Evidence for the kinetic partitioning of polymerase activity on G-quadruplex DNA

Biochemistry. 2015 May 26;54(20):3218-30. doi: 10.1021/acs.biochem.5b00060. Epub 2015 May 11.

Abstract

We have investigated the action of the human DNA polymerase ε (hpol ε) and η (hpol η) catalytic cores on G-quadruplex (G4) DNA substrates derived from the promoter of the c-MYC proto-oncogene. The translesion enzyme hpol η exhibits a 6.2-fold preference for binding to G4 DNA over non-G4 DNA, while hpol ε binds both G4 and non-G4 substrates with nearly equal affinity. Kinetic analysis of single-nucleotide insertion by hpol η reveals that it is able to maintain >25% activity on G4 substrates compared to non-G4 DNA substrates, even when the primer template junction is positioned directly adjacent to G22 (the first tetrad-associated guanine in the c-MYC G4 motif). Surprisingly, hpol η fidelity increases ~15-fold when copying G22. By way of comparison, hpol ε retains ~4% activity and has a 33-fold decrease in fidelity when copying G22. The fidelity of hpol η is ~100-fold greater than that of hpol ε when comparing the misinsertion frequencies of the two enzymes opposite a tetrad-associated guanine. The kinetic differences observed for the B- and Y-family pols on G4 DNA support a model in which a simple kinetic switch between replicative and TLS pols could help govern fork progress during G4 DNA replication.

Publication types

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

MeSH terms

  • Base Pair Mismatch
  • DNA Polymerase II / chemistry*
  • DNA Primers / chemistry
  • DNA Replication
  • DNA-Directed DNA Polymerase / chemistry*
  • G-Quadruplexes
  • Humans
  • Kinetics
  • Protein Binding
  • Proto-Oncogene Mas
  • Substrate Specificity

Substances

  • DNA Primers
  • MAS1 protein, human
  • Proto-Oncogene Mas
  • DNA Polymerase II
  • DNA-Directed DNA Polymerase
  • Rad30 protein