Extrachromosomal circular DNA is common in yeast

We performed a screen for extrachromosomal circular DNAs containing segments of genomic yeast DNA. We found 1,756 such extrachromosomal circular DNAs containing about 23% of the total yeast genomic information. The abundance of these circular forms of genomic DNA suggests that eccDNA formation might be a common mutation that can arise in any part of the genome, and not in only a few special loci. We propose that eccDNAs may be precursors to the copy number variation in eukaryotic genomes characteristic of both the evolutionary process and cancer progression.