Ubiquitination associated proteolysis inhibition impairs plus ended motor proteins dynamics during mitosis.

Kinesins (Kif4A and Eg5) are microtubule-based motor proteins known to play imperative roles in cellular activities like cell division, intracellular transport of organelles and signal transduction. Kif4A and Eg5 have surfaced as vital proteins due to their roles in sustaining the stability of the genome, regulation of mitosis and more importantly, its association with human cancers. To further our understanding regarding ubiquintination associated proteolysis inhibition on plus-end motor proteins dynamics during mitosis, we conducted Fluorescence Recovery after Photobleaching (FRAP) and Fluorescence Loss in Photobleaching (FLIP) experiments on Kif4A. Through these experiments, carbobenzoxyl-leucinyl-leucinyl-leucinal (MG132), a proteasome inhibitor, was shown to be responsible for slowing the movement of Kif4A possibly due to additional interacting protein partners to Kif4A. As previous studies have shown that the mobility of Eg5 motor protein is impaired in the presence of MG132 (unpublished work), we want to prove that there are interacting proteins bound to this motor protein. Immunoprecipitation and western blots were performed and results demonstrated that there were indeed proteins bound to Eg5 motor protein when mitotic HeLa were treated with MG132. In conclusion, our results illustrated that the presence of MG132 in mitotic HeLa cells essentially results in impairment of the mobility of Eg5 and Kif4A motor proteins, which is potentially a result of additional interacting partners with these motor proteins. Therefore, this bridges our understanding in the mechanisms of cell division.Bachelor of Science in Biological Science