{"gene":"SLFN12","run_date":"2026-06-10T07:46:35","timeline":{"discoveries":[{"year":2021,"finding":"SLFN12 is an RNase, and PDE3A binding increases SLFN12 RNase activity. PDE3A and SLFN12 form a heterotetramer stabilized by DNMDP binding. Interactions between the C-terminal alpha helix of SLFN12 and residues near the active site of PDE3A are required for complex formation, further stabilized by SLFN12-DNMDP interactions. SLFN12 RNase activity is required for DNMDP-induced cancer cell death.","method":"Structural analysis (cryo-EM/X-ray), in vitro RNase assay, mutagenesis of interface residues, functional viability assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — structure determination combined with in vitro RNase assay and mutagenesis, replicated by independent lab in same year","pmids":["34272366"],"is_preprint":false},{"year":2021,"finding":"High-resolution cryo-EM structure of PDE3A-SLFN12 heterotetramer shows a butterfly-like shape; molecular glues (anagrelide, nauclefine, DNMDP) bind the catalytic domain pocket of PDE3A, creating a modified interface that recruits the short helix (E552-I558) of SLFN12 via hydrophobic interactions. SLFN12 blocks protein translation leading to apoptosis.","method":"Cryo-EM structure determination of endogenous complex from HeLa cells, structure-based analog design with cellular apoptosis and xenograft assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution cryo-EM with multiple ligands, independently replicating the heterotetramer model from PMID:34272366","pmids":["34707099"],"is_preprint":false},{"year":2022,"finding":"The physiological RNase substrate of SLFN12 is tRNALeu(TAA). SLFN12 selectively digests tRNALeu(TAA), and velcrin-induced PDE3A-SLFN12 complex formation promotes this cleavage in vitro. Distinct sequences in the variable loop and acceptor stem of tRNALeu(TAA) are required for digestion. Velcrin treatment causes downregulation of tRNALeu(TAA), ribosome pausing at Leu-TTA codons, and global inhibition of protein synthesis, defining a mechanism of apoptosis initiation.","method":"In vitro RNase substrate assay, tRNA mutational analysis, ribosome profiling, global translation assays, velcrin treatment of sensitive cancer cells","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of substrate cleavage with mutagenesis of substrate sequences, corroborated by cellular ribosome pausing and translation inhibition assays","pmids":["36302897"],"is_preprint":false},{"year":2022,"finding":"PDE3A-SLFN12 complex formation induces dephosphorylation of SLFN12 at serines 368 and 573. Mutational analysis demonstrates that dephosphorylation at these residues is required for cell death induced by cytotoxic PDE3A modulators. Dephosphorylation promotes the rRNA RNase activity of SLFN12, and this nucleolytic activity is essential for SLFN12's cell-death-inducing function. Complex formation also increases cytoplasmic protein stability of SLFN12.","method":"Phosphoproteomics/western blot of SLFN12 phosphorylation states, site-directed mutagenesis of Ser368 and Ser573, in vitro RNase activity assay, cell viability assays","journal":"Cell chemical biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — mutational analysis of phosphosites combined with in vitro RNase assay and cell death functional readout, single lab but multiple orthogonal methods","pmids":["35104454"],"is_preprint":false},{"year":2022,"finding":"SLFN12 overexpression decreases CHK1 and CHK2 phosphorylation after treatment with the DNA-damaging agent camptothecin, and CHK1/CHK2 inhibition diminishes the cytotoxicity difference between SLFN12-overexpressing and baseline cells in response to carboplatin, placing SLFN12 upstream of the CHK1/2 checkpoint pathway in sensitization to DNA-damaging agents.","method":"Lentiviral SLFN12 overexpression, western blot for pCHK1/pCHK2, pharmacological CHK1/CHK2 inhibition (AZD7762), crystal violet cell viability assay in multiple TNBC cell lines","journal":"Cancer genomics & proteomics","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — genetic overexpression with pharmacological epistasis and functional readout in multiple cell lines, single lab","pmids":["35430566"],"is_preprint":false},{"year":2024,"finding":"SLFN12 RNase-mediated cell death activates the GCN2 (general control non-derepressible 2) kinase and its downstream integrated stress response as an effector pathway mediating anticancer activity downstream of PDE3A-SLFN12 complex formation.","method":"Molecular mechanism studies in patient-derived xenograft GIST models treated with OPB-171775 (PDE3A-SLFN12 complex inducer), pathway analysis identifying GCN2 activation","journal":"Clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — pathway identification in PDX models with pharmacodynamic marker analysis, single lab, limited mechanistic detail in abstract","pmids":["38864850"],"is_preprint":false},{"year":2024,"finding":"Velcrin compound BAY 2666605 induces PDE3A-SLFN12 complex formation, activating SLFN12 to cleave tRNALeu(TAA) and induce apoptosis in glioblastoma cells. BAY 2666605 crosses the blood-brain barrier and induces tumor regression in an orthotopic glioblastoma xenograft model.","method":"Cell viability, apoptosis, cell cycle, global translation assays in glioblastoma cell lines; orthotopic and subcutaneous xenograft models; transcriptional profiling","journal":"Neuro-oncology advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional assays with mechanistic endpoint (tRNALeu cleavage, translation inhibition) in multiple glioblastoma models, consistent with established mechanism","pmids":["39166256"],"is_preprint":false}],"current_model":"SLFN12 is a tRNA endonuclease (RNase) that is activated when molecular glue compounds (velcrins) induce its assembly into a heterotetramer with PDE3A; the C-terminal helix of SLFN12 docks into a modified surface near the PDE3A active site, and PDE3A binding both stabilizes SLFN12 and promotes its dephosphorylation at Ser368/Ser573, fully activating the RNase, which then selectively cleaves tRNALeu(TAA), causing ribosome pausing at Leu-TTA codons, global translation inhibition, integrated stress response (GCN2) activation, and ultimately apoptosis."},"narrative":{"mechanistic_narrative":"SLFN12 is a ribonuclease whose cytotoxic activity is conditionally switched on by molecular glue compounds (velcrins, including DNMDP, anagrelide, nauclefine, OPB-171775 and BAY 2666605) that drive its assembly with PDE3A into a butterfly-shaped heterotetramer, defining a drug-inducible mechanism of cancer cell death [PMID:34272366, PMID:34707099]. The glue binds the catalytic-domain pocket of PDE3A and remodels a surface that recruits the short C-terminal helix (E552-I558) of SLFN12 through hydrophobic contacts; this interface is required for complex formation and for compound-induced killing [PMID:34272366, PMID:34707099]. Complex formation activates SLFN12 by two coupled effects: it stabilizes cytoplasmic SLFN12 and promotes its dephosphorylation at Ser368 and Ser573, both of which are required to unleash full nucleolytic activity and cell death [PMID:35104454]. The activated RNase selectively cleaves tRNALeu(TAA) — recognition depending on sequences in the variable loop and acceptor stem — which downregulates this tRNA, stalls ribosomes at Leu-TTA codons, and globally inhibits protein synthesis [PMID:36302897]. The ensuing translational collapse triggers GCN2 kinase and its downstream integrated stress response as an effector arm of the apoptotic outcome [PMID:38864850]. Independently of the velcrin axis, SLFN12 overexpression dampens CHK1/CHK2 phosphorylation and sensitizes triple-negative breast cancer cells to DNA-damaging agents [PMID:35430566].","teleology":[{"year":2021,"claim":"Established that SLFN12 is itself an RNase and that its activity is gated by PDE3A binding within a molecular-glue-stabilized heterotetramer, identifying the structural basis of the drug-inducible complex.","evidence":"Cryo-EM/X-ray structure, in vitro RNase assays, interface mutagenesis and viability assays of the PDE3A-SLFN12-DNMDP complex","pmids":["34272366","34707099"],"confidence":"High","gaps":["The endogenous physiological trigger for complex formation in the absence of synthetic glues was not defined","The catalytic residues of the SLFN12 RNase active site were not pinpointed"]},{"year":2022,"claim":"Identified the physiological substrate as tRNALeu(TAA) and connected its cleavage to ribosome pausing and global translation arrest, providing the molecular basis of apoptosis initiation.","evidence":"In vitro substrate cleavage with tRNA mutagenesis, ribosome profiling, and global translation assays in velcrin-treated cancer cells","pmids":["36302897"],"confidence":"High","gaps":["Whether additional RNA species are cleaved in vivo was not resolved","The structural basis of tRNALeu(TAA) selectivity at the active site was not determined"]},{"year":2022,"claim":"Defined the post-translational switch controlling SLFN12 activation, showing that PDE3A binding triggers dephosphorylation at Ser368/Ser573 and stabilization that are jointly required for nuclease-dependent killing.","evidence":"Phosphosite mapping, Ser368/Ser573 mutagenesis, in vitro RNase assays and cell viability readouts","pmids":["35104454"],"confidence":"High","gaps":["The phosphatase responsible for SLFN12 dephosphorylation was not identified","How dephosphorylation mechanistically relieves the RNase was not structurally resolved"]},{"year":2022,"claim":"Placed SLFN12 upstream of the CHK1/CHK2 checkpoint as a sensitizer to DNA-damaging chemotherapy, suggesting a velcrin-independent role.","evidence":"Lentiviral overexpression, pCHK1/pCHK2 western blots, pharmacological CHK1/2 inhibition and viability assays in TNBC lines","pmids":["35430566"],"confidence":"Medium","gaps":["Whether RNase activity underlies the checkpoint effect was not tested","The direct molecular link between SLFN12 and CHK1/2 regulation was not established"]},{"year":2024,"claim":"Mapped GCN2/integrated stress response as the effector pathway downstream of SLFN12-driven translational arrest mediating anticancer activity in vivo.","evidence":"Pathway and pharmacodynamic analysis in PDX GIST models treated with the complex inducer OPB-171775","pmids":["38864850"],"confidence":"Medium","gaps":["The precise sensing step linking tRNA loss to GCN2 activation was not detailed","Contribution of GCN2 relative to other apoptotic routes was not quantified"]},{"year":2024,"claim":"Demonstrated translational applicability by showing a brain-penetrant velcrin engages the same tRNALeu cleavage mechanism to drive glioblastoma regression.","evidence":"Viability, apoptosis, translation assays and orthotopic xenograft regression with BAY 2666605 in glioblastoma models","pmids":["39166256"],"confidence":"Medium","gaps":["Tumor-type determinants of SLFN12/PDE3A dependence were not delineated","Resistance mechanisms to velcrin treatment were not addressed"]},{"year":null,"claim":"The endogenous, drug-independent physiological function and regulation of SLFN12 remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No native signal that triggers PDE3A-SLFN12 complex formation has been identified","The phosphatase and kinase regulating Ser368/Ser573 are unknown","Whether the CHK1/2 sensitization role depends on RNase activity is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0003723","term_label":"RNA binding","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[1,2,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,6]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[5]}],"complexes":["PDE3A-SLFN12 heterotetramer"],"partners":["PDE3A"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8IYM2","full_name":"Ribonuclease SLFN12","aliases":["Schlafen family member 12"],"length_aa":578,"mass_kda":67.0,"function":"Ribonuclease which is part of an E2/17beta-estradiol-induced pro-apoptotic signaling pathway. E2 stabilizes the PDE3A/SLFN12 complex in the cytosol, promoting the dephosphorylation of SLFN12 and activating its pro-apoptotic ribosomal RNA/rRNA ribonuclease activity. This apoptotic pathway might be relevant in tissues with high concentration of E2 and be for instance involved in placenta remodeling (PubMed:31420216, PubMed:34272366, PubMed:34707099, PubMed:35104454). May play a role in cell differentiation (PubMed:30045019)","subcellular_location":"Nucleus; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q8IYM2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLFN12","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SLFN12","total_profiled":1310},"omim":[{"mim_id":"614958","title":"SCHLAFEN FAMILY, MEMBER 14; SLFN14","url":"https://www.omim.org/entry/614958"},{"mim_id":"614957","title":"SCHLAFEN FAMILY, MEMBER 13; SLFN13","url":"https://www.omim.org/entry/614957"},{"mim_id":"614956","title":"SCHLAFEN FAMILY, MEMBER 12-LIKE; SLFN12L","url":"https://www.omim.org/entry/614956"},{"mim_id":"614955","title":"SCHLAFEN FAMILY, MEMBER 12; SLFN12","url":"https://www.omim.org/entry/614955"},{"mim_id":"614953","title":"SCHLAFEN FAMILY, MEMBER 11; SLFN11","url":"https://www.omim.org/entry/614953"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SLFN12"},"hgnc":{"alias_symbol":["FLJ10260"],"prev_symbol":[]},"alphafold":{"accession":"Q8IYM2","domains":[{"cath_id":"-","chopping":"5-108","consensus_level":"high","plddt":94.5911,"start":5,"end":108},{"cath_id":"3.30.950","chopping":"128-156_178-319","consensus_level":"high","plddt":91.896,"start":128,"end":319},{"cath_id":"-","chopping":"373-571","consensus_level":"high","plddt":78.5034,"start":373,"end":571}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYM2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYM2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IYM2-F1-predicted_aligned_error_v6.png","plddt_mean":82.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLFN12","jax_strain_url":"https://www.jax.org/strain/search?query=SLFN12"},"sequence":{"accession":"Q8IYM2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IYM2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IYM2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IYM2"}},"corpus_meta":[{"pmid":"34272366","id":"PMC_34272366","title":"Structure of PDE3A-SLFN12 complex reveals requirements for activation of SLFN12 RNase.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34272366","citation_count":73,"is_preprint":false},{"pmid":"34707099","id":"PMC_34707099","title":"Structure of PDE3A-SLFN12 complex and structure-based design for a potent apoptosis inducer of tumor cells.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34707099","citation_count":41,"is_preprint":false},{"pmid":"30379917","id":"PMC_30379917","title":"Increased DNA methylation of SLFN12 in CD4+ and CD8+ T cells from multiple sclerosis patients.","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/30379917","citation_count":35,"is_preprint":false},{"pmid":"36302897","id":"PMC_36302897","title":"Velcrin-induced selective cleavage of tRNALeu(TAA) by SLFN12 causes cancer cell death.","date":"2022","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/36302897","citation_count":35,"is_preprint":false},{"pmid":"35104454","id":"PMC_35104454","title":"Multiple PDE3A modulators act as molecular glues promoting PDE3A-SLFN12 interaction and induce SLFN12 dephosphorylation and cell death.","date":"2022","source":"Cell chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/35104454","citation_count":25,"is_preprint":false},{"pmid":"31749907","id":"PMC_31749907","title":"Optimization of PDE3A Modulators for SLFN12-Dependent Cancer Cell Killing.","date":"2019","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/31749907","citation_count":25,"is_preprint":false},{"pmid":"35430566","id":"PMC_35430566","title":"SLFN12 Over-expression Sensitizes Triple Negative Breast Cancer Cells to Chemotherapy Drugs and Radiotherapy.","date":"2022","source":"Cancer genomics & proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/35430566","citation_count":14,"is_preprint":false},{"pmid":"24689486","id":"PMC_24689486","title":"Novel TBL1XR1, EPHA7 and SLFN12 mutations in a Sezary syndrome patient discovered by whole exome sequencing.","date":"2014","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/24689486","citation_count":12,"is_preprint":false},{"pmid":"39437010","id":"PMC_39437010","title":"First-in-Human Dose-Escalation Study of the First-in-Class PDE3A-SLFN12 Complex Inducer BAY 2666605 in Patients with Advanced Solid Tumors Coexpressing SLFN12 and PDE3A.","date":"2024","source":"Clinical cancer research : an official journal of the American Association for Cancer Research","url":"https://pubmed.ncbi.nlm.nih.gov/39437010","citation_count":9,"is_preprint":false},{"pmid":"39166256","id":"PMC_39166256","title":"Velcrin molecular glues induce apoptosis in glioblastomas with high PDE3A and SLFN12 expression.","date":"2024","source":"Neuro-oncology advances","url":"https://pubmed.ncbi.nlm.nih.gov/39166256","citation_count":7,"is_preprint":false},{"pmid":"38864850","id":"PMC_38864850","title":"A PDE3A-SLFN12 Molecular Glue Exhibits Significant Antitumor Activity in TKI-Resistant Gastrointestinal Stromal Tumors.","date":"2024","source":"Clinical cancer research : an official journal of the American Association for Cancer Research","url":"https://pubmed.ncbi.nlm.nih.gov/38864850","citation_count":7,"is_preprint":false},{"pmid":"39411532","id":"PMC_39411532","title":"Discovery of BAY 2666605, a Molecular Glue for PDE3A and SLFN12.","date":"2024","source":"ACS medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/39411532","citation_count":6,"is_preprint":false},{"pmid":"35714590","id":"PMC_35714590","title":"A complex puzzle: Regulation of SLFN12 RNase activity by phosphorylation.","date":"2022","source":"Cell chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/35714590","citation_count":5,"is_preprint":false},{"pmid":"39740094","id":"PMC_39740094","title":"Deciphering the Role of SLFN12: A Novel Biomarker for Predicting Immunotherapy Outcomes in Glioma Patients Through Artificial Intelligence.","date":"2024","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39740094","citation_count":3,"is_preprint":false},{"pmid":"38832156","id":"PMC_38832156","title":"Overview of Structural and Functional Insights of SLFN12 Associated With Different Diseases.","date":"2024","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/38832156","citation_count":2,"is_preprint":false},{"pmid":"39594803","id":"PMC_39594803","title":"SLFN12 Expression Significantly Effects the Response to Chemotherapy Drugs in Triple-Negative Breast Cancer.","date":"2024","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/39594803","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.10.648087","title":"Phosphodiesterase 3A modulators sensitize tumor cells to Bcl-xL and Bcl-2/Bcl-xL inhibitors","date":"2025-04-10","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.10.648087","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9793,"output_tokens":2121,"usd":0.030597,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9001,"output_tokens":2506,"usd":0.053828,"stage2_stop_reason":"end_turn"},"total_usd":0.084425,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"SLFN12 is an RNase, and PDE3A binding increases SLFN12 RNase activity. PDE3A and SLFN12 form a heterotetramer stabilized by DNMDP binding. Interactions between the C-terminal alpha helix of SLFN12 and residues near the active site of PDE3A are required for complex formation, further stabilized by SLFN12-DNMDP interactions. SLFN12 RNase activity is required for DNMDP-induced cancer cell death.\",\n      \"method\": \"Structural analysis (cryo-EM/X-ray), in vitro RNase assay, mutagenesis of interface residues, functional viability assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structure determination combined with in vitro RNase assay and mutagenesis, replicated by independent lab in same year\",\n      \"pmids\": [\"34272366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"High-resolution cryo-EM structure of PDE3A-SLFN12 heterotetramer shows a butterfly-like shape; molecular glues (anagrelide, nauclefine, DNMDP) bind the catalytic domain pocket of PDE3A, creating a modified interface that recruits the short helix (E552-I558) of SLFN12 via hydrophobic interactions. SLFN12 blocks protein translation leading to apoptosis.\",\n      \"method\": \"Cryo-EM structure determination of endogenous complex from HeLa cells, structure-based analog design with cellular apoptosis and xenograft assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution cryo-EM with multiple ligands, independently replicating the heterotetramer model from PMID:34272366\",\n      \"pmids\": [\"34707099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The physiological RNase substrate of SLFN12 is tRNALeu(TAA). SLFN12 selectively digests tRNALeu(TAA), and velcrin-induced PDE3A-SLFN12 complex formation promotes this cleavage in vitro. Distinct sequences in the variable loop and acceptor stem of tRNALeu(TAA) are required for digestion. Velcrin treatment causes downregulation of tRNALeu(TAA), ribosome pausing at Leu-TTA codons, and global inhibition of protein synthesis, defining a mechanism of apoptosis initiation.\",\n      \"method\": \"In vitro RNase substrate assay, tRNA mutational analysis, ribosome profiling, global translation assays, velcrin treatment of sensitive cancer cells\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of substrate cleavage with mutagenesis of substrate sequences, corroborated by cellular ribosome pausing and translation inhibition assays\",\n      \"pmids\": [\"36302897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PDE3A-SLFN12 complex formation induces dephosphorylation of SLFN12 at serines 368 and 573. Mutational analysis demonstrates that dephosphorylation at these residues is required for cell death induced by cytotoxic PDE3A modulators. Dephosphorylation promotes the rRNA RNase activity of SLFN12, and this nucleolytic activity is essential for SLFN12's cell-death-inducing function. Complex formation also increases cytoplasmic protein stability of SLFN12.\",\n      \"method\": \"Phosphoproteomics/western blot of SLFN12 phosphorylation states, site-directed mutagenesis of Ser368 and Ser573, in vitro RNase activity assay, cell viability assays\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — mutational analysis of phosphosites combined with in vitro RNase assay and cell death functional readout, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"35104454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SLFN12 overexpression decreases CHK1 and CHK2 phosphorylation after treatment with the DNA-damaging agent camptothecin, and CHK1/CHK2 inhibition diminishes the cytotoxicity difference between SLFN12-overexpressing and baseline cells in response to carboplatin, placing SLFN12 upstream of the CHK1/2 checkpoint pathway in sensitization to DNA-damaging agents.\",\n      \"method\": \"Lentiviral SLFN12 overexpression, western blot for pCHK1/pCHK2, pharmacological CHK1/CHK2 inhibition (AZD7762), crystal violet cell viability assay in multiple TNBC cell lines\",\n      \"journal\": \"Cancer genomics & proteomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — genetic overexpression with pharmacological epistasis and functional readout in multiple cell lines, single lab\",\n      \"pmids\": [\"35430566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SLFN12 RNase-mediated cell death activates the GCN2 (general control non-derepressible 2) kinase and its downstream integrated stress response as an effector pathway mediating anticancer activity downstream of PDE3A-SLFN12 complex formation.\",\n      \"method\": \"Molecular mechanism studies in patient-derived xenograft GIST models treated with OPB-171775 (PDE3A-SLFN12 complex inducer), pathway analysis identifying GCN2 activation\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — pathway identification in PDX models with pharmacodynamic marker analysis, single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"38864850\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Velcrin compound BAY 2666605 induces PDE3A-SLFN12 complex formation, activating SLFN12 to cleave tRNALeu(TAA) and induce apoptosis in glioblastoma cells. BAY 2666605 crosses the blood-brain barrier and induces tumor regression in an orthotopic glioblastoma xenograft model.\",\n      \"method\": \"Cell viability, apoptosis, cell cycle, global translation assays in glioblastoma cell lines; orthotopic and subcutaneous xenograft models; transcriptional profiling\",\n      \"journal\": \"Neuro-oncology advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional assays with mechanistic endpoint (tRNALeu cleavage, translation inhibition) in multiple glioblastoma models, consistent with established mechanism\",\n      \"pmids\": [\"39166256\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLFN12 is a tRNA endonuclease (RNase) that is activated when molecular glue compounds (velcrins) induce its assembly into a heterotetramer with PDE3A; the C-terminal helix of SLFN12 docks into a modified surface near the PDE3A active site, and PDE3A binding both stabilizes SLFN12 and promotes its dephosphorylation at Ser368/Ser573, fully activating the RNase, which then selectively cleaves tRNALeu(TAA), causing ribosome pausing at Leu-TTA codons, global translation inhibition, integrated stress response (GCN2) activation, and ultimately apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLFN12 is a ribonuclease whose cytotoxic activity is conditionally switched on by molecular glue compounds (velcrins, including DNMDP, anagrelide, nauclefine, OPB-171775 and BAY 2666605) that drive its assembly with PDE3A into a butterfly-shaped heterotetramer, defining a drug-inducible mechanism of cancer cell death [#0, #1]. The glue binds the catalytic-domain pocket of PDE3A and remodels a surface that recruits the short C-terminal helix (E552-I558) of SLFN12 through hydrophobic contacts; this interface is required for complex formation and for compound-induced killing [#0, #1]. Complex formation activates SLFN12 by two coupled effects: it stabilizes cytoplasmic SLFN12 and promotes its dephosphorylation at Ser368 and Ser573, both of which are required to unleash full nucleolytic activity and cell death [#3]. The activated RNase selectively cleaves tRNALeu(TAA) — recognition depending on sequences in the variable loop and acceptor stem — which downregulates this tRNA, stalls ribosomes at Leu-TTA codons, and globally inhibits protein synthesis [#2]. The ensuing translational collapse triggers GCN2 kinase and its downstream integrated stress response as an effector arm of the apoptotic outcome [#5]. Independently of the velcrin axis, SLFN12 overexpression dampens CHK1/CHK2 phosphorylation and sensitizes triple-negative breast cancer cells to DNA-damaging agents [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2021,\n      \"claim\": \"Established that SLFN12 is itself an RNase and that its activity is gated by PDE3A binding within a molecular-glue-stabilized heterotetramer, identifying the structural basis of the drug-inducible complex.\",\n      \"evidence\": \"Cryo-EM/X-ray structure, in vitro RNase assays, interface mutagenesis and viability assays of the PDE3A-SLFN12-DNMDP complex\",\n      \"pmids\": [\"34272366\", \"34707099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The endogenous physiological trigger for complex formation in the absence of synthetic glues was not defined\", \"The catalytic residues of the SLFN12 RNase active site were not pinpointed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified the physiological substrate as tRNALeu(TAA) and connected its cleavage to ribosome pausing and global translation arrest, providing the molecular basis of apoptosis initiation.\",\n      \"evidence\": \"In vitro substrate cleavage with tRNA mutagenesis, ribosome profiling, and global translation assays in velcrin-treated cancer cells\",\n      \"pmids\": [\"36302897\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether additional RNA species are cleaved in vivo was not resolved\", \"The structural basis of tRNALeu(TAA) selectivity at the active site was not determined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the post-translational switch controlling SLFN12 activation, showing that PDE3A binding triggers dephosphorylation at Ser368/Ser573 and stabilization that are jointly required for nuclease-dependent killing.\",\n      \"evidence\": \"Phosphosite mapping, Ser368/Ser573 mutagenesis, in vitro RNase assays and cell viability readouts\",\n      \"pmids\": [\"35104454\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The phosphatase responsible for SLFN12 dephosphorylation was not identified\", \"How dephosphorylation mechanistically relieves the RNase was not structurally resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed SLFN12 upstream of the CHK1/CHK2 checkpoint as a sensitizer to DNA-damaging chemotherapy, suggesting a velcrin-independent role.\",\n      \"evidence\": \"Lentiviral overexpression, pCHK1/pCHK2 western blots, pharmacological CHK1/2 inhibition and viability assays in TNBC lines\",\n      \"pmids\": [\"35430566\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RNase activity underlies the checkpoint effect was not tested\", \"The direct molecular link between SLFN12 and CHK1/2 regulation was not established\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mapped GCN2/integrated stress response as the effector pathway downstream of SLFN12-driven translational arrest mediating anticancer activity in vivo.\",\n      \"evidence\": \"Pathway and pharmacodynamic analysis in PDX GIST models treated with the complex inducer OPB-171775\",\n      \"pmids\": [\"38864850\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The precise sensing step linking tRNA loss to GCN2 activation was not detailed\", \"Contribution of GCN2 relative to other apoptotic routes was not quantified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated translational applicability by showing a brain-penetrant velcrin engages the same tRNALeu cleavage mechanism to drive glioblastoma regression.\",\n      \"evidence\": \"Viability, apoptosis, translation assays and orthotopic xenograft regression with BAY 2666605 in glioblastoma models\",\n      \"pmids\": [\"39166256\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tumor-type determinants of SLFN12/PDE3A dependence were not delineated\", \"Resistance mechanisms to velcrin treatment were not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The endogenous, drug-independent physiological function and regulation of SLFN12 remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No native signal that triggers PDE3A-SLFN12 complex formation has been identified\", \"The phosphatase and kinase regulating Ser368/Ser573 are unknown\", \"Whether the CHK1/2 sensitization role depends on RNase activity is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0003723\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1, 2, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"PDE3A-SLFN12 heterotetramer\"],\n    \"partners\": [\"PDE3A\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}