MinION sequencing data of mtDNA from BH10 cells

Mitochondrial DNA (mtDNA) recombination in animals has remained enigmatic because of its uniparental inheritance and subsequent homoplasmic state, which excludes the biological need for genetic recombination, as well as limits tools to study it. However, molecular recombination is an important genome maintenance mechanism for all organisms, most notably being required for double-strand break repair. To demonstrate the existence of mtDNA recombination, we have taken advantage of a cell model with two different types of mitochondrial genomes and impaired ability to turn over broken mtDNA. The resulting excess of linear DNA fragments caused increased formation of cruciform mtDNA, appearance of heterodimeric mtDNA complexes and recombinant mtDNA genomes, detectable by Southern blot. Combining our observations with previously published work, we propose that the mitochondrial replisome can catalyze microhomology-mediated recombination of linear mtDNA ends, thus rendering a specialized mitochondrial recombinase unnecessary. The error-proneness of this system is likely to contribute to the formation of pathological mtDNA rearrangements.