DNA modification databases
Covalent DNA modifications, such as 5-methylcytosine (5mC), are increasingly the focus of numerous research programs. In eukaryotes, both 5mC and 5-hydroxymethylcytosine are now recognized as stable epigenetic marks, with diverse functions. Bacteria, archaea, and viruses contain various modified DNA nucleobases, including several in which one base is largely or entirely replaced by a particular covalent modification. Numerous databases describe RNA and histone modifications, but no database specifically catalogues DNA modifications, despite their broad importance as an element of epigenetic regulation.