TRL1 encodes tRNA ligase, which is essential for tRNA splicing (5, 6, 7). Trl1p has phosphodiesterase, polynucleotide kinase, and ligase activities; each activity resides in a different domain (2). In tRNA processing, an intron is removed from the tRNA transcript by the multisubunit tRNA splicing endonuclease (encoded by SEN2, SEN15, SEN34, and SEN54); the resulting half-molecules are joined by Trl1p (8, 7) and the splice junction 2'-phosphate is removed by the tRNA 2'-phosphotransferase encoded by TPT1 (reviewed in reference 9). Deletion of TRL1 is lethal; tRNA splicing intermediates accumulate in cells depleted of Trl1p or in trl1 temperature-sensitive mutants at the restrictive temperature (8). Trl1p is found at the inner nuclear membrane, although Trl1p is not an integral membrane protein (10, 3). Trl1p is also involved in splicing the mRNA encoding Hac1p, a transcription factor that activates the expression of genes induced by the unfolded protein response (11, 12). A tRNA ligase isolated from Candida albicans is 42% identical to Trl1p (1).

Last updated: 2008-09-03