Active DNA demethylation damages DNA

Description Active DNA demethylation maintains enhancer activity in nonproliferating cells but can damage DNA In mammalian genomes, cytosine residues can be covalently modified by addition of a methyl group. DNA methylation levels at gene regulatory regions change as cells respond to stimuli, but whether this is a cause or consequence of changes in gene expression is unknown. On page 983 of this issue, Wang et al. (1) show that active DNA demethylation is necessary for enhancer activation and lineage specification in postmitotic neurons and macrophages.