Eubacterial sigma-factors

Abstract

The initiation of transcription is the most important step for gene regulation in eubacteria. To initiate transcription, RNA polymerase has to associate with a small protein, known as a σ-factor. The σ-factor directs RNA polymerase to a specific class of promoter sequences. Most bacterial species synthesize several different σ-factors that recognize different consensus sequences. This variety in σ-factors provides bacteria with the opportunity to maintain basal gene expression as well as for regulation of gene expression in response to altered environmental or developmental signals. This review focuses on the function, regulation and distribution of the 14 different classes of σ-factors that are presently known.