Affinage

SNRPD3

Small nuclear ribonucleoprotein Sm D3 · UniProt P62318

Length
126 aa
Mass
13.9 kDa
Annotated
2026-06-10
14 papers in source corpus 11 papers cited in narrative 11 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

SNRPD3 (SmD3) is a core Sm-ring protein of the spliceosome that contributes directly to snRNP function and is essential for cell viability (PMID:25897024, PMID:34703654). Within U1 snRNP, SmD3 residues Glu37/Asp38 contact the U1-C (Yhc1) residue Arg21 to stabilize the U1 snRNP–5' splice site complex, and its Ser-Asn-Arg RNA-binding triad engages snRNA redundantly with the equivalent triad of SmB, placing SmD3 function at the U1–U2 snRNP interface (PMID:24497193, PMID:25897024). SmD3 levels regulate the abundance of U4 and U5 snRNAs and thereby control intronic snoRNA biogenesis and intron lariat accumulation while still supporting pre-mRNA splicing (PMID:22869524). SmD3 carries symmetrical dimethylarginine modifications on its C-terminal arginines; these are dispensable for snRNP assembly and nuclear import (PMID:16236255) but, when blocked by PRMT5 inhibition or loss of the adapter pICln, cause SmD3 to be detained on chromatin together with incompletely processed transcripts, indicating a role in homeostatic chromatin dissociation and RNA-processing completion [PMID:bio_10.1101_2024.08.09.607355]. In cancer, SNRPD3 forms a complex with MYCN and PRMT5 that maintains balanced alternative splicing of cell-cycle regulators required for neuroblastoma growth (PMID:38049564), and a somatic G96V substitution rewires DNM1L/DRP1 splicing to drive mitochondrial hyperfragmentation and hypoxia resistance (PMID:38241813); SNRPD3 also promotes endometrial cancer progression by preventing SREBF1 intron retention (PMID:41924775).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2004 Medium

    Established that SmD3 carries symmetrical dimethylarginine on specific C-terminal residues and that this modification is clinically relevant as a target of anti-Sm autoantibodies in lupus.

    Evidence Peptide ELISA comparing dimethylated vs. unmodified SmD3 peptides against SLE patient sera

    PMID:15642139

    Open questions at the time
    • Antibody-binding assay rather than direct biochemical mapping of the modification
    • Functional role of the sDMA modification not addressed
  2. 2005 Medium

    Resolved whether the C-terminal arginine methylation is needed for the canonical Sm-protein lifecycle, showing it is dispensable for snRNP assembly and nuclear import.

    Evidence Arginine-to-leucine mutagenesis of SmD3 with transient expression and assembly/import readouts

    PMID:16236255

    Open questions at the time
    • Did not identify what the modification IS required for
    • Single lab, single readout system
  3. 2012 Medium

    Linked SmD3 dosage to noncoding RNA biogenesis, showing haploinsufficiency selectively reduces U4/U5 snRNAs, snoRNAs, and intron lariats while sparing bulk splicing.

    Evidence Promoter-trap haploinsufficient CHO cells with Northern blot quantification of snRNAs, snoRNAs, and lariats

    PMID:22869524

    Open questions at the time
    • Mechanism by which SmD3 dosage selectively limits U4/U5 unclear
    • Single cell-line model
  4. 2014 High

    Defined a direct structural role for SmD3 in spliceosome activation by mapping the Glu37/Asp38–Yhc1 Arg21 contact that fortifies the U1–5'SS complex.

    Evidence Structure-guided mutagenesis of yeast SmD3 and Yhc1 with synthetic lethality and prp28 bypass genetic tests

    PMID:24497193

    Open questions at the time
    • Demonstrated in yeast; human U1 interface inferred
    • Does not address SmD3 contribution beyond U1
  5. 2015 High

    Established that SmD3's RNA-binding triad engages snRNA redundantly with SmB and that SmD3 function lies at the U1–U2 snRNP interface.

    Evidence Systematic alanine mutagenesis of SmD3 RNA-binding residues with genetic interaction tests against U1/U2 components in yeast

    PMID:25897024

    Open questions at the time
    • Redundancy mapped genetically, not structurally resolved in the assembled spliceosome
    • Yeast system
  6. 2019 Medium

    Uncovered crosstalk between the spliceosome and the ribosome via a physical SmD3–RpL18 interaction controlling both spliceosome and ribosome subunit levels.

    Evidence LC-MS/MS interactome and genetic manipulation in Drosophila and S2 cells

    PMID:30921522

    Open questions at the time
    • Limited biochemical follow-up on the interaction
    • Human relevance not tested
  7. 2021 Medium

    Demonstrated that SNRPD3 is essential for tumor cell viability, with p53-dependent senescence/mitotic catastrophe upon knockdown.

    Evidence CRISPRi and inducible shRNA knockdown with overexpression rescue in human and murine cell lines

    PMID:34703654

    Open questions at the time
    • Specific splicing targets mediating viability not defined
    • p53-dependence mechanism not resolved
  8. 2023 Medium

    Placed SNRPD3 in an oncogenic MYCN–SNRPD3–PRMT5 complex that tunes alternative splicing of cell-cycle regulators to support neuroblastoma growth.

    Evidence Co-IP of MYCN–SNRPD3 and SNRPD3–PRMT5, RNA-seq splicing analysis, knockdown/overexpression and PRMT5 inhibitor treatment

    PMID:38049564

    Open questions at the time
    • Direct vs. bridged nature of MYCN–SNRPD3 binding not dissected
    • Single tumor type
  9. 2024 Medium

    Showed that a somatic SNRPD3 G96V mutation rewires DNM1L/DRP1 splicing to drive mitochondrial fragmentation and hypoxia resistance.

    Evidence RNA-seq splicing analysis in wild-type vs. G96V cells under hypoxia, mitochondrial imaging, and Mdivi-1 rescue

    PMID:38241813

    Open questions at the time
    • How a single substitution alters DNM1L splice-site selection mechanistically unknown
    • Single study
  10. 2024 Medium

    Defined the functional requirement for arginine methylation, showing PRMT5/pICln loss detains SNRPD3 on chromatin with unprocessed transcripts, linking the modification to homeostatic chromatin dissociation.

    Evidence Spike-in fractionated transcriptomics and proteomics with PRMT5 inhibition, pICln knockdown, and arginine-mutant Sm controls (preprint)

    PMID:bio_10.1101_2024.08.09.607355

    Open questions at the time
    • Preprint, not yet peer-reviewed
    • Direct measurement on SNRPD3 inferred largely from SNRPB controls
  11. 2026 Medium

    Extended SNRPD3's pro-tumorigenic splicing role to endometrial cancer via prevention of SREBF1 intron retention driving lipid metabolism.

    Evidence SNRPD3 knockdown/overexpression with RNA-seq, SREBF1 epistasis, and xenograft/PDX models

    PMID:41924775

    Open questions at the time
    • How SNRPD3 selectively controls SREBF1 intron retention not defined
    • Generality across cancers unclear

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how SNRPD3's general Sm-ring function is reconciled with its selective control of specific splicing events (DNM1L, SREBF1, BIRC5/CDK10) that drive distinct cancer phenotypes.
  • No structural model linking SmD3 to selective intron retention/exon choice
  • Mechanism connecting arginine methylation status to transcript-specific outcomes unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 2 GO:0005198 structural molecule activity 2
Localization
GO:0005634 nucleus 2 GO:0005694 chromosome 1
Pathway
R-HSA-8953854 Metabolism of RNA 3 R-HSA-74160 Gene expression (Transcription) 2
Partners
CLNS1AMYCNPRMT5RPL18SNRPBSNRPC
Complex memberships
MYCN-SNRPD3-PRMT5 complexSm core ringU1 snRNP

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 Symmetrical dimethylarginine (sDMA) post-translational modification of SmD3 C-terminal arginines is NOT required for snRNP assembly or nuclear transport; mutating the modified arginines to leucines in SmD3 did not interfere with assembly or nuclear import of the transiently expressed variant. Site-directed mutagenesis (arginine-to-leucine substitutions) of SmD3, transient expression, and assessment of snRNP assembly and nuclear transport Biochemical and biophysical research communications Medium 16236255
2004 SmD3 carries symmetrical dimethylarginine at specific C-terminal residues (including position 112), and this modification is an essential component of a major autoepitope recognized by a subpopulation of anti-Sm antibodies in SLE patients. Immobilized synthetic peptide ELISA using dimethylated vs. unmodified SmD3 peptides to map autoantibody reactivity Arthritis research & therapy Medium 15642139
2012 Haploinsufficiency of SmD3 (one allele disrupted by proviral insertion) reduces snRNA U4 and U5 levels, decreases snoRNA expression and snoRNA-containing intron lariat abundance, implicating SmD3 as a critical regulator of intronic noncoding RNA biogenesis upstream of metabolic stress response pathways, while still supporting pre-mRNA splicing. Retroviral promoter trap mutagenesis to generate SmD3 haploinsufficient CHO cell lines; Northern blot and quantitative analysis of snRNAs, snoRNAs, and intron lariats Molecular and cellular biology Medium 22869524
2014 Yeast SmD3 residues Glu37/Asp38 contact Yhc1 (yeast U1-C) Arg21 to fortify the U1 snRNP–5' splice site complex; mutations at this interface synergize with mud2Δ and bypass the essential DEAD-box ATPase Prp28, consistent with destabilization of U1•5'SS interaction. Structure-guided mutagenesis of yeast SmD3 and Yhc1 combined with genetic interaction (synthetic lethality/suppression) assays in yeast Nucleic acids research High 24497193
2015 The RNA-binding triad of SmD3 (Ser-Asn-Arg) participates in snRNA binding with built-in redundancy with SmB's triad; simultaneous mutation of Asn or Arg in both SmD3 and SmB is lethal. SmD3 C-terminal truncations and RNA-site mutations are lethal in cells lacking U2 snRNP subunit Lea1, placing SmD3 function at the U1–U2 snRNP interface. Systematic alanine mutagenesis of SmD3 RNA-binding residues combined with synthetic lethality/genetic interaction assays (mud2Δ, lea1Δ, mud1Δ, nam8Δ) in yeast RNA (New York, N.Y.) High 25897024
2019 Drosophila SmD3 binds ribosomal protein RpL18 (a large ribosome subunit regulator), as identified by LC-MS/MS, and controls both spliceosome and ribosome subunit expression levels and function via RpL18, revealing a physical and functional crosstalk between the spliceosome and ribosome. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification of SmD3-interacting proteins; genetic manipulation in Drosophila and in vitro assays in Schneider 2 cells FASEB journal Medium 30921522
2023 MYCN directly binds SNRPD3 protein and the protein arginine methyltransferase PRMT5, leading to increased SNRPD3 arginine methylation; this MYCN–SNRPD3–PRMT5 complex maintains a balanced range of alternative splicing (including of cell cycle regulators BIRC5 and CDK10) required for neuroblastoma cell growth. Co-immunoprecipitation (MYCN–SNRPD3 and SNRPD3–PRMT5 interaction), RNA-seq for splicing analysis, SNRPD3 knockdown/MYCN overexpression functional assays, PRMT5 inhibitor (JNJ-64619178) treatment Oncogene Medium 38049564
2024 The cancer-associated SNRPD3 G96V substitution confers resistance to hypoxia by altering splicing of DNM1L mRNA (encoding DRP1), leading to excessive mitochondrial fragmentation; DRP1 inhibitor Mdivi-1 reverses the fragmentation and attenuates hypoxia resistance in mutant cells. RNA-seq splicing analysis in wild-type vs. G96V cells under hypoxia; mitochondrial morphology imaging; DRP1 inhibitor (Mdivi-1) treatment assay Biochemical and biophysical research communications Medium 38241813
2024 PRMT5 inhibition or knockdown of the PRMT5-SNRP adapter protein pICln causes SNRPD3 protein to be detained on chromatin together with incompletely processed polyadenylated transcripts (GRIPPs), indicating that PRMT5-mediated arginine methylation of Sm proteins including SNRPD3 is required for homeostatic chromatin dissociation and RNA processing completion. Nascent and total transcriptomics, spike-in controlled fractionated cell transcriptomics, fractionated cell proteomics; PRMT5 inhibition and pICln knockdown; inducible isogenic wild-type and arginine-mutant SNRPB as controls bioRxivpreprint Medium bio_10.1101_2024.08.09.607355
2021 CRISPRi knockdown of SNRPD3 in human tumor cells (A549, U251) induces apoptosis (in murine cells) or senescence/mitotic catastrophe depending on p53 status, and overexpression of SNRPD3 rescues cells from mitotic catastrophe, establishing SNRPD3 as essential for cell viability. CRISPRi knockdown, inducible shRNA expression, SNRPD3 overexpression rescue experiment in human and murine cell lines Molecular therapy. Nucleic acids Medium 34703654
2026 SNRPD3 promotes endometrial cancer cell proliferation, migration, and invasion by preventing intron retention in SREBF1 mRNA; silencing SNRPD3 increases SREBF1 intron retention, and SREBF1 depletion abolishes the proliferative and lipid-metabolic advantage conferred by SNRPD3 overexpression. SNRPD3 knockdown and overexpression in EC cell lines; RNA-seq/splicing analysis; xenograft and PDX tumor models; ASO-mediated silencing Biochemical and biophysical research communications Medium 41924775

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 Identification of a SmD3 epitope with a single symmetrical dimethylation of an arginine residue as a specific target of a subpopulation of anti-Sm antibodies. Arthritis research & therapy 59 15642139
1998 The Drosophila gene for antizyme requires ribosomal frameshifting for expression and contains an intronic gene for snRNP Sm D3 on the opposite strand. Molecular and cellular biology 34 9488472
2005 Improved serological differentiation between systemic lupus erythematosus and mixed connective tissue disease by use of an SmD3 peptide-based immunoassay. Clinical and diagnostic laboratory immunology 22 15642993
2014 Structure-function analysis of the Yhc1 subunit of yeast U1 snRNP and genetic interactions of Yhc1 with Mud2, Nam8, Mud1, Tgs1, U1 snRNA, SmD3 and Prp28. Nucleic acids research 20 24497193
2019 Small ribonucleoprotein particle protein SmD3 governs the homeostasis of germline stem cells and the crosstalk between the spliceosome and ribosome signals in Drosophila. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 18 30921522
2012 SmD3 regulates intronic noncoding RNA biogenesis. Molecular and cellular biology 18 22869524
2015 Structure-function analysis and genetic interactions of the Yhc1, SmD3, SmB, and Snp1 subunits of yeast U1 snRNP and genetic interactions of SmD3 with U2 snRNP subunit Lea1. RNA (New York, N.Y.) 17 25897024
2021 Arabidopsi s Spliceosome Factor SmD3 Modulates Immunity to Pseudomonas syringae Infection. Frontiers in plant science 14 34925413
2023 MYCN and SNRPD3 cooperate to maintain a balance of alternative splicing events that drives neuroblastoma progression. Oncogene 10 38049564
2002 P elements inserted in the vicinity of or within the Drosophila snRNP SmD3 gene nested in the first intron of the Ornithine Decarboxylase Antizyme gene affect only the expression of SmD3. Genetics 10 12072471
2021 Non-targeting control for MISSION shRNA library silences SNRPD3 leading to cell death or permanent growth arrest. Molecular therapy. Nucleic acids 9 34703654
2005 The symmetrical dimethylarginine post-translational modification of the SmD3 protein is not required for snRNP assembly and nuclear transport. Biochemical and biophysical research communications 6 16236255
2024 Cancer-associated SNRPD3 mutation confers resistance to hypoxia, which is attenuated by DRP1 inhibition. Biochemical and biophysical research communications 2 38241813
2026 SNRPD3 promotes endometrial cancer progression via regulating SREBF1 intron retention. Biochemical and biophysical research communications 0 41924775

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