Pseudouridine

Pseudouridine (abbreviated Ψ) is the C-glycoside isomer of the nucleoside uridine, and it is the most prevalent of the over one hundred different modified nucleosides found in RNA. Ψ is found in all species and in all classes of RNA except mRNA. Ψ is formed by enzymes called Ψ synthases, which post-transcriptionally isomerize specific uridine residues in RNA in a process termed pseudouridylation.