Aurora-A — A guardian of poles

Aurora/Ipl1-related kinases are evolutionally conserved serine/threonine kinases that regulate mitotic progression in various organisms. Humans have three classes of Aurora kinases (A, B and C). Aurora-A and -B are ubiquitously expressed and regulate cell-cycle events from G2 to M phase.Aurora-A is localized at centrosome during interphase, translocated to mitotic spindles in early mitotic phase and degraded after metaphase–anaphase transition. Activation of Aurora-A is required for mitotic entry, centrosome maturation, centrosome separation and chromosome alignment, and inactivation is also necessary for exit from mitosis.Human Aurora-A is frequently amplified in various cancers. The levels of Aurora-A mRNA and protein are increased in those tumours and the overexpression of Aurora-A efficiently transforms immortalized rodent fibroblasts, indicating that Aurora-A is an oncoprotein.Aurora-A kinase is activated by interaction with Ajuba and TPX2 during late G2 and mitotic phases, respectively.Overexpression of Aurora-A induces abnormalities in G2 checkpoint and spindle checkpoint and cytokinesis failure. Those abnormalities lead to chromosome instability but are not sufficient for tumorigenesis in animal models. Additional changes such as p53 inactivation and expression of pro-survival proteins might be required for Aurora-A-mediated tumorigenesis.Aurora-kinase inhibition effectively blocks cell growth and induces apoptosis in cancer cells. It might provide a new approach for the treatment of many human malignancies.