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 mo tor, KRP180, in positioning spindle poles during early sea urchin embryonic cell division using quantitative, real-time analysis. Immunolocalization r eveals that KRP180 concentrates on microtubules in the central spindle, but is absent from centrosomes. Microinjection of inhibitory antibodies and do minant negative constructs suggest that KRP180 is not required for the init ial separation of spindle poles, but instead functions to transiently posit ion spindle poles specifically during prometaphase.