Affinage

Showing PPP1R8 — NIPP1 is a alias.

PPP1R8

Nuclear inhibitor of protein phosphatase 1 · UniProt Q12972

Length
351 aa
Mass
38.5 kDa
Annotated
2026-06-10
47 papers in source corpus 33 papers cited in narrative 33 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PPP1R8/NIPP1 is a nuclear regulatory subunit of protein phosphatase 1 (PP1) that builds substrate-selective PP1 holoenzymes controlling pre-mRNA splicing, Polycomb-mediated gene silencing, the DNA-damage response, and cell proliferation (PMID:7499293, PMID:9858469, PMID:17724462, PMID:29898919). Through a centrally located inhibitory/PP1-binding domain (residues 143-217, with an RVxF motif at 200-203 and a ΦΦ-motif helix) it is among the most potent known PP1 inhibitors (Ki in the picomolar range) and engages PP1 at a unique, largely polar interaction surface that reshapes the holoenzyme's electrostatics and substrate selectivity (PMID:7499293, PMID:10318819, PMID:22940584). A second C-terminal PP1-binding element overlaps an RNA-binding domain (residues 330-351) that preferentially binds U-rich RNA and targets PP1 to RNA; PP1 inhibition requires the central and C-terminal sites cooperatively (PMID:9268347, PMID:11104670, PMID:10432294). The N-terminal FHA domain recognizes phosphorylated partners — the splicing factors SAP155/SF3b155 and CDC5L, the kinase MELK, and EZH2 — directing nuclear-speckle and spliceosomal targeting and substrate recruitment for the PP1:NIPP1 holoenzyme (PMID:10827081, PMID:11034904, PMID:12105215, PMID:14699119). Functionally, NIPP1:PP1 controls late spliceosome assembly (the B-to-C complex transition) by promoting SAP155 dephosphorylation, then sensing its own substrate state and dissociating (PMID:11909864, PMID:18842582). In parallel, NIPP1 recruits PP1 to chromatin in complex with PRC2 components EED and EZH2 (and HDAC2), where FHA docking onto CDK-phosphorylated EZH2 (Thr416) shields EZH2 from PP1 dephosphorylation, stabilizing EZH2 and sustaining H3K27me3 at proliferation-associated Polycomb targets (PMID:12788942, PMID:17724462, PMID:20671031, PMID:23241245, PMID:30305391). NIPP1 also gates the DNA-damage response: covalent PP1-NIPP1 holoenzymes drive R-loop accumulation, chromatin compaction, and suppressed double-strand-break repair, and the holoenzyme is switched on by post-translational signals — PKA phosphorylation of Ser199 next to the RVxF motif and Src-family-kinase phosphorylation of Tyr335 (driving C-terminal release and N-/C-terminal circularization) both activate PP1 toward FHA-recruited and histone substrates (PMID:29898919, PMID:33939241, PMID:38303113). Genetic loss is embryonic lethal at gastrulation from impaired proliferation, with conditional deletion producing tissue-specific defects in spermatogenesis, CNS myelination, and keratinocyte homeostasis (PMID:15199142, PMID:29042623, PMID:36198882, PMID:38431220).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 1995 High

    Established NIPP1 as a discrete, potent nuclear inhibitor of PP1 and localized its inhibitory activity to a defined central segment, answering what kind of regulator it is.

    Evidence cDNA cloning from bovine thymus with recombinant-fragment PP1 inhibition and phosphorylation assays

    PMID:7499293 PMID:8390458

    Open questions at the time
    • Did not define the structural basis of PP1 binding
    • Cellular substrates of the holoenzyme unknown
  2. 1997 High

    Mapped the kinase sites (PKA Ser178/Ser199, CK2 Thr161/Ser204) and showed phosphorylation regulates inhibitory potency, but within the holoenzyme activates PP1 without releasing NIPP1 — clarifying how the inhibitor is tuned.

    Evidence Baculovirus-expressed protein, tryptic phosphopeptide sequencing, quantitative PP1 inhibition assays

    PMID:9407077

    Open questions at the time
    • In vivo relevance of each phosphosite not established
    • Substrate consequences not measured
  3. 1997 High

    Revealed an unexpected RNA-binding activity in the C-terminus that targets PP1 to RNA, expanding NIPP1 from a simple inhibitor to a substrate-targeting subunit.

    Evidence North-Western, UV cross-linking, RNA mobility shift, poly(U)-Sepharose chromatography

    PMID:9268347

    Open questions at the time
    • Physiological RNA targets not identified
    • Functional consequence of RNA-targeting of PP1 untested at this stage
  4. 1999 High

    Dissected the modular architecture — a central inhibitory/RVxF site and a separate C-terminal PP1-binding/RNA-binding/cryptic endoribonuclease region — defining how distinct domains cooperate, and placed NIPP1:PP1 in nuclear speckles controlling pre-mRNA splicing.

    Evidence Yeast two-hybrid, far-Western, peptide competition, deletion fragments, immunodepletion with in vitro splicing assay

    PMID:10318819 PMID:10432294 PMID:11104670 PMID:9858469

    Open questions at the time
    • Direct splicing substrates of PP1:NIPP1 not yet identified
    • Physiological role of the latent endoribonuclease activity unknown
  5. 2000 High

    Identified the FHA domain as a phospho-dependent recruiter (CDC5L) and defined separable nuclear-import (central NLS) versus speckle-targeting (FHA) signals, explaining how NIPP1 is positioned and how it selects substrates.

    Evidence Yeast two-hybrid, co-IP/co-purification, EGFP-fusion live-cell microscopy, deletion mutagenesis

    PMID:10827081 PMID:11034904

    Open questions at the time
    • Full set of FHA ligands not yet enumerated
    • Whether FHA recruitment couples to PP1 catalysis unresolved here
  6. 2002 High

    Showed NIPP1 is a bona fide spliceosomal component acting at the B-to-C transition via its FHA domain, and identified SAP155 and MELK as additional phospho-dependent FHA ligands linking splicing control to cell-cycle kinases.

    Evidence In vitro spliceosome assembly assays, co-IP, kinase-inhibitor and phosphosite-mutant analyses

    PMID:11909864 PMID:12105215 PMID:14699119

    Open questions at the time
    • Direct dephosphorylation of spliceosomal substrates not yet demonstrated
    • Mechanism connecting MELK binding to splicing inhibition incompletely defined
  7. 2003 Medium

    Connected NIPP1 to Polycomb silencing by identifying EED interaction and transcriptional repressor activity, opening a chromatin role distinct from splicing.

    Evidence Yeast two-hybrid, co-IP, transcription reporter assays, domain mutagenesis

    PMID:12788942

    Open questions at the time
    • Requirement for PP1 catalysis in repression not established here
    • Genome-wide target spectrum unknown at this stage
  8. 2004 High

    Demonstrated NIPP1 is essential for cell proliferation and early development, establishing its physiological indispensability.

    Evidence Constitutive knockout mice, blastocyst outgrowth, RNAi, proliferation assays

    PMID:15199142

    Open questions at the time
    • Molecular cause of the proliferation defect not pinpointed
    • No viable null cell line, limiting mechanistic dissection
  9. 2008 High

    Provided the mechanistic logic of FHA-directed substrate dephosphorylation: NIPP1 senses hyperphosphorylated SAP155, recruits PP1, drives dephosphorylation, then releases — defining it as a substrate-cycling sensor.

    Evidence In vitro dephosphorylation reconstitution, co-IP, siRNA, truncation-mutant splicing assays

    PMID:18842582

    Open questions at the time
    • Generality of the sense-and-release cycle to other FHA ligands untested here
  10. 2012 High

    Resolved the structural basis of PP1 binding (intrinsically disordered domain forming a helix at a polar ΦΦ-motif site) and unified the chromatin model: FHA docking on CDK-phosphorylated EZH2 shields EZH2 from PP1, stabilizing it and retargeting Polycomb silencing of proliferation genes; also linked PP1:NIPP1 to Cdc42-dependent directional migration.

    Evidence NMR/crystallography with mutagenesis; co-IP, phospho-antibody, ChIP/DamID/ChIP-seq, electrotaxis with Cdc42 assays

    PMID:20671031 PMID:22815811 PMID:22940584 PMID:23241245

    Open questions at the time
    • How holoenzyme assembly is choreographed in vivo across substrates not fully integrated
    • Migration mechanism (PP1:NIPP1 substrates upstream of Cdc42) undefined
  11. 2017 High

    Extended the EZH2-stabilization model in vivo: testis-specific deletion causes germ-cell loss, and CDK-site EZH2 hyperphosphorylation leads to its degradation and loss of H3K27me3, establishing PP1:NIPP1 as an EZH2 stabilizer in a physiological setting.

    Evidence Conditional knockout, EZH2 phosphosite alanine mutants, protein half-life, H3K27me3 ChIP, ex vivo testis culture

    PMID:29042623 PMID:30305391

    Open questions at the time
    • Tissue-specific differences in the proliferation requirement not explained
    • Other dephosphorylation substrates contributing to germ-cell loss not excluded
  12. 2018 High

    Defined a DNA-damage/genome-stability function: an engineered hyperactive PP1-NIPP1 holoenzyme drives R-loop accumulation, chromatin compaction, and suppressed DSB repair, requiring both catalysis and FHA recruitment.

    Evidence Inducible PP1-NIPP1 fusion cell lines, R-loop and DSB assays, chromatin compaction and gene-expression readouts

    PMID:29898919

    Open questions at the time
    • Direct repair-pathway substrates dephosphorylated by the holoenzyme not identified
    • Whether endogenous (non-fused) NIPP1 acts the same way needed validation
  13. 2024 Medium

    Identified the activating switches of the holoenzyme: PKA phosphorylation of Ser199 dissociates NIPP1 to activate PP1γ toward H3-pThr11, and DNA-damage-triggered Src-family phosphorylation of Tyr335 releases the C-terminus and drives N-/C-terminal circularization to boost FHA-mediated substrate recruitment.

    Evidence In vitro PP1 activity/kinase assays, co-IP with phosphosites, Y335E knock-in cells, DSB quantification, ChIP

    PMID:33939241 PMID:38303113

    Open questions at the time
    • In vivo kinase responsible for each event under physiological DNA damage not fully defined
    • How circularization and dissociation are coordinated across substrate classes unresolved
  14. 2023 Medium

    Implicated the NIPP1 RNA-binding domain in proteotoxicity: loss or C-terminal truncation of the ortholog suppresses tau toxicity, and conditional CNS deletion alters tau phosphorylation and impairs myelination/conduction, linking NIPP1 to neuronal homeostasis.

    Evidence C. elegans CRISPR alleles, epistasis, behavioral/neurodegeneration scoring; mouse neural conditional knockout with phospho-tau, MBP, and electrophysiology

    PMID:36198882 PMID:37000013

    Open questions at the time
    • Molecular substrate connecting NIPP1 to tau phosphorylation unidentified
    • Cross-species relevance of the RNA-binding-domain requirement uncertain
  15. 2024 Medium

    Demonstrated cell-type-specific proliferation control in vivo: keratinocyte deletion triggers cell-cycle arrest, senescence, and DNA damage marker accumulation, linking NIPP1 loss to genome-stress phenotypes.

    Evidence Conditional knockout, primary and HaCaT keratinocytes, senescence/DNA-damage immunofluorescence, gene expression

    PMID:38431220

    Open questions at the time
    • Causal pathway from NIPP1 loss to senescence not mechanistically resolved
    • Relationship to the EZH2/Polycomb and R-loop functions not directly tested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the distinct activating signals (PKA-Ser199, SFK-Tyr335) and substrate-recruitment events are integrated to choose between splicing, Polycomb, and DNA-repair outputs in a given cell context remains unresolved.
  • No unified in vivo map of which substrates dominate per tissue
  • Direct repair and migration substrates of PP1:NIPP1 unidentified
  • Physiological role of the latent C-terminal endoribonuclease activity unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 4 GO:0140096 catalytic activity, acting on a protein 4 GO:0003723 RNA binding 3 GO:0060090 molecular adaptor activity 3 GO:0140098 catalytic activity, acting on RNA 1
Localization
GO:0000228 nuclear chromosome 2 GO:0005634 nucleus 2 GO:0005654 nucleoplasm 2
Pathway
R-HSA-4839726 Chromatin organization 4 R-HSA-74160 Gene expression (Transcription) 3 R-HSA-8953854 Metabolism of RNA 3 R-HSA-73894 DNA Repair 2
Partners
CDC5LEEDEZH2HDAC2MELKPPP1CAPPP1CCSF3B1
Complex memberships
PP1:NIPP1 holoenzymePRC2 (NIPP1·EED·EZH2)spliceosome

Evidence

Reading pass · 33 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1995 NIPP-1 was cloned from bovine thymus as a 351-residue nuclear protein (38.5 kDa calculated mass) that potently inhibits PP1 catalytic subunit; its central third (residues 143-217) is sufficient for PP1 inhibition (IC50 ~0.3 nM), and phosphorylation by PKA or CK2 reduces its inhibitory potency. The C-terminus of NIPP-1 is nearly identical to the human ard-1 protein, and their mRNAs are generated by alternative splicing of the same pre-mRNA. Western blot showed a single nuclear polypeptide of 47 kDa. cDNA cloning, bacterially expressed recombinant protein PP1 inhibition assay, phosphorylation assay, Western blot, Northern analysis The Journal of biological chemistry High 7499293
1993 NIPP-1a and NIPP-1b (16-18 kDa isoforms) are excellent substrates for PKA (Km = 0.1 µM); maximal PKA phosphorylation (1.5 mol phosphate/mol NIPP-1) caused an 8-fold increase in IC50 for PP1 inhibition and decreased binding of NIPP-1 to immobilized PP1. Dephosphorylation by PP2A (but not PP1) reactivated NIPP-1. The nuclear PP1 holoenzyme PP-1Nα containing NIPP-1 was activated 6-fold by PKA, opposite to the known inhibition of cytoplasmic PP1 by PKA. In vitro kinase assay, PP1 inhibition assay, immobilized PP1 binding assay, phosphatase reactivation assay The Journal of biological chemistry High 8390458
1997 Baculovirus-expressed NIPP-1 is a potent PP1 inhibitor (Ki = 9.9 pM). PKA phosphorylates Ser178 and Ser199; CK2 phosphorylates Thr161 and Ser204. At physiological ionic strength, phosphorylation by PKA or CK2 drastically reduced inhibitory potency of free NIPP-1. Phosphorylation of NIPP-1 within the PP1:NIPP-1 holoenzyme activated the holoenzyme without releasing NIPP-1. Baculovirus expression, in vitro kinase assay, tryptic phosphopeptide sequencing, phosphoamino acid analysis, PP1 inhibition assay The Journal of biological chemistry High 9407077
1997 NIPP-1 displays RNA-binding properties, preferentially binding U-rich sequences including AUUUA motifs; it also binds single-stranded DNA but not double-stranded DNA. The C-terminus of NIPP-1 mediates RNA binding. RNA binding was not affected by PKA or CK2 phosphorylation. PP1 catalytic subunit alone does not bind poly(U)-Sepharose but binds tightly after complexation with NIPP-1, suggesting NIPP-1 targets PP1 to RNA. North-Western analysis, UV cross-linking, RNA mobility-shift assay, poly(U)-Sepharose chromatography The Journal of biological chemistry High 9268347
1999 The PP1-binding and inhibitory function of NIPP-1 maps to the central domain (residues 143-217), with the inhibitory core narrowed to residues 191-200. A second non-inhibitory PP1-binding site contains the RVXF motif (residues 200-203); V201A and F203A substitutions or phosphorylation of Ser199 or Ser204 abolished PP1C binding at this site. The central domain peptide competed for PP1 inhibition by full-length NIPP-1 and inhibitor-1/inhibitor-2. Yeast two-hybrid, co-sedimentation, far-Western (digoxigenin-conjugated PP1C), synthetic peptide competition assay, site-directed mutagenesis The Journal of biological chemistry High 10318819
1999 NIPP1 exhibits a speckled nucleoplasmic distribution co-localizing with pre-mRNA splicing factors (including Sm proteins) in nuclear speckles. Sm splicing factor co-immunoprecipitates with NIPP1 from nuclear extracts. Immunodepletion of NIPP1 from nuclear extracts, or addition of a dominant-negative mutant lacking a functional PP1-binding site, greatly reduces pre-mRNA splicing activity in vitro, implicating the NIPP1-PP1 complex in splicing control. Immunofluorescence, co-immunoprecipitation, immunodepletion, in vitro splicing assay Journal of cell science High 9858469
1999 The C-terminal region of NIPP1 (residues 311-351) contains an additional PP1 inhibitory binding site with inhibitory core at residues 331-337. This site is regulated by tyrosine phosphorylation of Tyr335 (by Lyn kinase, but only in the presence of RNA) and by RNA addition, both of which decrease inhibitory potency. The RNA-binding domain maps to C-terminal residues 330-351. Full-length NIPP1 requires both the central and C-terminal PP1-binding domains cooperatively for inhibition of myelin basic protein dephosphorylation. Site-directed mutagenesis, in vitro PP1 inhibition assay, in vitro kinase assay with Lyn The Biochemical journal High 11104670
1999 The RNA-binding domain of NIPP1 maps to C-terminal residues 330-351; a synthetic peptide of this sequence equals intact NIPP1 in RNA-binding affinity. An alternatively spliced fragment NIPP1(225-351)/Ard1 displays single-strand Mg2+-dependent endoribonuclease activity. Full-length NIPP1 and NIPP1(143-351) lack endoribonuclease activity, indicating the central domain restrains this activity. The endoribonuclease catalytic site also resides in the C-terminal 22 residues. Recombinant fragment analysis, RNA-binding assay, endoribonuclease activity assay with recombinant fragments The Biochemical journal High 10432294
2000 The N-terminal FHA (Forkhead-Associated) domain of NIPP1 interacts with CDC5L (a regulator of G2/M progression and pre-mRNA splicing) in a phosphorylation-dependent manner; cyclin E-Cdk2 phosphorylation of CDC5L enables this interaction. CDC5L, NIPP1, and PP1 form a complex in rat liver nuclear extracts demonstrated by co-immunoprecipitation and co-purification. CDC5L and NIPP1 co-localize in nuclear speckles. The FHA domain blocks beta-globin pre-mRNA splicing in nuclear extracts, and an FHA mutation abolishing CDC5L interaction also cancels the anti-splicing effect. Yeast two-hybrid, co-immunoprecipitation, co-purification, immunofluorescence co-localization, in vitro splicing assay, site-directed mutagenesis The Journal of biological chemistry High 10827081
2000 Nuclear and subnuclear targeting of NIPP1 are mediated by distinct sequences: active nuclear import requires two independent NLS signals in the central domain (which partially overlap with PP1-binding sites), while concentration in nuclear speckles requires the FHA domain in the N-terminus. The FHA domain is also required for nuclear retention when active transport is blocked. EGFP fusion protein expression in HeLa/COS-1 cells, deletion mutagenesis, live-cell fluorescence microscopy Journal of cell science High 11034904
2002 NIPP1 is a component of spliceosomes in HeLa cell splicing extracts, requiring a functional FHA domain for spliceosomal interaction. Dominant-negative NIPP1 mutants lacking residues 225-329 block splicing at the transition between the B-complex and C-complex (a late phase of spliceosome assembly). This spliceosomal function is independent of PP1-binding and RNA-binding capacity. In vitro splicing assay, spliceosome complex analysis, site-directed mutagenesis, HeLa nuclear extracts The Journal of biological chemistry High 11909864
2002 The FHA domain of NIPP1 interacts in vitro and in vivo with the splicing factor SAP155/SF3b(155) in a phosphorylation-dependent manner, specifically requiring phosphorylation of TP dipeptide motifs in SAP155 by Ca2+-dependent, roscovitine-sensitive (CDK) kinases. Various phosphorylated TP motifs compete for the same FHA binding site. SAP155 phosphorylation is dramatically increased during mitosis. Co-immunoprecipitation, in vitro binding assay, mutagenesis, kinase inhibitor treatment, mitotic cell analysis The Journal of biological chemistry High 12105215
2003 The FHA domain of NIPP1 interacts with the cell cycle-regulated kinase MELK (maternal embryonic leucine zipper kinase), dependent on phosphorylation of Thr-478 of MELK and increased in mitotically arrested cells. Recombinant MELK (including kinase-dead mutant) inhibits an early step of spliceosome assembly in nuclear extracts, but a T478A MELK mutant that cannot bind NIPP1 lacks this splicing inhibition, indicating NIPP1 mediates MELK's inhibitory effect on splicing. Co-immunoprecipitation, in vitro spliceosome assembly assay, recombinant MELK protein, kinase-dead and phosphosite mutants The Journal of biological chemistry High 14699119
2003 NIPP1 interacts with the Polycomb group protein EED (embryonic ectoderm development) via two interaction domains in the central and C-terminal thirds of NIPP1, identified by yeast two-hybrid and confirmed in vivo. (d)G-rich nucleic acids potentiate the NIPP1-EED interaction and also decrease NIPP1's potency as a PP1 inhibitor, but do not prevent formation of a ternary NIPP1·EED·PP1 complex. NIPP1 acts as a transcriptional repressor of targeted genes through its EED interaction domain; histone deacetylase 2 (HDAC2) is also present in a complex with NIPP1. Yeast two-hybrid, co-immunoprecipitation, transcription reporter assay, domain mutagenesis The Journal of biological chemistry Medium 12788942
2004 NIPP1 knockout mice (NIPP1-/-) show severely retarded growth at E6.5 and are resorbed by E8.5; lethality is not associated with increased apoptosis but correlates with impaired cell proliferation. Blastocyst outgrowth and siRNA knockdown in cultured cells confirm an essential role for NIPP1 in cell proliferation. No viable NIPP1-/- cell lines could be established. Homologous recombination knockout, blastocyst outgrowth, RNA interference knockdown, cell proliferation assay Molecular and cellular biology High 15199142
2007 NIPP1 is required for EZH2-mediated trimethylation of histone H3 on Lys27 (H3K27me3) both during embryonic development and in proliferating cells. Knockdown of NIPP1 reduces H3K27me3 globally; NIPP1 and EZH2 silence a common set of genes; NIPP1 is associated with Polycomb target genes and H3K27me3-enriched regions. Knockdown of either NIPP1 or EZH2 causes loss of H3K27me3 at target loci. RNAi knockdown, ChIP, gene-expression profiling, NIPP1-deficient cells Oncogene High 17724462
2007 Transcriptional repression by NIPP1 is mediated by PRC2 components EED and EZH2: RNAi knockdown of EED or EZH2, or overexpression of catalytically dead EZH2, alleviates NIPP1-mediated repression. NIPP1 is present in a complex with EED and EZH2 in vivo and has distinct binding sites for these proteins. RNAi knockdown, co-immunoprecipitation, transcription reporter assay, catalytic-dead EZH2 mutant Biochimica et biophysica acta Medium 17804093
2008 NIPP1 recruits PP1 to SAP155 (Sap155) via its FHA domain, which recognizes hyperphosphorylated Sap155, and promotes Sap155 dephosphorylation. NIPP1 acts as a molecular sensor: it stimulates Sap155 dephosphorylation by PP1 in vitro by facilitating their interaction, then dissociates from Sap155 after dephosphorylation. A C-terminally truncated NIPP1 (NIPP1-ΔC) forms a hyperactive holoenzyme with PP1 that dramatically reduces Sap155 hyperphosphorylation and inhibits splicing. Co-immunoprecipitation, in vitro dephosphorylation assay, siRNA knockdown, overexpression of truncation mutants, splicing assay The Journal of biological chemistry High 18842582
2010 NIPP1 forms a complex with PP1 and PRC2 components (including EZH2) on chromatin. Knockdown of NIPP1 or PP1 reduces EZH2 association with a subset of its target genes; overexpression of NIPP1 retargets EZH2 from fully repressed to partially active PcG targets. A PP1-binding mutant of NIPP1 (NIPP1m) does not cause EZH2 redistribution and shows deficient chromatin binding at Polycomb target loci (DamID mapping). NIPP1 associates with multiple PcG target genes including the Homeobox A cluster. Co-immunoprecipitation, ChIP, DamID chromatin mapping, siRNA knockdown, overexpression Nucleic acids research High 20671031
2012 Crystal/NMR structure of the PP1-binding domain of NIPP1 shows it is intrinsically disordered and binds PP1 by forming an α-helix that engages PP1 at a unique interaction site using polar (not hydrophobic) contacts. The structure reveals a shared PP1 interaction site outside the RVxF motif, the ΦΦ motif. NIPP1:PP1 substrate selectivity is determined by altered electrostatics and enhanced substrate localization. Structural determination (NMR/crystallography with functional validation), mutagenesis, substrate specificity assay Structure High 22940584
2012 CDK-mediated phosphorylation of EZH2 at Thr416 creates a docking site for the FHA domain of NIPP1. Recruited NIPP1 inhibits PP1-mediated dephosphorylation of EZH2, thereby enabling net EZH2 phosphorylation. A NIPP1-binding mutant of EZH2 is hypophosphorylated; NIPP1 knockdown reduces endogenous EZH2 phosphorylation; PP1 loss is associated with EZH2 hyperphosphorylation. Genome-wide promoter profiling shows NIPP1-binding mutant EZH2 has deficient association with ~one-third of Polycomb target genes (proliferation-related). PP1 is identified as an EZH2 phosphatase. Co-immunoprecipitation, phospho-specific antibody, siRNA knockdown, genome-wide ChIP-seq/promoter binding profiling, site-directed mutagenesis Nucleic acids research High 23241245
2012 PP1/NIPP1 regulates directional cell migration: genetic disruption of PP1 or NIPP1 decreases directional migration; inducible NIPP1 expression switches HeLa directional response from cathodal to anodal in a PP1-dependent manner. PP1:NIPP1 upregulates Cdc42 GTPase signaling; pharmacological Cdc42 inhibition in NIPP1-overexpressing cells recovers cathodal migration. Electrotaxis assay, siRNA knockdown, inducible overexpression, Cdc42 activity assay, pharmacological inhibition PloS one Medium 22815811
2006 In hypoxia, PP1γ activity is inhibited at least in part through increased association with NIPP1, an event dependent on decreased basal cAMP/PKA signaling. A dominant-negative NIPP1 construct rescues CREB activity and CREB-dependent transcription in hypoxia, demonstrating NIPP1 mediates decreased PP1γ activity and altered metabolic gene expression under hypoxic conditions. Co-immunoprecipitation, dominant-negative NIPP1 expression, reporter assay, ATP measurement Journal of cellular physiology Medium 16826568
2015 Mild stable overexpression of NIPP1 in HeLa cells causes a massive induction of mesenchymal genes (smooth/cardiac-muscle and matrix markers), formation of actin-based stress fibers and retracting filopodia, and reduced proliferation. This mesenchymal transition requires functional substrate-binding (FHA) and PP1-binding domains of NIPP1, indicating it involves selective dephosphorylation of PP1:NIPP1 substrates. Stable inducible overexpression, gene expression analysis, immunofluorescence (actin cytoskeleton), domain mutagenesis FEBS letters Medium 25907536
2017 Inducible, testis-specific NIPP1 knockout in adult mice results in gradual loss of germ cells (Sertoli-cell only phenotype), decreased proliferation and survival of spermatogenic lineage cells including undifferentiated spermatogonia. NIPP1 removal from cultured testis slices and isolated germ cells also reduces proliferation, indicating a testis-intrinsic requirement. Tamoxifen-inducible Cre knockout, histology, proliferation assay, ex vivo testis culture, RNA sequencing Scientific reports High 29042623
2018 PP1:NIPP1 fusions (covalently linked holoenzyme) cause replication stress requiring both PP1 catalytic activity and FHA domain-mediated substrate recruitment. PP1-NIPP1 expression leads to accumulation of RNA-DNA hybrids (R-loops), enhanced chromatin compaction, diminished DNA double-strand break repair, and reduced expression of DNA damage signaling/repair proteins. Inducible stable cell lines with PP1-NIPP1 fusion proteins, R-loop detection, DSB assay, chromatin compaction assay, gene expression analysis Journal of cell science High 29898919
2018 Testis-specific NIPP1 deletion causes hyperphosphorylation of EZH2 at CDK sites Thr345 and Thr487 (due to loss of PP1-mediated dephosphorylation), leading to proteolytic EZH2 degradation and reduction in H3K27me3. Alanine mutations at these CDK sites prolong EZH2 half-life in germ cells. PP1:NIPP1 holoenzyme stabilizes EZH2 through dephosphorylation. Conditional knockout, phospho-specific antibody, alanine mutagenesis of EZH2, protein half-life assay, ChIP for H3K27me3 The Journal of biological chemistry High 30305391
2021 NIPP1 inhibits PP1γ-mediated dephosphorylation of histone H3-Thr11 (H3-pThr11) both in vivo and in vitro. Upon DNA damage, activated PKA phosphorylates NIPP1-Ser199 (adjacent to the PP1-binding RVxF motif), triggering dissociation of NIPP1 from PP1γ, thereby activating PP1γ and enabling H3-pThr11 dephosphorylation and transcriptional repression of E2F1 target genes. NIPP1 depletion reduces expression of E2F1 target genes. In vitro PP1 inhibition assay, co-immunoprecipitation, NIPP1 depletion, PKA inhibitor treatment, ChIP for H3-pThr11 Cancer science Medium 33939241
2023 In C. elegans, loss of sut-6/NIPP1 or a C-terminal truncation (W292X, removing the RNA-binding domain) suppresses tau toxicity, tau protein accumulation and neuronal loss. Epistasis studies show that sut-6 suppression of tauopathy is independent of other nuclear speckle-localized suppressors (sut-2, aly-1/aly-3, spop-1). Neuronal overexpression of the W292X mutant (but not wild-type SUT-6) reduces tau-mediated deficits, suggesting the RNA-binding domain is required for NIPP1/sut-6's role in tau toxicity. C. elegans genetic screen, CRISPR-generated alleles, behavioral assay, tau protein quantification, neurodegeneration scoring, epistasis analysis Human molecular genetics Medium 37000013
2024 DNA damage activates the PP1:NIPP1 holoenzyme through a Src-family kinase-mediated phosphorylation of NIPP1 at C-terminal Tyr335, causing partial dissociation of the NIPP1 C-terminus from the PP1 active site. The phospho-Y335 C-terminus then interacts with the NIPP1 N-terminus (circularization), enhancing substrate recruitment by the flanking FHA domain. Knock-in of phospho-mimetic Y335E NIPP1 causes hypo-phosphorylation of FHA ligands and accumulation of DNA double-strand breaks, confirming this activation mechanism contributes to DNA repair resolution. In vitro kinase assay (Src-family kinase), PP1 activity assay, co-immunoprecipitation, NIPP1 Y335E knock-in cells, DSB quantification The FEBS journal High 38303113
2000 NIPP-1 (Flag-tagged) co-immunoprecipitates with all three PP1 catalytic subunit isoforms (PP1α, PP1γ1, PP1δ) with similar efficiency in mammalian cells, indicating NIPP-1 interacts with PP1C through a region conserved among all three isoforms. Overexpression of Flag-tagged NIPP-1, co-immunoprecipitation with isoform-specific antibodies The Tohoku journal of experimental medicine Low 10896038
2022 Conditional knockout of NIPP1 from neural precursor cells in mice leads to significantly enhanced phosphorylation of tau, altered AKT and PP1 activity, decreased MBP expression in cortex, deficits in myelinated axon percentage and compound action potential conduction, and premature lethality. These findings establish a role for NIPP1 in regulating tau phosphorylation and CNS myelination in neural development. Conditional knockout mouse model, phospho-specific tau antibody, MBP immunostaining, electrophysiology (CAP recording), axon myelination quantification Molecular neurobiology Medium 36198882
2024 Embryonic deletion of NIPP1 in keratinocytes leads to cell cycle arrest and premature senescence, with increased expression of cell cycle inhibitors p21, p16/Ink4a, p19/Arf, accumulation of senescence-associated secretory phenotype factors, and elevated DNA damage markers (γH2AX, 53BP1) in primary keratinocytes and human NIPP1-depleted HaCaT keratinocytes. Conditional knockout, primary keratinocyte culture, immunofluorescence (senescence markers, DNA damage markers), gene expression analysis The Journal of investigative dermatology Medium 38431220

Source papers

Stage 0 corpus · 47 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1995 Molecular cloning of NIPP-1, a nuclear inhibitor of protein phosphatase-1, reveals homology with polypeptides involved in RNA processing. The Journal of biological chemistry 100 7499293
2000 NIPP1-mediated interaction of protein phosphatase-1 with CDC5L, a regulator of pre-mRNA splicing and mitotic entry. The Journal of biological chemistry 95 10827081
2003 Inhibition of spliceosome assembly by the cell cycle-regulated protein kinase MELK and involvement of splicing factor NIPP1. The Journal of biological chemistry 86 14699119
1999 Molecular determinants of nuclear protein phosphatase-1 regulation by NIPP-1. The Journal of biological chemistry 75 10318819
2007 The transcriptional repressor NIPP1 is an essential player in EZH2-mediated gene silencing. Oncogene 71 17724462
2012 The molecular basis for substrate specificity of the nuclear NIPP1:PP1 holoenzyme. Structure (London, England : 1993) 68 22940584
2002 Phosphorylation-dependent interaction between the splicing factors SAP155 and NIPP1. The Journal of biological chemistry 63 12105215
1993 Inactivation of nuclear inhibitory polypeptides of protein phosphatase-1 (NIPP-1) by protein kinase A. The Journal of biological chemistry 63 8390458
2000 The C-terminus of NIPP1 (nuclear inhibitor of protein phosphatase-1) contains a novel binding site for protein phosphatase-1 that is controlled by tyrosine phosphorylation and RNA binding. The Biochemical journal 59 11104670
1999 Nuclear organisation of NIPP1, a regulatory subunit of protein phosphatase 1 that associates with pre-mRNA splicing factors. Journal of cell science 59 9858469
2000 Nuclear and subnuclear targeting sequences of the protein phosphatase-1 regulator NIPP1. Journal of cell science 49 11034904
2008 Nuclear inhibitor of protein phosphatase-1 (NIPP1) directs protein phosphatase-1 (PP1) to dephosphorylate the U2 small nuclear ribonucleoprotein particle (snRNP) component, spliceosome-associated protein 155 (Sap155). The Journal of biological chemistry 48 18842582
1997 Properties and phosphorylation sites of baculovirus-expressed nuclear inhibitor of protein phosphatase-1 (NIPP-1). The Journal of biological chemistry 48 9407077
1994 ard-1: a human gene that reverses the effects of temperature-sensitive and deletion mutations in the Escherichia coli rne gene and encodes an activity producing RNase E-like cleavages. Proceedings of the National Academy of Sciences of the United States of America 44 7524097
2012 NIPP1 maintains EZH2 phosphorylation and promoter occupancy at proliferation-related target genes. Nucleic acids research 41 23241245
2002 The protein phosphatase-1 regulator NIPP1 is also a splicing factor involved in a late step of spliceosome assembly. The Journal of biological chemistry 40 11909864
1993 ARD 1, a 64-kDa guanine nucleotide-binding protein with a carboxyl-terminal ADP-ribosylation factor domain. The Journal of biological chemistry 37 8473324
2010 The phosphatase interactor NIPP1 regulates the occupancy of the histone methyltransferase EZH2 at Polycomb targets. Nucleic acids research 35 20671031
1997 NIPP-1, a nuclear inhibitory subunit of protein phosphatase-1, has RNA-binding properties. The Journal of biological chemistry 34 9268347
1997 ARD-1 cDNA from human cells encodes a site-specific single-strand endoribonuclease that functionally resembles Escherichia coli RNase E. The Journal of biological chemistry 32 9153239
2003 The protein phosphatase-1 (PP1) regulator, nuclear inhibitor of PP1 (NIPP1), interacts with the polycomb group protein, embryonic ectoderm development (EED), and functions as a transcriptional repressor. The Journal of biological chemistry 30 12788942
2004 The nuclear scaffold protein NIPP1 is essential for early embryonic development and cell proliferation. Molecular and cellular biology 28 15199142
2012 A role for PP1/NIPP1 in steering migration of human cancer cells. PloS one 24 22815811
2005 Down-regulation of the expression of the FIH-1 and ARD-1 genes at the transcriptional level by nickel and cobalt in the human lung adenocarcinoma A549 cell line. International journal of environmental research and public health 22 16705796
2002 Functional interaction between nuclear inhibitor of protein phosphatase type 1 (NIPP1) and protein phosphatase type 1 (PP1) in Drosophila: consequences of over-expression of NIPP1 in flies and suppression by co-expression of PP1. The Biochemical journal 22 12358598
2018 Overexpression of PP1-NIPP1 limits the capacity of cells to repair DNA double-strand breaks. Journal of cell science 18 29898919
2006 Regulation of protein phosphatase 1gamma activity in hypoxia through increased interaction with NIPP1: implications for cellular metabolism. Journal of cellular physiology 18 16826568
1999 Mapping of the RNA-binding and endoribonuclease domains of NIPP1, a nuclear targeting subunit of protein phosphatase 1. The Biochemical journal 16 10432294
2017 The protein phosphatase 1 regulator NIPP1 is essential for mammalian spermatogenesis. Scientific reports 15 29042623
2018 The deletion of the protein phosphatase 1 regulator NIPP1 in testis causes hyperphosphorylation and degradation of the histone methyltransferase EZH2. The Journal of biological chemistry 14 30305391
1999 Identification of MYPT1 and NIPP1 as subunits of protein phosphatase 1 in rat liver cytosol. FEBS letters 14 10428496
2015 Protein phosphatase PP1-NIPP1 activates mesenchymal genes in HeLa cells. FEBS letters 13 25907536
2007 The transcriptional repression by NIPP1 is mediated by Polycomb group proteins. Biochimica et biophysica acta 11 17804093
1999 Organization and alternate splice products of the gene encoding nuclear inhibitor of protein phosphatase-1 (NIPP-1). European journal of biochemistry 10 10103062
2016 Brief Report: The Deletion of the Phosphatase Regulator NIPP1 Causes Progenitor Cell Expansion in the Adult Liver. Stem cells (Dayton, Ohio) 9 27068806
2000 Increased expression of NIPP-1 mRNA correlates positively with malignant phenotype in rat hepatomas. International journal of oncology 9 10717244
2021 PP1 regulatory subunit NIPP1 regulates transcription of E2F1 target genes following DNA damage. Cancer science 8 33939241
2020 Enhanced DNA-repair capacity and resistance to chemically induced carcinogenesis upon deletion of the phosphatase regulator NIPP1. Oncogenesis 8 32123159
1999 Alternative splicing regulates the production of ARD-1 endoribonuclease and NIPP-1, an inhibitor of protein phosphatase-1, as isoforms encoded by the same gene. Gene 8 10564811
1997 Inhibition of translation by mRNA encoding NIPP-1, a nuclear inhibitor of protein phosphatase-1. European journal of biochemistry 8 9249054
2023 Sut-6/NIPP1 modulates tau toxicity. Human molecular genetics 7 37000013
2011 Regulation of growth factor receptor degradation by ADP-ribosylation factor domain protein (ARD) 1. Proceedings of the National Academy of Sciences of the United States of America 6 21653881
2020 Phosphatase Regulator NIPP1 Restrains Chemokine-Driven Skin Inflammation. The Journal of investigative dermatology 5 31972250
2024 DNA damage-induced allosteric activation of protein phosphatase PP1:NIPP1 through Src kinase-induced circularization of NIPP1. The FEBS journal 4 38303113
2022 Nuclear Inhibitor of Protein Phosphatase 1 (NIPP1) Regulates CNS Tau Phosphorylation and Myelination During Development. Molecular neurobiology 3 36198882
2000 Broad specificity in binding of NIPP-1, nuclear inhibitor of protein phosphatase-1, to PP1 isoforms in vivo. The Tohoku journal of experimental medicine 3 10896038
2024 Embryonic NIPP1 Depletion in Keratinocytes Triggers a Cell Cycle Arrest and Premature Senescence in Adult Mice. The Journal of investigative dermatology 0 38431220

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