Figure 1.

Summary of epigenetics. A: Mechanisms of epigenomic gene regulation. Gene regulation is controlled by multiple epigenetic mechanisms, including DNA methylation, histone post-translational modifications, chromatin remodeling, and ncRNAs. B: Epigenetic modifications regulate chromatin state. Heterochromatin is tightly packed DNA, in which DNA is often methylated and promoters (red lines) are inaccessible to DNA-binding proteins and transcriptional complexes, rendering such genes inactive or silenced. In euchromatin, DNA is unwound by chromatin regulators and accessible to transcriptional machinery, including RNA polymerase II (RNA pol II) and transcription factors (TFs), thus allowing transcription to occur. DNMT, DNA methyltransferase; H2A, H2B, H3, and H4, histone proteins; TET, Ten-eleven translocation proteins.