The influence of mutations upon the synthesis of RNA polymerase subunits in Escherichia coli cells

Abstract

The influence of mutations in structural genes of beta and beta subunits of RNA polymerase upon the synthesis of these subunits in E. coli cells have been investigated. An amber-mutation ts22 in the beta subunit gene decreases the intracellular concentration of this subunit and the rate of its synthesis. At the same time the concentration and the rate of beta subunit synthesis is increased. These suggest the compensatory activation of the RNA polymerase operon that takes place under the conditions of shortage of one of the subunits. Reversions as well as more effective suppression of ts22 amber mutation, achieved by streptomycin addition, substitution of su2 by sul, or by specific mutations, result in a rise of beta and drop of beta subunit concentration and synthesis in ts22 mutant. TsX missense-mutation in the beta subunit gene alters the properties of the enzyme increasing, at the same time, the concentration and the rate of synthesis of both beta and beta subunits, particularly at a nonpermissive temperature. This points to an inversely proportional relationship between the rate of synthesis of RNA polymerase subunits and the total intracellular activity of the enzyme. Extra subunits are rapidly degraded in ts22 and tsX mutants. The whole complex of our data and those of others suggest that the regulation of the synthesis of RNA polymerase subunits is accomplished by interaction of a negative and a positive mechanisms of regulation which include not only activators and repressors but the enzyme itself as well.