Incision at hypoxanthine residues in DNA by a mammalian homologue of the Escherichia coli antimutator enzyme endonuclease V.
Deamination of DNA bases can occur spontaneously, generating highly mutagenic lesions such as uracil and hypoxanthine. In Escherichia coli two enzymes initiate repair at hypoxanthine residues in DNA. The alkylbase DNA glycosylase, AlkA, initiates repair by removal of the damaged base, whereas endonuclease V, Endo V, hydrolyses the second phosphodiester bond 3' to the lesion. We have identified and characterised a mouse cDNA with striking homology to the E.coli nfi gene, which also has significant similarities to motifs required for catalytic activity of the UvrC endonuclease. The 37-kDa mouse enzyme (mEndo V) incises the DNA strand at the second phosphodiester bond 3' to hypoxanthine- and uracil-containing nucleotides. The activity of mEndo V is elevated on single-stranded DNA substrate in vitro. Expression of the mouse protein in a DNA repair-deficient E.coli alkA nfi strain suppresses its spontaneous mutator phenotype. We suggest that mEndo V initiates an alternative excision repair pathway for hypoxanthine removal. It thus appears that mEndo V has properties overlapping the function of alkylbase DNA glycosylase (Aag) in repair of deaminated adenine, which to some extent could explain the absence of phenotypic abnormalities associated with Aag knockout in mice.
Moe
Ane
A
Centre for Molecular Biology and Neuroscience and Institute of Medical Microbiology, University of Oslo, Rikshospitalet, N-0027 Oslo, Norway.
Ringvoll
Jeanette
J
Nordstrand
Line M
LM
Eide
Lars
L
Bjørås
Magnar
M
Seeberg
Erling
E
Rognes
Torbjørn
T
Klungland
Arne
A
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D017124:Conserved Sequence / Q000235:genetics; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004706:Endodeoxyribonucleases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D005816:Genetic Complementation Test; D006801:Humans; D019271:Hypoxanthine / Q000378:metabolism*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013489:Suppression, Genetic; D013941:Thymine / Q000378:metabolism; D014498:Uracil / Q000378:metabolism
D009841:Oligonucleotides; D012333:RNA, Messenger; D019271:Hypoxanthine; D014498:Uracil; D004247:DNA; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D013941:Thymine