Histograms of PCNE locations relative to their parent genes across all four organisms studied. The right and left panels show PCNE distributions upstream and downstream (bin width is 1 kb). There is an increase in elements near the TSS and at the 3′ end, but many conserved elements continue to be found throughout the 100-kb flanking regions. In fact, 48% are found more than 10 kb from their associated gene. The middle panel shows the distribution of elements found within the introns and UTRs of their parent genes, using relative bin sizes. The mean size of genes with PCNEs is 31.026 kb, so the space within each gene was divided into 31 equal bins, with a mean width of ∼1 kb.
