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Integration host factor affects expression of two genes at the conjugal transfer origin of plasmid R100
1Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas.
Molecular Microbiology
|June 1, 1990
Summary
Integration host factor (IHF) regulates antibiotic resistance plasmid transfer by binding near key promoters. Its absence reduces gene expression and transcript size, impacting plasmid conjugation.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Conjugative antibiotic resistance plasmids, like R100, are critical for bacterial adaptation and spread.
- Integration host factor (IHF) is a known DNA-binding protein involved in various genetic processes.
- The origin of transfer (oriT) and associated genes are essential for plasmid mobilization during conjugation.
Purpose of the Study:
- To investigate the role of Integration host factor (IHF) in the regulation of conjugative plasmid R100 transfer.
- To identify the binding sites of IHF near the R100 origin of transfer and associated promoters.
- To determine the impact of IHF on the expression of R100 genes involved in conjugation.
Main Methods:
- DNase I footprinting to map IHF binding sites near oriT and promoters.
- Chloramphenicol-resistance assays to measure relative promoter activities.
- Northern blot analyses to assess transcript levels and sizes.
Main Results:
- IHF binds to at least three sites near the R100 oriT, including regions adjacent to the gene X and traM promoters, and near the traJ promoter.
- Promoter activities of genes X, traJ, and traM are significantly reduced in himA mutants lacking IHF.
- Absence of IHF leads to a reduction in the size of the main gene X and traJ transcripts.
Conclusions:
- IHF plays a crucial role in the regulation of R100 plasmid conjugation.
- IHF binding to specific sites influences the expression and processing of key conjugation genes.
- Understanding IHF's function provides insights into the mechanisms of antibiotic resistance plasmid transfer.
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