Affinage

NSRP1

Nuclear speckle splicing regulatory protein 1 · UniProt Q9H0G5

Length
558 aa
Mass
66.4 kDa
Annotated
2026-06-10
11 papers in source corpus 8 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

NSRP1 (NSrp70/CCDC55) is a nuclear speckle-resident regulator of alternative splicing that controls splice-site selection of diverse pre-mRNA targets to govern cell fate, development, and signaling (PMID:21296756, PMID:34037780). It localizes to nuclear speckles and physically associates with the SR proteins SC35 and ASF/SF2 through its 290–471 aa region, while its N-terminal RRM-containing region (107–161 aa) is required for splicing activity, as demonstrated on CD44, Tra2β1, and Fas minigene reporters (PMID:21296756). Correct nuclear targeting depends on a C-terminal nuclear localization signal (aa 531–540, including critical residue Val532), and disruption of this NLS mislocalizes the protein to the cytosol (PMID:21296756, PMID:38808951). Through target-specific splicing control, NSRP1 promotes inclusion of skipped exons in NUMB pre-mRNA to drive TGFβ receptor 1 degradation and suppress TGFβ/SMAD-mediated EMT and breast cancer metastasis (PMID:35568738), and it regulates NSD2 exon 2 inclusion to restrain IFN signaling and CDK4/6 inhibitor resistance (PMID:39667501). NSRP1 is essential for early embryogenesis, with mouse knockout abolishing progeny and Xenopus knockdown blocking gastrulation and dorsal mesoderm induction (PMID:21296756, PMID:27638308), and conditional deletion in thymocytes impairs T cell maturation by dysregulating splicing of factors including SRSF1 (PMID:34037780). Biallelic loss-of-function variants that ablate the C-terminal NLS cause an NSRP1-associated neurodevelopmental disorder (PMID:34385670, PMID:38808951).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2011 High

    Established NSRP1 as a bona fide splicing regulator by defining where it acts (nuclear speckles), which factors it partners with, and which protein regions drive localization, binding, and splicing activity.

    Evidence Co-IP, confocal co-localization, minigene splicing reporters, deletion mutagenesis in cells

    PMID:21296756

    Open questions at the time
    • Endogenous physiological splicing targets not yet identified
    • Direct RNA binding by the N-terminal region not demonstrated
    • Structural basis of SC35/ASF-SF2 interaction unresolved
  2. 2011 High

    Demonstrated organismal necessity of NSRP1 by showing knockout mice fail to produce embryos, placing it among genes essential for early development.

    Evidence Constitutive gene knockout in mice

    PMID:21296756

    Open questions at the time
    • Developmental stage of lethality not pinpointed
    • Splicing targets responsible for the embryonic requirement unknown
  3. 2015 Medium

    Expanded the interactome beyond splicing factors to nuclear and neuronal partners, raising the possibility of roles outside canonical spliceosome assembly.

    Evidence Yeast two-hybrid screen, GST pull-down, confocal co-localization in neuronal cells

    PMID:26475744

    Open questions at the time
    • No functional consequence assigned to RanBP9/DISC1/CNR1 interactions
    • Single lab without reciprocal endogenous validation
    • Relevance to splicing function unclear
  4. 2016 Medium

    Showed the developmental requirement is conserved and mechanistically tied to mesoderm patterning, linking NSRP1 loss to defective gastrulation and dorsal mesoderm gene expression.

    Evidence Morpholino knockdown and activin A animal cap assays in Xenopus

    PMID:27638308

    Open questions at the time
    • Splicing targets driving the gastrulation phenotype not identified
    • Morpholino specificity not cross-validated genetically
  5. 2021 High

    Connected NSRP1 splicing activity to a defined cellular program by showing thymocyte-stage-specific function in T cell maturation via splicing of factors including SRSF1.

    Evidence CD4Cre conditional knockout mouse, RNA-seq splicing profiling, flow cytometry

    PMID:34037780

    Open questions at the time
    • Direct binding to SRSF1 transcript not shown
    • Causal splicing event linking to TCR signaling defect not isolated
  6. 2021 Medium

    Tied NSRP1 to human disease by showing biallelic last-exon frameshift variants escape NMD and remove the NLS, defining NLS loss as the pathogenic mechanism of an NSRP1 neurodevelopmental disorder.

    Evidence Exome sequencing, mutant transcript analysis, NMD-escape and NLS-loss prediction

    PMID:34385670

    Open questions at the time
    • No in-cell validation of mislocalization in this study
    • Genotype-phenotype relationship across patients not established
  7. 2022 High

    Provided a complete molecular mechanism in cancer by showing NSRP1 directly binds NUMB pre-mRNA to promote exon inclusion, driving TβR1 degradation and suppressing TGFβ-driven EMT and metastasis.

    Evidence RNA-seq, in vitro splicing assays, RNA pull-down, RIP, migration/invasion and in vivo assays, proteomics

    PMID:35568738

    Open questions at the time
    • RNA sequence element bound by NSRP1 not mapped
    • Generality of TβR1 lysosomal degradation across cell types untested
  8. 2024 Medium

    Validated the disease NLS mechanism experimentally by showing the p.Val532Glu missense variant mislocalizes NSRP1 to the cytosol, confirming Val532 is required for nuclear targeting.

    Evidence GFP-tagged WT vs mutant NSRP1 transfection in HEK293T, confocal microscopy

    PMID:38808951

    Open questions at the time
    • Effect of mislocalization on splicing output not measured
    • Single cell-line localization assay
  9. 2024 Medium

    Extended target-specific splicing control to immune signaling and drug resistance by showing NSRP1 regulates NSD2 exon 2 inclusion to restrain IFN signaling and CDK4/6 inhibitor resistance.

    Evidence NSRP1 knockdown/overexpression in MCF7, RNA-seq, splicing analysis, CDK4/6 inhibitor sensitivity assays

    PMID:39667501

    Open questions at the time
    • Direct binding to NSD2 pre-mRNA not demonstrated
    • Single cell line; clinical relevance untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • The RNA sequence determinants and global rules by which NSRP1 selects splice sites, and how its diverse target programs (NUMB, SRSF1, NSD2) are coordinated across tissues, remain undefined.
  • No consensus binding motif defined
  • No structural model of NSRP1 on RNA or with SR proteins
  • Tissue-specific target selection mechanism unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 4 GO:0003723 RNA binding 1
Localization
GO:0005634 nucleus 2 GO:0005654 nucleoplasm 1
Pathway
R-HSA-8953854 Metabolism of RNA 4 R-HSA-1266738 Developmental Biology 3

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 NSrp70 (NSRP1/CCDC55) localizes to nuclear speckles and physically interacts with splicing factors SC35 and ASF/SF2; it modulates alternative splice site selection in vivo using CD44, Tra2β1, and Fas minigene reporters. The region spanning amino acids 290–471 is critical for speckle localization and SC35/ASF/SF2 binding, the N-terminal region (107–161) is essential for pre-mRNA splicing activity, and the C-terminal 10 amino acids (531–540), including RD at positions 536–537, constitute a novel nuclear localization signal. Co-immunoprecipitation, co-localization by confocal microscopy, minigene splicing reporter assays, deletion mutagenesis, NSrp70 knockout mice Nucleic acids research High 21296756
2011 Knockout of the Nsrp1 (NSrp70) gene in mice results in a complete lack of progeny including fetal embryos, establishing that NSrp70 is essentially required for early embryonic development. Gene knockout in mice (loss-of-function) Nucleic acids research High 21296756
2015 NSRP1 (CCDC55) physically interacts with RanBP9 and DISC1, and co-localizes with RanBP9 in the nucleus of human neuronal cells. NSRP1 also interacts with the cannabinoid receptor CNR1 and cannabinoid receptor-interacting protein CNRIP1a, as demonstrated by yeast two-hybrid screening and GST pull-down assay. Yeast two-hybrid screening, GST pull-down assay, confocal laser scanning microscopy Neuroscience Medium 26475744
2016 Knockdown of NSrp70 in Xenopus embryos blocks gastrulation and convergent extension, and animal cap assays with activin A treatment show NSrp70 is required for dorsal mesoderm induction, with loss causing downregulation of dorsal mesoderm-specific genes. Morpholino knockdown in Xenopus, animal cap assay with activin A treatment, phenotypic readout of gastrulation and mesoderm markers Biochemical and biophysical research communications Medium 27638308
2021 NSrp70 is selectively expressed in developing thymocytes and is highest at the double-positive (DP) stage. Conditional knockout (CD4Cre-driven Nsrp1 cKO) causes severe defects in T cell maturation to single-positive thymocytes due to insufficient TCR signaling and dysregulated cell growth/death. NSrp70 controls thymocyte cell cycle and survival by regulating alternative splicing of various RNA splicing factors including the oncogenic splicing factor SRSF1. Conditional knockout mouse (CD4Cre), RNA-seq and splicing profiling, flow cytometry of thymic subsets Nucleic acids research High 34037780
2021 Biallelic loss-of-function frameshift variants in NSRP1 causing premature termination in the last exon are predicted to escape NMD and result in loss of the C-terminal nuclear localization signal required for NSRP1 function, establishing that NLS loss is a pathogenic mechanism in NSRP1-associated neurodevelopmental disorder. Exome sequencing, molecular analysis of mutant transcripts, prediction of NMD escape and NLS loss Genetics in medicine Medium 34385670
2022 NSrp70 suppresses breast cancer metastasis by promoting inclusion of skipped exons in NUMB pre-mRNA (inhibiting skipped-exon alternative splicing of NUMB), leading to increased TGFβ receptor 1 (TβR1) degradation via the lysosome pathway and suppression of TGFβ/SMAD-mediated EMT. Direct binding between NSrp70 and NUMB pre-mRNA was confirmed by RNA pull-down and RNA immunoprecipitation. RNA-seq with AS bioinformatics, in vitro splicing assays, RNA pull-down, RNA immunoprecipitation, in vitro and in vivo functional assays (migration/invasion), proteomic screen Oncogene High 35568738
2024 A missense variant p.Val532Glu in the nuclear localization signal of NSRP1 causes mislocalization of NSRP1 to the cytosol in HEK293T cells, confirming that the NLS (around Val532) is required for correct nuclear targeting of NSRP1. HEK293T transfection with GFP-tagged wild-type or mutant NSRP1, confocal microscopy for subcellular localization American journal of medical genetics. Part A Medium 38808951
2024 NSRP1 knockdown in MCF7 breast cancer cells activates the IFN signaling pathway and elevates IRPS gene expression; mechanistically, NSRP1 controls alternative splicing of NSD2 such that its knockdown increases inclusion of NSD2 exon 2, which elevates NSD2 protein expression and thereby activates the IFN signaling pathway, conferring CDK4/6 inhibitor resistance. NSRP1 knockdown and overexpression in MCF7 cells, RNA-seq, alternative splicing analysis, CDK4/6 inhibitor sensitivity assays The Journal of biological chemistry Medium 39667501

Source papers

Stage 0 corpus · 11 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 NSrp70 is a novel nuclear speckle-related protein that modulates alternative pre-mRNA splicing in vivo. Nucleic acids research 33 21296756
2021 Biallelic loss-of-function variants in the splicing regulator NSRP1 cause a severe neurodevelopmental disorder with spastic cerebral palsy and epilepsy. Genetics in medicine : official journal of the American College of Medical Genetics 16 34385670
2012 CCDC-55 is required for larval development and distal tip cell migration in Caenorhabditis elegans. Mechanisms of development 11 22285439
2021 NSrp70 is a lymphocyte-essential splicing factor that controls thymocyte development. Nucleic acids research 9 34037780
2024 Downregulation of the splicing regulator NSRP1 confers resistance to CDK4/6 inhibitors via activation of interferon signaling in breast cancer. The Journal of biological chemistry 8 39667501
2022 NSrp70 suppresses metastasis in triple-negative breast cancer by modulating Numb/TβR1/EMT axis. Oncogene 7 35568738
2015 The CCDC55 couples cannabinoid receptor CNR1 to a putative DISC1 schizophrenia pathway. Neuroscience 7 26475744
2016 NSrp70 is significant for embryonic growth and development, being a crucial factor for gastrulation and mesoderm induction. Biochemical and biophysical research communications 5 27638308
2014 Aberrant proteomic expression of NSRP70 and its clinical implications and connection to the transcriptional level in adult acute leukemia. Leukemia research 4 25176346
2024 Comprehensive Atlas of Alternative Splicing Reveals NSRP1 Promoting Adipogenesis through CCDC18. International journal of molecular sciences 2 38474122
2024 A milder form of NSRP1-associated neurodevelopmental disorder, caused by a missense variant in the nuclear localization signal. American journal of medical genetics. Part A 1 38808951

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