Regulation of mitosis by the motor Protein KIF9

The kinesin superfamily of microtubule motors is subdivided based upon structure and function. KIF9 is a member of the largely uncharacterized Kinesin-9 family. It was originally identified by sequence homology to other kinesins. Subsequent studies have indicated that KIF9 interacts with proteins involved in cell shape remodeling and cell migration. We have examined KIF9 function in mammalian cells using siRNA-mediated knockdown. By knocking down KIF9 expression in these cells, we have seen several effects on normal cell cycle progression. We have observed a decreased mitotic index, suggesting cells either fail to enter mitosis or abort the process prior to completion. Of the cells in that population that enter mitosis, we see a decrease in the number of cells in anaphase and telophase. Multinuclearity is greatly increased, indicating failure of cytokinesis. Interphase cells show decreased microtubule organization. We propose that KIF9 is important for normal completion of mitosis by regulating the contractile ring.