In vitro bypass of UV-induced lesions by Escherichia coli DNA polymerase I: specificity of nucleotide incorporation

Proc Natl Acad Sci U S A. 1983 Mar;80(6):1541-5. doi: 10.1073/pnas.80.6.1541.


A variety of DNA polymerases, synthesizing in vitro on an UV-irradiated phi X174 DNA template, terminate synthesis one nucleotide before the 3' pyrimidines of putative dimers on the template. We have devised a system using Escherichia coli DNA polymerase I (Klenow fragment) that can synthesize past at least some of these dimers. The bypass is carried out in a multistep process--first, the incorporation of nucleotides opposite the pyrimidines in the dimer and, then, the addition of nucleotides complementary to the bases distal to the dimer. The insertion of a nucleotide opposite the first (3') pyrimidine of a putative dimer in the presence of Mn2+ occurs in a concentration-dependent fashion with a 3- to 4-fold preference for purine nucleotides over pyrimidine nucleotides. In the presence of Mg2+, insertion is less frequent. Correlation of these results with in vivo mutation data suggests a role for the polymerase in determining the spectrum of base substitution mutagenesis in SOS induced cells.

Publication types

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

MeSH terms

  • Base Sequence
  • DNA Polymerase I / metabolism*
  • DNA Repair*
  • DNA, Bacterial / biosynthesis
  • DNA, Bacterial / radiation effects*
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / genetics
  • Mutation
  • Pyrimidine Dimers / genetics*
  • Ultraviolet Rays


  • DNA, Bacterial
  • Pyrimidine Dimers
  • DNA Polymerase I
  • DNA-Directed DNA Polymerase