The kinesin motor Kif9 regulates centriolar satellite positioning during interphase.

Centrosomes are the principal microtubule-organizing centers of the cell, are cellular hubs for protein degradation, and play an essential role in mitotic spindle function that ultimately regulates chromosome segregation during mitosis. Centrosome maturation is achieved by strict control of protein acquisition and phosphorylation prior to mitosis. Defects in this process during interphase promote fragmentation of pericentriolar material once cells enter mitosis due to the increased forces exerted over the centrosome by the mitotic spindle, finally culminating in multipolar spindles and chromosome missegregation. Centriolar satellites, membrane-less assemblies of proteins involved in the trafficking of proteins toward and away from the centrosome, are thought to contribute to centrosome biogenesis. Moreover, centriolar satellites also regulate the quantity of proteolytic factors reaching the centrosome. Here, we show that the microtubule plus-end-directed kinesin motor Kif9 localizes to centriolar satellites and regulates their pericentrosomal localization during interphase. Lack of Kif9 leads to aggregation of satellites closer to the centrosome and increased centrosomal protein degradation that disrupts centrosome maturation and results in chromosome congression and segregation defects during mitosis. Our data show that the kinesin Kif9 controls the position of centriolar satellites relative to the centrosome and reveal roles for Kif9 and centriolar satellites in the regulation of cellular proteostasis and mitosis.