SNRNP25

SNRNP25 is a structural subunit of the human U11 snRNP of the minor (U12-dependent) spliceosome, where it specifically recognizes U11 snRNA and is bridged to SNRNP48 via PDCD7 at the distal end of the particle, contributing to U12-type 5' splice site recognition (PMID:39809272). Loss of Snrnp25 in mice causes peri-implantation lethality, indicating it is essential for early mammalian development (PMID:40399475). A recurrent LRP1-SNRNP25 fusion gene in osteosarcoma drives cell invasion and migration through activation of the pJNK/37LRP/MMP2 signaling pathway (PMID:25300797, PMID:38678020).

1. 2014 Medium

   Identification of a recurrent LRP1-SNRNP25 fusion gene in osteosarcoma established that SNRNP25 participates in oncogenic gene fusions and that the fusion product promotes tumor cell migration and invasion.

   Evidence Transcriptome sequencing, RT-PCR, FISH validation, and overexpression migration/invasion assays in SAOS-2 osteosarcoma cells

   PMID:25300797

   Open questions at the time

   • Mechanism involves a fusion protein, not wild-type SNRNP25, so the contribution of SNRNP25 sequences to oncogenic activity is unclear
   • No loss-of-function study of the fusion was performed
   • Downstream signaling pathway of the fusion was not characterized
2. 2024 Medium

   Delineation of the signaling mechanism downstream of the LRP1-SNRNP25 fusion showed it physically interacts with pJNK and 37LRP to activate MMP2-dependent invasion, resolving the pathway through which the fusion drives osteosarcoma aggressiveness.

   Evidence Co-IP–mass spectrometry, epistasis experiments with JNK inhibitor SP600125 and 37LRP siRNA, Transwell/scratch assays, and in vivo xenograft validation

   PMID:38678020

   Open questions at the time

   • The contribution of SNRNP25 exon 2 sequences versus LRP1 exon 8 sequences to signaling activation has not been dissected
   • No structural information on the fusion protein
   • Endogenous expression levels and clinical penetrance of the fusion remain limited to small patient cohorts
3. 2025 High

   Cryo-EM structures of the human U11 snRNP revealed for the first time the precise architectural role of SNRNP25: it directly recognizes U11 snRNA and is positioned at the distal end of the particle, bridged to SNRNP48 by PDCD7, establishing its function in minor spliceosome assembly.

   Evidence Cryo-EM reconstruction of apo and substrate-bound 13-subunit human U11 snRNP

   PMID:39809272

   Open questions at the time

   • The specific RNA contacts made by SNRNP25 have not been mutationally validated
   • Functional consequences of SNRNP25 depletion on U12-type intron splicing efficiency have not been measured in human cells
   • No structure of the U11/U12 di-snRNP with SNRNP25 in the context of splice site recognition
4. 2025 Medium

   Genetic deletion mapping in mice identified Snrnp25 as the strongest candidate gene for peri-implantation lethality, demonstrating that minor spliceosome function is essential for the earliest stages of mammalian development.

   Evidence Molecular deletion mapping, sequence analysis, and expression profiling of the Hbab2(th) deletion spanning the Snrnp25 locus in mouse

   PMID:40399475

   Open questions at the time

   • Lethality has not been confirmed by targeted Snrnp25 knockout or rescue experiment
   • Other genes within the deletion interval have not been fully excluded
   • The specific splicing defects underlying embryonic lethality are unknown

• It remains unknown how SNRNP25 depletion affects global U12-type intron splicing, what structural determinants of SNRNP25 are critical for U11 snRNA binding, and whether SNRNP25 has functions outside the minor spliceosome.
• No transcriptome-wide splicing analysis upon SNRNP25 loss in mammalian cells
• No mutagenesis study of SNRNP25 RNA-binding residues
• Potential non-spliceosomal roles unexplored