Loss of p53 and centrosome hyperamplification.

Loss or mutational inactivation of p53 has been shown to lead to abnormal amplification of centrosomes through deregulation of the centrosome duplication cycle and failure to undergo cytokinesis. In mouse cells, most cases of centrosome hyperamplification are attributed to deregulation of centrosome duplication. The presence of excess copies of centrosomes increases the frequency of mitotic defects, leading to unbalanced chromosome transmission to daughter cells. p53 controls centrosome duplication via transactivation-dependent and transactivation-independent mechanisms. In its transactivation-dependent control, p21(Waf1/Cip1) acts as a major effector, likely guarding against untimely activation of CDK2/cyclin E kinase, hence ensuring the coordinated initiation of centrosome and DNA duplication. p53 appears to exert its transactivation-independent control through direct physical binding to the centrosomes.