Small nucleolar RNA SNORD116

SNORD116 (also known as HBII-85) 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-85 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.

In the human genome, HBII-85 is encoded in a tandemly repeated array with another C/D box snoRNA, HBII-52, in the Prader-Willi syndrome (PWS) region of chromosome 15. Unlike most other snoRNAs, HBII-85 is expressed prevalently in the brain (but is absent in PWS patients) and lacks any significant complementarity with ribosomal RNA.