Methylation and acetylation of DNA and histones, and gene structure of Foxp3. (A) Methylation of 5-position of cytosine by DNMTs. (B) Acetylation and deacetylation of lysine residues in histone molecules. (C) Gene structure of Foxp3 in different CD4⁺ T-cell subsets. Red bars represent noncoding exons; blue bars, coding exons; small boxes filled with black checks, cis-regulatory elements; +1, transcription start site. Upstream and intronic enhancers in naive T cells, activated T cells, and TGF-β–induced Tregs have methylated CpG (pink) and are transcriptionally inactive (marked as compact histone bundles), whereas these regions have unmethylated CpG (yellow) and are transcriptionally active (marked as separated histone bundles) in nTregs and DNMT inhibitor plus TGF-β–induced Tregs.