MARS response plots. Predicted gene expression versus amplitude for either one (2 D plots) or two marks (3 D plots) for (A) H3K27me2 (B) H3K36me3 (C) H3K79me3 (D) H4K20me1 (E) H4R3me2 (F) H4K20me1-H3K36me3 (G) H3K36me3-H4R3me2 and (H) H3K79me1-H3K79me3. Each axis represents the full range of expression and amplitude values. The trend of plots represents activating (positive slope) or repressive (negative slope) behavior. Many individual marks (A)-(E) and pairs (F)-(H) show some saturation effects and nonlinear behavior that could not be captured with a linear model; H3K36me3 (B), H4K20me1 (D) and H4R3me2 (E) show particularly distinct saturation effects. The combination H4K20me1-H3K36me3 (F) shows a dramatic nonlinear, synergistic activating effect. In contrast, the two marks in the combination H3K36me3-H4R3me2 (G) show opposing effects in that H3K36me3 activates and H4R3me2 represses gene expression.