uridylation

Uridylation is a post-transcriptional modification in which one or more uridine residues are added to the 3' end of RNA molecules. It is carried out by a family of enzymes known as terminal uridylyl transferases (TUTases), which catalyze template-independent addition of uridines to RNA termini. Uridylation can influence RNA stability, maturation, localization, and decay, depending on the RNA substrate and cellular context.

In animals and other eukaryotes, cytoplasmic TUTases such as TUT4 and TUT7 mediate uridylation of diverse RNAs. A well-known case is the regulation of let-7 microRNA maturation: Lin28 binds pre-let-7 and recruits TUT4/TUT7 to add short uridine tails, blocking Dicer processing and promoting degradation. Uridylation also marks certain mRNAs for decay through deadenylation-dependent or -independent pathways and can affect tail length and turnover rates.

Uridylation occurs across different RNA classes and organisms. It affects small noncoding RNAs, messenger RNAs, and improperly processed transcripts. In histone mRNA metabolism, uridylation of truncated transcripts promotes 3' to 5' decay by exosome-like pathways. In plants and fungi, uridylation participates in RNA surveillance and quality control, contributing to the regulation of gene expression at the RNA level.

Research on uridylation continues to reveal its roles in RNA metabolism and gene expression. Abnormal uridylation patterns have been linked to disease states, and TUTases are investigated as potential therapeutic targets. Techniques to profile 3' uridylation rely on specialized sequencing approaches to map uridylation tails on transcriptomes.