Molecular insight into the asymmetric distribution of pathogenetic human mitochondrial DNA deletions

Pathogenetic human mitochondrial DNA deletions occur very rarely in the minor region between the origins of replication. In order to understand the molecular basis of this asymmetry, we analyzed the structure of such a 4.680 kilobase deletion (position 471 - 5151). Directly repeated sequences ( 12 13 nucleotides) are present in the deletion junction, both promoters of heavy chain replication and both ribosomal RNA genes are deleted, and the 5′ extent further narrows the absolute limits of mitochondrial DNA deletions. Several factors are identified that may contribute to the paucity of minor region deletions.