3′-processing of yeast tRNATrp precedes 5′-processing

Previous analyses of eukaryotic pre-tRNAs processing have reported that 5'-cleavage by RNase P precedes 3'-maturation. Here we report that in contrast to all other yeast tRNAs analyzed to date, tRNA(Trp) undergoes 3'-maturation prior to 5'-cleavage. Despite its unusual processing pathway, pre-tRNA(Trp) resembles other pre-tRNAs, showing dependence on the essential Lsm proteins for normal processing and efficient association with the yeast La homolog, Lhp1p. tRNA(Trp) is also unusual in not requiring Lhp1p for 3' processing and stability. However, other Lhp1p-independent tRNAs, tRNA(2)(Lys) and tRNA(1)(Ile), follow the normal pathway of 5'-processing prior to 3-processing.