Small nucleolar RNA SNORD57

snoRNA U57 (also known as SNORD57) is a non-coding RNA (ncRNA) molecule which functions in the biogenesis (modification) of other small nuclear RNAs (snRNAs). This type of modifiying RNA is located in the nucleolus of the eukaryotic cell which is a major site of snRNA biogenesis. It is known as a small nucleolar RNA (snoRNA) and also often referred to as a guide RNA.

snoRNA U57 belongs to the C/D box class of snoRNAs which contain the conserved sequence motifs known as the C box (UGAUGA) and the D box (CUGA). Most of the members of the box C/D family function in directing site-specific 2'-O-methylation of substrate RNAs.

This snoRNA was originally cloned from human HeLa cells during a screen for intron encoded snoRNAs. Its is predicted to guide the 2'O-ribose methylation of 18S ribosomal RNA (rRNA) at residue A99 3.