{"gene":"CDS1","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":1996,"finding":"The yeast CDS1 gene on chromosome II encodes CDP-diacylglycerol synthase (CDS), an integral membrane protein essential for vegetative growth and spore germination. Null cds1 mutants are inviable, and CDS1 accounts for the majority (if not all) of CDP-diacylglycerol synthase activity in S. cerevisiae. Overexpression elevates phosphatidylinositol synthesis relative to phosphatidylserine, while reduced expression has the opposite effect, demonstrating that CDS1 activity controls the flux between these two phospholipid branches.","method":"Null mutant construction, GAL1-driven overexpression/depletion, enzymatic activity assays, phospholipid labeling","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution of enzymatic activity, null mutant lethality, multiple orthogonal assays in single rigorous study","pmids":["8557688"],"is_preprint":false},{"year":2019,"finding":"In H9c2 cardiomyoblasts, sustained vasopressin-induced phospholipase C activation selectively upregulates CDS1 mRNA (not CDS2 or TAMM41) through a pathway requiring protein kinase C and the transcription factor cFos (AP-1). CDS1 and CDS2 proteins localize to the endoplasmic reticulum, while TAMM41 localizes to mitochondria. This upregulation provides a compensatory mechanism to maintain phosphatidylinositol levels during chronic PLC signaling.","method":"Pharmacological inhibition (PKC inhibitor, AP-1 inhibitor T-5224), real-time PCR, immunoblotting for cFos, subcellular localization studies","journal":"Biochimica et biophysica acta. Molecular and cell biology of lipids","confidence":"Medium","confidence_rationale":"Tier 2 — multiple inhibitor approaches with defined pathway placement, single lab","pmids":["30862571"],"is_preprint":false},{"year":2025,"finding":"CDS1 and CDS2 form a synthetic lethal pair: CDS2 is an essential gene specifically in cancer cells with low CDS1 expression. CDS2 knockout disrupts phosphoinositide synthesis and induces apoptosis, and re-expression of CDS1 rescues the cell fitness defect, demonstrating functional redundancy between the two CDP-diacylglycerol synthase paralogs in maintaining phosphoinositide homeostasis.","method":"Genome-wide CRISPR-Cas9 single-gene and combinatorial paired-gene screening, CDS1 re-expression rescue assays, phosphoinositide synthesis measurement, in vivo xenograft validation","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 1-2 — combinatorial CRISPR screens with in vivo validation and biochemical rescue, strong evidence for functional redundancy","pmids":["40615675"],"is_preprint":false},{"year":2025,"finding":"Loss of CDS1 in nasopharyngeal carcinoma cells reduces CDP-diacylglycerol production, leading to accumulation of intracellular lipid droplets. CDS1 re-expression suppresses cell growth, migration, invasion, and tumor formation in vivo, and promotes NF-κB pathway activation with elevated inflammatory cytokines, suggesting CDS1 suppresses NPC by modulating lipid droplet levels and tumor immunogenicity.","method":"CDS1 knockdown and re-expression (loss-of-function/gain-of-function), colony formation assay, migration/invasion assays, in vivo tumor model, NF-κB pathway analysis, cytokine measurement","journal":"Cell adhesion & migration","confidence":"Medium","confidence_rationale":"Tier 2 — multiple functional assays with in vivo validation, single lab, mechanistic pathway partially defined","pmids":["40566856"],"is_preprint":false},{"year":2025,"finding":"CDS1 catalyzes synthesis and secretion of CDP-diacylglycerol (CDP-DAG), which binds to transcription factor CEBPG and induces ferroptosis in myeloid-derived suppressor cells (MDSCs), thereby relieving MDSC-mediated immunosuppression and enhancing cytotoxic T lymphocyte infiltration in colorectal cancer. CDP-DAG exhibits synergistic anti-tumor effects with anti-PDL1 therapy.","method":"Bioinformatic analysis, in vitro cellular models, in vivo tumor systems, CEBPG binding assays, ferroptosis assays, immune cell profiling, combination therapy experiments","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo validation with defined molecular mechanism, single lab","pmids":["41161459"],"is_preprint":false},{"year":2025,"finding":"In a mouse model of allergic asthma, bacterial cellulose downregulates epithelial CDS1 expression, resulting in decreased phosphatidylinositol (PI) and PI(4,5)P2 synthesis and suppression of PI3K/AKT signaling. CDS1 overexpression reverses these effects in vivo, confirming that CDS1-dependent PI synthesis is required to sustain PI3K/AKT pathway activity in airway epithelial cells.","method":"Mouse asthma model, intranasal treatment, single-cell RNA sequencing, metabolomics of BALF, CDS1 overexpression in vivo, PI/PIP2 quantification, PI3K/AKT pathway analysis","journal":"International journal of biological macromolecules","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo overexpression rescue confirms CDS1 as key node linking PI synthesis to PI3K/AKT, single lab","pmids":["41407218"],"is_preprint":false}],"current_model":"CDS1 encodes an essential integral membrane CDP-diacylglycerol synthase localized at the endoplasmic reticulum that converts phosphatidic acid to CDP-diacylglycerol, thereby controlling flux into phosphatidylinositol and phosphatidylserine biosynthesis; CDS1 is functionally redundant with its paralog CDS2 (forming a synthetic lethal pair), its expression is upregulated by PKC/cFos signaling downstream of PLC activation, and its catalytic product CDP-DAG sustains PI/PI(4,5)P2 levels required for PI3K/AKT signaling while also acting as an immunometabolic regulator that induces ferroptosis in MDSCs to relieve tumor immunosuppression."},"narrative":{"teleology":[],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":[],"other_free_text":[]},"mechanistic_narrative":"Insufficient on-target evidence to synthesize a narrative — discovery timeline does not match the canonical CDS1 protein."},"prefetch_data":{"uniprot":{"accession":"Q92903","full_name":"Phosphatidate cytidylyltransferase 1","aliases":["CDP-DAG synthase 1","CDP-DG synthase 1","CDP-diacylglycerol synthase 1","CDS 1","CDP-diglyceride pyrophosphorylase 1","CDP-diglyceride synthase 1","CTP:phosphatidate cytidylyltransferase 1"],"length_aa":461,"mass_kda":53.3,"function":"Catalyzes the conversion of phosphatidic acid (PA) to CDP-diacylglycerol (CDP-DAG), an essential intermediate in the synthesis of phosphatidylglycerol, cardiolipin and phosphatidylinositol (PubMed:25375833, PubMed:9407135). Exhibits almost no acyl chain preference for PA, showing no discrimination for the sn-1/sn-2 acyl chain composition of PAs (PubMed:25375833). Plays an important role in regulating the growth of lipid droplets which are storage organelles at the center of lipid and energy homeostasis (PubMed:26946540, PubMed:31548309). Positively regulates the differentiation and development of adipocytes (By similarity)","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/Q92903/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CDS1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000163624","cell_line_id":"CID000344","localizations":[{"compartment":"er","grade":3}],"interactors":[{"gene":"CDS2","stoichiometry":10.0},{"gene":"FASN","stoichiometry":0.2},{"gene":"ALDH3A2","stoichiometry":0.2},{"gene":"NSDHL","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000344","total_profiled":1310},"omim":[{"mim_id":"609265","title":"TUMOR PREDISPOSITION SYNDROME 4; TPDS4","url":"https://www.omim.org/entry/609265"},{"mim_id":"605893","title":"CDP-DIACYLGLYCEROL-INOSITOL 3-PHOSPHATIDYLTRANSFERASE; CDIPT","url":"https://www.omim.org/entry/605893"},{"mim_id":"604373","title":"CHECKPOINT KINASE 2; CHEK2","url":"https://www.omim.org/entry/604373"},{"mim_id":"603549","title":"CDP-DIACYLGLYCEROL SYNTHASE 2; CDS2","url":"https://www.omim.org/entry/603549"},{"mim_id":"603548","title":"CDP-DIACYLGLYCEROL SYNTHASE 1; CDS1","url":"https://www.omim.org/entry/603548"}],"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/CDS1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O96017","domains":[{"cath_id":"2.60.200.20","chopping":"93-202","consensus_level":"high","plddt":92.3037,"start":93,"end":202},{"cath_id":"3.30.200.20","chopping":"213-301","consensus_level":"high","plddt":80.6565,"start":213,"end":301},{"cath_id":"1.10.510.10","chopping":"306-497","consensus_level":"high","plddt":88.1994,"start":306,"end":497}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O96017","model_url":"https://alphafold.ebi.ac.uk/files/AF-O96017-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O96017-F1-predicted_aligned_error_v6.png","plddt_mean":76.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CDS1","jax_strain_url":"https://www.jax.org/strain/search?query=CDS1"},"sequence":{"accession":"O96017","fasta_url":"https://rest.uniprot.org/uniprotkb/O96017.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O96017/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O96017"}},"corpus_meta":[{"pmid":"10673501","id":"PMC_10673501","title":"The 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Activation depends on all six checkpoint Rad proteins (Rad1, Rad3, Rad9, Rad17, Rad26, Hus1), and Cds1 interacts physically with Rad26. Cds1 defines an S-phase-specific subpathway of the checkpoint response distinct from mitotic arrest checkpoints.\",\n      \"method\": \"Genetic epistasis, physical interaction (co-immunoprecipitation), kinase activity assays, cell cycle stage-specific activation analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal genetic and biochemical evidence, replicated in multiple subsequent studies\",\n      \"pmids\": [\"9450932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"In fission yeast, Cds1 enforces the replication checkpoint partly by phosphorylating Wee1 (an inhibitor of Cdc2) and by promoting accumulation of Mik1 (a second Cdc2 inhibitor) upon hydroxyurea treatment. Loss of both Cds1 and Chk1 abolishes HU-induced mitotic arrest.\",\n      \"method\": \"Genetic epistasis, kinase assays, Western blot for Mik1 levels\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, replicated in subsequent work\",\n      \"pmids\": [\"9572736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"In fission yeast, both Cds1 and Chk1 phosphorylate Cdc25 at serine residues (S99, S192, S359), promoting binding of 14-3-3 proteins to Cdc25 and preventing Cdc2 activation; this mechanism is required for the replication checkpoint.\",\n      \"method\": \"In vitro kinase assay, mutagenesis of Cdc25 phosphorylation sites, 14-3-3 binding assay, in vivo checkpoint analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with mutagenesis, confirmed in vivo, independently replicated\",\n      \"pmids\": [\"9774107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human Cds1 (hCds1/Chk2), a homolog of S. pombe Cds1, is phosphorylated and activated in response to ionizing radiation in an ATM-dependent manner and in response to hydroxyurea through an ATM-independent pathway. hCds1 phosphorylates Cdc25C to promote 14-3-3 protein binding, conserving this checkpoint mechanism from yeast to humans.\",\n      \"method\": \"Kinase assay, phosphorylation analysis, 14-3-3 binding assay, ATM-deficient cell lines\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, functional conservation demonstrated\",\n      \"pmids\": [\"10097108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human Cds1 directly phosphorylates and inactivates Cdc25 in vitro; Cdc25 activity decreases following ionizing radiation in an ATM-dependent manner; Cds1 is activated by DNA damage in human cells.\",\n      \"method\": \"In vitro kinase assay, Cdc25 activity assay, ATM-deficient cell lines, wortmannin inhibition\",\n      \"journal\": \"Current biology : CB\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzymatic assay with functional validation in cells\",\n      \"pmids\": [\"9889122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"In fission yeast, Cds1 and Chk1 both inhibit Cdc25 in vitro and in vivo; Cds1 and Chk1 phosphorylate Cdc25 predominantly on serine-99; the Cdc25-S99A mutation partially impairs both S-M replication and G2-M damage checkpoints in vivo.\",\n      \"method\": \"In vitro kinase assay, in vivo checkpoint assay, site-directed mutagenesis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro assay with mutagenesis confirmed in vivo\",\n      \"pmids\": [\"10198041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Signal specificity of Cds1 activation: Cds1 becomes concentrated in the nucleus only during S phase, correlating with its S-phase-specific activation by ionizing radiation. Cds1 actively suppresses a repair process that leads to Chk1 phosphorylation in HU-arrested cells, establishing a regulatory hierarchy between the two checkpoint kinases.\",\n      \"method\": \"Fluorescence microscopy (nuclear localization), kinase assays, genetic epistasis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional consequence, combined with genetic analysis\",\n      \"pmids\": [\"10330167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human Cds1 (Chk2) and Chk1 phosphorylate tetrameric p53 in vitro at multiple DNA damage-inducible sites including S20; Cds1 strongly prefers tetrameric over monomeric p53; overexpression or kinase-dead forms of Chk1 regulate p53 protein levels in transfected cells.\",\n      \"method\": \"In vitro kinase assay with recombinant proteins, mutagenesis, transfection/overexpression\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro kinase assay with mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"10673501\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"ATM phosphorylates human Cds1 at threonine-68 in vitro, and T68 is the principal irradiation-induced phosphorylation site in vivo. A non-phosphorylatable T68A mutant of Cds1 fails to be fully activated and shows reduced ability to induce G1 arrest in response to ionizing radiation.\",\n      \"method\": \"In vitro kinase assay (ATM phosphorylating Cds1), site-directed mutagenesis, in vivo phosphorylation mapping, functional G1 arrest assay\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro assay with mutagenesis, in vivo validation\",\n      \"pmids\": [\"11025670\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The FHA1 domain of fission yeast Cds1 interacts with Mus81, an evolutionarily conserved damage tolerance protein with an XPF endonuclease homology domain. Loss of Mus81 causes sensitivity to dNTP starvation, UV, and DNA polymerase impairment, and triggers a checkpoint-dependent mitotic delay. Cds1 is proposed to recruit to aberrant DNA structures via this interaction.\",\n      \"method\": \"Co-immunoprecipitation (FHA1 domain pulldown), genetic epistasis, sensitivity assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP with domain mapping, genetic validation\",\n      \"pmids\": [\"11073977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mrc1 (mediator of replication checkpoint) is required for activation of Cds1 during S phase in fission yeast. Mrc1 physically associates with Cds1 and is required for Rad3-dependent regulation of Cds1. Mrc1 expression is cell-cycle regulated, appearing coincident with S phase.\",\n      \"method\": \"Co-immunoprecipitation, genetic analysis (mrc1 deletion), kinase activity assay, cell cycle expression analysis\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP plus genetic and biochemical analysis\",\n      \"pmids\": [\"11715017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Rad3 and ATM phosphorylate fission yeast Cds1 at T11Q (threonine-11) in the N-terminal SQ/TQ domain in vitro. A T11A substitution abolishes Cds1 activation by hydroxyurea and eliminates S-M checkpoint enforcement and HU tolerance in vivo.\",\n      \"method\": \"In vitro kinase assay (Rad3, ATM on Cds1), site-directed mutagenesis (T11A), in vivo checkpoint and sensitivity assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase assay with mutagenesis, confirmed in vivo\",\n      \"pmids\": [\"11313465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Fission yeast Cds1 interacts with Rad60, a recombinational repair protein. Cds1 activation triggers phosphorylation and nuclear delocalization of Rad60. A Rad60 mutant resistant to Cds1 regulation renders cells specifically sensitive to replication fork arrest. Rad60 functions co-dependently with Smc5-Smc6 SMC complex.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, phosphorylation assay, genetic epistasis, subcellular localization\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP/MS plus genetic epistasis and functional mutagenesis\",\n      \"pmids\": [\"12897162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Fission yeast Swi1 (Tof1 homolog) is required for efficient activation of Cds1 at stalled replication forks. Swi1 and Cds1 together prevent fork collapse in rDNA repeats. Swi1 is recruited to chromatin during S phase. Mus81 is essential in swi1 but not cds1 mutants, indicating Swi1 has Cds1-independent functions.\",\n      \"method\": \"Genetic epistasis, chromatin fractionation (Swi1 recruitment), kinase activity assay (Cds1), DNA repair focus formation (Rad22)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including chromatin fractionation and genetic epistasis\",\n      \"pmids\": [\"14560029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Mrc1 is required for the initial Thr-11 phosphorylation of Cds1 by Rad3-Rad26 in fission yeast. Mrc1 specifically interacts with the FHA domain of Cds1 (yeast two-hybrid), and FHA domain mutations that abolish this interaction eliminate Thr-11 phosphorylation. A Rad26-Cds1 fusion protein partially bypasses the Mrc1 requirement, indicating Mrc1 recruits Cds1 to the Rad3-Rad26 kinase complex.\",\n      \"method\": \"Yeast two-hybrid, site-directed mutagenesis, in vivo phosphorylation assay, fusion protein epistasis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — yeast two-hybrid with domain mutagenesis, in vivo phosphorylation confirmed by fusion protein rescue\",\n      \"pmids\": [\"15173168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Cds1 regulates Mus81 via its FHA domain: a mutation in the Mus81 FHA-binding motif eliminates Cds1 binding and Cds1-dependent phosphorylation of Mus81. Upon HU-induced replication arrest, Mus81 undergoes extensive Cds1-dependent phosphorylation and dissociates from chromatin, preventing it from cleaving stalled forks and causing chromosomal rearrangements.\",\n      \"method\": \"Co-immunoprecipitation, mutagenesis of FHA-binding motif, chromatin fractionation, in vivo phosphorylation assay, genetic analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods with site-specific mutagenesis and chromatin fractionation\",\n      \"pmids\": [\"15805465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Cds1 in fission yeast is activated by a two-stage mechanism: (1) Mrc1 recruits Cds1 to stalled replication forks via interactions between the FHA domain of Cds1 and phosphorylated Rad3 consensus sites in Mrc1; Cds1 is primed by Rad3-dependent phosphorylation at Thr-11. (2) Primed Cds1 molecules dimerize via phospho-specific FHA domain interactions and are activated by trans-autophosphorylation.\",\n      \"method\": \"Biochemical reconstitution, mutagenesis, in vitro kinase assay, dimerization assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biochemical reconstitution with mutagenesis, mechanistically detailed\",\n      \"pmids\": [\"16618806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Active Cds1 in fission yeast is required to release the Cdc14-like phosphatase Flp1 from the nucleolus into the nucleus upon replication stress. Cds1 phosphorylates Flp1 (a Flp1 mutant lacking all Cds1 phosphorylation sites fails to relocalize). Nuclear Flp1 in turn promotes full Cds1 activation, establishing a positive feedback loop during replication checkpoint.\",\n      \"method\": \"Subcellular localization (fluorescence microscopy), phosphorylation site mutagenesis (flp1-9A), kinase activity assay, genetic analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization with functional mutagenesis and kinase activity measurement\",\n      \"pmids\": [\"18385517\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Cds1 activation loop autophosphorylation at Thr-328 is the only covalent modification required for kinase activation in vitro and in vivo after dimerization. The C-terminal 27-amino acid tail of Cds1 autoinhibits spontaneous autophosphorylation of Thr-328 in unprimed monomeric Cds1, preventing spurious checkpoint activation during normal cell cycles.\",\n      \"method\": \"In vitro kinase assay, mutagenesis (Thr-328 and C-terminal tail), genetic complementation in vivo\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro kinase reconstitution with mutagenesis, in vivo validation\",\n      \"pmids\": [\"19357077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"In fission yeast, Cds1 phosphorylates APC/C activator Ste9 in vitro, and Cds1-dependent inhibition/phosphorylation of Ste9 during S-phase arrest stabilizes the MBF activator Rep2 by preventing its ubiquitin-mediated proteolysis by APC/C-Ste9, thereby sustaining MBF-dependent gene transcription during replication stress.\",\n      \"method\": \"In vitro kinase assay (Cds1 on Ste9), ubiquitination assay, genetic analysis, protein stability assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro kinase assay with genetic validation, single lab\",\n      \"pmids\": [\"19596787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The S. cerevisiae CDS1 gene encodes CDP-diacylglycerol synthase; it is essential for cell growth and vegetative development. Overexpression increases synthase activity ~10-fold and elevates phosphatidylinositol synthesis relative to phosphatidylserine. Loss of CDS1 (null mutant) abolishes spore germination and vegetative growth.\",\n      \"method\": \"Gene deletion (null mutant), complementation assay, enzymatic activity assay (CDP-diacylglycerol synthase), phospholipid synthesis measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — enzymatic assay in null mutant background with complementation, multiple orthogonal methods\",\n      \"pmids\": [\"8557688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Xenopus Cds1 (Xcds1) is phosphorylated and activated by simple DNA molecules with double-stranded ends in cell-free egg extracts, but not by aphidicolin-induced replication blocks (which activate Xchk1 instead). This shows distinct signal inputs for Cds1 vs. Chk1 in vertebrate checkpoint responses.\",\n      \"method\": \"Cell-free Xenopus egg extract, immunodepletion, kinase activity assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-free reconstitution with immunodepletion and kinase assay\",\n      \"pmids\": [\"10793133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Xenopus Cds1 (XCds1) kinase activity is high in immature oocytes and is inactivated at the meiotic G2/M transition in a cyclin B-Cdc2-dependent (but not MAP kinase-dependent) manner. Overexpression of wild-type XCds1 delays M-phase entry after progesterone treatment, demonstrating a functional role in the physiological G2 arrest.\",\n      \"method\": \"Kinase activity assay during oocyte maturation, overexpression of wild-type and kinase-dead XCds1, cyclin B/MAP kinase inhibition\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional kinase assay with overexpression, single lab\",\n      \"pmids\": [\"11591827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Xenopus Cds1 constitutively associates with a Xenopus ATR complex under normal cell cycle conditions via a putative SH3-binding region (not its FHA domain). Upon double-stranded DNA ends, DNA-PK first phosphorylates XCds1 at serine-39, followed by phosphorylation of SQ sites by ATM/ATR/DNA-PK, inducing dissociation from the ATR complex and promoting full XCds1 activation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, phosphorylation site mutagenesis, Xenopus cell-free extract\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP with kinase assay and mutagenesis, single lab\",\n      \"pmids\": [\"15509799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In H9c2 cardiomyoblasts, vasopressin stimulation increases CDS1 (CDP-diacylglycerol synthase 1) mRNA selectively (not CDS2) through a signaling cascade involving phospholipase C, protein kinase C, and the transcription factor cFos. CDS1 and CDS2 proteins localize to the endoplasmic reticulum, while TAMM41 localizes to mitochondria.\",\n      \"method\": \"qRT-PCR, PKC inhibitor, AP-1 inhibitor (T-5224), cFos Western blot, subcellular localization\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological inhibition with mRNA/protein readouts, single lab\",\n      \"pmids\": [\"30862571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDS1 and CDS2 form a synthetic lethal pair in human uveal melanoma cells: CDS2 knockout in cells with low CDS1 expression disrupts phosphoinositide synthesis and induces apoptosis; re-expression of CDS1 rescues this fitness defect. This CDS1/CDS2 synthetic lethality is validated in vivo and extends across multiple cancer types.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 single-gene and combinatorial paired-gene screens, CDS1 re-expression rescue, in vivo validation, phosphoinositide measurement\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR screen with in vivo validation and biochemical rescue, strong\",\n      \"pmids\": [\"40615675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDS1 (CDP-diacylglycerol synthase 1) catalyzes synthesis and secretion of CDP-diacylglycerol (CDP-DAG) in colorectal cancer cells; CDP-DAG binds transcription factor CEBPG and induces ferroptosis in myeloid-derived suppressor cells (MDSCs), alleviating immunosuppression and enabling cytotoxic T lymphocyte infiltration.\",\n      \"method\": \"CDS1 knockout/overexpression in vitro and in vivo, CDP-DAG measurement, CEBPG binding assay, ferroptosis assay, immune cell analysis\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vitro and in vivo methods, single lab, mechanistic novelty\",\n      \"pmids\": [\"41161459\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CDS1 refers to two distinct proteins: (1) the checkpoint kinase Cds1/Chk2, which is activated during S phase by a two-stage mechanism involving Rad3/ATM-dependent phosphorylation of Thr-11 (or Thr-68 in humans) mediated by the scaffold Mrc1, followed by FHA-domain-mediated dimerization and trans-autophosphorylation of the activation loop (Thr-328), enabling Cds1 to phosphorylate and inhibit Cdc25, phosphorylate Wee1/Mik1, p53, BRCA1, and regulate substrates including Mus81 and Rad60 at stalled replication forks; and (2) CDP-diacylglycerol synthase 1 (CDS1), an ER-localized integral membrane enzyme that converts phosphatidic acid to CDP-diacylglycerol, which is essential for phosphatidylinositol and PIP2 resynthesis, regulated by PKC/cFos signaling, and forms a synthetic lethal pair with CDS2 for phosphoinositide homeostasis.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI need to carefully classify each paper before extracting discoveries.\n\n**Classification:**\n\nThe gene query is **CDS1** — which has TWO distinct meanings in the corpus:\n1. **CDP-diacylglycerol synthase 1** (human/mammalian enzyme in phospholipid metabolism) — the canonical human protein-coding gene CDS1 (HGNC)\n2. **Cds1 checkpoint kinase** (fission yeast S. pombe) — which is the ortholog of human **CHK2/CHEK2**, NOT CDS1\n\nThe HGNC gene CDS1 encodes CDP-diacylglycerol synthase 1. The checkpoint kinase papers (most of the corpus) describe Cds1/Chk2/CHEK2, which is a DIFFERENT human gene (CHEK2). These are **alias collisions** — \"Cds1\" in yeast checkpoint literature = human CHK2/CHEK2, not human CDS1.\n\n**KEEP papers about CDP-diacylglycerol synthase 1 (CDS1):**\n- [13] PMID:8557688 — Yeast CDS1 = CDP-diacylglycerol synthase, essential gene ✓\n- [34] PMID:40615675 — CDS1/CDS2 synthetic lethal, phosphoinositide synthesis ✓\n- [38] PMID:30862571 — CDS1 mRNA regulation, CDP-diacylglycerol synthase in cardiomyoblasts ✓\n- [40] PMID:17364441 — Porcine CDS1/CDS2 gene characterization ✓\n- [44] PMID:31394702 — CDS1 methylation in HCC, PI metabolism ✓\n- [49] PMID:40566856 — CDS1 in NPC, lipid metabolism ✓\n- [50] PMID:41407218 — CDS1, phosphatidylinositol metabolism, PI3K/AKT ✓\n- [52] PMID:41161459 — CDS1/CDP-DAG, ferroptosis in MDSCs ✓\n\n**EXCLUDE** (all checkpoint kinase Cds1/CHK2 papers, microbial CDS-1 papers, CTLA-4 CDS1 SNP paper, photosensitizer CDS1 paper, GWAS/expression papers): All others.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"The yeast CDS1 gene on chromosome II encodes CDP-diacylglycerol synthase (CDS), an integral membrane protein essential for vegetative growth and spore germination. Null cds1 mutants are inviable, and CDS1 accounts for the majority (if not all) of CDP-diacylglycerol synthase activity in S. cerevisiae. Overexpression elevates phosphatidylinositol synthesis relative to phosphatidylserine, while reduced expression has the opposite effect, demonstrating that CDS1 activity controls the flux between these two phospholipid branches.\",\n      \"method\": \"Null mutant construction, GAL1-driven overexpression/depletion, enzymatic activity assays, phospholipid labeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution of enzymatic activity, null mutant lethality, multiple orthogonal assays in single rigorous study\",\n      \"pmids\": [\"8557688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In H9c2 cardiomyoblasts, sustained vasopressin-induced phospholipase C activation selectively upregulates CDS1 mRNA (not CDS2 or TAMM41) through a pathway requiring protein kinase C and the transcription factor cFos (AP-1). CDS1 and CDS2 proteins localize to the endoplasmic reticulum, while TAMM41 localizes to mitochondria. This upregulation provides a compensatory mechanism to maintain phosphatidylinositol levels during chronic PLC signaling.\",\n      \"method\": \"Pharmacological inhibition (PKC inhibitor, AP-1 inhibitor T-5224), real-time PCR, immunoblotting for cFos, subcellular localization studies\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitor approaches with defined pathway placement, single lab\",\n      \"pmids\": [\"30862571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDS1 and CDS2 form a synthetic lethal pair: CDS2 is an essential gene specifically in cancer cells with low CDS1 expression. CDS2 knockout disrupts phosphoinositide synthesis and induces apoptosis, and re-expression of CDS1 rescues the cell fitness defect, demonstrating functional redundancy between the two CDP-diacylglycerol synthase paralogs in maintaining phosphoinositide homeostasis.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 single-gene and combinatorial paired-gene screening, CDS1 re-expression rescue assays, phosphoinositide synthesis measurement, in vivo xenograft validation\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — combinatorial CRISPR screens with in vivo validation and biochemical rescue, strong evidence for functional redundancy\",\n      \"pmids\": [\"40615675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Loss of CDS1 in nasopharyngeal carcinoma cells reduces CDP-diacylglycerol production, leading to accumulation of intracellular lipid droplets. CDS1 re-expression suppresses cell growth, migration, invasion, and tumor formation in vivo, and promotes NF-κB pathway activation with elevated inflammatory cytokines, suggesting CDS1 suppresses NPC by modulating lipid droplet levels and tumor immunogenicity.\",\n      \"method\": \"CDS1 knockdown and re-expression (loss-of-function/gain-of-function), colony formation assay, migration/invasion assays, in vivo tumor model, NF-κB pathway analysis, cytokine measurement\",\n      \"journal\": \"Cell adhesion & migration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple functional assays with in vivo validation, single lab, mechanistic pathway partially defined\",\n      \"pmids\": [\"40566856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDS1 catalyzes synthesis and secretion of CDP-diacylglycerol (CDP-DAG), which binds to transcription factor CEBPG and induces ferroptosis in myeloid-derived suppressor cells (MDSCs), thereby relieving MDSC-mediated immunosuppression and enhancing cytotoxic T lymphocyte infiltration in colorectal cancer. CDP-DAG exhibits synergistic anti-tumor effects with anti-PDL1 therapy.\",\n      \"method\": \"Bioinformatic analysis, in vitro cellular models, in vivo tumor systems, CEBPG binding assays, ferroptosis assays, immune cell profiling, combination therapy experiments\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo validation with defined molecular mechanism, single lab\",\n      \"pmids\": [\"41161459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a mouse model of allergic asthma, bacterial cellulose downregulates epithelial CDS1 expression, resulting in decreased phosphatidylinositol (PI) and PI(4,5)P2 synthesis and suppression of PI3K/AKT signaling. CDS1 overexpression reverses these effects in vivo, confirming that CDS1-dependent PI synthesis is required to sustain PI3K/AKT pathway activity in airway epithelial cells.\",\n      \"method\": \"Mouse asthma model, intranasal treatment, single-cell RNA sequencing, metabolomics of BALF, CDS1 overexpression in vivo, PI/PIP2 quantification, PI3K/AKT pathway analysis\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo overexpression rescue confirms CDS1 as key node linking PI synthesis to PI3K/AKT, single lab\",\n      \"pmids\": [\"41407218\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CDS1 encodes an essential integral membrane CDP-diacylglycerol synthase localized at the endoplasmic reticulum that converts phosphatidic acid to CDP-diacylglycerol, thereby controlling flux into phosphatidylinositol and phosphatidylserine biosynthesis; CDS1 is functionally redundant with its paralog CDS2 (forming a synthetic lethal pair), its expression is upregulated by PKC/cFos signaling downstream of PLC activation, and its catalytic product CDP-DAG sustains PI/PI(4,5)P2 levels required for PI3K/AKT signaling while also acting as an immunometabolic regulator that induces ferroptosis in MDSCs to relieve tumor immunosuppression.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CDS1 encodes CDP-diacylglycerol synthase 1, an endoplasmic reticulum-localized integral membrane enzyme that converts phosphatidic acid to CDP-diacylglycerol, a critical precursor for phosphatidylinositol and phosphoinositide biosynthesis [PMID:8557688, PMID:30862571]. CDS1 expression is transcriptionally upregulated via a phospholipase C–PKC–cFos signaling cascade in cardiomyoblasts [PMID:30862571], and CDS1 forms a synthetic lethal pair with CDS2, such that loss of both enzymes abolishes phosphoinositide synthesis and induces apoptosis across multiple cancer types [PMID:40615675]. CDS1-derived CDP-diacylglycerol can also be secreted and act extracellularly, binding the transcription factor CEBPG in myeloid-derived suppressor cells to induce ferroptosis and relieve immunosuppression in the tumor microenvironment [PMID:41161459]. Note: the fission yeast gene also named Cds1 encodes a checkpoint kinase (orthologous to human CHK2/CHEK2) that is activated during S phase via Mrc1-mediated recruitment to Rad3, undergoes FHA-domain-dependent dimerization and trans-autophosphorylation, and enforces the replication checkpoint by phosphorylating Cdc25, Wee1/Mik1, and Mus81 [PMID:9450932, PMID:16618806, PMID:15805465].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Identification of S. cerevisiae CDS1 as the gene encoding CDP-diacylglycerol synthase established that this enzyme is essential for viability and channels phosphatidic acid toward phosphatidylinositol synthesis rather than phosphatidylserine synthesis.\",\n      \"evidence\": \"Gene deletion, complementation, enzymatic activity assay, and phospholipid measurement in yeast\",\n      \"pmids\": [\"8557688\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian CDS1 had not yet been characterized\", \"Regulation of CDS1 expression was unknown\", \"Redundancy with other CDS isoforms was unaddressed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Fission yeast Cds1 kinase was shown to be an S-phase-specific checkpoint effector activated by DNA damage or replication arrest, dependent on all six checkpoint Rad proteins, and acting through phosphorylation of Cdc25 and regulation of Wee1/Mik1 — defining a dedicated S-phase checkpoint branch distinct from G2/M damage checkpoints.\",\n      \"evidence\": \"Genetic epistasis, co-immunoprecipitation with Rad26, kinase assays, in vitro Cdc25 phosphorylation and 14-3-3 binding in S. pombe\",\n      \"pmids\": [\"9450932\", \"9572736\", \"9774107\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of Cds1 activation (priming, dimerization) was unknown\", \"Mammalian conservation had not been tested\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Conservation of the Cds1/Chk2 checkpoint pathway to human cells was demonstrated: human Cds1 is activated by ionizing radiation in an ATM-dependent manner and phosphorylates Cdc25C to promote 14-3-3 binding, while Cds1 nuclear concentration during S phase explains its cell-cycle-stage specificity.\",\n      \"evidence\": \"Kinase assays in ATM-deficient human cell lines, 14-3-3 binding assays, fluorescence microscopy of Cds1 localization in S. pombe\",\n      \"pmids\": [\"10097108\", \"9889122\", \"10330167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The upstream priming kinase site in human Chk2 was not yet mapped\", \"How Cds1 is recruited to stalled forks was unknown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"ATM was identified as the kinase that primes human Cds1/Chk2 by phosphorylating Thr-68, establishing the initiating event for checkpoint activation; simultaneously, Cds1 was shown to phosphorylate p53 preferentially in its tetrameric form, linking the replication/damage checkpoint to transcriptional responses.\",\n      \"evidence\": \"In vitro kinase assays with recombinant ATM and Cds1, T68A mutagenesis, G1 arrest assays, p53 phosphorylation with oligomerization analysis\",\n      \"pmids\": [\"11025670\", \"10673501\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dimerization mechanism was not yet resolved\", \"How a scaffold mediates Cds1 priming was unknown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The FHA domain of Cds1 was shown to interact with the endonuclease Mus81, revealing a direct substrate-recruitment mechanism at stalled replication forks, while Xenopus Cds1 was found to be activated specifically by double-stranded DNA ends rather than replication blocks, distinguishing Cds1 signal inputs from Chk1.\",\n      \"evidence\": \"Co-immunoprecipitation with FHA domain mapping in S. pombe; cell-free Xenopus egg extract with immunodepletion\",\n      \"pmids\": [\"11073977\", \"10793133\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of Mus81 phosphorylation was unknown\", \"Whether Mus81 dissociates from chromatin upon phosphorylation was untested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Discovery of Mrc1 as the scaffold required for Cds1 activation, and identification of Rad3-dependent Thr-11 phosphorylation as the essential priming event in S. pombe, resolved how checkpoint signal specificity is achieved during S phase.\",\n      \"evidence\": \"Co-immunoprecipitation, mrc1 deletion genetics, T11A mutagenesis, kinase activity assays in S. pombe\",\n      \"pmids\": [\"11715017\", \"11313465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Mrc1 directly presents Cds1 to Rad3 was not shown\", \"The dimerization and trans-autophosphorylation step was not yet characterized\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Cds1 was found to regulate recombinational repair via phosphorylation and nuclear delocalization of Rad60 (which cooperates with the Smc5-Smc6 complex), and Swi1/Tof1 was identified as an additional factor required for efficient Cds1 activation at stalled forks, expanding the network of Cds1 substrates and upstream regulators.\",\n      \"evidence\": \"Co-immunoprecipitation, mass spectrometry, subcellular localization, chromatin fractionation, genetic epistasis in S. pombe\",\n      \"pmids\": [\"12897162\", \"14560029\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Rad60 delocalization prevents inappropriate recombination was not mechanistically detailed\", \"Swi1's physical mode of action on Cds1 activation was unclear\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Mrc1's FHA-domain interaction with Cds1 was shown to be required for Rad3-dependent Thr-11 phosphorylation, and a Rad26-Cds1 fusion partially bypassed Mrc1, proving that Mrc1 functions primarily as a scaffold to recruit Cds1 to the Rad3-Rad26 kinase complex.\",\n      \"evidence\": \"Yeast two-hybrid, FHA domain mutagenesis, fusion protein bypass, in vivo phosphorylation assay in S. pombe\",\n      \"pmids\": [\"15173168\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The structural basis of the FHA–Mrc1 interaction was not resolved\", \"Whether this mechanism is fully conserved in vertebrates was unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The functional consequence of Cds1-Mus81 interaction was resolved: Cds1-dependent phosphorylation of Mus81 dissociates it from chromatin at stalled replication forks, preventing inappropriate endonucleolytic cleavage and chromosomal rearrangements.\",\n      \"evidence\": \"Mutagenesis of Mus81 FHA-binding motif, chromatin fractionation, phosphorylation assays, genetic analysis in S. pombe\",\n      \"pmids\": [\"15805465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Mus81 chromatin dissociation is reversible upon checkpoint recovery was untested\", \"Structural basis of Mus81 regulation was lacking\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Biochemical reconstitution established the complete two-stage activation mechanism of Cds1: Mrc1-mediated recruitment and Rad3-dependent Thr-11 priming, followed by FHA-domain-mediated dimerization of primed Cds1 molecules and trans-autophosphorylation, providing a full mechanistic model for checkpoint kinase amplification.\",\n      \"evidence\": \"Biochemical reconstitution, dimerization assay, in vitro kinase assay with mutagenesis in S. pombe\",\n      \"pmids\": [\"16618806\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo stoichiometry and dynamics of dimerization were not measured\", \"Whether this two-stage mechanism is conserved for human Chk2 was not directly tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"A positive feedback loop was identified in which Cds1 phosphorylates the Cdc14-like phosphatase Flp1 to release it from the nucleolus, and nuclear Flp1 in turn promotes full Cds1 activation, explaining how checkpoint signaling is amplified during replication stress.\",\n      \"evidence\": \"Fluorescence microscopy, phosphorylation site mutagenesis (flp1-9A), kinase activity measurement in S. pombe\",\n      \"pmids\": [\"18385517\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The substrate(s) of Flp1 that feed back to Cds1 were not identified\", \"Whether this feedback loop operates in vertebrates was unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Thr-328 autophosphorylation was identified as the sole covalent modification required for Cds1 kinase activation after dimerization, and a C-terminal autoinhibitory tail was shown to suppress spurious activation of monomeric Cds1, explaining how checkpoint kinase quiescence is maintained during unperturbed S phase.\",\n      \"evidence\": \"In vitro kinase reconstitution, T328 and C-terminal tail mutagenesis, genetic complementation in S. pombe\",\n      \"pmids\": [\"19357077\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of C-terminal tail autoinhibition was not resolved\", \"Whether the autoinhibitory mechanism is conserved in human Chk2 was untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Transcriptional regulation of mammalian CDS1 (CDP-diacylglycerol synthase 1) was elucidated: vasopressin-stimulated PLC–PKC–cFos signaling selectively upregulates CDS1 but not CDS2, and both enzymes localize to the ER, establishing the signaling inputs controlling phosphoinositide precursor supply.\",\n      \"evidence\": \"qRT-PCR, PKC and AP-1 inhibitors, subcellular localization in H9c2 cardiomyoblasts\",\n      \"pmids\": [\"30862571\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether cFos directly binds the CDS1 promoter was not demonstrated\", \"Physiological consequence of CDS1 upregulation on PI levels was not measured\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"CDS1 and CDS2 were identified as a synthetic lethal gene pair: loss of CDS2 in CDS1-low cells abolishes phosphoinositide synthesis and induces apoptosis, validatable in vivo and rescuable by CDS1 re-expression, establishing functional redundancy and a therapeutic vulnerability across cancer types.\",\n      \"evidence\": \"Genome-wide CRISPR single-gene and combinatorial screens, CDS1 re-expression rescue, phosphoinositide measurement, in vivo xenograft in uveal melanoma and other cancer lines\",\n      \"pmids\": [\"40615675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CDS1-low tumors can adaptively upregulate CDS1 upon CDS2 inhibition is unknown\", \"Isoform-specific enzymatic kinetics and substrate preferences have not been compared\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"CDS1-produced CDP-diacylglycerol was found to function as a secreted signaling lipid that binds CEBPG in myeloid-derived suppressor cells to induce ferroptosis, connecting phospholipid metabolism to anti-tumor immune modulation.\",\n      \"evidence\": \"CDS1 knockout/overexpression, CDP-DAG measurement, CEBPG binding assay, ferroptosis and immune infiltration analysis in colorectal cancer models\",\n      \"pmids\": [\"41161459\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The mechanism by which CDP-DAG is secreted extracellularly is unknown\", \"Whether CEBPG-mediated ferroptosis operates in non-cancer immune contexts is untested\", \"Independent replication is needed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the structural basis for CDS1 vs. CDS2 substrate specificity and potential differential regulation; whether extracellular CDP-DAG signaling is a general feature of CDS1-expressing cells or a cancer-specific phenomenon; and whether the two-stage Cds1/Chk2 checkpoint kinase activation mechanism (reconstituted in yeast) is fully conserved in human cells.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal structure or cryo-EM structure of mammalian CDS1 exists\", \"Isoform-specific contributions of CDS1 vs CDS2 to specific phosphoinositide pools are not resolved\", \"In vivo dynamics of Chk2 dimerization in human cells remain uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [20, 25, 26]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [24]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [20, 24, 25, 26]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"CDS2\",\n      \"CEBPG\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"Insufficient on-target evidence to synthesize a narrative — discovery timeline does not match the canonical CDS1 protein.\",\n  \"teleology\": [],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [],\n    \"pathway\": [],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}\n```"}