Centrobin is required for the elongation of centrioles. (A and B) Centrobin is required for centriole elongation during normal centriole duplication. HeLa cells transfected with control or centrobin siRNA were treated with HU and stained with anti-centrobin, hSAS-6, and α-tubulin antibodies. The percentage of varied intensity of α-tubulin–positive centrioles was scored and plotted in B. (C and D) Centrobin was observed on the elongated portion of the mother centriole in addition to the elongating daughter centrioles. CPAP-induced PLSs were generated by inducing U2OS-CPAP cells with 1 µg/ml doxycycline for the indicated time points. Anti-centrobin and acetylated tubulin antibodies were used to stain centrioles/PLSs (C). In D, the cells were costained with anti–C-NAP1, centrobin, and α-tubulin antibodies. The illustration indicates the presence of centrobin on the elongated portion of the mother centriole as well. M and D refer to the mother and daughter centriole, respectively. (E and F) Knockdown of centrobin inhibits the elongation of PLSs. U2OS-CPAP cells were transfected with control or centrobin siRNAs for 72 h followed by doxycycline treatment for the indicated time points (E). The percentage of elongated versus nonelongated centrioles was quantified at the 72-h time point (F). Histograms are plotted as mean ± SEM (n = 3). Asterisks denote that the difference is significant, and P < 0.001. Bars, 1 µm.