Figure 7.

Unique Chromatin Architecture at CpG Islands

CpG islands utilize nonmethylated CpG dinucleotides to recruit the ZF-CxxC domain protein KDM2A, depleting these regions of H3K36me2 and creating a chromatin environment that is unique from bulk non-CpG island chromatin. CpG island chromatin is also modified by H3K4me3, and this relies on targeting of the Set1 complex by the ZF-CxxC domain containing CFP1 protein (A. Bird, personal communication). Another facet of CpG island chromatin is depletion of histone H1. Because CpG islands are usually part of regulatory regions or associated with transcription start sites, this unique chromatin architecture may function to differentiate these regulatory regions from bulk chromatin in large complex mammalian genomes.