Translocation of σ70 with RNA Polymerase during Transcription: Fluorescence Resonance Energy Transfer Assay for Movement Relative to DNA

Using fluorescence resonance energy transfer, we show that, in the majority of transcription complexes, σ70 is not released from RNA polymerase upon transition from initiation to elongation, but, instead, remains associated with RNA polymerase and translocates with RNA polymerase. The results argue against the presumption that there are necessary subunit-composition differences, and corresponding necessary mechanistic differences, in initiation and elongation. The methods of this report should be generalizable to monitor movement of any molecule relative to any nucleic acid.