title: DSK1, a kinesin-related protein involved in anaphase spindle elongation, is a component of a mitotic spindle matrix.
abstract: DSK1 is a kinesin-related protein that is involved in anaphase spindle elongation in the diatom Cylindrotheca fuisiformis [Wein et al., 1996: J. Cell Biol. 113:595-604]. DSK1 staining appeared to be concentrated in the gap that forms as the two half-spindles separate, suggesting that DSK1 may be part of a non-microtubule spindle matrix. We set out to investigate this possibility using three-dimensional high-resolution fluorescence microscopy, and biochemical methods of tubulin extraction. Three-dimensional fluorescence microscopy reveals that DSK1 remains in the midzone after the bulk of the microtubules from the two half-spindles have left the region. Biochemical studies show that CaCl2 extraction of tubulin from a mitotic spindle preparation does not extract similar proportions of DSK1 protein. Immunofluorescence confirms that this CaCl2 extraction leaves behind spindle-like bars that are recognized by anti-DSK1, but not by anti-tubulin antibodies. We conclude that DSK1 is part of, or attached to, a non-microtubule scaffold in the diatom central spindle. This discovery has implications for both the structural organization of the mitotic spindle and the mechanism of spindle elongation.
authors.affiliation: Federation of American Scientists, Washington, DC, USA.
authors.forename: H
authors.initials: H
authors.lastname: Wein
authors.forename: H W
authors.initials: HW
authors.lastname: Bass
authors.forename: W Z
authors.initials: WZ
authors.lastname: Cande
mesh_terms: D000705:Anaphase / Q000502:physiology; D017377:Diatoms / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D016547:Kinesins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008941:Spindle Apparatus / Q000378:metabolism*
chemical_list: D016547:Kinesins