A back-up glycosylase in Nth1 knock-out mice is a functional Nei (endonuclease VIII) homologue.
Thymine glycol, a potentially lethal DNA lesion produced by reactive oxygen species, can be removed by DNA glycosylase, Escherichia coli Nth (endonuclease III), or its mammalian homologue NTH1. We have found previously that mice deleted in the Nth homologue still retain at least two residual glycosylase activities for thymine glycol. We report herein that in cell extracts from the mNth1 knock-out mouse there is a third thymine glycol glycosylase activity that is encoded by one of three mammalian proteins with sequence similarity to E. coli Fpg (MutM) and Nei (endonuclease VIII). Tissue expression of this mouse Nei-like (designated as Neil1) gene is ubiquitous but much lower than that of mNth1 except in heart, spleen, and skeletal muscle. Recombinant NEIL1 can remove thymine glycol and 5-hydroxyuracil in double- and single-stranded DNA much more efficiently than 8-oxoguanine and can nick the strand by an associated (beta-delta) apurinic/apyrimidinic lyase activity. In addition, the mouse NEIL1 has a unique DNA glycosylase/lyase activity toward mismatched uracil and thymine, especially in U:C and T:C mismatches. These results suggest that NEIL1 is a back-up glycosylase for NTH1 with unique substrate specificity and tissue-specific expression.
Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan. mtakao@idac.tohoku.ac.jp
Masashi
M
Takao
Shin-Ichiro
S
Kanno
Kumiko
K
Kobayashi
Qiu-Mei
QM
Zhang
Shuji
S
Yonei
Gijbertus T J
GT
van der Horst
Akira
A
Yasui
D000595:Amino Acid Sequence; D000818:Animals; D020137:Base Pair Mismatch; D045647:DNA Glycosylases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000502:physiology*; D029968:Escherichia coli Proteins; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000502:physiology*; D009928:Organ Specificity; D017385:Sequence Homology; D013379:Substrate Specificity
D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); C106403:NTH protein, E coli; C468347:NTHL1 protein, human; C470703:Nthl1 protein, mouse; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C473634:NEIL1 protein, human