Figure 1.

Epigenetic mechanisms of gene silencing and activation. Nucleosomes are composed of DNA (black strip) wrapped around 4 couples of core histones. Histone tails and DNA cytosines may be modified by several enzymes (orange circles), which add or remove epigenetic marks. Local gene function results from the combined interaction of all epigenetic enzymes. Me, methylation; K, lysine; ub, ubiquitination; DNMT, DNA methyltransferase; PRC, Polycomb repressive complex; G9a, histone H3K9 methyltransferase; HAT, histone acetyltransferase; HDAC, histone deacetylase; KDM, lysine-specific demethylases.