A new class of uracil-DNA glycosylases related to human thymine-DNA glycosylase.
Mispairs in DNA of guanine with uracil and thymine can arise as a result of deamination of cytosine and 5-methylcytosine, respectively. In humans such mispairs are removed by thymine-DNA glycosylase (TDG). By deleting the carboxy and amino termini of this enzyme we have identified a core region capable of processing G/U but not G/T mispairs. We have further identified two bacterial proteins with strong sequence homology to this core and shown that the homologue from Escherichia coli (dsUDG) can remove uracil from G/U mispairs. This enzyme is likely to act as a back-up to the highly efficient and abundant enzyme uracil-DNA glycosylase (UDG) which is found in most organisms. Pupating insects have been reported to lack UDG activity, but we have identified an enzyme similar to dsUDG in cell lines from three different insect species. These data imply the existence of a family of double-strand-specific uracil-DNA glycosylases which, although they are subservient to UDG in most organisms, may constitute the first line of defence against the mutagenic effects of cytosine deamination in insects.
Gallinari
P
P
Istituto di Richerche di Biologia Molecolare P. Angeletti, Pomezia, Italy.
Jiricny
J
J
D000595:Amino Acid Sequence; D000818:Animals; D045647:DNA Glycosylases; D004260:DNA Repair; D003641:Deamination; D043224:Deoxyribonuclease (Pyrimidine Dimer); D004331:Drosophila melanogaster / Q000201:enzymology; D004706:Endodeoxyribonucleases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D012706:Serratia marcescens / Q000201:enzymology; D013941:Thymine / Q000378:metabolism; D044502:Thymine DNA Glycosylase; D014498:Uracil / Q000378:metabolism; D051981:Uracil-DNA Glycosidase
D011994:Recombinant Proteins; D014498:Uracil; D004706:Endodeoxyribonucleases; D043224:Deoxyribonuclease (Pyrimidine Dimer); D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D044502:Thymine DNA Glycosylase; D051981:Uracil-DNA Glycosidase; C113921:mismatch-specific thymine uracil-DNA glycosylase; D013941:Thymine