The G/T mismatch specific thymine DNA glycosylase (EC 3.2.2.-) removes the mismatched T with opposite a G residue by its DNA N-glycosylase activity. It is one of the essential components of a functional DNA demethylation complex in chicken embryos, and which also contains 5-methylcytosine DNA glycosylase (5-MCDG), RNA helicase, and G/T mismatch DNA glycosylase activities. The chicken homologue of human G/T mismatch DNA glycosylase shows 80% identity with the human G/T mismatch DNA glycosylase, and both the C- and N-terminal parts have about 50% identity. The recombinant chicken protein expressed in Escherichia coli has both G/T mismatch and 5-MCDG activities. Hemimethylated DNA is a better substrate than symmetrically methylated CpGs for the 5-MCDG activity. Deletion mutations indicate that G/T mismatch and 5-MCDG activities require the same areas of the N- and C-terminal parts of the protein.
Zhu, B, Zheng, Y, Angliker, H, Schwarz, S, Thiry, S, Siegmann, M, Jost, JP
Zhu, B, Zheng, Y, Hess, D, Angliker, H, Schwarz, S, Siegmann, M, Thiry, S, Jost, JP
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