RNPs

Ribonucleoproteins (RNPs) are complexes composed of RNA molecules bound to one or more proteins. They participate in almost every aspect of RNA metabolism, including transcription, processing, transport, translation, and surveillance. In cells, RNA often serves as a scaffold and functional component, while proteins provide specificity, catalytic activity, and regulation.

Common examples include small nuclear RNPs (snRNPs), which form the core of the spliceosome that removes introns from pre-mRNA; small nucleolar RNPs (snoRNPs) that guide chemical modifications of ribosomal RNA; and the telomerase RNP, which carries an RNA template with a reverse transcriptase to extend chromosome ends. The ribosome itself is a large RNP complex consisting of rRNA and multiple proteins. Other RNPs include heterogeneous nuclear RNPs (hnRNPs) involved in pre-mRNA processing and transport, and Argonaute-containing RNPs in RNA silencing that use small RNAs as guides.

RNP assembly is often coordinated with cellular compartments such as the nucleus and nucleolus and involves dedicated chaperones and assembly factors. For example, the SMN complex facilitates snRNP biogenesis. RNPs can be dynamic, assembling and disassembling as needed, with activity regulated by post-translational modifications and cellular signaling.

Disruptions to RNP biogenesis or function are linked to disease, including spinal muscular atrophy, certain cancers, and other RNA processing disorders. Research on RNPs employs methods such as immunoprecipitation, crosslinking and immunoprecipitation, RNA sequencing, and structural techniques to study composition, interactions, and function.