| Escherichia coli employ a complex network of regulatory systems that coordinate gene expression with cell growth. This network is capable of protecting the genetic and metabolic integrity of the cell from damage inflicted by aversive environmental conditions. Following exposure to certain forms of metabolic stress, cells alter genome-wide changes to their transcriptional profile. The global transcriptional profile of the cell can also be affected by the initiator of replication, DnaA, and the small molecule effector, ppGpp. Alternative sigma subunits of RNA polymerase are required for these large changes in the transcriptional profile. Many environmental stresses trigger the activation of the sigma factor, RpoS, which modulates expression of nearly 500 genes. Here we examine the regulation of the growth phase and DNA damage inducible stabilizer of RpoS, IraD. We show that iraD transcription is regulated by ppGpp and DnaA. This regulation by ppGpp and DnaA connects RpoS to a novel DNA damage pathway via IraD. |
