Affinage

CTPS2

CTP synthase 2 · UniProt Q9NRF8

Length
586 aa
Mass
65.7 kDa
Annotated
2026-06-09
31 papers in source corpus 12 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/7 claims corpus-supported (86%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CTPS2 is a CTP synthase that catalyzes the de novo, glutamine-dependent conversion of UTP to CTP, the rate-limiting step in pyrimidine nucleotide biosynthesis, and as such supports cell proliferation (PMID:16179339, PMID:37348953). Its activity is tuned by intracellular substrate and product levels: the Km for UTP and IC50 for CTP product inhibition sit near physiological concentrations, so UTP and CTP pools directly set enzyme output (PMID:20739275), and cryo-EM shows that CTPS2 assembles into filaments whose subunits switch cooperatively between active and inactive conformations, coupling oligomeric state to control of ammonia channeling between active sites (PMID:31873303). CTP feedback inhibition is structurally explained by CTP binding two inhibitory sites that clash with substrate; CTPS2 is more sensitive to this feedback than the paralog CTPS1, and a single amino acid distinguishes their susceptibility to CTPS1-selective small molecules (PMID:34583994). Activity is further restrained by casein kinase 1 phosphorylation at Ser568, which preferentially dampens glutamine-dependent (glutaminase) activity (PMID:20739275). CTPS2 directly heterotetramerizes with CTPS1 independently of filament formation, and in this complex it lowers CTPS1 activity and heightens its CTP feedback sensitivity, positioning CTPS2 as a modulator of overall cellular CTP synthesis (PMID:40957650). Functionally CTPS2 makes a modest contribution to proliferation when CTPS1 is present but becomes essential in its absence, and it is dispensable for embryonic development whereas CTPS1 is not (PMID:37348953, PMID:38438357). Beyond CTP synthesis, CTPS2 supports the DNA damage response, with its loss elevating DNA damage and impairing repair in a manner rescued by CTP or glutamine (PMID:36635772).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2005 Medium

    Established that human CTPS2 encodes a catalytically active CTP synthase rather than an inactive paralog, by showing it produces CTP in vivo.

    Evidence Genetic complementation of S. cerevisiae ura7Δura8Δ lethality plus CTP synthase activity assays

    PMID:16179339

    Open questions at the time
    • Did not resolve regulation or how CTPS2 differs functionally from CTPS1
    • Heterologous yeast system, not native human cells
  2. 2010 High

    Defined how CTPS2 activity is set, showing both intracellular nucleotide pools and casein kinase 1 phosphorylation at Ser568 govern enzyme output.

    Evidence Kinetic enzyme assays on purified hCTPS2 plus 32P labeling, phosphopeptide mapping, S568A mutagenesis, and in vitro CK1 kinase assay

    PMID:20739275

    Open questions at the time
    • Physiological trigger for CK1 phosphorylation in cells not identified
    • How Ser568 phosphorylation mechanistically targets the glutaminase domain not structurally resolved
  3. 2011 Medium

    Linked CTPS2-driven UTP/CTP supply to chemosensitivity, showing CTPS2 levels determine response to pyrimidine antimetabolites.

    Evidence siRNA knockdown of CTPS2 in colorectal cancer lines with cell-cycle, apoptosis, and uridine-rescue assays

    PMID:21378502

    Open questions at the time
    • Does not distinguish CTPS2-specific from total CTP-pool effects
    • Single cancer-type context
  4. 2019 High

    Explained how CTPS2 achieves regulation beyond tetramer-level cooperativity by resolving filament-coupled conformational switching and its link to ammonia channeling.

    Evidence Cryo-EM of CTPS2 filaments captured in active and inactive states

    PMID:31873303

    Open questions at the time
    • Functional consequence of filament formation in living cells not established by structure alone
    • Does not address heterotypic CTPS1/CTPS2 assemblies
  5. 2020 Medium

    Identified cellular machinery for CTPS filament assembly, placing cytoophidia formation under SNAP29 control along the keratin network and linking filaments to activity suppression.

    Evidence APEX2 proximity labeling, SNAP29 knockdown, super-resolution imaging, enzymatic assays under glutamine deprivation

    PMID:32184263

    Open questions at the time
    • CTPS1 versus CTPS2 specific contributions to the labeled filaments not separated
    • Mechanism by which SNAP29 promotes assembly unknown
  6. 2021 High

    Provided the structural basis of CTP feedback inhibition and the determinant of CTPS1-versus-CTPS2 inhibitor selectivity, explaining why CTPS2 is more feedback-sensitive.

    Evidence Cryo-EM of CTPS1/CTPS2 filaments with CTP and inhibitors plus mutagenesis of the selectivity residue

    PMID:34583994

    Open questions at the time
    • Does not address CTPS2 selective inhibition
    • In-cell relevance of the differential feedback sensitivity not tested here
  7. 2021 Medium

    Demonstrated functional redundancy between CTPS1 and CTPS2 in a proliferating cell context, with double loss producing DNA damage and proliferation defects rescued by cytidine.

    Evidence CRISPR single/double knockout in EBV-transformed lymphoblastoid cells with proliferation, DNA damage, and cytidine-rescue assays

    PMID:34281398

    Open questions at the time
    • Quantitative contribution of CTPS2 versus CTPS1 not separated
    • Mechanism linking nucleotide depletion to DNA damage not defined
  8. 2023 High

    Quantified the proliferative hierarchy of the two isoforms, showing CTPS2 contributes modestly when CTPS1 is present but becomes essential in its absence.

    Evidence Genetic inactivation/complementation and enzymatic activity assays with 3-deaza-uridine inhibition

    PMID:37348953

    Open questions at the time
    • Molecular reason for lower intrinsic CTPS2 activity not fully resolved
    • Tissue-context dependence of redundancy not mapped
  9. 2023 Medium

    Connected CTPS2 to genome maintenance via a physical interaction with BRCA1, with CTPS2 loss impairing DNA repair in leukemia cells.

    Evidence Co-immunoprecipitation, siRNA knockdown, RNA-seq, DNA damage assays, rescue with CTP or glutamine

    PMID:36635772

    Open questions at the time
    • Single Co-IP without reciprocal validation
    • Cannot separate a direct BRCA1-complex role from indirect effects of CTP depletion
  10. 2024 High

    Resolved the in vivo non-redundancy, showing Ctps2 is dispensable for embryonic development while both isoforms are required for TCR-driven T cell proliferation.

    Evidence Conditional and inducible Ctps1/Ctps2 knockout mice with developmental and T cell proliferation analyses

    PMID:38438357

    Open questions at the time
    • Tissue-specific roles of CTPS2 outside the immune system not defined
    • Why CTPS2 cannot substitute for CTPS1 during development not mechanistically explained
  11. 2025 Medium

    Reframed CTPS2 as a direct modulator of CTPS1, showing heterotetramer formation lowers CTPS1 activity and increases its CTP feedback sensitivity, independent of filament assembly.

    Evidence Co-localization imaging, Co-IP, enzymatic assays on CTPS1/CTPS2 complexes, H355A mutagenesis, and CTP feedback assays

    PMID:40957650

    Open questions at the time
    • Single-study, single-lab characterization of the heterocomplex
    • In vivo stoichiometry and regulation of CTPS1:CTPS2 complexes unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How CTPS2 abundance, phosphorylation, and heterocomplex formation are coordinated to set CTP supply across different tissues and proliferative states remains unresolved.
  • No integrated model linking CK1 phosphorylation, filament state, and CTPS1 heterotetramer formation in cells
  • CTPS2-selective regulatory inputs versus shared CTP-pool effects not disentangled

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 3 GO:0016874 ligase activity 2 GO:0098772 molecular function regulator activity 1 GO:0140096 catalytic activity, acting on a protein 1
Localization
GO:0005829 cytosol 2 GO:0005856 cytoskeleton 1
Pathway
R-HSA-1430728 Metabolism 2 R-HSA-73894 DNA Repair 2
Partners
BRCA1CTPS1SLC38A6SNAP29
Complex memberships
CTPS cytoophidia (filaments)CTPS1/CTPS2 heterotetramer

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2019 Cryo-EM structures reveal that human CTPS2 filaments dynamically switch between active and inactive conformational states in response to changes in substrate and product levels. Linking the conformational state of many CTPS2 subunits in a filament results in highly cooperative regulation, greatly exceeding the limits of cooperativity for the CTPS2 tetramer alone. The structures reveal a link between conformation and control of ammonia channeling between the enzyme's active sites. Cryo-EM structural determination of CTPS2 filaments in active and inactive states Nature structural & molecular biology High 31873303
2010 Human CTPS2 is phosphorylated at Ser568 by casein kinase 1, both in vitro and in vivo, and this phosphorylation inhibits CTPS2 enzymatic activity; the S568A mutation significantly increased hCTPS2 activity. The phosphorylation effect was greater on glutamine-dependent than ammonia-dependent activity, suggesting that phosphorylation at Ser568 influences the glutaminase domain. Metabolic 32P labeling, phosphoamino acid and phosphopeptide mapping, site-directed mutagenesis (S568A), in vitro kinase assay with casein kinase 1 The Journal of biological chemistry High 20739275
2010 Kinetic analysis showed that hCTPS2 is maximally active at physiological concentrations of ATP, GTP, and glutamine, while the Km for UTP and IC50 for CTP product inhibition are close to their physiological concentrations, indicating that intracellular UTP and CTP concentrations precisely regulate hCTPS2 activity. Kinetic enzyme assays with purified hCTPS1 and hCTPS2 The Journal of biological chemistry Medium 20739275
2005 Human CTPS1 and CTPS2 genes are functionally expressed in S. cerevisiae ura7Δura8Δ double mutant, complementing the lethal phenotype lacking CTP synthase activity. CTPS2 was shown to encode an active CTP synthase enzyme able to produce CTP in vivo. Genetic complementation in S. cerevisiae, immunoblot analysis, CTP synthase activity assay, in vivo CTP synthesis measurement The Journal of biological chemistry Medium 16179339
2021 Cryo-EM structures reveal that CTP regulates both CTPS1 and CTPS2 isoforms by binding in two inhibitory sites that clash with substrates. CTPS1 is less sensitive to CTP feedback inhibition than CTPS2, consistent with its role in increasing CTP levels during proliferation. Small-molecule CTPS1-selective inhibitors mimic CTP binding in one inhibitory site, where a single amino acid substitution explains selectivity for CTPS1 over CTPS2. Cryo-EM structures of CTPS1 and CTPS2 filaments with inhibitors and CTP, site-directed mutagenesis identifying the amino acid conferring selectivity Proceedings of the National Academy of Sciences of the United States of America High 34583994
2023 CTPS2 contributes to cell proliferation, but its contribution is modest when CTPS1 is expressed. However, CTPS2 becomes essential for proliferation in the absence of CTPS1. CTPS1 has higher intrinsic enzymatic activity than CTPS2 and is more resistant to inhibition by 3-deaza-uridine. CTPS1 and/or CTPS2 genetic inactivation, complementation experiments, enzymatic activity assays, 3-deaza-uridine inhibition assay Life science alliance High 37348953
2021 In EBV-transformed lymphoblastoid cell lines (LCLs), double CTPS1/2 knockout caused stronger DNA damage and proliferation defects than CTPS1 knockout alone, indicating partially redundant roles of CTPS1 and CTPS2 in EBV-transformed B cells. Cytidine rescued CTPS1/2 deficiency phenotypes. CRISPR knockout of CTPS1 and/or CTPS2, proliferation assays, DNA damage assays, cytidine rescue experiments mBio Medium 34281398
2024 Conditional deletion of Ctps2 (but not Ctps1) is NOT embryonic lethal in mice, while deletion of Ctps1 is embryonic lethal. Both CTPS1 and CTPS2 are required for T cell proliferation following TCR stimulation. Conditional and inducible Ctps1 and Ctps2 knockout mice, embryonic development analysis, T cell proliferation assays Nature communications High 38438357
2011 Reduction of CTPS2 expression by siRNA increased resistance of colorectal cancer cell lines to 5-FU and FUDR, significantly reducing S-phase accumulation and apoptosis following 5-FU treatment. Exposure to uridine (a precursor to CTPS2 substrate UTP) also increased 5-FU resistance. siRNA knockdown of CTPS2 in DLD1 and LS174T cell lines, cell cycle analysis, apoptosis assay, uridine supplementation Cancer biology & therapy Medium 21378502
2023 CTPS2 mediates DNA damage response by physically interacting with BRCA1 protein in chronic lymphocytic leukemia cells, as demonstrated by co-immunoprecipitation. Silencing CTPS2 elevated DNA damage and decreased DNA repair, and these effects were reversed by CTP or glutamine addition. Co-immunoprecipitation (CoIP), siRNA knockdown, RNA-seq, DNA damage assays, rescue with CTP or glutamine Experimental hematology & oncology Medium 36635772
2025 CTPS1 and CTPS2 directly interact with each other independent of polymerization and cytoophidia formation, forming heterotetramers. When CTPS1 is associated with CTPS2, CTPS1 enzymatic activity is decreased and becomes more sensitive to CTP product negative feedback inhibition, demonstrating that CTPS2 modulates CTPS1 activity. CTPS2-containing filaments (cytoophidia) are dependent on CTPS1 expression, and both proteins co-localize in cytoophidia when co-expressed. CTPS1H355A and CTPS2H355A mutants unable to form cytoophidia can sustain normal cell proliferation. Co-localization imaging, co-immunoprecipitation, enzymatic activity assays with CTPS1/CTPS2 complexes, site-directed mutagenesis (H355A), CTP feedback inhibition assays Life science alliance Medium 40957650
2021 CTPS2 was identified as a potential interacting partner of the glutamine transporter SNAT6 in neurons, based on proximity ligation assay and co-localization analysis, suggesting CTPS2 participates in a complex near the pre-synaptic terminal of excitatory neurons. Proximity ligation assay (PLA), immunolabeling with co-localization analysis International journal of molecular sciences Low 33503881
2020 CTPS1 and CTPS2 form filamentous structures (cytoophidia) under glutamine deprivation. Using CTPS-APEX2-mediated in vivo proximity labeling, SNAP29 was identified as a regulator of spatiotemporal CTPS filament assembly along the cytokeratin (keratin 8) network. Knockdown of SNAP29 interfered with filament assembly and relieved filament-induced suppression of CTPS enzymatic activity. APEX2 proximity labeling, SNAP29 knockdown, super-resolution imaging, enzymatic activity assay Journal of cell science Medium 32184263

Source papers

Stage 0 corpus · 31 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 CTP synthase 1 deficiency in humans reveals its central role in lymphocyte proliferation. Nature 178 24870241
2008 CTP synthetase and its role in phospholipid synthesis in the yeast Saccharomyces cerevisiae. Progress in lipid research 68 18439916
2019 Coupled structural transitions enable highly cooperative regulation of human CTPS2 filaments. Nature structural & molecular biology 59 31873303
2022 Combined Inactivation of CTPS1 and ATR Is Synthetically Lethal to MYC-Overexpressing Cancer Cells. Cancer research 46 35022212
2021 Structural basis for isoform-specific inhibition of human CTPS1. Proceedings of the National Academy of Sciences of the United States of America 33 34583994
2010 Regulation of human cytidine triphosphate synthetase 2 by phosphorylation. The Journal of biological chemistry 33 20739275
2005 Expression of Human CTP synthetase in Saccharomyces cerevisiae reveals phosphorylation by protein kinase A. The Journal of biological chemistry 33 16179339
2004 The modulation of osteogenesis in vitro by calcium titanium phosphate coatings. Biomaterials 31 15109851
2021 Epstein-Barr Virus Induced Cytidine Metabolism Roles in Transformed B-Cell Growth and Survival. mBio 29 34281398
2019 Uridine/UMP metabolism and their function on the gut in segregated early weaned piglets. Food & function 28 31231750
2021 Extraction, Structural Characterization, and Anti-Hepatocellular Carcinoma Activity of Polysaccharides From Panax ginseng Meyer. Frontiers in oncology 25 34912721
2021 Glutamine Uptake via SNAT6 and Caveolin Regulates Glutamine-Glutamate Cycle. International journal of molecular sciences 22 33503881
2023 CTPS1 is a novel therapeutic target in multiple myeloma which synergizes with inhibition of CHEK1, ATR or WEE1. Leukemia 20 37898670
2023 Differential roles of CTP synthetases CTPS1 and CTPS2 in cell proliferation. Life science alliance 19 37348953
2023 CTP Synthase 1 Is a Novel Therapeutic Target in Lymphoma. HemaSphere 13 37008165
2020 SNAP29 mediates the assembly of histidine-induced CTP synthase filaments in proximity to the cytokeratin network. Journal of cell science 13 32184263
2011 Low cytosine triphosphate synthase 2 expression renders resistance to 5-fluorouracil in colorectal cancer. Cancer biology & therapy 13 21378502
2018 Inhibition of the Neuronal Calcium Sensor DREAM Modulates Presenilin-2 Endoproteolysis. Frontiers in molecular neuroscience 11 30559648
2022 A multiauxotrophic CHO cell line for the rapid isolation of producers of diverse or high levels of recombinant proteins. Biotechnology and bioengineering 9 35249214
2024 Inactivation of cytidine triphosphate synthase 1 prevents fatal auto-immunity in mice. Nature communications 8 38438357
2023 CTP synthase 2 predicts inferior survival and mediates DNA damage response via interacting with BRCA1 in chronic lymphocytic leukemia. Experimental hematology & oncology 8 36635772
2023 Genome-wide association study reveals the candidate genes for reproduction traits in Yunong black pigs. Animal genetics 7 36650110
2022 Combined metabolomics and proteomics to reveal beneficial mechanisms of Dendrobium fimbriatum against gastric mucosal injury. Frontiers in pharmacology 6 36110550
2011 Comprehensive evaluation of the contribution of X chromosome genes to platinum sensitivity. Molecular cancer therapeutics 6 21252287
2022 Identification of a novel microdeletion causative of Nance-Horan syndrome. Molecular genetics & genomic medicine 5 35122698
2017 Identification of cytidine-5-triphosphate synthase1-selective inhibitory peptide from random peptide library displayed on T7 phage. Peptides 5 28676225
2004 Organization and annotation of the Xcat critical region: elimination of seven positional candidate genes. Genomics 4 15081118
2023 Stem cell factor modulates HIF-1α levels and diminishes 5-FU sensitivity in 5-FU resistant pancreatic cells by altering the anabolic glucose metabolism. Journal of biochemical and molecular toxicology 1 37718545
2018 The Challenge of Next Generation Sequencing in a Boy With Severe Mononucleosis and EBV-related Lymphoma. Journal of pediatric hematology/oncology 1 29176466
2026 Spliceosomal component SNRPE drives cell proliferation by regulating CTP synthase 1 mRNA splicing in ovarian cancer. Oncogene 0 41933137
2025 CTPS2 regulates CTP synthetase activity by interacting with CTPS1. Life science alliance 0 40957650

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