An evolutionarily conserved element in initiator tRNAs prompts ultimate steps in ribosome maturation

Ribosomes are complex molecular machines requiring an intricate pathway for their biogenesis. Deficiencies in ribosome biogenesis result in inefficient and inaccurate translation, causing cellular toxicities and ribosomopathies. As ribosomes have multiple functions during the translation process, how cells ensure fidelity of the newly synthesized ribosomes for their functions has remained unclear. The immature ribosomes possess rRNAs whose ends have not been fully processed. What licenses final trimming of immature rRNAs is also unclear. Here, using Escherichia coli, we show that participation of initiator tRNA via its universally conserved three consecutive GC base pairs, in the first round of the initiation complex formation licenses the final steps of ribosome biogenesis by signaling RNases to trim the immature 16S rRNAs.