In molecular biology, SNORD15 (also known as U15) is a non-coding RNA (ncRNA) molecule which functions in the modification of small nuclear RNAs (snRNAs, also a type of ncRNAs). This type of modifying RNA is usually 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.
U15 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.[1] U15 is predicted to guide the 2'O-ribose methylation of 28S ribosomal RNA (rRNA) residue A3764.[2][3]
snoR75 from Arabidopsis thaliana[6] and homologues in rice Oryza sativa and other plants are alternatively known as U15, and, despite a significantly shorter sequence length, appear to be related.[7]