ABSTRACT

Wein H, Bass H.W., and Cande W.Z. (1998)
  DSK1, a kinesin-related protein involved in anaphase spindle elongation,
  is a component of the mitotic spindle matrix.
  Cell Motility and Cytoskeleton41(3):224-224.
    (PubMed Ab).

Summary
	DSK1 is a kinesin-related protein that is involved in anaphase 
spindle elongation in the diatom Cylindrotheca fusiformis (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.


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