E. Model. Plk4 plays a decisive role in not only centriole duplication but also centriolar satellite integrity and primary cilium formation. The latter two roles, at least in part, are executed via PCM1 phosphorylation. Plk4 directly or indirectly phosphorylates PCM1 at S372 (I), which promotes its own dimerisation/oligomerisation (II) and interaction with other components of centriolar satellites (III). These processes ensure PCM1 acts as a structural platform for centriolar satellites. Processes II and III are not necessarily sequential steps. It is shown that centriolar satellites and PCM1 play a critical role in centriole duplication and assembly [25, 49]. Under conditions of serum starvation or developmental cues, centriolar satellites deliver various factors from the cytoplasm to the basal body, thereby helping formation of cilia [26, 30, 37, 50, 51]. 