pavarotti encodes a kinesin-like protein required to organize the central spindle and contractile ring for cytokinesis

Abstract

Mutations in the Drosophila gene pavarotti result in the formation of abnormally large cells in the embryonic nervous system. In mitotic cycle 16, cells of pav mutant embryos undergo normal anaphase but then develop an abnormal telophase spindle and fail to undertake cytokinesis. We show that the septin Peanut, actin, and the actin-associated protein Anillin, do not become correctly localized in pav mutants. pav encodes 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 during 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 the contractile ring, and to mobilize mitotic regulator proteins.

Role of the Midbody Matrix in Cytokinesis: RNAi and Genetic Rescue Analysis of the Mammalian Motor Protein CHO1

“…The homologues of MKLP1/CHO1 studied thus far function in cytokinesis in diverse organisms (Adams et al, 1998;Powers et al, 1998;Raich et al, 1998;Chen et al, 2002;Matuliene and Kuriyama, 2002). However, there is some controversy regarding the stage of cytokinesis in which these proteins are involved.…”

“…In C. elegans, the role of ZEN-4 appears to be restricted to completion of cytokinesis and maintenance of cell separation (Powers et al, 1998;Raich et al, 1998;Jantsch-Plunger et al, 2000;Severson et al, 2000). In contrast, Drosophila PAV-KLP has been suggested to be essential for assembly of the contractile ring and initiation of cytokinesis (Adams et al, 1998;Somma et al, 2002;Somers and Saint, 2003). Somers and Saint (2003) have recently proposed that the complex of PAV-KLP and RacGAP50C plays a role in positioning of Pebble RhoGEF at the equator of the cell cortex through direct interaction between RhoGAP and RhoGEF.…”

“…Two structures of the mitotic spindle, spindle asters (Rappaport, 1961) and the central spindle, have been implicated in induction of cleavage furrows. Although the central spindle appears to be essential in triggering cytokinesis in Drosophila (Adams et al, 1998;Giansanti et al, 1998;Somma et al, 2002;Somers and Saint, 2003) and mammalian cells (Cao and Wang, 1996), the same structure is largely dispensable for the furrow initiation in other systems, such as marine invertebrate eggs (Rappaport, 1961;Rappaport and Rappaport, 1983) and Caenorhabditis elegans (Raich et al, 1998;Jantsch-Plunger et al, 2000;Severson et al, 2000). Nonetheless, the presence of a central spindle has been shown to be essential for completion of cytokinesis in most systems (Wheatley and Wang, 1996;Raich et al, 1998;Jantsch-Plunger et al, 2000;Severson et al, 2000;Chen et al, 2002, Alsop andZhang, 2003).…”

“…The protein, named CHO1, turned out to be a plus-end-directed motor protein present in a wide range of organisms from humans (MKLP1: Nislow et al, 1992) and Drosophila (PAV-KLP: Adams et al, 1998) to C. elegans (ZEN-4: Raich et al, 1998). All those molecules are composed of well-conserved three subdomains: the mechanochemical motor domain at the N terminus, the central ␣-helical coiled-coil stalk, and the C-terminal globular tail.…”

“…However, CHO1 represents a unique isotype, in which an actin-binding sequence encoded by exon 18 is included in the middle of the tail domain . Members of the MKLP1 subfamily (Miki et al, 2001) have been shown to function in cytokinesis in different species (Adams et al, 1998;Powers et al, 1998;Raich et al, 1998;Chen et al, 2002;Matuliene and Kuriyama, 2002). In humans and C. elegans, the motor proteins interact with a GAP for Rho family GTPases, which facilitates microtubule bundling and formation of the spindle midzone and midbody (Mishima et al, 2002).…”