Transient and dynamic DNA supercoiling potently stimulates the promoter in .

The inactive prokaryotic promoter (P) contains a single A-to-G point mutation in the -10 region of the leucine operon promoter, which causes leucine auxotrophy. This promoter can be activated by (-) DNA supercoiling in strains. However, whether this activation arises from global, permanent, or transient, dynamic supercoiling is still not fully understood. In this article, using a newly established system carrying a pair of divergently coupled promoters, an IPTG-inducible promoter and P that control the expression of and (the firefly luciferase gene), respectively, we demonstrate that transient, dynamic (-) DNA supercoiling provided by divergent transcription in both wild-type and strains can potently activate P We found that this activation depended on the promoter strength and the length of RNA transcripts, which are functional characteristics of transcription-coupled DNA supercoiling (TCDS) precisely predicted by the twin-supercoiled domain model of transcription in which a (+) supercoiled domain is produced ahead of the RNA polymerase and a (-) supercoiled domain behind it. We also demonstrate that TCDS can be generated on topologically open DNA molecules, linear DNA molecules, in , suggesting that topological boundaries or barriers are not required for the production of TCDS This work demonstrates that transient, dynamic TCDS by RNA polymerases is a major chromosome remodeling force in and greatly influences the nearby, coupled promoters/transcription.