2µ circle

The 2µ circle is a circular plasmid composed of about 6.000 bp of double-stranded DNA, comprising approximately 1.5-5% of total nuclear DNA. It’s found in the nucleus in most strains of Saccharomyces cerevisiae at a copy number of about 60. No sequences homologous of 2µ circle have been found in chromosomal DNA.

2μ circle can also serve as a model system for specialized recombination in a eukaryotic cell with the possibility that this system will provide insights into an unusual form of gene regulation.

The principal element in the strategy of 2 μm circle for persistence as a parasitic DNA species is its ability to raise its copy number.