I.n vitro transcription of adenovirus 2 DNA. I. Characterization of promoters for E. coli RNA polymerase.

E coli RNA polymerase holoenzyme is able to recognize transcription initiation sites on Adenovirus 2 DNA that are functionally indistinguishable from promoters for the enzyme on phage DNAs. The complexes formed between the polymerase and the DNA at these sites can exist in two states-either as I (initiation) complexes, from which rapid RNA chain initiation is not possible, or as RS (rapid starting) "rifampicin resistant" complexes, from which rapid RNA chain initiation can occur. When transcription is limited to that initiated from stable, rifmapicin-resistant pre-initiation complexes, initiation is strictly dependent on the presence of sigma factor; in addition, the frequency of initiation exhibits sigmoidal dependence on the temperature at which pre-initiation complexes are allowed to form, with a transition temperature of 26-28 degrees C. The average half-time for initiation of RNA chains from sites on Ad 2 DNA is shown to be comparable to half-times for initiation of RNA chains from promoters on T7 and lambda DNAs. At saturating levels of enzyme, the half-times are 0.6, 0.9, and 1.6 sec for lambda b2, Ad 2 and T7 DNAs, respectively. The existence of efficient, phage-like promoters for E coli RNA polymerase on Ad 2 DNA suggests to us that such promoters may be closely related functionally and spatially to promoters for mammalian RNA polymerases.