PLK1 controls centriole distal appendage formation and centrobin removal via independent pathways

Centrioles are central structural elements of centrosomes and cilia. In human cells, daughter centrioles are assembled adjacent to existing centrioles in S-phase and reach their full functionality with the formation of distal and subdistal appendages one-and-a-half cell cycles later, as they exit their second mitosis. Current models postulate that the centriolar protein centrobin acts as placeholder for distal appendage proteins that must be removed to complete distal appendage formation. Here, we investigated, in non-transformed human epithelial RPE1 cells, the mechanisms controlling centrobin removal and its effect on distal appendage formation. Our data are consistent with a speculative model in which centrobin is removed from older centrioles due to a higher affinity for the newly born daughter centrioles, under the control of the centrosomal kinase PLK1. This removal also depends on the presence of subdistal appendage proteins on the oldest centriole. Removing centrobin, however, is not required for the recruitment of distal appendage proteins, even though this process is equally dependent on PLK1. We conclude that PLK1 kinase regulates centrobin removal and distal appendage formation during centriole maturation via separate pathways.