Aurora A Kinase Begins to Localize to the Centrosome in the S-phase of the Cell Cycle in the XL2 Cell Line

BACKGROUND: The centrosome is one of the principal cell hubs, where numerous proteins important for intracellular regulatory processes are concentrated. One of them, serine-threonine kinase 6, alias Aurora A, is involved in centrosome duplication and mitotic spindle formation and maintenance. METHODS: Long-term vital observations of cells, immunofluorescence analysis of protein localization, synchronization of cells at different phases of the cell cycle, Western blot analysis of protein content were used in the work. RESULTS: In this study, we investigated the dynamics of Aurora A protein accumulation and degradation in the XL2 Xenopus cell line during its 28-hour cell cycle. Using Western blot and immunofluorescence analyses, we demonstrated that Aurora A disappeared from the centrosome within one hour following mitosis and was not redistributed to other cell compartments. Using double Aurora A/Bromodeoxyuridine immunofluorescence labeling of the cells with precisely determined cell cycle stages, we observed that Aurora A reappeared in the centrosome during the S-phase, which was earlier than reported for all other known proteins with mitosis-specific centrosomal localization. Moreover, Aurora A accumulation in the centrosomal region and centrosome separation were asynchronous in the sister cells. CONCLUSIONS: The reported data allowed us to hypothesize that Aurora A is one of the primary links in coordinating centrosome separation and constructing the mitotic spindle.