title: Cyclobutane pyrimidine dimers and (6-4) photoproducts block polymerization by DNA polymerase I.
abstract: Bipyrimidine cyclobutane dimers and 6-4'-(pyrimidin-2'-one)-pyrimidine photoproducts are the major adducts formed in DNA following exposure to ultraviolet light. The relationship between the type and frequency of UV-induced DNA damage and the effects of such damage on DNA replication were investigated. UV-irradiated M13 phage DNA was employed in polymerization reactions with the Kenow fragment of Escherichia coli DNA polymerase I. The locations and frequencies of polymerase termination events occurring within a defined sequence of M13 DNA were compared with measurements of the locations and frequencies of UV-induced DNA damage of the same DNA sequence by using UV-specific enzymatic and chemical methods. The results indicate that both cyclobutane dimers and (6-4) photoproducts quantitatively block polymerization by DNA polymerase I.
mesh_terms: D003090:Coliphages / Q000235:genetics; D004256:DNA Polymerase I / Q000037:antagonists & inhibitors*; D004261:DNA Replication / Q000528:radiation effects; D004279:DNA, Viral / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005814:Genes, Viral; D007700:Kinetics; D011740:Pyrimidine Dimers; D011744:Pyrimidinones; D013604:T-Phages / Q000201:enzymology; D013698:Templates, Genetic; D014466:Ultraviolet Rays
chemical_list: D004279:DNA, Viral; D011740:Pyrimidine Dimers; D011744:Pyrimidinones; D004256:DNA Polymerase I