Figure 4:

The Independent-Activation-Communication (IAC) model. A gene described by the IAC model follows Assumptions 1–6 for the component graphs $H_1,\dots ,H_N$. The ordered pair of binary digits for the vertices in each $H_i$ represent the activation and communication status, respectively, of each enhancer. Each $H_i$ has the same structure as the graph in Fig.2d, but different labels, and represents the independence of activation and communication within each enhancer. Each $H_i$ is assumed to have the same degradation rate which is omitted for clarity. See also Fig.S1.