Asymmetries in promoter proximal histone modifications around the transcription start site. (a,b) H2A.Z (a) and H4K5ac (b) have higher modification levels upstream of the start site of CpG promoter genes. (c) The asymmetry of each promoter proximal modification is quantified for all highly expressed CpG (red) and non-CpG (blue) promoter genes. Here the number of modified histone reads between the transcription start site (TSS) and 500 bp upstream of the start site is divided by the number of reads between the start site and 500 bp downstream. Box plots indicate the range and 25, 50 and 75 percentile of the asymmetry score for the 500 highly expressed genes. Significant differences in the distributions between CpG and non-CpG promoter genes are indicated by an asterisk (Wilcoxon signed rank test, P < 0.05).
Vavouri and Lehner Genome Biology 2012 13:R110 doi:10.1186/gb-2012-13-11-r110