The effects of KCl concentration on the transcription byE. coli RNA polymerase

The specificity ofin vitro transcription of T7 DNA byE. coli RNA polymerase was found to be remarkably influenced by the KCl concentration. At the lower KCl concentration, not onlyr-strand of early region but also late region andl-strand were transcribed. Such non-specific transcription was shown to be reduced by elevation of KCl concentration in the reaction mixture for RNA synthesis. At the higher KCl concentration than 0.2M, the RNA complementary tor-strand of early region was exclusively synthesized, the specificity of which is the same as the earlyin vivo transcription inE. coli infected with T7 phage.