1. A new class of uracil-DNA glycosylases related to human thymine-DNA glycosylase.
- Author
-
Gallinari P and Jiricny J
- Subjects
- Amino Acid Sequence, Animals, Deamination, Deoxyribonuclease (Pyrimidine Dimer), Drosophila melanogaster enzymology, Endodeoxyribonucleases classification, Endodeoxyribonucleases genetics, Escherichia coli enzymology, Humans, Mice, Molecular Sequence Data, N-Glycosyl Hydrolases classification, N-Glycosyl Hydrolases genetics, Recombinant Proteins genetics, Recombinant Proteins metabolism, Sequence Deletion, Sequence Homology, Amino Acid, Serratia marcescens enzymology, Thymine metabolism, Uracil metabolism, Uracil-DNA Glycosidase, DNA Glycosylases, DNA Repair, Endodeoxyribonucleases metabolism, N-Glycosyl Hydrolases metabolism, Thymine DNA Glycosylase
- Abstract
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.
- Published
- 1996
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