Ribosomal protein genes are of ten controlled by auto regulatory mechanisms in which a protein encoded in the operon can either bind to newly synthesized rRNA during rapid growth or to a similar target in its mRNA during poor growth conditions. The rplJL operon encodes the ribosomal L10(L12) 4 complex. In Escherichia coli L10(L12) 4 represses its translation by binding to the rplJL leader transcript. We identified three RNA structures in the Bacillus subtilis rplJL leader transcript that function as an antiantiterminator, antiterminator or intrinsic terminator. Expression studies with transcriptional and translational fusions indicated that L10(L12) 4 represses rplJL expression at the transcriptional level. RNA-binding studies demonstrated that L10(L12) 4 stabilizes the anti-antiterminator structure, while in vitro transcription results indicated that L10(L12) 4 promotestermination. Disruption of anti-antiterminator, antiterminator or terminator function by competitor oligonucleotides in vitro and by mutations in vivo demonstrated that each structure functions as predicted.Thus, rplJL expression is regulated by anautogenous transcription attenuation mechanism inwhich L10(L12) 4 binding to the anti-antiterminatorstructure promotes termination. We also found thattranslation of a leader peptide increases rplJL expression, presumably by inhibiting Rho-dependent termination. Thus, the rplJL operon of B. subtilis is regulated by transcription attenuation and antitermination mechanisms.
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