The Xenopus chromokinesin Xkid is essential for metaphase chromosome alignment and must be degraded to allow anaphase chromosome movement.
At anaphase, the linkage betweeh sister chromatids is dissolved and the separated sisters move toward opposite poles of the spindle. We developed a method to purify metaphase and anaphase chromosomes from frog egg extracts and identified proteins that leave chromosomes at anaphase using a new form of expression screening. This approach identified Xkid, a Xenopus homolog of human Kid (kinesin-like DNA binding protein) as a protein that is degraded in anaphase by ubiquitin-mediated proteolysis. Immunodepleting Xkid from egg extracts prevented normal chromosome alignment on the metaphase spindle. Adding a mild excess of wild-type or nondegradable Xkid to egg extracts prevented the separated chromosomes from moving toward the poles. We propose that Xkid provides the metaphase force that pushes chromosome arms toward the equator of the spindle and that its destruction is needed for anaphase chromosome movement.
Funabiki
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Department of Physiology, University of California, San Francisco 94143, USA. hironori@mcb.harvard.edu
Murray
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D000595:Amino Acid Sequence; D000705:Anaphase / Q000235:genetics*; D000818:Animals; D002875:Chromosomes / Q000502:physiology*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D016547:Kinesins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D018386:Kinetochores / Q000502:physiology; D008677:Metaphase / Q000235:genetics*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D008941:Spindle Apparatus / Q000502:physiology; D014452:Ubiquitins / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins
D004268:DNA-Binding Proteins; C098764:KIF22 protein, human; C490913:KIFF22 protein, Xenopus; D014452:Ubiquitins; D029867:Xenopus Proteins; D016547:Kinesins