Differential sensitivity of gene expression in vitro to inhibitors of DNA gyrase.

Abstract

The antibiotics coumermycin A1, novobiocin and oxolinic acid, which are specific inhibitors of DNA gyrase, were used to study the coupled transcription and translation of several bacterial and plasmid genes in a DNA-directed cell-free system [Escherichia coli]. The expression of different genes is reduced to different extents by inhibition of DNA gyrase activity. Among the genes tested, the lac operon, an rRNA gene and the colicin gene of colicin E1 plasmid were the most sensitive, while the trp operon and some other genes in colicin E1 plasmid were relatively unaffected by the inhibitors. These results, together with earlier work on the transcription of circular DNA templates, indicate that DNA supercoiling can significantly enhance transcription from certain promoters.