FIG. 3.

Effect of altered NTP pools on start site selection at fis P. (A) Results of primer extension reactions with 10 μg of total RNA from RO934 transformed with plasmids containing either the wild-type (WT), 10T→A, or A₄ fis P. Cells were cultured in N⁻C⁻ medium containing either uracil (URA) or 5′-UMP. Signals resulting from initiation at 6G or 8C in the wild-type promoter are indicated on the left. (B) The percentage of each transcript was determined for the wild-type and 10T→A fis promoters from two primer extension assays on a total-RNA preparation made from each bacterial culture carrying one of the fis promoters on a plasmid. Quantification was done as described in the legend to Fig. 1. The fis P's analyzed and the mapped start site positions are indicated beneath the bars.