RPP25L

Model summary

A nuclear RNA-binding adaptor that assembles and stabilizes ribonucleoprotein machines for noncoding RNA maturation. Its Alba-like core binds structured RNA and recruits partner proteins to organize assemblies that remove the 5′ leader of pre-tRNA and support nucleolar RNA-processing pathways. Operating within the nucleoplasm and nucleolus, it likely scaffolds endonuclease-containing complexes and snoRNP modules to coordinate precise RNA cleavage and folding.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The sequence is dominated by an Alba-like nucleic acid-binding core: IPR051958 (Alba-like nucleic acid-binding family, residues 1–136) spans essentially the full length, establishing the overall fold and oligomerization propensity characteristic of Alba proteins. Nested within this, IPR036882 (Alba-like domain superfamily, residues 24–125) and the more specific IPR002775 (DNA/RNA-binding protein Alba-like domain, residues 27–88) define a central β-strand-rich nucleic acid-binding module. The ordered layout—an N-to-C continuous Alba scaffold with a tightly bounded core—causes high-affinity binding to structured RNAs and single-stranded nucleic acids and promotes cooperative assembly with other RNA-processing factors. This architecture directly supports two molecular functions: RNA binding (GO:0003723) via the Alba nucleic acid-binding surface and protein binding (GO:0005515) via Alba-driven oligomerization and adaptor interfaces.

2. 02

   From this molecular foundation, I infer the biological role.

   Alba folds specialize in organizing ribonucleoprotein assemblies that mature noncoding RNAs. The explicit coupling of an Alba core to nuclear RNA-processing pathways points to participation in endonucleolytic maturation events. In particular, the pathway of tRNA 5'-leader removal (GO:0001682) is executed by ribonuclease P and allied complexes; an Alba-based RNA-binding adaptor is well-suited to chaperone pre-tRNA folding and recruit nuclease modules. The same logic extends to nucleolar pathways where small nucleolar RNPs guide rRNA and snoRNA maturation.

3. 03

   Cellular localization follows from the complex context.

   The nucleic acid-binding Alba scaffold is soluble and lacks transmembrane features, favoring nuclear and nucleolar residency. Its role in pre-tRNA and snoRNA pathways anchors it in the nucleoplasm (GO:0005654) and nucleolus (GO:0005730). The explicit association with multiple nuclear ribonucleoprotein assemblies—ribonuclease P complex (GO:0030677), sno(s)RNA-containing ribonucleoprotein complex (GO:0005732), and ribonuclease MRP complex (GO:0000172)—emerges naturally from the Alba-driven propensity to assemble and stabilize RNA-processing machines.

4. 04

   Mechanistically, I propose that the Alba-like domain binds and organizes structured RNA substrates and auxiliary proteins to form higher-order RNP assemblies.

   By stabilizing pre-tRNA architecture and docking endonuclease modules, it promotes precise 5'-leader excision. In the nucleolus, the same scaffold likely coordinates snoRNP-guided maturation and surveillance. This model predicts transient interactions with nucleolar assembly factors and RNA-processing nucleases. I hypothesize partners such as nucleolin and nucleophosmin as nucleolar organizers, and core components of RNase P/MRP pathways (e.g., POP1/POP5-like scaffolds and MRP subunits) that together choreograph RNA cleavage and folding within nuclear RNP hubs.