Abstract
Although correct tRNA 3¢ ends are crucial for protein biosynthesis, generation of mature tRNA 3¢ ends in eukaryotes is poorly understood and has so far only been investigated in vitro. We report here for the first time that eukaryotic tRNA 3¢ end matur- ation is catalysed by the endonuclease RNase Z in vivo. Silencing of the JhI-1 gene (RNase Z homo- log) in vivo with RNAi in Drosophila S2 cultured cells causes accumulation of nuclear and mitochon- drial pre-tRNAs, suggesting that JhI-1 encodes both forms of the tRNA 3¢ endonuclease RNase Z, and establishing its biological role in endonucleolytic tRNA 3¢ end processing. In addition our data show that in vivo 5¢ processing of nuclear and mitochon- drial pre-tRNAs occurs before 3¢ processing.