A point mutation in a mitochondrial tRNA gene abolishes its 3' end processing.

A temperature sensitive mutation mapping in the tRNA region of the mitochondrial genome of S. cerevisiae has been found to abolish 3' processing of tRNA(asp). Mutant cells grown for a few generations at the non-permissive temperature were found to specifically lack mature tRNA(asp) and to accumulate 3' unprocessed precursors of this tRNA. The accumulation of precursors of other mitochondrial tRNAs was also observed under the same conditions. After longer incubation times, a generalized decrease of mitochondrial transcripts could be observed. The mutation was genetically mapped in a limited region surrounding the tRNA(asp) gene and found, by sequencing, to consist of a C- greater than T transition at position 61 of the tRNA(asp) gene.