DNA was extracted by phenol/choloroform method. 5hmC enrichment was performed using a previously described procedure with an improved selective chemical labeling method (Song et al, Nature Biotechnology, 2011). DNA libraries were generated following the Illumina protocol for “Preparing Samples for ChIP Sequencing of DNA” (Part# 111257047 Rev. A) using 25-50 ng of input genomic DNA or 5hmC-captured DNA to initiate the protocol. [Song, C.X., Szulwach, K.E., Fu, Y., Dai, Q., Yi, C., Li, X., Li, Y., Chen, C.H., Zhang, W., Jian, X., Wang, J., Zhang, L., Looney, T.J., Zhang, B., Godley, L.A., Hicks, L.M., Lahn, B.T., Jin, P., and He, C. (2011) Selective chemical labeling reveals the genome-wide distribution of 5-hydroxymethylcytosine. Nature Biotechnology, 29(1): 68-72.] Enriched DNA from MeDIP were subjected to library construction using the NEBNext ChIP-Seq Library Prep Reagent Set for Illumina according the manufacturer’s protocol.