Abstract
Repression of transcription of the abrB gene is essential to expression of many of the postexponential genes in Bacillus. The repression is due to the activity of the response regulator protein Spo0A. We have used in vitro transcription and DNase I and hydroxyl radical footprinting to explore the mechanism of transcription inhibition. Spo0A binds to specific DNA sequences (0A boxes), and two such boxes are found downstream of the tandem promoters for the abrB gene. The data indicate that both RNA polymerase and Spo0A bind simultaneously to a DNA fragment containing the promoters and the 0A boxes. The Spo0A prevents the polymerase from inducing DNA strand denaturation at the promoter for the abrB gene.
Highlights
When Bacillus subtilis reaches the end of logarithmic growth, it enters a transition state in which cells express genes designed to search for alternative nutrient sources
The repression is due to the binding of Spo0A protein to two consensus binding sites (TGTCGAA, termed 0A boxes), which are located between positions ϩ11 and ϩ17 and positions ϩ21 and ϩ27, relative to the downstream (P2) of two reported transcription initiation start sites (P1 and P2; Ref. 10)
The experiments we reported were designed to distinguish between three models for repression of abrB transcription by Spo0A
Summary
When Bacillus subtilis reaches the end of logarithmic growth, it enters a transition state in which cells express genes designed to search for alternative nutrient sources. These genes, such as proteases, amylases are under the direct control of a set of proteins termed transition state regulators [1,2,3]. One model is the formation of a DNA loop between a Spo0A binding site that is upstream of the promoter (at position Ϫ214, relative to P2) and the Spo0A binding sites downstream of P2. Both RNA polymerase and Spo0A bind simultaneously to the promoter region; the polymerase is prevented from initiating, or possibly elongating, RNA synthesis
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