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.