The inhibition of RNA polymerase by daunomycin

The effect of daunomycin on the in vitro activity of Escherichia coli DNA-dependent RNA polymerase has been studied under a variety of experimental conditions. The inhibition of RNA synthesis by this DNA-binding antibiotic is overcome by an increase in the DNA concentration but is unaffected by an increase in the concentration of the RNA polymerase. It is concluded that, under conditions used, the inhibition is predominantly due to the interaction of the drug with the template DNA. At the concentration used (20 μM), daunomycin is able to inhibit RNA polymerization even after its initiation. However, the possibility remains that other steps are sensitive to daunomycin. A comparison of the effect of daunomycin on RNA synthesis using different DNAs as templates suggests that the extent of inhibition depends on base composition and on the secondary structure of the DNA. The effect of base composition on the melting temperature of antibiotic-DNA complexes is consistent with the inhibiting effect on RNA synthesis.     

Feedback regulation of RNA polymerase subunit synthesis after the conditional overproduction of RNA polymerase in Escherichia coli

Summary The and subunit of RNA polymerase are thought to be controlled by a translational feedback mechanism regulated by the concentration of RNA polymerase holoenzyme. To study this regulation in vivo, an inducible RNA polymerase overproduction system was developed. This system utilizes plasmids from two incompatibility groups that carry RNA polymerase subunit genes under lac promoter/operator control. When the structural genes encoding the components of core RNA polymerase (, and ) or holoenzyme (, , and ⁷⁰) are present on the plasmids, induction of the lac promoter results in a two fold increase in the concentration of functional RNA polymerase. The induction of RNA polymerase overproduction is characterized by an initial large burst of synthesis followed by a gradual decrease as the concentration of RNA polymerase increases. Overproduction of RNA polymerase in a strain carrying an electrophoretic mobility mutation in the rpoB gene results in the specific repression of synthesis off the chromosome. These results indicate that RNA polymerase feedback regulation controls synthesis in vivo.     

Monoclonal antibodies inhibiting RNA polymerase from Escherichia coli

Monoclonal hybridoma antibodies directed against RNA polymerase from E. coli have been obtained. Only a few have been found to inhibit the enzyme activity. Antibodies produced by two clones, PYN-1 and PYN-2, inhibit RNA polymerase at the stage of RNA chain elongation. The PYN-1 antibodies react with the beta'-subunit of the enzyme. The PYN-2 antibodies react with the beta-subunit and with its 130 kDa amber fragment.