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. 1972 Jan;69(1):143–146. doi: 10.1073/pnas.69.1.143

An Activity from Mammalian Cells That Untwists Superhelical DNA—A Possible Swivel For DNA Replication

James J Champoux 1, Renato Dulbecco 1
PMCID: PMC427563  PMID: 4333036

Abstract

Nuclei from secondary mouse-embryo cells contain an activity capable of untwisting closed-circular DNAs containing either negative or positive superhelical turns. The activity has no apparent effect on a closed-circular DNA containing no superhelical turns, and is not due to the combined action of an endonuclease and polynucleotide ligase. The enzyme apparently acts by introducing a single-strand nick into the DNA, forming a DNA-enzyme complex that allows the strands to rotate relative to the helix axis before reversing the reaction and sealing the break. The enzyme might possibly serve as a swivel during DNA replication.

Keywords: polyoma, ethidium bromide, mouse-embryo cells, dye binding assay

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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