutagenesis in a single focused study\",\n      \"pmids\": [\"27773687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human SNU23 (ZMAT2) and yeast Snu23 both form higher-order complexes with their respective Prp38 proteins and with MFAP1/Spp381 via equivalent interfaces; cross-species interaction studies showed that these proteins constitute an evolutionarily conserved Snu23–Prp38–MFAP1/Spp381 sub-complex, repositioned from a tri-snRNP module in yeast to a B-specific module in metazoa.\",\n      \"method\": \"In vitro binding studies, cross-species pulldown experiments, bioinformatics ortholog inference\",\n      \"journal\": \"BMC evolutionary biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal binding studies across species with functional rescue assay, single lab\",\n      \"pmids\": [\"28335716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ZMAT2 is an interactor of the pre-spliceosome required to maintain epidermal keratinocytes in an undifferentiated, proliferative state; RNA immunoprecipitation showed ZMAT2 associates with transcripts involved in cell adhesion, and siRNA knockdown of ZMAT2 caused aberrant splicing of cell adhesion-related transcripts, with functional interactions identified between ZMAT2 and epigenetic modifiers ING5, SMARCA5, BRD1, UHRF1, BPTF, and SMARCC2.\",\n      \"method\": \"siRNA knockdown, RNA immunoprecipitation (RIP), transcriptome-wide RNA splicing analysis, computational modeling, experimental validation of protein interactions\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RIP, transcriptome splicing, perturbation screen), single lab\",\n      \"pmids\": [\"30380419\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structure of human B complex dimers revealed that SNU23 (ZMAT2) interacts with FBP21 and PRP38 at the U6/5′ splice site helix, contributing to 5′ splice site recognition; the structure also localized SNU23 within the molecular architecture of the human B complex.\",\n      \"method\": \"Cryo-EM structure of human spliceosomal B complex dimers\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structural determination with enhanced resolution providing direct visualization of SNU23 molecular contacts\",\n      \"pmids\": [\"38383864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ZMAT2 undergoes phase separation to form liquid droplet condensates in HCC cells and forms protein–nucleic acid condensates with TRIM28 mRNA; ZMAT2 knockdown causes skipping of 25 bases in exon 11 of TRIM28 leading to nonsense-mediated decay, resulting in increased ROS accumulation and reduced cell proliferation.\",\n      \"method\": \"RNAseq, RIP-seq, ZMAT2 knockdown, phase separation assay (liquid droplet condensate imaging), ROS measurement, cell proliferation assay\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RNAseq, RIPseq, condensate imaging, functional rescue), single lab\",\n      \"pmids\": [\"39164737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In zebrafish, zmat2 knockdown causes pectoral fin defects and embryo dorsalization consistent with reduced BMP signaling; these phenotypes were partially rescued by zbmp2b RNA overexpression and fully rescued by wild-type zzmat2 overexpression, but not by overexpression of the disease-associated mutant form, establishing ZMAT2 as a regulator of skeletal development through the BMP signaling pathway.\",\n      \"method\": \"Zebrafish morpholino knockdown, in situ hybridization, immunohistochemistry, mRNA rescue experiments with wild-type and mutant zmat2\",\n      \"journal\": \"Bone\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined phenotypic readout, epistasis via RNA rescue, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"32247068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Using single-molecule CoSMoS imaging, Snu23 (ZMAT2 ortholog) was shown to bind and release from spliceosomes simultaneously with Prp38 and Spp381 as a BCP subcomplex; BCP proteins associate with pre-mRNA after tri-snRNP binding and are released predominantly after U4 snRNP dissociation and NTC association; under low ATP, BCP pre-associates with the tri-snRNP. This recruitment pathway is conserved between yeast and humans.\",\n      \"method\": \"Colocalization Single Molecule Spectroscopy (CoSMoS) real-time imaging of splicing dynamics in yeast\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct real-time single-molecule visualization of binding dynamics with mechanistic resolution of assembly order, replicated in peer-reviewed publication\",\n      \"pmids\": [\"39995036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Yeast Snu23 was identified as a direct substrate of the DNA damage checkpoint kinase Rad53, phosphorylated by Rad53 in vitro, placing ZMAT2/Snu23 as a target of the DNA damage response kinase cascade.\",\n      \"method\": \"Mass spectrometry-based phosphoproteomic screen, in vitro kinase assay\",\n      \"journal\": \"G3 (Bethesda, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro kinase assay confirmed phosphorylation, but functional consequence of this modification was not established for Snu23 specifically\",\n      \"pmids\": [\"30377154\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ZMAT2 (hSNU23/Snu23) is a spliceosomal B complex protein that, together with PRP38 and MFAP1/Spp381, forms a conserved BCP subcomplex that binds the spliceosome after tri-snRNP association, stabilizes U6 ACAGAGA stem–pre-mRNA and Brr2–U4 snRNA interactions via contacts with the PRP8 N-terminal domain, and is released after U4 snRNP dissociation during catalytic activation; it additionally undergoes phase separation to form condensates that regulate alternative splicing of specific targets such as TRIM28, maintains epidermal progenitor cell identity by splicing cell adhesion transcripts in cooperation with chromatin modifiers, and modulates BMP signaling during skeletal development.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ZMAT2 (hSNU23/Snu23) is a spliceosomal protein that contributes to the assembly and catalytic activation of the pre-catalytic B complex [#0, #7]. It nucleates a conserved trimeric subcomplex with PRP38 and MFAP1/Spp381, contacting PRP38 through an ER/K-motif-stabilized single \\u03b1-helix and acting as an intermittent scaffold that facilitates spliceosome remodeling [#1, #2]. Within the B complex, ZMAT2 binds the PRP8 N-terminal domain and stabilizes the U6 ACAGAGA stem\\u2013pre-mRNA and Brr2\\u2013U4 snRNA interactions [#0], and in the human complex it interacts with FBP21 and PRP38 at the U6/5\\u2032 splice site helix to support 5\\u2032 splice site recognition [#4]. Real-time single-molecule imaging established that ZMAT2 binds and releases from the spliceosome together with PRP38 and Spp381 as a single BCP module, associating after tri-snRNP binding and dissociating predominantly after U4 snRNP release upon NTC association [#7]. Beyond core splicing, ZMAT2 maintains epidermal keratinocytes in an undifferentiated, proliferative state by binding and correctly splicing cell-adhesion transcripts in functional cooperation with chromatin modifiers [#3], undergoes phase separation into condensates that regulate alternative splicing of TRIM28 mRNA to control ROS levels and proliferation [#5], and acts as a regulator of skeletal development through the BMP signaling pathway [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established the structural basis by which ZMAT2 engages its splicing partners, answering how the protein is organized within a remodeling module.\",\n      \"evidence\": \"Crystal structure, in vitro binding, and ER/K-motif mutagenesis of the Snu23\\u2013Prp38\\u2013MFAP1 trimer\",\n      \"pmids\": [\"27773687\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how the trimer docks onto the full spliceosome\", \"Functional consequence of disrupting the ER/K helix in cells not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed ZMAT2 within the pre-catalytic B complex and defined its RNA-stabilizing role, answering what the protein physically does during spliceosome assembly.\",\n      \"evidence\": \"Near-atomic cryo-EM of the yeast B complex spliceosome\",\n      \"pmids\": [\"28530653\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Static structure does not capture binding/release dynamics\", \"Human complex architecture not directly resolved here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated evolutionary conservation of the Snu23\\u2013Prp38\\u2013MFAP1/Spp381 subcomplex across yeast and metazoa, answering whether the module is repositioned between species.\",\n      \"evidence\": \"Cross-species in vitro binding and pulldown experiments with ortholog inference\",\n      \"pmids\": [\"28335716\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding assays in vitro, not in assembled spliceosomes\", \"Single-lab data\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified a tissue-level role for ZMAT2 in maintaining epidermal progenitor identity through splicing of adhesion transcripts, extending its function beyond generic core splicing.\",\n      \"evidence\": \"siRNA knockdown, RIP, transcriptome splicing analysis, and protein-interaction validation in keratinocytes\",\n      \"pmids\": [\"30380419\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between adhesion-transcript splicing and chromatin modifiers not resolved\", \"Direct vs indirect effects on individual transcripts unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked ZMAT2/Snu23 to the DNA damage response as a phosphorylation target of Rad53, raising the possibility that splicing assembly is regulated by checkpoint signaling.\",\n      \"evidence\": \"Phosphoproteomic screen and in vitro kinase assay in yeast\",\n      \"pmids\": [\"30377154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of phosphorylation not established\", \"In vitro phosphorylation only; physiological relevance untested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established ZMAT2 as a regulator of skeletal development via BMP signaling, answering whether the gene has an organismal developmental function.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with wild-type and mutant mRNA rescue\",\n      \"pmids\": [\"32247068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between ZMAT2 splicing activity and BMP pathway not defined\", \"Morpholino approach without genetic mutant confirmation\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Resolved ZMAT2 contacts in the human B complex and connected them to 5\\u2032 splice site recognition, extending the yeast structural model to humans.\",\n      \"evidence\": \"Cryo-EM of human spliceosomal B complex dimers\",\n      \"pmids\": [\"38383864\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of B-complex dimerization not established\", \"Dynamics of FBP21\\u2013SNU23 contact not captured\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a non-canonical condensate-forming behavior of ZMAT2 that regulates alternative splicing of TRIM28 and controls ROS and proliferation in cancer cells.\",\n      \"evidence\": \"RNAseq, RIP-seq, condensate imaging, ROS and proliferation assays in HCC cells\",\n      \"pmids\": [\"39164737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relationship between condensate formation and core spliceosome function unclear\", \"Generality of phase separation beyond TRIM28 not assessed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined the real-time assembly order of the BCP module, answering when ZMAT2 binds and is released relative to tri-snRNP and U4 dissociation.\",\n      \"evidence\": \"Single-molecule CoSMoS imaging of splicing dynamics in yeast\",\n      \"pmids\": [\"39995036\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether human BCP follows identical kinetics not directly imaged\", \"Regulation of the low-ATP pre-association state in vivo unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ZMAT2's core spliceosomal role mechanistically connects to its tissue-specific functions in epidermal identity, BMP-dependent skeletal development, and condensate-driven alternative splicing remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking core B-complex activity to selective target splicing\", \"Physiological role of phosphorylation and phase separation not integrated\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 4, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [0, 4, 7]}\n    ],\n    \"complexes\": [\n      \"spliceosomal B complex\",\n      \"Snu23-Prp38-MFAP1/Spp381 (BCP) subcomplex\"\n    ],\n    \"partners\": [\n      \"PRP38\",\n      \"MFAP1\",\n      \"PRP8\",\n      \"FBP21\",\n      \"RAD53\",\n      \"TRIM28\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}