title: Cytosine photoproduct-DNA glycosylase in Escherichia coli and cultured human cells.
abstract: Ultraviolet irradiation of DNA produces a variety of pyrimidine base damages. The activities of Escherichia coli endonuclease III and a human lymphoblast endonuclease that incises ultraviolet-irradiated DNA at modified cytosine moieties were compared. Both the bacterial and human enzymes release this cytosine photoproduct as a free base. These glycosylase activities are linear with times of reaction, quantities of enzyme, and irradiation dosages of the substrates. Both enzyme activities are similarly inhibited by the addition of monovalent and divalent cations. Analysis by DNA sequencing identified loci of endonucleolytic incision as cytosines. These are neither cyclobutane pyrimidine dimers, 6-(1,2-dihydro-2-oxo-4-pyrimidinyl)-5-methyl-2,4(1H,3H)-pyrimidinediones, nor apyrimidinic sites. This cytosine photoproduct is separable from unmodified cytosine by high-performance liquid chromatography. This separation should facilitate identification of this modified cytosine and elucidation of its biological significance.
authors.affiliation: Department of Pathology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: R B
authors.initials: RB
authors.lastname: Weiss
authors.forename: P E
authors.initials: PE
authors.lastname: Gallagher
authors.forename: T P
authors.initials: TP
authors.lastname: Brent
authors.forename: N J
authors.initials: NJ
authors.lastname: Duker
mesh_terms: D001483:Base Sequence; D002478:Cells, Cultured; D045647:DNA Glycosylases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity; D013604:T-Phages / Q000201:enzymology*
chemical_list: D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; C032219:UV endonuclease; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C059701:cytosine-DNA glycosidase