Calcium depletion destabilises kinetochore fibres by the removal of CENP-F from the kinetochore

The attachment of spindle fibres to the kinetochore is an important process that ensures successful completion of the cell division. The Ca(2+) concentration increases during the mitotic phase and contributes microtubule stability. However, its role in the spindle organisation in mitotic cells remains controversial. Here, we investigated the role of Ca(2+) on kinetochore fibres in living cells. We found that depletion of Ca(2+) during mitosis reduced kinetochore fibre stability. Reduction of kinetochore fibre stability was not due to direct inhibition of microtubule polymerisation by Ca(2+)-depletion but due to elimination of one dynamic component of kinetochore, CENP-F from the kinetochore. This compromised the attachment of kinetochore fibres to the kinetochore which possibly causes mitotic defects induced by the depletion of Ca(2+).