{"gene":"GMPS","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2021,"finding":"SNORD50A/B small nucleolar RNAs enhance the interaction between E3 ubiquitin ligase TRIM21 and GMPS by forming a complex among them, promoting GMPS ubiquitination and cytoplasmic sequestration; loss of SNORD50A/B releases GMPS to translocate into the nucleus, where GMPS recruits USP7 and forms a complex with p53, decreasing p53 ubiquitination and stabilizing p53 protein.","method":"Co-immunoprecipitation, western blot, immunofluorescence, functional overexpression/knockout studies in breast cancer cells","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP demonstrating TRIM21-GMPS-SNORD50A/B complex, USP7-GMPS-p53 complex, nuclear translocation assay, multiple orthogonal methods, functional validation with KO/OE","pmids":["33742136"],"is_preprint":false},{"year":2020,"finding":"TRIM21 acts as an E3 ubiquitin ligase that mediates GMPS ubiquitination and degradation, thereby reducing nuclear GMPS availability and suppressing TP53 expression; SERPINB5 serves as an adaptor protein that prevents GMPS from entering the nucleus and recruits TRIM21 for GMPS ubiquitination.","method":"Co-immunoprecipitation, western blot, mass spectrometry identification of GMPS as TRIM21 target, immunofluorescence, overexpression/knockout cell lines, in vivo xenograft models","journal":"Journal of biomedical science","confidence":"High","confidence_rationale":"Tier 2 / Strong — mass spectrometry identification plus Co-IP, epistasis established by SERPINB5/TRIM21/GMPS overexpression and knockout experiments, multiple orthogonal methods, replicated in vivo","pmids":["32005234"],"is_preprint":false},{"year":2024,"finding":"GMPS promotes PD-L1 expression in hepatocellular carcinoma by enhancing the interaction between PD-L1 and the catalytic subunit STT3A of oligosaccharyltransferase (OST), acting as an additional module connecting the Sec61 channel complex and STT3A, thereby facilitating translocation and N-glycosylation of PD-L1 and reducing its ubiquitination-mediated degradation.","method":"Proteomic and scRNA-seq analyses, co-immunoprecipitation, western blot, pharmacological inhibition with angustmycin A, in vivo tumor models","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP establishing GMPS-STT3A-PD-L1 complex, pharmacological validation, single lab with multiple methods but mechanism of GMPS bridging Sec61-STT3A inferred rather than fully reconstituted","pmids":["39690246"],"is_preprint":false},{"year":2021,"finding":"GMPS functions in the de novo purine biosynthesis pathway utilizing a glutamine amide to synthesize guanosine monophosphate; pharmacological inhibition or knockdown of GMPS significantly decreases prostate cancer cell growth and alters glutamine metabolism, as demonstrated by [15N-(amide)]glutamine and [U-13C5]glutamine metabolic tracing.","method":"siRNA knockdown, pharmacological inhibition, isotope metabolic tracing ([15N]-glutamine, [U-13C5]-glutamine), PC-3 xenograft mouse model","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isotope tracing provides direct mechanistic evidence for GMPS catalytic function in glutamine amide transfer, validated in vivo; single lab","pmids":["33768538"],"is_preprint":false},{"year":2000,"finding":"GMPS (Guanosine 5'-Monophosphate Synthetase) gene on chromosome 3q24 is fused in-frame with MLL in a t(3;11)(q25;q23) translocation in treatment-related acute myeloid leukemia, producing a chimeric MLL-GMPS fusion transcript that is alternatively spliced.","method":"cDNA panhandle PCR, reverse transcription, Southern blot analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct molecular identification of fusion transcript by PCR/sequencing in a single patient; establishes GMPS chromosomal location and fusion but no mechanistic follow-up of the fusion protein","pmids":["11110714"],"is_preprint":false},{"year":2013,"finding":"The GATase subunit of archaeal (Methanocaldococcus jannaschii) GMPS has a solution structure with a seven-stranded mixed β-sheet fenced by five α-helices; NMR chemical shift perturbation mapping identified a common surface on GATase responsible for both Mg2+ binding and interaction with the ATPPase subunit, with GATase-Mg2+ having Kd ~1 mM and GATase-ATPPase interaction falling in intermediate chemical exchange.","method":"Solution NMR structure determination, 15N backbone relaxation, NMR chemical shift perturbation mapping, gel filtration chromatography","journal":"Biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — high-resolution NMR structure with functional interaction mapping, but from archaeal (non-mammalian) GMPS; single study","pmids":["23724776"],"is_preprint":false},{"year":2025,"finding":"GMPS promotes lung cancer cell migration through the SERPINB2-uPA axis, with DNMT1 serving as an intermediate factor by which GMPS regulates SERPINB2 expression; knockdown of GMPS inhibits tumor progression in NSCLC.","method":"Lentiviral overexpression and knockout cell lines, RNA sequencing, western blot, animal experiments","journal":"Cellular oncology (Dordrecht, Netherlands)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway placed by RNA-seq and western blot in KO/OE cells plus in vivo, single lab, DNMT1-SERPINB2-uPA axis established by functional experiments","pmids":["40498285"],"is_preprint":false},{"year":2025,"finding":"Extracellular matrix (ECM) bio-scaffolds enhance guanylate production in pancreatic ductal adenocarcinoma cells via upregulation of GMPS (and IMPDH) expression, with increased guanylates alleviating oxaliplatin-induced DNA damage; GMPS expression correlates with matrisomal and DNA repair gene expression in PDAC patient samples.","method":"In vitro ECM bio-scaffolds, multi-omics integration, metabolic tracing, gene expression correlation in patient samples","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — metabolic tracing supports guanylate production but GMPS-specific mechanism not directly isolated from IMPDH; preprint, single lab, no direct GMPS mutagenesis or reconstitution","pmids":[],"is_preprint":true}],"current_model":"GMPS (guanosine monophosphate synthetase) catalyzes the final step of de novo GMP synthesis by transferring a glutamine amide to XMP; in the nucleus, GMPS recruits USP7 to form a complex with p53, stabilizing p53 by reducing its ubiquitination, while in the cytoplasm GMPS is subject to TRIM21-mediated ubiquitination and degradation facilitated by SERPINB5 as an adaptor (and promoted by SNORD50A/B), linking GMPS subcellular localization to p53 stability; additionally, GMPS can act as a scaffold enhancing STT3A-mediated N-glycosylation of PD-L1, and promotes cancer cell migration via a DNMT1/SERPINB2/uPA axis."},"narrative":{"mechanistic_narrative":"GMPS catalyzes the final, glutamine-amide-dependent step of de novo GMP synthesis, converting XMP to GMP, and this catalytic activity supports cancer cell proliferation and reshapes glutamine metabolism, as shown by isotope tracing and the growth defects following GMPS inhibition or knockdown in prostate cancer [PMID:33768538]. Beyond its metabolic role, GMPS has a nuclear, non-catalytic function in p53 regulation: nuclear GMPS recruits the deubiquitinase USP7 into a complex with p53, decreasing p53 ubiquitination and stabilizing the protein [PMID:33742136]. GMPS subcellular partitioning is therefore the key control point — cytoplasmic GMPS is targeted by the E3 ligase TRIM21 for ubiquitination and degradation, with SERPINB5 acting as an adaptor that prevents nuclear entry and recruits TRIM21, while SNORD50A/B small nucleolar RNAs further promote the TRIM21–GMPS interaction and cytoplasmic sequestration; loss of these restraints releases GMPS to the nucleus to stabilize p53 [PMID:33742136, PMID:32005234]. GMPS additionally moonlights as a scaffold that bridges the Sec61 channel and the oligosaccharyltransferase subunit STT3A to enhance N-glycosylation and stability of PD-L1 in hepatocellular carcinoma [PMID:39690246], and promotes lung cancer cell migration through a DNMT1/SERPINB2/uPA axis [PMID:40498285]. The GATase subunit of the enzyme adopts a defined fold with a surface mediating Mg2+ binding and contact with the ATPPase subunit, as resolved in an archaeal ortholog [PMID:23724776].","teleology":[{"year":2000,"claim":"Established the GMPS chromosomal locus and showed it can be disrupted by oncogenic translocation, the first link between GMPS and malignancy.","evidence":"cDNA panhandle PCR and Southern blot identifying an in-frame MLL-GMPS fusion in treatment-related AML","pmids":["11110714"],"confidence":"Medium","gaps":["Single patient with no functional characterization of the fusion protein","Does not establish whether GMPS contributes function to the chimera"]},{"year":2013,"claim":"Resolved the structural basis of the GATase subunit's Mg2+ binding and its interaction surface with the ATPPase subunit, defining intersubunit coupling within the synthetase.","evidence":"Solution NMR structure, backbone relaxation and chemical shift perturbation mapping of archaeal (M. jannaschii) GMPS GATase","pmids":["23724776"],"confidence":"Medium","gaps":["Archaeal rather than mammalian enzyme","Does not address full-length holoenzyme catalysis or nuclear moonlighting functions"]},{"year":2020,"claim":"Defined how cytoplasmic GMPS is restrained, showing TRIM21-mediated ubiquitination and SERPINB5-adaptor-controlled nuclear exclusion link GMPS localization to TP53 expression.","evidence":"Mass spectrometry, Co-IP, overexpression/knockout cell lines and xenografts","pmids":["32005234"],"confidence":"High","gaps":["Does not resolve the structural basis of SERPINB5-GMPS-TRIM21 assembly","Mechanism of nuclear import upon adaptor loss not detailed"]},{"year":2021,"claim":"Identified SNORD50A/B snoRNAs as upstream modulators that promote TRIM21–GMPS complex formation and cytoplasmic sequestration, and confirmed the nuclear GMPS–USP7–p53 stabilizing complex.","evidence":"Reciprocal Co-IP, immunofluorescence translocation assays, and KO/OE functional studies in breast cancer cells","pmids":["33742136"],"confidence":"High","gaps":["How snoRNAs physically template the TRIM21-GMPS interaction is not structurally defined","Quantitative contribution of nuclear GMPS to total p53 pool unclear"]},{"year":2021,"claim":"Provided direct metabolic evidence that GMPS catalytic glutamine-amide transfer drives guanylate synthesis required for cancer cell growth.","evidence":"siRNA knockdown, pharmacological inhibition, [15N]-/[U-13C5]-glutamine isotope tracing, and PC-3 xenografts","pmids":["33768538"],"confidence":"Medium","gaps":["Single tumor type and lab","Does not separate catalytic from scaffolding contributions to the growth phenotype"]},{"year":2024,"claim":"Revealed a catalysis-independent scaffolding role in which GMPS bridges the Sec61 channel and STT3A to enhance PD-L1 N-glycosylation and stability.","evidence":"Proteomics/scRNA-seq, Co-IP, angustmycin A inhibition, and in vivo tumor models in HCC","pmids":["39690246"],"confidence":"Medium","gaps":["The bridging mechanism between Sec61 and STT3A is inferred, not reconstituted","Single-lab finding without orthogonal structural validation"]},{"year":2025,"claim":"Placed GMPS in a pro-migratory pathway acting through DNMT1 to regulate the SERPINB2-uPA axis in lung cancer.","evidence":"Lentiviral KO/OE cell lines, RNA-seq, western blot, and animal experiments in NSCLC","pmids":["40498285"],"confidence":"Medium","gaps":["Direct biochemical link between GMPS and DNMT1 not established","Single lab; mechanism of DNMT1 regulation of SERPINB2 not fully resolved"]},{"year":null,"claim":"How GMPS catalytic guanylate output, nuclear p53 stabilization, and ER scaffolding functions are coordinately switched in a single cell remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the mammalian holoenzyme in its nuclear moonlighting state","Regulatory hierarchy among localization, catalysis, and scaffolding undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[3]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[3]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,2,6]}],"complexes":[],"partners":["USP7","TRIM21","SERPINB5","STT3A","TP53"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P49915","full_name":"GMP synthase [glutamine-hydrolyzing]","aliases":["GMP synthetase","Glutamine amidotransferase"],"length_aa":693,"mass_kda":76.7,"function":"Catalyzes the conversion of xanthine monophosphate (XMP) to GMP in the presence of glutamine and ATP through an adenyl-XMP intermediate","subcellular_location":"Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/P49915/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/GMPS","classification":"Common Essential","n_dependent_lines":972,"n_total_lines":1208,"dependency_fraction":0.804635761589404},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SAR1B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GMPS","total_profiled":1310},"omim":[{"mim_id":"610552","title":"UBIQUITIN-LIKE MODIFIER-ACTIVATING ENZYME 5; UBA5","url":"https://www.omim.org/entry/610552"},{"mim_id":"608657","title":"JUN DIMERIZATION PROTEIN 2; JDP2","url":"https://www.omim.org/entry/608657"},{"mim_id":"606542","title":"HISTONE DEACETYLASE 7A; HDAC7A","url":"https://www.omim.org/entry/606542"},{"mim_id":"604787","title":"ADP-RIBOSYLATION FACTOR-LIKE GTPase 4C; ARL4C","url":"https://www.omim.org/entry/604787"},{"mim_id":"602719","title":"TRANSFORMER 2 BETA HOMOLOG; TRA2B","url":"https://www.omim.org/entry/602719"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"testis","ntpm":93.8}],"url":"https://www.proteinatlas.org/search/GMPS"},"hgnc":{"alias_symbol":["GATD7"],"prev_symbol":[]},"alphafold":{"accession":"P49915","domains":[{"cath_id":"3.40.50.880","chopping":"27-209","consensus_level":"high","plddt":88.6085,"start":27,"end":209},{"cath_id":"3.40.50.620","chopping":"218-433","consensus_level":"high","plddt":84.2499,"start":218,"end":433},{"cath_id":"-","chopping":"457-680","consensus_level":"medium","plddt":91.9463,"start":457,"end":680}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P49915","model_url":"https://alphafold.ebi.ac.uk/files/AF-P49915-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P49915-F1-predicted_aligned_error_v6.png","plddt_mean":86.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GMPS","jax_strain_url":"https://www.jax.org/strain/search?query=GMPS"},"sequence":{"accession":"P49915","fasta_url":"https://rest.uniprot.org/uniprotkb/P49915.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P49915/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P49915"}},"corpus_meta":[{"pmid":"8719784","id":"PMC_8719784","title":"Inhibition of cyclic GMP-dependent protein kinase-mediated effects by (Rp)-8-bromo-PET-cyclic GMPS.","date":"1995","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/8719784","citation_count":99,"is_preprint":false},{"pmid":"33742136","id":"PMC_33742136","title":"The noncoding RNAs SNORD50A and SNORD50B-mediated TRIM21-GMPS interaction promotes the growth of p53 wild-type breast cancers by degrading p53.","date":"2021","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/33742136","citation_count":49,"is_preprint":false},{"pmid":"32005234","id":"PMC_32005234","title":"TRIM21-SERPINB5 aids GMPS repression to protect nasopharyngeal carcinoma cells from radiation-induced apoptosis.","date":"2020","source":"Journal of biomedical science","url":"https://pubmed.ncbi.nlm.nih.gov/32005234","citation_count":43,"is_preprint":false},{"pmid":"21828132","id":"PMC_21828132","title":"Bone marrow-derived CMPs and GMPs represent highly functional proangiogenic cells: implications for ischemic cardiovascular disease.","date":"2011","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/21828132","citation_count":42,"is_preprint":false},{"pmid":"33768538","id":"PMC_33768538","title":"Inhibition of guanosine monophosphate synthetase (GMPS) blocks glutamine metabolism and prostate cancer growth.","date":"2021","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/33768538","citation_count":35,"is_preprint":false},{"pmid":"11110714","id":"PMC_11110714","title":"t(3;11) translocation in treatment-related acute myeloid leukemia fuses MLL with the GMPS (GUANOSINE 5' MONOPHOSPHATE SYNTHETASE) gene.","date":"2000","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/11110714","citation_count":23,"is_preprint":false},{"pmid":"39690246","id":"PMC_39690246","title":"A STT3A-dependent PD-L1 glycosylation modification mediated by GMPS drives tumor immune evasion in hepatocellular carcinoma.","date":"2024","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/39690246","citation_count":21,"is_preprint":false},{"pmid":"20045992","id":"PMC_20045992","title":"Genetic variations in the HGPRT, ITPA, IMPDH1, IMPDH2, and GMPS genes in Japanese individuals.","date":"2009","source":"Drug metabolism and pharmacokinetics","url":"https://pubmed.ncbi.nlm.nih.gov/20045992","citation_count":20,"is_preprint":false},{"pmid":"11670875","id":"PMC_11670875","title":"Diminishing Dynamic Motion Problems of Platinum Anticancer Drug Adducts of Guanine Derivatives with the Hybrid Ligand Approach: Evidence for Cis Interligand Interactions Especially between 3'-GMP's.","date":"1999","source":"Inorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11670875","citation_count":12,"is_preprint":false},{"pmid":"34203217","id":"PMC_34203217","title":"Discovery of Novel GMPS Inhibitors of Candidatus Liberibacter Asiaticus by Structure Based Design and Enzyme 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enhance the interaction between E3 ubiquitin ligase TRIM21 and GMPS by forming a complex among them, promoting GMPS ubiquitination and cytoplasmic sequestration; loss of SNORD50A/B releases GMPS to translocate into the nucleus, where GMPS recruits USP7 and forms a complex with p53, decreasing p53 ubiquitination and stabilizing p53 protein.\",\n      \"method\": \"Co-immunoprecipitation, western blot, immunofluorescence, functional overexpression/knockout studies in breast cancer cells\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP demonstrating TRIM21-GMPS-SNORD50A/B complex, USP7-GMPS-p53 complex, nuclear translocation assay, multiple orthogonal methods, functional validation with KO/OE\",\n      \"pmids\": [\"33742136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TRIM21 acts as an E3 ubiquitin ligase that mediates GMPS ubiquitination and degradation, thereby reducing nuclear GMPS availability and suppressing TP53 expression; SERPINB5 serves as an adaptor protein that prevents GMPS from entering the nucleus and recruits TRIM21 for GMPS ubiquitination.\",\n      \"method\": \"Co-immunoprecipitation, western blot, mass spectrometry identification of GMPS as TRIM21 target, immunofluorescence, overexpression/knockout cell lines, in vivo xenograft models\",\n      \"journal\": \"Journal of biomedical science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mass spectrometry identification plus Co-IP, epistasis established by SERPINB5/TRIM21/GMPS overexpression and knockout experiments, multiple orthogonal methods, replicated in vivo\",\n      \"pmids\": [\"32005234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GMPS promotes PD-L1 expression in hepatocellular carcinoma by enhancing the interaction between PD-L1 and the catalytic subunit STT3A of oligosaccharyltransferase (OST), acting as an additional module connecting the Sec61 channel complex and STT3A, thereby facilitating translocation and N-glycosylation of PD-L1 and reducing its ubiquitination-mediated degradation.\",\n      \"method\": \"Proteomic and scRNA-seq analyses, co-immunoprecipitation, western blot, pharmacological inhibition with angustmycin A, in vivo tumor models\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP establishing GMPS-STT3A-PD-L1 complex, pharmacological validation, single lab with multiple methods but mechanism of GMPS bridging Sec61-STT3A inferred rather than fully reconstituted\",\n      \"pmids\": [\"39690246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GMPS functions in the de novo purine biosynthesis pathway utilizing a glutamine amide to synthesize guanosine monophosphate; pharmacological inhibition or knockdown of GMPS significantly decreases prostate cancer cell growth and alters glutamine metabolism, as demonstrated by [15N-(amide)]glutamine and [U-13C5]glutamine metabolic tracing.\",\n      \"method\": \"siRNA knockdown, pharmacological inhibition, isotope metabolic tracing ([15N]-glutamine, [U-13C5]-glutamine), PC-3 xenograft mouse model\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isotope tracing provides direct mechanistic evidence for GMPS catalytic function in glutamine amide transfer, validated in vivo; single lab\",\n      \"pmids\": [\"33768538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GMPS (Guanosine 5'-Monophosphate Synthetase) gene on chromosome 3q24 is fused in-frame with MLL in a t(3;11)(q25;q23) translocation in treatment-related acute myeloid leukemia, producing a chimeric MLL-GMPS fusion transcript that is alternatively spliced.\",\n      \"method\": \"cDNA panhandle PCR, reverse transcription, Southern blot analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct molecular identification of fusion transcript by PCR/sequencing in a single patient; establishes GMPS chromosomal location and fusion but no mechanistic follow-up of the fusion protein\",\n      \"pmids\": [\"11110714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The GATase subunit of archaeal (Methanocaldococcus jannaschii) GMPS has a solution structure with a seven-stranded mixed β-sheet fenced by five α-helices; NMR chemical shift perturbation mapping identified a common surface on GATase responsible for both Mg2+ binding and interaction with the ATPPase subunit, with GATase-Mg2+ having Kd ~1 mM and GATase-ATPPase interaction falling in intermediate chemical exchange.\",\n      \"method\": \"Solution NMR structure determination, 15N backbone relaxation, NMR chemical shift perturbation mapping, gel filtration chromatography\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — high-resolution NMR structure with functional interaction mapping, but from archaeal (non-mammalian) GMPS; single study\",\n      \"pmids\": [\"23724776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GMPS promotes lung cancer cell migration through the SERPINB2-uPA axis, with DNMT1 serving as an intermediate factor by which GMPS regulates SERPINB2 expression; knockdown of GMPS inhibits tumor progression in NSCLC.\",\n      \"method\": \"Lentiviral overexpression and knockout cell lines, RNA sequencing, western blot, animal experiments\",\n      \"journal\": \"Cellular oncology (Dordrecht, Netherlands)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway placed by RNA-seq and western blot in KO/OE cells plus in vivo, single lab, DNMT1-SERPINB2-uPA axis established by functional experiments\",\n      \"pmids\": [\"40498285\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Extracellular matrix (ECM) bio-scaffolds enhance guanylate production in pancreatic ductal adenocarcinoma cells via upregulation of GMPS (and IMPDH) expression, with increased guanylates alleviating oxaliplatin-induced DNA damage; GMPS expression correlates with matrisomal and DNA repair gene expression in PDAC patient samples.\",\n      \"method\": \"In vitro ECM bio-scaffolds, multi-omics integration, metabolic tracing, gene expression correlation in patient samples\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — metabolic tracing supports guanylate production but GMPS-specific mechanism not directly isolated from IMPDH; preprint, single lab, no direct GMPS mutagenesis or reconstitution\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"GMPS (guanosine monophosphate synthetase) catalyzes the final step of de novo GMP synthesis by transferring a glutamine amide to XMP; in the nucleus, GMPS recruits USP7 to form a complex with p53, stabilizing p53 by reducing its ubiquitination, while in the cytoplasm GMPS is subject to TRIM21-mediated ubiquitination and degradation facilitated by SERPINB5 as an adaptor (and promoted by SNORD50A/B), linking GMPS subcellular localization to p53 stability; additionally, GMPS can act as a scaffold enhancing STT3A-mediated N-glycosylation of PD-L1, and promotes cancer cell migration via a DNMT1/SERPINB2/uPA axis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GMPS catalyzes the final, glutamine-amide-dependent step of de novo GMP synthesis, converting XMP to GMP, and this catalytic activity supports cancer cell proliferation and reshapes glutamine metabolism, as shown by isotope tracing and the growth defects following GMPS inhibition or knockdown in prostate cancer [#3]. Beyond its metabolic role, GMPS has a nuclear, non-catalytic function in p53 regulation: nuclear GMPS recruits the deubiquitinase USP7 into a complex with p53, decreasing p53 ubiquitination and stabilizing the protein [#0]. GMPS subcellular partitioning is therefore the key control point — cytoplasmic GMPS is targeted by the E3 ligase TRIM21 for ubiquitination and degradation, with SERPINB5 acting as an adaptor that prevents nuclear entry and recruits TRIM21, while SNORD50A/B small nucleolar RNAs further promote the TRIM21–GMPS interaction and cytoplasmic sequestration; loss of these restraints releases GMPS to the nucleus to stabilize p53 [#0, #1]. GMPS additionally moonlights as a scaffold that bridges the Sec61 channel and the oligosaccharyltransferase subunit STT3A to enhance N-glycosylation and stability of PD-L1 in hepatocellular carcinoma [#2], and promotes lung cancer cell migration through a DNMT1/SERPINB2/uPA axis [#6]. The GATase subunit of the enzyme adopts a defined fold with a surface mediating Mg2+ binding and contact with the ATPPase subunit, as resolved in an archaeal ortholog [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established the GMPS chromosomal locus and showed it can be disrupted by oncogenic translocation, the first link between GMPS and malignancy.\",\n      \"evidence\": \"cDNA panhandle PCR and Southern blot identifying an in-frame MLL-GMPS fusion in treatment-related AML\",\n      \"pmids\": [\"11110714\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single patient with no functional characterization of the fusion protein\", \"Does not establish whether GMPS contributes function to the chimera\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the structural basis of the GATase subunit's Mg2+ binding and its interaction surface with the ATPPase subunit, defining intersubunit coupling within the synthetase.\",\n      \"evidence\": \"Solution NMR structure, backbone relaxation and chemical shift perturbation mapping of archaeal (M. jannaschii) GMPS GATase\",\n      \"pmids\": [\"23724776\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Archaeal rather than mammalian enzyme\", \"Does not address full-length holoenzyme catalysis or nuclear moonlighting functions\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined how cytoplasmic GMPS is restrained, showing TRIM21-mediated ubiquitination and SERPINB5-adaptor-controlled nuclear exclusion link GMPS localization to TP53 expression.\",\n      \"evidence\": \"Mass spectrometry, Co-IP, overexpression/knockout cell lines and xenografts\",\n      \"pmids\": [\"32005234\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve the structural basis of SERPINB5-GMPS-TRIM21 assembly\", \"Mechanism of nuclear import upon adaptor loss not detailed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified SNORD50A/B snoRNAs as upstream modulators that promote TRIM21–GMPS complex formation and cytoplasmic sequestration, and confirmed the nuclear GMPS–USP7–p53 stabilizing complex.\",\n      \"evidence\": \"Reciprocal Co-IP, immunofluorescence translocation assays, and KO/OE functional studies in breast cancer cells\",\n      \"pmids\": [\"33742136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How snoRNAs physically template the TRIM21-GMPS interaction is not structurally defined\", \"Quantitative contribution of nuclear GMPS to total p53 pool unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided direct metabolic evidence that GMPS catalytic glutamine-amide transfer drives guanylate synthesis required for cancer cell growth.\",\n      \"evidence\": \"siRNA knockdown, pharmacological inhibition, [15N]-/[U-13C5]-glutamine isotope tracing, and PC-3 xenografts\",\n      \"pmids\": [\"33768538\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single tumor type and lab\", \"Does not separate catalytic from scaffolding contributions to the growth phenotype\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Revealed a catalysis-independent scaffolding role in which GMPS bridges the Sec61 channel and STT3A to enhance PD-L1 N-glycosylation and stability.\",\n      \"evidence\": \"Proteomics/scRNA-seq, Co-IP, angustmycin A inhibition, and in vivo tumor models in HCC\",\n      \"pmids\": [\"39690246\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The bridging mechanism between Sec61 and STT3A is inferred, not reconstituted\", \"Single-lab finding without orthogonal structural validation\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placed GMPS in a pro-migratory pathway acting through DNMT1 to regulate the SERPINB2-uPA axis in lung cancer.\",\n      \"evidence\": \"Lentiviral KO/OE cell lines, RNA-seq, western blot, and animal experiments in NSCLC\",\n      \"pmids\": [\"40498285\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical link between GMPS and DNMT1 not established\", \"Single lab; mechanism of DNMT1 regulation of SERPINB2 not fully resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GMPS catalytic guanylate output, nuclear p53 stabilization, and ER scaffolding functions are coordinately switched in a single cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of the mammalian holoenzyme in its nuclear moonlighting state\", \"Regulatory hierarchy among localization, catalysis, and scaffolding undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"USP7\", \"TRIM21\", \"SERPINB5\", \"STT3A\", \"TP53\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}