Baculoviral IAP Repeat-Containing Protein 5 (BIRC5) belongs to the IAP family. BIRC5 exists as a homodimer in the apo state and as a monomer in the CPC-bound state. BIRC5 contains one BIR repeat and is expressed only in fetal kidney and liver, and to lesser extent, lung and brain. BIRC5 functions as a multitasking protein that has dual roles in promoting cell proliferation and preventing apoptosis. BIRC5 is also a component of a chromosome passage protein complex (CPC), which is essential for chromosome alignment and segregation during mitosis and cytokinesis. BIRC5 acts as an important regulator of the localization of this complex.