Pseudouridylation is a biochemical process where the nucleoside uridine in RNA is modified to form pseudouridine. This modification changes the structure of the RNA, which can affect its stability and function. Pseudouridine is commonly found in various types of RNA, including transfer RNA (tRNA) and ribosomal RNA (rRNA). This modification is catalyzed by specific enzymes known as pseudouridine synthases. Pseudouridylation plays a crucial role in the regulation of gene expression and the overall functionality of RNA molecules. It is also implicated in various biological processes, including protein synthesis and RNA splicing.