[Effect of DNA supercoiling on transcription performed by normal and mutant Escherichia coli RNA-polymerases]

A specific DNA-gyrase, inhibitor, coumermycin A1, causes differential changes in the spectrum of proteins synthesized in E. coli wild types cells, while protein spectrum in the mutant cells with coumermycin-resistant DNA-gyrase is left unaffected. The mutation of RNA-polymerase RpoB265 lowers the sensitivity of bacteria to coumermycin A1, whereas the RpoC3 enhances it. The differences between the normal and mutant RpoB265 RNA polymerases on interaction in vitro with ColE1 DNA plasmid depend on its supercoiling. No dependences of this kind were detected when comparing the normal and RpoC3-RNA polymerase. The obtained data indicate that the template supercoiling may significantly affect the transcription in vivo and that the properties of RNA polymerase may in some cases define this influence.