Required for the activation of Aurora-A (aur) at the onset of mitosis. Interacts with aur. Shuttles between the cytoplasm and the nucleus. In interphase cells, it is nuclear. Upon entry into mitosis, it is excluded from the nucleus and translocates into the cytoplasm in a Cdc2-dependent manner (By similarity). Phosphorylated by aur. Belongs to the BORA family.