Affinage

NKAP

NF-kappa-B-activating protein · UniProt Q8N5F7

Length
415 aa
Mass
47.1 kDa
Annotated
2026-04-29
32 papers in source corpus 18 papers cited in narrative 18 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

NKAP is a multifunctional nuclear protein that integrates transcriptional repression, RNA processing, and mitotic chromosome alignment. It physically associates with HDAC3 via residues F347/Y352 to repress Notch target genes and maintain RNA polymerase II pausing, thereby preventing R-loop accumulation and genome instability; this NKAP–HDAC3 axis is essential for hematopoietic stem cell maintenance, αβ T cell maturation, iNKT cell development, and regulatory T cell survival (PMID:19409814, PMID:23481390, PMID:30804042, PMID:37322264). NKAP localizes to nuclear speckles where it binds RNA and splicing factors including FUS/TLS via its RS domain, participates in pre-mRNA splicing, and functions as an m6A reader that recruits SFPQ to regulate SLC7A11 mRNA processing and suppress ferroptosis (PMID:24353314, PMID:35064112). During mitosis, NKAP is SUMOylated and recruited to kinetochores by Bub3, where it anchors CENP-E via BubR1 to enable proper chromosome alignment (PMID:27694884). Mutations disrupting the NKAP–HDAC3 interaction cause a human developmental disorder with transcriptomic dysregulation of long, exon-rich genes (PMID:31587868).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2009 High

    The fundamental question of NKAP's cellular function was answered: it operates as a transcriptional repressor through HDAC3 association and Notch corepressor complex membership, explaining why its loss derepresses Notch targets and blocks αβ T cell development.

    Evidence Co-IP, ChIP, and Lck-cre conditional knockout in mouse T cells

    PMID:19409814

    Open questions at the time
    • Exact DNA-binding mechanism of NKAP unresolved
    • Whether NKAP functions beyond the Notch pathway unknown
    • Structural basis of NKAP–HDAC3 interaction not mapped
  2. 2010 High

    NKAP's role was extended beyond T cell development to adult hematopoietic stem cell maintenance, establishing it as a broad requirement for hematopoiesis rather than a lineage-specific factor.

    Evidence Mx1-cre inducible conditional knockout, radiation chimeras, cell cycle/apoptosis assays

    PMID:20610818

    Open questions at the time
    • Whether HSC failure is Notch-dependent or involves additional targets unknown
    • Direct transcriptional targets in HSCs not identified
  3. 2011 High

    NKAP was shown to be required for post-selection T cell maturation and entry into the long-lived naive pool, separating its function from positive selection and simple survival.

    Evidence CD4-cre conditional knockout with Bcl-2 transgene rescue ruling out survival defect

    PMID:21624937

    Open questions at the time
    • Molecular mechanism of maturation block not defined
    • Whether NKAP acts through HDAC3 in this context not tested
  4. 2013 High

    Two new dimensions of NKAP function were established: genetic epistasis showed that NKAP–HDAC3 cooperation drives iNKT development, while biochemical studies revealed a distinct role in nuclear speckles where NKAP binds RNA and splicing factors to regulate pre-mRNA splicing.

    Evidence HDAC3 conditional KO comparison for iNKT; CLIP-seq, pull-down, in vitro splicing, domain deletion for splicing role

    PMID:23481390 PMID:24353314

    Open questions at the time
    • Specific splicing targets regulated by NKAP not catalogued genome-wide
    • Whether splicing and transcriptional repression functions are separable in vivo unknown
  5. 2016 High

    NKAP was revealed to have a mitotic function entirely distinct from its interphase roles: SUMOylation-dependent kinetochore localization enables NKAP to anchor CENP-E via Bub3/BubR1 for chromosome alignment.

    Evidence siRNA knockdown, live-cell imaging, SUMOylation-deficient mutant, co-IP

    PMID:27694884

    Open questions at the time
    • SUMOylation site(s) on NKAP not mapped
    • Whether mitotic NKAP function is linked to its splicing or transcriptional roles unknown
  6. 2018 Medium

    NKAP's requirement for T cell peripheral survival was extended to regulatory T cells, and NKAP-deficient T cells were found to be susceptible to complement attack.

    Evidence Foxp3-YFP-cre conditional knockout, complement susceptibility assay

    PMID:29366602

    Open questions at the time
    • Why NKAP-deficient cells become complement-susceptible not mechanistically explained
    • Whether Treg function (suppressive capacity) is independently affected unknown
  7. 2019 High

    A cluster of studies mapped the minimal HDAC3-binding site to F347/Y352 and demonstrated that the Y352A mutation recapitulates full NKAP deficiency in T cell maturation, Treg maintenance, iNKT development, and HSC survival — but not MEF proliferation — establishing that NKAP operates in HDAC3-dependent and -independent complexes in different cell types.

    Evidence Alanine scanning mutagenesis with linked conditional deletion/re-expression in vivo across multiple cre systems

    PMID:30804042 PMID:31387873

    Open questions at the time
    • Identity of HDAC3-independent NKAP complex in MEFs unknown
    • Whether the RS-domain/splicing axis accounts for HDAC3-independent functions not tested
  8. 2019 Medium

    NKAP-deficient T cells were found to accumulate lipid peroxides and undergo ferroptosis, providing a mechanistic link between NKAP loss and peripheral T cell death.

    Evidence Lipid peroxide measurement by flow cytometry, complement pathway genetic ablation

    PMID:31175160

    Open questions at the time
    • Whether ferroptosis is a direct consequence of splicing defects or transcriptional derepression unclear
    • Ferroptosis pathway components directly regulated by NKAP not identified
  9. 2019 Medium

    Human mutations in the NKAP C-terminal HDAC3-binding region were linked to a developmental disorder with dysregulation of long, exon-rich genes, establishing clinical relevance and suggesting that NKAP–HDAC3 preferentially regulates complex gene architectures.

    Evidence Transcriptome analysis of patient cells, zebrafish nkap truncation model

    PMID:31587868

    Open questions at the time
    • Number of families small
    • Whether long-gene bias reflects splicing versus transcriptional defect unresolved
    • No structural model of NKAP–HDAC3 complex
  10. 2022 Medium

    NKAP was identified as an m6A reader that binds the RGAC motif on SLC7A11 mRNA and recruits SFPQ to promote its splicing, linking NKAP's RNA-binding activity to epitranscriptomic regulation and ferroptosis suppression in glioblastoma.

    Evidence RNA immunoprecipitation, METTL3 knockdown, RNA-seq in glioblastoma cells

    PMID:35064112

    Open questions at the time
    • m6A reading specificity not structurally characterized
    • Whether m6A reader function extends to other NKAP splicing targets unknown
    • Single lab, not independently replicated
  11. 2023 High

    The NKAP–HDAC3 complex was shown to prevent R-loop accumulation by maintaining RNA Pol II pausing, with HDAC3 stabilizing NKAP protein independently of deacetylase activity — revealing a genome integrity function and a non-enzymatic role for HDAC3.

    Evidence DRIP-seq, DNA fiber assays, XPF/XPG double knockout epistasis, RNA Pol II ChIP

    PMID:37322264

    Open questions at the time
    • Genome-wide identification of loci protected by NKAP–HDAC3 from R-loops incomplete
    • Whether R-loop prevention is related to the splicing role at those loci unclear

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include: the structural basis of NKAP's multifunctionality (how a single protein acts as transcriptional repressor, splicing factor, m6A reader, and kinetochore anchor); whether its splicing, transcriptional, and mitotic functions are separable in vivo; and the full spectrum of human disease caused by NKAP mutations.
  • No crystal or cryo-EM structure of NKAP or its complexes
  • Separation-of-function alleles for splicing vs transcription not generated
  • Genome-wide catalog of direct NKAP splicing targets in primary cells lacking

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 2 GO:0098772 molecular function regulator activity 2 GO:0140110 transcription regulator activity 2
Localization
GO:0005634 nucleus 3 GO:0005694 chromosome 1
Pathway
R-HSA-168256 Immune System 4 R-HSA-74160 Gene expression (Transcription) 2 R-HSA-8953854 Metabolism of RNA 2 R-HSA-1640170 Cell Cycle 1 R-HSA-4839726 Chromatin organization 1 R-HSA-73894 DNA Repair 1
Partners
BUB1BBUB3CENP-EFUSHDAC3MARCKSSFPQ
Complex memberships
NKAP–HDAC3 complexNotch corepressor complex

Evidence

Reading pass · 18 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 NKAP functions as a transcriptional repressor by associating with HDAC3 and forming part of a DNA-binding complex; it also associates with the Notch corepressor complex, and its loss leads to 8-20-fold upregulation of Notch target genes (Hes1, Deltex1, CD25), blocking αβ T cell development. Genetic complementation screen, co-immunoprecipitation, chromatin immunoprecipitation, conditional knockout (Lck-cre) Immunity High 19409814
2011 NKAP is required cell-intrinsically for post-selection T cell maturation and acquisition of functional competency; loss of NKAP blocks entry into the long-lived naive peripheral T cell pool without affecting positive selection, and this is not rescued by a Bcl-2 transgene. CD4-cre conditional knockout, Bcl-2 transgene rescue experiment, functional assays on peripheral T cells The Journal of experimental medicine High 21624937
2013 NKAP is required for iNKT cell development (blocked at DP stage) through a mechanism dependent on its association with HDAC3; deletion of HDAC3 causes a similar developmental block, indicating functional interaction between NKAP and HDAC3 in iNKT development. CD4-cre conditional knockout, TCR transgene rescue, HDAC3 conditional knockout comparison Nature communications High 23481390
2013 NKAP localizes to nuclear speckles (via its basic domain), binds RNA (both spliced mRNA and unspliced pre-mRNA), interacts with RNA-binding proteins and splicing factors including FUS/TLS (through its RS domain interacting with RGG1/RGG3 domains of FUS/TLS), associates with U1, U4, and U5 snRNAs, and its knockdown increases pre-mRNA levels, establishing a role in RNA splicing. NKAP-specific antibody localization, pull-down experiments, in vitro splicing assays, CLIP-seq, siRNA knockdown with pre-mRNA quantification Nucleic acids research High 24353314
2010 NKAP is required for adult hematopoietic stem cell maintenance and survival in a cell-intrinsic manner; its deletion leads to decreased HSC proliferation and increased apoptosis associated with upregulation of CDKIs p21Cip1/Waf1 and p19Ink4d. Conditional knockout (Mx1-cre, inducible), radiation chimera experiments, mixed bone marrow chimeras, cell cycle and apoptosis assays Blood High 20610818
2016 NKAP is SUMOylated predominantly during mitosis, and this SUMOylation is required for NKAP to bind CENP-E; NKAP dynamically localizes to kinetochores, and Bub3 recruits NKAP to stabilize CENP-E binding to BubR1 at kinetochores, enabling proper chromosome alignment. siRNA knockdown, live-cell imaging, co-immunoprecipitation, SUMOylation-deficient mutant expression, chromosome alignment assays Nature communications High 27694884
2019 The interaction between NKAP and HDAC3 is critical for T cell maturation; a point mutation Y352A in NKAP abrogates NKAP-HDAC3 association without altering NKAP localization or expression, and mice expressing NKAP(Y352A) recapitulate full NKAP deficiency in T cell maturation, Treg maintenance, and iNKT development. Alanine scanning mutagenesis, transgenic cre-mediated linked deletion/re-expression system in vivo, co-immunoprecipitation ImmunoHorizons High 31387873
2019 Y352 and F347 residues in NKAP constitute the minimal HDAC3-binding site; the Y352A mutation abrogates NKAP-HDAC3 association and prevents rescue of HSC maintenance and survival but not proliferation in MEFs, demonstrating that NKAP functions in different complexes in different cell types. Serial truncation and alanine scanning mutagenesis, co-immunoprecipitation, linked conditional deletion/re-expression in vivo (Mx1-cre/poly-IC), MEF proliferation assays Journal of immunology High 30804042
2022 NKAP acts as an m6A reader that binds the RGAC motif on SLC7A11 transcript; upon binding, NKAP recruits splicing factor SFPQ to promote TTS splicing and last-exon retention of SLC7A11 mRNA, requiring METTL3-mediated m6A methylation, thereby suppressing ferroptosis in glioblastoma cells. RNA immunoprecipitation, co-immunoprecipitation, m6A inhibitor (cycloleucine) treatment, METTL3 knockdown, RNA-sequencing, mass spectrometry Cell death & disease Medium 35064112
2023 NKAP forms a protein complex with HDAC3 to prevent R-loop accumulation and maintain genome integrity; NKAP depletion causes R-loop-dependent DNA damage and replication fork defects, which are processed into DSBs by XPF/XPG endonucleases; HDAC3 stabilizes NKAP protein independently of its deacetylase activity; NKAP prevents R-loop formation by maintaining RNA polymerase II pausing. Co-immunoprecipitation, DRIP-seq (R-loop mapping), DNA fiber assays, comet assay, siRNA knockdown, XPF/XPG double knockout, RNA Pol II ChIP Cell death and differentiation High 37322264
2019 NKAP directly binds the Notch1 promoter and trans-activates Notch1 transcription in glioma cells, thereby promoting tumor-associated macrophage polarization and recruitment through upregulation of SDF-1 and M-CSF. ChIP, RNA sequencing, luciferase reporter assay, siRNA knockdown, xenograft models Journal of experimental & clinical cancer research Medium 31277684
2019 Deletion of NKAP in hematopoietic progenitors induces a senescent phenotype with upregulation of p16INK4a; combined deficiency of p16INK4a and p21Cip1 shifts the consequence of NKAP deficiency from senescence to apoptosis in ex vivo cultures, but does not reverse hematopoietic failure in vivo. Inducible conditional knockout (Mx1-cre), ex vivo culture, double CDKI knockout epistasis, senescence assays Frontiers in cell and developmental biology Medium 31632967
2019 NKAP-deficient peripheral T cells accumulate lipid peroxides and undergo ferroptosis; complement (via MBL2) contributes to clearance of NKAP-deficient T cells but is not the primary cause of lymphopenia, as genetic ablation of lectin and classical complement pathways blocks C3 deposition but does not restore cellularity. Complement pathway knockout (genetic ablation of MBL1, MBL2, C4), lipid peroxide measurement, flow cytometry, in vitro complement deposition assay Journal of immunology Medium 31175160
2019 NKAP interacts with HDAC3 through its C-terminal region; missense mutations in this C-terminal region (associated with human developmental disorder) abrogate this interaction and cause transcriptome changes characterized by downregulation of long genes with higher exon numbers; C-terminally truncated NKAP in zebrafish causes severe developmental defects. Transcriptome analysis of patient cells, zebrafish nkap mutant model, interaction domain mapping American journal of human genetics Medium 31587868
2021 MARCKS protein directly binds NKAP; upon MARCKS phosphorylation at Ser159 and Ser163 (by cigarette smoke), the MARCKS-NKAP interaction is inhibited, leading to NF-κB signaling activation. Functional proteomics (interactome), direct binding assay, phosphomimetic mutant analysis, NF-κB reporter assay Theranostics Medium 33754052
2018 NKAP is required for Treg maturation and peripheral survival in a cell-intrinsic manner; NKAP-deficient Tregs retain a recent thymic emigrant phenotype and are attacked by complement in the periphery, similar to conventional T cells. Foxp3-YFP-cre conditional knockout, flow cytometry, complement susceptibility assay Journal of autoimmunity Medium 29366602
2024 The GRAS1 lncRNA directly binds NKAP protein; GRAS1 knockdown leads to proteasome-dependent degradation of NKAP protein, and overexpression of either GRAS1 or NKAP rescues DNA damage caused by GRAS1 knockdown. RNA antisense purification and mass spectrometry (RAP-MS), NKAP overexpression rescue, proteasome inhibitor experiment bioRxivpreprint Medium 38645172
2024 NKAP p.R330C mutation alters intra-nuclear distribution of NKAP and disrupts its interaction with HDAC3, leading to dysregulation of cardiac morphogenesis genes (DHRS3, DNAH11, JAG1) and congenital heart defects. HEK293T transfection with mutant NKAP, transcriptome analysis, co-immunoprecipitation for HDAC3 binding, immunofluorescence for nuclear distribution Journal of cellular and molecular medicine Low 38647244

Source papers

Stage 0 corpus · 32 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2022 RNA binding protein NKAP protects glioblastoma cells from ferroptosis by promoting SLC7A11 mRNA splicing in an m6A-dependent manner. Cell death & disease 101 35064112
2009 NKAP is a transcriptional repressor of notch signaling and is required for T cell development. Immunity 82 19409814
2011 NKAP is required for T cell maturation and acquisition of functional competency. The Journal of experimental medicine 48 21624937
2013 The transcriptional repressor NKAP is required for the development of iNKT cells. Nature communications 45 23481390
2013 NKAP is a novel RS-related protein that interacts with RNA and RNA binding proteins. Nucleic acids research 44 24353314
2016 SUMOylated NKAP is essential for chromosome alignment by anchoring CENP-E to kinetochores. Nature communications 38 27694884
2021 MARCKS cooperates with NKAP to activate NF-kB signaling in smoke-related lung cancer. Theranostics 36 33754052
2010 Adult hematopoietic stem cells require NKAP for maintenance and survival. Blood 35 20610818
2016 NKAP Regulates Invariant NKT Cell Proliferation and Differentiation into ROR-γt-Expressing NKT17 Cells. Journal of immunology (Baltimore, Md. : 1950) 28 27183586
2020 Silencing of lncRNA MIAT alleviates LPS-induced pneumonia via regulating miR-147a/NKAP/NF-κB axis. Aging 27 33318298
2019 NKAP alters tumor immune microenvironment and promotes glioma growth via Notch1 signaling. Journal of experimental & clinical cancer research : CR 27 31277684
2019 MiR-4766-5p Inhibits The Development And Progression Of Gastric Cancer By Targeting NKAP. OncoTargets and therapy 20 31802890
2019 Missense Mutations in NKAP Cause a Disorder of Transcriptional Regulation Characterized by Marfanoid Habitus and Cognitive Impairment. American journal of human genetics 16 31587868
2018 Treg-specific deletion of NKAP results in severe, systemic autoimmunity due to peripheral loss of Tregs. Journal of autoimmunity 14 29366602
2022 IL-1β promotes hypoxic vascular endothelial cell proliferation through the miR-24-3p/NKAP/NF-κB axis. Bioscience reports 10 35005769
2018 NKAP functions as an oncogene and its expression is induced by CoCl2 treatment in breast cancer via AKT/mTOR signaling pathway. Cancer management and research 10 30464609
2023 NKAP acts with HDAC3 to prevent R-loop associated genome instability. Cell death and differentiation 9 37322264
2020 NKAP promotes renal cell carcinoma growth via AKT/mTOR signalling pathway. Cell biochemistry and function 9 32032976
2019 NKAP plays an oncogenic function partly through AKT signaling pathway in hepatocellular carcinoma. Neoplasma 9 31305121
2019 NKAP Regulates Senescence and Cell Death Pathways in Hematopoietic Progenitors. Frontiers in cell and developmental biology 9 31632967
2014 The Notch co-repressor protein NKAP is highly expressed in adult mouse subventricular zone neural progenitor cells. Neuroscience 9 24583034
2019 The oncogenic role of NKAP in the growth and invasion of colon cancer cells. Oncology reports 8 31545474
2019 NKAP Must Associate with HDAC3 to Regulate Hematopoietic Stem Cell Maintenance and Survival. Journal of immunology (Baltimore, Md. : 1950) 6 30804042
2019 Murine T Cell Maturation Entails Protection from MBL2, but Complement Proteins Do Not Drive Clearance of Cells That Fail Maturation in the Absence of NKAP. Journal of immunology (Baltimore, Md. : 1950) 6 31175160
2019 The Interaction between NKAP and HDAC3 Is Critical for T Cell Maturation. ImmunoHorizons 6 31387873
2019 NKAP functions as an oncogene in Ewing sarcoma cells partly through the AKT signaling pathway. Experimental and therapeutic medicine 5 31555387
2024 From phenotype to mechanism: Prenatal spectrum of NKAP mutation-related disorder and its pathogenesis inducing congenital heart disease. Journal of cellular and molecular medicine 3 38647244
2022 LncRNA LINC00707 serves as a sponge of miR-382-5p to alleviate lipopolysaccharide (LPS)-induced WI-38 cell injury through upregulating NKAP in infantile pneumonia. Autoimmunity 2 35593504
2025 NKAP overexpression promotes gastric cancer immune escape by inducing IL-10 secretion from mature dendritic cells during anti-PD-L1 therapy. Journal of gastrointestinal oncology 1 40950333
2024 GRAS1 non-coding RNA protects against DNA damage and cell death by binding and stabilizing NKAP. bioRxiv : the preprint server for biology 1 38645172
2026 Deleterious NKAP Mutations Are Associated with Musculoskeletal Abnormalities in Hemizygous Males and Skewed X Chromosome Inactivation in Heterozygous Females. International journal of molecular sciences 0 41828556
2026 Marfanoid phenotype with intellectual disability associated with NKAP mutation: a case report. Journal of medical case reports 0 41917976