DNA cytosine methylation (5mC) is highly abundant in mammalian cells and is associated with transcriptional repression. Recently, hydroxymethylcytosine (hmC) has been detected at high levels in certain human cell types; however, its roles are unknown. Due to the structural similarity between 5mC and hmC, it is unclear whether 5mC analyses can discriminate between these nucleotides. Here we show...
