Embryo microinjections were performed as described in Farrell et al. (2012) (link). JabbaTrap and Cdc25 (twine) mRNAs were synthesized using the CellScript T7 mRNA production system and injected at a concentration of 600 ng/µL. dsRNA against the cyclins A, B, and B3 was prepared as described in McCleland and O'Farrell (2008) (link). Imaging was performed using a spinning-disk confocal microscope as described in Seller and O'Farrell (2018) (link). Image processing and analysis were done using Volocity (PerkinElmer) and ImageJ. When quantifying the accumulation of HP1a at a TALE-light-labeled satellite repeat, a Volocity protocol (described in Supplemental Fig. S3A) was used to first identify the region of the nucleus labeled by the TALE-light probe. The mean intensity from the HP1a channel in this region was calculated for each time point. After setting the intensity at the beginning of interphase 14 as zero, the mean intensity of HP1a at the repeat was graphed over time. Unless noted otherwise, all images are presented as Z-stack projections.