Abstract
Nuclear genes encoding tRNATyr and tRNAMet-e are interrupted by introns in plants. Pre-tRNA splicing requires the concerted action of three enzymes in yeast cells and plants: an endonuclease (Sen), a tRNA ligase (tRL) and a 2'-phosphotransferase (Pt). We have investigated the subcellular localization of the enzymes. The results show that all enzymes are localized predominantly in the nucleus. tRL and Pt, both containing chloroplast transit signals (CTSs) at the N-termini, are also targeted to the chloroplasts. Moreover, Pt was targeted to the mitochondria. Nucleotide analysis revealed that the context around the first initiation codon in tRL genes from several plants is not optimal for the efficient initiation of translation in plants, suggesting the possibilities that the first AUG is partially skipped to start a translation at the second AUG (or third AUG). Taken together, an alternative initiation in the translation level may result in a multiple targeting to cellular compartments.
