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. 1972 Jan;69(1):143-6.
doi: 10.1073/pnas.69.1.143.

An activity from mammalian cells that untwists superhelical DNA--a possible swivel for DNA replication (polyoma-ethidium bromide-mouse-embryo cells-dye binding assay)

J J Champoux, R Dulbecco

An activity from mammalian cells that untwists superhelical DNA--a possible swivel for DNA replication (polyoma-ethidium bromide-mouse-embryo cells-dye binding assay)

J J Champoux et al. Proc Natl Acad Sci U S A. 1972 Jan.

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.

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