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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Neuropharmacology. 2013 Aug 16;0:10.1016/j.neuropharm.2013.07.036. doi: 10.1016/j.neuropharm.2013.07.036

Fig 4. Euchromatization.

Fig 4

1. The first step in the progression from restrictive heterochromatin to transcriptionally permissive euchromatin begins with the removal of histone marks such as, dimethylated lysine 9 of histone 3 (H3K9me2), and H3K9 acetylation. Restrictive histone modifications bar the DNA demethylation complex from accessing the underlying cytosine. 2. H3K9 demethylation and acetylation allow for transcription factor binding as well as the binding of the mediators of DNA demethylation. Histone acetylation and the DNA demethylation process promote the addition of Poly(ADP-Ribose) polymers (PAR) to histone lysine residues such as H3K27. 3. Once DNA is demethylated a H3K4 methyltransferase can bind. Methylated H3K4 prevents DNMT binding thereby maintaining the unmethylated DNA state.