IN-VIVO EFFECT OF DNA RELAXATION ON THE TRANSCRIPTION OF GENE RPOH INESCHERICHIA-COLI

The in vivo effect of Novobiocin, a gyrase inhibitor, on the transcrip tion of gene rpoH which codes for sigma(32), the main positive regulat or of the heat-shock response, was studied. Novobiocin induced a three -fold increase and a slight decrease in the activity of the rpoH promo ters P1 and P4, respectively. The Novobiocin-induced increase in the a ctivity of promoter P1 correlates with an increase in the amount of pr oteins sigma(32) and DnaK. These results suggest that the increase in expression of the heat-shock proteins induced by gyrase inhibitors is probably due to the increased activity of P1 on relaxed DNA. (C) 1997 Elsevier Science B.V.