E.coli MG16556/pCA24N-dinJ treated with erythromycin vs. MG16556/pCA24N

Antitoxins are becoming recognized as proteins that regulate more than their own synthesis; for example, we found previously that antitoxin MqsA represses the gene encoding the stationary phase sigma factor RpoS. Here, we investigated the physiological role of antitoxin DinJ of the DinJ/YafQ toxin/antitoxin system and found DinJ also affects the general stress response by decreasing RpoS levels. Corroborating the reduced RpoS levels upon producing DinJ, catalase activity, cell adhesins, and cyclic diguanylate decreased while swimming increased. Using a transcriptome search and DNA-binding assays, we determined that the mechanism by which DinJ reduces RpoS is by repressing cspE which encodes cold-shock protein CspE that inhibits translation of rpoS mRNA. Hence, DinJ influences the general stress response indirectly by regulating cspE.

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Hu Y, Benedik MJ, Wood TK