Abstract
Mitotic spindle assembly is a highly regulated process, crucial to ensure the correct segregation of duplicated chromosomes in daughter cells and to avoid aneuploidy, a common feature of tumors. Among the most important spindle regulators is Aurora-A, a mitotic centrosomal kinase frequently overexpressed in tumors. Here, we investigated the role of Aurora-A in spindle pole organization in human cells. We show that RNA interference-mediated Aurora-A inactivation causes pericentriolar material fragmentation in prometaphase, yielding the formation of spindles with supernumerary poles. This fragmentation does not necessarily involve centrioles and requires microtubules (MTs). Aurora-A-depleted prometaphases mislocalize the MT-stabilizing protein colonic hepatic tumor-overexpressed gene (ch-TOG), which abnormally accumulates at spindle poles, as well as the mitotic centromere-associated kinesin (MCAK), the major functional antagonist of ch-TOG, which delocalizes from poles. ch-TOG is required for extrapole formation in prometaphases lacking Aurora-A, because co-depletion of Aurora-A and ch-TOG mitigates the fragmented pole phenotype. These results indicate a novel function of Aurora-A, the regulation of ch-TOG and MCAK localization, and highlight a common pathway involving the three factors in control of spindle pole integrity.
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