Molecular Basis of Genomic Instability in Breast Cancer: Regulation of the Centrosome Duplication Cycle

Abstract : Alterations in the expression and activity of the centrosomal kinase, Aurora-A/STK15, affect genomic stability, disrupt the fidelity of centrosome duplication, and induce cellular transformation. In 2003, we finished task 1 and 2. From June 1, 2003 to May 31, 2004, we further Charcterized a mitotic spindle-associated protein, astrin/DEEPEST, which is identified as an Aurora-A interacting protein by a two-hybrid screen. Astrin is co-expressed with Aurora-A at mitosis and colocalizes to the mitotic spindles, as well as to the outer kinetochore. RNAi depletion of astrin abolishes the Aurora-A mitotic spindle localization. Depletion of astrin, which interacts with alpha-tubulin, also induces Eg5 depedent multipolar spindle from de novo synthesized centrosomes without recruiting centrin 2 protein. Astrin silencing leads to a moderate G2/M cell cycle delay, caused by de=localization of cyclin B1-CDK1 from the centrosome and spindles, which resembles the G2/M arrest phenotypes in siAurora treated cells. Double-inactivation of both astrin and Aurora-A shows mitotic arrest phenotypes similar to depletion of siAurora-A alone, suggesting that astrin acts upstream of Aurora-A/ Overexpression of astrin caused premature senescence in primary human fibroblast by inducing p53 overexpression.