(A) H3K27me3 levels over the entire FLC locus in a simulated PRE excision experiment. A fully spread state is simulated; the nucleation region (with any assembly elements) is removed (at day 11 in the simulations), thereby interrupting the looping reactions and compromising the spread state. Varying levels of PRC2 feedbacks (, right) are simulated in the body region when the nucleation region is removed, with each level averaged over 4000 realisations. (B,C) Simulated dynamics (lines) of assembly, as well as nucleation and body region H3K27me3 levels, for Lov-1 accession. Lov-1 is simulated with the parameter for transcription activation (α) in the warm higher than in ColFRI (specified in Materials and methods). (B) Cold treatment (blue background) is followed by warm conditions (red background). Experimental H3K27me3 ChIP data (black circles, error bars: sem) (Qüesta et al., 2020). (C) Simulated dynamics in the warm after 2, 4, 8, or 12 weeks of cold treatment. The 12-week data in the warm is the same as in (B). Simulated assembly and H3K27me3 levels are fraction of maximum possible occupancy in relevant region, each averaged over 4000 realisations. In Figure 4—figure supplement 1, non-replicating Lov-1 cells are simulated.