tRNA synthetases are recruited to yeast ribosomes by rRNA expansion segment 7L but do not require association for func-tionality

Ribosomes expanded during evolution on the protein and rRNA level. The expanded regions do not change the active sites of ribosomes and thus do not alter the peptide bond formation reaction catalysed by the ribosome. To what purpose these expansions were selected is not fully understood. Here, we deleted one rRNA expansion segment (ES7La) and addressed physiological consequences. We found a mild ribosome biogenesis defect accompanied by slightly reduced translation. On a molecular level, ribosomes displayed reduced association to three aminoacyl-tRNA synthetases. Loss of ribosome binding however did not alter synthetase activity suggesting, that tRNAs are not channelled for enhanced local translation in the case of these synthetases.