Al. Pidoux et al., FISSION YEAST PKL1 IS A KINESIN-RELATED PROTEIN INVOLVED IN MITOTIC SPINDLE FUNCTION, Molecular biology of the cell, 7(10), 1996, pp. 1639-1655
We have used anti-peptide antibodies raised against highly conserved r
egions of the kinesin motor domain to identify kinesin-related protein
s in the fission yeast Schizosaccharomyces pombe. Here we report the i
dentification of a new kinesin-related protein, which we have named pk
l1. Sequence homology and domain organization place pkl1 in the Kar3/n
cd subfamily of kinesin-related proteins. Bacterially expressed pkl1 f
usion proteins display microtubule-stimulated ATPase activity, nucleot
ide-sensitive binding, and bundling of microtubules. Immunofluorescenc
e studies with affinity-purified antibodies indicate that the pkl1 pro
tein localizes to the nucleus and the mitotic spindle. Pkl1 null mutan
ts are viable but have increased sensitivity to microtubule-disrupting
drugs. Disruption of pkl1(+) suppresses mutations in another kinesin-
related protein, cut7, which is known to act in the spindle. Overexpre
ssion of pkl1 to very high levels causes a similar phenotype to that s
een in cut7 mutants: V-shaped and star-shaped microtubule structures a
re observed, which we interpret to be spindles with unseparated spindl
e poles. These observations suggest that pkl1 and cut7 provide opposin
g forces in the spindle. We propose that pkl1 functions as a microtubu
le-dependent motor that is involved in microtubule organization in the
mitotic spindle.