Selective chemical labeling reveals the genome-wide distribution of 5-hydroxymethylcytosine.
Song C-X., Szulwach KE., Fu Y., Dai Q., Yi C., Li X., Li Y., Chen C-H., Zhang W., Jian X., Wang J., Zhang L., Looney TJ., Zhang B., Godley LA., Hicks LM., Lahn BT., Jin P., He C.
In contrast to 5-methylcytosine (5-mC), which has been studied extensively, little is known about 5-hydroxymethylcytosine (5-hmC), a recently identified epigenetic modification present in substantial amounts in certain mammalian cell types. Here we present a method for determining the genome-wide distribution of 5-hmC. We use the T4 bacteriophage β-glucosyltransferase to transfer an engineered glucose moiety containing an azide group onto the hydroxyl group of 5-hmC. The azide group can be chemically modified with biotin for detection, affinity enrichment and sequencing of 5-hmC-containing DNA fragments in mammalian genomes. Using this method, we demonstrate that 5-hmC is present in human cell lines beyond those previously recognized. We also find a gene expression level-dependent enrichment of intragenic 5-hmC in mouse cerebellum and an age-dependent acquisition of this modification in specific gene bodies linked to neurodegenerative disorders.