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Kif18A’s Tail Goes the Distance

September 23, 2011 | Melissa Marino

Mitosis, the process by which chromosomes are separated during cell division, requires tight regulation of the string-like structures (microtubules) that originate at the cell poles, attach to chromosomes, and pull them apart. Kif18A, a motor protein involved in properly aligning chromosomes for mitosis, accumulates at the “plus”-ends of microtubules – the dynamic ends that attach to chromosomes – and suppresses their dynamics (the plus ends are constantly elongating and shrinking).

In the Sept. 2 issue of Molecular Cell, Ryoma Ohi, Ph.D., and colleagues identify the protein’s “tail” section as being crucial to its function. By creating Kif18A mutants, they showed that accumulation of the protein at microtubule plus-ends depends on the C-terminal tail domain, whereas suppression of microtubule growth depends on the N-terminal motor domain. The tail region works by “tethering” the motor to the microtubule track, thereby increasing the distance that the protein can move along microtubules.

Since some chemotherapy drugs, like Taxol, act by disrupting microtubule dynamics, the findings may have implications for cancer therapeutics.