Abstract
Centrosome amplification in cancer cells produces excess centrosomes that cluster and decluster throughout the cell cycle, a process critical for tumorigenesis. Here, we identify the mitotic kinesin HSET as a multifaceted regulator of these dynamics in cancer cells. Beyond microtubule crosslinking, HSET co-condensates with the centrosomal protein CDK5RAP2 and actively transports it toward microtubule minus ends. This directed delivery concentrates centrosomes at spindle poles, thereby limiting centrosome dispersal and contributing to centrosome coalescence. Notably, HSET-driven transport enables effective transport of CDK5RAP2 condensates, independently of size, thereby overcoming cytosolic viscosity to cluster large foci of pericentriolar material within cells. Furthermore, HSET's ATP-independent self-assembly prevents centrosomal declustering, preserving centrosome integrity during mitotic progression. These activities position HSET as a critical regulator of centrosome clustering and integrity, with its mitosis-specific upregulation providing another layer of cell cycle control over centrosome assembly and underscoring its potential as a target for cancer therapeutics.