The essential function of the Trypanosoma brucei Trl1 homolog in procyclic cells is maturation of the intron-containing tRNA^Tyr

Abstract

Trypanosoma brucei, the etiologic agent of sleeping sickness, encodes a single intron-containing tRNA, tRNA^Tyr, and splicing is essential for its viability. In Archaea and Eukarya, tRNA splicing requires a series of enzymatic steps that begin with intron cleavage by a tRNA-splicing endonuclease and culminates with joining the resulting tRNA exons by a splicing tRNA ligase. Here we explored the function of TbTrl1, the T. brucei homolog of the yeast Trl1 tRNA ligase. We used a combination of RNA interference and molecular biology approaches to show that down-regulation of TbTrl1 expression leads to accumulation of intron-containing tRNA^Tyr and a concomitant growth arrest at the G1 phase. These defects were efficiently rescued by expression of an “intronless” version of tRNA^Tyr in the same RNAi cell line. Taken together, these experiments highlight the crucial importance of the TbTrl1 for tRNA^Tyr maturation and viability, while revealing tRNA splicing as its only essential function.