Figure 3

Dual action of histones. Both trans-acting chromatin regulators and histones tend to have opposite effects in HNHP and LNHP genes. For each mutation from[18], we plot the fraction of genes in the HNHP group and in the LNHP group that decreased expression. Consistently with that observed in Figure2, we find that mutating as much as ∼50% of chromatin regulators results in the de-activation of the majority of the LNHP genes, but de-repression of most of the HNHP genes. In addition, and perhaps more importantly, we observe that 81% of mutations in histones also exhibit this behavior. This is probably crucial, and indicates that histones by themselves are needed for repression of HNHP genes and, at the same time, activation of LNHP.