Fig. 2: DNA synthesis in late mitosis promotes timely nuclear division.

a Cells arrested in metaphase by treatment with nocodazole and released from metaphase in fresh medium (-HU), or treated with 0.1 M HU for 30 min and released from the metaphase block in fresh medium containing HU (+HU) (see Methods). Arrowheads point to chromatin bridges labeled with Htb2-mCherry; the chromatin bridge lifetime is indicated by double-headed arrows. Asterisks mark contraction of the actomyosin ring labeled with Myo1-GFP. Images were acquired every 2 min. The time relative to imaging start is indicated in minutes. b–e The time of nuclear division and bridge lifetime for cells blocked in metaphase at the permissive condition, and released from the metaphase arrest after inhibition of DNA synthesis. Nuclear division is defined as the time between release from metaphase and resolution of chromatin bridges (final DNA segregation). Bridge duration is defined as the time between anaphase onset (nuclear elongation) and bridge resolution. Cells were either released from a metaphase arrest in the presence of HU at 30 °C, or arrested in metaphase at 25 °C and released at the restrictive temperature to inactivate DNA replication. Arrest conditions and fluorescent reporters are indicated at the top of each panel. f The time of cytokinesis (membrane closure at the bud neck, monitored with GFP-CAAX) for cells expressing the indicated reporters and released from a metaphase arrest in the presence or absence of 0.1 M HU at 30 °C. Representative cells are shown; asterisks indicate cytokinesis. The number of cells (n, pooled from at least two independent experiments) is indicated. p values are from two-sided Mann-Whitney, Fisher’s Exact tests. Scale bars in a, f: 2 µm.