Maternal factor that plays a role in epigenetic chromatin reprogramming during early development of the zygote. Involved in the regulation of gametic DNA demethylation by inducing the conversion of the modified genomic base 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). Interacts with histone H3. Interacts with histone H4. Localizes in female and male zygote pronucleus. Associates preferentially with the paternal chromatin during zygote development.