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A Rho for the kinetochore

Chromosome alignment on the spindle (top) is lost if Cdc42 is inactivated (bottom). Narumiya/Macmillan

Results from Shingo Yasuda, Shuh Narumiya (Kyoto University, Kyoto, Japan), and colleagues reveal microtubules at the cell cortex, are also needed for microtubule–kinetochore attachments, thus uniting two previously distant fields of study.

Rho GTPases are needed during cytokinesis, when Rho helps build a contractile actin ring. Another Rho family member, Cdc42, is now shown to be required for nuclear division. Without its activity, chromosomes failed to make bipolar attachments. Some chromosomes were attached to one pole or the other, suggesting that correction of monoorientation, rather than capture itself, is controlled by the GTPase.

Rho GTPases control both cortical and kinetochore capture by activating a formin homologue, mDia. At the cortex in yeast, an mDia1 homologue polymerizes long actin tracks that EB1-bound microtubules use to find their way to the cortex. At the mammalian kinetochore, mDia3 was needed for Cdc42-regulated biorientation. Narumiya would be surprised if actin tracks also guide microtubules to kinetochores, but since he does not know yet what the kinetochore target of mDia3 is, "we do not exclude any possibility," he says.

Reference:

Yasuda, S., et al. 2004. Nature. 428:767–771.[CrossRef][Medline]

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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This Article Full Text (PDF, 699K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Social Bookmarking                            What's this?