Fig. 2.

RNA-based regulation of the SOS-responsive toxins TisB and DinQ. The loci for tisB/istR-1 (a) and dinQ/agrAB (b) are depicted in the upper part of the figure. Arrows indicate promoters and red boxes represent binding sites for LexA. In both cases, primary mRNAs (+1) are translationally inert due to secondary structures that prevent ribosome binding. 5′ processing generates translationally active mRNAs (tisB +42 or dinQ +44) with accessible sites for ribosome loading. The active mRNAs are either inhibited by their cognate RNA antitoxins, or translated into toxin. Both TisB and DinQ are implicated in persister formation under SOS conditions. AUG/GUG: start codon; SD Shine-Dalgarno sequence, RSS ribosome standby site. See text for details