Mismatch extension ability of yeast and human DNA polymerase eta

J Biol Chem. 2001 Jan 19;276(3):2263-6. doi: 10.1074/jbc.M009049200. Epub 2000 Oct 27.


DNA polymerase eta (Poleta) functions in error-free replication of UV-damaged DNA, and in vitro it efficiently bypasses a cis-syn T-T dimer by incorporating two adenines opposite the lesion. Steady state kinetic studies have shown that both yeast and human Poleta are low-fidelity enzymes, and they misincorporate nucleotides with a frequency of 10(-2)-10(-3) on both undamaged and T-T dimer-containing DNA templates. To better understand the role of Poleta in error-free translesion DNA synthesis, here we examine the ability of Poleta to extend from base mismatches. We find that both yeast and human Poleta extend from mismatched base pairs with a frequency of approximately 10(-3) relative to matched base pairs. In the absence of efficient extension of mismatched primer termini, the ensuing dissociation of Poleta from DNA may favor the excision of mismatched nucleotides by a proofreading exonuclease. Thus, we expect DNA synthesis by Poleta to be more accurate than that predicted from the fidelity of nucleotide incorporation alone.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Base Pair Mismatch*
  • Base Sequence
  • DNA Primers
  • DNA-Directed DNA Polymerase / metabolism*
  • Humans
  • Saccharomyces cerevisiae / enzymology*


  • DNA Primers
  • DNA-Directed DNA Polymerase
  • Rad30 protein