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 ...

, Small nucleolar RNA SNORD113 (also known as C/D box snoRNA 14q(I)) is 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 ...

molecule which is located in the imprinted human 14q32 locus and may play a role in the evolution and/or mechanism of the

epigenetic In biology, epigenetics is the study of changes in gene expression that happen without changes to the DNA sequence. The Greek prefix ''epi-'' (ἐπι- "over, outside of, around") in ''epigenetics'' implies features that are "on top of" or "in ...

imprinting process. In humans the imprinted domain at 14q32 contains two clusters of tandemly repeated small nucleolar RNAs named 14q(I) and 14q(II) snoRNAs. These two clusters contain 9 and 31 highly related snoRNAs respectively. These two related snoRNAs are known as SNORD113 and SNORD114 respectively in the HGNC approved

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

symbol nomenclature. The snoRNAs found in each cluster are clearly related and are simply referred to with a 1-9 or 1-31 suffix. All the snoRNAs in these clusters are

intron An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e., a region inside a gene."The notion of the cistron .e., gen ...

encoded and are processed from the tissue-specific non-coding human MEG8 RNA, which lies downstream of the imprinted genes DLK1 and GTL2. SNORD113 and SNORD114 belong to the C/D box class of snoRNAs which contain the conserved

sequence motif In biology, a sequence motif is a nucleotide or amino-acid sequence pattern that is widespread and usually assumed to be related to biological function of the macromolecule. For example, an ''N''-glycosylation site motif can be defined as ''A ...

s 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. However, SNORD113 and SNORD114 differ from most C/D box snoRNAs in their expression profiles (which is tissue specific) and the lack of complementarity to

rRNA 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 ...

and

SnRNA 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 transcrib ...

. As a result, they are not predicted to guide to 2'O-methylation of a rRNA or snRNA. Homologues of SNORD113 and SNORD114 are found in the imprinted non-coding mouse transcript Rian where they are again found in tandem array of 9 highly related snoRNAs. These snoRNAs also display tissue specific (brain) expression. C/D box snoRNAs were also identified in the rat non-coding Bsr (brain-specific repetitive) RNA. Another imprinted human locus 15q11q13 encodes tandemly repeated C/D box snoRNA genes which are expressed only from the paternal

chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...

. Studies of human and mouse model systems have shown that deletion of the 29 copies of the C/D box snoRNA SNORD116 (HBII-85) from this locus has been shown to be the primary cause of Prader-Willi syndrome. A possible role for tandemly repeated C/D snoRNA genes in the evolution and/or mechanism of the epigenetic imprinting process has been suggested.

References

External links

* * * {{Small nucleolar RNA Small nuclear RNA