Figure 2.
Various epigenetic modifications include acetylation, (de)methylation, and phosphorylation. DNA methylation involves the addition of a methyl (-CH3) group to the fifth position of cytosine known as methylcytosine (5-mC). This process is carried by DNA methyltransferases while the demethylation process is aided by DNA demethylase. Acetylation, i.e., the addition of negatively charged acetyl group to lysine residues on histone proteins is regulated by two opposing enzymes, i.e., histone acetyltransferases (HATs) and histone deacetylases (HDACs). Acetyl group addition is catalyzed by HATs while the removal of acetyl groups is catalyzed by HDACs. Phosphorylation is one of the important histone modifications. Histone phosphorylation plays a role in DNA repair, synchronization of chromosome segregation, and cell division. Histone tails can be phosphorylated by various protein kinases and dephosphorylated by phosphatases. All the histone modifications lead to the regulation of gene expression.