siRNA knockdown screen of CDK7 downstream CDKs. (A and B) The knockdown efficiency of indicated siRNAs in RPE-1 cells was accessed by western blotting (A) or qPCR (B). The molecular weigth standards (kD) are labeled on the right. Quantified data are presented as mean ± SD. N = 3 independent experiments. Statistical analyses were performed by two-tailed unpaired Student’s t test. (C) The effect of indicated CDKs knockdown on axoneme polyglutamylation in RPE-1 cells. Quantified data are presented as mean ± SEM. Statistical analyses were performed by one-way ANOVA analyses with Tukey’s post-hoc test for multiple comparisons. N ≥ 50 cilia. **P < 0.01; ***P < 0.001. Source data are available for this figure: SourceData FS3.