Single-molecule study of transcriptional pausing and arrest by E-coli RNA polymerase

Using an optical-trap/flow-control video microscopy technique, we followed transcription by single molecules of Escherichia coli RNA polymerase in rea l time over long template distances. These studies reveal that RNA polymera se molecules possess different intrinsic transcription rates and different propensities to pause and stop. The data also show that reversible pausing is a kinetic intermediate between normal elongation and the arrested state. The conformational metastability of RNA polymerase revealed by this single -molecule study of transcription has direct implications for the mechanisms of gene regulation in both bacteria and eukaryotes.