Mechanism limiting centrosome duplication to once per cell cycle

The centrosome is duplicated just once per cell cycle so that there is one centrosome at the beginning of the cell cycle and two in mitosis. Defects in this process can cause genome instability and even cancer. An in vitro study points to a strikingly similarity between the way cells control centrosome duplication and chromosome segregation. The pair of centrioles in the centrosome disengage at the end of mitosis, a process requiring separase, a protease involved in sister chromatid separation at mitosis. The separated centrioles are a substrate for duplication in the next cell cycle. Newly duplicated centrioles are paired, so they cannot duplicate again until passage through mitosis, when they are freed to duplicate by separase-mediated disengagement. This work reveals a common mechanism behind the two cellular processes that result in exact duplication once per cycle.