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Updated: Aug 8, 2026

Genome-wide Purification of Extrachromosomal Circular DNA from Eukaryotic Cells
Published on: April 4, 2016
Circular DNA of 3T6R50 double minute chromosomes
A M van der Bliek1, C R Lincke, P Borst
1Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam.
Abstract:
In pulsed field gradient gel electrophoresis (PFGE) the intact deproteinized circular DNA of Mycoplasma (800 kb) and Escherichia coli (4700 kb) remains trapped in the slot. We show here that gamma-irradiation of the DNA in agarose plugs is a convenient method to partially convert these circles into full-length linears, migrating with the expected mobility in PFGE. We have used this method to study the structure of Double Minute chromosomes (DMs) from the methotrexate (MTX)-resistant mouse cell line 3T6R50. Intact deproteinized DM DNA is immobile in these gels, but is converted into a single band of about 2500 kb by either gamma-irradiation, DNaseI in the presence of Mn2+, or restriction enzymes. We conclude that the DM DNA in 3T6R50 cells consists of a homogeneous population of 2500-kb circles.
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