A tetrameric kinesin, Kif25, suppresses centrosome separation to establish proper spindle orientation

Microtubules tether centrosomes together during interphase (1). How this is accomplished and what benefit it provides to the cell is not known. We have identified a bipolar, minus-end directed kinesin, Kif25, that suppresses centrosome separation. Kif25 is required to prevent premature centrosome separation during interphase. We show that premature centrosome separation leads to microtubule-dependent nuclear translocation, culminating in eccentric nuclear positioning that disrupts the cortical spindle positioning machinery. Kif25’s activity during interphase is required to maintain a centered nucleus to ensure the spindle is stably oriented at the onset of mitosis.