Functional analysis of H. sapiens DNA polymerase gamma spacer mutation W748S with and without common variant E1143G

Biochim Biophys Acta. 2010 Jun;1802(6):545-51. doi: 10.1016/j.bbadis.2010.02.003. Epub 2010 Feb 12.


Mitochondrial DNA polymerase, POLG, is the sole DNA polymerase found in animal mitochondria. In humans, POLGalpha W748S in cis with an E1143G mutation has been linked to a new type of recessive ataxia, MIRAS, which is the most common inherited ataxia in Finland. We investigated the biochemical phenotypes of the W748S amino acid change, using recombinant human POLG. We measured processive and non-processive DNA polymerase activity, DNA binding affinity, enzyme processivity, and subunit interaction with recombinant POLGbeta. In addition, we studied the effects of the W748S and E1143G mutations in primary human cell cultures using retroviral transduction. Here, we examined cell viability, mitochondrial DNA copy number, and products of mitochondrial translation. Our results indicate that the W748S mutant POLGalpha does not exhibit a clear biochemical phenotype, making it indistinguishable from wild type POLGalpha and as such, fail to replicate previously published results. Furthermore, results from the cell models were concurrent with the findings from patients, and support our biochemical findings.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Catalytic Domain / genetics
  • Cells, Cultured
  • DNA Polymerase gamma
  • DNA Primers / genetics
  • DNA, Intergenic / genetics
  • DNA, Mitochondrial / genetics
  • DNA-Directed DNA Polymerase / chemistry
  • DNA-Directed DNA Polymerase / genetics*
  • DNA-Directed DNA Polymerase / metabolism*
  • Genes, Recessive
  • Genetic Variation*
  • Humans
  • In Vitro Techniques
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Mutation, Missense*
  • Protein Subunits
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Spinocerebellar Degenerations / enzymology
  • Spinocerebellar Degenerations / genetics
  • Syndrome


  • DNA Primers
  • DNA, Intergenic
  • DNA, Mitochondrial
  • Protein Subunits
  • Recombinant Proteins
  • DNA Polymerase gamma
  • DNA-Directed DNA Polymerase
  • POLG protein, human