CDK7 suppresses axoneme polyglutamylation. (A) CDK7 selective inhibitors increase the length of glutamylated axoneme in RPE-1 cells. Cells were treated with THZ1 (1 mM) or BS-181 (10 mM) for 24 h in a serum-free medium. ARL13B was used as a marker of cilium. The glutamylated axoneme was labeled by antibody GT335. (B) THZ1 partially rescues the axoneme polyglutamylation in CCP5-YFP overexpressed RPE-1 cells. (C) The knockdown efficiency of CDK7 siRNA was accessed by western blotting. The molecular weigth standards (kD) are labeled on the right. (D) Knockdown of CDK7 partially rescues the axoneme polyglutamylation in CCP5-YFP overexpressed RPE-1 cells. (E) Knockdown of CDK7 restores the axoneme polyglutamylation in TTLL5-depleted 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 ≥ 40 cilia. ***P < 0.001. n.s: not significant. Scale bars: 2 μm. Source data are available for this figure: SourceData F1.