In vivo correlation between DNA supercoiling and transcription.
The superhelical density of pMT plasmid DNA in Escherichia coli cells was measured as a function of the transcriptional activity, which was reduced by treatment with coumermycin or oxolinic acid. Superhelicity was assayed by agarose gel electrophoresis of DNA extracted from cells gently lysed by sarkosyl. Coumermycin treatment reduced the proportion of supercoiled plasmid DNA in concert with a decrease in the rate of plasmid-coded synthesis of trp mRNA, implying a correlation between supercoiling of DNA and its suitability for transcription. On the other hand, the oxolinic acid-induced loss of supercoiled plasmid DNA was relatively small, while concomitant inhibition of trp mRNA synthesis was very severe. Treatment of the cells with these two drugs never removed all of supertwists from the pMT plasmids carried.
D049933:Aminocoumarins; D003090:Coliphages / Q000235:genetics; D003374:Coumarins / Q000494:pharmacology; D004250:DNA Topoisomerases, Type II / Q000502:physiology*; D004278:DNA, Superhelical / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D009690:Nucleic Acid Conformation; D010093:Oxolinic Acid / Q000494:pharmacology; D010957:Plasmids; D011758:Pyrroles / Q000494:pharmacology; D013698:Templates, Genetic; D059005:Topoisomerase II Inhibitors; D014158:Transcription, Genetic / Q000187:drug effects
D049933:Aminocoumarins; D003374:Coumarins; D004278:DNA, Superhelical; D011758:Pyrroles; D059005:Topoisomerase II Inhibitors; D004250:DNA Topoisomerases, Type II; D010093:Oxolinic Acid; C004628:coumermycin