Selective inhibition of RNA polymerase by polynucleotides



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RNA polymerase, purified by a modification of the method of Furth, Hurwitz and Anders (1962) and Maitra and Hurwitz (1967) was inhibited as much as 99% by poly G. Inhibition of the reaction was also effected with poly A and poly U. Poly C, however, stimulated the reaction. This pattern of polynucleotide effects was observed on calf thymus, denatured calf thymus, [lambda], and T4 templates. Enzyme isolated by purification on a T4 DNA column was also shown to be strongly inhibited by poly G, with poly A and poly U again exerting a lesser inhibitory effect. In this case, however, poly C also inhibited the reaction. This was the effect observed when calf thymus, denatured calf thymus and [lambda] DNA was employed as template. When T4 DNA was employed as template in the reaction mixtures with this enzyme, poly G, poly A and poly C elicited the responses just described, but poly U unexpectedly produced a stimulatory response. The primary, although probably not exclusive factor in the effect of polyribonucleotides on the DNA-dependent RNA polymerase catalyzed synthesis of RNA appeared to be the binding of the polynucleotide to the enzyme. There were some indications that DNA might play some role in the reaction, but if so, the role of the template is a minor one. Possible mechanisms for the polynucleotide effects are discussed.