Figure 7. Inhibition and overexpression of Dot1: Section of phase space for fixed Sas2 activity () and Sir2 activity () showing the effect of varying Dot1 activity () with Sir cooperative binding rate ().

The self-adjusting Sir binding owing to titration effect maintains the system on the zero-velocity line (grey line). The bivalent state (magenta) is stable for high and —overexpression of Dot1 pushes the system into this phase. The wild-type bistability (silenced-active-bistable) region is the overlap of the green and red regions. Inhibition of Dot1 pushes the system to another bistable region with silenced and intermediate states stable—the overlap of the red and blue region.