CHAPTER 3: RNA Polymerase as a Torsional Motor

As a torsional motor, RNA polymerase (RNAP) generates torque and drives DNA into supercoiled forms. Torque and DNA supercoiling, in turn, play important roles in regulating transcription. The diverse and widespread effects of torsion on transcription indicate that torsion itself may serve as an important point of regulation by the cell. Although biologically important, the torsional characteristics of RNAPs and their regulation have, until recently, remained poorly understood due to the technical challenges in directly measuring real-time torque in biomolecular systems. In this chapter, we describe how transcription-generated torque has been measured, enabling the characterization of RNAP's torque generation characteristics. Additionally, we focus on recent studies demonstrating that RNAP's torque generation capacity can be regulated by a transcription factor, and discuss the biological implications of these new discoveries.