Figure 2. Cdk1 inhibition at anaphase onset accelerates NER.

(a) and (b) Control and Cdk1-inhibited Drosophila S2 cells at anaphase onset (A.O.) stably expressing Lamin B-GFP/mCherry-α-tubulin. Scale bars are 5 μm. Time is in min:sec. Panels on the right side show the corresponding collapsed kymographs. Dashed lines indicate the moment of NER. (c) and (d) Quantification of anaphase duration (control n=16 cells; Cdk1i n=15 cells) and half-spindle elongation velocity (control n=16 cells; Cdk1i, n=13 cells), respectively, in the conditions shown in (a) and (b). Statistical significance was tested with an unpaired t-test.

Figure 2—figure supplement 1. Cdk1 inhibition during anaphase is required for mitotic exit.

(a) Control Drosophila S2 cell stably expressing H2B-GFP/mCherry-α-tubulin transiently expressing ΔCycB1-GFP, showing the expected anaphase arrest. (b) The same experimental set-up was used for Cdk1 inhibition at anaphase onset (A.O.). Cyclin B1-GFP localization and H2B-GFP are highlighted in inverted grayscale. Note the centrosomal pool (magenta dashed circles) that remains during the anaphase arrest and the midzone localization of Cyclin B1-GFP after Cdk1 inhibition (magenta arrowheads). (c) Drosophila S2 cell stably expressing H2B-GFP/mCherry-α-tubulin transiently expressing ΔCycB3-GFP where a strong anaphase arrest can be observed. Time is in min:sec. Scale bars are 5 μm. (e) and (f) Normalized pole-to-pole distance and half-spindle elongation velocity in WT (n=8 cells), ΔCycB1 (n=9 cells) and ΔCycB3 (n=4 cells), showing impaired spindle elongation after expression of non-degradable Cyclin B1 or Cyclin B3. Statistical significance of (e) and (f) was tested with a t-test and a nonparametric Mann-Whitney test, respectively.