Human CRL2^ZYG11A/B functions redundantly with APC/C to promote mitotic progression. (A) DIC micrographs of U2OS cells treated with the indicated siRNA and proTAME as they progress through mitosis. Bars, 20 µm. Bar graph of mitotic timing ± SEM for U2OS cells treated with the indicated siRNA in the presence of proTAME. The timing of control siGFP without proTAME is from Fig. 4 B and presented in the figure for comparison. The timings are from four independent experiments: control siRNA + proTAME, n = 23; and ZYG11A/B siRNA + proTAME, n = 25. (B) Inhibition of Cdk1 activity by the addition of the Cdk-inhibitor RO-3306 (arrows) allows mitotic exit. Data from three independent experiments are shown. (C) Bar graph of mitotic timing ± SEM for IMR90-hTERT cells treated with the indicated siRNA in the presence of proTAME. The timings are from two to three independent experiments; for conditions listed from top to bottom, n = 12, 13, and 10, respectively. *, P < 0.05; ***, P < 0.001; ****, P < 0.0001.