Supercoils in Prokaryotic DNA Restrained in vivo

Cells of Escherichia coli containing the plasmid F were γ -irradiated with various doses to introduce determined numbers of single-strand breaks in the F DNA. The cells were then incubated to permit repair of the breaks while DNA gyrase was inhibited with coumermycin to limit restoration of any rela...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1980-03, Vol.77 (3), p.1331-1335
Main Authors: Pettijohn, David E., Pfenninger, Oswald
Format: Article
Language:English
Subjects:
Aminocoumarins
B lymphocytes
Biochemistry
Bromides
Chromosomes
Coumarins - pharmacology
DNA
DNA repair
DNA Repair - drug effects
DNA, Bacterial - radiation effects
DNA, Superhelical - radiation effects
Escherichia coli
F Factor
Gamma Rays
Irradiation
Molecules
Nucleic Acid Conformation - radiation effects
Nucleosomes
Prokaryotic cells
Pyrroles - pharmacology
Topoisomerase II Inhibitors
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Summary:Cells of Escherichia coli containing the plasmid F were γ -irradiated with various doses to introduce determined numbers of single-strand breaks in the F DNA. The cells were then incubated to permit repair of the breaks while DNA gyrase was inhibited with coumermycin to limit restoration of any relaxed supercoils. Repaired, covalently continuous F DNA was isolated and its superhelical density was measured by two different methods. Both indicated that a major part (50-60%) of the negative superhelical turns were maintained in the repaired molecules, suggesting that the supercoils are restrained in vivo.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.77.3.1331