Non-Cell Cycle Functions of the CDK Network in Ciliogenesis: Recycling the Cell Cycle Oscillator

Cyclin-dependent kinases are Ser/Thr protein kinases best known for their cell cycle roles, where CDK1 triggers mitotic onset in all eukaryotes. CDKs are also involved in various other cellular processes, some of which, such as transcription and centrosome duplication, are coupled to cell cycle progression. A new study suggests that the mitotic CDK network is active at low levels in non-dividing, differentiating precursors of multiciliated cells, and that it drives ciliogenesis. Manipulating the activity of CDK1 or PLK1 altered transitions between the amplification, growth, and disengagement phases, in a manner analogous to the control of passage through different phases of mitosis. How the dynamics of the mitotic kinase network are controlled in these post-mitotic cells, and whether other cell cycle regulators are also involved, remains unknown. In the present mini-review we suggest that the redeployment of cell cycle regulators to control steps of differentiation in non-dividing cells might be a more general, hitherto under-recognized, feature of cell regulation.