title: Efficient repair of abasic sites in DNA by mitochondrial enzymes.
abstract: Mutations in mitochondrial DNA (mtDNA) cause a variety of relatively rare human diseases and may contribute to the pathogenesis of other, more common degenerative diseases. This stimulates interest in the capacity of mitochondria to repair damage to mtDNA. Several recent studies have shown that some types of damage to mtDNA may be repaired, particularly if the lesions can be processed through a base excision mechanism that employs an abasic site as a common intermediate. In this paper, we demonstrate that a combination of enzymes purified from Xenopus laevis mitochondria efficiently repairs abasic sites in DNA. This repair pathway employs a mitochondrial class II apurinic/apyrimidinic (AP) endonuclease to cleave the DNA backbone on the 5' side of an abasic site. A deoxyribophosphodiesterase acts to remove the 5' sugar-phosphate residue left by AP endonuclease. mtDNA polymerase gamma fills the resulting 1-nucleotide gap. The remaining nick is sealed by an mtDNA ligase. We report the first extensive purification of mtDNA ligase as a 100-kDa enzyme that functions with an enzyme-adenylate intermediate and is capable of ligating oligo(dT) strands annealed to poly(rA). These properties together with preliminary immunological evidence suggest that mtDNA may be related to nuclear DNA ligase III.
authors.affiliation: Department of Pharmacological Sciences, State University of New York at Stony Brook, 11794-8651, USA.
authors.forename: K G
authors.initials: KG
authors.lastname: Pinz
authors.forename: D F
authors.initials: DF
authors.lastname: Bogenhagen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019757:Carbon-Oxygen Lyases / Q000145:classification / Q000378:metabolism*; D002458:Cell Fractionation; D004247:DNA / Q000096:biosynthesis; D011088:DNA Ligases / Q000378:metabolism*; D000074002:DNA Polymerase gamma; D004260:DNA Repair; D004272:DNA, Mitochondrial; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D043223:Deoxyribonuclease IV (Phage T4-Induced); D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D013698:Templates, Genetic; D014982:Xenopus laevis
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA; D000074002:DNA Polymerase gamma; D004259:DNA-Directed DNA Polymerase; D043223:Deoxyribonuclease IV (Phage T4-Induced); C058246:DNA deoxyribophosphodiesterase; D010727:Phosphoric Diester Hydrolases; D019757:Carbon-Oxygen Lyases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D011088:DNA Ligases