Epigenetic mechanism of gene expression silencing. (a) In unmethylated DNA (depicted by white hollow circles on left) transcription factors (TF) are free to bind gene promotor regions. In hypermethylated DNA (depicted in red filled-in circles on the right) TF are blocked from binding to gene promotor regions leading to functional silencing of gene expression. (b) Histone deacetylation by methyl-CpG-binding domain protein (MPD)/histone deacetylase (HDAC) complexes promotes a condensed structure which inhibit normal gene transcription. (With permission from [4].)
