Facile synthesis of hydroxymethylcytosine-containing oligonucleotides and their reactivity upon osmium oxidation.

DNA strands containing a 5-hydroxymethylcytosine ((hm)C), which have recently been found in neuron cells and embryonic stem cells, were synthesized through a facile synthetic technique. The (hm)C-containing strands were efficiently oxidized at (hm)C using an osmium oxidation assay. The (hm)C was oxidized as easily as 5-methylcytosine, which can be distinguished from unmethylated cytosine.