Region 4 of σ as a target for transcription regulation

Bacterial sigma factors play a key role in promoter recognition, making direct contact with conserved promoter elements. Most sigma factors belong to the sigma(70) family, named for the primary sigma factor in Escherichia coli . Members of the sigma(70) family typically share four conserved regions and, here, we focus on region 4, which is directly involved in promoter recognition and serves as a target for a variety of regulators of transcription initiation. We review recent advances in the understanding of the mechanism of action of regulators that target region 4 of sigma.