{"gene":"SLC35F2","run_date":"2026-04-28T20:42:07","timeline":{"discoveries":[{"year":2014,"finding":"SLC35F2 functions as a drug importer that enables cellular uptake of the anticancer compound YM155; SLC35F2-dependent import of YM155 leads to DNA damage through intercalation, and knockout of SLC35F2 abolishes YM155-mediated DNA damage toxicity both in vitro and in vivo.","method":"Haploid genetic screen, targeted genome editing (CRISPR/knockout), in vitro and in vivo drug sensitivity assays","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1–2 — haploid genetic screen + genome editing + in vivo validation; foundational discovery replicated across multiple subsequent studies","pmids":["25064833"],"is_preprint":false},{"year":2021,"finding":"USP32, a deubiquitinating enzyme, destabilizes SLC35F2 protein via ER-associated degradation, reducing SLC35F2 levels and conferring YM155 resistance; USP32 and SLC35F2 expression are negatively correlated across cancer cell lines.","method":"CRISPR-based genome-scale USP knockout screen, in vitro and in vivo experiments including protein stability assays","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 — CRISPR screen plus functional validation, single lab","pmids":["34815782"],"is_preprint":false},{"year":2023,"finding":"SLC35F2 inhibits ferroptosis in pancreatic cancer cells by competitively binding the E3 ubiquitin ligase SYVN1, thereby stabilizing TRIM59 and promoting TRIM59-mediated p53 degradation.","method":"Co-immunoprecipitation, protein interaction studies, in vitro and in vivo ferroptosis assays, protein 3D structure analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2–3 — co-IP plus functional rescue, single lab with multiple orthogonal approaches","pmids":["37740007"],"is_preprint":false},{"year":2023,"finding":"APC/C^Cdh1 E3 ubiquitin ligase complex interacts with SLC35F2, promotes its ubiquitination, and reduces SLC35F2 protein half-life, thereby controlling SLC35F2 protein turnover; depletion of APC/C^Cdh1 increases SLC35F2 levels and promotes SLC35F2-mediated cell proliferation, migration, and invasion.","method":"Immunoprecipitation, Duolink proximity ligation assay, in vitro ubiquitination assay, CRISPR/Cas9 knockdown, half-life analysis","journal":"Biochimica et biophysica acta. General subjects","confidence":"Medium","confidence_rationale":"Tier 1–2 — in vitro ubiquitination assay plus co-IP and PLA plus CRISPR rescue; single lab","pmids":["37689217"],"is_preprint":false},{"year":2023,"finding":"βTrCP1 E3 ubiquitin ligase interacts with SLC35F2, promotes its ubiquitination, reduces SLC35F2 protein half-life, and depletion of βTrCP1 accumulates SLC35F2 protein and promotes SLC35F2-mediated cell growth, migration, invasion, and colony formation.","method":"Co-immunoprecipitation, ubiquitination assay, protein half-life analysis, siRNA knockdown, oncogenic assays in HeLa cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1–3 — ubiquitination assay plus co-IP, single lab with multiple methods","pmids":["37801987"],"is_preprint":false},{"year":2025,"finding":"SLC35F2 is the sole high-affinity transporter for the micronutrients queuosine (Km 174 nM) and queuine (Km 67 nM) in human cells; SLC35F2 localizes to the cell membrane and Golgi apparatus; it does not transport canonical ribonucleobases or ribonucleosides, indicating high substrate selectivity.","method":"Cross-species bioinformatic search, gene disruption in human HeLa cells, competitive uptake assays, immunofluorescence localization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1–2 — genetic validation across species plus quantitative transport assays plus localization; multiple orthogonal methods in single study","pmids":["40526720"],"is_preprint":false},{"year":2023,"finding":"Decitabine (DAC) upregulates SLC35F2 expression through an AKT- and p38 MAPK-mediated pathway involving Ca2+/ROS-dependent signaling, Sp1 transcription factor, TET dioxygenases, and p300; elevated SLC35F2 expression is required for the synergistic cytotoxicity of DAC and YM155 in AML cells.","method":"Pharmacological inhibitors, ectopic expression/knockdown, Western blotting, reporter assays in AML cell lines","journal":"Apoptosis : an international journal on programmed cell death","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple signaling pathway experiments, single lab, no structural validation","pmids":["38066391"],"is_preprint":false},{"year":2021,"finding":"Increased SLC35F2 expression in AML U937 cells enhances cellular sensitivity to YM155-mediated cytotoxicity, consistent with its role as a YM155 importer.","method":"Continuous hydroquinone exposure to generate SLC35F2-overexpressing cells, cell viability and apoptosis assays","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, indirect upregulation model, no direct transport assay","pmids":["33831396"],"is_preprint":false},{"year":2025,"finding":"SLC35F2 knockdown activates the cAMP signaling pathway and upregulates the transcription factor CREB1 in NSCLC cells, suppressing proliferation, migration, and invasion, indicating SLC35F2 drives NSCLC progression via modulation of the cAMP/CREB1 axis.","method":"RT-qPCR, Western blot, CCK-8, EdU, colony formation, flow cytometry, Transwell assays, functional enrichment analysis","journal":"Cytotechnology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, no direct molecular interaction or structural data, pathway placement is indirect","pmids":["40667522"],"is_preprint":false},{"year":2013,"finding":"siRNA-mediated knockdown of SLC35F2 in lung cancer H1299 cells reduces proliferation and migration, and causes G0/G1 cell cycle arrest with decreased S and G2/M phase fractions, indicating SLC35F2 promotes cell cycle progression.","method":"Lentiviral siRNA knockdown, CCK-8 proliferation assay, Transwell migration assay, FACS cell cycle analysis","journal":"Cancer cell international","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single knockdown approach, no molecular mechanism identified","pmids":["23879892"],"is_preprint":false}],"current_model":"SLC35F2 is a plasma membrane and Golgi-localized solute carrier that functions as the primary high-affinity transporter for the micronutrients queuine and queuosine, and also imports the anticancer compound YM155 to enable its DNA-damaging activity; its protein stability is regulated by multiple E3 ubiquitin ligases (APC/C^Cdh1, βTrCP1) and the deubiquitinase USP32, and it promotes cancer cell survival partly by stabilizing TRIM59 to suppress p53-mediated ferroptosis via competitive interaction with the E3 ligase SYVN1."},"narrative":{"teleology":[{"year":2013,"claim":"Initial evidence that SLC35F2 is not merely a passive transporter but actively promotes cancer cell proliferation and cell cycle progression, raising the question of its molecular function.","evidence":"siRNA knockdown in H1299 lung cancer cells caused G0/G1 arrest and reduced proliferation and migration","pmids":["23879892"],"confidence":"Low","gaps":["Single knockdown approach with no molecular mechanism identified","No transport substrate or direct molecular target defined","Not independently confirmed in additional cell lines"]},{"year":2014,"claim":"A haploid genetic screen identified SLC35F2 as the obligate importer of the anticancer compound YM155, establishing that it functions as a drug transporter whose loss abolishes YM155-mediated DNA damage — the first defined transport substrate for this orphan SLC.","evidence":"Haploid genetic screen in KBM7 cells, CRISPR knockout validation, in vitro and in vivo drug sensitivity assays","pmids":["25064833"],"confidence":"High","gaps":["Endogenous physiological substrate unknown","Transport mechanism (electrochemical coupling, stoichiometry) not characterized","No structural model of SLC35F2"]},{"year":2021,"claim":"Discovery that the deubiquitinase USP32 destabilizes SLC35F2 via ER-associated degradation revealed that SLC35F2 protein levels are actively controlled by the ubiquitin-proteasome system, providing a mechanism for acquired YM155 resistance.","evidence":"Genome-scale USP CRISPR knockout screen with protein stability assays and in vivo experiments","pmids":["34815782"],"confidence":"Medium","gaps":["Mechanism by which a DUB promotes degradation rather than stabilization is unusual and not fully resolved","No identification of the E3 ligase counteracting USP32 at the ER","Correlation between USP32 and SLC35F2 across cancers not confirmed by direct genetic epistasis in patients"]},{"year":2023,"claim":"Parallel studies identified APC/C^Cdh1 and βTrCP1 as two distinct E3 ubiquitin ligases that ubiquitinate SLC35F2 and control its protein half-life, establishing that SLC35F2 stability is a convergence point for multiple degradation pathways that in turn regulate pro-tumorigenic phenotypes.","evidence":"In vitro ubiquitination assays, co-IP, proximity ligation, and half-life analyses in cancer cell lines","pmids":["37689217","37801987"],"confidence":"Medium","gaps":["Degron motifs on SLC35F2 recognized by each E3 ligase not mapped","Functional interplay or redundancy between APC/C^Cdh1, βTrCP1, and USP32 not tested in the same system","Whether ubiquitination regulates SLC35F2 transporter activity or only protein abundance is unknown"]},{"year":2023,"claim":"Beyond its transporter role, SLC35F2 was shown to suppress ferroptosis in pancreatic cancer by a protein–protein interaction mechanism: it competitively sequesters SYVN1 away from TRIM59, stabilizing TRIM59 which then degrades p53 — revealing a non-canonical scaffolding/adaptor function.","evidence":"Co-immunoprecipitation, competitive binding assays, in vitro and in vivo ferroptosis assays, protein structure modeling","pmids":["37740007"],"confidence":"Medium","gaps":["Whether the SYVN1 interaction interface overlaps with SLC35F2 transport function is unknown","Generalizability beyond pancreatic cancer not tested","Structural basis for competitive SYVN1 binding not resolved at atomic level"]},{"year":2023,"claim":"Decitabine-induced upregulation of SLC35F2 transcription via AKT/p38 MAPK–Sp1–TET–p300 signaling established a pharmacologically actionable transcriptional circuit controlling SLC35F2 expression and YM155 synergy in AML.","evidence":"Pharmacological inhibitors, reporter assays, ectopic expression and knockdown in AML cell lines","pmids":["38066391"],"confidence":"Medium","gaps":["Direct TET-mediated demethylation at the SLC35F2 promoter not demonstrated by bisulfite sequencing","Whether this transcriptional circuit operates in non-AML contexts is unknown"]},{"year":2025,"claim":"The long-standing question of SLC35F2's endogenous physiological substrate was resolved: it is the sole high-affinity transporter for queuine and queuosine in human cells, localizing to the plasma membrane and Golgi, and displaying high selectivity against canonical nucleobases.","evidence":"Cross-species bioinformatic identification, genetic disruption in HeLa cells, competitive radiolabeled uptake assays, immunofluorescence","pmids":["40526720"],"confidence":"High","gaps":["Transport mechanism (coupling ion, conformational cycle) not defined","No high-resolution structure of SLC35F2","Physiological consequences of queuine/queuosine transport loss in vivo (animal models) not reported"]},{"year":null,"claim":"Key open questions remain: the structural basis for SLC35F2's dual substrate recognition (queuine/queuosine vs. YM155), the transport mechanism and energy coupling, and whether its non-canonical scaffolding interactions with SYVN1/TRIM59 are structurally and functionally separable from its transport activity.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of SLC35F2","Transport energetics and ion coupling unknown","Relationship between transport function and protein–protein interaction functions not dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[5]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,3,4]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2]}],"complexes":[],"partners":["USP32","CDH1","BTRC","SYVN1","TRIM59"],"other_free_text":[]},"mechanistic_narrative":"SLC35F2 is a solute carrier family member that functions as the primary high-affinity transporter of the micronutrients queuine (Km ~67 nM) and queuosine (Km ~174 nM) and also mediates cellular import of the anticancer compound YM155, linking its transport activity to both tRNA modification and drug sensitivity [PMID:40526720, PMID:25064833]. SLC35F2 localizes to the plasma membrane and Golgi apparatus and exhibits high substrate selectivity, excluding canonical ribonucleobases and ribonucleosides [PMID:40526720]. SLC35F2 protein turnover is tightly regulated by multiple E3 ubiquitin ligases — APC/C^Cdh1 and βTrCP1 — which ubiquitinate and destabilize it, with the deubiquitinase USP32 paradoxically also promoting its degradation via ER-associated pathways [PMID:37689217, PMID:37801987, PMID:34815782]. Beyond its transporter function, SLC35F2 suppresses ferroptosis in pancreatic cancer by competitively binding the E3 ligase SYVN1, thereby stabilizing TRIM59 and enhancing TRIM59-mediated p53 degradation [PMID:37740007]."},"prefetch_data":{"uniprot":{"accession":"Q8IXU6","full_name":"Queuine/queuosine transporter SLC35F2","aliases":["Solute carrier family 35 member F2"],"length_aa":374,"mass_kda":41.2,"function":"High affinity plasma membrane importer of the nucleobase queuine (q) and its nucleoside queuosine (Q), two bacterially derived micronutrients acquired from the gut microbiome and diet. Following cellular uptake, queuosine is incorporated at the wobble base (position 34) of tRNAs that decode histidine, tyrosine, aspartate, and asparagine codons, which is important for efficient translation","subcellular_location":"Cell membrane; Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/Q8IXU6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLC35F2","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000110660","cell_line_id":"CID001343","localizations":[{"compartment":"vesicles","grade":3},{"compartment":"golgi","grade":2}],"interactors":[{"gene":"CTBP1","stoichiometry":0.2},{"gene":"CTBP2","stoichiometry":0.2},{"gene":"HDAC2","stoichiometry":0.2},{"gene":"RAB11A","stoichiometry":0.2},{"gene":"RAB11B","stoichiometry":0.2},{"gene":"RAB11B;RAB11A","stoichiometry":0.2},{"gene":"ATP6V0A1","stoichiometry":0.2},{"gene":"STX7","stoichiometry":0.2},{"gene":"TFRC","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001343","total_profiled":1310},"omim":[{"mim_id":"620350","title":"SOLUTE CARRIER FAMILY 35, MEMBER F2; SLC35F2","url":"https://www.omim.org/entry/620350"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"salivary gland","ntpm":35.2}],"url":"https://www.proteinatlas.org/search/SLC35F2"},"hgnc":{"alias_symbol":["FLJ13018"],"prev_symbol":[]},"alphafold":{"accession":"Q8IXU6","domains":[{"cath_id":"-","chopping":"37-341","consensus_level":"medium","plddt":89.6888,"start":37,"end":341}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXU6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXU6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IXU6-F1-predicted_aligned_error_v6.png","plddt_mean":82.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC35F2","jax_strain_url":"https://www.jax.org/strain/search?query=SLC35F2"},"sequence":{"accession":"Q8IXU6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IXU6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IXU6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IXU6"}},"corpus_meta":[{"pmid":"25064833","id":"PMC_25064833","title":"The solute carrier SLC35F2 enables YM155-mediated DNA damage toxicity.","date":"2014","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/25064833","citation_count":140,"is_preprint":false},{"pmid":"34815782","id":"PMC_34815782","title":"USP32 confers cancer cell resistance to YM155 via promoting ER-associated degradation of solute carrier protein SLC35F2.","date":"2021","source":"Theranostics","url":"https://pubmed.ncbi.nlm.nih.gov/34815782","citation_count":23,"is_preprint":false},{"pmid":"21874247","id":"PMC_21874247","title":"Highly expressed SLC35F2 in non-small cell lung cancer is associated with pathological staging.","date":"2011","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/21874247","citation_count":23,"is_preprint":false},{"pmid":"37740007","id":"PMC_37740007","title":"SLC35F2-SYVN1-TRIM59 axis critically regulates ferroptosis of pancreatic cancer cells by inhibiting endogenous p53.","date":"2023","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/37740007","citation_count":22,"is_preprint":false},{"pmid":"33418944","id":"PMC_33418944","title":"SLC35F2, a Transporter Sporadically Mutated in the Untranslated Region, Promotes Growth, Migration, and Invasion of Bladder Cancer Cells.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33418944","citation_count":15,"is_preprint":false},{"pmid":"23879892","id":"PMC_23879892","title":"Influence on the behavior of lung cancer H1299 cells by silencing SLC35F2 expression.","date":"2013","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/23879892","citation_count":13,"is_preprint":false},{"pmid":"33831396","id":"PMC_33831396","title":"Inhibition of Sp1-mediated survivin and MCL1 expression cooperates with SLC35F2 and myeloperoxidase to modulate YM155 cytotoxicity to human leukemia cells.","date":"2021","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33831396","citation_count":12,"is_preprint":false},{"pmid":"31849485","id":"PMC_31849485","title":"Knockdown of SLC35F2 Inhibits the Proliferation and Metastasis of Bladder Cancer Cells.","date":"2019","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/31849485","citation_count":9,"is_preprint":false},{"pmid":"38066391","id":"PMC_38066391","title":"Synergistic cytotoxicity of decitabine and YM155 in leukemia cells through upregulation of SLC35F2 and suppression of MCL1 and survivin expression.","date":"2023","source":"Apoptosis : an international journal on programmed cell death","url":"https://pubmed.ncbi.nlm.nih.gov/38066391","citation_count":9,"is_preprint":false},{"pmid":"37689217","id":"PMC_37689217","title":"E3 ubiquitin ligase APC/CCdh1 regulates SLC35F2 protein turnover and inhibits cancer progression in HeLa cells.","date":"2023","source":"Biochimica et biophysica acta. General subjects","url":"https://pubmed.ncbi.nlm.nih.gov/37689217","citation_count":4,"is_preprint":false},{"pmid":"38679209","id":"PMC_38679209","title":"ONC212 enhances YM155 cytotoxicity by triggering SLC35F2 expression and NOXA-dependent MCL1 degradation in acute myeloid leukemia cells.","date":"2024","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/38679209","citation_count":3,"is_preprint":false},{"pmid":"40526720","id":"PMC_40526720","title":"The oncogene SLC35F2 is a high-specificity transporter for the micronutrients queuine and queuosine.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/40526720","citation_count":2,"is_preprint":false},{"pmid":"37801987","id":"PMC_37801987","title":"βTrCP1 promotes SLC35F2 protein ubiquitination and inhibits cancer progression in HeLa cells.","date":"2023","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/37801987","citation_count":0,"is_preprint":false},{"pmid":"40667522","id":"PMC_40667522","title":"SLC35F2 promotes the progression of NSCLC via regulating CREB1 expression.","date":"2025","source":"Cytotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/40667522","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.29.25326633","title":"Separating the genetics of disease, treatment and treatment response using graphical modeling and large-scale electronic health records","date":"2025-04-30","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.29.25326633","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.07.15.603529","title":"Memorization Bias Impacts Modeling of Alternative Conformational States of Symmetric Solute Carrier Membrane Proteins with Methods from Deep Learning","date":"2024-07-17","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.15.603529","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9953,"output_tokens":2311,"usd":0.032262},"stage2":{"model":"claude-opus-4-6","input_tokens":5642,"output_tokens":2264,"usd":0.127215},"total_usd":0.159477,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"SLC35F2 functions as a drug importer that enables cellular uptake of the anticancer compound YM155; SLC35F2-dependent import of YM155 leads to DNA damage through intercalation, and knockout of SLC35F2 abolishes YM155-mediated DNA damage toxicity both in vitro and in vivo.\",\n      \"method\": \"Haploid genetic screen, targeted genome editing (CRISPR/knockout), in vitro and in vivo drug sensitivity assays\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — haploid genetic screen + genome editing + in vivo validation; foundational discovery replicated across multiple subsequent studies\",\n      \"pmids\": [\"25064833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP32, a deubiquitinating enzyme, destabilizes SLC35F2 protein via ER-associated degradation, reducing SLC35F2 levels and conferring YM155 resistance; USP32 and SLC35F2 expression are negatively correlated across cancer cell lines.\",\n      \"method\": \"CRISPR-based genome-scale USP knockout screen, in vitro and in vivo experiments including protein stability assays\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR screen plus functional validation, single lab\",\n      \"pmids\": [\"34815782\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SLC35F2 inhibits ferroptosis in pancreatic cancer cells by competitively binding the E3 ubiquitin ligase SYVN1, thereby stabilizing TRIM59 and promoting TRIM59-mediated p53 degradation.\",\n      \"method\": \"Co-immunoprecipitation, protein interaction studies, in vitro and in vivo ferroptosis assays, protein 3D structure analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP plus functional rescue, single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"37740007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"APC/C^Cdh1 E3 ubiquitin ligase complex interacts with SLC35F2, promotes its ubiquitination, and reduces SLC35F2 protein half-life, thereby controlling SLC35F2 protein turnover; depletion of APC/C^Cdh1 increases SLC35F2 levels and promotes SLC35F2-mediated cell proliferation, migration, and invasion.\",\n      \"method\": \"Immunoprecipitation, Duolink proximity ligation assay, in vitro ubiquitination assay, CRISPR/Cas9 knockdown, half-life analysis\",\n      \"journal\": \"Biochimica et biophysica acta. General subjects\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination assay plus co-IP and PLA plus CRISPR rescue; single lab\",\n      \"pmids\": [\"37689217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"βTrCP1 E3 ubiquitin ligase interacts with SLC35F2, promotes its ubiquitination, reduces SLC35F2 protein half-life, and depletion of βTrCP1 accumulates SLC35F2 protein and promotes SLC35F2-mediated cell growth, migration, invasion, and colony formation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, protein half-life analysis, siRNA knockdown, oncogenic assays in HeLa cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–3 — ubiquitination assay plus co-IP, single lab with multiple methods\",\n      \"pmids\": [\"37801987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SLC35F2 is the sole high-affinity transporter for the micronutrients queuosine (Km 174 nM) and queuine (Km 67 nM) in human cells; SLC35F2 localizes to the cell membrane and Golgi apparatus; it does not transport canonical ribonucleobases or ribonucleosides, indicating high substrate selectivity.\",\n      \"method\": \"Cross-species bioinformatic search, gene disruption in human HeLa cells, competitive uptake assays, immunofluorescence localization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic validation across species plus quantitative transport assays plus localization; multiple orthogonal methods in single study\",\n      \"pmids\": [\"40526720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Decitabine (DAC) upregulates SLC35F2 expression through an AKT- and p38 MAPK-mediated pathway involving Ca2+/ROS-dependent signaling, Sp1 transcription factor, TET dioxygenases, and p300; elevated SLC35F2 expression is required for the synergistic cytotoxicity of DAC and YM155 in AML cells.\",\n      \"method\": \"Pharmacological inhibitors, ectopic expression/knockdown, Western blotting, reporter assays in AML cell lines\",\n      \"journal\": \"Apoptosis : an international journal on programmed cell death\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple signaling pathway experiments, single lab, no structural validation\",\n      \"pmids\": [\"38066391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Increased SLC35F2 expression in AML U937 cells enhances cellular sensitivity to YM155-mediated cytotoxicity, consistent with its role as a YM155 importer.\",\n      \"method\": \"Continuous hydroquinone exposure to generate SLC35F2-overexpressing cells, cell viability and apoptosis assays\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, indirect upregulation model, no direct transport assay\",\n      \"pmids\": [\"33831396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SLC35F2 knockdown activates the cAMP signaling pathway and upregulates the transcription factor CREB1 in NSCLC cells, suppressing proliferation, migration, and invasion, indicating SLC35F2 drives NSCLC progression via modulation of the cAMP/CREB1 axis.\",\n      \"method\": \"RT-qPCR, Western blot, CCK-8, EdU, colony formation, flow cytometry, Transwell assays, functional enrichment analysis\",\n      \"journal\": \"Cytotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, no direct molecular interaction or structural data, pathway placement is indirect\",\n      \"pmids\": [\"40667522\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"siRNA-mediated knockdown of SLC35F2 in lung cancer H1299 cells reduces proliferation and migration, and causes G0/G1 cell cycle arrest with decreased S and G2/M phase fractions, indicating SLC35F2 promotes cell cycle progression.\",\n      \"method\": \"Lentiviral siRNA knockdown, CCK-8 proliferation assay, Transwell migration assay, FACS cell cycle analysis\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single knockdown approach, no molecular mechanism identified\",\n      \"pmids\": [\"23879892\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC35F2 is a plasma membrane and Golgi-localized solute carrier that functions as the primary high-affinity transporter for the micronutrients queuine and queuosine, and also imports the anticancer compound YM155 to enable its DNA-damaging activity; its protein stability is regulated by multiple E3 ubiquitin ligases (APC/C^Cdh1, βTrCP1) and the deubiquitinase USP32, and it promotes cancer cell survival partly by stabilizing TRIM59 to suppress p53-mediated ferroptosis via competitive interaction with the E3 ligase SYVN1.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SLC35F2 is a solute carrier family member that functions as the primary high-affinity transporter of the micronutrients queuine (Km ~67 nM) and queuosine (Km ~174 nM) and also mediates cellular import of the anticancer compound YM155, linking its transport activity to both tRNA modification and drug sensitivity [PMID:40526720, PMID:25064833]. SLC35F2 localizes to the plasma membrane and Golgi apparatus and exhibits high substrate selectivity, excluding canonical ribonucleobases and ribonucleosides [PMID:40526720]. SLC35F2 protein turnover is tightly regulated by multiple E3 ubiquitin ligases — APC/C^Cdh1 and βTrCP1 — which ubiquitinate and destabilize it, with the deubiquitinase USP32 paradoxically also promoting its degradation via ER-associated pathways [PMID:37689217, PMID:37801987, PMID:34815782]. Beyond its transporter function, SLC35F2 suppresses ferroptosis in pancreatic cancer by competitively binding the E3 ligase SYVN1, thereby stabilizing TRIM59 and enhancing TRIM59-mediated p53 degradation [PMID:37740007].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Initial evidence that SLC35F2 is not merely a passive transporter but actively promotes cancer cell proliferation and cell cycle progression, raising the question of its molecular function.\",\n      \"evidence\": \"siRNA knockdown in H1299 lung cancer cells caused G0/G1 arrest and reduced proliferation and migration\",\n      \"pmids\": [\"23879892\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single knockdown approach with no molecular mechanism identified\",\n        \"No transport substrate or direct molecular target defined\",\n        \"Not independently confirmed in additional cell lines\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A haploid genetic screen identified SLC35F2 as the obligate importer of the anticancer compound YM155, establishing that it functions as a drug transporter whose loss abolishes YM155-mediated DNA damage — the first defined transport substrate for this orphan SLC.\",\n      \"evidence\": \"Haploid genetic screen in KBM7 cells, CRISPR knockout validation, in vitro and in vivo drug sensitivity assays\",\n      \"pmids\": [\"25064833\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Endogenous physiological substrate unknown\",\n        \"Transport mechanism (electrochemical coupling, stoichiometry) not characterized\",\n        \"No structural model of SLC35F2\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Discovery that the deubiquitinase USP32 destabilizes SLC35F2 via ER-associated degradation revealed that SLC35F2 protein levels are actively controlled by the ubiquitin-proteasome system, providing a mechanism for acquired YM155 resistance.\",\n      \"evidence\": \"Genome-scale USP CRISPR knockout screen with protein stability assays and in vivo experiments\",\n      \"pmids\": [\"34815782\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which a DUB promotes degradation rather than stabilization is unusual and not fully resolved\",\n        \"No identification of the E3 ligase counteracting USP32 at the ER\",\n        \"Correlation between USP32 and SLC35F2 across cancers not confirmed by direct genetic epistasis in patients\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Parallel studies identified APC/C^Cdh1 and βTrCP1 as two distinct E3 ubiquitin ligases that ubiquitinate SLC35F2 and control its protein half-life, establishing that SLC35F2 stability is a convergence point for multiple degradation pathways that in turn regulate pro-tumorigenic phenotypes.\",\n      \"evidence\": \"In vitro ubiquitination assays, co-IP, proximity ligation, and half-life analyses in cancer cell lines\",\n      \"pmids\": [\"37689217\", \"37801987\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Degron motifs on SLC35F2 recognized by each E3 ligase not mapped\",\n        \"Functional interplay or redundancy between APC/C^Cdh1, βTrCP1, and USP32 not tested in the same system\",\n        \"Whether ubiquitination regulates SLC35F2 transporter activity or only protein abundance is unknown\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Beyond its transporter role, SLC35F2 was shown to suppress ferroptosis in pancreatic cancer by a protein–protein interaction mechanism: it competitively sequesters SYVN1 away from TRIM59, stabilizing TRIM59 which then degrades p53 — revealing a non-canonical scaffolding/adaptor function.\",\n      \"evidence\": \"Co-immunoprecipitation, competitive binding assays, in vitro and in vivo ferroptosis assays, protein structure modeling\",\n      \"pmids\": [\"37740007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the SYVN1 interaction interface overlaps with SLC35F2 transport function is unknown\",\n        \"Generalizability beyond pancreatic cancer not tested\",\n        \"Structural basis for competitive SYVN1 binding not resolved at atomic level\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Decitabine-induced upregulation of SLC35F2 transcription via AKT/p38 MAPK–Sp1–TET–p300 signaling established a pharmacologically actionable transcriptional circuit controlling SLC35F2 expression and YM155 synergy in AML.\",\n      \"evidence\": \"Pharmacological inhibitors, reporter assays, ectopic expression and knockdown in AML cell lines\",\n      \"pmids\": [\"38066391\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct TET-mediated demethylation at the SLC35F2 promoter not demonstrated by bisulfite sequencing\",\n        \"Whether this transcriptional circuit operates in non-AML contexts is unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The long-standing question of SLC35F2's endogenous physiological substrate was resolved: it is the sole high-affinity transporter for queuine and queuosine in human cells, localizing to the plasma membrane and Golgi, and displaying high selectivity against canonical nucleobases.\",\n      \"evidence\": \"Cross-species bioinformatic identification, genetic disruption in HeLa cells, competitive radiolabeled uptake assays, immunofluorescence\",\n      \"pmids\": [\"40526720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Transport mechanism (coupling ion, conformational cycle) not defined\",\n        \"No high-resolution structure of SLC35F2\",\n        \"Physiological consequences of queuine/queuosine transport loss in vivo (animal models) not reported\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions remain: the structural basis for SLC35F2's dual substrate recognition (queuine/queuosine vs. YM155), the transport mechanism and energy coupling, and whether its non-canonical scaffolding interactions with SYVN1/TRIM59 are structurally and functionally separable from its transport activity.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No atomic-resolution structure of SLC35F2\",\n        \"Transport energetics and ion coupling unknown\",\n        \"Relationship between transport function and protein–protein interaction functions not dissected\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 3, 4]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"USP32\",\n      \"CDH1\",\n      \"BTRC\",\n      \"SYVN1\",\n      \"TRIM59\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}