title: Identification of high excision capacity for 5-hydroxymethyluracil mispaired with guanine in DNA of Escherichia coli MutM, Nei and Nth DNA glycosylases.
abstract: The oxidation and deamination of 5-methylcytosine (5mC) in DNA generates a base-pair between 5-hydroxymethyluracil (5hmU) and guanine. 5hmU normally forms a base-pair with adenine. Therefore, the conversion of 5mC to 5hmU is a potential pathway for the generation of 5mC to T transitions. Mammalian cells have high levels of activity of 5hmU-DNA glycosylase, which excises 5hmU from DNA. However, glycosylases that similarly excise 5hmU have not been observed in yeast or Escherichia coli. Recently, we found that E.coli MutM, Nei and Nth have DNA glycosylase activity for 5-formyluracil, which is another type of oxidation product of the thymine methyl group. In this study, we examined whether or not E.coli MutM, Nei and Nth have also DNA glycosylase activity that acts on 5hmU in vitro. When incubated with synthetic duplex oligonucleotides containing 5hmU:G or 5hmU:A, purified MutM, Nei and Nth cleaved the 5hmU:G oligonucleotide 58, 5 and 37 times, respectively, more efficiently than the 5hmU:A oligonucleotide. In E.coli, the 5hmU-DNA glycosylase activities of MutM, Nei and Nth may play critical roles in the repair of 5hmU:G mispairs to avoid 5mC to T transitions.
authors.affiliation: Laboratory of Radiation Biology, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Hori
authors.forename: Shuji
authors.initials: S
authors.lastname: Yonei
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugiyama
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Kino
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Qiu-Mei
authors.initials: QM
authors.lastname: Zhang
mesh_terms: D020137:Base Pair Mismatch; D001483:Base Sequence; D045647:DNA Glycosylases; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D006147:Guanine / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D010432:Pentoxyl / Q000031:analogs & derivatives* / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D029968:Escherichia coli Proteins; D009841:Oligonucleotides; C008055:5-hydroxymethyluracil; D006147:Guanine; D010432:Pentoxyl; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli