Fine-tuned growth phase control of dps, encoding a DNA protection protein, by FIS and H-NS.

Dps, a ferritin-like DNA-binding protein, protects bacterial DNA against oxidative stress and hyper-compacts the nucleoid into a crystalline-like structure. In Escherichia coli, transcription of dps from a single promoter is directed by sigma S-RNA polymerase in stationary phase and by sigma 70-RNA polymerase in fast-dividing cells exposed to oxidative stress. In this issue of Molecular Microbiology, Grainger and co-workers demonstrate that the nucleoid-associated proteins, FIS and H-NS, control sigma factor selection at the dps promoter by a novel mechanism. The finding suggests a simple mechanism of growth phase control of Dps production and has implications for the response to oxidative stress by pathogenic enterobacteria.