Revised transcription map of the late region of bacteriophage T7 DNA.

The genes in the late region of the bacteriophage T7 genome are transcribed by a phage-specified RNA polymerase in two temporal classes (II and III). Through the use of an agarose-formaldehyde gel system that permits the resolution of high-molecular-weight RNAs, transcription of template DNA that had been cut with various restriction endonucleases, and transcription of isolated restriction fragments from the class II region, six previously unreported promoters utilized by the phage RNA polymerase in vitro have been mapped between 28 and 46% of the T7 genome. No evidence could be found for the existence of a promoter at 61% that had previously been reported to give rise to a diffuse band (species I RNA) in acrylamide-agarose gels.