LC-MS/MS analyses were performed as reported27 (link). Briefly, 1 μg of genomic DNA or S9.6 immunoprecipitated DNA was digested with a mixture of nuclease P1 (Roche), snake venom phosphodiesterase (Worthington) and alkaline phosphatase (Fermentas). One hundred nanograms of digested DNA were subjected to LC-MS/MS analysis. Data were normalized using internal isotopic standards for each 5mC oxidation derivative.