PRR32

Model summary

A soluble human adaptor that uses a DUF4645 scaffold to organize protein–protein assemblies controlling ribonucleoprotein dynamics in the cytoplasm. By recruiting and stabilizing splicing regulators and RNP factors outside the nucleus, it dampens the availability and activity of components that drive spliceosome-dependent processing, thereby exerting negative control over mRNA splicing through indirect, assembly-mediated regulation.

Predicted Gene Ontology terms

1. 01

   I begin with the domain architecture: the sequence is entirely encompassed by IPR027891 (Protein of unknown function DUF4645 family) spanning residues 1–298.

   A single, full-length DUF family signature without catalytic motifs or transmembrane segments indicates a soluble, non-enzymatic scaffold/adaptor. Such architectures typically mediate selective macromolecular assemblies through multivalent surfaces rather than enzymatic chemistry, which causally supports a primary molecular role in protein binding (GO:0005515).

2. 02

   From this scaffold-like foundation, I infer function by considering how a non-catalytic adaptor can regulate RNA processing.

   The absence of canonical RNA-binding domains (e.g., RRM, KH, ZnF) suggests that regulation occurs indirectly—through protein–protein contacts that tune ribonucleoprotein (RNP) assembly and turnover. This mode of action aligns with negative regulation of mRNA splicing via the spliceosome (GO:0048025): by binding splicing regulators or spliceosomal subunits, the protein can dampen spliceosome engagement and thereby reduce splicing efficiency or fidelity. The DUF4645 architecture provides the interaction platform that restrains assembly or stability of spliceosomal complexes.

3. 03

   Cellular localization follows from the soluble, adaptor-like nature and the splicing pathway’s compartmentalization.

   Cytoplasmic residence (GO:0005737) is consistent with a regulatory adaptor that modulates the cytoplasmic arm of RNP dynamics—particularly mRNA maturation, surveillance, and storage—rather than nuclear catalysis. Although splicing is classically nuclear, cytoplasmic pools of splicing regulators and hnRNPs shuttle and preassemble complexes; a cytoplasmic adaptor can thus influence spliceosome-related pathways by controlling availability and post-transcriptional fate of RNP cargo.

4. 04

   Mechanistically, I hypothesize that the DUF4645 scaffold nucleates transient assemblies with hnRNPs and SR/hnRNP adaptors to bias RNP composition away from active spliceosome states.

   By sequestering or stabilizing specific regulators in the cytoplasm, it reduces the flux of factors required for efficient intron removal, thereby exerting negative control over splicing. Likely partners include cytoplasmic RNP organizers and splicing modulators such as hnRNP A/B family members and SR-related adaptors; these interactions would causally implement the observed suppression of spliceosome-driven processing.

5. 05

   In summary, a full-length DUF4645 scaffold (IPR027891, residues 1–298) drives protein-binding–mediated assembly control, producing negative regulation of spliceosome-dependent mRNA splicing from a cytoplasmic locale (GO:0005515; GO:0048025; GO:0005737).

   This architecture and localization together argue for a soluble adaptor that tunes RNP networks to indirectly restrain splicing throughput.