A32
Centrosome overduplication requires Cdk2 activity, nuclear export, microtubules, dynein and Hsp90
Suzanna L Prosser, Andrew M Fry
University of Leicester, Leicester, UK
Background
Cells contain a single centrosome that organizes the microtubule network in cells. It duplicates once per cell cycle such that there are two centrosomes present at the time the cell enters mitosis. Each centrosome organises a pole of the mitotic spindle thereby establishing bipolarity. The presence of too many centrosomes can lead to the formation of multipolar spindles and the uneven segregation of chromosomes. Indeed, cancer cells frequently display supernumerary centrosomes that can contribute to chromosome segregation errors and aneuploidy.
Method
Prolonged S-phase arrest can induce centrosome overduplication in p53-deficient cells. This assay has been used in CHO, U2OS and p53-/- MEF cells to elucidate a pathway for centrosome overduplication using a range of pharmacological inhibitors.
Results
Distinct granules containing the protein centrin were identified as early intermediates in centrosome overduplication, and were found to form within the nucleus in a Cdk2-dependent manner. These foci are then trafficked to the cytoplasm, dependent on the nuclear export machinery, where they recruit modified tubulin, PCM-1 and pericentrin. Microtubules and dynein are required for the focusing of these foci around the centrosome and the formation of recognisable centriole structures. Hsp90 is then required for the recruitment of γ-tubulin to form functional microtubule organising centres.
Conclusions
We have identified distinct roles for Cdk2 activity, nuclear export, microtubules, dynein and Hsp90 in the overduplication of functional centrosomes. This increases our understanding of how supernumerary centrosomes are generated in cells, whilst identifying key events that may be targeted to prevent centrosome overduplication in cancer cells.
