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. 2007 Mar 21;104(13):5521–5526. doi: 10.1073/pnas.0609746104

Fig. 1.

Fig. 1.

Dinucleotide periodicities around CpG dinucleotides. (A) Nucleosome-like dinucleotide distributions around CpG dinucleotides. (Left) Shown are the dinucleotide densities around 8 million intergenic nonrepetitive human CpG dinucleotides that are not part of CpG islands. The data show strong periodicity of ApA/TpT/TpA dinucleotide densities peaking at 10-bp intervals from the CpG. GpCs densities are also periodic but peak at 5-bp distance from the CpG. Similar periodicities are known to be associated with sequences that are tightly bound to nucleosomes. CpG islands lack both ApA/TpT/TpA and GpC nucleosomal periodicities (Right). (B) CpGs that are diverged in chimp exhibit weaker periodicities. Shown are dinucleotide frequency data for 650,000 human CpG dinucleotides that mutated to TpG or CpA in chimp. The profiles reveal much reduced ApA/TpT/TpA and GpC periodicities and lower G + C content (see SI Fig. 7 for further analysis).