Spatial relationship of the Fis binding sites for Hin recombinational enhancer activity.
Site-specific recombination reactions involve the joining or rearrangement of discrete DNA segments in a highly precise manner. A site-specific DNA inversion regulates the expression of flagellin genes in Salmonella by switching the orientation of a promoter. Analysis of the reaction has shown that, in addition to DNA sequences at the two boundaries of the 1-kilobase invertible segment where strand exchange occurs, another cis acting sequence is required for efficient inversion. This 60-base-pair enhancer-like sequence can function at many different locations and in either orientation in a plasmid substrate. It includes two binding sites for a host protein called Factor II or Fis (refs 4 and 5). Here we have investigated the importance of the spatial relationship between the two Fis binding sites for enhancer activity and have found that the correct helical positioning of the binding sites on the DNA is critical. However, this result could not be accounted for by effects on Fis binding. We propose a model for enhancer function in which the enhancer region acts to align the recombination sites into a specific conformation required for productive synapsis.
Johnson
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Department of Biological Chemistry, University of California, Los Angeles School of Medicine 90024.
Glasgow
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Simon
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D001426:Bacterial Proteins / Q000378:metabolism; D001482:Base Composition; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D009154:Mutation; D009690:Nucleic Acid Conformation; D010957:Plasmids; D011995:Recombination, Genetic; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; C440502:integration host factor, E coli; D004247:DNA