Figure 11. Model depicting mechanism of generation of ‘9 bp deletion’ seen in the mitochondrial genome.

When mitochondria are under stress, Endonuclease G releases into matrix from inner membrane space. In the matrix, Endonuclease G binds and induces cleavage at single-double stranded junctions of G4 DNA as indicated by arrows. Exonuclease action (CtIP/MRE11/Exo G) exposes the direct repeats/microhomology region, which is then paired with the help of unknown proteins, most likely using direct repeats. Ligation of broken ends can result in a ‘9 bp deletion’ at the Region I of the mitochondrial genome.