The spindle protein CHICA mediates localization of the chromokinesin Kid to the mitotic spindle.
Microtubule-based motor proteins provide essential forces for bipolar organization of spindle microtubules and chromosome movement, prerequisites of chromosome segregation during the cell cycle. Here, we describe the functional characterization of a novel spindle protein, termed "CHICA," that was originally identified in a proteomic survey of the human spindle apparatus [1]. We show that CHICA localizes to the mitotic spindle and is both upregulated and phosphorylated during mitosis. CHICA-depleted cells form shorter spindles and fail to organize a proper metaphase plate, highly reminiscent of the phenotype observed upon depletion of the chromokinesin Kid, a key mediator of polar ejection forces [2-6]. We further show that CHICA coimmunoprecipitates with Kid and is required for the spindle localization of Kid without affecting its chromosome association. Moreover, upon depletion of either CHICA or Kid (or both proteins simultaneously), chromosomes collapse onto the poles of monastrol-induced monopolar spindles. We conclude that CHICA represents a novel interaction partner of the chromokinesin Kid that is required for the generation of polar ejection forces and chromosome congression.
Santamaria
Anna
A
Department of Cell Biology, Max-Planck Institute of Biochemistry, Martinsried 82152, Germany.
Nagel
Susanna
S
Department of Cell Biology, Max-Planck Institute of Biochemistry, Martinsried 82152, Germany.
Sillje
Herman H W
HHW
Department of Cell Biology, Max-Planck Institute of Biochemistry, Martinsried 82152, Germany.
Nigg
Erich A
EA
Department of Cell Biology, Max-Planck Institute of Biochemistry, Martinsried 82152, Germany. Electronic address: nigg@biochem.mpg.de.
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D002875:Chromosomes / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins; D008938:Mitosis / Q000502:physiology*; D008941:Spindle Apparatus / Q000378:metabolism*
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C530359:FAM83D protein, human; C098764:KIF22 protein, human; D008869:Microtubule-Associated Proteins; D016547:Kinesins