molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...

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

non-coding RNA A non-coding RNA (ncRNA) is a functional RNA molecule that is not 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 important types of non-c ...

(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 splicing speckles and Cajal bodies of the cell nucleus in eukaryotic cells. The length of an average snRNA is approximately 150 nucleotides. They are transcribe ...

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

nucleolus The nucleolus (, plural: nucleoli ) is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis, which is the synthesis of ribosomes. The nucleolus also participates in the formation of sig ...

of the

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

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 In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

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 genetic disorder caused by a loss of function of specific genes on chromosome 15. In newborns, symptoms include weak muscles, poor feeding, and slow development. Beginning in childhood, those affected become c ...

(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 to ...

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, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be in ...

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

References

External links

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