Contributions of UP elements and the transcription factor FIS to expression from the seven rrn P1 promoters in Escherichia coli

The high activity of the rrnB P1 promoter in Escherichia coli results from a cis-acting DNA sequence, the UP element, and a trans-acting transcription factor, FIS. In this study, we examine the effects of FIS and the UP eleme nt at the other six rrn P1 promoters. We find that UP elements are present at all of the rrn P1 promoters, but they make different relative contributi ons to promoter activity. Similarly, FIS binds upstream of, and activates, all seven rrn P1 promoters but to different extents. The total number of FI S binding sites, as well as their positions relative to the transcription s tart site, differ at each rrn P1 promoter. Surprisingly, the FIS sites upst ream of site I play a much larger role in transcription from most rrn P1 pr omoters compared to rrnB P1. Our studies indicate that the overall activiti es of the seven rrn P1 promoters are similar, and the same contributors are responsible for these high activities, but these inputs make different rel ative contributions and may act through slightly different mechanisms at ea ch promoter. These studies have implications for the control of gene expres sion of unlinked multigene families.