G/T mismatch-specific thymine DNA glycosylase (TDG)

DNA glycosylase that plays an integral role in active DNA demethylation: specifically recognizes and binds 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) in the context of CpG sites and mediates their excision via base-excision repair (BER) to put in an unmethylated cytosine. Cannot eliminate 5- hydroxymethylcytosine (5hmC).

According to an alternative model, involved in DNA demethylation by mediating DNA glycolase activity toward 5-hydroxymethyluracil (5hmU) produced by deamination of 5hmC. Also involved in DNA repair by acting as a thymine-DNA glycosylase that mediates correction of G/T mispairs to G/C pairs: in the DNA of higher eukaryotes, hydrolytic deamination of 5- methylcytosine to thymine contributes to the formation of G/T mismatches.