New substrates for old enzymes. 5-Hydroxy-2'-deoxycytidine and 5-hydroxy-2'-deoxyuridine are substrates for Escherichia coli endonuclease III and formamidopyrimidine DNA N-glycosylase, while 5-hydroxy-2'-deoxyuridine is a substrate for uracil DNA N-glycosylase.
5-Hydroxy-2'-deoxycytidine (5-OHdC) and 5-hydroxy-2'-deoxyuridine (5-OHdU) are major products of oxidative DNA damage with mutagenic potential. Until now, no enzymatic activity responsible for their removal has been identified. We report here that both 5-OHdC and 5-OHdU are substrates for Escherichia coli endonuclease III and formamidopyrimidine DNA N-glycosylase (FPG). 5-OHdU is also a substrate for uracil DNA N-glycosylase. Consistent with their mechanisms of action on previously described substrates, endonuclease III removes 5-OHdC and 5-OHdU via a N-glycosylase/beta-elimination reaction, FPG follows a N-glycosylase/beta,delta-elimination reaction, and uracil N-glycosylase removes 5-OHdU by N-glycosylase action leaving behind an abasic site. Endonuclease III removes both lesions more efficiently than FPG, and both endonuclease III and FPG remove 5-OHdC slightly more efficiently than 5-OHdU. Uracil DNA N-glycosylase removes 5-OHdU more efficiently than the other two enzymes and has no activity on 5-OHdC even when present in great excess. Analysis of crude extracts obtained from wild type and endonuclease III deletion mutants of E. coli correlated well with data obtained with the purified enzymes.
Department of Microbiology and Molecular Genetics, University of Vermont, Burlington 05405.
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Hatahet
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Kow
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Purmal
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Cunningham
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Wallace
D001483:Base Sequence; D045647:DNA Glycosylases; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000378:metabolism; D043224:Deoxyribonuclease (Pyrimidine Dimer); D003857:Deoxyuridine / Q000031:analogs & derivatives* / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D013379:Substrate Specificity; D051981:Uracil-DNA Glycosidase
D029968:Escherichia coli Proteins; D009838:Oligodeoxyribonucleotides; D003841:Deoxycytidine; C074088:5-hydroxy-2'-deoxyuridine; C074071:5-hydroxy-2'-deoxycytidine; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D003857:Deoxyuridine