Get Induces Replication-independent Active DNA ... - Jbc

Active DNA demethylation refers to an enzymatic process that removes or modifies the methyl group from 5mC. By contrast, passive DNA demethylation refers to loss of 5mC during successive rounds of replication in the absence of functional DNA methylation maintenance machinery.

Hear this out loud PauseOverall, these results suggest that DNA methylation can be both active, by being a likely cause of gene expression variation levels, or passive, by being a consequence or an independent mark of gene expression levels. Figure 4. Passive and active roles of DNA methylation in gene regulation.

DNA methylation can be influenced by environmental factors such as diet, hormones, stress, drugs, or exposure to environmental chemicals, suggesting that environmental factors may contribute to adverse neurodevelopmental outcomes of relevance to ASD via effects on DNA methylation in the developing brain.

Hear this out loud PauseDNA demethylation can be expressed in two different mechanisms: active and passive demethylation (Fig. 18.2). Passive demethylation happens mainly during DNA replication where the newly synthesized DNA strand is not targeted and methylated by DNA methyltransferases.

Hear this out loud PauseThere are currently two classes of DNA methyltransferases: 1) the de novo class or enzymes that create new methylation marks on the DNA; 2) a maintenance class that recognizes the methylation marks on the parental strand of DNA and transfers new methylation to the daughter strands after DNA replication.

Hear this out loud PauseIn the “replication-independent” active demethylation, TET dioxygenases sequentially oxidize 5mC to 5-hydroxymethylcytosine (5hmC), and further to 5-formylcytosine (5fC), and finally to 5-carboxylcytosine (5caC). 5fC and 5caC are then removed by base excision repair (BER), namely by DNA glycosylases (Figure 2).