Location of binding sites for RNA polymerase II from wheat germ and from human placenta on adenovirus 2 DNA.

Electron microscopic visualization of binary complexes between eukaryotic RNA polymerases and Adenovirus 2 (Ad 2) DNA was used to locate specific binding sites for the enzymes. RNA polymerase II from human placenta binds to 10--16 distinct sites depending on the ratio of enzyme to DNA and the divalent cation present in the binding mixture. Wheat germ RNA polymerase binds to 12--14 strong binding sites and 2--3 weaker sites, all but one of which correspond to binding sites for the placental enzyme. At least six of the strong binding sites for both enzymes correspond to promoters known to be active in vivo. As a test of the two-state model for transcription initiation, we examined binding of wheat germ RNA polymerase II to Ad 2 DNA at 0 degrees and 37 degrees. The extent of binding was the same at the two temperatures and the distributions of binary complexes were virtually identical. This observation, in conjunction with results presented previously, is strong support for the existence of I and RS complexes in eukaryotic systems.