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 d isrupts the complementary base pairing that stabilizes the translation initiation complex with E. coli mRNAs. It has been reported that prod uction of specialized ribosomes does not cause the inhibition of chrom osomal rRNA synthesis that follows production of wild-type ribosomes. We proposed that enabling translation on specialized ribosomes by prov iding mRNA with a complementary mutation in the Shine-Dalgarno region would restore feedback regulation and inhibit chromosomal rRNA synthes is. With both our system and the system studied previously, we saw fee dback regulation regardless of whether the specialized ribosomes were translating. As reported previously, transcription from plasmid-borne promoters decreased as chromosomal rRNA synthesis was repressed, sugge sting that the lambda P-L and tac promoters may be sensitive to the ef fector(s) of feedback regulation. (C) 1995 Academic Press, Inc.