Induction of protein aggregation and starvation response by tRNA modification defects.

Posttranscriptional modifications of anticodon loops contribute to the decoding efficiency of tRNAs by supporting codon recognition and loop stability. Consistently, strong synthetic growth defects are observed in yeast strains simultaneously lacking distinct anticodon loop modifications. These phenotypes are accompanied by translational inefficiency of certain mRNAs and disturbed protein homeostasis resulting in accumulation of protein aggregates. Different combinations of anticodon loop modification defects were shown to affect distinct tRNAs but provoke common transcriptional changes that are reminiscent of the cellular response to nutrient starvation. Multiple mechanisms may be involved in mediating inadequate starvation response upon loss of critical tRNA modifications. Recent evidence suggests protein aggregate induction to represent one such trigger.