INTEGRATION HOST FACTOR POSITIVELY REGULATES CYSJIH TRANSCRIPTION

We report the identification of integration host factor (IHF) as an ad ditional element involved in the regulation of the cysJIH promoter of Salmonella typhimurium and Escherichia coli. An IHF-binding site was l ocated in the regulatory region of the cysJIH promoter by using two me thods, protection against DNase I digestion and hydroxyl radical cleav age. The positive influence of IHF on in vitro run-off transcription f rom the cysJIH promoter is shown. The in vivo observations suggest tha t IHF is necessary for full expression of cysJIH in stationary phase b ut not during exponential growth.