Increased activity and fidelity of DNA polymerase beta on single-nucleotide gapped DNA

J Biol Chem. 1997 Oct 31;272(44):27501-4. doi: 10.1074/jbc.272.44.27501.


DNA polymerase beta (pol beta) is an error-prone polymerase that plays a central role in mammalian base excision repair. To better characterize the mechanisms governing rat pol beta activity, we examined polymerization on synthetic primer-templates of different structure. Steady-state kinetic analyses revealed that the catalytic efficiency of pol beta (kcat/Km,dNTPapp) is strongly influenced by gap size and the presence of a phosphate group at the 5'-margin of the gap. pol beta exhibited the highest catalytic efficiency on 5'-phosphorylated 1-nucleotide gapped DNA. This efficiency was >/=500 times higher than on non-phosphorylated 1-nucleotide and 6-nucleotide (with or without PO4) gapped DNAs and 2,500 times higher than on primer-template with no gaps. The nucleotide insertion fidelity of pol beta, as judged by its ability to form G-N mispairs, was also higher (10-100 times) on 5'-phosphorylated single-nucleotide gapped DNA compared with the other DNA substrates studied. These data suggest that a primary function of mammalian pol beta is to fill 5'-phosphorylated 1-nucleotide gaps.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catalysis
  • DNA / metabolism*
  • DNA Polymerase beta / metabolism*
  • Kinetics
  • Molecular Sequence Data
  • Phosphorylation
  • Rats
  • Recombinant Proteins / metabolism
  • Substrate Specificity


  • Recombinant Proteins
  • DNA
  • DNA Polymerase beta

Associated data

  • GENBANK/J02482