What is "pseudouridine"

n. (label en biochemistry genetics) An isomer of uridine associated with RNA

Pseudouridine (abbreviated by the Greek letter psi- Ψ) is an isomer of the nucleoside uridine in which the uracil is attached via a carbon-carbon instead of a nitrogen-carbon glycosidic bond. It is the most prevalent of the over one hundred different modified nucleosides found in RNA. Ψ is found in all species and in many classes of RNA. Ψ is formed by enzymes called Ψ synthases, which post-transcriptionally isomerize specific uridine residues in RNA in a process termed pseudouridylation.

It is commonly found in tRNA, associated with thymidine and cytosine in the TΨC arm and is one of the invariant regions of tRNA.The function of it is not very clear, but it is expected to play a role in association with aminoacyl transferases during their interaction with tRNA, and hence in the initiation of translation. Recent studies suggest it may offer protection from radiation.