Affinage

CTDSPL2

CTD small phosphatase-like protein 2 · UniProt Q05D32

Length
466 aa
Mass
53.0 kDa
Annotated
2026-06-09
16 papers in source corpus 10 papers cited in narrative 10 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

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).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2007 Medium

    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

    PMID:17487459

    Open questions at the time
    • 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
  2. 2014 High

    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

    PMID:25100727

    Open questions at the time
    • Specific phospho-residues on Smad1/5/8 not mapped
    • Does not address how substrate selection is achieved versus the CTD
  3. 2016 High

    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

    PMID:26674342 PMID:26920047

    Open questions at the time
    • Proteomic interactors not functionally validated
    • Mechanism of chromatin tethering and release unknown
    • Link between CTD dephosphorylation and silenced-region targeting not mechanistically resolved
  4. 2017 High

    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

    PMID:28851713 PMID:28915671

    Open questions at the time
    • Tissue-specific contribution of the knockout not dissected
    • Avian fibroblast phenotypes use a non-mammalian system and overexpression
  5. 2018 High

    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

    PMID:29618518

    Open questions at the time
    • Snail phospho-site(s) targeted not specified
    • Relationship to the BMP/FoxO substrate repertoire and substrate specificity unresolved
  6. 2021 High

    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

    PMID:34813892

    Open questions at the time
    • How CDK1 phosphorylation alters CTDSPL2 catalytic activity or localization not defined
    • Direct phosphatase substrates linking CTDSPL2 to p21/p27 not identified
  7. 2024 Medium

    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

    PMID:39209829

    Open questions at the time
    • Whether JAK1 is a dephosphorylation substrate or a non-catalytic partner unresolved
    • Mechanism of CTDSPL2-driven CD4+ T cell exclusion not established
  8. 2026 Medium

    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

    PMID:42041204

    Open questions at the time
    • Causal chain from SCYL1-S754 dephosphorylation to vesicle secretion not mechanistically traced
    • Single lab, single study

Open questions

Synthesis pass · forward-looking unresolved questions
  • 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.
  • 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

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 5 GO:0016787 hydrolase activity 2
Localization
GO:0005634 nucleus 2 GO:0005694 chromosome 1
Pathway
R-HSA-162582 Signal Transduction 4 R-HSA-74160 Gene expression (Transcription) 2 R-HSA-1640170 Cell Cycle 1
Partners
CDK1FOXO1FOXO3JAK1SCYL1SMAD1SNAI1

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 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. In vitro phosphatase activity assay with recombinant truncated protein Molecular and cellular biochemistry Medium 17487459
2014 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. Co-immunoprecipitation, in vitro dephosphorylation assay, siRNA knockdown with reporter and differentiation assays The Journal of biological chemistry High 25100727
2016 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. In vitro CTD phosphatase assay, siRNA knockdown with Pol II CTD phospho-specific immunoblotting, cell fractionation, chromatin immunoprecipitation (ChIP), immunofluorescence Journal of biochemistry High 26920047
2016 Proteomic screening by immunoprecipitation of inducible CTDSPL2 from nuclear extracts identified several nuclear interacting partners of CTDSPL2. Inducible expression system, immunoprecipitation, shotgun proteomics (mass spectrometry) BMB reports Low 26674342
2017 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. In vitro dephosphorylation assay, Co-immunoprecipitation, ectopic expression/knockdown with glucose production assay, SCP4 knockout mouse model Diabetes High 28851713
2017 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. Overexpression in primary chick embryo fibroblasts, cell migration assay, oxidative stress apoptosis assay, primary cell immortalization assay Oncotarget Medium 28915671
2018 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. Co-immunoprecipitation, in vitro dephosphorylation assay, ubiquitination assay, siRNA knockdown with EMT marker analysis and migration assay Open biology High 29618518
2021 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. Phos-tag electrophoresis, CDK1 kinase assay with phosphorylation-site mutagenesis, siRNA/CRISPR depletion with mitotic phenotype analysis, RT2 cell cycle array, xenograft tumor model Cancer letters High 34813892
2024 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. Co-immunoprecipitation, siRNA knockdown with PI3K/AKT pathway readouts, mouse xenograft model, immune cell infiltration analysis Cell death discovery Medium 39209829
2026 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. Co-immunoprecipitation, phosphorylation-site mutagenesis (S754A), nanoparticle tracking analysis, in vitro cell viability/apoptosis assays, in vivo tumorigenesis assay Cell cycle (Georgetown, Tex.) Medium 42041204

Source papers

Stage 0 corpus · 16 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2014 C-terminal domain (CTD) small phosphatase-like 2 modulates the canonical bone morphogenetic protein (BMP) signaling and mesenchymal differentiation via Smad dephosphorylation. The Journal of biological chemistry 37 25100727
2017 SCP4 Promotes Gluconeogenesis Through FoxO1/3a Dephosphorylation. Diabetes 24 28851713
2017 Integration of ALV into CTDSPL and CTDSPL2 genes in B-cell lymphomas promotes cell immortalization, migration and survival. Oncotarget 18 28915671
2021 The phosphatase CTDSPL2 is phosphorylated in mitosis and a target for restraining tumor growth and motility in pancreatic cancer. Cancer letters 17 34813892
2018 C-terminal domain small phosphatase-like 2 promotes epithelial-to-mesenchymal transition via Snail dephosphorylation and stabilization. Open biology 13 29618518
2007 Expression and characterization of HSPC129, a RNA polymerase II C-terminal domain phosphatase. Molecular and cellular biochemistry 12 17487459
2016 Human SCP4 is a chromatin-associated CTD phosphatase and exhibits the dynamic translocation during erythroid differentiation. Journal of biochemistry 11 26920047
2014 The diverse roles of RNA polymerase II C-terminal domain phosphatase SCP1. BMB reports 11 24755554
2016 A systematic study of nuclear interactome of C-terminal domain small phosphatase-like 2 using inducible expression system and shotgun proteomics. BMB reports 7 26674342
2023 Hypermethylation of CTDSPL2 prior to necrotizing enterocolitis onset. Epigenomics 4 37309586
2025 The phosphatase CTDSPL2 promotes proliferation, invasion, metastasis and regorafenib resistance in osteosarcoma. Journal of bone oncology 3 40352265
2025 A Transcriptomic Signature of Depressive Symptoms in Late Life. Biological psychiatry global open science 2 40094036
2024 CTDSPL2 promotes the progression of non-small lung cancer through PI3K/AKT signaling via JAK1. Cell death discovery 1 39209829
2024 Association of exposure to second-hand smoke during childhood with blood DNA methylation. Environment international 1 39693780
2026 CTDSPL2 facilitates resistance to paclitaxel in breast cancer cells by suppressing SCYL1 phosphorylation. Cell cycle (Georgetown, Tex.) 0 42041204
2026 CTDSPL2: A Comprehensive Review from Molecular Structure to Clinical Applications. The international journal of biochemistry & cell biology 0 42208850

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