NEK7 is essential for centriole duplication and centrosomal accumulation of pericentriolar material proteins in interphase cells

The centrosomes in dividing cells follow a series of cyclical events of duplication and separation, which are tightly linked to the cell cycle. Serine/threonine-protein kinase NEK7 (NEK7) is a centrosomal kinase that is required for proper spindle formation during mitosis. In this study, we observed that centriole duplication was inhibited in NEK7-depleted cells. Ectopic expression of centrosome-directed NEK7 led to the formation of extra centrioles in a kinase-activity-dependent manner. We also observed extra centriole formation in centrosome-directed NEK6-expressing cells, suggesting that NEK6 and NEK7 might share biological activities that induce centriole duplication. The centrosomal pericentriolar material (PCM) proteins were significantly reduced in NEK7-depleted cells. The PCM proteins in NEK7-depleted cells did not accumulate at the centrosomes, even if the cells exited mitosis and progressed to the G2 phase. These results revealed that NEK7 is essential for PCM accumulation in a cell cycle stage-specific manner. Furthermore, HeLa cells depleted of NEK7 during S phase retained a higher quantity of PCM proteins and exhibited a less severe mitotic phenotype. On the basis of these results, we propose that NEK7 is involved in the recruitment of PCM proteins, which are necessary for both centriole duplication and spindle pole formation. Our study revealed that NEK7 activity is required for centrosome cycle progression not only at M phase, but also at G1 phase.