{"gene":"CTDSPL2","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2007,"finding":"HSPC129 (CTDSPL2) encodes a Mg2+-dependent CTD phosphatase; a truncated form lacking the first 156 N-terminal amino acids exhibits Mg2+-dependent phosphatase activity at pH 5.0 and dephosphorylates the RNA polymerase II CTD in vitro.","method":"In vitro phosphatase activity assay with recombinant truncated protein","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay establishing CTD phosphatase activity, single lab, single method","pmids":["17487459"],"is_preprint":false},{"year":2014,"finding":"CTDSPL2/SCP4 physically interacts with and specifically dephosphorylates Smad1/5/8 in the nucleus, thereby attenuating BMP-induced transcriptional responses; knockdown in C2C12 cells increases BMP target gene expression and promotes osteogenic differentiation.","method":"Co-immunoprecipitation, in vitro dephosphorylation assay, siRNA knockdown with reporter and differentiation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — reciprocal Co-IP plus in vitro phosphatase assay plus loss-of-function phenotype, single lab with multiple orthogonal methods","pmids":["25100727"],"is_preprint":false},{"year":2016,"finding":"SCP4/CTDSPL2 is a chromatin-associated, Ser5-preferential CTD phosphatase; siRNA knockdown in HeLa cells increases Pol II phosphorylation at Ser5 and Ser7 but not Ser2; SCP4 localizes exclusively to chromatin, particularly transcriptionally silenced regions, and is released from chromatin with cytoplasmic accumulation during hemin-induced erythroid differentiation of K562 cells.","method":"In vitro CTD phosphatase assay, siRNA knockdown with Pol II CTD phospho-specific immunoblotting, cell fractionation, chromatin immunoprecipitation (ChIP), immunofluorescence","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzymatic assay, cellular knockdown with quantitative phospho-readout, fractionation and ChIP, multiple orthogonal methods in single study","pmids":["26920047"],"is_preprint":false},{"year":2016,"finding":"Proteomic screening by immunoprecipitation of inducible CTDSPL2 from nuclear extracts identified several nuclear interacting partners of CTDSPL2.","method":"Inducible expression system, immunoprecipitation, shotgun proteomics (mass spectrometry)","journal":"BMB reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single pulldown-based proteomic screen, no functional validation of individual interactions reported in abstract","pmids":["26674342"],"is_preprint":false},{"year":2017,"finding":"SCP4/CTDSPL2 directly dephosphorylates FoxO1 and FoxO3a, promoting their nuclear retention and transcriptional activation of PEPCK1 and G6PC genes; ectopic SCP4 expression increases hepatic glucose production while SCP4 knockdown inhibits it; SCP4 gene ablation causes hypoglycemia in neonatal mice.","method":"In vitro dephosphorylation assay, Co-immunoprecipitation, ectopic expression/knockdown with glucose production assay, SCP4 knockout mouse model","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro phosphatase assay, Co-IP, gain/loss-of-function in cells, and in vivo knockout phenotype; multiple orthogonal methods, single lab","pmids":["28851713"],"is_preprint":false},{"year":2017,"finding":"Overexpression of CTDSPL2 in chick embryo fibroblasts promotes cell migration and protects cells from apoptosis induced by oxidative stress; truncated viral fusion transcripts of CTDSPL2 promote immortalization in primary cell culture.","method":"Overexpression in primary chick embryo fibroblasts, cell migration assay, oxidative stress apoptosis assay, primary cell immortalization assay","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — gain-of-function with multiple cellular phenotypic readouts, but in avian cells and single lab","pmids":["28915671"],"is_preprint":false},{"year":2018,"finding":"CTDSPL2/SCP4 physically interacts with and directly dephosphorylates Snail, suppressing ubiquitin-dependent proteasomal degradation of Snail and consequently enhancing TGFβ-induced EMT; SCP4 knockdown in MCF10A cells attenuates cell migration.","method":"Co-immunoprecipitation, in vitro dephosphorylation assay, ubiquitination assay, siRNA knockdown with EMT marker analysis and migration assay","journal":"Open biology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — Co-IP plus in vitro phosphatase assay plus ubiquitination assay plus loss-of-function phenotype; multiple orthogonal methods, single lab","pmids":["29618518"],"is_preprint":false},{"year":2021,"finding":"CTDSPL2 is phosphorylated at T86, S104, and S134 by CDK1 during mitosis; CTDSPL2 depletion causes mitotic defects and prolonged mitosis, and reduces proliferation, migration, and invasion in pancreatic cancer cells; a phosphorylation-deficient mutant of CTDSPL2 exerts dominant negative effects; CTDSPL2 regulates p21 and p27 as downstream targets, and inhibition of p21/p27 partially rescues CTDSPL2-deficiency phenotypes.","method":"Phos-tag electrophoresis, CDK1 kinase assay with phosphorylation-site mutagenesis, siRNA/CRISPR depletion with mitotic phenotype analysis, RT2 cell cycle array, xenograft tumor model","journal":"Cancer letters","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro kinase assay with mutagenesis, epistasis (p21/p27 rescue), in vivo xenograft, multiple orthogonal methods in single study","pmids":["34813892"],"is_preprint":false},{"year":2024,"finding":"CTDSPL2 interacts with JAK1 and positively regulates JAK1 expression, thereby activating the PI3K/AKT signaling pathway and promoting NSCLC cell proliferation, migration, and invasion; CTDSPL2 silencing also enhances CD4+ T cell infiltration into tumors.","method":"Co-immunoprecipitation, siRNA knockdown with PI3K/AKT pathway readouts, mouse xenograft model, immune cell infiltration analysis","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — Co-IP showing interaction with JAK1, pathway activation supported by signaling readouts, single lab single study","pmids":["39209829"],"is_preprint":false},{"year":2026,"finding":"CTDSPL2 binds SCYL1 via Co-IP and dephosphorylates SCYL1 at serine 754; CTDSPL2 knockdown in PTX-resistant breast cancer cells increases SCYL1 phosphorylation at S754, and this effect is blocked by S754A mutation of SCYL1; CTDSPL2 knockdown suppresses extracellular vesicle secretion, reduces proliferation, and increases apoptosis and DNA damage in PTX-resistant cells.","method":"Co-immunoprecipitation, phosphorylation-site mutagenesis (S754A), nanoparticle tracking analysis, in vitro cell viability/apoptosis assays, in vivo tumorigenesis assay","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus mutagenesis validating phosphorylation site, multiple cellular phenotypes, single lab","pmids":["42041204"],"is_preprint":false}],"current_model":"CTDSPL2/SCP4 is a nuclear, chromatin-associated, Mg2+-dependent FCP/SCP-family phosphatase that preferentially dephosphorylates Ser5 of the RNA Pol II CTD, and also acts as a multi-substrate signaling phosphatase—directly dephosphorylating Smad1/5/8 (attenuating BMP signaling), FoxO1/3a (promoting hepatic gluconeogenesis), and Snail (stabilizing it to enhance EMT)—while itself being phosphorylated by CDK1 at T86/S104/S134 during mitosis to regulate cell cycle progression through p21 and p27; it also interacts with JAK1 to activate PI3K/AKT signaling and dephosphorylates SCYL1-S754 to modulate paclitaxel resistance."},"narrative":{"mechanistic_narrative":"CTDSPL2 (SCP4) is a nuclear, Mg2+-dependent FCP/SCP-family phosphatase that functions both as an RNA polymerase II CTD phosphatase and as a multi-substrate signaling phosphatase controlling differentiation, metabolism, and cell proliferation [PMID:17487459, PMID:26920047, PMID:28851713]. Its catalytic core, residing C-terminal to an N-terminal region of ~156 residues, dephosphorylates the Pol II CTD in vitro, and in cells the enzyme is chromatin-associated and preferentially removes Ser5 phosphorylation, localizing to transcriptionally silenced regions and redistributing to the cytoplasm during erythroid differentiation [PMID:17487459, PMID:26920047]. Beyond the transcriptional machinery, CTDSPL2 directly dephosphorylates a set of signaling substrates with distinct biological outputs: it dephosphorylates nuclear Smad1/5/8 to attenuate BMP signaling and restrain osteogenic differentiation [PMID:25100727]; it dephosphorylates FoxO1/FoxO3a to promote their nuclear retention and transactivation of the gluconeogenic genes PEPCK1 and G6PC, with knockout mice developing neonatal hypoglycemia [PMID:28851713]; and it dephosphorylates Snail to block its ubiquitin-dependent degradation, thereby enhancing TGFβ-induced EMT and cell migration [PMID:29618518]. CTDSPL2 activity is itself coupled to the cell cycle: CDK1 phosphorylates it at T86/S104/S134 during mitosis, and its loss causes mitotic defects and impaired proliferation, migration, and invasion through the downstream cell-cycle regulators p21 and p27 [PMID:34813892]. In cancer contexts it interacts with JAK1 to activate PI3K/AKT signaling [PMID:39209829] and dephosphorylates SCYL1 at Ser754 to modulate extracellular vesicle secretion and paclitaxel resistance [PMID:42041204].","teleology":[{"year":2007,"claim":"Established that the uncharacterized HSPC129/CTDSPL2 gene product is an enzyme — a Mg2+-dependent phosphatase capable of acting on the RNA Pol II CTD — defining its biochemical class.","evidence":"In vitro phosphatase assay with a recombinant truncated protein lacking the first 156 N-terminal residues","pmids":["17487459"],"confidence":"Medium","gaps":["Activity shown only at non-physiological pH 5.0 with a truncated construct","No cellular substrate or in vivo CTD context established","Role of the N-terminal 156 residues unresolved"]},{"year":2014,"claim":"Identified the first physiological signaling substrate, showing CTDSPL2/SCP4 dephosphorylates Smad1/5/8 to act as a negative regulator of BMP signaling and differentiation.","evidence":"Co-IP, in vitro dephosphorylation, and siRNA knockdown with reporter and osteogenic differentiation assays in C2C12 cells","pmids":["25100727"],"confidence":"High","gaps":["Specific phospho-residues on Smad1/5/8 not mapped","Does not address how substrate selection is achieved versus the CTD"]},{"year":2016,"claim":"Defined the cellular CTD phosphatase function and localization, showing chromatin-restricted SCP4 preferentially removes Pol II Ser5 phosphorylation and is regulated by chromatin release during differentiation.","evidence":"In vitro CTD phosphatase assay, siRNA knockdown with phospho-specific immunoblotting, fractionation, ChIP, and immunofluorescence in HeLa/K562 cells; plus a proteomic IP screen for nuclear partners","pmids":["26920047","26674342"],"confidence":"High","gaps":["Proteomic interactors not functionally validated","Mechanism of chromatin tethering and release unknown","Link between CTD dephosphorylation and silenced-region targeting not mechanistically resolved"]},{"year":2017,"claim":"Extended CTDSPL2 into metabolic control, demonstrating it dephosphorylates FoxO1/3a to drive hepatic gluconeogenesis, with an in vivo knockout phenotype confirming physiological relevance.","evidence":"In vitro dephosphorylation, Co-IP, gain/loss-of-function glucose production assays, and SCP4 knockout mice; separate gain-of-function work in avian fibroblasts linked CTDSPL2 to migration and apoptosis protection","pmids":["28851713","28915671"],"confidence":"High","gaps":["Tissue-specific contribution of the knockout not dissected","Avian fibroblast phenotypes use a non-mammalian system and overexpression"]},{"year":2018,"claim":"Showed CTDSPL2 promotes EMT by dephosphorylating Snail to block its proteasomal degradation, defining a phosphatase-stabilization mechanism for a transcription factor.","evidence":"Co-IP, in vitro dephosphorylation, ubiquitination assay, and siRNA knockdown with EMT marker and migration analysis in MCF10A cells","pmids":["29618518"],"confidence":"High","gaps":["Snail phospho-site(s) targeted not specified","Relationship to the BMP/FoxO substrate repertoire and substrate specificity unresolved"]},{"year":2021,"claim":"Placed CTDSPL2 under cell-cycle control, showing CDK1 phosphorylates it during mitosis and that this regulates proliferation and tumor growth via p21/p27.","evidence":"Phos-tag electrophoresis, CDK1 kinase assay with site mutagenesis, siRNA/CRISPR depletion with mitotic phenotyping, cell-cycle array, and xenograft model in pancreatic cancer cells","pmids":["34813892"],"confidence":"High","gaps":["How CDK1 phosphorylation alters CTDSPL2 catalytic activity or localization not defined","Direct phosphatase substrates linking CTDSPL2 to p21/p27 not identified"]},{"year":2024,"claim":"Linked CTDSPL2 to receptor-kinase signaling in lung cancer, showing it interacts with JAK1 to activate PI3K/AKT and influence anti-tumor immunity.","evidence":"Co-IP, siRNA knockdown with PI3K/AKT readouts, xenograft model, and immune infiltration analysis in NSCLC","pmids":["39209829"],"confidence":"Medium","gaps":["Whether JAK1 is a dephosphorylation substrate or a non-catalytic partner unresolved","Mechanism of CTDSPL2-driven CD4+ T cell exclusion not established"]},{"year":2026,"claim":"Identified SCYL1-Ser754 as a CTDSPL2 substrate relevant to chemoresistance, connecting the phosphatase to extracellular vesicle secretion and paclitaxel survival.","evidence":"Co-IP, S754A phospho-site mutagenesis, nanoparticle tracking analysis, viability/apoptosis assays, and in vivo tumorigenesis in PTX-resistant breast cancer cells","pmids":["42041204"],"confidence":"Medium","gaps":["Causal chain from SCYL1-S754 dephosphorylation to vesicle secretion not mechanistically traced","Single lab, single study"]},{"year":null,"claim":"How CTDSPL2 achieves its broad substrate repertoire — selecting among the Pol II CTD, Smad, FoxO, Snail, and SCYL1 in a context-dependent manner — and how its chromatin association and mitotic phosphorylation gate substrate choice remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural basis for substrate recognition reported","No unified model reconciling transcriptional CTD activity with cytoplasmic/signaling substrates","Substrate-targeting subunits or scaffolds not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,4,6,9]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1,3]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,4,6,8]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,2]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[7]}],"complexes":[],"partners":["SMAD1","FOXO1","FOXO3","SNAI1","CDK1","JAK1","SCYL1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q05D32","full_name":"CTD small phosphatase-like protein 2","aliases":["Small C-terminal domain phosphatase 4","SCP4","Small CTD phosphatase 4"],"length_aa":466,"mass_kda":53.0,"function":"Serine/threonine phosphatase that promotes gluconeogenesis by dephosphorylating FOXO1 and FOXO3A, promoting their nuclear retention and enhancing their transcriptional activity on PCK1 and G6PC1, key enzymes in hepatic gluconeogenesis (PubMed:28851713). Essential for proper embryonic skeletal development by regulating chondrocyte survival through dephosphorylation of FOXO3 (By similarity). By maintaining FOXO3 in its active, dephosphorylated form, inhibits excessive apoptosis of chondrocytes, which is essential for normal endochondral ossification and cartilage formation (By similarity)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q05D32/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CTDSPL2","classification":"Not Classified","n_dependent_lines":142,"n_total_lines":1208,"dependency_fraction":0.11754966887417219},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HIST2H2BE","stoichiometry":0.2},{"gene":"MYO1E","stoichiometry":0.2},{"gene":"NUMA1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CTDSPL2","total_profiled":1310},"omim":[{"mim_id":"618739","title":"CTD SMALL PHOSPHATASE-LIKE PROTEIN 2; CTDSPL2","url":"https://www.omim.org/entry/618739"},{"mim_id":"604238","title":"SNAIL FAMILY TRANSCRIPTIONAL REPRESSOR 1; SNAI1","url":"https://www.omim.org/entry/604238"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CTDSPL2"},"hgnc":{"alias_symbol":["HSPC129","FLJ10523"],"prev_symbol":[]},"alphafold":{"accession":"Q05D32","domains":[{"cath_id":"3.40.50.1000","chopping":"288-299_329-461","consensus_level":"high","plddt":97.3139,"start":288,"end":461}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05D32","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q05D32-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q05D32-F1-predicted_aligned_error_v6.png","plddt_mean":65.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CTDSPL2","jax_strain_url":"https://www.jax.org/strain/search?query=CTDSPL2"},"sequence":{"accession":"Q05D32","fasta_url":"https://rest.uniprot.org/uniprotkb/Q05D32.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q05D32/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05D32"}},"corpus_meta":[{"pmid":"25100727","id":"PMC_25100727","title":"C-terminal domain (CTD) small phosphatase-like 2 modulates the canonical bone morphogenetic protein (BMP) signaling and mesenchymal differentiation via Smad dephosphorylation.","date":"2014","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25100727","citation_count":37,"is_preprint":false},{"pmid":"28851713","id":"PMC_28851713","title":"SCP4 Promotes Gluconeogenesis Through FoxO1/3a Dephosphorylation.","date":"2017","source":"Diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/28851713","citation_count":24,"is_preprint":false},{"pmid":"28915671","id":"PMC_28915671","title":"Integration of ALV into CTDSPL and CTDSPL2 genes in B-cell lymphomas promotes cell immortalization, migration and survival.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/28915671","citation_count":18,"is_preprint":false},{"pmid":"34813892","id":"PMC_34813892","title":"The phosphatase CTDSPL2 is phosphorylated in mitosis and a target for restraining tumor growth and motility in pancreatic cancer.","date":"2021","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/34813892","citation_count":17,"is_preprint":false},{"pmid":"29618518","id":"PMC_29618518","title":"C-terminal domain small phosphatase-like 2 promotes epithelial-to-mesenchymal transition via Snail dephosphorylation and stabilization.","date":"2018","source":"Open biology","url":"https://pubmed.ncbi.nlm.nih.gov/29618518","citation_count":13,"is_preprint":false},{"pmid":"17487459","id":"PMC_17487459","title":"Expression and characterization of HSPC129, a RNA polymerase II C-terminal domain phosphatase.","date":"2007","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17487459","citation_count":12,"is_preprint":false},{"pmid":"24755554","id":"PMC_24755554","title":"The diverse roles of RNA polymerase II C-terminal domain phosphatase SCP1.","date":"2014","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/24755554","citation_count":11,"is_preprint":false},{"pmid":"26920047","id":"PMC_26920047","title":"Human SCP4 is a chromatin-associated CTD phosphatase and exhibits the dynamic translocation during erythroid differentiation.","date":"2016","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26920047","citation_count":11,"is_preprint":false},{"pmid":"26674342","id":"PMC_26674342","title":"A systematic study of nuclear interactome of C-terminal domain small phosphatase-like 2 using inducible expression system and shotgun proteomics.","date":"2016","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/26674342","citation_count":7,"is_preprint":false},{"pmid":"37309586","id":"PMC_37309586","title":"Hypermethylation of CTDSPL2 prior to necrotizing enterocolitis onset.","date":"2023","source":"Epigenomics","url":"https://pubmed.ncbi.nlm.nih.gov/37309586","citation_count":4,"is_preprint":false},{"pmid":"40352265","id":"PMC_40352265","title":"The phosphatase CTDSPL2 promotes proliferation, invasion, metastasis and regorafenib resistance in osteosarcoma.","date":"2025","source":"Journal of bone oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40352265","citation_count":3,"is_preprint":false},{"pmid":"40094036","id":"PMC_40094036","title":"A Transcriptomic Signature of Depressive Symptoms in Late Life.","date":"2025","source":"Biological psychiatry global open science","url":"https://pubmed.ncbi.nlm.nih.gov/40094036","citation_count":2,"is_preprint":false},{"pmid":"39209829","id":"PMC_39209829","title":"CTDSPL2 promotes the progression of non-small lung cancer through PI3K/AKT signaling via JAK1.","date":"2024","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/39209829","citation_count":1,"is_preprint":false},{"pmid":"39693780","id":"PMC_39693780","title":"Association of exposure to second-hand smoke during childhood with blood DNA methylation.","date":"2024","source":"Environment international","url":"https://pubmed.ncbi.nlm.nih.gov/39693780","citation_count":1,"is_preprint":false},{"pmid":"42208850","id":"PMC_42208850","title":"CTDSPL2: A Comprehensive Review from Molecular Structure to Clinical Applications.","date":"2026","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/42208850","citation_count":0,"is_preprint":false},{"pmid":"42041204","id":"PMC_42041204","title":"CTDSPL2 facilitates resistance to paclitaxel in breast cancer cells by suppressing SCYL1 phosphorylation.","date":"2026","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/42041204","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9117,"output_tokens":2632,"usd":0.033416,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9905,"output_tokens":3525,"usd":0.068825,"stage2_stop_reason":"end_turn"},"total_usd":0.102241,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"HSPC129 (CTDSPL2) encodes a Mg2+-dependent CTD phosphatase; a truncated form lacking the first 156 N-terminal amino acids exhibits Mg2+-dependent phosphatase activity at pH 5.0 and dephosphorylates the RNA polymerase II CTD in vitro.\",\n      \"method\": \"In vitro phosphatase activity assay with recombinant truncated protein\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay establishing CTD phosphatase activity, single lab, single method\",\n      \"pmids\": [\"17487459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CTDSPL2/SCP4 physically interacts with and specifically dephosphorylates Smad1/5/8 in the nucleus, thereby attenuating BMP-induced transcriptional responses; knockdown in C2C12 cells increases BMP target gene expression and promotes osteogenic differentiation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro dephosphorylation assay, siRNA knockdown with reporter and differentiation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — reciprocal Co-IP plus in vitro phosphatase assay plus loss-of-function phenotype, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"25100727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"SCP4/CTDSPL2 is a chromatin-associated, Ser5-preferential CTD phosphatase; siRNA knockdown in HeLa cells increases Pol II phosphorylation at Ser5 and Ser7 but not Ser2; SCP4 localizes exclusively to chromatin, particularly transcriptionally silenced regions, and is released from chromatin with cytoplasmic accumulation during hemin-induced erythroid differentiation of K562 cells.\",\n      \"method\": \"In vitro CTD phosphatase assay, siRNA knockdown with Pol II CTD phospho-specific immunoblotting, cell fractionation, chromatin immunoprecipitation (ChIP), immunofluorescence\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzymatic assay, cellular knockdown with quantitative phospho-readout, fractionation and ChIP, multiple orthogonal methods in single study\",\n      \"pmids\": [\"26920047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Proteomic screening by immunoprecipitation of inducible CTDSPL2 from nuclear extracts identified several nuclear interacting partners of CTDSPL2.\",\n      \"method\": \"Inducible expression system, immunoprecipitation, shotgun proteomics (mass spectrometry)\",\n      \"journal\": \"BMB reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single pulldown-based proteomic screen, no functional validation of individual interactions reported in abstract\",\n      \"pmids\": [\"26674342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SCP4/CTDSPL2 directly dephosphorylates FoxO1 and FoxO3a, promoting their nuclear retention and transcriptional activation of PEPCK1 and G6PC genes; ectopic SCP4 expression increases hepatic glucose production while SCP4 knockdown inhibits it; SCP4 gene ablation causes hypoglycemia in neonatal mice.\",\n      \"method\": \"In vitro dephosphorylation assay, Co-immunoprecipitation, ectopic expression/knockdown with glucose production assay, SCP4 knockout mouse model\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro phosphatase assay, Co-IP, gain/loss-of-function in cells, and in vivo knockout phenotype; multiple orthogonal methods, single lab\",\n      \"pmids\": [\"28851713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Overexpression of CTDSPL2 in chick embryo fibroblasts promotes cell migration and protects cells from apoptosis induced by oxidative stress; truncated viral fusion transcripts of CTDSPL2 promote immortalization in primary cell culture.\",\n      \"method\": \"Overexpression in primary chick embryo fibroblasts, cell migration assay, oxidative stress apoptosis assay, primary cell immortalization assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — gain-of-function with multiple cellular phenotypic readouts, but in avian cells and single lab\",\n      \"pmids\": [\"28915671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CTDSPL2/SCP4 physically interacts with and directly dephosphorylates Snail, suppressing ubiquitin-dependent proteasomal degradation of Snail and consequently enhancing TGFβ-induced EMT; SCP4 knockdown in MCF10A cells attenuates cell migration.\",\n      \"method\": \"Co-immunoprecipitation, in vitro dephosphorylation assay, ubiquitination assay, siRNA knockdown with EMT marker analysis and migration assay\",\n      \"journal\": \"Open biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — Co-IP plus in vitro phosphatase assay plus ubiquitination assay plus loss-of-function phenotype; multiple orthogonal methods, single lab\",\n      \"pmids\": [\"29618518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CTDSPL2 is phosphorylated at T86, S104, and S134 by CDK1 during mitosis; CTDSPL2 depletion causes mitotic defects and prolonged mitosis, and reduces proliferation, migration, and invasion in pancreatic cancer cells; a phosphorylation-deficient mutant of CTDSPL2 exerts dominant negative effects; CTDSPL2 regulates p21 and p27 as downstream targets, and inhibition of p21/p27 partially rescues CTDSPL2-deficiency phenotypes.\",\n      \"method\": \"Phos-tag electrophoresis, CDK1 kinase assay with phosphorylation-site mutagenesis, siRNA/CRISPR depletion with mitotic phenotype analysis, RT2 cell cycle array, xenograft tumor model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro kinase assay with mutagenesis, epistasis (p21/p27 rescue), in vivo xenograft, multiple orthogonal methods in single study\",\n      \"pmids\": [\"34813892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CTDSPL2 interacts with JAK1 and positively regulates JAK1 expression, thereby activating the PI3K/AKT signaling pathway and promoting NSCLC cell proliferation, migration, and invasion; CTDSPL2 silencing also enhances CD4+ T cell infiltration into tumors.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown with PI3K/AKT pathway readouts, mouse xenograft model, immune cell infiltration analysis\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — Co-IP showing interaction with JAK1, pathway activation supported by signaling readouts, single lab single study\",\n      \"pmids\": [\"39209829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CTDSPL2 binds SCYL1 via Co-IP and dephosphorylates SCYL1 at serine 754; CTDSPL2 knockdown in PTX-resistant breast cancer cells increases SCYL1 phosphorylation at S754, and this effect is blocked by S754A mutation of SCYL1; CTDSPL2 knockdown suppresses extracellular vesicle secretion, reduces proliferation, and increases apoptosis and DNA damage in PTX-resistant cells.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation-site mutagenesis (S754A), nanoparticle tracking analysis, in vitro cell viability/apoptosis assays, in vivo tumorigenesis assay\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus mutagenesis validating phosphorylation site, multiple cellular phenotypes, single lab\",\n      \"pmids\": [\"42041204\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CTDSPL2/SCP4 is a nuclear, chromatin-associated, Mg2+-dependent FCP/SCP-family phosphatase that preferentially dephosphorylates Ser5 of the RNA Pol II CTD, and also acts as a multi-substrate signaling phosphatase—directly dephosphorylating Smad1/5/8 (attenuating BMP signaling), FoxO1/3a (promoting hepatic gluconeogenesis), and Snail (stabilizing it to enhance EMT)—while itself being phosphorylated by CDK1 at T86/S104/S134 during mitosis to regulate cell cycle progression through p21 and p27; it also interacts with JAK1 to activate PI3K/AKT signaling and dephosphorylates SCYL1-S754 to modulate paclitaxel resistance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CTDSPL2 (SCP4) is a nuclear, Mg2+-dependent FCP/SCP-family phosphatase that functions both as an RNA polymerase II CTD phosphatase and as a multi-substrate signaling phosphatase controlling differentiation, metabolism, and cell proliferation [#0, #2, #4]. Its catalytic core, residing C-terminal to an N-terminal region of ~156 residues, dephosphorylates the Pol II CTD in vitro, and in cells the enzyme is chromatin-associated and preferentially removes Ser5 phosphorylation, localizing to transcriptionally silenced regions and redistributing to the cytoplasm during erythroid differentiation [#0, #2]. Beyond the transcriptional machinery, CTDSPL2 directly dephosphorylates a set of signaling substrates with distinct biological outputs: it dephosphorylates nuclear Smad1/5/8 to attenuate BMP signaling and restrain osteogenic differentiation [#1]; it dephosphorylates FoxO1/FoxO3a to promote their nuclear retention and transactivation of the gluconeogenic genes PEPCK1 and G6PC, with knockout mice developing neonatal hypoglycemia [#4]; and it dephosphorylates Snail to block its ubiquitin-dependent degradation, thereby enhancing TGFβ-induced EMT and cell migration [#6]. CTDSPL2 activity is itself coupled to the cell cycle: CDK1 phosphorylates it at T86/S104/S134 during mitosis, and its loss causes mitotic defects and impaired proliferation, migration, and invasion through the downstream cell-cycle regulators p21 and p27 [#7]. In cancer contexts it interacts with JAK1 to activate PI3K/AKT signaling [#8] and dephosphorylates SCYL1 at Ser754 to modulate extracellular vesicle secretion and paclitaxel resistance [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that the uncharacterized HSPC129/CTDSPL2 gene product is an enzyme — a Mg2+-dependent phosphatase capable of acting on the RNA Pol II CTD — defining its biochemical class.\",\n      \"evidence\": \"In vitro phosphatase assay with a recombinant truncated protein lacking the first 156 N-terminal residues\",\n      \"pmids\": [\"17487459\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Activity shown only at non-physiological pH 5.0 with a truncated construct\", \"No cellular substrate or in vivo CTD context established\", \"Role of the N-terminal 156 residues unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified the first physiological signaling substrate, showing CTDSPL2/SCP4 dephosphorylates Smad1/5/8 to act as a negative regulator of BMP signaling and differentiation.\",\n      \"evidence\": \"Co-IP, in vitro dephosphorylation, and siRNA knockdown with reporter and osteogenic differentiation assays in C2C12 cells\",\n      \"pmids\": [\"25100727\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Specific phospho-residues on Smad1/5/8 not mapped\", \"Does not address how substrate selection is achieved versus the CTD\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the cellular CTD phosphatase function and localization, showing chromatin-restricted SCP4 preferentially removes Pol II Ser5 phosphorylation and is regulated by chromatin release during differentiation.\",\n      \"evidence\": \"In vitro CTD phosphatase assay, siRNA knockdown with phospho-specific immunoblotting, fractionation, ChIP, and immunofluorescence in HeLa/K562 cells; plus a proteomic IP screen for nuclear partners\",\n      \"pmids\": [\"26920047\", \"26674342\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Proteomic interactors not functionally validated\", \"Mechanism of chromatin tethering and release unknown\", \"Link between CTD dephosphorylation and silenced-region targeting not mechanistically resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended CTDSPL2 into metabolic control, demonstrating it dephosphorylates FoxO1/3a to drive hepatic gluconeogenesis, with an in vivo knockout phenotype confirming physiological relevance.\",\n      \"evidence\": \"In vitro dephosphorylation, Co-IP, gain/loss-of-function glucose production assays, and SCP4 knockout mice; separate gain-of-function work in avian fibroblasts linked CTDSPL2 to migration and apoptosis protection\",\n      \"pmids\": [\"28851713\", \"28915671\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Tissue-specific contribution of the knockout not dissected\", \"Avian fibroblast phenotypes use a non-mammalian system and overexpression\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed CTDSPL2 promotes EMT by dephosphorylating Snail to block its proteasomal degradation, defining a phosphatase-stabilization mechanism for a transcription factor.\",\n      \"evidence\": \"Co-IP, in vitro dephosphorylation, ubiquitination assay, and siRNA knockdown with EMT marker and migration analysis in MCF10A cells\",\n      \"pmids\": [\"29618518\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Snail phospho-site(s) targeted not specified\", \"Relationship to the BMP/FoxO substrate repertoire and substrate specificity unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Placed CTDSPL2 under cell-cycle control, showing CDK1 phosphorylates it during mitosis and that this regulates proliferation and tumor growth via p21/p27.\",\n      \"evidence\": \"Phos-tag electrophoresis, CDK1 kinase assay with site mutagenesis, siRNA/CRISPR depletion with mitotic phenotyping, cell-cycle array, and xenograft model in pancreatic cancer cells\",\n      \"pmids\": [\"34813892\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"How CDK1 phosphorylation alters CTDSPL2 catalytic activity or localization not defined\", \"Direct phosphatase substrates linking CTDSPL2 to p21/p27 not identified\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked CTDSPL2 to receptor-kinase signaling in lung cancer, showing it interacts with JAK1 to activate PI3K/AKT and influence anti-tumor immunity.\",\n      \"evidence\": \"Co-IP, siRNA knockdown with PI3K/AKT readouts, xenograft model, and immune infiltration analysis in NSCLC\",\n      \"pmids\": [\"39209829\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Whether JAK1 is a dephosphorylation substrate or a non-catalytic partner unresolved\", \"Mechanism of CTDSPL2-driven CD4+ T cell exclusion not established\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identified SCYL1-Ser754 as a CTDSPL2 substrate relevant to chemoresistance, connecting the phosphatase to extracellular vesicle secretion and paclitaxel survival.\",\n      \"evidence\": \"Co-IP, S754A phospho-site mutagenesis, nanoparticle tracking analysis, viability/apoptosis assays, and in vivo tumorigenesis in PTX-resistant breast cancer cells\",\n      \"pmids\": [\"42041204\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Causal chain from SCYL1-S754 dephosphorylation to vesicle secretion not mechanistically traced\", \"Single lab, single study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CTDSPL2 achieves its broad substrate repertoire — selecting among the Pol II CTD, Smad, FoxO, Snail, and SCYL1 in a context-dependent manner — and how its chromatin association and mitotic phosphorylation gate substrate choice remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No structural basis for substrate recognition reported\", \"No unified model reconciling transcriptional CTD activity with cytoplasmic/signaling substrates\", \"Substrate-targeting subunits or scaffolds not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 4, 6, 9]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 4, 6, 8]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SMAD1\", \"FOXO1\", \"FOXO3\", \"SNAI1\", \"CDK1\", \"JAK1\", \"SCYL1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}