SNU13

SNU13 is a highly conserved RNA-binding protein that serves as a core component of box C/D small nucleolar ribonucleoprotein particles (snoRNPs) and is present in the nucleus. It is encoded by the SNU13 gene in many eukaryotes and has orthologs across yeasts, plants, and animals. In budding yeast, Snu13p is a key snoRNP component involved in ribosomal RNA maturation.

Functionally, SNU13 binds to the K-turn motif of box C/D snoRNAs and acts as a molecular scaffold that recruits essential components of the snoRNP, including fibrillarin, NOP56, and NOP58, to form an active complex. Through this assembly, box C/D snoRNPs guide site-specific 2'-O-methylation of ribosomal RNA and participate in snoRNA processing.

Structurally, SNU13 belongs to the L7Ae family of RNA-binding proteins and recognizes RNA structural motifs rather than long sequences. Structural studies show a compact fold that makes specific contacts with kink-turn RNA, enabling stable interaction with the snoRNA and proper assembly of the snoRNP core.

Localization and evolution are marked by nucleolar confinement, with additional presence in nuclear subdomains such as Cajal bodies, reflecting its role in snoRNA maturation and ribosome biogenesis. SNU13 is highly conserved, with archaeal L7Ae as a distant homolog, highlighting the ancient and widespread role of kink-turn recognition in RNP assembly.

Clinical relevance is limited to indirect effects: perturbations of snoRNP components, including SNU13, can disrupt rRNA modification and ribosome biogenesis, potentially impacting cellular growth and fitness.