In molecular biology, small nucleolar RNA derived microRNAs are microRNAs (miRNA) derived from

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). MicroRNAs are usually derived from precursors known as pre-miRNAs, these pre-miRNAs are recognised and cleaved from a pri-miRNA precursor by the

Pasha Pasha, Pacha or Paşa ( ota, پاشا; tr, paşa; sq, Pashë; ar, باشا), in older works sometimes anglicized as bashaw, was a higher rank in the Ottoman Empire, Ottoman political and military system, typically granted to governors, gener ...

and Drosha proteins. However some microRNAs,

mirtrons Mirtrons are a type of microRNAs that are located in the introns of the mRNA encoding host genes. These short hairpin introns formed via atypical miRNA biogenesis pathways. Mirtrons arise from the spliced-out introns and are known to function in g ...

, are known to be derived from introns via a different pathway which bypasses Pasha and Drosha. Some microRNAs are also known to be derived from small nucleolar RNA.

Discovery

Small nucleolar RNA derived microRNA was first described in 2008. The

protozoal Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

intestinal parasite '' Giardia lamblia'' lacks the Drosha protein involved in pre-miRNA cleavage from pri-miRNA. However the miRNA processing protein dicer is found in ''Giardia''. A 26

nucleotide Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules wi ...

RNA, miR2, is processed from the ''Giardia lamblia'' snoRNA GlsR17 by dicer. MiR2 is a microRNA which may regulate the expression of variant surface proteins. Also in 2008, a small RNA was found to be cleaved from SCARNA15, a Human small Cajal body-specific RNA, by Dicer. This small RNA was found to function as a microRNA. Potential microRNAs were also identified in several other Human snoRNAs.

''Giardia'' snoRNA-derived miRNAs

''Giardia lamblia'' produces at least 20 snoRNAs. SnoRNAs guide the modification of

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 ribosoma ...

, and contain a region of 10–21 nucleotides which is complementary to the target RNA. Five of the ''Giardia lamblia'' snoRNAs have no complementarities to rRNA, implying that they may have a different function. MicroRNAs are derived from five of the box C/D snoRNAs from ''Giardia lamblia'': *The microRNA miR2 is derived from the snoRNA GlsR17 and may regulate the expression of variant surface proteins *The microRNA miR3 is derived from the snoRNA GlsR16 *The microRNA miR5 is derived from the snoRNA GlsR2. MiR5 may regulate the expression of several different genes, including four kinases and three variant surface proteins. The variant surface proteins are different from those potentially regulated by miR2 *The microRNA miR6 is derived from the snoRNA GlsR1. The predicted target sites for this miRNA include variant surface proteins *The microRNA miR10 is derived from the snoRNA GlsR8. The predicted target sites for this miRNA include variant surface proteins

References

{{reflist RNA Non-coding RNA

Discovery

''Giardia'' snoRNA-derived miRNAs

See also

References