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. 2019 Dec 6;48(2):501–516. doi: 10.1093/nar/gkz1133

Figure 6.

Figure 6.

Proposed working model of holo-WhiB1 in transcriptional regulation via interaction with σA4. (A) Diagram that demonstrates the αCTD-mediated transcription factor–independent activation by recognizing the up element (UP) of the target promoters. (B and C) Diagrams of the Class I and Class II transcription activation, respectively. The 3D structures of the cyclic AMP receptor protein (CRP) bound RNAP–DNA complexes for the CRP-dependent Class I and Class II transcription activation (PDB IDs: 3IYD and 5I2D, respectively) are used as models. (D and E) Diagrams of the proposed working model for holo-WhiB1 in transcriptional regulation via interaction with σA4. Panel D illustrates that WhiB1 binding to σA4 can block the binding site for activators or αCTD, and thus repress transcription. Panel E shows that WhiB1 binding to σA4 in RNAP, either alone or in concert with a to-be-defined transcription regulator, may stabilize the interaction between RNAP and a specific subset of promoters, and thus activate transcription.