Effect of the lambda repressor on the binding of RNA polymerase to DNA

Experiments were designed with the aim of understanding the mechanism whereby the lambda repressor inhibits messenger RNA synthesis. Complexes containing lambda DNA and RNA polymerase were isolated from repressed and derepressed lysogens and analyzed for the relative amounts of RNA polymerase per phage genome. The data indicate that the repressor inhibits the binding of RNA polymerase to promoter sites known to be under direct control of the repressor.