Mitosis is a highly regulated set of events that culminates in cell division and the segregation of an equal amount of genetic material to two daughter cells. XPMC2H is a protein that has been implicated in cell division, but its exact role is uncertain. It is linked to suppressing tumors by correcting mitotic defects, regulating transcription, and modifying ribosomes. The Spin3 protein is associated with mitotic spindle organization and stability; however, its physiological function is also unknown. To clarify the roles of XPMC2H and Spin3 in cell division, their complexes were purified so that their protein interactors could be identified. In addition, the cellular consequences of modulating the protein levels of XPMC2H and Spin3 were analyzed in human cancer cells. XPMC2H was found to localize to the nucleus, specifically to the DNA, while Spin3 was found to localize to the mitotic spindles. Lowering the expression levels of either protein causes human cells to become irregularly shaped, abnormally sized, and multi-nucleated. Lastly, I discovered that Spin3 interacts with the PRMT5 complex.