The σ24 Subunit of Escherichia coli RNA Polymerase Can Induce Transcriptional Pausing in vitro

The bacterium Escherichia coli has seven σ subunits that bind core RNA polymerase and are necessary for promoter recognition. It was previously shown that the σ70 and σ38 subunits can also interact with the transcription elongation complex (TEC) and stimulate pausing by recognizing DNA sequences similar to the–10 element of promoters. In this study, we analyzed the ability of the σ32, σ28, and σ24 subunits to induce pauses in reconstituted TECs containing corresponding–10 consensus elements. It was found that the σ24 subunit can induce a transcriptional pause depending on the presence of the–10 element. Pause formation is suppressed by the Gre factors, suggesting that the paused complex adopts a backtracked conformation. Some natural promoters contain potential signals of σ24-dependent pauses in the initially transcribed regions, suggesting that such pauses may have regulatory functions in transcription.