Flow cytometric timing of SNAP-macroH2A incorporation. (A) The time line of synchronizing and labeling cells. Newly synthesized macroH2A was labeled with SNAP substrate JF646 at each 2-h time point after release from thymidine block. (B) Flow cytometric analysis of preexisting (Oregon Green) and newly incorporated macroH2A (JF646), with cell cycle timing data derived from Fucci experiments shown in Fig. S3. The gray shading illustrates the interval of transition from preexisting macroH2A (hours 2–10, S/G2) to an enrichment for newly incorporated macroH2A (hours 18–22, G1).