Targeted deletion of alkylpurine-DNA-N-glycosylase in mice eliminates repair of 1,N6-ethenoadenine and hypoxanthine but not of 3,N4-ethenocytosine or 8-oxoguanine.
It has previously been reported that 1,N6-ethenoadenine (epsilonA), deaminated adenine (hypoxanthine, Hx), and 7,8-dihydro-8-oxoguanine (8-oxoG), but not 3,N4-ethenocytosine (epsilonC), are released from DNA in vitro by the DNA repair enzyme alkylpurine-DNA-N-glycosylase (APNG). To assess the potential contribution of APNG to the repair of each of these mutagenic lesions in vivo, we have used cell-free extracts of tissues from APNG-null mutant mice and wild-type controls. The ability of these extracts to cleave defined oligomers containing a single modified base was determined. The results showed that both testes and liver cells of these knockout mice completely lacked activity toward oligonucleotides containing epsilonA and Hx, but retained wild-type levels of activity for epsilonC and 8-oxoG. These findings indicate that (i) the previously identified epsilonA-DNA glycosylase and Hx-DNA glycosylase activities are functions of APNG; (ii) the two structurally closely related mutagenic adducts epsilonA and epsilonC are repaired by separate gene products; and (iii) APNG does not contribute detectably to the repair of 8-oxoG.
Hang
B
B
Donner Laboratory, Lawrence Berkeley National Laboratory, University of California, 94720, USA.
Singer
B
B
Margison
G P
GP
Elder
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RH
D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D002474:Cell-Free System; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D045647:DNA Glycosylases; D004260:DNA Repair; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006868:Hydrolysis; D019271:Hypoxanthine / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D009699:N-Glycosyl Hydrolases / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
C018289:3,N(4)-ethenocytosine; D011994:Recombinant Proteins; C004981:1,N(6)-ethenoadenine; D019271:Hypoxanthine; C024829:8-hydroxyguanine; D006147:Guanine; D003596:Cytosine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C076131:DNA-3-methyladenine glycosidase II; D000225:Adenine