Figure 1.

Regulation of Ciliogenesis by Inputs from the Cell Cycle. Cilium length is indicated by axonemal microtubules (grey rods) bound by the ciliary membrane (green line) throughout the cell cycle (CC) in proliferating cells (S, G2, M, and G1 phases), and during exit into and entry from cell quiescence (G0 phase). The mother centriole is indicated by the grey cylinder; only two microtubule doublets are shown for clarity. Stable, acetylated tubulin is indicated at G1/G0 with acetyl groups (Ac) shown as tan circles. The various proteins that are discussed in the main text are highlighted in different colors: the Aurora A (AURKA)–HDAC6 ciliary disassembly pathway is shown in orange and browns, and the kinesin-13 family members (KIF2A and KIF24) that mediate microtubule depolymerization are colored in greens. ‘P’ in a yellow circle indicates protein phosphorylation. Other centrosomal proteins are colored in blues. The role of Kif24 throughout the cell cycle is unclear, and other regulatory proteins are likely to be involved in regulation of the CP110–Cep97 scaffold and phosphorylation by Nek2 during G1/S. AURKA also appears to activate Kif2a during G1/S, but then negatively regulates it by phosphorylation during M. In this and other figures, the shorter arrow-headed lines indicate positive regulatory or activating effects, whereas bar-headed lines indicate negative inhibitory effects. Dashed arrows indicate an inferred physical translocation or post-translational modification of a protein. Purple bold arrows indicate additional regulatory inputs from the cell cycle (‘CC’, circular purple icon).