In vivo transcription of the E. coli uvrB gene: both promoters are inducible by UV.

The transcriptional activity of the tandem promoters of the Escherichia coli uvrB gene was measured in vivo. Both promoters are shown to be inducible by UV irradiation. P1, the most proximal promoter, is responsible for the main part of transcription both in uninduced and induced cells. Plasmids have been constructed carrying small deletions in the lexA binding site that overlaps with P2, the distal promoter. These deletions result in constitutive transcription from P1. This indicates that the DNA region which contains P2 functions mainly as a target site for regulation of P1 transcription in vivo.