BIRC5, also known as Survivin and EPR-1, is a member of theIAP family. IAP family members usually contain multiple baculovirus IAP repeat (BIR) domains, but BIRC5 has only a single BIR domain. It is expressed cell cycle-dependently and highly expressed at mitosis. As a multitasking protein, BIRC5 has dual roles in promoting cell proliferation and preventing apoptosis. Survivin is a component of a chromosome passage protein complex (CPC) which is essential for chromosome alignment and segregation during mitosis and cytokinesis. Survivin acts as an important regulator of the localization of this complex. It may counteract a default induction of apoptosis in G2/M phase.