A flexible partnership: the CytR anti-activator and the cAMP–CRP activator protein, comrades in transcription control



A vital point in gene regulation is control at the level of transcription initiation. Recent research has established that this regulation can involve sophisticated networks of interacting proteins that modulate the activity of the transcription machinery by DNA looping, direct protein–protein interactions or changing DNA topology in the promoter region. This MicroReview focuses on our investigations of a relatively simple prokaryotic gene regulatory system, the Escherichia coli CytR regulon, which exhibits a number of these features. This work has opened the door to the molecular understanding of how a prokaryotic repressor can be correctly positioned at specific DNA sequences with the help of a global activator, and how the repressor subsequently inhibits factor-dependent transcription initiation.