A Kinesin-Related Protein, Krp₁₈₀, Positions Prometaphase Spindle Poles during Early Sea Urchin Embryonic Cell Division

We have investigated the intracellular roles of an Xklp2-related kinesin motor, KRP₁₈₀, in positioning spindle poles during early sea urchin embryonic cell division using quantitative, real-time analysis. Immunolocalization reveals that KRP₁₈₀ concentrates on microtubules in the central spindle, but is absent from centrosomes. Microinjection of inhibitory antibodies and dominant negative constructs suggest that KRP₁₈₀ is not required for the initial separation of spindle poles, but instead functions to transiently position spindle poles specifically during prometaphase.