Fig. 1.

Effects of DNA methylation and histone modifications in transcription of CpG island-containing genes. a Chromatin with unmethylated cytosine residues (open circles) within CpG islands and adjacent shores is associated with trimethylation of histone H3 on lysine 4 (H3K4me2) and transcriptional activation. b Chromatin with hypermethylated cytosine residues within CpG islands and shores (black circles) is associated with H3K9 trimethylation (H3K9me3) and transcriptional silencing. c Methylation of cytosine residues located in the shores of the CpG island is sufficient for transcriptional repression, even when the CpG island is hypomethylated. Histone modifications associated with methylation in CpG shores has not been determined. d Hydroxymethylcytosine residues (H) are associated with H3K4 methylation (H3K4me1) and H3K27 acetylation and transcriptional activation typical of an open chromatin structure