SRRM3

Model summary

A nuclear splicing scaffold that organizes pre-mRNA processing in human cells. It uses an N-terminal splicing-assembly module and a long serine/arginine-rich body to recruit and stabilize spliceosomal factors, while a C-terminal interaction region anchors the complex within nuclear speckles and surrounding nucleoplasm. By concentrating and coordinating splicing components, it promotes spliceosome assembly and modulates alternative splicing decisions central to gene expression.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The N-terminal third contains IPR047489 (Serine/arginine repetitive matrix protein 3, cwf21 domain, residues 34–101), which overlaps with IPR013170 (mRNA splicing factor Cwf21 domain, residues 55–100). This tandem annotation marks a conserved Cwf21-like module that nucleates spliceosomal assembly by binding other splicing factors and stabilizing pre-mRNA–protein complexes. The central body is encompassed by IPR052109 (Serine/arginine repetitive matrix protein family, residues 6–373), indicating an SR-rich, low-complexity scaffold typical of SRRM proteins that organize exon-definition assemblies. The C-terminus carries IPR029360 (Serine/arginine repetitive matrix protein, C-terminal domain, residues 528–579), a region known to mediate higher-order interactions and anchoring within nuclear speckles and spliceosomal subcomplexes. The ordered layout—an N-terminal Cwf21-like core, a long SR-rich scaffold, and a C-terminal interaction module—creates a multivalent assembly platform specialized for spliceosome function.

2. 02

   This architecture dictates molecular function as protein binding (GO:0005515).

   The Cwf21-like domains provide specific docking surfaces for spliceosomal proteins, while the SR-rich scaffold and C-terminal module expand binding valency and avidity. Such a scaffold does not catalyze chemistry directly; instead, it stabilizes and positions factors that execute splicing.

3. 03

   From this binding-centric mechanism, the biological process follows: mRNA splicing via the spliceosome (GO:0000398).

   The Cwf21 module seeds assembly of early spliceosomal complexes, and the SR-rich body supports exon-definition and splice-site pairing. The C-terminal domain consolidates interactions that maintain spliceosome integrity through assembly, catalysis, and disassembly cycles.

4. 04

   Cellular localization is inferred from function and composition.

   SR-rich splicing scaffolds concentrate in nuclear speckles and the surrounding nucleoplasm, consistent with a soluble nuclear environment that supplies and recycles splicing factors. Thus, the cellular component is the nucleoplasm (GO:0005654), with enrichment at speckle-associated spliceosomal assemblies.

5. 05

   Mechanistically, the protein acts as a modular organizer that couples pre-mRNA engagement with factor recruitment.

   The N-terminal Cwf21-like core initiates spliceosome assembly; the central SR-rich tract provides phase-separation-prone scaffolding that concentrates splicing determinants; and the C-terminal domain secures higher-order associations and nuclear retention. Likely interaction partners include core spliceosomal subunits and SR-family adaptors that together drive intron recognition and exon inclusion. I hypothesize associations with U2AF heterodimer components and SF3 complexes for early recognition, with SR proteins that tune exon definition, and with snRNP particles that execute catalysis—forming a dynamic network that biases alternative splicing outcomes in the nucleoplasm.