title: In vitro replication of mutagen-damaged DNA: sites of termination.
abstract: We have examined the effect of DNA lesions, which in vivo are potentially mutagenic, on in vitro DNA synthesis carried out by a number of purified DNA polymerases using a 0X174 template. Both acetyl aminofluorene (AAF) adducts and UV-induced pyrimidine dimers are blocks to elongation by DNA polymerases. On UV-irradiated DNA templates synthesis terminates one nucleotide before the sites of pyrimidine dimers with all of the enzymes tested: Pol I and Pol III holoenzyme from Escherichia coli, T4 DNA polymerase, avian myeloblastosis virus reverse transcriptase and a mammalian DNA polymerase alpha. With AAF, which reacts at the C-8 position of guanine, differences are observed between the above enzymes, with the latter two inserting a nucleotide opposite the site of the lesion. Substitution of Mn2+ for Mg2+ as the cation in the Pol I reactions causes changes in the termination pattern on both UV-irradiated and AAF-reacted templates. The significance of these results to the process of inducible error-prone repair and the possible bypass of lesions in the DNA is discussed.
mesh_terms: D010584:Bacteriophage phi X 174 / Q000235:genetics; D001483:Base Sequence; D004256:DNA Polymerase I / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D004260:DNA Repair; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D009153:Mutagens; D011740:Pyrimidine Dimers / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D009153:Mutagens; D011740:Pyrimidine Dimers; D004256:DNA Polymerase I; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase