Fig. 4.

Model for on/off HO expression and its memory. (A) Model for bimodal HO expression and the effect from different factors. We propose that the on/off HO expression is caused by the mutual exclusion of nucleosome and SBF (green arrow). Factors solely working upstream the SBF binding (red) would regulate the HO firing frequency, factors solely working downstream (blue) would regulate the firing amplitude, and factors working both up and downstream (orange) would have a mixed effect on HO expression. (B) Model for the memory of HOpr expression in swi5 cells. Based on our experimental results, we hypothesized that differential concentrations of histone acetylation following an on- or off-cycle would lead to the apparent memory. A detailed explanation of the model is provided in the main text. The model in SWI5 cells is shown in Fig. S2.