molecular biology Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...

, SNORD116 (also known as HBII-85) is a

non-coding RNA A non-coding RNA (ncRNA) is a functional RNA molecule that is not Translation (genetics), translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally imp ...

(ncRNA) molecule which functions in the modification of other

small nuclear RNA Small nuclear RNA (snRNA) is a class of small RNA molecules that are found within the Cell nucleus#Splicing speckles, splicing speckles and Cajal body, Cajal bodies of the cell nucleus in eukaryotic cells. The length of an average snRNA is approxi ...

s (snRNAs). This type of modifying RNA is usually located in the

nucleolus The nucleolus (; : nucleoli ) is the largest structure in the cell nucleus, nucleus of eukaryote, eukaryotic cell (biology), cells. It is best known as the site of ribosome biogenesis. The nucleolus also participates in the formation of signa ...

of the

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

cell which is a major site of snRNA biogenesis. It is known as a

small nucleolar RNA In molecular biology, small nucleolar RNAs (snoRNAs) are a class of small RNA molecules that primarily guide chemical modifications of other RNAs, mainly ribosomal RNAs, transfer RNAs and small nuclear RNAs. There are two main classes of snoRNA, t ...

(snoRNA) and also often referred to as a guide RNA. SNORD116 belongs to the C/D box class of snoRNAs which contain the

conserved sequence In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids ( DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ...

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 Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...

of substrate RNAs. In the human genome, there are 29 tandemnly repeated copies of SNORD116, followed by 48 copies of another C/D box snoRNA, SNORD115, in the

Prader–Willi syndrome Prader–Willi syndrome (PWS) is a rare genetic disorder caused by a loss of function of specific genes on chromosome 15. In newborns, symptoms include hypotonia, weak muscles, poor feeding, and slow development. Beginning in childhood, those ...

(PWS) region of chromosome 15. Unlike most other snoRNAs, SNORD116 is expressed prevalently in the brain (but is absent in PWS patients) and lacks any significant complementarity with

ribosomal RNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...

. Mouse models of PWS show similar symptoms to humans (

hyperphagia Polyphagia, or hyperphagia, is an abnormally strong, incessant sensation of hunger or desire to eat often leading to overeating. In contrast to an increase in appetite following exercise, polyphagia does not subside after eating and often leads ...

and growth deficiency), providing further evidence that PWS is directly linked to the deletion of SNORD116. More evidence comes from the discovery of two individuals that share many traits of PWS sufferers, both have atypical microdeletions on chromosome 15q11–13, the intersection of which contains only the SNORD116 snoRNAs. The targets of SNORD116 are unknown, however a bioinformatic screen located 23 possible targets within protein-coding genes, of these a large fraction were found to be

alternatively spliced Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative RNA splicing, splicing process during gene expression that allows a single gene to produce different splice variants. For example, some exons of a gene ma ...

, suggesting a role of SNORD116 in the regulation of alternative splicing.

References

External links

*
snoRNAbase page for SNORD116
{{Small nucleolar RNA Small nuclear RNA