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J. Cell Biol.,
Volume 141, Number 4, May 18, 1998 849-862
* Institut Jacques Monod, Department of Supramolecular and Cellular Biology, CNRS-University of Paris VI & VII, 75251 Paris Cedex 05, France; CLIPs (cytoplasmic linker proteins) are a
class of proteins believed to mediate the initial, static
interaction of organelles with microtubules. CLIP-170,
the CLIP best characterized to date, is required for in
vitro binding of endocytic transport vesicles to microtubules. We report here that CLIP-170 transiently associates with prometaphase chromosome kinetochores and
codistributes with dynein and dynactin at kinetochores,
but not polar regions, during mitosis. Like dynein and
dynactin, a fraction of the total CLIP-170 pool can be
detected on kinetochores of unattached chromosomes but not on those that have become aligned at the
metaphase plate. The COOH-terminal domain of
CLIP-170, when transiently overexpressed, localizes to
kinetochores and causes endogenous full-length CLIP-170 to be lost from the kinetochores, resulting in a delay in prometaphase. Overexpression of the dynactin
subunit, dynamitin, strongly reduces the amount of
CLIP-170 at kinetochores suggesting that CLIP-170 targeting may involve the dynein/dynactin complex.
Thus, CLIP-170 may be a linker for cargo in mitosis as
well as interphase. However, dynein and dynactin staining at kinetochores are unaffected by this treatment
and further overexpression studies indicate that neither
CLIP-170 nor dynein and dynactin are required for the formation of kinetochore fibers. Nevertheless, these results strongly suggest that CLIP-170 contributes in
some way to kinetochore function in vivo.
Department of Cell Biology, Sciences III, University of Geneva, 4CH-1211 Geneva, Switzerland; § Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218
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