Mechanism of active DNA demethylation during embryonic development and cellular differentiation in vertebrates

Incubation of hemimethylated and labelled oligodeoxynucleotides with nuclear extracts from differentiating chicken embryos and mouse myoblasts resulted in the replacement of m5C by C. One of the enzymes involved is m5CpG endonuclease. It cleaves only m5CpG and not, m5CpT, m5CpA, m5CpC or m6ApT. The enzyme is not sequence specific and catalyses the reaction in the presence of high concentrations of EDTA or EGTA.