Figure 1.

Sketch illustrating the multi-layered control of gene expression by various epigenetic processes. DNA is subject to direct chemical modification by addition or removal of methyl groups at cytosine bases. Epigenetic processes regulating gene expression at a higher level of DNA compaction include histone tail modifications and control of chromatin accessibility by ATP dependent chromatin remodeling complexes. Once transcribed, mRNA can be further regulated by the microRNA network which provides an additional layer of epigenetic control of gene expression. Together, these epigenetic mechanisms function in concert to help fine-tune gene expression within the cell.