Figure 1. Incomplete DNA replication in C. elegans early embryos leads to unloading of the CMG helicase from chromatin by the CDC-48_UFD-1_NPL-4 segregase.

(A) Illustration of the first cell cycle in the C. elegans early embryo. (B) Worms expressing GFP-RPA-1 and mCherry-Histone H2B were exposed to the indicated RNAi treatments (control = no RNAi). Images of whole embryos are shown, during prophase of the first embryonic cell cycle (two minutes before nuclear envelope breakdown), in order to illustrate the efficiency of RPA-1 depletion. (C) Worms expressing GFP-PSF-1 and mCherry-Histone H2B were exposed to the indicated RNAi treatments, before time-lapse imaging of the first mitosis in isolated embryos. The arrows indicate persistence of CMG on mitotic chromatin. (D) Worms expressing the indicated GFP-tagged replication proteins, together with mCherry-Histone H2B, were exposed to the same range of RNAi treatments as in (C). Examples are shown of the metaphase stage of the first embryonic mitosis. Scale bars = 20 µm in (B) and 5 µm in (C and D). Quantification of microscopy data is provided in Figure 1—figure supplement 1.

Figure 1—figure supplement 1. Quantification of C. elegans microscopy data in Figure 1.

The figure presents quantification of the microscopy data for the experiments in Figure 1B (A), Figure 1C (B–E) and Figure 1D (F–H). The signals for GFP-PSF-1 (D), mCherry-Histone-H2B (E), GFP-CDC-45 (G) and GFP-SLD-5 (H) were quantified as described in Materials and methods.

Figure 1—figure supplement 2. Condensation is profoundly defective following depletion of RNR-1 and NPL-4 in C. elegans early embryos.

(A) Videos of embryos expressing GFP-KLE-2 and mCherry-Histone, treated with the indicated RNAi. (B) Quantification of the microscopy data in (A). (C) Videos of embryos expressing GFP-CAPG-1 and mCherry-Histone, treated with the indicated RNAi. Arrows denote defective chromatin condensation. (D) Quantification of the microscopy data in (C).