FIG. 3.
Determination of transcriptional start sites of the virR operon of R. equi. Fluorescent primer extension was carried out with a Cy5-labeled primer and 5 μg of total cellular RNA extracted from R. equi cells grown under inducing conditions (37°C and pH 6.5). The upper panels show the D4-labeled primer extension products combined with DNA size standards and analyzed with a CEQ 8000 fragment analysis system. The lower panels show dideoxy sequencing reactions spiked with the D4-labeled primer extension products. The arrows indicate the transcriptional start sites where the D4-labeled cDNA and sequencing products overlapped. (A) Determination of the PvirR transcriptional start site, using D4-VIR5022. (B) Determination of the Porf5 transcriptional start site, using D4-2IntPex5564. AU, arbitrary units.