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  • Title: The role of LRP and H-NS in transcription regulation: involvement of synergism, allostery and macromolecular crowding.
    Author: Pul U, Wurm R, Wagner R.
    Journal: J Mol Biol; 2007 Feb 23; 366(3):900-15. PubMed ID: 17196617.
    Abstract:
    LRP has recently been shown to interact with the regulatory regions of bacterial ribosomal RNA promoters. Here we study details of the LRP-rDNA interaction by gel retardation and high-resolution footprinting techniques. We show that a second regulator for rRNA transcription, H-NS, facilitates the formation of a higher-order LRP-nucleoprotein complex, probably acting transiently as a DNA chaperone. The macromolecular crowding substance ectoine stabilizes the formation of this dynamic complex, while the amino acid leucine, as a metabolic effector, has the opposite effect. DNase I and hydroxyl radical footprint experiments with LRP-DNA complexes reveal a periodic change of the target DNA structure, which implies extensive DNA wrapping reaching into the promoter core region. We show furthermore that LRP binding is able to constrain supercoils, providing a link between DNA topology and regulation. The results support the conclusion that the bacterial DNA-binding protein LRP, assisted by H-NS, forms a repressive nucleoprotein structure involved in regulation of rRNA transcription. The formation of this regulatory structure appears to be directly affected by environmental changes.
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