Synthesis of non-translating or translating specialized ribosomes causes feedback regulation of ribosomal RNA synthesis in Escherichia coli.

Specialized ribosomes carry a mutant anti-Shine-Dalgarno region that disrupts the complementary base pairing that stabilizes the translation initiation complex with E. coli mRNAs. It has been reported that production of specialized ribosomes does not cause the inhibition of chromosomal rRNA synthesis that follows production of wild-type ribosomes. We proposed that enabling translation on specialized ribosomes by providing mRNA with a complementary mutation in the Shine-Dalgarno region would restore feedback regulation and inhibit chromosomal rRNA synthesis. With both our system and the system studied previously, we saw feedback regulation regardless of whether the specialized ribosomes were translating. As reported previously, transcription from plasmid-borne promoters decreased as chromosomal rRNA synthesis was repressed, suggesting that the lambda PL and tac promoters may be sensitive to the effector(s) of feedback regulation.