Small nucleolar RNA SNORD66

SNORD66 (also known as HBII-142) is a non-coding RNA (ncRNA) molecule which functions in the modification of other small nuclear RNAs (snRNAs). This type of modifiying 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.

HBII-142 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.

HBII-142 is the human orthologue of the mouse MBII-142 snoRNA and is predicted to guide 2'O-ribose methylation of 18S ribosomal RNA (rRNA) at residue C1272.