PMID:11972787
| Citation |
Waldron, DE, Owen, P and Dorman, CJ (2002) Competitive interaction of the OxyR DNA-binding protein and the Dam methylase at the antigen 43 gene regulatory region in Escherichia coli. Mol. Microbiol. 44:509-20 |
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| Abstract |
The antigen 43 surface protein of Escherichia coli is expressed in a phase-variable manner by a mechanism involving alternative activation and repression of transcription of the agn43 gene. The repressor is the OxyR DNA-binding protein, and its binding site was found to be located downstream of the agn43 transcription start site in a region of DNA that encompasses three 5'-GATC-3' sequences that are subject to Dam-mediated DNA methylation. It has been suggested previously that the phase-variable expression of antigen 43 results from a competition between Dam methylase and the OxyR repressor for these sites. The 5'-GATC-3' sequences were inactivated for methylation by site-directed mutagenesis, and all possible combinations of inactive and active sites were assessed for effects on phase-variable expression of the agn43 gene. Inactivation of any 5'-GATC-3' site individually had no effect; at least two sites had to be inactivated to disrupt the normal pattern of expression. Studies of OxyR interaction with agn43 DNA showed that methylation of any two 5'-GATC-3' sites was necessary and sufficient to block binding of the repressor. It was also found that the adenines of the second and third 5'-GATC-3' sites are required for OxyR binding, demonstrating that the sites for Dam methylation and for repressor binding are intimately associated. This is consistent with a competition model in which Dam and OxyR share a preference for specific DNA sequences in the regulatory region of the agn43 gene. |
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| Keywords |
Adhesins, Bacterial; Antigens, Bacterial/genetics; Bacterial Outer Membrane Proteins/genetics; Bacterial Proteins/metabolism; Base Sequence; Codon/genetics; DNA Primers; DNA-Binding Proteins; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins; Molecular Sequence Data; Regulatory Sequences, Nucleic Acid; Repressor Proteins/metabolism; Sequence Alignment; Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism; Transcription Factors/metabolism |
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