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. Author manuscript; available in PMC: 2019 Jan 11.
Published in final edited form as: Cell. 2017 Dec 7;172(1-2):344–357.e15. doi: 10.1016/j.cell.2017.11.017

Figure 7. Modes of Mfd regulation of transcription.

Figure 7

When a TEC encounters a major obstacle in the absence of Mfd and other anti-backtracking factors, the TEC may become stalled and experience extensive backtracking (A). Mfd is able to prevent TEC backtracking and/or rescue a backtracked complex into elongation. If a TEC elongates steadily after the initial rescue, Mfd detaches from the DNA (B). However, if a TEC stalls frequently, Mfd will use the release and catch-up mechanism to continue to facilitate elongation through multiple obstacles (C). When an obstacle becomes insurmountable, Mfd terminates transcription by disrupting the TEC, resulting in eventual dissociation of Mfd and RNAP from the DNA (D).