DNA glycosylase activities for thymine residues oxidized in the methyl group are functions of the hNEIL1 and hNTH1 enzymes in human cells.
Bacteria and eukaryotes possess redundant activities that recognize and remove oxidatively damaged bases from DNA through base excision repair. DNA glycosylases excise damaged bases to initiate the base excision repair pathway. hOgg1 and hNTH1, homologues of E. coli MutM and Nth, respectively, had been identified and characterized in human cells. Recent works revealed that human cells have three orthologues of E. coli Nei, hNEIL1, hNEIL2 and hNEIL3. In the present experiments, hNEIL1 protected the E. coli nth nei mutant from lethal effect of hydrogen peroxide and high frequency of spontaneous mutations under aerobic conditions. Furthermore, hNEIL1 efficiently cleaved double stranded oligonucleotides containing 5-formyluracil (5-foU) and 5-hydroxymethyluracil (5-hmU) in vitro via beta- and delta-elimination reactions. Similar activities were detected with hNTH1. These results indicate that hNEIL1 and hNTH1 are DNA glycosylases that excise 5-foU and 5-hmU as efficiently as Tg in human cells.
Zhang
Qiu-Mei
QM
Laboratory of Radiation Biology, Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Yonekura
Shin-Ichiro
S
Takao
Masashi
M
Yasui
Akira
A
Sugiyama
Hiroshi
H
Yonei
Shuji
S
D003001:Cloning, Molecular; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D043224:Deoxyribonuclease (Pyrimidine Dimer) / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D009154:Mutation / Q000235:genetics; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D010432:Pentoxyl / Q000031:analogs & derivatives* / Q000378:metabolism; D013941:Thymine / Q000031:analogs & derivatives* / Q000378:metabolism; D014498:Uracil / Q000031:analogs & derivatives* / Q000378:metabolism
D018076:DNA, Complementary; D009841:Oligonucleotides; C007777:5-formyluracil; C029389:thymine glycol; C008055:5-hydroxymethyluracil; D014498:Uracil; D010432:Pentoxyl; D006861:Hydrogen Peroxide; D043224:Deoxyribonuclease (Pyrimidine Dimer); C468347:NTHL1 protein, human; D045647:DNA Glycosylases; C473634:NEIL1 protein, human; D013941:Thymine