The centrosome is the major microtubule-organizing centre in animal cells. It contains a pair of microtubule-containing centrioles and a cloud of pericentriolar material (PCM) and is duplicated once per cell cycle during G1/S phase. Without the correct number of centrosomes, cells cannot divide properly, but little is known about how new ones are assembled. On , Ryoko Kuriyama and co-authors provide the first thorough analysis of centrosome replication by describing the process in hydroxyurea-treated CHO cells expressing GFP-tagged centrin2 (which labels the centrioles and PCM). Hydroxyurea arrests cells in G1/S and S phase and, in CHO cells, uncouples the centrosome cycle from the cell cycle, which leads to the production of multiple centrosomes. Using fluorescent imaging of live cells and antibody labelling of centrosome components in fixed cells, the authors show that after hydroxyurea treatment the existing centrosome directs an initial cycle of centriole/centrosome duplication. Prolonged treatment with hydroxyurea induces the random formation of numerous, highly mobile centrin-containing cytoplasmic foci that, the authors suggest, are likely to be involved in centrosome biogenesis.
