Enhancement of CEP215 dynamics for spindle pole assembly during mitosis.

The microtubule-organizing activity of centrosomes fluctuates during the cell cycle, reaching the highest levels at M phase. CEP215 (also known as CDK5RAP2) is a key pericentriolar material (PCM) protein for microtubule organization of the human centrosome. Here, we provide evidence that CEP215 exhibits a dynamically suppressed, solid-like state in interphase centrosomes, and becomes a more dynamic state in mitotic centrosomes. Specific interaction with PCNT, another centrosome protein, is crucial for diffusible molecular dynamicity of the CEP215 protein. We also found that the cluster formation activity of CEP215 is impaired in a light-inducible system when its coiled-coil domains (CCDs) are truncated. Defects in spindle pole assembly and spindle formation were accompanied in the cells whose CEP215 is replaced with the CCD-truncated mutants. Our results support the notion that the diffusible mobility of CEP215 is enhanced by both homotypic and heterotypic interactions among CCDs, especially at mitotic spindle poles. This work highlights that biophysical properties of the PCM proteins at the centrosomes fluctuate during the cell cycle.