Centriolar SAS-4 is in dynamic equilibrium with the cytoplasmic pool during late S phase and early prophase but becomes stable to exchange in late prophase. (A and B) Three examples of centrosomes in GFP:SAS-4 embryos, generated as in Fig. 1 A, photobleached in S phase/early prophase (A; bleached at 693, 756, and 424 s before cytokinesis onset, from top to bottom, respectively) and late prophase/prometaphase (B; bleached at 120, 336, and 170 s before cytokinesis onset, from top to bottom, respectively). Times are in seconds after photobleaching. (C) Recruitment profile of centrosomal GFP:SAS-4 after HU treatment. Recruitment curves were generated after time-aligning the data points with respect to centriole separation as described in Fig. 2 E. Error bars indicate the 90% confidence interval. (D) Three examples of photobleached centrosomes in embryos arrested in S phase by HU treatment. Times are given in seconds after photobleaching. (E) Summary of fluorescence recovery after photobleaching analysis. Bars, 5 μm.