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In vivo correlation between DNA supercoiling and transcription
Gene
|March 1, 1981
Summary
Bacterial plasmid superhelicity, crucial for DNA transcription, was investigated. Inhibiting DNA gyrase with coumermycin or oxolinic acid reduced supercoiling and gene expression, but the drugs affected transcription differently.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Plasmid DNA superhelicity is vital for various cellular processes, including transcription.
- DNA gyrase plays a critical role in regulating DNA supercoiling.
- Understanding the relationship between superhelicity and transcriptional activity is essential.
Purpose of the Study:
- To investigate the impact of inhibiting DNA gyrase on plasmid DNA superhelicity.
- To determine the correlation between plasmid supercoiling and transcriptional activity in Escherichia coli.
- To compare the effects of coumermycin and oxolinic acid on plasmid superhelicity and gene expression.
Main Methods:
- Measurement of pMT plasmid DNA superhelical density in Escherichia coli.
- Treatment of cells with coumermycin and oxolinic acid to inhibit DNA gyrase.
- Assay of DNA superhelicity using agarose gel electrophoresis.
- Quantification of plasmid-coded messenger RNA (mRNA) synthesis.
Main Results:
- Coumermycin treatment reduced both plasmid supercoiling and trp mRNA synthesis, indicating a correlation.
- Oxolinic acid caused severe inhibition of trp mRNA synthesis with only a minor reduction in plasmid supercoiling.
- Neither drug completely eliminated supertwists from the pMT plasmids.
Conclusions:
- Plasmid DNA supercoiling is closely linked to its suitability for transcription.
- Different DNA gyrase inhibitors exhibit distinct effects on superhelicity and transcriptional inhibition.
- Complete removal of supertwists is not achieved by these inhibitors, suggesting complex regulatory mechanisms.