PAVAROTTI ENCODES A KINESIN-LIKE PROTEIN REQUIRED TO ORGANIZE THE CENTRAL SPINDLE AND CONTRACTILE RING FOR CYTOKINESIS

Mutations in the Drosophila gene pavarotti result in the formation of abnormally large cells in the embryonic nervous system. In mitotic cyc le 16, cells of pav mutant embryos undergo normal anaphase but then de velop an abnormal telophase spindle and fail to undertake cytokinesis. We show that the septin Peanut, actin, and the actin-associated prote in Anillin, do not become correctly localized in pav mutants. pav enco des a kinesin-like protein, PAV-KLP, related to the mammalian MKLP-1. In cellularized embryos, the protein is localized to centrosomes early in mitosis, and to the midbody region of the spindle in late anaphase and telophase. We show that Polo kinase associates with PAV-KLP with which it shows an overlapping pattern of subcellular localization duri ng the mitotic cycle and this distribution is disrupted in pav mutants . We suggest that PAV-KLP is required both to establish the structure of the telophase spindle to provide a framework for the assembly of th e contractile ring, and to mobilize mitotic regulator proteins.