DNA methylation is a key layer of epigenetic regulation. The deposition of methylation marks relies on the catalytic activity of DNA methyltransferases (DNMTs), and their active removal relies on the activity of ten–eleven translocation (TET) enzymes. Paradoxically, in important biological contexts these antagonistic factors are co-expressed and target overlapping genomic regions. The ensuing cyclic biochemistry of cytosine modifications gives rise to a continuous, out-of-thermal equilibrium transition through different methylation states. But what is the purpose of this intriguing turnover of DNA methylation? Recent evidence demonstrates that methylation turnover is enriched at gene distal regulatory elements, including enhancers, and can give rise to large-scale oscillatory dynamics. We discuss this phenomenon and propose that DNA methylation turnover might facilitate key lineage decisions.

DNA甲基化是表观遗传调控的关键层。甲基化标记的沉积依赖于 DNA 甲基转移酶 (DNMT) 的催化活性，其主动去除依赖于十-十一转位 (TET) 酶的活性。矛盾的是，在重要的生物学背景下，这些拮抗因子是共同表达的，并针对重叠的基因组区域。随后胞嘧啶修饰的循环生物化学通过不同的甲基化状态产生连续的、非热平衡转变。但这种有趣的 DNA 甲基化转变的目的是什么？最近的证据表明，甲基化周转在基因远端调控元件（包括增强子）处富集，并且可以引起大规模振荡动力学。