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. Author manuscript; available in PMC: 2021 Jan 17.
Published in final edited form as: J Mol Biol. 2019 Sep 5;432(2):343–357. doi: 10.1016/j.jmb.2019.08.019

Fig. 7.

Fig. 7

SinR bends DNA. (a) Fluorescently labeled substrate based on the tapA-sipW-tasA promoter. 6-FAM (green star) gives off a fluorescent signal when DNA is linear. The bending of DNA by SinR brings the 6-FAM into proximity to the Black Hole Quencher-1 (black square) and reduces the fluorescent signal. (b) Model of the SinR tetramer bound to the tapA-sipW-tasA promoter. (c) SinR bends the DNA. Fluorescent signal decreases with increasing concentrations of SinR. Assay was repeated in triplicate with three technical replicates per experiment. (d) SinI inhibits SinR from bending the DNA. Incubating SinR with SinI in increasing concentrations prevents the loss of fluorescent signal. Assay was repeated in triplicate with three technical replicates per experiment. (e) Proposed mechanism for gene regulation by SinR and SinI using the DNA-bending model. SinR bends DNA, blocking RNA polymerase from binding to the promoter. The introduction of SinI forms SinR-SinI heterodimers that cannot effectively bind and bend the DNA. Released from the physical restraint, the DNA is now exposed to RNA polymerase which can initiate transcription.