DNMT3A mutants commonly found in MBD4-deficient patients impair the glycosylase activity of TDG. (A) Gel image of glycosylase assay with mutant DNMT3A. Addition of mutant DNMT3A does not potentiate TDG activity and even inhibits TDG activity at higher concentrations. (B-E) Quantification of each DNMT3A mutant tested in panel A, relative to unstimulated TDG.