FIG. 2.

Primer extension analysis of the transcription start site. The autoradiogram shows a primer extension experiment performed with RNA extracted from strain JH642 incubated at 20°C for 45 min after shifting from 37°C. Lanes A, C, G, and T show sequencing reactions performed on des with the primer extension oligonucleotide. The horizontal arrow indicates the hybridizing extension product corresponding to the C residue taken to be the start of transcription. The vertical arrow indicates the direction of transcription.