Cep57 and Cep57L1 redundantly regulate centriole engagement during interphase. (A) Cep57/Cep57L1 codepletion induced four separated centrioles and more than four centrioles in the G₂ phase. HeLa cells were treated with siControl or siCep57/Cep57L1 for 36 h in the presence of EdU (S phase marker; cyan) for the last 30 min before fixation and immunostained with antibodies against CP110 (red) and CENP-F (green). Scale bars, 5 µm in the low-magnification view, 1 µm in the inset. (B) Histograms represent the number of centrioles in the G₁, S, and G₂ phases treated with the indicated siRNAs in A. (C) Histograms represent the frequency of cells in the S and G₂ phases treated with the indicated siRNAs exhibiting the indicated phenotype. Values are mean percentages ± SD from three independent experiments (n = 30 for each experiment) in B and C. (D) Time-lapse observation of cells upon Cep57/Cep57L1 codepletion. NEBD indicates nuclear envelope breakdown. HeLa cells stably expressing GFP-centrin1 (HeLa-GFP-centrin1, green) were treated with siControl or siCep57/Cep57L1 in the presence of SiR-DNA (200 nM, red). Scale bar, 5 µm. (E) Cumulative scatterplot indicates the duration from cell roundup to centriole disengagement observed in D. Orange open circles indicate precocious centriole disengagement accompanied by centriole reduplication. The normal distribution of datasets was confirmed using the Kolmogorov–Smirnov test in E. A two-tailed, unpaired Student’s t test was used in E to obtain the P value. ***, P < 0.001.