Specificity of sigma-dependent binding of RNA polymerase to DNA

Summary Although a large number of E. coli RNA polymerase molecules can bind to phage T3 DNA, not more than three remain bound per DNA template after addition of poly inosinic acid (poly I) which has a high affinity for the enzyme. These stable complexes are able to initiate RNA chains without lag as the enzyme is resistant against rifampicin if substrate is added simultaneously with the drug. Poly I resistant complexes decay very rapidly in the cold (Fig. 2) and are not formed in the absence of the polymerase factor (Table 2). The data provide additional support for the idea that the factor effects the binding of the enzymes to specific sites on the DNA template.