Transcription factor regulation of RNA polymerase’s torque generation capacity

Significance RNA polymerase (RNAP) carries out transcription from DNA to RNA. The double-stranded helical nature of DNA necessitates RNAP rotation of DNA during active elongation, leading to DNA supercoiling and the accumulation of torsional stress, which may ultimately stall transcription. As a torsional motor, RNAP generates and works against torsion, but it remains unclear whether and how RNAP’s torque generation capacity may be regulated. In this work, real-time single-molecule transcriptional assays revealed that, in response to increased torsion, RNAP extensively backtracks along DNA and ultimately becomes stalled. A transcription factor, GreB, can effectively increase RNAP’s stall torque by limiting RNAP backtracking. This work provides the first illustration of how a transcription factor can regulate the capacity of transcriptional torque generation.