Evidence for a role of CLIP-170 in the establishment of metaphase chromosome alignment.
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.
Dujardin
D
D
Institut Jacques Monod, Department of Supramolecular and Cellular Biology, CNRS-University of Paris VI & VII, 75251 Paris Cedex 05, France.
Wacker
U I
UI
Moreau
A
A
Schroer
T A
TA
Rickard
J E
JE
De Mey
J R
JR
D000818:Animals; D019556:COS Cells; D051836:COUP Transcription Factors; D002875:Chromosomes / Q000502:physiology*; D002877:Chromosomes, Human / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000032:analysis; D000072159:Dynactin Complex; D004398:Dyneins / Q000032:analysis; D004705:Endocytosis; D006367:HeLa Cells; D006801:Humans; D008677:Metaphase; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000096:biosynthesis / Q000502:physiology*; D008938:Mitosis; D009363:Neoplasm Proteins; D010641:Phenotype; D011987:Receptors, Steroid; D011994:Recombinant Proteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000032:analysis; D014162:Transfection; D014407:Tumor Cells, Cultured
D051836:COUP Transcription Factors; C000606361:DCTN2 protein, human; D004268:DNA-Binding Proteins; D000072159:Dynactin Complex; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D014157:Transcription Factors; C076744:cytoplasmic linker protein 170; D004398:Dyneins