Double strand break rejoining by mammalian mitochondrial extracts

• Published in: Nucleic acids research Vol. 27; no. 4; pp. 1198 - 1204
• Main Authors: Lakshmipathy, Uma, Campbell, Colin
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 15-02-1999; Oxford Publishing Limited (England)
• Subjects: Animals; Cell Extracts; DNA Damage; DNA Repair; DNA, Mitochondrial; Escherichia coli; Mice; Mitochondria; Mutagenesis; Rats; Rats, Inbred F344
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/27.4.1198

DNA end-joining was measured by incubating linearized plasmid DNA with mitochondrial protein extracts. A spectrum of end-joined molecules ranging from recircularized monomer to dimer and higher molecular weight forms was observed. The DNA end-joining reaction required ATP and Mg2+, and was inhibited by sodium chloride. Both cohesive- and blunt-ended DNA molecules were end-joined, although the former were more efficient substrates. Molecular analysis of rejoined molecules revealed that >95% of the linearized DNA were precisely end-joined. The few imprecisely end-joined molecules recovered, sustained deletions that spanned direct repeat sequences. The deletions observed are strikingly similar to those present in mitochondrial genomes of patients with Kearns-Sayre or Pearson syndromes, certain ophthalmic myopathies and the aged. These results suggest that mammalian mitochondria possess a DNA double strand break repair activity similar to that seen in the nucleus, and that this repair pathway may play a role in the generation of mitochondrial DNA deletions associated with a number of human pathologies.