title: In vitro bypass of UV-induced lesions by Escherichia coli DNA polymerase I: specificity of nucleotide incorporation.
abstract: 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.
mesh_terms: D001483:Base Sequence; D004256:DNA Polymerase I / Q000378:metabolism*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000528:radiation effects*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D009154:Mutation; D011740:Pyrimidine Dimers / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D011740:Pyrimidine Dimers; D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase