Trypanosome Mitochondrial 3′ Terminal Uridylyl Transferase (TUTase): The Key Enzyme in U-Insertion/Deletion RNA Editing

A 3′ terminal RNA uridylyltransferase was purified from mitochondria of Leishmania tarentolae and the gene cloned and expressed from this species and from Trypanosoma brucei. The enzyme is specific for 3′ U-addition in the presence of Mg2+. TUTase is present in vivo in at least two stable configurations: one contains a ∼500 kDa TUTase oligomer and the other a ∼700 kDa TUTase complex. Anti-TUTase antiserum specifically coprecipitates a small portion of the p45 and p50 RNA ligases and approximately 40% of the guide RNAs. Inhibition of TUTase expression in procyclic T. brucei by RNAi downregulates RNA editing and appears to affect parasite viability.