title: Digestion of damaged DNA by the T7 DNA polymerase-exonuclease.
abstract: We have investigated the 3'-5'-exonuclease activity of phage T7 DNA polymerase for its usefulness as an approach for the detection of lesions in DNA. Unlike the T4 DNA polymerase-exonuclease, which is commonly used to map the position and frequency of lesions in very small DNA fragments, T7 DNA polymerase-exonuclease is able to hydrolyse almost completely the large fragments from KpnI-restricted mammalian DNA. However, we found that the exonuclease was also able to hydrolyse DNA containing several kinds of lesions: cyclobutane pyrimidine dimers, thymine glycols, and mono-adducts of 4'-hydroxymethyl-4,5',8-trimethylpsoralen and 5'-methyl-isopsoralen. Modifications of the reaction conditions did not significantly alter the extent of hydrolysis. These properties distinguish the T7 DNA polymerase-exonuclease from the T4 DNA polymerase-exonuclease and make the T7 DNA polymerase-exonuclease unsuitable for detecting several types of lesions in DNA.
authors.affiliation: Department of Biological Sciences, Stanford University, CA 94305-5020.
authors.forename: D R
authors.initials: DR
authors.lastname: Koehler
authors.forename: P C
authors.initials: PC
authors.lastname: Hanawalt
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D004249:DNA Damage; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D043211:Exodeoxyribonuclease V; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D005363:Ficusin / Q000494:pharmacology; D006868:Hydrolysis; D014466:Ultraviolet Rays
chemical_list: D004247:DNA; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase; D005090:Exodeoxyribonucleases; D043211:Exodeoxyribonuclease V; D005363:Ficusin