XKLP2, A NOVEL XENOPUS CENTROSOMAL KINESIN-LIKE PROTEIN REQUIRED FOR CENTROSOME SEPARATION DURING MITOSIS

We describe a novel Xenopus plus end-directed kinesin-like protein (KL P), Xklp2, localized on centrosomes throughout the cell cycle and on s pindle pole microtubules during metaphase. Using mitotic spindles asse mbled in Xenopus egg extracts and different recombinant GST-Xklp2 muta nts, we show that this motor is targeted to spindle poles through its C-terminal domain. Xklp2-truncated polypeptides lacking the motor doma in block centrosome separation and disrupt preassembled metaphase spin dles. Antibodies directed against the tail of Xklp2 have a similar eff ect. These results show that Xklp2 protein is required for centrosome separation and maintenance of spindle bipolarity. This study is an exa mple of the application of the dominant negative mutant effect on spin dle assembly in Xenopus egg extracts, demonstrating the usefulness of this approach in probing the function of proteins in this system.