Transcription unit mapping in bacteriophage T7. I. In vivo transcription by Escherichia coli RNA polymerase.

Premature termination of transcription at UV lesions in DNA permits a study of the sequential order of transcription by E. coli RNA polymerase of the genes in the early region of T7. This analysis is extended to the transcription by E. coli polymerase of the late region of T7 by deleting the early terminator. The results demonstrate the existence of a single large transcription unit spanning the early region, with a promotor located at the left end of the T7 genome. Furthermore, there are no initiation sites for E. coli RNA polymerase in the late region. When E. coli polymerase transcribes the late region, it does so exclusively by initiation at the early promotor.