A novel interaction between DNA ligase III and DNA polymerase gamma plays an essential role in mitochondrial DNA stability

Biochem J. 2007 Feb 15;402(1):175-86. doi: 10.1042/BJ20061004.


The data in the present study show that DNA polymerase gamma and DNA ligase III interact in mitochondrial protein extracts from cultured HT1080 cells. An interaction was also observed between the two recombinant proteins in vitro. Expression of catalytically inert versions of DNA ligase III that bind DNA polymerase gamma was associated with reduced mitochondrial DNA copy number and integrity. In contrast, overexpression of wild-type DNA ligase III had no effect on mitochondrial DNA copy number or integrity. Experiments revealed that wild-type DNA ligase III facilitates the interaction of DNA polymerase gamma with a nicked DNA substrate in vitro, and that the zinc finger domain of DNA ligase III is required for this activity. Mitochondrial protein extracts prepared from cells overexpressing a DNA ligase III protein that lacked the zinc finger domain had reduced base excision repair activity compared with extracts from cells overexpressing the wild-type protein. These data support the interpretation that the interaction of DNA ligase III and DNA polymerase gamma is required for proper maintenance of the mammalian mitochondrial genome.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • DNA Ligase ATP
  • DNA Ligases / genetics
  • DNA Ligases / metabolism*
  • DNA Polymerase gamma
  • DNA Repair / physiology
  • DNA, Mitochondrial / metabolism*
  • DNA-Directed DNA Polymerase / metabolism*
  • Humans
  • Immunoprecipitation
  • Poly-ADP-Ribose Binding Proteins
  • Protein Structure, Tertiary
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Tumor Cells, Cultured
  • Xenopus Proteins
  • Zinc Fingers


  • DNA, Mitochondrial
  • Poly-ADP-Ribose Binding Proteins
  • Recombinant Proteins
  • Xenopus Proteins
  • DNA Polymerase gamma
  • DNA-Directed DNA Polymerase
  • DNA Ligases
  • DNA Ligase ATP
  • DNA ligase III alpha protein, Xenopus
  • LIG3 protein, human