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J Cell Biol. October 18, 1999; 147 (2): 351-66.

The kinesin-related protein, HSET, opposes the activity of Eg5 and cross-links microtubules in the mammalian mitotic spindle.

Mountain V , Simerly C , Howard L , Ando A , Schatten G , Compton DA .

We have prepared antibodies specific for HSET, the human homologue of the KAR3 family of minus end-directed motors. Immuno-EM with these antibodies indicates that HSET frequently localizes between microtubules within the mammalian metaphase spindle consistent with a microtubule cross-linking function. Microinjection experiments show that HSET activity is essential for meiotic spindle organization in murine oocytes and taxol-induced aster assembly in cultured cells. However, inhibition of HSET did not affect mitotic spindle architecture or function in cultured cells, indicating that centrosomes mask the role of HSET during mitosis. We also show that (acentrosomal) microtubule asters fail to assemble in vitro without HSET activity, but simultaneous inhibition of HSET and Eg5, a plus end-directed motor, redresses the balance of forces acting on microtubules and restores aster organization. In vivo, centrosomes fail to separate and monopolar spindles assemble without Eg5 activity. Simultaneous inhibition of HSET and Eg5 restores centrosome separation and, in some cases, bipolar spindle formation. Thus, through microtubule cross-linking and oppositely oriented motor activity, HSET and Eg5 participate in spindle assembly and promote spindle bipolarity, although the activity of HSET is not essential for spindle assembly and function in cultured cells because of centrosomes.

PubMed ID: 10525540
PMC ID: PMC2174226
Article link: J Cell Biol.
Grant support: GM51542 NIGMS NIH HHS , R37WD12913 PHS HHS , R01 GM051542 NIGMS NIH HHS , R37 GM051542 NIGMS NIH HHS , GM51542 NIGMS NIH HHS , R37WD12913 PHS HHS

Genes referenced: adcyap1r1 dnai1 dync1li1 kif11 kifc1 numa1 tbx2

Antibodies referenced: Kifc1 Ab1

Rieder, 1982, Pubmed[+]

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