The fidelity of DNA polymerase beta during distributive and processive DNA synthesis

J Biol Chem. 1999 Feb 5;274(6):3642-50. doi: 10.1074/jbc.274.6.3642.


During base excision repair, DNA polymerase beta fills 1-6-nucleotide gaps processively, reflecting a contribution of both its 8- and 31-kDa domains to DNA binding. Here we report the fidelity of pol beta during synthesis to fill gaps of 1, 5, 6, or >300 nucleotides. Error rates during distributive synthesis by recombinant rat and human polymerase (pol) beta with a 390-base gap are similar to each other and to previous values with pol beta purified from tissues. The base substitution fidelity of human pol beta when processively filling a 5-nucleotide gap is similar to that with a 361-nucleotide gap, but "closely-spaced" substitutions are produced at a rate at least 60-fold higher than for distributive synthesis. Base substitution fidelity when filling a 1-nucleotide gap is higher than when filling a 5-nucleotide gap, suggesting a contribution of the 8-kDa domain to the dNTP binding pocket and/or a difference in base stacking or DNA structure imposed by pol beta. Nonetheless, 1-nucleotide gap filling is inaccurate, even generating complex substitution-addition errors. Finally, the single-base deletion error rate during processive synthesis to fill a 6-nucleotide gap is indistinguishable from that of distributive synthesis to fill a 390-nucleotide gap. Thus the mechanism of processivity by pol beta does not allow the enzyme to suppress template misalignments.

MeSH terms

  • Animals
  • Base Sequence
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Replication*
  • DNA, Recombinant
  • Frameshift Mutation
  • Humans
  • Molecular Sequence Data
  • Rats
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism


  • DNA, Recombinant
  • Recombinant Proteins
  • DNA Polymerase beta