TUTases

TUTases, or terminal uridylyl transferases, are enzymes that catalyze the template-independent addition of uridine residues to the 3' ends of RNA molecules. They belong to the nucleotidyl transferase superfamily and use UTP as the donor substrate to append uridines, forming short or extended polyuridylate tails. Catalysis generally requires divalent metal ions such as Mg2+ or Mn2+.

Substrates for TUTases include various RNA classes, such as precursor microRNAs, histone mRNA, small RNAs, and RNA decay intermediates. Uridylation can promote RNA degradation by recruiting decay factors or, in some contexts, stabilize certain RNAs. The effect is context- and enzyme-dependent, reflecting diverse roles in RNA metabolism, surveillance, and maturation.

In animals and fungi, cytoplasmic TUTases such as TUT4 and TUT7 are well characterized; they can cooperate with RNA-binding proteins like LIN28 to uridylate let-7 family precursors, inhibiting maturation and promoting degradation. Other TUTases contribute to RNA processing in the nucleus or cytoplasm; for example, TUT1 is implicated in U6 snRNA maturation. In plants and other organisms, a variety of TUTases participate in RNA tailing, surveillance, and quality control.

Evolutionary distribution of TUTases spans eukaryotes with varying gene repertoires; many organisms possess multiple TUTases localized to distinct cellular compartments, enabling specialized functions in RNA metabolism.

Clinical and research relevance: aberrant RNA uridylation has been linked to development, cancer biology, and viral replication in certain systems. Techniques to study TUTases include in vitro activity assays with labeled UTP and RNA substrates, and high-throughput sequencing approaches to map uridylation patterns.