SNRNP35

Model summary

A nuclear RNA-binding assembly factor that organizes spliceosomal ribonucleoprotein particles. Its central RNA-recognition module binds snRNA and pre-mRNA to nucleate and stabilize complexes that execute intron removal in both the major and minor splicing pathways. Operating primarily in the nucleoplasm with transient nucleolar residency for assembly and maturation, it scaffolds protein-protein and RNA-RNA contacts that build and maintain U1 and U11/U12 particles, thereby ensuring efficient pre-mRNA splicing.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The core of the protein is an RNA-recognition module: IPR034146 (snRNP35, RNA recognition motif, residues 47–137) sits within IPR000504 (RNA recognition motif domain, residues 51–129), and both are encompassed by IPR035979 (RNA-binding domain superfamily, residues 44–158) and IPR012677 (Nucleotide-binding alpha-beta plait domain superfamily, residues 46–159). This layered arrangement defines a canonical RRM fold that binds single-stranded RNA and organizes ribonucleoprotein assemblies. The N-to-C coverage of IPR051183 (U1 snRNP 70 kDa and U11/U12 snRNP 35 kDa family, residues 5–234) specifies membership in the U1/U11/U12 snRNP families, pinpointing a role in spliceosomal RNP complexes. The ordered layout—an N-terminal family signature leading into a central RRM core—causes high-affinity RNA engagement and multivalent protein contacts that together define assembly and stabilization of spliceosomal particles.

2. 02

   From this architecture, the molecular function resolves as twofold.

   The RRM-centered core directly confers RNA binding and RNP assembly, while the extended family signature and low-complexity flanks favor multivalent interfaces that mediate protein-protein contacts. This supports GO:0005515 protein binding and strongly implies RNA-binding capacity that underlies spliceosomal assembly and specificity.

3. 03

   These molecular activities drive the biological process of pre-mRNA splicing.

   The RRM fold and U1/U12-family signature together position the protein within the spliceosome pathway, where it contributes to intron definition and exon pairing. This mechanistically aligns with GO:0008380 RNA splicing: the RRM binds snRNA/pre-mRNA substrates, and the family context channels this binding into the specialized machinery that catalyzes intron removal.

4. 04

   Cellular localization follows from function and assembly dynamics.

   Spliceosomal assembly and catalysis occur in the nucleus, particularly within the nucleoplasm where active splicing factories reside, consistent with GO:0005654 nucleoplasm. The presence of snRNP biogenesis and RNP maturation pathways in the nucleolus explains observed nucleolar residency (GO:0005730 nucleolus), where transient assembly and quality control steps occur. The explicit association with the U12-type spliceosomal complex (GO:0005689) is explained by the U11/U12 family signature: this protein stabilizes the minor spliceosome that handles U12-type introns.

5. 05

   Putting these strands together, I infer a mechanism in which the RRM-centered module binds and organizes snRNA/pre-mRNA, while auxiliary surfaces recruit partner proteins to stabilize the U1 and U11/U12 spliceosomal particles.

   This dual engagement enables assembly and maintenance of both major and minor spliceosomes. Likely interaction partners include other U1/U12 snRNP components and auxiliary splicing factors that dock onto RRMs and low-complexity regions to coordinate splice-site recognition and catalytic activation.