In G1/S phase a single centrosome is located in close apposition to the nuclear envelope. Centrosome duplication is
controlled by centriole replication. The mother and daughter centrioles are disengaged at the end of mitosis. After centriole disengagement, a proteinaceous linker is established between the 2 centrioles and physically connects them during interphase until mitosis. Building of the new centriole begins in early s phase with the formation of a procentriole at each centriole. One new daughter centriole forms perpendicular to each mother centriole during S phase, and the new daughter centri ole gradually elongates during S and G2 phases. In late G2 phase, the amount of PCM proteins surrounding the centrioles increases, and the 2 centrosomes separate by dissolution of the linker that connects the 2 centrosomes. The separated
centrosomes then move to opposite sides of the cell to form the spindle poles. Many of the proteins involved in the centrosome cycle have been identified and characterized(Figure 1). In this review we summarize research findings related to the centro- some cycle.