Interaction of RNA Polymerase from <i>Escherichia coli</i> with DNA Selection of Initiation Sites on T₇ DNA

Abstract

Rifampicin‐resistant complexes were formed on T 7 DNA at various molar ratios of RNA polymerase to DNA using the asymmetry of transcription as a criterion of specific initiation. Totally asymmetric transcription was only obtained with less than four RNA polymerases per T 7 DNA molecules. Under these conditions incorporation of [γ‐ 32 P]ATP or [γ‐ 32 P]GTP indicated that there is a strong promoter site initiating with ATP on the H strand of the T 7 genome. At higher enzyme : DNA ratios (≥4) rifampicin‐resistant RNA synthesis increases with the preincubation temperature of the binary enzyme · DNA complex, more chains are initiated, both by ATP and GTP, and transcription also occurs on the L strand of the DNA.